JP2011060467A - Negative electrode material for lithium ion secondary battery and method for manufacturing the same - Google Patents
Negative electrode material for lithium ion secondary battery and method for manufacturing the same Download PDFInfo
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Abstract
【課題】出力特性、サイクル特性および初期効率に優れたリチウムイオン二次電池に好適なリチウムイオン二次電池用負極材料の製造方法を提供する。
【解決手段】本発明のリチウムイオン二次電池用電極材料の製造方法は、炭素質物質前駆体と第１黒鉛粒子とを混合し、熱処理する熱処理工程；得られた熱処理物を粉砕して平均粒子径１０μｍ未満の粒子を得る粉砕工程；得られた平均粒子径１０μｍ未満の粒子とポリエチレン粒子および／またはポリスチレン粒子とを混合し、熱処理する被覆工程；を含むことを特徴とする。
【選択図】なしA method for producing a negative electrode material for a lithium ion secondary battery suitable for a lithium ion secondary battery having excellent output characteristics, cycle characteristics, and initial efficiency is provided.
A method for producing an electrode material for a lithium ion secondary battery according to the present invention includes a heat treatment step in which a carbonaceous material precursor and first graphite particles are mixed and heat-treated; A pulverizing step for obtaining particles having a particle size of less than 10 μm; a coating step for mixing the obtained particles having an average particle size of less than 10 μm with polyethylene particles and / or polystyrene particles and heat-treating them.
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Description
本発明は、リチウムイオン二次電池用負極材料およびその製造方法に関するものである。 The present invention relates to a negative electrode material for a lithium ion secondary battery and a method for producing the same.
リチウムイオン二次電池は、高容量、小型軽量といった特徴を有することから、携帯電話、ノートパソコン、デジタルカメラなどの用途に多く用いられている。また、高出力を要する電動工具には、ニッケル・カドミウム蓄電池やニッケル・水素蓄電池が従来から主に用いられてきたが、電動工具にも高出力に対応したリチウムイオン二次電池の普及が進んでいる。さらに、リチウムイオン二次電池は、高出力かつ優れたサイクル特性が要求されるハイブリッド電気自動車（ＨＥＶ）への適用も検討されている。 Lithium ion secondary batteries are characterized by high capacity, small size, and light weight, and are therefore widely used in applications such as mobile phones, notebook computers, and digital cameras. In addition, nickel-cadmium storage batteries and nickel-hydrogen storage batteries have been mainly used for power tools that require high output. However, lithium-ion secondary batteries that support high power have been widely used in power tools. Yes. Furthermore, application of lithium ion secondary batteries to hybrid electric vehicles (HEV) that require high output and excellent cycle characteristics is also being studied.
出力特性やサイクル特性に優れたリチウムイオン二次電池に関する技術としては、例えば、特許文献１には、黒鉛部分と非晶質炭素部分とを複合してなる黒鉛−非晶質炭素複合材料の製造法であり、前記非晶質炭素部分の前駆体の重合が脱水素酸触媒存在下で行われることを特徴とする黒鉛−非晶質炭素複合材料の製造法が開示されている。しかし、特許文献１では、１〜９サイクル目のサイクル特性については評価されているが、高レートでの出力特性が評価されておらず、出力特性が向上しているか明確でなく、また初回充放電効率（初期効率）は、高いものでも８６％程度であり、優れているとはいえない（特許文献１、表１、図１参照）。 As a technique related to a lithium ion secondary battery excellent in output characteristics and cycle characteristics, for example, Patent Document 1 discloses the production of a graphite-amorphous carbon composite material formed by combining a graphite portion and an amorphous carbon portion. And a method for producing a graphite-amorphous carbon composite material, wherein the polymerization of the precursor of the amorphous carbon portion is carried out in the presence of a dehydrogenation acid catalyst. However, in Patent Document 1, although the cycle characteristics of the first to ninth cycles are evaluated, the output characteristics at a high rate are not evaluated, it is not clear whether the output characteristics are improved, and the initial charge is not achieved. Even if the discharge efficiency (initial efficiency) is high, it is about 86% and cannot be said to be excellent (see Patent Document 1, Table 1, and FIG. 1).
特許文献２には、炭素前駆体を焼成して得られる炭素質粉末からなるリチウム二次電池用負極活物質であって、該炭素質粉末は、結晶面の間隔d(002)が３．４５〜３．５５Å、ＢＥＴ法による窒素の吸着における全細孔容積が０．０２ｃｍ3／ｇ以下で、かつ孔径５Å以下の細孔容積が１×１０-5〜４×１０-4ｃｍ3／ｇであることを特徴とする負極活物質が開示されている。特許文献２では、石油または石炭系タール乃至はピッチを焼成したものを負極材として用いることにより高出力化を図っているが、サイクル特性については評価されておらず、放電効率（初期効率）は高いものでも８６％程度であり、優れているとはいえない（特許文献２、段落００１３、表２参照）。 Patent Document 2 discloses a negative electrode active material for a lithium secondary battery made of a carbonaceous powder obtained by firing a carbon precursor, and the carbonaceous powder has a crystal plane spacing d (002) of 3.45. ~ 3.55Å, the total pore volume in the adsorption of nitrogen by BET method is 0.02cm 3 / g or less, and the pore volume of pore diameter of 5Å or less is 1 × 10 -5 to 4 × 10 -4 cm 3 / g A negative electrode active material characterized by the above is disclosed. In Patent Document 2, although high output is achieved by using petroleum or coal-based tar or pitch-fired as a negative electrode material, cycle characteristics are not evaluated, and discharge efficiency (initial efficiency) is Even if it is high, it is about 86% and cannot be said to be excellent (see Patent Document 2, Paragraph 0013, Table 2).
特許文献３には、窒素吸着等温線からＢＥＴ法により求められる全比表面積が１０〜４０ｍ2／ｇで、かつＢＪＨ法により求められるメソポア領域の比表面積が１０〜４０ｍ2／ｇであり、さらに前記全比表面積に対する前記メソポア領域の比表面積の比が０．７以上である炭素材料が開示されている。特許文献４には、電子顕微鏡により測定した算術平均一次粒子径ｄｎが１５０〜１０００ｎｍ、揮発分Ｖｍが５．０％以下、ディスクセントリフュージ装置（ＤＣＦ）により測定したストークスモード径Ｄｓｔとその半値幅ΔＤｓｔの比ΔＤｓｔ／Ｄｓｔが０．４０〜１．１０、Ｘ線回折法により測定した結晶子格子面間隔（ｄ００２）が０．３７０ｎｍ以下、の炭素微小球からなることを特徴とするリチウム二次電池用負極材が開示されている。 In Patent Document 3, the total specific surface area determined by the BET method from the nitrogen adsorption isotherm is 10 to 40 m 2 / g, the specific surface area of the mesopore region determined by the BJH method is 10 to 40 m 2 / g, A carbon material in which the ratio of the specific surface area of the mesopore region to the total specific surface area is 0.7 or more is disclosed. In Patent Document 4, the arithmetic average primary particle diameter dn measured by an electron microscope is 150 to 1000 nm, the volatile component Vm is 5.0% or less, the Stokes mode diameter Dst measured by a disk centrifuging device (DCF) and its half-value width ΔDst. A lithium secondary battery comprising carbon microspheres having a ratio ΔDst / Dst of 0.40 to 1.10 and a crystallite lattice spacing (d002) measured by an X-ray diffraction method of 0.370 nm or less A negative electrode material is disclosed.
特許文献５には、黒鉛粒子（１）１００重量部とポリスチレン粒子（２）０．５〜５０重量部とを物理的に混合すること、不活性ガス雰囲気中、この混合物を前記ポリスチレン粒子（２）の熱分解温度以上の温度で熱処理すること、この熱処理により、前記ポリスチレン粒子（２）の熱分解成分を気相で拡散させて前記黒鉛粒子（１）の表面に該熱分解成分による被膜層を形成させると共に該被膜層が炭化して被覆層となった複合粒子を得ること、を特徴とするリチウムイオン二次電池用負極材料の製造法が開示されている。 In Patent Document 5, 100 parts by weight of graphite particles (1) and 0.5 to 50 parts by weight of polystyrene particles (2) are physically mixed, and this mixture is added to the polystyrene particles (2) in an inert gas atmosphere. The thermal decomposition component of the polystyrene particles (2) is diffused in the gas phase by this heat treatment at a temperature equal to or higher than the thermal decomposition temperature of the graphite particles (1). And producing a composite particle in which the coating layer is carbonized to form a coating layer is disclosed.
上記のように、出力特性やサイクル特性に優れたリチウムイオン二次電池に関する技術が、種々開発されているが、さらなる向上が求められている。また、出力特性やサイクル特性の向上に加えて、初期特性を向上させることについても検討の余地があった。 As described above, various technologies related to lithium ion secondary batteries excellent in output characteristics and cycle characteristics have been developed, and further improvements are required. In addition to improving the output characteristics and cycle characteristics, there is room for further study on improving the initial characteristics.
本発明は、上記課題に鑑みてなされたものであって、出力特性、サイクル特性および初期効率に優れたリチウムイオン二次電池に好適なリチウムイオン二次電池用負極材料、並びに、該リチウムイオン二次電池用負極材料の製造方法を提供することを目的とする。 The present invention has been made in view of the above problems, and is a negative electrode material for a lithium ion secondary battery suitable for a lithium ion secondary battery excellent in output characteristics, cycle characteristics, and initial efficiency, and the lithium ion secondary battery. It aims at providing the manufacturing method of the negative electrode material for secondary batteries.
