JP2007227138A - Electrode for nonaqueous secondary battery, and non-aqueous electrolyte secondary battery using the same - Google Patents

Electrode for nonaqueous secondary battery, and non-aqueous electrolyte secondary battery using the same Download PDF

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JP2007227138A
JP2007227138A JP2006046553A JP2006046553A JP2007227138A JP 2007227138 A JP2007227138 A JP 2007227138A JP 2006046553 A JP2006046553 A JP 2006046553A JP 2006046553 A JP2006046553 A JP 2006046553A JP 2007227138 A JP2007227138 A JP 2007227138A
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active material
secondary battery
electrolyte secondary
nucleus
negative electrode
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Kaoru Inoue
薫 井上
Gohei Suzuki
剛平 鈴木
Kazusato Fujikawa
万郷 藤川
Takayuki Shirane
隆行 白根
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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
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    • Y02E60/10—Energy storage using batteries

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery provided with high capacity and practical cycle characteristics, by using a compound active material in which carbon nanofibers (CNFs) are made to adhere to a preferred active material nucleus for increasing its capacity. <P>SOLUTION: In a negative electrode for the nonaqueous electrolyte secondary battery, a first compound negative electrode active material 34A, containing a first active material nucleus 35A to which the first CNF 36A of a large compressive stress, is adhered, and a second compound negative electrode active material 34B, containing a second active material nucleus 35B to which a second CNF 36B of a small compressive stress is adhered, are provided mixedly. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、非水電解質二次電池に関し、より詳しくはカーボンナノファイバを活物質核に付着させた複合負極活物質を含む非水電解質二次電池用電極とそれを用いた非水電解質二次電池に関する。   The present invention relates to a non-aqueous electrolyte secondary battery, and more specifically, a non-aqueous electrolyte secondary battery electrode including a composite negative electrode active material in which carbon nanofibers are attached to an active material core, and a non-aqueous electrolyte secondary battery using the same It relates to batteries.

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、黒鉛などの炭素材料が非水電解質二次電池の負極活物質として実用化されている。しかしながらその理論容量密度は３７２ｍＡｈ／ｇである。そこで、さらに非水電解質二次電池を高エネルギー密度化するために、リチウムと合金化するケイ素（Ｓｉ）、スズ（Ｓｎ）、ゲルマニウム（Ｇｅ）やこれらの酸化物および合金などが検討されている。これらの負極活物質材料の理論容量密度は、炭素材料に比べて大きい。特にＳｉ粒子や酸化ケイ素粒子などの含ケイ素粒子は安価なため、幅広く検討されている。   As electronic devices become more portable and cordless, expectations for non-aqueous electrolyte secondary batteries that are small and lightweight and have high energy density are increasing. Currently, carbon materials such as graphite are put into practical use as negative electrode active materials for non-aqueous electrolyte secondary batteries. However, its theoretical capacity density is 372 mAh / g. Therefore, silicon (Si), tin (Sn), germanium (Ge), and oxides and alloys thereof, which are alloyed with lithium, are being studied in order to further increase the energy density of nonaqueous electrolyte secondary batteries. . The theoretical capacity density of these negative electrode active material materials is larger than that of carbon materials. In particular, silicon-containing particles such as Si particles and silicon oxide particles are widely studied because they are inexpensive.

しかしながら、通常非水電解質二次電池の負極活物質として用いられる炭素材料は放電状態における体積に対する充電状態における体積の比が１．１以下であるのに対し、理論容量密度が炭素材料より大きく８３３ｍＡｈ／ｃｍ３を超えるこれらの材料では１．２以上の大きな体積変化が起こる。この大きな体積変化により活物質粒子は微粉化し、その結果、活物質粒子間の導電性が低下する。そのため、充分な充放電サイクル特性（以下、「サイクル特性」という）が得られていない。 However, the carbon material normally used as the negative electrode active material of the non-aqueous electrolyte secondary battery has a ratio of the volume in the charged state to the volume in the discharged state of 1.1 or less, whereas the theoretical capacity density is larger than that of the carbon material and is 833 mAh. For these materials above / cm 3 , a large volume change of 1.2 or more occurs. Due to this large volume change, the active material particles are pulverized, and as a result, the conductivity between the active material particles is lowered. Therefore, sufficient charge / discharge cycle characteristics (hereinafter referred to as “cycle characteristics”) are not obtained.

そこでリチウム合金を形成しうる金属または半金属を含む粒子を活物質核に、複数の炭素繊維を結合させて複合粒子化させることが提案されている。この構成では、活物質核の体積変化が起こっても導電性が確保され、サイクル特性が維持できることが報告されている（例えば、特許文献１）。
特開２００４−３４９０５６号公報 Thus, it has been proposed to combine a plurality of carbon fibers into composite particles by using particles containing a metal or semimetal capable of forming a lithium alloy as an active material nucleus. In this configuration, it has been reported that conductivity is ensured and cycle characteristics can be maintained even if the volume of the active material nucleus changes (for example, Patent Document 1).
JP 2004-349056 A

しかしながらリチウム合金を形成しうる金属または半金属を含む活物質核に、複数の炭素繊維を結合させて複合粒子化させた場合でも、無作為に炭素繊維を配置すると、充電時に膨張した活物質核が放電時に収縮することで炭素繊維同士が互いに遠ざかる。したがって充放電を繰り返すと接触していた炭素繊維同士が徐々に非接触の状態になる。そのため充放電を繰り返すほど負極中の導電性が低下し、充放電容量が低下する。すなわち、サイクル特性が低い。   However, even when a plurality of carbon fibers are bonded to an active material nucleus containing a metal or metalloid capable of forming a lithium alloy to form composite particles, if carbon fibers are randomly arranged, the active material nucleus expanded during charging. The carbon fibers are moved away from each other by shrinking during discharge. Therefore, when charging and discharging are repeated, the carbon fibers that have been in contact with each other gradually become in a non-contact state. Therefore, the electrical conductivity in a negative electrode falls, and charging / discharging capacity falls, so that charging / discharging is repeated. That is, the cycle characteristics are low.

本発明は、上記の課題を解決するものであり、高容量密度を有する活物質核を用い、サイクル特性を改善することで高容量かつ長寿命な非水電解質二次電池を実現する非水電解質二次電池用負極を提供することを目的とする。   The present invention solves the above problems, and uses a non-aqueous electrolyte that realizes a high-capacity and long-life non-aqueous electrolyte secondary battery by using an active material nucleus having a high capacity density and improving cycle characteristics. It aims at providing the negative electrode for secondary batteries.

上記目的を達成するために本発明の非電解質二次電池用電極は、活物質核に圧縮応力の大きいカーボンナノファイバ（ＣＮＦ）が付着した複合活物質と、活物質核に圧縮応力の小さいＣＮＦが付着した複合活物質とを含むことを特徴とする。ここで活物質核の放電状態における体積Ｂに対する充電状態における体積Ａの比Ａ／Ｂは、１．２以上であり、その理論容量密度は炭素材料より大きく８３３ｍＡｈ／ｃｍ３を超える。 In order to achieve the above object, the electrode for a non-electrolyte secondary battery of the present invention includes a composite active material in which carbon nanofibers (CNF) having a large compressive stress are attached to an active material nucleus, and a CNF having a small compressive stress to the active material nucleus. And a composite active material to which is attached. Here, the ratio A / B of the volume A in the charged state to the volume B in the discharged state of the active material nucleus is 1.2 or more, and its theoretical capacity density is larger than that of the carbon material and exceeds 833 mAh / cm 3 .

圧縮応力の大きいＣＮＦは形状の維持性が高く、隣接する複合活物質の他のＣＮＦと絡んで互いの接触を保てる半面、圧縮応力の大きさゆえに充電時に活物質核が膨張した際にＣＮＦの反発力が強いために、隣接する複合活物質を弾き返し、負極の変形を促す。そこで圧縮応力の小さいＣＮＦを適量活用し、上述した反発力を抑制することにより、高容量ながら充放電によって膨張・収縮する活物質核を用いた場合でも、非水電解質二次電池のサイクル特性を実用的なレベルに高めることができる。   CNF with high compressive stress has high maintainability of the shape and can be kept in contact with other CNFs of the adjacent composite active material. On the other hand, when the active material nucleus expands during charging due to the large compressive stress, Since the repulsive force is strong, it repels the adjacent composite active material and promotes deformation of the negative electrode. Therefore, by utilizing an appropriate amount of CNF with a small compressive stress and suppressing the repulsive force described above, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved even when using an active material core that expands and contracts due to charge and discharge despite its high capacity. Can be raised to a practical level.

本発明の非水電解質二次電池用電極を用いれば、高容量と実用的なサイクル特性とを実現することができる非水電解質二次電池を提供することができる。   If the electrode for nonaqueous electrolyte secondary batteries of this invention is used, the nonaqueous electrolyte secondary battery which can implement | achieve high capacity | capacitance and practical cycling characteristics can be provided.

本発明の第１の発明は、リチウムイオンの吸蔵・放出が可能な第１の活物質核に第１のＣＮＦが付着した第１の複合活物質と、リチウムイオンの吸蔵・放出が可能な第２の活物質核に第１のＣＮＦより圧縮応力の小さい第２のＣＮＦが付着した第２の複合活物質とを有する非水電解質二次電池用電極である。第１、第２の活物質核の放電状態における体積Ｂに対する充電状態における体積Ａの比Ａ／Ｂは、１．２以上である。第１の活物質核に付着した圧縮応力の大きい第１のＣＮＦは他のＣＮＦと絡んで互いの接触を保てる。ここへ圧縮応力の小さい第２のＣＮＦが付着した第２の活物質核を含む第２の複合活物質を添加することにより、第１の活物質核の膨張に伴う第１のＣＮＦの反発を抑制することにより、高容量ながら充放電によって膨張・収縮する活物質核を用いた場合でも、非水電解質二次電池のサイクル特性を実用的なレベルに高めることができる。   According to a first aspect of the present invention, there is provided a first composite active material in which a first CNF is attached to a first active material nucleus capable of occluding and releasing lithium ions, and a first composite active material capable of occluding and releasing lithium ions. This is an electrode for a nonaqueous electrolyte secondary battery having a second composite active material in which a second CNF having a compressive stress smaller than that of the first CNF is attached to the second active material nucleus. The ratio A / B of the volume A in the charged state to the volume B in the discharged state of the first and second active material nuclei is 1.2 or more. The first CNF having a large compressive stress attached to the first active material nucleus is entangled with other CNFs and can maintain mutual contact. By adding the second composite active material including the second active material nucleus to which the second CNF having a small compressive stress is attached, the repulsion of the first CNF accompanying the expansion of the first active material nucleus is prevented. By suppressing, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved to a practical level even when an active material core that expands and contracts by charge and discharge with high capacity is used.

本発明の第２の発明は、第１の発明において第１のＣＮＦと第２のＣＮＦとは実質的に同程度のバネ定数を有するとともに第２のＣＮＦは第１のＣＮＦより短い非水電解質二次電池用負極である。この構成はＣＮＦの成長時間を変えることにより第１の発明を容易に具現化できる一手段である。   According to a second aspect of the present invention, in the first aspect, the first CNF and the second CNF have substantially the same spring constant, and the second CNF is shorter than the first CNF. It is a negative electrode for secondary batteries. This configuration is one means that can easily embody the first invention by changing the growth time of CNF.

本発明の第３の発明は、第１の発明において第１の活物質核の平均粒径と第２の活物質核の平均粒径とが実質的に同等であり、複合活物質全体に占める第１の複合活物質の重量比率を３０％以上、５０％以下とした非水電解質二次電池用負極である。第１の活物質核の平均粒径と第２の活物質核の平均粒径とが実質的に同等な場合、このような重量比率とすることによりＣＮＦ同士の接触を保ちつつ、第１のＣＮＦによる反発が抑制されるためサイクル特性向上の観点から好ましい。   In the third invention of the present invention, in the first invention, the average particle diameter of the first active material nucleus and the average particle diameter of the second active material nucleus are substantially equal, and occupy the entire composite active material. A negative electrode for a non-aqueous electrolyte secondary battery in which the weight ratio of the first composite active material is 30% or more and 50% or less. When the average particle diameter of the first active material nucleus and the average particle diameter of the second active material nucleus are substantially equal, the weight ratio is such that the CNFs are kept in contact with each other. Since repulsion by CNF is suppressed, it is preferable from the viewpoint of improving cycle characteristics.

本発明の第４の発明は、第１の発明において第１の活物質核の平均粒径を、第２の活物質核の平均粒径より大きくした非水電解質二次電池用負極である。活物質核の平均粒径を異ならせることにより、負極構成時に粒径の小さい第２の活物質核を有する第２の複合活物質が平均粒径の大きい第１の活物質核を有する第１の複合活物質同士の隙間に配置されるので、第１、第２の複合活物質の充填性が向上するのと同時に、その表面に付着させたＣＮＦ同士が接触する機会を増すことができる。そのため高容量化とサイクル特性の向上との観点から好ましい。   A fourth invention of the present invention is a negative electrode for a non-aqueous electrolyte secondary battery in which the average particle diameter of the first active material nucleus is larger than the average particle diameter of the second active material nucleus in the first invention. By making the average particle diameter of the active material nuclei different, the second composite active material having the second active material nuclei having a small particle diameter when the negative electrode is configured has the first active material nuclei having the large average particle diameter. Since it is arranged in the gap between the composite active materials, the filling properties of the first and second composite active materials are improved, and at the same time, the chances of contacting CNFs attached to the surfaces thereof can be increased. Therefore, it is preferable from the viewpoint of increasing the capacity and improving the cycle characteristics.

本発明の第５の発明は、第４の発明において複合活物質全体に占める第１の複合活物質の重量比率を第２の複合活物質の重量比率より大きくした非水電解質二次電池用負極である。第４の発明の効果が顕著に発揮されるのは平均粒径の小さい第２の活物質核を有する第２の複合活物質が平均粒径の大きい第１の活物質核を有する第１の複合活物質同士の隙間に配置される状態の存在確率が大きい場合である。したがって第１の複合活物質の重量比率が第２の複合活物質の重量比率より大きいことが好ましい。   According to a fifth aspect of the present invention, there is provided a negative electrode for a non-aqueous electrolyte secondary battery in which the weight ratio of the first composite active material in the total composite active material in the fourth invention is greater than the weight ratio of the second composite active material. It is. The effect of the fourth invention is remarkably exhibited when the second composite active material having the second active material nucleus having a small average particle diameter has the first active material nucleus having the large average particle diameter. This is a case where the existence probability of the state of being arranged in the gap between the composite active materials is large. Therefore, the weight ratio of the first composite active material is preferably larger than the weight ratio of the second composite active material.

本発明の第６の発明は、第５の発明において第１の複合活物質の重量比率を７０％以上、９０％以下とした非水電解質二次電池用負極である。このような重量比率で第１の活物質核を用いることにより、より顕著に第４の発明の効果が得られる。   The sixth invention of the present invention is a negative electrode for a non-aqueous electrolyte secondary battery in which the weight ratio of the first composite active material is 70% or more and 90% or less in the fifth invention. By using the first active material nucleus in such a weight ratio, the effect of the fourth invention can be obtained more remarkably.

本発明の第７の発明は、第１の発明において第２の活物質核の平均粒径を、第１の活物質核の平均粒径より大きくした非水電解質二次電池用負極である。活物質核の平均粒径を異ならせることにより、負極構成時に粒径の小さい第１の活物質核を有する第１の複合活物質が平均粒径の大きい第２の活物質核を有する第２の複合活物質同士の隙間に配置されるので、第１、第２の複合活物質の充填性が向上する。また、平均粒径の大きい第２の活物質核からなる第２の複合活物質は、第２の活物質核の粒径が第２の複合活物質の粒径に対して相対的に大きくなるために圧縮応力が小さくなる。したがって第２の活物質核に付着した第２のＣＮＦによる反発で引き起こされる負極の膨張は小さくなる。このように高容量化とサイクル特性の向上との観点から好ましい。   A seventh invention of the present invention is the negative electrode for a non-aqueous electrolyte secondary battery in which the average particle diameter of the second active material nucleus is larger than the average particle diameter of the first active material nucleus in the first invention. By making the average particle size of the active material nuclei different, the first composite active material having the first active material nuclei having a small particle size when the negative electrode is configured has the second active material nuclei having the large average particle size. Therefore, the filling properties of the first and second composite active materials are improved. Further, in the second composite active material composed of the second active material core having a large average particle size, the particle size of the second active material core is relatively larger than the particle size of the second composite active material. Therefore, the compressive stress is reduced. Therefore, the expansion of the negative electrode caused by the repulsion by the second CNF attached to the second active material nucleus is reduced. Thus, it is preferable from the viewpoint of increasing the capacity and improving the cycle characteristics.

