JP2008066128A - Negative electrode active material for lithium ion battery, and its manufacturing method, cathode for lithium ion battery, and lithium ion battery - Google Patents

Negative electrode active material for lithium ion battery, and its manufacturing method, cathode for lithium ion battery, and lithium ion battery Download PDF

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JP2008066128A
JP2008066128A JP2006243116A JP2006243116A JP2008066128A JP 2008066128 A JP2008066128 A JP 2008066128A JP 2006243116 A JP2006243116 A JP 2006243116A JP 2006243116 A JP2006243116 A JP 2006243116A JP 2008066128 A JP2008066128 A JP 2008066128A
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lithium ion
negative electrode
ion battery
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Shinichiro Sugi
信一郎 杉
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Bridgestone Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode active material for a lithium ion battery which is higher in charge and discharge capacity than a conventional one. <P>SOLUTION: The negative electrode active material for the lithium ion battery composed of a carbon material and silicon carbide is manufactured after passing through a process of coating or mixing polysilane to the carbon material, and a process of heat treating the carbon material in which polysilane is coated or mixed to form silicon carbide on the carbon material. As the carbon material, a carbon fiber which is formed by oxidizing and polymerizing a compound having an aromatic ring, by forming a fibril state polymer, and by calcining the fibril state polymer is preferable. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、リチウムイオン電池用負極活物質の製造方法、該方法で製造されたリチウムイオン電池用負極活物質、該リチウムイオン電池用負極活物質を含むリチウムイオン電池用負極及び該リチウムイオン電池用負極を具えたリチウムイオン電池に関し、特に充放電容量が高いリチウムイオン電池用負極活物質に関するものである。   The present invention relates to a method for producing a negative electrode active material for a lithium ion battery, a negative electrode active material for a lithium ion battery produced by the method, a negative electrode for a lithium ion battery comprising the negative electrode active material for the lithium ion battery, and the lithium ion battery The present invention relates to a lithium ion battery including a negative electrode, and particularly relates to a negative electrode active material for a lithium ion battery having a high charge / discharge capacity.

昨今、携帯用端末やモバイル通信機器として、リチウムイオン電池が広く普及している。該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高いため、該リチウムイオン電池を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使用することも検討されている。   Recently, lithium ion batteries are widely used as portable terminals and mobile communication devices. Since the lithium ion battery has the highest energy density among the existing secondary batteries, it is considered to use the lithium ion battery as an auxiliary power source for a hybrid vehicle or a fuel cell vehicle or as a large power source for stationary use. .

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、黒鉛等の炭素材料）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得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。 The lithium ion battery is an electrolysis in which a negative electrode (for example, a carbon material such as 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 dissolves lithium ions. A battery having a structure facing each other through a liquid, and generally has a structure in which a porous polymer film that can permeate an electrolytic solution is disposed between both electrodes in order to prevent a short circuit between a positive electrode and a negative electrode Yes.

そして、上記リチウムイオン電池の負極に用いられる炭素材料としては、一般に、黒鉛（ソフトカーボン）が使用されており、該黒鉛は、充放電のサイクル特性、充放電効率（特に、初期の充放電効率）が高いという利点を有する。しかしながら、黒鉛を用いた場合、リチウムイオンが黒鉛にインターカレートされてＬｉＣ6が形成されると、それ以上リチウムを挿入することができない。従って、黒鉛を用いた場合、充放電容量は理論容量である372mAh/gが限界である。一方、高容量が得られる負極活物質としてハードカーボンが検討されているが、ソフトカーボンに比べて初期充放電効率が低く、また、体積あたりの放電容量が黒鉛に劣るという問題を有している。
ＣＭＣ出版，「二次電池材料この１０年と今後」 In general, graphite (soft carbon) is used as the carbon material used for the negative electrode of the lithium ion battery, and the graphite has charge / discharge cycle characteristics, charge / discharge efficiency (particularly, initial charge / discharge efficiency). ) Is high. However, when graphite is used, when lithium ions are intercalated into graphite to form LiC 6 , no more lithium can be inserted. Therefore, when graphite is used, the charge / discharge capacity is limited to a theoretical capacity of 372 mAh / g. On the other hand, hard carbon has been studied as a negative electrode active material capable of obtaining a high capacity, but it has problems that initial charge / discharge efficiency is lower than that of soft carbon, and discharge capacity per volume is inferior to graphite. .
CMC Publishing, “Secondary battery materials for the past 10 years and beyond”

そこで、本発明の目的は、従来よりも充放電容量が高いリチウムイオン電池用負極活物質及びその製造方法を提供することにある。また、本発明の他の目的は、かかるリチウムイオン電池用負極活物質を含むリチウムイオン電池用負極及び該リチウムイオン電池用負極を具えたリチウムイオン電池を提供することにある。   Then, the objective of this invention is providing the negative electrode active material for lithium ion batteries whose charging / discharging capacity is higher than before, and its manufacturing method. Another object of the present invention is to provide a negative electrode for a lithium ion battery comprising such a negative electrode active material for a lithium ion battery and a lithium ion battery comprising the negative electrode for a lithium ion battery.

