JP2007018794A - Carbon material electrode, its manufacturing method and nonaqueous electrolyte secondary battery - Google Patents
Carbon material electrode, its manufacturing method and nonaqueous electrolyte secondary battery Download PDFInfo
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Abstract
Description
本発明は、炭素材電極及びその製造方法、並びに該炭素材電極を負極として備えた非水電解液二次電池に関し、特に、リチウムイオン電池、ハイブリッドキャパシタ、電気二重層キャパシタ等の大容量、大出力が要求される電源の電極に関するものである。 The present invention relates to a carbon material electrode, a method for producing the same, and a non-aqueous electrolyte secondary battery including the carbon material electrode as a negative electrode, and in particular, a large capacity, large capacity such as a lithium ion battery, a hybrid capacitor, and an electric double layer capacitor. The present invention relates to an electrode of a power supply that requires output.
昨今、携帯用端末やモバイル通信機器として広く普及したリチウムイオン電池やキャパシタが、ハイブリッド自動車や燃料電池自動車の補助電源として、あるいは定置用大型電源としても注目を集めており、広く研究が行われている。中でも、リチウムイオン電池は、現存する二次電池の中でも最もエネルギー密度が大きいことから、更なる広範囲な適用に期待がかかっている。 Recently, lithium-ion batteries and capacitors, which have been widely used as portable terminals and mobile communication devices, are attracting attention as auxiliary power sources for hybrid vehicles and fuel cell vehicles, or as large-scale power sources for stationary use. Yes. In particular, lithium ion batteries have the highest energy density among existing secondary batteries, and are expected to be used in a wider range of applications.
上記リチウムイオン電池は、リチウムイオンを電気化学的に吸蔵・離脱可能な層状構造の正極（例えば、ＬｉＣｏＯ2）と同特性を有する負極（例えば、黒鉛）がリチウムイオンを溶解した電解液を介して対向した構造を有する電池であり、一般に、正極と負極との短絡を防止するために電解液を透過しうる多孔質ポリマー膜が両極材の間に配置された構造を有している。上記電極系の場合、充電によってリチウムイオンが負極層間で還元され電気を蓄えた状態、例えば、Ｃ6Ｌｉとなって固定される。この際、正極からはＬｉが放出され、例えば、Ｌｉ0.44ＣｏＯ2のような構造をとる。このように非常に高い還元状態となった負極と、非常に高い酸化状態になった正極とを外部負荷の下で放電すると、非常に電圧が高く、且つ高容量の電気を取り出すことができる。なお、リチウムイオン電池は、正負極間の層をＬｉイオンが出入りする電池であるため、一般に、ロッキングチェアー電池と呼ばれることが多い。 The lithium ion battery includes a negative electrode (for example, graphite) having the same characteristics as a positive electrode (for example, LiCoO 2 ) having a layered structure capable of electrochemically inserting and extracting lithium ions via an electrolytic solution in which lithium ions are dissolved. A battery having a structure opposite to each other, and generally has a structure in which a porous polymer film capable of permeating an electrolytic solution is disposed between both electrodes in order to prevent a short circuit between a positive electrode and a negative electrode. In the case of the above electrode system, the lithium ions are reduced between the negative electrode layers by charging and stored in a state where electricity is stored, for example, C 6 Li and fixed. At this time, Li is released from the positive electrode, and takes a structure such as Li 0.44 CoO 2 , for example. As described above, when the negative electrode in a very high reduction state and the positive electrode in a very high oxidation state are discharged under an external load, a very high voltage and high capacity electricity can be taken out. In addition, since a lithium ion battery is a battery in which Li ions enter and exit the layer between the positive and negative electrodes, it is generally often called a rocking chair battery.
上記リチウムイオン電池は、１９９２年に市場に投入され、その後２０００年まで年率にして30％以上の急成長を見せた電池である。市場投入当時のリチウムイオン電池の電池容量は、１８６５０型電池にして800mAh程度であったが、２００５年現在ではその容量は2500mAhに達しており、実に3倍の容量向上が実現された。この電池容量の向上は、主に負極の単位重量あたりの容量の向上によってもたらされたものであるが、負極の黒鉛の容量も限界に近づいており、現在、大きなブレークスルー技術の開発が嘱望されている。 The lithium-ion battery was put on the market in 1992, and thereafter showed rapid growth of 30% or more until 2000. The battery capacity of the lithium-ion battery at the time of market introduction was about 800 mAh for a 18650 type battery. However, as of 2005, the capacity reached 2500 mAh, and the capacity was actually tripled. This increase in battery capacity is mainly due to the increase in capacity per unit weight of the negative electrode, but the capacity of graphite in the negative electrode is approaching its limit, and the development of a large breakthrough technology is currently envy. Has been.
このように負極容量設計がほぼ限界にきており、新たな負極の出現が望まれているリチウムイオン電池において、近年、ＳｉやＳｎ等のリチウムイオンを電気化学的に大量に吸蔵・脱離できる金属が注目されている。なお、黒鉛の吸蔵・脱離能力が372mAh/gであるのに対し、これら金属の吸蔵・脱離能力は約3000〜4000mAh/gに上ることが知られている。 Thus, in the lithium ion battery in which the negative electrode capacity design has almost reached its limit, and a new negative electrode is desired, in recent years, lithium ions such as Si and Sn can be electrochemically occluded and desorbed in large quantities. Metal is drawing attention. It is known that the occlusion / desorption ability of these metals is about 3000 to 4000 mAh / g, whereas the occlusion / desorption ability of graphite is 372 mAh / g.
しかしながら、これら金属は、リチウムの吸蔵・脱離に伴う体積膨張・収縮が極めて大きく、例えば、Ｓｉの場合は吸蔵によりその体積が200％となるため、充放電サイクルが進むにつれＣｕ等からなる集電体から剥離してしまい、電極として機能しなくなるという大きな間題点を抱えている。 However, these metals have extremely large volume expansion / contraction due to insertion / extraction of lithium. For example, in the case of Si, the volume becomes 200% by occlusion. It has a big problem that it peels off from the electric body and does not function as an electrode.
これに対して、金属状のシリコン等をそのまま用いるのではなく、表面にカーボンをコーティンクしたシリコン粒子を使用する等して、異種物質で膨張・収縮に伴う体積変化を吸収する試みも見られるが、依然として本質的な問題の解決には至っていない。 On the other hand, there is an attempt to absorb volume change due to expansion / contraction with a different substance by using silicon particles coated with carbon on the surface instead of using metallic silicon or the like as it is. Still, the essential problem has not been solved.
そこで、本発明の目的は、上記従来技術の問題を解決し、電極中の金属の利用率が高く、且つ該金属の電気化学反応に伴う体積変化を効率よく吸収することが可能な電源用電極及びその製造方法を提供することにある。 Accordingly, an object of the present invention is to solve the above-described problems of the prior art, have a high utilization rate of the metal in the electrode, and can efficiently absorb the volume change caused by the electrochemical reaction of the metal. And a manufacturing method thereof.
本発明者らは、上記目的を達成するために鋭意検討した結果、３次元連続状で網目構造を有する炭素繊維に化学メッキで金属微粒子を担持することにより、金属微粒子を炭素繊維表面にのみ担持することができ、且つ該炭素繊維が３次元網目状に連続しており導電性に優れるため、金属の利用効率を大幅に向上させることができ、更には炭素繊維の網目構造の空隙が担持された金属微粒子の体積膨張を吸収するため、電極として使用した際のサイクル特性が非常に優れることを見出し、本発明を完成させるに至った。 As a result of intensive studies to achieve the above object, the present inventors supported metal fine particles only on the surface of carbon fibers by supporting metal fine particles by chemical plating on carbon fibers having a three-dimensional continuous network structure. Since the carbon fibers are continuous in a three-dimensional network and are excellent in conductivity, the metal utilization efficiency can be greatly improved, and voids in the carbon fiber network structure are supported. In order to absorb the volume expansion of the fine metal particles, the inventors have found that the cycle characteristics when used as an electrode are extremely excellent, and have completed the present invention.
