JP2014086285A - Composition for battery electrode and manufacturing method of electrode for battery using the same - Google Patents
Composition for battery electrode and manufacturing method of electrode for battery using the same Download PDFInfo
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Abstract
Description
本発明は、電池電極用組成物およびそれを用いた電池用電極の製造方法に関する。 The present invention relates to a battery electrode composition and a method for producing a battery electrode using the same.
リチウムイオン電池は、ニッケルカドミウム電池やニッケル水素電池と比較して、体積エネルギー密度と重量エネルギー密度が大きく、急速充放電特性に優れており、小型軽量化が可能である、といった点から注目されているが、使用されるモバイル機器等の高性能化の要求から更なる特性向上が求められている。
リチウムイオン電池としては、正極活物質であるリチウム複合酸化物と負極活物質である炭素の間を非水系電解液を介してリチウムイオンが移動し、充放電を繰り返すことによって二次電池として機能する。
このようなリチウムイオン電池は、エネルギー密度を向上させるため、シート状の正極および負極をセパレータを介して対向させ、積層または捲回の状態でアルミ製深絞りケースやアルミ箔に樹脂を積層したラミネート外装材内に納められている。
Lithium-ion batteries are attracting attention because they have a large volumetric energy density and weight energy density compared to nickel cadmium batteries and nickel metal hydride batteries, have excellent rapid charge / discharge characteristics, and can be reduced in size and weight. However, further improvement in characteristics is required due to the demand for higher performance of mobile devices used.
As a lithium ion battery, lithium ions move between a lithium composite oxide, which is a positive electrode active material, and carbon, which is a negative electrode active material, via a non-aqueous electrolyte, and function as a secondary battery by repeating charge and discharge. .
In order to improve the energy density, such a lithium ion battery is a laminate in which a sheet-like positive electrode and a negative electrode are opposed to each other through a separator, and a resin is laminated on an aluminum deep-drawn case or aluminum foil in a laminated or wound state. It is stored in the exterior material.
ところで、リチウムイオン電池の電極は、正極および負極それぞれ集電体に活物質と、活物質を結着させるバインダ樹脂とを含むスラリーを塗工し、乾燥することにより形成される。バインダ樹脂としては、有機溶剤系のポリフッ化ビニリデン（ＰＶｄＦ）あるいは水分散系のスチレン−ブタジエンゴム（ＳＢＲ）が多く用いられている。ＰＶｄＦは接着性に劣るために活物質に対してＰＶｄＦの使用量を多くする必要があり、十分な特性が得られにくい。また、ＳＢＲは僅かな使用量の違いで電池特性に大きな影響が出ることや、良好な塗工性を得るために増粘剤としてカルボキシメチルセルロース（ＣＭＣ）を添加する必要があるなどの課題を抱えている。 By the way, the electrode of a lithium ion battery is formed by applying and drying a slurry containing an active material and a binder resin for binding the active material to each of the positive electrode and the negative electrode current collector. As the binder resin, organic solvent-based polyvinylidene fluoride (PVdF) or water-dispersed styrene-butadiene rubber (SBR) is often used. Since PVdF is inferior in adhesiveness, it is necessary to increase the amount of PVdF used relative to the active material, and it is difficult to obtain sufficient characteristics. In addition, SBR has problems such as having a large effect on battery characteristics due to a slight difference in the amount used, and adding carboxymethyl cellulose (CMC) as a thickener to obtain good coating properties. ing.
これらの課題を解決するため、様々な試みがなされてきた。
特許文献１では、分子量の大きなＣＭＣをバインダとして用いることで活物質への被覆を抑制し、イオンの輸送経路を確保することにより、低温下での出力特性の低下を抑制する方法が開示されている。しかし、該方法を用いるとバインダへの活物質の良好な分散性が得られず、活物質が偏析するために均一な電池特性が得られにくく、また充放電に伴う膨潤収縮挙動の影響で活物質の脱落が起こり易く、良好なサイクル特性が得られにくい。また、特許文献２では、バインダとしてＣＭＣを用いた際のイオン伝導性向上のためにアルカリ金属塩を多量に混在させる方法が開示されている。しかし、該方法を用いると水との親和性が増大するために電池製造工程における湿度管理が困難になる。さらに、過剰なイオンの存在によりリチウムイオンの移動が阻害され、出力特性に支障が出る。
Various attempts have been made to solve these problems.
Patent Document 1 discloses a method for suppressing a decrease in output characteristics at low temperatures by suppressing the covering of the active material by using CMC having a large molecular weight as a binder and securing an ion transport route. Yes. However, when this method is used, good dispersibility of the active material in the binder cannot be obtained, the active material segregates, and it is difficult to obtain uniform battery characteristics, and the active material is affected by the swelling and shrinkage behavior associated with charge and discharge. It is easy for the material to fall off, and it is difficult to obtain good cycle characteristics. Patent Document 2 discloses a method in which a large amount of an alkali metal salt is mixed in order to improve ion conductivity when CMC is used as a binder. However, when this method is used, the affinity with water is increased, making it difficult to manage the humidity in the battery manufacturing process. Furthermore, the movement of lithium ions is hindered by the presence of excessive ions, which impedes output characteristics.
本発明は以上のような背景技術を考慮してなされたもので、電池用電極の組成設計の自由度が向上し、生産性に優れ、良好なサイクル特性に加え、出力特性に優れた電池電極用組成物およびそれを用いた電池用電極を提供することを目的とする。 The present invention has been made in consideration of the background art as described above, and the degree of freedom in the composition design of the battery electrode is improved, the productivity is excellent, the battery electrode is excellent in output characteristics in addition to good cycle characteristics. It is an object to provide an electrode composition and a battery electrode using the same.
上記課題を解決するために、本発明における請求項１に記載した発明は、少なくとも、活物質と、カルボキシル基を有する繊維状多糖類と、分散媒とを含むことを特徴とする電池電極用組成物を提供するものである。 In order to solve the above problems, the invention according to claim 1 of the present invention comprises at least an active material, a fibrous polysaccharide having a carboxyl group, and a dispersion medium, characterized in that the composition for a battery electrode is provided. It provides things.
次に、請求項２に記載した発明は、請求項１に記載した構成に対し、前記カルボキシル基を有する繊維状多糖類がセルロース繊維であることを特徴とするものである。 Next, the invention described in claim 2 is characterized in that, in the configuration described in claim 1, the fibrous polysaccharide having a carboxyl group is a cellulose fiber.
次に、請求項３に記載した発明は、請求項１または２に記載した構成に対し、前記セルロース繊維の繊維幅が２ｎｍ以上５０ｎｍ以下であり、前記セルロース繊維の長さが０．５μｍ以上５０μｍ以下であることを特徴とするものである。 Next, in the invention described in claim 3, the fiber width of the cellulose fiber is 2 nm or more and 50 nm or less, and the length of the cellulose fiber is 0.5 μm or more and 50 μm in the configuration described in claim 1 or 2. It is characterized by the following.
次に、請求項４に記載した発明は、請求項２または請求項３に記載した構成に対し、前記セルロース繊維のカルボキシル基量がセルロース重量に対して０．５ｍｍｏｌ／ｇ以上３．０ｍｍｏｌ／ｇ以下であることを特徴とするものである。 Next, in the invention described in claim 4, in the structure described in claim 2 or 3, the amount of carboxyl groups of the cellulose fiber is 0.5 mmol / g or more and 3.0 mmol / g with respect to the weight of cellulose. It is characterized by the following.
