JP2004273444A - Lithium secondary battery, active substance for negative electrode thereof and negative electrode thereof - Google Patents
Lithium secondary battery, active substance for negative electrode thereof and negative electrode thereof Download PDFInfo
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- JP2004273444A JP2004273444A JP2004036952A JP2004036952A JP2004273444A JP 2004273444 A JP2004273444 A JP 2004273444A JP 2004036952 A JP2004036952 A JP 2004036952A JP 2004036952 A JP2004036952 A JP 2004036952A JP 2004273444 A JP2004273444 A JP 2004273444A
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- active material
- negative electrode
- secondary battery
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- lithium secondary
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
Description
本発明は、リチウム二次電池用負極活物質、リチウム二次電池負極及びリチウム二次電池に関する。詳しくは、本発明は、活物質層の薄肉化による高出力・高入力化が可能で、しかも長寿命で安全性の高い、自動車用リチウム二次電池に適したリチウム二次電池用負極活物質と、この負極活物質を用いたリチウム二次電池負極及びリチウム二次電池に関する。 The present invention relates to a negative electrode active material for a lithium secondary battery, a negative electrode for a lithium secondary battery, and a lithium secondary battery. More specifically, the present invention relates to a negative electrode active material for a lithium secondary battery, which is capable of high output and high input by thinning the active material layer, and has a long life and high safety, which is suitable for a lithium secondary battery for an automobile. And a lithium secondary battery negative electrode and a lithium secondary battery using the negative electrode active material.
従来、ノート型パソコンや、携帯電話、自動車用などの駆動用電源として、各種二次電池が開発されているが、昨今の高機能化と、特に自動車用途での加速性などの要求から、大電流を放出あるいは充電可能な、高出力・高入力性の二次電池が求められている。 Conventionally, various secondary batteries have been developed as power supplies for driving notebook computers, mobile phones, and automobiles. However, due to recent demands for higher functionality and acceleration, especially for automobiles, the demand for such batteries has increased. There is a need for a high-output, high-input secondary battery capable of discharging or charging current.
即ち、電気ドリルやカッターなどのコードレス機器、電気自動車やハイブリッド自動車用の電池では、大電流によるモーター駆動が必要である。特にハイブリッド自動車用の電池は、高容量である必要はなく、エンジン動力をアシストするモーターを瞬間的に作動させるための高出力性能や自動車が停止する時のエネルギーを回生するための高入力特性が望まれている。 That is, in a cordless device such as an electric drill and a cutter, and a battery for an electric vehicle or a hybrid vehicle, the motor needs to be driven by a large current. In particular, batteries for hybrid vehicles do not need to have high capacity, but have high output performance for instantaneously operating a motor that assists engine power and high input characteristics for regenerating energy when the vehicle stops. Is desired.
一方で、リチウム二次電池は、小電流で放電した際のエネルギー密度（Ｗｈ／ｋｇ）、パワー密度（Ｗ／ｋｇ）では優れているものの、高電流放電（大きいパワーでの放電）では、電池の耐久劣化までを考慮すると、ニッケル水素二次電池などに比べて、必ずしも優れた高出力特性が得られている訳ではなかった。このようなことから、リチウム二次電池には、大きな電流値による短時間の充放電サイクル特性の改善が望まれる。なお、このような性能は、従来のモバイル機器向けリチウム二次電池としての使用形態には要求されることのなかったものである。 On the other hand, a lithium secondary battery is excellent in energy density (Wh / kg) and power density (W / kg) when discharged with a small current, but is not good in high current discharge (discharge with large power). In consideration of the durability deterioration of the battery, high output characteristics superior to nickel-metal hydride secondary batteries or the like were not necessarily obtained. For this reason, it is desired that the lithium secondary battery has an improved short-time charge / discharge cycle characteristic with a large current value. Note that such performance is not required for a usage form as a conventional lithium secondary battery for mobile devices.
リチウム二次電池において、個々の電池（単セル）の出力性を増すために大電流を取り出すには、単セルの極板をより薄肉化することが望まれる。単セルをより薄肉化するには、電池を構成する正極、負極等の部材を薄肉化する必要がある。従来、リチウム二次電池の活物質層は、集電体上に、リチウムを吸蔵・放出可能な活物質を、結着及び増粘効果を有する有機物と共に、水或いは有機溶媒に分散させた分散液（スラリー）を塗布、乾燥することにより形成されているが、活物質層を薄くすると、塗工量が不均一となり、充放電の繰り返しにより、リチウム金属が析出し、短絡を起こしてしまい、電池寿命及び安全性の点で問題があった。特に、自動車用途においては、安全性を確保することは極めて重要であり、大きな課題であった。 In a lithium secondary battery, in order to take out a large current in order to increase the output power of each battery (single cell), it is desired to make the electrode plate of the single cell thinner. In order to make a unit cell thinner, it is necessary to make members such as a positive electrode and a negative electrode constituting the battery thinner. Conventionally, an active material layer of a lithium secondary battery is a dispersion in which an active material capable of absorbing and releasing lithium is dispersed in water or an organic solvent together with an organic substance having a binding and thickening effect on a current collector. (Slurry) is applied and dried. However, if the active material layer is thinned, the coating amount becomes uneven, and lithium metal is precipitated by repeated charge / discharge, causing a short circuit. There was a problem in terms of life and safety. In particular, in automotive applications, ensuring safety is extremely important and a major issue.
ＷＯ００／０２２６８７号には、リチウム電池用炭素材料として、特定の比表面積、アスペクト比、タッピング嵩密度を備えた黒鉛粉末であって、粒径３μｍ以下及び／又は５３μｍ以上の粒子を実質的に含まない黒鉛粉末が記載されている。ＷＯ００／０２２６８７号においては、粒径５３μｍ以上の大きな粒子の混入がセパレータを傷付ける原因となることが指摘されている。しかしながら、ＷＯ００／０２２６８７号では、粒径５３μｍ以上の粒子は、その含有量が１重量％以下となるように分級すれば良いとされており、実施例では、２７０メッシュ（５３μｍ）の篩で篩っているに過ぎず、粒径５３μｍ未満の粒子が残留し、また、扁平な黒鉛粒子では、２７０メッシュの篩で数回篩っても、粒径５３μｍ以上の粒子は、通常５体積％程度残留してしまう。 WO 00/022687 describes, as a carbon material for a lithium battery, a graphite powder having a specific specific surface area, an aspect ratio, and a tapping bulk density, which substantially contains particles having a particle size of 3 μm or less and / or 53 μm or more. No graphite powder is described. In WO 00/022687, it is pointed out that mixing of large particles having a particle size of 53 μm or more causes damage to the separator. However, according to WO 00/022687, particles having a particle size of 53 μm or more may be classified so that the content is 1% by weight or less. In the examples, the particles are sieved with a 270 mesh (53 μm) sieve. Particles having a particle size of less than 53 μm remain. In the case of flat graphite particles, even if the particles are sieved several times with a 270 mesh sieve, the particles having a particle size of 53 μm or more are usually about 5% by volume. Will remain.
このような粗大粒子の残留する黒鉛粒子では、活物質層を薄く形成した場合の不均一性、これに起因する繰り返し充放電によるリチウム金属の析出の問題を解決することはできず、特に、５０μｍ以下もの薄肉化された活物質層を形成した負極にあっては、この問題が顕著である。
本発明は上記従来の問題点を解決し、活物質層の薄肉化が可能なリチウム二次電池用負極活物質、即ち、活物質層を５０μｍ以下に薄肉化した場合であっても、均一な活物質層を形成することができ、充放電を繰り返しても、リチウム金属の析出の問題のない活物質と、この活物質を用いてなる薄肉化が可能なリチウム二次電池負極と、この負極を用いてなる、高出力・高入力特性に優れ、電池寿命が長く安全性の高いリチウム二次電池を提供することを目的とする。 The present invention solves the conventional problems described above, the negative electrode active material for a lithium secondary battery capable of thinning the active material layer, that is, even when the active material layer is thinned to 50 μm or less, the uniformity An active material capable of forming an active material layer and having no problem of deposition of lithium metal even when charging and discharging are repeated; a lithium secondary battery negative electrode that can be thinned using the active material; It is an object of the present invention to provide a lithium secondary battery which is excellent in high output / high input characteristics, has a long battery life, and is highly safe.
本発明のリチウム二次電池用負極活物質は、炭素質粉末状のリチウム二次電池用負極活物質において、該活物質粉末１００ｇを２ｇのカルボキシメチルセルロースと共に２００ｇの水に分散させてなる分散液について、ＪＩＳ Ｋ５４００ 粒ゲージ法による分散度に準拠して測定される、粒が現れ始める粒子径（以下、これを、「最大分散粒子径」という）が、５０μｍ以下であることを特徴とする。 The negative electrode active material for a lithium secondary battery of the present invention is a dispersion liquid obtained by dispersing 100 g of the active material powder in 200 g of water together with 2 g of carboxymethyl cellulose in a carbonaceous powdery negative electrode active material for a lithium secondary battery. The particle diameter at which particles begin to appear (hereinafter referred to as “maximum dispersed particle diameter”), which is measured based on the degree of dispersion by the JIS K5400 particle gauge method, is 50 μm or less.
即ち、本発明者らは、本発明の課題を解決すべく鋭意検討した結果、負極活物質の物性を選ぶことによって、活物質層を薄肉化しても繰り返し充放電によるリチウム金属の析出による短絡の問題は防止され、長寿命で安全性の高い、高出力・高入力性のリチウム二次電池を実現することができることを見出し、本発明を完成させた。 That is, the present inventors have conducted intensive studies to solve the problems of the present invention, and as a result, by selecting the physical properties of the negative electrode active material, even if the active material layer is thinned, short-circuiting due to repeated deposition of lithium metal due to charge and discharge is possible. The problem was prevented, and it was found that a lithium secondary battery having a long life, high safety, high output and high input could be realized, and the present invention was completed.
本発明のリチウム二次電池用負極活物質は、上述のＪＩＳ Ｋ５４００ 粒ゲージ法による分散度に準拠して測定される、粒子径３５μｍ以上５０μｍ以下の粒が１０個以下であることが好ましい。 The negative electrode active material for a lithium secondary battery of the present invention preferably has 10 or less particles having a particle diameter of 35 μm or more and 50 μm or less, which are measured based on the degree of dispersion according to the above-mentioned JIS K5400 particle gauge method.
本発明のリチウム二次電池負極は、集電体上に、活物質と、結着及び増粘効果を有する有機物とを含有する活物質層を形成してなるリチウム二次電池負極において、該活物質層の厚さが５０μｍ以下であり、ＪＩＳ Ｂ０６０１に準拠して測定される算術平均粗さ（Ｒa）が、５μｍ以下であることを特徴とする。 The negative electrode for a lithium secondary battery according to the present invention is a negative electrode for a lithium secondary battery in which an active material layer containing an active material and an organic substance having a binding and thickening effect is formed on a current collector. The thickness of the material layer is 50 μm or less, and the arithmetic average roughness (Ra) measured according to JIS B0601 is 5 μm or less.
本発明のリチウム二次電池は、リチウムを吸蔵・放出可能な正極、リチウムを吸蔵・放出可能な負極、及び、電解質を有するリチウム二次電池において、該負極として、このような本発明のリチウム二次電池負極を用いたことを特徴とする。 The lithium secondary battery of the present invention is a lithium secondary battery having a positive electrode capable of storing and releasing lithium, a negative electrode capable of storing and releasing lithium, and an electrolyte. It is characterized by using a secondary battery negative electrode.
本発明のリチウム二次電池用負極活物質によれば、５０μｍ以下の薄肉の活物質層であっても、均一で、繰り返し充放電によるリチウム金属の析出の問題のない活物質層を形成することができる。５０μｍ以下の薄肉であっても、表面が高度に均一化された活物質層を有する本発明のリチウム二次電池負極であれば、負極の薄肉化、長寿命化、安全性の向上が可能であり、この負極を用いた本発明のリチウム二次電池によれば、高出力・高入力特性に優れ、長寿命で安全性の高いリチウム二次電池が提供される。このような本発明のリチウム二次電池は、特に高出力性が要求される自動車用リチウム二次電池等として工業的に極めて有用である According to the negative electrode active material for a lithium secondary battery of the present invention, even if the active material layer is a thin active material layer having a thickness of 50 μm or less, it is possible to form an active material layer that is uniform and has no problem of lithium metal deposition due to repeated charge and discharge. Can be. Even if the thickness is 50 μm or less, the negative electrode of the lithium secondary battery of the present invention having an active material layer with a highly uniform surface can make the negative electrode thinner, have a longer life, and have improved safety. According to the lithium secondary battery of the present invention using the negative electrode, a lithium secondary battery having excellent high output and high input characteristics, a long life and high safety is provided. Such a lithium secondary battery of the present invention is extremely useful industrially as a lithium secondary battery for an automobile, which particularly requires high output power.
以下に本発明を更に詳細に説明する。 Hereinafter, the present invention will be described in more detail.
まず、本発明のリチウム二次電池用負極活物質について説明する。 First, the negative electrode active material for a lithium secondary battery of the present invention will be described.
本発明のリチウム二次電池用負極活物質は、炭素質粉末状のリチウム二次電池用負極活物質であって、次の特定の物性を満たすことを必須とする。 The negative electrode active material for a lithium secondary battery of the present invention is a negative electrode active material for a lithium secondary battery in the form of a carbonaceous powder, and is required to satisfy the following specific physical properties.
即ち、この活物質粉末１００ｇと、２ｇのカルボキシメチルセルロースと２００ｇの水からなる分散液（以下「試料分散液」と称す場合がある。）について、ＪＩＳ Ｋ５４００ 粒ゲージ法による分散度に準拠して測定される、粒が現れ始める最大分散粒子径が、５０μｍ以下であることが必要である。 That is, a dispersion composed of 100 g of this active material powder, 2 g of carboxymethylcellulose and 200 g of water (hereinafter sometimes referred to as “sample dispersion”) is measured in accordance with the degree of dispersion according to JIS K5400 particle gauge method. It is necessary that the maximum dispersed particle diameter at which the particles begin to appear is 50 μm or less.
ここで、試料分散液は、活物質粉末、カルボキシメチルセルロース及び水の上記所定量を、２５℃で、遊星型二軸混練機を用いて、公転７８０ｒｐｍ、自転１４４ｒｐｍで３０分間混合した状態の分散液とする。 Here, the sample dispersion is a dispersion in which the above-mentioned predetermined amounts of the active material powder, carboxymethyl cellulose and water are mixed at 25 ° C. for 30 minutes at a revolution of 780 rpm and a rotation of 144 rpm using a planetary twin-screw kneader. And
本発明においては、上述の試料分散液についてＪＩＳ Ｋ５４００ 粒ゲージ法によって測定される、粒が現れ始める粒子径を最大分散粒子径とするが（分布図法）、測定対象の試料分散液中では、活物質及び／又はカルボキシメチルセルロースが、通常ある程度の凝集を起こしているため、粒ゲージ法による分散度の測定において、粒が線条に観察されることが多い。従って、このような場合には、線条の現れ始める粒子径を最大分散粒子径とする（線条法）。 In the present invention, the particle size at which particles begin to appear as measured by the JIS K5400 particle gauge method for the above-mentioned sample dispersion is defined as the maximum dispersion particle size (distribution diagram). Since the substance and / or carboxymethylcellulose usually cause a certain degree of aggregation, in the measurement of the degree of dispersion by the particle gauge method, particles are often observed in the striatum. Therefore, in such a case, the particle diameter at which the line starts to appear is defined as the maximum dispersed particle diameter (the linear method).
以下に、本発明で特定される負極活物質の物性が、負極活物質層の薄肉化に有効である理由について説明する。 Hereinafter, the reason why the physical properties of the negative electrode active material specified in the present invention are effective for reducing the thickness of the negative electrode active material layer will be described.
負極活物質層は、通常、負極活物質と、結着及び増粘効果を有する有機物（以下「結着剤」と称す場合がある。）を、水あるいは有機溶媒中に分散させたスラリー状のもの（以下「活物質スラリー」と称す場合がある。）を、金属箔などの集電体上に薄く塗布・乾燥する工程、続いて所定の厚み・密度まで圧密するプレス工程により形成される。活物質スラリーを集電体上に薄く塗布する工程では、通常、活物質スラリーをブレードなどを用いて所定の厚みですり切る方法、あるいは細くスリット状に開口部を設けたノズルから一定量のスラリーを吐出し、集電体上に均一に塗りつける方法が採用されている。 The negative electrode active material layer is usually a slurry in which the negative electrode active material and an organic substance having a binding and thickening effect (hereinafter sometimes referred to as a “binder”) are dispersed in water or an organic solvent. An object (hereinafter sometimes referred to as an “active material slurry”) is formed on a current collector such as a metal foil by a thin coating and drying process, followed by a pressing process for consolidating to a predetermined thickness and density. In the process of applying the active material slurry thinly on the current collector, the active material slurry is usually sliced at a predetermined thickness using a blade or the like, or a predetermined amount of slurry is supplied from a nozzle having a thin slit-shaped opening. And a method of uniformly applying the ink on the current collector.
ところで、負極活物質層の形成に用いられる活物質スラリーには、負極活物質としての炭素質粉末の製造過程で種々の原因により持ち込まれたり、また、活物質層形成工程における塗布条件下で凝集ないし粗大化することにより生じた粗大粒子が含まれているが、活物質スラリー中にこのような粗大粒子が存在すると、これがブレードの間隙やノズル開口部に滞留し、その後にスラリーが十分供給されなくなるため、この滞留部位に相当する集電体上の活物質スラリーの塗布量が不充分となり、その後、乾燥、プレスして形成される活物質層の厚みに著しい不均一を生じる。このように粗大粒子が、すり切り用ブレードや吐出ノズルに滞留しない場合でも、活物質層中の粗大粒子は、プレス後も負極極板上の突起物として存在し、表面均一性を著しく妨げる原因となる。 By the way, the active material slurry used for forming the negative electrode active material layer is brought in for various reasons in the production process of the carbonaceous powder as the negative electrode active material, or aggregates under application conditions in the active material layer forming step. Or coarse particles generated by coarsening are included, but when such coarse particles are present in the active material slurry, they stay in gaps between the blades and nozzle openings, and thereafter the slurry is sufficiently supplied. Therefore, the applied amount of the active material slurry on the current collector corresponding to the stagnation portion becomes insufficient, and thereafter, the thickness of the active material layer formed by drying and pressing becomes extremely uneven. Thus, even when the coarse particles do not stay in the cutting blade or the discharge nozzle, the coarse particles in the active material layer are present as projections on the negative electrode plate even after pressing, which is a cause that significantly impairs the surface uniformity. Become.