上記課題を解決することができた本発明のリチウムイオン二次電池用負極材料の製造方法は、炭素質物質前駆体と第１黒鉛粒子とを混合し、熱処理する熱処理工程；得られた熱処理物を粉砕して平均粒子径１０μｍ未満の粒子を得る粉砕工程；得られた平均粒子径１０μｍ未満の粒子とポリエチレン粒子および／またはポリスチレン粒子とを混合し、熱処理する被覆工程；を含むことを特徴とする。 The method for producing a negative electrode material for a lithium ion secondary battery according to the present invention that has solved the above-mentioned problems is a heat treatment step in which a carbonaceous material precursor and first graphite particles are mixed and heat-treated; A pulverizing step for obtaining particles having an average particle size of less than 10 μm; and a coating step for mixing the obtained particles having an average particle size of less than 10 μm with polyethylene particles and / or polystyrene particles and heat-treating the particles. To do.
本発明の製造方法により得られるリチウムイオン二次電池用負極材料は、炭素質物質と第１黒鉛粒子から構成される複合黒鉛粒子が、適度な硬さを有し電極材をプレスする際に配向しにくいため、粒子間の通液性が維持される。また、黒鉛粒子はその結晶構造による制約から、エッジ部分でのみリチウムイオンの授受が行われるが、本発明の製造方法では、粒子表面にポリエチレンおよび／またはポリスチレンの熱分解性成分に由来する低結晶性炭素が形成されるため、この低結晶性炭素部分からもリチウムイオンとの反応が進行する。また、粒子表面がポリエチレンおよび／またはポリスチレンの熱分解性成分に由来する低結晶性炭素で被覆されているため、電解液との反応性が小さい。これらの結果、本発明の製造方法により得られるリチウムイオン二次電池用負極材料を導電材として用いることにより、出力特性、サイクル特性および初期効率に優れたリチウムイオン二次電池が得られる。 The negative electrode material for a lithium ion secondary battery obtained by the production method of the present invention has a composite graphite particle composed of a carbonaceous material and first graphite particles having an appropriate hardness and orientation when pressing an electrode material. Therefore, liquid permeability between particles is maintained. In addition, graphite particles are exchanged with lithium ions only at the edge part due to restrictions due to their crystal structure, but in the production method of the present invention, a low crystal derived from a thermally decomposable component of polyethylene and / or polystyrene on the particle surface. Since reactive carbon is formed, the reaction with lithium ions also proceeds from this low crystalline carbon portion. Moreover, since the particle | grain surface is coat | covered with the low crystalline carbon derived from the thermally decomposable component of polyethylene and / or polystyrene, the reactivity with electrolyte solution is small. As a result, by using the negative electrode material for a lithium ion secondary battery obtained by the production method of the present invention as a conductive material, a lithium ion secondary battery excellent in output characteristics, cycle characteristics and initial efficiency can be obtained.
前記製造方法は、前記炭素質物質前駆体と第１黒鉛粒子に加えて、さらに前記第１黒鉛粒子よりも平均粒子径の小さい微粒子炭素質物質を混合し、熱処理し、粉砕して平均粒子径１０μｍ未満の粒子を得ることが好ましい。 In the manufacturing method, in addition to the carbonaceous material precursor and the first graphite particles, a fine particle carbonaceous material having an average particle size smaller than that of the first graphite particles is further mixed, heat-treated and pulverized to obtain an average particle size. It is preferred to obtain particles of less than 10 μm.
また、前記製造方法は、前記平均粒子径１０μｍ未満の粒子と、該粒子よりも平均粒子径が大きい第２黒鉛粒子とを混合した後、得られた混合物とポリエチレンおよび／またはポリスチレン粒子とを混合し、熱処理することが好ましい。 In addition, in the production method, the particles having an average particle diameter of less than 10 μm and the second graphite particles having an average particle diameter larger than the particles are mixed, and then the obtained mixture is mixed with polyethylene and / or polystyrene particles. It is preferable to perform heat treatment.
本発明には、前記製造方法により得られたことを特徴とするリチウムイオン二次電池用負極材料、前記リチウムイオン二次電池用負極材料を用いたことを特徴とするリチウムイオン二次電池用負極および、該リチウムイオン二次電池用負極を用いたことを特徴とするリチウムイオン二次電池も含まれる。 In the present invention, a negative electrode material for a lithium ion secondary battery obtained by the production method, and a negative electrode for a lithium ion secondary battery, characterized in that the negative electrode material for a lithium ion secondary battery is used. And the lithium ion secondary battery characterized by using this negative electrode for lithium ion secondary batteries is also contained.
本発明によれば、出力特性、サイクル特性および初期効率に優れたリチウムイオン二次電池が得られる。 According to the present invention, a lithium ion secondary battery excellent in output characteristics, cycle characteristics, and initial efficiency can be obtained.
本発明のリチウムイオン二次電池用負極材料の製造方法は、炭素質物質前駆体と第１黒鉛粒子とを混合し、熱処理する熱処理工程；得られた熱処理物を粉砕して平均粒子径１０μｍ未満の粒子を得る粉砕工程；得られた平均粒子径１０μｍ未満の粒子とポリエチレン粒子および／またはポリスチレン粒子とを混合し、熱処理する被覆工程；を含むことを特徴とする。 The method for producing a negative electrode material for a lithium ion secondary battery according to the present invention comprises a heat treatment step in which a carbonaceous material precursor and first graphite particles are mixed and heat-treated; the obtained heat-treated product is pulverized to have an average particle diameter of less than 10 μm A pulverizing step of obtaining particles of the above; a coating step of mixing and heat-treating the obtained particles having an average particle diameter of less than 10 μm and polyethylene particles and / or polystyrene particles.
以下、本発明のリチウムイオン二次電池用負極材料（以下、単に「負極材料」と称することがある。）の製造方法について、詳細に説明する。前記熱処理工程では、炭素質物質前駆体と第１黒鉛粒子とを混合し、熱処理することにより、炭素質物質と第１黒鉛粒子とを含有する熱処理物を得る。本工程により得られた熱処理物は、炭素質物質を介して、第１黒鉛粒子同士が固着された複合物となっている。 Hereinafter, a method for producing a negative electrode material for a lithium ion secondary battery of the present invention (hereinafter, simply referred to as “negative electrode material”) will be described in detail. In the heat treatment step, the carbonaceous material precursor and the first graphite particles are mixed and heat treated to obtain a heat treated product containing the carbonaceous material and the first graphite particles. The heat-treated product obtained in this step is a composite in which the first graphite particles are fixed to each other through a carbonaceous material.
前記炭素質物質前駆体（炭化水素基含有化合物）としては、例えば、コールタールピッチ、石油系ピッチ、合成ピッチなどのピッチ；石油系油（石油系重質油の接触分解油、熱分解油、常圧残油、減圧残油など）および石炭系油などの重質油；ナフタレン、アントラセン、フェナントレン、ピレン、クリセン、ペリレンなどの縮合多環芳香族を熱処理して得られるタール；塩化ビニール、塩化ビニリデン、ポリアクリロニトリル、フェノール樹脂、芳香族ポリアミド、フルフリルアルコール樹脂、イミド樹脂などの樹脂；などが挙げられる。これらの炭素質物質前駆体は単独で使用してもよいし、２種以上を併用してもよい。これらの中でもピッチが好ましく、コールタールピッチがより好適である。 Examples of the carbonaceous material precursor (hydrocarbon group-containing compound) include pitches such as coal tar pitch, petroleum pitch, and synthetic pitch; petroleum oil (catalytic cracking oil, pyrolysis oil of heavy petroleum oil, Normal pressure residue, reduced pressure residue, etc.) and heavy oil such as coal oil; tar obtained by heat treatment of condensed polycyclic aromatics such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, perylene; vinyl chloride, chloride Examples thereof include resins such as vinylidene, polyacrylonitrile, phenol resin, aromatic polyamide, furfuryl alcohol resin, and imide resin. These carbonaceous material precursors may be used alone or in combination of two or more. Among these, pitch is preferable, and coal tar pitch is more preferable.
前記第１黒鉛粒子は、天然黒鉛粒子および人造黒鉛粒子のいずれでも良い。なお、本発明において、単に「粒子」という場合にはその形状は特に限定されず、球状、不定形状、鱗片状などを含むものとする。前記天然黒鉛粒子としては、例えば、鱗状黒鉛粒子、鱗片状黒鉛粒子、土状黒鉛粒子が挙げられる。これらの天然黒鉛粒子は、８５質量％〜９９質量％の純度を有する黒鉛を使用することが好ましく、公知の方法で黒鉛純度を９９質量％以上に高めたものを使用することがより好適である。前記人造黒鉛としては、例えば、コールタールピッチ、石油系ピッチ、アスファルト分解ピッチ、合成ピッチなどのピッチ；ナフタレン、アントラセン、フェナントレン、ピレン、クリセン、ペリレンなどの縮合多環芳香族を熱処理して得られるタール；石油系油及び石炭系油等の重質油；塩化ビニール、塩化ビニリデン、ポリアクリロニトリル、フェノール樹脂、芳香族ポリアミド、フルフリルアルコール樹脂、イミド樹脂等の樹脂；等を黒鉛化するまで高温熱処理して製造した黒鉛粒子を挙げることができる。これらの黒鉛粒子は、単独で使用してもよいし、２種以上を併用してもよい。これらの中でも本発明において、第１黒鉛粒子としては、天然黒鉛粒子が好ましく、鱗片状黒鉛粒子がより好ましい。 The first graphite particles may be natural graphite particles or artificial graphite particles. In the present invention, when the term “particle” is simply used, the shape is not particularly limited, and includes a spherical shape, an indefinite shape, a scale shape, and the like. Examples of the natural graphite particles include scaly graphite particles, scaly graphite particles, and earthy graphite particles. As these natural graphite particles, it is preferable to use graphite having a purity of 85% by mass to 99% by mass, and it is more preferable to use a graphite having a purity of 99% by mass or more by a known method. . The artificial graphite can be obtained, for example, by heat treatment of pitches such as coal tar pitch, petroleum-based pitch, asphalt cracking pitch, and synthetic pitch; and condensed polycyclic aromatics such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, and perylene. Tar; Heavy oils such as petroleum oils and coal oils; Resin such as vinyl chloride, vinylidene chloride, polyacrylonitrile, phenol resin, aromatic polyamide, furfuryl alcohol resin, imide resin; High-temperature heat treatment until graphitizing And graphite particles produced as described above. These graphite particles may be used alone or in combination of two or more. Among these, in the present invention, as the first graphite particles, natural graphite particles are preferable, and scaly graphite particles are more preferable.