次に、請求項５に記載した発明は、前記セルロース繊維のカルボキシル基の少なくとも一部がカルボン酸塩であることを特徴とする請求項２乃至４のいずれか１項に記載の電池電極用組成物とするものである。 Next, in the invention described in claim 5, the composition for battery electrodes according to any one of claims 2 to 4, wherein at least a part of the carboxyl groups of the cellulose fiber is a carboxylate. It is a thing.
次に、請求項６に記載した発明は、カルボキシル基を有する繊維状多糖類を分散媒に分散させて、繊維状多糖類と前記分散媒とを含む調製液を調製する工程と、
前記調製液に活物質を分散させて、前記繊維状多糖類と前記活物質と前記分散媒とを含む分散液を調製する工程と、
をこの順に有し、前記分散液が請求項１乃至請求項５に記載のいずれか１項に記載の電池電極用組成物であることを特徴とする電池電極用組成物の製造方法である。
Next, the invention described in claim 6 is a step of dispersing a fibrous polysaccharide having a carboxyl group in a dispersion medium to prepare a preparation liquid containing the fibrous polysaccharide and the dispersion medium;
A step of dispersing an active material in the preparation liquid to prepare a dispersion liquid containing the fibrous polysaccharide, the active material, and the dispersion medium;
In this order, the dispersion is the battery electrode composition according to any one of claims 1 to 5, wherein the battery electrode composition is a method for producing a battery electrode composition.
次に、請求項７に記載した発明は、カルボキシル基を有する繊維状多糖類と活物質とを分散媒に分散させて、前記繊維状多糖類と前記活物質と前記分散媒とを含む分散液を調製する工程を有し、前記分散液が請求項１乃至請求項５に記載のいずれか１項に記載の電池電極用組成物であることを特徴とする電池電極用組成物の製造方法である。 Next, the invention described in claim 7 is a dispersion liquid in which a fibrous polysaccharide having a carboxyl group and an active material are dispersed in a dispersion medium, and the fibrous polysaccharide, the active material, and the dispersion medium are contained. A method for producing a battery electrode composition, wherein the dispersion is the battery electrode composition according to any one of claims 1 to 5. is there.
次に、請求項８に記載した発明は、カルボキシル基を有する繊維状多糖類を分散媒に分散させて、第一の繊維状多糖類と前記分散媒とを含む第一の調製液を調製する工程と、
前記第一の調製液に活物質を分散させて、前記第一の繊維状多糖類と前記活物質と前記分散液とを含む第二の調製液を調製する工程と、
前記第二の調製液を分散処理して、前記カルボキシル基を有する繊維状多糖類と前記活物質と前記分散媒とを含む調製液を調製する工程と、
をこの順に有し、前記分散液が請求項１乃至請求項５に記載のいずれか１項に記載の電池電極用組成物であることを特徴とする電池電極用組成物の製造方法である。
Next, the invention described in claim 8 is to prepare a first preparation liquid containing the first fibrous polysaccharide and the dispersion medium by dispersing the fibrous polysaccharide having a carboxyl group in the dispersion medium. Process,
A step of dispersing an active material in the first preparation liquid to prepare a second preparation liquid containing the first fibrous polysaccharide, the active material, and the dispersion;
A step of dispersing the second preparation liquid to prepare a preparation liquid containing the fibrous polysaccharide having the carboxyl group, the active material, and the dispersion medium;
In this order, the dispersion is the battery electrode composition according to any one of claims 1 to 5, wherein the battery electrode composition is a method for producing a battery electrode composition.
次に、請求項９に記載した発明は、少なくとも、活物質と、カルボキシル基を有する繊維状多糖類と、分散媒とを含む電池電極用組成物を塗工する工程と、塗工した電池電極用組成物を乾燥させる工程と、を有することを特徴とする電池用電極及びその製造方法である。 Next, the invention described in claim 9 includes a step of applying a battery electrode composition containing at least an active material, a fibrous polysaccharide having a carboxyl group, and a dispersion medium, and a coated battery electrode A battery electrode and a method for producing the same.
本発明によれば、電池用電極の組成設計の自由度が向上し、生産性に優れ、かつ、良好なサイクル特性に加え、出力特性に優れた電池用電極を製造することができる。
組成設計に関しては、本発明によると分散液中に存在する繊維状多糖類は分子量が維持された状態で分散されているため、分子鎖同士の絡み合いが生じる。これにより増粘効果が得られる。低濃度においても増粘傾向が強いため、塗工性向上のためのＣＭＣ等の増粘剤を添加する必要がない。
生産性に関しては、本発明によると分散液中に存在する繊維状多糖類が本来有する水酸基、及び化学的処理により付与したカルボキシル基と、個々の活物質の表面に存在するカルボキシル基や水酸基が相互作用し、さらに繊維状多糖類のカルボキシル基が部分的に電離していることにより互いに静電反発しているため、活物質が分散しやすくまた分散状態での安定性が良い。分散性に優れているために分散媒の低減が可能であることから乾燥に要する時間が短縮されることによる。
サイクル特性に関しては、本発明によると繊維状多糖類は分子内や分子間の水素結合が発達しているために力学的強度に優れ、またナノオーダーの繊維同士の絡み合いにより活物質が捕捉されることにより活物質の脱落が少なくなる。さらに、親水性が非常に高いために非水系である電解液に対して親和性が低く、耐膨潤性に優れる。そのため、結着性に優れ、かつ電解液耐性に優れる。
出力特性に関しては、本発明によるとナノオーダーに分散された繊維状多糖類の繊維が剛直な分子骨格により形成されている。このため、活物質を包含し、活物質同士あるいは活物質と集電体を結着する際に、活物質を完全に被覆することがなく、電解液から活物質へのリチウムイオン移動に対する抵抗が大幅に低減される。そのため、内部抵抗が大幅に低減される。
ADVANTAGE OF THE INVENTION According to this invention, the freedom degree of the composition design of the battery electrode improves, it is excellent in productivity, and in addition to favorable cycling characteristics, the battery electrode excellent in output characteristics can be manufactured.
Regarding composition design, according to the present invention, the fibrous polysaccharides present in the dispersion are dispersed in a state in which the molecular weight is maintained, so that the molecular chains are entangled. This provides a thickening effect. Since the thickening tendency is strong even at a low concentration, it is not necessary to add a thickener such as CMC for improving the coatability.
In terms of productivity, according to the present invention, the hydroxyl groups inherent in the fibrous polysaccharides present in the dispersion and the carboxyl groups imparted by chemical treatment, and the carboxyl groups and hydroxyl groups present on the surface of each active material interact with each other. In addition, since the carboxyl groups of the fibrous polysaccharide are partially ionized, they are electrostatically repelled from each other, so that the active materials are easily dispersed and the stability in the dispersed state is good. This is because the time required for drying is shortened because the dispersion medium can be reduced because of its excellent dispersibility.
Regarding cycle characteristics, according to the present invention, fibrous polysaccharides have excellent mechanical strength due to the development of intramolecular and intermolecular hydrogen bonds, and active materials are captured by entanglement of nano-order fibers. This reduces the loss of the active material. Further, since the hydrophilicity is very high, the affinity for non-aqueous electrolyte is low, and the swelling resistance is excellent. Therefore, the binding property is excellent and the electrolytic solution resistance is excellent.