本発明者は、上記目的を達成するために鋭意検討した結果、炭素材料にポリシラン溶液を塗布又は混合した後、熱処理し、炭素材料上に炭化ケイ素を生成させて得た炭素材料と炭化ケイ素との複合材料を、リチウムイオン電池の負極活物質として使用することで、リチウムイオン電池の充放電容量が大きく向上することを見出し、本発明を完成させるに至った。   As a result of earnest studies to achieve the above object, the present inventor has applied or mixed a polysilane solution to a carbon material, followed by heat treatment to produce silicon carbide on the carbon material and silicon carbide. By using this composite material as a negative electrode active material of a lithium ion battery, it was found that the charge / discharge capacity of the lithium ion battery was greatly improved, and the present invention was completed.

即ち、本発明の炭素材料と炭化ケイ素とからなるリチウムイオン電池用負極活物質の製造方法は、
炭素材料にポリシランを塗布又は混合する工程と、
前記ポリシランが塗布又は混合された炭素材料を熱処理して、炭素材料上に炭化ケイ素（ＳｉＣ）を生成させる工程と
を含むことを特徴とする。 That is, a method for producing a negative electrode active material for a lithium ion battery comprising the carbon material of the present invention and silicon carbide,
Applying or mixing polysilane to the carbon material;
Heat-treating the carbon material coated or mixed with the polysilane to produce silicon carbide (SiC) on the carbon material.

本発明のリチウムイオン電池用負極活物質の製造方法の好適例においては、前記炭素材料が、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、該フィブリル状ポリマーを焼成して生成させた炭素繊維である。   In a preferred embodiment of the method for producing a negative electrode active material for a lithium ion battery according to the present invention, the carbon material is produced by oxidative polymerization of a compound having an aromatic ring to produce a fibril-like polymer, and firing the fibril-like polymer. Carbon fiber.

本発明のリチウムイオン電池用負極活物質の製造方法の他の好適例においては、前記ポリシランが塗布又は混合された炭素材料を不活性ガス雰囲気中で熱処理して、ポリシランをポリカルボシランに変換し、更に、空気中及び不活性ガス雰囲気中で熱処理して、前記ポリカルボシランを炭化ケイ素に変換して、炭素材料上に炭化ケイ素を生成させる。ここで、前記ポリシランが式：［−Ｓｉ(ＣＨ3)2−］で表わされる繰り返し単位からなり、前記ポリカルボシランが式：［−ＳｉＨ(ＣＨ3)−ＣＨ2−］で表わされる繰り返し単位からなることが好ましい。 In another preferred embodiment of the method for producing a negative electrode active material for a lithium ion battery of the present invention, the carbon material coated or mixed with the polysilane is heat-treated in an inert gas atmosphere to convert the polysilane to polycarbosilane. Further, heat treatment is performed in air and in an inert gas atmosphere to convert the polycarbosilane into silicon carbide, thereby generating silicon carbide on the carbon material. Here, the polysilane comprises a repeating unit represented by the formula: [—Si (CH 3 ) 2 —], and the polycarbosilane comprises a repeating unit represented by the formula: [—SiH (CH 3 ) —CH 2 —]. Preferably it consists of.

本発明のリチウムイオン電池用負極活物質の製造方法の他の好適例においては、前記ポリシランが塗布又は混合された炭素材料を不活性ガス雰囲気中で紫外線照射し、更に、減圧下で熱処理して、前記ポリシランを炭化ケイ素に変換して、炭素材料上に炭化ケイ素を生成させる。ここで、前記ポリシランは、式：［−Ｓｉ(ＣＨ3)2−］で表わされる繰り返し単位と、式：［−Ｓｉ(ＣＨ3)(Ｃ6Ｈ5)−］で表わされる繰り返し単位とからなることが好ましい。 In another preferred embodiment of the method for producing a negative electrode active material for a lithium ion battery according to the present invention, the carbon material coated or mixed with the polysilane is irradiated with ultraviolet rays in an inert gas atmosphere, and further subjected to heat treatment under reduced pressure. The polysilane is converted into silicon carbide to produce silicon carbide on the carbon material. Here, the polysilane is composed of a repeating unit represented by the formula: [—Si (CH 3 ) 2 —] and a repeating unit represented by the formula: [—Si (CH 3 ) (C 6 H 5 ) —]. It is preferable to become.

本発明のリチウムイオン電池用負極活物質の製造方法において、前記炭化ケイ素は、β型の炭化ケイ素（β-ＳｉＣ）であることが好ましい。   In the method for producing a negative electrode active material for a lithium ion battery of the present invention, the silicon carbide is preferably β-type silicon carbide (β-SiC).

また、本発明のリチウムイオン電池用負極活物質は、上記の方法で製造されたことを特徴とし、本発明のリチウムイオン電池用負極は、該リチウムイオン電池用負極活物質を含むことを特徴とし、本発明のリチウムイオン電池は、該リチウムイオン電池用負極を具えることを特徴とする。   The negative electrode active material for lithium ion batteries of the present invention is manufactured by the above method, and the negative electrode for lithium ion batteries of the present invention includes the negative electrode active material for lithium ion batteries. The lithium ion battery of the present invention includes the negative electrode for a lithium ion battery.