本発明の第８の発明は、第７の発明において複合活物質全体に占める第２の複合活物質の重量比率を第１の複合活物質の重量比率より大きくした非水電解質二次電池用負極である。第７の発明の効果が顕著に発揮されるのは平均粒径の小さい第１の活物質核を有する第１の複合活物質が平均粒径の大きい第２の活物質核を有する第２の複合活物質同士の隙間に配置される状態の存在確率が大きい場合である。したがって第２の複合活物質の重量比率が第１の複合活物質の重量比率より大きいことが好ましい。   According to an eighth aspect of the present invention, there is provided a negative electrode for a non-aqueous electrolyte secondary battery in which the weight ratio of the second composite active material in the total composite active material in the seventh invention is greater than the weight ratio of the first composite active material. It is. The effect of the seventh invention is remarkably exhibited when the first composite active material having the first active material nucleus having a small average particle diameter has the second active material nucleus having the large average particle diameter. This is a case where the existence probability of the state of being arranged in the gap between the composite active materials is large. Accordingly, the weight ratio of the second composite active material is preferably larger than the weight ratio of the first composite active material.

本発明の第９の発明は、第８の発明において第２の複合活物質の重量比率を７０％以上、９０％以下とした非水電解質二次電池用負極である。このような重量比率で第２の複合活物質を用いることにより、より顕著に第７の発明の効果が得られる。   A ninth invention of the present invention is a negative electrode for a non-aqueous electrolyte secondary battery in which the weight ratio of the second composite active material is 70% or more and 90% or less in the eighth invention. By using the second composite active material at such a weight ratio, the effect of the seventh invention can be obtained more remarkably.

本発明の第１０の発明は、第１の発明において第１の活物質核と第２の活物質核とを実質的に同じ物質とした非水電解質二次電池用負極である。このように単一の活物質核を用いれば充放電反応も単一になるため充放電時の電圧変動も比較的単純になる。   A tenth aspect of the present invention is a negative electrode for a non-aqueous electrolyte secondary battery in which the first active material nucleus and the second active material nucleus are substantially the same in the first invention. In this way, if a single active material nucleus is used, the charge / discharge reaction becomes single, so that the voltage fluctuation during charge / discharge becomes relatively simple.

本発明の第１１の発明は、第１０の発明において第１の活物質核と第２の活物質核とをケイ素を含む材料で構成した非水電解質二次電池用負極である。含ケイ素粒子は活物質核として高容量密度であるため好ましい。   An eleventh invention of the present invention is a negative electrode for a non-aqueous electrolyte secondary battery in which the first active material nucleus and the second active material nucleus are made of a material containing silicon in the tenth invention. Silicon-containing particles are preferred because of their high capacity density as active material nuclei.

本発明の第１２の発明は、第１０の発明において第１の活物質核と第２の活物質核とを酸化ケイ素とし、ケイ素に対する酸素の比率を０．３以上、１．３以下とした非水電解質二次電池用負極である。含ケイ素粒子の中でもこのような組成範囲の酸化ケイ素を用いることにより、活物質容量を確保しつつ、充放電による体積変化を抑制することができる。   According to a twelfth aspect of the present invention, in the tenth aspect, the first active material nucleus and the second active material nucleus are silicon oxide, and the ratio of oxygen to silicon is 0.3 or more and 1.3 or less. It is a negative electrode for nonaqueous electrolyte secondary batteries. By using silicon oxide having such a composition range among the silicon-containing particles, volume change due to charge / discharge can be suppressed while securing the active material capacity.

本発明の第１３の発明は、上記いずれかの非水電解質二次電池用電極を用いて構成した非水電解質二次電池である。   A thirteenth aspect of the present invention is a nonaqueous electrolyte secondary battery configured using any one of the above nonaqueous electrolyte secondary battery electrodes.

以下、本発明の構成を負極に適用した実施の形態について、図面を参照しながら説明する。なお、本発明は、本明細書に記載された基本的な特徴に基づく限り、以下に記載の内容に限定されるものではない。   Hereinafter, embodiments in which the configuration of the present invention is applied to a negative electrode will be described with reference to the drawings. The present invention is not limited to the contents described below as long as it is based on the basic characteristics described in this specification.

（実施の形態１）
図１は、本発明の実施の形態１による非水電解質二次電池の断面図である。図２は、図１に示す非水電解質二次電池の負極合剤層における複合負極活物質の概念図である。このコイン型の電池は、非水電解質二次電池用電極である負極１と、負極１に対向し放電時にリチウムイオンを還元する非水電解質二次電池用第２電極である正極２と、負極１と正極２との間に介在しリチウムイオンを伝導する非水電解質３とを有する。すなわち、正極２は負極１とは異なる電位でリチウムイオンの吸蔵・放出が可能である。負極１および正極２は、非水電解質３とともにガスケット４と蓋体５とを用いてケース６内に収納されている。正極２は集電体７と正極活物質を含む正極合剤層８からなる。負極１は集電体１０と、その表面に設けられた負極合剤層１２とを有する。 (Embodiment 1)
FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention. FIG. 2 is a conceptual diagram of a composite negative electrode active material in the negative electrode mixture layer of the nonaqueous electrolyte secondary battery shown in FIG. The coin-type battery includes a negative electrode 1 that is an electrode for a nonaqueous electrolyte secondary battery, a positive electrode 2 that is a second electrode for a nonaqueous electrolyte secondary battery that faces the negative electrode 1 and reduces lithium ions during discharge, and a negative electrode 1 and a non-aqueous electrolyte 3 that conducts lithium ions. That is, the positive electrode 2 can occlude and release lithium ions at a potential different from that of the negative electrode 1. The negative electrode 1 and the positive electrode 2 are accommodated in a case 6 using a gasket 4 and a lid 5 together with a nonaqueous electrolyte 3. The positive electrode 2 includes a current collector 7 and a positive electrode mixture layer 8 including a positive electrode active material. The negative electrode 1 has a current collector 10 and a negative electrode mixture layer 12 provided on the surface thereof.

正極合剤層８はＬｉＣｏＯ２やＬｉＮｉＯ２、ＬｉＭｎ２Ｏ４、またはこれらの混合あるいは複合化合物などのような含リチウム複合酸化物を正極活物質として含む。正極活物質としては上記以外に、ＬｉＭＰＯ４（Ｍ＝Ｖ、Ｆｅ、Ｎｉ、Ｍｎ）の一般式で表されるオリビン型リン酸リチウム、Ｌｉ２ＭＰＯ４Ｆ（Ｍ＝Ｖ、Ｆｅ、Ｎｉ、Ｍｎ）の一般式で表されるフルオロリン酸リチウムなども利用可能である。さらにこれら含リチウム化合物の一部を異種元素で置換してもよい。金属酸化物、リチウム酸化物、導電剤などで表面処理してもよく、表面を疎水化処理してもよい。 The positive electrode mixture layer 8 includes a lithium-containing composite oxide such as LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , or a mixture or composite compound thereof as a positive electrode active material. In addition to the above, as the positive electrode active material, olivine type lithium phosphate represented by the general formula of LiMPO 4 (M = V, Fe, Ni, Mn), Li 2 MPO 4 F (M = V, Fe, Ni, Mn) ) Lithium fluorophosphate represented by the general formula can also be used. Further, a part of these lithium-containing compounds may be substituted with a different element. Surface treatment may be performed with a metal oxide, lithium oxide, a conductive agent, or the like, or the surface may be subjected to a hydrophobic treatment.

正極合剤層８はさらに導電剤と、結着剤とを含む。導電剤としては、天然黒鉛や人造黒鉛のグラファイト類、アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラックなどのカーボンブラック類、炭素繊維や金属繊維などの導電性繊維類、フッ化カーボン、アルミニウムなどの金属粉末類、酸化亜鉛やチタン酸カリウムなどの導電性ウィスカー類、酸化チタンなどの導電性金属酸化物、フェニレン誘導体などの有機導電性材料を用いることができる。   The positive electrode mixture layer 8 further includes a conductive agent and a binder. As the conductive agent, natural graphite and artificial graphite graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black and other carbon black, conductive fibers such as carbon fiber and metal fiber, Metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenylene derivatives can be used.

また結着剤としては、負極１に用いるものと同様のものを用いることができる。すなわち、ＰＶＤＦ、ポリテトラフルオロエチレン、ポリエチレン、ポリプロピレン、アラミド樹脂、ポリアミド、ポリイミド、ポリアミドイミド、ポリアクリルニトリル、ポリアクリル酸、ポリアクリル酸メチルエステル、ポリアクリル酸エチルエステル、ポリアクリル酸ヘキシルエステル、ポリメタクリル酸、ポリメタクリル酸メチルエステル、ポリメタクリル酸エチルエステル、ポリメタクリル酸ヘキシルエステル、ポリ酢酸ビニル、ポリビニルピロリドン、ポリエーテル、ポリエーテルサルフォン、ヘキサフルオロポリプロピレン、スチレンブタジエンゴム、カルボキシメチルセルロースなどが使用可能である。また、テトラフルオロエチレン、ヘキサフルオロエチレン、ヘキサフルオロプロピレン、パーフルオロアルキルビニルエーテル、フッ化ビニリデン、クロロトリフルオロエチレン、エチレン、プロピレン、ペンタフルオロプロピレン、フルオロメチルビニルエーテル、アクリル酸、ヘキサジエンより選択された２種以上の材料の共重合体を用いてもよい。またこれらのうちから選択された２種以上を混合して用いてもよい。   Moreover, as a binder, the thing similar to what is used for the negative electrode 1 can be used. That is, PVDF, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, polyacrylic acid hexyl ester, poly Methacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid hexyl ester, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene butadiene rubber, carboxymethylcellulose, etc. can be used It is. Two types selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene A copolymer of the above materials may be used. Two or more selected from these may be mixed and used.

正極２に用いる集電体７としては、アルミニウム（Ａｌ）、炭素、導電性樹脂などが使用可能である。またこのいずれかの材料に、カーボンなどで表面処理したものを用いてもよい。   As the current collector 7 used for the positive electrode 2, aluminum (Al), carbon, conductive resin, or the like can be used. Further, any of these materials may be surface-treated with carbon or the like.

非水電解質３には有機溶媒に溶質を溶解した非水溶液系の電解質溶液や、これらを含み高分子で非流動化されたいわゆるポリマー電解質層が適用可能である。少なくとも電解質溶液を用いる場合には正極２と負極１との間にポリエチレン、ポリプロピレン、アラミド樹脂、アミドイミド、ポリフェニレンサルファイド、ポリイミドなどからなる不織布や微多孔膜などのセパレータ（図示せず）を用い、これに電解質溶液を含浸させるのが好ましい。またセパレータの内部あるいは表面には、アルミナ、マグネシア、シリカ、チタニアなどの耐熱性フィラーを含んでもよい。セパレータとは別に、これらのフィラーと、電極に用いるのと同様の結着剤とから構成される耐熱層を設けてもよい。   As the non-aqueous electrolyte 3, a non-aqueous electrolyte solution in which a solute is dissolved in an organic solvent, or a so-called polymer electrolyte layer containing these and non-fluidized with a polymer can be applied. When using at least an electrolyte solution, a separator (not shown) such as a nonwoven fabric or a microporous film made of polyethylene, polypropylene, aramid resin, amideimide, polyphenylene sulfide, polyimide, etc. is used between the positive electrode 2 and the negative electrode 1. It is preferable to impregnate the electrolyte solution. Further, the inside or the surface of the separator may contain a heat resistant filler such as alumina, magnesia, silica, titania. Apart from the separator, a heat-resistant layer composed of these fillers and a binder similar to that used for the electrode may be provided.

非水電解質３の材料は、活物質の酸化還元電位などを基に選択される。非水電解質３に用いるのが好ましい溶質としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｌＣｌ４、ＬｉＳｂＦ６、ＬｉＳＣＮ、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）、ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２、ＬｉＡｓＦ６、ＬｉＢ１０Ｃｌ１０、低級脂肪族カルボン酸リチウム、ＬｉＦ、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、クロロボランリチウム、ビス（１，２−ベンゼンジオレート（２−）−Ｏ，Ｏ’）ほう酸リチウム、ビス（２，３−ナフタレンジオレート（２−）−Ｏ，Ｏ’）ほう酸リチウム、ビス（２，２’−ビフェニルジオレート（２−）−Ｏ，Ｏ’）ほう酸リチウム、ビス（５−フルオロ−２−オレート−１−ベンゼンスルホン酸−Ｏ，Ｏ’）ほう酸リチウムなどのほう酸塩類、テトラフェニルホウ酸リチウムなど、一般にリチウム電池で使用されている塩類が適用できる。 The material of the nonaqueous electrolyte 3 is selected based on the redox potential of the active material. Solutes preferably used for the non-aqueous electrolyte 3 include LiPF 6 , LiBF 4 , LiClO 4 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCF 3 SO 3 , LiN (CF 3 SO 2 ), LiN (C 2 F 5 SO 2) 2, LiAsF 6, LiB 10 Cl 10, lower aliphatic lithium carboxylate, LiF, LiCl, LiBr, LiI, chloroborane lithium, bis (1,2-benzene diolate (2 -) - O, O ') Lithium borate, bis (2,3-naphthalenedioleate (2-)-O, O ′) lithium borate, bis (2,2′-biphenyldiolate (2-)-O, O ′) lithium borate, bis ( 5-fluoro-2-olate-1-benzenesulfonic acid-O, O ′) borates such as lithium borate, lithium tetraphenylborate Salts generally used in lithium batteries such as um are applicable.

さらに上記塩を溶解させる有機溶媒には、エチレンカーボネート（ＥＣ）、プロピレンカーボネート、ブチレンカーボネート、ビニレンカーボネート、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート、エチルメチルカーボネート（ＥＭＣ）、ジプロピルカーボネート、ギ酸メチル、酢酸メチル、プロピオン酸メチル、プロピオン酸エチル、ジメトキシメタン、γ−ブチロラクトン、γ−バレロラクトン、１，２−ジエトキシエタン、１，２−ジメトキシエタン、エトキシメトキシエタン、トリメトキシメタン、テトラヒドロフラン、２−メチルテトラヒドロフランなどのテトラヒドロフラン誘導体、ジメチルスルホキシド、１，３−ジオキソラン、４−メチル−１，３−ジオキソランなどのジオキソラン誘導体、ホルムアミド、アセトアミド、ジメチルホルムアミド、アセトニトリル、プロピルニトリル、ニトロメタン、エチルモノグライム、リン酸トリエステル、酢酸エステル、プロピオン酸エステル、スルホラン、３−メチルスルホラン、１，３−ジメチル−２−イミダゾリジノン、３−メチル−２−オキサゾリジノン、プロピレンカーボネート誘導体、エチルエーテル、ジエチルエーテル、１，３−プロパンサルトン、アニソール、フルオロベンゼンなどの１種またはそれ以上の混合物など、一般にリチウム電池で使用されているような溶媒が適用できる。   Further, the organic solvent for dissolving the salt includes ethylene carbonate (EC), propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate, ethyl methyl carbonate (EMC), dipropyl carbonate, methyl formate, acetic acid. Methyl, methyl propionate, ethyl propionate, dimethoxymethane, γ-butyrolactone, γ-valerolactone, 1,2-diethoxyethane, 1,2-dimethoxyethane, ethoxymethoxyethane, trimethoxymethane, tetrahydrofuran, 2-methyl Tetrahydrofuran derivatives such as tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, dioxolane derivatives such as 4-methyl-1,3-dioxolane, formamide, aceto Toamide, dimethylformamide, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, acetate ester, propionate ester, sulfolane, 3-methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl 2-Oxazolidinone, propylene carbonate derivatives, ethyl ether, diethyl ether, 1,3-propane sultone, anisole, mixtures of one or more such as fluorobenzene, and the like, commonly used in lithium batteries Applicable.

