JP2006244984A - Composite particle for electrode, its manufacturing method, and nonaqueous electrolyte secondary battery - Google Patents

Composite particle for electrode, its manufacturing method, and nonaqueous electrolyte secondary battery Download PDF

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JP2006244984A
JP2006244984A JP2005240956A JP2005240956A JP2006244984A JP 2006244984 A JP2006244984 A JP 2006244984A JP 2005240956 A JP2005240956 A JP 2005240956A JP 2005240956 A JP2005240956 A JP 2005240956A JP 2006244984 A JP2006244984 A JP 2006244984A
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particles
active material
carbon
electrode
particle
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Sumuto Ishida
澄人 石田
Hiroaki Matsuda
博明 松田
Koji Yoshizawa
浩司 芳澤
Yasutaka Furuyui
康隆 古結
Takuma Asari
琢磨 浅利
Takashi Otsuka
隆 大塚
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for giving a battery excellent in the initial charge-discharge character and the charge-discharge cyclic character thereof. <P>SOLUTION: The composite particle for the electrode contains an active material particle, a carbon nano-fiber bonded on the surface of the active material particle, and a catalyst element for accelerating the growth of the carbon nano-fiber. The active material particle comprises an electrochemical active phase. The catalyst element used includes Au, Ag, Pt, Ru, Ir, Cu, Fe, Co, Ni, Mo, Mn or the like. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、リチウムの充放電が可能な活物質粒子を改良した複合粒子に関し、詳しくは、カーボンナノファイバが表面に結合した活物質粒子に関する。本発明の複合粒子を含む電極は、優れた初期充放電特性およびサイクル特性を有する非水電解質二次電池やキャパシタを与える。   The present invention relates to composite particles obtained by improving active material particles capable of charging / discharging lithium, and more particularly to active material particles having carbon nanofibers bonded to the surface. The electrode containing the composite particles of the present invention provides a nonaqueous electrolyte secondary battery or capacitor having excellent initial charge / discharge characteristics and cycle characteristics.

電子機器のポータブル化、コードレス化が進むにつれて、小型、軽量で、かつ高エネルギー密度を有する非水電解質二次電池への期待は高まりつつある。現在、非水電解質二次電池の負極活物質としては、黒鉛などの炭素材料が実用化されている。黒鉛は、理論上、炭素原子６個に対してリチウム原子１個を吸蔵できる。一方、非水電解質二次電池の正極活物質としては、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4などのリチウム含有金属酸化物が実用化されている。 As electronic devices become more portable and cordless, expectations for non-aqueous electrolyte secondary batteries that are small, light, and have high energy density are increasing. Currently, carbon materials such as graphite have been put into practical use as negative electrode active materials for non-aqueous electrolyte secondary batteries. Theoretically, graphite can occlude one lithium atom for every six carbon atoms. On the other hand, lithium-containing metal oxides such as LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 have been put to practical use as positive electrode active materials for nonaqueous electrolyte secondary batteries.

黒鉛の理論容量密度は３７２ｍＡｈ／ｇである。しかし、不可逆容量による容量ロスなどがあり、実際の放電容量密度は３１０〜３３０ｍＡｈ／ｇ程度に低下する。基本的には、この容量密度以上でリチウムイオンを吸蔵および放出できる炭素材料を得ることは困難である。そこで、更に高エネルギー密度の電池が求められる中、理論容量密度の高い負極活物質として、リチウムと合金化するＳｉ、Ｓｎ、Ｇｅやこれらの酸化物などが期待されている。   The theoretical capacity density of graphite is 372 mAh / g. However, there is a capacity loss due to irreversible capacity, and the actual discharge capacity density is reduced to about 310 to 330 mAh / g. Basically, it is difficult to obtain a carbon material that can occlude and release lithium ions above this capacity density. Therefore, while a battery having a higher energy density is demanded, Si, Sn, Ge alloyed with lithium and oxides thereof are expected as a negative electrode active material having a high theoretical capacity density.

しかし、Ｓｉ、Ｓｎ、Ｇｅやこれらの酸化物は、電子伝導性が非常に低いため、導電剤を混合しなければ電池の内部抵抗が大きくなり、実用的でない。そこで、微粒黒鉛粉末やカーボンブラックを導電剤として用いることが検討されている（特許文献１）。導電剤をＳｉ、Ｓｎ、Ｇｅやこれらの酸化物と混合することで、電池の初期充放電特性は向上する。   However, since Si, Sn, Ge, and their oxides have very low electronic conductivity, the internal resistance of the battery is increased unless a conductive agent is mixed, which is not practical. Therefore, it has been studied to use fine graphite powder or carbon black as a conductive agent (Patent Document 1). By mixing the conductive agent with Si, Sn, Ge or their oxides, the initial charge / discharge characteristics of the battery are improved.

Ｓｉやその酸化物は、特に導電性が乏しい。よって、その表面をＣＶＤ（化学蒸着）法によりカーボンコートすることで、電子伝導性を確保し、充電前の極板抵抗を低減することが提案されている（特許文献２、３）。   Si and its oxide are particularly poor in conductivity. Therefore, it has been proposed that the surface is carbon-coated by a CVD (chemical vapor deposition) method to ensure electron conductivity and reduce electrode plate resistance before charging (Patent Documents 2 and 3).

高い導電性を示すことで知られるカーボンナノファイバを導電剤として用いることも提案されている（特許文献４）。   The use of carbon nanofibers known to exhibit high conductivity as a conductive agent has also been proposed (Patent Document 4).

活物質粒子の導電性のさらなる向上のために、Ｃｒ、Ｂ、Ｐ等を添加したり、カーボンナノファイバと活物質とをボールミルで混合したりすることも検討されている（非特許文献１）。   In order to further improve the conductivity of the active material particles, addition of Cr, B, P, or the like, or mixing the carbon nanofibers and the active material with a ball mill has been studied (Non-Patent Document 1). .

リチウム含有金属酸化物についても、電子伝導性が乏しいため、一般に導電剤を混合した状態で正極に用いられている（非特許文献２）。導電剤としては、様々なカーボン種が検討されている。カーボン種の形状や添加量についても検討が重ねられている（特許文献５、６、７）。
特開平４−１８８５６０号公報 特開２００２−４２８０６号公報 特開２００４−４７４０４号公報 特開２００３−７７４７６号公報 特開昭６０−６５４６２号公報 特開平４−１９０５６１号公報 特開平４−２１５２５２号公報 「エレクトロケミストリー（Electrochemistry）」、２００３年、第７１巻、第１２号、ｐ．１１０５−１１０７ 金村聖志編集、「２１世紀のリチウム二次電池技術」、ＣＭＣ出版、ｐ．１２５−１２８ Lithium-containing metal oxides are also used for positive electrodes in a mixed state with a conductive agent because they have poor electronic conductivity (Non-patent Document 2). Various carbon species have been studied as the conductive agent. Studies have been repeated on the shape and amount of carbon species (Patent Documents 5, 6, and 7).
Japanese Patent Laid-Open No. 4-188560 JP 2002-42806 A JP 2004-47404 A JP 2003-77476 A JP 60-65462 A Japanese Patent Laid-Open No. 4-190561 JP-A-4-215252 “Electrochemistry”, 2003, Vol. 71, No. 12, p. 1105-1107 Edited by Satoshi Kanamura, “21st Century Lithium Secondary Battery Technology”, CMC Publishing, p. 125-128

上述のように、炭素材料の代替品として検討されている負極活物質は、導電性が乏しく、これを単独で用いた電池は充放電特性が良くない。そのため、導電剤を併用したり、活物質表面をカーボンコートしたりすることにより、導電性ネットワークが構築されている。   As described above, the negative electrode active material being studied as an alternative to the carbon material has poor conductivity, and a battery using this alone has poor charge / discharge characteristics. Therefore, a conductive network is constructed by using a conductive agent in combination or by coating the surface of the active material with carbon.

しかし、炭素材料の代替品として検討されている負極活物質は、充放電サイクル時に、リチウムとの合金化反応とリチウム脱離反応とを繰り返すため、活物質粒子が膨張および収縮する。そのため、粒子間の電子伝導ネットワークが徐々に切断され、電池の内部抵抗が上昇し、満足できるサイクル特性を実現できない。   However, since the negative electrode active material considered as a substitute for the carbon material repeats an alloying reaction with lithium and a lithium desorption reaction during a charge / discharge cycle, the active material particles expand and contract. For this reason, the electron conduction network between the particles is gradually cut, the internal resistance of the battery is increased, and satisfactory cycle characteristics cannot be realized.

活物質にＣｒ、Ｂ、Ｐ等の元素を添加したり、活物質とカーボンナノファイバとをボールミルで混合したりしても、結局は活物質粒子間の電子伝導ネットワークは徐々に切断されるため、十分満足できるサイクル特性は得られない。   Even if elements such as Cr, B, and P are added to the active material, or the active material and the carbon nanofiber are mixed by a ball mill, the electron conduction network between the active material particles is gradually cut after all. Therefore, a sufficiently satisfactory cycle characteristic cannot be obtained.

正極活物質も導電性が乏しいため、導電剤として様々なカーボン種を併用することが提案されているが、正極活物質は、充放電サイクル時に、リチウムの挿入反応と脱離反応とを繰り返すため、同じく活物質粒子が膨張および収縮する。そのため、粒子間の電子伝導ネットワークが徐々に切断され、優れた高出力放電特性やサイクル特性を実現することは困難である。さらに、導電剤と正極活物質とでは密度差が非常に大きいため、正極活物質と導電剤とを均一に混合、分散させることは極めて難しい。   Since the positive electrode active material also has poor conductivity, it has been proposed to use various carbon species as a conductive agent. However, the positive electrode active material repeats lithium insertion and desorption reactions during charge and discharge cycles. Similarly, the active material particles expand and contract. Therefore, the electron conduction network between the particles is gradually cut, and it is difficult to realize excellent high-output discharge characteristics and cycle characteristics. Furthermore, since the density difference between the conductive agent and the positive electrode active material is very large, it is extremely difficult to uniformly mix and disperse the positive electrode active material and the conductive agent.

本発明は、活物質粒子、活物質粒子の表面に結合したカーボンナノファイバ、および、カーボンナノファイバの成長を促進する触媒元素を含み、活物質粒子が、電気化学的活性相からなる、電極用複合粒子に関する。   The present invention includes an active material particle, a carbon nanofiber bonded to the surface of the active material particle, and a catalytic element that promotes the growth of the carbon nanofiber, and the active material particle includes an electrochemically active phase. It relates to composite particles.

本発明の電極用複合粒子は、カーボンナノファイバの成長を促進する触媒元素が存在する活物質粒子の表面に、カーボンナノファイバを成長させることにより得ることができる。 The composite particle for an electrode of the present invention can be obtained by growing a carbon nanofiber on the surface of an active material particle on which a catalytic element that promotes the growth of the carbon nanofiber is present.

電極用複合粒子は、活物質粒子と、カーボンナノファイバと、触媒元素のみからなるものでもよく、電極用複合粒子の機能を損なわない範囲で、他の要素を含んでもよい。他の要素としては、例えば導電性ポリマー等が挙げられる。   The electrode composite particles may be composed only of active material particles, carbon nanofibers, and catalytic elements, and may contain other elements as long as the function of the electrode composite particles is not impaired. Examples of other elements include conductive polymers.

触媒元素は、Ａｕ、Ａｇ、Ｐｔ、Ｒｕ、Ｉｒ、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種であることが好ましい。
触媒元素は、粒径１ｎｍ〜１０００ｎｍの金属粒子または／および金属酸化物粒子（触媒粒子）の状態で存在することが好ましい。すなわち、触媒粒子は、金属粒子の状態でもよく、金属酸化物粒子の状態でもよい。また、触媒粒子は、金属と金属酸化物を含む粒子でもよい。２種以上の触媒粒子を組み合わせて用いてもよい。触媒粒子の粒径は、ＳＥＭ観察、ＴＥＭ観察等で測定することができる。 The catalyst element is preferably at least one selected from the group consisting of Au, Ag, Pt, Ru, Ir, Cu, Fe, Co, Ni, Mo, and Mn.
The catalyst element is preferably present in the form of metal particles and / or metal oxide particles (catalyst particles) having a particle diameter of 1 nm to 1000 nm. That is, the catalyst particles may be in the form of metal particles or metal oxide particles. The catalyst particles may be particles containing a metal and a metal oxide. Two or more kinds of catalyst particles may be used in combination. The particle size of the catalyst particles can be measured by SEM observation, TEM observation, or the like.

触媒粒子は、活物質粒子の表層部および／またはカーボンナノファイバの自由端に存在する。すなわち、本発明は、触媒元素が、少なくとも活物質粒子の表層部に存在する場合と、カーボンナノファイバの成長末端に担持されている場合とを含む。なお、後者の場合において、触媒元素が、さらに活物質粒子の表層部にも存在していてもよい。なお、触媒元素は、更に、活物質粒子の内部にも存在してもよい。   The catalyst particles are present on the surface layer of the active material particles and / or the free ends of the carbon nanofibers. That is, the present invention includes a case where the catalytic element is present at least in the surface layer portion of the active material particles and a case where the catalytic element is supported on the growth end of the carbon nanofiber. In the latter case, the catalyst element may be further present in the surface layer portion of the active material particles. Note that the catalyst element may also be present inside the active material particles.

カーボンナノファイバの少なくとも一端は、樹脂成分を介さずに活物質粒子の表面に結合している。具体的には、カーボンナノファイバは、その成長の開始点となる活物質粒子の表面において、活物質粒子と結合している。また、カーボンナノファイバは、少なくともその成長の開始点となる一端において、活物質粒子の表面と化学結合している。カーボンナノファイバの成長末端は、通常自由端である。ただし、カーボンナノファイバの両端が活物質粒子の表面と結合していてもよい。   At least one end of the carbon nanofiber is bonded to the surface of the active material particle without a resin component. Specifically, the carbon nanofiber is bonded to the active material particle on the surface of the active material particle that is the starting point of the growth. Further, the carbon nanofiber is chemically bonded to the surface of the active material particle at least at one end which is the starting point of the growth. The growth end of the carbon nanofiber is usually a free end. However, both ends of the carbon nanofiber may be bonded to the surface of the active material particles.

カーボンナノファイバが成長しても、触媒元素が活物質粒子から脱離しない場合、触媒元素は、カーボンナノファイバの固定端に存在する。すなわち、触媒元素は、カーボンナノファイバと活物質粒子との結合部に存在する。この場合、触媒元素が活物質粒子に担持された状態の電極用複合粒子が得られる。   Even if the carbon nanofiber grows, if the catalytic element does not desorb from the active material particles, the catalytic element is present at the fixed end of the carbon nanofiber. That is, the catalytic element is present at the joint between the carbon nanofibers and the active material particles. In this case, composite particles for electrodes in a state where the catalytic element is supported on the active material particles are obtained.

カーボンナノファイバの成長に伴い、触媒元素が活物質粒子から脱離する場合、触媒元素は、カーボンナノファイバの先端、すなわち自由端に存在する。この場合、カーボンナノファイバの一端が活物質粒子の表面に結合し、他端が触媒元素を担持した状態の電極用複合粒子が得られる。   When the catalytic element is detached from the active material particles as the carbon nanofiber grows, the catalytic element is present at the tip of the carbon nanofiber, that is, the free end. In this case, composite particles for an electrode are obtained in which one end of the carbon nanofiber is bonded to the surface of the active material particle and the other end carries a catalytic element.

電極用複合粒子中には、触媒元素を固定端に有するカーボンナノファイバと、触媒元素を自由端に有するカーボンナノファイバとが、混在していてもよい。また、一つの活物質粒子に、触媒元素を固定端に有するカーボンナノファイバと、触媒元素を自由端に有するカーボンナノファイバとが、それぞれ結合していてもよい。   In the electrode composite particles, carbon nanofibers having a catalyst element at a fixed end and carbon nanofibers having a catalyst element at a free end may be mixed. Moreover, the carbon nanofiber which has a catalyst element in the fixed end, and the carbon nanofiber which has a catalyst element in the free end may each couple | bonded with one active material particle.

カーボンナノファイバの成長が終了するまでの間、触媒元素は良好な触媒作用を発揮することが望まれる。そのためには、触媒元素が、活物質粒子の表層部もしくはカーボンナノファイバの自由端において、金属状態で存在することが望ましい。触媒元素は、例えば粒径１ｎｍ〜１０００ｎｍの金属粒子の状態で存在することが望まれる。一方、カーボンナノファイバの成長終了後においては、触媒元素からなる金属粒子を酸化することが望ましい。   It is desired that the catalytic element exhibits good catalytic action until the growth of the carbon nanofibers is completed. For this purpose, it is desirable that the catalytic element exists in a metallic state at the surface layer portion of the active material particles or at the free end of the carbon nanofiber. The catalyst element is desirably present in a state of metal particles having a particle diameter of 1 nm to 1000 nm, for example. On the other hand, after the growth of the carbon nanofiber is completed, it is desirable to oxidize the metal particles made of the catalytic element.