本発明によれば、炭素材料にポリシラン溶液を塗布又は混合した後、熱処理し、炭素材料上に炭化ケイ素を生成させることで、充放電容量が高いリチウムイオン電池用負極活物質を製造することができる。また、該リチウムイオン電池用負極活物質を用いることで、リチウムイオン電池の充放電容量が大きく向上させることができる。   According to the present invention, a negative electrode active material for a lithium ion battery having a high charge / discharge capacity can be produced by applying or mixing a polysilane solution to a carbon material, followed by heat treatment to generate silicon carbide on the carbon material. it can. Moreover, the charge / discharge capacity of a lithium ion battery can be greatly improved by using the negative electrode active material for a lithium ion battery.

＜リチウムイオン電池用負極活物質及びその製造方法＞
以下に、本発明のリチウムイオン電池用負極活物質及びその製造方法を詳細に説明する。本発明のリチウムイオン電池用負極活物質の製造方法は、炭素材料にポリシランを塗布又は混合する工程と、前記ポリシランが塗布又は混合された炭素材料を熱処理して、炭素材料上に炭化ケイ素を生成させる工程とを含み、本発明のリチウムイオン電池用負極活物質は、該方法で製造されたことを特徴とする。本発明のリチウムイオン電池用負極活物質は、表面がリチウムイオンの吸着に適しているため、リチウムイオンを多量に吸着することができる。そのため、本発明のリチウムイオン電池用負極活物質を用いたリチウムイオン電池は、充放電容量が従来のリチウムイオン電池に比べて大幅に向上している。 <Anode active material for lithium ion battery and method for producing the same>
Below, the negative electrode active material for lithium ion batteries of this invention and its manufacturing method are demonstrated in detail. The method for producing a negative electrode active material for a lithium ion battery according to the present invention includes a step of applying or mixing polysilane to a carbon material, and heat-treating the carbon material coated or mixed with the polysilane to produce silicon carbide on the carbon material. The negative electrode active material for a lithium ion battery of the present invention is characterized by being produced by the method. Since the surface of the negative electrode active material for a lithium ion battery of the present invention is suitable for adsorption of lithium ions, a large amount of lithium ions can be adsorbed. Therefore, the charge / discharge capacity of the lithium ion battery using the negative electrode active material for lithium ion battery of the present invention is greatly improved as compared with the conventional lithium ion battery.

本発明の負極活物質の製造方法に用いる炭素材料は、リチウムイオンを電気化学的に吸蔵・離脱可能であることを要し、かかる炭素材料の中でも、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、該フィブリル状ポリマーを焼成して生成させた炭素繊維が特に好ましい。従来のリチウムイオン電池の負極に用いられている炭素材料は、通常粉末であり、電池の充放電サイクルに伴って、負極の膨張及び収縮が起こる結果、電気的に絶縁となる部分が生じて充放電容量が低下することがある。しかしながら、上記炭素繊維は、３次元的に連続した構造を有するため、電池の充放電サイクルに伴って、負極の膨張及び収縮が起こっても、電気的に絶縁となる部分が生じ難く、充放電容量が低下し難い。そのため、上記炭素繊維を負極活物質に用いたリチウムイオン電池は、サイクル特性が従来のリチウムイオン電池に比べて大幅に向上している。   The carbon material used in the method for producing a negative electrode active material of the present invention requires that lithium ions can be occluded / released electrochemically. Among such carbon materials, a compound having an aromatic ring is subjected to oxidative polymerization to produce fibrils. Particularly preferred is a carbon fiber produced by forming a polymer and firing the fibril polymer. The carbon material used for the negative electrode of the conventional lithium ion battery is usually a powder, and as a result of the expansion and contraction of the negative electrode accompanying the charge / discharge cycle of the battery, an electrically insulating part is generated and charged. The discharge capacity may decrease. However, since the carbon fiber has a three-dimensionally continuous structure, even if the negative electrode expands and contracts with the charge / discharge cycle of the battery, it is difficult to produce an electrically insulating portion. Capacity is difficult to decrease. Therefore, the lithium ion battery using the carbon fiber as a negative electrode active material has significantly improved cycle characteristics as compared with a conventional lithium ion battery.

上記フィブリル状ポリマーの原料となる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よいし、二種以上の混合物として用いてもよい。   Examples of the compound having an aromatic ring as a raw material for the fibril-like polymer 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 singly 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、一般に三次元連続構造を有し、直径が30nm〜数百nmであることが好ましく、40nm〜500nmであることが更に好ましく、長さが0.5μm〜100mmであることが好ましく、1μm〜10mmであることが更に好ましい。   The fibrillar polymer obtained by oxidative polymerization of the compound having an aromatic ring generally has a three-dimensional continuous structure, and preferably has a diameter of 30 nm to several hundred nm, more preferably 40 nm to 500 nm, The length is preferably 0.5 μm to 100 mm, and more preferably 1 μm to 10 mm.

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、導電性に優れた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。なお、重合の際に混在させる酸としては、種々のものを使用することができ、ＨＢＦ4、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。 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. be able to. As the acid to be mixed in the polymerization, can be used various ones, HBF 4, H 2 SO 4 , HCl, may be exemplified HClO 4 or the like. 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.

