JP2016110969A - Negative electrode active material for lithium ion secondary battery, and manufacturing method thereof - Google Patents

Negative electrode active material for lithium ion secondary battery, and manufacturing method thereof Download PDF

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JP2016110969A
JP2016110969A JP2015056646A JP2015056646A JP2016110969A JP 2016110969 A JP2016110969 A JP 2016110969A JP 2015056646 A JP2015056646 A JP 2015056646A JP 2015056646 A JP2015056646 A JP 2015056646A JP 2016110969 A JP2016110969 A JP 2016110969A
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negative electrode
active material
electrode active
graphite
lithium ion
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JP6759527B2 (en
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日出彦 三崎
Hidehiko Misaki
日出彦 三崎
阿部昌則
Masanori Abe
徹 津吉
Toru Tsuyoshi
徹 津吉
太地 荒川
Taichi Arakawa
太地 荒川
宏平 岩永
Kohei Iwanaga
宏平 岩永
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Tosoh Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

PROBLEM TO BE SOLVED: To provide: a negative electrode active material for a lithium ion secondary battery superior in cycle characteristics while keeping a high initial efficiency and a high battery capacity; and a method for manufacturing such a negative electrode active material.SOLUTION: A negative electrode active material for a lithium ion secondary battery comprises: a Si compound; and a carbonaceous material or a combination of a carbonaceous material and graphite. The negative electrode active material is obtained by the steps of: mixing a Si compound, a carbon precursor and as required, graphite powder; granulating and compacting the mixture; pulverizing the mixture to form composite particles; sintering the composite particles in an inert gas atmosphere; and performing a wind power classification of composite powder subjected to the pulverization and conglobation, or sintered powder.SELECTED DRAWING: None

Description

本発明は、リチウムイオン２次電池用負極活物質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 active material for a lithium ion secondary battery and a method for producing the same.

スマートフォン、タブレット型端末などモバイル機器の高性能化や、ＥＶ、ＰＨＥＶなどリチウムイオン２次電池を搭載した車両の普及に伴い、リチウムイオン２次電池の高容量化の要求が高まっている。現在、リチウムイオン２次電池の負極材には主に黒鉛が用いられているが、さらなる高容量化のため、理論容量が高く、リチウムイオンを吸蔵・放出可能な元素であるシリコンやスズ等の金属、もしくは他の元素との合金を用いた負極材の開発が活発化している。   As mobile devices such as smartphones and tablet terminals have higher performance and vehicles equipped with lithium ion secondary batteries such as EVs and PHEVs have been demanded to increase the capacity of lithium ion secondary batteries. At present, graphite is mainly used as the negative electrode material of lithium ion secondary batteries. However, for further increase in capacity, the theoretical capacity is high, and elements such as silicon and tin that can absorb and release lithium ions are used. Development of negative electrode materials using metals or alloys with other elements has been activated.

一方、これらのリチウムイオンを吸蔵・放出可能な金属材料からなる活物質は、充電によってリチウムと合金化した際に、著しく体積膨張することが知られている。そのため、活物質が割れて微細化し、さらにこれらを用いた負極も構造が破壊されて導電性が切断される。従って、これらの金属材料を用いた負極はサイクル経過によって容量が著しく低下することが課題となっている。   On the other hand, it is known that an active material made of a metal material capable of inserting and extracting lithium ions significantly expands when alloyed with lithium by charging. Therefore, the active material is cracked and refined, and the structure of the negative electrode using these is also broken and the conductivity is cut. Therefore, the negative electrode using these metal materials has a problem that the capacity is remarkably lowered with the passage of cycles.

この課題に対し、これらの金属材料を微粒子化し、炭素質物や黒鉛などで複合化する手法が提案されている。このような複合粒子は、これらの金属材料がリチウムと合金化し、微細化しても炭素質物や黒鉛によって導電性が確保されるため、これらの材料を単独で負極材として用いるよりもサイクル特性が著しく向上することが知られている。例えば、特許文献１には、負極の活物質は炭素質物層が表面に形成された微粒子を含み、該微粒子はＭｇ、Ａｌ、Ｓｉ、Ｃａ、ＳｎおよびＰｂから選ばれる少なくとも一種の元素からなると共に、平均粒径が１〜５００ｎｍであり、かつ前記活物質中の微粒子の原子比率は１５重量％以上であることが開示されている。   In response to this problem, a technique has been proposed in which these metal materials are made into fine particles and combined with carbonaceous material or graphite. Such composite particles have significantly higher cycle characteristics than the use of these materials alone as a negative electrode material, because these metal materials are alloyed with lithium and conductivity is ensured by carbonaceous materials and graphite even when they are miniaturized. It is known to improve. For example, in Patent Document 1, the active material of the negative electrode includes fine particles having a carbonaceous material layer formed on the surface, and the fine particles are composed of at least one element selected from Mg, Al, Si, Ca, Sn, and Pb. In addition, it is disclosed that the average particle diameter is 1 to 500 nm, and the atomic ratio of the fine particles in the active material is 15% by weight or more.

また、特許文献２には、金属粒子が複数相の炭素中に埋設され、該炭素は黒鉛および非晶質炭素を含むものである金属炭素複合体粒子が開示され、前記金属粒子について、Ｍｇ、Ａｌ、Ｓｉ、Ｚｎ、Ｇｅ、Ｂｉ、Ｉｎ、Ｐｄ、Ｐｔのいずれかからなり、平均粒子径は０．１〜２０μｍが好ましいと記載されている。また、特許文献３には、負極活物質が、黒鉛コア粒子と、該黒鉛コア粒子を被覆する炭素被膜（シェル）と、該炭素被膜内部に分散して位置する金属粒子とを含む、いわゆるコアシェル構造であり、前記黒鉛コア粒子の平均粒径は１〜２０μｍ、前記炭素被膜のコーティング厚さは１〜４μｍ、前記リチウムと合金化する金属としては、Ｃｒ、Ｓｎ、Ｓｉ、Ａｌ、Ｍｎ、Ｎｉ、Ｚｎ、Ｃｏ、Ｉｎ、Ｃｄ、Ｂｉ、Ｐｂ、Ｖからなる群から選択される少なくともいずれか１つの物質を含み、平均粒径は０．０１〜１．０μｍが好ましいと開示されている。   Patent Document 2 discloses metal-carbon composite particles in which metal particles are embedded in a plurality of phases of carbon, and the carbon contains graphite and amorphous carbon. The metal particles include Mg, Al, It is described that any one of Si, Zn, Ge, Bi, In, Pd, and Pt is used, and the average particle diameter is preferably 0.1 to 20 μm. Patent Document 3 discloses a so-called core shell in which the negative electrode active material includes graphite core particles, a carbon coating (shell) that covers the graphite core particles, and metal particles that are dispersed and positioned inside the carbon coating. The graphite core particles have an average particle size of 1 to 20 μm, the coating thickness of the carbon coating is 1 to 4 μm, and the metals alloyed with lithium include Cr, Sn, Si, Al, Mn, Ni , Zn, Co, In, Cd, Bi, Pb, and V, and at least one substance selected from the group consisting of V and an average particle size of 0.01 to 1.0 μm is preferable.

さらに、特許文献４には、ＢＥＴ比表面積３０ｍ２／ｇ以上の膨張黒鉛または薄片状黒鉛と、リチウムイオンと化合可能な電池活物質とを混合して混合物を得る混合工程と、該混合物に球形化処理を施し、黒鉛およびリチウムイオンと化合可能な電池活物質を含有する略球状のリチウム２次電池用複合活物質を製造する球形化工程とを有する、リチウム２次電池用複合活物質の製造方法が開示され、前記リチウムイオンと化合可能な電池活物質について、Ｓｉ、Ｓｎ、Ａｌ、Ｓｂ、Ｉｎから選ばれる少なくとも１種の元素を含有し、平均粒子径は１μｍ以下が好ましいと記載されている。 Furthermore, Patent Document 4 discloses a mixing step of obtaining a mixture by mixing expanded graphite or flaky graphite having a BET specific surface area of 30 m 2 / g or more and a battery active material that can be combined with lithium ions, and adding a spherical shape to the mixture. A composite active material for a lithium secondary battery having a spheroidizing step of manufacturing a substantially spherical composite active material for a lithium secondary battery containing a battery active material that can be combined with graphite and lithium ions A method is disclosed, and the battery active material that can be combined with lithium ions contains at least one element selected from Si, Sn, Al, Sb, and In, and the average particle diameter is preferably 1 μm or less. Yes.

上記複合粒子を用いる方法では、複合粒子を負極薄膜中に密に充填するほど負極のエネルギー密度が高くなり、電池としての性能が向上する。また、複合粒子を均一に、かつなるべく等方的に充填することにより、リチウムの脱挿入が均一に行われ、局所的な負極の劣化を避けることができ、サイクル寿命が向上する。例えば、特許文献５には、鱗片状の天然黒鉛粒子に由来する球状黒鉛粒子を含むリチウム２次電池用負極材が開示されており、その円形度は０．８５以上が好ましいと記載されている。   In the method using the composite particles, the energy density of the negative electrode increases as the composite particles are densely packed in the negative electrode thin film, and the performance as a battery is improved. In addition, by uniformly and as isotropically filling the composite particles, lithium can be desorbed and inserted uniformly, local deterioration of the negative electrode can be avoided, and cycle life is improved. For example, Patent Document 5 discloses a negative electrode material for a lithium secondary battery including spherical graphite particles derived from scaly natural graphite particles, and describes that the circularity is preferably 0.85 or more. .

特開平１０−３９２０号公報Japanese Patent Laid-Open No. 10-3920 特開２０００−２７２９１１号公報JP 2000-272911 A 特開２０１０−１２９５４５号公報JP 2010-129545 A 特許第５２２７４８３号公報Japanese Patent No. 5227483 特開２０１２−２２１９５１号公報JP2012-221951A

本発明は、ＳｉまたはＳｉ合金（以下、併せて「Ｓｉ化合物」という）と、炭素質物または炭素質物と黒鉛とを含んで複合化したリチウムイオン２次電池用負極活物質に関するものであり、優れたエネルギー密度とサイクル寿命を有するリチウムイオン２次電池を与える負極活物質およびその製造方法を提供することにある。   The present invention relates to a negative electrode active material for a lithium ion secondary battery comprising Si or Si alloy (hereinafter collectively referred to as “Si compound”) and a carbonaceous material or a carbonaceous material and graphite in combination. Another object of the present invention is to provide a negative electrode active material that can provide a lithium ion secondary battery having high energy density and cycle life, and a method for producing the same.

本発明者らは先の課題を解決すべく鋭意検討を重ねた結果、Ｓｉ化合物と、炭素質物または炭素質物と黒鉛とを、含んでなるリチウムイオン２次電池用負極活物質において、該複合材料の粒子サイズ、および形状を制御することにより、高いエネルギー密度とサイクル寿命を有するリチウムイオン２次電池を与える負極活物質が得られることを見出し、本発明を完成するに至った。   As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the composite material is a negative electrode active material for a lithium ion secondary battery comprising a Si compound and a carbonaceous material or a carbonaceous material and graphite. By controlling the particle size and shape, it was found that a negative electrode active material providing a lithium ion secondary battery having high energy density and cycle life can be obtained, and the present invention has been completed.

すなわち本発明は、ＳｉまたはＳｉ合金と、炭素質物または炭素質物と黒鉛とを、含んでなるリチウムイオン２次電池用負極活物質において、該負極活物質の平均粒径（Ｄ５０）が１〜４０μｍであり、かつ平均円形度が０．７〜１．０の略球状の複合粒子であることを特徴とするリチウムイオン２次電池用負極活物質である。   That is, the present invention relates to a negative electrode active material for a lithium ion secondary battery comprising Si or a Si alloy and a carbonaceous material or a carbonaceous material and graphite, wherein the average particle size (D50) of the negative electrode active material is 1 to 40 μm. And a negative active material for a lithium ion secondary battery characterized by being substantially spherical composite particles having an average circularity of 0.7 to 1.0.

以下、本発明のリチウムイオン２次電池用負極活物質について詳細に説明する。   Hereinafter, the negative electrode active material for a lithium ion secondary battery of the present invention will be described in detail.

本発明でいうＳｉとは、純度が９８重量％程度の汎用グレードの金属シリコン、純度が２〜４Ｎのケミカルグレードの金属シリコン、塩素化して蒸留精製した４Ｎより高純度のポリシリコン、単結晶成長法による析出工程を経た超高純度の単結晶シリコン、もしくはそれらに周期表１３族もしくは１５族元素をドーピングして、ｐ型またはｎ型としたもの、半導体製造プロセスで発生したウエハの研磨や切断の屑、プロセスで不良となった廃棄ウエハなど、汎用グレードの金属シリコン以上の純度のものであれば特に限定されない。   In the present invention, Si is a general grade metal silicon having a purity of about 98% by weight, a chemical grade metal silicon having a purity of 2 to 4N, polysilicon having a purity higher than 4N purified by chlorination and distillation, and single crystal growth Polishing or cutting of ultra-high purity single crystal silicon that has undergone a deposition process by the method, or those doped with elements of Group 13 or 15 of the periodic table to be p-type or n-type, or wafers generated in the semiconductor manufacturing process There is no particular limitation as long as it has a purity equal to or higher than that of general-purpose grade metal silicon, such as scraps of waste and waste wafers that have become defective in the process.

本発明でいうＳｉ合金とは、Ｓｉが主成分の合金である。前記Ｓｉ合金において、Ｓｉ以外に含まれる元素としては、周期表２〜１５族の元素の一つ以上が好ましく、合金に含まれる相の融点が９００℃以上となる元素の選択および／または添加量が好ましい。   The Si alloy referred to in the present invention is an alloy containing Si as a main component. In the Si alloy, the element contained other than Si is preferably one or more elements of Groups 2 to 15 of the periodic table, and the selection and / or addition amount of the element having a melting point of the phase contained in the alloy of 900 ° C. or more. Is preferred.

本発明のリチウムイオン２次電池用負極活物質において、Ｓｉ化合物の平均粒径（Ｄ５０）は０．０１〜５μｍが好ましく、さらに好ましくは０．０１〜１μｍであり、特に好ましくは０．０５〜０．６μｍである。０．０１μｍより小さいと、表面酸化による容量や初期効率の低下が激しく、５μｍより大きいと、リチウム挿入による膨張で割れが激しく生じ、サイクル劣化が激しくなりやすい。なお、平均粒径（Ｄ５０）はレーザー粒度分布計で測定した体積平均の粒子径である。   In the negative electrode active material for a lithium ion secondary battery of the present invention, the average particle size (D50) of the Si compound is preferably 0.01 to 5 μm, more preferably 0.01 to 1 μm, particularly preferably 0.05 to. 0.6 μm. If it is smaller than 0.01 μm, the capacity and initial efficiency due to surface oxidation are drastically reduced, and if it is larger than 5 μm, cracking is severely caused by expansion due to lithium insertion, and cycle deterioration tends to be severe. The average particle size (D50) is a volume average particle size measured with a laser particle size distribution meter.

Ｓｉ化合物の含有量は１０〜８０重量％が好ましく、１５〜５０重量％が特に好ましい。Ｓｉ化合物の含有量が１０重量％未満の場合、従来の黒鉛に比べて十分に大きい容量が得られず、８０重量％より大きい場合、サイクル劣化が激しくなりやすい。   The content of the Si compound is preferably 10 to 80% by weight, particularly preferably 15 to 50% by weight. When the content of the Si compound is less than 10% by weight, a sufficiently large capacity cannot be obtained as compared with the conventional graphite, and when it is more than 80% by weight, the cycle deterioration tends to become severe.

本発明でいう炭素質物とは、非晶質もしくは微結晶の炭素物質であり、２０００℃を超
える熱処理で黒鉛化する易黒鉛化炭素（ソフトカーボン）と、黒鉛化しにくい難黒鉛化炭
素（ハードカーボン）がある。 The carbonaceous material referred to in the present invention is an amorphous or microcrystalline carbon material, and easily graphitized carbon (soft carbon) that is graphitized by a heat treatment exceeding 2000 ° C. and non-graphitizable carbon (hard carbon) that is difficult to graphitize. )

本発明のリチウムイオン２次電池用負極活物質において、炭素質物が含まれる場合、炭素質物の含有量は９０〜２０重量％が好ましく、４０〜２０重量％が特に好ましい。炭素質物の含有量が２０重量％未満の場合、炭素質物がＳｉ化合物を覆うことができず、導電パスが不十分となって容量劣化が激しく起こりやすく、９０重量％より大きい場合、容量が十分に得られない。   In the negative electrode active material for a lithium ion secondary battery of the present invention, when a carbonaceous material is contained, the content of the carbonaceous material is preferably 90 to 20% by weight, particularly preferably 40 to 20% by weight. When the content of carbonaceous material is less than 20% by weight, the carbonaceous material cannot cover the Si compound, and the conductive path becomes insufficient, and capacity deterioration is likely to occur severely. It is not obtained.