さらに、ビニレンカーボネート、シクロヘキシルベンゼン、ビフェニル、ジフェニルエーテル、ビニルエチレンカーボネート、ジビニルエチレンカーボネート、フェニルエチレンカーボネート、ジアリルカーボネート、フルオロエチレンカーボネート、カテコールカーボネート、酢酸ビニル、エチレンサルファイト、プロパンサルトン、トリフルオロプロピレンカーボネート、ジベニゾフラン、２，４−ジフルオロアニソール、ｏ−ターフェニル、ｍ−ターフェニルなどの添加剤を含んでいてもよい。   Furthermore, vinylene carbonate, cyclohexyl benzene, biphenyl, diphenyl ether, vinyl ethylene carbonate, divinyl ethylene carbonate, phenyl ethylene carbonate, diallyl carbonate, fluoroethylene carbonate, catechol carbonate, vinyl acetate, ethylene sulfite, propane sultone, trifluoropropylene carbonate, Additives such as dibenisofuran, 2,4-difluoroanisole, o-terphenyl, m-terphenyl may be included.

なお、非水電解質３は、ポリエチレンオキサイド、ポリプロピレンオキサイド、ポリホスファゼン、ポリアジリジン、ポリエチレンスルフィド、ポリビニルアルコール、ポリフッ化ビニリデン、ポリヘキサフルオロプロピレンなどの高分子材料の１種またはそれ以上の混合物などに上記溶質を混合して、固体電解質として用いてもよい。また、上記有機溶媒と混合してゲル状で用いてもよい。さらに、リチウム窒化物、リチウムハロゲン化物、リチウム酸素酸塩、Ｌｉ４ＳｉＯ４、Ｌｉ４ＳｉＯ４−ＬｉＩ−ＬｉＯＨ、Ｌｉ３ＰＯ４−Ｌｉ４ＳｉＯ４、Ｌｉ２ＳｉＳ３、Ｌｉ３ＰＯ４−Ｌｉ２Ｓ−ＳｉＳ２、硫化リン化合物などの無機材料を固体電解質として用いてもよい。 In addition, the nonaqueous electrolyte 3 may be formed by mixing one or more polymer materials such as polyethylene oxide, polypropylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, polyhexafluoropropylene, and the like. A solute may be mixed and used as a solid electrolyte. Moreover, you may mix with the said organic solvent and use it in a gel form. Further, lithium nitride, lithium halide, lithium oxyacid salt, Li 4 SiO 4, Li 4 SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 4 SiO 4, Li 2 SiS 3, Li 3 PO 4 -Li Inorganic materials such as 2 S—SiS 2 and phosphorus sulfide compounds may be used as the solid electrolyte.

負極合剤層１２は図２に示すように、第１の複合負極活物質３４Ａと第２の複合負極活物質３４Ｂを含む。第１の複合負極活物質３４Ａは少なくともリチウムイオンの吸蔵放出が可能な第１の活物質核３５Ａとその表面に付着させた第１のカーボンナノファイバ（以下、ＣＮＦと略す）３６Ａを有する。第２の複合負極活物質３４Ｂは少なくともリチウムイオンの吸蔵放出が可能な第２の活物質核３５Ｂとその表面に付着させた第２のＣＮＦ３６Ｂを有する。第１、第２のＣＮＦ３６Ａ、３６Ｂは、第１、第２の活物質核３５Ａ、３５Ｂの表面に付着あるいは固着しており、電池内では集電に対する抵抗が小さくなり、高い電子伝導性が維持される。第１の活物質核３５Ａと第２の活物質核３５Ｂとは実質的に平均粒径が同じである。第１のＣＮＦ３６Ａは第２のＣＮＦ３６Ｂに比べ圧縮応力が大きい。   As shown in FIG. 2, the negative electrode mixture layer 12 includes a first composite negative electrode active material 34A and a second composite negative electrode active material 34B. The first composite negative electrode active material 34A has at least a first active material core 35A capable of occluding and releasing lithium ions and a first carbon nanofiber (hereinafter abbreviated as CNF) 36A attached to the surface thereof. The second composite negative electrode active material 34B has at least a second active material nucleus 35B capable of occluding and releasing lithium ions and a second CNF 36B attached to the surface thereof. The first and second CNFs 36A and 36B are attached or fixed to the surfaces of the first and second active material nuclei 35A and 35B, so that resistance to current collection is reduced in the battery, and high electronic conductivity is maintained. Is done. The first active material nucleus 35A and the second active material nucleus 35B have substantially the same average particle diameter. The first CNF 36A has a larger compressive stress than the second CNF 36B.

負極合剤層１２はさらに図示しない結着剤を含む。結着剤としては、例えばポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン、ポリエチレン、ポリプロピレン、アラミド樹脂、ポリアミド、ポリイミド、ポリアミドイミド、ポリアクリルニトリル、ポリアクリル酸、ポリアクリル酸メチルエステル、ポリアクリル酸エチルエステル、ポリアクリル酸ヘキシルエステル、ポリメタクリル酸、ポリメタクリル酸メチルエステル、ポリメタクリル酸エチルエステル、ポリメタクリル酸ヘキシルエステル、ポリ酢酸ビニル、ポリビニルピロリドン、ポリエーテル、ポリエーテルサルフォン、ヘキサフルオロポリプロピレン、スチレンブタジエンゴム、カルボキシメチルセルロースなどが使用可能である。また、テトラフルオロエチレン、ヘキサフルオロエチレン、ヘキサフルオロプロピレン、パーフルオロアルキルビニルエーテル、フッ化ビニリデン、クロロトリフルオロエチレン、エチレン、プロピレン、ペンタフルオロプロピレン、フルオロメチルビニルエーテル、アクリル酸、ヘキサジエンより選択された２種以上の材料の共重合体を用いてもよい。   The negative electrode mixture layer 12 further contains a binder (not shown). Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, and polyacrylic acid. Ethyl ester, polyacrylic acid hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid hexyl ester, polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyether sulfone, hexafluoropolypropylene, Styrene butadiene rubber, carboxymethyl cellulose and the like can be used. Two types selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene A copolymer of the above materials may be used.

集電体１０には、ステンレス鋼、ニッケル、銅、チタンなどの金属箔、炭素や導電性樹脂の薄膜などが利用可能である。さらに、カーボン、ニッケル、チタンなどで表面処理を施してもよい。   The current collector 10 can be made of a metal foil such as stainless steel, nickel, copper, or titanium, or a thin film of carbon or conductive resin. Further, surface treatment may be performed with carbon, nickel, titanium or the like.

次に第１、第２の複合負極活物質３４Ａ、３４Ｂについて詳細に説明する。第１、第２の活物質核３５Ａ、３５Ｂとしては、ケイ素（Ｓｉ）やスズ（Ｓｎ）などのように正極合剤層８に含まれる正極活物質材料よりも卑な電位でリチウムイオンを大量に吸蔵放出可能な材料を用いることができる。このような材料であれば、単体、合金、化合物、固溶体および含ケイ素材料や含スズ材料を含む複合活物質の何れであっても、本発明の効果を発揮させることは可能である。特に含ケイ素材料は容量密度が大きく安価であるため好ましい。すなわち、含ケイ素材料として、Ｓｉ、ＳｉＯｘ（０．０５＜ｘ＜１．９５）、またはこれらのいずれかにＢ、Ｍｇ、Ｎｉ、Ｔｉ、Ｍｏ、Ｃｏ、Ｃａ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｎ、Ｎｂ、Ｔａ、Ｖ、Ｗ、Ｚｎ、Ｃ、Ｎ、Ｓｎからなる群から選択される少なくとも１つ以上の元素でＳｉの一部を置換した合金や化合物、または固溶体などを用いることができる。含スズ材料としてはＮｉ２Ｓｎ４、Ｍｇ２Ｓｎ、ＳｎＯｘ（０＜ｘ＜２）、ＳｎＯ２、ＳｎＳｉＯ３、ＬｉＳｎＯなどが適用できる。 Next, the first and second composite negative electrode active materials 34A and 34B will be described in detail. As the first and second active material nuclei 35A and 35B, a large amount of lithium ions is produced at a base potential lower than that of the positive electrode active material contained in the positive electrode mixture layer 8, such as silicon (Si) or tin (Sn). A material that can be occluded and released can be used. With such a material, the effect of the present invention can be exhibited with any of a simple substance, an alloy, a compound, a solid solution, and a composite active material including a silicon-containing material and a tin-containing material. In particular, a silicon-containing material is preferable because it has a large capacity density and is inexpensive. That is, as a silicon-containing material, Si, SiO x (0.05 <x <1.95), or any of these, B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn An alloy, a compound, a solid solution, or the like in which a part of Si is substituted with at least one element selected from the group consisting of Nb, Ta, V, W, Zn, C, N, and Sn can be used. As the tin-containing material, Ni 2 Sn 4 , Mg 2 Sn, SnO x (0 <x <2), SnO 2 , SnSiO 3 , LiSnO, or the like can be applied.

これらの材料は単独で第１、第２の活物質核３５Ａ、３５Ｂを構成してもよく、また複数種の材料により第１、第２の活物質核３５Ａ、３５Ｂを構成してもよい。上記複数種の材料により第１、第２の活物質核３５Ａ、３５Ｂを構成する例として、Ｓｉと酸素と窒素とを含む化合物やＳｉと酸素とを含み、Ｓｉと酸素との構成比率が異なる複数の化合物の複合物などが挙げられる。この中でもＳｉＯｘ（０．３≦ｘ≦１．３）は、放電容量密度が大きく、かつ充電時の膨張率がＳｉ単体より小さいため好ましい。 These materials alone may constitute the first and second active material nuclei 35A and 35B, and the first and second active material nuclei 35A and 35B may be constituted by a plurality of types of materials. As an example of constituting the first and second active material nuclei 35A and 35B by the plural kinds of materials described above, a compound containing Si, oxygen and nitrogen, Si and oxygen are contained, and the composition ratio of Si and oxygen is different. Examples include a composite of a plurality of compounds. Among these, SiO x (0.3 ≦ x ≦ 1.3) is preferable because it has a large discharge capacity density and an expansion coefficient lower than that of Si.

また、第１の活物質核３５Ａと第２の活物質核３５Ｂとは実質的に同組成で構成することが好ましい。このように単一の材料で第１、第２の活物質核３５Ａ、３５Ｂを構成することにより充放電反応も単一になるため充放電時の電圧変動も比較的単純になる。   Further, it is preferable that the first active material nucleus 35A and the second active material nucleus 35B have substantially the same composition. By configuring the first and second active material nuclei 35A and 35B with a single material in this way, the charge / discharge reaction becomes single, so that the voltage fluctuation during charge / discharge becomes relatively simple.

第１、第２のＣＮＦ３６Ａ、３６Ｂは、第１、第２の活物質核３５Ａ、３５Ｂの表面に担持された触媒元素（図示せず）を核として成長して形成される。触媒元素として銅（Ｃｕ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ニッケル（Ｎｉ）、モリブデン（Ｍｏ）およびマンガン（Ｍｎ）よりなる群から選択された少なくとも１種を用いることができ、第１、第２のＣＮＦ３６Ａ、３６Ｂの成長を促進する。このように第１、第２のＣＮＦ３６Ａ、３６Ｂが第１、第２の活物質核３５Ａ、３５Ｂの表面に付着していることにより良好な充放電特性が期待できる。また触媒元素の介在によって第１、第２の活物質核３５Ａ、３５Ｂへの結合力が強く、負極合剤層１２を集電体１０上に塗布する際の圧延負荷に対する負極１の耐久性を向上させることができる。   The first and second CNFs 36A and 36B are formed by growing using catalyst elements (not shown) supported on the surfaces of the first and second active material nuclei 35A and 35B as nuclei. As the catalyst element, at least one selected from the group consisting of copper (Cu), iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo) and manganese (Mn) can be used. , To promote the growth of the second CNFs 36A, 36B. Thus, since the first and second CNFs 36A and 36B are attached to the surfaces of the first and second active material nuclei 35A and 35B, good charge / discharge characteristics can be expected. Further, due to the presence of the catalytic element, the bonding strength to the first and second active material nuclei 35A and 35B is strong, and the durability of the negative electrode 1 against the rolling load when the negative electrode mixture layer 12 is applied on the current collector 10 is increased. Can be improved.

第１、第２のＣＮＦ３６Ａ、３６Ｂ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、触媒元素が第１、第２の活物質核３５Ａ、３５Ｂの表層部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、第１、第２のＣＮＦ３６Ａ、３６Ｂ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。   Until the growth of the first and second CNFs 36A and 36B is completed, in order for the catalytic element to exhibit good catalytic action, the catalytic element is a surface layer portion of the first and second active material nuclei 35A and 35B. It is desirable to exist in a metallic state. 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 first and second CNFs 36A and 36B is completed, it is desirable to oxidize the metal particles made of the catalyst element.

第１、第２のＣＮＦ３６Ａ、３６Ｂの繊維長は、１ｎｍ〜１ｍｍが好ましく、５００ｎｍ〜１００μｍがさらに好ましい。第１、第２のＣＮＦ３６Ａ、３６Ｂ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りすぎ、また繊維長が１ｍｍを超えると、活物質密度や容量が小さくなる傾向がある。   The fiber lengths of the first and second CNFs 36A and 36B are preferably 1 nm to 1 mm, and more preferably 500 nm to 100 μm. When the fiber length of the first and second CNFs 36A and 36B is less than 1 nm, the effect of increasing the conductivity of the electrode is too small, and when the fiber length exceeds 1 mm, the active material density and capacity tend to decrease.

第１、第２のＣＮＦ３６Ａ、３６Ｂの形態は、特に限定されないが、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た少なくとも１種からなることが望ましい。第１、第２のＣＮＦ３６Ａ、３６Ｂは、成長する過程で触媒元素を自身の内部に取り込んでもよい。また、第１、第２のＣＮＦ３６Ａ、３６Ｂの繊維径は１ｎｍ〜１０００ｎｍが好ましく、１０ｎｍ〜３００ｎｍがさらに好ましい。   The form of the first and second CNFs 36A and 36B is not particularly limited, but is preferably at least one selected from the group consisting of tubular carbon, accordion carbon, plate carbon, and herringbone carbon. . The first and second CNFs 36 </ b> A and 36 </ b> B may take the catalytic element into the inside during the growth process. The fiber diameters of the first and second CNFs 36A and 36B are preferably 1 nm to 1000 nm, and more preferably 10 nm to 300 nm.

触媒元素は、金属状態で第１、第２のＣＮＦ３６Ａ、３６Ｂ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第１、第２の活物質核３５Ａ、３５Ｂを、第１、第２のＣＮＦ３６Ａ、３６Ｂの原料ガスを含む高温雰囲気中に導入すると、第１、第２のＣＮＦ３６Ａ、３６Ｂ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、第１、第２のＣＮＦ３６Ａ、３６Ｂは成長しない。   The catalytic element provides an active point for growing the first and second CNFs 36A and 36B in a metallic state. That is, when the first and second active material nuclei 35A and 35B exposed on the surface in a metallic state are introduced into a high-temperature atmosphere containing the source gases of the first and second CNFs 36A and 36B, the first and second The growth of the second CNFs 36A and 36B proceeds. When the catalytic element is not present on the surface of the active material particles, the first and second CNFs 36A and 36B do not grow.