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等を用い、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. Used As an example of methods for the synthesis of fibrillar polymer by electrolytic oxidative polymerization method, stainless steel as a working electrode and a counter electrode, platinum, a plate or a porous material or the like made of a good conductive 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、焼成、好ましくは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, then fired, preferably fired in a non-oxidizing atmosphere and carbonized. A fibril-like three-dimensional 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.

上記フィブリル状ポリマーを焼成して得られる三次元連続構造を有する炭素繊維は、直径が30nm〜数百nmであることが好ましく、40nm〜500nmであることが更に好ましく、長さが0.5μm〜100mmであることが好ましく、1μm〜10mmであることが更に好ましく、表面抵抗が106〜10-2Ωであることが好ましく、104〜10-2Ωであることが更に好ましい。また、該炭素繊維は、残炭率が95〜30％であることが好ましく、90〜40％であることが更に好ましい。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 having a three-dimensional continuous structure obtained by firing the fibril-like polymer preferably has a diameter of 30 nm to several hundred nm, more preferably 40 nm to 500 nm, and a length of 0.5 μm to 100 mm. Preferably, the thickness is 1 μm to 10 mm, the surface resistance is preferably 10 6 to 10 −2 Ω, and more preferably 10 4 to 10 −2 Ω. Further, the carbon fiber preferably has a residual carbon ratio of 95 to 30%, and more 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.

本発明の負極活物質の製造方法に用いるポリシランは、特に限定されるものではなく、従来、炭化ケイ素の原料として用いられている種々のポリシランを使用することができる。該ポリシランとしては、例えば、式：［Ｓｉ(ＣＨ3)2］n、式：［Ｓｉ(ＣＨ3)(Ｃ6Ｈ5)］m［Ｓｉ(ＣＨ3)2］n等で表わされるポリシラン（式中、ｎ及びｍは、繰り返し単位数である）を例示することができる。 The polysilane used for the manufacturing method of the negative electrode active material of this invention is not specifically limited, The various polysilane conventionally used as a raw material of silicon carbide can be used. Examples of the polysilane include polysilanes represented by the formula: [Si (CH 3 ) 2 ] n , formula: [Si (CH 3 ) (C 6 H 5 )] m [Si (CH 3 ) 2 ] n and the like ( In the formula, n and m are the number of repeating units).

本発明の負極活物質の製造方法では、上記炭素材料に、上記ポリシランを塗布又は混合する。ここで、ポリシランをトルエン等の有機溶媒に溶解させ、溶液として炭素材料に塗布したり、炭素材料と混合することが好ましい。なお、溶液濃度は、特に限定されず、目的とする負極活物質中の炭化ケイ素含有率等に応じて適宜選択することができる。また、溶液の塗布又は混合の後には、真空下で乾燥する等して、ポリシランを炭素材料上に定着させることが好ましい。   In the method for producing a negative electrode active material of the present invention, the polysilane is applied or mixed with the carbon material. Here, it is preferable that polysilane is dissolved in an organic solvent such as toluene and applied as a solution to the carbon material or mixed with the carbon material. The solution concentration is not particularly limited, and can be appropriately selected according to the silicon carbide content in the target negative electrode active material. Further, after application or mixing of the solution, it is preferable to fix the polysilane on the carbon material by drying under vacuum or the like.

本発明の負極活物質の製造方法では、次に、ポリシランが塗布又は混合された炭素材料を熱処理して、炭素材料上に炭化ケイ素を生成させる。ここで、熱処理による炭化ケイ素の製造方法としては、（１）ポリシランが塗布又は混合された炭素材料を不活性ガス雰囲気中で、例えば、400〜500℃で熱処理して、ポリシランをポリカルボシランに変換し、その後、空気中で、例えば、300〜450℃で熱処理し、更に、不活性ガス雰囲気中で、例えば、1000〜1500℃で熱処理して、ポリカルボシランを炭化ケイ素に変換する方法や、（２）ポリシランが塗布又は混合された炭素材料を不活性ガス雰囲気中で紫外線照射し、更に、減圧下、例えば、1000〜1200℃で熱処理して、ポリシランを炭化ケイ素に変換する方法が挙げられる。なお、上記不活性ガスとしては、アルゴン、窒素等が挙げられる。   In the method for producing a negative electrode active material of the present invention, next, a carbon material coated or mixed with polysilane is heat-treated to generate silicon carbide on the carbon material. Here, as a method for producing silicon carbide by heat treatment, (1) a carbon material coated or mixed with polysilane is heat-treated in an inert gas atmosphere at, for example, 400 to 500 ° C. to convert polysilane to polycarbosilane. And then heat-treating in air, for example, at 300 to 450 ° C., and further heat-treating in an inert gas atmosphere, for example, at 1000 to 1500 ° C. to convert polycarbosilane to silicon carbide, (2) A method of converting polysilane into silicon carbide by irradiating a carbon material coated or mixed with polysilane with ultraviolet rays in an inert gas atmosphere and further heat-treating it under reduced pressure, for example, at 1000 to 1200 ° C. It is done. Examples of the inert gas include argon and nitrogen.