前記第１黒鉛粒子のＢＥＴ比表面積は５ｍ2／ｇ以上が好ましく、より好ましくは７ｍ2／ｇ以上、さらに好ましくは１０ｍ2／ｇ以上であり、５０ｍ2／ｇ以下が好ましく、より好ましくは３０ｍ2／ｇ以下、さらに好ましくは２０ｍ2／ｇ以下である。ＢＴＥ比表面積が５ｍ2／ｇ以上であれば、反応面積が大きくなり急速充放電特性がより良好となり、５０ｍ2／ｇ以下であれば、最終的に得られる負極材料の比表面積が大きくなり過ぎず、電解液の分解反応を抑制できる。 BET specific surface area of the first graphite particle is preferably not less than 5 m 2 / g, more preferably 7m 2 / g or more, more preferably 10 m 2 / g or more, is preferably from 50 m 2 / g, more preferably 30m 2 / g or less, more preferably 20 m 2 / g or less. If the BTE specific surface area is 5 m 2 / g or more, the reaction area becomes large and rapid charge / discharge characteristics become better. If the BTE specific surface area is 50 m 2 / g or less, the specific surface area of the finally obtained negative electrode material becomes too large. Therefore, the decomposition reaction of the electrolytic solution can be suppressed.
前記第１黒鉛粒子の平均粒子径は１μｍ以上が好ましく、より好ましくは２μｍ以上、さらに好ましくは４μｍ以上であり、５０μｍ以下が好ましく、より好ましくは３０μｍ以下、さらに好ましくは２０μｍ以下である。前記第１黒鉛粒子の平均粒子径が１μｍ以上であれば、比表面積が大きくなり過ぎず、電解液の分解反応を抑制でき、５０μｍ以下であれば、相対的に比表面積が大きくなるため、反応面積が大きくなり急速充放電特性がより良好となる。ここで、本願において平均粒子径とは、特に記載がない限り、水に分散させた試料を、レーザ回折式粒度分布測定装置（例えば、島津製作所製の「ＳＡＬＤ（登録商標）−２０００」）により測定して、求められる体積基準メディアン径である。 The average particle diameter of the first graphite particles is preferably 1 μm or more, more preferably 2 μm or more, further preferably 4 μm or more, preferably 50 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less. If the average particle diameter of the first graphite particles is 1 μm or more, the specific surface area does not become too large and the decomposition reaction of the electrolytic solution can be suppressed. If the average particle diameter is 50 μm or less, the specific surface area becomes relatively large. The area becomes larger and the rapid charge / discharge characteristics become better. Here, in the present application, unless otherwise specified, the average particle size refers to a sample dispersed in water using a laser diffraction particle size distribution measuring apparatus (for example, “SALD (registered trademark) -2000” manufactured by Shimadzu Corporation). The volume-based median diameter obtained by measurement.
前記炭素質物質前駆体と第１黒鉛粒子とを混合する方法は、特に限定されず、材料の融点や軟化点によるが、例えば、第１黒鉛粒子および炭素質物質前駆体がいずれも固体の状態で機械的に混合する方法；炭素質物質前駆体が液体の状態で機械的に混合する方法；炭素質物質前駆体を溶媒（例えば、Ｎ−メチルピロリドン）に溶解させた後、これらを混合する方法などの従来用いられる方法を採用すればよい。また混合する際の温度は、使用する原料の融点や軟化点以上、硬化温度や揮発温度以下など、使用する原料に応じて適宜決定すればよい。 The method of mixing the carbonaceous material precursor and the first graphite particles is not particularly limited and depends on the melting point and softening point of the material. For example, the first graphite particles and the carbonaceous material precursor are both in a solid state. A method in which the carbonaceous material precursor is mechanically mixed in a liquid state; after the carbonaceous material precursor is dissolved in a solvent (for example, N-methylpyrrolidone), these are mixed. A conventionally used method such as a method may be employed. Moreover, what is necessary is just to determine suitably the temperature at the time of mixing according to the raw material to be used, such as more than melting | fusing point and softening point of the raw material to be used, and below a curing temperature and volatilization temperature.
炭素質物質前駆体と第１黒鉛粒子との混合比は、第１黒鉛粒子１００質量部に対して、炭素質物質前駆体を５質量部以上とすることが好ましく、より好ましくは１０質量部以上、さらに好ましくは２０質量部以上であり、１００質量部以下とすることが好ましく、より好ましくは８０質量部以下、さらに好ましくは５０質量部以下である。第１黒鉛粒子１００質量部に対して炭素質物質前駆体が５質量部以上であれば、炭素質物質による黒鉛の造粒効果がより良好となり、１００質量部以下であれば、得られる熱処理物において、相対的に黒鉛の含有量が多くなり、放電容量がより良好となる。 The mixing ratio of the carbonaceous material precursor and the first graphite particles is preferably 5 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the first graphite particles. More preferably, it is 20 parts by mass or more, preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 50 parts by mass or less. If the carbonaceous material precursor is 5 parts by mass or more with respect to 100 parts by mass of the first graphite particles, the granulation effect of graphite by the carbonaceous material becomes better. , The content of graphite is relatively increased, and the discharge capacity is further improved.
また、本発明においては、前記炭素質物質前駆体と第１黒鉛粒子に加えて、さらに前記第１黒鉛粒子よりも高比表面積を有する小粒径な炭素物質(以下、「微粒子炭素質物質」と称する場合がある。）を用いる態様も好ましい。このような微粒子炭素質物質を前記炭素質物質前駆体に分散させておくことにより、得られる負極材の粒子内の導電性を向上させることができ、得られるリチウムイオン二次電池の出力特性をより向上させることができる。 In the present invention, in addition to the carbonaceous material precursor and the first graphite particles, a carbon material having a smaller particle diameter (hereinafter referred to as “particulate carbonaceous material”) having a higher specific surface area than the first graphite particles. In some cases, an embodiment using the above is also preferable. By dispersing such a particulate carbonaceous material in the carbonaceous material precursor, the conductivity in the particles of the obtained negative electrode material can be improved, and the output characteristics of the resulting lithium ion secondary battery can be improved. It can be improved further.
前記微粒子炭素質物質は、前記第１黒鉛粒子よりも小粒径のものであれば特に限定されない。前記微粒子炭素質物質としては、例えば、カーボンブラック、炭素繊維、カーボンナノチューブ、黒鉛化カーボンブラックなどが挙げられ、これらの中でもカーボンブラックが好適である。これらの微粒子炭素質物質は単独で使用してもよいし、２種以上を併用してもよい。 The particulate carbonaceous material is not particularly limited as long as it has a smaller particle size than the first graphite particles. Examples of the particulate carbonaceous material include carbon black, carbon fiber, carbon nanotube, graphitized carbon black and the like. Among these, carbon black is preferable. These particulate carbonaceous materials may be used alone or in combination of two or more.
前記微粒子炭素質物質のＢＥＴ比表面積は１０ｍ2／ｇ以上が好ましく、より好ましくは２０ｍ2／ｇ以上、さらに好ましくは３０ｍ2／ｇ以上であり、１０００ｍ2／ｇ以下が好ましく、より好ましくは５００ｍ2／ｇ以下、さらに好ましくは２００ｍ2／ｇ以下である。微粒子炭素質物質のＢＴＥ比表面積が１０ｍ2／ｇ以上であれば、第１黒鉛粒子との接点が増加し、導電性改善効果がより良好となり、１０００ｍ2／ｇ以下であれば、電解液の分解反応を抑制できる。 The BET specific surface area of the particulate carbonaceous material is preferably 10 m 2 / g or more, more preferably 20 m 2 / g or more, still more preferably 30 m 2 / g or more, preferably 1000 m 2 / g or less, more preferably 500 m. 2 / g or less, more preferably 200 m 2 / g or less. If the BTE specific surface area of the particulate carbonaceous material is 10 m 2 / g or more, the contact point with the first graphite particles is increased and the effect of improving the conductivity is improved. If the BTE specific surface area is 1000 m 2 / g or less, the electrolyte solution Decomposition reaction can be suppressed.