第１、第２の活物質核３５Ａ、３５Ｂの表面に触媒元素からなる金属粒子を設ける方法は、特に限定されないが、例えば固体の金属粒子を第１、第２の活物質核３５Ａ、３５Ｂと混合することが考えられる。また金属粒子の原料である金属化合物の溶液に、第１、第２の活物質核３５Ａ、３５Ｂを浸漬する方法が好適である。溶液に浸漬後の第１、第２の活物質核３５Ａ、３５Ｂから溶媒を除去し、必要に応じて加熱処理すると、表面に均一にかつ高分散状態で、粒径１ｎｍ〜１０００ｎｍ、好ましくは１０ｎｍ〜１００ｎｍの触媒元素からなる金属粒子を担持した第１、第２の活物質核３５Ａ、３５Ｂを得ることが可能である。   A method of providing metal particles made of a catalytic element on the surfaces of the first and second active material nuclei 35A and 35B is not particularly limited. For example, solid metal particles may be combined with the first and second active material nuclei 35A and 35B. Mixing is conceivable. A method of immersing the first and second active material nuclei 35A and 35B in a solution of a metal compound that is a raw material of the metal particles is preferable. When the solvent is removed from the first and second active material nuclei 35A and 35B after being immersed in the solution and subjected to heat treatment as necessary, the particle size is 1 nm to 1000 nm, preferably 10 nm, uniformly and highly dispersed on the surface. It is possible to obtain the first and second active material nuclei 35A and 35B carrying metal particles made of a catalytic element of ˜100 nm.

触媒元素からなる金属粒子の粒径が１ｎｍ未満の場合、金属粒子の生成が非常に難しく、また１０００ｎｍを超えると、金属粒子の大きさが極端に不均一となり、第１、第２のＣＮＦ３６Ａ、３６Ｂを成長させることが困難になったり、導電性に優れた電極が得られなくなったりすることがある。そのため、触媒元素からなる金属粒子の粒径は１ｎｍ以上、１０００ｎｍ以下であることが望ましい。   When the particle size of the metal particles composed of the catalytic element is less than 1 nm, it is very difficult to generate the metal particles. When the particle size exceeds 1000 nm, the size of the metal particles becomes extremely non-uniform, and the first and second CNFs 36A, It may be difficult to grow 36B, or an electrode having excellent conductivity may not be obtained. Therefore, the particle size of the metal particles made of the catalyst element is desirably 1 nm or more and 1000 nm or less.

上記溶液を得るための金属化合物としては、硝酸ニッケル、硝酸コバルト、硝酸鉄、硝酸銅、硝酸マンガン、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。また溶液に用いる溶媒には、化合物の溶解度、電気化学的活性相との適性を考慮して、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を選択すればよい。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。   Examples of the metal compound for obtaining the solution include nickel nitrate, cobalt nitrate, iron nitrate, copper nitrate, manganese nitrate, hexaammonium hexamolybdate tetrahydrate and the like. A suitable solvent may be selected from water, an organic solvent, and a mixture of water and an organic solvent in consideration of the solubility of the compound and suitability for the electrochemically active phase. As the organic solvent, for example, ethanol, isopropyl alcohol, toluene, benzene, hexane, tetrahydrofuran and the like can be used.

一方、触媒元素を含む合金粒子を合成し、これを第１、第２の活物質核３５Ａ、３５Ｂとして用いることもできる。この場合、Ｓｉ、Ｓｎなどと触媒元素との合金を、通常の合金製造方法により合成する。Ｓｉ元素やＳｎ元素などは、電気化学的にリチウムと反応して合金を生成するので、電気化学的活性相が形成される。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。   On the other hand, alloy particles containing a catalyst element can be synthesized and used as the first and second active material nuclei 35A and 35B. In this case, an alloy of Si, Sn and the like and a catalytic element is synthesized by a normal alloy manufacturing method. Since Si element, Sn element and the like electrochemically react with lithium to form an alloy, an electrochemically active phase is formed. 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.

触媒元素からなる金属粒子もしくは金属相は、第１、第２の活物質核３５Ａ、３５Ｂ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。金属粒子もしくは金属相の含有量が少なすぎると、第１、第２のＣＮＦ３６Ａ、３６Ｂ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。一方、触媒元素からなる金属粒子もしくは金属相の含有量が多すぎると、触媒元素の凝集により、不均一で太い繊維径の第１、第２のＣＮＦ３６Ａ、３６Ｂが成長するため、合剤層中の導電性や活物質密度の低下につながる。また、電気化学的活性相の割合が相対的に少なくなり、第１、第２の複合負極活物質３４Ａ、３４Ｂを高容量の電極材料とすることが困難となる。   The metal particles or metal phase comprising the catalytic element is preferably 0.01% to 10% by weight of the first and second active material nuclei 35A and 35B, and preferably 1% to 3% by weight. More desirable. If the content of the metal particles or the metal phase is too small, it takes a long time to grow the first and second CNFs 36A and 36B, and the production efficiency may decrease. On the other hand, if the content of the metal particles or metal phase composed of the catalyst element is too large, the first and second CNFs 36A and 36B having non-uniform and thick fiber diameters grow due to aggregation of the catalyst element. Lead to a decrease in the electrical conductivity and active material density. In addition, the proportion of the electrochemically active phase is relatively reduced, and it becomes difficult to use the first and second composite negative electrode active materials 34A and 34B as high-capacity electrode materials.

次に、第１の活物質核３５Ａと第１のＣＮＦ３６Ａとから構成された第１の複合負極活物質３４Ａの製造方法について述べる。この製造方法は以下の４つのステップで構成される。   Next, a manufacturing method of the first composite negative electrode active material 34A composed of the first active material nucleus 35A and the first CNF 36A will be described. This manufacturing method includes the following four steps.

（ａ）リチウムの吸蔵放出が可能な第１の活物質核３５Ａの少なくとも表層部に、第１のＣＮＦ３６Ａの成長を促進するＣｕ、Ｆｅ、Ｃｏ、Ｎｉ、ＭｏおよびＭｎよりなる群から選択された少なくとも１種の触媒元素を設けるステップ。   (A) selected from the group consisting of Cu, Fe, Co, Ni, Mo, and Mn that promotes the growth of the first CNF 36A in at least the surface layer portion of the first active material nucleus 35A capable of occluding and releasing lithium Providing at least one catalytic element;

（ｂ）炭素含有ガスおよび水素ガスを含む雰囲気中で、第１の活物質核３５Ａの表面に、第１のＣＮＦ３６Ａを成長させるステップ。   (B) A step of growing the first CNF 36A on the surface of the first active material nucleus 35A in an atmosphere containing a carbon-containing gas and a hydrogen gas.

（ｃ）不活性ガス雰囲気中で、第１のＣＮＦ３６Ａが付着した第１の活物質核３５Ａを４００℃以上、１６００℃以下で焼成するステップ。   (C) A step of firing the first active material core 35A to which the first CNF 36A is attached in an inert gas atmosphere at 400 ° C. or higher and 1600 ° C. or lower.

（ｄ）第１のＣＮＦ３６Ａが付着した第１の活物質核３５Ａを解砕してタップ密度を０．４２ｇ／ｃｍ３以上、０．９１ｇ／ｃｍ３以下に調整するステップ。 (D) first and then disintegrated tap density of the active material core 35A 0.42 g / cm 3 or more, the step of adjusting the 0.91 g / cm 3 or less adhering the first CNF36A.

ステップ（ｃ）の後、さらに、大気中で第１の複合負極活物質３４Ａを１００℃以上、４００℃以下で熱処理して触媒元素を酸化してもよい。１００℃以上、４００℃以下の熱処理であれば、第１のＣＮＦ３６Ａを酸化させずに触媒元素だけを酸化することが可能である。   After step (c), the catalytic element may be oxidized by further heat-treating the first composite negative electrode active material 34A in the atmosphere at 100 ° C. or higher and 400 ° C. or lower. If the heat treatment is performed at 100 ° C. or higher and 400 ° C. or lower, it is possible to oxidize only the catalytic element without oxidizing the first CNF 36A.

ステップ（ａ）としては、第１の活物質核３５Ａの表面に触媒元素からなる金属粒子を担持するステップ、触媒元素を含む第１の活物質核３５Ａの表面を還元するステップ、Ｓｉ元素やＳｎ元素と触媒元素との合金粒子を合成するステップなどが挙げられる。ただしステップ（ａ）は上記に限られるものではない。   As the step (a), a step of supporting metal particles made of a catalytic element on the surface of the first active material nucleus 35A, a step of reducing the surface of the first active material nucleus 35A containing the catalytic element, an Si element or Sn Examples include a step of synthesizing alloy particles of an element and a catalytic element. However, step (a) is not limited to the above.

次に、ステップ（ｂ）において、第１の活物質核３５Ａの表面に第１のＣＮＦ３６Ａ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第１の活物質核３５Ａを、第１のＣＮＦ３６Ａの原料ガスを含む高温雰囲気中に導入すると第１のＣＮＦ３６Ａの成長が進行する。例えばセラミック製反応容器に第１の活物質核３５Ａ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る。その後、第１のＣＮＦ３６Ａの原料ガスである炭素含有ガスと水素ガスとを反応容器に導入する。反応容器内の温度が１００℃未満では、第１のＣＮＦ３６Ａ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、原料ガスの分解が促進され第１のＣＮＦ３６Ａが成長し難くなる。   Next, conditions for growing the first CNF 36A on the surface of the first active material nucleus 35A in step (b) will be described. When the first active material nucleus 35A having the catalytic element at least in the surface layer portion is introduced into a high temperature atmosphere containing the source gas of the first CNF 36A, the growth of the first CNF 36A proceeds. For example, the first active material core 35A is put into a ceramic reaction vessel, and the temperature is raised to 100 ° C to 1000 ° C, preferably 300 ° C to 600 ° C in an inert gas or a gas having a reducing power. Thereafter, a carbon-containing gas and a hydrogen gas, which are source gases for the first CNF 36A, are introduced into the reaction vessel. When the temperature in the reaction vessel is lower than 100 ° C., the growth of the first CNF 36A 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., the decomposition of the raw material gas is promoted, and the first CNF 36A becomes difficult to grow.

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、一酸化炭素などを用いることができる。混合ガスにおける炭素含有ガスのモル比（体積比）は、２０％〜８０％が好適である。第１の活物質核３５Ａ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、触媒元素の還元と第１のＣＮＦ３６Ａの成長とを並行して進行させることができる。第１のＣＮＦ３６Ａの成長を終了させる際には、炭素含有ガスと水素ガスと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する。   As the source gas, a mixed gas of carbon-containing gas and hydrogen gas is suitable. As the carbon-containing gas, methane, ethane, ethylene, butane, carbon monoxide, or the like can be used. The molar ratio (volume ratio) of the carbon-containing gas in the mixed gas is preferably 20% to 80%. When the catalytic element in the metallic state is not exposed on the surface of the first active material nucleus 35A, the reduction of the catalytic element and the growth of the first CNF 36A are performed in parallel by controlling the ratio of the hydrogen gas more. Can be advanced. When the growth of the first CNF 36A is terminated, the mixed gas of carbon-containing gas and hydrogen gas is replaced with an inert gas, and the inside of the reaction vessel is cooled to room temperature.

続いて、ステップ（ｃ）にて、第１のＣＮＦ３６Ａが付着した第１の活物質核３５Ａを、不活性ガス雰囲気中にて４００℃以上、１６００℃以下で焼成する。このようにすることで電池の初期充電時に進行する電解質と第１のＣＮＦ３６Ａ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ため好ましい。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、第１の活物質核３５Ａの電気化学的活性相と第１のＣＮＦ３６Ａ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、第１の活物質核３５Ａの電気化学的活性相がＳｉである場合には、Ｓｉと第１のＣＮＦ３６Ａ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。なお、第１の活物質核３５ＡがＳｉの場合、焼成温度は１０００℃以上、１６００℃以下が特に好ましい。なお、成長条件によって第１のＣＮＦ３６Ａの結晶性を高めることもできる。このように第１のＣＮＦ３６Ａの結晶性が高い場合には電解質と第１のＣＮＦ３６Ａとの不可逆反応も抑制されるため、ステップ（ｃ）は必須ではない。   Subsequently, in step (c), the first active material core 35A to which the first CNF 36A is attached is fired at 400 ° C. or higher and 1600 ° C. or lower in an inert gas atmosphere. By doing in this way, since the irreversible reaction of the electrolyte and 1st CNF36A which advance at the time of the initial stage charge of a battery is suppressed, and the outstanding charging / discharging efficiency can be obtained, it is preferable. If such a firing process is not performed, or if 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 decrease. When the firing temperature exceeds 1600 ° C., the electrochemically active phase of the first active material core 35A reacts with the first CNF 36A to deactivate the active phase, or the electrochemically active phase is reduced. May cause a decrease in capacity. For example, when the electrochemically active phase of the first active material nucleus 35A is Si, Si reacts with the first CNF 36A to generate inactive silicon carbide, and the charge / discharge capacity of the battery Cause a decline. When the first active material core 35A is Si, the firing temperature is particularly preferably 1000 ° C. or higher and 1600 ° C. or lower. Note that the crystallinity of the first CNF 36A can be increased depending on growth conditions. Thus, when the crystallinity of 1st CNF36A is high, since an irreversible reaction of electrolyte and 1st CNF36A is also suppressed, step (c) is not essential.

不活性ガス中で焼成後の第１の複合負極活物質３４Ａ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第１のＣＮＦ３６Ａが燃焼してしまうことがある。   The first composite negative electrode active material 34A after firing in an inert gas further oxidizes at least a part (for example, the surface) of metal particles or a metal phase composed of a catalytic element in the atmosphere at 100 ° C. or higher, Heat treatment is preferably performed at 400 ° C. or lower. 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 first CNF 36A may burn.

ステップ（ｄ）では第１のＣＮＦ３６Ａが付着した焼成後の第１の活物質核３５Ａを解砕する。このようにすることにより、充填性の良好な第１の複合負極活物質３４Ａが得られるため好ましい。ただし、タップ密度が０．４２ｇ／ｃｍ３以上、０．９１ｇ／ｃｍ３以下の場合は必ずしも解砕する必要はない。すなわち、充填性のよい活物質核を原料に用いた場合、解砕する必要がない場合もある。 In step (d), the fired first active material core 35A to which the first CNF 36A is attached is crushed. By doing in this way, since the 1st composite negative electrode active material 34A with favorable filling property is obtained, it is preferable. However, the tap density of 0.42 g / cm 3 or more, it is not always necessary to crushing in the case of 0.91 g / cm 3 or less. That is, when an active material nucleus with good filling properties is used as a raw material, it may not be necessary to crush.

第２の活物質核３５Ｂと第２のＣＮＦ３６Ｂとから構成された第２の複合負極活物質３４Ｂも基本的には第１の複合負極活物質３４Ａと同様にして製造できる。ここで、第１のＣＮＦ３６Ａは第２のＣＮＦ３６Ｂよりも圧縮応力が大きい。この差は、ステップ（ａ）で第１のＣＮＦ３６Ａの成長を促進する触媒元素を設けるステップで触媒径を変える制御をすることによって太さの異なるＣＮＦを成長させたり、また、ＣＮＦの成長ステップでその反応時間を変えることによってＣＮＦの長さを変えたりすることによって実現できる。図３は、ＣＮＦの長さを変えることで圧縮応力の異なる第１、第２のＣＮＦ３６Ａ、３６Ｂを設けた状態を示している。   The second composite negative electrode active material 34B composed of the second active material nucleus 35B and the second CNF 36B can also be manufactured basically in the same manner as the first composite negative electrode active material 34A. Here, the first CNF 36A has a larger compressive stress than the second CNF 36B. This difference is caused by growing CNFs having different thicknesses by controlling the catalyst diameter in the step of providing a catalytic element that promotes the growth of the first CNF 36A in step (a), or in the step of growing CNF. This can be realized by changing the length of CNF by changing the reaction time. FIG. 3 shows a state in which the first and second CNFs 36A and 36B having different compressive stresses are provided by changing the length of the CNF.