上記（１）の方法では、ポリシランとして、式：［−Ｓｉ(ＣＨ3)2−］で表わされる繰り返し単位からなるポリシランを使用することが好ましく、この場合、式：［−ＳｉＨ(ＣＨ3)−ＣＨ2−］で表わされる繰り返し単位からなるポリカルボシランが生成する。一方、上記（２）の方法では、ポリシランとして、式：［−Ｓｉ(ＣＨ3)2−］で表わされる繰り返し単位と式：［−Ｓｉ(ＣＨ3)(Ｃ6Ｈ5)−］で表わされる繰り返し単位とからなるポリシランを使用することが好ましい。なお、上記記（１）又は（２）の方法で炭素材料上に形成される炭化ケイ素は、通常、β型の炭化ケイ素である。 In the method (1), it is preferable to use a polysilane composed of a repeating unit represented by the formula: [—Si (CH 3 ) 2 —] as the polysilane. In this case, the formula: [—SiH (CH 3 ) A polycarbosilane composed of a repeating unit represented by —CH 2 —] is produced. On the other hand, in the above method (2), the polysilane is represented by the formula: [—Si (CH 3 ) 2 —] and the formula: [—Si (CH 3 ) (C 6 H 5 ) —]. It is preferable to use polysilane composed of repeating units. In addition, the silicon carbide formed on the carbon material by the above method (1) or (2) is usually β-type silicon carbide.

上述した方法で製造されるリチウムイオン電池用負極活物質は、炭素材料と、該炭素材料上に形成された炭化ケイ素とからなり、リチウムイオンを多量に吸着することができる。なお、本発明のリチウムイオン電池用負極活物質における炭化ケイ素の含有率は、5〜20質量％の範囲が好ましい。   The negative electrode active material for a lithium ion battery produced by the above-described method is composed of a carbon material and silicon carbide formed on the carbon material, and can adsorb a large amount of lithium ions. In addition, the content rate of the silicon carbide in the negative electrode active material for lithium ion batteries of this invention has the preferable range of 5-20 mass%.

＜リチウムイオン電池用負極＞
次に、本発明のリチウムイオン電池用負極を詳細に説明する。本発明のリチウムイオン電池用負極は、上記リチウムイオン電池用負極活物質を含むことを特徴とする。ここで、本発明のリチウムイオン電池用負極における上記リチウムイオン電池用負極活物質の含有率は、負極全体の50〜100質量％であることが好ましい。負極中の上記負極活物質の含有率が50質量％未満では、リチウムイオン電池の単位質量当りの充放電容量を十分に向上させられないことがある。 <Anode for lithium ion battery>
Next, the negative electrode for a lithium ion battery of the present invention will be described in detail. The negative electrode for a lithium ion battery according to the present invention is characterized by including the above negative electrode active material for a lithium ion battery. Here, it is preferable that the content rate of the said negative electrode active material for lithium ion batteries in the negative electrode for lithium ion batteries of this invention is 50-100 mass% of the whole negative electrode. When the content of the negative electrode active material in the negative electrode is less than 50% by mass, the charge / discharge capacity per unit mass of the lithium ion battery may not be sufficiently improved.

本発明のリチウムイオン電池用負極には、必要に応じて導電助剤、結着剤を混合することができ、導電助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。   The negative electrode for a lithium ion battery of the present invention can be mixed with a conductive auxiliary agent and a binder as necessary. Examples of the conductive auxiliary agent include acetylene black, and the binder is polyvinylidene fluoride ( PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC) and the like. These additives can be used at a blending ratio similar to the conventional one.

本発明のリチウムイオン電池用負極の形状としては、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 negative electrode for lithium ion batteries 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.

＜リチウムイオン電池＞
次に、本発明のリチウムイオン電池を詳細に説明する。本発明のリチウムイオン電池は、上述したリチウムイオン電池用負極を備え、更に、正極、電解質、セパレーター等のリチウムイオン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。本発明のリチウムイオン電池は、上述したリチウムイオン電池用負極を備えるため、充放電容量が高い。 <Lithium ion battery>
Next, the lithium ion battery of the present invention will be described in detail. The lithium ion battery of the present invention includes the above-described negative electrode for a lithium ion battery, and further includes other members that are usually used in the technical field of lithium ion batteries, such as a positive electrode, an electrolyte, and a separator. Since the lithium ion battery of the present invention includes the above-described negative electrode for a lithium ion battery, the charge / discharge capacity is high.

本発明のリチウムイオン電池の正極の活物質としては、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4、ＬｉＦｅＯ2及びＬｉＦｅＰＯ4等のリチウム含有複合酸化物、リチウム金属、Ｖ2Ｏ5、Ｖ6Ｏ13、ＭｎＯ2、ＭｎＯ3等の金属酸化物、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。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。上記正極には、必要に応じて導電助剤、結着剤を混合することができ、該導電助剤及び結着剤としては、上述の負極の項で例示したものを、従来と同様の配合割合で用いることができる。 Examples of the active material for the positive electrode of the lithium ion battery of the present invention include lithium-containing composite oxides such as LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiFeO 2, and LiFePO 4 , lithium metal, V 2 O 5 , and V 6 O 13. Preferable examples include metal oxides such as MnO 2 and MnO 3 , metal sulfides such as TiS 2 and MoS 2 , and conductive polymers such as polyaniline. These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together. If necessary, the positive electrode can be mixed with a conductive additive and a binder, and as the conductive auxiliary and binder, those exemplified in the above-mentioned negative electrode are blended in the same manner as in the past. Can be used in proportions.