Regarding the output characteristics, according to the present invention, the fibers of fibrous polysaccharide dispersed in the nano order are formed of a rigid molecular skeleton. For this reason, when the active material is included and the active materials are bound to each other or between the active material and the current collector, the active material is not completely covered, and resistance to lithium ion transfer from the electrolyte to the active material is reduced. It is greatly reduced. For this reason, the internal resistance is greatly reduced.
本発明は、少なくとも、活物質と、カルボキシル基を有する繊維状多糖類と、分散媒とを含むことを特徴とする電池電極用組成物である。
以下、本発明の一実施形態について説明する。
本発明に用いる活物質としては、特に限定されず、通常負極用活物質としては炭素質材料が用いられる。黒鉛、ハードカーボン、グラファイト、フラーレン、カーボンナノチューブ、カーボンナノホーン、カーボンナノファイバー、を挙げることができ、これらを物理的、化学的処理した物質の何れを用いてもよい。また、金属酸化物、特にチタン酸リチウムが実用化されておりこれを用いてもよい。
The present invention is a battery electrode composition comprising at least an active material, a fibrous polysaccharide having a carboxyl group, and a dispersion medium.
Hereinafter, an embodiment of the present invention will be described.
The active material used in the present invention is not particularly limited, and a carbonaceous material is usually used as the negative electrode active material. Examples thereof include graphite, hard carbon, graphite, fullerene, carbon nanotube, carbon nanohorn, and carbon nanofiber, and any of materials obtained by physically or chemically treating these may be used. In addition, metal oxides, particularly lithium titanate, have been put into practical use and may be used.
また、前処理として炭素質材料に表面処理を施しても良い。表面処理としては、酸化処理、グラフト重合反応、カップリング処理、機械的処理、プラズマ処理、黒鉛化、賦活化処理などを挙げることができる。前処理を施すことにより、炭素質材料の表面状態を変化させ各種官能基を導入したり、有機層を形成することによってマトリックス樹脂との反応や相溶性を向上させたり、また、炭素質材料自体の凝集を阻害することにより分散性を向上させることができる。 Moreover, you may surface-treat to a carbonaceous material as pretreatment. Examples of the surface treatment include oxidation treatment, graft polymerization reaction, coupling treatment, mechanical treatment, plasma treatment, graphitization, activation treatment, and the like. By applying pre-treatment, the surface state of the carbonaceous material is changed to introduce various functional groups, and by forming an organic layer, the reaction and compatibility with the matrix resin is improved, or the carbonaceous material itself The dispersibility can be improved by inhibiting the aggregation of.
さらに、イオン伝導性を向上させるため、導電助剤を含んでも良い。あらゆるカーボンブラック（ファーネスブラック、チャンネルブラック、サーマルブラック、アセチレンブラック、ケッチェンブラック、ランプブラック）を挙げることができ、これらを物理的、化学的処理した物質の何れを用いてもよい。 Furthermore, in order to improve ion conductivity, you may include a conductive support agent. Any carbon black (furnace black, channel black, thermal black, acetylene black, ketjen black, lamp black) can be mentioned, and any of materials obtained by physically or chemically treating these may be used.
繊維状多糖類としては、セルロース繊維、キチン、キトサンなどが挙げられ、特に構造配列が規則的であり剛直な骨格を有するセルロース繊維が好ましい。セルロース繊維の原料となるセルロースとしては、木材パルプ、非木材パルプ、コットン、バクテリアセルロース等を用いることができる。 Examples of fibrous polysaccharides include cellulose fibers, chitin, and chitosan. In particular, cellulose fibers having a regular structural arrangement and a rigid skeleton are preferable. Wood pulp, non-wood pulp, cotton, bacterial cellulose, and the like can be used as cellulose that is a raw material for cellulose fibers.
さらに、その繊維幅は２ｎｍ以上５０ｎｍ以下であり、長さが０．５μｍ以上５０μｍ以下であることを特徴とする。この範囲であれば、活物質と相互作用できる部位が多数存在するため分散性が良くなり、また活物質同士の導電ネットワークが形成されるため電気化学的安定性が良好となる。さらに、セルロース繊維同士の絡み合い構造によって電解液に対しての膨潤耐性に優れ、活物質が捕捉されるために脱落しにくくなり、電池としての良好なサイクル特性を得ることができる。一方、繊維幅が５０ｎｍを超えるとセルロース繊維の全体積に占める表面積の割合が相対的に小さくなり、活物質と相互作用できる部位が減るため、活物質を効率的に分散させることが出来なくなる。また、長さが０．５μｍ未満だとセルロース繊維同士の絡み合いが十分に行えず、膜の強度低下の原因になってしまうため好ましくない。さらに、長さが５０μｍを超えるとセルロース繊維同士の絡み合いが大きくなるために繊維は分散しにくく、沈殿を形成しやすくなるため分散安定性が低下する。繊維の幅や長さは、水などの溶媒に固形分濃度０．００１％程度に希釈した繊維をガラス等平滑な基板上に展開し、乾燥させたものをＡＦＭやＴＥＭなどを用いて測定することができる。 Furthermore, the fiber width is 2 nm or more and 50 nm or less, and the length is 0.5 μm or more and 50 μm or less. Within this range, dispersibility is improved because there are many sites capable of interacting with the active material, and electrochemical stability is improved because a conductive network between the active materials is formed. Furthermore, the entangled structure of cellulose fibers is excellent in swelling resistance to the electrolytic solution, and since the active material is captured, it is difficult to fall off, and good cycle characteristics as a battery can be obtained. On the other hand, if the fiber width exceeds 50 nm, the ratio of the surface area to the total volume of the cellulose fibers becomes relatively small, and the number of sites capable of interacting with the active material is reduced, so that the active material cannot be efficiently dispersed. On the other hand, if the length is less than 0.5 μm, the cellulose fibers cannot be sufficiently entangled with each other, which causes a decrease in the strength of the film. Furthermore, when the length exceeds 50 μm, the entanglement between the cellulose fibers increases, so that the fibers are difficult to disperse, and the precipitate is easily formed, so that the dispersion stability is lowered. The width and length of the fiber are measured by using a fiber diluted with a solvent such as water to a solid content concentration of about 0.001% on a smooth substrate such as glass and dried using AFM or TEM. be able to.