即ち、本発明の炭素材電極は、３次元連続状炭素繊維に化学メッキ（無電解メッキ）により金属微粒子を担持してなることを特徴とする。ここで、本発明の炭素材電極は、３次元連続状炭素繊維と、該炭素繊維上に化学メッキで担持された金属微粒子とからなり、３次元連続状炭素繊維が導電体として機能する一方、金属微粒子が電気吸蔵体或いはリチウム吸蔵体として機能する。 That is, the carbon material electrode of the present invention is characterized in that metal fine particles are supported on a three-dimensional continuous carbon fiber by chemical plating (electroless plating). Here, the carbon material electrode of the present invention comprises a three-dimensional continuous carbon fiber and metal fine particles supported by chemical plating on the carbon fiber, while the three-dimensional continuous carbon fiber functions as a conductor, The metal fine particles function as an electric occlusion body or a lithium occlusion body.
本発明の炭素材電極の好適例においては、前記３次元連続状炭素繊維が、芳香環を有する化合物を酸化重合して得られるフィブリル状ポリマーを非酸化性雰囲気中で焼成して得たものである。ここで、前記芳香環を有する化合物としては、アニリン、ピロール、チオフェン、及びそれらの誘導体からなる群から選択される少なくとも一種の化合物が好ましい。また、前記酸化重合としては、電解酸化重合が好ましい。 In a preferred example of the carbon material electrode of the present invention, the three-dimensional continuous carbon fiber is obtained by firing a fibril polymer obtained by oxidative polymerization of a compound having an aromatic ring in a non-oxidizing atmosphere. is there. Here, the compound having an aromatic ring is preferably at least one compound selected from the group consisting of aniline, pyrrole, thiophene, and derivatives thereof. The oxidative polymerization is preferably electrolytic oxidative polymerization.
本発明の炭素材電極においては、前記金属微粒子を構成する金属がリチウムを吸蔵・脱離可能な金属であることが好ましい。ここで、該金属微粒子は、Ｓｎ、Ｓｉ、Ｐｂ、Ａｌ、Ａｕ、Ｐｔ、Ｉｎ、Ｚｎ、Ｃｄ、Ａｇ及びＭｇからなる群から選択される少なくとも一種の金属を含むことが好ましく、Ｓｎ及び／又はＳｉを含むことが特に好ましい。 In the carbon material electrode of the present invention, the metal constituting the metal fine particles is preferably a metal capable of inserting and extracting lithium. Here, the metal fine particles preferably include at least one metal selected from the group consisting of Sn, Si, Pb, Al, Au, Pt, In, Zn, Cd, Ag, and Mg, and Sn and / or It is particularly preferable that Si is included.
本発明の炭素材電極は、前記３次元連続状炭素繊維の空隙の50体積％以下が前記金属微粒子で充填されていることが好ましい。この場合、充放電サイクルにおいて、炭素繊維上に担持された金属微粒子が膨張しても、炭素材電極全体としての膨張が十分に防止されている。 In the carbon material electrode of the present invention, 50% by volume or less of the voids of the three-dimensional continuous carbon fiber is preferably filled with the metal fine particles. In this case, even if the metal fine particles supported on the carbon fiber expand in the charge / discharge cycle, the expansion of the entire carbon material electrode is sufficiently prevented.
また、本発明の金属微粒子を３次元連続状炭素繊維に担持してなる炭素材電極の製造方法は、
(i)芳香環を有する化合物を酸化重合してフィブリル状ポリマーを生成させる工程と、
(ii)前記フィブリル状ポリマーを非酸化性雰囲気中で焼成して３次元連続状炭素繊維を生成させる工程と、
(iii)前記３次元連続状炭素繊維に化学メッキ（無電解メッキ）により金属微粒子を担持する工程と
を含むことを特徴とする。
In addition, a method for producing a carbon material electrode in which the metal fine particles of the present invention are supported on a three-dimensional continuous carbon fiber,
(i) a step of oxidatively polymerizing a compound having an aromatic ring to produce a fibrillated polymer;
(ii) firing the fibrillated polymer in a non-oxidizing atmosphere to form a three-dimensional continuous carbon fiber;
(iii) a step of supporting metal fine particles on the three-dimensional continuous carbon fiber by chemical plating (electroless plating).
更に、本発明の非水電解液二次電池は、上記の炭素材電極を負極として備えることを特徴とする。 Furthermore, the non-aqueous electrolyte secondary battery of the present invention is characterized by including the above carbon material electrode as a negative electrode.
本発明によれば、３次元連続状炭素繊維に金属微粒子を化学メッキで担持してなり、電極中の金属の利用率が高く、且つ該金属の電気化学反応に伴う体積変化を効率よく吸収することが可能な炭素材電極を提供することができる。また、該炭素材電極を負極として備え、サイクル特性に優れた非水電解液二次電池を提供することができる。 According to the present invention, metal fine particles are supported on a three-dimensional continuous carbon fiber by chemical plating, the utilization rate of the metal in the electrode is high, and the volume change accompanying the electrochemical reaction of the metal is efficiently absorbed. The carbon material electrode which can be provided can be provided. Moreover, the non-aqueous electrolyte secondary battery provided with this carbon material electrode as a negative electrode and excellent in cycle characteristics can be provided.
＜炭素材電極及びその製造方法＞
以下に、本発明の炭素材電極及びその製造方法を詳細に説明する。本発明の炭素材電極は、３次元連続状炭素繊維に化学メッキで金属微粒子を担持してなる。本発明の炭素材電極を構成する３次元連続状炭素繊維は、３次元連続状であるため、導電性が高く、金属微粒子上で起こる酸化・還元反応に伴う電子を効果的に集電体に伝導することができる。そのため、本発明の炭素材電極には、特に外部から導電体を追加付与する必要はない。また、本発明の炭素材電極においては、金属が微粒子状に担持されているため、金属の比表面積、即ち、反応面積が大きい。そのため、本発明の炭素材電極は、大電流での充電や放電特性にも優れる。更に、本発明の炭素材電極においては、３次元連続状炭素繊維が３次元網目構造を有し、該網目構造が金属微粒子の電気化学反応に伴う体積変化を効率よく吸収するため、炭素材電極全体としての体積変化が殆どなく、隣接する集電体等と剥離することがない。そのため、本発明の炭素材電極を用いた電源は、充放電サイクル特性に優れている。また更に、化学メッキで金属微粒子を３次元連続状炭素繊維上に析出させるため、金属微粒子が炭素繊維と接触した状態で析出させることができ、金属微粒子と炭素繊維との接触性が優れる。その結果、炭素材電極における金属の利用効率の向上が達成される上、該炭素材電極を用いた電源の内部抵抗を低減することもできる。
<Carbon material electrode and manufacturing method thereof>
Below, the carbon material electrode of this invention and its manufacturing method are demonstrated in detail. The carbon material electrode of the present invention comprises metal fine particles supported on a three-dimensional continuous carbon fiber by chemical plating. Since the three-dimensional continuous carbon fiber constituting the carbon material electrode of the present invention is three-dimensional continuous, it has high conductivity, and the electrons accompanying oxidation / reduction reactions occurring on the metal fine particles are effectively used as a current collector. Can conduct. Therefore, it is not necessary to add a conductor to the carbon material electrode of the present invention from the outside. Further, in the carbon material electrode of the present invention, since the metal is supported in the form of fine particles, the specific surface area of the metal, that is, the reaction area is large. Therefore, the carbon material electrode of the present invention is excellent in charging and discharging characteristics at a large current. Furthermore, in the carbon material electrode of the present invention, the three-dimensional continuous carbon fiber has a three-dimensional network structure, and the network structure efficiently absorbs the volume change accompanying the electrochemical reaction of the metal fine particles. There is almost no volume change as a whole, and there is no separation from the adjacent current collector. Therefore, the power supply using the carbon material electrode of the present invention is excellent in charge / discharge cycle characteristics. Furthermore, since the metal fine particles are deposited on the three-dimensional continuous carbon fiber by chemical plating, the metal fine particles can be deposited in contact with the carbon fibers, and the contact property between the metal fine particles and the carbon fibers is excellent. As a result, the utilization efficiency of the metal in the carbon material electrode can be improved, and the internal resistance of the power source using the carbon material electrode can be reduced.