次に負極合剤層１２における第１、第２の複合負極活物質３４Ａ、３４Ｂの状態とその効果について説明する。図２に示すように、本実施の形態における負極合剤層１２では、圧縮応力の大きい第１のＣＮＦ３６Ａを含む第１の複合負極活物質３４Ａと圧縮応力の小さい第２のＣＮＦ３６Ｂを含む第２の複合負極活物質３４Ｂとが混在している。第１のＣＮＦ３６Ａは他の第１のＣＮＦ３６Ａや第２のＣＮＦ３６Ｂと絡んで互いの接触を保てる半面、圧縮応力が大きいために反発力が大きく充電時に第１の活物質核３５Ａが膨張した際に第１のＣＮＦ３６Ａが反発して第１の活物質核３５Ａを弾き返し、負極１の変形を促す。そこで圧縮応力の小さい第２のＣＮＦ３６Ｂを適量活用し、上述した反発を抑制することにより、高容量ながら課題の多い第１、第２の活物質核３５Ａ、３５Ｂを用いた場合でも、非水電解質二次電池のサイクル特性を実用的なレベルに高めることができる。   Next, the state and effect of the first and second composite negative electrode active materials 34A and 34B in the negative electrode mixture layer 12 will be described. As shown in FIG. 2, in the negative electrode mixture layer 12 in the present embodiment, the second composite negative electrode active material 34 </ b> A including the first CNF 36 </ b> A having a high compressive stress and the second CNF 36 </ b> B having a low compressive stress are included. The composite negative electrode active material 34B is mixed. The first CNF 36A is entangled with the other first CNF 36A and the second CNF 36B, and can maintain contact with each other. On the other hand, when the first active material core 35A expands during charging due to a large repulsive force due to a large compressive stress. The first CNF 36 </ b> A repels and repels the first active material nucleus 35 </ b> A to promote deformation of the negative electrode 1. Therefore, by utilizing an appropriate amount of the second CNF 36B having a small compressive stress and suppressing the above-mentioned repulsion, even when the first and second active material nuclei 35A and 35B having many problems are used, the non-aqueous electrolyte is used. The cycle characteristics of the secondary battery can be improved to a practical level.

なお第１、第２のＣＮＦ３６Ａ、３６Ｂの圧縮応力の大きさは以下のようにして判断できる。まず第１、第２のＣＮＦ３６Ａ、３６Ｂの径が略同一でバネ定数が実質的に同等である場合、長いものほど圧縮応力は高い。また第１、第２のＣＮＦ３６Ａ、３６Ｂの長さが略同一である場合、径が大きいのほど圧縮応力は高い。さらに第１、第２のＣＮＦ３６Ａ、３６Ｂの径・長さともに略同一である場合、第１、第２の活物質核３５Ａ、３５Ｂの表面に対する付着の角度が直角に近いものほど圧縮応力は高い。以上の判断は、走査型電子顕微鏡あるいは透過型電子顕微鏡による外観観察や、複合活物質から超音波でＣＮＦを脱離させて、フロー式の粒子画像解析法で解析することによって可能である。   The magnitude of the compressive stress of the first and second CNFs 36A and 36B can be determined as follows. First, when the diameters of the first and second CNFs 36A and 36B are substantially the same and the spring constants are substantially equal, the longer the CNFs 36A and 36B, the higher the compressive stress. When the lengths of the first and second CNFs 36A and 36B are substantially the same, the larger the diameter, the higher the compressive stress. Further, when the diameters and lengths of the first and second CNFs 36A and 36B are substantially the same, the compressive stress is higher as the angle of attachment to the surface of the first and second active material nuclei 35A and 35B is closer to a right angle. . The above determination can be made by observing the appearance with a scanning electron microscope or a transmission electron microscope, or by detaching CNF from the composite active material with ultrasonic waves and analyzing it by a flow type particle image analysis method.

図２では、第１のＣＮＦ３６Ａの長さを第２のＣＮＦ３６Ｂの長さより長くすることにより第１のＣＮＦ３６Ａの圧縮応力を第２のＣＮＦ３６Ｂの圧縮応力より大きくしているが、第１のＣＮＦ３６Ａ、３６Ｂの径を１０〜１００ｎｍ、長さを１０〜３０μｍ、第２のＣＮＦ３６Ｂの長さに対する第１のＣＮＦ３６Ａの長さの比率を２〜７とすれば、本発明の効果が得られやすい。   In FIG. 2, the first CNF 36A is made longer than the second CNF 36B by making the length of the first CNF 36A longer than that of the second CNF 36B, but the first CNF 36A, If the diameter of 36B is 10 to 100 nm, the length is 10 to 30 μm, and the ratio of the length of the first CNF 36A to the length of the second CNF 36B is 2 to 7, the effect of the present invention can be easily obtained.

なお第１、第２の活物質核３５Ａ、３５Ｂの平均粒径が実質的に同等である場合、第１の活物質核３５Ａに圧縮応力が大きい第１のＣＮＦ３６Ａを付着させた第１の複合負極活物質３４Ａと第２の活物質核３５Ｂに圧縮応力が小さい第２のＣＮＦ３６Ｂを付着させた第２の複合負極活物質３４Ｂとの重量比が３０：７０から５０：５０の範囲であることが好ましい。第１の複合負極活物質３４Ａと第２の複合負極活物質３４Ｂとの重量比が３０：７０より小さい場合、圧縮応力の大きい第１のＣＮＦ３６Ａが不足するため他の第１、第２のＣＮＦ３６Ａ、３６Ｂとの接触を保つのが困難になり、サイクル特性が若干低下する。また第１の複合負極活物質３４Ａと第２の複合負極活物質３４Ｂとの重量比が５０：５０を超える場合、充電時に第１、第２の活物質核３５Ａ、３５Ｂが膨張した際に第１のＣＮＦ３６Ａの反発がやや大きくなり、負極１が変形しやすくなってサイクル特性がやや低下する。   When the average particle diameters of the first and second active material nuclei 35A and 35B are substantially equal, the first composite in which the first CNF 36A having a large compressive stress is attached to the first active material nuclei 35A. The weight ratio between the negative active material 34A and the second composite negative active material 34B in which the second CNF 36B having a small compressive stress is attached to the second active material core 35B is in the range of 30:70 to 50:50. Is preferred. When the weight ratio of the first composite negative electrode active material 34A and the second composite negative electrode active material 34B is smaller than 30:70, the first CNF 36A having a large compressive stress is insufficient, and the other first and second CNFs 36A. , It becomes difficult to maintain contact with 36B, and the cycle characteristics slightly deteriorate. In addition, when the weight ratio of the first composite negative electrode active material 34A and the second composite negative electrode active material 34B exceeds 50:50, the first and second active material nuclei 35A and 35B expand when the first and second active material nuclei 35A and 35B expand. The repulsion of 1 CNF 36A is slightly increased, the negative electrode 1 is easily deformed, and the cycle characteristics are slightly deteriorated.

なお、図３の概念図に示すように、第１の活物質核３５Ａの平均粒径が第２の活物質核３５Ｂの平均粒径より大きいことが好ましい。このように第１、第２の活物質核３５Ａ、３５Ｂの粒径を異ならせることにより、負極合剤層１２中で粒径の小さい第２の活物質核３５Ｂが粒径の大きい第１の活物質核３５Ａの隙間に配置される。そのため第１、第２の複合負極活物質３４Ａ、３４Ｂの充填性が向上する。このため表面に付着させた第１のＣＮＦ３６Ａ同士、あるいは第１のＣＮＦ３６Ａと第２のＣＮＦ３６Ｂとが接触する機会が増える。そのためサイクル特性がさらに向上する。   As shown in the conceptual diagram of FIG. 3, the average particle diameter of the first active material nucleus 35A is preferably larger than the average particle diameter of the second active material nucleus 35B. In this way, by making the particle sizes of the first and second active material nuclei 35A and 35B different, the second active material nucleus 35B having a small particle size in the negative electrode mixture layer 12 has a large particle size. It arrange | positions in the clearance gap between the active material nucleus 35A. Therefore, the filling properties of the first and second composite negative electrode active materials 34A and 34B are improved. For this reason, the chance that the first CNFs 36A attached to the surface or the first CNF 36A and the second CNF 36B come into contact with each other increases. Therefore, cycle characteristics are further improved.

この効果のメカニズムは鋭意解析中であるが、第２の活物質核３５Ｂが第１のＣＮＦ３６Ａの圧縮応力を緩和する役割を担っていると考えられる。この状態で第１のＣＮＦ３６Ａは第２のＣＮＦ３６Ｂと強固に絡み合えるので、放電時に第１の活物質核３５Ａが収縮して第１の活物質核３５Ａ同士の距離が大きくなった際に、第１のＣＮＦ３６Ａ同士が接触していた部分が徐々に非接触になっていくという不具合を起こすことはない。なお負極合剤層１２における第１、第２の活物質核３５Ａ、３５Ｂの充填密度が向上するため、電池容量も増加する。これらの効果によって、実用的なサイクル特性を有する非水電解質二次電池が得られる。   Although the mechanism of this effect is under intensive analysis, it is considered that the second active material nucleus 35B plays a role of relaxing the compressive stress of the first CNF 36A. In this state, the first CNF 36A can be tightly entangled with the second CNF 36B. Therefore, when the first active material nucleus 35A contracts during discharge and the distance between the first active material nuclei 35A increases, There is no problem that the portions where the CNFs 36A are in contact with each other gradually become non-contact. In addition, since the filling density of the first and second active material nuclei 35A and 35B in the negative electrode mixture layer 12 is improved, the battery capacity is also increased. By these effects, a nonaqueous electrolyte secondary battery having practical cycle characteristics can be obtained.

また、第１の活物質核３５Ａの平均粒径が第２の活物質核３５Ｂの平均粒径より大きい場合、第１、第２の複合負極活物質３４Ａ、３４Ｂの総重量に占める第１の複合負極活物質３４Ａの重量比率が第２の複合負極活物質３４Ｂの重量比率より大きいことが好ましい。これにより、第２の活物質核３５Ｂが第１の活物質核３５Ａ同士の隙間に入り込んで上述の効果が得られやすい。また、第１の複合負極活物質３４Ａの重量比率は７０％以上、９０％以下であることがさらに好ましい。第１の複合負極活物質３４Ａの重量比率がこの範囲を逸脱すると、第２の活物質核３５Ｂが第１の活物質核３５Ａの隙間に配置されることによる上述の効果が低下する。すなわち、第１の複合負極活物質３４Ａの重量比率がこの範囲にあることにより上述の効果が顕著に現れる。   Further, when the average particle diameter of the first active material nucleus 35A is larger than the average particle diameter of the second active material nucleus 35B, the first weight occupying the total weight of the first and second composite negative electrode active materials 34A, 34B. The weight ratio of the composite negative electrode active material 34A is preferably larger than the weight ratio of the second composite negative electrode active material 34B. As a result, the second active material nucleus 35B enters the gap between the first active material nuclei 35A, and the above-described effects are easily obtained. The weight ratio of the first composite negative electrode active material 34A is more preferably 70% or more and 90% or less. When the weight ratio of the first composite negative electrode active material 34A deviates from this range, the above-described effect due to the second active material core 35B being disposed in the gap between the first active material cores 35A decreases. That is, when the weight ratio of the first composite negative electrode active material 34A is within this range, the above-described effect is remarkably exhibited.

逆に、図４の概念図に示すように、第２の活物質核３５Ｂの平均粒径が第１の活物質核３５Ａの平均粒径より大きくてもよい。粒径が大きい第２の活物質核３５Ｂの隙間に粒径の小さい第１の活物質核３５Ａが配置されるので充填性が向上し、これらの表面に付着させた第２のＣＮＦ３６Ｂと第１のＣＮＦ３６Ａとが接触する機会が増える。この構造では第２の活物質核３５Ｂの表面に付着させた第２のＣＮＦ３６Ｂの圧縮応力が相対的に小さいので、第１のＣＮＦ３６Ａの大きい圧縮応力によって起こる充填時の反発が抑制され、第１、第２の活物質核３５Ａ、３５Ｂの充填性をさらに高めることができる。一方、第２のＣＮＦ３６Ｂの圧縮応力が小さいため相互に絡み合う力が小さく、放電時に第１、第２の活物質核３５Ａ、３５Ｂの距離が大きくなった際に、第２のＣＮＦ３６Ｂ同士が接触していた部分が徐々に非接触になっていく。ここで第１の活物質核３５Ａの表面に付着させた第１のＣＮＦ３６Ａの圧縮応力が相対的に大きいことにより、第１のＣＮＦ３６Ａが第２のＣＮＦ３６Ｂと強固に絡み合える。このため第２のＣＮＦ３６Ｂ同士の非接触箇所の増加を防ぐことができる。さらに充放電に伴う第１、第２の活物質核３５Ａ、３５Ｂの膨張収縮率が同じであっても、粒径が小さいために第１の活物質核３５Ａの膨張収縮の絶対量もまた小さい。そのため、充電時に第１の活物質核３５Ａが第２の活物質核３５Ｂ同士の間隔を押し広げて負極１を変形させるような不具合を起こすことはない。これらの効果によって、実用的なサイクル特性を有する非水電解質二次電池が得られる。   Conversely, as shown in the conceptual diagram of FIG. 4, the average particle diameter of the second active material nucleus 35B may be larger than the average particle diameter of the first active material nucleus 35A. Since the first active material core 35A having a small particle size is disposed in the gap between the second active material cores 35B having a large particle size, the filling property is improved, and the second CNF 36B and the first CNF 36B attached to these surfaces are improved. The chance of contact with CNF36A increases. In this structure, since the compressive stress of the second CNF 36B attached to the surface of the second active material nucleus 35B is relatively small, repulsion during filling caused by the large compressive stress of the first CNF 36A is suppressed, and the first CNF 36A is suppressed. The filling properties of the second active material nuclei 35A and 35B can be further enhanced. On the other hand, since the compressive stress of the second CNF 36B is small, the force entangled with each other is small. When the distance between the first and second active material nuclei 35A and 35B is increased during discharge, the second CNFs 36B come into contact with each other. The part that had been gradually becoming non-contact. Here, since the compressive stress of the first CNF 36A attached to the surface of the first active material nucleus 35A is relatively large, the first CNF 36A can be firmly entangled with the second CNF 36B. For this reason, the increase in the non-contact location of 2nd CNF36B can be prevented. Furthermore, even if the first and second active material nuclei 35A and 35B associated with charge / discharge have the same expansion / contraction rate, the absolute amount of expansion / contraction of the first active material nuclei 35A is also small due to the small particle size. . Therefore, the first active material nucleus 35A does not cause a problem that the negative electrode 1 is deformed by expanding the interval between the second active material nuclei 35B during charging. By these effects, a nonaqueous electrolyte secondary battery having practical cycle characteristics can be obtained.

また、第２の活物質核３５Ｂの平均粒径が第１の活物質核３５Ａの平均粒径より大きい場合、第１、第２の複合負極活物質３４Ａ、３４Ｂの総重量に占める第２の複合負極活物質３４Ｂの重量比率が第１の複合負極活物質３４Ａの重量比率より大きいことが好ましい。これにより、第１の活物質核３５Ａが第２の活物質核３５Ｂ同士の隙間に入り込んで上述の効果が得られやすい。また、第２の複合負極活物質３４Ｂの重量比率は７０％以上、９０％以下であることがさらに好ましい。第２の複合負極活物質３４Ｂの重量比率がこの範囲を逸脱すると、第１の活物質核３５Ａが第２の活物質核３５Ｂの隙間に配置されることによる上述の効果が低下する。すなわち、第２の複合負極活物質３４Ｂの重量比率がこの範囲にあることにより上述の効果が顕著に現れる。   Further, when the average particle diameter of the second active material nucleus 35B is larger than the average particle diameter of the first active material nucleus 35A, the second weight of the total weight of the first and second composite negative electrode active materials 34A, 34B The weight ratio of the composite negative electrode active material 34B is preferably larger than the weight ratio of the first composite negative electrode active material 34A. Thereby, the first active material nucleus 35A enters the gap between the second active material nuclei 35B, and the above-described effect is easily obtained. The weight ratio of the second composite negative electrode active material 34B is more preferably 70% or more and 90% or less. When the weight ratio of the second composite negative electrode active material 34B deviates from this range, the above-described effect due to the first active material core 35A being disposed in the gap between the second active material cores 35B decreases. That is, when the weight ratio of the second composite negative electrode active material 34B is within this range, the above-described effect is remarkably exhibited.