負極活物質層が不均一である、あるいは負極極板上に凹凸や突起物のある負極を電池に用いた場合、そうした表面不均一性のある部位を中心に、電流密度に疎密が生じ、長期間の充放電を経ることで、電流の集中した部位にリチウム金属が析出し、ひいては発火事故等の原因ともなる。従って、活物質層の均一性は、電流密度が大きい電池ほど、或いは瞬間的に大電流を流すパルス充放電用の電池ほど、高精度に求められる。 When a negative electrode having a non-uniform negative electrode active material layer or a negative electrode having irregularities or protrusions on the negative electrode plate is used for a battery, current density varies mainly in a portion having such surface non-uniformity, resulting in a long and narrow current density. After a period of charge / discharge, lithium metal is deposited at a portion where current is concentrated, which may cause a fire accident or the like. Therefore, the uniformity of the active material layer is required to have higher accuracy as the battery has a higher current density or a battery for pulse charging and discharging in which a large current flows instantaneously.
前述のＷＯ００／０２２６８７号には、セパレータの傷付きを防ぐために活物質中の粗大粒子を排除することが記載されているが、負極極板上の活物質層は、単にセパレータを傷付けない、即ち、セパレータ厚みを突き破らない程度の均一性では不十分であり、長期間の充放電サイクルを経ても、電流密度の均一性を保ち得るだけの高精度な均一性が必要である。 In the above-mentioned WO 00/022687, it is described that coarse particles in the active material are removed in order to prevent the separator from being damaged. However, the active material layer on the negative electrode plate does not simply damage the separator. However, uniformity that does not break through the thickness of the separator is not sufficient, and high-precision uniformity that can maintain uniformity of current density even after a long-term charge / discharge cycle is required.
本発明者らは、このような要求性能を満たす極板を得るためには、活物質中の粗大粒子を、単なる篩分けにより除去するのではなく、特定の条件で予め除去しておくことが重要であることを見出した。そして、この粗大粒子を排除する条件について検討する過程において、本発明者らは、黒鉛粉末などの炭素質粉末は、通常は必ずしも真球ではなく、単純な粒径の値で、その活物質層塗布形成時の活物質スラリーにおける挙動を捕らえることができないことに着目した。そして、所定の水分散液中での粗大粒子の挙動を個々の粒で観測することで、活物質粉体中の、希少ではあるが、活物質層に本質的な影響を及ぼす粗大粒子、即ち、単にセパレータの傷付きの有無に影響するものではなく、前述の電流密度の疎密化やリチウム金属の析出等の原因となる粗大粒子の存在を確認し、いかなる粉体特性を満たせば、十分な性能を得ることができるか、その評価手法と取得手法を見出し、本発明を完成させた。 The present inventors have found that in order to obtain an electrode plate that satisfies such required performance, coarse particles in the active material are not removed by simple sieving, but are removed in advance under specific conditions. I found it important. In the process of examining the conditions for eliminating the coarse particles, the present inventors have found that a carbonaceous powder such as a graphite powder is usually not necessarily a true sphere, but a simple particle size, and the active material layer is not necessarily spherical. We focused on the fact that the behavior of the active material slurry during coating formation could not be captured. Then, by observing the behavior of the coarse particles in a predetermined aqueous dispersion in individual particles, in the active material powder, a rare, but coarse particles that essentially affect the active material layer, that is, It does not merely affect the presence / absence of scratches on the separator, but confirms the presence of coarse particles that cause the above-mentioned densification of the current density or the precipitation of lithium metal, etc. The present inventor has found an evaluation method and an acquisition method of whether or not performance can be obtained, and completed the present invention.
即ち、本発明では、粗大粒子を排除する条件として、前述の試料分散液について、ＪＩＳ Ｋ５４００による粒ゲージ測定により最大分散粒子径を測定し、この最大分散粒子径を基準とし、この値が５０μｍ以下となるような粗大粒子を含まない負極活物質とする。 That is, in the present invention, as a condition for eliminating coarse particles, the maximum dispersion particle diameter of the above-described sample dispersion liquid is measured by a particle gauge measurement according to JIS K5400, and the value is 50 μm or less based on the maximum dispersion particle diameter. The negative electrode active material does not contain coarse particles such that
このように、試料分散液をＪＩＳ Ｋ５４００ 粒ゲージ法で測定することによって、炭素質粉末状の負極活物質の製造過程で種々の原因により持ち込まれたり、また、活物質層形成工程における塗布条件で凝集ないし粗大化することにより生じる粗大粒子を検知ないし予測することができる。本発明においては、この測定によって、粒が現れ始める粒子径が５０μｍ以下となる炭素質粉末状の負極活物質を用いることにより、形成される活物質層表面の厚みムラを防止し、高度に均一なものとして電流密度の疎密を抑制する。特に、本発明においては、このような条件で粗大粒子のない活物質とすることにより、５０μｍ以下というような極めて薄肉に形成した活物質層においても、該粗大粒子が活物質層中で、充放電の繰り返しによりリチウム金属が析出する際のある種の核として作用することを抑制し、後述する実施例によって説明されるような優れた電池特性を得ることができるものと推定される。 As described above, by measuring the sample dispersion liquid by the JIS K5400 particle gauge method, it can be brought in for various reasons in the production process of the carbonaceous powdery negative electrode active material, or can be applied under the application conditions in the active material layer forming step. Coarse particles generated by aggregation or coarsening can be detected or predicted. In the present invention, by using the negative electrode active material in the form of a carbonaceous powder in which the particle diameter at which particles start to appear is 50 μm or less, the thickness unevenness on the surface of the formed active material layer is prevented, and the uniformity is high. In particular, the current density is suppressed. In particular, in the present invention, by using an active material having no coarse particles under such conditions, even in an extremely thin active material layer having a thickness of 50 μm or less, the coarse particles can be filled in the active material layer. It is presumed that it is possible to suppress the lithium metal from acting as a certain nucleus at the time of deposition due to repetition of discharge, and to obtain excellent battery characteristics as described in Examples described later.
本発明において、上記最大分散粒子径の上限は５０μｍ以下、好ましくは３５μｍ以下、更に好ましくは３０μｍ以下、最も好ましくは２５μｍ以下であり、下限は５μｍ以上、好ましくは１０μｍ以上である。最大分散粒子径が５０μｍを超えるような活物質では、形成される活物質層内において、前述の粗大粒子が充放電の繰り返しによりリチウム金属が析出するある種の核として作用し、リチウム金属の析出が進み、短絡を起こす原因となるものと考えられるため、最大分散粒子径は５０μｍ以下とする。最大分散粒子径の好ましい上限は、負極集電体上に形成される活物質層の厚みとその均一性により、５０μｍ以下の範囲で適宜決定される。一方、最大分散粒子径の好ましい下限は、これが小さすぎると充填性を損ないやすくなることによるものであり、通常、５μｍ以上とする。 In the present invention, the upper limit of the maximum dispersed particle diameter is 50 μm or less, preferably 35 μm or less, more preferably 30 μm or less, and most preferably 25 μm or less, and the lower limit is 5 μm or more, preferably 10 μm or more. In an active material having a maximum dispersed particle diameter of more than 50 μm, the coarse particles described above act as a kind of nucleus on which lithium metal is precipitated by repeated charge and discharge in the formed active material layer, and the lithium metal is deposited. The maximum dispersed particle diameter is set to 50 μm or less because it is considered to cause a short circuit. The preferable upper limit of the maximum dispersed particle diameter is appropriately determined within a range of 50 μm or less depending on the thickness of the active material layer formed on the negative electrode current collector and its uniformity. On the other hand, a preferable lower limit of the maximum dispersed particle diameter is that if the particle diameter is too small, the filling property is liable to be impaired, and is usually 5 μm or more.
本発明のリチウム二次電池用負極活物質はまた、前記試料分散液について、ＪＩＳ Ｋ５４００ 粒ゲージ法による分散度に準拠して測定される、粒子径３５μｍ以上５０μｍ以下の粒（以下「３５〜５０μｍ粒数」と称す。）が１０個以下であることが好ましい。この３５〜５０μｍ粒数の上限は、より好ましくは８個以下、特に好ましくは５個以下である。下限については、少なければ少ないほど良いが、２個程度であれば、差し支えない。 The negative electrode active material for a lithium secondary battery of the present invention also has a particle diameter of 35 μm to 50 μm (hereinafter referred to as “35 to 50 μm”) of the sample dispersion, which is measured based on the degree of dispersion according to JIS K5400 particle gauge method. The number of particles is preferably 10 or less. The upper limit of the number of particles of 35 to 50 μm is more preferably 8 or less, and particularly preferably 5 or less. As for the lower limit, the smaller the better, the better.
本発明のリチウム二次電池用負極活物質はまた、前記試料分散液について、ＪＩＳ Ｋ５４００粒ゲージ法による分散度に準拠して測定される線条痕の占める割合が、ゲージ幅方向に５０％以上に達する粒子径（以下、これを、「平均分散粒子径」と称す。）が、通常４０μｍ以下、好ましくは３５μｍ以下、更に好ましくは３０μｍ以下、最も好ましくは２５μｍ以下であることが好ましい。即ち、前述の試料分散液におけるＪＩＳ Ｋ５４００に準拠した粒ゲージ測定方法では、通常、粗大粒子が線条痕として記録される。この粗大粒子が活物質に含まれる割合を示す指標として、線条痕がゲージ幅に占める割合が５０％以上に達する粒子径を採用した。 In the negative electrode active material for a lithium secondary battery according to the present invention, the ratio of the streak trace of the sample dispersion liquid measured in accordance with the degree of dispersion according to JIS K5400 grain gauge method is 50% or more in the gauge width direction. (Hereinafter, referred to as “average dispersed particle size”) is usually 40 μm or less, preferably 35 μm or less, more preferably 30 μm or less, and most preferably 25 μm or less. That is, in the above-described method of measuring the particle gauge of the sample dispersion liquid according to JIS K5400, coarse particles are usually recorded as streak marks. As an index indicating the ratio of the coarse particles contained in the active material, a particle diameter at which the ratio of the streak to the gauge width reaches 50% or more was adopted.
なお、上記のＪＩＳ Ｋ５４００粒ゲージ測定において、測定される粒子径は必ずしも、活物質粉末の粒子径ではなく、試料分散液中の分散粒子の粒子径であり、活物質粉末及び／又はカルボキシメチルセルロースが凝集してなる凝集粒子の粒子径なども含まれる。 In the above JIS K5400 particle gauge measurement, the measured particle size is not necessarily the particle size of the active material powder, but the particle size of the dispersed particles in the sample dispersion liquid. The particle size of the aggregated particles formed by aggregation is also included.
本発明のリチウム二次電池用負極活物質はまた、レーザー回折式粒径分布計により測定された活物質粉末としての平均粒子径（Ｄ５０）及び最大粒子径（Ｄｍａｘ）が次のような値であることが好ましい。 The negative electrode active material for a lithium secondary battery of the present invention also has an average particle diameter (D 50 ) and a maximum particle diameter (D max ) as an active material powder measured by a laser diffraction type particle size distribution meter as follows. It is preferably a value.
［活物質粉末の平均粒子径（Ｄ５０）］
平均粒子径（Ｄ５０）は、レーザー回折式粒径分布計において、体積基準粒子径分布のメジアン径（５０％粒子径）である。本発明の負極活物質の炭素質粉末において、この（Ｄ５０）は、通常２０μｍ以下、好ましくは１５μｍ以下、更に好ましくは１３μｍ以下、特に好ましくは１０〜１３μｍである。
[Average particle diameter of active material powder (D 50 )]
The average particle diameter (D 50 ) is a median diameter (50% particle diameter) of a volume-based particle diameter distribution in a laser diffraction particle size distribution meter. In the carbonaceous powder of the negative electrode active material of the present invention, this (D 50 ) is usually 20 μm or less, preferably 15 μm or less, more preferably 13 μm or less, particularly preferably 10 to 13 μm.
即ち、前述のＪＩＳ Ｋ５４００粒ゲージ法による粒子径は、実際に活物質層を形成した場合、活物質層内に存在し得る粗大粒子の最大粒子径に対応するのに対して、レーザー回折式粒径分布径で測定される活物質の平均粒子径は、活物質粒子の平均的な大きさを示す。従って、レーザー回折式粒径分布計で得られる値は、電極厚みとの相関を示す指標ではなく、電池性能との相関を図る上で重要な指標となる。 That is, while the particle diameter according to the JIS K5400 particle gauge method corresponds to the maximum particle diameter of the coarse particles that can be present in the active material layer when the active material layer is actually formed, the laser diffraction particle size The average particle diameter of the active material measured by the diameter distribution diameter indicates an average size of the active material particles. Therefore, the value obtained by the laser diffraction type particle size distribution meter is not an index indicating the correlation with the electrode thickness, but an important index in assuring the correlation with the battery performance.
活物質の平均粒子径（Ｄ５０）が上記上限を超えると活物質内へのリチウムイオンの拡散性が悪化し、電池の入出力特性が低下する。この平均粒子径（Ｄ５０）の下限は通常５μｍ以上、好ましくは７μｍ以上である。平均粒子径（Ｄ５０）が５μｍ未満の活物質を用いると、活物質の充填性が悪化するため、平均粒子径（Ｄ５０）は５μｍ以上が好ましい。 If the average particle diameter (D 50 ) of the active material exceeds the upper limit, the diffusibility of lithium ions into the active material deteriorates, and the input / output characteristics of the battery deteriorate. The lower limit of the average particle diameter (D 50 ) is usually 5 μm or more, preferably 7 μm or more. When an active material having an average particle size (D 50 ) of less than 5 μm is used, the filling property of the active material is deteriorated. Therefore, the average particle size (D 50 ) is preferably 5 μm or more.
［活物質の最大粒子径（Ｄｍａｘ）］
レーザー回折式粒径分布計による最大粒子径（Ｄｍａｘ）の上限は、通常７０μｍ以下、好ましくは６０μｍ以下、更に好ましくは５２μｍ以下、特に好ましくは４５μｍ以下、中でも特に好ましくは４５〜５２μｍであり、下限値は通常２０μｍ以上である。最大粒子径（Ｄｍａｘ）が２０μ未満の活物質を用いると、活物質の充填性が悪化するばかりでなく、電池電極内の空隙構造が細分化され、リチウムイオンの移動が妨げられ、電池出力が低下する。そのため、最大粒子径（Ｄｍａｘ）は２０μｍ以上が好ましい。
[Maximum particle size of active material (D max )]
The upper limit of the maximum particle diameter (D max ) measured by a laser diffraction type particle size distribution analyzer is usually 70 μm or less, preferably 60 μm or less, more preferably 52 μm or less, particularly preferably 45 μm or less, and particularly preferably 45 to 52 μm, The lower limit is usually at least 20 μm. When an active material having a maximum particle diameter (D max ) of less than 20 μm is used, not only does the filling property of the active material deteriorate, but also the void structure in the battery electrode is fragmented, and the movement of lithium ions is hindered. Decreases. Therefore, the maximum particle size (D max ) is preferably 20 μm or more.
前述の如く、ＪＩＳ Ｋ５４００粒ゲージ法による最大分散粒子径は、スラリー状の活物質が実際に集電体上に塗布される状況に即した値であるのに対し、レーザー回折式粒径分布径による最大粒子径（Ｄｍａｘ）は、個々の粒子を球換算した粒子径分布に従って算出された最大粒子径（１００％粒子径）である。即ち、ＪＩＳ Ｋ５４００粒ゲージ法の最大分散粒子径は、均一な極板を得るのに障害となる粗大粒子の大きさと個数を示す。更にこの最大分散粒子径では、例えば扁平な異方性を有する粒子であれば、測定時にその長軸方向をゲージ面と平行にして測定される確率が高いため、レーザー回折式粒径分布径で測定される最大粒子径（Ｄｍａｘ）よりも低い値が得られる場合がある。 As described above, the maximum dispersed particle diameter according to the JIS K5400 particle gauge method is a value according to the situation where the slurry-like active material is actually applied onto the current collector, whereas the laser diffraction particle diameter distribution diameter is different. maximum particle size by (D max) is the maximum particle size of the individual particles were calculated according to the particle size distribution was in terms of sphere (100% particle diameter). That is, the maximum dispersed particle diameter according to the JIS K5400 grain gauge method indicates the size and the number of coarse particles which are an obstacle to obtaining a uniform electrode plate. Further, at this maximum dispersed particle diameter, for example, if the particles have a flat anisotropy, since there is a high probability that the major axis direction is measured in parallel with the gauge surface at the time of measurement, the laser diffraction particle size distribution diameter A value lower than the measured maximum particle diameter (D max ) may be obtained.
更に、本発明のリチウム二次電池用負極活物質は、窒素ガス吸着法によるＢＥＴ法比表面積の上限が通常１３ｍ２／ｇ以下、好ましくは８ｍ２／ｇ以下、更に好ましくは５ｍ２／ｇ以下、特に好ましくは２．５〜４．５ｍ２／ｇであり、下限が通常１ｍ２／ｇ以上、好ましくは２ｍ２／ｇ以上、更に好ましくは２．５ｍ２／ｇ以上であることが好ましい。この値が上記上限を超えると、保存耐久性が悪化しやすくなり、下限を下回ると、入出力特性が悪化しやすくなる。 Further, in the negative electrode active material for a lithium secondary battery of the present invention, the upper limit of the BET specific surface area by nitrogen gas adsorption is usually 13 m 2 / g or less, preferably 8 m 2 / g or less, more preferably 5 m 2 / g or less. Particularly preferably, it is 2.5 to 4.5 m 2 / g, and the lower limit is usually 1 m 2 / g or more, preferably 2 m 2 / g or more, more preferably 2.5 m 2 / g or more. If this value exceeds the above upper limit, the storage durability tends to deteriorate, and if it falls below the lower limit, the input / output characteristics tend to deteriorate.
次に、本発明のリチウム二次電池用負極活物質を構成する炭素質粉末材料について説明する。 Next, the carbonaceous powder material constituting the negative electrode active material for a lithium secondary battery of the present invention will be described.