また、セルロース繊維のカルボキシル基量はセルロース重量に対して、０．５ｍｍｏｌ／ｇ以上３．０ｍｍｏｌ／ｇ以下であることが望ましい。この範囲のカルボキシル基量を有するセルロース繊維は分散処理を施した際の分散性が良好であり、活物質の有する官能基との相互作用が十分であるため、良好な分散性が得られる。さらに、カルボキシル基の一部がカルボン酸塩であることを特徴とする。例えば、カルボキシル基の対イオンとなるカチオンは、アルカリ金属イオン（リチウム、ナトリウム、カリウム等）、アルカリ土類金属（カルシウム等）、アンモニウムイオン、有機オニウム（各種脂肪族アミン、芳香族アミン、ジアミンなどのアミン類や水酸化テトラメチルアンモニウム、水酸化テトラエチルアンモニウム、水酸化テトラｎ−ブチルアンモニウム、水酸化ベンジルトリメチルアンモニウム、水酸化２−ヒドロキシエチルトリメチルアンモニウム、などＮＲ４ＯＨ（Ｒはアルキル基、またはベンジル基、またはフェニル基、またはヒドロキシアルキル基で、４つのＲが同一でも異なっていてもよい。）で表される水酸化アンモニウム化合物、水酸化テトラエチルホスホニウムなどの水酸化ホスホニウム化合物、水酸化オキソニウム化合物、水酸化スルホニウム化合物など）の対イオンが挙げられる。また、これらを２種以上混合して塩を形成することもできる。 Moreover, it is desirable that the amount of carboxyl groups in the cellulose fiber is 0.5 mmol / g or more and 3.0 mmol / g or less with respect to the weight of cellulose. Cellulose fibers having an amount of carboxyl groups in this range have good dispersibility when subjected to a dispersion treatment, and sufficient interaction with the functional group of the active material is obtained, so that good dispersibility is obtained. Furthermore, a part of the carboxyl group is a carboxylate. For example, the cation serving as a counter ion of the carboxyl group includes alkali metal ions (lithium, sodium, potassium, etc.), alkaline earth metals (calcium, etc.), ammonium ions, organic oniums (various aliphatic amines, aromatic amines, diamines, etc.) Amines such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, benzyltrimethylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide, NR4OH (where R is an alkyl group or benzyl group, Or a phenyl group or a hydroxyalkyl group, and four Rs may be the same or different.) Ammonium hydroxide compound, phosphonium hydroxide compound such as tetraethylphosphonium hydroxide, oxohydroxide Um compounds include counterions such as hydroxide sulfonium compounds). Two or more of these can be mixed to form a salt.
セルロース繊維の有するカルボキシル基が電離することにより静電反発が増大し、セルロース繊維の分散性が保持されると考えられている。そのため、カルボキシル基の一部がイオン化した状態を維持していることが望ましい。また、対イオンとしてナトリウムイオンなどの金属イオンが多量に存在すると、電析や副反応の恐れがあり、好ましくない場合がある。この時、有機オニウムを用いることにより、これらの問題を解決することができる。 It is considered that the electrostatic repulsion increases by the ionization of the carboxyl group of the cellulose fiber, and the dispersibility of the cellulose fiber is maintained. Therefore, it is desirable to maintain a state in which a part of the carboxyl group is ionized. In addition, if a large amount of metal ions such as sodium ions are present as counter ions, there is a risk of electrodeposition or side reaction, which may not be preferable. At this time, these problems can be solved by using organic onium.
セルロースにカルボキシル基を導入する方法としては、現在いくつか化学処理の方法が報告されている。例えばカルボキシメチルセルロース等、分子分散した水溶性多糖類を用いると活物質の表面に水溶性多糖類が覆い被さり、電極の内部抵抗が高くなることにより、結果的に電池特性低下を招く恐れがある。そこで、本発明のように繊維状であり分散性が良好で、且つ活物質が効率的にセルロースのカルボキシル基と相互作用できる構造を有するためには、剛直な骨格を保持した高結晶性のセルロースにカルボキシル基を導入し、且つカルボキシル基が繊維表面に緻密で規則的に存在することが望ましい。 As a method for introducing a carboxyl group into cellulose, several chemical treatment methods are currently reported. For example, when a molecularly dispersed water-soluble polysaccharide such as carboxymethylcellulose is used, the surface of the active material is covered with the water-soluble polysaccharide, and the internal resistance of the electrode increases, resulting in a decrease in battery characteristics. Therefore, in order to have a structure that is fibrous, has good dispersibility, and the active material can efficiently interact with the carboxyl groups of cellulose as in the present invention, highly crystalline cellulose that retains a rigid skeleton. It is desirable that a carboxyl group is introduced into the fiber and that the carboxyl group is present densely and regularly on the fiber surface.
具体的には、次の方法が望ましい。２，２，６，６−テトラメチル−１−ピペジニルオキシラジカル（ＴＥＭＰＯ）を触媒として使用し、ｐＨを調整しながら次亜塩素酸ナトリウム等の酸化剤、臭化ナトリウム等の臭化物を用いて処理する。この方法によると、ＴＥＭＰＯの立体障害により結晶性を有する繊維最小単位であるミクロフィブリルの表面に存在するセルロースＣ６位の一級水酸基のみが選択的にカルボキシル基へと酸化される。導入されたカルボキシル基の静電反発によってミクロフィブリルの結合が弱まるために低エネルギー投入による機械的処理によって、高分散した高結晶性を有する繊維状セルロースが得られる。さらに、本方法を利用すると、得られたセルロース繊維の分子量低下が抑えられるため、高い力学強度が保持されることから優れたサイクル特性が得られる。 Specifically, the following method is desirable. 2,2,6,6-tetramethyl-1-pipedinyloxy radical (TEMPO) is used as a catalyst, and an oxidizing agent such as sodium hypochlorite and bromide such as sodium bromide are used while adjusting pH. To process. According to this method, only the primary hydroxyl group at the cellulose C6 position existing on the surface of microfibril, which is the minimum fiber unit having crystallinity, is selectively oxidized to a carboxyl group due to the steric hindrance of TEMPO. Since the binding of microfibrils is weakened by electrostatic repulsion of the introduced carboxyl group, highly dispersed fibrous cellulose having high crystallinity can be obtained by mechanical treatment with low energy input. Furthermore, when this method is used, since the molecular weight reduction of the obtained cellulose fiber is suppressed, a high mechanical strength is maintained, so that excellent cycle characteristics can be obtained.
以下、上記化学処理の具体的な方法を説明する。
水中で分散させたセルロースにニトロキシラジカルと臭化ナトリウムとを添加して室温で攪拌しながら次亜塩素酸ナトリウム水溶液を添加してセルロースの酸化を行う。酸化反応中に水酸化ナトリウム等アルカリ溶液を添加し、反応系内のｐＨを９〜１１に制御する。この時、セルロース繊維表面のＣ６位の水酸基がカルボキシル基に酸化される。十分水洗し、得られたセルロースを繊維状に分散したものを分散液の構成材料として用いることが出来る。なお、酸化剤としては、次亜ハロゲン酸又はその塩、亜ハロゲン酸又はその塩が使用でき、次亜塩素酸ナトリウムが好ましい。臭化物としては、臭化リチウム、臭化カリウム、臭化ナトリウム等が挙げられ、臭化ナトリウムが好ましい。上記の方法によりカルボキシル基を有するＴＥＭＰＯ酸化セルロースが得られる。
Hereinafter, a specific method of the chemical treatment will be described.
Nitroxyl radical and sodium bromide are added to cellulose dispersed in water, and sodium hypochlorite aqueous solution is added with stirring at room temperature to oxidize the cellulose. An alkaline solution such as sodium hydroxide is added during the oxidation reaction, and the pH in the reaction system is controlled to 9-11. At this time, the hydroxyl group at the C6 position on the surface of the cellulose fiber is oxidized to a carboxyl group. A material obtained by thoroughly washing with water and dispersing the obtained cellulose in a fibrous form can be used as a constituent material of the dispersion. In addition, as an oxidizing agent, hypohalous acid or its salt, a halogenous acid or its salt can be used, and sodium hypochlorite is preferable. Examples of the bromide include lithium bromide, potassium bromide, sodium bromide and the like, and sodium bromide is preferable. By the above method, TEMPO oxidized cellulose having a carboxyl group is obtained.