前記微粒子炭素質物質の平均粒子径と前記第１黒鉛粒子の平均粒子径との比（微粒子炭素質物質／第１黒鉛粒子）は０．００５以上が好ましく、より好ましくは０．０１以上であり、０．２以下が好ましく、より好ましくは０．１以下である。前記平均粒子径の比が上記範囲内あれば、微粒子炭素質物質による導電性改善効果がより良好となる。 The ratio of the average particle size of the fine carbonaceous material to the average particle size of the first graphite particles (fine carbonaceous material / first graphite particles) is preferably 0.005 or more, more preferably 0.01 or more. 0.2 or less, more preferably 0.1 or less. When the ratio of the average particle diameter is within the above range, the conductivity improving effect by the fine particle carbonaceous material becomes better.
前記微粒子炭素質物質を用いる場合には、微粒子炭素質物質と第１黒鉛粒子との混合比は、第１黒鉛粒子１００質量部に対して、微粒子炭素質物質を０．１質量部以上とすることが好ましく、より好ましくは１質量部以上、さらに好ましくは３質量部以上であり、３０質量部以下とすることが好ましく、より好ましくは２０質量部以下、さらに好ましくは１０質量部以下である。第１黒鉛粒子１００質量部に対して微粒子炭素質物質が０．１質量部以上であれば、微粒子炭素質物質による導電性改善効果がより良好となり、３０質量部以下であれば、第１黒鉛粒子の配合比率が充分に高く、得られるリチウムイオン二次電池の放電容量がより良好となる。なお、微粒子炭素質物質を用いる場合の混合方法も特に限定されず、例えば、前記炭素質物質前駆体と第１黒鉛粒子との混合方法として例示した方法を採用すればよい。 When the particulate carbonaceous material is used, the mixing ratio of the particulate carbonaceous material and the first graphite particles is 0.1 parts by mass or more of the particulate carbonaceous material with respect to 100 parts by mass of the first graphite particles. It is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less. If the particulate carbonaceous material is 0.1 parts by mass or more with respect to 100 parts by mass of the first graphite particles, the conductivity improving effect by the particulate carbonaceous material becomes better, and if it is 30 parts by mass or less, the first graphite The mixing ratio of the particles is sufficiently high, and the resulting lithium ion secondary battery has a better discharge capacity. In addition, the mixing method in the case of using a fine particle carbonaceous material is not specifically limited, For example, the method illustrated as a mixing method of the said carbonaceous material precursor and 1st graphite particle may be employ | adopted.
前記炭素質物質前駆体と第１黒鉛粒子との混合物を熱処理する条件は、次の通りである。熱処理温度は、５００℃以上が好ましく、より好ましくは６００℃以上、さらに好ましくは７００℃以上であり、１６００℃以下が好ましく、より好ましくは１５００℃以下である。また、熱処理時間は０．１時間以上が好ましく、より好ましくは０．５時間以上であり、５時間以下が好ましく、より好ましくは３時間以下である。熱処理条件を上記範囲内とすることにより、炭素質物質前駆体を非晶質炭素に変化させることができる。なお、熱処理時の雰囲気は、アルゴン、ヘリウム、窒素などの不活性ガス雰囲気が好ましい。 Conditions for heat-treating the mixture of the carbonaceous material precursor and the first graphite particles are as follows. The heat treatment temperature is preferably 500 ° C. or higher, more preferably 600 ° C. or higher, still more preferably 700 ° C. or higher, preferably 1600 ° C. or lower, more preferably 1500 ° C. or lower. The heat treatment time is preferably 0.1 hour or longer, more preferably 0.5 hour or longer, 5 hours or shorter, more preferably 3 hours or shorter. By setting the heat treatment condition within the above range, the carbonaceous material precursor can be changed to amorphous carbon. Note that the atmosphere during the heat treatment is preferably an inert gas atmosphere such as argon, helium, or nitrogen.
次に、粉砕工程について説明する。前記粉砕工程では、前記熱処理工程で得られた熱処理物を粉砕して、平均粒子径１０μｍ未満の粒子（以下、「複合黒鉛粒子」と称することがある。）を得る。 Next, the grinding process will be described. In the pulverization step, the heat-treated product obtained in the heat treatment step is pulverized to obtain particles having an average particle diameter of less than 10 μm (hereinafter sometimes referred to as “composite graphite particles”).
熱処理物を粉砕する方法は、特に限定されるものでなく、ジェットミル、ディスクミル、ボールミル、ビーズミルなどを用いて行えばよい。熱処理物を粉砕して得られる複合黒鉛粒子の平均粒子径は１０μｍ未満が好ましい。該粒子の平均粒子径を１０μｍ未満とすることにより、リチウムイオンとの反応面積が増大して、得られるリチウムイオン二次電池の出力特性が向上する。なお、該複合黒鉛粒子の平均粒子径の下限値は特に限定されないが、３μｍが好ましい。 The method for pulverizing the heat-treated product is not particularly limited, and may be performed using a jet mill, a disk mill, a ball mill, a bead mill, or the like. The average particle size of the composite graphite particles obtained by pulverizing the heat-treated product is preferably less than 10 μm. By setting the average particle size of the particles to less than 10 μm, the reaction area with lithium ions is increased, and the output characteristics of the obtained lithium ion secondary battery are improved. The lower limit of the average particle diameter of the composite graphite particles is not particularly limited, but 3 μm is preferable.
このようにして得られた複合黒鉛粒子をリチウムイオン二次電池用負極材料に用いる、特に導電材として用いることにより、リチウムイオン二次電池のサイクル特性が向上する。すなわち、導電材として、鱗片状黒鉛粒子をそのまま用いた場合には、黒鉛粒子間の接点が増加し導電性が向上するが、鱗片状黒鉛は、圧縮によって配向しやすいため、電解液の通液性が低下する。これに対して、複合黒鉛粒子は、平均粒子径が１０μｍ未満と小さいため、黒鉛粒子間の接点を十分に増加させることができる。さらに、複合黒鉛粒子は、第１黒鉛粒子が炭素物質前駆体により被覆、凝集化された構造をとり、十分に硬度が高められているため、圧縮によっても配向しにくく、電解液の通液性が良好となる。 By using the composite graphite particles thus obtained as a negative electrode material for a lithium ion secondary battery, particularly as a conductive material, the cycle characteristics of the lithium ion secondary battery are improved. That is, when the flaky graphite particles are used as they are as the conductive material, the contact between the graphite particles is increased and the conductivity is improved. However, since the flaky graphite is easily oriented by compression, the electrolyte solution is passed therethrough. Sex is reduced. On the other hand, since the composite graphite particles have a small average particle diameter of less than 10 μm, it is possible to sufficiently increase the contact points between the graphite particles. Furthermore, the composite graphite particles have a structure in which the first graphite particles are coated and agglomerated with a carbon material precursor and have a sufficiently high hardness, so that they are difficult to be oriented even by compression, and the electrolyte permeability is low. Becomes better.
次に、被覆工程について説明する。前記被覆工程では、前記粉砕工程で得られた平均粒子径１０μｍ未満の粒子（複合黒鉛粒子）と、ポリエチレン粒子および／またはポリスチレン粒子とを混合し、熱処理する。本工程を経ることにより、複合黒鉛粒子表面は、ポリエチレンおよび／またはポリスチレンの熱分解成分（例えば、ポリスチレンでは、トルエン、スチレン、スチレン２量体、スチレン３量体など）に由来する低結晶性炭素によって被覆される。このように粒子表面が安定な低結晶性炭素に被覆されることにより、粒子表面が不活性化され電解液の分解が抑制されるため、得られるリチウムイオン二次電池の初期効率が向上する。また、黒鉛粒子は、通常その結晶構造による制約からエッジ部分でのみリチウムイオンの授受が行われるが、基底面上に被覆した低結晶性炭素部分からもリチウムイオンとの反応が進行するようになるため、得られるリチウムイオン二次電池の出力特性が向上する。 Next, the covering process will be described. In the coating step, particles (composite graphite particles) having an average particle diameter of less than 10 μm obtained in the pulverization step are mixed with polyethylene particles and / or polystyrene particles and heat-treated. By passing through this step, the surface of the composite graphite particle becomes a low crystalline carbon derived from a thermal decomposition component of polyethylene and / or polystyrene (for example, polystyrene, toluene, styrene, styrene dimer, styrene trimer, etc.). Is covered. Since the particle surface is thus coated with stable low crystalline carbon, the particle surface is inactivated and decomposition of the electrolytic solution is suppressed, so that the initial efficiency of the obtained lithium ion secondary battery is improved. In addition, graphite particles usually give and receive lithium ions only at the edge due to restrictions due to their crystal structure, but the reaction with lithium ions also proceeds from the low crystalline carbon part coated on the basal plane. Therefore, the output characteristics of the obtained lithium ion secondary battery are improved.
なお、ポリエチレン粒子および／またはポリスチレン粒子の代わりに、熱分解に際して気相拡散しにくい樹脂（例えば、フェノール樹脂）を使用すると、気相拡散しにくいため、複合黒鉛粒子表面を十分に被覆することができない。また、気相拡散せずに残留した炭化物により複合黒鉛粒子同士が固着したり、炭化物の塊ができたりするため、本発明の効果が得られない。また、例えばスチレン（モノマー）を用いた場合、熱分解成分はトルエンまたはスチレンであり、複合黒鉛粒子表面を低結晶性炭素により被覆し難く、複合黒鉛粒子表面の不活性化や、リチウムイオンとの反応面積増大が十分でなく、本発明の効果が得られない。 If a resin (for example, a phenol resin) that hardly diffuses in the gas phase during thermal decomposition is used in place of the polyethylene particles and / or polystyrene particles, it is difficult to diffuse in the gas phase. Can not. Further, the composite graphite particles are fixed to each other by the carbide remaining without being diffused in the gas phase, or a lump of carbide is formed, so that the effect of the present invention cannot be obtained. For example, when styrene (monomer) is used, the thermal decomposition component is toluene or styrene, and it is difficult to cover the surface of the composite graphite particles with low crystalline carbon, and the surface of the composite graphite particles is inactivated The reaction area is not sufficiently increased, and the effects of the present invention cannot be obtained.