本発明においては、上記金属微粒子の炭素繊維上への担持法として、化学メッキ法（無電解メッキ法）を採用する。該化学メッキ法では、メッキしたい金属イオンと還元剤とを含む容液を調製し、該溶液に上記炭素繊維を浸漬することで、メッキされる金属イオンが還元剤との反応で還元され金属となって炭素繊維上に析出する。ここで、還元剤の還元力が強過ぎる場合には、炭素繊維を浸漬する前に金属イオンが還元されて溶液中に沈降してしまう。従って、炭素繊維を浸漬することで、還元剤或いは金属イオンが炭素繊維に吸着し、その結果、電子状態が変化する（還元電位が変わる）ことでメッキが開始されることが好ましい。そのため、メッキされる金属イオンの還元され易さに応じて、適宜還元剤を選択することが好ましい。また、上記溶液中には、更に錯体形成剤を添加することが好ましく、該錯体形成剤としては、エチレンジアミン四酢酸二ナトリウム、クエン酸ナトリウム、ニトリロ三酢酸等が挙げられる。なお、金属イオンの種類及び濃度、還元剤の種類及び濃度、メッキ時間（浸漬時間）、メッキ浴の温度等を適宜選択することで、析出させる金属微粒子の量、粒径、形態、付着状況等を変えることができる。 In the present invention, a chemical plating method (electroless plating method) is employed as a method for supporting the metal fine particles on the carbon fiber. In the chemical plating method, a solution containing a metal ion to be plated and a reducing agent is prepared, and by immersing the carbon fiber in the solution, the metal ion to be plated is reduced by reaction with the reducing agent and the metal. And deposited on the carbon fiber. Here, when the reducing power of the reducing agent is too strong, the metal ions are reduced and settled in the solution before dipping the carbon fiber. Therefore, it is preferable that the plating is started when the reducing agent or the metal ion is adsorbed to the carbon fiber by immersing the carbon fiber, and as a result, the electronic state is changed (the reduction potential is changed). Therefore, it is preferable to select a reducing agent as appropriate according to the ease of reduction of the metal ions to be plated. Further, it is preferable to further add a complex-forming agent to the above solution, and examples of the complex-forming agent include ethylenediaminetetraacetic acid disodium, sodium citrate, nitrilotriacetic acid and the like. It should be noted that the amount, particle size, form, adhesion status, etc. of the metal fine particles to be deposited by appropriately selecting the type and concentration of metal ions, the type and concentration of reducing agent, the plating time (dipping time), the temperature of the plating bath, etc. Can be changed.
上記３次元連続状炭素繊維は、例えば、芳香環を有する化合物を酸化重合してフィブリル状ポリマーを生成させた後、該フィブリル状ポリマーを非酸化性雰囲気中で焼成することで得られる。上記芳香環を有する化合物としては、ベンゼン環を有する化合物、芳香族複素環を有する化合物を挙げることができる。ここで、ベンゼン環を有する化合物としては、アニリン及びアニリン誘導体が好まく、芳香族複素環を有する化合物としては、ピロール、チオフェン及びこれらの誘導体が好ましい。これら芳香環を有する化合物は、一種単独で用いても、二種以上の混合物として用いてもよい。 The three-dimensional continuous carbon fiber can be obtained, for example, by oxidizing a compound having an aromatic ring to produce a fibril polymer, and then firing the fibril polymer in a non-oxidizing atmosphere. Examples of the compound having an aromatic ring include a compound having a benzene ring and a compound having an aromatic heterocyclic ring. Here, aniline and aniline derivatives are preferred as the compound having a benzene ring, and pyrrole, thiophene and derivatives thereof are preferred as the compound having an aromatic heterocycle. These compounds having an aromatic ring may be used alone or as a mixture of two or more.
上記芳香環を有する化合物を酸化重合して得られるフィブリル状ポリマーは、直径が30nm〜数百nmで、好ましくは40nm〜500nmであり、長さが0.5μm〜100mmで、好ましくは1μm〜10mmである。 The fibrillar polymer obtained by oxidative polymerization of the compound having an aromatic ring has a diameter of 30 nm to several hundreds of nm, preferably 40 nm to 500 nm, and a length of 0.5 μm to 100 mm, preferably 1 μm to 10 mm. is there.
上記酸化重合法としては、電解酸化重合法及び化学的酸化重合法等の種々の方法が利用できるが、中でも電解酸化重合法が好ましい。また、酸化重合においては、原料の芳香環を有する化合物と共に、酸を混在させることが好ましい。この場合、酸の負イオンがドーパントとして合成されるフィブリル状ポリマー中に取り込まれ、導電性に優れるフィブリル状ポリマーが得られ、このフィブリル状ポリマーを用いることにより炭素繊維の導電性を更に向上させることができる。 As the oxidative polymerization method, various methods such as an electrolytic oxidative polymerization method and a chemical oxidative polymerization method can be used. Among them, the electrolytic oxidative polymerization method is preferable. Moreover, in oxidative polymerization, it is preferable to mix an acid with the compound which has a raw material aromatic ring. In this case, the negative ion of the acid is taken into the fibril polymer synthesized as a dopant to obtain a fibril polymer excellent in conductivity, and the conductivity of the carbon fiber is further improved by using this fibril polymer. Can do.
この点について更に詳述すると、例えば、重合原料としてアニリンを用いた場合、アニリンをＨＢＦ4を混在させた状態で酸化重合して得られるポリアニリンは、通常下記式（Ａ）〜（Ｄ）：
に示した４種のポリアニリンが混在した状態、即ち、ベンゾノイド＝アミン状態（式Ａ）、ベンゾノイド＝アンモニウム状態（式Ｂ）、ドープ＝セミキノンラジカル状態（式Ｃ）及びキノイド＝ジイミン状態（式Ｄ）の混合状態になる。ここで、上記各状態の混合比率は特に制限されるものではないが、ドープ＝セミキノンラジカル状態（式Ｃ）を多く含んでいる方がキノイド＝ジイミン状態（式Ｄ）が大部分であるよりも得られる炭素繊維の残炭率及び導電率が高くなる。従って、ドープ＝セミキノンラジカル状態（式Ｃ）を多く含むポリアニリンを得るためには、重合時に酸を混在させることが好ましい。なお、重合の際に混在させる酸としては、上記ＨＢＦ4に限定されるものではなく、種々のものを使用することができ、ＨＢＦ4の他、Ｈ2ＳＯ4、ＨＣｌ、ＨＣｌＯ4等を例示することができる。ここで、該酸の濃度は、0.1〜3mol/Lの範囲が好ましく、0.5〜2.5mol/Lの範囲が更に好ましい。
More specifically, for example, when aniline is used as a polymerization raw material, polyaniline obtained by oxidative polymerization of aniline in a state where HBF 4 is mixed is usually represented by the following formulas (A) to (D):
In the state where the four polyanilines shown in FIG. 4 are mixed, that is, benzonoid = amine state (formula A), benzonoid = ammonium state (formula B), dope = semiquinone radical state (formula C) and quinoid = diimine state (formula D) ). Here, the mixing ratio of each of the above states is not particularly limited, but the quinoid = diimine state (formula D) is mostly contained when the dope = semiquinone radical state (formula C) is contained in a large amount. Further, the carbon residue and conductivity of the carbon fiber obtained are increased. Therefore, in order to obtain polyaniline containing a large amount of dope = semiquinone radical state (formula C), it is preferable to mix an acid during polymerization. As the acid to be mixed in the polymerization, is not limited to the above HBF 4, can be used various ones, other HBF 4, H 2 SO 4, HCl, illustrate HClO 4, etc. can do. Here, the concentration of the acid is preferably in the range of 0.1 to 3 mol / L, and more preferably in the range of 0.5 to 2.5 mol / L.
上記ドープ＝セミキノンラジカル状態（式Ｃ）の含有割合（ドーピングレベル）は適宜調節することができ、この含有割合（ドーピングレベル）を調節することにより、得られる炭素繊維の残炭率及び導電率を制御することができ、ドーピングレベルを高くすることにより得られる炭素繊維の残炭率及び導電率が共に高くなる。なお、特に限定されるものではないが、このドープ＝セミキノンラジカル状態（式Ｃ）の含有割合（ドーピングレベル）は、通常0.01〜50％の範囲とすることが好ましい。 The content ratio (doping level) of the dope = semiquinone radical state (formula C) can be adjusted as appropriate, and by adjusting the content ratio (doping level), the residual carbon ratio and conductivity of the carbon fiber obtained. It is possible to control the residual carbon ratio and conductivity of the carbon fiber obtained by increasing the doping level. Although not particularly limited, the content ratio (doping level) of the dope = semiquinone radical state (formula C) is usually preferably in the range of 0.01 to 50%.