なお、セルロースに含有されるカルボキシル基量は以下の方法にて算出される。化学処理したセルロースの乾燥重量換算０．２ｇをビーカーにとり、イオン交換水８０ｍｌを添加する。そこに０．０１Ｍ塩化ナトリウム水溶液５ｍｌを加え、攪拌させながら０．１Ｍ塩酸を加えて全体がｐＨ２．８となるように調整した。ここに自動滴定装置（東亜ディーケーケー（株）社製、ＡＵＴ−７０１）を用いて０．１Ｍ水酸化ナトリウム水溶液を０．０５ｍｌ／３０秒で注入し、３０秒毎の電導度とｐＨ値を測定し、ｐＨ１１まで測定を続けた。得られた電導度曲線から水酸化ナトリウムの滴定量を求め、カルボキシル基含有量を算出した。 In addition, the amount of carboxyl groups contained in cellulose is calculated by the following method. 0.2 g of dry weight conversion of chemically treated cellulose is taken in a beaker, and 80 ml of ion exchange water is added. Thereto was added 5 ml of 0.01 M sodium chloride aqueous solution, and 0.1 M hydrochloric acid was added while stirring to adjust the whole to pH 2.8. Using an automatic titrator (AUT-701, manufactured by Toa DKK Co., Ltd.), 0.1M sodium hydroxide aqueous solution was injected at 0.05 ml / 30 seconds, and the conductivity and pH value were measured every 30 seconds. The measurement was continued until pH 11. A titration amount of sodium hydroxide was determined from the obtained conductivity curve, and the carboxyl group content was calculated.
ＴＥＭＰＯ酸化処理されたセルロースは分子量をある程度保持されるため、繊維の絡み合いによって得られる分散液は低濃度でも高い粘度特性を有する。塗工性を良好にするため、分散液の粘度を調整することができる。粘度を調整する方法としては、原料セルロースの種類を適宜選択したり分散液の濃度を調整する他、ＴＥＭＰＯ酸化処理したセルロースを分散処理前に物理的或いは化学的に処理を施すことができる。具体的には、水酸化ナトリウム水溶液に晒すアルカリ処理、紫外線照射によりβ脱離を促進させる紫外線照射処理、酵素による分解を促す酵素処理などが挙げられる。 Since TEMPO-oxidized cellulose retains molecular weight to some extent, a dispersion obtained by entanglement of fibers has high viscosity characteristics even at a low concentration. In order to improve the coatability, the viscosity of the dispersion can be adjusted. As a method for adjusting the viscosity, in addition to appropriately selecting the type of raw material cellulose and adjusting the concentration of the dispersion, cellulose subjected to TEMPO oxidation treatment can be physically or chemically treated before the dispersion treatment. Specifically, an alkali treatment exposed to an aqueous sodium hydroxide solution, an ultraviolet irradiation treatment that promotes β-elimination by ultraviolet irradiation, an enzyme treatment that promotes degradation by an enzyme, and the like can be mentioned.
ところで、分散媒としては、水、または水と有機溶剤との混合溶剤が挙げられる。ここで用いられる有機溶剤としては、水と均一に混和可能な水溶性有機溶剤であればよく、たとえばメタノール、エタノール、２−プロパノール（ＩＰＡ）などのアルコール類、アセトン、メチルエチルケトン（ＭＥＫ）などのケトン類、１，４−ジオキサン、テトラヒドロフラン（ＴＨＦ）などのエーテル類、Ｎ，Ｎ−ジメチルホルムアミド（ＤＭＦ）、Ｎ，Ｎ−ジメチルアセトアミド（ＤＭＡｃ）、ジメチルスルホキシド（ＤＭＳＯ）、アセトニトリル、酢酸エチルなどが挙げられる。これらのいずれか１種単独でも、２種以上の混合溶媒でもよい。分散媒として、水と水溶性有機溶剤との混合溶剤を用いる場合、その配合比は水溶性有機溶剤の種類や水と水溶性有機溶剤との親和性などを考慮して適宜決定される。 Incidentally, examples of the dispersion medium include water or a mixed solvent of water and an organic solvent. The organic solvent used here may be a water-soluble organic solvent that is uniformly miscible with water. For example, alcohols such as methanol, ethanol, 2-propanol (IPA), ketones such as acetone, methyl ethyl ketone (MEK), and the like. , Ethers such as 1,4-dioxane, tetrahydrofuran (THF), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetonitrile, ethyl acetate, etc. It is done. Any one of these may be used alone, or two or more mixed solvents may be used. When a mixed solvent of water and a water-soluble organic solvent is used as the dispersion medium, the blending ratio is appropriately determined in consideration of the type of the water-soluble organic solvent and the affinity between water and the water-soluble organic solvent.
また、金属等を含んでも良い。金属としては、金、銀、白金、パラジウム、ルテニウム、イリジウム、ロジウム、オスミウムの白金族元素の他、鉄、鉛、銅、クロム、コバルト、ニッケル、マンガン、バナジウム、モリブデン、ガリウム、アルミニウムなどの金属またはこれらの合金、または酸化物、複酸化物、炭化物などを用いることができる。金属の担持方法としては、金属または金属酸化物等の微粒子を混合する他、水或いは水系溶剤に分散したカルボキシル基を有する繊維状多糖類分散中で金属または金属酸化物の錯体を形成し、還元剤を添加することで金属粒子として析出させることができる。この方法を用いると、微小な金属粒子が繊維表面に均一に固定化されるため、微量な金属量であっても効率的に効果を発揮させることができる。 Moreover, a metal etc. may be included. Metals such as gold, silver, platinum, palladium, ruthenium, iridium, rhodium, and osmium, as well as metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum Alternatively, alloys thereof, oxides, double oxides, carbides, or the like can be used. As a method for supporting the metal, in addition to mixing fine particles such as metal or metal oxide, a metal or metal oxide complex is formed in a dispersion of a fibrous polysaccharide having a carboxyl group dispersed in water or an aqueous solvent. By adding an agent, it can be deposited as metal particles. When this method is used, fine metal particles are uniformly immobilized on the fiber surface, so that the effect can be efficiently exhibited even with a small amount of metal.
なお、凝集や沈殿が生成しない範囲においては、より繊維同士の静電反発を増大させる目的や分散液の粘度を制御する目的で、水溶性多糖類を含む各種添加物、各種樹脂を含んでも良い。例えば、化学修飾したセルロース、カラギーナン、キサンタンガム、アルギン酸ナトリウム、寒天、可溶化澱粉や、消泡剤、水溶性高分子、合成高分子等を用いることができる。あるいは塗工性やぬれ性など機能性付与などの為に、各種溶剤を含んでもよい。アルコール類、セルソルブ類、グリコール類、グリセリンなどを用いることができる。 In addition, in the range where aggregation and precipitation are not generated, various additives including water-soluble polysaccharides and various resins may be included for the purpose of increasing electrostatic repulsion between fibers and controlling the viscosity of the dispersion. . For example, chemically modified cellulose, carrageenan, xanthan gum, sodium alginate, agar, solubilized starch, antifoaming agent, water-soluble polymer, synthetic polymer and the like can be used. Alternatively, various solvents may be included for imparting functionality such as coatability and wettability. Alcohols, cell solves, glycols, glycerin and the like can be used.