前記ポリエチレン粒子としては、ポリエチレンから構成される粒子であれば、特に限定されない。前記ポリエチレン粒子および／またはポリスチレン粒子の平均粒子径は、０．１μｍ以上が好ましく、より好ましくは１μｍ以上、さらに好ましくは５０μｍ以上であり、２０ｍｍ以下が好ましく、より好ましくは１０ｍｍ以下、さらに好ましくは５ｍｍ以下である。ポリエチレン粒子および／またはポリスチレン粒子の平均粒子径が上記範囲内であれば、複合黒鉛粒子との混合効率がより向上する。 The polyethylene particles are not particularly limited as long as they are particles composed of polyethylene. The average particle diameter of the polyethylene particles and / or polystyrene particles is preferably 0.1 μm or more, more preferably 1 μm or more, further preferably 50 μm or more, preferably 20 mm or less, more preferably 10 mm or less, and further preferably 5 mm. It is as follows. When the average particle diameter of the polyethylene particles and / or polystyrene particles is within the above range, the mixing efficiency with the composite graphite particles is further improved.
前記複合黒鉛粒子と、ポリエチレン粒子および／またはポリスチレン粒子との混合方法は特に限定されないが、ポリエチレン粒子およびポリスチレン粒子の融点以下の温度で、機械的に混合することが好ましい。 The mixing method of the composite graphite particles and the polyethylene particles and / or polystyrene particles is not particularly limited, but it is preferable to mechanically mix the composite graphite particles at a temperature lower than the melting point of the polyethylene particles and the polystyrene particles.
前記複合黒鉛粒子とポリエチレン粒子および／またはポリスチレン粒子との混合比は、複合黒鉛粒子１００質量部に対して、ポリエチレン粒子および／またはポリスチレン粒子を０．１質量部以上とすることが好ましく、より好ましくは０．５質量部以上、さらに好ましくは１質量部以上であり、１００質量部以下とすることが好ましく、より好ましくは５０質量部以下、さらに好ましくは２０質量部以下である。複合黒鉛粒子１００質量部に対してポリエチレン粒子および／またはポリスチレン粒子が０．１質量部以上であれば、複合黒鉛粒子表面がポリエチレンおよび／またはポリスチレンの熱分解成分に由来する低結晶性炭素によって十分に被覆され、電解液の分解がより抑制される。また、複合黒鉛粒子１００質量部に対してポリエチレン粒子および／またはポリスチレン粒子が１００質量部以下であれば、相対的に黒鉛粒子の割合が小さくなりすぎず、電池容量の低下をより抑制することができる。 The mixing ratio of the composite graphite particles and the polyethylene particles and / or polystyrene particles is preferably 0.1 parts by mass or more of polyethylene particles and / or polystyrene particles, more preferably 100 parts by mass of the composite graphite particles. Is 0.5 parts by mass or more, more preferably 1 part by mass or more, preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 20 parts by mass or less. If the polyethylene particles and / or polystyrene particles are 0.1 parts by mass or more with respect to 100 parts by mass of the composite graphite particles, the surface of the composite graphite particles is sufficiently due to the low crystalline carbon derived from the thermal decomposition component of polyethylene and / or polystyrene. And the decomposition of the electrolytic solution is further suppressed. Further, if the polyethylene particles and / or polystyrene particles are 100 parts by mass or less with respect to 100 parts by mass of the composite graphite particles, the proportion of the graphite particles is not relatively reduced, and the battery capacity can be further prevented from decreasing. it can.
前記複合黒鉛粒子とポリエチレン粒子および／またはポリスチレン粒子との混合物を熱処理する条件は、次の通りである。熱処理温度は、５００℃以上が好ましく、より好ましくは６００℃以上、さらに好ましくは８００℃以上であり、２８００℃以下が好ましく、より好ましくは２０００℃以下、さらに好ましくは１３００℃以下である。また、熱処理時間は０．０１時間以上が好ましく、より好ましくは０．１時間以上、さらに好ましくは０．５時間以上であり、５時間以下が好ましく、より好ましくは４時間以下、さらに好ましくは２時間以下である。熱処理条件を上記範囲内とすることにより、ポリエチレンおよび／またはポリスチレンの分解成分を低結晶性炭素に変化させることができ。なお、熱処理時の雰囲気は、アルゴン、ヘリウム、窒素などの不活性ガス雰囲気が好ましい。 Conditions for heat-treating the mixture of the composite graphite particles and the polyethylene particles and / or polystyrene particles are as follows. The heat treatment temperature is preferably 500 ° C. or more, more preferably 600 ° C. or more, further preferably 800 ° C. or more, preferably 2800 ° C. or less, more preferably 2000 ° C. or less, and further preferably 1300 ° C. or less. The heat treatment time is preferably 0.01 hours or more, more preferably 0.1 hours or more, still more preferably 0.5 hours or more, preferably 5 hours or less, more preferably 4 hours or less, still more preferably 2 hours. Below time. By setting the heat treatment condition within the above range, the decomposition component of polyethylene and / or polystyrene can be changed to low crystalline carbon. Note that the atmosphere during the heat treatment is preferably an inert gas atmosphere such as argon, helium, or nitrogen.
また、本発明においては、前記平均粒子径１０μｍ未満の粒子（複合黒鉛粒子）と、該粒子よりも平均粒子径が大きい第２黒鉛粒子とを混合した後、得られた混合物とポリエチレンおよび／またはポリスチレン粒子とを混合し、熱処理する態様も好ましい。前記複合黒鉛粒子よりも平均粒子径の大きい第２黒鉛粒子を混合することにより、リチウムイオン二次電池用負極を作製した際に、第２黒鉛粒子間に複合黒鉛粒子が介在するような構成となり電極密度がより向上する。また、この際、複合黒鉛粒子が導電材として作用して黒鉛粒子間の接点が増加し、さらに複合黒鉛粒子がプレスにより配向しにくいので通液性も維持されため、得られるリチウムイオン二次電池の出力特性、サイクル特性がより向上する。 In the present invention, the particles (composite graphite particles) having an average particle diameter of less than 10 μm and the second graphite particles having an average particle diameter larger than the particles are mixed, and then the obtained mixture and polyethylene and / or An embodiment in which polystyrene particles are mixed and heat-treated is also preferable. By mixing the second graphite particles having an average particle size larger than that of the composite graphite particles, the composite graphite particles are interposed between the second graphite particles when a negative electrode for a lithium ion secondary battery is produced. The electrode density is further improved. Also, at this time, the composite graphite particles act as a conductive material to increase the number of contacts between the graphite particles, and the composite graphite particles are not easily oriented by pressing, so that the liquid permeability is maintained, so that the obtained lithium ion secondary battery The output characteristics and cycle characteristics are improved.
前記第２黒鉛粒子は、前記複合黒鉛粒子よりも平均粒子径が大きいものであれば、特に限定されず、前記第１黒鉛粒子に用いることができるものとして例示した天然黒鉛粒子および人造黒鉛粒子のいずれでも良く、これらを単独で使用してもよいし、２種以上を併用してもよい。なお、負極材への通液性をより向上できることから、前記第２黒鉛粒子としては、球形粒子が好ましく、天然黒鉛が球形化されている粒子、例えば、鱗片状天然黒鉛粒子を球形化した球形化黒鉛粒子がより好適である。なお、球形化天然黒鉛粒子は、本発明者らが先に提案した方法（特開平１１−２６３６１２号）やこれに類似する方法で製造できる。 The second graphite particles are not particularly limited as long as the average particle diameter is larger than that of the composite graphite particles, and natural graphite particles and artificial graphite particles exemplified as those that can be used for the first graphite particles. Any of these may be used alone, or two or more of them may be used in combination. In addition, since the liquid permeability to the negative electrode material can be further improved, the second graphite particles are preferably spherical particles, and particles in which natural graphite is spheroidized, for example, spherical particles obtained by spheroidizing flaky natural graphite particles. Graphitized particles are more preferred. Spherical natural graphite particles can be produced by the method previously proposed by the present inventors (Japanese Patent Laid-Open No. 11-263612) or a method similar thereto.
前記第２黒鉛粒子の平均粒子径は４μｍ以上が好ましく、より好ましくは６μｍ以上、さらに好ましくは８μｍ以上であり、５０μｍ以下が好ましく、より好ましくは３０μｍ以下、さらに好ましくは２０μｍ以下である。第２黒鉛粒子の平均粒子径が４μｍ以上であれば、第２黒鉛粒子間に複合黒鉛粒子が介在し易くなり、また、５０μｍ以下であれば、リチウムイオン二次電池用負極において、厚み６０μｍ程度の負極材層を形成し易くなる。 The average particle diameter of the second graphite particles is preferably 4 μm or more, more preferably 6 μm or more, further preferably 8 μm or more, preferably 50 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less. If the average particle diameter of the second graphite particles is 4 μm or more, the composite graphite particles are likely to intervene between the second graphite particles. If the average particle diameter is 50 μm or less, the thickness of the negative electrode for a lithium ion secondary battery is about 60 μm. It becomes easy to form the negative electrode material layer.
