JP6412520B2 - Carbonaceous coated graphite particles for lithium ion secondary battery anode material, lithium ion secondary battery anode and lithium ion secondary battery - Google Patents

Carbonaceous coated graphite particles for lithium ion secondary battery anode material, lithium ion secondary battery anode and lithium ion secondary battery Download PDF

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JP6412520B2
JP6412520B2 JP2016095119A JP2016095119A JP6412520B2 JP 6412520 B2 JP6412520 B2 JP 6412520B2 JP 2016095119 A JP2016095119 A JP 2016095119A JP 2016095119 A JP2016095119 A JP 2016095119A JP 6412520 B2 JP6412520 B2 JP 6412520B2
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negative electrode
secondary battery
lithium ion
ion secondary
graphite particles
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JP2016225287A (en
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間所　靖
靖 間所
江口　邦彦
邦彦 江口
哲夫 塩出
哲夫 塩出
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JFE Chemical Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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

Description

本発明は、リチウムイオン二次電池負極材料用炭素質被覆黒鉛粒子、リチウムイオン二次電池用負極およびその負極を用いたリチウムイオン二次電池に関する。   The present invention relates to a carbon-coated graphite particle for a lithium ion secondary battery negative electrode material, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery using the negative electrode.

リチウムイオン二次電池は携帯電子機器に広く搭載されており、ハイブリッド自動車や電気自動車への利用も始まっている。このような状況の中で、リチウムイオン二次電池には一層の高容量、高速充放電特性、サイクル特性が要求されている。
リチウムイオン二次電池は、負極、正極および非水電解質を主たる構成要素としており、リチウムイオンが放電過程および充電過程で負極と正極との間を移動することで二次電池として作用する。現在、上記負極材料には黒鉛が広く用いられている。黒鉛は天然黒鉛と人造黒鉛に大別される。天然黒鉛は結晶性が高く容量が高いという利点を有するが、鱗片形状ゆえ電極内で粒子が一方向に配向してしまい、高速充放電特性やサイクル特性に劣るという欠点があった。 Lithium ion secondary batteries are widely used in portable electronic devices, and have started to be used in hybrid and electric vehicles. Under such circumstances, lithium ion secondary batteries are required to have higher capacity, faster charge / discharge characteristics, and cycle characteristics.
The lithium ion secondary battery has a negative electrode, a positive electrode, and a non-aqueous electrolyte as main components, and acts as a secondary battery by moving lithium ions between the negative electrode and the positive electrode during a discharging process and a charging process. Currently, graphite is widely used as the negative electrode material. Graphite is roughly classified into natural graphite and artificial graphite. Natural graphite has the advantage of high crystallinity and high capacity, but due to the scale shape, the particles are oriented in one direction within the electrode, resulting in inferior high-speed charge / discharge characteristics and cycle characteristics.

これを補うために、鱗片形状の黒鉛を球状に加工し、さらに表面被覆処理を施した材料が多く提案されている。球状化された天然黒鉛の表面には電解液との反応性が高いエッジ面が少なからず露出しており、被覆の目的はそのエッジ面を封止し、副反応を抑制することである。近年、携帯機器の大型化などにともない電池のさらなる高エネルギー密度化が求められており、それにともない負極に対してもさらなる高密度化が可能であることが求められている。しかしながら従来の被覆天然黒鉛においては被覆層の強度が十分ではなく、高密度化によって被覆層に割れや亀裂などを生じてしまい、結果として初期効率やサイクル特性などが低下してしまうという問題があった。   In order to compensate for this, many materials have been proposed in which scaly graphite is processed into a spherical shape and surface-treated. The surface of the spheroidized natural graphite has an exposed edge surface that is highly reactive with the electrolytic solution. The purpose of coating is to seal the edge surface and suppress side reactions. In recent years, there has been a demand for higher energy density of batteries with the increase in size of portable devices, and accordingly, further increase in the density of negative electrodes is also required. However, in the conventional coated natural graphite, the strength of the coating layer is not sufficient, and cracking or cracking occurs in the coating layer due to the increase in density, resulting in a decrease in initial efficiency and cycle characteristics. It was.

これに対して特許文献１には、球形化黒鉛を等方的に加圧することを特徴とするリチウムイオン二次電池負極材料の製造方法が開示されている。また特許文献２には、天然黒鉛球状化粒子および／または天然黒鉛塊状化粒子が加圧処理された加圧黒鉛粒子の表面に炭化物からなる被覆層が形成されていることを特徴とするリチウムイオン二次電池用黒鉛材料が開示されている。
これらは高密度で等方性の高い黒鉛粒子を負極材料に用いる効果として、同一負極密度では黒鉛粒子間の空隙が広くなるので電解液の通液性を向上できること、またプレス成形して負極を作製しても黒鉛の結晶構造が配向しにくく電解液の通液性を損なうことがないこと、を説明している。
しかしながらこれらの方法を用いても、電池性能の改良効果はまだ十分とは言えない状況である。 On the other hand, Patent Document 1 discloses a method for producing a negative electrode material for a lithium ion secondary battery, characterized in that spheroidized graphite is isotropically pressurized. Patent Document 2 discloses a lithium ion characterized in that a coating layer made of carbide is formed on the surface of pressurized graphite particles obtained by pressurizing natural graphite spheroidized particles and / or natural graphite agglomerated particles. A graphite material for a secondary battery is disclosed.
These are the effects of using high density and highly isotropic graphite particles in the negative electrode material. The gap between the graphite particles is widened at the same negative electrode density, so that the liquid permeability of the electrolyte can be improved. It explains that the crystal structure of graphite is difficult to be oriented even when fabricated, and the liquid permeability of the electrolytic solution is not impaired.
However, even if these methods are used, the effect of improving the battery performance is not yet sufficient.

特許第４４９９４９８号公報Japanese Patent No. 4499498 特開２０１１−６０４６５号公報JP 2011-60465 A

本発明は上記の事情に鑑みてなされたものである。すなわち、リチウムイオン二次電池負極材料に用いた場合に、優れた電池特性を得ることが可能な負極材料を提供することを目的とする。また、その負極材料の製造方法と、その負極材料を含有する負極、およびその負極を用いたリチウムイオン二次電池を提供することを目的とする。ここで、優れた電池特性とは、高い放電容量、高い初回充放電効率、高い高速充放電特性および優れたサイクル特性である。   The present invention has been made in view of the above circumstances. That is, it aims at providing the negative electrode material which can acquire the outstanding battery characteristic, when it uses for a lithium ion secondary battery negative electrode material. Moreover, it aims at providing the manufacturing method of the negative electrode material, the negative electrode containing the negative electrode material, and the lithium ion secondary battery using the negative electrode. Here, the excellent battery characteristics are high discharge capacity, high initial charge / discharge efficiency, high high-speed charge / discharge characteristics, and excellent cycle characteristics.

本発明は、球状または楕円体状の黒鉛粒子を芯材として、該芯材が異方的に加圧してなる黒鉛芯材であり、該芯材の表面の少なくとも一部に炭素質からなる被覆層を有する炭素質被覆黒鉛粒子であることを特徴とするリチウムイオン二次電池負極材料用の炭素質被覆黒鉛粒子である。
リチウムイオン二次電池の負極はその製造工程において、設計された電極密度を実現するためにプレス成形がなされる。通常そのプレス成形にはロールプレスが用いられており、電極を構成する負極材料に対しては異方的な圧力が加わる。本発明はこの点に着目してなされたものであり、すなわち負極材料に予め異方的な加圧処理を施しておくことで、負極を作製する際のプレス成形による粒子の変形、およびそれにともなう被覆層の損傷を抑制し、電極密度を高密度にしても高い初回充放電効率や高速充放電特性、およびサイクル特性を維持することができる。 The present invention relates to a graphite core material in which spherical or ellipsoidal graphite particles are used as a core material, and the core material is anisotropically pressed, and at least a part of the surface of the core material is coated with carbonaceous material. It is carbonaceous covering graphite particle for lithium ion secondary battery negative electrode materials characterized by being carbonaceous covering graphite particle which has a layer.
The negative electrode of the lithium ion secondary battery is press-molded in the manufacturing process in order to realize the designed electrode density. Usually, a roll press is used for the press molding, and an anisotropic pressure is applied to the negative electrode material constituting the electrode. The present invention has been made paying attention to this point, that is, by subjecting the negative electrode material to anisotropic pressure treatment in advance, deformation of the particles due to press molding at the time of producing the negative electrode, and accompanying it Damage to the coating layer can be suppressed, and high initial charge / discharge efficiency, high-speed charge / discharge characteristics, and cycle characteristics can be maintained even when the electrode density is increased.

本発明の炭素質被覆黒鉛粒子は、リチウムイオン二次電池負極材料として良好な放電容量、初回充放電効率、高速充放電特性およびサイクル特性を同時に満たす。そのため、本発明の負極材料を用いてなるリチウムイオン二次電池は、近年の電池の高エネルギー高密度化に対する要望を満たし、搭載する機器の小型化および高性能化に有用である。   The carbonaceous coated graphite particles of the present invention simultaneously satisfy good discharge capacity, initial charge / discharge efficiency, high-speed charge / discharge characteristics, and cycle characteristics as a negative electrode material for a lithium ion secondary battery. Therefore, the lithium ion secondary battery using the negative electrode material of the present invention satisfies the recent demand for higher energy density of the battery, and is useful for downsizing and higher performance of the mounted device.

本発明の負極の電池特性を評価するための評価電池の断面図である。It is sectional drawing of the evaluation battery for evaluating the battery characteristic of the negative electrode of this invention.

以下、本発明をより具体的に説明する。
１．黒鉛質粒子
〔球状および／または楕円体状黒鉛〕
本発明の黒鉛質粒子の原料は、球状または楕円体状の平均粒径１〜５０μｍ、好ましくは平均アスペクト比５以下、平均粒径５〜３０μｍの範囲である黒鉛粒子を用いる。平均アスペクト比２以下、平均比表面積は１０ｍ2／ｇ以下であることがより好ましく、８ｍ2／ｇ以下であることが特に好ましい。 Hereinafter, the present invention will be described more specifically.
1. Graphite particles (spherical and / or ellipsoidal graphite)
As the raw material of the graphite particles of the present invention, graphite particles having a spherical or ellipsoidal average particle diameter of 1 to 50 μm, preferably an average aspect ratio of 5 or less and an average particle diameter of 5 to 30 μm are used. The average aspect ratio is 2 or less and the average specific surface area is more preferably 10 m 2 / g or less, and particularly preferably 8 m 2 / g or less.