本発明でいう黒鉛とは、グラフェン層がｃ軸に平行な結晶であり、鉱石を精製した天然黒鉛、石油や石炭のピッチを黒鉛化した人造黒鉛等があり、原料の形状としては鱗片状、小判状もしくは球状、円柱状もしくはファイバー状等がある。また、それらの黒鉛を酸処理、酸化処理した後、熱処理することにより膨張させ、黒鉛層間の一部が剥離してアコーディオン状となった膨張黒鉛もしくは膨張黒鉛の粉砕物、または超音波等により層間剥離させたグラフェン等も用いることができる。本発明の負極活物質に含まれる黒鉛の粒子サイズは、負極活物質粒子のサイズより小さければ特に限定はなく、黒鉛粒子の厚みは活物質の平均粒径（Ｄ５０）の１／５以下であることが好ましい。黒鉛の添加により活物質粒子の導電性および強度が高まり、充放電のレート特性およびサイクル特性が向上する。黒鉛粒子のＸ線回折で測定される（００２）面の面間隔ｄ００２は０．３３８ｎｍ以下であることが好ましく、これは高度に黒鉛化が進んだ黒鉛を意味している。ｄ００２がこの値を超える場合、黒鉛による導電性向上効果が小さくなる。   The graphite referred to in the present invention is a crystal whose graphene layer is parallel to the c-axis, natural graphite obtained by refining ore, artificial graphite obtained by graphitizing the pitch of oil or coal, etc. There are oval or spherical, cylindrical or fiber shapes. In addition, these graphites are subjected to acid treatment, oxidation treatment, and then expanded by heat treatment. Part of the graphite layer is exfoliated to form an accordion shape, or a pulverized product of expanded graphite, or an ultrasonic layer or the like. Exfoliated graphene or the like can also be used. The particle size of the graphite contained in the negative electrode active material of the present invention is not particularly limited as long as it is smaller than the size of the negative electrode active material particles, and the thickness of the graphite particles is 1/5 or less of the average particle diameter (D50) of the active material. It is preferable. Addition of graphite increases the conductivity and strength of the active material particles, and improves charge / discharge rate characteristics and cycle characteristics. The (002) plane spacing d002 measured by X-ray diffraction of graphite particles is preferably 0.338 nm or less, which means highly graphitized graphite. When d002 exceeds this value, the effect of improving conductivity by graphite becomes small.

また、本発明でいう、黒鉛は、純度９９．９重量％以上、若しくは不純物量１０００ｐｐｍ以下であり、Ｓ量が０．３重量％以下及び／又はＢＥＴ比表面積が４０ｍ２／ｇ以下であることが好ましい。純度が９９．９重量％よりも少なく、若しくは不純物量が１０００ｐｐｍよりも多いと、不純物由来のＳＥＩ形成による不可逆容量が多くなるため、初回の充電容量に対する放電容量である初回充放電効率が低くなる傾向がある。また、Ｓ量が０．３重量％よりも高くなると同様に不可逆容量が高くなるため、初回充放電効率が低くなる。さらに好ましくは、Ｓ量が０．１重量％以下が好ましい。黒鉛のＢＥＴ比表面積が４０ｍ２／ｇよりも高いと、電解液との反応する面積が多くなるため、初回充放電効率が低くなると思われる。 In the present invention, graphite has a purity of 99.9% by weight or more, or an impurity amount of 1000 ppm or less, an S amount of 0.3% by weight or less, and / or a BET specific surface area of 40 m 2 / g or less. Is preferred. If the purity is less than 99.9% by weight or the amount of impurities is more than 1000 ppm, the irreversible capacity due to the formation of SEI derived from impurities increases, so the initial charge / discharge efficiency, which is the discharge capacity with respect to the initial charge capacity, decreases. Tend. Moreover, since the irreversible capacity | capacitance similarly becomes high when S amount becomes higher than 0.3 weight%, initial charge / discharge efficiency becomes low. More preferably, the amount of S is preferably 0.1% by weight or less. If the BET specific surface area of graphite is higher than 40 m 2 / g, the area that reacts with the electrolytic solution increases, so the initial charge / discharge efficiency is likely to be low.

不純物は、ＩＣＰ発光分光分析法により、以下の２６元素（Ａｌ、Ｃａ、Ｃｒ、Ｆｅ、Ｋ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｖ、Ｚｎ、Ｚｒ、Ａｇ、Ａｓ、Ｂａ、Ｂｅ、Ｃｄ、Ｃｏ、Ｃｕ、Ｍｏ、Ｐｂ、Ｓｂ、Ｓｅ、Ｔｈ、Ｔｌ、Ｕ）の不純物半定量値により測定する。また、Ｓ量の測定は、酸素フラスコ燃焼法で燃焼吸収処理した後、フィルター濾過してイオンクロマトグラフィー（ＩＣ）測定により行う。   Impurities were analyzed by ICP emission spectroscopic analysis with the following 26 elements (Al, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, V, Zn, Zr, Ag, As, Ba, Be, Cd, Co). , Cu, Mo, Pb, Sb, Se, Th, Tl, U). In addition, the amount of S is measured by ion chromatography (IC) measurement after filtering and filtering with an oxygen flask combustion method.

本発明のリチウムイオン２次電池用負極活物質において、炭素質物と黒鉛が含まれる場合、各々の含有量は５〜４０重量％と２０〜８０重量％の割合が好ましく、８〜３０重量％と４０〜７０重量％の割合が特に好ましい。炭素質物の含有量が５重量％未満の場合、炭素質物がＳｉ化合物および黒鉛を覆うことができず、Ｓｉ化合物と黒鉛との接着が不十分となり、活物質粒子の形成が困難となりやすい。また、４０重量％より大きい場合、導電性が炭素質物より高い黒鉛の効果が十分に引き出されない。一方、黒鉛の含有量が２０重量％未満の場合、炭素質物より高い導電性を有する黒鉛の効果が十分でなく、８０重量％より多い場合、従来の黒鉛に比べて十分に大きい容量が得られない。   In the negative electrode active material for a lithium ion secondary battery of the present invention, when a carbonaceous material and graphite are contained, the respective contents are preferably 5 to 40% by weight and 20 to 80% by weight, and 8 to 30% by weight. A proportion of 40 to 70% by weight is particularly preferred. When the content of the carbonaceous material is less than 5% by weight, the carbonaceous material cannot cover the Si compound and graphite, adhesion between the Si compound and graphite becomes insufficient, and formation of active material particles tends to be difficult. Moreover, when larger than 40 weight%, the effect of the graphite whose electroconductivity is higher than a carbonaceous material is not fully drawn out. On the other hand, when the graphite content is less than 20% by weight, the effect of graphite having higher conductivity than the carbonaceous material is not sufficient, and when it is more than 80% by weight, a sufficiently large capacity can be obtained compared to conventional graphite. Absent.

本発明のリチウムイオン２次電池用負極活物質は、略球状の複合粒子であり、その平均粒径（Ｄ５０）が１〜４０μｍであり、好ましくは２〜３０μｍであり、特に好ましくは２〜２０μｍである。平均粒径（Ｄ５０）が１μｍ未満の場合、かさ高くなって高密度の電極が作製しにくくなり、４０μｍを超える場合、塗布した電極の凹凸が激しくなって均一な電極が作製しにくくなる。また、前記Ｓｉ化合物の平均粒径が該負極活物質の平均粒径の１／５以下であり、前記炭素質物が、少なくとも活物質表面を覆っていることが好ましい。   The negative electrode active material for a lithium ion secondary battery of the present invention is a substantially spherical composite particle having an average particle diameter (D50) of 1 to 40 μm, preferably 2 to 30 μm, particularly preferably 2 to 20 μm. It is. When the average particle diameter (D50) is less than 1 μm, it becomes bulky and it becomes difficult to produce a high-density electrode, and when it exceeds 40 μm, the unevenness of the applied electrode becomes intense and it becomes difficult to produce a uniform electrode. Moreover, it is preferable that the average particle diameter of the Si compound is 1/5 or less of the average particle diameter of the negative electrode active material, and the carbonaceous material covers at least the active material surface.

略球状の複合粒子とは、粉砕等により生成した粒子の角が取れているもの、球状もしくは回転楕円体形状、円板もしくは小判形状で厚みを有して角が丸いもの、またはそれらが変形したもので角が丸いものなどを含み、その円形度は０．７〜１．０である。なお、円形度は走査型電子顕微鏡で撮影した粒子像を画像解析して測定した。すなわち、粒子の投影面積（Ａ）と周囲長（ＰＭ）を写真から測定し、等しい周囲長（ＰＭ）を持つ真円の面積を（Ｂ）とした時に、円形度はＡ／Ｂで定義される。前記真円の半径をｒとした時、ＰＭ＝２πｒ、及びＢ＝πｒ２が成り立つので、これより円形度Ａ／Ｂ＝Ａ×４π／（ＰＭ）２で算出される。これにより任意の１００個以上の複合粒子のうち、短軸長さが１μｍ未満の扁平状微粒子を除いた略球状粒子の平均値を複合粒子の平均円形度とした。また扁平状微粒子とは、粉砕等により生成した粒子の角が取れているもの、円板もしくは小判型形状で厚みを有して角が丸いもの、またはそれらが変形したもので角が丸いものなどを含み、走査型電子顕微鏡で撮影した粒子像の短軸長が１μｍ未満のものとした。この扁平状微粒子の含有率は扁平微粒子の投影面積合計を全粒子の投影面積合計で除したものと定義した。形状が丸みを帯びることにより複合粒子のかさ密度が高まり、負極にした時の充填密度が高まる。また、前記炭素質物が、少なくとも活物質表面を覆っていることにより、充放電の過程で電解液に溶媒和したリチウムイオンが、前記炭素質物の表面で溶媒から離れて、リチウムイオンのみがＳｉ化合物および／または黒鉛と反応するため、溶媒の分解生成物が生成しにくくなり、充放電の効率が高まる。 The substantially spherical composite particles are those in which the corners of particles generated by pulverization, etc. are removed, spherical or spheroid shapes, discs or oval shapes with rounded corners, or deformed Including those having rounded corners, the circularity is 0.7 to 1.0. The circularity was measured by image analysis of a particle image taken with a scanning electron microscope. That is, when the projected area (A) and the perimeter (PM) of a particle are measured from a photograph and the area of a perfect circle having the same perimeter (PM) is (B), the circularity is defined as A / B. The When the radius of the true circle is r, PM = 2πr and B = πr 2 are established, and from this, the circularity A / B = A × 4π / (PM) 2 is calculated. Thereby, the average value of the substantially spherical particles excluding the flat fine particles having a minor axis length of less than 1 μm among the arbitrary 100 or more composite particles was defined as the average circularity of the composite particles. In addition, flat fine particles are those in which the corners of particles generated by pulverization, etc. are rounded, those having a round shape with a disc or oval shape, or those in which they are deformed and rounded in corners, etc. The short axis length of the particle image taken with a scanning electron microscope was less than 1 μm. The content of the flat fine particles was defined as the total projected area of the flat fine particles divided by the total projected area of all the particles. When the shape is rounded, the bulk density of the composite particles is increased, and the packing density when the negative electrode is formed is increased. Further, since the carbonaceous material covers at least the active material surface, lithium ions solvated in the electrolytic solution during the charge / discharge process are separated from the solvent on the surface of the carbonaceous material, and only lithium ions are Si compounds. Since it reacts with graphite and / or graphite, it becomes difficult to produce a decomposition product of the solvent, and the efficiency of charging and discharging is increased.

略球状の複合粒子の平均円形度が低下すると、かさ密度が低下し、負極にした時の充填密度が低下し、また複合粒子同士の接触点及び領域が減少するため、充放電時の複合粒子の体積膨張伸縮により、電気的導通が絶たれる確率が増え、サイクル容量維持率が低下する傾向にある。複合粒子が略球状粒と扁平状の複合微粒子から構成される場合は、扁平状微粒子の含有量増加に伴い、扁平状微粒子が略球状粒子間の間隙を埋める形となるため、充放電時の体積膨張収縮においても電気的導通が維持される。平均粒径（Ｄ５０）が１〜１０μｍであり、ＳＥＭ像観察により計測された短軸長１μｍ未満の扁平状微粒子を１重量％以上８０重量％以下含む場合、該負極活物質は優れたサイクル容量維持率を示す。扁平状微粒子の含有率が１重量％未満の場合及び／又は略球状粒子の円形度が０．７未満の場合はサイクル容量維持率の改善効果は認められない。   When the average circularity of the substantially spherical composite particles decreases, the bulk density decreases, the packing density when the negative electrode is made, and the contact points and regions between the composite particles decrease. Due to the volume expansion / contraction, the probability that the electrical continuity is interrupted increases, and the cycle capacity retention rate tends to decrease. When the composite particles are composed of substantially spherical particles and flat composite fine particles, the flat fine particles fill the gaps between the substantially spherical particles as the content of the flat fine particles increases. Electrical conduction is maintained even in volume expansion and contraction. When the average particle size (D50) is 1 to 10 μm and the flat particles having a minor axis length of less than 1 μm measured by SEM image observation are contained in an amount of 1 wt% to 80 wt%, the negative electrode active material has an excellent cycle capacity. Indicates the maintenance rate. When the content of the flat fine particles is less than 1% by weight and / or when the circularity of the substantially spherical particles is less than 0.7, the effect of improving the cycle capacity retention rate is not recognized.

本発明のリチウムイオン２次電池用負極活物質においては、前記Ｓｉ化合物が、前記炭素質物と共に０．２μｍ以下の厚みの黒鉛薄層の間に挟まった構造であり、その構造が積層および／または網目状に広がっており、該黒鉛薄層が活物質粒子の表面付近で湾曲して活物質粒子を覆っており、さらに、最外層の表面を前記炭素質物が覆っていることが好ましい。   In the negative electrode active material for a lithium ion secondary battery of the present invention, the Si compound is sandwiched between graphite thin layers having a thickness of 0.2 μm or less together with the carbonaceous material, and the structure is laminated and / or It is preferable that the graphite thin layer is spread in a network shape, the graphite thin layer is curved near the surface of the active material particles to cover the active material particles, and the surface of the outermost layer is covered with the carbonaceous material.

本発明でいう黒鉛薄層とは、先に述べた黒鉛を酸処理、酸化処理した後、熱処理することにより膨張させて黒鉛層間の一部が剥離してアコーディオン状となった膨張黒鉛もしくは膨張黒鉛の粉砕物、超音波等により層間剥離させたグラフェン等、またはこれらが圧縮力を受けることで生成した、グラフェン１層（厚み０．０００３μｍ）〜数百層（厚み〜０．２μｍ）からなる黒鉛薄層である。黒鉛薄層の厚みは薄い方が、黒鉛薄層間に挟まれたＳｉ化合物と、炭素質物の層が薄くなって、Ｓｉ化合物への電子の伝達が良くなり、厚みが０．２μｍを超えると黒鉛薄層の電子伝達効果が薄まる。黒鉛薄層を断面で見て線状の場合、その長さは負極活物質粒子のサイズの半分以上あることが電子伝達に好ましく、負極活物質粒子のサイズと同等程度であることがさらに好ましい。黒鉛薄層が網目状の場合、黒鉛薄層の網が負極活物質粒子のサイズの半分以上に渡って繋がっていることが電子伝達に好ましく、負極活物質粒子のサイズと同等程度であることがさらに好ましい。   In the present invention, the graphite thin layer refers to expanded graphite or expanded graphite in which the above-mentioned graphite is subjected to acid treatment and oxidation treatment and then expanded by heat treatment, and a part of the graphite layer is peeled off to form an accordion shape. , Pulverized material, graphene delaminated by ultrasonic waves, or the like, or graphite made of a graphene layer (thickness 0.0003 μm) to several hundred layers (thickness 0.2 μm) produced by receiving a compressive force. It is a thin layer. When the thickness of the graphite thin layer is thinner, the Si compound sandwiched between the graphite thin layers and the carbonaceous material layer become thinner, and the transmission of electrons to the Si compound is improved, and the thickness exceeds 0.2 μm. The electron transfer effect of the graphite thin layer is diminished. When the graphite thin layer is linear when viewed in cross section, its length is preferably at least half the size of the negative electrode active material particles for electron transfer, and more preferably about the same as the size of the negative electrode active material particles. When the graphite thin layer is network-like, it is preferable for electron transfer that the graphite thin layer network is connected to more than half of the size of the negative electrode active material particles, and it may be about the same size as the negative electrode active material particles. Further preferred.