活物質の「炭素質」とは、リチウムを吸蔵及び放出し得る炭素質材料を含むものであれば特に限定されないが、その具体例としては、黒鉛質、非晶質、黒鉛質・非晶質の複合系があり、本発明ではいずれのものであっても良い。 The “carbonaceous” of the active material is not particularly limited as long as it contains a carbonaceous material capable of occluding and releasing lithium, and specific examples thereof include graphite, amorphous, and graphite / amorphous. And in the present invention, any of them may be used.
黒鉛質とは、人造黒鉛、天然黒鉛、メソフェーズピッチ系黒鉛、黒鉛化炭素繊維、これらの高純度精製品、これらの再加熱処理品、或いはこれらの混合物から選ばれる黒鉛質炭素であって、その形態として、例えば、異なる種類の黒鉛質炭素粒子が混在した混合粒子や、黒鉛質炭素微粒子が等方的に多数結合した造粒粒子が挙げられる。また、以下の粉末状態にあるものが好適に用いられる。 Graphite is artificial graphite, natural graphite, mesophase pitch graphite, graphitized carbon fiber, these high-purity purified products, these reheated products, or a mixture of these, and is a graphitic carbon selected from the group consisting of: Examples of the form include mixed particles in which different types of graphitic carbon particles are mixed, and granulated particles in which a number of graphitic carbon fine particles are isotropically bonded. Further, those in the following powder state are preferably used.
即ち、結晶面（００２）の面間隔ｄ００２が０．３４８ｎｍ以下、且つ積層層の厚さＬｃが１０ｎｍ以上である黒鉛粉体を用いることが好ましい。結晶面（００２）の面間隔ｄ００２が０．３３８ｎｍ以下、且つ積層層の厚さＬｃが２０ｎｍ以上のであるものは更に好ましく、結晶面（００２）の面間隔ｄ００２が０．３３７ｎｍ以下、且つ積層層の厚さＬｃが４０ｎｍ以上であるものは最も好ましい。 That is, it is preferable to use a graphite powder having a plane distance d 002 of the crystal plane (002) of 0.348 nm or less and a thickness Lc of the laminated layer of 10 nm or more. It is more preferable that the plane distance d 002 of the crystal plane (002) is 0.338 nm or less and the thickness Lc of the laminated layer is 20 nm or more, and the plane distance d 002 of the crystal plane (002) is 0.337 nm or less, and It is most preferable that the thickness Lc of the laminated layer is 40 nm or more.
また、リチウムイオンが黒鉛層間に格納されて生成する層間化合物であるＣ6Ｌｉを基準にした炭素１ｇあたりの容量理論値は３７２ｍＡｈである。このようにして選定した黒鉛質は、充放電レートを０．２ｍＡ／ｃｍ2とした、リチウム金属対極を用いた半電池による電気容量測定において、比容量が３２０ｍＡＨ／ｇ以上、より好ましくは３４０ｍＡｈ／ｇ以上、更に好ましくは３５０ｍＡＨ／ｇ以上と、上記理論に近ければ近いほど好適に用いられる。 The theoretical capacity per g of carbon is 372 mAh based on C 6 Li, which is an intercalation compound generated by storing lithium ions between graphite layers. The graphite material thus selected has a specific capacity of 320 mAH / g or more, more preferably 340 mAh / g, in a capacity measurement by a half-cell using a lithium metal counter electrode at a charge / discharge rate of 0.2 mA / cm 2. g or more, more preferably 350 mAH / g or more.
非晶質とは、その結晶面（００２）の面間隔ｄ００２が０．３４９ｎｍ以上、且つ積層層の厚さＬｃが１０ｎｍ未満である炭素質粉体を用いることが好ましい。結晶面（００２）の面間隔ｄ００２が０．３４９ｎｍ以上０．３５５ｎｍ以下、且つＣ軸方向の結晶子の厚さＬｃが７ｎｍ以下であるものは更に好ましく、特にＬｃについては、１．５〜１０ｎｍ、更には１．５〜５ｎｍであるものが最も好ましい。
非晶質は、その形態として、例えば、異なる種類の非晶質炭素粒子が混在した混合粒子や、非晶質炭素微粒子が多数結合した造粒粒子が挙げられる。
The term “amorphous” means that a carbonaceous powder having a plane distance d 002 of the crystal plane (002) of 0.349 nm or more and a thickness Lc of the laminated layer of less than 10 nm is preferably used. It is more preferable that the plane distance d 002 of the crystal plane (002) is 0.349 nm or more and 0.355 nm or less, and the crystallite thickness Lc in the C-axis direction is 7 nm or less. Most preferably, it is 10 nm, more preferably 1.5 to 5 nm.
Examples of the amorphous form include mixed particles in which different types of amorphous carbon particles are mixed, and granulated particles in which a large number of amorphous carbon fine particles are bonded.
黒鉛質・非晶質の複合系としては、前記した黒鉛質材料及び非晶質材料を含む形態に特に制限はないが、例えば、黒鉛質粉末を非晶質材料で一部又は全部被覆したもの、黒鉛質粉末と非晶質材料の混合体、黒鉛微粒子が非晶質あるいはその黒鉛化物を介して、少なくとも一部が等方的に多数結合した人造黒鉛等が挙げられる。これらの中でも、黒鉛質粉末を非晶質材料で一部又は全部被覆したものが、高容量、高出力特性と大電流によるパルスサイクル耐久性の性能が得られる点で、特に大型駆動電源、電気自動車、ハイブリッド自動車の用途において好適に用いられる。 The graphite / amorphous composite system is not particularly limited in the form containing the above-mentioned graphite material and amorphous material, and may be, for example, a graphite powder partially or wholly coated with an amorphous material. And a mixture of graphite powder and an amorphous material, and artificial graphite in which graphite fine particles are amorphous or in which at least a part thereof is isotropically bonded in large numbers via a graphitized product thereof. Among them, graphite powder partially or entirely coated with an amorphous material has high capacity, high output characteristics, and pulse cycle durability due to large current. It is suitable for use in automobiles and hybrid vehicles.
これら黒鉛質、非晶質等を含めて、本発明の炭素質粉末状負極活物質の物性としては、波長５１４．３ｎｍのアルゴンイオンレーザー光を用いたラマンスペクトルにおいて、その１５８０〜１６２０ｃｍ-1の範囲に現れるピーク強度をＩＡ、そのピークの半値幅をΔν、１３５０〜１３７０ｃｍ-1の範囲に現れるピーク強度をＩＢとしたときの、ピーク強度比Ｒ（＝ＩＢ／ＩＡ）の上限が０．７以下であるものが好ましく、０．５以下であるものはより好ましく、０．３以下であるものは更に好ましい。また、このピーク強度比Ｒの下限が０．０１以上であるものが好ましい。更に、前記半値幅Δνの上限が６０ｃｍ-1以下、好ましくは４０ｃｍ-1以下、より好ましくは３０ｃｍ-1以下、特に好ましくは２４ｃｍ-1以下であるものが好ましい。この半値幅Δνの下限は、狭いほど好ましいが、通常は１４ｃｍ-1以上である。 The physical properties of the carbonaceous powdered negative electrode active material of the present invention, including these graphite materials and amorphous materials, are as follows: Raman spectrum of 1580 to 1620 cm −1 in Raman spectrum using argon ion laser light having a wavelength of 514.3 nm. When the peak intensity appearing in the range is IA and the half width of the peak is Δν, and the peak intensity appearing in the range of 1350 to 1370 cm −1 is IB, the upper limit of the peak intensity ratio R (= IB / IA) is 0.7. The following is preferable, the one having 0.5 or less is more preferable, and the one having 0.3 or less is further preferable. Further, it is preferable that the lower limit of the peak intensity ratio R is 0.01 or more. Further, the upper limit of the half width Δν is preferably 60 cm −1 or less, preferably 40 cm −1 or less, more preferably 30 cm −1 or less, and particularly preferably 24 cm −1 or less. The lower limit of the half width Δν is preferably as narrow as possible, but is usually 14 cm −1 or more.
本発明の活物質に適用される炭素質材料の製法は特に限定されるものではないが、例えば以下に述べる炭素前駆体から、適宜、焼成条件を変えることによって、炭化、又は黒鉛化することにより得ることができる。 The method for producing the carbonaceous material applied to the active material of the present invention is not particularly limited.For example, from a carbon precursor described below, by appropriately changing the firing conditions, carbonizing, or graphitizing Obtainable.
この場合、液相で炭素化を進行させる炭素前駆体としては、軟ピッチから硬ピッチまでのコールタールピッチ、或いは乾留液化油などの石炭系重質油、常圧残油、減圧残油の直流系重質油、原油、ナフサなどの熱分解時に副生するエチレンタール等分解系石油重質油、更にアセナフチレン、デカシクレン、アントラセン、フェナントレンなどの芳香族炭化水素、フェナジンやアクリジンなどのＮ環化合物、チオフェン、ビチオフェンなどのＳ環化合物、ビフェニル、テルフェニルなどのポリフェニレン、ポリ塩化ビニル、ポリビニルアルコール、ポリビニルブチラール、これらのものの不溶化処理品、含窒素性のポリアクニロニトリル、ポリピロールなどの有機高分子、含硫黄性のポリチオフェン、ポリスチレンなどの有機高分子、セルロース、リグニン、マンナン、ポリガラクトウロン酸、キトサン、サッカロースに代表される多糖類などの天然高分子、ポリフェニレンサルファイド、ポリフェニレンオキシド等の熱可塑性樹脂、フルフリルアルコール樹脂、フェノール−ホルムアルデヒド樹脂、イミド樹脂等の熱硬化性樹脂、以上のものとベンゼン、トルエン、キシレン、キノリン、ｎ−へキサンなどの低分子有機溶媒の混合品、などから選ばれる一種以上の炭素化可能な有機化合物が用いられる。 In this case, as a carbon precursor for promoting carbonization in the liquid phase, coal tar pitch from soft pitch to hard pitch, or coal-based heavy oil such as dry-distilled liquefied oil, normal pressure residual oil, and direct current of reduced pressure residual oil Heavy oil, crude oil, cracked petroleum heavy oil such as ethylene tar by-produced during thermal cracking of naphtha, etc., as well as aromatic hydrocarbons such as acenaphthylene, decacyclene, anthracene, and phenanthrene; N-ring compounds such as phenazine and acridine; S-ring compounds such as thiophene and bithiophene, polyphenylenes such as biphenyl and terphenyl, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized products thereof, and organic polymers such as nitrogen-containing polyacylonitrile and polypyrrole; Organic polymers such as sulfur-containing polythiophene and polystyrene, cellulose Lignin, mannan, polygalacturonic acid, chitosan, natural polymers such as polysaccharides represented by saccharose, thermoplastic resins such as polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin and the like One or more carbonizable organic compounds selected from thermosetting resins, mixtures of the above with low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, n-hexane, and the like are used.
以下に、炭素質粉末状のリチウム二次電池用負極活物質を得るための一般的手法を説明する。 Hereinafter, a general method for obtaining a carbonaceous powdered negative electrode active material for a lithium secondary battery will be described.
炭素質粉末状負極活物質を製造するには、まず、黒鉛質粉末及び／又は非晶質粉末を、粉砕、分級する。黒鉛質粉末、非晶質粉末の粉砕には、高速回転粉砕機（ハンマーミル、ピンミルなど）や、各種ボールミル（転動式、振動式、遊星式など）、攪拌ミル（ビーズミルなど）、スクリーンミル、ターボミル、ジェットミル等、好ましい粒径域に粉砕できるものであれば、あらゆる粉砕機が使用できる。また、粉砕は湿式でも乾式でも実施可能である。 In order to produce the carbonaceous powdered negative electrode active material, first, the graphite powder and / or the amorphous powder are pulverized and classified. For pulverizing graphite powder and amorphous powder, high-speed rotary pulverizer (hammer mill, pin mill, etc.), various ball mills (rolling type, vibration type, planetary type, etc.), stirring mill (beads mill, etc.), screen mill Any pulverizer can be used as long as it can be pulverized to a preferable particle size range, such as a turbo mill and a jet mill. Further, the pulverization can be carried out by a wet method or a dry method.
得られた粉末を所定の粒径範囲とするための分級操作は、粒子の分離が可能であれば何れでも良く、乾式でも湿式でも実施可能である。湿式あるいは乾式の篩法や強制渦流式遠心分級機（ミクロンセパレータ、ターボプレックス、ターボクラシファイアー、スーパーセパレータ）、慣性分級機（エルボジェットなど）等の気流式分級機、更に湿式の沈降分離法や遠心分級法も採用できる。 The classification operation for bringing the obtained powder into a predetermined particle size range is not particularly limited as long as the particles can be separated, and can be carried out by either a dry method or a wet method. Pneumatic classifiers such as wet or dry sieve method, forced vortex centrifugal classifier (micron separator, turboplex, turbo classifier, super separator), inertial classifier (elbow jet, etc.), and wet sedimentation method A centrifugal classification method can also be adopted.
また、本発明では、黒鉛質として、異なる種類の黒鉛質炭素粒子が混在した混合粒子を用いる場合には、適宜複数種の黒鉛質炭素粒子を所望の種類及び比率で混合すればよい。また、黒鉛質として、黒鉛質炭素微粒子が等方的に多数結合した造粒粒子を用いる場合の製法としては、例えば、一種あるいは２種以上の黒鉛質炭素微粒子と炭素前駆体とを、更に必要に応じて溶媒（通常、トルエン、キシレン等の芳香族炭化水素系溶媒等の有機溶媒等）と共に混合機或いは混練機を用いて混合し、黒鉛質炭素微粒子と同等の結晶構造となるまで、通常２８００℃以上、中でも２９００℃以上、通常３５００℃以下、中でも３１００℃以下程度の温度下で、通常、前記混合物が酸化し難い条件で加熱処理することが好ましく、例えば真空中、混合物や、加熱処理の過程で原料に由来して発生する揮発ガス雰囲気中、窒素等の不活性ガス雰囲気下で焼成、その後、適宜、粉砕、分級し所望の粒度に調整する方法が挙げられる。この際、黒鉛質炭素微粒子と炭素前駆体と必要に応じて溶媒を混合し、一旦、通常、ブロック状、棒状等の形状に成形して加熱、焼成処理を行う。なお、ここで用いる混合機としては、高速剪断ミキサー、ビーズミル、ヘンシェルキミサー、内部にシャフトとシャフトに固定された攪拌翼が位相を変えて複数配置された混合槽を具備したミキサー等の縦型あるいは横型の混合機が挙げられる。また、混練機としては、混合槽の側面に沿ってシグマ型等の攪拌翼が回転するいわゆるニーダー形式の装置や、通常樹脂加工等にも用いられる一軸あるいは二軸の混練機等の混練機が挙げられる。 Further, in the present invention, when a mixed particle in which different types of graphitic carbon particles are mixed is used as the graphite, a plurality of types of graphitic carbon particles may be appropriately mixed in a desired type and ratio. In addition, as a production method in the case of using granulated particles in which a large number of graphitic carbon fine particles are isotropically bonded as the graphite, for example, one or more types of graphitic carbon fine particles and a carbon precursor are further required. Mixed with a solvent (usually, an organic solvent such as an aromatic hydrocarbon solvent such as toluene and xylene) using a mixer or a kneader, until the crystal structure equivalent to the graphitic carbon fine particles is obtained. At a temperature of 2800 ° C. or higher, especially 2900 ° C. or higher, usually 3500 ° C. or lower, and especially 3100 ° C. or lower, it is usually preferable to heat-treat the mixture under conditions in which the mixture is not easily oxidized. Baking in an atmosphere of a volatile gas generated from the raw materials in the process of step (b) in an atmosphere of an inert gas such as nitrogen, and then appropriately pulverizing and classifying to adjust to a desired particle size. At this time, the graphitic carbon fine particles, the carbon precursor, and a solvent are mixed as necessary, and the mixture is usually once formed into a block shape, a rod shape, or the like, and then subjected to heating and firing. The mixing machine used here is a vertical type such as a high-speed shearing mixer, a bead mill, a Henschel Kimiser, a mixer having a mixing tank in which a shaft and a plurality of stirring blades fixed to the shaft are arranged in different phases. Alternatively, a horizontal mixer may be used. Further, as the kneader, a kneader such as a so-called kneader type device in which a stirring blade such as a sigma type rotates along the side surface of the mixing tank, or a single-shaft or twin-shaft kneader usually used also for resin processing or the like is used. No.
また、本発明では、非晶質として、異なる種類の非晶質炭素粒子が混在した混合粒子を用いる場合には、適宜複数種の非晶質炭素粒子を所望の種類及び比率で混合すればよい。また、非晶質として、非晶質炭素微粒子が多数結合した造粒粒子を用いる場合の製法としては、例えば、１種あるいは２種以上の非晶質炭素微粒子と炭素前駆体とを、更に必要に応じて溶媒（通常、トルエン、キシレン、等の芳香族炭化水素系溶媒等の有機溶媒等）と共に混合機或いは混練機を用いて混合し、炭素前駆体が黒鉛構造には成長しない温度、通常７００℃以上、好ましくは８００℃以上、中でも１０００℃以上、通常２８００℃以下、中でも２０００℃以下、特に１５００℃以下程度の温度下で、通常、前記混合物が酸化し難い条件で加熱処理することが好ましく、例えば真空中、混合物や加熱処理の過程で原料に由来して発生する揮発ガス雰囲気中、窒素等の不活性ガス雰囲気下で焼成、その後、適宜、粉砕、分級し所望の粒度に調整することが挙げられる。ここで用いる混合機としては、高速剪断ミキサー、ビーズミル、ヘンシェルキミサー、内部にシャフトとシャフトに固定された攪拌翼が位相を変えて複数配置された混合槽を具備したミキサー等の縦型あるいは横型の混合機が挙げられる。また、混練機としては、混合槽の側面に沿ってシグマ型等の攪拌翼が回転するいわゆるニーダー形式の装置や、通常樹脂加工等にも用いられる一軸あるいは二軸の混練機等の混練機が挙げられる。 Further, in the present invention, when using mixed particles in which different types of amorphous carbon particles are mixed as amorphous, a plurality of types of amorphous carbon particles may be appropriately mixed in a desired type and ratio. . In addition, as a manufacturing method in the case of using granulated particles in which a large number of amorphous carbon fine particles are bonded as amorphous, for example, one or more types of amorphous carbon fine particles and a carbon precursor are further required. Mixed with a solvent (usually an organic solvent such as an aromatic hydrocarbon solvent such as toluene, xylene, etc.) using a mixer or a kneader according to the temperature at which the carbon precursor does not grow into a graphite structure, usually At a temperature of 700 ° C. or higher, preferably 800 ° C. or higher, especially 1000 ° C. or higher, usually 2800 ° C. or lower, especially 2000 ° C. or lower, particularly at a temperature of about 1500 ° C. or lower, the mixture is usually subjected to heat treatment under conditions where oxidation is difficult. Preferably, for example, firing in a vacuum, in an atmosphere of a volatile gas generated from the raw material in the course of the mixture or the heat treatment, or in an atmosphere of an inert gas such as nitrogen, and then appropriately pulverizing and classifying to obtain desired particles And the like be adjusted to. As the mixer used here, a vertical or horizontal mixer such as a high-speed shearing mixer, a bead mill, a Henschel Kimiser, a mixer having a mixing tank in which a shaft and a plurality of stirring blades fixed to the shaft are arranged in different phases, and the like are used. Mixer. Further, as the kneader, a kneader such as a so-called kneader type device in which a stirring blade such as a sigma type rotates along the side surface of the mixing tank, or a kneader such as a single-shaft or twin-shaft kneader usually used for resin processing or the like is also used. No.