なお第１の活物質核３５Ａと第２の活物質核３５Ｂとは実質的に同じ物質とすることが好ましい。このように同組成の材料を用いれば充放電反応も単一になるため充放電時の電圧変動も比較的単純になる。   The first active material nucleus 35A and the second active material nucleus 35B are preferably substantially the same material. If a material having the same composition is used in this way, the charge / discharge reaction becomes single, and the voltage fluctuation during charge / discharge becomes relatively simple.

次に、本発明の各実施の形態における具体的な実施例について説明する。なお、以下の実施例では、負極１の効果を明確にする目的で、正極２の代わりに金属リチウムを用いて図１と同様のコイン型二次電池を作製し評価した。   Next, specific examples in each embodiment of the present invention will be described. In the following examples, for the purpose of clarifying the effect of the negative electrode 1, a coin-type secondary battery similar to that in FIG. 1 was fabricated and evaluated using metal lithium instead of the positive electrode 2.

（１）負極の作製
第１、第２の活物質核３５Ａ、３５Ｂとして、サンプル１では、粒径１０μｍ以下に粉砕したＯ／Ｓｉ比（ケイ素に対する酸素の比率）がモル比で１．０１である酸化ケイ素を使用した。 (1) Production of negative electrode As the first and second active material nuclei 35A and 35B, in sample 1, the O / Si ratio (ratio of oxygen to silicon) pulverized to a particle size of 10 μm or less is 1.01 in terms of molar ratio. Some silicon oxide was used.

また、触媒元素をこの酸化ケイ素粒子の表層部に結合するために、硝酸鉄９水和物（特級）１ｇをイオン交換水１００ｇに溶解させた溶液を使用した。なお、酸化ケイ素粒子のモル比の測定は、ＪＩＳ Ｚ２６１３に基づく重量分析法に準じて行った。この酸化ケイ素粒子と硝酸鉄溶液との混合物を、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、酸化ケイ素粒子の表層部に均一に、かつ高分散状態で、粒径が、１ｎｍ〜１０００ｎｍの硝酸鉄を担持させた。   Further, in order to bind the catalyst element to the surface layer portion of the silicon oxide particles, a solution in which 1 g of iron nitrate nonahydrate (special grade) was dissolved in 100 g of ion-exchanged water was used. The molar ratio of the silicon oxide particles was measured according to a gravimetric analysis method based on JIS Z2613. The mixture of the silicon oxide particles and the iron nitrate solution is stirred for 1 hour, and then the water is removed by an evaporator, so that the particle size is 1 nm to 1 nm in a uniform and highly dispersed state on the surface layer of the silicon oxide particles. 1000 nm iron nitrate was supported.

次に、この硝酸鉄を担持した第１、第２の活物質核３５Ａ、３５Ｂ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５００℃まで昇温させた。その後、ヘリウムガスを、水素ガス５０体積％と一酸化炭素ガス５０体積％との混合ガスにより置換し、５００℃で保持した。この際の反応時間を、第１の活物質核３５Ａでは４０分、第２の活物質核３５Ｂでは７分とした。これにより、硝酸鉄を還元するとともに第１、第２の活物質核３５Ａ、３５Ｂの表面に、繊維径が約８０ｎｍのプレート状の第１、第２のＣＮＦ３６Ａ、３６Ｂを成長させた。第１のＣＮＦ３６Ａの繊維長は２２μｍ、第２のＣＮＦ３６Ｂの繊維長は７μｍであった。   Next, the first and second active material nuclei 35A and 35B carrying iron nitrate were put into a ceramic reaction vessel and heated to 500 ° 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 carbon monoxide gas, and maintained at 500 ° C. The reaction time at this time was 40 minutes for the first active material nucleus 35A and 7 minutes for the second active material nucleus 35B. As a result, iron nitrate was reduced, and plate-shaped first and second CNFs 36A and 36B having a fiber diameter of about 80 nm were grown on the surfaces of the first and second active material nuclei 35A and 35B. The fiber length of the first CNF 36A was 22 μm, and the fiber length of the second CNF 36B was 7 μm.

次に、混合ガスを再びヘリウムガスにより置換し、反応容器内を室温になるまで冷却させた。成長した第１、第２のＣＮＦ３６Ａ、３６Ｂの量は、酸化ケイ素１００重量部当たりそれぞれ６７重量部、２０重量部であった。このようにして第１、第２の複合負極活物質３４Ａ、３４Ｂを得た。これらを等重量ずつ採り、乾式で混合した。以下、この混合物を単に複合負極活物質と呼ぶ。   Next, the mixed gas was replaced with helium gas again, and the reaction vessel was cooled to room temperature. The amounts of the grown first and second CNFs 36A and 36B were 67 parts by weight and 20 parts by weight, respectively, per 100 parts by weight of silicon oxide. In this way, first and second composite negative electrode active materials 34A and 34B were obtained. These were taken in equal weights and mixed dry. Hereinafter, this mixture is simply referred to as a composite negative electrode active material.

次に、ペースト作製のために、複合負極活物質の１００重量部に対し、結着剤として平均分子量が１５万のポリアクリル酸１％水溶液を固形分に換算して１０重量部と、コアシェル型変性スチレン−ブタジエン共重合体を１０重量部とを混合し、さらに蒸留水２００重量部を添加して混合分散し、負極合剤ペーストを調製した。   Next, for preparing a paste, 10 parts by weight of a 1% polyacrylic acid aqueous solution having an average molecular weight of 150,000 as a binder in terms of solid content with respect to 100 parts by weight of the composite negative electrode active material, a core-shell type 10 parts by weight of the modified styrene-butadiene copolymer was mixed, and 200 parts by weight of distilled water was further added and mixed and dispersed to prepare a negative electrode mixture paste.

この負極合剤ペーストを用いて、厚さ１４μｍのＣｕ箔よりなる集電体１０の片面にドクターブレード法により塗布、乾燥し、乾燥後の総厚み（銅箔を含む）が１００μｍとなるように負極合剤層１２を形成した。その後、直径１２．５ｍｍの円形に打ち抜いて負極１を得た。   Using this negative electrode mixture paste, the current collector 10 made of Cu foil having a thickness of 14 μm is coated and dried by the doctor blade method so that the total thickness (including the copper foil) after drying is 100 μm. A negative electrode mixture layer 12 was formed. Thereafter, the negative electrode 1 was obtained by punching into a circle having a diameter of 12.5 mm.

サンプル２〜５では、第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間を変えた以外はサンプル１と同様にして負極１を得た。サンプル２では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ８０分、３分とし、第１のＣＮＦ３６Ａの繊維長を３３μｍ、第２のＣＮＦ３６Ｂの繊維長を５μｍとした。サンプル３では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ５５分、５分とし、第１のＣＮＦ３６Ａの繊維長を２７μｍ、第２のＣＮＦ３６Ｂの繊維長を６μｍとした。サンプル４では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ２５分、９分とし、第１のＣＮＦ３６Ａの繊維長を１７μｍ、第２のＣＮＦ３６Ｂの繊維長を９μｍとした。サンプル５では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ２０分、１１分とし、第１のＣＮＦ３６Ａの繊維長を１４μｍ、第２のＣＮＦ３６Ｂの繊維長を１０μｍとした。   In samples 2 to 5, negative electrode 1 was obtained in the same manner as sample 1 except that the growth times of the first and second CNFs 36A and 36B were changed. In sample 2, the growth time of the first and second CNFs 36A and 36B was 80 minutes and 3 minutes, respectively, the fiber length of the first CNF 36A was 33 μm, and the fiber length of the second CNF 36B was 5 μm. In sample 3, the growth time of the first and second CNFs 36A and 36B was 55 minutes and 5 minutes, respectively, the fiber length of the first CNF 36A was 27 μm, and the fiber length of the second CNF 36B was 6 μm. In sample 4, the growth times of the first and second CNFs 36A and 36B were 25 minutes and 9 minutes, respectively, the fiber length of the first CNF 36A was 17 μm, and the fiber length of the second CNF 36B was 9 μm. In sample 5, the growth times of the first and second CNFs 36A and 36B were 20 minutes and 11 minutes, respectively, the fiber length of the first CNF 36A was 14 μm, and the fiber length of the second CNF 36B was 10 μm.

サンプル６〜９では、第１、第２の複合負極活物質３４Ａ、３４Ｂ全体に占める第１複合負極活物質３４Ａの配合比率を重量比率でそれぞれ２５％、３０％、６０％、７５％とした。これ以外はサンプル１と同様にして負極１を得た。   In Samples 6 to 9, the blending ratio of the first composite negative electrode active material 34A in the entire first and second composite negative electrode active materials 34A and 34B was 25%, 30%, 60%, and 75%, respectively, by weight ratio. . Except for this, the negative electrode 1 was obtained in the same manner as the sample 1.

サンプルＡ１では、第１、第２の活物質核３５Ａ、３５Ｂとしてそれぞれ平均粒径１５μｍ、５μｍに粉砕しＯ／Ｓｉ比（ケイ素に対する酸素の比率）がモル比で１．０１である酸化ケイ素を使用した。また第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ２０分、２０分とし、第１のＣＮＦ３６Ａの繊維長を２２μｍ、第２のＣＮＦ３６Ｂの繊維長を７μｍとした。成長した第１、第２のＣＮＦ３６Ａ、３６Ｂの量は、酸化ケイ素１００重量部当たりそれぞれ４５重量部、４１重量部であった。それ以外はサンプル１と同様にして負極１を得た。なお、第１、第２の複合負極活物質３４Ａ、３４Ｂ全体に占める第１複合負極活物質３４Ａの配合比率はそれぞれ８０％、２０％とした。   In sample A1, silicon oxide having an O / Si ratio (ratio of oxygen to silicon) of 1.01 in terms of a molar ratio obtained by pulverizing the first and second active material nuclei 35A and 35B to an average particle diameter of 15 μm and 5 μm, respectively. used. The growth time of the first and second CNFs 36A and 36B was 20 minutes and 20 minutes, respectively, the fiber length of the first CNF 36A was 22 μm, and the fiber length of the second CNF 36B was 7 μm. The amounts of the grown first and second CNFs 36A and 36B were 45 parts by weight and 41 parts by weight, respectively, per 100 parts by weight of silicon oxide. Otherwise, the negative electrode 1 was obtained in the same manner as the sample 1. The mixing ratio of the first composite negative electrode active material 34A in the entire first and second composite negative electrode active materials 34A and 34B was 80% and 20%, respectively.

サンプルＡ２〜Ａ５では、サンプルＡ１と同様の第１、第２の活物質核３５Ａ、３５Ｂを用い、第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間を変えた以外はサンプルＡ１と同様にして負極１を得た。サンプルＡ２では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ３８分、１２分とし、第１のＣＮＦ３６Ａの繊維長を３３μｍ、第２のＣＮＦ３６Ｂの繊維長を５μｍとした。サンプルＡ３では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ３０分、１４分とし、第１のＣＮＦ３６Ａの繊維長を２７μｍ、第２のＣＮＦ３６Ｂの繊維長を６μｍとした。サンプルＡ４では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ１４分、２７分とし、第１のＣＮＦ３６Ａの繊維長を１７μｍ、第２のＣＮＦ３６Ｂの繊維長を９μｍとした。サンプルＡ５では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ１０分、３０分とし、第１のＣＮＦ３６Ａの繊維長を１４μｍ、第２のＣＮＦ３６Ｂの繊維長を１０μｍとした。   In Samples A2 to A5, the same negative electrode as Sample A1, except that the same first and second active material nuclei 35A and 35B as Sample A1 were used, and the growth times of the first and second CNFs 36A and 36B were changed. 1 was obtained. In sample A2, the growth times of the first and second CNFs 36A and 36B were 38 minutes and 12 minutes, respectively, the fiber length of the first CNF 36A was 33 μm, and the fiber length of the second CNF 36B was 5 μm. In sample A3, the growth times of the first and second CNFs 36A and 36B were 30 minutes and 14 minutes, respectively, the fiber length of the first CNF 36A was 27 μm, and the fiber length of the second CNF 36B was 6 μm. In sample A4, the growth times of the first and second CNFs 36A and 36B were 14 minutes and 27 minutes, respectively, the fiber length of the first CNF 36A was 17 μm, and the fiber length of the second CNF 36B was 9 μm. In sample A5, the growth times of the first and second CNFs 36A and 36B were 10 minutes and 30 minutes, respectively, the fiber length of the first CNF 36A was 14 μm, and the fiber length of the second CNF 36B was 10 μm.

サンプルＡ６〜Ａ９では、第１、第２の複合負極活物質３４Ａ、３４Ｂ全体に占める第１複合負極活物質３４Ａの配合比率を重量比率でそれぞれ４０％、３０％、１０％、５％とした。これ以外はサンプル１と同様にして負極１を得た。   In Samples A6 to A9, the blending ratio of the first composite negative electrode active material 34A in the entire first and second composite negative electrode active materials 34A and 34B was 40%, 30%, 10%, and 5%, respectively. . Except for this, the negative electrode 1 was obtained in the same manner as the sample 1.

サンプルＢ１では、第１、第２の活物質核３５Ａ、３５Ｂとしてそれぞれ平均粒径５μｍ、１５μｍに粉砕しＯ／Ｓｉ比（ケイ素に対する酸素の比率）がモル比で１．０１である酸化ケイ素を使用した。第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ１２０分、５分とし、第１のＣＮＦ３６Ａの繊維長を２２μｍ、第２のＣＮＦ３６Ｂの繊維長を７μｍとした。成長した第１、第２のＣＮＦ３６Ａ、３６Ｂの量は、酸化ケイ素１００重量部当たりそれぞれ１３３重量部、１６重量部であった。それ以外はサンプル１と同様にして負極１を得た。なお、第１、第２の複合負極活物質３４Ａ、３４Ｂ全体に占める第１、第２の複合負極活物質３４Ａ、３４Ｂの配合比率はそれぞれ８０％、２０％とした。   In sample B1, silicon oxide having an O / Si ratio (ratio of oxygen to silicon) of 1.01 in terms of a molar ratio obtained by pulverizing the first and second active material nuclei 35A and 35B to an average particle diameter of 5 μm and 15 μm, respectively. used. The growth time of the first and second CNFs 36A and 36B was 120 minutes and 5 minutes, respectively, the fiber length of the first CNF 36A was 22 μm, and the fiber length of the second CNF 36B was 7 μm. The amounts of the grown first and second CNFs 36A and 36B were 133 parts by weight and 16 parts by weight, respectively, per 100 parts by weight of silicon oxide. Otherwise, the negative electrode 1 was obtained in the same manner as the sample 1. The blending ratio of the first and second composite negative electrode active materials 34A and 34B in the entire first and second composite negative electrode active materials 34A and 34B was 80% and 20%, respectively.