前記第２黒鉛粒子を用いる場合、前記複合黒鉛粒子と第２黒鉛粒子の質量比（複合黒鉛粒子／第２黒鉛粒子）は４０〜５／６０〜９５が好ましく、より好ましくは３０〜１０／７０〜９０である。また、前記複合黒鉛粒子と第２黒鉛粒子との合計１００質量部に対して、ポリエチレン粒子および／またはポリスチレン粒子を１質量部以上とすることが好ましく、より好ましくは５質量部以上であり、３０質量部以下とすることが好ましく、より好ましくは１５質量部以下である。なお、第２黒鉛粒子を用いる場合の混合方法も特に限定されないが、ポリエチレン粒子およびポリスチレン粒子の融点以下の温度で、機械的に混合することが好ましい。 When the second graphite particles are used, the mass ratio of the composite graphite particles to the second graphite particles (composite graphite particles / second graphite particles) is preferably 40 to 5/60 to 95, more preferably 30 to 10/70. ~ 90. Further, the total amount of the composite graphite particles and the second graphite particles is preferably 100 parts by mass, and the polyethylene particles and / or polystyrene particles are preferably 1 part by mass or more, more preferably 5 parts by mass or more, 30 The amount is preferably not more than part by mass, and more preferably not more than 15 parts by mass. In addition, although the mixing method in the case of using 2nd graphite particle | grains is not specifically limited, It is preferable to mix mechanically at the temperature below melting | fusing point of a polyethylene particle and a polystyrene particle.
本発明のリチウムイオン二次電池用負極材料は、上記製造方法により得られることを特徴とする。本発明の負極材料を用いることにより、出力特性、サイクル特性および初期効率に優れたリチウムイオン二次電池が得られる。 The negative electrode material for a lithium ion secondary battery of the present invention is obtained by the above production method. By using the negative electrode material of the present invention, a lithium ion secondary battery excellent in output characteristics, cycle characteristics and initial efficiency can be obtained.
本発明のリチウムイオン二次電池用負極は、前記本発明の負極材料を用いることを特徴とする。前記リチウムイオン二次電池用負極は、公知の方法により製造できる。例えば、集電板の表面に、本発明の負極材料とバインダーを分散させたスラリーを塗布し、次に乾燥することにより製造できる。集電板としては、一般的に銅箔が使用される。また、バインダーは、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、フッ化ビニリデン／ヘキサフルオロプロピレン共重合体、テトラフルオロエチレン／ヘキサフルオロプロピレン／フッ化ビニリデン共重合体などのフッ素系高分子化合物；カルボキシメチルセルロース、スチレン−ブタジエンゴム、アクリロニトリル−ブタジエンゴムなどが使用される。これらのバインダーは、通常、溶剤に溶解して使用される。 The negative electrode material of the present invention is used for the negative electrode for a lithium ion secondary battery of the present invention. The negative electrode for a lithium ion secondary battery can be produced by a known method. For example, it can be produced by applying a slurry in which the negative electrode material of the present invention and a binder are dispersed to the surface of the current collector plate, and then drying. As the current collector plate, a copper foil is generally used. The binder is a fluorine-based polymer compound such as polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer; carboxymethyl cellulose, Styrene-butadiene rubber, acrylonitrile-butadiene rubber or the like is used. These binders are usually used after being dissolved in a solvent.
本発明のリチウムイオン二次電池は前記本発明のリチウムイオン二次電池用負極を用いたことを特徴とする。前記リチウムイオン二次電池は、負極の他、正極、電解液およびセパレータを主要構成としており、負極に前記本発明のリチウムイオン二次電池用負極を使用している。前記正極材料としては、例えば、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＮｉ1-yＣｏｙＯ2、ＬｉＭｎＯ2、ＬｉＭｎ2Ｏ4、ＬｉＦｅＯ2などが挙げられる。また、正極のバインダーとしては、例えば、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリ四フッ化エチレン（ＰＴＦＥ）などを採用できる。また、導電材として、カーボンブラックなどを混合しても良い。電解液としては、例えば、エチレンカーボネート（ＥＣ）などの有機溶媒や、該有機溶媒とジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、１，２−ジメトキシエタン、１，２−ジエトキシメタン、エトキシメトキシエタンなどの低沸点溶媒との混合溶媒に、ＬｉＰＦ6やＬｉＢＦ4、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＡｓＦ6などの電解液溶質（電解質塩）を溶解した溶液が用いられる。セパレータとしては、例えば、ポリエチレンやポリプロピレンなどのポリオレフィンを主成分とした不織布、クロス、微孔フィルム等が用いられる。 The lithium ion secondary battery of the present invention uses the negative electrode for a lithium ion secondary battery of the present invention. The lithium ion secondary battery mainly includes a positive electrode, an electrolytic solution, and a separator in addition to the negative electrode, and the negative electrode for a lithium ion secondary battery according to the present invention is used as the negative electrode. As the cathode material, for example, LiCoO 2, LiNiO 2, LiNi 1-y Co y O 2, LiMnO 2, LiMn 2 O 4, LiFeO 2 , and the like. Moreover, as a binder of a positive electrode, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), etc. are employable, for example. Further, carbon black or the like may be mixed as a conductive material. Examples of the electrolytic solution include an organic solvent such as ethylene carbonate (EC), the organic solvent and dimethyl carbonate (DMC), diethyl carbonate (DEC), 1,2-dimethoxyethane, 1,2-diethoxymethane, and ethoxy. A solution in which an electrolyte solution solute (electrolyte salt) such as LiPF 6 , LiBF 4 , LiClO 4 , LiCF 3 SO 3 , or LiAsF 6 is dissolved in a mixed solvent with a low boiling point solvent such as methoxyethane is used. As the separator, for example, a nonwoven fabric, a cloth, a microporous film, or the like whose main component is a polyolefin such as polyethylene or polypropylene is used.
以下に実施例を挙げて本発明をより具体的に説明するが、本発明は、下記実施例によって限定されるものではなく、前・後記の趣旨に適合しうる範囲で適宜変更して実施することも可能であり、それらはいずれも本発明の技術的範囲に包含される。 The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.
［評価方法］
１．初期効率
電池の充電を、０．２Ｃの定電流値で電圧が０．０７Ｖになるまで行い、続けて、０．０７Ｖの定電圧で電流値が０．０７ｍＡになるまで行い、充電容量を測定した。次に、電池の放電を０．２Ｃの定電流値で電圧が１．５Ｖになるまで行い、放電容量を測定した。なお、電池の充放電は、２５℃で行った。電池の初期効率を、一回目の充電容量と一回目の放電容量から下記式（１）により算出した。
[Evaluation methods]
1. Initial efficiency The battery is charged at a constant current value of 0.2 C until the voltage reaches 0.07 V, and then at a constant voltage of 0.07 V until the current value reaches 0.07 mA, and the charge capacity is measured. did. Next, the battery was discharged at a constant current value of 0.2 C until the voltage reached 1.5 V, and the discharge capacity was measured. In addition, charging / discharging of the battery was performed at 25 degreeC. The initial efficiency of the battery was calculated by the following formula (1) from the first charge capacity and the first discharge capacity.
２．サイクル特性
電池の充電を、１Ｃの定電流で４．２Ｖまで行った後、続けて、４．２Ｖの定電圧で電流値が０．２ｍＡになるまで行った。次に、電池の放電を、１Ｃの定流値で電圧が３．０Ｖになるまで行い、放電容量を測定した。この充放電サイクルを５０回繰り返した。なお、電池の充放電は、２５℃で行った。電池のサイクル特性を１サイクル目の放電容量と５０サイクル目の放電容量から下記式（２）により算出した。
2. Cycle characteristics The battery was charged up to 4.2 V at a constant current of 1 C, and then continuously until the current value reached 0.2 mA at a constant voltage of 4.2 V. Next, the battery was discharged until the voltage reached 3.0 V at a constant current value of 1 C, and the discharge capacity was measured. This charge / discharge cycle was repeated 50 times. In addition, charging / discharging of the battery was performed at 25 degreeC. The cycle characteristics of the battery were calculated by the following formula (2) from the discharge capacity at the first cycle and the discharge capacity at the 50th cycle.
３．出力特性
電池のＳＯＣ（state of charge）を５０％に調節した後、１Ｃの定電流値で放電し１０秒目の電圧を測定した。同様にして、順次３Ｃ、５Ｃの定電流値で放電し１０秒目の電圧を測定した。なお、電池の充放電は、−２０℃で行った。得られた値から電流電圧特性直線を作成し、１．０Ｖに外挿した場合の電流値を算出し出力特性（ｍＡ）とした。
3. Output Characteristics After adjusting the SOC (state of charge) of the battery to 50%, the battery was discharged at a constant current value of 1 C, and the voltage at 10 seconds was measured. In the same manner, the batteries were sequentially discharged at a constant current value of 3C and 5C, and the voltage at 10 seconds was measured. In addition, charging / discharging of the battery was performed at -20 degreeC. A current-voltage characteristic straight line was created from the obtained values, and the current value when extrapolated to 1.0 V was calculated as the output characteristic (mA).