電解酸化重合によりフィブリル状ポリマーを得る場合には、芳香環を有する化合物を含む溶液中に作用極及び対極となる一対の電極板を浸漬し、両極間に前記芳香環を有する化合物の酸化電位以上の電圧を印加するか、または該芳香環を有する化合物が重合するのに充分な電圧が確保できるような条件の電流を通電すればよく、これにより作用極上にフィブリル状ポリマーが生成する。この電解酸化重合法によるフィブリル状ポリマーの合成方法の一例を挙げると、作用極及び対極としてステンレススチール、白金、カーボン等の良導電性物質からなる板や多孔質材などを用い、これらをＨ2ＳＯ4、ＨＢＦ4等の酸及び芳香環を有する化合物を含む電解溶液中に浸漬し、両極間に0.1〜1000mA/cm2、好ましくは0.2〜100mA/cm2の電流を通電して、作用極側にフィブリル状ポリマーを重合析出させる方法などが例示される。ここで、芳香環を有する化合物の電解溶液中の濃度は、0.05〜3mol/Lの範囲が好ましく、0.25〜1.5mol/Lの範囲が更に好ましい。また、電解溶液には、上記成分に加え、ｐＨを調製するために可溶性塩等を適宜添加してもよい。 In the case of obtaining a fibrillated polymer by electrolytic oxidation polymerization, a pair of electrode plates serving as a working electrode and a counter electrode are immersed in a solution containing a compound having an aromatic ring, and the oxidation potential of the compound having an aromatic ring between both electrodes is exceeded. Or a current having such a condition that a voltage sufficient to polymerize the compound having an aromatic ring may be applied, whereby a fibril polymer is formed on the working electrode. Using this and an example of a method of synthesizing fibrillar polymer by electrolytic oxidative polymerization method, stainless steel as a working electrode and a counter electrode, platinum, and good conductivity made of a material plate or a porous material such as carbon, these and H 2 SO 4, was immersed in an electrolyte solution containing a compound having an acid and an aromatic ring of HBF 4, etc., 0.1~1000mA / cm 2 between the electrodes, preferably by passing current of 0.2~100mA / cm 2, a working electrode Examples thereof include a method of polymerizing and depositing a fibrillated polymer on the side. Here, the concentration of the compound having an aromatic ring in the electrolytic solution is preferably in the range of 0.05 to 3 mol / L, and more preferably in the range of 0.25 to 1.5 mol / L. Moreover, in addition to the said component, you may add a soluble salt etc. to an electrolyte solution suitably in order to adjust pH.
上述のように、炭素繊維のドーピングレベルを調節することにより、得られる炭素繊維の導電率及び残炭率を制御することができるが、ドーピングレベルの調節は、得られたフィブリル状ポリマーを何らかの方法で還元すればよく、その手法に特に制限はない。具体例としては、アンモニア水溶液又はヒドラジン水溶液などに浸漬する方法、電気化学的に還元電流を付加する方法などが挙げられる。この還元レベルによりフィブリル状ポリマーに含まれるドーパント量の制御を行うことができ、この場合、還元処理によってフィブリル状ポリマー中のドーパント量は減少する。また、重合時において酸濃度を制御することにより重合過程でドーピングレベルをある程度調節することもできるが、ドーピングレベルが大きく異なる種々のサンプルを得ることは難しく、このため上記還元法が好適に採用される。なお、このように含有割合を調節したドーパントは、後述する焼成処理後も、その焼成条件を制御することによって得られる炭素繊維中に保持され、これにより炭素繊維の導電率及び残炭率が制御される。 As described above, by adjusting the doping level of the carbon fiber, it is possible to control the conductivity and the residual carbon ratio of the obtained carbon fiber. There is no particular limitation on the method. Specific examples include a method of immersing in an aqueous ammonia solution or an aqueous hydrazine solution, a method of electrochemically applying a reduction current, and the like. The amount of dopant contained in the fibril-like polymer can be controlled by this reduction level. In this case, the amount of dopant in the fibril-like polymer is reduced by the reduction treatment. Although the doping level can be adjusted to some extent during the polymerization process by controlling the acid concentration during the polymerization, it is difficult to obtain various samples with greatly different doping levels. Therefore, the above reduction method is preferably employed. The In addition, the dopant which adjusted the content rate in this way is hold | maintained in the carbon fiber obtained by controlling the baking conditions also after the baking process mentioned later, and, thereby, the electrical conductivity and residual carbon rate of carbon fiber are controlled. Is done.
上記のようにして作用極上に得られたフィブリル状ポリマーを、水や有機溶剤等の溶媒で洗浄し、乾燥させた後、非酸化性雰囲気中で焼成して炭化することで、フィブリル状で３次元連続状の炭素繊維が得られる。ここで、乾燥方法としては、特に制限されるものではないが、風乾、真空乾燥の他、流動床乾燥装置、気流乾燥機、スプレードライヤー等を使用した方法を例示することができる。また、焼成条件としては、特に限定されるものではなく、最適導電率となるように設定すればよいが、特に高導電率を必要とする場合は、温度500〜3000℃、好ましくは600〜2800℃で、0.5〜6時間とすることが好ましい。なお、非酸化性雰囲気としては、窒素雰囲気、アルゴン雰囲気、ヘリウム雰囲気等を挙げることができ、場合によっては水素雰囲気とすることもできる。 The fibrillated polymer obtained on the working electrode as described above is washed with a solvent such as water or an organic solvent, dried, and then baked and carbonized in a non-oxidizing atmosphere. A dimensionally continuous carbon fiber is obtained. Here, the drying method is not particularly limited, and examples thereof include a method using a fluidized bed drying device, an air dryer, a spray dryer, etc., in addition to air drying and vacuum drying. In addition, the firing conditions are not particularly limited, and may be set so as to obtain an optimum conductivity. Particularly, when high conductivity is required, the temperature is 500 to 3000 ° C., preferably 600 to 2800. The temperature is preferably 0.5 to 6 hours at ° C. Note that examples of the non-oxidizing atmosphere include a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere, and in some cases, a hydrogen atmosphere can also be used.
上記炭素繊維は、直径が30nm〜数百nm、好ましくは40nm〜500nmであり、長さが0.5μm〜100mm、好ましくは1μm〜10mmであり、表面抵抗が106〜10-2Ω、好ましくは104〜10-2Ωである。また、該炭素繊維は、残炭率が95〜30％、好ましくは90〜40％である。該炭素繊維は、カーボン全体が３次元に連続した構造を有するため、粒状カーボンよりも導電性が高い。 The carbon fiber has a diameter of 30 nm to several hundred nm, preferably 40 nm to 500 nm, a length of 0.5 μm to 100 mm, preferably 1 μm to 10 mm, and a surface resistance of 10 6 to 10 −2 Ω, preferably 10 4 to 10 −2 Ω. The carbon fiber has a residual carbon ratio of 95 to 30%, preferably 90 to 40%. Since the carbon fiber has a structure in which the entire carbon is three-dimensionally continuous, the carbon fiber has higher conductivity than the granular carbon.
本発明の炭素材電極の金属微粒子を構成する金属は、特に限定されるものではなく、炭素材電極の用途に応じて選択することができる。ここで、炭素繊維上に担持される金属微粒子の粒径は、0.5〜20nmの範囲が好ましい。また、金属微粒子の担持率は、炭素繊維1gに対して0.05〜5gの範囲が好ましい。更に、本発明の炭素材電極においては、上記３次元連続状炭素繊維の空隙の50体積％以下が金属微粒子で充填されていることが好ましい。この場合、充放電サイクルにおいて、炭素繊維上に担持された金属微粒子が膨張・収縮しても、炭素材電極全体としての体積変化が十分に防止されている。 The metal which comprises the metal fine particle of the carbon material electrode of this invention is not specifically limited, It can select according to the use of a carbon material electrode. Here, the particle size of the metal fine particles supported on the carbon fiber is preferably in the range of 0.5 to 20 nm. Further, the supporting rate of the metal fine particles is preferably in the range of 0.05 to 5 g with respect to 1 g of carbon fiber. Furthermore, in the carbon material electrode of the present invention, it is preferable that 50% by volume or less of the voids of the three-dimensional continuous carbon fiber are filled with metal fine particles. In this case, even if the metal fine particles supported on the carbon fiber expand and contract in the charge / discharge cycle, the volume change of the carbon material electrode as a whole is sufficiently prevented.