本発明のリチウムイオン電池の電解質としては、非水電解液やポリマー電解質を使用することができる。該非水電解液は、通常、非プロトン性有機溶媒に支持塩を溶解させてなり、所望に応じて各種添加剤を含有してもよい。ここで、該非プロトン性溶媒としては、１,２-ジメトキシエタン、テトラヒドロフラン、ジメチルカーボネート、ジエチルカーボネート、ジフェニルカーボネート、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、γ-バレロラクトン、エチルメチルカーボネート等が挙げられる。また、支持塩としては、ＬｉＰＦ6、ＬｉＣｌＯ4、ＬｉＢＦ4、ＬｉＣＦ3ＳＯ3、ＬｉＡｓＦ6、ＬｉＣ4Ｆ9ＳＯ3、Ｌｉ(ＣＦ3ＳＯ2)2Ｎ及びＬｉ(Ｃ2Ｆ5ＳＯ2)2Ｎ等のリチウム塩が挙げられる。なお、非水電解液中の支持塩の濃度としては、特に限定されるものではないが、0.2〜1.5mol/L（Ｍ）の範囲が好ましい。 As the electrolyte of the lithium ion battery of the present invention, a nonaqueous electrolytic solution or a polymer electrolyte can be used. The nonaqueous electrolytic solution is usually prepared by dissolving a supporting salt in an aprotic organic solvent, and may contain various additives as desired. Here, examples of the aprotic solvent include 1,2-dimethoxyethane, tetrahydrofuran, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, and ethyl methyl carbonate. . As supporting salts, LiPF 6 , LiClO 4 , LiBF 4 , LiCF 3 SO 3 , LiAsF 6 , LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 2 N and Li (C 2 F 5 SO 2 ) 2 lithium salt such as N. The concentration of the supporting salt in the nonaqueous electrolytic solution is not particularly limited, but is preferably in the range of 0.2 to 1.5 mol / L (M).

また、上記ポリマー電解質は、ポリマーと上記支持塩とを含むことが好ましく、更に上記非プロトン性有機溶媒を含むことが更に好ましく、目的に応じて種々の添加剤を更に含有してもよい。上記ポリマー電解質に用いるポリマーとしては、ポリマー電池用のゲル電解質に通常用いられるポリマーの総てを用いることができ、具体的には、ポリエチレンオキシド、ポリプロピレンオキシド、ポリアクリレート、ポリアクリロニトリル、エチレンオキシドユニットを含むポリアクリレート等が挙げられる。   The polymer electrolyte preferably contains a polymer and the supporting salt, more preferably contains the aprotic organic solvent, and may further contain various additives depending on the purpose. As the polymer used for the polymer electrolyte, all polymers usually used for gel electrolytes for polymer batteries can be used, and specifically include polyethylene oxide, polypropylene oxide, polyacrylate, polyacrylonitrile, ethylene oxide units. Polyacrylate etc. are mentioned.

本発明のリチウムイオン電池に使用できる他の部材としては、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。これらは、単体でも、混合物でも、共重合体でもよい。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 lithium ion battery of the present invention include a separator interposed between positive and negative electrodes in a role of preventing current short-circuiting due to contact between both electrodes. As the material of the separator, it is possible to reliably prevent contact between the two electrodes and to allow the electrolyte to pass through or to contain, for example, synthesis of polytetrafluoroethylene, polypropylene, polyethylene, cellulose, polybutylene terephthalate, polyethylene terephthalate, etc. Preferred examples include resin non-woven fabrics and thin layer films. These may be a single substance, a mixture or a copolymer. Among these, a polypropylene or polyethylene microporous film having a thickness of about 20 to 50 μm, a film made of cellulose, polybutylene terephthalate, polyethylene terephthalate, or the like is 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リチウムイオン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、リチウムイオン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、リチウムイオン電池を作製することができる。   The form of the lithium ion 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 preferably exemplified. . In the case of the button type, a lithium ion 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 a spiral structure, for example, a lithium ion battery can be 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.

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.