本発明においては、黒鉛薄層が活物質粒子の表面付近で湾曲して活物質粒子を覆うことが好ましい。そのような形状にすることで、黒鉛薄層端面から電解液が侵入して、Ｓｉ化合物や黒鉛薄層端面と電解液が直接接して、充放電時に反応物が形成され、効率が下がるというリスクが低減する。   In the present invention, the graphite thin layer is preferably curved near the surface of the active material particles to cover the active material particles. By adopting such a shape, there is a risk that the electrolyte enters from the end face of the graphite thin layer, the Si compound or the end face of the graphite thin layer is in direct contact with the electrolyte, and a reaction product is formed during charge and discharge, resulting in reduced efficiency. Is reduced.

本発明のリチウムイオン２次電池用負極活物質においては、前記Ｓｉ化合物の含有量が１０〜８０重量％、前記炭素質物の含有量が９０〜２０重量％であることが好ましい。   In the negative electrode active material for a lithium ion secondary battery of the present invention, the Si compound content is preferably 10 to 80% by weight, and the carbonaceous material content is preferably 90 to 20% by weight.

また、本発明のリチウムイオン２次電池用負極活物質においては、前記Ｓｉ化合物の含有量が１０〜６０重量％、前記炭素質物の含有量が５〜４０重量％、前記黒鉛の含有量が２０〜８０重量％であることが好ましい。   In the negative electrode active material for a lithium ion secondary battery of the present invention, the content of the Si compound is 10 to 60% by weight, the content of the carbonaceous material is 5 to 40% by weight, and the content of the graphite is 20%. It is preferably ˜80% by weight.

本発明のリチウムイオン２次電池負極活物質では、ＢＥＴ比表面積が０．５〜８０ｍ２／ｇであることが好ましい。 In the lithium ion secondary battery negative electrode active material of the present invention, the BET specific surface area is preferably 0.5 to 80 m 2 / g.

本発明のリチウムイオン２次電池用負極活物質において、前記炭素質物は、後述する炭素前駆体が負極活物質内部で炭化し、炭素物質を形成したものである。そのため、充放電の過程で電解液に溶媒和したリチウムイオンが、直接Ｓｉ化合物及び／又は黒鉛に接触しにくい構造となっており、ＢＥＴ比表面積が０．５〜６０ｍ２／ｇであることにより、表面での炭素質物と電解液の反応も少なく保たれるため、充放電の効率がより高まる。 In the negative electrode active material for a lithium ion secondary battery of the present invention, the carbonaceous material is a carbon material formed by carbonizing a carbon precursor described later inside the negative electrode active material. Therefore, the lithium ions solvated in the electrolyte during charging and discharging have a structure that is difficult to directly contact the Si compound and / or graphite, and the BET specific surface area is 0.5 to 60 m 2 / g. Moreover, since the reaction between the carbonaceous material and the electrolytic solution on the surface is kept small, the charge / discharge efficiency is further increased.

次に、本発明のリチウムイオン２次電池用負極活物質の製造方法について説明する。   Next, the manufacturing method of the negative electrode active material for lithium ion secondary batteries of this invention is demonstrated.

本発明のリチウムイオン２次電池用負極活物質の製造方法は、Ｓｉ化合物、炭素前駆体、さらに必要に応じて黒鉛を混合する工程と、造粒・厚密化する工程と、粉砕して複合粒子を形成する工程と、該複合粒子を不活性雰囲気中で焼成する工程を含むものである。   The method for producing a negative electrode active material for a lithium ion secondary battery of the present invention comprises a step of mixing an Si compound, a carbon precursor, and, if necessary, a graphite, a step of granulating and densifying, and a pulverized composite It includes a step of forming particles and a step of firing the composite particles in an inert atmosphere.

原料であるＳｉ化合物は、平均粒径（Ｄ５０）が０．０１〜５μｍの粉末を使用することが好ましい。所定の粒子径のＳｉ化合物を得るためには、上述のＳｉ化合物の原料（インゴット、ウエハ、粉末などの状態）を粉砕機で粉砕し、場合によっては分級機を用いる。インゴット、ウエハなどの塊の場合、最初はジョークラッシャー等の粗粉砕機を用いて粉末化することができる。その後、例えば、ボール、ビーズなどの粉砕媒体を運動させ、その運動エネルギーによる衝撃力や摩擦力、圧縮力を利用して被砕物を粉砕するボールミル、媒体撹拌ミルや、ローラによる圧縮力を利用して粉砕を行うローラミルや、被砕物を高速で内張材に衝突もしくは粒子相互に衝突させ、その衝撃による衝撃力によって粉砕を行うジェットミルや、ハンマー、ブレード、ピンなどを固設したローターの回転による衝撃力を利用して被砕物を粉砕するハンマーミル、ピンミル、ディスクミルや、剪断力を利用するコロイドミルや高圧湿式対向衝突式分散機「アルティマイザー」などを用いて微粉砕することができる。   As the Si compound as a raw material, it is preferable to use a powder having an average particle diameter (D50) of 0.01 to 5 μm. In order to obtain a Si compound having a predetermined particle diameter, the above-described Si compound raw material (ingot, wafer, powder, etc.) is pulverized by a pulverizer, and in some cases, a classifier is used. In the case of a lump such as an ingot or a wafer, it can be first pulverized using a coarse pulverizer such as a jaw crusher. After that, for example, a ball or bead is used to move the grinding medium, and the impact force, frictional force, or compression force of the kinetic energy is used to grind the material to be crushed, the media agitation mill, or the compression force of the roller. Rotation of a roller mill that pulverizes, a jet mill that collides crushed objects with the lining material or collides with each other at high speed, and pulverizes by the impact force of the impact, and a rotor with a fixed hammer, blade, pin, etc. It can be finely pulverized by using a hammer mill, pin mill, disk mill that pulverizes the material to be crushed using the impact force of the colloid, a colloid mill that uses shear force, or a high-pressure wet-on-front collision disperser "Ultimizer". .

粉砕は、湿式、乾式共に用いることができる。さらに微粉砕するには、例えば、湿式のビーズミルを用い、ビーズの径を段階的に小さくすること等により非常に細かい粒子を得ることができる。また、粉砕後に粒度分布を整えるため、乾式分級や湿式分級もしくはふるい分け分級を用いることができる。乾式分級は、主として気流を用い、分散、分離（細粒子と粗粒子の分離）、捕集（固体と気体の分離）、排出のプロセスが逐次もしくは同時に行われ、粒子相互間の干渉、粒子の形状、気流の乱れ、速度分布、静電気の影響などで分級効率を低下させないように、分級をする前に前処理（水分、分散性、湿度などの調整）を行うか、使用される気流の水分や酸素濃度を調整して行う。乾式で分級機が一体となっているタイプでは、一度に粉砕、分級が行われ、所望の粒度分布とすることが可能となる。   The pulverization can be used for both wet and dry processes. For further fine pulverization, very fine particles can be obtained, for example, by using a wet bead mill and gradually reducing the diameter of the beads. In order to adjust the particle size distribution after pulverization, dry classification, wet classification, or sieving classification can be used. In the dry classification, the process of dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are performed sequentially or simultaneously, mainly using air flow. Pre-classification (adjustment of moisture, dispersibility, humidity, etc.) before classification, or the moisture in the airflow used so that the classification efficiency is not lowered due to the influence of shape, air flow disturbance, velocity distribution, static electricity, etc. Adjust the oxygen concentration. In a dry type in which a classifier is integrated, pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.

別の所定の粒子径のＳｉ化合物を得る方法としては、プラズマやレーザー等でＳｉ化合物を加熱して蒸発させ、不活性ガス中で凝固させて得る方法、ガス原料を用いてＣＶＤやプラズマＣＶＤ等で得る方法があり、これらの方法は０．１μｍ以下の超微粒子を得るのに適している。   As another method for obtaining a Si compound having a predetermined particle size, a method in which the Si compound is heated and evaporated by plasma or laser and solidified in an inert gas, or a CVD or plasma CVD using a gas raw material is used. These methods are suitable for obtaining ultrafine particles of 0.1 μm or less.

原料の炭素前駆体としては、炭素を主体とする炭素系化合物で、不活性ガス雰囲気中での熱処理により炭素質物になるものであれば特に限定はなく、石油系ピッチ、石炭系ピッチ、合成ピッチ、タール類、セルロース、スクロース、ポリ塩化ビニル、ポリビニルアルコール、フェノール樹脂、フラン樹脂、フルフリルアルコール、ポリスチレン、エポキシ樹脂、ポリアクリロニトリル、メラミン樹脂、アクリル樹脂、ポリアミドイミド樹脂、ポリアミド樹脂、ポリイミド樹脂等が使用できる。さらに、後述する複合粒子を形成する工程において、粉砕された粒子が再結着して略球状の複合粒子を形成することができる点で、強い結着力を有する炭素前駆体を用いることが好ましい。特に、前記炭素前駆体が炭素系化合物であり、その重量平均分子量（Ｍｗ）が１０００以下である場合に強い結着力を発現するため好ましい。   The carbon precursor of the raw material is not particularly limited as long as it is a carbon-based compound mainly composed of carbon and becomes a carbonaceous material by heat treatment in an inert gas atmosphere. Petroleum pitch, coal pitch, synthetic pitch , Tars, cellulose, sucrose, polyvinyl chloride, polyvinyl alcohol, phenol resin, furan resin, furfuryl alcohol, polystyrene, epoxy resin, polyacrylonitrile, melamine resin, acrylic resin, polyamideimide resin, polyamide resin, polyimide resin, etc. Can be used. Furthermore, in the step of forming composite particles described later, it is preferable to use a carbon precursor having a strong binding force in that the pulverized particles can be rebound to form substantially spherical composite particles. In particular, when the carbon precursor is a carbon-based compound and the weight average molecular weight (Mw) is 1000 or less, a strong binding force is expressed, which is preferable.

原料である黒鉛は、天然黒鉛、石油や石炭のピッチを黒鉛化した人造黒鉛等が利用でき、鱗片状、小判状もしくは球状、円柱状もしくはファイバー状等が用いられる。また、それらの黒鉛を酸処理、酸化処理した後、熱処理することにより膨張させて黒鉛層間の一部が剥離してアコーディオン状となった膨張黒鉛もしくは膨張黒鉛の粉砕物、または超音波等により層間剥離させたグラフェン等も用いることができる。膨張黒鉛もしくは膨張黒鉛の粉砕物はその他の黒鉛に比べて可とう性に優れており、後述する複合粒子を形成する工程において、粉砕された粒子が再結着して略球状の複合粒子を容易に形成することができる。上記の点で、膨張黒鉛もしくは膨張黒鉛の粉砕物を用いることが好ましい。原料の黒鉛は予め混合工程で使用可能な大きさに整えて使用し、混合前の粒子サイズとしては天然黒鉛や人造黒鉛では１〜１００μｍ、膨張黒鉛もしくは膨張黒鉛の粉砕物、グラフェンでは５μｍ〜５ｍｍ程度である。   As the raw material graphite, natural graphite, artificial graphite obtained by graphitizing the pitch of petroleum or coal, and the like can be used, and scaly, oval or spherical, cylindrical or fiber-like are used. In addition, these graphites are subjected to acid treatment, oxidation treatment, and then expanded by heat treatment, and a portion of the graphite layer is exfoliated to form an accordion shape, or a pulverized product of expanded graphite, or an ultrasonic wave, etc. Exfoliated graphene or the like can also be used. Expanded graphite or a pulverized product of expanded graphite is superior in flexibility to other graphites, and in the process of forming composite particles, which will be described later, the pulverized particles can be rebound to easily form substantially spherical composite particles. Can be formed. In view of the above, it is preferable to use expanded graphite or a pulverized product of expanded graphite. The raw material graphite is preliminarily adjusted to a size that can be used in the mixing process, and the particle size before mixing is 1 to 100 μm for natural graphite or artificial graphite, or 5 μm to 5 mm for expanded graphite or expanded graphite pulverized product, graphene Degree.

これらのＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛との混合は、炭素前駆体が加熱により軟化、液状化するものである場合は、加熱下でＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛を混練することによって行うことができる。また、炭素前駆体が溶媒に溶解するものである場合には、溶媒にＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛を投入し、炭素前駆体が溶解した溶液中でＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛を分散、混合し、次いで溶媒を除去することで行うことができる。用いる溶媒は、炭素前駆体を溶解できるものであれば特に制限なく使用できる。例えば、炭素前駆体としてピッチ、タール類を用いる場合には、キノリン、ピリジン、トルエン、ベンゼン、テトラヒドロフラン、クレオソート油等が使用でき、ポリ塩化ビニルを用いる場合には、テトラヒドロフラン、シクロヘキサノン、ニトロベンゼン等が使用でき、フェノール樹脂、フラン樹脂を用いる場合には、エタノール、メタノール等が使用できる。   Mixing with these Si compounds, carbon precursors, and, if necessary, graphite, when the carbon precursors are softened or liquefied by heating, the Si compounds, carbon precursors, and further necessary under heating Accordingly, it can be performed by kneading graphite. When the carbon precursor is dissolved in a solvent, the Si compound, the carbon precursor, and, if necessary, graphite are added to the solvent, and the Si compound and the carbon precursor are dissolved in the solution in which the carbon precursor is dissolved. Body, and if necessary, graphite can be dispersed and mixed, and then the solvent can be removed. The solvent to be used can be used without particular limitation as long as it can dissolve the carbon precursor. For example, when pitch or tar is used as the carbon precursor, quinoline, pyridine, toluene, benzene, tetrahydrofuran, creosote oil or the like can be used, and when polyvinyl chloride is used, tetrahydrofuran, cyclohexanone, nitrobenzene or the like can be used. When phenol resin or furan resin is used, ethanol, methanol or the like can be used.

混合方法としては、炭素前駆体を加熱軟化させる場合は、混練機（ニーダー）を用いることができる。溶媒を用いる場合は、上述の混練機の他、ナウターミキサー、レーディゲミキサー、ヘンシェルミキサ、ハイスピードミキサー、ホモミキサー等を用いることができる。また、これらの装置でジャケット加熱したり、その後、振動乾燥機、パドルドライヤーなどで溶媒を除去する。   As a mixing method, when the carbon precursor is heat-softened, a kneader (kneader) can be used. In the case of using a solvent, in addition to the above-described kneader, a Nauter mixer, a Roedige mixer, a Henschel mixer, a high speed mixer, a homomixer, or the like can be used. Further, the jacket is heated with these apparatuses, and then the solvent is removed with a vibration dryer, a paddle dryer or the like.

これらの装置で、炭素前駆体を固化、または、溶媒除去の過程における撹拌をある程度の時間続けることで、Ｓｉ化合物、炭素前駆体、さらに必要に応じて黒鉛との混合物は造粒・圧密化される。また、炭素前駆体を固化、または溶媒除去後の混合物をローラーコンパクタ等の圧縮機によって圧縮し、解砕機で粗粉砕することにより、造粒・圧密化することができる。これらの造粒・圧密化物の大きさは、その後の粉砕工程での取り扱いの容易さから０．１〜５ｍｍが好ましい。   With these devices, the carbon precursor is solidified, or stirring in the process of solvent removal is continued for a certain amount of time, so that the Si compound, the carbon precursor, and, if necessary, the mixture with graphite are granulated and consolidated. The Further, the carbon precursor is solidified or the mixture after removing the solvent is compressed by a compressor such as a roller compactor and coarsely pulverized by a crusher, whereby granulation and consolidation can be achieved. The size of the granulated / consolidated product is preferably 0.1 to 5 mm in view of ease of handling in the subsequent pulverization step.