リチウムイオン二次電池用負極材料の作製
製造例１
平均粒子径２０μｍの鱗片状天然黒鉛をカウンタージェットミル（「ホソカワミクロン社製、型式「１００ＡＦＧ」）を用いて、試料量２００ｇ、ノズル吐出空気圧０．２０ＭＰａ、操作時間２０分の条件で球形化し、平均粒子径１２μｍの球形化黒鉛粒子を得た。
第１黒鉛粒子としての鱗片状黒鉛（平均粒子径６μｍ、比表面積１５ｍ2／ｇ）２１０ｇ、炭素質物質前駆体としてのコールタールピッチ（Ｖｏｌａｔｉｌｅ Ｍａｔｔｅｒ４０質量％）９０ｇおよび溶媒としてのＮＭＰ（Ｎ−メチルピロリドン）（キシダ化学社製、一級試薬）２００ｇを撹拌、混合した。得られた混合物を窒素雰囲気下、８００℃で２時間熱処理し、更に窒素雰囲気下、１１００℃で２時間熱処理して塊状の複合黒鉛を得た。得られた塊状複合黒鉛を、ジェットミルを用いて粉砕し粒径を調整して、平均粒子径６μｍの複合黒鉛粒子１を得た。
第２黒鉛粒子としての前記球形化黒鉛粒子、複合黒鉛粒子１およびポリスチレン粒子（キシダ化学社製、粒子径３ｍｍ）を、質量比で７３：１８：９の割合で混合し、窒素雰囲気下、８００℃で２時間熱処理することによりリチウムイオン二次電池用負極材料Ａを得た。
Production Example 1 of Anode Material for Lithium Ion Secondary Battery
Using a counter jet mill (model “100AFG” manufactured by Hosokawa Micron Corporation), flaky natural graphite having an average particle diameter of 20 μm is spheroidized under the conditions of a sample amount of 200 g, a nozzle discharge air pressure of 0.20 MPa, and an operation time of 20 minutes. Spherical graphite particles having a particle diameter of 12 μm were obtained.
Scalar graphite (average particle diameter 6 μm, specific surface area 15 m 2 / g) 210 g as first graphite particles, coal tar pitch (Volatyl Matter 40% by mass) 90 g as a carbonaceous material precursor, and NMP (N-methyl as a solvent) Pyrrolidone) (Kishida Chemical Co., Ltd., first grade reagent) 200 g was stirred and mixed. The obtained mixture was heat-treated at 800 ° C. for 2 hours under a nitrogen atmosphere, and further heat-treated at 1100 ° C. for 2 hours under a nitrogen atmosphere to obtain massive composite graphite. The obtained massive composite graphite was pulverized using a jet mill and the particle size was adjusted to obtain composite graphite particles 1 having an average particle size of 6 μm.
The spheroidized graphite particles, the composite graphite particles 1 and the polystyrene particles (manufactured by Kishida Chemical Co., Ltd., particle diameter: 3 mm) as the second graphite particles are mixed at a mass ratio of 73: 18: 9, and the mixture is added under a nitrogen atmosphere. The negative electrode material A for lithium ion secondary batteries was obtained by heat-processing at 2 degreeC for 2 hours.
製造例２
第１黒鉛粒子としての鱗片状黒鉛（平均粒子径６μｍ、比表面積１５ｍ2／ｇ）１９７ｇ、微粒子炭素質物質としてのカーボンブラック（三菱化学社製、ＨＰ２５２、平均粒子径０．４μｍ）１３．２ｇ、炭素質物質前駆体としてのコールタールピッチ（Ｖｏｌａｔｉｌｅ Ｍａｔｔｅｒ４０質量％）９０ｇおよび溶媒としてのＮＭＰ（Ｎ−メチルピロリドン）（キシダ化学社製、一級試薬）２００ｇを撹拌、混合した。得られた混合物を窒素雰囲気下、８００℃で２時間熱処理し、更に窒素雰囲気下、１１００℃で２時間熱処理して塊状の複合黒鉛を得た。得られた塊状複合黒鉛を、ジェットミルを用いて粉砕し粒径を調整して、平均粒子径６μｍの複合黒鉛粒子２を得た。
第２黒鉛粒子として製造例１で得た球形化黒鉛粒子、上記複合黒鉛粒子２およびポリスチレン粒子（キシダ化学社製、粒子径３ｍｍ）を、質量比で７３：１８：９の割合で混合し、窒素雰囲気下、８００℃で２時間熱処理することによりリチウムイオン二次電池用負極材料Ｂを得た。
Production Example 2
Scale-like graphite as the first graphite particles (average particle diameter 6 μm, specific surface area 15 m 2 / g) 197 g, carbon black as the particulate carbonaceous material (manufactured by Mitsubishi Chemical Corporation, HP252, average particle diameter 0.4 μm) 13.2 g Then, 90 g of coal tar pitch (Volatile Matter 40% by mass) as a carbonaceous material precursor and 200 g of NMP (N-methylpyrrolidone) (manufactured by Kishida Chemical Co., Ltd., primary reagent) as a solvent were stirred and mixed. The obtained mixture was heat-treated at 800 ° C. for 2 hours under a nitrogen atmosphere, and further heat-treated at 1100 ° C. for 2 hours under a nitrogen atmosphere to obtain massive composite graphite. The obtained massive composite graphite was pulverized using a jet mill and the particle size was adjusted to obtain composite graphite particles 2 having an average particle size of 6 μm.
The spherical graphite particles obtained in Production Example 1 as the second graphite particles, the composite graphite particles 2 and the polystyrene particles (manufactured by Kishida Chemical Co., Ltd., particle diameter: 3 mm) are mixed at a mass ratio of 73: 18: 9, A negative electrode material B for a lithium ion secondary battery was obtained by heat treatment at 800 ° C. for 2 hours in a nitrogen atmosphere.
製造例３
製造例１で得た球形化黒鉛粒子１００ｇとポリスチレン粒子（キシダ化学社製、粒子径３ｍｍ）１０ｇとを混合し、窒素雰囲気下、８００℃で２時間熱処理することにより、改質粒子を得た。
得られた改質粒子と製造例１で得た複合黒鉛粒子１とを、質量比で８０：２０の割合で混合することによりリチウムイオン二次電池用負極材料Ｃを得た。
Production Example 3
The modified particles were obtained by mixing 100 g of the spheroidized graphite particles obtained in Production Example 1 and 10 g of polystyrene particles (manufactured by Kishida Chemical Co., Ltd., particle diameter: 3 mm) and heat-treating them at 800 ° C. for 2 hours in a nitrogen atmosphere. .
The obtained modified particles and the composite graphite particles 1 obtained in Production Example 1 were mixed at a mass ratio of 80:20 to obtain a negative electrode material C for a lithium ion secondary battery.
製造例４
製造例３で得た改質粒子を、そのままリチウムイオン二次電池用負極材料Ｄとして用いた。
Production Example 4
The modified particles obtained in Production Example 3 were used as they were as the negative electrode material D for lithium ion secondary batteries.
リチウムイオン二次電池用負極の作製
リチウムイオン二次電池用負極材料Ａ〜Ｄを用いて、リチウムイオン二次電池用負極Ａ〜Ｄを次のようにして作製した。まず、リチウムイオン二次電池用負極材料１００質量部、ＣＭＣ（カルボキシメチルセルロース）水溶液（濃度２．０質量％）５０質量部、ＳＢＲ（スチレンブタジエンゴム）分散液（ＳＢＲ含有率；５．０質量％、分散媒；水）２０質量部、純水３０質量部を、撹拌機を用いて撹拌し電極材スラリーを得た。
Production of Negative Electrode for Lithium Ion Secondary Battery Using negative electrode materials A to D for lithium ion secondary batteries, negative electrodes A to D for lithium ion secondary batteries were produced as follows. First, 100 parts by mass of a negative electrode material for a lithium ion secondary battery, 50 parts by mass of a CMC (carboxymethylcellulose) aqueous solution (concentration: 2.0% by mass), an SBR (styrene butadiene rubber) dispersion (SBR content: 5.0% by mass) , Dispersion medium; water) 20 parts by mass and 30 parts by mass of pure water were stirred using a stirrer to obtain an electrode material slurry.
得られた電極材スラリーを銅箔（厚み；１８μｍ）上に塗布した後、１００℃に設定した乾燥機で１０分間乾燥した。乾燥後、電極材膜が形成された銅箔を、直径１．６ｃｍの円形に打ち抜いた後、この直径１．６ｃｍ銅箔の電極材付着量を測定すると９ｍｇであった。電極材膜が形成された銅箔をローラープレス機でプレスして、銅箔上に形成された電極材膜の密度を１．３０ｇ／ｃｍ3に調整し、リチウムイオン二次電池用負極Ａ〜Ｄを作製した。 After apply | coating the obtained electrode material slurry on copper foil (thickness; 18 micrometers), it dried for 10 minutes with the dryer set to 100 degreeC. After drying, the copper foil on which the electrode material film was formed was punched into a circle having a diameter of 1.6 cm, and the amount of the electrode material attached to the 1.6 cm diameter copper foil was measured to be 9 mg. The copper foil on which the electrode material film was formed was pressed with a roller press to adjust the density of the electrode material film formed on the copper foil to 1.30 g / cm 3 , and the negative electrodes A to A for lithium ion secondary batteries D was produced.