市販品の球状または楕円体状に加工された天然黒鉛粒子を用いることもできる。球状または楕円体状以外の形状の天然黒鉛、例えば鱗片状の黒鉛粒子の場合は、天然の鱗片状黒鉛を、機械的外力で造粒球状化して球状黒鉛粒子とする。球状または楕円体状に加工する方法は、例えば、接着剤や樹脂などの造粒助剤の共存下で複数の鱗片状黒鉛を混合する方法、複数の鱗片状の黒鉛に接着剤を用いずに機械的外力を加える方法、両者の併用などが挙げられる。しかし、造粒助剤を用いずに機械的外力を加えて球状に造粒する方法が最も好ましい。機械的外力とは、機械的に粉砕および造粒することであり、鱗片状黒鉛を造粒して球状化することができる。鱗片状黒鉛の粉砕装置としては、例えば、加圧ニーダー、二本ロールなどの混練機、回転ボールミル、カウンタジェットミル（ホソカワミクロン（株）製）、カレントジェット（日清エンジニアリング（株）製）などの粉砕装置が使用可能である。
上記粉砕品は、その表面が鋭角な部分を有しているが、粉砕品を造粒球状化して使用しても良い。粉砕品の造粒球状化装置としては、例えば、ＧＲＡＮＵＲＥＸ（フロイント産業（株）製）、ニューグラマシン（（株）セイシン企業）、アグロマスター（ホソカワミクロン（株）製）などの造粒機、ハイブリダイゼーション（（株）奈良機械製作所製）、メカノマイクロス（（株）奈良機械製作所製）、メカノフュージョンシステム（ホソカワミクロン（株）製）などのせん断圧縮加工装置が使用可能である。 Commercially available natural graphite particles processed into a spherical or ellipsoidal shape can also be used. In the case of natural graphite having a shape other than spherical or ellipsoidal shape, for example, flaky graphite particles, natural flaky graphite is granulated by mechanical external force to obtain spherical graphite particles. The method of processing into a spherical or ellipsoidal shape is, for example, a method of mixing a plurality of scaly graphites in the presence of a granulating aid such as an adhesive or a resin, without using an adhesive for a plurality of scaly graphites. Examples include a method of applying a mechanical external force, a combination of both. However, the most preferable method is to apply a mechanical external force to granulate into a spherical shape without using a granulating aid. The mechanical external force is mechanically pulverizing and granulating, and scaly graphite can be granulated and spheroidized. Examples of the flaky graphite crusher include a pressure kneader, a kneader such as a two-roll mill, a rotating ball mill, a counter jet mill (manufactured by Hosokawa Micron Corporation), a current jet (manufactured by Nisshin Engineering Co., Ltd.), and the like. A grinding device can be used.
The pulverized product has an acute-angled surface, but the pulverized product may be granulated and used. Examples of granulated spheroidizers for pulverized products include granulators such as GRANUREX (manufactured by Freund Sangyo Co., Ltd.), Newgra Machine (manufactured by Seisin Co., Ltd.), Agromaster (manufactured by Hosokawa Micron Co., Ltd.), and hybridization. Shear compression processing apparatuses such as (manufactured by Nara Machinery Co., Ltd.), mechanomicros (manufactured by Nara Machinery Co., Ltd.), and mechanofusion system (manufactured by Hosokawa Micron Co., Ltd.) can be used.

本発明の黒鉛質粒子のＸ線回折の測定値であるＬｃは４０ｎｍ以上、Ｌａは４０ｎｍ以上が好ましい。ここで、Ｌｃは黒鉛構造のｃ軸方向の結晶子の大きさＬｃ（００２）、Ｌａはａ軸方向の結晶子の大きさＬａ（１１０）である。ｄ００２が０．３３７ｎｍ以下、アルゴンレーザーを用いたラマン分光法により測定した１３６０ｃｍ-1ピーク強度（Ｉ1360）と１５８０ｃｍ-1ピーク強度（Ｉ1580）の比Ｉ1360／Ｉ1580（Ｒ値）が０．０６〜０．３０、および１５８０ｃｍ-1バンドの半値幅が１０〜６０であるのが好ましい。 Lc, which is a measured value of X-ray diffraction of the graphite particles of the present invention, is preferably 40 nm or more, and La is preferably 40 nm or more. Here, Lc is the crystallite size Lc (002) in the c-axis direction of the graphite structure, and La is the crystallite size La (110) in the a-axis direction. d002 is 0.337 nm or less, and the ratio I 1360 / I 1580 (R value) of 1360 cm −1 peak intensity (I 1360 ) and 1580 cm −1 peak intensity (I 1580 ) measured by Raman spectroscopy using an argon laser is 0. It is preferable that the half widths of the 0.06 to 0.30 and 1580 cm −1 bands are 10 to 60.

〔異方的に加圧してなる黒鉛質粒子〕
本発明の黒鉛質粒子は、上記球状または楕円体状黒鉛を異方的に加圧してなる。結果として本発明の黒鉛質粒子は異方的に加圧された方向では密度が高くその直角方向では密度が低い配向性を有している。
本発明の黒鉛質粒子は、水銀圧入法で測定した５００ｎｍ以下の大きさの細孔容積が０．１００ｍＬ／ｇ以下が好ましく、または水銀圧入法で測定した１００〜２００ｎｍの大きさの細孔容積が０．０２ｍＬ／ｇ以下であることが好ましい。この範囲を超えると負極を作製する際の結着材が該細孔に浸透してしまい、電極剥離強度が低下するおそれがある。 [Graphic particles formed by anisotropic pressure]
The graphite particles of the present invention are formed by anisotropically pressing the spherical or ellipsoidal graphite. As a result, the graphite particles of the present invention have an orientation in which the density is high in the anisotropically pressed direction and the density is low in the perpendicular direction.
The graphite particles of the present invention preferably have a pore volume of 500 nm or less as measured by mercury intrusion method of 0.100 mL / g or less, or a pore volume of 100 to 200 nm as measured by mercury intrusion method. Is preferably 0.02 mL / g or less. If this range is exceeded, the binder used to produce the negative electrode may permeate into the pores, which may reduce the electrode peel strength.

２．炭素質被覆黒鉛粒子
本発明のリチウムイオン二次電池負極材料用炭素質被覆黒鉛粒子は、上述した異方的に加圧してなる黒鉛質粒子の表面の少なくとも一部に炭素質材料を有する。すなわち、該黒鉛質粒子の表面の少なくとも一部が炭素質材料で被覆されている。その製造方法は限定されないが、好ましくは炭素質前駆体を原料として後述する製造方法によって、黒鉛質粒子の表面の少なくとも一部が炭素質材料で被覆される。用いられる炭素質材料の前駆体としては、タールピッチ類および／または樹脂類が例示される。具体的には、重質油、特にタールピッチ類としては、コールタール、タール軽油、タール中油、タール重油、ナフタリン油、アントラセン油、コールタールピッチ、ピッチ油、メソフェーズピッチ、酸素架橋石油ピッチ、ヘビーオイルなどが挙げられる。樹脂類としては、ポリビニルアルコール、ポリアクリル酸などの熱可塑性樹脂、フェノール樹脂、フラン樹脂などの熱硬化性樹脂が例示される。好ましくは樹脂類を含まず、タールピッチ類のみとするとコスト的に有利である。炭素質材料の前駆体は上記に例示したいかなるものを用いてもよいが、コールタールピッチが８０質量％以上であるのが特に好ましい。 2. Carbonaceous coated graphite particles The carbonaceous coated graphite particles for a negative electrode material of a lithium ion secondary battery of the present invention have a carbonaceous material on at least a part of the surface of the above-mentioned anisotropically pressed graphite particles. That is, at least a part of the surface of the graphite particles is covered with the carbonaceous material. Although the manufacturing method is not limited, Preferably, at least a part of the surface of the graphite particles is coated with a carbonaceous material by a manufacturing method described later using a carbonaceous precursor as a raw material. Examples of the precursor of the carbonaceous material used include tar pitches and / or resins. Specifically, heavy oils, particularly tar pitches, include coal tar, tar light oil, tar medium oil, tar heavy oil, naphthalene oil, anthracene oil, coal tar pitch, pitch oil, mesophase pitch, oxygen-crosslinked petroleum pitch, heavy Examples include oil. Examples of the resins include thermoplastic resins such as polyvinyl alcohol and polyacrylic acid, and thermosetting resins such as phenol resins and furan resins. It is advantageous in terms of cost if only tar pitches are used without containing resins. Any of the carbonaceous material precursors exemplified above may be used, but the coal tar pitch is particularly preferably 80% by mass or more.

本発明の炭素質被覆黒鉛粒子において、炭素質材料の含有量は、炭素質被覆黒鉛粒子中の黒鉛質粒子１００質量部に対して０．１〜３．０質量部である。炭素質材料の含有量が０．１質量部未満の場合は、活性な黒鉛エッヂ面を完全に被覆することが難しくなり、初回充放電効率が低下することがある。一方、３．０質量部を越える場合には、相対的に放電容量の低い炭素材料の割合が高すぎて、炭素質被覆黒鉛粒子の放電容量が低下する。また、炭素質材料を形成するための原料（熱硬化性樹脂類やタールピッチ類）の割合が多く、被覆工程やその後の熱処理工程において、粒子が融着しやすく、最終的に得られる炭素質被覆黒鉛粒子の炭素質材料層の一部に割れや剥離を生じ、初期充放電効率の低下を生じることがある。炭素質材料の含有量は、炭素質被覆黒鉛粒子中の黒鉛質粒子１００質量部に対して、０．３〜３．０質量部、さらには１．０〜３．０質量部であることが好ましい。なお、炭素質材料の含有量は炭素質被覆黒鉛粒子全体の平均として上記範囲内にあればよい。個々の粒子全てが上記範囲内にある必要はなく、上記範囲以外の粒子を一部含んでいてもよい。   In the carbonaceous coated graphite particles of the present invention, the content of the carbonaceous material is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the graphite particles in the carbonaceous coated graphite particles. When the content of the carbonaceous material is less than 0.1 parts by mass, it is difficult to completely cover the active graphite edge surface, and the initial charge / discharge efficiency may be lowered. On the other hand, when it exceeds 3.0 parts by mass, the ratio of the carbon material having a relatively low discharge capacity is too high, and the discharge capacity of the carbonaceous coated graphite particles is lowered. In addition, the ratio of raw materials (thermosetting resins and tar pitches) for forming the carbonaceous material is large, and the particles are easily fused in the coating process and the subsequent heat treatment process. In some cases, a part of the carbonaceous material layer of the coated graphite particles is cracked or peeled off, resulting in a decrease in initial charge / discharge efficiency. The content of the carbonaceous material is 0.3 to 3.0 parts by mass, and further 1.0 to 3.0 parts by mass with respect to 100 parts by mass of the graphite particles in the carbonaceous coated graphite particles. preferable. The content of the carbonaceous material may be in the above range as an average of the entire carbonaceous coated graphite particles. It is not necessary that all the individual particles are within the above range, and some particles outside the above range may be included.