本発明では、電池の用途に応じて、黒鉛質粉体と非晶質粉体を任意の量比で混合して用いることもできる。この場合、黒鉛質粉体と非晶質粉体の混合割合は、如何なる量比でも使用可能であるが、黒鉛質粉体と非晶質粉体の合計量に対する黒鉛質粉体の重量比は、好ましくは５０％以上、更に好ましくは７０％以上である。黒鉛質粉体と非晶質粉体の合計量に対する非晶質粉体の割合が多いと非晶質に特徴的な不可逆容量の影響が大きくなるので、通常、４０％以下とするのが良い。 In the present invention, the graphite powder and the amorphous powder can be mixed and used in an arbitrary ratio depending on the use of the battery. In this case, the mixing ratio of the graphite powder and the amorphous powder can be used at any ratio, but the weight ratio of the graphite powder to the total amount of the graphite powder and the amorphous powder is , Preferably at least 50%, more preferably at least 70%. When the ratio of the amorphous powder to the total amount of the graphite powder and the amorphous powder is large, the influence of the irreversible capacity characteristic of the amorphous becomes large. .
更に、本発明では、黒鉛質粉体を母剤として、非晶質炭素を複合化した粉体も活物質として使用可能である。この場合、母剤としての黒鉛質粉体は、前述の黒鉛質炭素の要件を満たすと共に、以下の粒径及び比表面積の要件を満たすものから選択可能である。一方、複合化される非晶質としては、前述の非晶質炭素の要件を満たすものから選択可能である。 Further, in the present invention, a composite powder of amorphous carbon using graphite powder as a base material can be used as an active material. In this case, the graphitic powder as the base material can be selected from those satisfying the above-described requirements for the graphitic carbon and satisfying the following requirements for the particle size and specific surface area. On the other hand, the amorphous material to be composited can be selected from those satisfying the above-described requirements for amorphous carbon.
母剤となる黒鉛質粉体の好ましい粒径と比表面積は、次の通りである。レーザー回折式粒径分布計において、平均粒子径（Ｄ５０）が、通常２０μｍ以下、好ましくは１５μｍ以下、更に好ましくは１３μｍ以下、特に好ましくは８〜１３μｍ。ＢＥＴ比表面積は、１５ｍ２／ｇ以下、好ましくは２ｍ２／ｇ以上１３ｍ２／ｇ以下、更に好ましくは３ｍ２／ｇ以上１２ｍ２／ｇ以下、最も好ましくは、８ｍ２／ｇ以上１２ｍ２／ｇ以下である。 The preferred particle size and specific surface area of the graphite powder as the base material are as follows. In the laser diffraction particle size distribution analyzer, the average particle diameter (D 50), typically 20μm or less, preferably 15μm or less, more preferably 13μm or less, particularly preferably 8～13Myuemu. BET specific surface area, 15 m 2 / g or less, preferably 2m 2 / g or more 13m 2 / g or less, more preferably 3m 2 / g or more 12m 2 / g or less, and most preferably, 8m 2 / g or more 12m 2 / g or less.
黒鉛質と非晶質の複合化は、非晶質を得るための炭素前駆体をそのまま用いて炭素前駆体と黒鉛質粉体との混合物を加熱処理し、その後粉砕処理して複合粉体を得る方法、前述の非晶質粉体を予め作成しておき、黒鉛質粉体と混合し、加熱処理して複合化する方法、前述の非晶質粉体を予め作成しておき、黒鉛質粉体と非晶質粉体と炭素前駆体とを混合し、加熱処理して複合化する方法などが採用可能である。なお、後二者の予め非晶質粉体を用意しておく方法では、平均粒子径が黒鉛質粒子の平均粒径の１０分の１以下の非晶質粒子を用いることが好ましい。 The composite of graphite and amorphous is obtained by heating the mixture of the carbon precursor and the graphite powder using the carbon precursor for obtaining the amorphous as it is, and then pulverizing it to form the composite powder. A method of preparing the above-mentioned amorphous powder in advance, mixing it with the graphite powder, and performing a heat treatment to form a composite; A method in which the powder, the amorphous powder, and the carbon precursor are mixed and heat-treated to form a composite can be employed. In the latter two methods of preparing amorphous powder in advance, it is preferable to use amorphous particles having an average particle diameter of 1/10 or less of the average particle diameter of the graphite particles.
通常、かかる黒鉛質粒子、あるいは黒鉛質粒子と非晶質粒子の混合物と炭素前駆体を混合したものを加熱し中間物質を得て、その後炭化焼成、粉砕することにより、最終的に黒鉛粒子に非晶質物を複合化させた黒鉛非晶質複合粉末を得ることができるが、このような黒鉛非晶質複合粉末中の非晶質物の割合は５０重量％以下、好ましくは２５重量％以下、更に好ましくは１５重量％以下、特に好ましくは１０重量％以下で、０．１重量％以上、好ましくは０．５重量％以上、更に好ましくは１重量％以上、特に好ましくは２重量％以上となるように調整するのがよい。 Usually, such graphite particles, or a mixture of a mixture of graphite particles and amorphous particles and a mixture of carbon precursors are heated to obtain an intermediate substance, and then carbonized, baked and pulverized to finally form graphite particles. A graphite amorphous composite powder obtained by compounding an amorphous substance can be obtained. The proportion of the amorphous substance in such a graphite amorphous composite powder is 50% by weight or less, preferably 25% by weight or less, It is more preferably at most 15% by weight, particularly preferably at most 10% by weight, at least 0.1% by weight, preferably at least 0.5% by weight, more preferably at least 1% by weight, particularly preferably at least 2% by weight. It is better to adjust as follows.
かかる黒鉛非晶質複合粉末を得るための製造工程は、通常、以下の４工程に分けられる。 The production process for obtaining such a graphite amorphous composite powder is generally divided into the following four processes.
第１工程：黒鉛質粒子あるいは黒鉛質粒子と非晶質粒子の混合粉体と炭素前駆体、更に必要に応じて溶媒とを種々の市販の混合機や混練機等を用いて混合し、混合物を得る。 First step: Graphite particles or a mixed powder of graphite particles and amorphous particles, a carbon precursor, and, if necessary, a solvent are mixed using various commercially available mixers, kneaders and the like, and the mixture is mixed. Get.
第２工程：必要に応じ前記混合物を攪拌しながら加熱し、溶媒を除去した中間物質を得る。 Second step: If necessary, the mixture is heated with stirring to obtain an intermediate from which the solvent has been removed.
第３工程：前記混合物又は中間物質を、窒素ガス、炭酸ガス、アルゴンガス等の不活性ガス雰囲気下で７００℃以上２８００℃以下に加熱し、黒鉛非晶質複合物質を得る。 Third step: The mixture or the intermediate substance is heated to 700 ° C. or more and 2800 ° C. or less in an atmosphere of an inert gas such as nitrogen gas, carbon dioxide gas, and argon gas to obtain a graphite amorphous composite material.
第４工程：前記複合物質を必要に応じて粉砕、解砕、分級処理など粉体加工する。 Fourth step: The composite material is subjected to powder processing such as pulverization, crushing, and classification as required.
これらの工程中、第２工程及び第４工程は場合によっては省略可能であり、第４工程は第３工程の前に行っても良い。 In these steps, the second step and the fourth step can be omitted in some cases, and the fourth step may be performed before the third step.
また、第３工程の加熱処理条件としては、熱履歴温度条件が重要である。その温度下限は炭素前駆体の種類、その熱履歴によっても若干異なるが通常７００℃以上、好ましくは９００℃以上である。一方、上限温度は基本的に黒鉛粒子核の結晶構造を上回る構造秩序を有しない温度まで上げることができる。従って熱処理の上限温度としては、通常２８００℃以下、好ましくは２０００℃以下、更に好ましくは１５００℃以下が好ましい範囲である。このような熱処理条件において、昇温速度、冷却速度、熱処理時間などは目的に応じて任意に設定することができる。また、比較的低温領域で熱処理した後、所定の温度に昇温することもできる。なお、本工程に用いる反応機は回分式でも連続式でも又、一基でも複数基でも良い。 As the heat treatment conditions in the third step, heat history temperature conditions are important. The lower limit of the temperature slightly varies depending on the type of the carbon precursor and its thermal history, but is usually 700 ° C. or higher, preferably 900 ° C. or higher. On the other hand, the upper limit temperature can be raised to a temperature that does not basically have a structural order exceeding the crystal structure of the graphite particle nucleus. Therefore, the upper limit temperature of the heat treatment is usually 2800 ° C. or lower, preferably 2000 ° C. or lower, more preferably 1500 ° C. or lower. Under such heat treatment conditions, the rate of temperature rise, cooling rate, heat treatment time and the like can be arbitrarily set according to the purpose. After the heat treatment in a relatively low temperature range, the temperature can be raised to a predetermined temperature. The reactor used in this step may be a batch type or a continuous type, and may be a single unit or a plurality of units.
このようにして得られた黒鉛質に非晶質を複合させた材料は、ラマンスペクトル分析によるピーク強度比Ｒ値や、１５８０ｃｍ-1の付近のピークの半値幅Δν、Ｘ線広角回折の回折図において得られるｄ００２、Ｌｃの値において、黒鉛質材料の結晶化度を上回らないこと、即ちＲ値は黒鉛質のその値以上で、半値幅Δνは黒鉛質のその値以上、ｄ００２値は黒鉛質のその値以上で、Ｌｃは黒鉛質のその値以下であることが好ましい。具体的な黒鉛非晶質複合粉末材料のＲ値としては、０．０１以上１．０以下、好ましくは０．０５以上０．８以下、より好ましくは０．２以上０．７以下、更に好ましくは０．３以上０．５以下の範囲で、かつ、母剤となる黒鉛質の値以上であることが挙げられる。 The thus obtained graphitic material obtained by combining amorphous with amorphous material has a peak intensity ratio R value by Raman spectrum analysis, a half width Δν of a peak near 1580 cm −1 , and a diffraction pattern of X-ray wide angle diffraction. In the values of d 002 and Lc obtained in the above, the crystallinity of the graphitic material should not be exceeded, that is, the R value is equal to or more than that of graphite, the half-value width Δν is equal to or more than that of graphite, and the d 002 value is It is preferable that Lc be equal to or more than that value of graphite and equal to or less than that value of graphite. As the R value of the specific graphite amorphous composite powder material, 0.01 or more and 1.0 or less, preferably 0.05 or more and 0.8 or less, more preferably 0.2 or more and 0.7 or less, still more preferably Is in the range of 0.3 or more and 0.5 or less, and is not less than the value of graphite as a base material.
このような黒鉛非晶質複合粉末材料は、黒鉛質炭素に特徴的な低電位な充放電曲線を有することから発現する高出力な性質と、非晶質炭素に特徴的な優れたリチウム受け入れ性とを兼ね備えているため、高出力でかつ高パルス耐久性な性能が得られることから、本発明の活物質としてより好適であり、このことは、大型駆動電源、電気自動車、特にハイブリッド自動車の用途においてより顕著である。 Such a graphite amorphous composite powder material has a high output property exhibited by having a low potential charge / discharge curve characteristic of graphitic carbon, and an excellent lithium acceptability characteristic of amorphous carbon. Since they have both high power and high pulse durability, they are more suitable as the active material of the present invention. Is more remarkable.
以下に、上述のようにして製造される炭素質粉末状であって、前述の特定の最大分散粒子径、更には３５〜５０μｍ粒数、平均分散粒子径等の条件を満たす、本発明のリチウム二次電池用負極活物質を調製する方法について説明する。 Hereinafter, the lithium of the present invention, which is in the form of a carbonaceous powder produced as described above, and which satisfies the above-mentioned specific maximum dispersed particle size, and further satisfies the conditions of 35 to 50 μm particle size, average dispersed particle size, and the like. A method for preparing a negative electrode active material for a secondary battery will be described.
従来、リチウム二次電池用負極活物質は、黒鉛質粉末、非晶質粉末、黒鉛質・非晶質の複合化粉末を粉砕、分級して用いられていたが、従来の通常の分級では、篩の目開きを選択しても、扁平な粒子などは篩を通ってしまい、このような粗大粒子が、一度混入してしまうと取り除くことができず、この粗大粒子が、セパレータを傷付けることはなくても、活物質層内でリチウム金属の析出の核になるなど、電池性能に悪影響を及ぼしていた。 Conventionally, a negative electrode active material for a lithium secondary battery has been used by pulverizing and classifying graphite powder, amorphous powder, and composite powder of graphite and amorphous, but in the conventional normal classification, Even if the sieve opening is selected, flat particles and the like pass through the sieve, and such coarse particles cannot be removed once mixed, and the coarse particles may damage the separator. Even if not, the battery performance was adversely affected, such as being a nucleus for lithium metal deposition in the active material layer.
本発明では、前述の特定の最大分散粒子径、更には３５〜５０μｍ粒数、平均分散粒子径等の条件を満たす活物質を得るために、例えば、次のような技術的工夫をする。 In the present invention, in order to obtain an active material that satisfies the conditions of the above-mentioned specific maximum dispersed particle diameter, furthermore, the number of particles of 35 to 50 μm, the average dispersed particle diameter, and the like, for example, the following technical contrivance is made.
(1) 篩分け操作を繰り返すことにより、粗大粒子を確実に除去する。通常、ＡＳＴＭ４００メッシュ以下の篩で、２回以上、好ましくは４回以上篩分けを繰り返すことで、扁平な粒子の篩分けを行って粗大粒子を確実に除去する。 (1) The coarse particles are surely removed by repeating the sieving operation. Usually, by repeating sieving twice or more, preferably four or more times with a sieve having an ASTM of 400 mesh or less, sieving of flat particles is performed and coarse particles are surely removed.
(2) 湿式篩を用いて、分級効率を上げる。 (2) Use a wet sieve to increase the classification efficiency.
例えば、媒体として、水、エタノール等のアルコール類等の活物質粉末との反応性のない液体、あるいはその混合液を用い、篩上で、固形分濃度として、通常１重量％以上、中でも５重量％以上で、通常２０重量％以下、中でも１０重量％以下程度に維持されるようにするのが良い。この固形分濃度が２０重量％を超えると、活物質粉末が目詰まりを起こしやすく生産性が低下しやすくなる。また、粗大粒子が篩上の媒体液面方向に移行することでより分離が確実になるが、固形分濃度が２０重量％を超えると粗大粒子が媒体液面方向に移行しにくい傾向がある。一方、固形分濃度が１重量％を下回ると、生産性が低下し、かえって扁平な粗大粒子が回転して篩の目開きを通過してしまう機会が増えやすくなる。 For example, as a medium, a liquid having no reactivity with active material powder such as water, alcohols such as ethanol, or a mixture thereof is used. On a sieve, a solid content concentration is usually 1% by weight or more, especially 5% by weight. % Or more, usually at most 20% by weight, especially at most about 10% by weight. When the solid content exceeds 20% by weight, the active material powder is likely to be clogged, and the productivity is likely to be reduced. In addition, the separation of the coarse particles in the direction of the liquid surface of the medium on the sieve is more reliable. However, when the solid content exceeds 20% by weight, the coarse particles tend to be hard to move in the direction of the liquid surface of the medium. On the other hand, when the solid content concentration is less than 1% by weight, the productivity is lowered, and the chances of the flat coarse particles rotating and passing through the openings of the sieve are more likely to increase.
このような湿式篩を、２回以上、更には４回以上通過させる処理を行うのが好ましい。なお、後述する、風力式分級機と湿式分級機とを組み合わせて用いることもできる。 It is preferable to perform the treatment of passing through such a wet sieve twice or more, more preferably four or more times. It should be noted that a wind classifier and a wet classifier, which will be described later, can be used in combination.
(3) 風力式分級を通常２回以上、好ましくは４回以上繰り返すことによって、粗大粒子を確実に除去する。通常、この上限回数としては、対象とする活物質の性状により異なり一概に言えないが、１０回以下、中でも８回以下程度である。 (3) Coarse particles are surely removed by repeating the wind classification usually twice or more, preferably four or more times. Usually, the upper limit number varies depending on the properties of the target active material and cannot be unconditionally determined, but is not more than 10 times, especially about 8 times or less.
用いる風力式分級機の風量が大きすぎると、粗大粒子が含まれたまま活物質粉末が取り出されてしまう。また、処理する活物質粉末の供給量が多すぎると、粒子あたりの気流から受けるエネルギーが小さく、分級点の調整が困難で、目的とする活物質粉末が製造しにくい。更に、扁平な活物質粒子の風力分級においては、粗大粒子であるほど気流の当たる方向によって抵抗の差が大きくなりやすいため、より制御上の工夫を要する。 If the air volume of the air classifier used is too large, the active material powder is taken out while containing coarse particles. If the supply amount of the active material powder to be treated is too large, the energy received from the airflow per particle is small, it is difficult to adjust the classification point, and it is difficult to produce the desired active material powder. Furthermore, in the air classification of flat active material particles, the coarser the particles, the greater the difference in resistance depending on the direction in which the air current is applied, and thus requires more control.
風力分級をより確実にするためには、粗大粒子が気流によって小粒子に同伴して浮遊し混入してしまうことがないようにするために、処理量を少なくして、粗大粒子の落下がスムーズに行われるようにすると良い。また、粗粉を含まない粉体を効率良く分級するためには、原料供給量を低減させることが有効である。因みに、その低減の程度は、一般的な粗大粒子を含む従来条件に対して４分の１〜３分の１の粉体供給量が好ましい。 In order to make air classification more reliable, in order to prevent coarse particles from being suspended and mixed with small particles due to airflow, the amount of treatment is reduced, and coarse particles fall smoothly. It is good to be performed. Further, in order to efficiently classify the powder that does not contain coarse powder, it is effective to reduce the supply amount of the raw material. Incidentally, the degree of the reduction is preferably a powder supply amount of 1/4 to 1/3 of the conventional condition including general coarse particles.