サンプルＢ２〜Ｂ５では、サンプルＢ１と同様の第１、第２の活物質核３５Ａ、３５Ｂを用い、第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間を変えた以外はサンプルＡ１と同様にして負極１を得た。サンプルＢ２では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ２４０分、３分とし、第１のＣＮＦ３６Ａの繊維長を３３μｍ、第２のＣＮＦ３６Ｂの繊維長を５μｍとした。サンプルＢ３では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ１８０分、４分とし、第１のＣＮＦ３６Ａの繊維長を２７μｍ、第２のＣＮＦ３６Ｂの繊維長を６μｍとした。サンプルＢ４では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ８０分、８分とし、第１のＣＮＦ３６Ａの繊維長を１７μｍ、第２のＣＮＦ３６Ｂの繊維長を９μｍとした。サンプルＢ５では第１、第２のＣＮＦ３６Ａ、３６Ｂの成長時間をそれぞれ５５分、１０分とし、第１のＣＮＦ３６Ａの繊維長を１４μｍ、第２のＣＮＦ３６Ｂの繊維長を１０μｍとした。   Samples B2 to B5 are the same as Sample A1 except that the first and second active material nuclei 35A and 35B are the same as Sample B1 and the growth times of the first and second CNFs 36A and 36B are changed. 1 was obtained. In sample B2, the growth times of the first and second CNFs 36A and 36B were 240 minutes and 3 minutes, respectively, the fiber length of the first CNF 36A was 33 μm, and the fiber length of the second CNF 36B was 5 μm. In sample B3, the growth times of the first and second CNFs 36A and 36B were 180 minutes and 4 minutes, respectively, the fiber length of the first CNF 36A was 27 μm, and the fiber length of the second CNF 36B was 6 μm. In sample B4, the growth times of the first and second CNFs 36A and 36B were 80 minutes and 8 minutes, respectively, the fiber length of the first CNF 36A was 17 μm, and the fiber length of the second CNF 36B was 9 μm. In sample B5, the growth times of the first and second CNFs 36A and 36B were 55 minutes and 10 minutes, respectively, the fiber length of the first CNF 36A was 14 μm, and the fiber length of the second CNF 36B was 10 μm.

サンプルＢ６〜Ｂ９では、第１、第２の複合負極活物質３４Ａ、３４Ｂ全体に占める第２の複合負極活物質３４Ｂの配合比率を重量比率でそれぞれ６０％、７０％、９０％、９５％とした。これ以外はサンプルＢ１と同様にして負極１を得た。   In Samples B6 to B9, the blending ratio of the second composite negative electrode active material 34B in the entire first and second composite negative electrode active materials 34A and 34B is 60%, 70%, 90%, and 95% by weight, respectively. did. Other than this, Anode 1 was obtained in the same manner as Sample B1.

なお、比較のため、以下のサンプルを作製した。サンプルＣ１、Ｃ２ではそれぞれ、サンプル１における第１の複合負極活物質３４Ａのみ、第２の複合負極活物質３４Ｂのみを使用した。それ以外はサンプル１と同様にして負極１を得た。サンプルＣ３では、サンプルＡ１と同様の第１、第２の活物質核３５Ａ、３５Ｂを用い、その両方にサンプルＡ１における第１のＣＮＦ３６Ａと同様の繊維長２２μｍのＣＮＦを付着させた。それ以外はサンプルＡ１と同様にして負極１を得た。サンプルＣ４では、サンプルＢ１と同様の第１、第２の活物質核３５Ａ、３５Ｂを用い、その両方にサンプルＢ１における第２のＣＮＦ３６Ｂと同様の繊維長２２μｍのＣＮＦを付着させた。それ以外はサンプルＢ１と同様にして負極１を得た。   For comparison, the following samples were prepared. In Samples C1 and C2, only the first composite negative electrode active material 34A and the second composite negative electrode active material 34B in Sample 1 were used, respectively. Otherwise, the negative electrode 1 was obtained in the same manner as the sample 1. In sample C3, first and second active material nuclei 35A and 35B similar to those in sample A1 were used, and CNF having a fiber length of 22 μm similar to the first CNF 36A in sample A1 was attached to both of them. Otherwise, the negative electrode 1 was obtained in the same manner as the sample A1. In sample C4, first and second active material nuclei 35A and 35B similar to those in sample B1 were used, and CNF having a fiber length of 22 μm similar to the second CNF 36B in sample B1 was attached to both of them. Otherwise, the negative electrode 1 was obtained in the same manner as the sample B1.

（２）電池の作製と評価
上記のように作製した負極１を、直径２０ｍｍ、厚さ１．６ｍｍのケース６に挿入した。その上に厚さ２０μｍのセパレータを介してリチウム金属を配置後、非水電解質３である電解液を数滴注入し、封口して理論容量５ｍＡｈ前後の電池を作製した。電解液は、ＥＣ：ＥＭＣ＝３：７（体積比）である混合溶媒に１．０ｍｏｌ／ｄｍ３のＬｉＰＦ６を溶解させて調製した。 (2) Production and Evaluation of Battery The negative electrode 1 produced as described above was inserted into a case 6 having a diameter of 20 mm and a thickness of 1.6 mm. On top of that, lithium metal was placed through a separator having a thickness of 20 μm, and then a few drops of the electrolyte solution as the non-aqueous electrolyte 3 were injected and sealed to prepare a battery having a theoretical capacity of about 5 mAh. The electrolytic solution was prepared by dissolving 1.0 mol / dm 3 of LiPF 6 in a mixed solvent with EC: EMC = 3: 7 (volume ratio).

このようにして作製した各電池を０．５ｍＡの定電流で０Ｖまで放電し、続いて０．５ｍＡの定電流で１Ｖまで充電した。この操作を３回繰り返した。この３回目の充電容量を初期容量とした。その後、０．５ｍＡの定電流で０Ｖまで放電し、続いて０．５ｍＡの定電流で１Ｖまで充電する充放電サイクルを１００回繰り返した。そして１００回目の充電容量を初期容量で除して容量維持率を算出し、サイクル特性の指標とした。なお、本実施例では金属リチウムより電位の貴な負極１を金属リチウムと組み合わせて電池を構成しているため、充電により負極１がリチウムイオンを放出し、放電により負極１がリチウムイオンを吸蔵する。すなわち、通常の電池の場合と逆になっている。   Each battery thus produced was discharged to 0 V with a constant current of 0.5 mA, and then charged to 1 V with a constant current of 0.5 mA. This operation was repeated three times. This third charge capacity was defined as the initial capacity. Thereafter, a charge / discharge cycle of discharging to 0 V with a constant current of 0.5 mA and subsequently charging to 1 V with a constant current of 0.5 mA was repeated 100 times. The capacity retention rate was calculated by dividing the 100th charge capacity by the initial capacity, and used as an index of cycle characteristics. In this embodiment, the negative electrode 1 having a potential higher than that of metallic lithium is combined with metallic lithium to form a battery. Therefore, the negative electrode 1 releases lithium ions by charging, and the negative electrode 1 absorbs lithium ions by discharging. . That is, it is the reverse of the case of a normal battery.

まずサンプル１〜９とサンプルＣ１、Ｃ２の諸元と評価結果を（表１）に示す。   First, the specifications and evaluation results of Samples 1 to 9 and Samples C1 and C2 are shown in (Table 1).

Figure 2007227138
Figure 2007227138

サンプル１とサンプルＣ１、Ｃ２とを比較すると、明らかにサンプル１のほうが良好なサイクル特性を示している。サンプル１では負極合剤層１２中で長さが異なり圧縮応力の異なる第１、第２のＣＮＦ３６Ａ、３６Ｂがそれぞれ設けられた第１、第２の複合負極活物質３４Ａ、３４Ｂが混在している。圧縮応力の大きい第１のＣＮＦ３６Ａは他の第１のＣＮＦ３６Ａや第２のＣＮＦ３６Ｂと絡んで互いの接触を保てる。ここへ圧縮応力の小さい第２のＣＮＦ３６Ｂが付着した第２の複合負極活物質３４Ｂが添加されることにより、第１のＣＮＦ３６Ａによる反発が抑制されている。このため第１のＣＮＦ３６Ａによる負極１の変形が抑制されることにより、サイクル特性が向上している。   When sample 1 is compared with samples C1 and C2, sample 1 clearly shows better cycle characteristics. In the sample 1, the first and second composite negative electrode active materials 34A and 34B provided with the first and second CNFs 36A and 36B having different lengths and different compressive stresses in the negative electrode mixture layer 12 are mixed. . The first CNF 36A having a large compressive stress is entangled with the other first CNF 36A and the second CNF 36B and can maintain contact with each other. The repulsion by the first CNF 36A is suppressed by adding the second composite negative electrode active material 34B to which the second CNF 36B having a small compressive stress is attached. Therefore, the cycle characteristics are improved by suppressing the deformation of the negative electrode 1 by the first CNF 36A.

一方、サンプルＣ１では全ての第１、第２の活物質核３５Ａ、３５Ｂに圧縮応力の大きい第１のＣＮＦ３６Ａが付着しているため、充放電に伴う第１の活物質核３５Ａの膨張、収縮により負極１が変形するためサイクル特性が低下している。またサンプルＣ２では全ての第１、第２の活物質核３５Ａ、３５Ｂに圧縮応力の小さい第２のＣＮＦ３６Ｂが付着している。そのため、第２のＣＮＦ３６Ｂ同士の接触が充分でなく、負極合剤層１２内の導電ネットワークの形成が充分ではない。そのためサイクル特性が低下している。   On the other hand, in the sample C1, since the first CNF 36A having a large compressive stress is attached to all the first and second active material nuclei 35A and 35B, the expansion and contraction of the first active material nuclei 35A due to charge / discharge. As a result, the negative electrode 1 is deformed, so that the cycle characteristics are degraded. In the sample C2, the second CNF 36B having a small compressive stress is attached to all the first and second active material nuclei 35A and 35B. Therefore, the contact between the second CNFs 36B is not sufficient, and the formation of the conductive network in the negative electrode mixture layer 12 is not sufficient. Therefore, cycle characteristics are degraded.

サンプル１〜５の中では、特にサンプル１のサイクル特性が良好であり、次いでサンプル３、４が良好となっている。以上より、第１、第２のＣＮＦ３６Ａ、３６Ｂの長さの比率には好ましい範囲があることがわかる。すなわち、第１、第２のＣＮＦ３６Ａ、３６Ｂの長さの比は大きすぎても小さすぎても好ましくない。これは第１のＣＮＦ３６Ａが長すぎると圧縮応力が大きすぎて第１の活物質核３５Ａの膨張に伴う応力を第２の複合負極活物質３４Ｂが吸収できないからである。また第１、第２のＣＮＦ３６Ａ、３６Ｂの長さの比が小さいと、両者の長さが異なることによる効果が減少するためと考えられる。   Among samples 1 to 5, the cycle characteristics of sample 1 are particularly good, and then samples 3 and 4 are good. From the above, it can be seen that there is a preferred range for the ratio of the lengths of the first and second CNFs 36A and 36B. That is, it is not preferable that the ratio of the lengths of the first and second CNFs 36A and 36B is too large or too small. This is because if the first CNF 36A is too long, the compressive stress is too large and the second composite negative electrode active material 34B cannot absorb the stress accompanying the expansion of the first active material core 35A. Further, it is considered that if the ratio of the lengths of the first and second CNFs 36A and 36B is small, the effect due to the difference in length between the two decreases.

サンプル１およびサンプル６〜９の比較では、第１の複合負極活物質３４Ａの重量比率が３０％〜５０％の場合にサイクル特性が良好である。このように第１、第２の活物質核３５Ａ、３５Ｂの平均粒径が同等である場合には、このような重量比率とすることが好ましい。   In comparison between Sample 1 and Samples 6 to 9, the cycle characteristics are good when the weight ratio of the first composite negative electrode active material 34A is 30% to 50%. Thus, when the average particle diameters of the first and second active material nuclei 35A and 35B are equal, it is preferable to set such a weight ratio.

次にサンプルＡ１〜Ａ９とサンプルＣ３の諸元と評価結果を（表２）に示す。   Next, the specifications and evaluation results of Samples A1 to A9 and Sample C3 are shown in (Table 2).

Figure 2007227138
Figure 2007227138

サンプルＡ１とサンプルＣ３とを比較すると、明らかにサンプルＡ１のほうが良好なサイクル特性を示している。サンプルＡ１では負極合剤層１２中に、長さが長く圧縮応力の大きい第１のＣＮＦ３６Ａが平均粒径の大きい第１の活物質核３５Ａに付着した第１の複合負極活物質３４Ａと、長さが短く圧縮応力の小さい第２のＣＮＦ３６Ｂが平均粒径の小さい第２の活物質核３５Ｂに付着した第２の複合負極活物質３４Ｂが混在している。この状態では、第１の活物質核３５Ａ同士の隙間に第２の活物質核３５Ｂが入り込む。この状態で第１のＣＮＦ３６Ａは第２のＣＮＦ３６Ｂと強固に絡み合えるので、放電時に第１の活物質核３５Ａが収縮して第１の活物質核３５Ａ同士の距離が大きくなった際に、第１のＣＮＦ３６Ａ同士が接触していた部分が徐々に非接触になっていくという不具合を起こすことはない。そのためサイクル特性が向上している。   Comparing sample A1 and sample C3, sample A1 clearly shows better cycle characteristics. In the sample A1, in the negative electrode mixture layer 12, the first composite negative electrode active material 34A in which the first CNF 36A having a long length and a large compressive stress is attached to the first active material core 35A having a large average particle size, The second composite negative electrode active material 34B in which the second CNF 36B having a short length and a small compressive stress is attached to the second active material core 35B having a small average particle size is mixed. In this state, the second active material nucleus 35B enters the gap between the first active material nuclei 35A. In this state, the first CNF 36A can be tightly entangled with the second CNF 36B. Therefore, when the first active material nucleus 35A contracts during discharge and the distance between the first active material nuclei 35A increases, There is no problem that the portions where the CNFs 36A are in contact with each other gradually become non-contact. Therefore, the cycle characteristics are improved.

一方、サンプルＣ３では第１、第２の活物質核３５Ａ、３５Ｂともに、長さが長く圧縮応力の大きい第１のＣＮＦ３６Ａと同様のＣＮＦが付着している。そのため充電により第１、第２の活物質核３５Ａ、３５Ｂが膨張した際の第１のＣＮＦ３６Ａ同士の反発が大きく、負極１が変形する。そのためサイクル特性が低い。   On the other hand, in the sample C3, CNF similar to the first CNF 36A having a long length and a large compressive stress is attached to both the first and second active material nuclei 35A and 35B. Therefore, the repulsion between the first CNFs 36A when the first and second active material nuclei 35A and 35B expand due to charging is large, and the negative electrode 1 is deformed. Therefore, the cycle characteristics are low.

サンプルＡ１〜Ａ５の中では、特にサンプルＡ１のサイクル特性が良好であり、次いでサンプルＡ３、Ａ４が良好となっている。以上より、サンプルＡ１〜Ａ５の場合と同様に、第１のＣＮＦ３６Ａ、３６Ｂの長さの比率には好ましい範囲があることがわかる。   Among samples A1 to A5, the cycle characteristics of sample A1 are particularly good, and then samples A3 and A4 are good. From the above, it can be seen that the ratio of the lengths of the first CNFs 36A and 36B has a preferable range, as in the case of samples A1 to A5.

サンプルＡ１およびサンプルＡ６〜Ａ９の比較では、第１の複合負極活物質３４Ａの重量比率が７０％〜９０％の場合にサイクル特性が良好である。このように第１の活物質核３５Ａの平均粒径が第２の活物質核３５Ｂの平均粒径より大きい場合には、このような重量比率とすることが好ましい。   In comparison between Sample A1 and Samples A6 to A9, the cycle characteristics are good when the weight ratio of the first composite negative electrode active material 34A is 70% to 90%. Thus, when the average particle diameter of the first active material nucleus 35A is larger than the average particle diameter of the second active material nucleus 35B, such a weight ratio is preferable.

次にサンプルＢ１〜Ｂ９とサンプルＣ４の諸元と評価結果を（表３）に示す。   Next, specifications and evaluation results of Samples B1 to B9 and Sample C4 are shown in (Table 3).