カーボンナノファイバの繊維長は、例えば、１ｎｍ〜１ｍｍである。また、カーボンナノファイバは、複合粒子の電子伝導性を向上させる観点から、繊維径１ｎｍ〜４０ｎｍの微細なファイバを含むことが好ましく、繊維径１ｎｍ〜４０ｎｍの微細なファイバと繊維径４０〜２００ｎｍの大きなファイバとを同時に含むことがより好ましい。繊維長および繊維径は、ＳＥＭ観察、ＴＥＭ観察等で測定することができる。   The fiber length of the carbon nanofiber is, for example, 1 nm to 1 mm. Moreover, it is preferable that a carbon nanofiber contains a fine fiber with a fiber diameter of 1 nm to 40 nm and a fine fiber with a fiber diameter of 1 nm to 40 nm and a fiber diameter of 40 to 200 nm from the viewpoint of improving the electronic conductivity of the composite particles. More preferably, a large fiber is included at the same time. The fiber length and fiber diameter can be measured by SEM observation, TEM observation, or the like.

カーボンナノファイバは、チューブ状カーボン、アコーディオン状カーボン、プレート状カーボンおよびヘーリング・ボーン状カーボンよりなる群から選択される少なくとも１種を含むことが好ましい。カーボンナノファイバは、前記群から選ばれる少なくとも１種のみからなるものでもよく、他の状態のカーボンナノファイバを含んでもよい。   The carbon nanofibers preferably include at least one selected from the group consisting of tubular carbon, accordion carbon, plate carbon, and herringbone carbon. The carbon nanofiber may be composed of at least one selected from the above group, and may include carbon nanofibers in other states.

本発明の電極用複合粒子は、以下のカテゴリーＡ〜Ｃに分別できる。
［Ａ］カテゴリーＡの電極用複合粒子の電気化学的活性相は、例えば、周期律表３Ｂ、４Ｂおよび５Ｂ族元素よりなる群から選択される少なくとも１種の金属もしくは半金属元素の化合物もしくは合金もしくは単体を含む。
ここで、化合物は、酸化物、窒化物、酸窒化物、炭化物および硫化物よりなる群から選択される少なくとも１種であることが望ましい。電気化学的活性相が、少なくとも酸化物を含む場合、その酸化物は、アモルファスであることが望ましい。また、前記合金は、複合粒子の電子伝導性を向上させる観点から、半金属元素と遷移金属元素との合金であることが望ましい。 The composite particles for an electrode of the present invention can be classified into the following categories A to C.
[A] The electrochemically active phase of the composite particles for electrodes of category A is, for example, a compound or alloy of at least one metal or metalloid element selected from the group consisting of elements of the periodic tables 3B, 4B and 5B Or a simple substance is included.
Here, the compound is desirably at least one selected from the group consisting of oxides, nitrides, oxynitrides, carbides and sulfides. When the electrochemically active phase includes at least an oxide, the oxide is desirably amorphous. The alloy is preferably an alloy of a metalloid element and a transition metal element from the viewpoint of improving the electronic conductivity of the composite particles.

周期律表３Ｂ、４Ｂおよび５Ｂ族の金属もしくは半金属元素としては、Ａｌ、Ｓｉ、Ｇａ、Ｇｅ、Ｉｒ、Ｓｎ、Ｓｂ、Ｔｌ、Ｐｂ、Ｂｉなどが挙げられるが、高エネルギー密度の材料を得る観点から、Ｓｉ、Ｓｎ、Ｇｅなどが好ましい。金属もしくは半金属元素が、Ｓｉ、ＳｎおよびＧｅよりなる群から選択される少なくとも１種である場合、化合物は、酸化物、窒化物および酸窒化物よりなる群から選択される少なくとも１種であることが好ましい。例えば、酸化物としては、ＳｎＯ、ＳｎＯ2、ＧｅＯ、ＧｅＯ2、ＰｂＯ、ＳｂＯ2などが挙げられる。 Examples of the metals or metalloid elements of Group 3B, 4B and 5B of the periodic table include Al, Si, Ga, Ge, Ir, Sn, Sb, Tl, Pb, Bi, and the like, and a material having a high energy density is obtained. From the viewpoint, Si, Sn, Ge and the like are preferable. When the metal or metalloid element is at least one selected from the group consisting of Si, Sn and Ge, the compound is at least one selected from the group consisting of oxide, nitride and oxynitride It is preferable. For example, examples of the oxide include SnO, SnO 2 , GeO, GeO 2 , PbO, and SbO 2 .

なお、半金属元素の単体よりも、半金属元素を含む化合物（酸化物、窒化物、酸窒化物、炭化物、硫化物など）を用いる方が好ましい。その理由は以下のとおりである。   Note that it is preferable to use a compound (oxide, nitride, oxynitride, carbide, sulfide, or the like) containing a metalloid element rather than a single metalloid element. The reason is as follows.

例えば半金属元素であるＳｉは、リチウムを吸蔵する能力を有することから、高容量の活物質として有望視されている。しかし、ケイ素単体がリチウムを電気化学的に吸蔵し、放出する反応は、非常に複雑な結晶変化を伴う。反応の進行に伴い、Ｓｉの組成と結晶構造は、Ｓｉ（結晶構造：Ｆｄ３ｍ）、ＬｉＳｉ（結晶構造：Ｉ４１／ａ）、Ｌｉ2Ｓｉ（結晶構造：Ｃ２／ｍ）、Ｌｉ7Ｓｉ2（Ｐｂａｍ）、Ｌｉ22Ｓｉ5（Ｆ２３）の間を変化する。また、複雑な結晶構造の変化に伴って、Ｓｉの体積は約４倍に膨張する。よって、充放電サイクルを繰り返すにつれて、活物質粒子の破壊が進行する。また、リチウムとケイ素との結合が形成されることにより、ケイ素が初期に有していたリチウムの挿入サイトが損なわれ、サイクル寿命が著しく低下する。 For example, Si, which is a metalloid element, is promising as a high-capacity active material because it has the ability to occlude lithium. However, the reaction in which silicon alone occludes and releases lithium electrochemically involves a very complicated crystal change. As the reaction proceeds, the composition and crystal structure of Si are Si (crystal structure: Fd3m), LiSi (crystal structure: I41 / a), Li 2 Si (crystal structure: C2 / m), Li 7 Si 2 (Pbam). ), Li 22 Si 5 (F23). In addition, the volume of Si expands about four times as the complex crystal structure changes. Therefore, destruction of the active material particles proceeds as the charge / discharge cycle is repeated. In addition, the formation of a bond between lithium and silicon impairs the lithium insertion site that silicon originally had, thereby significantly reducing the cycle life.

上記のような問題に対し、微結晶ケイ素もしくはアモルファスケイ素を用いることも提案されている。しかし、膨張による活物質粒子の破壊をある程度抑制する効果しか得られない。そのため、ケイ素とリチウムとの結合が原因となるリチウム挿入サイトの破壊は抑制することができない。   In order to solve the above problems, it has been proposed to use microcrystalline silicon or amorphous silicon. However, only an effect of suppressing the destruction of the active material particles due to expansion to some extent can be obtained. Therefore, destruction of the lithium insertion site caused by the bond between silicon and lithium cannot be suppressed.

一方、Ｓｉ化合物である酸化ケイ素の場合、ケイ素原子は酸素原子と共有結合している。よって、Ｓｉがリチウムと結合するためには、ケイ素原子と酸素原子との共有結合を切断する必要がある。そのため、リチウムが挿入されても、酸化ケイ素骨格の破壊は抑制される傾向がある。すなわち、酸化ケイ素とＬｉとの反応は、酸化ケイ素骨格を維持しながら進行すると考えられる。他の半金属元素の化合物についても、同様の効果を期待することができる。   On the other hand, in the case of silicon oxide which is a Si compound, a silicon atom is covalently bonded to an oxygen atom. Therefore, in order for Si to bond to lithium, it is necessary to break the covalent bond between the silicon atom and the oxygen atom. Therefore, even if lithium is inserted, the destruction of the silicon oxide skeleton tends to be suppressed. That is, it is considered that the reaction between silicon oxide and Li proceeds while maintaining the silicon oxide skeleton. Similar effects can be expected for compounds of other metalloid elements.

特に、酸化物、窒化物および硫化物の場合、活物質粒子の表面に、確実に、触媒元素を固定化できる点でも有利である。これは、活物質粒子表面に存在する酸素、窒素もしくはイオウ原子が、触媒元素と結合するためと考えられる。また、活物質粒子表面の酸素、窒素もしくはイオウ原子の電子吸引効果により、触媒元素の金属への還元性が向上し、緩やかな還元条件でも高い触媒活性を得ることができると考えられる。   In particular, in the case of oxides, nitrides, and sulfides, it is advantageous in that the catalyst element can be reliably fixed on the surface of the active material particles. This is presumably because oxygen, nitrogen or sulfur atoms present on the surface of the active material particles are combined with the catalytic element. In addition, it is considered that due to the electron withdrawing effect of oxygen, nitrogen, or sulfur atoms on the surface of the active material particles, the reducibility of the catalytic element to metal is improved, and high catalytic activity can be obtained even under mild reducing conditions.

酸化物以外の電気化学的活性相を用いる場合にも、活物質粒子の表面に、酸化物層を形成することが好ましい。すなわち、活物質粒子として、周期律表３Ｂ、４Ｂおよび５Ｂ族元素よりなる群から選択される少なくとも１種の金属もしくは半金属元素の単体からなる核と、その核の表面を被覆する酸化物層とを有する粒子を用いることもできる。例えば、ケイ素単体からなる核とその核の表面を被覆する酸化ケイ素（ＳｉＯやＳｉＯ2）層を有する活物質粒子を好ましく用いることができる。活物質粒子の破壊を抑制する効果を得る観点からは、酸化物層の厚さは５〜２０ｎｍであることが望ましい。例えば酸化ケイ素を大気中で０．５時間以上焼成することにより、好適な厚さの酸化物層を形成することができる。 Even when an electrochemically active phase other than an oxide is used, it is preferable to form an oxide layer on the surface of the active material particles. That is, as active material particles, a nucleus composed of a simple substance of at least one metal or metalloid element selected from the group consisting of Group 3B, 4B and 5B group elements, and an oxide layer covering the surface of the nucleus It is also possible to use particles having For example, active material particles having a nucleus made of silicon alone and a silicon oxide (SiO or SiO 2 ) layer covering the surface of the nucleus can be preferably used. From the viewpoint of obtaining the effect of suppressing the destruction of the active material particles, the thickness of the oxide layer is desirably 5 to 20 nm. For example, an oxide layer having a suitable thickness can be formed by baking silicon oxide in the atmosphere for 0.5 hour or more.

［Ｂ］カテゴリーＢの電極用複合粒子の電気化学的活性相は、例えば、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素を含む。このような電気化学的活性相として、例えば、層状構造（例えばＲ３ｍ）を有するリチウム含有遷移金属酸化物が挙げられる。リチウム含有遷移金属酸化物において、酸素は、立方最密充填の配列を有することが好ましい。リチウム含有遷移金属酸化物としては、例えばＬｉＣｏＯ2、ＬｉＮｉＯ2などのように、ＬｉxＭ1-yＬyＯ2（ただし、０＜ｘ≦１．２、０≦ｙ≦１、元素Ｍは、ＣｏおよびＮｉよりなる群から選択される少なくとも１種、元素Ｌは、Ａｌ、Ｍｎ、Ｍｇ、Ｔｉ、Ｃｒ、Ｆｅ、Ｎｂ、Ｍｏ、Ｔａ、ＺｒおよびＳｒよりなる群から選択される少なくとも１種）で表されるものを挙げることができる。また、ＬｉＦｅＰＯ4、ＬｉＣｏＰＯ4などのオリビン化合物を用いることもできる。 [B] The electrochemically active phase of the composite particles for electrodes of category B includes, for example, at least one metal element selected from the group consisting of Cu, Fe, Co, Ni, Mo, and Mn. Examples of such an electrochemically active phase include a lithium-containing transition metal oxide having a layered structure (for example, R3m). In the lithium-containing transition metal oxide, oxygen preferably has a cubic close packed arrangement. Examples of the lithium-containing transition metal oxide include Li x M 1-y L y O 2 (where Li <0 ≦ x ≦ 1.2, 0 ≦ y ≦ 1, element M is LiCoO 2 , LiNiO 2, etc.) , At least one selected from the group consisting of Co and Ni, and the element L is at least one selected from the group consisting of Al, Mn, Mg, Ti, Cr, Fe, Nb, Mo, Ta, Zr and Sr ) Can be mentioned. Also, olivine compounds such as LiFePO 4 and LiCoPO 4 can be used.

［Ｃ］カテゴリーＢの電極用複合粒子の電気化学的活性相は、例えば、ＲｕＯ2、ＭｏＯ2、Ａｌ2Ｏ3などが挙げられる。 [C] Examples of the electrochemically active phase of category B electrode composite particles include RuO 2 , MoO 2 , and Al 2 O 3 .

カテゴリーＡの電極用複合粒子は、非水電解質二次電池の負極材料として好適である。カテゴリーＢの電極用複合粒子は、非水電解質二次電池の正極材料として好適である。カテゴリーＣの電極用複合粒子は、電気化学キャパシタの電極材料として好適である。   Category A composite particles for electrodes are suitable as negative electrode materials for non-aqueous electrolyte secondary batteries. Category B electrode composite particles are suitable as positive electrode materials for non-aqueous electrolyte secondary batteries. The composite particles for category C electrodes are suitable as electrode materials for electrochemical capacitors.

本発明は、また、電気化学的活性相からなり、少なくとも表層部に、カーボンナノファイバの成長を促進する触媒元素を有する活物質粒子を調製する工程Ａ、炭素含有ガスを含む雰囲気中で、活物質粒子の表面にカーボンナノファイバを成長させる工程Ｂ、および、不活性ガス雰囲気中で、カーボンナノファイバが結合した活物質粒子を４００℃以上、１６００℃以下で焼成する工程Ｃを含む電極用複合粒子の製造法に関する。   The present invention also includes a step A of preparing active material particles comprising a catalytic element that consists of an electrochemically active phase and promotes the growth of carbon nanofibers at least in the surface layer portion, in an atmosphere containing a carbon-containing gas. A composite for an electrode comprising a step B of growing carbon nanofibers on the surface of material particles and a step C of firing active material particles bonded with carbon nanofibers in an inert gas atmosphere at 400 ° C. or higher and 1600 ° C. or lower. The present invention relates to a method for producing particles.

工程Ａは、例えば、電気化学的活性相からなる粒子の表面に、Ａｕ、Ａｇ、Ｐｔ、Ｒｕ、Ｉｒ、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素からなる粒子（触媒粒子）を担持する工程を有する。   The step A includes, for example, at least one selected from the group consisting of Au, Ag, Pt, Ru, Ir, Cu, Fe, Co, Ni, Mo, and Mn on the surface of the particle composed of the electrochemically active phase. A step of supporting particles (catalyst particles) made of a metal element.

工程Ａは、例えば、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素を含む電気化学的活性相からなる粒子の表面を還元する工程を有する。   Step A includes, for example, a step of reducing the surface of particles made of an electrochemically active phase containing at least one metal element selected from the group consisting of Cu, Fe, Co, Ni, Mo, and Mn.

工程Ａは、例えば、周期律表３Ｂ、４Ｂおよび５Ｂ族元素よりなる群から選ばれる少なくとも１種の金属もしくは半金属元素と、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素との合金粒子を合成する工程を有する。   Step A is, for example, selected from the group consisting of at least one metal or metalloid element selected from the group consisting of Group 3B, 4B and 5B group elements and Cu, Fe, Co, Ni, Mo and Mn. And synthesizing alloy particles with at least one metal element.

本発明の製造法は、工程Ｃの後、さらに、大気中で、複合粒子を１００℃以上、４００℃以下で熱処理する工程を有することが望ましい。この工程により、触媒元素を酸化することができる。１００℃以上、４００℃以下の熱処理であれば、カーボンナノファイバを酸化させずに金属元素だけを酸化することが可能である。   The production method of the present invention desirably has a step of heat-treating the composite particles at 100 ° C. or higher and 400 ° C. or lower after step C in the atmosphere. By this step, the catalytic element can be oxidized. If the heat treatment is performed at 100 ° C. or more and 400 ° C. or less, it is possible to oxidize only the metal element without oxidizing the carbon nanofibers.