また、耐水性、電解液耐性を向上させるために各種架橋剤を含んでもよい。例えば、オキサゾリン、ジビニルスルホン、カルボジイミド、ジヒドラジン、ジヒドラジド、エピクロルヒドリン、グリオキザール、有機チタン化合物、有機ジルコニウム化合物などを用いることができる。また、反応性を向上させるなどの目的で、酸やアルカリを添加することによってｐＨを調整することができる。 Moreover, in order to improve water resistance and electrolyte solution resistance, various crosslinking agents may be included. For example, oxazoline, divinyl sulfone, carbodiimide, dihydrazine, dihydrazide, epichlorohydrin, glyoxal, organic titanium compound, organic zirconium compound, and the like can be used. Further, for the purpose of improving the reactivity, the pH can be adjusted by adding an acid or an alkali.
次に、分散液の製造方法について説明する。
分散液の製造方法については、大きく分けて（１）〜（３）の３つの方法があるが、各種物性や用途に合わせていずれかの方法を選択することができる。
Next, the manufacturing method of a dispersion liquid is demonstrated.
There are roughly three methods (1) to (3) for producing the dispersion, and any method can be selected according to various physical properties and applications.
方法（１）では、カルボキシル基を有する多糖類を分散媒にナノオーダーの繊維状に分散させた調製液を予め準備し、ここに活物質を混合して分散させることにより、活物質の分散液を調製する。この方法を用いると、多糖類を分散させる際のせん断応力などの過剰な負荷を活物質に与えずに済む。そのため、比較的アスペクト比の大きな活物質を用いる際も活物質の構造を破壊することなく電池電極用組成物を調製することができる。また、多糖類の分散度を厳密に制御することが可能となる。さらに、調製液を調製する工程においてｐＨをｐＨ４以上ｐＨ１２以下の範囲に調整する。特に、ｐＨをｐＨ６．５以上ｐＨ１２以下のアルカリ性に調整することが望ましい。アルカリ性にすることにより、多糖類のカルボキシル基同士の静電反発が起こりやすくなるため、多糖類及び活物質の分散性が向上する。ここで、ｐＨ４未満でも機械的分散処理により多糖類を分散することは可能であるが、長時間・高エネルギーを要する分散処理により、得られる繊維の繊維径は本発明の他の製造方法で分散させたものより大きくなる。 In the method (1), a preparation liquid in which a polysaccharide having a carboxyl group is dispersed in a nano-order fiber in a dispersion medium is prepared in advance, and the active material is mixed and dispersed therein, thereby dispersing the active material dispersion liquid. To prepare. When this method is used, it is not necessary to give an excessive load to the active material such as shear stress when the polysaccharide is dispersed. Therefore, even when an active material having a relatively large aspect ratio is used, a battery electrode composition can be prepared without destroying the structure of the active material. In addition, the degree of dispersion of the polysaccharide can be strictly controlled. Further, in the step of preparing the preparation solution, the pH is adjusted to a range of pH 4 or more and pH 12 or less. In particular, it is desirable to adjust the pH to alkalinity of pH 6.5 or more and pH 12 or less. By making it alkaline, electrostatic repulsion between the carboxyl groups of the polysaccharide is likely to occur, so that the dispersibility of the polysaccharide and the active material is improved. Here, it is possible to disperse polysaccharides by mechanical dispersion treatment even at a pH lower than 4, but the fiber diameter of the fibers obtained by dispersion treatment requiring a long time and high energy is dispersed by another production method of the present invention. Larger than the one
次に、方法（２）では、カルボキシル基を有する多糖類と活物質を分散媒に混合した後に分散させる。この方法を用いると、多糖類の分散及び活物質の分散が同時に進行するため、調製に要する時間及びエネルギーを少なくすることができる。さらに、カルボキシル基を有する多糖類と活物質を分散媒に混合した後に、分散させる前または後にｐＨ４以上ｐＨ１２以下の範囲、好ましくはｐＨ６．５以上ｐＨ１２以下に調整する。これにより、多糖類及び活物質の分散性が向上する。 Next, in the method (2), the polysaccharide having a carboxyl group and the active material are mixed in a dispersion medium and then dispersed. When this method is used, since the dispersion of the polysaccharide and the dispersion of the active material proceed simultaneously, the time and energy required for the preparation can be reduced. Further, after the polysaccharide having a carboxyl group and the active material are mixed in a dispersion medium, the pH is adjusted to a range of pH 4 to pH 12, preferably pH 6.5 to pH 12 before or after dispersion. Thereby, the dispersibility of a polysaccharide and an active material improves.
次に、方法（３）では、カルボキシル基を有する多糖類を分散媒に部分的に分散させ、そこに活物質を混合した後にさらに分散処理を施す。この方法を用いると、多糖類の構造や分子量、表面状態により分散性しにくい場合や粘度上昇が起こる場合においても良好な電池電極用組成物を得ることができる。また、活物質を混合した後に任意の分散処理を施すことにより、活物質の分散性の制御が可能となる。また、多糖類の分散及び活物質の分散を一連のバッチにて行うことが可能となるため、作業性が向上する。さらに、カルボキシル基を有する多糖類を分散媒に部分的に分散させる際にｐＨ４以上ｐＨ１２以下の範囲、好ましくはｐＨ６．５以上ｐＨ１２以下に調整する。これにより、方法（１）、（２）と同様のメカニズムにて多糖類及び活物質の分散性が向上する。 Next, in the method (3), the polysaccharide having a carboxyl group is partially dispersed in a dispersion medium, and the active material is mixed therewith, followed by further dispersion treatment. When this method is used, a favorable battery electrode composition can be obtained even when it is difficult to disperse due to the structure, molecular weight, or surface state of the polysaccharide, or when viscosity increases. Moreover, the dispersibility of the active material can be controlled by performing an arbitrary dispersion treatment after mixing the active material. Moreover, since dispersion | distribution of a polysaccharide and dispersion | distribution of an active material can be performed in a series of batches, workability | operativity improves. Further, when the polysaccharide having a carboxyl group is partially dispersed in the dispersion medium, the pH is adjusted in the range of pH 4 to pH 12, preferably pH 6.5 to pH 12. Thereby, the dispersibility of a polysaccharide and an active material improves by the mechanism similar to method (1) and (2).
なお、カルボキシル基を有する多糖類の分散方法及び活物質を混合させ分散液を調製する際の分散方法としては特に限定しないが、各種の粉砕機、混合機、攪拌機、超音波による分散などが使用される。例えば、ディスパー、プラネタリミキサー、高速回転ミキサー、シェアミキサー、ブレンダー、超音波ホモジナイザー、高圧ホモジナイザー、ボールミル等のせん断力或いは衝突による処理方法、ワーリングブレンダー、フラッシュミキサー、タービュライザーなどを用いることができ、またこれらを組み合わせることも出来る。また、処理中に摩擦熱により発熱した場合適宜冷却することができる。これにより、多糖類は分散されナノオーダーの繊維状となり、サイクル特性や出力特性に優れた電池電極用組成物が調製される。 The dispersion method for the polysaccharide having a carboxyl group and the dispersion method for preparing the dispersion by mixing the active material are not particularly limited, but various pulverizers, mixers, agitators, ultrasonic dispersion, etc. are used. Is done. For example, disperse, planetary mixer, high-speed rotating mixer, shear mixer, blender, ultrasonic homogenizer, high-pressure homogenizer, treatment method by shearing force or collision such as ball mill, Waring blender, flash mixer, turbulizer, etc. can be used. These can also be combined. Further, when heat is generated by frictional heat during the treatment, it can be appropriately cooled. Thereby, polysaccharide is disperse | distributed and it becomes a nano-order fiber form and the composition for battery electrodes excellent in cycling characteristics and output characteristics is prepared.