また本発明の炭素質被覆黒鉛粒子は、水銀ポロシメータで測定した細孔径１．１μｍ以下の細孔容積は０．１００ｍＬ／ｇ以下であり、かつ該細孔容積に対する細孔径０．５４μｍ以下の細孔容積の比率は８０％以上である。細孔径１．１μｍ以下の細孔容積が０．１００ｍＬ／ｇを超える場合には、負極を作製する際の結着材が該細孔に浸透してしまい、電極剥離強度が低下し、サイクル特性が低下するおそれがある。また該細孔容積に対する細孔径０．５４μｍ以下の細孔容積の比率が８０％未満の場合にも、やはり負極を作製する際の結着材が該細孔に浸透してしまい、十分な電極剥離強度が得られず、サイクル特性が低下するおそれがある。
本発明の炭素質被覆黒鉛質粒子は、水銀ポロシメータで測定した細孔径１．１μｍ以下の細孔容積が０．０９０ｍＬ／ｇ以下であることが好ましく、０．０８５ｍＬ／ｇ以下であることがさらに好ましい。
本発明の炭素質被覆黒鉛質粒子は、該細孔容積（細孔径１．１μｍ以下の細孔容積）に対する細孔径０．５４μｍ以下の細孔容積の比率は８１％以上であることが好ましく、８２％以上であることがさらに好ましい。 The carbon-coated graphite particles of the present invention have a pore volume of not more than 0.100 mL / g and a pore diameter of not more than 0.54 μm with respect to the pore volume, as measured with a mercury porosimeter. The ratio of the pore volume is 80% or more. When the pore volume with a pore diameter of 1.1 μm or less exceeds 0.100 mL / g, the binder used in the production of the negative electrode penetrates into the pores, and the electrode peel strength decreases, resulting in cycle characteristics. May decrease. In addition, even when the ratio of the pore volume with a pore diameter of 0.54 μm or less to the pore volume is less than 80%, the binder used in the production of the negative electrode also penetrates into the pores, and the sufficient electrode The peel strength cannot be obtained, and the cycle characteristics may be deteriorated.
The carbon-coated graphite particles of the present invention preferably have a pore volume of 1.1 μm or less as measured with a mercury porosimeter of 0.090 mL / g or less, and more preferably 0.085 mL / g or less. preferable.
In the carbon-coated graphite particles of the present invention, the ratio of the pore volume having a pore diameter of 0.54 μm or less to the pore volume (pore volume having a pore diameter of 1.1 μm or less) is preferably 81% or more, More preferably, it is 82% or more.

また本発明の炭素質被覆黒鉛粒子のフタル酸ジブチル（ＤＢＰ）吸油量は３６．１〜４０．０ｍＬ／１００ｇである。この数値範囲外の場合には、負極を作製する際の結着材が該細孔に浸透してしまい、電極剥離強度が低下し、サイクル特性が低下するおそれがある。
また本発明の黒鉛質粒子は、フタル酸ジブチル（ＤＢＰ）吸油量が３６．１〜３８．０ｍＬ／１００ｇであることが好ましく、３６．１〜３７．０ｍＬ／１００ｇであることがさらに好ましい。 The carbonaceous dibutylphthalate (DBP) oil absorption of the coated graphite particles of the present invention is 36.1~ 40.0mL / 100g. When the value is outside this numerical range , the binder used in the production of the negative electrode penetrates into the pores, and the electrode peel strength is lowered and the cycle characteristics may be lowered .
The graphite particles of the present invention is preferably dibutyl phthalate (DBP) oil absorption amount is 36.1~ 38.0mL / 100g, further preferably 36.1~ 37.0mL / 100g.

最終製品である炭素質被覆黒鉛粒子の平均粒子径は１〜５０μｍの範囲であることが好ましく、５〜３０μｍの範囲であることがさらに好ましい。ＢＥＴ法により測定した比表面積は６．０ｍ2／ｇ以下であることが好ましく、４．０ｍ2／ｇ以下であることがさらに好ましい。
また、上記炭素質被覆黒鉛粒子が、アルゴンレーザーを用いたラマン分光法により測定した１３６０ｃｍ-1ピーク強度（Ｉ1360）と１５８０ｃｍ-1ピーク強度（Ｉ1580）の比Ｉ1360／Ｉ1580（Ｒ値）が黒鉛のＲ値より大きく、０．０５〜０．８０であることが好ましい。 The average particle diameter of the carbon-coated graphite particles as the final product is preferably in the range of 1 to 50 μm, and more preferably in the range of 5 to 30 μm. The specific surface area measured by the BET method is preferably 6.0 m 2 / g or less, and more preferably 4.0 m 2 / g or less.
The carbon-coated graphite particles had a ratio I 1360 / I 1580 (R value) of 1360 cm −1 peak intensity (I 1360 ) and 1580 cm −1 peak intensity (I 1580 ) measured by Raman spectroscopy using an argon laser. ) Is larger than the R value of graphite and is preferably 0.05 to 0.80.

３．炭素質被覆黒鉛粒子の製造方法
〔加圧工程〕
本発明の炭素質被覆黒鉛粒子の製造方法は、限定されないが、好ましくはまず上述した球状および／または楕円体状黒鉛に異方的な加圧処理を行う。異方的な加圧処理とは圧力を特定の方向に掛けることをいい、等方的加圧ではないことをいう。等方的加圧は例えば、ガス、液体などの加圧媒体を用いて等方的に加圧する方法であり、後述する比較例２，３では冷間静水圧プレスを使用した。
異方的加圧は、好ましくは一方向または二方向からの加圧である。異方的加圧の方法は特に限定されず、例えば金型プレス、ロールプレス、押出成形などが挙げられ、通常は常温、空気中で行う。加圧力や異方的な方向は限定されないが、炭素質被覆黒鉛粒子をリチウムイオン二次電池負極材料に用いる際の負極形成工程の加圧力、異方的な加圧方向に相当する程度で行うのが好ましい。加圧力については、例えば、内容積が２０００〜３０００ｃｍ3の金型に５〜１０ｃｍ高さで充填し圧力４０〜３００ＭＰａで加圧する。 3. Method for producing carbon-coated graphite particles (pressurizing step)
The method for producing the carbonaceous coated graphite particles of the present invention is not limited, but preferably, the above-mentioned spherical and / or ellipsoidal graphite is first subjected to anisotropic pressure treatment. Anisotropic pressurization means applying a pressure in a specific direction, not an isotropic pressurization. Isotropic pressurization is, for example, a method of isotropic pressurization using a pressurizing medium such as gas or liquid. In Comparative Examples 2 and 3 described later, a cold isostatic press was used.
The anisotropic pressurization is preferably pressurization from one direction or two directions. The method of anisotropic pressurization is not particularly limited, and examples thereof include a mold press, a roll press, and extrusion molding. The applied pressure and the anisotropic direction are not limited, but are performed to the extent corresponding to the applied pressure in the negative electrode forming step when the carbonaceous coated graphite particles are used for the negative electrode material of the lithium ion secondary battery and the anisotropic pressure direction. Is preferred. As for the applied pressure, for example, a mold having an internal volume of 2000 to 3000 cm 3 is filled at a height of 5 to 10 cm and pressurized at a pressure of 40 to 300 MPa.

加圧処理で固着を生じた場合などは、必要に応じて、加圧処理のあとに解砕工程を導入してもよい。加圧処理の際、炭素質または黒鉛質の繊維、非晶質ハードカーボンなどの炭素質前駆体材料、有機材料、無機材料、金属材料を加えてもよいし加えなくてもよい。加えた場合は加圧方向と非加圧方向との組合せが複雑となりそのため加圧結果が等方的加圧により近くなる。加えない場合は加圧結果がより単純になり加圧方向と非加圧方向との配向性の差が加圧処理時に他の材料を加えた場合より大きくなる。   When fixing is caused by the pressure treatment, a crushing step may be introduced after the pressure treatment, if necessary. During the pressure treatment, carbonaceous or graphite fibers, carbonaceous precursor materials such as amorphous hard carbon, organic materials, inorganic materials, and metal materials may or may not be added. When added, the combination of the pressurizing direction and the non-pressurizing direction becomes complicated, so that the pressurization result becomes closer to isotropic pressurization. When not added, the pressing result becomes simpler and the difference in orientation between the pressing direction and the non-pressing direction becomes larger than when other materials are added during the pressing process.

〔混合工程〕
得られた加圧処理物は炭素質前駆体と混合する。混合工程は均質に混合できれば特に限定されず公知の混合方法を用いることができる。好ましくは固体の黒鉛質粒子と固体または半固体（粘調液状を含む）の炭素質前駆体とを混合する。重質油は、常温で固体である。
タール軽油、タール中油等の液体の炭素質前駆体を溶媒として混合した場合には２００℃以下程度の温度で予め溶媒を揮発させて次の焼成工程を行うのが好ましい。混合比率は最終製品の比率で黒鉛質粒子１００質量部に対し、炭素質材料０．１〜３．０質量部の範囲となるように原料を混合する。混合は後述する加熱工程のための昇温工程とともに行っても良い。加熱混合の方法は特に限定されないが、ヒーターや熱媒などの加熱機構を有する二軸式のニーダーなどが例示される。混合処理の際、炭素質または黒鉛質の繊維、非晶質ハードカーボンなどの炭素質前駆体材料、有機材料、無機材料、金属材料を加えてもよい。混合工程はのちに記載する焼成工程と同時に行っても、混合後焼成してもよい。 [Mixing process]
The obtained pressure-treated product is mixed with a carbonaceous precursor. A mixing process will not be specifically limited if it can mix uniformly, A well-known mixing method can be used. Preferably, solid graphite particles and a solid or semi-solid (including viscous liquid) carbonaceous precursor are mixed. Heavy oil is solid at room temperature.
When a liquid carbonaceous precursor such as tar light oil or tar medium oil is mixed as a solvent, it is preferable to volatilize the solvent in advance at a temperature of about 200 ° C. or lower to perform the next firing step. The mixing ratio is such that the raw material is mixed so that the final product is in the range of 0.1 to 3.0 parts by mass of the carbonaceous material with respect to 100 parts by mass of the graphite particles. You may perform mixing with the temperature rising process for the heating process mentioned later. The heating and mixing method is not particularly limited, and examples thereof include a biaxial kneader having a heating mechanism such as a heater and a heat medium. During the mixing process, carbonaceous or graphite fibers, carbonaceous precursor materials such as amorphous hard carbon, organic materials, inorganic materials, and metal materials may be added. The mixing step may be performed simultaneously with the baking step described later or may be performed after mixing.