本発明の製造法は、例えば、触媒元素がＮｉであり、炭素含有ガスが、エチレンであり、カーボンナノファイバが、へーリング・ボーン状である場合が特に好ましい。これは、へーリングボーン状カーボンは、低結晶性の炭素からなるため、柔軟性が高く、充放電に伴う活物質の膨張および収縮を緩和し易いためである。   In the production method of the present invention, for example, the case where the catalytic element is Ni, the carbon-containing gas is ethylene, and the carbon nanofiber is in a herringbone shape is particularly preferable. This is because herringbone-like carbon is made of low crystalline carbon and thus has high flexibility and easily relaxes expansion and contraction of the active material that accompanies charge and discharge.

本発明は、更に、リチウムの充放電が可能な正極、カテゴリーＡに含まれる複合粒子を含む負極、および非水電解質を含む、非水電解質二次電池に関する。   The present invention further relates to a non-aqueous electrolyte secondary battery including a positive electrode capable of charging and discharging lithium, a negative electrode including composite particles included in category A, and a non-aqueous electrolyte.

本発明は、更に、カテゴリーＢに含まれる正極、リチウムの充放電が可能な負極、および非水電解質を含む、非水電解質二次電池に関する。   The present invention further relates to a non-aqueous electrolyte secondary battery including a positive electrode included in category B, a negative electrode capable of charging and discharging lithium, and a non-aqueous electrolyte.

本発明は、更に、カテゴリーＢに含まれる正極、カテゴリーＡに含まれる負極、および非水電解質を含む、非水電解質二次電池に関する。   The present invention further relates to a non-aqueous electrolyte secondary battery including a positive electrode included in category B, a negative electrode included in category A, and a non-aqueous electrolyte.

本発明は、更に、カテゴリーＣに含まれる電極、および、電解質を含む、電気化学キャパシタに関する。   The present invention further relates to an electrochemical capacitor comprising an electrode included in category C and an electrolyte.

本発明の電極用複合粒子においては、カーボンナノファイバが活物質粒子の表面に結合している。よって、これを含む電極は電子伝導性が高く、優れた初期充放電特性を有する電池が得られる。また、活物質粒子が膨張と収縮を繰り返しても、カーボンナノファイバと活物質粒子との接触は常に維持される。よって、本発明の電極用複合粒子を用いれば、充放電サイクル特性に優れた電池が得られる。   In the composite particle for an electrode of the present invention, the carbon nanofiber is bonded to the surface of the active material particle. Therefore, an electrode including this has high electron conductivity, and a battery having excellent initial charge / discharge characteristics can be obtained. Moreover, even if the active material particles repeat expansion and contraction, the contact between the carbon nanofibers and the active material particles is always maintained. Therefore, if the composite particle for an electrode of the present invention is used, a battery having excellent charge / discharge cycle characteristics can be obtained.

また、カーボンナノファイバは、活物質粒子の膨張および収縮に伴う応力を吸収するバッファ層の役割を果たす。よって、正極と負極とをセパレータを介して捲回して構成された電極群において、挫屈が抑制される。挫屈に伴う集電体の亀裂も抑制される。   Carbon nanofibers also serve as a buffer layer that absorbs stress associated with expansion and contraction of the active material particles. Therefore, buckling is suppressed in the electrode group configured by winding the positive electrode and the negative electrode through the separator. Current collector cracks due to buckling are also suppressed.

気相反応で得られるカーボンナノファイバのなかには、電気化学的にリチウムの挿入と脱離を行うことが可能なものも存在すると考えられる。   It is considered that some carbon nanofibers obtained by gas phase reaction can electrochemically insert and desorb lithium.

本発明の電極用複合粒子は、活物質粒子、活物質粒子の表面に結合したカーボンナノファイバ、および、カーボンナノファイバの成長を促進する触媒元素を含む。
活物質粒子は、電気化学的活性相からなる。活物質粒子は、複数の粒子からなる造粒体であるよりも、単一の粒子からなる方が好ましい。単一の粒子は、充放電時に活物質の膨張および収縮に伴う崩壊を起こしにくい。できるだけ粒子の割れを抑制する観点から、単一の粒子からなる活物質粒子の平均粒径は、１〜２０μｍであることが好ましい。複数の粒子からなる造粒体は、上記範囲よりも粒径が大きくなるため、充放電時に膨張および収縮のストレスを受けて、崩壊する場合がある。 The composite particle for an electrode of the present invention includes active material particles, carbon nanofibers bonded to the surface of the active material particles, and a catalytic element that promotes the growth of the carbon nanofibers.
The active material particles are composed of an electrochemically active phase. The active material particles are preferably composed of a single particle rather than a granulated body composed of a plurality of particles. Single particles are unlikely to collapse due to expansion and contraction of the active material during charge and discharge. From the viewpoint of suppressing the cracking of the particles as much as possible, the average particle diameter of the active material particles made of a single particle is preferably 1 to 20 μm. Since a granulated body composed of a plurality of particles has a particle size larger than the above range, it may collapse due to expansion and contraction stress during charge and discharge.

触媒元素としては、特に限定されないが、Ａｕ、Ａｇ、Ｐｔ、Ｒｕ、Ｉｒ、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種を好ましく用いることができる。触媒元素が活物質粒子の最表面に存在する場合、触媒元素は、金属状態もしくは酸化物の状態であることが好ましい。   The catalyst element is not particularly limited, but at least one selected from the group consisting of Au, Ag, Pt, Ru, Ir, Cu, Fe, Co, Ni, Mo, and Mn can be preferably used. When the catalytic element is present on the outermost surface of the active material particles, the catalytic element is preferably in a metal state or an oxide state.

カーボンナノファイバの成長が終了するまでの間、触媒元素が良好な触媒作用を発揮するためには、触媒元素は金属状態で存在することが望ましい。通常、触媒元素は、粒径１ｎｍ〜１０００ｎｍの金属粒子もしくは酸化物粒子（触媒粒子）の状態で存在することが好ましく、粒径１０〜１００ｎｍの触媒粒子の状態で存在することが、更に好ましい。   Until the growth of the carbon nanofibers is completed, it is desirable that the catalytic element exists in a metallic state in order for the catalytic element to exhibit good catalytic action. Usually, the catalyst element is preferably present in the state of metal particles or oxide particles (catalyst particles) having a particle size of 1 nm to 1000 nm, and more preferably in the state of catalyst particles having a particle size of 10 to 100 nm.

触媒元素は、金属状態ではカーボンナノファイバを成長させるための活性点を与える。すなわち触媒元素が金属状態で表面に露出した活物質粒子を、カーボンナノファイバの原料ガスを含む高温雰囲気中に導入すると、カーボンナノファイバの成長が進行する。活物質粒子の表面に触媒元素が存在しない場合には、カーボンナノファイバの成長は認められない。なお、カーボンナノファイバの成長に伴い、触媒元素が活物質粒子の表層部から脱離してもよい。この場合、触媒粒子が、カーボンナノファイバの先端、すなわち自由端に担持された状態の複合粒子が得られる。   The catalytic element provides an active site for growing carbon nanofibers in the metallic state. That is, when the active material particles whose catalytic elements are exposed in a metallic state are introduced into a high-temperature atmosphere containing the carbon nanofiber source gas, the growth of the carbon nanofibers proceeds. When no catalytic element is present on the surface of the active material particles, the growth of carbon nanofibers is not recognized. As the carbon nanofiber grows, the catalyst element may be detached from the surface layer portion of the active material particles. In this case, composite particles are obtained in which the catalyst particles are supported on the tips of the carbon nanofibers, that is, the free ends.

ただし、触媒元素を活物質粒子の表層部、すなわちカーボンナノファイバの固定端に有するカーボンナノファイバと、触媒元素を自由端に有するカーボンナノファイバとが、混在していてもよい。   However, the carbon nanofiber having the catalytic element at the surface layer portion of the active material particle, that is, the fixed end of the carbon nanofiber, and the carbon nanofiber having the catalytic element at the free end may be mixed.

活物質粒子の表面にカーボンナノファイバを直接成長させた場合、活物質粒子の表面とカーボンナノファイバとの結合は、結着剤などの樹脂成分を介するものではなく、化学結合そのものである。そのため電池内では集電に対する抵抗が小さくなり、高い電子伝導性が確保される。従って、良好な初期充放電特性が期待できる。   When carbon nanofibers are directly grown on the surface of the active material particles, the bond between the surface of the active material particles and the carbon nanofiber is not a resin component such as a binder but a chemical bond itself. Therefore, resistance to current collection is reduced in the battery, and high electron conductivity is ensured. Therefore, good initial charge / discharge characteristics can be expected.

また、電池の充放電サイクルの繰り返しにより、活物質粒子の膨張と収縮が生じても、カーボンナノファイバと活物質表面との接続が維持されるため、電子伝導ネットワークが損傷を受けにくい。従って、本発明の複合粒子によれば、充放電特性、高出力放電特性、サイクル特性等に優れた電池を得ることができる。   In addition, even if the active material particles expand and contract due to repeated charge and discharge cycles of the battery, the connection between the carbon nanofibers and the active material surface is maintained, so that the electron conduction network is not easily damaged. Therefore, according to the composite particles of the present invention, a battery having excellent charge / discharge characteristics, high output discharge characteristics, cycle characteristics, and the like can be obtained.

図１は、本発明の電極用複合粒子の一例の構造を概念的に示したものである。
複合粒子１０は、活物質粒子１１、活物質粒子１１の表面に存在する触媒粒子１２、触媒粒子１２を基点として成長したカーボンナノファイバ１３を有する。このような複合粒子は、カーボンナノファイバが成長しても、触媒元素が活物質粒子から脱離しない場合に得られる。この場合、触媒粒子は、活物質粒子の表面とカーボンナノファイバとの結合部、すなわち固定端に存在する。 FIG. 1 conceptually shows the structure of an example of the composite particle for an electrode of the present invention.
The composite particle 10 includes active material particles 11, catalyst particles 12 existing on the surface of the active material particles 11, and carbon nanofibers 13 grown from the catalyst particles 12 as a base point. Such composite particles are obtained when the carbon nanofiber grows and the catalytic element does not desorb from the active material particles. In this case, the catalyst particles are present at the joint between the surface of the active material particles and the carbon nanofibers, that is, at the fixed end.

図２は、本発明の電極用複合粒子の別の一例の構造を概念的に示したものである。
複合粒子２０は、活物質粒子２１、活物質粒子２１の表面に一端が結合したカーボンナノファイバ２３、カーボンナノファイバ２３の他端に担持された触媒粒子２２を有する。このような複合粒子は、カーボンナノファイバの成長に伴い、触媒粒子が活物質粒子の表層部から脱離する場合に得られる。この場合、触媒粒子は、カーボンナノファイバの先端、すなわち自由端に存在する。 FIG. 2 conceptually shows the structure of another example of the composite particle for an electrode of the present invention.
The composite particle 20 includes an active material particle 21, a carbon nanofiber 23 having one end bonded to the surface of the active material particle 21, and a catalyst particle 22 supported on the other end of the carbon nanofiber 23. Such composite particles are obtained when the catalyst particles are detached from the surface layer portion of the active material particles as the carbon nanofiber grows. In this case, the catalyst particles are present at the tip, that is, the free end of the carbon nanofiber.

触媒粒子１２、２２は、触媒元素からなり、カーボンナノファイバを成長させるための触媒として作用する。活物質粒子１１、２１の平均粒径は、特に限定されないが、１〜２０μｍが好適である。   The catalyst particles 12 and 22 are made of a catalyst element and act as a catalyst for growing carbon nanofibers. The average particle diameter of the active material particles 11 and 21 is not particularly limited, but is preferably 1 to 20 μm.

活物質粒子の表面に触媒粒子を設ける方法は、特に限定されないが、例えば電気化学的活性相からなる粒子の表面に触媒粒子を担持させる方法（方法１）、触媒元素を含む活物質粒子の表面を還元して、活物質粒子の表面に触媒粒子を生成させる方法（方法２）などが好適である。
方法１は、電気化学的活性相からなる粒子であればどのような粒子に対しても適用できるが、方法２は、触媒元素を含む活物質粒子に対してのみ適用できる。 The method of providing the catalyst particles on the surface of the active material particles is not particularly limited. For example, the method of supporting the catalyst particles on the surface of particles composed of an electrochemically active phase (Method 1), the surface of the active material particles containing the catalyst element A method (method 2) in which the catalyst particles are reduced to generate catalyst particles on the surface of the active material particles is suitable.
Method 1 can be applied to any particles as long as they are composed of an electrochemically active phase, but method 2 can be applied only to active material particles containing a catalytic element.

電気化学的活性相からなる粒子の表面に触媒粒子を担持させる方法１の場合、固体の触媒粒子を電気化学的活性相からなる粒子と混合することも考えられるが、触媒粒子の原料である金属化合物の溶液に、電気化学的活性相からなる粒子を浸漬する方法が好適である。溶液に浸漬後の粒子から溶媒を除去し、必要に応じて加熱処理すると、表面に均一かつ高分散状態で、粒径１ｎｍ〜１０００ｎｍ、好ましくは１０〜１００ｎｍの触媒粒子を担持した活物質粒子を得ることが可能である。   In the case of Method 1 in which catalyst particles are supported on the surface of particles composed of an electrochemically active phase, it is conceivable to mix solid catalyst particles with particles composed of an electrochemically active phase. A method of immersing particles comprising an electrochemically active phase in a compound solution is preferred. When the solvent is removed from the particles after being immersed in the solution and heat treatment is performed as necessary, active material particles carrying catalyst particles having a particle diameter of 1 nm to 1000 nm, preferably 10 to 100 nm, in a uniform and highly dispersed state on the surface. It is possible to obtain.

触媒粒子の粒径を１ｎｍ未満とすることは、非常に難しい。一方、触媒粒子の粒径が１０００ｎｍを超えると、触媒粒子の大きさが極端に不均一となり、カーボンナノファイバを成長させることが困難になり、もしくは導電性に優れた電極が得られなくなることがある。   It is very difficult to make the particle size of the catalyst particles less than 1 nm. On the other hand, if the particle size of the catalyst particles exceeds 1000 nm, the size of the catalyst particles becomes extremely non-uniform, making it difficult to grow carbon nanofibers or failing to obtain an electrode with excellent conductivity. is there.

溶液を得るための金属化合物としては、硝酸ニッケル六水和物、硝酸コバルト六水和物、硝酸鉄九水和物、硝酸銅三水和物、硝酸マンガン六水和物、七モリブデン酸六アンモニウム四水和物などを挙げることができるが、これらに限定されない。   Metal compounds for obtaining the solution include nickel nitrate hexahydrate, cobalt nitrate hexahydrate, iron nitrate nonahydrate, copper nitrate trihydrate, manganese nitrate hexahydrate, hexaammonium heptamolybdate Although tetrahydrate etc. can be mentioned, it is not limited to these.

溶液の溶媒は、化合物の溶解度、電気化学的活性相との相性を考慮して選択される。例えば、水、有機溶媒および水と有機溶媒との混合物の中から好適なものが選択される。有機溶媒としては、例えばエタノール、イソプロピルアルコール、トルエン、ベンゼン、ヘキサン、テトラヒドロフランなどを用いることができる。   The solvent of the solution is selected in consideration of the solubility of the compound and the compatibility with the electrochemically active phase. For example, a suitable one is selected from water, an organic solvent, and a mixture of water and an organic solvent. As the organic solvent, for example, ethanol, isopropyl alcohol, toluene, benzene, hexane, tetrahydrofuran and the like can be used.

方法２の場合、触媒元素を含む活物質粒子、例えばＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4などのリチウム含有金属酸化物粒子を、水素ガスなどの還元力のあるガス雰囲気下で加熱することで、粒子表面にＣｏ、Ｎｉ、Ｍｎなどの金属粒子を生成させることができる。この場合にも、還元条件を制御することで、活物質粒子の表層部に粒径１ｎｍ〜１０００ｎｍ、好ましくは１０ｎｍ〜１００ｎｍの触媒粒子を生成させることができる。 In the case of Method 2, active material particles containing a catalytic element, for example, lithium-containing metal oxide particles such as LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 are heated in a reducing gas atmosphere such as hydrogen gas. Then, metal particles such as Co, Ni, and Mn can be generated on the particle surface. Also in this case, by controlling the reducing conditions, catalyst particles having a particle diameter of 1 nm to 1000 nm, preferably 10 nm to 100 nm can be generated on the surface layer portion of the active material particles.