（実施例１）
＜三次元連続状炭素繊維の製造＞
アニリン 0.5mol/Lと硫酸 1.0mol/Lとを含む酸性水溶液中に、作用極としてカーボンペーパー［東レ製］を設置し、対極として白金板を設置し、室温にて35mA/cm2の定電流を印加し、合計電気量が3Ｃ/cm2になるまで電解酸化重合を行い、作用極上にポリアニリンを電析させた。得られたポリアニリンを純水で十分に洗浄した後、24時間真空乾燥した。その後、得られたポリアニリンをカーボンペーパーごとＡｒ減圧雰囲気中3℃/分の昇温速度で950℃まで加熱し、該温度で1時間保持して焼成処理を行った。得られた焼成物をＳＥＭで観察したところ、直径が50〜300nmのフィブリル状で三次元連続状の炭素繊維が、カーボンペーパー上に形成されていることが確認された。 (Example 1)
<Manufacture of three-dimensional continuous carbon fiber>
In an acidic aqueous solution containing aniline 0.5 mol / L and sulfuric acid 1.0 mol / L, carbon paper [manufactured by Toray] was installed as the working electrode, a platinum plate was installed as the counter electrode, and a constant current of 35 mA / cm 2 at room temperature. Was applied, and electrolytic oxidation polymerization was performed until the total amount of electricity reached 3 C / cm 2 , and polyaniline was electrodeposited on the working electrode. The obtained polyaniline was thoroughly washed with pure water and then vacuum-dried for 24 hours. Thereafter, the obtained polyaniline was heated together with carbon paper to 950 ° C. at a rate of temperature increase of 3 ° C./min in an Ar reduced pressure atmosphere, and held at that temperature for 1 hour to perform a 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 50 to 300 nm were formed on the carbon paper.

＜炭素繊維上への炭化ケイ素の形成＞
上記の方法で製造した炭素繊維に、式：［Ｓｉ(ＣＨ3)2］nで表わされるポリシランのトルエン溶液（濃度：10質量％）を塗布し、真空下で乾燥して、炭素繊維上にポリシランを定着させた。その後、アルゴン雰囲気下で、ポリシランが定着した炭素繊維を450℃で焼成し、ポリシランを式：［ＳｉＨ(ＣＨ3)−ＣＨ2］nで表わされるポリカルボシランに変換させた。得られた混合物を空気中において350℃で焼成し、更に、窒素気流下において1300℃で焼成を行い、炭素繊維−炭化ケイ素複合体（炭化ケイ素含有率：5質量％）を製造した。 <Formation of silicon carbide on carbon fiber>
To the carbon fiber produced by the above method, a toluene solution (concentration: 10% by mass) of polysilane represented by the formula: [Si (CH 3 ) 2 ] n is applied, dried under vacuum, and applied onto the carbon fiber. Polysilane was fixed. Thereafter, the carbon fiber fixed with polysilane was baked at 450 ° C. in an argon atmosphere to convert the polysilane to polycarbosilane represented by the formula: [SiH (CH 3 ) —CH 2 ] n . The obtained mixture was fired at 350 ° C. in air, and further fired at 1300 ° C. in a nitrogen stream to produce a carbon fiber-silicon carbide composite (silicon carbide content: 5 mass%).

＜電極及び電池の作製、並びに評価＞
次に、得られた炭素繊維−炭化ケイ素複合体をカーボンペーパーごと16mmφのサイズに打ち抜き、負極を作製した。この負極を用いて、リチウムメタルを正極とするハーフセルを組み立て、充放電試験を行った。なお、電解液としては、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）の濃度で溶解させた非水電解液を使用した。また、充放電試験において、充電は、0.5mAの定電流で充電後、定電圧で5分間保持して行い、放電は、0.5mAの定電流で放電し、下限電圧を1.5Ｖとした。その結果、得られたハーフセルは、初回の放電容量が300Ah/kgで、20サイクル後の放電容量が310Ah/kgであり、放電容量が従来の電池に比べて大きいことが確認された。 <Production and Evaluation of Electrode and Battery>
Next, the obtained carbon fiber-silicon carbide composite was punched out together with carbon paper into a size of 16 mmφ to produce a negative electrode. Using this negative electrode, a half cell having lithium metal as the positive electrode was assembled, and a charge / discharge test was conducted. As the electrolytic solution, the concentration of the mixed solvent (EC / EMC volume ratio = 1/2) to, LiPF 6 (the supporting salt) 1M (mol / L) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) The non-aqueous electrolyte dissolved in (1) was used. In the charge / discharge test, charging was performed at a constant current of 0.5 mA and then held for 5 minutes at a constant voltage. Discharging was performed at a constant current of 0.5 mA and the lower limit voltage was 1.5V. As a result, the obtained half cell had an initial discharge capacity of 300 Ah / kg, a discharge capacity after 20 cycles of 310 Ah / kg, and the discharge capacity was confirmed to be larger than that of the conventional battery.

（比較例１）
ハードカーボン［クレハ化学社製］と、導電助剤としての熱処理アセチレンブラックとを1：1の質量比で使用し、少量のエタノールを滴下して混練りし、得られた混練物をＳＵＳ３１６（16mmφ）メッシュに圧着して、負極を作製した。こうして作製した負極を用いる以外は、実施例１と同様にしてハーフセルを組み立て、充放電試験を行った。その結果、得られたハーフセルは、初回の放電容量が260Ah/kgで、20サイクル後の放電容量が170Ah/kgであり、放電容量が実施例の電池に比べて著しく小さいことが確認された。 (Comparative Example 1)
Using hard carbon [manufactured by Kureha Chemical Co., Ltd.] and heat-treated acetylene black as a conductive auxiliary agent in a mass ratio of 1: 1, a small amount of ethanol was dropped and kneaded, and the obtained kneaded product was SUS316 (16 mmφ) ) A negative electrode was prepared by pressure bonding to a mesh. A half cell was assembled in the same manner as in Example 1 except that the negative electrode thus prepared was used, and a charge / discharge test was performed. As a result, the obtained half cell had an initial discharge capacity of 260 Ah / kg, a discharge capacity after 20 cycles of 170 Ah / kg, and the discharge capacity was confirmed to be significantly smaller than that of the battery of the example.