また、粉体の分級室の、気流導入位置から目的とする粉体を含有する気流の抜き出し口までの気流空間を縦方向に長めにとるなどの工夫も大切である。 It is also important to take measures such as making the airflow space from the airflow introduction position to the airflow outlet containing the target powder in the powder classification chamber longer in the vertical direction.
風力式分級の具体的条件としては、平均粒子径（Ｄ５０）が２０μｍ以下の粉体の風力式分級について、工業的な分級機としては、通常、下限としては５ｍ３／分以上、中でも１０ｍ３／分以上、上限としては８０ｍ３／分以下、中でも５０ｍ３／分以下の、活物質粉体に反応性のない気体流、通常は、空気を供給することにより、下限としては、通常０．５ｋｇ／分以上、中でも１ｋｇ／分以上、上限としては、通常１０ｋｇ／分以下、中でも８ｋｇ／分以下の処理速度で粉体を分級するのが良い。 As a specific condition of the wind classification, as for an air classification of powder having an average particle diameter (D 50 ) of 20 μm or less, an industrial classifier usually has a lower limit of 5 m 3 / min or more, especially 10 m or more. 3 / min or more, with an upper limit of 80 m 3 / min or less, especially 50 m 3 / min or less, a gas flow not reactive with the active material powder, usually air is supplied, and the lower limit is usually 0 m 2 / min. It is preferable to classify the powder at a processing rate of not less than 0.5 kg / min, especially not less than 1 kg / min, and not more than 10 kg / min, especially not more than 8 kg / min.
次に、本発明のリチウム二次電池負極について説明する。 Next, the lithium secondary battery negative electrode of the present invention will be described.
本発明のリチウム二次電池負極は、集電体上に、負極活物質と、結着及び増粘効果を有する有機物とを含有する活物質層（以下「負極合剤層」と称す場合がある。）を形成してなるものであり、活物質層の厚さが５０μｍ以下であり、ＪＩＳ Ｂ０６０１に準拠して測定される算術平均粗さ（Ｒａ）が５μｍ以下であることを特徴とする。このように活物質層を薄肉化しても、表面が高度に均一化された活物質層であれば、後述する実施例に示すように、パルス充放電の長期サイクル特性に優れたリチウム二次電池を実現することができる。 The negative electrode for a lithium secondary battery of the present invention has an active material layer (hereinafter sometimes referred to as a “negative electrode mixture layer”) containing a negative electrode active material and an organic substance having a binding and thickening effect on a current collector. ), Wherein the thickness of the active material layer is 50 μm or less, and the arithmetic average roughness (Ra) measured according to JIS B0601 is 5 μm or less. Even if the thickness of the active material layer is reduced in this way, as long as the active material layer has a highly uniform surface, as shown in Examples described later, a lithium secondary battery having excellent long-term cycle characteristics of pulse charge and discharge is provided. Can be realized.
なお、この表面粗さ（Ｒa）は、レーザー顕微鏡を用い、ＪＩＳ Ｂ０６０１に従って、中心線平均粗さ（Ｒa）をレーザー回折式粒径分布計で計測される前述の平均粒子径（Ｄ５０）の１０倍を目安にした測定区間内で算出することにより行われる。活物質粉体の粒子径にもよるが、通常この測定区間は１００μｍで実施するのが適当である。 The surface roughness (Ra) is determined by using a laser microscope according to JIS B0601, and measuring the center line average roughness (Ra) with the above-mentioned average particle diameter (D 50 ) measured by a laser diffraction type particle size distribution analyzer. This is performed by calculating within a measurement section with 10 times as a standard. Although it depends on the particle diameter of the active material powder, it is usually appropriate to carry out this measurement section at 100 μm.
この活物質層の表面粗さ（Ｒa）の上限は５μｍ以下、好ましくは２μｍ以下であり、下限は小さいほど良いが、０．１μｍ程度であればリチウム金属の析出を確実に防止することができる。 The upper limit of the surface roughness (Ra) of this active material layer is 5 μm or less, preferably 2 μm or less, and the lower limit is better, but if it is about 0.1 μm, precipitation of lithium metal can be reliably prevented. .
通常、活物質層は集電体の両面に設けられることが多いが、本発明のリチウム二次電池負極によれば、活物質層1層（片側）の厚さを、１００μｍ以下、中でも８０μｍ以下、その中でも５０μｍ以下、特に４０μｍ以下、例えば３０〜４０μｍに薄肉化することもできる。 Usually, the active material layer is often provided on both sides of the current collector, but according to the negative electrode of the lithium secondary battery of the present invention, the thickness of one active material layer (one side) is 100 μm or less, particularly 80 μm or less. In particular, the thickness can be reduced to 50 μm or less, particularly 40 μm or less, for example, 30 to 40 μm.
このような本発明のリチウム二次電池負極の活物質層は、前述の本発明のリチウム二次電池用負極活物質を活物質として用いることにより実現することができる。 Such an active material layer of the negative electrode for a lithium secondary battery of the present invention can be realized by using the above-described negative electrode active material for a lithium secondary battery of the present invention as an active material.
負極活物質層（負極合剤層）は、前述の如く、通常、負極活物質と結着及び増粘効果を有する有機物を水系溶媒あるいは有機溶媒中に分散させたスラリー状のものを、金属箔などの集電体上に薄く塗布・乾燥する工程、続いて所定の厚み・密度まで圧密するプレス工程により形成される。負極活物質層（負極合剤層）の密度は、通常０．９ｇ／ｃｍ３以上、中でも１．２ｇ／ｃｍ３以上、特に１．５ｇ／ｃｍ３以上であり、通常２．２ｇ／ｃｍ３以下、中でも１．９ｇ／ｃｍ３以下、特に１．７ｇ／ｃｍ３以下であることが好ましい。 As described above, the negative electrode active material layer (negative electrode mixture layer) is usually formed by dispersing an organic substance having a binding and thickening effect with the negative electrode active material in an aqueous solvent or an organic solvent, as a metal foil. For example, it is formed by a process of applying and drying thinly on a current collector, followed by a pressing process of compacting to a predetermined thickness and density. The density of the negative electrode active material layer (negative electrode mixture layer) is usually 0.9 g / cm 3 or more, particularly 1.2 g / cm 3 or more, particularly 1.5 g / cm 3 or more, and usually 2.2 g / cm 3. It is preferably 1.9 g / cm 3 or less, particularly preferably 1.7 g / cm 3 or less.
負極活物質層の形成に用いられる、結着及び増粘効果を有する有機物としては、特に制限はないが、通常、熱可塑性樹脂、熱硬化性樹脂のいずれであってもよい。本発明において好ましいものとして結着剤は、例えば、ポリエチレン、ポリプロピレン、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、スチレンブタジエンゴム、テトラフルオロエチレン−ヘキサフルオロエチレン共重合体、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体（ＦＥＰ）、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体（ＰＦＡ）、フッ化ビニリデン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−クロロトリフルオロエチレン共重合体、エチレン−テトラフルオロエチレン共重合体（ＥＴＦＥ樹脂）、ポリクロロトリフルオロエチレン（ＰＣＴＦＥ）、フッ化ビニリデン−ペンタフルオロプロピレン共重合体、プロピレン−テトラフルオロエチレン共重合体、エチレン−クロロトリフルオロエチレン共重合体（ＥＣＴＦＥ）、フッ化ビニリデン−ヘキサフルオロプロピレン−テトラフルオロエチレン共重合体、フッ化ビニリデン−パーフルオロメチルビニルエーテル−テトラフルオロエチレン共重合体、エチレン−アクリル酸共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−メタクリル酸共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−アクリル酸メチル共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−メタクリル酸メチル共重合体又は前記材料の（Ｎａ＋）イオン架橋体を挙げることができ、これらの材料を単独又は混合物として用いることができる。これらの材料の中でより好ましい材料は、スチレンブタジエンゴム、ポリフッ化ビニリデン、エチレン−アクリル酸共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−メタクリル酸共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−アクリル酸メチル共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−メタクリル酸メチル共重合体又は前記材料の（Ｎａ＋）イオン架橋体である。 The organic substance having a binding and thickening effect used for forming the negative electrode active material layer is not particularly limited, but may be usually a thermoplastic resin or a thermosetting resin. Preferred examples of the binder in the present invention include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, and tetrafluoroethylene. -Hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene -Tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoro Ethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, ethylene -An acrylic acid copolymer or a (Na + ) ion cross-linked product of the above material, an ethylene-methacrylic acid copolymer or a (Na + ) ion cross-linked product of the above material, an ethylene-methyl acrylate copolymer or ( Na + ) ion crosslinked product, ethylene-methyl methacrylate copolymer or (Na + ) ion crosslinked product of the above materials can be mentioned, and these materials can be used alone or as a mixture. Among these materials, more preferred materials are styrene-butadiene rubber, polyvinylidene fluoride, ethylene-acrylic acid copolymer or (Na + ) ion cross-linked product of the above material, ethylene-methacrylic acid copolymer or ( A (Na + ) ion cross-linked product, an ethylene-methyl acrylate copolymer or a (Na + ) ion cross-linked product of the above material, an ethylene-methyl methacrylate copolymer or a (Na + ) ion cross-linked product of the above material.
負極活物質層には、必要に応じて、負極用導電剤を用いることもできる。負極用導電剤は、電子伝導性材料で、活物質層の均一性を損なわないものであれば何でもよい。例えば、天然黒鉛（鱗片状黒鉛など）、人造黒鉛、膨張黒鉛などのグラファイト類、アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラック等のカ−ボンブラック類、炭素繊維、金属繊維などの導電性繊維類、銅、ニッケル等の金属粉末類及びポリフェニレン誘導体などの有機導電性材料などを単独又はこれらの混合物として含ませることができる。これらの導電剤のなかで、人造黒鉛、アセチレンブラック、炭素繊維が特に好ましい。通常、導電剤は、平均粒径が、３μｍ以下、中でも１μｍ以下の粒径のものを用いることが極板での粗大粒子の形成を抑える点でより効果的である。導電剤の平均粒径の下限は、数ｎｍ程度であれば、極板の性能上特に支障はない。 In the negative electrode active material layer, a negative electrode conductive agent can be used as necessary. The negative electrode conductive agent may be any material as long as it is an electron conductive material and does not impair the uniformity of the active material layer. For example, graphites such as natural graphite (flaky graphite, etc.), artificial graphite, expanded graphite, carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fibers, Conductive fibers such as metal fibers, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite, acetylene black and carbon fiber are particularly preferred. Usually, it is more effective to use a conductive agent having an average particle diameter of 3 μm or less, especially 1 μm or less, in terms of suppressing formation of coarse particles on the electrode plate. If the lower limit of the average particle size of the conductive agent is about several nm, there is no particular problem in the performance of the electrode plate.
負極活物質層には、上記導電剤の他、更にフィラー、分散剤、イオン伝導体、圧力増強剤及びその他の各種添加剤を配合することができる。フィラーは、構成された電池において、化学変化を起こさない繊維状材料であれば何でも用いることができる。通常、ポリプロピレン、ポリエチレンなどのオレフィン系ポリマー、ガラス、炭素などの繊維が用いられる。 In addition to the above-mentioned conductive agent, a filler, a dispersant, an ionic conductor, a pressure enhancer and other various additives can be added to the negative electrode active material layer. As the filler, any fibrous material that does not cause a chemical change in the configured battery can be used. Usually, fibers such as olefin polymers such as polypropylene and polyethylene, glass, and carbon are used.
活物質スラリーの調製には、水系溶媒又は有機溶媒が分散媒として用いられる。 In preparing the active material slurry, an aqueous solvent or an organic solvent is used as a dispersion medium.
水系溶媒としては、通常、水が用いられるが、これにエタノール等のアルコール類、Ｎ−メチルピロリドン等の環状アミド類等の添加剤を水に対して、３０重量％以下程度まで添加することもできる。 As the aqueous solvent, water is usually used, and additives such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone may be added up to about 30% by weight or less based on water. it can.
また、有機溶媒としては、通常、Ｎ−メチルピロリドン等の環状アミド類、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド等の直鎖状アミド類、アニソール、トルエン、キシレン等の芳香族炭化水素類、ブタノール、シクロヘキサノール等のアルコール類が挙げられ、中でも、Ｎ−メチルピロリドン等の環状アミド類、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド等の直鎖状アミド類等が好ましい。 As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbons such as anisole, toluene and xylene are usually used. Examples thereof include hydrogens, alcohols such as butanol and cyclohexanol, and among them, cyclic amides such as N-methylpyrrolidone and linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. .
活物質、結着剤である結着及び増粘効果を有する有機物、及び必要に応じて配合される負極用導電剤、その他フィラー等をこれらの溶媒に混合して活物質スラリーを調製し、これを負極用集電体に所定の厚みとなるように塗布することにより負極活物質層が形成される。 An active material, an organic substance having a binding and thickening effect as a binder, and a conductive agent for a negative electrode to be blended as required, and other fillers are mixed with these solvents to prepare an active material slurry. Is applied to the negative electrode current collector so as to have a predetermined thickness to form a negative electrode active material layer.
なお、この活物質スラリー中の活物質の濃度の上限は通常７０重量％以下、好ましくは５５重量％以下であり、下限は通常３０重量％以上、好ましくは４０重量％以上である。活物質の濃度がこの上限を超えると活物質スラリー中の活物質が凝集しやすくなり、下限を下回ると活物質スラリーの保存中に活物質が沈降しやすくなる。 The upper limit of the concentration of the active material in the active material slurry is usually 70% by weight or less, preferably 55% by weight or less, and the lower limit is usually 30% by weight or more, preferably 40% by weight or more. When the concentration of the active material exceeds the upper limit, the active material in the active material slurry tends to aggregate, and when the concentration is lower than the lower limit, the active material easily precipitates during storage of the active material slurry.
また、活物質スラリー中の結着剤の濃度の上限は通常３０重量％以下、好ましくは１０重量％以下であり、下限は通常０．１重量％以上、好ましくは０．５重量以上である。結着剤の濃度がこの上限を超えると電極の内部抵抗が大きくなり、下限を下回ると得られた電極と電極粉体の結着性に劣るものとなる。 The upper limit of the concentration of the binder in the active material slurry is usually 30% by weight or less, preferably 10% by weight or less, and the lower limit is usually 0.1% by weight or more, preferably 0.5% by weight or more. If the concentration of the binder exceeds the upper limit, the internal resistance of the electrode increases, and if the concentration is lower than the lower limit, the obtained electrode and the electrode powder have poor binding properties.
更に、活物質スラリー中の前述の負極用導電剤の濃度は０〜５重量％であることが好ましく、その他のフィラー等の濃度は０〜３０重量％であることが好ましい。 Further, the concentration of the above-mentioned negative electrode conductive agent in the active material slurry is preferably 0 to 5% by weight, and the concentration of other fillers and the like is preferably 0 to 30% by weight.
負極用集電体としては、構成された電池において化学変化を起こさない電子伝導体であれば何でも良い。例えば、材料としてステンレス鋼、ニッケル、銅、チタン、炭素、導電性樹脂などの他に、銅やステンレス鋼の表面にカーボン、ニッケルあるいはチタンを処理させたものなどが用いられる。特に、銅あるいは銅合金が好ましい。これらの材料の表面を酸化して用いることもできる。また、表面処理により集電体表面に凹凸を付けることが望ましい。形状は、フォイルの他、フィルム、シート、ネット、パンチングされたもの、ラス体、多孔質体、発泡体、繊維群の成形体などが用いられる。このような負極集電体の厚みは、特に限定されないが、１〜５００μｍのものが用いられる。 As the current collector for the negative electrode, any electronic conductor that does not cause a chemical change in the configured battery may be used. For example, in addition to stainless steel, nickel, copper, titanium, carbon, conductive resin, and the like, a material obtained by treating the surface of copper or stainless steel with carbon, nickel, or titanium is used. Particularly, copper or a copper alloy is preferable. The surface of these materials can be oxidized and used. In addition, it is desirable to make the current collector surface uneven by surface treatment. As the shape, in addition to the foil, a film, a sheet, a net, a punched material, a lath body, a porous body, a foam, a molded body of a fiber group, and the like are used. Although the thickness of such a negative electrode current collector is not particularly limited, a thickness of 1 to 500 μm is used.
なお、本発明においては、前述の負極活物質層の表面平均粗さ（Ｒa）５μｍ以下を満たすために、活物質、結着剤、必要に応じてその他の成分を溶媒中に配合してなる活物質スラリーを、集電体上への塗布に先立ち、篩による濾過を行っても良い。この場合、通常、ＡＳＴＭ２７０メッシュ（目開き５３μｍ）以下、好ましくはＡＳＴＭ３２５メッシュ以下（目開き４３μｍ）、更に好ましくはＡＳＴＭ４００メッシュ以下（目開き３５μｍ）の篩を用いて、通常１回以上、好ましくは２回以上、濾過操作を行うことが好ましい。この濾過操作における温度条件の下限は、通常５℃以上、特に１０℃以上であり、上限は５０℃以下、特に３０℃以下とするのが好ましい。この温度条件が、上記上限を超えると分散媒が蒸発しやすくなり、下限を下回ると分散媒の粘度が上昇しやすくなる。 In the present invention, in order to satisfy the above-mentioned surface average roughness (Ra) of the negative electrode active material layer of 5 μm or less, an active material, a binder, and other components as necessary are mixed in a solvent. Prior to coating the active material slurry on the current collector, filtration using a sieve may be performed. In this case, usually, using a sieve having an ASTM of 270 mesh or less (mesh size of 53 μm), preferably ASTM 325 mesh or less (mesh size of 43 μm), more preferably ASTM 400 mesh or less (mesh size of 35 μm), usually at least once, preferably at least 2 times. It is preferable to perform the filtration operation more than once. The lower limit of the temperature condition in this filtration operation is usually 5 ° C. or higher, particularly 10 ° C. or higher, and the upper limit is preferably 50 ° C. or lower, particularly preferably 30 ° C. or lower. When the temperature condition exceeds the above upper limit, the dispersion medium tends to evaporate, and when the temperature condition falls below the lower limit, the viscosity of the dispersion medium tends to increase.