また、方法３として、触媒元素を含む合金粒子を合成し、これを活物質粒子として用いることもできる。この場合、例えば周期律表３Ｂ、４Ｂおよび５Ｂ族元素よりなる群から選ばれる少なくとも１種の金属もしくは半金属元素と触媒元素との合金を、通常の合金製造法により合成する。周期律表３Ｂ、４Ｂおよび５Ｂ族元素より選ばれる金属もしくは半金属元素は、電気化学的にＬｉと反応してＬｉ合金を生成するから、電気化学的活性相を形成する。一方、触媒元素からなる金属相の少なくとも一部は、例えば粒径１０ｎｍ〜１００ｎｍの粒子状で合金粒子の表面に露出する。   Further, as method 3, alloy particles containing a catalytic element can be synthesized and used as active material particles. In this case, for example, an alloy of at least one metal or metalloid element selected from the group consisting of Group 3B, 4B and 5B elements and a catalytic element is synthesized by a normal alloy manufacturing method. A metal or metalloid element selected from Group 3B, 4B and 5B group elements of the periodic table electrochemically reacts with Li to form a Li alloy, thus forming an electrochemically active phase. On the other hand, at least a part of the metal phase composed of the catalytic element is exposed on the surface of the alloy particles in the form of particles having a particle diameter of 10 nm to 100 nm, for example.

触媒粒子もしくは触媒元素からなる金属相は、活物質粒子の０．０１重量％〜１０重量％であることが望ましく、１重量％〜３重量％であることがさらに望ましい。触媒粒子もしくは触媒元素からなる金属相の量が少なすぎると、カーボンナノファイバを成長させるのに長時間を要し、生産効率が低下する場合がある。触媒粒子もしくは触媒元素からなる金属相の量が多すぎると、触媒元素の凝集により、不均一で太い繊維径のカーボンナノファイバが成長するため、電極の導電性や活物質密度の低下に繋がる。また、電気化学的活性相の割合が相対的に少なくなり、複合粒子を高容量の電極材料とすることが困難となる場合がある。   The metal phase composed of catalyst particles or catalyst elements is preferably 0.01% by weight to 10% by weight of the active material particles, and more preferably 1% by weight to 3% by weight. If the amount of the metal phase composed of catalyst particles or catalyst elements is too small, it takes a long time to grow carbon nanofibers, which may reduce the production efficiency. When the amount of the catalyst phase or the metal phase composed of the catalyst element is too large, carbon nanofibers having non-uniform and large fiber diameters grow due to aggregation of the catalyst elements, leading to a decrease in the conductivity and active material density of the electrode. In addition, the proportion of the electrochemically active phase may be relatively reduced, and it may be difficult to make the composite particles into a high-capacity electrode material.

カーボンナノファイバの繊維長は１ｎｍ〜１ｍｍが好ましく、５００ｎｍ〜５００μｍがさらに好ましい。カーボンナノファイバの繊維長が１ｎｍ未満では、電極の導電性を高める効果が小さくなる。一方、繊維長が１ｍｍを超えると、電極の活物質密度や容量が小さくなる傾向がある。また、カーボンナノファイバの繊維径は１ｎｍ〜１０００ｎｍが好ましく、５０ｎｍ〜３００ｎｍが更に好ましい。   The fiber length of the carbon nanofiber is preferably 1 nm to 1 mm, and more preferably 500 nm to 500 μm. When the fiber length of the carbon nanofiber is less than 1 nm, the effect of increasing the conductivity of the electrode is reduced. On the other hand, when the fiber length exceeds 1 mm, the active material density and capacity of the electrode tend to decrease. The fiber diameter of the carbon nanofiber is preferably 1 nm to 1000 nm, and more preferably 50 nm to 300 nm.

カーボンナノファイバの一部は、複合粒子の電子伝導性を向上させる観点から、繊維径１ｎｍ〜４０ｎｍの微細なファイバであることが好ましい。例えば、繊維径４０ｎｍ以下の微細なファイバと、繊維径５０ｎｍ以上の大きなファイバとを同時に含むことが好ましく、繊維径３０ｎｍ以下の微細なファイバと、繊維径８０ｎｍ以上の大きなファイバとを同時に含むことが更に好ましい。   Part of the carbon nanofibers is preferably a fine fiber having a fiber diameter of 1 nm to 40 nm from the viewpoint of improving the electronic conductivity of the composite particles. For example, it is preferable to include a fine fiber having a fiber diameter of 40 nm or less and a large fiber having a fiber diameter of 50 nm or more at the same time, and to simultaneously include a fine fiber having a fiber diameter of 30 nm or less and a large fiber having a fiber diameter of 80 nm or more. Further preferred.

活物質粒子の表面に成長させるカーボンナノファイバの量は、活物質粒子１００重量部あたり、５重量部〜１５０重量部であることが望ましく、１０〜１００重量部であることが更に好ましい。カーボンナノファイバの量が少なすぎると、電極の導電性を高めたり、電池の充放電特性やサイクル特性を高めたりする効果が十分に得られないことがある。カーボンナノファイバの量が多くても、電極の導電性、電池の充放電特性やサイクル特性の観点からは問題ないが、電極の活物質密度や容量が小さくなる。   The amount of carbon nanofibers grown on the surface of the active material particles is preferably 5 to 150 parts by weight, more preferably 10 to 100 parts by weight, per 100 parts by weight of the active material particles. If the amount of the carbon nanofiber is too small, the effect of increasing the conductivity of the electrode or improving the charge / discharge characteristics and cycle characteristics of the battery may not be sufficiently obtained. Even if the amount of carbon nanofibers is large, there is no problem from the viewpoint of electrode conductivity, battery charge / discharge characteristics, and cycle characteristics, but the active material density and capacity of the electrodes are reduced.

次に、活物質粒子の表面にカーボンナノファイバを成長させる際の条件について説明する。
少なくとも表層部に触媒元素を有する活物質粒子を、カーボンナノファイバの原料ガスを含む高温雰囲気中に導入すると、カーボンナノファイバの成長が進行する。例えばセラミック製反応容器に、活物質粒子を投入し、不活性ガスもしくは還元力を有するガス中で１００〜１０００℃、好ましくは３００〜６００℃の高温になるまで昇温させ、その後、カーボンナノファイバの原料ガスを反応容器に導入する。反応容器内の温度が１００℃未満では、カーボンナノファイバの成長が起こらないか、成長が遅すぎて、生産性が損なわれる。また、反応容器内の温度が１０００℃を超えると、反応ガスの分解が促進され、カーボンナノファイバが生成し難くなる。 Next, conditions for growing carbon nanofibers on the surface of the active material particles will be described.
When active material particles having a catalytic element at least in the surface layer portion are introduced into a high-temperature atmosphere containing a raw material gas for carbon nanofibers, the growth of carbon nanofibers proceeds. For example, active material particles are put into a ceramic reaction vessel and heated to 100 to 1000 ° C., preferably 300 to 600 ° C. in an inert gas or a gas having a reducing power, and then carbon nanofibers. The raw material gas is introduced into the reaction vessel. If the temperature in the reaction vessel is lower than 100 ° C., the growth of carbon nanofiber does not occur or the growth is too slow, and the productivity is impaired. On the other hand, when the temperature in the reaction container exceeds 1000 ° C., decomposition of the reaction gas is promoted, and it becomes difficult to produce carbon nanofibers.

原料ガスとしては、炭素含有ガスと水素ガスとの混合ガスが好適である。炭素含有ガスとしては、メタン、エタン、エチレン、ブタン、一酸化炭素、アセチレンなど、炭素元素を含むガスを用いることができる。炭素含有ガスと水素ガスとの混合比は、モル比（体積比）で、２：８〜８：２が好適である。活物質粒子の表面に金属状態の触媒元素が露出していない場合には、水素ガスの割合を多めに制御することで、触媒元素の還元とカーボンナノファイバの成長とを並行して進行させることができる。   As the source gas, a mixed gas of carbon-containing gas and hydrogen gas is suitable. As the carbon-containing gas, a gas containing a carbon element such as methane, ethane, ethylene, butane, carbon monoxide, or acetylene can be used. The mixing ratio of the carbon-containing gas and the hydrogen gas is preferably 2: 8 to 8: 2 in terms of molar ratio (volume ratio). When the catalytic element in the metallic state is not exposed on the surface of the active material particles, the reduction of the catalytic element and the growth of the carbon nanofibers can proceed in parallel by controlling the hydrogen gas ratio to a large extent. Can do.

カーボンナノファイバの成長を終了させる際には、炭素含有ガスと水素ガスの混合ガスを、不活性ガスに置換し、反応容器内を室温まで冷却させる。
続いて、カーボンナノファイバが結合した活物質粒子を、不活性ガス雰囲気中で４００℃以上、１６００℃以下で、例えば３０分〜２時間かけて焼成することで、電池の初期充電時に進行する電解液とカーボンナノファイバとの不可逆反応が抑制され、優れた充放電効率を得ることができる。 When terminating the growth of the carbon nanofiber, the mixed gas of the carbon-containing gas and hydrogen gas is replaced with an inert gas, and the inside of the reaction vessel is cooled to room temperature.
Subsequently, the active material particles bonded with the carbon nanofibers are baked at 400 ° C. or higher and 1600 ° C. or lower, for example, for 30 minutes to 2 hours in an inert gas atmosphere. Irreversible reaction between the liquid and the carbon nanofiber is suppressed, and excellent charge / discharge efficiency can be obtained.

このような焼成行程を行わないか、もしくは焼成温度が４００℃未満では、上記の不可逆反応が抑制されず、電池の充放電効率が低下することがある。また、焼成温度が１６００℃を超えると、活物質粒子の電気化学的活性相とカーボンナノファイバとが反応して、活性相が不活性化したり、電気化学的活性相が還元されて、容量低下を引き起こしたりすることがある。例えば、活物質粒子の電気化学的活性相がＳｉである場合には、Ｓｉとカーボンナノファイバとが反応して、不活性な炭化ケイ素が生成してしまい、電池の充放電容量の低下を引き起こす。また、正極活物質として知られるリチウム含有酸化物は、１０００℃を超える温度では、熱還元されることがある。
例えば、リチウム含有酸化物の焼成温度は７００℃以上１０００℃以下が特に好ましく、Ｓｉの焼成温度は１０００℃以上１６００℃以下が特に好ましい。 If such a firing process is not performed or the firing temperature is less than 400 ° C., the above irreversible reaction may not be suppressed, and the charge / discharge efficiency of the battery may be reduced. Also, when the firing temperature exceeds 1600 ° C., the electrochemically active phase of the active material particles reacts with the carbon nanofibers, the active phase is inactivated, or the electrochemically active phase is reduced, resulting in a decrease in capacity. It may cause. For example, when the electrochemically active phase of the active material particles is Si, Si and carbon nanofibers react to generate inactive silicon carbide, which causes a decrease in charge / discharge capacity of the battery. . In addition, lithium-containing oxides known as positive electrode active materials may be thermally reduced at temperatures exceeding 1000 ° C.
For example, the firing temperature of the lithium-containing oxide is particularly preferably 700 ° C. or more and 1000 ° C. or less, and the firing temperature of Si is particularly preferably 1000 ° C. or more and 1600 ° C. or less.

不活性ガス中で焼成後の複合粒子は、さらに触媒元素からなる金属粒子もしくは金属相の少なくとも一部（例えば表面）を酸化するために、大気中で、１００℃以上、４００℃以下で熱処理することが好ましい。熱処理温度が１００℃未満では、金属を酸化することは困難であり、４００℃を超えると、成長させたカーボンナノファイバが燃焼してしまうことがある。   The composite particles after firing in an inert gas are further heat-treated at 100 ° C. or more and 400 ° C. or less in the atmosphere in order to oxidize at least a part (for example, the surface) of the metal particles or metal phase comprising the catalyst element. It is preferable. If the heat treatment temperature is less than 100 ° C., it is difficult to oxidize the metal, and if it exceeds 400 ° C., the grown carbon nanofibers may burn.

触媒元素からなる金属粒子もしくは金属相を酸化せずに複合粒子を電極材料として用いた場合、特にＮｉやＣｕは３Ｖ以上の酸化電位において溶解し、負極側で還元されて析出し、電池の不良を招く可能性がある。１００℃以上、４００℃以下の温度で複合粒子を熱処理することで、カーボンナノファイバを酸化させずに金属粒子や金属相だけを適度に酸化させることが可能であり、上記のような電池の不良を抑制することができる。   When composite particles are used as electrode materials without oxidizing metal particles or metal phases composed of catalytic elements, especially Ni and Cu dissolve at an oxidation potential of 3 V or more, and are reduced and deposited on the negative electrode side, resulting in defective batteries. May be incurred. By heat-treating the composite particles at a temperature of 100 ° C. or higher and 400 ° C. or lower, it is possible to appropriately oxidize only the metal particles and the metal phase without oxidizing the carbon nanofibers. Can be suppressed.

カーボンナノファイバは、成長する過程で触媒元素を自身の内部に取りこんでもよい。また、活物質粒子の表面に成長するカーボンナノファイバは、チューブ状態、アコーディオン状態、プレート状態、ヘーリング・ボーン状態のものを含むことがある。これらのうちでは、特に、非晶質状態であるヘーリング・ボーン状態のカーボンナノファイバが好ましい。ヘーリング・ボーン状態のカーボンナノファイバは、炭素の結晶性が低いため、柔軟であり、活物質粒子の膨張による応力を緩和する能力が高い。   Carbon nanofibers may incorporate catalytic elements into themselves during the process of growth. The carbon nanofibers grown on the surface of the active material particles may include those in a tube state, an accordion state, a plate state, and a herring bone state. Of these, carbon nanofibers in a herring-bone state that is in an amorphous state are particularly preferable. Since the carbon nanofibers in the herring-bone state are low in crystallinity of carbon, they are flexible and have a high ability to relieve stress due to expansion of the active material particles.

ヘーリング・ボーン状態のカーボンナノファイバを成長させる場合、例えば、触媒には、銅ニッケル合金（銅とニッケルのモル比は３：７）を用い、５５０〜６５０℃の温度で反応を行うことが望ましい。また、原料ガス中の炭素含有ガスには、エチレンガスなどを用いることが好ましい。炭素含有ガスと水素ガスとの混合比は、モル比（体積比）で、２：８〜８：２が好適である。   When growing a carbon nanofiber in a herring-bone state, for example, it is desirable to use a copper-nickel alloy (molar ratio of copper to nickel is 3: 7) as a catalyst and perform the reaction at a temperature of 550 to 650 ° C. . Moreover, it is preferable to use ethylene gas etc. for the carbon containing gas in source gas. The mixing ratio of the carbon-containing gas and the hydrogen gas is preferably 2: 8 to 8: 2 in terms of molar ratio (volume ratio).

チューブ状態のカーボンナノファイバを成長させる場合、例えば、触媒には、鉄ニッケル合金（鉄とニッケルのモル比６：４）を用い、６００〜７００℃の温度で反応を行うことが望ましい。また、原料ガス中の炭素含有ガスには、一酸化炭素などを用いることが好ましい。炭素含有ガスと水素ガスとの混合比は、モル比（体積比）で、２：８〜８：２が好適である。   When growing carbon nanofibers in a tube state, for example, it is desirable to use an iron nickel alloy (molar ratio of iron to nickel 6: 4) as a catalyst and perform the reaction at a temperature of 600 to 700 ° C. Moreover, it is preferable to use carbon monoxide etc. for the carbon containing gas in source gas. The mixing ratio of the carbon-containing gas and the hydrogen gas is preferably 2: 8 to 8: 2 in terms of molar ratio (volume ratio).

プレート状態のカーボンナノファイバを成長させる場合、例えば、触媒には、鉄を用い、５５０〜６５０℃の温度で反応を行うことが望ましい。また、原料ガス中の炭素含有ガスには、一酸化炭素などを用いることが好ましい。炭素含有ガスと水素ガスとの混合比は、モル比（体積比）で、２：８〜８：２が好適である。
なお、チューブ状態のカーボンナノファイバや、プレート状態のカーボンナノファイバは、ヘーリング・ボーン状態のカーボンナノファイバに比べ、結晶性が高いため、極板を高密度化する場合に適している。 When growing plate-like carbon nanofibers, for example, it is desirable to use iron as a catalyst and perform the reaction at a temperature of 550 to 650 ° C. Moreover, it is preferable to use carbon monoxide etc. for the carbon containing gas in source gas. The mixing ratio of the carbon-containing gas and the hydrogen gas is preferably 2: 8 to 8: 2 in terms of molar ratio (volume ratio).
In addition, since the carbon nanofiber in a tube state and the carbon nanofiber in a plate state have higher crystallinity than the carbon nanofiber in a herring bone state, it is suitable for increasing the density of the electrode plate.