Claims (10)

炭素材料にポリシランを塗布又は混合する工程と、
前記ポリシランが塗布又は混合された炭素材料を熱処理して、炭素材料上に炭化ケイ素を生成させる工程と
を含む、炭素材料と炭化ケイ素とからなるリチウムイオン電池用負極活物質の製造方法。 Applying or mixing polysilane to the carbon material;
And a step of heat-treating the carbon material coated or mixed with the polysilane to form silicon carbide on the carbon material. A method for producing a negative electrode active material for a lithium ion battery comprising a carbon material and silicon carbide. 前記炭素材料が、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、該フィブリル状ポリマーを焼成して生成させた炭素繊維であることを特徴とする請求項１に記載のリチウムイオン電池用負極活物質の製造方法。   2. The lithium ion according to claim 1, wherein the carbon material is a carbon fiber formed by oxidative polymerization of a compound having an aromatic ring to form a fibril polymer, and firing the fibril polymer. 3. A method for producing a negative electrode active material for a battery. 前記ポリシランが塗布又は混合された炭素材料を不活性ガス雰囲気中で熱処理して、ポリシランをポリカルボシランに変換し、更に、空気中及び不活性ガス雰囲気中で熱処理して、前記ポリカルボシランを炭化ケイ素に変換して、炭素材料上に炭化ケイ素を生成させることを特徴とする請求項１に記載のリチウムイオン電池用負極活物質の製造方法。   The carbon material coated or mixed with the polysilane is heat-treated in an inert gas atmosphere to convert the polysilane to polycarbosilane, and further heat-treated in the air and in an inert gas atmosphere to obtain the polycarbosilane. The method for producing a negative electrode active material for a lithium ion battery according to claim 1, wherein the method is converted into silicon carbide to produce silicon carbide on the carbon material. 前記ポリシランが式：［−Ｓｉ(ＣＨ3)2−］で表わされる繰り返し単位からなり、前記ポリカルボシランが式：［−ＳｉＨ(ＣＨ3)−ＣＨ2−］で表わされる繰り返し単位からなることを特徴とする請求項３に記載のリチウムイオン電池用負極活物質の製造方法。 The polysilane has the formula: consisting repeating unit represented by said polycarbosilane has the formula [- - Si (CH 3) 2]: [- SiH (CH 3) -CH 2 -] by a repeating unit represented by The manufacturing method of the negative electrode active material for lithium ion batteries of Claim 3 characterized by these. 前記ポリシランが塗布又は混合された炭素材料を不活性ガス雰囲気中で紫外線照射し、更に、減圧下で熱処理して、前記ポリシランを炭化ケイ素に変換して、炭素材料上に炭化ケイ素を生成させることを特徴とする請求項１に記載のリチウムイオン電池用負極活物質の製造方法。   The carbon material coated or mixed with the polysilane is irradiated with ultraviolet light in an inert gas atmosphere, and further heat-treated under reduced pressure to convert the polysilane into silicon carbide, thereby generating silicon carbide on the carbon material. The manufacturing method of the negative electrode active material for lithium ion batteries of Claim 1 characterized by these. 前記ポリシランが、式：［−Ｓｉ(ＣＨ3)2−］で表わされる繰り返し単位と、式：［−Ｓｉ(ＣＨ3)(Ｃ6Ｈ5)−］で表わされる繰り返し単位とからなることを特徴とする請求項５に記載のリチウムイオン電池用負極活物質の製造方法。 The polysilane consists of a repeating unit represented by the formula: [—Si (CH 3 ) 2 —] and a repeating unit represented by the formula: [—Si (CH 3 ) (C 6 H 5 ) —]. The manufacturing method of the negative electrode active material for lithium ion batteries of Claim 5 characterized by the above-mentioned. 前記炭化ケイ素がβ型の炭化ケイ素であることを特徴とする請求項１、３及び５のいずれかに記載のリチウムイオン電池用負極活物質の製造方法。   The method for producing a negative electrode active material for a lithium ion battery according to any one of claims 1, 3, and 5, wherein the silicon carbide is β-type silicon carbide. 請求項１〜７のいずれかに記載の方法で製造されたリチウムイオン電池用負極活物質。   The negative electrode active material for lithium ion batteries manufactured by the method in any one of Claims 1-7. 請求項８に記載のリチウムイオン電池用負極活物質を含むリチウムイオン電池用負極。   The negative electrode for lithium ion batteries containing the negative electrode active material for lithium ion batteries of Claim 8. 請求項９に記載のリチウムイオン電池用負極を具えたリチウムイオン電池。   A lithium ion battery comprising the negative electrode for a lithium ion battery according to claim 9.
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