造粒・圧密化物の粉砕方法は、圧縮力を利用して被砕物を粉砕するボールミル、媒体撹拌ミルや、ローラによる圧縮力を利用して粉砕を行うローラミルや、被砕物を高速で内張材に衝突もしくは粒子相互に衝突させ、その衝撃による衝撃力によって粉砕を行うジェットミルや、ハンマー、ブレード、ピンなどを固設したローターの回転による衝撃力を利用して被砕物を粉砕するハンマーミル、ピンミル、ディスクミル等の乾式の粉砕方法が好ましい。また、粉砕後に粒度分布を整えるため、風力分級、ふるい分け等の乾式分級が用いられる。粉砕機と分級機が一体となっているタイプでは、一度に粉砕、分級が行われ、所望の粒度分布とすることが可能となる。   The granulated / consolidated material is pulverized by ball mill, medium agitation mill, roller mill for pulverizing using the compressive force of the roller, or lining material to be crushed at high speed. A jet mill that collides with each other or collides with each other and crushes by the impact force of the impact, a hammer mill that crushes the material to be crushed using the impact force of the rotation of a rotor with a fixed hammer, blade, pin, etc. A dry pulverization method such as a pin mill or a disk mill is preferred. In order to adjust the particle size distribution after pulverization, dry classification such as air classification and sieving is used. In the type in which the pulverizer and the classifier are integrated, pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.

粉砕して得られた複合粒子は、アルゴンガスや窒素ガス気流中、もしくは真空など不活性雰囲気中で焼成する。焼成温度は６００〜１２００℃とすることが好ましい。焼成温度が６００℃未満であると、炭素前駆体由来の非晶質炭素の不可逆容量が大きく、またサイクル特性が悪いため、電池の特性が低下する傾向にある。一方、焼成温度が１２００℃を超える場合、Ｓｉ化合物と炭素前駆体由来の非晶質炭素や黒鉛との反応が起こる可能性が強くなり、放電容量の低下が発生する傾向にある。   The composite particles obtained by pulverization are fired in an argon gas or nitrogen gas stream or in an inert atmosphere such as a vacuum. The firing temperature is preferably 600 to 1200 ° C. When the firing temperature is less than 600 ° C., the irreversible capacity of the amorphous carbon derived from the carbon precursor is large, and the cycle characteristics are poor, so that the battery characteristics tend to deteriorate. On the other hand, when the firing temperature exceeds 1200 ° C., there is a strong possibility that a reaction between the Si compound and the amorphous carbon or graphite derived from the carbon precursor occurs, and the discharge capacity tends to decrease.

本発明のリチウムイオン２次電池用負極活物質の製造方法は、Ｓｉ化合物、炭素前駆体、さらに必要に応じて黒鉛を、該炭素前駆体が溶解する溶媒に混合分散する工程と、造粒・厚密化する工程と、粉砕および球形化処理して形状が丸みを帯びた複合粒子を形成する工程と、該複合粒子を不活性雰囲気中で焼成する工程を含むことが好ましい。   The method for producing a negative electrode active material for a lithium ion secondary battery of the present invention comprises a step of mixing and dispersing a Si compound, a carbon precursor, and optionally graphite in a solvent in which the carbon precursor is dissolved, It is preferable to include a step of densification, a step of forming composite particles having a round shape by pulverization and spheronization, and a step of firing the composite particles in an inert atmosphere.

造粒・圧密化物を粉砕して球形化処理を施す方法としては、上述の粉砕方法により粉砕して粒度を整えた後、専用の球形化装置を通す方法と、上述のジェットミルやローターの回転による衝撃力を利用して被砕物を粉砕する方法を繰り返す、もしくは処理時間を延長することで球形化する方法がある。専用の球形化装置としては、ホソカワミクロン社のファカルティ（登録商標）、ノビルタ（登録商標）、メカノフュージョン（登録商標）、日本コークス工業社のＣＯＭＰＯＳＩ、奈良機械製作所社のハイブリダイゼーションシステム、アーステクニカ社のクリプトロンオーブ、クリプトロンエディ等が挙げられる。   As a method of pulverizing the granulated / consolidated product and subjecting it to spheronization, it is pulverized by the above-mentioned pulverization method to adjust the particle size, and then passed through a dedicated spheronization device, and the above-mentioned jet mill or rotor rotation. There is a method of spheroidizing by repeating the method of pulverizing the material to be crushed by using the impact force of or by extending the processing time. Specialized spheroidizing devices include Hosokawa Micron's Faculty (registered trademark), Nobilta (registered trademark), Mechano-Fusion (registered trademark), Nippon Coke Industries' COMPOSI, Nara Machinery Co., Ltd. hybridization system, Earth Technica's Examples include kryptron orb and kryptron eddy.

また、本発明のリチウムイオン２次電池用負極活物質の製造方法は、Ｓｉ化合物、炭素前駆体、膨張黒鉛または薄片状黒鉛を、該炭素前駆体が溶解する溶媒に混合分散する工程と、造粒・厚密化する工程と、粉砕および球形化処理して略球状の複合粒子を形成する工程と、該複合粒子を不活性雰囲気中で焼成する工程を含むことが好ましい。   The method for producing a negative electrode active material for a lithium ion secondary battery according to the present invention comprises a step of mixing and dispersing a Si compound, a carbon precursor, expanded graphite or flaky graphite in a solvent in which the carbon precursor is dissolved, It is preferable to include a step of grain / thickening, a step of pulverizing and spheronizing to form substantially spherical composite particles, and a step of firing the composite particles in an inert atmosphere.

膨張黒鉛や薄片状黒鉛は、天然黒鉛や人造黒鉛を酸処理、酸化処理した酸処理黒鉛を原料とする。膨張黒鉛は、酸処理黒鉛を熱処理することにより膨張させて黒鉛層間の一部が剥離してアコーディオン状となったものである。また、膨張黒鉛の粉砕物、もしくは超音波等により層間剥離させたグラフェンが薄片状黒鉛である。膨張黒鉛においては、酸処理を十分に行い、熱処理の温度勾配を大きくすることで大きく膨張させることが可能であり、混合分散を十分に行うことで出来上がった負極活物質の黒鉛薄層の厚みを薄くできるため、良好な電気伝導性、サイクル特性を得ることができる。   Expanded graphite and flaky graphite are made from acid-treated graphite obtained by acid-treating and oxidizing natural graphite and artificial graphite. Expanded graphite is an acid-treated graphite that is expanded by heat treatment, and part of the graphite layer is peeled off to form an accordion. In addition, exfoliated graphite is pulverized, or graphene delaminated with ultrasonic waves or the like is flaky graphite. In expanded graphite, it can be expanded greatly by sufficiently performing acid treatment and increasing the temperature gradient of heat treatment, and the thickness of the graphite thin layer of the negative electrode active material obtained by sufficiently mixing and dispersing can be increased. Since it can be made thin, good electrical conductivity and cycle characteristics can be obtained.

このようにして得られる本発明のリチウムイオン２次電池用負極活物質は、リチウム２次電池の負極材料として用いることができる。   The negative electrode active material for lithium ion secondary batteries of the present invention thus obtained can be used as a negative electrode material for lithium secondary batteries.

本発明の負極活物質は、例えば、有機系結着剤、導電助剤および溶剤と混練して、シート状、ペレット状等の形状に成形するか、または集電体に塗布し、該集電体と一体化してリチウム２次電池用負極とされる。   The negative electrode active material of the present invention is, for example, kneaded with an organic binder, a conductive additive and a solvent, and formed into a sheet shape, a pellet shape or the like, or applied to a current collector, and the current collector The negative electrode for a lithium secondary battery is integrated with the body.

有機系結着剤としては、例えばポリエチレン、ポリプロピレン、エチレンプロピレンポリマー、ブタジエンゴム、スチレンブタジエンゴム、ブチルゴム、イオン導電性の大きな高分子化合物が使用できる。イオン導電率の大きな高分子化合物としては、ポリ弗化ビニリデン、ポリエチレンオキサイド、ポリエピクロロヒドリン、ポリフォスファゼン、ポリアクリロニトリル、ポリイミド等が使用できる。有機系結着剤の含有量は、負極材全体に対して３〜２０重量％含有させることが好ましい。また、有機系結着剤の他に粘度調整剤として、カルボキシメチルセルロース、ポリアクリル酸ソーダ、その他のアクリル系ポリマー、または脂肪酸エステル等を添加しても良い。   As the organic binder, for example, polyethylene, polypropylene, ethylene propylene polymer, butadiene rubber, styrene butadiene rubber, butyl rubber, and a polymer compound having a large ion conductivity can be used. Polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polyimide and the like can be used as the polymer compound having a high ionic conductivity. The content of the organic binder is preferably 3 to 20% by weight based on the whole negative electrode material. In addition to the organic binder, carboxymethyl cellulose, polysodium acrylate, other acrylic polymers, or fatty acid esters may be added as a viscosity modifier.

導電助剤の種類は特に限定はなく、構成された電池において、分解や変質を起こさない電子伝導性の材料であれば良く、具体的にはＡｌ，Ｔｉ，Ｆｅ，Ｎｉ，Ｃｕ，Ｚｎ，Ａｇ，Ｓｎ，Ｓｉ等の金属粉末や金属繊維、または天然黒鉛、人造黒鉛、各種のコークス粉末、メソフェーズ炭素、気相成長炭素繊維、ピッチ系炭素繊維、ＰＡＮ系炭素繊維、各種の樹脂焼成体等の黒鉛などを用いることができる。導電助剤の添加量は、負極材全体中に対して０〜２０重量％であり、さらには１〜１０重量％が好ましい。導電助剤量が少ないと、負極材の導電性に乏しい場合があり、初期抵抗が高くなる傾向がある。一方、導電助剤量の増加は電池容量の低下につながるおそれがある。   The type of the conductive auxiliary agent is not particularly limited, and may be any electron conductive material that does not cause decomposition or alteration in the constructed battery. Specifically, Al, Ti, Fe, Ni, Cu, Zn, Ag , Sn, Si and other metal powders and metal fibers, natural graphite, artificial graphite, various coke powders, mesophase carbon, vapor-grown carbon fiber, pitch-based carbon fiber, PAN-based carbon fiber, various resin fired bodies, etc. Graphite or the like can be used. The addition amount of the conductive assistant is 0 to 20% by weight, more preferably 1 to 10% by weight, based on the whole negative electrode material. When the amount of the conductive auxiliary agent is small, the negative electrode material may have poor conductivity, and the initial resistance tends to be high. On the other hand, an increase in the amount of conductive aid may lead to a decrease in battery capacity.

前記溶剤としては特に制限はなく、Ｎ−メチル−２−ピロリドン、ジメチルホルムアミド、イソプロパノール、純水等が挙げられ、その量に特に制限はない。集電体としては、例えばニッケル、銅等の箔、メッシュなどが使用できる。一体化は、例えばロール、プレス等の成形法で行うことができる。   There is no restriction | limiting in particular as said solvent, N-methyl- 2-pyrrolidone, a dimethylformamide, isopropanol, a pure water etc. are mentioned, There is no restriction | limiting in particular in the quantity. As the current collector, for example, a foil such as nickel or copper, a mesh, or the like can be used. The integration can be performed by a molding method such as a roll or a press.

このようにして得られた負極は、セパレータを介して正極を対向して配置し、電解液を注入することにより、従来のシリコンを負極材料に用いたリチウム２次電池と比較して、サイクル特性に優れ、高容量、高初期効率という優れた特性を有するリチウム２次電池を作製することができる。   The negative electrode thus obtained has a cycle characteristic compared to a lithium secondary battery using conventional silicon as a negative electrode material by placing the positive electrode opposite to each other with a separator interposed therebetween and injecting an electrolytic solution. In addition, a lithium secondary battery having excellent characteristics such as high capacity and high initial efficiency can be manufactured.

正極に用いられる材料については、例えばＬｉＮｉＯ２、ＬｉＣｏＯ２、ＬｉＭｎ２Ｏ４、ＬｉＮｉｘＭｎｙＣｏ１−ｘ−ｙＯ２、ＬｉＦｅＰＯ４、Ｌｉ０．５Ｎｉ０．５Ｍｎ１．５Ｏ４、Ｌｉ２ＭｎＯ３−ＬｉＭＯ２（Ｍ＝Ｃｏ，Ｎｉ，Ｍｎ）等を単独または混合して使用することができる。 The material used for the positive electrode, for example LiNiO 2, LiCoO 2, LiMn 2 O 4, LiNi x Mn y Co 1-x-y O 2, LiFePO 4, Li 0.5 Ni 0.5 Mn 1.5 O 4 Li 2 MnO 3 —LiMO 2 (M═Co, Ni, Mn) or the like can be used alone or in combination.

電解液としては、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＡｓＦ６、ＬｉＢＦ４、ＬｉＳＯ３ＣＦ３等のリチウム塩を、例えばエチレンカーボネート、ジエチルカーボネート、ジメトキシエタン、ジメチルカーボネート、テトラヒドロフラン、プロピレンカーボネート等の非水系溶剤に溶解させた、いわゆる有機電解液を使用することができる。さらには、イミダゾリウム、アンモニウム、およびピリジニウム型のカチオンを用いたイオン液体を使用することができる。対アニオンは特に限定はなく、ＢＦ４ −、ＰＦ６ −、（ＣＦ３ＳＯ２）２Ｎ−等が挙げられる。イオン液体は前述の有機電解液溶媒と混合して使用することが可能である。電解液には、ビニレンカーボネートやフロロエチレンカーボネートの様なＳＥＩ（固体電解質界面層）形成剤を添加することもできる。 As an electrolytic solution, a lithium salt such as LiClO 4 , LiPF 6 , LiAsF 6 , LiBF 4 , LiSO 3 CF 3 is used as a non-aqueous solvent such as ethylene carbonate, diethyl carbonate, dimethoxyethane, dimethyl carbonate, tetrahydrofuran, and propylene carbonate. A so-called dissolved organic electrolyte solution can be used. Furthermore, ionic liquids using imidazolium, ammonium, and pyridinium type cations can be used. The counter anion is not particularly limited, and examples thereof include BF 4 − , PF 6 − , (CF 3 SO 2 ) 2 N − and the like. The ionic liquid can be used by mixing with the organic electrolyte solvent described above. An SEI (solid electrolyte interface layer) forming agent such as vinylene carbonate or fluoroethylene carbonate can also be added to the electrolytic solution.

また、上記塩類をポリエチレンオキサイド、ポリホスファゼン、ポリアジリジン、ポリエチレンスルフィド等やこれらの誘導体、混合物、複合体等に混合された固体電解質を用いることもできる。この場合、固体電解質はセパレータも兼ねることができ、セパレータは不要となる、セパレータとしては、例えばポリエチレン、ポリプロピレン等のポリオレフィンを主成分とした不織布、クロス、微孔フィルムまたはこれらを組み合わせたものを使用することができる。   In addition, a solid electrolyte obtained by mixing the above salts with polyethylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, or the like, or a derivative, mixture, or complex thereof can also be used. In this case, the solid electrolyte can also serve as a separator, and the separator becomes unnecessary. As the separator, for example, a nonwoven fabric mainly composed of polyolefin such as polyethylene or polypropylene, cloth, microporous film, or a combination thereof is used. can do.

本発明によれば、複合粒子を、高いかさ密度を有する略球形状粒子にすることにより、高いエネルギー密度と優れたサイクル特性を有する負極形成に適した負極活物質が得られる。また、微粒子のシリコンによる粒子当たりの膨張体積の低減と、炭素質物の複合化によって、電解液とシリコンの反応を抑えることにより優れたサイクル特性と高い初期効率が得られる。   According to the present invention, by making the composite particles into substantially spherical particles having a high bulk density, a negative electrode active material suitable for forming a negative electrode having a high energy density and excellent cycle characteristics can be obtained. Moreover, excellent cycle characteristics and high initial efficiency can be obtained by suppressing the reaction between the electrolytic solution and silicon by reducing the expansion volume per particle by the fine silicon particles and by combining the carbonaceous material.