次に、上述の複合粒子を含む非水電解質二次電池用電極について説明する。
例えば円筒形もしくは角形の非水電解質二次電池に用いる一般的な電極は、電極合剤を集電体に担持させた極板を、所定形状に加工すれば得られる。電極合剤は、通常、複合粒子および樹脂結着剤を必須成分として含む。電極合剤には、任意成分として、導電剤、増粘剤等を、本発明の効果を大きく損なわない範囲で含めることができる。結着剤としては、ポリフッ化ビニリデン（ＰＶＤＦ）等のフッ素樹脂、スチレンブタジエンゴム（ＳＢＲ）等のゴム性状樹脂、アクリル酸、アクリロニトリルもしくはアクリル酸エステル単位を含むゴム性状樹脂等が用いられる。導電剤としては、カーボンブラック等が好ましく用いられる。増粘剤には、カルボキシメチルセルロース（ＣＭＣ）等が好ましく用いられる。 Next, the electrode for nonaqueous electrolyte secondary batteries containing the above composite particles will be described.
For example, a general electrode used for a cylindrical or square non-aqueous electrolyte secondary battery can be obtained by processing an electrode plate carrying an electrode mixture on a current collector into a predetermined shape. The electrode mixture usually contains composite particles and a resin binder as essential components. In the electrode mixture, a conductive agent, a thickener, and the like can be included as optional components within a range that does not significantly impair the effects of the present invention. As the binder, a fluorine resin such as polyvinylidene fluoride (PVDF), a rubber-like resin such as styrene butadiene rubber (SBR), a rubber-like resin containing acrylic acid, acrylonitrile or an acrylate ester unit, or the like is used. As the conductive agent, carbon black or the like is preferably used. As the thickener, carboxymethylcellulose (CMC) or the like is preferably used.

電極合剤は、スラリー状にするために液状成分と混合され、得られたスラリーは集電体の両面に塗工され、乾燥される。その後、集電体に担持された電極合剤を集電体と共に圧延し、所定サイズに裁断すれば、電極が得られる。なお、ここで説明した方法は一例に過ぎず、他のどのような方法で電極を作製してもよい。また、電極の種類や形状は限定されず、例えば複合粒子をコイン形電池の電極に利用することもできる。   The electrode mixture is mixed with a liquid component to form a slurry, and the resulting slurry is applied to both sides of the current collector and dried. Thereafter, the electrode mixture carried on the current collector is rolled together with the current collector and cut into a predetermined size to obtain an electrode. Note that the method described here is merely an example, and the electrode may be manufactured by any other method. Moreover, the kind and shape of an electrode are not limited, For example, a composite particle can also be utilized for the electrode of a coin-type battery.

得られた電極と、対極と、セパレータとを用いて電極群が構成される。セパレータには、ポリオレフィン樹脂製の微多孔フィルムが好ましく用いられるが、特に限定されない。   An electrode group is configured using the obtained electrode, the counter electrode, and the separator. As the separator, a microporous film made of polyolefin resin is preferably used, but is not particularly limited.

電極群は、非水電解液と共に電池ケース内に収容される。非水電解液には、一般に、リチウム塩を溶解させた非水溶媒が用いられる。リチウム塩は、特に限定されないが、例えばＬｉＰＦ6、ＬｉＢＦ4等が好ましく用いられる。また、非水溶媒は、特に限定されないが、例えばエチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート等の炭酸エステルが好ましく用いられる。 The electrode group is accommodated in the battery case together with the non-aqueous electrolyte. In general, a nonaqueous solvent in which a lithium salt is dissolved is used for the nonaqueous electrolyte. Lithium salt is not particularly limited, for example LiPF 6, LiBF 4 or the like are preferably used. The non-aqueous solvent is not particularly limited, but for example, carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferably used.

以下、本発明を実施例および比較例に基づいて具体的に説明するが、以下の実施例は本発明の実施態様の一部を例示するものに過ぎず、本発明はこれらの実施例に限定されるものではない。   EXAMPLES Hereinafter, the present invention will be specifically described based on examples and comparative examples. However, the following examples are merely illustrative of some of the embodiments of the present invention, and the present invention is limited to these examples. It is not done.

関東化学（株）製の硝酸ニッケル６水和物（特級）１ｇをイオン交換水１００ｇに溶解させた。得られた溶液を、１０μｍ以下に粉砕した（株）高純度化学研究所製のケイ素粒子（Ｓｉ）１００ｇと混合した。この混合物を１時間攪拌後、エバポレータ装置で水分を除去することで、ケイ素粒子の表面に硝酸ニッケルを担持させた。   1 g of nickel nitrate hexahydrate (special grade) manufactured by Kanto Chemical Co., Ltd. was dissolved in 100 g of ion-exchanged water. The obtained solution was mixed with 100 g of silicon particles (Si) manufactured by Kojundo Chemical Laboratory Co., Ltd., pulverized to 10 μm or less. After stirring this mixture for 1 hour, the water was removed by an evaporator device, thereby supporting nickel nitrate on the surface of the silicon particles.

硝酸ニッケルを担持したケイ素粒子を、セラミック製反応容器に投入し、ヘリウムガス存在下で５５０℃まで昇温させた。その後、ヘリウムガスを水素ガス５０体積％とメタンガス５０体積％の混合ガスに置換し、反応容器内を５５０℃で３時間保持した。その結果、ケイ素粒子の表面に、およそ繊維径８０ｎｍで、繊維長５００μｍのチューブ状のカーボンナノファイバが成長した。その後、混合ガスをヘリウムガスに置換し、反応容器内を室温になるまで冷却させた。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１００重量部であった。   Silicon particles carrying nickel nitrate were put into a ceramic reaction vessel and heated to 550 ° C. in the presence of helium gas. Thereafter, the helium gas was replaced with a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas, and the inside of the reaction vessel was kept at 550 ° C. for 3 hours. As a result, tubular carbon nanofibers having a fiber diameter of about 80 nm and a fiber length of 500 μm were grown on the surface of the silicon particles. Thereafter, the mixed gas was replaced with helium gas, and the inside of the reaction vessel was cooled to room temperature. The amount of the grown carbon nanofiber was 100 parts by weight per 100 parts by weight of the active material particles.

なお、ケイ素粒子に担持された硝酸ニッケルは、粒径１００ｎｍ程度の粒子状に還元されていた。ニッケル粒子の粒径、繊維径、繊維長は、それぞれＳＥＭで観察した。カーボンナノファイバの重量は、それを成長させる前後の活物質粒子の重量変化から測定した。ＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   The nickel nitrate supported on the silicon particles was reduced to particles having a particle size of about 100 nm. The particle diameter, fiber diameter, and fiber length of the nickel particles were each observed with an SEM. The weight of the carbon nanofiber was measured from the change in the weight of the active material particles before and after the carbon nanofiber was grown. SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

得られた複合粒子の５００倍拡大写真を図３に示す。図３の円で囲まれた部分の５００００倍拡大写真を図４に示す。図４より、円内領域にカーボンナノファイバが成長していることが確認できる。図５に、得られた複合粒子の３００００倍拡大写真を示す。図５中、活物質粒子３１の表面には、大きなカーボンナノファイバ３２と微細カーボンナノファイバ３３の存在が観察できる。   A 500 times magnified photograph of the obtained composite particles is shown in FIG. FIG. 4 shows a 50000 times magnified photograph of a portion surrounded by a circle in FIG. From FIG. 4, it can be confirmed that the carbon nanofibers are growing in the in-circle region. FIG. 5 shows a 30000 times magnified photograph of the obtained composite particles. In FIG. 5, the presence of large carbon nanofibers 32 and fine carbon nanofibers 33 can be observed on the surface of the active material particles 31.

その後、複合粒子をアルゴンガス中で１０００℃まで昇温し、複合粒子を１０００℃で１時間焼成し、非水電解質二次電池の電極材料Ａとした。   Thereafter, the composite particles were heated to 1000 ° C. in argon gas, and the composite particles were fired at 1000 ° C. for 1 hour to obtain an electrode material A for a nonaqueous electrolyte secondary battery.

硝酸ニッケル６水和物１ｇの代わりに、関東化学（株）製の硝酸コバルト６水和物（特級）１ｇをイオン交換水１００ｇに溶解させたこと以外、実施例１同様の操作を行い、非水電解質二次電池の電極材料Ｂとした。なお、ケイ素粒子に担持されたコバルト粒子の粒径は、実施例１のニッケル粒子とほぼ同じであった。成長したへーリング・ボーン状のカーボンナノファイバの繊維径、繊維長、活物質粒子に対する重量割合は、実施例１とほぼ同じであった。ここでもＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   The same operation as in Example 1 was performed except that 1 g of cobalt nitrate hexahydrate (special grade) manufactured by Kanto Chemical Co., Ltd. was dissolved in 100 g of ion-exchanged water instead of 1 g of nickel nitrate hexahydrate. It was set as the electrode material B of a water electrolyte secondary battery. Note that the particle size of the cobalt particles supported on the silicon particles was almost the same as that of the nickel particles of Example 1. The fiber diameter, fiber length, and weight ratio of the grown herringbone carbon nanofibers to the active material particles were almost the same as in Example 1. Here too, SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

１０μｍ以下に粉砕したケイ素粒子２０重量％と１０μｍ以下に粉砕した関東化学（株）製のニッケル粒子８０重量％とを混合した。得られた混合物に対し、メカニカルアロイ法で剪断力を印加して、平均粒径２０μｍのＮｉＳｉ合金粒子を得た。得られたＮｉＳｉ合金粒子をケイ素粒子の代わりに用いたこと以外、実施例１同様の操作を行い、非水電解質二次電池の電極材料Ｃとした。なお、ＮｉＳｉ合金粒子に担持されたニッケル粒子の粒径は、実施例１のニッケル粒子とほぼ同じであった。成長したチューブ状のカーボンナノファイバの繊維径、繊維長、活物質粒子に対する重量割合は、実施例１とほぼ同じであった。ここでもＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   20% by weight of silicon particles ground to 10 μm or less and 80% by weight of nickel particles manufactured by Kanto Chemical Co., Ltd. ground to 10 μm or less were mixed. A shear force was applied to the obtained mixture by a mechanical alloy method to obtain NiSi alloy particles having an average particle diameter of 20 μm. Except that the obtained NiSi alloy particles were used in place of the silicon particles, the same operation as in Example 1 was performed to obtain an electrode material C for a nonaqueous electrolyte secondary battery. The particle size of the nickel particles carried on the NiSi alloy particles was almost the same as the nickel particles of Example 1. The tube-shaped carbon nanofibers grown had substantially the same fiber diameter, fiber length, and weight ratio to the active material particles as in Example 1. Here too, SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

硝酸ニッケル６水和物１ｇの代わりに、硝酸ニッケル６水和物０．５ｇと硝酸コバルト６水和物０．５ｇをイオン交換水１００ｇに溶解させたこと以外、実施例１同様の操作を行い、非水電解質二次電池の電極材料Ｄとした。なお、ケイ素粒子に担持されたコバルト粒子およびニッケル粒子の粒径は、それぞれ実施例１のニッケル粒子とほぼ同じであった。成長したチューブ状のカーボンナノファイバの繊維径、繊維長、活物質粒子に対する重量割合も、実施例１とほぼ同じであった。ここでもＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   The same operation as in Example 1 was performed except that 0.5 g of nickel nitrate hexahydrate and 0.5 g of cobalt nitrate hexahydrate were dissolved in 100 g of ion-exchanged water instead of 1 g of nickel nitrate hexahydrate. An electrode material D for a non-aqueous electrolyte secondary battery was obtained. In addition, the particle diameters of the cobalt particles and the nickel particles supported on the silicon particles were almost the same as the nickel particles of Example 1, respectively. The fiber diameter, fiber length, and weight ratio with respect to the active material particles of the grown tubular carbon nanofibers were almost the same as in Example 1. Here too, SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を５分間に変更したこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｅとした。成長したカーボンナノファイバは、およそ繊維長０．５ｎｍで、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１重量部以下であった。   The same operation as in Example 1 was performed except that the growth time of carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 5 minutes. Electrode material E was designated. The grown carbon nanofibers had a fiber length of approximately 0.5 nm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 1 part by weight or less per 100 parts by weight of the active material particles.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を２０時間に変更したこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｆとした。成長したカーボンナノファイバは、およそ繊維長３ｍｍ以上、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり２００重量部であった。ここでもＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   The same operation as in Example 1 was performed except that the growth time of the carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 20 hours, and the nonaqueous electrolyte secondary battery was An electrode material F was obtained. The grown carbon nanofibers had a fiber length of about 3 mm or more and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 200 parts by weight per 100 parts by weight of the active material particles. Here too, SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

カーボンナノファイバ成長後の複合粒子の焼成処理を１００℃で行ったこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｇとした。   An electrode material G for a non-aqueous electrolyte secondary battery was obtained by performing the same operation as in Example 1 except that the composite particles after carbon nanofiber growth were baked at 100 ° C.

カーボンナノファイバ成長後の複合粒子の焼成処理を１７００℃で行ったこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｈとした。   The same operation as in Example 1 was performed except that the composite particles after the carbon nanofiber growth were baked at 1700 ° C. to obtain an electrode material H for a nonaqueous electrolyte secondary battery.

比較例１Comparative Example 1

１０μｍ以下に粉砕したケイ素粒子１００重量部と、導電剤としてアセチレンブラック（ＡＢ）１０重量部とを、乾式混合し、非水電解質二次電池の電極材料Ｉとした。   100 parts by weight of silicon particles pulverized to 10 μm or less and 10 parts by weight of acetylene black (AB) as a conductive agent were dry-mixed to obtain an electrode material I for a nonaqueous electrolyte secondary battery.

比較例２Comparative Example 2

硝酸ニッケル６水和物１ｇをイオン交換水１００ｇに溶解させた。得られた溶液をアセチレンブラック（ＡＢ）５ｇと混合した。この混合物を１時間攪拌後、エバポレータ装置で水分を除去することで、アセチレンブラックにニッケル粒子を担持させた。次に、ニッケル粒子を担持したアセチレンブラックを、大気中３００℃で焼成することで、粒径０．１μｍ以下の酸化ニッケル粒子を得た。   1 g of nickel nitrate hexahydrate was dissolved in 100 g of ion-exchanged water. The resulting solution was mixed with 5 g of acetylene black (AB). After stirring this mixture for 1 hour, the moisture was removed by an evaporator device to support nickel particles on acetylene black. Next, acetylene black carrying nickel particles was baked at 300 ° C. in the air to obtain nickel oxide particles having a particle size of 0.1 μm or less.

得られた酸化ニッケル粒子をセラミック製反応容器に投入し、ヘリウムガス存在下で５５０℃まで昇温させた。その後、ヘリウムガスを水素ガス５０体積％とメタンガス５０体積％の混合ガスに置換し、反応容器内を５５０℃で３時間保持した。その結果、およそ繊維径８０ｎｍで繊維長５００μｍのチューブ状のカーボンナノファイバが生成した。その後、混合ガスをヘリウムガスに置換し、反応容器内を室温になるまで冷却させた。   The obtained nickel oxide particles were put into a ceramic reaction vessel and heated to 550 ° C. in the presence of helium gas. Thereafter, the helium gas was replaced with a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas, and the inside of the reaction vessel was kept at 550 ° C. for 3 hours. As a result, a tubular carbon nanofiber having a fiber diameter of about 80 nm and a fiber length of 500 μm was produced. Thereafter, the mixed gas was replaced with helium gas, and the inside of the reaction vessel was cooled to room temperature.

得られたカーボンナノファイバ（ＣＮＦ）を塩酸水溶液で洗浄して、ニッケル粒子を除去し、触媒元素を含まないカーボンナノファイバを得た。このカーボンナノファイバ１００重量部と、１０μｍ以下に粉砕したケイ素粒子１００重量部とを、乾式混合し、非水電解質二次電池の電極材料Ｊとした。   The obtained carbon nanofiber (CNF) was washed with an aqueous hydrochloric acid solution to remove nickel particles, thereby obtaining a carbon nanofiber containing no catalyst element. 100 parts by weight of the carbon nanofibers and 100 parts by weight of silicon particles pulverized to 10 μm or less were dry-mixed to obtain an electrode material J for a nonaqueous electrolyte secondary battery.