本発明の炭素材電極をリチウムイオン電池の負極として用いる場合、上記金属微粒子に用いる金属としては、リチウムを吸蔵・脱離可能な金属が好ましく、Ｓｎ、Ｓｉ、Ｐｂ、Ａｌ、Ａｕ、Ｐｔ、Ｉｎ、Ｚｎ、Ｃｄ、Ａｇ及びＭｇ等が更に好ましく、Ｓｎ及びＳｉがより一層好ましい。これら金属は、一種単独で用いてもよいし、二種以上の合金として用いてもよい。この他、目的に応じて金属の種類を選択することで、本発明の炭素材電極は、電気二重層キャパシタやレドックスキャパシタ用電極としても機能する。 When the carbon material electrode of the present invention is used as a negative electrode of a lithium ion battery, the metal used for the metal fine particles is preferably a metal capable of inserting and extracting lithium, and Sn, Si, Pb, Al, Au, Pt, In Zn, Cd, Ag, Mg, and the like are more preferable, and Sn and Si are even more preferable. These metals may be used individually by 1 type, and may be used as 2 or more types of alloys. In addition, the carbon material electrode of the present invention also functions as an electrode for an electric double layer capacitor or a redox capacitor by selecting a metal type according to the purpose.
本発明の炭素材電極は、特に限定されるものではないが、その後使用される電源デバイスにおける集電体を用い、該集電体上で３次元連続状炭素繊維を合成し、更に化学メッキで金属微粒子を担持することで、集電体の塗工工程が省略できる。例えば、リチウムイオン電池用負極として活用することを前提に炭素材電極を作製する場合には、銅集電体上に３次元連続状炭素繊維を形成し、該炭素繊維上に化学メッキによりシリコンやスズ等の金属微粒子を担持し、該金属微粒子担持炭素繊維を加熱乾燥した後、プレスすることで、そのままリチウムイオン電池用負極として用いることができる。なお、担持される金属微粒子が酸化し易い場合は、ＨＦ処理やＨ2雰囲気下でのアニーリングを施して、金属微粒子表面に生成した金属酸化物層を除去することが好ましく、これらの処理によって、炭素材電極の性能を向上させることができる。 The carbon material electrode of the present invention is not particularly limited, but using a current collector in a power device used thereafter, a three-dimensional continuous carbon fiber is synthesized on the current collector, and further, chemical plating is performed. By carrying the metal fine particles, the current collector coating step can be omitted. For example, when a carbon material electrode is manufactured on the assumption that it is used as a negative electrode for a lithium ion battery, a three-dimensional continuous carbon fiber is formed on a copper current collector, and silicon or silicon is formed on the carbon fiber by chemical plating. It can be used as it is as a negative electrode for a lithium ion battery by supporting metal fine particles such as tin and heating and drying the metal fine particle-supported carbon fibers and then pressing. When the supported metal fine particles are easily oxidized, it is preferable to remove the metal oxide layer generated on the surface of the metal fine particles by performing HF treatment or annealing in an H 2 atmosphere. The performance of the carbon material electrode can be improved.
本発明の炭素材電極の形状としては、特に制限はなく、電極として公知の形状の中から適宜選択することができる。例えば、シート状、円柱形状、板状形状、スパイラル形状等が挙げられる。 There is no restriction | limiting in particular as a shape of the carbon material electrode of this invention, It can select suitably from well-known shapes as an electrode. For example, a sheet shape, a columnar shape, a plate shape, a spiral shape, and the like can be given.
＜非水電解液二次電池＞
次に、本発明の非水電解液二次電池を詳細に説明する。本発明の非水電解液二次電池は、負極として上述した炭素材電極を備えることを特徴とし、その他、正極と、非水電解液とを備え、更に必要に応じて、セパレーター等の非水電解液二次電池の技術分野で通常使用されている他の部材を備える。
<Nonaqueous electrolyte secondary battery>
Next, the nonaqueous electrolyte secondary battery of the present invention will be described in detail. The non-aqueous electrolyte secondary battery of the present invention is characterized by including the carbon material electrode described above as a negative electrode, and further includes a positive electrode and a non-aqueous electrolyte, and further, if necessary, non-aqueous such as a separator. Other members that are usually used in the technical field of electrolyte secondary batteries are provided.
本発明の非水電解液二次電池の正極活物質としては、Ｖ2Ｏ5、Ｖ6Ｏ13、ＭｎＯ2、ＭｎＯ3等の金属酸化物、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4、ＬｉＦｅＯ2及びＬｉＦｅＰＯ4等のリチウム含有複合酸化物、ＴｉＳ2、ＭｏＳ2等の金属硫化物、ポリアニリン等の導電性ポリマー等が好適に挙げられる。上記リチウム含有複合酸化物は、Ｆｅ、Ｍｎ、Ｃｏ及びＮｉからなる群から選択される２種又は３種の遷移金属を含む複合酸化物であってもよく、この場合、該複合酸化物は、ＬｉＦｅxＣｏyＮｉ(1-x-y)Ｏ2（式中、０≦ｘ＜１、０≦ｙ＜１、０＜ｘ＋ｙ≦１）、ＬｉＭｎxＦｅyＯ2-x-y、あるいはＬｉＮｉxＣｏyＭｎ1-x-yＯ2等で表される。これらの中でも、高容量で安全性が高く、更には電解液の濡れ性に優れる点で、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4、ＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ2が特に好適である。これら正極活物質は、１種単独で使用してもよく、２種以上を併用してもよい。
As the positive electrode active material of the non-aqueous electrolyte secondary battery of the present invention, metal oxides such as V 2 O 5 , V 6 O 13 , MnO 2 , MnO 3 , LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiFeO Preferred examples include lithium-containing composite oxides such as 2 and LiFePO 4 , metal sulfides such as TiS 2 and MoS 2 , and conductive polymers such as polyaniline. The lithium-containing composite oxide may be a composite oxide containing two or three transition metals selected from the group consisting of Fe, Mn, Co, and Ni. In this case, the composite oxide includes: LiFe x Co y Ni (wherein, 0 ≦ x <1,0 ≦ y <1,0 <x + y ≦ 1) (1-xy)
上記正極には、必要に応じて導電剤、結着剤を混合することができ、導電剤としてはアセチレンブラック等が挙げられ、結着剤としてはポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、スチレン・ブタジエンゴム（ＳＢＲ）、カルボキシメチルセルロース（ＣＭＣ）等が挙げられる。これらの添加剤は、従来と同様の配合割合で用いることができる。また、上記正極の形状としては、特に制限はなく、電極として公知の形状の中から適宜選択することができる。例えば、シート状、円柱形状、板状形状、スパイラル形状等が挙げられる。 The positive electrode can be mixed with a conductive agent and a binder as necessary. Examples of the conductive agent include acetylene black, and the binder includes polyvinylidene fluoride (PVDF), polytetrafluoroethylene ( PTFE), styrene / butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like. These additives can be used at a blending ratio similar to the conventional one. Moreover, there is no restriction | limiting in particular as a shape of the said positive electrode, It can select suitably from well-known shapes as an electrode. For example, a sheet shape, a columnar shape, a plate shape, a spiral shape, and the like can be given.