Figure 2007227138
Figure 2007227138

サンプルＢ１とサンプルＣ４とを比較すると、明らかにサンプルＢ１のほうが良好なサイクル特性を示している。サンプルＢ１では負極合剤層１２中に、長さが長く圧縮応力の大きい第１のＣＮＦ３６Ａが平均粒径の小さい第１の活物質核３５Ａに付着した第１の複合負極活物質３４Ａと、長さが短く圧縮応力の小さい第２のＣＮＦ３６Ｂが平均粒径の大きい第２の活物質核３５Ｂに付着した第２の複合負極活物質３４Ｂが混在している。この状態では、第１の活物質核３５Ａ同士の隙間に第２の活物質核３５Ｂが入り込む。この状態で第１のＣＮＦ３６Ａは第２のＣＮＦ３６Ｂと強固に絡み合えるので、放電時に第２の活物質核３５Ｂが収縮して第２の活物質核３５Ｂ同士の距離が大きくなった際に、第２のＣＮＦ３６Ｂ同士が接触していた部分が徐々に非接触になっていくという不具合を起こすことはない。そのためサイクル特性が向上している。   Comparing sample B1 and sample C4, sample B1 clearly shows better cycle characteristics. In the sample B1, the first composite negative electrode active material 34A in which the first CNF 36A having a long length and a large compressive stress is attached to the first active material core 35A having a small average particle size in the negative electrode mixture layer 12; The second composite negative electrode active material 34B in which the second CNF 36B having a short length and a small compressive stress is attached to the second active material core 35B having a large average particle size is mixed. In this state, the second active material nucleus 35B enters the gap between the first active material nuclei 35A. In this state, the first CNF 36A can be tightly entangled with the second CNF 36B. Therefore, when the second active material nucleus 35B contracts during discharge and the distance between the second active material nuclei 35B increases, There is no problem that the portions where the two CNFs 36B are in contact with each other gradually become non-contact. Therefore, the cycle characteristics are improved.

一方、サンプルＣ４では第１、第２の活物質核３５Ａ、３５Ｂともに、長さが長く圧縮応力の大きい第２のＣＮＦ３６Ｂが付着している。そのため充電により第１、第２の活物質核３５Ａ、３５Ｂが膨張した際の第２のＣＮＦ３６Ｂ同士の反発が大きく、負極１が変形する。そのためサイクル特性が低い。   On the other hand, in the sample C4, the second CNF 36B having a long length and a large compressive stress is attached to both the first and second active material nuclei 35A and 35B. Therefore, the repulsion between the second CNFs 36B when the first and second active material nuclei 35A and 35B expand due to charging is large, and the negative electrode 1 is deformed. Therefore, the cycle characteristics are low.

サンプルＢ１〜Ｂ５の中では、特にサンプルＢ１のサイクル特性が良好であり、次いでサンプルＢ３、Ｂ４が良好となっている。以上より、サンプル１〜５の場合と同様に、第１、第２のＣＮＦ３６Ａ、３６Ｂの長さの比率には好ましい範囲があることがわかる。   Among samples B1 to B5, the cycle characteristics of sample B1 are particularly good, and then samples B3 and B4 are good. From the above, it can be seen that the ratio of the lengths of the first and second CNFs 36A and 36B has a preferable range, as in the case of samples 1 to 5.

サンプルＢ１およびサンプルＢ６〜Ｂ９の比較では、第２の複合負極活物質３４Ｂの重量比率が７０％〜９０％の場合にサイクル特性が良好である。このように第２の活物質核３５Ｂの平均粒径が第１の活物質核３５Ａの平均粒径より大きい場合には、このような重量比率とすることが好ましい。   In comparison between Sample B1 and Samples B6 to B9, the cycle characteristics are good when the weight ratio of the second composite negative electrode active material 34B is 70% to 90%. Thus, when the average particle diameter of the second active material nucleus 35B is larger than the average particle diameter of the first active material nucleus 35A, such a weight ratio is preferable.

なお、本実施例ではコイン型二次電池について説明したが、本発明に係わる電池の形状は、これに限定するものではなく、平型電池、捲回式の円筒型電池、捲回式または積層構造の角形電池にも適用することができる。また、本実施の形態では圧縮応力の異なる２種類の第１、第２のＣＮＦ３６Ａ、３６Ｂを用いた例を説明したが、圧縮応力の異なる３種類以上のＣＮＦを用いてもよい。   In this embodiment, the coin-type secondary battery has been described. However, the shape of the battery according to the present invention is not limited to this, and a flat battery, a wound cylindrical battery, a wound type, or a stacked type is used. The present invention can also be applied to a prismatic battery having a structure. In this embodiment, an example using two types of first and second CNFs 36A and 36B having different compressive stresses has been described, but three or more types of CNFs having different compressive stresses may be used.

また、上記説明では本発明の構成を負極に適用した場合について説明したが、活物質核の放電状態における体積に対する充電状態における体積の比が１．２以上であれば、正極に適用してもよい。この場合には非水電解質二次電池用電極は正極、非水電解質二次電池用電極とは異なる電位でリチウムイオンの吸蔵・放出が可能な非水電解質二次電池用第２電極は負極となる。   In the above description, the configuration of the present invention is applied to the negative electrode. However, if the ratio of the volume in the charged state to the volume in the discharged state of the active material nucleus is 1.2 or more, the structure can be applied to the positive electrode. Good. In this case, the electrode for the non-aqueous electrolyte secondary battery is a positive electrode, and the second electrode for the non-aqueous electrolyte secondary battery capable of inserting and extracting lithium ions at a different potential from the electrode for the non-aqueous electrolyte secondary battery is a negative electrode. Become.

本発明は、リチウムイオンの吸蔵・放出が可能で放電状態における体積に対する充電状態における体積の比が、１．２以上である活物質核に圧縮応力の異なるＣＮＦが付着した２種類以上の複合負極活物質を用いて負極合剤層を形成している。このような構成により、実用的なサイクル特性を有する非水電解質二次電池が得られる。すなわち本発明は、炭素材料よりも高容量密度な活物質核にＣＮＦが付着した複合負極活物質を用いる非水電解質二次電池のサイクル特性向上に寄与する。そのため、今後大きな需要が期待されるリチウム二次電池の高エネルギー密度に寄与できる。   The present invention provides two or more types of composite negative electrodes in which CNFs having different compressive stresses are attached to active material cores capable of inserting and extracting lithium ions and having a volume ratio in a charged state to a volume in a discharged state of 1.2 or more. A negative electrode mixture layer is formed using an active material. With such a configuration, a nonaqueous electrolyte secondary battery having practical cycle characteristics can be obtained. That is, the present invention contributes to improving the cycle characteristics of a nonaqueous electrolyte secondary battery using a composite negative electrode active material in which CNF is attached to an active material nucleus having a higher capacity density than that of a carbon material. Therefore, it can contribute to the high energy density of the lithium secondary battery, which is expected to have a great demand in the future.

本発明の実施の形態１による非水電解質二次電池の断面図Sectional drawing of the nonaqueous electrolyte secondary battery by Embodiment 1 of this invention 本発明の実施の形態１における負極中の複合負極活物質の概略図Schematic of the composite negative electrode active material in the negative electrode in Embodiment 1 of the present invention 本発明の実施の形態１における負極中の複合負極活物質の他の概略図The other schematic of the composite negative electrode active material in the negative electrode in Embodiment 1 of this invention 本発明の実施の形態１における負極中の複合負極活物質のさらに他の概略図Still another schematic diagram of the composite negative electrode active material in the negative electrode in Embodiment 1 of the present invention

符号の説明Explanation of symbols

１ 負極
２ 正極
３ 非水電解質
４ ガスケット
５ 蓋体
６ ケース
７，１０ 集電体
８ 正極合剤層
１２ 負極合剤層
３４Ａ 第１の複合負極活物質
３４Ｂ 第２の複合負極活物質
３５Ａ 第１の活物質核
３５Ｂ 第２の活物質核
３６Ａ 第１のカーボンナノファイバ（ＣＮＦ）
３６Ｂ 第２のカーボンナノファイバ（ＣＮＦ） DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Positive electrode 3 Nonaqueous electrolyte 4 Gasket 5 Lid 6 Case 7, 10 Current collector 8 Positive electrode mixture layer 12 Negative electrode mixture layer 34A First composite negative electrode active material 34B Second composite negative electrode active material 35A First Active material core 35B second active material core 36A first carbon nanofiber (CNF)
36B Second carbon nanofiber (CNF)

Claims (13)

リチウムイオンの吸蔵・放出が可能な第１の活物質核に第１のカーボンナノファイバを付着させた第１の複合負極活物質と、リチウムイオンの吸蔵・放出が可能な第２の活物質核に第２のカーボンナノファイバを付着させた第２の複合活物質とからなり、第２の複合活物質を圧縮したときの圧縮応力が第１の複合活物質を圧縮した時の圧縮応力より小さいことを特徴とし、かつ前記第１、第２の活物質核の放電状態における体積に対する充電状態における体積の比を１．２以上とした非水電解質二次電池用電極。 A first composite negative electrode active material in which a first carbon nanofiber is attached to a first active material nucleus capable of occluding and releasing lithium ions; and a second active material nucleus capable of occluding and releasing lithium ions. And a second composite active material having a second carbon nanofiber attached thereto, and the compressive stress when compressing the second composite active material is smaller than the compressive stress when compressing the first composite active material An electrode for a non-aqueous electrolyte secondary battery in which the ratio of the volume in the charged state to the volume in the discharged state of the first and second active material nuclei is 1.2 or more. 前記第１のカーボンナノファイバと前記第２のカーボンナノファイバとは同等のバネ定数を有するとともに前記第２のカーボンナノファイバを前記第１のカーボンナノファイバより短くした請求項１に記載の非水電解質二次電池用電極。 2. The non-aqueous solution according to claim 1, wherein the first carbon nanofiber and the second carbon nanofiber have an equivalent spring constant and the second carbon nanofiber is shorter than the first carbon nanofiber. Electrode for secondary battery. 前記第１の活物質核の平均粒径と前記第２の活物質核の平均粒径とが同等であり、前記第１の複合活物質と前記第２の複合活物質とを含む複合活物質全体に占める前記第１の複合活物質の重量比率を３０％以上、５０％以下とした請求項１に記載の非水電解質二次電池用電極。 A composite active material in which an average particle diameter of the first active material nucleus and an average particle diameter of the second active material nucleus are equal, and the first composite active material and the second composite active material are included. The electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein a weight ratio of the first composite active material to the whole is 30% or more and 50% or less. 前記第１の活物質核の平均粒径を、前記第２の活物質核の平均粒径より大きくした請求項１に記載の非水電解質二次電池用電極。 The electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein an average particle diameter of the first active material nucleus is larger than an average particle diameter of the second active material nucleus. 前記第１の複合活物質と前記第２の複合活物質とを含む複合活物質全体に占める前記第１の複合活物質の重量比率を、前記第２の複合活物質の重量比率より大きくした請求項４に記載の非水電解質二次電池用電極。 Claims wherein the weight ratio of the first composite active material in the total composite active material including the first composite active material and the second composite active material is greater than the weight ratio of the second composite active material. Item 5. The nonaqueous electrolyte secondary battery electrode according to Item 4. 前記第１の複合活物質の重量比率を７０％以上、９０％以下とした請求項５に記載の非水電解質二次電池用電極。 The electrode for a non-aqueous electrolyte secondary battery according to claim 5, wherein a weight ratio of the first composite active material is 70% or more and 90% or less. 前記第２の活物質核の平均粒径を、前記第１の活物質核の平均粒径より大きくした請求項１に記載の非水電解質二次電池用電極。 The electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein an average particle diameter of the second active material nucleus is larger than an average particle diameter of the first active material nucleus. 前記第１の複合活物質と前記第２の複合活物質とを含む複合活物質全体に占める前記第２の複合活物質の重量比率を、前記第１の複合活物質の重量比率より大きくした請求項７に記載の非水電解質二次電池用電極。 Claims wherein the weight ratio of the second composite active material in the total composite active material including the first composite active material and the second composite active material is larger than the weight ratio of the first composite active material. Item 8. A nonaqueous electrolyte secondary battery electrode according to Item 7. 前記第２の複合活物質の重量比率を７０％以上、９０％以下とした請求項８に記載の非水電解質二次電池用電極。 The electrode for a nonaqueous electrolyte secondary battery according to claim 8, wherein a weight ratio of the second composite active material is 70% or more and 90% or less. 前記第１の活物質核と前記第２の活物質核とを同じ物質とした請求項１に記載の非水電解質二次電池用電極。 The electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the first active material nucleus and the second active material nucleus are the same material. 前記非水電解質二次電池用電極は負極であり、前記第１の活物質核と前記第２の活物質核とがケイ素を含む材料で構成した請求項１０に記載の非水電解質二次電池用電極。 The nonaqueous electrolyte secondary battery according to claim 10, wherein the electrode for the nonaqueous electrolyte secondary battery is a negative electrode, and the first active material nucleus and the second active material nucleus are made of a material containing silicon. Electrode. 前記第１の活物質核と前記第２の活物質核とが酸化ケイ素であり、ケイ素に対する酸素の比率を０．３以上、１．３以下とした請求項１１に記載の非水電解質二次電池用電極。 The nonaqueous electrolyte secondary according to claim 11, wherein the first active material nucleus and the second active material nucleus are silicon oxide, and a ratio of oxygen to silicon is 0.3 or more and 1.3 or less. Battery electrode. 請求項１から１２のいずれか一項に記載の非水電解質二次電池用電極と、前記非水電解質二次電池用電極とは異なる電位でリチウムイオンの吸蔵・放出が可能な非水電解質二次電池用第２電極と、前記非水電解質二次電池用電極と前記非水電解質二次電池用第２電極との間に介在させた非水電解質とを備えた非水電解質二次電池。 The non-aqueous electrolyte secondary battery capable of inserting and extracting lithium ions at a potential different from that of the non-aqueous electrolyte secondary battery electrode according to any one of claims 1 to 12 and the non-aqueous electrolyte secondary battery electrode. A nonaqueous electrolyte secondary battery comprising: a second electrode for a secondary battery; and a nonaqueous electrolyte interposed between the electrode for a nonaqueous electrolyte secondary battery and the second electrode for a nonaqueous electrolyte secondary battery.
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Cited By (6)

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JP2009016265A (en) * 2007-07-06 2009-01-22 Showa Denko Kk Electrode for lithium battery, manufacturing method of electrode for lithium battery, lithium battery, and manufacturing method for lithium battery
JP2009245773A (en) * 2008-03-31 2009-10-22 Sanyo Electric Co Ltd Lithium secondary battery and its manufacturing method
JP2011192453A (en) * 2010-03-12 2011-09-29 Shin-Etsu Chemical Co Ltd Negative electrode material for nonaqueous electrolyte secondary battery, method of manufacturing the same, lithium ion secondary battery, and electrochemical capacitor
JP2012099341A (en) * 2010-11-02 2012-05-24 Shin Etsu Chem Co Ltd Negative electrode material for nonaqueous electrolyte secondary battery and method for producing the same, lithium ion secondary battery, and electrochemical capacitor
JP2013008696A (en) * 2012-09-18 2013-01-10 Shin Etsu Chem Co Ltd Method of manufacturing negative electrode material for nonaqueous electrolyte secondary battery
JP2015511374A (en) * 2012-12-21 2015-04-16 エルジー・ケム・リミテッド Negative electrode material for lithium secondary battery, method for producing the same, and lithium secondary battery including the same

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009016265A (en) * 2007-07-06 2009-01-22 Showa Denko Kk Electrode for lithium battery, manufacturing method of electrode for lithium battery, lithium battery, and manufacturing method for lithium battery
JP2009245773A (en) * 2008-03-31 2009-10-22 Sanyo Electric Co Ltd Lithium secondary battery and its manufacturing method
JP2011192453A (en) * 2010-03-12 2011-09-29 Shin-Etsu Chemical Co Ltd Negative electrode material for nonaqueous electrolyte secondary battery, method of manufacturing the same, lithium ion secondary battery, and electrochemical capacitor
JP2012099341A (en) * 2010-11-02 2012-05-24 Shin Etsu Chem Co Ltd Negative electrode material for nonaqueous electrolyte secondary battery and method for producing the same, lithium ion secondary battery, and electrochemical capacitor
JP2013008696A (en) * 2012-09-18 2013-01-10 Shin Etsu Chem Co Ltd Method of manufacturing negative electrode material for nonaqueous electrolyte secondary battery
JP2015511374A (en) * 2012-12-21 2015-04-16 エルジー・ケム・リミテッド Negative electrode material for lithium secondary battery, method for producing the same, and lithium secondary battery including the same

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