リチウムイオン二次電池の作製
リチウムイオン二次電池用の正極としては、初期効率、出力特性を算出するためのリチウムイオン二次電池用にはリチウム箔を用い、サイクル特性を算出するためのリチウムイオン二次電池用にはＬｉＣｏＯ2を活物質とする電極を用いた。ＬｉＣｏＯ2を活物質とする電極は、次のようにして作製した。ＬｉＣｏＯ2９０質量部に対して、バインダーとしてポリフッ化ビニリデン（ＰＶｄＦ）５質量部、導電材としてカーボンブラック５質量部を混合し、これにＮ−メチル−２−ピロリドン（ＮＭＰ）２００質量部を加えて電極材スラリーを作製した。得られた電極材スラリーをアルミニウム箔（厚み；３０μｍ）上に塗布し、１００℃に設定した乾燥機で２０分間乾燥した。乾燥後、電極材膜が形成されたアルミニウム箔を直径１．６ｃｍの円形に打ち抜いた後、この直径１．６ｃｍのアルミニウム箔の電極材塗布量を測定すると４５ｍｇであった。電極材膜が形成されたアルミニウム箔をローラープレス機でプレスして、アルミニウム箔上に形成された電極材膜の密度を２．８ｇ／ｃｍ3に調整し、リチウムイオン二次電池用正極を作製した。
Preparation of lithium ion secondary battery As positive electrode for lithium ion secondary battery, lithium ion is used for lithium ion secondary battery for calculating initial efficiency and output characteristics, and lithium ion for calculating cycle characteristics An electrode using LiCoO 2 as an active material was used for the secondary battery. An electrode using LiCoO 2 as an active material was produced as follows. To 90 parts by mass of LiCoO 2, 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder and 5 parts by mass of carbon black as a conductive material are mixed, and 200 parts by mass of N-methyl-2-pyrrolidone (NMP) is added thereto. Thus, an electrode material slurry was prepared. The obtained electrode material slurry was applied onto an aluminum foil (thickness: 30 μm) and dried for 20 minutes with a dryer set at 100 ° C. After drying, the aluminum foil on which the electrode material film was formed was punched into a circle having a diameter of 1.6 cm, and the amount of the electrode material applied to the aluminum foil having a diameter of 1.6 cm was measured to be 45 mg. The aluminum foil on which the electrode material film is formed is pressed with a roller press, and the density of the electrode material film formed on the aluminum foil is adjusted to 2.8 g / cm 3 to produce a positive electrode for a lithium ion secondary battery. did.
上記正極と前記リチウムイオン電池用負極Ａ〜Ｄとを、セパレータ（Ｃｅｌｇａｒｄ社製、「セルガード（登録商標） ＃３５０１」）を介して対向させて、ステンレス鋼製セルに組み込み、リチウムイオン二次電池（コイン型）を作製した。電池の組み立てはアルゴンガス雰囲気下で行い、電解液としては、１Ｍ ＬｉＰＦ６／（ＥＣ＋ＤＭＣ）（三菱化学社製、「ソルライト（登録商標）」）０．０５ｍｌを用いた。ここで、１ＭＬｉＰＦ６／（ＥＣ＋ＤＭＣ）とは、エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）を容積比１：１で混合した溶媒に、ＬｉＰＦ６を１Ｍの濃度になるように溶解したものである。得られたリチウムイオン二次電池についての評価結果を表１に示した。 The positive electrode and the negative electrodes A to D for the lithium ion battery are opposed to each other through a separator (Celgard, “Celguard (registered trademark) # 3501”) and incorporated in a stainless steel cell, and a lithium ion secondary battery (Coin type) was produced. The battery was assembled in an argon gas atmosphere, and 0.05 ml of 1M LiPF 6 / (EC + DMC) (manufactured by Mitsubishi Chemical Corporation, “Sollite (registered trademark)”) was used as the electrolyte. Here, 1M LiPF 6 / (EC + DMC) is obtained by dissolving LiPF 6 to a concentration of 1M in a solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed at a volume ratio of 1: 1. . The evaluation results for the obtained lithium ion secondary battery are shown in Table 1.
リチウムイオン二次電池用負極材料ＡおよびＢは、複合黒鉛粒子と第２黒鉛粒子の混合物をポリスチレン粒子と混合して熱処理して得られたもの、すなわち、表面が熱分解成分により被覆された第２黒鉛粒子に、導電材として表面が熱分解成分により被覆された複合黒鉛粒子が配合された負極材料である。これらの負極材料ＡおよびＢを用いたリチウムイオン二次電池ＡおよびＢは、初期効率、サイクル特性および出力特性が全て優れている。また、これらの電池ＡおよびＢの結果から、複合黒鉛粒子に微粒子炭素質物質を含有させることにより、得られるリチウムイオン二次電池の出力特性がさらに向上することがわかる。 The negative electrode materials A and B for lithium ion secondary batteries are obtained by heat-treating a mixture of composite graphite particles and second graphite particles with polystyrene particles, that is, a surface whose surface is coated with a pyrolysis component. This is a negative electrode material in which composite graphite particles whose surfaces are coated with pyrolytic components are blended with 2 graphite particles. Lithium ion secondary batteries A and B using these negative electrode materials A and B are all excellent in initial efficiency, cycle characteristics, and output characteristics. Further, from the results of these batteries A and B, it is understood that the output characteristics of the obtained lithium ion secondary battery are further improved by incorporating the fine carbonaceous material into the composite graphite particles.
リチウムイオン二次電池用負極材料Ｃは、複合黒鉛粒子がポリスチレン粒子の熱分解成分で被覆されていない場合、すなわち、表面が熱分解成分により被覆された第２黒鉛粒子に、導電材として表面が熱分解成分により被覆されていない複合黒鉛粒子が配合された負極材料である。この負極材料Ｃを用いたリチウムイオン二次電池Ｃは、初期効率、サイクル特性および出力特性がいずれも劣っており、初期効率が特に劣っていた。これは、複合黒鉛粒子が熱分解成分で被覆されておらず、粒子表面での電解液の分解が抑制されないためリチウムイオン二次電池の初期効率が低下したと考えられる。 When the composite graphite particles are not coated with the pyrolysis component of the polystyrene particles, that is, the second graphite particles whose surface is coated with the pyrolysis component, the surface of the negative electrode material C for a lithium ion secondary battery as a conductive material is used. It is a negative electrode material in which composite graphite particles not coated with a pyrolytic component are blended. The lithium ion secondary battery C using this negative electrode material C was inferior in initial efficiency, cycle characteristics, and output characteristics, and was particularly inferior in initial efficiency. This is considered that the initial efficiency of the lithium ion secondary battery was lowered because the composite graphite particles were not coated with the pyrolysis component and the decomposition of the electrolyte solution on the particle surface was not suppressed.
リチウムイオン二次電池用負極材料Ｄは、導電材としての複合黒鉛粒子を配合していない負極材料である。この負極材料Ｄを用いたリチウムイオン二次電池Ｄは、初期効率は優れるものの、サイクル特性および出力特性がいずれも劣っており、サイクル特性が特に劣っていた。これは、複合黒鉛粒子を用いていないため、充放電サイクルを繰り返すと黒鉛粒子間の接点が維持されず、導電性が低下するためと考えられる。 The negative electrode material D for lithium ion secondary batteries is a negative electrode material that does not contain composite graphite particles as a conductive material. Although the lithium ion secondary battery D using this negative electrode material D has excellent initial efficiency, both the cycle characteristics and the output characteristics are inferior, and the cycle characteristics are particularly inferior. This is presumably because the composite graphite particles are not used, and therefore, the contact between the graphite particles is not maintained when the charge / discharge cycle is repeated, and the conductivity is lowered.
本発明は、出力特性、サイクル特性および初期効率に優れたリチウムイオン二次電池の製造に有用である。 The present invention is useful for producing a lithium ion secondary battery excellent in output characteristics, cycle characteristics, and initial efficiency.
Claims (6)
得られた熱処理物を粉砕して平均粒子径１０μｍ未満の粒子を得る粉砕工程；
得られた平均粒子径１０μｍ未満の粒子とポリエチレン粒子および／またはポリスチレン粒子とを混合し、熱処理する被覆工程；
を含むことを特徴とするリチウムイオン二次電池用負極材料の製造方法。 A heat treatment step in which the carbonaceous material precursor and the first graphite particles are mixed and heat-treated;
A pulverization step of pulverizing the obtained heat-treated product to obtain particles having an average particle size of less than 10 μm;
A coating step in which the obtained particles having an average particle diameter of less than 10 μm and polyethylene particles and / or polystyrene particles are mixed and heat-treated;
The manufacturing method of the negative electrode material for lithium ion secondary batteries characterized by including.
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| JP2013201058A (en) * | 2012-03-26 | 2013-10-03 | Toyota Motor Corp | Anode active material for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery |
| JP2015185445A (en) * | 2014-03-25 | 2015-10-22 | 三菱化学株式会社 | Carbon material for nonaqueous secondary battery negative electrode and nonaqueous secondary battery |
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| JPWO2022265040A1 (en) * | 2021-06-18 | 2022-12-22 | ||
| WO2022265040A1 (en) * | 2021-06-18 | 2022-12-22 | Ｅｎｅｏｓ株式会社 | Method for producing artificial graphite material for lithium ion secondary battery negative electrodes, artificial graphite material for lithium ion secondary battery negative electrodes, negative electrode for lithium ion secondary batteries, and lithium ion secondary battery |
| EP4358190A4 (en) * | 2021-06-18 | 2025-08-06 | Eneos Corp | Method for producing artificial graphite material for lithium-ion secondary battery negative electrodes, negative electrode for lithium-ion secondary battery |
| CN114864869A (en) * | 2022-05-30 | 2022-08-05 | 上海瑞浦青创新能源有限公司 | Negative electrode and preparation method and application thereof |
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