本発明の非水電解液二次電池に用いる非水電解液は、非プロトン性有機溶媒に支持塩を溶解させてなることが好ましい。該非水電解液には、更に、目的に応じて種々の添加剤を添加することができる。上記非水電解液に用いる非プロトン性有機溶媒としては、特に制限はないが、電解液の粘度を低く抑える観点から、エーテル化合物やエステル化合物等が好ましい。具体的には、１,２-ジメトキシエタン（ＤＭＥ）、テトラヒドロフラン（ＴＨＦ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、ジフェニルカーボネート、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、γ-ブチロラクトン（ＧＢＬ）、γ-バレロラクトン、エチルメチルカーボネート（ＥＭＣ）、メチルフォルメート（ＭＦ）等が好適に挙げられる。これらの中でも、エチレンカーボネート、プロピレンカーボネート、γ-ブチロラクトン等の環状エステル化合物、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート等の鎖状エステル化合物、１,２-ジメトキシエタン等の鎖状エーテル化合物が好ましい。特に、環状のエステル化合物は、比誘電率が高く、リチウム塩等の溶解性に優れる点で好適であり、鎖状のエステル化合物及びエーテル化合物は、低粘度であるため電解液の低粘度化の点で好適である。これらは１種単独で使用してもよく、２種以上を併用してもよいが、２種以上を併用するのが好適である。 The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is preferably formed by dissolving a supporting salt in an aprotic organic solvent. Various additives can be further added to the non-aqueous electrolyte depending on the purpose. The aprotic organic solvent used in the nonaqueous electrolytic solution is not particularly limited, but is preferably an ether compound or an ester compound from the viewpoint of keeping the viscosity of the electrolytic solution low. Specifically, 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), dimethyl carbonate (DMC), diethyl carbonate (DEC), diphenyl carbonate, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), γ-valerolactone, ethyl methyl carbonate (EMC), methyl formate (MF) and the like are preferable. Among these, cyclic ester compounds such as ethylene carbonate, propylene carbonate, and γ-butyrolactone, chain ester compounds such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, and chain ether compounds such as 1,2-dimethoxyethane are preferable. In particular, a cyclic ester compound is suitable in that it has a high relative dielectric constant and excellent solubility in lithium salts and the like, and a chain ester compound and an ether compound have a low viscosity. This is preferable in terms of points. These may be used individually by 1 type, may use 2 or more types together, but it is suitable to use 2 or more types together.
また、上記支持塩としては、リチウムイオンのイオン源となる支持塩が好ましい。該支持塩としては、特に制限はないが、例えば、ＬｉＣｌＯ4、ＬｉＢＦ4、ＬｉＰＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＡｓＦ6、ＬｉＣ4Ｆ9ＳＯ3、Ｌｉ(ＣＦ3ＳＯ2)2Ｎ及びＬｉ(Ｃ2Ｆ5ＳＯ2)2Ｎ等のリチウム塩が好適に挙げられる。これらの中でも、不燃性に優れる点で、ＬｉＰＦ6が更に好ましい。これら支持塩は、１種単独で使用してもよく、２種以上を組み合わせて用いてもよい。ここで、非水電解液における支持塩の濃度としては、0.2〜1.5mol/L（Ｍ）の範囲が好ましく、0.5〜1mol/L（Ｍ）の範囲が更に好ましい。支持塩の濃度が0.2mol/L未満では、電解液の導電性を充分に確保することができず、電池の放電特性及び充電特性に支障をきたすことがあり、1.5mol/Lを超えると、電解液の粘度が上昇し、リチウムイオンの移動度を充分に確保できないため、前述と同様に電解液の導電性を充分に確保できず、電池の放電特性及び充電特性に支障をきたすことがある。 Moreover, as said support salt, the support salt used as the ion source of lithium ion is preferable. The supporting salt is not particularly limited, and for example, LiClO 4 , LiBF 4 , LiPF 6 , LiCF 3 SO 3 , LiAsF 6 , LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 2 N and Li ( Preferable examples include lithium salts such as C 2 F 5 SO 2 ) 2 N. Among these, LiPF 6 is more preferable in terms of excellent nonflammability. These supporting salts may be used alone or in combination of two or more. Here, the concentration of the supporting salt in the nonaqueous electrolytic solution is preferably in the range of 0.2 to 1.5 mol / L (M), and more preferably in the range of 0.5 to 1 mol / L (M). If the concentration of the supporting salt is less than 0.2 mol / L, the conductivity of the electrolyte cannot be sufficiently ensured, and the discharge characteristics and charging characteristics of the battery may be hindered. Since the viscosity of the electrolytic solution increases and the mobility of lithium ions cannot be ensured sufficiently, the conductivity of the electrolytic solution cannot be sufficiently ensured in the same manner as described above, which may hinder battery discharge characteristics and charge characteristics. .
本発明の非水電解液二次電池に使用できる他の部材としては、非水電解液二次電池において、正負極間に、両極の接触による電流の短絡を防止する役割で介在させるセパレーターが挙げられる。セパレーターの材質としては、両極の接触を確実に防止し得、且つ電解液を通したり含んだりできる材料、例えば、ポリテトラフルオロエチレン、ポリプロピレン、ポリエチレン、セルロース系、ポリブチレンテレフタレート、ポリエチレンテレフタレート等の合成樹脂製の不織布、薄層フィルム等が好適に挙げられる。これらの中でも、厚さ20〜50μm程度のポリプロピレン又はポリエチレン製の微孔性フィルム、セルロース系、ポリブチレンテレフタレート、ポリエチレンテレフタレート等のフィルムが特に好適である。本発明では、上述のセパレーターの他にも、通常電池に使用されている公知の各部材が好適に使用できる。 Other members that can be used in the non-aqueous electrolyte secondary battery of the present invention include a separator interposed in the non-aqueous electrolyte secondary battery between positive and negative electrodes to prevent current short-circuit due to contact between both electrodes. It is done. As the material of the separator, it is possible to reliably prevent contact between the two electrodes, and a material that can pass or contain the electrolyte, such as polytetrafluoroethylene, polypropylene, polyethylene, cellulose, polybutylene terephthalate, polyethylene terephthalate, etc. Preferred examples include resin non-woven fabrics and thin layer films. Of these, polypropylene or polyethylene microporous films having a thickness of about 20 to 50 μm, cellulose-based films, polybutylene terephthalate, polyethylene terephthalate, and the like are particularly suitable. In the present invention, in addition to the separators described above, known members that are normally used in batteries can be suitably used.
以上に説明した本発明の非水電解液二次電池の形態としては、特に制限はなく、コインタイプ、ボタンタイプ、ペーパータイプ、角型又はスパイラル構造の円筒型電池等、種々の公知の形態が好適に挙げられる。ボタンタイプの場合は、シート状の正極及び負極を作製し、該正極及び負極でセパレーターを挟む等して、非水電解液二次電池を作製することができる。また、スパイラル構造の場合は、例えば、シート状の正極を作製して集電体を挟み、これに、シート状の負極を重ね合わせて巻き上げる等して、非水電解液二次電池を作製することができる。 The form of the non-aqueous electrolyte secondary battery of the present invention described above is not particularly limited, and various known forms such as a coin type, a button type, a paper type, a square type or a spiral type cylindrical battery are available. Preferably mentioned. In the case of the button type, a non-aqueous electrolyte secondary battery can be manufactured by preparing a sheet-like positive electrode and negative electrode and sandwiching a separator between the positive electrode and the negative electrode. In the case of the spiral structure, for example, a non-aqueous electrolyte secondary battery is manufactured by preparing a sheet-like positive electrode, sandwiching a current collector, and stacking and winding up the sheet-like negative electrode on the current collector. be able to.
以下に、実施例を挙げて本発明を更に詳しく説明するが、本発明は下記の実施例に何ら限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.
＜３次元連続状炭素繊維の製造例＞
アニリンモノマー 0.5mol/LとＨＢＦ4 1.0mol/Lとを含む酸性水溶液中に、銅製の作用極を設置し、対極として白金板を使用して、室温にて10mA/cm2の定電流で10分間電解重合を行い、ポリアニリンを作用極上に電析させた。得られたポリアニリンをイオン交換水で洗浄し、更に24時間真空乾燥した後、ＳＥＭで観察したところ、フィブリル状ポリアニリンが生成していることを確認した。
<Production example of three-dimensional continuous carbon fiber>
A copper working electrode was placed in an acidic aqueous solution containing 0.5 mol / L of aniline monomer and 1.0 mol / L of HBF 4 , and a platinum plate was used as the counter electrode, with a constant current of 10 mA / cm 2 at room temperature. Electropolymerization was performed for a minute, and polyaniline was electrodeposited on the working electrode. The obtained polyaniline was washed with ion-exchanged water, further vacuum-dried for 24 hours, and then observed with SEM. As a result, it was confirmed that fibrillar polyaniline was produced.