〔焼成工程〕
得られた混合物は７００〜２２００℃で焼成する。焼成処理の方法は特に限定されないが、攪拌しながら焼成するのが好ましく、ロータリーキルンを使用することが、均質な焼成ができるので好ましい。焼成温度は最終的に到達する温度が前記範囲内であれば、複数段階で熱処理を行ってもよい。雰囲気は酸化性または非酸化性のいずれであってもよく、段階ごとに両者を使い分けてもよい。非酸化性雰囲気は、アルゴン、ヘリウム、窒素等が例示できる。焼成時間は５分〜３０時間が好ましい。また昇温時および焼成時の温度プロファイルとしては、直線的な昇温、一定間隔で温度をホールドする段階的な昇温などの様々な形態をとることが可能である。
本発明の炭素質被覆黒鉛粒子の製造方法は、焼成後に粉砕工程を含まないのが好ましい。また焼成処理の前に、異種の黒鉛材料同士を、付着、埋設、複合して用いても良い。炭素質または黒鉛質の繊維、非晶質ハードカーボンなどの炭素質前駆体材料、有機材料、無機材料、金属材料を芯材の黒鉛粒子に付着、埋設、複合してから用いてもよい。 [Baking process]
The resulting mixture is fired at 700-2200 ° C. The method for the baking treatment is not particularly limited, but baking is preferably performed while stirring, and the use of a rotary kiln is preferable because homogeneous baking can be performed. As long as the final temperature reaches the firing temperature, the heat treatment may be performed in a plurality of stages. The atmosphere may be oxidizing or non-oxidizing, and both may be used properly at each stage. Examples of the non-oxidizing atmosphere include argon, helium, and nitrogen. The firing time is preferably 5 minutes to 30 hours. Further, the temperature profile at the time of temperature rise and firing can take various forms such as a linear temperature rise and a stepwise temperature rise in which the temperature is held at a constant interval.
The method for producing carbonaceous coated graphite particles of the present invention preferably does not include a pulverization step after firing. Further, different types of graphite materials may be attached, embedded, or combined before firing. Carbonaceous or graphite fibers, carbonaceous precursor materials such as amorphous hard carbon, organic materials, inorganic materials, and metal materials may be attached to, embedded in, or combined with the graphite particles of the core material.

４．負極
本発明はまた、上述の炭素質被覆黒鉛粒子を含有するリチウムイオン二次電池用負極であり、また該負極を用いるリチウムイオン二次電池である。
本発明のリチウムイオン二次電池用の負極は、通常の負極の成形方法に準じて作製されるが、化学的、電気化学的に安定な負極を得ることができる方法であれば何ら制限されない。負極の作製時には、本発明の炭素質被覆黒鉛粒子に結合剤を加えて、予め調製した負極合剤を用いることが好ましい。結合剤としては、電解質に対して、化学的および電気化学的に安定性を示すものが好ましく、例えば、ポリテトラフルオロエチレン、ポリフッ化ビニリデンなどのフッ素系樹脂粉末、ポリエチレン、ポリビニルアルコールなどの樹脂粉末、カルボキシメチルセルロースなどが用いられる。これらを併用することもできる。結合剤は、通常、負極合剤の全量（乾燥基準）中の１〜２０質量％程度の割合で用いられる。したがって本発明の炭素質被覆黒鉛粒子は通常９９〜８０質量％の割合（乾燥基準）で用いられる。 4). Negative electrode The present invention is also a negative electrode for a lithium ion secondary battery containing the above-mentioned carbonaceous coated graphite particles, and a lithium ion secondary battery using the negative electrode.
The negative electrode for a lithium ion secondary battery of the present invention is produced according to a normal negative electrode molding method, but is not limited as long as it is a method capable of obtaining a chemically and electrochemically stable negative electrode. In producing the negative electrode, it is preferable to use a negative electrode mixture prepared in advance by adding a binder to the carbonaceous coated graphite particles of the present invention. As the binder, those showing chemical and electrochemical stability with respect to the electrolyte are preferable. For example, fluorine-based resin powders such as polytetrafluoroethylene and polyvinylidene fluoride, and resin powders such as polyethylene and polyvinyl alcohol Carboxymethyl cellulose and the like are used. These can also be used together. The binder is usually used at a ratio of about 1 to 20% by mass in the total amount (dry basis) of the negative electrode mixture. Therefore, the carbonaceous coated graphite particles of the present invention are usually used at a ratio of 99 to 80% by mass (dry basis).

より具体的には、まず、本発明の負極材料を分級などにより所望の粒度に調整し、結合剤と混合して得た混合物を溶剤に分散させ、ペースト状にして負極合剤を調製する。すなわち、本発明の負極材料と、結合剤を、水、イソプロピルアルコール、Ｎ−メチルピロリドン、ジメチルホルムアミドなどの溶剤と混合して得たスラリーを、公知の攪拌機、混合機、混練機、ニーダーなどを用いて攪拌混合して、ペーストを調製する。該ペーストを、集電材の片面または両面に塗布し、乾燥すれば、負極合剤層が均一かつ強固に接着した負極が得られる。負極合剤層の膜厚は１０〜２００μｍ、好ましくは２０〜１００μｍである。   More specifically, first, the negative electrode material of the present invention is adjusted to a desired particle size by classification or the like, and a mixture obtained by mixing with a binder is dispersed in a solvent to prepare a negative electrode mixture in the form of a paste. That is, a slurry obtained by mixing the negative electrode material of the present invention and a binder with a solvent such as water, isopropyl alcohol, N-methylpyrrolidone, dimethylformamide, etc., using a known stirrer, mixer, kneader, kneader, etc. Use to stir and mix to prepare paste. When the paste is applied to one or both sides of the current collector and dried, a negative electrode in which the negative electrode mixture layer is uniformly and firmly bonded is obtained. The film thickness of the negative electrode mixture layer is 10 to 200 μm, preferably 20 to 100 μm.

本発明の炭素質被覆黒鉛粒子を含有する負極合剤から製造される負極は、黒鉛粒子の状態で異方的に加圧されているので、負極合剤層を形成したのち、負極を作製する際にプレス成型を行わない場合でも電極密度を比較的高くすることができる。
また、本発明の負極は、本発明の負極材料と、ポリエチレン、ポリビニルアルコールなどの樹脂粉末を乾式混合し、金型内でホットプレス成型して作製することもできる。
負極合剤層を形成した後、プレス加圧などの圧着を行うと、負極合剤層と集電体との接着強度をより高めることができる。
負極の作製に用いる集電体の形状としては、特に限定されることはないが、箔状、メッシュ、エキスパンドメタルなどの網状などである。集電材の材質としては、銅、ステンレス、ニッケルなどが好ましい。集電体の厚みは、箔状の場合で５〜２０μｍ程度であるのが好ましい。
なお、本発明の負極は、本発明の目的を損なわない範囲で、異種の黒鉛質材料、非晶質ハードカーボンなどの炭素質材料、有機物、金属、金属化合物などを混合しても、内包しても、被覆しても、または積層してもよい。 Since the negative electrode produced from the negative electrode mixture containing carbonaceous coated graphite particles of the present invention is anisotropically pressurized in the state of graphite particles, the negative electrode is prepared after forming the negative electrode mixture layer. Even when press molding is not performed, the electrode density can be made relatively high.
The negative electrode of the present invention can also be produced by dry-mixing the negative electrode material of the present invention and resin powders such as polyethylene and polyvinyl alcohol and hot pressing in a mold.
When the negative electrode mixture layer is formed and then pressure bonding such as pressurization is performed, the adhesive strength between the negative electrode mixture layer and the current collector can be further increased.
The shape of the current collector used for producing the negative electrode is not particularly limited, but may be a foil shape, a mesh shape, a net shape such as expanded metal, or the like. The material for the current collector is preferably copper, stainless steel, nickel or the like. The thickness of the current collector is preferably about 5 to 20 μm in the case of a foil.
It should be noted that the negative electrode of the present invention can be included even if different types of graphite materials, carbonaceous materials such as amorphous hard carbon, organic substances, metals, metal compounds, and the like are mixed within a range that does not impair the object of the present invention. Alternatively, it may be coated or laminated.

本発明の炭素質被覆黒鉛粒子を含有する負極合剤から製造される負極は、黒鉛粒子の状態で異方的に加圧されているので、負極合剤層を形成したのち、負極を作製する際のプレス加圧による粒子の変形、およびそれにともなう被覆層の損傷を抑制し、電極密度が高密度であっても高い初回充放電効率や高速充放電特性、およびサイクル特性を維持することができる。   Since the negative electrode produced from the negative electrode mixture containing carbonaceous coated graphite particles of the present invention is anisotropically pressurized in the state of graphite particles, the negative electrode is prepared after forming the negative electrode mixture layer. This suppresses the deformation of the particles due to press pressurization and damage to the coating layer, and maintains high initial charge / discharge efficiency, high-speed charge / discharge characteristics, and cycle characteristics even when the electrode density is high. .

〔正極〕
本発明のリチウム二次電池に用いる正極は、例えば正極材料と結合剤および導電剤よりなる正極合剤を集電体の表面に塗布することにより形成される。正極の材料（正極活物質）は、充分量のリチウムを吸蔵／離脱し得るものを選択するのが好ましく、リチウム含有遷移金属酸化物、遷移金属カルコゲン化物、バナジウム酸化物およびそのリチウム化合物などのリチウム含有化合物、一般式ＭXＭｏ6Ｓ8-Y（式中Ｍは少なくとも一種の遷移金属元素であり、Ｘは０≦Ｘ≦４、Ｙは０≦Ｙ≦１の範囲の数値である）で表されるシェブレル相化合物、活性炭、活性炭素繊維などである。 [Positive electrode]
The positive electrode used in the lithium secondary battery of the present invention is formed, for example, by applying a positive electrode mixture comprising a positive electrode material, a binder and a conductive agent to the surface of the current collector. The positive electrode material (positive electrode active material) is preferably selected from materials that can occlude / release a sufficient amount of lithium, and lithium such as lithium-containing transition metal oxides, transition metal chalcogenides, vanadium oxides, and lithium compounds thereof. Containing compound, general formula M X Mo 6 S 8-Y (wherein M is at least one transition metal element, X is a value in the range of 0 ≦ X ≦ 4, Y is 0 ≦ Y ≦ 1) Chevrel phase compounds, activated carbon, activated carbon fibers and the like.

バナジウム酸化物は、Ｖ2Ｏ5、Ｖ6Ｏ13、Ｖ2Ｏ4、Ｖ3Ｏ8で示されるものである。
リチウム含有遷移金属酸化物は、リチウムと遷移金属との複合酸化物であり、リチウムと２種類以上の遷移金属を固溶したものであってもよい。複合酸化物は単独で使用しても、２種類以上を組み合わせて使用してもよい。 The vanadium oxide is represented by V 2 O 5 , V 6 O 13 , V 2 O 4 , or V 3 O 8 .
The lithium-containing transition metal oxide is a composite oxide of lithium and a transition metal, and may be a solid solution of lithium and two or more transition metals. The composite oxide may be used alone or in combination of two or more.