実施例１で得られた負極活物質粒子のＳＥＭによる２次電子像である。2 is a secondary electron image of the negative electrode active material particles obtained in Example 1 by SEM. 実施例１で得られた負極活物質粒子断面のＦＥ−ＳＥＭによる２次電子像である。2 is a secondary electron image obtained by FE-SEM of a cross section of a negative electrode active material particle obtained in Example 1. FIG. 実施例２で得られた負極活物質粒子のＳＥＭによる２次電子像である。2 is a secondary electron image of the negative electrode active material particles obtained in Example 2 by SEM. 実施例３で得られた負極活物質粒子のＳＥＭによる２次電子像である。3 is a secondary electron image by SEM of negative electrode active material particles obtained in Example 3. FIG. 実施例３で得られた負極活物質粒子断面のＦＥ−ＳＥＭによる２次電子像である。4 is a secondary electron image obtained by FE-SEM of a cross section of a negative electrode active material particle obtained in Example 3. FIG. 実施例４で得られた負極活物質粒子のＳＥＭによる２次電子像である。4 is a secondary electron image of the negative electrode active material particles obtained in Example 4 by SEM. 実施例５で得られた負極活物質粒子のＳＥＭによる２次電子像である。7 is a secondary electron image of the negative electrode active material particles obtained in Example 5 by SEM. 実施例６で得られた負極活物質粒子のＳＥＭによる２次電子像である。4 is a secondary electron image of the negative electrode active material particles obtained in Example 6 by SEM. 比較例１で得られた負極活物質粒子のＳＥＭによる２次電子像である。2 is a secondary electron image of the negative electrode active material particles obtained in Comparative Example 1 by SEM. 比較例２で得られた負極活物質粒子のＳＥＭによる２次電子像である。3 is a secondary electron image of the negative electrode active material particles obtained in Comparative Example 2 by SEM. 比較例３で得られた負極活物質粒子のＳＥＭによる２次電子像である。It is a secondary electron image by SEM of the negative electrode active material particles obtained in Comparative Example 3.

以下、実施例および比較例により本発明を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。   EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these Examples.

実施例１
平均粒径（Ｄ５０）が７μｍのケミカルグレードの金属Ｓｉ（純度３Ｎ）をエタノールに２５重量％混合し、直径０．３ｍｍのジルコニアビーズを用いた微粉砕湿式ビーズミルを６時間行い、平均粒径（Ｄ５０）が０．３μｍ、乾燥時のＢＥＴ比表面積が６０ｍ２／ｇの超微粒子Ｓｉスラリーを得た。 Example 1
A chemical grade metal Si (purity 3N) having an average particle size (D50) of 7 μm was mixed with ethanol at 25% by weight, and a finely pulverized wet bead mill using zirconia beads having a diameter of 0.3 mm was performed for 6 hours. An ultrafine Si slurry having a D50) of 0.3 μm and a dry BET specific surface area of 60 m 2 / g was obtained.

粒子径０．５ｍｍ（（２００）面方向の幅）、厚み０．０２ｍｍの天然黒鉛を、濃硫酸に硝酸ナトリウム１重量％、過マンガン酸カリウム７重量％を添加した液に２４時間浸漬し、その後、水洗して乾燥し、酸処理黒鉛を得た。この酸処理黒鉛を振動粉末供給器に入れ、１０Ｌ／分の流量の窒素ガスに乗せて電気ヒーターで８５０℃に加熱した長さ１ｍ、内径１１ｍｍのムライト管に通し、端面から大気に放出し、亜硫酸等のガスを上部に排気、下部に膨張黒鉛をステンレス容器で捕集した。膨張黒鉛の（２００）面方向の幅は０．５ｍｍで元の黒鉛の値を保っていたが、厚みは４ｍｍと２００倍に膨張し、外観はコイル状であり、ＳＥＭ観察で黒鉛層が剥離し、アコーディオン状であることが確認された。   Natural graphite having a particle diameter of 0.5 mm (width in the (200) plane direction) and a thickness of 0.02 mm is immersed in a solution obtained by adding 1 wt% sodium nitrate and 7 wt% potassium permanganate to concentrated sulfuric acid for 24 hours. Thereafter, it was washed with water and dried to obtain acid-treated graphite. This acid-treated graphite was placed in a vibrating powder feeder, placed on nitrogen gas at a flow rate of 10 L / min, passed through a mullite tube having a length of 1 m and an inner diameter of 11 mm heated to 850 ° C. with an electric heater, and released from the end face to the atmosphere. A gas such as sulfurous acid was exhausted at the top, and expanded graphite was collected at the bottom in a stainless steel container. The expanded graphite had a (200) plane width of 0.5 mm and maintained the original graphite value, but the thickness expanded to 4 mm and 200 times, the appearance was coiled, and the graphite layer was peeled off by SEM observation. The accordion was confirmed.

上記超微粒子Ｓｉスラリーを２４ｇ、上記膨張黒鉛を１２ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝４６０）を５ｇ、エタノール１．６Ｌを撹拌容器に入れて、１５分間の超音波処理後、ホモミキサーで３０分混合撹拌した。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で６５℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに２日間乾燥して、２０ｇの混合乾燥物（軽装かさ密度６７ｇ／Ｌ）を得た。   24 g of the ultrafine Si slurry, 12 g of the expanded graphite, 5 g of a resol type phenolic resin (weight average molecular weight (Mw) = 460), 1.6 L of ethanol were placed in a stirring vessel, and after ultrasonic treatment for 15 minutes The mixture was stirred with a homomixer for 30 minutes. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 65 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while evacuating, passed through a mesh with a mesh opening of 2 mm, and further dried for 2 days to obtain 20 g of a mixed dried product (light bulk density 67 g / L).

この混合乾燥物を３本ロールミルに２回通し、粒度２ｍｍ、軽装かさ密度３８５ｇ／Ｌに造粒・圧密化した。   This mixed dried product was passed through a three-roll mill twice, and granulated and consolidated to a particle size of 2 mm and a light bulk density of 385 g / L.

次に、この造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで９００秒粉砕し、同時に球形化し、軽装かさ密度６５０ｇ／Ｌの球形化粉末を得た。得られた粉末をアルミナボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成した。その後、目開き４５μｍのメッシュを通し、平均粒径（Ｄ５０）が１９μｍ、軽装かさ密度が７６１ｇ／Ｌの負極活物質を得た。   Next, the granulated / consolidated product was placed in a new power mill and pulverized at 21000 rpm for 900 seconds while being cooled with water. At the same time, it was spheroidized to obtain a spheroidized powder having a light bulk density of 650 g / L. The obtained powder was put into an alumina boat and fired at a maximum temperature of 900 ° C. for 1 hour while flowing nitrogen gas in a tubular furnace. Thereafter, a negative active material having an average particle diameter (D50) of 19 μm and a light bulk density of 761 g / L was obtained through a mesh having an opening of 45 μm.

図１に、得られた負極活物質粒子のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球形状となっており、その平均円形度は０．７４であり、扁平状微粒子の含有率は０重量％であった。   FIG. 1 shows an SEM image of the obtained negative electrode active material particles. The negative electrode active material particle graphite thin layer (12) is curved and has a substantially spherical shape covering the active material particle, the average circularity is 0.74, and the content of flat fine particles is 0% by weight. there were.

図２に、得られた負極活物質粒子をイオンビームで切断した断面のＦＥ−ＳＥＭによる２次電子像を示す。負極活物質粒子は略球状となっており、負極活物質粒子内部は０．０５〜０．２μｍの長さのＳｉの微粒子が炭素質物と共に０．０２〜０．２μｍの厚みの黒鉛薄層（１１）の間（１３）（隙間は０．０５〜１μｍ）に挟まった構造が網目状に広がり、積層していた。炭素質物はＳｉの微粒子に密着して覆っていた。また、活物質粒子の表面付近では、黒鉛薄層（１２）が湾曲して活物質粒子を覆っていた。   In FIG. 2, the secondary electron image by the FE-SEM of the cross section which cut | disconnected the obtained negative electrode active material particle with the ion beam is shown. The negative electrode active material particles have a substantially spherical shape, and the inside of the negative electrode active material particles is a fine graphite layer having a thickness of 0.02 to 0.2 μm along with carbonaceous matter with Si fine particles having a length of 0.05 to 0.2 μm ( 11) (13) (gap is 0.05 to 1 μm), the structure sandwiched between the layers spreads and is laminated. The carbonaceous material was in close contact with and covered the Si fine particles. Further, near the surface of the active material particles, the graphite thin layer (12) was curved to cover the active material particles.

窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は５０ｍ２／ｇであった。粉末Ｘ線回折では黒鉛の（００２）面に対応する回折線が見られ、ｄ００２は０．３３６ｎｍであった。また、その付近に炭素質物の非晶質炭素化に由来する非常にブロードな回折線が観察された。Ｓｉの（１００）面に対応する回折線が見られ、ｄ００２は０．３１４ｎｍであった。 The BET specific surface area by the BET method using nitrogen gas was 50 m 2 / g. In powder X-ray diffraction, a diffraction line corresponding to the (002) plane of graphite was observed, and d002 was 0.336 nm. In addition, a very broad diffraction line derived from amorphous carbonization of the carbonaceous material was observed in the vicinity thereof. A diffraction line corresponding to the (100) plane of Si was observed, and d002 was 0.314 nm.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９５．２重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．６重量％と、バインダとしてカルボキシメチルセルロース（ＣＭＣ）１．６重量％とスチレンブタジエンゴム（ＳＢＲ）２．６重量％、水とを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
The obtained negative electrode active material is 95.2% by weight (content in the total solid content, the same applies hereinafter), acetylene black 0.6% by weight as a conductive auxiliary, and carboxymethyl cellulose (CMC) 1 as a binder. A negative electrode mixture-containing slurry was prepared by mixing 0.6 wt%, styrene butadiene rubber (SBR) 2.6 wt%, and water.

得られたスラリーを、アプリケータを用いて固形分塗布量が３．５ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが２９μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 3.5 mg / cm 2 and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat-treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 29 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒を使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置（北斗電工製ＳＭ−８）に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolytic solution used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1. The cell for evaluation was further put in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to a charge / discharge device (SM-8 manufactured by Hokuto Denko).

「評価条件」
評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。 "Evaluation conditions"
The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

実施例２
実施例１と同様に製造した超微粒子Ｓｉスラリーを３６ｇ、膨張黒鉛を１８ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝４９０）を７．５ｇ、エタノール２．４Ｌを撹拌容器に入れて、１５分間の超音波処理を行った。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で５０℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに２日間乾燥して、３２ｇの混合乾燥物（軽装かさ密度６６ｇ／Ｌ）を得た。 Example 2
36 g of ultrafine Si slurry produced in the same manner as in Example 1, 18 g of expanded graphite, 7.5 g of resol type phenol resin (weight average molecular weight (Mw) = 490), and 2.4 L of ethanol were placed in a stirring vessel. And sonication for 15 minutes. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 50 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while evacuating, passed through a mesh with a mesh opening of 2 mm, and further dried for 2 days to obtain 32 g of a mixed dried product (light bulk density 66 g / L).

この混合乾燥物を３本ロールミルに２回通し、粒度２ｍｍ、軽装かさ密度３４０ｇ／Ｌに造粒・圧密化した。   This mixed dried product was passed through a three-roll mill twice, and granulated and consolidated to a particle size of 2 mm and a light bulk density of 340 g / L.

次に、この造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで９００秒粉砕し、同時に球形化し、軽装かさ密度４９０ｇ／Ｌの球形化粉末を得た。   Next, this granulated / consolidated product was placed in a new power mill and pulverized at 21000 rpm for 900 seconds while cooling with water, and at the same time, spheroidized to obtain a spheroidized powder having a light bulk density of 490 g / L.

得られた粉末をアルミナボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成した。その後、目開き４５μｍのメッシュを通し、平均粒径（Ｄ５０）が９μｍ、軽装かさ密度５６７ｇ／Ｌの負極活物質を得た。   The obtained powder was put into an alumina boat and fired at a maximum temperature of 900 ° C. for 1 hour while flowing nitrogen gas in a tubular furnace. Thereafter, a negative electrode active material having an average particle diameter (D50) of 9 μm and a light bulk density of 567 g / L was obtained through a mesh having an opening of 45 μm.

図３に、得られた負極活物質のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球形状となっており、その平均円形度は０．７７であり、扁平状微粒子の含有率は０重量％であった
窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は４７ｍ２／ｇであった。粉末Ｘ線回折では黒鉛の（００２）面に対応する回折線が見られ、ｄ００２は０．３３６ｎｍであった。また、その付近に炭素質物の非晶質炭素化に由来する非常にブロードな回折線が観察された。Ｓｉの（１００）面に対応する回折線が見られ、ｄ００２は０．３１４ｎｍであった。 FIG. 3 shows an SEM image of the obtained negative electrode active material. The negative electrode active material particle graphite thin layer (12) is curved and has a substantially spherical shape covering the active material particle, the average circularity is 0.77, and the content of flat fine particles is 0% by weight. The BET specific surface area by the BET method using nitrogen gas was 47 m 2 / g. In powder X-ray diffraction, a diffraction line corresponding to the (002) plane of graphite was observed, and d002 was 0.336 nm. In addition, a very broad diffraction line derived from amorphous carbonization of the carbonaceous material was observed in the vicinity thereof. A diffraction line corresponding to the (100) plane of Si was observed, and d002 was 0.314 nm.

得られた負極活物質を用いたリチウムイオン２次電池を以下のようにして作製した。   A lithium ion secondary battery using the obtained negative electrode active material was produced as follows.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９０．９重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．４重量％と、バインダとしてポリフッ化ビニリデン（ＰＶＤＦ）８．７重量％、ＮＭＰとを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
With respect to 90.9 wt% of the obtained negative electrode active material (content in the total solid content, the same applies hereinafter), acetylene black 0.4 wt% as a conductive auxiliary and polyvinylidene fluoride (PVDF) as a binder A negative electrode mixture-containing slurry was prepared by mixing 8.7% by weight of NMP.

得られたスラリーを、アプリケータを用いて固形分塗布量が１．８ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが１７μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 1.8 mg / cm 2, and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat-treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 17 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１６ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒を使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, 16 mmφ and 0.2 mm thick metal lithium, and a stainless steel foil of the base material into the electrolyte solution. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolytic solution used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1. The evaluation cell was further placed in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to the charge / discharge device.

「評価条件」
評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、１．４ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、１．４ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。 "Evaluation conditions"
The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V with a constant current of 1.4 mA until the current value reached 0.2 mA with a constant voltage of 0.01 V. The discharge was performed at a constant current of 1.4 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

実施例３
平均粒径（Ｄ５０）が７μｍのケミカルグレードの金属Ｓｉ（純度３Ｎ）をエタノールに２１重量％混合し、直径０．３ｍｍのジルコニアビーズを用いた微粉砕湿式ビーズミルを６時間行い、平均粒径（Ｄ５０）０．３μｍ、乾燥時のＢＥＴ比表面積が１００ｍ２／ｇの超微粒子Ｓｉスラリーを得た。 Example 3
Chemical grade metal Si (purity 3N) having an average particle size (D50) of 7 μm was mixed with ethanol in an amount of 21% by weight and subjected to fine grinding wet bead mill using zirconia beads having a diameter of 0.3 mm for 6 hours. D50) An ultrafine Si slurry having a diameter of 0.3 μm and a dry BET specific surface area of 100 m 2 / g was obtained.

粒子径０．３ｍｍ（（２００）面方向の幅）、厚み１０μｍの酸処理した天然黒鉛を振動粉末供給器に入れ、１２Ｌ／分の流量の窒素ガスに乗せて電気ヒーターで８５０℃に加熱した長さ１ｍ、内径２０ｍｍのムライト管に通し、端面から大気に放出し、亜硫酸等のガスを上部に排気、下部に膨張黒鉛をステンレス容器で捕集した。膨張黒鉛の（２００）面方向の幅は０．３ｍｍで元の黒鉛の値を保っていたが、厚みは２．４ｍｍと２４０倍に膨張し、外観はコイル状であり、ＳＥＭ観察で黒鉛層が剥離し、アコーディオン状であることが確認された。   Acid-treated natural graphite having a particle diameter of 0.3 mm (width in the (200) plane direction) and a thickness of 10 μm was placed in a vibrating powder feeder, placed on nitrogen gas at a flow rate of 12 L / min, and heated to 850 ° C. with an electric heater. It was passed through a mullite tube having a length of 1 m and an inner diameter of 20 mm, discharged from the end face to the atmosphere, and a gas such as sulfurous acid was exhausted at the top and expanded graphite was collected at the bottom in a stainless steel container. The expanded graphite had a (200) plane width of 0.3 mm and maintained the original graphite value, but the thickness expanded 2.4 times to 2.4 mm, the appearance was coiled, and the graphite layer was observed by SEM observation. Was peeled off and confirmed to be in the form of an accordion.