本発明の電池電極用組成物を用いて電極を製造する方法として、上記のようにして得られた電池電極用組成物を集電体上に塗工し、乾燥させることにより電極表面に活物質を固定する方法が挙げられる。 As a method for producing an electrode using the battery electrode composition of the present invention, the battery electrode composition obtained as described above is applied onto a current collector and dried to obtain an active material on the electrode surface. The method of fixing is mentioned.
集電体の材料としては導電性であれば特に限定されず、鉄、銅、ニッケル、ステンレス鋼、ニッケルメッキ鋼などの金属材料、カーボンクロス、カーボンペーパーなどが挙げられる。 The material of the current collector is not particularly limited as long as it is conductive, and examples thereof include metal materials such as iron, copper, nickel, stainless steel, nickel-plated steel, carbon cloth, and carbon paper.
集電体上に活物質を固定した後にこれらを圧縮することが好ましい。圧縮することにより、活物質同士がより近接に配置されるようになるため、電気特性が向上する。 It is preferable to compress these after fixing the active material on the current collector. By compressing, since the active materials are arranged closer to each other, the electrical characteristics are improved.
以下に、本発明の電池電極用組成物を利用して製造したリチウムイオン電池用負極を実施例として記載する。ただし、本発明はこれら実施例に限定されるものではない。 Below, the negative electrode for lithium ion batteries manufactured using the composition for battery electrodes of this invention is described as an Example. However, the present invention is not limited to these examples.
＜実施例１＞
〔ＴＥＭＰＯ酸化セルロースの製造方法〕
以下に示す方法でＴＥＭＰＯ酸化セルロースを得た。
（１）試薬・材料
セルロース：漂白クラフトパルプ（フレッチャー チャレンジ カナダ社製、Ｍａｃｈｅｎｚｉｅ）。
ＴＥＭＰＯ：市販品（東京化成工業株式会社製、９８％）。
次亜塩素酸ナトリウム：市販品（和光純薬株式会社製、Ｃｌ：５％）。
臭化ナトリウム：市販品（和光純薬株式会社製）。
（２）セルロースのＴＥＭＰＯ酸化反応
２Ｌのガラスビーカー中に、乾燥質量１０ｇの漂白クラフトパルプとイオン交換水５００ｍｌとを投入して一晩静置し、パルプを膨潤させた。これを温調付きウォーターバスにより３０．０℃に温度調整し、ＴＥＭＰＯ０．１ｇと臭化ナトリウム１ｇを添加して撹拌し、パルプ懸濁液とした。さらに撹拌しながら、セルロース質量当たり５ｍｍｏｌ／ｇの次亜塩素酸ナトリウムを添加した。この際、約１Ｍの水酸化ナトリウム水溶液を添加してパルプ懸濁液のｐＨを約１０．５に保持した。その後、２時間反応を行い、イオン交換水でパルプを充分に水洗して、ＴＥＭＰＯ酸化セルロースを得た。
（３）ＴＥＭＰＯ酸化セルロースの分散処理
得られたＴＥＭＰＯ酸化セルロースをイオン交換水中で所定濃度となるように調整し、ミキサー（大阪ケミカル、アブソルートミル、１４，０００ｒｐｍ）を用いて３０分間撹拌し、微細化することにより透明なＴＥＭＰＯ酸化セルロース水分散体（固形分濃度２質量％）を得た。
〔リチウムイオン電池用負極の製造方法〕
上記の方法により得たＴＥＭＰＯ酸化セルロース水分散体に活物質として球状黒鉛を、さらに導電性助剤としてアセチレンブラックを添加し、固形分がＴＥＭＰＯ酸化セルロース：活物質：導電性助剤＝１：９２：７とした。これをディスパーにて十分に攪拌しながら蒸留水を徐々に添加し、全体の濃度が５０質量％となる均一なスラリーを得た。得られたスラリーの粘度はＥ型粘度計に８００ｍＰａ・ｓであった。これを２０μｍの銅箔上にドクターブレード法にて塗布し、１２０℃で３０分間乾燥した。さらにロールプレスすることでリチウムイオン電池用負極を作製した。得られた負極の電極密度は１．６ｇ／ｃｍ３であった。
〔リチウムイオン電池の作製方法〕
正極として３００μｍのＬｉ箔を用い、活物質を固定した負極および正極真空乾燥した後、電極打ち抜き機によりφ１５ｍｍに打ち抜き、φ１６ｍｍに打ち抜いたポリプロピレン製不織布をセパレータとしてこれを介して負極の活物質側と正極が対向するように配置した。これを２０ｍｍ角のステンレス製皿内に設置し、ジエチルカーボネートとジメチルカーボネートとエチレンカーボネートを１：１：１の体積比で混合した溶媒に電解質として１ＭのＬｉＰＦ６を溶解させた電解液を注入し、２０ｍｍ角のステンレス製蓋を被せて挟み込み、加圧することでコイン型のハーフセルを作製した。
<Example 1>
[Method for producing TEMPO-oxidized cellulose]
TEMPO oxidized cellulose was obtained by the following method.
(1) Reagent / Material Cellulose: Bleached kraft pulp (Fletcher Challenge Canada, Machenzie).
TEMPO: Commercial product (Tokyo Chemical Industry Co., Ltd., 98%).
Sodium hypochlorite: a commercial product (Wako Pure Chemical Industries, Ltd., Cl: 5%).
Sodium bromide: Commercial product (Wako Pure Chemical Industries, Ltd.).
(2) TEMPO oxidation reaction of cellulose A 2 L glass beaker was charged with 10 g of dry kraft pulp and 500 ml of ion-exchanged water and allowed to stand overnight to swell the pulp. The temperature was adjusted to 30.0 ° C. with a water bath with temperature control, 0.1 g of TEMPO and 1 g of sodium bromide were added and stirred to obtain a pulp suspension. Furthermore, 5 mmol / g sodium hypochlorite per cellulose mass was added with stirring. At this time, about 1 M aqueous sodium hydroxide solution was added to maintain the pH of the pulp suspension at about 10.5. Thereafter, the reaction was performed for 2 hours, and the pulp was sufficiently washed with ion-exchanged water to obtain TEMPO oxidized cellulose.
(3) Dispersion treatment of TEMPO oxidized cellulose The obtained TEMPO oxidized cellulose was adjusted to a predetermined concentration in ion-exchanged water, and stirred for 30 minutes using a mixer (Osaka Chemical, Absolute Mill, 14,000 rpm). As a result, a transparent TEMPO-oxidized cellulose aqueous dispersion (solid content concentration 2 mass%) was obtained.