リチウム含有遷移金属酸化物は、具体的には、ＬｉＭ1 1-XＭ2 XＯ2（式中Ｍ1、Ｍ2は少なくとも一種の遷移金属元素であり、Ｘは０≦Ｘ≦１の範囲の数値である）、またはＬｉＭ1 1-YＭ2 YＯ4（式中Ｍ1、Ｍ2は少なくとも一種の遷移金属元素であり、Ｙは０≦Ｙ≦１の範囲の数値である）で示される。
Ｍ1、Ｍ2で示される遷移金属元素は、Ｃｏ、Ｎｉ、Ｍｎ、Ｃｒ、Ｔｉ、Ｖ、Ｆｅ、Ｚｎ、Ａｌ、Ｉｎ、Ｓｎなどであり、好ましいのはＣｏ、Ｆｅ、Ｍｎ、Ｔｉ、Ｃｒ、Ｖ、Ａｌなどである。好ましい具体例は、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎＯ2、ＬｉＮｉ0.9Ｃｏ0.1Ｏ2、ＬｉＮｉ0.5Ｃｏ0.5Ｏ2などである。
リチウム含有遷移金属酸化物は、例えば、リチウム、遷移金属の酸化物、水酸化物、塩類等を出発原料とし、これら出発原料を所望の金属酸化物の組成に応じて混合し、酸素雰囲気下６００〜１０００℃の温度で焼成することにより得ることができる。 Specifically, the lithium-containing transition metal oxide is LiM 1 1-X M 2 X O 2 (wherein M 1 and M 2 are at least one transition metal element, and X is in the range of 0 ≦ X ≦ 1. LiM 1 1-Y M 2 Y O 4 (wherein M 1 and M 2 are at least one transition metal element, and Y is a value in the range of 0 ≦ Y ≦ 1). Indicated.
The transition metal elements represented by M 1 and M 2 are Co, Ni, Mn, Cr, Ti, V, Fe, Zn, Al, In, Sn, etc., preferably Co, Fe, Mn, Ti, Cr , V, Al, etc. Preferable specific examples include LiCoO 2 , LiNiO 2 , LiMnO 2 , LiNi 0.9 Co 0.1 O 2 , LiNi 0.5 Co 0.5 O 2 and the like.
Examples of the lithium-containing transition metal oxide include lithium, transition metal oxides, hydroxides, salts, and the like as starting materials, and these starting materials are mixed in accordance with the composition of the desired metal oxide, and are mixed under an oxygen atmosphere. It can be obtained by firing at a temperature of ˜1000 ° C.

正極活物質は、前記化合物を単独で使用しても２種類以上併用してもよい。例えば、正極中に炭酸リチウム等の炭素塩を添加することができる。また、正極を形成するに際しては、従来公知の導電剤や結着剤などの各種添加剤を適宜に使用することができる。   The positive electrode active material may be used alone or in combination of two or more. For example, a carbon salt such as lithium carbonate can be added to the positive electrode. Moreover, when forming a positive electrode, conventionally well-known various additives, such as a electrically conductive agent and a binder, can be used suitably.

〔正極の製造〕
正極は、前記正極材料、結合剤、および正極に導電性を付与するための導電剤よりなる正極合剤を、集電体の両面に塗布して正極合剤層を形成して作製される。結合剤としては、負極の作製に使用されるものと同じものが使用可能である。導電剤としては、黒鉛化物、カーボンブラックなど公知のものが使用される。
集電体の形状は特に限定されないが、箔状またはメッシュ、エキスパンドメタル等の網状等のものが用いられる。集電体の材質は、アルミニウム、ステンレス、ニッケル等である。その厚さは１０〜４０μｍのものが好適である。
正極も負極と同様に、正極合剤を溶剤中に分散させペースト状にし、このペースト状の正極合剤を集電体に塗布、乾燥して正極合剤層を形成してもよく、正極合剤層を形成した後、さらにプレス加圧等の圧着を行ってもよい。これにより正極合剤層が均一且つ強固に集電材に接着される。 [Production of positive electrode]
The positive electrode is produced by applying a positive electrode mixture comprising the positive electrode material, a binder, and a conductive agent for imparting conductivity to the positive electrode on both sides of the current collector to form a positive electrode mixture layer. As the binder, the same one as that used for producing the negative electrode can be used. As the conductive agent, known materials such as graphitized materials and carbon black are used.
The shape of the current collector is not particularly limited, but a foil shape or a mesh shape such as a mesh or expanded metal is used. The material of the current collector is aluminum, stainless steel, nickel or the like. The thickness is preferably 10 to 40 μm.
Similarly to the negative electrode, the positive electrode mixture may be formed in a paste by dispersing the positive electrode mixture in a solvent, and the paste-like positive electrode mixture may be applied to a current collector and dried to form a positive electrode mixture layer. After forming the agent layer, pressure bonding such as press pressing may be further performed. As a result, the positive electrode mixture layer is uniformly and firmly bonded to the current collector.

〔非水電解質〕
本発明のリチウムイオン二次電池に用いられる非水電解質としては、通常の非水電解液に使用される電解質塩である、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＣｌＯ4、ＬｉＢ（Ｃ6Ｈ5）、ＬｉＣｌ、ＬｉＢｒ、ＬｉＣＦ3ＳＯ3、ＬｉＣＨ3ＳＯ3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ2）3、ＬｉＮ（ＣＦ3ＣＨ2ＯＳＯ2）2、ＬｉＮ（ＣＦ3ＣＦ2ＯＳＯ2）2、ＬｉＮ（ＨＣＦ2ＣＦ2ＣＨ2ＯＳＯ2）2、ＬｉＮ（（ＣＦ3）2ＣＨＯＳＯ2）2、ＬｉＢ［｛Ｃ6Ｈ3（ＣＦ3）2｝］4、ＬｉＡｌＣｌ4、ＬｉＳｉＦ6などのリチウム塩を用いることができる。酸化安定性の点からは、特に、ＬｉＰＦ6、ＬｉＢＦ4が好ましい。
電解液中の電解質塩濃度は０．１〜５．０ｍｏｌ／Ｌが好ましく、０．５〜３．０ｍｏｌ／Ｌがより好ましい。
非水電解質は液状の非水電解質としてもよく、固体電解質またはゲル電解質などの高分子電解質としてもよい。前者の場合、非水電解質電池は、いわゆるリチウムイオン二次電池として構成され、後者の場合は、非水電解質電池は高分子固体電解質、高分子ゲル電解質電池などの高分子電解質電池として構成される。 [Non-aqueous electrolyte]
The non-aqueous electrolyte used in the lithium ion secondary battery of the present invention, an electrolyte salt used in the conventional non-aqueous electrolyte, LiPF 6, LiBF 4, LiAsF 6, LiClO 4, LiB (C 6 H 5 ), LiCl, LiBr, LiCF 3 SO 3 , LiCH 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiN (CF 3 CH 2 OSO 2 ) 2 , LiN (CF 3 CF 2 OSO 2) 2, LiN ( HCF 2 CF 2 CH 2 OSO 2) 2, LiN ((CF 3) 2 CHOSO 2) 2, LiB [{C 6 H 3 (CF 3) 2}] 4, LiAlCl 4, Lithium salts such as LiSiF 6 can be used. From the viewpoint of oxidation stability, LiPF 6 and LiBF 4 are particularly preferable.
The electrolyte salt concentration in the electrolytic solution is preferably 0.1 to 5.0 mol / L, and more preferably 0.5 to 3.0 mol / L.
The non-aqueous electrolyte may be a liquid non-aqueous electrolyte or a polymer electrolyte such as a solid electrolyte or a gel electrolyte. In the former case, the non-aqueous electrolyte battery is configured as a so-called lithium ion secondary battery, and in the latter case, the non-aqueous electrolyte battery is configured as a polymer electrolyte battery such as a polymer solid electrolyte or a polymer gel electrolyte battery. .

非水電解質液を調製するための溶媒としては、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネートなどのカーボネート、１、１−または１、２−ジメトキシエタン、１、２−ジエトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、γ−ブチロラクトン、１、３−ジオキソラン、４−メチル−１、３−ジオキソラン、アニソール、ジエチルエーテルなどのエーテル、スルホラン、メチルスルホランなどのチオエーテル、アセトニトリル、クロロニトリル、プロピオニトリルなどのニトリル、ホウ酸トリメチル、ケイ酸テトラメチル、ニトロメタン、ジメチルホルムアミド、Ｎ−メチルピロリドン、酢酸エチル、トリメチルオルトホルメート、ニトロベンゼン、塩化ベンゾイル、臭化ベンゾイル、テトラヒドロチオフェン、ジメチルスルホキシド、３−メチル−２−オキサゾリドン、エチレングリコール、ジメチルサルファイトなどの非プロトン性有機溶媒などを用いることができる。   As a solvent for preparing the nonaqueous electrolyte solution, carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, 1,1- or 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, ethers such as anisole and diethyl ether, thioethers such as sulfolane and methylsulfolane, acetonitrile, chloronitrile, propionitrile, etc. Nitrile, trimethyl borate, tetramethyl silicate, nitromethane, dimethylformamide, N-methylpyrrolidone, ethyl acetate, trimethyl orthoformate, nitrobenzene, benzoyl chloride, Benzoyl, tetrahydrothiophene, dimethyl sulfoxide, 3-methyl-2-oxazolidone, ethylene glycol, aprotic organic solvents such as dimethyl sulfite may be used.

一般に黒鉛負極材を用いる場合、電解液はプロピレンカーボネート（ＰＣ）を含まない系が使用されている。ＰＣは黒鉛表面で分解反応を起こしやすく、ガス発生による電池内圧の上昇、また、負極材上に分解反応生成物（ＳＥＩ被膜）を大量に生成させるため電池特性を低下させることになるので好ましくないとされている。本発明の炭素質被覆黒鉛粒子は球状および／または楕円体状黒鉛が異方的に加圧され、さらに炭素質被覆されているので、炭素質被覆黒鉛粒子表面とプロピレンカーボネートとの反応性が低く、電解液にプロピレンカーボネートを含んでいてもリチウムイオン二次電池の負極材料に用いた場合の電池特性に遜色がない。   In general, when a graphite negative electrode material is used, an electrolyte solution containing no propylene carbonate (PC) is used. PC is not preferable because it tends to cause a decomposition reaction on the graphite surface, increases the internal pressure of the battery due to gas generation, and reduces the battery characteristics because a large amount of decomposition reaction products (SEI coating) are generated on the negative electrode material. It is said that. In the carbon-coated graphite particles of the present invention, spherical and / or ellipsoidal graphite is anisotropically pressurized and further coated with carbon, so the reactivity between the surface of the carbon-coated graphite particles and propylene carbonate is low. Even if propylene carbonate is contained in the electrolyte, the battery characteristics when used as a negative electrode material for a lithium ion secondary battery are comparable.