上記超微粒子Ｓｉスラリーを９５．７ｇ、上記膨張黒鉛を３７．５ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝３７０）を２３．５ｇ、エタノール５Ｌを撹拌容器に入れ、ホモミキサーで６０分混合撹拌した。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で６０℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに１日間乾燥して、８０ｇの混合乾燥物（軽装かさ密度８７ｇ／Ｌ）を得た。   95.7 g of the ultrafine Si slurry, 37.5 g of the expanded graphite, 23.5 g of a resol type phenolic resin (weight average molecular weight (Mw) = 370), and 5 L of ethanol were placed in a stirring vessel, and 60 minutes with a homomixer. Mix and stir for minutes. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 60 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while being evacuated, passed through a mesh with a mesh opening of 2 mm, and further dried for 1 day to obtain 80 g of a mixed dried product (light bulk density 87 g / L).

この混合乾燥物を３本ロールミルに２回通し、目開き１ｍｍの篩を通し、軽装かさ密度５２８ｇ／Ｌに造粒・圧密化した。   This mixed dried product was passed through a three-roll mill twice, passed through a sieve having an opening of 1 mm, and granulated and consolidated to a light bulk density of 528 g / L.

次に、この造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで９００秒粉砕し、同時に球形化し、軽装かさ密度６３３ｇ／Ｌ、得られた粉末を石英
ボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成した。その後、目開き４５μｍのメッシュを通し、平均粒径（Ｄ５０）が１７．５μｍ、軽装かさ密度が８０７ｇ／Ｌの複合粒子を得た。 Next, this granulated / consolidated product is placed in a new power mill, water-cooled and pulverized at 21000 rpm for 900 seconds. At the same time, it is spheroidized, and the resulting bulk density is 633 g / L. While flowing nitrogen gas in a furnace, firing was performed at a maximum temperature of 900 ° C. for 1 hour. Thereafter, a mesh having an opening of 45 μm was passed through to obtain composite particles having an average particle diameter (D50) of 17.5 μm and a light bulk density of 807 g / L.

この複合粒子を風力分級装置（ホソカワミクロン製 ＡＴＰ−２０）に投入し、分級機回転速度６０，０００ｒｐｍ、風量８ｍ３／ｍにて分級し、集塵バグフィルターで微粒粉を捕捉し、平均粒径（Ｄ５０）が４．８μｍ、軽装かさ密度が２０４ｇ／Ｌの負極活物質を得た。図４に、得られた負極活物質粒子のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球状粒子の他に扁平状微粒子が含まれており、平均円形度は０．７５であり、扁平状微粒子の含有率は７７．９重量％であった。窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は５６ｍ２／ｇであった。 The composite particles are put into an air classifier (ATP-20 manufactured by Hosokawa Micron), classified at a classifier rotation speed of 60,000 rpm and an air volume of 8 m 3 / m, and fine particles are captured by a dust collecting bag filter, and the average particle diameter A negative electrode active material having a (D50) of 4.8 μm and a light bulk density of 204 g / L was obtained. FIG. 4 shows an SEM image of the obtained negative electrode active material particles. In addition to the substantially spherical particles in which the negative electrode active material particle graphite thin layer (12) is curved and covers the active material particles, flat fine particles are contained, the average circularity is 0.75, and the inclusion of flat fine particles The rate was 77.9% by weight. The BET specific surface area by the BET method using nitrogen gas was 56 m 2 / g.

図５に、得られた負極活物質粒子をイオンビームで切断した断面のＦＥ−ＳＥＭによる２次電子像を示す。負極活物質粒子は略球状粒子と扁平状微粒子から構成されており、略球状粒子内部はＳｉの微粒子が炭素質物と共に黒鉛薄層に挟まった構造が網目状に広がり、積層していた。炭素質物はＳｉの微粒子に密着して覆っていた。また、活物質粒子の表面付近では、黒鉛薄層が湾曲して活物質粒子を覆っていた。扁平状微粒子は積層数は少ないが上記略球状粒子と同様な構造であり、その表面は黒鉛薄層もしくは炭素物質に覆われている。   In FIG. 5, the secondary electron image by the FE-SEM of the cross section which cut | disconnected the obtained negative electrode active material particle with the ion beam is shown. The negative electrode active material particles are composed of substantially spherical particles and flat fine particles, and inside the substantially spherical particles, a structure in which Si fine particles are sandwiched between carbonaceous materials and a graphite thin layer spreads in a network shape and is laminated. The carbonaceous material was in close contact with and covered the Si fine particles. Further, near the surface of the active material particles, the graphite thin layer was curved to cover the active material particles. Although the flat fine particles have a small number of layers, they have a structure similar to that of the substantially spherical particles, and the surface thereof is covered with a thin graphite layer or a carbon material.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９５．４重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．５重量％と、バインダとしてカルボキシメチルセルロース（ＣＭＣ）１．５重量％とスチレンブタジエンゴム（ＳＢＲ）２．６重量％、水とを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
The obtained negative electrode active material is 95.4% by weight (content in the total solid content; the same applies hereinafter), acetylene black 0.5% by weight as a conductive additive, and carboxymethyl cellulose (CMC) 1 as a binder. A negative electrode mixture-containing slurry was prepared by mixing 0.5 wt%, styrene butadiene rubber (SBR) 2.6 wt%, and water.

得られたスラリーを、アプリケータを用いて固形分塗布量が１．５ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが１６μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 1.5 mg / cm 2 and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 16 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、にＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｖｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置（北斗電工製ＳＭ−８）に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used was a mixture of ethylene carbonate and diethyl carbonate having a volume ratio of 1: 1, FEC (fluoroethylene carbonate), and LiPF 6 dissolved to a concentration of 1.2 vol / L. The cell for evaluation was further put in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to a charge / discharge device (SM-8 manufactured by Hokuto Denko).

評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。   The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

実施例４
平均粒径（Ｄ５０）が７μｍのケミカルグレードの金属Ｓｉ（純度３Ｎ）をエタノールに２４重量％混合し、直径０．３ｍｍのジルコニアビーズを用いた微粉砕湿式ビーズミルを６時間行い、平均粒径（Ｄ５０）０．３μｍ、乾燥時のＢＥＴ比表面積が１００ｍ２／ｇの超微粒子Ｓｉスラリーを得た。 Example 4
A chemical grade metal Si (purity 3N) having an average particle size (D50) of 7 μm was mixed with ethanol in an amount of 24% by weight and subjected to a fine pulverization wet bead mill using zirconia beads having a diameter of 0.3 mm for 6 hours. D50) An ultrafine Si slurry having a diameter of 0.3 μm and a dry BET specific surface area of 100 m 2 / g was obtained.

粒子径０．３ｍｍ（（２００）面方向の幅）、厚み１０μｍの酸処理した天然黒鉛を振動粉末供給器に入れ、１２Ｌ／分の流量の窒素ガスに乗せて電気ヒーターで８５０℃に加熱した長さ１ｍ、内径２０ｍｍのムライト管に通し、端面から大気に放出し、亜硫酸等のガスを上部に排気、下部に膨張黒鉛をステンレス容器で捕集した。膨張黒鉛の（２００）面方向の幅は０．３ｍｍで元の黒鉛の値を保っていたが、厚みは２．４ｍｍと２４０倍に膨張し、外観はコイル状であり、ＳＥＭ観察で黒鉛層が剥離し、アコーディオン状であることが確認された。   Acid-treated natural graphite having a particle diameter of 0.3 mm (width in the (200) plane direction) and a thickness of 10 μm was placed in a vibrating powder feeder, placed on nitrogen gas at a flow rate of 12 L / min, and heated to 850 ° C. with an electric heater. It was passed through a mullite tube having a length of 1 m and an inner diameter of 20 mm, discharged from the end face to the atmosphere, and a gas such as sulfurous acid was exhausted at the top and expanded graphite was collected at the bottom in a stainless steel container. The expanded graphite had a (200) plane width of 0.3 mm and maintained the original graphite value, but the thickness expanded 2.4 times to 2.4 mm, the appearance was coiled, and the graphite layer was observed by SEM observation. Was peeled off and confirmed to be in the form of an accordion.

上記超微粒子Ｓｉスラリーを９８．８ｇ、上記膨張黒鉛を４８．０ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝３７０）を２０．０ｇ、エタノール５．９Ｌを撹拌容器に入れ、ホモミキサーで９０分混合撹拌した。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で６０℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに１日間乾燥して、８６ｇの混合乾燥物（軽装かさ密度７７ｇ／Ｌ）を得た。   98.8 g of the ultrafine Si slurry, 48.0 g of the expanded graphite, 20.0 g of a resol type phenol resin (weight average molecular weight (Mw) = 370), and 5.9 L of ethanol were placed in a stirring vessel. And stirred for 90 minutes. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 60 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while evacuating, passed through a mesh with a mesh opening of 2 mm, and further dried for 1 day to obtain 86 g of a mixed dried product (light bulk density 77 g / L).

この混合乾燥物を３本ロールミルに２回通し、目開き１ｍｍの篩を通し、軽装かさ密度３０３ｇ／Ｌに造粒・圧密化した。   This mixed dried product was passed through a three-roll mill twice, passed through a sieve having an opening of 1 mm, and granulated and consolidated to a light bulk density of 303 g / L.

次に、この造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで９００秒粉砕し、同時に球形化し、軽装かさ密度４７８ｇ／Ｌの球形化粉末を得た。得られた粉末を石英ボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成した。その後、目開き４５μｍのメッシュを通し、平均粒径（Ｄ５０）が１６．５μｍ、軽装かさ密度が５７３ｇ／Ｌの複合粒子を得た。   Next, the granulated / consolidated product was placed in a new power mill and pulverized at 21000 rpm for 900 seconds while being cooled with water, and simultaneously spheronized to obtain a spheroidized powder having a light bulk density of 478 g / L. The obtained powder was put into a quartz boat and fired at a maximum temperature of 900 ° C. for 1 hour while flowing nitrogen gas in a tubular furnace. Thereafter, a mesh having an opening of 45 μm was passed through to obtain composite particles having an average particle diameter (D50) of 16.5 μm and a light bulk density of 573 g / L.

この複合粒子を風力分級装置（ホソカワミクロン製 ＡＴＰ−５０）に投入し、分級機回転速度１８、０００ｒｐｍ、風量１．６ｍ３／ｍｉｎ、サイクロン捕集機にて微粒粉を捕捉し、それぞれ、平均粒径（Ｄ５０）が５．９μｍ、軽装かさ密度が２９３ｇ／Ｌ及びの負極活物質を得た。図６に、得られた負極活物質粒子のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球状粒子の他に扁平状微粒子が含まれており、平均円形度は０．７４であり，扁平状微粒子の含有率は１．８重量％であった。
窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は３０ｍ２／ｇであった。 This composite particle is put into an air classifier (ATP-50 manufactured by Hosokawa Micron), fine particle is captured by a classifier rotation speed of 18,000 rpm, an air volume of 1.6 m 3 / min, and a cyclone collector. A negative electrode active material having a diameter (D50) of 5.9 μm and a light bulk density of 293 g / L was obtained. FIG. 6 shows an SEM image of the obtained negative electrode active material particles. In addition to the substantially spherical particles in which the negative electrode active material particle graphite thin layer (12) is curved and covers the active material particles, flat fine particles are contained, the average circularity is 0.74, and the inclusion of flat fine particles The rate was 1.8% by weight.
The BET specific surface area by the BET method using nitrogen gas was 30 m 2 / g.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９５．６重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．５重量％と、バインダとしてカルボキシメチルセルロース（ＣＭＣ）１．５重量％とスチレンブタジエンゴム（ＳＢＲ）２．４重量％、水とを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
The obtained negative electrode active material is 95.6% by weight (content in the total solid content; the same applies hereinafter), acetylene black 0.5% by weight as a conductive auxiliary, and carboxymethyl cellulose (CMC) 1 as a binder. A negative electrode mixture-containing slurry was prepared by mixing 0.5 wt%, styrene butadiene rubber (SBR) 2.4 wt%, and water.

得られたスラリーを、アプリケータを用いて固形分塗布量が２．５ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが２１μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 2.5 mg / cm 2 and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat-treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 21 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加材にＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｖｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置（北斗電工製ＳＭ−８）に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, FEC (fluoroethylene carbonate) as the additive, and LiPF 6 dissolved to a concentration of 1.2 vol / L. did. The cell for evaluation was further put in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to a charge / discharge device (SM-8 manufactured by Hokuto Denko).

評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。   The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

実施例５
平均粒径（Ｄ５０）が７μｍのケミカルグレードの金属Ｓｉ（純度３Ｎ）をエタノールに２５重量％混合し、直径０．３ｍｍのジルコニアビーズを用いた微粉砕湿式ビーズミルを６時間行い、平均粒径（Ｄ５０）０．４μｍ、乾燥時のＢＥＴ比表面積が６０ｍ２／ｇの超微粒子Ｓｉスラリーを得た。 Example 5
A chemical grade metal Si (purity 3N) having an average particle size (D50) of 7 μm was mixed with ethanol at 25% by weight, and a finely pulverized wet bead mill using zirconia beads having a diameter of 0.3 mm was performed for 6 hours. D50) An ultrafine Si slurry with 0.4 μm and a dry BET specific surface area of 60 m 2 / g was obtained.

粒子径０．１５ｍｍ（（２００）面方向の幅）、厚み１０μｍ、純度９９．９重量％以上であり、Ｓ量が０．３重量％以下の酸処理した高純度天然黒鉛を振動粉末供給器に入れ、１２Ｌ／分の流量の窒素ガスに乗せて電気ヒーターで８５０℃に加熱した長さ１ｍ、内径１１ｍｍのムライト管に通し、端面から大気に放出し、亜硫酸等のガスを上部に排気、下部に膨張黒鉛をステンレス容器で捕集した。膨張黒鉛の（２００）面方向の幅は０．１５ｍｍで元の黒鉛の値を保っていたが、厚みは０．４ｍｍと４０倍に膨張し、外観はコイル状であり、ＳＥＭ観察で黒鉛層が剥離し、アコーディオン状であることが確認された。   Vibrating powder feeder using acid-treated high-purity natural graphite having a particle diameter of 0.15 mm (width in the (200) plane direction), a thickness of 10 μm, a purity of 99.9% by weight or more, and an S content of 0.3% by weight or less Put into nitrogen gas at a flow rate of 12 L / min and pass through a mullite tube with a length of 1 m and an inner diameter of 11 mm heated to 850 ° C. with an electric heater, discharged from the end face to the atmosphere, and a gas such as sulfurous acid exhausted to the top, Expanded graphite was collected in a stainless steel container at the bottom. The width of the expanded graphite in the (200) plane direction was 0.15 mm and the original graphite value was maintained, but the thickness expanded to 40 mm, 0.4 mm, the appearance was coiled, and the graphite layer was observed by SEM observation. Was peeled off and confirmed to be in the form of an accordion.

上記超微粒子Ｓｉスラリーを４６６．４ｇ、上記膨張黒鉛を４２６．２ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝４６０）を８６．５ｇ、エタノール６．４Ｌを撹拌容器に入れ、インラインミキサーで２６分混合撹拌した。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で６０℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに１日間乾燥して、５８８ｇの混合乾燥物（軽装かさ密度１７０ｇ／Ｌ）を得た。   466.4 g of the ultrafine Si slurry, 426.2 g of the expanded graphite, 86.5 g of a resol type phenolic resin (weight average molecular weight (Mw) = 460), and 6.4 L of ethanol are placed in a stirring vessel. And stirred for 26 minutes. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 60 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while being evacuated, passed through a mesh with a mesh opening of 2 mm, and further dried for 1 day to obtain 588 g of a mixed dried product (light bulk density 170 g / L).

この混合乾燥物を３本ロールミルに２回通し、目開き１ｍｍの篩を通し、軽装かさ密３０８ｇ／Ｌに造粒・圧密化した。   This mixed dried product was passed through a three-roll mill twice, passed through a sieve having an opening of 1 mm, and granulated and consolidated to a lightly packed compact 308 g / L.