[Method for producing negative electrode for lithium ion battery]
Spherical graphite is added as an active material to the TEMPO oxidized cellulose aqueous dispersion obtained by the above method, and acetylene black is added as a conductive auxiliary agent. The solid content is TEMPO oxidized cellulose: active material: conductive auxiliary agent = 1: 92. : 7. Distilled water was gradually added while sufficiently stirring this with a disper to obtain a uniform slurry having a total concentration of 50% by mass. The viscosity of the obtained slurry was 800 mPa · s in an E-type viscometer. This was applied onto a 20 μm copper foil by a doctor blade method and dried at 120 ° C. for 30 minutes. Furthermore, the negative electrode for lithium ion batteries was produced by roll-pressing. The electrode density of the obtained negative electrode was 1.6 g / cm 3 .
[Production method of lithium ion battery]
Using a 300 μm Li foil as the positive electrode, vacuum drying the positive electrode with the active material fixed and the positive electrode, punching to 15 mm by an electrode punching machine, and using a polypropylene nonwoven fabric punched to 16 mm as a separator, the active material side of the negative electrode It arrange | positioned so that a positive electrode may oppose. This was placed in a 20 mm square stainless steel dish, and an electrolyte solution in which 1 M LiPF6 was dissolved as an electrolyte was poured into a solvent in which diethyl carbonate, dimethyl carbonate, and ethylene carbonate were mixed at a volume ratio of 1: 1: 1. A coin-shaped half cell was produced by putting a 20 mm square stainless steel lid and sandwiching and pressing.
（サイクル特性）
上記の方法で作製した電池を室温にて電流密度０．４ｍＡ／ｃｍ２で電圧０．０５Ｖから１．０Ｖの間で、充放電サイクル試験を実施した。サイクル回数１回目と１００回目の充電時の容量を測定した。測定結果を表１に示す。
（出力特性）
上記の方法で作製した電池を室温にて電流密度０．４ｍＡ／ｃｍ２で電圧０．０５Ｖまで充電し、３０分保持後に１．０Ｖまで放電した。放電の際の電流密度を０．４ｍＡ／ｃｍ２、２．０ｍＡ／ｃｍ２、４．０ｍＡ／ｃｍ２、８．０ｍＡ／ｃｍ２、２０ｍＡ／ｃｍ２とし、充電容量に対する各電流での放電容量を測定した。測定結果を表２に示す。
(Cycle characteristics)
The battery produced by the above method was subjected to a charge / discharge cycle test at room temperature at a current density of 0.4 mA / cm 2 and a voltage of 0.05 V to 1.0 V. The capacities at the first and 100th cycles were measured. The measurement results are shown in Table 1.
(Output characteristics)
The battery produced by the above method was charged to a voltage of 0.05 V at a current density of 0.4 mA / cm 2 at room temperature, and discharged to 1.0 V after holding for 30 minutes. The current density during discharge 0.4mA / cm 2, 2.0mA / cm 2, 4.0mA / cm 2, and 8.0mA / cm 2, 20mA / cm 2, discharge capacity at each current to the charge capacity Was measured. The measurement results are shown in Table 2.
＜比較例１＞
負極用バインダとしてＴＥＭＰＯ酸化セルロースの代わりに市販の微細セルロース（ダイセルファインケム社製、セリッシュＫＹ１００Ｇ）を用いた以外は実施例１と同様に評価した。
<Comparative Example 1>
Evaluation was conducted in the same manner as in Example 1 except that a commercially available fine cellulose (Daicel Finechem, Selish KY100G) was used as the negative electrode binder instead of TEMPO oxidized cellulose.
＜比較例２＞
負極用バインダとしてＴＥＭＰＯ酸化セルロースの代わりに市販の微細セルロース（ダイセルファインケム社製、ＣＭＣ１３８０）を用いた以外は実施例１と同様に評価した。
＜比較例３＞
負極用バインダとしてＴＥＭＰＯ酸化セルロースの代わりに市販の微細セルロース（ダイセルファインケム社製、ＣＭＣ１３８０）とＳＢＲを重量比で１：１に混合したものを用いた以外は実施例１と同様に評価した。
<Comparative example 2>
Evaluation was conducted in the same manner as in Example 1 except that a commercially available fine cellulose (CMC1380, manufactured by Daicel Finechem Co., Ltd.) was used instead of TEMPO oxidized cellulose as the binder for the negative electrode.
<Comparative Example 3>
Evaluation was conducted in the same manner as in Example 1 except that a commercially available fine cellulose (CMC1380, manufactured by Daicel FineChem) and SBR were mixed in a weight ratio of 1: 1 instead of TEMPO-oxidized cellulose as the negative electrode binder.
表１のように、ＴＥＭＰＯ酸化セルロースが存在することにより、サイクル特性や出力特性が大幅に向上することが認められた。 As shown in Table 1, it was recognized that the presence of TEMPO-oxidized cellulose significantly improved cycle characteristics and output characteristics.
本発明によれば、電池用電極の組成設計の自由度が向上し、生産性に優れ、良好なサイクル特性に加え、出力特性に優れた電池用電極を製造することができる。特にリチウムイオン電池負極として有用である。 ADVANTAGE OF THE INVENTION According to this invention, the freedom degree of the composition design of a battery electrode improves, it is excellent in productivity, and in addition to a favorable cycle characteristic, the battery electrode excellent in the output characteristic can be manufactured. It is particularly useful as a lithium ion battery negative electrode.
Claims (9)
前記調製液に活物質を分散させて、前記繊維状多糖類と前記活物質と前記分散媒とを含む分散液を調製する工程と、
をこの順に有し、前記分散液が請求項１乃至請求項５に記載のいずれか１項に記載の電池電極用組成物であることを特徴とする電池電極用組成物の製造方法。 A step of dispersing a fibrous polysaccharide having a carboxyl group in a dispersion medium to prepare a preparation liquid containing the fibrous polysaccharide and the dispersion medium;
A step of dispersing an active material in the preparation liquid to prepare a dispersion liquid containing the fibrous polysaccharide, the active material, and the dispersion medium;
In this order, the dispersion is the battery electrode composition according to any one of claims 1 to 5. A method for producing a battery electrode composition, comprising:
前記第一の調製液に活物質を分散させて、前記第一の繊維状多糖類と前記活物質と前記分散液とを含む第二の調製液を調製する工程と、
前記第二の調製液を分散処理して、前記カルボキシル基を有する繊維状多糖類と前記活物質と前記分散媒とを含む調製液を調製する工程と、
をこの順に有し、前記分散液が請求項１乃至請求項５に記載のいずれか１項に記載の電池電極用組成物であることを特徴とする電池電極用組成物の製造方法。 A step of dispersing a fibrous polysaccharide having a carboxyl group in a dispersion medium to prepare a first preparation liquid containing the first fibrous polysaccharide and the dispersion medium;
A step of dispersing an active material in the first preparation liquid to prepare a second preparation liquid containing the first fibrous polysaccharide, the active material, and the dispersion;
A step of dispersing the second preparation liquid to prepare a preparation liquid containing the fibrous polysaccharide having the carboxyl group, the active material, and the dispersion medium;
In this order, the dispersion is the battery electrode composition according to any one of claims 1 to 5. A method for producing a battery electrode composition, comprising:
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