非水電解質を高分子固体電解質または高分子ゲル電解質などの高分子電解質とする場合には、マトリクスとして可塑剤（非水電解液）でゲル化された高分子を用いることが好ましい。前記マトリクスを構成する高分子としては、ポリエチレンオキサイドやその架橋体などのエーテル系高分子化合物、ポリメタクリレート系高分子化合物、ポリアクリレート系高分子化合物、ポリビニリデンフルオライドやビニリデンフルオライド−ヘキサフルオロプロピレン共重合体などのフッ素系高分子化合物などを用いることが特に好ましい。
前記高分子固体電解質または高分子ゲル電解質には、可塑剤が配合されるが、該可塑剤としては、前記の電解質塩や非水溶媒が使用可能である。高分子ゲル電解質の場合、可塑剤である非水電解液中の電解質塩濃度は０．１〜５．０ｍｏｌ／Ｌが好ましく、０．５〜２．０ｍｏｌ／Ｌがより好ましい。 When the non-aqueous electrolyte is a polymer electrolyte such as a polymer solid electrolyte or a polymer gel electrolyte, it is preferable to use a polymer gelled with a plasticizer (non-aqueous electrolyte) as a matrix. Examples of the polymer constituting the matrix include ether-based polymer compounds such as polyethylene oxide and cross-linked products thereof, polymethacrylate-based polymer compounds, polyacrylate-based polymer compounds, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene. It is particularly preferable to use a fluorine-based polymer compound such as a copolymer.
The polymer solid electrolyte or polymer gel electrolyte is mixed with a plasticizer, and as the plasticizer, the electrolyte salt and the non-aqueous solvent can be used. In the case of a polymer gel electrolyte, the electrolyte salt concentration in the non-aqueous electrolyte that is a plasticizer is preferably 0.1 to 5.0 mol / L, and more preferably 0.5 to 2.0 mol / L.

高分子固体電解質の作製方法は特に限定されないが、例えば、マトリクスを構成する高分子化合物、リチウム塩および非水溶媒（可塑剤）を混合し、加熱して高分子化合物を溶融する方法、有機溶剤に高分子化合物、リチウム塩、および非水溶媒（可塑剤）を溶解させた後、混合用有機溶剤を蒸発させる方法、重合性モノマー、リチウム塩および非水溶媒（可塑剤）を混合し、混合物に紫外線、電子線または分子線などを照射して、重合性モノマーを重合させ、ポリマーを得る方法などを挙げることができる。
ここで、前記固体電解質中の非水溶媒（可塑剤）の割合は１０〜９０質量％が好ましく、３０〜８０質量％がより好ましい。１０質量％未満であると導電率が低くなり、９０質量％を超えると機械的強度が弱くなり、成膜しにくくなる。 The method for producing the polymer solid electrolyte is not particularly limited. For example, a method of mixing a polymer compound constituting a matrix, a lithium salt, and a nonaqueous solvent (plasticizer) and heating to melt the polymer compound, an organic solvent A method in which a polymer compound, a lithium salt, and a non-aqueous solvent (plasticizer) are dissolved in, and an organic solvent for mixing is evaporated, a polymerizable monomer, a lithium salt, and a non-aqueous solvent (plasticizer) are mixed, and the mixture is mixed Examples thereof include a method of polymerizing a polymerizable monomer by irradiating an ultraviolet ray, an electron beam, a molecular beam or the like to obtain a polymer.
Here, the ratio of the non-aqueous solvent (plasticizer) in the solid electrolyte is preferably 10 to 90% by mass, and more preferably 30 to 80% by mass. If it is less than 10% by mass, the electrical conductivity will be low, and if it exceeds 90% by mass, the mechanical strength will be weak and film formation will be difficult.

〔セパレータ〕
本発明のリチウムイオン二次電池においては、セパレータを使用することもできる。セパレータの材質は特に限定されるものではないが、例えば、織布、不織布、合成樹脂製微多孔膜などを用いることができる。前記セパレータの材質としては、合成樹脂製微多孔膜が好適であるが、なかでもポリオレフィン系微多孔膜が、厚さ、膜強度、膜抵抗の面で好適である。具体的には、ポリエチレンおよびポリプロピレン製微多孔膜、またはこれらを複合した微多孔膜等が好適である。 [Separator]
In the lithium ion secondary battery of the present invention, a separator can also be used. Although the material of a separator is not specifically limited, For example, a woven fabric, a nonwoven fabric, a synthetic resin microporous film, etc. can be used. As a material for the separator, a microporous membrane made of synthetic resin is suitable. Among them, a polyolefin microporous membrane is suitable in terms of thickness, membrane strength, and membrane resistance. Specifically, polyethylene and polypropylene microporous membranes, or microporous membranes composed of these are suitable.

〔リチウムイオン二次電池の製造〕
本発明のリチウムイオン二次電池は、上述した構成の負極、正極および非水電解質を、例えば、負極、非水電解質、正極の順で積層し、電池の外装材内に収容することで構成される。さらに、負極と正極の外側に非水電解質を配するようにしてもよい。
また、本発明のリチウムイオン二次電池の構造は特に限定されず、その形状、形態についても特に限定されるものではなく、用途、搭載機器、要求される充放電容量などに応じて、円筒型、角型、コイン型、ボタン型などの中から任意に選択することができる。より安全性の高い密閉型非水電解液電池を得るためには、過充電などの異常時に電池内圧上昇を感知して電流を遮断させる手段を備えたものを用いることが好ましい。
リチウムイオン二次電池が高分子固体電解質電池や高分子ゲル電解質電池の場合には、ラミネートフィルムに封入した構造とすることもできる。 [Manufacture of lithium ion secondary batteries]
The lithium ion secondary battery of the present invention is configured by laminating the negative electrode, the positive electrode, and the nonaqueous electrolyte having the above-described configuration in the order of, for example, the negative electrode, the nonaqueous electrolyte, and the positive electrode, and accommodating the laminate in the battery exterior material. The Further, a non-aqueous electrolyte may be disposed outside the negative electrode and the positive electrode.
In addition, the structure of the lithium ion secondary battery of the present invention is not particularly limited, and the shape and form thereof are not particularly limited, and are cylindrical, depending on the application, mounted equipment, required charge / discharge capacity, and the like. , Square shape, coin shape, button shape, and the like. In order to obtain a sealed nonaqueous electrolyte battery with higher safety, it is preferable to use a battery equipped with means for detecting an increase in the internal pressure of the battery and shutting off the current when an abnormality such as overcharging occurs.
In the case where the lithium ion secondary battery is a polymer solid electrolyte battery or a polymer gel electrolyte battery, a structure in which the lithium ion secondary battery is enclosed in a laminate film may be used.

次に本発明を実施例により具体的に説明するが、本発明はこれら実施例に限定されるものではない。また以下の実施例および比較例では、図１に示すように、少なくとも表面の一部に本発明の負極合剤２が付着した集電体（負極）７ｂとリチウム箔よりなる対極（正極）４から構成される単極評価用のボタン型二次電池を作製して評価した。実電池は、本発明の概念に基づき、公知の方法に準じて作製することができる。
本明細書における各物性は以下の方法により測定する。
１）平均粒子径（μｍ）：レーザー回折式粒度分布計により測定した粒度分布の累積度数が、体積百分率で５０％となる粒子径とした。
２）炭素質の割合（％）：炭素質前駆体の原料（複数種の場合を含む）単体に炭素質被覆黒鉛粒子と同一の熱履歴を付与して、炭素質単体の炭化物を調製し、原料の残炭率を求めた。得られた残炭率から換算して炭素質被覆黒鉛粒子に占める炭素質の割合を算出した。
３）細孔容積（ｍＬ／ｇ）：水銀圧入法で測定して細孔径と細孔容積との関係を求め、細孔径１．１μｍ以下、および０．５４μｍ以下の全細孔容積を算出した。
４）ＤＢＰ吸油量（ｍＬ／１００ｇ）：ＪＩＳ Ｋ６２１７に則り、測定材料を４０ｇ投入し、滴下速度４ｍＬ／ｍｉｎ、回転数を１２５ｒｐｍの条件でトルクの最大値が確認されるまで測定を実施した。測定開始から最大トルクを示す間の範囲で、最大トルクの７０％のトルクを示した時の滴下油量を、材料１００ｇ当たりに換算して算出した。 EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the following Examples and Comparative Examples, as shown in FIG. 1, a current collector (negative electrode) 7b having a negative electrode mixture 2 of the present invention attached to at least a part of its surface and a counter electrode (positive electrode) 4 made of lithium foil. A button-type secondary battery for single electrode evaluation composed of An actual battery can be produced according to a known method based on the concept of the present invention.
Each physical property in this specification is measured by the following method.
1) Average particle size (μm): The particle size at which the cumulative frequency of the particle size distribution measured with a laser diffraction particle size distribution meter is 50% by volume percentage.
2) Carbonaceous ratio (%): A carbonaceous precursor raw material (including a plurality of types) is provided with the same thermal history as the carbonaceous coated graphite particles to prepare a carbonaceous carbide. The residual coal rate of the raw material was obtained. The ratio of carbonaceous matter in the carbonaceous coated graphite particles was calculated in terms of the residual carbon ratio obtained.
3) Pore volume (mL / g): Measured by mercury porosimetry to determine the relationship between the pore diameter and the pore volume, and calculated the total pore volume with a pore diameter of 1.1 μm or less and 0.54 μm or less. .
4) DBP oil absorption (mL / 100 g): According to JIS K6217, 40 g of measurement material was added, and measurement was performed until the maximum value of torque was confirmed under the conditions of a dropping speed of 4 mL / min and a rotation speed of 125 rpm. The amount of oil dropped when the torque was 70% of the maximum torque in the range from the start of measurement to the maximum torque was calculated per 100 g of material.