次に、上記ポリアニリンを銅作用極ごとＡｒ雰囲気中3℃/分の昇温速度で950℃まで加熱し、その後950℃で1時間保持して焼成処理した。得られた焼成物をＳＥＭで観察したところ、直径が40〜100nmのフィブリル状で３次元連続状の炭素繊維が、銅作用極上に生成していることを確認した。なお、該炭素繊維は、残炭率が45％で、表面抵抗が1.0Ωであった（三菱油化製, Loresta IP又はHiresta IPで測定）。 Next, the polyaniline was heated to 950 ° C. at a rate of temperature increase of 3 ° C./min in an Ar atmosphere together with the copper working electrode, and then held at 950 ° C. for 1 hour for firing treatment. When the obtained fired product was observed by SEM, it was confirmed that fibril-like and three-dimensional continuous carbon fibers having a diameter of 40 to 100 nm were formed on the copper working electrode. The carbon fiber had a residual carbon ratio of 45% and a surface resistance of 1.0Ω (measured by Mitsubishi Yuka, Loresta IP or Hiresta IP).
（実施例１）
メッキ金属であるＳｎ2+（塩化第一スズ）0.08mol/Lと、還元剤であるＴｉ3+（三塩化チタン）0.10mol/Lとを含み、更に、これらイオンの錯体形成剤としてエチレンジアミン四酢酸二ナトリウム 0.08mol/L、クエン酸ナトリウム 0.35mol/L、及びニトリロ三酢酸 0.2mol/Lを含む溶液を調製し、更に、アンモニア水を用いてｐＨを９に調整した。この溶液を80℃に加熱した状態で、上記の方法で作製した３次元連続状炭素繊維を10分間浸漬し、Ｓｎの化学メッキを実施した。その結果、３次元連続状炭素繊維の空隙の10体積％がＳｎ微粒子で埋められたＳｎ担持炭素繊維が得られた。なお、炭素繊維の空隙の充填率は、次のようにして測定した。
Example 1
It contains Sn 2+ (stannous chloride) 0.08 mol / L as a plating metal and 0.10 mol / L Ti 3+ (titanium trichloride) as a reducing agent. A solution containing disodium acetate 0.08 mol / L, sodium citrate 0.35 mol / L, and nitrilotriacetic acid 0.2 mol / L was prepared, and the pH was adjusted to 9 using aqueous ammonia. In a state where this solution was heated to 80 ° C., the three-dimensional continuous carbon fiber produced by the above method was immersed for 10 minutes to perform chemical plating of Sn. As a result, an Sn-supported carbon fiber in which 10% by volume of the voids of the three-dimensional continuous carbon fiber was filled with Sn fine particles was obtained. The filling rate of the carbon fiber voids was measured as follows.
＜炭素繊維の空隙充填率＞
まず、Ｓｎ担持前の炭素繊維についてその嵩密度を求め、真密度との関係から空隙率を求める。この空隙率と未担持の炭素繊維の見かけ体積から空隙の体積を求める。更に、Ｓｎ担持炭素繊維の重量と未担持炭素繊維の重量差からＳｎ担持重量を求め、これをＳｎの真密度で除して、Ｓｎの占有する体積を求める。得られたＳｎ占有体積と先に求めた空隙体積の関係から、Ｓｎ充填率を算出する。
<Carbon fiber void filling factor>
First, the bulk density is calculated | required about the carbon fiber before Sn carrying | support, and the porosity is calculated | required from a relationship with a true density. From the porosity and the apparent volume of the unsupported carbon fiber, the volume of the void is determined. Further, the Sn-supported weight is obtained from the difference between the weight of the Sn-supported carbon fiber and the unsupported carbon fiber, and this is divided by the true density of Sn to determine the volume occupied by Sn. The Sn filling rate is calculated from the relationship between the obtained Sn occupation volume and the previously obtained void volume.
また、上記のようにして得られたＳｎ担持炭素繊維をＳＥＭで確認したところ、担持されたＳｎの粒径は、15〜40nmであった。更に、得られたＳｎ担持炭素繊維に有機溶媒（酢酸エチルとエタノールとの50/50質量％混合溶媒）を加えて混練した後、該混練物を厚さ25μmの銅箔（集電体）にドクターブレードで塗工し、更に熱風乾燥（100〜120℃）して、厚さ60μmの負極シートを作製した。 Moreover, when the Sn carrying | support carbon fiber obtained by the above was confirmed by SEM, the particle size of carried Sn was 15-40 nm. Further, an organic solvent (50/50 mass% mixed solvent of ethyl acetate and ethanol) was added to the obtained Sn-supported carbon fiber and kneaded, and then the kneaded product was added to a copper foil (current collector) having a thickness of 25 μm. Coating was performed with a doctor blade, and further hot air drying (100 to 120 ° C.) was performed to prepare a negative electrode sheet having a thickness of 60 μm.
また、ＬｉＣｏＯ2（正極活物質）94質量部に対して、アセチレンブラック（導電剤）3質量部と、ポリフッ化ビニリデン（結着剤）3質量部とを添加し、有機溶媒（酢酸エチルとエタノールとの50/50質量％混合溶媒）で混練した後、該混練物を厚さ25μmのアルミニウム箔（集電体）にドクターブレードで塗工し、更に熱風乾燥（100〜120℃）して、厚さ80μmの正極シートを作製した。 Further, 3 parts by mass of acetylene black (conductive agent) and 3 parts by mass of polyvinylidene fluoride (binder) are added to 94 parts by mass of LiCoO 2 (positive electrode active material), and an organic solvent (ethyl acetate and ethanol) is added. 50/50 mass% mixed solvent) and the kneaded product is applied to a 25 μm thick aluminum foil (current collector) with a doctor blade, and further dried with hot air (100 to 120 ° C.), A positive electrode sheet having a thickness of 80 μm was produced.
更に、エチレンカーボネート（ＥＣ）及びエチルメチルカーボネート（ＥＭＣ）の混合溶媒（ＥＣ／ＥＭＣ体積比＝１／２）に、ＬｉＰＦ6（支持塩）を1Ｍ（mol/L）の濃度で溶解させて非水電解液を調製した。 Further, LiPF 6 (supporting salt) was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC / EMC volume ratio = 1/2) at a concentration of 1 M (mol / L) to remove A water electrolyte was prepared.
次に、上記正極シート及び上記負極シートをそれぞれφ16mmに打ち抜いたものを正極及び負極とし、セルロースセパレーター［日本高度紙工業社製ＴＦ４０３０］を介して正負極を対座させ、上記非水電解液を注入し封口して、4mAh級のリチウムイオン電池（２０１６コイン型）を作製した。 Next, the positive electrode sheet and the negative electrode sheet punched to φ16 mm are used as the positive electrode and the negative electrode, the positive and negative electrodes are faced through a cellulose separator [TF4030 made by Nippon Kogyo Paper Industries Co., Ltd.], and the non-aqueous electrolyte is injected. Then, a 4 mAh-class lithium ion battery (2016 coin type) was produced.
（実施例２）
実施例１と同様の手法で、30分間Ｓｎの化学メッキを実施した。その結果、３次元連続状炭素繊維の空隙の25体積％がＳｎ微粒子で埋められたＳｎ担持炭素繊維が得られた。なお、ＳＥＭで確認したところ、担持されたＳｎの粒径は、30〜80nmであった。また、得られたＳｎ担持炭素繊維を用いて、実施例１と同様にしてリチウムイオン電池を作製した。
(Example 2)
In the same manner as in Example 1, Sn chemical plating was performed for 30 minutes. As a result, Sn-supported carbon fibers in which 25% by volume of voids in the three-dimensional continuous carbon fibers were filled with Sn fine particles were obtained. In addition, when confirmed with SEM, the particle size of the supported Sn was 30 to 80 nm. Further, using the obtained Sn-supported carbon fiber, a lithium ion battery was produced in the same manner as in Example 1.