また、この濾過操作において、篩目の下側は、濾過が進行するに従い、大気圧よりも加圧されてくるため、定期的に大気開放して圧力を大気圧に戻すのが好ましい。更に、篩下側を減圧状態にしても良い。このときの減圧条件としては１０〜３０ｋＰａ程度の減圧が好ましい。また、篩上側には、スクレパーを取り付け、分散液が篩目に常に均一に接するように、塗り付けるように攪拌することも好ましい。 In this filtration operation, the lower side of the sieve is pressurized to a pressure higher than the atmospheric pressure as the filtration proceeds, so that it is preferable to periodically release the pressure to the atmosphere and return the pressure to the atmospheric pressure. Further, the lower side of the sieve may be in a reduced pressure state. The reduced pressure condition at this time is preferably reduced pressure of about 10 to 30 kPa. It is also preferable to attach a scraper on the upper side of the sieve and stir so that the dispersion liquid is always uniformly contacted with the sieve.
次に、リチウムを吸蔵・放出可能な正極、リチウムを吸蔵・放出可能な負極、及び、電解質を有し、負極として、このような本発明のリチウム二次電池負極を用いた、本発明のリチウム二次電池について説明する。 Next, the positive electrode capable of occluding and releasing lithium, the negative electrode capable of occluding and releasing lithium, and the electrolyte, wherein the lithium secondary battery negative electrode of the present invention is used as the negative electrode. The secondary battery will be described.
本発明のリチウム二次電池における正極極板も、負極極板と同様に集電体上に、正極活物質と、結着及び増粘効果を有する有機物（結着剤）を含有する活物質層（以下「正極合剤層」と称す場合がある。）を形成してなり、負極活物質層と同様、正極活物質層も、通常、正極活物質と結着及び増粘効果を有する有機物を水あるいは有機溶媒中に分散させたスラリー状のものを、金属箔などの集電体上に薄く塗布・乾燥する工程、続いて所定の厚み・密度まで圧密するプレス工程により形成される。 The positive electrode plate in the lithium secondary battery of the present invention also has a positive electrode active material and an active material layer containing an organic substance (binder) having a binding and thickening effect on a current collector, similarly to the negative electrode plate. (Hereinafter, may be referred to as a “positive electrode mixture layer”). Like the negative electrode active material layer, the positive electrode active material layer also generally includes an organic material having a binding and thickening effect with the positive electrode active material. It is formed by a step of thinly applying and drying a slurry in water or an organic solvent on a current collector such as a metal foil, and then a pressing step of compacting to a predetermined thickness and density.
正極活物質材料には、リチウムを吸蔵・放出できる機能を有している限り特に制限はないが、例えば、リチウム含有遷移金属酸化物を用いることができる。 The positive electrode active material is not particularly limited as long as it has a function of absorbing and releasing lithium. For example, a lithium-containing transition metal oxide can be used.
リチウム含有遷移金属酸化物としては、例えば、ＬｉxＣｏＯ2、ＬｉxＮｉＯ2、ＬｉxＭｎＯ2、ＬｉxＣｏyＮｉ1-yＯ2、ＬｉxＣｏyＭ1-yＯz、ＬｉxＮｉ1-yＭｙＯz、ＬｉxＭｎ2Ｏ4、ＬｉxＭｎ2-yＭyＯ4（Ｍ＝Ｎａ、Ｍｇ、Ｓｃ、Ｙ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｌ、Ｃｒ、Ｐｂ、Ｓｂ、Ｂのうち少なくとも一種。ｘ＝０〜１．２、ｙ＝０〜０．９、ｚ＝２．０〜２．３）が挙げられる。ここで、上記のｘ値は、充放電開始前の値であり、充放電により増減する。更にＣｏ、Ｎｉ、Ｍｎの一部を他の遷移金属などの元素で置き換えたものを使用することもできる。ただし、遷移金属カルコゲン化物、バナジウム酸化物及びそのリチウム化合物、ニオブ酸化物及びそのリチウム化合物、有機導電性物質を用いた共役系ポリマー、シェブレル相化合物等の他の正極材料を用いることも可能である。また、複数の異なった正極材料を混合して用いることも可能である。正極活物質粒子の平均粒径は、特に限定はされないが、１〜３０μｍであることが好ましい。 Examples of the lithium-containing transition metal oxide include Li x CoO 2 , Li x NiO 2 , Li x MnO 2 , Li x Co y Ni 1-y O 2 , Li x Co y M 1-y O z , Li x Ni 1-y M y O z , Li x Mn 2 O 4, Li x Mn 2-y M y O 4 (M = Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al , Cr, Pb, Sb, and B. x = 0 to 1.2, y = 0 to 0.9, and z = 2.0 to 2.3). Here, the above-mentioned x value is a value before the start of charge / discharge, and increases / decreases due to charge / discharge. Further, a material in which part of Co, Ni, and Mn is replaced with an element such as another transition metal may be used. However, other positive electrode materials such as transition metal chalcogenides, vanadium oxides and lithium compounds thereof, niobium oxides and lithium compounds thereof, conjugated polymers using organic conductive substances, and Chevrel phase compounds can also be used. . It is also possible to use a mixture of a plurality of different positive electrode materials. The average particle size of the positive electrode active material particles is not particularly limited, but is preferably 1 to 30 μm.
正極活物質層には、正極用導電剤を用いることができる。正極用導電剤は、用いる正極材料の充放電電位において、化学変化を起こさない電子伝導性材料であれば何でも良い。例えば、天然黒鉛（鱗片状黒鉛など）、人造黒鉛などのグラファイト類、アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラック等のカ−ボンブラック類、炭素繊維、金属繊維などの導電性繊維類、フッ化カーボン、アルミニウム等の金属粉末類、酸化亜鉛、チタン酸カリウムなどの導電性ウィスカー類、酸化チタンなどの導電性金属酸化物あるいはポリフェニレン誘導体などの有機導電性材料などを単独又はこれらの混合物として含ませることができる。これらの導電剤のなかで、人造黒鉛、アセチレンブラックが特に好ましい。導電剤の添加量は、特に限定されないが、正極材料に対して１〜５０重量％が好ましく、特に１〜３０重量％が好ましい。カーボンやグラファイトでは、２〜１５重量％が特に好ましい。 For the positive electrode active material layer, a positive electrode conductive agent can be used. The conductive agent for the positive electrode may be any electronic conductive material that does not cause a chemical change at the charge / discharge potential of the positive electrode material used. For example, graphites such as natural graphite (flaky graphite), artificial graphite, etc., carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, metal fiber, etc. Conductive fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide and organic conductive materials such as polyphenylene derivatives. It can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite and acetylene black are particularly preferred. The amount of the conductive agent is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 1 to 30% by weight based on the positive electrode material. For carbon and graphite, 2 to 15% by weight is particularly preferred.
正極活物質層の形成に用いられる結着及び増粘効果を有する有機物としては、特に制限はなく、熱可塑性樹脂、熱硬化性樹脂のいずれであっても良い。例えば、ポリエチレン、ポリプロピレン、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、スチレンブタジエンゴム、テトラフルオロエチレン−ヘキサフルオロエチレン共重合体、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体（ＦＥＰ）、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体（ＰＦＡ）、フッ化ビニリデン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−クロロトリフルオロエチレン共重合体、エチレン−テトラフルオロエチレン共重合体（ＥＴＦＥ樹脂）、ポリクロロトリフルオロエチレン（ＰＣＴＦＥ）、フッ化ビニリデン−ペンタフルオロプロピレン共重合体、プロピレン−テトラフルオロエチレン共重合体、エチレン−クロロトリフルオロエチレン共重合体（ＥＣＴＦＥ）、フッ化ビニリデン−ヘキサフルオロプロピレン−テトラフルオロエチレン共重合体、フッ化ビニリデン−パーフルオロメチルビニルエーテル−テトラフルオロエチレン共重合体、エチレン−アクリル酸共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−メタクリル酸共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−アクリル酸メチル共重合体又は前記材料の（Ｎａ＋）イオン架橋体、エチレン−メタクリル酸メチル共重合体又は前記材料の（Ｎａ＋）イオン架橋体を挙げることができ、これらの材料を単独又は混合物として用いることができる。これらの材料の中でより好ましい材料はポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）である。 The organic substance having a binding and thickening effect used for forming the positive electrode active material layer is not particularly limited, and may be any of a thermoplastic resin and a thermosetting resin. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin) , Polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoro Oroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer or the aforementioned material (Na + ) ion crosslinked product, ethylene-methacrylic acid copolymer or (Na + ) ion crosslinked product of the above-mentioned material, ethylene-methyl acrylate copolymer or (Na + ) ion crosslinked product of the above material, ethylene-methacrylic Examples thereof include an acid methyl copolymer and a (Na + ) ion crosslinked product of the above materials, and these materials can be used alone or as a mixture. Among these materials, more preferred materials are polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).
正極活物質層には、上記導電剤の他、更にフィラー、分散剤、イオン伝導体、圧力増強剤及びその他の各種添加剤を配合することができる。フィラーは、構成された電池において、化学変化を起こさない繊維状材料であれば何でも用いることができる。通常、ポリプロピレン、ポリエチレンなどのオレフィン系ポリマー、ガラス、炭素などの繊維が用いられる。フィラーの添加量は特に限定されないが、活物質層中の含有量として０〜３０重量％が好ましい。 In addition to the above-mentioned conductive agent, the positive electrode active material layer may further contain a filler, a dispersant, an ionic conductor, a pressure enhancer, and other various additives. As the filler, any fibrous material that does not cause a chemical change in the configured battery can be used. Usually, fibers such as olefin polymers such as polypropylene and polyethylene, glass, and carbon are used. The amount of the filler is not particularly limited, but is preferably 0 to 30% by weight as the content in the active material layer.
正極活物質スラリーの調製には、負極活物質スラリーの分散媒として前述したものと同様の水系溶媒又は有機溶媒が用いられる。 In preparing the positive electrode active material slurry, the same aqueous solvent or organic solvent as described above is used as a dispersion medium for the negative electrode active material slurry.
活物質、結着剤である結着及び増粘効果を有する有機物及び必要に応じて配合される正極用導電剤、その他フィラー等をこれらの溶媒に混合して活物質スラリーを調製し、これを正極用集電体に所定の厚みとなるように塗布することにより正極活物質層が形成される。 An active material, an organic material having a binding and thickening effect as a binder and a conductive agent for a positive electrode to be blended as necessary, and other fillers are mixed with these solvents to prepare an active material slurry. A positive electrode active material layer is formed by applying a predetermined thickness to the positive electrode current collector.
なお、この活物質スラリー中の活物質の濃度の上限は通常７０重量％以下、好ましくは５５重量％以下であり、下限は通常３０重量％以上、好ましくは４０重量％以上である。活物質の濃度がこの上限を超えると活物質スラリー中の活物質が凝集しやすくなり、下限を下回ると活物質スラリーの保存中に活物質が沈降しやすくなる。 The upper limit of the concentration of the active material in the active material slurry is usually 70% by weight or less, preferably 55% by weight or less, and the lower limit is usually 30% by weight or more, preferably 40% by weight or more. When the concentration of the active material exceeds the upper limit, the active material in the active material slurry tends to aggregate, and when the concentration is lower than the lower limit, the active material easily precipitates during storage of the active material slurry.
また、活物質スラリー中の結着剤の濃度の上限は通常３０重量％以下、好ましくは１０重量％以下であり、下限は通常０．１重量％以上、好ましくは０．５重量以上である。結着剤の濃度がこの上限を超えると電極の内部抵抗が大きくなり、下限を下回ると得られた電極と電極粉体の結着性に劣るものとなる。 The upper limit of the concentration of the binder in the active material slurry is usually 30% by weight or less, preferably 10% by weight or less, and the lower limit is usually 0.1% by weight or more, preferably 0.5% by weight or more. If the concentration of the binder exceeds the upper limit, the internal resistance of the electrode increases, and if the concentration is lower than the lower limit, the obtained electrode and the electrode powder have poor binding properties.
正極用集電体としては、用いる正極材料の充放電電位において化学変化を起こさない電子伝導体であれば何でも良い。例えば、材料としてステンレス鋼、アルミニウム、チタン、炭素、導電性樹脂などの他に、アルミニウムやステンレス鋼の表面にカーボンあるいはチタンを処理させたものが用いられる。特に、アルミニウムあるいはアルミニウム合金が好ましい。これらの材料の表面を酸化して用いることもできる。また、表面処理により集電体表面に凹凸を付けることが望ましい。形状は、フォイルの他、フィルム、シート、ネット、パンチされたもの、ラス体、多孔質体、発泡体、繊維群、不織布体の成形体などが用いられる。このような正極集電体の厚みは、特に限定されないが、１〜５００μｍのものが用いられる。 As the current collector for the positive electrode, any electronic conductor that does not cause a chemical change in the charge / discharge potential of the positive electrode material to be used may be used. For example, in addition to stainless steel, aluminum, titanium, carbon, conductive resin, and the like, a material obtained by treating the surface of aluminum or stainless steel with carbon or titanium is used. Particularly, aluminum or an aluminum alloy is preferable. The surface of these materials can be oxidized and used. In addition, it is desirable to make the current collector surface uneven by surface treatment. As the shape, in addition to a foil, a film, a sheet, a net, a punched material, a lath body, a porous body, a foamed body, a fiber group, a molded body of a nonwoven fabric body, and the like are used. The thickness of such a positive electrode current collector is not particularly limited, but a thickness of 1 to 500 μm is used.
本発明のリチウム二次電池において、負極板と正極板の構成は、少なくとも正極活物質層面の対向面に負極活物質層面が存在していることが好ましい。 In the configuration of the negative electrode plate and the positive electrode plate in the lithium secondary battery of the present invention, it is preferable that the negative electrode active material layer surface exists at least on the surface facing the positive electrode active material layer surface.
本発明のリチウム二次電池に用いられる電解質としては、非水溶媒と、その溶媒に溶解するリチウム塩とから構成される非水電解液が挙げられる。 Examples of the electrolyte used in the lithium secondary battery of the present invention include a non-aqueous electrolyte composed of a non-aqueous solvent and a lithium salt dissolved in the solvent.
非水溶媒としては、例えば、エチレンカーボネ−ト（ＥＣ）、プロピレンカ−ボネ−ト（ＰＣ）、ブチレンカーボネート（ＢＣ）、ビニレンカーボネート（ＶＣ）などの環状カーボネート類、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）、ジプロピルカーボネート（ＤＰＣ）などの鎖状カーボネート類、ギ酸メチル、酢酸メチル、プロピオン酸メチル、プロピオン酸エチルなどの脂肪族カルボン酸エステル類、γ−ブチロラクトン等のγ−ラクトン類、１，２−ジメトキシエタン（ＤＭＥ）、１，２−ジエトキシエタン（ＤＥＥ）、エトキシメトキシエタン（ＥＭＥ）等の鎖状エーテル類、テトラヒドロフラン、２−メチルテトラヒドロフラン等の環状エーテル類、ジメチルスルホキシド、１，３−ジオキソラン、ホルムアミド、アセトアミド、ジメチルホルムアミド、ジオキソラン、アセトニトリル、プロピルニトリル、ニトロメタン、エチルモノグライム、リン酸トリエステル、トリメトキシメタン、ジオキソラン誘導体、スルホラン、メチルスルホラン、１，３−ジメチル−２−イミダゾリジノン、３−メチル−２−オキサゾリジノン、プロピレンカーボネート誘導体、テトラヒドロフラン誘導体、エチルエーテル、１，３−プロパンサルトン、アニソール、ジメチルスルホキシド、Ｎ−メチルピロリドン、などの非プロトン性有機溶媒を挙げることができ、これらの一種または二種以上を混合して使用する。なかでも環状カーボネートと鎖状カーボネートとの混合系、または環状カーボネートと鎖状カーボネート及び脂肪族カルボン酸エステルとの混合系が好ましい。 Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), Chain carbonates such as diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC); aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate; Γ-lactones such as butyrolactone, chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE) and ethoxymethoxyethane (EME), tetrahydrofuran, 2-methyltetrahydrofuran and the like Cyclic ethers, dimethyl sulf Foxide, 1,3-dioxolan, formamide, acetamide, dimethylformamide, dioxolan, acetonitrile, propyl nitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolan derivative, sulfolane, methylsulfolane, 1,3-dimethyl Aprotic organic solvents such as -2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propanesultone, anisole, dimethylsulfoxide, N-methylpyrrolidone, etc. These may be used alone or in combination of two or more. Among them, a mixed system of a cyclic carbonate and a chain carbonate, or a mixed system of a cyclic carbonate, a chain carbonate and an aliphatic carboxylic acid ester is preferable.
これらの溶媒に溶解するリチウム塩としては、たとえばＬｉＣｌＯ4、ＬｉＢＦ4、ＬｉＰＦ6、ＬｉＡｌＣｌ4、ＬｉＳｂＦ6、ＬｉＳＣＮ、ＬｉＣｌ、ＬｉＣＦ3ＳＯ3、ＬｉＣＦ3ＣＯ2、Ｌｉ（ＣＦ3ＳＯ2）2、ＬｉＡｓＦ6、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＢ10Ｃｌ10、低級脂肪族カルボン酸リチウム、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、クロロボランリチウム、四フェニルホウ酸リチウム、イミド類等を挙げることができ、これらの一種又は二種以上を組み合わせて使用することができるが、特にＬｉＰＦ6を含ませることがより好ましい。 Examples of lithium salts dissolved in these solvents include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCl, LiCF 3 SO 3 , LiCF 3 CO 2 , Li (CF 3 SO 2 ) 2 , LiAsF 6 , LiN (CF 3 SO 2 ) 2 , LiB 10 Cl 10 , lithium lower aliphatic carboxylate, LiCl, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate, imides and the like can be mentioned. One kind or a combination of two or more kinds can be used, but it is particularly preferable to include LiPF 6 .
本発明における特に好ましい非水電解液は、エチレンカーボネートとエチルメチルカーボネートを少なくとも含み、支持塩としてＬｉＰＦ6を含む電解液である。 A particularly preferred non-aqueous electrolyte in the present invention is an electrolyte containing at least ethylene carbonate and ethyl methyl carbonate, and containing LiPF 6 as a supporting salt.