比較例３Comparative Example 3

１０μｍ以下に粉砕したケイ素粒子をセラミック製反応容器に投入し、ヘリウムガス存在下で１０００℃まで昇温させた。その後、ヘリウムガスをベンゼンガス５０体積％とヘリウムガス５０体積％の混合ガスに置換し、反応容器内を１０００℃で１時間保持した。その結果、ケイ素粒子の表面に、厚さ約５００ｎｍのカーボン層が生成した。その後、混合ガスをヘリウムガスに置換し、反応容器内を室温になるまで冷却させ、非水電解質二次電池の電極材料Ｋを得た。   Silicon particles pulverized to 10 μm or less were put into a ceramic reaction vessel and heated to 1000 ° C. in the presence of helium gas. Thereafter, the helium gas was replaced with a mixed gas of 50% by volume of benzene gas and 50% by volume of helium gas, and the inside of the reaction vessel was kept at 1000 ° C. for 1 hour. As a result, a carbon layer having a thickness of about 500 nm was formed on the surface of the silicon particles. Thereafter, the mixed gas was replaced with helium gas, the inside of the reaction vessel was cooled to room temperature, and an electrode material K for a nonaqueous electrolyte secondary battery was obtained.

比較例４Comparative Example 4

ケイ素粒子１００重量部に、関東化学（株）製のクロム粉末を０．０２重量部添加した。得られた混合物を、ボールミルを用いて１０時間混合し、クロム含有ケイ素粒子を得た。その後、クロム含有ケイ素粒子７０重量部と、比較例２で用いたのと同じカーボンナノファイバ３０重量部とを、ボールミルで混合し、ケイ素粒子が１０μｍ以下になるまで粉砕した。   0.02 parts by weight of chromium powder manufactured by Kanto Chemical Co., Ltd. was added to 100 parts by weight of silicon particles. The obtained mixture was mixed for 10 hours using a ball mill to obtain chromium-containing silicon particles. Thereafter, 70 parts by weight of chromium-containing silicon particles and 30 parts by weight of the same carbon nanofibers used in Comparative Example 2 were mixed by a ball mill and pulverized until the silicon particles became 10 μm or less.

得られた混合物を、セラミック製反応容器に投入し、ヘリウムガス存在下で７００℃まで昇温させた。その後、ヘリウムガスをメタンガス１００体積％に置換し、反応容器内を７００℃で６時間保持した。その結果、ケイ素粒子の表面に、厚さ約１００ｎｍのカーボン層が生成した。その後、メタンガスガスをヘリウムガスに置換し、反応容器内を室温になるまで冷却させ、非水電解質二次電池の電極材料Ｌとした。   The obtained mixture was put into a ceramic reaction vessel and heated to 700 ° C. in the presence of helium gas. Thereafter, helium gas was replaced with 100% by volume of methane gas, and the inside of the reaction vessel was kept at 700 ° C. for 6 hours. As a result, a carbon layer having a thickness of about 100 nm was formed on the surface of the silicon particles. Thereafter, the methane gas was replaced with helium gas, the inside of the reaction vessel was cooled to room temperature, and an electrode material L for a nonaqueous electrolyte secondary battery was obtained.

［評価］
実施例１〜８および比較例１〜４で製造された電極材料に、フッ化ビニリデン樹脂からなる結着剤と、Ｎ−メチル−２−ピロリドン（ＮＭＰ）とを混合して、合剤スラリーを調製した。そのスラリーを厚さ１５μｍのＣｕ箔上にキャスティングし、乾燥後、合剤を圧延して、電極板を得た。得られた電極板の合剤密度は０．８〜１．４ｇ／ｃｍ3であった。 [Evaluation]
A binder slurry made of vinylidene fluoride resin and N-methyl-2-pyrrolidone (NMP) were mixed with the electrode materials produced in Examples 1 to 8 and Comparative Examples 1 to 4, and a mixture slurry was prepared. Prepared. The slurry was cast on a Cu foil having a thickness of 15 μm, and after drying, the mixture was rolled to obtain an electrode plate. The mixture density of the obtained electrode plate was 0.8 to 1.4 g / cm 3 .

この電極板を８０℃のオーブンで十分に乾燥させ、作用極を得た。リチウム金属箔を作用極の対極として用い、作用極で規制されたコイン型リチウムイオン電池を作製した。非水電解液としては、エチレンカーボネートとジエチルカーボネートとの体積１：１の混合溶媒にＬｉＰＦ6を１．０Ｍ（ｍｏｌ／Ｌ）の濃度で溶解させたものを使用した。 This electrode plate was sufficiently dried in an oven at 80 ° C. to obtain a working electrode. Using a lithium metal foil as a counter electrode of the working electrode, a coin-type lithium ion battery regulated by the working electrode was produced. As the non-aqueous electrolyte, a solution in which LiPF 6 was dissolved at a concentration of 1.0 M (mol / L) in a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate was used.

得られたコイン型リチウムイオン電池に関し、０．０５Ｃの充放電速度で、初期充電容量と初期放電容量を測定し、活物質重量当りの初期放電容量を求めた。さらに、初期充電容量に対する初期放電容量の割合を百分率値で求め、充放電効率とした。
０．０５Ｃの充放電速度で得られた初期放電容量に対する、同充放電速度で充放電を５０サイクル繰り返した時の放電容量の割合を百分率値で求め、サイクル効率とした。結果を表１に示す。 With respect to the obtained coin-type lithium ion battery, the initial charge capacity and the initial discharge capacity were measured at a charge / discharge rate of 0.05 C, and the initial discharge capacity per active material weight was determined. Furthermore, the ratio of the initial discharge capacity with respect to the initial charge capacity was obtained as a percentage value, and was defined as charge / discharge efficiency.
The ratio of the discharge capacity when 50 cycles of charge and discharge were repeated at the same charge / discharge rate with respect to the initial discharge capacity obtained at a charge / discharge rate of 0.05 C was determined as a percentage value, and was defined as cycle efficiency. The results are shown in Table 1.

表１に示したように、実施例１〜８で製造された電極材料を利用した電池において、触媒種の違いによる差は確認されず、活物質重量当りの初期放電容量、充放電効率およびサイクル効率共に、カーボンナノファイバを含まない比較例１よりも優れていた。比較例１では、充放電による活物質の膨張と収縮によって、活物質粒子表面とカーボンブラックとの電子伝導ネットワークが切断されたために、サイクル特性に劣化が生じたものである。   As shown in Table 1, in the batteries using the electrode materials manufactured in Examples 1 to 8, the difference due to the difference in the catalyst type was not confirmed, the initial discharge capacity per active material weight, the charge and discharge efficiency and the cycle Both efficiencies were superior to Comparative Example 1 which did not contain carbon nanofibers. In Comparative Example 1, since the electron conduction network between the active material particle surface and the carbon black was cut by the expansion and contraction of the active material due to charge and discharge, the cycle characteristics deteriorated.

カーボンナノファイバを活物質粒子と乾式混合した比較例２の電極材料を用いた電池では、実施例１〜８の電池と比較して、充放電効率とサイクル効率に、急激な低下が確認された。これは、充放電による活物質の膨張と収縮によって、活物質粒子表面とカーボンナノファイバとの電子伝導ネットワークが切断されたためである。   In the battery using the electrode material of Comparative Example 2 in which carbon nanofibers were dry-mixed with active material particles, a rapid decrease was confirmed in charge / discharge efficiency and cycle efficiency as compared with the batteries of Examples 1-8. . This is because the electron conduction network between the active material particle surface and the carbon nanofibers was cut by the expansion and contraction of the active material due to charge and discharge.

活物質粒子の表面をカーボン層でコートした比較例３の電極材料を用いた電池でも、実施例１〜８の電池と比較して、充放電効率とサイクル効率に、急激な低下が確認された。これは、充放電による活物質の膨張と収縮によって活物質粒子間の電子伝導ネットワークが切断されたためである。   Even in the battery using the electrode material of Comparative Example 3 in which the surface of the active material particles was coated with a carbon layer, a rapid decrease was confirmed in charge / discharge efficiency and cycle efficiency as compared with the batteries of Examples 1-8. . This is because the electron conduction network between the active material particles is cut by the expansion and contraction of the active material due to charge and discharge.

クロムを添加した活物質粒子とカーボンナノファイバとの混合物をボールミルで混合し、さらに粒子表面をカーボン層でコートした比較例４の電極材料を用いた電池でも、実施例１〜８の電池と比較して、充放電効率とサイクル効率に、急激な低下が確認された。これも、充放電による活物質の膨張と収縮によって活物質粒子間の電子伝導ネットワークが切断されたためである。   A battery using the electrode material of Comparative Example 4 in which a mixture of chromium-added active material particles and carbon nanofibers was mixed with a ball mill and the particle surface was coated with a carbon layer was also compared with the batteries of Examples 1-8. As a result, a rapid drop in charge / discharge efficiency and cycle efficiency was confirmed. This is also because the electron conduction network between the active material particles was cut by the expansion and contraction of the active material due to charge and discharge.

カーボンナノファイバの長さを０．５ｎｍと短く成長させた実施例５の複合粒子を用いた電池のサイクル特性は、実施例１〜４と比較して、低減していた。初期には、活物質表面に形成されたカーボンナノファイバで導電性が保たれていたと考えられる。しかし、充放電により活物質の膨張と収縮が繰り返されることで、徐々に粒子間の導電性が失われたものと考えられる。   The cycle characteristics of the battery using the composite particles of Example 5 in which the length of the carbon nanofiber was grown as short as 0.5 nm were reduced as compared with Examples 1 to 4. In the initial stage, it is considered that the conductivity was maintained by the carbon nanofiber formed on the surface of the active material. However, it is considered that the conductivity between particles is gradually lost due to repeated expansion and contraction of the active material due to charge and discharge.

逆に、カーボンナノファイバを長く成長させた実施例６の複合粒子を用いた電池では、活物質重量当りの初期放電容量、充放電効率およびサイクル効率共に、実施例１〜４と同じレベルであった。しかし、極板としての放電容量は約６７％低減することが確認された。これは、極板中におけるカーボンナノファイバの割合が活物質量に対して相対的に増えたためである。   On the other hand, in the battery using the composite particles of Example 6 in which carbon nanofibers were grown for a long time, the initial discharge capacity, the charge / discharge efficiency, and the cycle efficiency per active material weight were the same level as in Examples 1-4. It was. However, it was confirmed that the discharge capacity as an electrode plate was reduced by about 67%. This is because the proportion of carbon nanofibers in the electrode plate has increased relative to the amount of active material.

カーボンナノファイバ成長後の焼成処理を１００℃で行った実施例７の複合粒子を用いた電池の初期充放電効率は、実施例１〜４と比較して、低減した。これは、１００℃の焼成では、カーボンナノファイバ表面に付着している水素イオンやメチル基、水酸基などの官能基が除去されず、電解液と不可逆反応を生じたためである。   The initial charge / discharge efficiency of the battery using the composite particles of Example 7 in which the firing process after the carbon nanofiber growth was performed at 100 ° C. was reduced as compared with Examples 1-4. This is because the functional groups such as hydrogen ions, methyl groups, and hydroxyl groups adhering to the carbon nanofiber surface were not removed by firing at 100 ° C., and an irreversible reaction with the electrolytic solution occurred.

一方、カーボンナノファイバ成長後の焼成処理を１７００℃で行った実施例８の複合粒子を用いた電池の活物質重量当りの初期放電容量は、実施例１〜４と比較して、低減している。この場合、カーボンナノファイバ表面に付着している水素イオンやメチル基、水酸基などの官能基は完璧に除去されると考えられる。しかし、ケイ素と炭素とが反応して、電気化学的に不活性な炭化ケイ素を形成したため、活物質重量当りの初期放電容量が低下したものである。   On the other hand, the initial discharge capacity per active material weight of the battery using the composite particles of Example 8 in which the firing treatment after carbon nanofiber growth was performed at 1700 ° C. was reduced as compared with Examples 1-4. Yes. In this case, it is considered that functional groups such as hydrogen ions, methyl groups, and hydroxyl groups attached to the carbon nanofiber surface are completely removed. However, since silicon and carbon react to form electrochemically inactive silicon carbide, the initial discharge capacity per weight of the active material is reduced.

平均粒径１０μｍのＬｉＣｏＯ2粒子をセラミック製反応容器に投入し、ヘリウムガス存在下で５５０℃まで昇温させた。その後、ヘリウムガスを水素ガス５０体積％とメタンガス５０体積％の混合ガスに置換し、反応容器内を５５０℃で３時間保持した。その結果、ＬｉＣｏＯ2粒子の表面に、およそ繊維径８０ｎｍで、繊維長５００μｍのチューブ状のカーボンナノファイバが成長した。その後、混合ガスをヘリウムガスに置換し、反応容器内を室温になるまで冷却させた。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１００重量部であった。ＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。 LiCoO 2 particles having an average particle diameter of 10 μm were put into a ceramic reaction vessel and heated to 550 ° C. in the presence of helium gas. Thereafter, the helium gas was replaced with a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas, and the inside of the reaction vessel was kept at 550 ° C. for 3 hours. As a result, tubular carbon nanofibers having a fiber diameter of about 80 nm and a fiber length of 500 μm were grown on the surface of the LiCoO 2 particles. Thereafter, the mixed gas was replaced with helium gas, and the inside of the reaction vessel was cooled to room temperature. The amount of the grown carbon nanofiber was 100 parts by weight per 100 parts by weight of the active material particles. SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

その後、複合粒子をアルゴンガス中で７００℃まで昇温し、複合粒子を７００℃で１時間焼成した。その後さらに、大気中で３００℃まで昇温し、複合粒子を２時間熱処理して、非水電解質二次電池の電極材料Ｍとした。   Thereafter, the composite particles were heated to 700 ° C. in argon gas, and the composite particles were fired at 700 ° C. for 1 hour. Thereafter, the temperature was further raised to 300 ° C. in the atmosphere, and the composite particles were heat-treated for 2 hours to obtain an electrode material M for a nonaqueous electrolyte secondary battery.

硝酸ニッケル６水和物１ｇをイオン交換水１００ｇに溶解させた。得られた溶液を平均粒径１０μｍのＬｉＣｏＯ2粒子１００ｇと混合した。この混合物を１時間攪拌後、エバポレータ装置で水分を除去することで、ＬｉＣｏＯ2粒子の表面に硝酸ニッケルを担持した。 1 g of nickel nitrate hexahydrate was dissolved in 100 g of ion-exchanged water. The obtained solution was mixed with 100 g of LiCoO 2 particles having an average particle diameter of 10 μm. After the mixture was stirred for 1 hour, the water was removed by an evaporator device to support nickel nitrate on the surface of the LiCoO 2 particles.

硝酸ニッケルを担持したＬｉＣｏＯ2粒子を、セラミック製反応容器に投入し、その表面にカーボンナノファイバを成長させたこと以外、実施例９と同様の操作を行い、非水電解質二次電池の電極材料Ｎとした。成長したチューブ状カーボンナノファイバは、およそ繊維径８０ｎｍ、繊維長５００μｍ、活物質粒子に対する重量割合は、実施例１とほぼ同じであった。ＬｉＣｏＯ2粒子に担持された硝酸ニッケルは、粒径１００ｎｍ程度のニッケル粒子に還元されていた。ＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。 LiCoO 2 particles supporting nickel nitrate were put into a ceramic reaction vessel, and the same operation as in Example 9 was performed except that carbon nanofibers were grown on the surface thereof. N. The grown tubular carbon nanofibers had a fiber diameter of about 80 nm, a fiber length of 500 μm, and the weight ratio to the active material particles was almost the same as in Example 1. The nickel nitrate supported on the LiCoO 2 particles was reduced to nickel particles having a particle size of about 100 nm. SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

ＬｉＣｏＯ2粒子の代わりにＬｉＭｎ2Ｏ4を用いたこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料Ｏとした。ＬｉＭｎ2Ｏ4粒子に担持されたニッケル粒子の粒径は、実施例１０のニッケル粒子とほぼ同じであった。成長したカーボンナノファイバの繊維径、繊維長、活物質粒子に対する重量割合は、実施例１０とほぼ同じであった。ＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。 Except that LiMn 2 O 4 was used instead of LiCoO 2 particles, the same operation as in Example 10 was performed to obtain an electrode material O for a nonaqueous electrolyte secondary battery. The particle size of the nickel particles supported on the LiMn 2 O 4 particles was almost the same as the nickel particles of Example 10. The weight ratio of the grown carbon nanofiber to the fiber diameter, fiber length, and active material particles was almost the same as in Example 10. SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

硝酸ニッケル６水和物１ｇの代わりに、硝酸ニッケル６水和物０．５ｇと硝酸コバルト６水和物０．５ｇをイオン交換水１００ｇに溶解させたこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料Ｐとした。なお、ＬｉＣｏＯ2粒子に担持されたコバルト粒子およびニッケル粒子の粒径は、それぞれ実施例１０のニッケル粒子とほぼ同じであった。成長したチューブ状カーボンナノファイバの繊維径、繊維長、活物質粒子に対する重量割合は、実施例１０とほぼ同じであった。ＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。 Instead of 1 g of nickel nitrate hexahydrate, the same operation as in Example 10 was performed except that 0.5 g of nickel nitrate hexahydrate and 0.5 g of cobalt nitrate hexahydrate were dissolved in 100 g of ion-exchanged water. The electrode material P of the nonaqueous electrolyte secondary battery was obtained. In addition, the particle diameters of the cobalt particles and the nickel particles carried on the LiCoO 2 particles were almost the same as those of the nickel particles of Example 10, respectively. The weight ratio of the grown tubular carbon nanofibers to the fiber diameter, fiber length, and active material particles was substantially the same as in Example 10. SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を５分間に変更したこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料Ｑとした。成長したカーボンナノファイバは、およそ繊維長０．５ｎｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１重量部以下であった。ＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   The same operation as in Example 10 was performed except that the carbon nanofiber growth time was changed to 5 minutes in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas, and the nonaqueous electrolyte secondary battery was Electrode material Q was designated. The grown carbon nanofibers had a fiber length of approximately 0.5 nm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 1 part by weight or less per 100 parts by weight of the active material particles. SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を２０時間に変更したこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料Ｒとした。成長したカーボンナノファイバは、およそ繊維長３ｍｍ以上、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり２００重量部であった。ＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   The same operation as in Example 10 was performed except that the growth time of carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 20 hours, and the non-aqueous electrolyte secondary battery was An electrode material R was obtained. The grown carbon nanofibers had a fiber length of about 3 mm or more and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 200 parts by weight per 100 parts by weight of the active material particles. SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

カーボンナノファイバ成長後の複合粒子の焼成処理を１００℃で行ったこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料Ｓとした。   An electrode material S of a nonaqueous electrolyte secondary battery was obtained by performing the same operation as in Example 10 except that the composite particles after the carbon nanofiber growth were baked at 100 ° C.