（実施例３）
実施例１と同様の手法で90分間Ｓｎの化学メッキを実施した。その結果、３次元連続状炭素繊維の空隙の48体積％がＳｎ微粒子で埋められたＳｎ担持炭素繊維が得られた。なお、ＳＥＭで確認したところ、担持されたＳｎの粒径は、60〜150nmであった。また、得られたＳｎ担持炭素繊維を用いて、実施例１と同様にしてリチウムイオン電池を作製した。
(Example 3)
Chemical plating of Sn was performed for 90 minutes by the same method as in Example 1. As a result, an Sn-supported carbon fiber in which 48% by volume of voids in the three-dimensional continuous carbon fiber were filled with Sn fine particles was obtained. In addition, when confirmed with SEM, the particle size of the supported Sn was 60 to 150 nm. Further, using the obtained Sn-supported carbon fiber, a lithium ion battery was produced in the same manner as in Example 1.
（実施例４）
実施例１と同様の手法による30分間のＳｎ化学メッキを、メッキ浴を交換しながら３回繰り返した。その結果、３次元連続状炭素繊維の空隙の約55体積％がＳｎ微粒子で埋められたＳｎ担持炭素繊維が得られた。なお、ＳＥＭで確認したところ、担持されたＳｎの粒径は、35〜290nm程度であった。また、得られたＳｎ担持炭素繊維を用いて、実施例１と同様にしてリチウムイオン電池を作製した。
Example 4
Sn chemical plating for 30 minutes by the same method as in Example 1 was repeated three times while changing the plating bath. As a result, Sn-supported carbon fibers in which about 55% by volume of voids in the three-dimensional continuous carbon fibers were filled with Sn fine particles were obtained. As confirmed by SEM, the particle size of the supported Sn was about 35 to 290 nm. Further, using the obtained Sn-supported carbon fiber, a lithium ion battery was produced in the same manner as in Example 1.
＜電池のサイクル特性評価＞
上記のようにして得られた各電池に対して、20℃の環境下で、上限電圧4.3Ｖ、下限電圧3.0Ｖ、放電電流50mA、充電電流50mAの条件で充放電を行い、この時の放電容量を既知の電極重量で除することにより初期放電容量（mAh/g）を求めた。更に、同様の充放電条件で10サイクルまで充放電を繰り返して、各サイクル後の放電容量を求め、下記の式：
容量残存率＝各サイクル後の放電容量／初期放電容量×１００（％）
に従って各サイクルの容量残存率を算出し、電池のサイクル特性の指標とした。結果を図１に示す。
<Evaluation of battery cycle characteristics>
Each battery obtained as described above is charged and discharged under the conditions of an upper limit voltage of 4.3 V, a lower limit voltage of 3.0 V, a discharge current of 50 mA, and a charge current of 50 mA in an environment of 20 ° C. The initial discharge capacity (mAh / g) was determined by dividing the capacity by the known electrode weight. Furthermore, charge / discharge was repeated up to 10 cycles under the same charge / discharge conditions, and the discharge capacity after each cycle was determined.
Capacity remaining rate = discharge capacity after each cycle / initial discharge capacity × 100 (%)
Thus, the capacity remaining rate of each cycle was calculated and used as an index of the battery cycle characteristics. The results are shown in FIG.
図１から、３次元連続状炭素繊維の空隙の50体積％以下がＳｎ微粒子で埋められたＳｎ担持炭素繊維からなる負極を用いた実施例１〜３のリチウムイオン電池は、特に優れたサイクル特性を有することが分る。これは、充放電に伴うＳｎの体積膨張率が約200％であるため、Ｓｎを炭素繊維の空隙の50体積％以下担持した場合、充放電に伴うＳｎの体積膨張が網目構造を有する炭素繊維によって吸収され、負極全体としての膨張が外見上現れないことによるものと考えられる。 From FIG. 1, the lithium ion batteries of Examples 1 to 3 using the negative electrode made of Sn-supported carbon fiber in which 50% by volume or less of the voids of the three-dimensional continuous carbon fiber are filled with Sn fine particles are particularly excellent in cycle characteristics. It can be seen that This is because the volume expansion rate of Sn accompanying charging / discharging is about 200%. Therefore, when Sn is supported by 50% by volume or less of the voids of the carbon fiber, the volume expansion of Sn accompanying charging / discharging has a network structure. It is considered that the expansion of the negative electrode as a whole does not appear in appearance.
一方、３次元連続状炭素繊維の空隙の50体積％超がＳｎ微粒子で埋められたＳｎ担持炭素繊維からなる負極を用いた実施例４のリチウムイオン電池は、サイクル特性が実施例１〜３に比べて悪かったため、金属微粒子の充填率は３次元連続状炭素繊維の空隙の50体積％以下であることが好ましいことが確認された。これは、本発明で用いる３次元連続状炭素繊維は、金属微粒子が体積膨張しても、炭素材電極全体としての体積膨張を緩和できるものの、上述のように充放電に伴うＳｎの体積膨張率が約200％であるため、Ｓｎを炭素繊維の空隙の50体積％を超えて担持した場合、充放電によって炭素繊維の網目構造の一部が壊れ、該部分の導通が遮断されるため、充放電容量が低下したものと思われる。 On the other hand, the lithium ion battery of Example 4 using a negative electrode made of Sn-supported carbon fiber in which more than 50% by volume of voids in the three-dimensional continuous carbon fiber were filled with Sn fine particles had a cycle characteristic of Examples 1 to 3. It was confirmed that the filling rate of the metal fine particles was preferably 50% by volume or less of the voids of the three-dimensional continuous carbon fiber because it was worse than that. This is because the three-dimensional continuous carbon fiber used in the present invention can alleviate the volume expansion of the carbon material electrode as a whole even if the metal fine particles expand, but the volume expansion rate of Sn accompanying charge / discharge as described above. Therefore, when Sn is supported over 50% by volume of the voids of the carbon fiber, a part of the network structure of the carbon fiber is broken by charging / discharging, and the conduction of the part is interrupted. The discharge capacity seems to have decreased.
Claims (9)
(ii)前記フィブリル状ポリマーを非酸化性雰囲気中で焼成して３次元連続状炭素繊維を生成させる工程と、
(iii)前記３次元連続状炭素繊維に化学メッキにより金属微粒子を担持する工程と
を含む、金属微粒子を３次元連続状炭素繊維に担持してなる炭素材電極の製造方法。 (i) a step of oxidatively polymerizing a compound having an aromatic ring to produce a fibrillated polymer;
(ii) firing the fibrillated polymer in a non-oxidizing atmosphere to form a three-dimensional continuous carbon fiber;
(iii) A method for producing a carbon material electrode comprising supporting metal fine particles on a three-dimensional continuous carbon fiber, comprising the step of supporting metal fine particles on the three-dimensional continuous carbon fiber by chemical plating.
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| CN104393299A (en) * | 2014-09-23 | 2015-03-04 | 西北师范大学 | Nanometer silicon-polythiophene electric conduction composite material for lithium ion battery, and preparation method thereof |
| CN109411756A (en) * | 2018-09-21 | 2019-03-01 | 中国科学院物理研究所 | A kind of secondary cell carbon three-dimensional structure electrode and its preparation method and application |
| JPWO2018051925A1 (en) * | 2016-09-16 | 2019-06-27 | 日本ゼオン株式会社 | Composite, negative electrode for lithium ion secondary battery, and method of manufacturing composite |
| CN109950635A (en) * | 2019-03-19 | 2019-06-28 | 西安交通大学 | A kind of all solid state continuous fiber lithium ion battery structure and its 3D printing manufacturing process |
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| CN104393299A (en) * | 2014-09-23 | 2015-03-04 | 西北师范大学 | Nanometer silicon-polythiophene electric conduction composite material for lithium ion battery, and preparation method thereof |
| JPWO2018051925A1 (en) * | 2016-09-16 | 2019-06-27 | 日本ゼオン株式会社 | Composite, negative electrode for lithium ion secondary battery, and method of manufacturing composite |
| JP2019135689A (en) * | 2018-02-05 | 2019-08-15 | トヨタ自動車株式会社 | Anode for metal secondary battery, metal secondary battery, and manufacturing method of metal secondary battery |
| CN109411756A (en) * | 2018-09-21 | 2019-03-01 | 中国科学院物理研究所 | A kind of secondary cell carbon three-dimensional structure electrode and its preparation method and application |
| CN109950635A (en) * | 2019-03-19 | 2019-06-28 | 西安交通大学 | A kind of all solid state continuous fiber lithium ion battery structure and its 3D printing manufacturing process |
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