このような電解質を電池内に添加する量は、特に限定されないが、正極材料や負極材料の量や電池のサイズによって必要量を用いることができる。支持電解質であるリチウム塩の非水溶媒に対する溶解量は、特に限定されないが、０．２〜２ｍｏｌ／ｌが好ましい。特に、０．５〜１．５ｍｏｌ／ｌとすることがより好ましい。 The amount of such an electrolyte to be added to the battery is not particularly limited, but a required amount can be used depending on the amounts of the positive electrode material and the negative electrode material and the size of the battery. The amount of the lithium salt as the supporting electrolyte dissolved in the nonaqueous solvent is not particularly limited, but is preferably 0.2 to 2 mol / l. In particular, it is more preferably 0.5 to 1.5 mol / l.
また、電解質としては、上述のような電解液の他に次の様な固体電解質も用いることができる。固体電解質としては、無機固体電解質と有機固体電解質に分けられる。無機固体電解質には、Ｌｉの窒化物、ハロゲン化物、酸素酸塩などがよく知られている。なかでもＬｉ4ＳｉＯ4、Ｌｉ4ＳｉＯ4−ＬｉＩ−ＬｉＯＨ、xＬｉ3ＰＯ4−(1-x)Ｌｉ4ＳｉＯ4、Ｌｉ2ＳｉＳ3、Ｌｉ3ＰＯ4−Ｌｉ2Ｓ−ＳｉＳ2、硫化リン化合物などが有効である。有機固体電解質では、例えば、ポリエチレンオキサイド、ポリプロピレンオキサイド、ポリホスファゼン、ポリアジリジン、ポリエチレンスルフィド、ポリビニルアルコール、ポリフッ化ビニリデン、ポリヘキサフルオロプロピレンなどやこれらの誘導体、混合物、複合体などのポリマー材料が有効である。 As the electrolyte, the following solid electrolyte can be used in addition to the above-described electrolyte solution. Solid electrolytes are classified into inorganic solid electrolytes and organic solid electrolytes. Well-known inorganic solid electrolytes include nitrides, halides, and oxyacid salts of Li. Of these Li 4 SiO 4, Li 4 SiO 4 -LiI-LiOH, xLi 3 PO 4 - (1-x) Li 4 SiO 4, Li 2 SiS 3, Li 3 PO 4 -Li 2 S-SiS 2, phosphosulfurized Compounds and the like are effective. In the organic solid electrolyte, for example, polymer materials such as polyethylene oxide, polypropylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, polyhexafluoropropylene, and derivatives, mixtures, and composites thereof are effective. is there.
更に、放電や充放電特性を改良する目的で、他の化合物を電解質に添加することも有効である。このような添加剤としては、例えば、トリエチルフォスファイト、トリエタノールアミン、環状エーテル、エチレンジアミン、ｎ−グライム、ピリジン、ヘキサリン酸トリアミド、ニトロベンゼン誘導体、クラウンエーテル類、第四級アンモニウム塩、エチレングリコールジアルキルエーテル等を挙げることができる。 Further, it is effective to add another compound to the electrolyte for the purpose of improving the discharge and charge / discharge characteristics. Such additives include, for example, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, pyridine, hexaphosphoric triamide, nitrobenzene derivatives, crown ethers, quaternary ammonium salts, ethylene glycol dialkyl ether And the like.
本発明に用いられるセパレータとしては、大きなイオン透過度と、所定の機械的強度を有する、絶縁性の微多孔性薄膜が用いられる。また、このセパレータは一定温度以上で孔を閉塞し、抵抗をあげる機能を持つことが好ましい。耐有機溶剤性と疎水性の面から、セパレータとしては、ポリプロピレン、ポリエチレンなどの単独又は組み合わせたオレフィン系ポリマーあるいはガラス繊維などからつくられたシートや不織布または織布が用いられる。セパレータの孔径は、電極より脱離した正負極材料、結着剤、導電剤が透過しない範囲であることが望ましく、例えば、０．０１〜１μｍであるものが望ましい。セパレータの厚みは、一般的には、１０〜３００μｍが用いられる。また、空孔率は、電子やイオンの透過性と素材や膜厚に応じて決定されるが、一般的には３０〜８０％であることが望ましい。 As the separator used in the present invention, an insulating microporous thin film having high ion permeability and predetermined mechanical strength is used. Further, it is preferable that this separator has a function of closing a hole at a certain temperature or higher to increase resistance. In terms of organic solvent resistance and hydrophobicity, a sheet, a nonwoven fabric, or a woven fabric made of an olefin polymer such as polypropylene or polyethylene alone or in combination or glass fiber is used as the separator. The pore size of the separator is desirably in a range that does not allow the positive and negative electrode materials, the binder, and the conductive agent detached from the electrode to permeate, for example, 0.01 to 1 μm. Generally, the thickness of the separator is 10 to 300 μm. The porosity is determined according to the electron and ion permeability, the material and the film thickness, but is generally preferably 30 to 80%.
また、ポリマー材料に、溶媒とその溶媒に溶解するリチウム塩とから構成される有機電解液を吸収保持させたものを正極合剤、負極合剤に含ませ、更に有機電解液を吸収保持するポリマーからなる多孔性のセパレータを正極、負極と一体化した電池を構成することも可能である。このポリマー材料としては、有機電解液を吸収保持できるものであれば良いが、特にフッ化ビニリデンとヘキサフルオロプロピレンの共重合体が好ましい。 Further, a polymer material in which an organic electrolyte composed of a solvent and a lithium salt dissolved in the solvent is absorbed and retained is included in the positive electrode mixture and the negative electrode mixture, and a polymer that absorbs and retains the organic electrolyte is further included. It is also possible to configure a battery in which a porous separator made of is integrated with a positive electrode and a negative electrode. As the polymer material, any material can be used as long as it can absorb and hold an organic electrolytic solution, and a copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferable.
このようなセパレータの厚みの上限は通常６０μｍ以下、好ましくは５０μｍ以下、更に好ましくは３０μｍ以下であり、下限は通常１０μｍ以上、好ましくは１５μｍ以上である。セパレータの厚みが上記上限を超えると電池の内部抵抗が上昇しやすくなり、下限を下回ると正負極が短絡しやすくなる。 The upper limit of the thickness of such a separator is usually 60 μm or less, preferably 50 μm or less, more preferably 30 μm or less, and the lower limit is usually 10 μm or more, preferably 15 μm or more. When the thickness of the separator exceeds the above upper limit, the internal resistance of the battery tends to increase, and when the thickness is below the lower limit, the positive and negative electrodes tend to short-circuit.
本発明のリチウム二次電池の形状は特に制限されず、コイン型、ボタン型、シート型、積層型、円筒型、偏平型、角型のいずれでも良く、また、小型のリチウム二次電池に限らず、電気自動車等に用いる大型のものなどいずれのタイプのものにも適用することができる。 The shape of the lithium secondary battery of the present invention is not particularly limited, and may be any of a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a square type, and is limited to a small lithium secondary battery. Instead, the present invention can be applied to any type such as a large one used for an electric vehicle or the like.
本発明のリチウム二次電池は、携帯情報端末、携帯電子機器、家庭用小型電力貯蔵装置、自動二輪車、電気自動車、ハイブリッド電気自動車等に用いることができるが、特にこれらに限定されるわけではない。 The lithium secondary battery of the present invention can be used for a portable information terminal, a portable electronic device, a small household power storage device, a motorcycle, an electric vehicle, a hybrid electric vehicle, and the like, but is not particularly limited thereto. .
本発明によれば、ＪＩＳ Ｋ５４００粒ゲージ測定による最大分散粒子径が５０μｍ以下の負極活物質を用いることにより、パルスサイクルにおける内部抵抗上昇、負極表面上のリチウム金属析出を有効に抑制することができ、例えば、１０Ｃ（電池容量の１０倍の電気量を１時間でながす電流値）１０秒パルス（１０Ｃ電流を１０秒続ける）充放電を１０万サイクル実施した場合に、その内部抵抗の上昇（換言すれば出力の低下）を１０％以内に収めることができ、リチウム二次電池の高電流値におけるパルス充放電サイクル特性を大幅に改善することができる。 According to the present invention, by using a negative electrode active material having a maximum dispersed particle diameter of 50 μm or less according to JIS K5400 particle gauge measurement, it is possible to effectively suppress an increase in internal resistance in a pulse cycle and precipitation of lithium metal on a negative electrode surface. For example, when charging / discharging is carried out for 100,000 cycles of 10 seconds (current value of 10 times the amount of battery capacity in one hour) (10 C current is maintained for 10 seconds), the internal resistance rises (in other words, (Reduction of the output) can be kept within 10%, and the pulse charge / discharge cycle characteristics at a high current value of the lithium secondary battery can be greatly improved.
従って、本発明によれば、例えば、リチウム二次電池として、１０Ｃの高負荷電流条件でパルス充放電サイクル試験を実施したときに、２０万サイクルを経ても安定して充放電を繰り返し、７０％以上の電池容量回復率を示す、高出力・高入力性のリチウム二次電池が提供される。このような高出力・高入力特性を示す本発明のリチウム二次電池は、上述の幅広いリチウム二次電池の用途のうち、特に、高出力・高入力性が要求される電気ドリルやカッターなどの大型駆動電源や、電気自動車、ハイブリッド電気自動車等、とりわけ、ハイブリッド自動車用のリチウム二次電池として好適である。 Therefore, according to the present invention, for example, when a pulse charge / discharge cycle test is performed under a high load current condition of 10 C as a lithium secondary battery, charge / discharge is repeatedly performed stably even after 200,000 cycles, and 70% A high-output / high-input lithium secondary battery exhibiting the above-described battery capacity recovery rate is provided. The lithium secondary battery of the present invention exhibiting such high output and high input characteristics is particularly suitable for electric drills and cutters that require high output and high input performance among the above-mentioned wide applications of lithium secondary batteries. It is suitable as a large driving power source, an electric vehicle, a hybrid electric vehicle, and the like, particularly, a lithium secondary battery for a hybrid vehicle.
以下に実施例及び比較例を挙げて本発明をより具体的に説明するが、本発明はその要旨を超えない限り、以下の実施例により何ら限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples at all unless the gist of the present invention is exceeded.
実施例１
表１における実施例４に記載される、市販の天然黒鉛粉末と、ナフサ熱分解時に得られる石油系重質油を混合し、不活性ガス中で９００℃の炭化処理を施し、しかる後に焼結物を粉砕・分級処理することにより、黒鉛粒子表面が非晶質炭素で被覆された非晶質被覆黒鉛を得た。分級処理に際しては、粗大粒子の混入を防ぐため、ＡＳＴＭ４００メッシュの篩いを５回繰り返して非晶質被覆黒鉛よりなる負極活物質粉末を得た。残炭率から、得られた負極活物質粉末は、黒鉛１００重量部に対して２重量部の非晶質炭素で被覆されていることが確認された。
Example 1
A commercially available natural graphite powder described in Example 4 in Table 1 and a petroleum heavy oil obtained during naphtha pyrolysis were mixed, carbonized at 900 ° C. in an inert gas, and then sintered. The product was pulverized and classified to obtain amorphous coated graphite in which the graphite particle surface was coated with amorphous carbon. At the time of the classification treatment, in order to prevent mixing of coarse particles, ASTM 400 mesh sieve was repeated five times to obtain a negative electrode active material powder composed of amorphous-coated graphite. From the residual carbon ratio, it was confirmed that the obtained negative electrode active material powder was coated with 2 parts by weight of amorphous carbon based on 100 parts by weight of graphite.
この活物質粉末に対し、以下の手法に従って、Ｘ線測定、ラマン測定、レーザー回折式粒径分布測定、比表面積測定、ＪＩＳ Ｋ５４００ 粒ゲージ測定による各種分析を行った。その結果を表１に記載する。 The active material powder was subjected to various analyzes by X-ray measurement, Raman measurement, laser diffraction particle size distribution measurement, specific surface area measurement, and JIS K5400 particle gauge measurement according to the following methods. Table 1 shows the results.
（１）Ｘ線回折
試料に対して約１５重量％のＸ線標準高純度シリコン粉末を加えて混合し、試料セルに詰め、グラファイトモノクロメーターで単色化したＣｕＫα線を線源とし、反射式ディフラクトメーター法によって、広角Ｘ線回折曲線を測定した。測定により得られた広角Ｘ線回折曲線を学振法に基づき、（００２）面の面間隔（ｄ００２）及びＣ軸方向の結晶子の大きさ（Ｌｃ）を測定した。
(1) X-ray diffraction About 15% by weight of an X-ray standard high-purity silicon powder is added to a sample and mixed, packed into a sample cell, and a CuKα ray monochromatized by a graphite monochromator is used as a radiation source, and a reflection type diffraction is used. The wide-angle X-ray diffraction curve was measured by the fractometer method. Based on the Gakushin method, the wide-angle X-ray diffraction curve obtained by the measurement was used to measure the plane spacing (d 002 ) of the (002) plane and the crystallite size (Lc) in the C-axis direction.
（２）ラマン測定
波長５１４．５ｎｍのアルゴンイオンレーザー光を用いたラマンスペクトル分析において、１５８０〜１６２０ｃｍ-1のピーク強度ＩＡとその半値幅Δν、１３５０〜１３７０ｃｍ-1のピーク強度ＩＢを測定し、その強度の比Ｒ＝ＩＢ／ＩＡを測定した。試料の調製にあたっては、粉末状態のものを自然落下によりセルに充填し、セル内のサンプル表面にレーザー光を照射しながら、セルをレーザー光と垂直な面内で回転させて測定を行った。
(2) Raman measurement In Raman spectrum analysis using an argon ion laser beam having a wavelength of 514.5 nm, a peak intensity IA of 1580 to 1620 cm -1 and a half value width Δν thereof, and a peak intensity IB of 1350 to 1370 cm -1 were measured. The intensity ratio R = IB / IA was measured. In preparing the sample, the powder was filled in the cell by gravity drop, and the cell was rotated in a plane perpendicular to the laser light while irradiating the sample surface in the cell with the laser light.
（３）体積基準平均粒子径・最大粒子径測定
界面活性剤にポリオキシエチレン（２０）ソルビタンモノラウレートの２体積％水溶液を約１ｃｃ用い、これを予め活物質粉末に混合し、しかる後にイオン交換水を分散媒として、レーザー回折式粒度分布計にて、体積基準平均粒子径（Ｄ５０）と最大粒子径（Ｄｍａｘ）を測定した。
(3) Measurement of volume-based average particle diameter and maximum particle diameter About 1 cc of a 2% by volume aqueous solution of polyoxyethylene (20) sorbitan monolaurate was used as a surfactant, and this was mixed in advance with the active material powder, and then ionized. Using exchanged water as a dispersion medium, the volume-based average particle diameter (D 50 ) and the maximum particle diameter (D max ) were measured with a laser diffraction particle size distribution meter.
（４）比表面積測定
予備乾燥として３５０℃に加熱し、１５分間窒素ガスを流した後、窒素ガス吸着による相対圧０．３におけるＢＥＴ１点法によって測定した。
(4) Measurement of specific surface area Heating was performed at 350 ° C. as predrying, nitrogen gas was flowed for 15 minutes, and measurement was performed by a BET one-point method at a relative pressure of 0.3 by nitrogen gas adsorption.
（５）粒ゲージ測定
活物質粉末１００ｇとカルボキシメチルセルロース２ｇと水２００ｇを０．８Ｌの遊星運動式二軸混練機を用いて、公転７８０ｒｐｍ、自転１４４回転、温度２５℃で、３０分間混合した。次に得られた分散液について、ＪＩＳ Ｋ５４００に準拠した粒ゲージ試験器を使用して、粒が現れ始める最大分散粒子径と、粗大粒子が作る線条痕の本数から、３５〜５０μｍ粒数を測定した。また、線条痕の占める割合が、ゲージ幅方向に５０％以上に達する平均分散粒子径を測定した。
(5) Measurement of Particle Gauge 100 g of the active material powder, 2 g of carboxymethylcellulose, and 200 g of water were mixed for 30 minutes at a revolution of 780 rpm, 144 revolutions, and a temperature of 25 ° C. using a 0.8 L planetary motion twin-screw kneader. Next, for the obtained dispersion, using a particle gauge tester based on JIS K5400, from the maximum dispersed particle diameter at which particles begin to appear and the number of streaks formed by coarse particles, the number of particles of 35 to 50 μm was determined. It was measured. The average dispersed particle diameter at which the ratio of the linear streak reached 50% or more in the gauge width direction was measured.
次に得られた非晶質被覆黒鉛粉末を負極活物質として、以下の手順で電池を作製し、以下の手法に従って、負極極板の表面粗さ測定と電池性能評価を行い、結果を表１に示した。 Next, using the obtained amorphous-coated graphite powder as a negative electrode active material, a battery was prepared in the following procedure, and the surface roughness of the negative electrode plate was measured and the battery performance was evaluated according to the following method. It was shown to.
［正極の作製］
正極活物質としてのニッケル酸リチウム（ＬｉＮｉＯ２）９０重量％と、導電剤としてのアセチレンブラック５重量％と、結着剤としてのポリフッ化ビニリデン（ＰＶｄＦ）５重量％とを、Ｎ−メチルピロリドン溶媒中で混合して、スラリー化した後、厚さ２０μｍのアルミ箔の両面に塗布して乾燥し、更にプレス機で７０μｍの厚さとなるように圧延した。これを幅５２mm、長さ８３０mmに切り出し、正極とした。
[Preparation of positive electrode]
90% by weight of lithium nickelate (LiNiO 2 ) as a positive electrode active material, 5% by weight of acetylene black as a conductive agent, and 5% by weight of polyvinylidene fluoride (PVdF) as a binder were mixed with an N-methylpyrrolidone solvent. After mixing in a slurry, the slurry was applied to both sides of a 20-μm-thick aluminum foil, dried, and further rolled to a thickness of 70 μm by a press. This was cut out to a width of 52 mm and a length of 830 mm to obtain a positive electrode.