（実施例１）
［負極材料である炭素質被覆黒鉛粒子の作製］
平均粒子径１５μｍの球状に加工された天然黒鉛粒子を、金型プレス機を用い５０ＭＰａで異方的に加圧した。これを平均粒子径が１５μｍとなるように解砕したのち、１００質量部に対して、コールタールピッチ（残炭率５０％）のタール中油溶液を、固形分比率が２．０質量部となるように添加し、二軸ニーダーで１５０℃に加熱して６０分混合した。得られた混合物を、管状炉を用い窒素２Ｌ／ｍｉｎ流通下１３００℃で３時間の熱処理を行うことで最終製品を得た。
［負極合剤ペーストの作製］
前記負極材料の９８質量部、結合剤としてのカルボキシメチルセルロース１質量部、およびスチレン−ブタジエンゴム１質量部を水に入れ、攪拌して負極合剤ペーストを調製した。
［作用電極（負極）の作製］
前記負極合剤ペーストを銅箔に均一な厚さで塗布し、真空中９０℃で溶剤を揮発させ、乾燥し、負極合剤層をロールプレスによって加圧し電極密度を１．７０ｇ／ｃｍ3に調整した。銅箔と負極合剤層を直径１５．５ｍｍの円柱状に打抜いて、集電体と、該集電体に密着した負極合剤とからなる作用電極（負極）を作製した。
［対極（正極）の作製］
リチウム金属箔をニッケルネットに押付け、直径１５．５ｍｍの円形状に打抜いて、ニッケルネットからなる集電体と、この集電体に密着したリチウム金属箔（厚み０．５ｍｍ）からなる対極（正極）を作製した。
［電解液、セパレータ］
エチレンカーボネート３３ｖｏｌ％−メチルエチルカーボネート６７ｖｏｌ％の混合溶剤に、ＬｉＰＦ6を１ｍｏｌ／Ｌとなる濃度で溶解させ、非水電解液を調製した。得られた非水電解液をポリプロピレン多孔質体（厚み２０μｍ）に含浸させ、電解液が含浸したセパレータを作製した。 Example 1
[Production of carbon-coated graphite particles as negative electrode material]
Natural graphite particles processed into a spherical shape with an average particle diameter of 15 μm were anisotropically pressurized at 50 MPa using a mold press. After pulverizing this so that the average particle diameter is 15 μm, the tar-in-oil solution of coal tar pitch (residual carbon ratio 50%) becomes 2.0 parts by mass with respect to 100 parts by mass. And heated to 150 ° C. with a biaxial kneader and mixed for 60 minutes. The obtained mixture was heat-treated at 1300 ° C. for 3 hours under a flow of nitrogen 2 L / min using a tubular furnace to obtain a final product.
[Preparation of negative electrode mixture paste]
98 parts by mass of the negative electrode material, 1 part by mass of carboxymethyl cellulose as a binder, and 1 part by mass of styrene-butadiene rubber were placed in water and stirred to prepare a negative electrode mixture paste.
[Production of working electrode (negative electrode)]
The negative electrode mixture paste is applied to a copper foil with a uniform thickness, the solvent is volatilized at 90 ° C. in a vacuum, and the negative electrode mixture layer is pressed by a roll press so that the electrode density is 1.70 g / cm 3 . It was adjusted. The copper foil and the negative electrode mixture layer were punched into a cylindrical shape having a diameter of 15.5 mm to prepare a working electrode (negative electrode) composed of a current collector and a negative electrode mixture adhered to the current collector.
[Production of counter electrode (positive electrode)]
A lithium metal foil is pressed against a nickel net and punched into a circular shape with a diameter of 15.5 mm. A current collector made of nickel net and a counter electrode made of a lithium metal foil (thickness 0.5 mm) in close contact with the current collector ( Positive electrode) was prepared.
[Electrolyte, separator]
LiPF 6 was dissolved at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate 33 vol% -methyl ethyl carbonate 67 vol% to prepare a non-aqueous electrolyte. The obtained nonaqueous electrolytic solution was impregnated into a polypropylene porous body (thickness 20 μm) to produce a separator impregnated with the electrolytic solution.

［評価電池の作製］
評価電池として図１に示すボタン型二次電池を作製した。
外装カップ１と外装缶３は、その周縁部において絶縁ガスケット６を介在させ、両周縁部をかしめて密閉した。その内部に外装缶３の内面から順に、ニッケルネットからなる集電体７ａ、リチウム箔よりなる円筒状の対極（正極）４、電解液が含浸されたセパレータ５、負極合剤２が付着した銅箔からなる集電体（負極）７ｂが積層された電池系である。
前記評価電池は電解液を含浸させたセパレータ５を集電体７ｂと、集電体７ａに密着した対極４との間に挟んで積層した後、集電体７ｂを外装カップ１内に、対極４を外装缶３内に収容して、外装カップ１と外装缶３とを合わせ、さらに、外装カップ１と外装缶３との周縁部に絶縁ガスケット６を介在させ、両周縁部をかしめて密閉して作製した。充放電特性は以下の方法により測定した。結果を表１に示した。
［充放電試験］
回路電圧が１ｍＶに達するまで０．９ｍＡの定電流充電を行った後、回路電圧が１ｍＶに達した時点で定電圧充電に切替え、さらに電流値が２０μＡになるその間の通電量から充電容量（単位：ｍＡｈ／ｇ）を求めた。その後、１０分間休止した。次に０．９ｍＡの電流値で、回路電圧が１．５Ｖに達するまで定電流放電を行い、この間の通電量から放電容量（単位：ｍＡｈ／ｇ）を求めた。これを第１サイクルとした。次いで充電電流を１Ｃ、放電電流を２Ｃとして、第１サイクルと同様に充放電を行った。１Ｃ、２Ｃの電流値は、第１サイクルの放電容量と負極の活物質重量から計算した。
初回充放電効率は次式（１）から計算した。
初回充放電効率（％）＝１００×（（第１サイクルの充電容量−第１サイクルの放電容量）／第１サイクルの放電容量）・・・（１）
また、１Ｃ充電率は次式（２）から計算した。
１Ｃ充電率（％）＝１００×（１Ｃ電流値におけるＣＣ部分の充電容量／第１サイクルの放電容量）・・・（２）
また、２Ｃ放電率は次式（３）から計算した。
２Ｃ放電率（％）＝１００×（２Ｃ電流値における放電容量／第１サイクルの放電容量）・・・（３）
また、サイクル特性は以下のように測定した。回路電圧が１ｍＶに達するまで１Ｃ電流値で定電流充電を行った後、定電圧充電に切替え、電流値が２０μＡになるまで充電を続けた後、１０分間休止した。次に２Ｃの電流値で、回路電圧が１．５Ｖに達するまで定電流放電を行った。この充放電を５０回繰り返し、得られた放電容量から、次式（４）を用いてサイクル特性を計算した。
サイクル特性（％）＝１００×（第５０サイクルの放電容量／第１サイクルの放電容量）・・・（４）
なおこの試験では、リチウムイオンを負極材料に吸蔵する過程を充電、負極材料からリチウムイオンが脱離する過程を放電とした。 [Production of evaluation battery]
A button-type secondary battery shown in FIG. 1 was prepared as an evaluation battery.
The exterior cup 1 and the exterior can 3 were sealed by interposing an insulating gasket 6 at the peripheral portion thereof and caulking both peripheral portions. A copper current collector 7 a made of nickel net, a cylindrical counter electrode (positive electrode) 4 made of lithium foil, a separator 5 impregnated with an electrolytic solution, and a negative electrode mixture 2 are attached to the inside of the outer can 3 in that order. This is a battery system in which a current collector (negative electrode) 7b made of foil is laminated.
In the evaluation battery, the separator 5 impregnated with the electrolytic solution was laminated between the current collector 7b and the counter electrode 4 in close contact with the current collector 7a, and then the current collector 7b was placed in the outer cup 1 4 is accommodated in the outer can 3, the outer cup 1 and the outer can 3 are combined, and further, an insulating gasket 6 is interposed between the outer peripheral portion of the outer cup 1 and the outer can 3, and both peripheral portions are caulked and sealed. And produced. The charge / discharge characteristics were measured by the following method. The results are shown in Table 1.
[Charge / discharge test]
After constant current charging of 0.9 mA until the circuit voltage reaches 1 mV, switching to constant voltage charging is performed when the circuit voltage reaches 1 mV, and further, the charging capacity (unit: : MAh / g). Then, it rested for 10 minutes. Next, constant current discharge was performed at a current value of 0.9 mA until the circuit voltage reached 1.5 V, and the discharge capacity (unit: mAh / g) was determined from the amount of electricity supplied during this period. This was the first cycle. Next, charging and discharging were performed in the same manner as in the first cycle, with the charging current being 1C and the discharging current being 2C. The current values of 1C and 2C were calculated from the discharge capacity of the first cycle and the active material weight of the negative electrode.
The initial charge / discharge efficiency was calculated from the following equation (1).
Initial charge / discharge efficiency (%) = 100 × ((first cycle charge capacity−first cycle discharge capacity) / first cycle discharge capacity) (1)
Moreover, 1C charge rate was computed from following Formula (2).
1C charge rate (%) = 100 × (charge capacity of CC portion at 1C current value / discharge capacity of first cycle) (2)
The 2C discharge rate was calculated from the following equation (3).
2C discharge rate (%) = 100 × (discharge capacity at 2C current value / discharge capacity of first cycle) (3)
The cycle characteristics were measured as follows. After constant current charging at 1 C current value until the circuit voltage reached 1 mV, switching to constant voltage charging was continued until the current value reached 20 μA, and then rested for 10 minutes. Next, constant current discharge was performed at a current value of 2C until the circuit voltage reached 1.5V. This charge / discharge was repeated 50 times, and the cycle characteristics were calculated from the obtained discharge capacity using the following equation (4).
Cycle characteristics (%) = 100 × (50th cycle discharge capacity / first cycle discharge capacity) (4)
In this test, the process of occluding lithium ions in the negative electrode material was charged, and the process of detaching lithium ions from the negative electrode material was discharge.

（実施例２）
実施例１において、電池性能評価時の電極密度を１．７５ｇ／ｃｍ3とする以外は、実施例１と同様にして評価した。評価結果を表１に示した。 (Example 2)
In Example 1, evaluation was performed in the same manner as in Example 1 except that the electrode density at the time of battery performance evaluation was 1.75 g / cm 3 . The evaluation results are shown in Table 1.

（実施例３）
実施例１において、炭素質被覆量を表１に示す量に変更した以外は、実施例１と同様にして、炭素質被覆黒鉛粒子を製造し、実施例１と同様に評価電池を作製し評価した。 (Example 3)
In Example 1, except that the carbonaceous coating amount was changed to the amount shown in Table 1, carbonaceous coated graphite particles were produced in the same manner as in Example 1, and evaluation batteries were produced and evaluated in the same manner as in Example 1. did.

（実施例４）
実施例１において、加圧処理時の圧力を１００ＭＰａとする以外は、実施例１と同様にして、炭素質被覆黒鉛粒子を製造し、電極密度を１．７０ｇ／ｃｍ3として評価した。評価結果を表１に示した。 Example 4
In Example 1, carbonaceous coated graphite particles were produced in the same manner as in Example 1 except that the pressure during the pressure treatment was 100 MPa, and the electrode density was evaluated as 1.70 g / cm 3 . The evaluation results are shown in Table 1.

（実施例５）
実施例１において、加圧処理時の圧力を１５０ＭＰａとする以外は、実施例１と同様にして、炭素質被覆黒鉛粒子を製造し、電極密度を１．７０ｇ／ｃｍ3として評価した。評価結果を表１に示した。 (Example 5)
In Example 1, carbonaceous coated graphite particles were produced in the same manner as in Example 1 except that the pressure during the pressure treatment was 150 MPa, and the electrode density was evaluated as 1.70 g / cm 3 . The evaluation results are shown in Table 1.

（実施例６）
実施例１において、炭素質被覆量を表１に示す量に変更した以外は、実施例１と同様にして評価した。評価結果を表１に示した。 (Example 6)
Evaluation was made in the same manner as in Example 1 except that the carbonaceous coating amount was changed to the amount shown in Table 1 in Example 1. The evaluation results are shown in Table 1.

（比較例１）
実施例１において、加圧処理を行わない以外は、実施例１と同様にして、炭素質被覆黒鉛粒子を製造し、実施例１と同様に評価電池を作製し評価した。 (Comparative Example 1)
In Example 1, carbonaceous coated graphite particles were produced in the same manner as in Example 1 except that no pressure treatment was performed, and an evaluation battery was produced and evaluated in the same manner as in Example 1.