カーボンナノファイバ成長後の複合粒子の焼成処理を１５００℃で行ったこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料Ｔとした。   An electrode material T for a nonaqueous electrolyte secondary battery was obtained by performing the same operation as in Example 10 except that the composite particles after carbon nanofiber growth were fired at 1500 ° C.

比較例５Comparative Example 5

平均粒径１０μｍのＬｉＣｏＯ2粒子１００重量部と、導電剤としてアセチレンブラック（ＡＢ）５重量部とを、乾式混合し、非水電解質二次電池の電極材料Ｕとした。 100 parts by weight of LiCoO 2 particles having an average particle size of 10 μm and 5 parts by weight of acetylene black (AB) as a conductive agent were dry-mixed to obtain an electrode material U for a nonaqueous electrolyte secondary battery.

比較例６Comparative Example 6

比較例２で製造したのと同じ、触媒元素を含まないカーボンナノファイバを５重量部と、平均粒径１０μｍのＬｉＣｏＯ2粒子１００重量部とを、乾式混合し、非水電解質二次電池の電極材料Ｖとした。 As in the case of Comparative Example 2, 5 parts by weight of carbon nanofibers containing no catalyst element and 100 parts by weight of LiCoO 2 particles having an average particle size of 10 μm were dry-mixed to form an electrode for a nonaqueous electrolyte secondary battery. Material V was designated.

［評価］
実施例９〜１６および比較例５、６で製造された電極材料に、フッ化ビニリデン樹脂からなる結着剤と、ＮＭＰとを混合して、合剤スラリーを調製し、そのスラリーを厚さ１５μｍのＡｌ箔上にキャスティングし、乾燥後、合剤を圧延して、電極板を得た。得られた電極板の合剤密度は３．３ｇ／ｃｍ3であった。 [Evaluation]
The electrode materials manufactured in Examples 9 to 16 and Comparative Examples 5 and 6 were mixed with a binder made of vinylidene fluoride resin and NMP to prepare a mixture slurry, and the slurry was 15 μm in thickness. The mixture was cast on an Al foil and dried, and the mixture was rolled to obtain an electrode plate. The mixture density of the obtained electrode plate was 3.3 g / cm 3 .

この電極板を８０℃のオーブンで十分に乾燥させ、作用極を得た。リチウム金属箔を作用極の対極として用い、作用極で規制されたコイン型リチウムイオン電池を作製した。非水電解液としては、エチレンカーボネートとジエチルカーボネートとの体積１：１の混合溶媒にＬｉＰＦ6を１．０Ｍの濃度で溶解させたものを使用した。 This electrode plate was sufficiently dried in an oven at 80 ° C. to obtain a working electrode. Using a lithium metal foil as a counter electrode of the working electrode, a coin-type lithium ion battery regulated by the working electrode was produced. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF 6 at a concentration of 1.0 M in a mixed solvent of ethylene carbonate and diethyl carbonate in a volume of 1: 1 was used.

得られたコイン型リチウムイオン電池に関し、０．２Ｃの速度で充放電を行い活物質重量当りの初期放電容量を求めた。
また、電池を０．２Ｃの速度で充電し、１．０Ｃもしくは２．０Ｃの各速度で放電を行い、１．０Ｃ放電容量に対する２．０Ｃ放電容量の割合を百分率値で求め、放電効率とした。
さらに、１．０Ｃの充放電速度で得られた初期放電容量に対する、同充放電速度で充放電を２００サイクル繰り返した時の放電容量の割合を百分率値で求め、サイクル効率とした。結果を表２に示す。 The obtained coin-type lithium ion battery was charged and discharged at a rate of 0.2 C, and the initial discharge capacity per active material weight was determined.
In addition, the battery is charged at a rate of 0.2 C, discharged at each rate of 1.0 C or 2.0 C, the ratio of the 2.0 C discharge capacity to the 1.0 C discharge capacity is obtained as a percentage value, and the discharge efficiency and did.
Furthermore, the ratio of the discharge capacity when 200 cycles of charge / discharge were repeated at the same charge / discharge rate with respect to the initial discharge capacity obtained at a charge / discharge rate of 1.0 C was obtained as a percentage value, and was defined as cycle efficiency. The results are shown in Table 2.

表２に示したように、実施例９〜１６で製造された電極材料を利用した電池において、活物質および触媒の種類にかかわらず、いずれも理論容量に近い初期放電容量が得られた。また、放電効率およびサイクル効率共に、比較例５、６よりも優れていた。   As shown in Table 2, in the batteries using the electrode materials produced in Examples 9 to 16, an initial discharge capacity close to the theoretical capacity was obtained regardless of the type of active material and catalyst. Moreover, both the discharge efficiency and the cycle efficiency were superior to those of Comparative Examples 5 and 6.

導電剤をＬｉＣｏＯ2粒子と乾式混合させた比較例５、６の電極材料を用いた電池では、充放電によるＬｉＣｏＯ2粒子の膨張と収縮により、活物質表面と導電剤との電子伝導ネットワークが切断されたために、初期放電効率およびサイクル特性が劣ったものと考えられる。 Conductive agent in battery using the electrode material of Comparative Examples 5 and 6 obtained by mixing LiCoO 2 particles and dry conditions by the expansion and contraction of the LiCoO 2 particles by charge and discharge, the electron conductivity network between the active material surface and the conductive agent cleavage Therefore, it is considered that the initial discharge efficiency and the cycle characteristics are inferior.

カーボンナノファイバの長さを０．５ｎｍと短く成長させた実施例１３の複合粒子を用いた電池のサイクル効率は、実施例１０と比較して、極端に低減していた。これは、初期状態では、活物質表面に形成されたカーボンナノファイバで導電性が保たれていたが、充放電により活物質の膨張と収縮が繰り返されることで、徐々に粒子間の導電性が失われたものと考えられる。   Compared with Example 10, the cycle efficiency of the battery using the composite particles of Example 13 in which the length of the carbon nanofiber was grown as short as 0.5 nm was extremely reduced. In the initial state, the conductivity was maintained by the carbon nanofibers formed on the surface of the active material, but the expansion and contraction of the active material was repeated by charging and discharging, so that the conductivity between the particles gradually increased. It is thought to have been lost.

逆に、カーボンナノファイバを長く成長させた実施例１４の複合粒子を用いた電池では、活物質重量当りの初期放電容量、放電効率およびサイクル効率共に、実施例１０と同じレベルであったが、極板当りの放電容量が低減することが確認された。これは、極板中におけるカーボンナノファイバの割合が活物質量に対して相対的に増えたためである。   Conversely, in the battery using the composite particles of Example 14 in which the carbon nanofibers were grown for a long time, the initial discharge capacity per unit weight of the active material, the discharge efficiency, and the cycle efficiency were the same level as in Example 10, It was confirmed that the discharge capacity per electrode plate was reduced. This is because the proportion of carbon nanofibers in the electrode plate has increased relative to the amount of active material.

カーボンナノファイバ成長後の焼成処理を１００℃で行った実施例１５の複合粒子を用いた電池の放電効率は、実施例１０と比較して、低減した。これは、１００℃の焼成では、カーボンナノファイバ表面に付着している水素イオンやメチル基、水酸基などの官能基が除去されず、電解液と不可逆反応を生じたためである。   Compared with Example 10, the discharge efficiency of the battery using the composite particles of Example 15 in which the baking treatment after carbon nanofiber growth was performed at 100 ° C. was reduced. This is because the functional groups such as hydrogen ions, methyl groups, and hydroxyl groups adhering to the carbon nanofiber surface were not removed by firing at 100 ° C., and an irreversible reaction with the electrolytic solution occurred.

一方、カーボンナノファイバ成長後の焼成処理を１５００℃で行った実施例１６の複合粒子を用いた電池の活物質重量当りの初期放電容量は、実施例１０と比較して、低減した。この場合、カーボンナノファイバ表面に付着している水素イオンやメチル基、水酸基などの官能基は完璧に除去されるものの、ＬｉＣｏＯ2が還元分解されて、電気化学的に不活性なＣｏ2Ｏ3などの酸化コバルトを形成したため、初期放電容量が低下したものである。 On the other hand, the initial discharge capacity per active material weight of the battery using the composite particles of Example 16 in which the firing treatment after the carbon nanofiber growth was performed at 1500 ° C. was reduced as compared with Example 10. In this case, although functional groups such as hydrogen ions, methyl groups, and hydroxyl groups attached to the surface of the carbon nanofiber are completely removed, LiCoO 2 is reduced and decomposed to be electrochemically inactive Co 2 O 3. As a result, the initial discharge capacity is reduced.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を１０分間に変更したこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｗとした。成長したカーボンナノファイバは、およそ繊維長５００ｎｍで、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり５重量部以下であった。   The same operation as in Example 1 was performed except that the growth time of the carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 10 minutes, and the nonaqueous electrolyte secondary battery was Electrode material W was designated. The grown carbon nanofibers had a fiber length of approximately 500 nm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 5 parts by weight or less per 100 parts by weight of the active material particles.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を３０分間に変更したこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｘとした。成長したカーボンナノファイバは、およそ繊維長１０μｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１０重量部であった。   The same operation as in Example 1 was performed except that the carbon nanofiber growth time was changed to 30 minutes in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas, and the nonaqueous electrolyte secondary battery was Electrode material X was designated. The grown carbon nanofibers had a fiber length of about 10 μm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 10 parts by weight per 100 parts by weight of the active material particles.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を６０分間に変更したこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｙとした。成長したカーボンナノファイバは、およそ繊維長５０μｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり３０重量部であった。   The same operation as in Example 1 was performed except that the growth time of the carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 60 minutes, and the nonaqueous electrolyte secondary battery was An electrode material Y was obtained. The grown carbon nanofibers had a fiber length of about 50 μm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 30 parts by weight per 100 parts by weight of the active material particles.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を９０分間に変更したこと以外、実施例１と同様の操作を行い、非水電解質二次電池の電極材料Ｚとした。成長したカーボンナノファイバは、およそ繊維長１００μｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり５０重量部であった。   The same operation as in Example 1 was performed except that the growth time of the carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 90 minutes, and the nonaqueous electrolyte secondary battery was Electrode material Z was designated. The grown carbon nanofibers had a fiber length of about 100 μm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 50 parts by weight per 100 parts by weight of the active material particles.

［評価］
実施例１７〜２０で製造された電極材料を用いて、実施例１と同様のコイン型リチウムイオン電池を作製し、実施例１と同様に、活物質重量当たりの初期放電容量、充放電効率、およびサイクル効率を求めた。結果を表３に示す。 [Evaluation]
Using the electrode materials manufactured in Examples 17 to 20, a coin-type lithium ion battery similar to that in Example 1 was produced, and as in Example 1, the initial discharge capacity per active material weight, the charge and discharge efficiency, And the cycle efficiency was determined. The results are shown in Table 3.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を１０分間に変更したこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料αとした。成長したカーボンナノファイバは、およそ繊維長５００ｎｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり５重量部であった。   The same operation as in Example 10 was performed except that the growth time of the carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 10 minutes, and the non-aqueous electrolyte secondary battery was The electrode material was α. The grown carbon nanofibers had a fiber length of approximately 500 nm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 5 parts by weight per 100 parts by weight of the active material particles.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を３０分間に変更したこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料βとした。成長したカーボンナノファイバは、およそ繊維長１０μｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１０重量部であった。   The same operation as in Example 10 was performed except that the growth time of the carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 30 minutes, and the nonaqueous electrolyte secondary battery was The electrode material was β. The grown carbon nanofibers had a fiber length of about 10 μm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 10 parts by weight per 100 parts by weight of the active material particles.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を６０分間に変更したこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料γとした。成長したカーボンナノファイバは、およそ繊維長５０μｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり３０重量部であった。   The same operation as in Example 10 was performed except that the growth time of carbon nanofibers in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas was changed to 60 minutes, and the nonaqueous electrolyte secondary battery was The electrode material was γ. The grown carbon nanofibers had a fiber length of about 50 μm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 30 parts by weight per 100 parts by weight of the active material particles.

水素ガス５０体積％とメタンガス５０体積％との混合ガス中での、カーボンナノファイバの成長時間を９０分間に変更したこと以外、実施例１０と同様の操作を行い、非水電解質二次電池の電極材料δとした。成長したカーボンナノファイバは、およそ繊維長１００μｍ、繊維径８０ｎｍであった。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり５０重量部であった。   The same operation as in Example 10 was performed except that the carbon nanofiber growth time was changed to 90 minutes in a mixed gas of 50% by volume of hydrogen gas and 50% by volume of methane gas, and the nonaqueous electrolyte secondary battery was The electrode material was designated as δ. The grown carbon nanofibers had a fiber length of about 100 μm and a fiber diameter of 80 nm. The amount of the grown carbon nanofiber was 50 parts by weight per 100 parts by weight of the active material particles.

［評価］
実施例２１〜２４で製造された電極材料を用いて、実施例９と同様のコイン型リチウムイオン電池を作製し、実施例９と同様に、活物質重量当たりの初期放電容量、放電効率、およびサイクル効率を求めた。結果を表４に示す。 [Evaluation]
Using the electrode materials manufactured in Examples 21 to 24, a coin-type lithium ion battery similar to that in Example 9 was produced, and as in Example 9, the initial discharge capacity per active material weight, the discharge efficiency, and Cycle efficiency was determined. The results are shown in Table 4.