［負極の作製］
負極活物質９４重量部にカルボキシメチルセルロースとスチレン−ブタジエンゴム（ＳＢＲ）を固形分で各々３重量部となるように加え、蒸留水を分散媒として攪拌混合し、負極活物質スラリーとした。得られたスラリーは、通常既に均一に混合されているが、必要に応じてＡＳＴＭ３２５メッシュ（目開き４３μｍ）の篩で３回濾過（裏ごし）を行った。裏ごしにより、スラリー中にまれに残留している活物質粉体の凝集物を破砕除去することができる。厚さ１８μｍの銅箔上にこの負極活物質スラリーを均一に塗布、乾燥後、更にプレス機で厚み４０μｍに圧延したものを、幅５６mm、長さ８５０mmに切り出し、負極とした。これらの作業は２５℃の環境下で行った。
[Preparation of negative electrode]
Carboxymethylcellulose and styrene-butadiene rubber (SBR) were added to 94 parts by weight of the negative electrode active material so as to have a solid content of 3 parts by weight, respectively, and stirred and mixed with distilled water as a dispersion medium to obtain a negative electrode active material slurry. The obtained slurry is usually already uniformly mixed. However, if necessary, the slurry was filtered (screened) three times through an ASTM 325 mesh (opening: 43 μm) sieve. By the straining, aggregates of the active material powder rarely remaining in the slurry can be crushed and removed. This negative electrode active material slurry was uniformly applied on a copper foil having a thickness of 18 μm, dried, and then rolled to a thickness of 40 μm with a press machine, and cut out into a width of 56 mm and a length of 850 mm to obtain a negative electrode. These operations were performed in an environment at 25 ° C.
［電解液の調製］
乾燥アルゴン雰囲気下で、精製したエチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）及びジエチルカーボネート（ＤＥＣ）の体積比３：３：４の混合溶媒に、１ｍｏｌ／リットルの濃度で、充分に乾燥したヘキサフルオロリン酸リチウム（ＬｉＰＦ６）を電解質として溶解させ、電解液とした。
[Preparation of electrolyte solution]
Under a dry argon atmosphere, in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) in a volume ratio of 3: 3: 4, a sufficiently dried hexagon at a concentration of 1 mol / L was used. Lithium fluorophosphate (LiPF 6 ) was dissolved as an electrolyte to obtain an electrolytic solution.
［電池の組立］
正極と負極は、多孔質ポリエチレンシートのセパレータ（厚さ２５μｍ）をはさんで捲回して電極群とし、電池缶に封入した。その後、電極群を装填した電池缶に上記電解液を５ミリリットル注入し、電極に充分浸透させ、かしめ成形を行って１８６５０型円筒電池を作成した。
[Battery assembly]
The positive electrode and the negative electrode were wound around a separator (thickness: 25 μm) of a porous polyethylene sheet to form an electrode group, which was sealed in a battery can. Thereafter, 5 ml of the above-mentioned electrolyte solution was injected into a battery can in which the electrode group was loaded, sufficiently penetrated the electrodes, and caulked to form a 18650 type cylindrical battery.
（６）負極板の表面粗さ測定
作製した負極について、レーザー顕微鏡を使用して、表面粗さ測定を実施した。レーザー回折式粒径分布計で計測される負極活物質の平均粒子径（Ｄ５０）の１０倍の区間範囲を目安に測定を行い、これを５回繰り返した。実施例１では、１００μｍの区間で測定した。それぞれの測定データに対して、ＪＩＳ Ｂ０６０１Ｂに準拠して、算術平均粗さ（Ｒa）の算出し、それらの平均値を表面粗さ（Ｒa）とした。
(6) Measurement of Surface Roughness of Negative Electrode Plate The surface roughness of the prepared negative electrode was measured using a laser microscope. The measurement was performed with a range of 10 times the average particle diameter (D 50 ) of the negative electrode active material measured by a laser diffraction type particle size distribution meter as a guide, and this was repeated five times. In Example 1, the measurement was performed in a section of 100 μm. Arithmetic average roughness (Ra) was calculated for each measurement data in accordance with JIS B0601B, and the average value was defined as surface roughness (Ra).
（７）電池性能の評価
１）初期充放電
２５℃の室温環境下で充放電（容量確認）を行い、この結果を基にそれぞれのリチウム二次電池の充電状態を５０％に調整した。
２）初期出力評価
２５℃の室温環境下で、１）の状態の電池を、１／４Ｃ、１／２Ｃ、１．０Ｃ、１．５Ｃ、２．５Ｃ、３．０Ｃ（１時間率の放電容量による定格容量を１時間で放電する電流値を１Ｃとする、以下同様）の各電流値で１０秒間定電流放電させ、各条件での放電における１０秒後の電圧降下を測定した。それらの測定値から放電下限電圧を３．０Ｖとした際に、１０秒間流すことのできる電流値Ｉを算出し、３．０×Ｉ（Ｗ）という式で計算される値をそれぞれの電池の初期出力とした。表１には、後述の比較例電池１の出力を１００％としたときの出力比を示す。
３）高温サイクル試験
高温サイクル試験は、リチウム二次電池の実使用上限温度と目される６０℃の高温環境下にて行った。２）で出力評価の終了した電池に対し、充電上限電圧４．１Ｖまで２Ｃの定電流定電圧法で充電した後、放電終止電圧３．０Ｖまで２Ｃの定電流で放電する充放電サイクルを１サイクルとし、このサイクルを５００サイクルまで繰り返した。このときの１サイクル目の放電容量に対する５００サイクル目の放電容量の割合を容量維持率とした。
４）パルスサイクル試験
パルスサイクル試験は、室温環境下２５℃で行った。２）で出力評価の終了した電池を充電状態５０％に調整し、その電圧を中心に、１０Ｃの高負荷電流を充電方向、放電方向ともに約１０秒通電し、休止時間も含め１サイクル１５秒の試験を連続的に繰り返した。１０万サイクル時点で電池を取り出し、次の手順でパルスサイクル後の回復率を算出した。１／２Ｃの電流値で、３．０Ｖまで放電した後、４．１Ｖまで充電し、再び３．０Ｖまで放電した時の放電容量を分子とし、１）の初期充放電での放電容量を分母として、回復率とした。
(7) Evaluation of battery performance 1) Initial charge / discharge Charge / discharge (confirmation of capacity) was performed in a room temperature environment of 25 ° C., and based on the result, the charge state of each lithium secondary battery was adjusted to 50%.
2) Initial output evaluation Under a room temperature environment of 25 ° C., the battery in the state of 1) was discharged at １ ／ C, ２C, 1.0C, 1.5C, 2.5C, 3.0C (1 hour discharge). A constant current was discharged for 10 seconds at each of the following current values (the current value at which the rated capacity according to the capacity was discharged in 1 hour is 1C), and the voltage drop after 10 seconds in the discharge under each condition was measured. When the discharge lower limit voltage is set to 3.0 V, a current value I that can flow for 10 seconds is calculated from the measured values, and the value calculated by the formula of 3.0 × I (W) is calculated for each battery. Initial output. Table 1 shows an output ratio when an output of a comparative example battery 1 described later is set to 100%.
3) High-temperature cycle test The high-temperature cycle test was performed in a high-temperature environment of 60 ° C., which is regarded as the upper limit of the actual use temperature of the lithium secondary battery. The battery whose output has been evaluated in 2) is charged by a constant current / constant voltage method of 2 C up to a charge upper limit voltage of 4.1 V, and then discharged at a constant current of 2 C up to a discharge end voltage of 3.0 V in one charge / discharge cycle. This cycle was repeated up to 500 cycles. At this time, the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle was defined as the capacity retention ratio.
4) Pulse cycle test The pulse cycle test was performed at 25 ° C in a room temperature environment. The battery whose output has been evaluated in 2) is adjusted to a charged state of 50%, and a high load current of 10 C is applied for about 10 seconds in both the charging direction and the discharging direction, centering on the voltage, and 15 seconds per cycle including the pause time. Was repeated continuously. The battery was taken out at the time of 100,000 cycles, and the recovery rate after the pulse cycle was calculated by the following procedure. At a current value of 1/2 C, the battery is discharged to 3.0 V, charged to 4.1 V, and discharged to 3.0 V again. As the recovery rate.
実施例２
黒鉛１００重量部に対して、非晶質炭素８重量部の非晶質被覆黒鉛粉末を製造したこと以外は、実施例１と同様にして負極活物質粉末を調製し、同様に各種評価を行って、結果を表１に示した。
Example 2
A negative electrode active material powder was prepared in the same manner as in Example 1, except that amorphous carbon-coated graphite powder of 8 parts by weight of amorphous carbon was manufactured with respect to 100 parts by weight of graphite, and various evaluations were similarly performed. The results are shown in Table 1.
実施例３
黒鉛１００重量部に対して、非晶質炭素１８重量部の非晶質被覆黒鉛粉末を製造したこと以外は、実施例１と同様にして負極活物質粉末を調製し、同様に各種評価を行って、結果を表１に示した。
Example 3
A negative electrode active material powder was prepared in the same manner as in Example 1 except that amorphous carbon-coated graphite powder of 18 parts by weight of amorphous carbon was manufactured with respect to 100 parts by weight of graphite, and various evaluations were similarly performed. The results are shown in Table 1.
実施例４
市販の天然黒鉛粉末を分級処理したこと以外は、実施例１と同様にして負極活物質粉末を調製し、同様に各種評価を行って、結果を表１に示した。
Example 4
Except that a commercially available natural graphite powder was classified, a negative electrode active material powder was prepared in the same manner as in Example 1, and various evaluations were similarly performed. The results are shown in Table 1.
実施例５
後述の比較例１で調製した粒子径が全体に大きい非晶質被覆黒鉛粉末をＡＳＴＭ４００メッシュの篩に５回通過させて、粗大粒子の除去を精密に行ったこと以外は、実施例１と同様にして負極活物質粉末を調製し、同様に各種評価を行って、結果を表１に示した。
Example 5
Same as Example 1 except that the amorphous-coated graphite powder having a large particle diameter prepared in Comparative Example 1 described below was passed through an ASTM 400 mesh sieve five times to precisely remove coarse particles. The negative electrode active material powder was prepared in the same manner as above, and various evaluations were similarly performed. The results are shown in Table 1.
実施例６
後述の比較例２に記載の、多数の黒鉛微粒子がバインダーピッチの黒鉛化物を介して等方的に結合した人造黒鉛粉末をＡＳＴＭ４００メッシュの篩に５回通過させて、粗大粒子の除去を精密に行ったこと以外は、実施例１と同様にして負極活物質粉末を調製し、同様に各種評価を行って、結果を表１に示した。
Example 6
The artificial graphite powder in which a large number of graphite fine particles areotropically bonded via a graphitized binder pitch as described later in Comparative Example 2 was passed through an ASTM 400 mesh sieve five times to precisely remove coarse particles. Except having performed, a negative electrode active material powder was prepared in the same manner as in Example 1, and various evaluations were similarly performed. The results are shown in Table 1.
実施例７
市販の非晶質炭素粉末を分級処理したこと以外は、実施例１と同様にして負極活物質粉末を調製し、同様に各種評価を行って、結果を表１に示した。
Example 7
Except that a commercially available amorphous carbon powder was classified, a negative electrode active material powder was prepared in the same manner as in Example 1, and various evaluations were similarly performed. The results are shown in Table 1.
比較例1
粒子径が全体に大きい非晶質被覆黒鉛粉末を負極活物質に使用すること以外は、実施例１と同様にして各種評価を行い、結果を表１に示した。
Comparative Example 1
Various evaluations were performed in the same manner as in Example 1 except that the amorphous-coated graphite powder having a large particle diameter was used as the negative electrode active material, and the results are shown in Table 1.
なお、この際、負極活物質スラリーの塗布に先立ち、裏ごし作業を実施したが、篩上には多数の粗大粒子が残留した。しかし、こうした作業だけでは、粗大粒子の除去は十分でなく、粒ゲージ試験では、多数の線条痕がゲージ上に残る結果となった。 At this time, prior to the application of the negative electrode active material slurry, a flattening operation was performed, but a large number of coarse particles remained on the sieve. However, such an operation alone was not enough to remove coarse particles, and the grain gauge test resulted in many streaks remaining on the gauge.
得られた電池は、初期出力が低い値を示した。更にパルスサイクル試験においては、２０万サイクルに到達する前に、測定中に電池電圧が３Ｖ以下に低下し、サイクル測定を中断する結果とった。電圧異常の原因は、電池素子内の局部短絡によるものと推定された。 The obtained battery exhibited a low initial output. Further, in the pulse cycle test, before reaching 200,000 cycles, the battery voltage dropped to 3 V or less during the measurement, and the cycle measurement was interrupted. The cause of the abnormal voltage was presumed to be a local short circuit in the battery element.
比較例２
バインダーピッチ中に黒鉛微粒子を多数分散させ、黒鉛化と粉体加工処理を施し、黒鉛化物がバインダーピッチの黒鉛化物を介して等方的に結合した人造黒鉛粉末を作成した。この人造黒鉛粉末を負極活物質粉末としたこと以外は、実施例１と同様にして各種評価を行い、結果を表１に示した。
Comparative Example 2
A large number of graphite fine particles were dispersed in the binder pitch, subjected to graphitization and powder processing, and an artificial graphite powder in which the graphitized material was isotropically bonded via the graphitized binder pitch was prepared. Various evaluations were performed in the same manner as in Example 1 except that this artificial graphite powder was used as the negative electrode active material powder. The results are shown in Table 1.
得られた電池は、比較例１と同様に、パルスサイクル試験が途中中断する結果となった。 In the obtained battery, similarly to Comparative Example 1, the pulse cycle test was interrupted halfway.
比較例３
比較例１に記載の粒子径が全体に大きい非晶質被覆黒鉛粉末をＡＳＴＭ４００メッシュの篩に１回通過させたものを負極活物質粉末としたこと以外は、実施例１と同様にして各種評価を行い、結果を表１に示した。
Comparative Example 3
Various evaluations were performed in the same manner as in Example 1 except that the amorphous coated graphite powder having a large particle diameter described in Comparative Example 1 was passed once through an ASTM 400 mesh sieve to obtain a negative electrode active material powder. And the results are shown in Table 1.
得られた電池は、比較例１と同様に、パルスサイクル試験が途中中断する結果となった。 In the obtained battery, similarly to Comparative Example 1, the pulse cycle test was interrupted halfway.
Claims (4)
該活物質粉末１００ｇを２ｇのカルボキシメチルセルロースと共に２００ｇの水に分散させてなる分散液について、ＪＩＳ Ｋ５４００ 粒ゲージ法による分散度に準拠して測定される、粒が現れ始める粒子径が、５０μｍ以下であることを特徴とするリチウム二次電池用負極活物質。 In the negative electrode active material for a lithium secondary battery in the form of carbonaceous powder,
For a dispersion obtained by dispersing 100 g of the active material powder in 200 g of water together with 2 g of carboxymethylcellulose, the particle diameter at which the particles begin to appear, measured according to the degree of dispersion according to JIS K5400 particle gauge method, is 50 μm or less. A negative electrode active material for a lithium secondary battery, comprising:
該活物質層の厚さが５０μｍ以下であり、ＪＩＳ Ｂ０６０１に準拠して測定される算術平均粗さ（Ｒa）が５μｍ以下であることを特徴とするリチウム二次電池負極。 On a current collector, an active material and an active material layer containing an organic material having a binding and thickening effect, in a lithium secondary battery negative electrode,
A negative electrode for a lithium secondary battery, wherein the thickness of the active material layer is 50 μm or less, and the arithmetic average roughness (Ra) measured according to JIS B0601 is 5 μm or less.
該負極として、請求項３に記載のリチウム二次電池負極を用いたことを特徴とするリチウム二次電池。 In a positive electrode capable of storing and releasing lithium, a negative electrode capable of storing and releasing lithium, and a lithium secondary battery having an electrolyte,
A lithium secondary battery using the lithium secondary battery negative electrode according to claim 3 as the negative electrode.
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| JP2006202499A (en) * | 2005-01-18 | 2006-08-03 | Dainippon Printing Co Ltd | Electroluminescence element |
| JP4508882B2 (en) * | 2005-01-18 | 2010-07-21 | 大日本印刷株式会社 | Electroluminescence element |
| JP2007087814A (en) * | 2005-09-22 | 2007-04-05 | Toyota Motor Corp | Lithium secondary battery |
| JP2009545875A (en) * | 2006-07-31 | 2009-12-24 | エルジー・ケム・リミテッド | Capacitor-battery hybrid electrode assembly |
| US8574736B2 (en) | 2006-07-31 | 2013-11-05 | Lg Chem, Ltd. | Hybrid-typed electrode assembly of capacitor-battery structure |
| JP2009123715A (en) * | 2007-06-28 | 2009-06-04 | Hitachi Maxell Ltd | Lithium ion secondary battery |
| WO2009157507A1 (en) * | 2008-06-25 | 2009-12-30 | 日立マクセル株式会社 | Lithium ion secondary cell |
| JP2010034024A (en) * | 2008-06-25 | 2010-02-12 | Hitachi Maxell Ltd | Lithium-ion secondary battery |
| JP2010113874A (en) * | 2008-11-05 | 2010-05-20 | Furukawa Battery Co Ltd:The | Method for manufacturing positive electrode for lithium secondary battery, and lithium secondary battery |
| US8617508B2 (en) | 2009-09-18 | 2013-12-31 | Jx Nippon Oil & Energy Corporation | Carbon material for negative electrode of lithium secondary battery and method for producing the same |
| WO2011034152A1 (en) * | 2009-09-18 | 2011-03-24 | Ｊｘ日鉱日石エネルギー株式会社 | Negative electrode carbon material for lithium secondary battery and method for manufacturing same |
| JP2011146365A (en) * | 2009-12-14 | 2011-07-28 | Hitachi Maxell Energy Ltd | Electrochemical element |
| JP2013229300A (en) * | 2012-03-27 | 2013-11-07 | Tdk Corp | Lithium ion secondary battery |
| JPWO2015152093A1 (en) * | 2014-03-31 | 2017-04-13 | 株式会社クレハ | Non-aqueous electrolyte secondary battery negative electrode carbonaceous material, non-aqueous electrolyte secondary battery negative electrode, non-aqueous electrolyte secondary battery and vehicle |
| JP2016181409A (en) * | 2015-03-24 | 2016-10-13 | 株式会社Ｇｓユアサ | Power storage element |
| JPWO2018128179A1 (en) * | 2017-01-06 | 2019-01-10 | 日立化成株式会社 | Negative electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery, and lithium ion secondary battery |
| CN110168787A (en) * | 2017-01-06 | 2019-08-23 | 日立化成株式会社 | Lithium ion secondary battery cathode material, lithium ion secondary battery cathode and lithium ion secondary battery |
| CN110168787B (en) * | 2017-01-06 | 2022-05-03 | 昭和电工材料株式会社 | Negative electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery, and lithium ion secondary battery |
| CN113871733A (en) * | 2021-08-31 | 2021-12-31 | 湖南立方新能源科技有限责任公司 | Lithium supplementing method for diaphragm and application thereof |
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