（比較例２）
実施例１において、加圧処理の方法を冷間静水圧プレスとして５０ＭＰａを等方的に加圧する以外は、実施例１と同様にして、被覆天然黒鉛材料を製造し、実施例１と同様に評価電池を作製し評価した。 (Comparative Example 2)
In Example 1, a coated natural graphite material was produced in the same manner as in Example 1 except that 50 MPa was isotropically pressurized using a cold isostatic press as the method of pressure treatment. An evaluation battery was prepared and evaluated.

（比較例３）
比較例２において、電池性能評価時の電極密度を１．７５ｇ／ｃｍ3とする以外は、比較例２と同様にして評価した。評価結果を表１に示した。 (Comparative Example 3)
In Comparative Example 2, the evaluation was performed in the same manner as in Comparative Example 2 except that the electrode density during battery performance evaluation was 1.75 g / cm 3 . The evaluation results are shown in Table 1.

（比較例４）
実施例１において炭素質被覆量を表１に示す量に変更した以外は、実施例１と同様にして、炭素質被覆黒鉛粒子を製造し、実施例１と同様に評価電池を作製し評価した。 (Comparative Example 4)
Except that the carbonaceous coating amount was changed to the amount shown in Table 1 in Example 1, carbonaceous coated graphite particles were produced in the same manner as in Example 1, and evaluation batteries were produced and evaluated in the same manner as in Example 1. .

（比較例５）
実施例１において炭素質被覆量を表１に示す量に変更した以外は、実施例１と同様にして、炭素質被覆黒鉛粒子を製造し、実施例１と同様に評価電池を作製し評価した。 (Comparative Example 5)
Except that the carbonaceous coating amount was changed to the amount shown in Table 1 in Example 1, carbonaceous coated graphite particles were produced in the same manner as in Example 1, and evaluation batteries were produced and evaluated in the same manner as in Example 1. .

（比較例６）
実施例１において、加圧処理時の圧力を１０ＭＰａとする以外は、実施例１と同様にして評価した。評価結果を表１に示した。 (Comparative Example 6)
In Example 1, it evaluated similarly to Example 1 except the pressure at the time of a pressurizing process being 10 Mpa. The evaluation results are shown in Table 1.

（比較例７）
実施例１において、加圧処理時の圧力を１０ＭＰａとし、炭素質被覆量を３．０質量部とする以外は、実施例１と同様にして評価した。評価結果を表１に示した。 (Comparative Example 7)
In Example 1, it evaluated similarly to Example 1 except the pressure at the time of a pressurizing process being 10 Mpa, and making a carbonaceous coating amount into 3.0 mass parts. The evaluation results are shown in Table 1.

（比較例８）
実施例１において、加圧処理時の圧力を３０ＭＰａとし、炭素質被覆量を３．０質量部とする以外は、実施例１と同様にして評価した。評価結果を表１に示した。 (Comparative Example 8)
In Example 1, it evaluated similarly to Example 1 except the pressure at the time of a pressurizing process being 30 Mpa, and making a carbonaceous coating amount into 3.0 mass parts. The evaluation results are shown in Table 1.

（比較例９）
実施例１において、加圧処理時の圧力を１０ＭＰａとし、炭素質被覆量を０．１５質量部とする以外は、実施例１と同様にして評価した。評価結果を表１に示した。 (Comparative Example 9)
In Example 1, it evaluated similarly to Example 1 except the pressure at the time of a pressurizing process being 10 Mpa, and making a carbonaceous coating amount into 0.15 mass part. The evaluation results are shown in Table 1.

異方的に加圧してなる黒鉛質粒子が、下記（１）〜（３）を満足する実施例１〜６は、放電容量、初回充放電効率、高速充放電特性およびサイクル特性が良好である。実施例１、２の比較から明らかなように、電極密度をより高くしてもこの特性は維持される。
（１）炭素質材料の含有量が、炭素質被覆黒鉛質粒子中の異方的に加圧してなる黒鉛質粒子１００質量部に対して０．１〜３．０質量部。
（２）水銀ポロシメータで測定した細孔径１．１μｍ以下の細孔容積が０．１００ｍＬ／ｇ以下であり、かつ該細孔容積に対する細孔径０．５４μｍ以下の細孔容積の比率が８０％以上。
（３）フタル酸ジブチル（ＤＢＰ）吸油量が３６．１〜４０．０ｍＬ／１００ｇ。
一方、黒鉛質粒子が加圧処理されていない比較例１、等方的に加圧処理されている比較例２、３、炭素質材料の被覆量が０．１％未満の比較例４、炭素質材料の被覆量が３％超の比較例５、細孔径１．１μｍ以下の細孔容積が０．１００ｍＬ／ｇ超、該細孔容積に対する細孔径０．５４μｍ以下の細孔容積の比率が８０％未満、かつ、ＤＢＰ吸油量が４０．０ｍＬ／１００ｇ超の比較例６、細孔径１．１μｍ以下の細孔容積が０．１ｍＬ／ｇ超の比較例７、細孔径１．１μｍ以下の細孔容積に対する細孔径０．５４μｍ以下の細孔容積の比率が８０％未満の比較例８、細孔径１．１μｍ以下の細孔容積が０．１００ｍＬ／ｇ超、かつ、ＤＢＰ吸油量が４０．０ｍＬ／１００ｇ超の比較例９は、高い放電容量、高い初回充放電効率、高い高速充放電特性および優れたサイクル特性を同時に達成することができなかった。等方的に加圧処理されている比較例２、３については、電極密度をより高くした場合、初回充放電効率、高速充放電特性およびサイクル特性の低下が確認された。 Examples 1-6 in which the graphite particles formed by anisotropic pressure satisfy the following (1) to (3) have good discharge capacity, initial charge / discharge efficiency, high-speed charge / discharge characteristics, and cycle characteristics. . As is clear from the comparison between Examples 1 and 2, this characteristic is maintained even when the electrode density is increased.
(1) The content of the carbonaceous material is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the graphite particles formed by anisotropic pressure in the carbonaceous coated graphite particles.
(2) The pore volume with a pore diameter of 1.1 μm or less measured with a mercury porosimeter is 0.100 mL / g or less, and the ratio of the pore volume with a pore diameter of 0.54 μm or less to the pore volume is 80% or more .
(3) Dibutyl phthalate (DBP) oil absorption is 36.1-40.0 mL / 100 g .
On the other hand, Comparative Example 1 in which the graphite particles are not pressure-treated, Comparative Examples 2 and 3 in which the isotropic pressure treatment is performed, Comparative Example 4 in which the coating amount of the carbonaceous material is less than 0.1%, carbon Comparative Example 5 in which the covering amount of the porous material exceeds 3%, the pore volume with a pore diameter of 1.1 μm or less exceeds 0.100 mL / g, and the ratio of the pore volume with a pore diameter of 0.54 μm or less to the pore volume is Comparative Example 6 having a DBP oil absorption of less than 80% and a DBP oil absorption of more than 40.0 mL / 100 g, Comparative Example 7 having a pore volume of 1.1 μm or less and a pore volume of more than 0.1 mL / g, and a pore diameter of 1.1 μm or less Comparative Example 8 in which the ratio of the pore volume with a pore diameter of 0.54 μm or less to the pore volume is less than 80%, the pore volume with a pore diameter of 1.1 μm or less exceeds 0.100 mL / g, and the DBP oil absorption is 40 Comparative Example 9 of more than 0.0 mL / 100 g has high discharge capacity, high initial charge / discharge efficiency, high high-speed charge / discharge It could not be achieved sex and excellent cycle characteristics at the same time. In Comparative Examples 2 and 3 subjected to isotropic pressure treatment, when the electrode density was further increased, it was confirmed that the initial charge / discharge efficiency, high-speed charge / discharge characteristics, and cycle characteristics were lowered.

本発明の炭素質被覆黒鉛質粒子からなる負極材料は、リチウムイオン二次電池負極材料として良好な放電容量、初回充放電効率、高速充放電特性、およびサイクル特性を有する負極材料である。その特性を活かして、小型から大型までの高性能なリチウムイオン二次電池の負極に使用することができる。   The negative electrode material composed of carbonaceous coated graphite particles of the present invention is a negative electrode material having a good discharge capacity, initial charge / discharge efficiency, high-speed charge / discharge characteristics, and cycle characteristics as a negative electrode material for a lithium ion secondary battery. Taking advantage of these characteristics, it can be used for negative electrodes of high-performance lithium ion secondary batteries ranging from small to large.

１ 外装カップ
２ 負極合剤
３ 外装缶
４ 対極
５ 電解質溶液含浸セパレータ
６ 絶縁ガスケット
７ａ、７ｂ 集電体 DESCRIPTION OF SYMBOLS 1 Exterior cup 2 Negative electrode mixture 3 Exterior can 4 Counter electrode 5 Electrolyte solution impregnation separator 6 Insulation gasket 7a, 7b Current collector

Claims (3)

球状および／または楕円体状黒鉛を異方的に加圧してなる黒鉛質粒子の表面の少なくとも一部に炭素質材料を有する炭素質被覆黒鉛質粒子であって、前記炭素質被覆黒鉛質粒子が下記（１）〜（３）を満足するリチウムイオン二次電池負極材料用黒鉛質粒子。
（１）該炭素質材料の含有量が、前記炭素質被覆黒鉛質粒子中の前記異方的に加圧してなる黒鉛質粒子１００質量部に対して０．１〜３．０質量部。
（２）水銀ポロシメータで測定した細孔径１．１μｍ以下の細孔容積が０．１００ｍＬ／ｇ以下であり、かつ該細孔容積に対する細孔径０．５４μｍ以下の細孔容積の比率が８０％以上。
（３）フタル酸ジブチル（ＤＢＰ）吸油量が３６．１〜４０．０ｍＬ／１００ｇ。 Carbonaceous coated graphite particles having a carbonaceous material on at least a part of the surface of graphite particles obtained by anisotropically pressing spherical and / or ellipsoidal graphite, wherein the carbonaceous coated graphite particles are Graphite particles for a lithium ion secondary battery negative electrode material satisfying the following (1) to (3).
(1) The content of the carbonaceous material is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the graphite particles formed by anisotropic pressure in the carbonaceous coated graphite particles.
(2) The pore volume with a pore diameter of 1.1 μm or less measured with a mercury porosimeter is 0.100 mL / g or less, and the ratio of the pore volume with a pore diameter of 0.54 μm or less to the pore volume is 80% or more .
(3) Dibutyl phthalate (DBP) oil absorption is 36.1-40.0 mL / 100 g . 請求項１に記載のリチウムイオン二次電池負極材料用黒鉛質粒子を含有するリチウムイオン二次電池負極。   The lithium ion secondary battery negative electrode containing the graphite particle for lithium ion secondary battery negative electrode materials of Claim 1. 請求項２に記載のリチウムイオン二次電池負極を有するリチウムイオン二次電池。   The lithium ion secondary battery which has a lithium ion secondary battery negative electrode of Claim 2.
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