関東化学（株）製の硝酸ニッケル６水和物（特級）１ｇをイオン交換水１００ｇに溶解させた。得られた溶液を、１０μｍ以下に粉砕した（株）高純度化学研究所製のケイ素粒子１００ｇと混合した。この混合物を１時間攪拌後、エバポレータ装置で水分を除去することで、ケイ素粒子の表面に硝酸ニッケルを担持させた。
硝酸ニッケルを担持したケイ素粒子を、セラミック製反応容器に投入し、ヘリウムガス存在下で５５０℃まで昇温させた。その後、ヘリウムガスを水素ガス２０体積％とエチレンガス８０体積％の混合ガスに置換し、反応容器内を５４０℃で、３時間保持した。その結果、ケイ素粒子の表面に、およそ繊維径８０ｎｍで、繊維長５００μｍのへーリング・ボーン状のカーボンナノファイバが成長した。その後、混合ガスをヘリウムガスに置換し、反応容器内を室温になるまで冷却させた。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１００重量部であった。ここでもＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。 1 g of nickel nitrate hexahydrate (special grade) manufactured by Kanto Chemical Co., Ltd. was dissolved in 100 g of ion-exchanged water. The obtained solution was mixed with 100 g of silicon particles manufactured by Kojundo Chemical Lab. After stirring this mixture for 1 hour, the water was removed by an evaporator device, thereby supporting nickel nitrate on the surface of the silicon particles.
Silicon particles carrying nickel nitrate were put into a ceramic reaction vessel and heated to 550 ° C. in the presence of helium gas. Thereafter, the helium gas was replaced with a mixed gas of 20% by volume of hydrogen gas and 80% by volume of ethylene gas, and the inside of the reaction vessel was held at 540 ° C. for 3 hours. As a result, a herringbone carbon nanofiber having a fiber diameter of about 80 nm and a fiber length of 500 μm was grown on the surface of the silicon particle. Thereafter, the mixed gas was replaced with helium gas, and the inside of the reaction vessel was cooled to room temperature. The amount of the grown carbon nanofiber was 100 parts by weight per 100 parts by weight of the active material particles. Here too, SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

［評価］
実施例２５で製造された電極材料を用いて、実施例１と同様の負極を作製した。得られた負極に、抵抗加熱によるリチウム蒸着装置を用いて、不可逆容量に相当するリチウムを付与した。
ＬｉＮｉ0.8Ｃｏ0.17Ａｌ0.03Ｏ2を１００重量部と、ポリフッ化ビニリデンからなる結着剤を１０重量部と、カーボンブラックを５重量部と、適量のＮ−メチル−２−ピロリドン（ＮＭＰ）とを混合して、正極合剤スラリーを調製した。このスラリーを、厚さ１５μｍのＡｌ箔上にキャスティングし、乾燥後、正極合剤を圧延して、正極合剤層を形成し、正極を得た。
こうして得られたリチウムを導入した負極を用い、正極活物質としてＬｉＮｉ0.8Ｃｏ0.17Ａｌ0.03Ｏ2を含む正極を用いたこと以外、実施例１と同様にして、コイン型リチウムイオン電池を作製し、実施例１と同様に評価した。その結果、負極活物質重量当たりの初期放電容量は３８０１ｍＡｈ／ｇ、放電効率は８６％、サイクル効率は９１％であった。 [Evaluation]
Using the electrode material produced in Example 25, a negative electrode similar to Example 1 was produced. Lithium corresponding to irreversible capacity was imparted to the obtained negative electrode using a lithium vapor deposition apparatus by resistance heating.
100 parts by weight of LiNi 0.8 Co 0.17 Al 0.03 O 2 , 10 parts by weight of a binder made of polyvinylidene fluoride, 5 parts by weight of carbon black, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) The mixture was mixed to prepare a positive electrode mixture slurry. The slurry was cast on an Al foil having a thickness of 15 μm, and after drying, the positive electrode mixture was rolled to form a positive electrode mixture layer, whereby a positive electrode was obtained.
A coin-type lithium ion battery was produced in the same manner as in Example 1 except that the thus obtained negative electrode into which lithium was introduced and a positive electrode containing LiNi 0.8 Co 0.17 Al 0.03 O 2 as a positive electrode active material was used. Evaluation was performed in the same manner as in Example 1. As a result, the initial discharge capacity per negative electrode active material weight was 3801 mAh / g, the discharge efficiency was 86%, and the cycle efficiency was 91%.

なお、負極へのリチウムの導入方法は、上記に限らず、例えば負極にリチウム箔を貼り付けてから電池を組み立てたり、電池内にリチウム粉末を導入したりしてもよい。   The method of introducing lithium into the negative electrode is not limited to the above, and for example, a battery may be assembled after a lithium foil is attached to the negative electrode, or lithium powder may be introduced into the battery.

１０μｍ以下に粉砕した（株）高純度化学研究所製のケイ素粒子を、空気中で、６００℃で、１時間加熱し、ケイ素粒子の表面に厚さ２０ｎｍの酸化ケイ素層を形成した。得られた酸化ケイ素層を有するケイ素粒子を用いたこと以外、実施例１と同様の操作を行った。その結果、酸化ケイ素層を有するケイ素粒子の表面には、およそ繊維径８０ｎｍで、繊維長５００μｍのチューブ状のカーボンナノファイバが成長した。成長したカーボンナノファイバの量は、活物質粒子１００重量部あたり１００重量部であった。ここでもＳＥＭ観察では、繊維径約８０ｎｍのファイバの他に、繊維径３０ｎｍ以下の微細なファイバの存在が確認された。   Silicon particles manufactured by Kojundo Chemical Laboratory Co., Ltd., pulverized to 10 μm or less, were heated in air at 600 ° C. for 1 hour to form a silicon oxide layer having a thickness of 20 nm on the surface of the silicon particles. The same operation as in Example 1 was performed except that the obtained silicon particles having a silicon oxide layer were used. As a result, tubular carbon nanofibers having a fiber diameter of about 80 nm and a fiber length of 500 μm were grown on the surface of the silicon particles having the silicon oxide layer. The amount of the grown carbon nanofiber was 100 parts by weight per 100 parts by weight of the active material particles. Here too, SEM observation confirmed the presence of fine fibers having a fiber diameter of 30 nm or less in addition to fibers having a fiber diameter of about 80 nm.

得られた電極材料を用いて、実施例１と同様にして、コイン型リチウムイオン電池を作製し、実施例１と同様に評価したところ、活物質重量当たりの初期放電容量は３８００ｍＡｈ／ｇ、放電効率は９０％、サイクル効率は９５％であった。   Using the obtained electrode material, a coin-type lithium ion battery was produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity per active material weight was 3800 mAh / g, and discharge was performed. The efficiency was 90% and the cycle efficiency was 95%.

本発明は、電気化学素子の電極に用いられる活物質粒子の全般に適用可能である。本発明は、優れた初期充放電特性もしくはサイクル特性を有する非水電解質二次電池やキャパシタを与える複合粒子（電極材料）を提供するものである。本発明は、非水電解質二次電池の正極活物質および負極活物質、さらにはキャパシタの活物質（誘電材料）のいずれを改良する場合に対しても効果があり、活物質の種類も特に限定されない。   The present invention is applicable to all active material particles used for electrodes of electrochemical devices. The present invention provides a composite particle (electrode material) that provides a nonaqueous electrolyte secondary battery or capacitor having excellent initial charge / discharge characteristics or cycle characteristics. INDUSTRIAL APPLICABILITY The present invention is effective for improving both the positive electrode active material and negative electrode active material of a nonaqueous electrolyte secondary battery, and further the active material (dielectric material) of a capacitor, and the type of active material is also particularly limited Not.

本発明の複合粒子の構造を概念的に示す図である。It is a figure which shows notionally the structure of the composite particle of this invention. 本発明の別の複合粒子の構造を概念的に示す図である。It is a figure which shows notionally the structure of another composite particle of this invention. 実施例１で得られた複合粒子表面の５００倍拡大ＳＥＭ写真である。2 is a 500 times magnified SEM photograph of the composite particle surface obtained in Example 1. FIG. 実施例１で得られた複合粒子表面の要部の５００００倍拡大ＳＥＭ写真である。3 is a 50000 times magnified SEM photograph of the main part of the composite particle surface obtained in Example 1. FIG. 実施例１で得られた複合粒子表面の要部の３００００倍拡大ＳＥＭ写真である。3 is a 30000 times enlarged SEM photograph of the main part of the composite particle surface obtained in Example 1. FIG.

符号の説明Explanation of symbols

１０ 複合粒子
１１ 活物質粒子
１２ 触媒粒子
１３ カーボンナノファイバ
２０ 複合粒子
２１ 活物質粒子
２２ 触媒粒子
２３ カーボンナノファイバ
３１ 活物質粒子
３２ 大きいカーボンナノファイバ
３３ 微細カーボンナノファイバ DESCRIPTION OF SYMBOLS 10 Composite particle 11 Active material particle 12 Catalyst particle 13 Carbon nanofiber 20 Composite particle 21 Active material particle 22 Catalyst particle 23 Carbon nanofiber 31 Active material particle 32 Large carbon nanofiber 33 Fine carbon nanofiber

Claims (20)

活物質粒子、前記活物質粒子の表面に結合したカーボンナノファイバ、および、カーボンナノファイバの成長を促進する触媒元素を含み、前記活物質粒子が、電気化学的活性相からなる、電極用複合粒子。   Electrode composite particles comprising active material particles, carbon nanofibers bonded to the surface of the active material particles, and a catalytic element that promotes the growth of the carbon nanofibers, wherein the active material particles comprise an electrochemically active phase . 前記触媒元素が、Ａｕ、Ａｇ、Ｐｔ、Ｒｕ、Ｉｒ、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種である、請求項１記載の電極用複合粒子。   The composite particle for electrodes according to claim 1, wherein the catalyst element is at least one selected from the group consisting of Au, Ag, Pt, Ru, Ir, Cu, Fe, Co, Ni, Mo, and Mn. 前記触媒元素が、少なくとも前記活物質粒子の表層部またはカーボンナノファイバの先端に存在する、請求項１記載の電極用複合粒子。   The composite particle for an electrode according to claim 1, wherein the catalytic element is present at least at a surface layer portion of the active material particle or at a tip of the carbon nanofiber. 前記触媒元素が、前記活物質粒子の表層部に、粒径１ｎｍ〜１０００ｎｍの金属粒子または／および金属酸化物粒子の状態で存在する、請求項１記載の電極用複合粒子。   2. The composite particle for an electrode according to claim 1, wherein the catalyst element is present in a state of metal particles and / or metal oxide particles having a particle diameter of 1 nm to 1000 nm in a surface layer portion of the active material particles. 前記カーボンナノファイバの少なくとも一端が、前記活物質粒子の表面と化学結合している、請求項１記載の電極用複合粒子。   The composite particle for an electrode according to claim 1, wherein at least one end of the carbon nanofiber is chemically bonded to a surface of the active material particle. 前記カーボンナノファイバの繊維長が、１ｎｍ〜１ｍｍである、請求項１記載の電極用複合粒子。   The composite particle for an electrode according to claim 1, wherein a fiber length of the carbon nanofiber is 1 nm to 1 mm. 前記カーボンナノファイバが、繊維径１ｎｍ〜４０ｎｍのファイバを含む、請求項１記載の電極用複合粒子。   The composite particle for an electrode according to claim 1, wherein the carbon nanofiber includes a fiber having a fiber diameter of 1 nm to 40 nm. 前記カーボンナノファイバが、チューブ状カーボン、アコーディオン状カーボン、プレート状カーボンおよびヘーリング・ボーン状カーボンよりなる群から選択される少なくとも１種からなる、請求項１記載の電極用複合粒子。   2. The composite particle for an electrode according to claim 1, wherein the carbon nanofiber comprises at least one selected from the group consisting of tubular carbon, accordion carbon, plate carbon and herringbone carbon. 前記電気化学的活性相が、周期律表３Ｂ、４Ｂおよび５Ｂ族元素よりなる群から選択される少なくとも１種の金属もしくは半金属元素を含み、前記金属もしくは半金属元素を含む相が、化合物、合金または単体である、請求項１記載の電極用複合粒子。   The electrochemically active phase contains at least one metal or metalloid element selected from the group consisting of elements of the periodic tables 3B, 4B and 5B, and the phase containing the metal or metalloid element comprises a compound, The composite particle for an electrode according to claim 1, which is an alloy or a simple substance. 前記化合物が、酸化物、窒化物、酸窒化物、炭化物および硫化物よりなる群から選択される少なくとも１種である、請求項９記載の電極用複合粒子。   The composite particle for an electrode according to claim 9, wherein the compound is at least one selected from the group consisting of oxide, nitride, oxynitride, carbide and sulfide. 前記金属もしくは半金属元素が、Ｓｉ、ＳｎおよびＧｅよりなる群から選択される少なくとも１種であり、前記化合物が、酸化物、窒化物および酸窒化物よりなる群から選択される少なくとも１種である、請求項９記載の電極用複合粒子。   The metal or metalloid element is at least one selected from the group consisting of Si, Sn and Ge, and the compound is at least one selected from the group consisting of oxide, nitride and oxynitride. The composite particle for an electrode according to claim 9. 前記活物質粒子が、周期律表３Ｂ、４Ｂおよび５Ｂ族元素よりなる群から選択される少なくとも１種の金属もしくは半金属元素の単体からなる核と、前記核の表面を被覆する酸化物層とを有する、請求項１記載の電極用複合粒子。   A core composed of at least one metal or metalloid element selected from the group consisting of Group 3B, 4B and 5B elements of the periodic table, and an oxide layer covering the surface of the core; The composite particle for an electrode according to claim 1, comprising: 前記電気化学的活性相が、層状構造を有するリチウム含有遷移金属酸化物であり、前記リチウム含有遷移金属酸化物が、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素を含む、請求項１記載の電極用複合粒子。   The electrochemically active phase is a lithium-containing transition metal oxide having a layered structure, and the lithium-containing transition metal oxide is at least one selected from the group consisting of Cu, Fe, Co, Ni, Mo, and Mn. The composite particle for an electrode according to claim 1, comprising a seed metal element. 電気化学的活性相からなり、少なくとも表層部に、カーボンナノファイバの成長を促進する触媒元素を有する活物質粒子を調製する工程Ａ、
炭素含有ガスを含む雰囲気中で、前記活物質粒子の表面にカーボンナノファイバを成長させる工程Ｂ、および
不活性ガス雰囲気中で、前記カーボンナノファイバが結合した活物質粒子を４００℃以上１６００℃以下で焼成する工程Ｃ、を含む、電極用複合粒子の製造法。 Step A, comprising an electrochemically active phase and preparing active material particles having a catalytic element that promotes the growth of carbon nanofibers at least on the surface layer portion,
Step B of growing carbon nanofibers on the surface of the active material particles in an atmosphere containing a carbon-containing gas, and active material particles bonded with the carbon nanofibers in an inert gas atmosphere are 400 ° C. or higher and 1600 ° C. or lower. The manufacturing method of the composite particle for electrodes including the process C baked with. 工程Ａが、電気化学的活性相からなる粒子の表面に、Ａｕ、Ａｇ、Ｐｔ、Ｒｕ、Ｉｒ、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素からなる粒子を担持する工程を有する、請求項１４記載の電極用複合粒子の製造法。   Step A includes at least one metal element selected from the group consisting of Au, Ag, Pt, Ru, Ir, Cu, Fe, Co, Ni, Mo, and Mn on the surface of the particle including the electrochemically active phase. The method for producing composite particles for an electrode according to claim 14, comprising a step of supporting particles comprising 工程Ａが、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素を含む電気化学的活性相からなる粒子の表面を還元する工程を有する、請求項１４記載の電極用複合粒子の製造法。   The step A has a step of reducing the surface of the particle composed of an electrochemically active phase containing at least one metal element selected from the group consisting of Cu, Fe, Co, Ni, Mo and Mn. The manufacturing method of the composite particle for electrodes as described. 工程Ａが、周期律表３Ｂ、４Ｂおよび５Ｂ族元素よりなる群から選ばれる少なくとも１種の金属もしくは半金属元素と、Ｃｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択される少なくとも１種の金属元素との合金粒子を合成する工程を有する、請求項１４記載の電極用複合粒子の製造法。   Step A is at least one metal or metalloid element selected from the group consisting of Group 3B, 4B and 5B elements of the periodic table, and at least selected from the group consisting of Cu, Fe, Co, Ni, Mo and Mn The manufacturing method of the composite particle for electrodes of Claim 14 which has the process of synthesize | combining the alloy particle with 1 type of metal elements. 工程Ｃの後、さらに、大気中で、前記複合粒子を１００℃以上、４００℃以下で熱処理する工程、を有する、請求項１４記載の電極用複合粒子の製造法。   The method for producing composite particles for an electrode according to claim 14, further comprising a step of heat-treating the composite particles at 100 ° C. or more and 400 ° C. or less in the atmosphere after Step C. 前記触媒元素が、Ｎｉであり、前記炭素含有ガスが、エチレンであり、前記カーボンナノファイバが、へーリング・ボーン状である、請求項１４記載の電極用複合粒子の製造法。   The method for producing composite particles for an electrode according to claim 14, wherein the catalytic element is Ni, the carbon-containing gas is ethylene, and the carbon nanofibers are in a herringbone shape. 充放電が可能な正極、充放電が可能な負極、および非水電解質を含み、
前記正極および前記負極の少なくとも一方が、請求項１記載の複合粒子を含む、非水電解質二次電池。



Including a positive electrode capable of charge / discharge, a negative electrode capable of charge / discharge, and a non-aqueous electrolyte,
The nonaqueous electrolyte secondary battery in which at least one of the positive electrode and the negative electrode includes the composite particles according to claim 1.



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