次に、この造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで９００秒粉砕し、同時に球形化し、軽装かさ密度４３７ｇ／Ｌの球形化粉末を得た。   Next, this granulated / consolidated product was placed in a new power mill and pulverized at 21000 rpm for 900 seconds while cooling with water, and at the same time, spheronized to obtain a spheroidized powder having a light bulk density of 437 g / L.

得られた粉末を石英ボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成し、軽装かさ密度が５４９ｇ／Ｌの複合粒子を得た。この複合粒子を風力分級装置（ホソカワミクロン製 ＡＴＰ−５０）に投入し、分級機回転速度５０００ｒｐｍ、風量１．６ｍ３／ｍｉｎ、サイクロン捕集機にて微粒粉を捕捉し、平均粒径（Ｄ５０）が１０．０μｍ、軽装かさ密度が５５８ｇ／Ｌの負極活物質を得た。図７に、得られた負極活物質粒子のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球状粒子の他に扁平状微粒子が含まれており、平均円形度は０．７０であり、扁平状微粒子の含有率は１．２重量％であった。窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は２９．０ｍ２／ｇであった。 The obtained powder was put in a quartz boat and fired at a maximum temperature of 900 ° C. for 1 hour while flowing nitrogen gas in a tubular furnace to obtain composite particles having a light bulk density of 549 g / L. The composite particles are put into an air classifier (ATP-50 manufactured by Hosokawa Micron), and the fine particle is captured by a cyclone collector with a classifier rotating speed of 5000 rpm and an air volume of 1.6 m 3 / min, and the average particle diameter (D50) Was 10.0 μm, and a lightly loaded bulk density of 558 g / L was obtained. FIG. 7 shows an SEM image of the obtained negative electrode active material particles. In addition to the substantially spherical particles in which the negative electrode active material particle graphite thin layer (12) is curved to cover the active material particles, flat fine particles are contained, the average circularity is 0.70, and the inclusion of flat fine particles The rate was 1.2% by weight. The BET specific surface area by the BET method using nitrogen gas was 29.0 m 2 / g.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９５．４重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．５重量％と、バインダとしてカルボキシメチルセルロース（ＣＭＣ）１．５重量％とスチレンブタジエンゴム（ＳＢＲ）２．６重量％、水とを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
The obtained negative electrode active material is 95.4% by weight (content in the total solid content; the same applies hereinafter), acetylene black 0.5% by weight as a conductive additive, and carboxymethyl cellulose (CMC) 1 as a binder. A negative electrode mixture-containing slurry was prepared by mixing 0.5 wt%, styrene butadiene rubber (SBR) 2.6 wt%, and water.

得られたスラリーを、アプリケータを用いて固形分塗布量が３．０ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが２２μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 3.0 mg / cm 2 and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat-treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 22 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加材にＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｍｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置（北斗電工製ＳＭ−８）に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used is a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, FEC (fluoroethylene carbonate) as the additive, and LiPF 6 dissolved to a concentration of 1.2 mol / L. did. The cell for evaluation was further put in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to a charge / discharge device (SM-8 manufactured by Hokuto Denko).

評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。   The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

実施例６
平均粒径（Ｄ５０）が７μｍのケミカルグレードの金属Ｓｉ（純度３Ｎ）をエタノールに２５重量％混合し、直径０．３ｍｍのジルコニアビーズを用いた微粉砕湿式ビーズミルを６時間行い、平均粒径（Ｄ５０）０．４μｍ、乾燥時のＢＥＴ比表面積が６０ｍ２／ｇの超微粒子Ｓｉスラリーを得た。 Example 6
A chemical grade metal Si (purity 3N) having an average particle size (D50) of 7 μm was mixed with ethanol at 25% by weight, and a finely pulverized wet bead mill using zirconia beads having a diameter of 0.3 mm was performed for 6 hours. D50) An ultrafine Si slurry with 0.4 μm and a dry BET specific surface area of 60 m 2 / g was obtained.

粒子径０．１５ｍｍ（（２００）面方向の幅）、厚み１０μｍ、純度９９．９重量％以上であり、Ｓ量が０．３重量％以下の酸処理した高純度天然黒鉛を振動粉末供給器に入れ、１２Ｌ／分の流量の窒素ガスに乗せて電気ヒーターで８５０℃に加熱した長さ１ｍ、内径１１ｍｍのムライト管に通し、端面から大気に放出し、亜硫酸等のガスを上部に排気、下部に膨張黒鉛をステンレス容器で捕集した。膨張黒鉛の（２００）面方向の幅は０．１５ｍｍで元の黒鉛の値を保っていたが、厚みは０．４ｍｍと４０倍に膨張し、外観はコイル状であり、ＳＥＭ観察で黒鉛層が剥離し、アコーディオン状であることが確認された。   Vibrating powder feeder using acid-treated high-purity natural graphite having a particle diameter of 0.15 mm (width in the (200) plane direction), a thickness of 10 μm, a purity of 99.9% by weight or more, and an S content of 0.3% by weight or less Put into nitrogen gas at a flow rate of 12 L / min and pass through a mullite tube with a length of 1 m and an inner diameter of 11 mm heated to 850 ° C. with an electric heater, discharged from the end face to the atmosphere, and a gas such as sulfurous acid exhausted to the top, Expanded graphite was collected in a stainless steel container at the bottom. The width of the expanded graphite in the (200) plane direction was 0.15 mm and the original graphite value was maintained, but the thickness expanded to 40 mm, 0.4 mm, the appearance was coiled, and the graphite layer was observed by SEM observation. Was peeled off and confirmed to be in the form of an accordion.

上記超微粒子Ｓｉスラリーを１４５．７ｇ、上記膨張黒鉛を１３３．２ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝４６０）を２７ｇ、エタノール２Ｌを撹拌容器に入れ、インラインミキサーで８．２５分混合撹拌した。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で６０℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに１日間乾燥して、１８８ｇの混合乾燥物（軽装かさ密度１３２ｇ／Ｌ）を得た。   145.7 g of the ultrafine Si slurry, 133.2 g of the expanded graphite, 27 g of resol type phenolic resin (weight average molecular weight (Mw) = 460), 2 L of ethanol were placed in a stirring vessel, and 8.25 using an in-line mixer. Mix and stir for minutes. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 60 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while being evacuated, passed through a mesh with a mesh opening of 2 mm, and further dried for 1 day to obtain 188 g of a mixed dried product (light bulk density 132 g / L).

この混合乾燥物を３本ロールミルに２回通し、目開き１ｍｍの篩を通し、軽装かさ密２３５ｇ／Ｌに造粒・圧密化した。   This mixed dried product was passed through a three-roll mill twice, passed through a sieve having an opening of 1 mm, and granulated and consolidated to a lightly packed compact 235 g / L.

次に、この造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで９００秒粉砕し、同時に球形化し、軽装かさ密度４７６ｇ／Ｌの球形化粉末を得た。   Next, this granulated / consolidated product was placed in a new power mill and pulverized at 21000 rpm for 900 seconds while being cooled with water. At the same time, it was spheroidized to obtain a spheroidized powder having a light bulk density of 476 g / L.

得られた粉末を石英ボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成し、軽装かさ密度が６４１ｇ／Ｌの複合粒子を得た。その後、目開き４５μｍのメッシュを通し、平均粒径（Ｄ５０）が１７．６μｍ、軽装かさ密度が６２９ｇ／Ｌの負極活物質を得た。図８に、得られた負極活物質粒子のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球状粒子の他に扁平状微粒子が含まれており、平均円形度は０．７２であり、扁平状微粒子の含有率は１．１重量％であった。窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は３７ｍ２／ｇであった。 The obtained powder was put into a quartz boat and fired at a maximum temperature of 900 ° C. for 1 hour while flowing nitrogen gas in a tubular furnace to obtain composite particles having a light bulk density of 641 g / L. Thereafter, a negative active material having an average particle diameter (D50) of 17.6 μm and a light bulk density of 629 g / L was obtained through a mesh having an opening of 45 μm. FIG. 8 shows an SEM image of the obtained negative electrode active material particles. In addition to the substantially spherical particles in which the negative electrode active material particle graphite thin layer (12) is curved and covers the active material particles, flat fine particles are contained, the average circularity is 0.72, and the inclusion of flat fine particles The rate was 1.1% by weight. The BET specific surface area by the BET method using nitrogen gas was 37 m 2 / g.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９５．４重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．５重量％と、バインダとしてカルボキシメチルセルロース（ＣＭＣ）１．５重量％とスチレンブタジエンゴム（ＳＢＲ）２．６重量％、水とを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
The obtained negative electrode active material is 95.4% by weight (content in the total solid content; the same applies hereinafter), acetylene black 0.5% by weight as a conductive additive, and carboxymethyl cellulose (CMC) 1 as a binder. A negative electrode mixture-containing slurry was prepared by mixing 0.5 wt%, styrene butadiene rubber (SBR) 2.6 wt%, and water.

得られたスラリーを、アプリケータを用いて固形分塗布量が３．６ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが３６μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 3.6 mg / cm 2 and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 36 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加材にＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｍｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置（北斗電工製ＳＭ−８）に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used is a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, FEC (fluoroethylene carbonate) as the additive, and LiPF 6 dissolved to a concentration of 1.2 mol / L. did. The cell for evaluation was further put in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to a charge / discharge device (SM-8 manufactured by Hokuto Denko).

評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。   The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

比較例１
混合工程において、超微粒子Ｓｉスラリーを３６ｇ、膨張黒鉛を１８ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝３．６×１０３）を７．５ｇ、エタノール２．４Ｌを撹拌容器に入れて、工程を実施した以外は実施例２と同様の方法で平均粒径（Ｄ５０）が４．２μｍ、軽装かさ密度２５０ｇ／Ｌの球形化粉末を得た。 Comparative Example 1
In the mixing step, 36 g of ultrafine Si slurry, 18 g of expanded graphite, 7.5 g of resol type phenol resin (weight average molecular weight (Mw) = 3.6 × 10 3 ), and 2.4 L of ethanol are put in a stirring vessel. A spherical powder having an average particle size (D50) of 4.2 μm and a light bulk density of 250 g / L was obtained in the same manner as in Example 2 except that the steps were performed.

この球形化粉末から実施例２と同様の方法で負極活物質、負極、評価用セルの順に作製し、セル評価した。   A negative electrode active material, a negative electrode, and an evaluation cell were prepared in this order from the spheroidized powder in the same manner as in Example 2, and the cells were evaluated.

図９に、得られた負極活物質のＳＥＭ像を示す。粒子は略球状にはならず、微細な粉末と扁平状粒子となっており、その平均円形度は０．６５であり、扁平状微粒子の含有率は０．３重量％であった。窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は３３ｍ２／ｇであった。 FIG. 9 shows an SEM image of the obtained negative electrode active material. The particles were not substantially spherical, but were fine powder and flat particles, the average circularity was 0.65, and the content of flat particles was 0.3% by weight. The BET specific surface area by the BET method using nitrogen gas was 33 m 2 / g.

得られた負極活物質を用いたリチウムイオン２次電池を以下のようにして作製した。   A lithium ion secondary battery using the obtained negative electrode active material was produced as follows.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９０．８重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．５重量％と、バインダとしてＰＶＤＦ８．７重量％、ＮＭＰとを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
With respect to 90.8% by weight of the obtained negative electrode active material (content in the total solid content, the same shall apply hereinafter), acetylene black 0.5% by weight as a conductive assistant, PVDF 8.7% by weight as a binder, NMP was mixed to prepare a negative electrode mixture-containing slurry.

得られたスラリーを、アプリケータを用いて固形分塗布量が２．２ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが１７μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 2.2 mg / cm 2 and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat-treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 17 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１６ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒を使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, 16 mmφ and 0.2 mm thick metal lithium, and a stainless steel foil of the base material into the electrolyte solution. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolytic solution used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1. The evaluation cell was further placed in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to the charge / discharge device.

「評価条件」
評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、１．４ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、１．４ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。 "Evaluation conditions"
The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V with a constant current of 1.4 mA until the current value reached 0.2 mA with a constant voltage of 0.01 V. The discharge was performed at a constant current of 1.4 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

比較例２
平均粒径（Ｄ５０）が７μｍのケミカルグレードの金属Ｓｉ（純度３Ｎ）をエタノールに２３重量％混合し、直径０．３ｍｍのジルコニアビーズを用いた微粉砕湿式ビーズミルを６時間行い、平均粒径（Ｄ５０）０．３μｍ、乾燥時のＢＥＴ比表面積が１００ｍ２／ｇの超微粒子Ｓｉスラリーを得た。 Comparative Example 2
A chemical grade metal Si (purity 3N) having an average particle size (D50) of 7 μm was mixed with ethanol in an amount of 23% by weight and subjected to a fine pulverization wet bead mill using zirconia beads having a diameter of 0.3 mm for 6 hours. D50) An ultrafine Si slurry having a diameter of 0.3 μm and a dry BET specific surface area of 100 m 2 / g was obtained.

粒子径０．３ｍｍ（（２００）面方向の幅）、厚み１０μｍの酸処理した天然黒鉛を振動粉末供給器に入れ、１２Ｌ／分の流量の窒素ガスに乗せて電気ヒーターで８５０℃に加熱した長さ１ｍ、内径２０ｍｍのムライト管に通し、端面から大気に放出し、亜硫酸等のガスを上部に排気、下部に膨張黒鉛をステンレス容器で捕集した。膨張黒鉛の（２００）面方向の幅は０．３ｍｍで元の黒鉛の値を保っていたが、厚みは２．４ｍｍと２４０倍に膨張し、外観はコイル状であり、ＳＥＭ観察で黒鉛層が剥離し、アコーディオン状であることが確認された。   Acid-treated natural graphite having a particle diameter of 0.3 mm (width in the (200) plane direction) and a thickness of 10 μm was placed in a vibrating powder feeder, placed on nitrogen gas at a flow rate of 12 L / min, and heated to 850 ° C. with an electric heater. It was passed through a mullite tube having a length of 1 m and an inner diameter of 20 mm, discharged from the end face to the atmosphere, and a gas such as sulfurous acid was exhausted at the top and expanded graphite was collected at the bottom in a stainless steel container. The expanded graphite had a (200) plane width of 0.3 mm and maintained the original graphite value, but the thickness expanded 2.4 times to 2.4 mm, the appearance was coiled, and the graphite layer was observed by SEM observation. Was peeled off and confirmed to be in the form of an accordion.

上記超微粒子Ｓｉスラリーを１０２．６ｇ、上記膨張黒鉛を４８．０ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝３７０）を２０．０ｇ、エタノール５．９Ｌを撹拌容器に入れ、ホモミキサーで９０分混合撹拌した。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で６０℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに１日間乾燥して、８６ｇの混合乾燥物（軽装かさ密度６６ｇ／Ｌ）を得た。   102.6 g of the ultrafine Si slurry, 48.0 g of the expanded graphite, 20.0 g of a resol-type phenol resin (weight average molecular weight (Mw) = 370), and 5.9 L of ethanol were placed in a stirring vessel. And stirred for 90 minutes. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 60 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while being evacuated, passed through a 2 mm mesh, and further dried for 1 day to obtain 86 g of a mixed dried product (light bulk density 66 g / L).

この混合乾燥物を３本ロールミルに２回通し、目開き１ｍｍの篩を通し、軽装かさ密度２８７ｇ／Ｌに造粒・圧密化した後、大気中１５０℃の温度で２時間の加熱処理を行った。   This mixed dried product is passed through a three-roll mill twice, passed through a 1 mm sieve, granulated and compacted to a light bulk density of 287 g / L, and then heat-treated at 150 ° C. for 2 hours in the atmosphere. It was.

次に、この加熱処理した造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで３００秒粉砕し、同時に球形化し、軽装かさ密度２２５ｇ／Ｌの球形化粉末を得た。得られた粉末を石英ボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成した後、目開き４５μｍのメッシュを通して複合粒子を得た。   Next, the granulated / consolidated product subjected to the heat treatment was placed in a new power mill and pulverized at 21000 rpm for 300 seconds while being cooled with water, and spheroidized at the same time to obtain a spheroidized powder having a light bulk density of 225 g / L. The obtained powder was put into a quartz boat and fired at a maximum temperature of 900 ° C. for 1 hour while flowing nitrogen gas in a tubular furnace, and then composite particles were obtained through a mesh having an opening of 45 μm.

この複合粒子を風力分級装置（ホソカワミクロン製 ＡＴＰ−５０）に投入し、分級機回転速度１８、０００ｒｐｍ、風量１．６ｍ３／ｍｉｎ、サイクロン捕集機にて微粒粉を捕捉し、それぞれ、平均粒径（Ｄ５０）が４．３μｍ、軽装かさ密度が２７０ｇ／Ｌ及びの負極活物質を得た。図１０に、得られた負極活物質粒子のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球状粒子の他に扁平状微粒子が含まれており、平均円形度は０．５６であり、扁平状微粒子の含有率は３０．９重量％であった。窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は４７ｍ２／ｇであった。 This composite particle is put into an air classifier (ATP-50 manufactured by Hosokawa Micron), fine particle is captured by a classifier rotation speed of 18,000 rpm, an air volume of 1.6 m 3 / min, and a cyclone collector. A negative electrode active material having a diameter (D50) of 4.3 μm and a light bulk density of 270 g / L was obtained. FIG. 10 shows an SEM image of the obtained negative electrode active material particles. In addition to the substantially spherical particles in which the negative electrode active material particle graphite thin layer (12) is curved and covers the active material particles, flat fine particles are contained, the average circularity is 0.56, and the inclusion of flat fine particles The rate was 30.9% by weight. The BET specific surface area by the BET method using nitrogen gas was 47 m 2 / g.

「リチウムイオン２次電池用負極の作製」
得られた負極活物質を９５．５重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてアセチレンブラック０．５重量％と、バインダとしてカルボキシメチルセルロース（ＣＭＣ）１．５重量％とスチレンブタジエンゴム（ＳＢＲ）２．５重量％、水とを混合して負極合剤含有スラリーを調製した。 “Preparation of negative electrode for lithium ion secondary battery”
The obtained negative electrode active material is 95.5% by weight (content in the total solid content; the same shall apply hereinafter), acetylene black 0.5% by weight as a conductive auxiliary, and carboxymethyl cellulose (CMC) 1 as a binder. A negative electrode mixture-containing slurry was prepared by mixing 0.5 wt%, styrene butadiene rubber (SBR) 2.5 wt%, and water.

得られたスラリーを、アプリケータを用いて固形分塗布量が３．１ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて０．５時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で３時間熱処理して、厚みが２８μｍの負極合剤層を形成したリチウムイオン２次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 3.1 mg / cm 2 and dried at 110 ° C. in a vacuum dryer for 0.5 hours. . After drying, the lithium ion 2 was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat treated at 110 ° C. for 3 hours under vacuum to form a negative electrode mixture layer having a thickness of 28 μm. A negative electrode for a secondary battery was obtained.

「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加材にＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｖｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置（北斗電工製ＳＭ−８）に接続した。 "Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, FEC (fluoroethylene carbonate) as the additive, and LiPF 6 dissolved to a concentration of 1.2 vol / L. did. The cell for evaluation was further put in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to a charge / discharge device (SM-8 manufactured by Hokuto Denko).

評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。   The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test.

また、サイクル特性は、前記充放電条件にて３０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。   In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 30 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.

比較例３
実施例３で得られた焼成粉を目開き４５μｍの篩をかけた際に、得られた４５μｍ以上の粒子を、目開き５３μｍのメッシュを通し、平均粒径が（Ｄ５０）が５４．８μｍ、軽装かさ密度９３５ｇ／Ｌの複合粒子を得た。図１１に、得られた負極活物質粒子のＳＥＭ像を示す。負極活物質粒子黒鉛薄層（１２）が湾曲して活物質粒子を覆った略球状形状となっており、その平均円形度は０．７３であり、扁平状微粒子の含有量は０重量％であった。窒素ガスを用いたＢＥＴ法によるＢＥＴ比表面積は９２ｍ２／ｇであった。 Comparative Example 3
When the baked powder obtained in Example 3 was passed through a sieve having an opening of 45 μm, the obtained particles of 45 μm or more were passed through a mesh having an opening of 53 μm, and the average particle diameter (D50) was 54.8 μm. Composite particles having a light bulk density of 935 g / L were obtained. FIG. 11 shows an SEM image of the obtained negative electrode active material particles. The negative electrode active material particle graphite thin layer (12) is curved and has a substantially spherical shape covering the active material particle, the average circularity is 0.73, and the content of flat fine particles is 0% by weight. there were. The BET specific surface area by the BET method using nitrogen gas was 92 m 2 / g.

実施例１〜６の結果と比較例１〜３の結果を表１に示す。   Table 1 shows the results of Examples 1 to 6 and Comparative Examples 1 to 3.

Figure 2016110969
表１から明らかなように、実施例１〜２のリチウムイオン２次電池は、高容量で、初期充放電効率が高く、充放電サイクル特性が良好である。
Figure 2016110969
 As is clear from Table 1, the lithium ion secondary batteries of Examples 1 and 2 have a high capacity, high initial charge / discharge efficiency, and good charge / discharge cycle characteristics.

実施例３〜６の扁平状微粒を子１％以上８０％以下含む負極活物質を使用した、リチウムイオン二次電池は、実施例１〜２よりさらに充放電サイクル特性は良好である。また実施例５及び６では高純度黒鉛をその原料として使用しているため、初期充放電効率がさらに高い値となっている。   The lithium ion secondary battery using the negative electrode active material containing the flat fine particles of Examples 3 to 6 in an amount of 1% to 80% has better charge / discharge cycle characteristics than Examples 1-2. In Examples 5 and 6, high-purity graphite is used as a raw material, so that the initial charge / discharge efficiency is a higher value.

これに対し、比較例１のリチウムイオン２次電池は、平均円形度が低いため、そのサイクル維持率は実施例１〜６より劣る。比較例２のリチウムイオン２次電池は適当量の扁平状微粒子を含んでいるが、平均円形度が低いため、充放電サイクル特性が同じ扁平状粒子を特定量含む実施例３〜５より劣る。また比較例３は複合粒子の粒径が大きすぎるため、電極形成が出来ず、評価不可能であった。   On the other hand, since the average circularity of the lithium ion secondary battery of Comparative Example 1 is low, the cycle retention rate is inferior to that of Examples 1-6. Although the lithium ion secondary battery of Comparative Example 2 contains an appropriate amount of flat particles, the average circularity is low, so that the charge / discharge cycle characteristics are inferior to those of Examples 3 to 5 containing a specific amount of flat particles. In Comparative Example 3, the composite particles were too large in size, so that the electrode could not be formed and evaluation was impossible.

本発明であるリチウムイオン２次電池負極活物質およびその製造方法は、高容量で長寿命が必要とされるリチウムイオン２次電池に利用することができる。   The negative electrode active material for lithium ion secondary battery and the method for producing the same of the present invention can be used for a lithium ion secondary battery that requires a high capacity and a long life.

１１ 負極活物質内部の黒鉛薄層
１２ 負極活物質表面付近の黒鉛薄層
１３ Ｓｉ微粒子と炭素質物の層 11 Thin graphite layer inside negative electrode active material 12 Thin graphite layer near negative electrode active material surface 13 Si fine particle and carbonaceous material layer

Claims (16)

ＳｉまたはＳｉ合金と、炭素質物または炭素質物と黒鉛とを、含んでなるリチウムイオン２次電池用負極活物質において、該負極活物質の平均粒径（Ｄ５０）が１〜４０μｍであり、かつ平均円形度が０．７〜１．０の略球状の複合粒子であることを特徴とするリチウムイオン２次電池用負極活物質。 In the negative electrode active material for a lithium ion secondary battery comprising Si or Si alloy, carbonaceous material or carbonaceous material and graphite, the average particle diameter (D50) of the negative electrode active material is 1 to 40 μm, and the average A negative electrode active material for a lithium ion secondary battery, wherein the negative electrode active material is a substantially spherical composite particle having a circularity of 0.7 to 1.0. 該負極活物質の平均粒径（Ｄ５０）が１〜１０μｍであり、ＳＥＭ像観察により計測された短軸長１μｍ未満の扁平状微粒子を１重量％以上、８０重量％以下含む複合粒子であることを特徴とする請求項１に記載のリチウムイオン２次電池用負極活物質。 The average particle diameter (D50) of the negative electrode active material is 1 to 10 μm, and the composite particles include 1 to 80% by weight of flat fine particles having a minor axis length of less than 1 μm measured by SEM image observation. The negative electrode active material for a lithium ion secondary battery according to claim 1. 前記ＳｉまたはＳｉ合金の平均粒径（Ｄ５０）が０．０１〜５μｍであり、炭素質物が少なくとも活物質表面を覆っていることを特徴とする請求項１又は２に記載のリチウムイオン２次電池用負極活物質。 3. The lithium ion secondary battery according to claim 1, wherein an average particle diameter (D50) of the Si or Si alloy is 0.01 to 5 μm, and a carbonaceous material covers at least an active material surface. Negative electrode active material. 前記ＳｉまたはＳｉ合金の平均粒径（Ｄ５０）が０．０１〜１μｍであり、炭素質物が少なくとも活物質表面を覆っていることを特徴とする請求項１又は２に記載のリチウムイオン２次電池用負極活物質。 3. The lithium ion secondary battery according to claim 1, wherein an average particle diameter (D50) of the Si or Si alloy is 0.01 to 1 μm, and a carbonaceous material covers at least an active material surface. Negative electrode active material. 前記ＳｉまたはＳｉ合金が、炭素質物と共に０．２μｍ以下の厚みの黒鉛薄層の間に挟まった構造であり、その構造が積層及び／又は網目状に広がっており、該黒鉛薄層が活物質粒子の表面付近で湾曲して活物質粒子を覆っており、最外層の表面を炭素質物が覆っていることを特徴とする請求項１〜４のいずれか１項に記載のリチウムイオン２次電池用負極活物質。 The Si or Si alloy has a structure sandwiched between carbonaceous materials and a thin graphite layer having a thickness of 0.2 μm or less, and the structure spreads in a laminated and / or network shape, and the thin graphite layer is an active material. The lithium ion secondary battery according to any one of claims 1 to 4, wherein the active material particles are curved in the vicinity of the surface of the particles, and the surface of the outermost layer is covered with a carbonaceous material. Negative electrode active material. 該黒鉛は、ＩＣＰ発光分光分析法による２６元素（Ａｌ、Ｃａ、Ｃｒ、Ｆｅ、Ｋ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｖ、Ｚｎ、Ｚｒ、Ａｇ、Ａｓ、Ｂａ、Ｂｅ、Ｃｄ、Ｃｏ、Ｃｕ、Ｍｏ、Ｐｂ、Ｓｂ、Ｓｅ、Ｔｈ、Ｔｌ、Ｕ）の不純物半定量値より求めた純度が９９．９重量％以上、若しくは不純物量１０００ｐｐｍ以下で酸素フラスコ燃焼法によるイオンクロマトグラフィー（ＩＣ）測定法によるＳ量が０．３重量％以下、及び／又はＢＥＴ比表面積４０ｍ２／ｇ以下であることを特徴とする請求項１〜５のいずれか１項に記載のリチウムイオン２次電池用負極活物質。 The graphite is composed of 26 elements (Al, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, V, Zn, Zr, Ag, As, Ba, Be, Cd, Co, Cu, by ICP emission spectroscopy. , Mo, Pb, Sb, Se, Th, Tl, U) Ion chromatography (IC) measurement by oxygen flask combustion method when the purity determined from the semi-quantitative value of impurities is 99.9% by weight or more, or the impurity amount is 1000 ppm or less amount S 0.3 wt% or less by law, and / or a negative electrode for a lithium ion secondary battery according to any one of claims 1 to 5, equal to or less than the BET specific surface area of 40 m 2 / g Active material. 前記ＳｉまたはＳｉ合金の含有量が１０〜８０重量％、前記炭素質物の含有量が９０〜２０重量％であることを特徴とする請求項１〜６のいずれか１項に記載のリチウムイオン２次電池用負極活物質。 The lithium ion 2 according to any one of claims 1 to 6, wherein a content of the Si or Si alloy is 10 to 80% by weight, and a content of the carbonaceous material is 90 to 20% by weight. Negative electrode active material for secondary battery. 前記ＳｉまたはＳｉ合金の含有量が１０〜６０重量％、前記炭素質物の含有量が５〜４０重量％、前記黒鉛の含有量が２０〜８０重量％であることを特徴とする請求項１〜６のいずれか１項に記載のリチウムイオン２次電池用負極活物質。 The content of the Si or Si alloy is 10 to 60% by weight, the content of the carbonaceous material is 5 to 40% by weight, and the content of the graphite is 20 to 80% by weight. 6. The negative electrode active material for a lithium ion secondary battery according to any one of 6 above. ＢＥＴ比表面積が０．５〜８０ｍ２／ｇであることを特徴とする請求項１〜８いずれか１項に記載のリチウムイオン２次電池用負極活物質。 BET specific surface area is 0.5-80 m < 2 > / g, The negative electrode active material for lithium ion secondary batteries of any one of Claims 1-8 characterized by the above-mentioned. ＳｉまたはＳｉ合金、炭素前駆体、および黒鉛を混合する工程と、造粒・圧密化する工程と、混合物を粉砕および球形化処理して略球状の複合粒子を形成する工程と、該複合粒子を不活性ガス雰囲気中で焼成する工程とを含むことを特徴とする請求項１〜９のいずれか１項に記載のリチウムイオン２次電池用負極活物質の製造方法。 A step of mixing Si or an Si alloy, a carbon precursor, and graphite, a step of granulating and compacting, a step of grinding and spheroidizing the mixture to form substantially spherical composite particles, and the composite particles The method for producing a negative electrode active material for a lithium ion secondary battery according to any one of claims 1 to 9, further comprising a step of firing in an inert gas atmosphere. 球形化処理において、粉砕された粒子を再結着させて略球状の複合粒子を形成することを特徴とする請求項１０に記載のリチウムイオン２次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium ion secondary battery according to claim 10, wherein in the spheronization treatment, the pulverized particles are rebound to form substantially spherical composite particles. ＳｉまたはＳｉ合金、炭素前駆体、および黒鉛を混合する工程と、造粒・圧密化する工程と、混合物を粉砕および球形化処理して略球状の複合粒子を形成する工程と、該複合粒子を不活性ガス雰囲気中で焼成する工程と、粉砕および球形処理した粉体、もしくは焼成粉を風力分級する工程を含むことを特徴とする請求項１〜９のいずれか１項に記載のリチウムイオン２次電池用負極活物質の製造方法。 A step of mixing Si or an Si alloy, a carbon precursor, and graphite, a step of granulating and compacting, a step of grinding and spheroidizing the mixture to form substantially spherical composite particles, and the composite particles The lithium ion 2 according to any one of claims 1 to 9, comprising a step of firing in an inert gas atmosphere and a step of air classification of the pulverized and spherically processed powder or the fired powder. The manufacturing method of the negative electrode active material for secondary batteries. 球形化処理において、粉砕された粒子を再結着させて略球状の複合粒子と扁平状微粒子を形成することもしくは略球状複合粒子と扁平状微粒子を混合、撹拌、分級することを特徴とする請求項１２に記載のリチウムイオン２次電池用負極活物質の製造方法。 In the spheronization treatment, the pulverized particles are rebound to form substantially spherical composite particles and flat fine particles, or the substantially spherical composite particles and flat fine particles are mixed, stirred, and classified. Item 13. A method for producing a negative electrode active material for a lithium ion secondary battery according to Item 12. 炭素前駆体が、重量平均分子量（Ｍｗ）１０００以下の炭素系化合物であることを特徴とする請求項１０〜１３のいずれか１項に記載のリチウムイオン２次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium ion secondary battery according to any one of claims 10 to 13, wherein the carbon precursor is a carbon-based compound having a weight average molecular weight (Mw) of 1000 or less. 黒鉛が、膨張黒鉛または薄片状黒鉛であることを特徴とする請求項１０〜１４のいずれか１項に記載のリチウムイオン２次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium ion secondary battery according to any one of claims 10 to 14, wherein the graphite is expanded graphite or flaky graphite. 複合粒子を不活性雰囲気中で焼成する工程の温度が、６００〜１２００℃であることを特徴とする請求項１０〜１５のいずれか１項に記載のリチウムイオン２次電池用負極活物質の製造方法。 The temperature of the process which bakes a composite particle in inert atmosphere is 600-1200 degreeC, The manufacture of the negative electrode active material for lithium ion secondary batteries of any one of Claims 10-15 characterized by the above-mentioned. Method.
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