JP2013214503A - Carbon-sulfur complex, electrochemical element using the same, and lithium ion battery - Google Patents
Carbon-sulfur complex, electrochemical element using the same, and lithium ion battery Download PDFInfo
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Abstract
Description
本発明は、カーボン硫黄複合体に関する。本発明のカーボン硫黄複合体は、例えばリチウムイオン電池などの電気化学素子の電極に好適に使用可能である。 The present invention relates to a carbon sulfur composite. The carbon sulfur composite of the present invention can be suitably used for an electrode of an electrochemical element such as a lithium ion battery.
本発明のカーボン硫黄複合体の用途は特に制限されないが、説明の便宜の点から、以下では、主に二次電池、特にリチウムイオン電池の電極に関連する先行技術に関して説明する。 Although the use of the carbon-sulfur composite of the present invention is not particularly limited, for the convenience of explanation, the following description will be made mainly on the prior art related to the electrode of the secondary battery, particularly the lithium ion battery.
リチウムイオン電池は、従来のニッケルカドミウム電池やニッケル水素電池に比べて、高電圧・高エネルギー密度が得られる電池として小型・軽量化が図れることから、携帯電話やラップトップパソコンなど情報関連のモバイル通信電子機器や電動工具類などに広く用いられている。今後更に環境問題を解決する一つの手段として電気自動車・ハイブリッド電気自動車などに搭載する車載用途、および家庭や産業用などの電力貯蔵用途などに利用拡大が進むと見られており、これら用途に向けて電池の更なる高容量化が切望されている。 Compared to conventional nickel cadmium batteries and nickel metal hydride batteries, lithium-ion batteries can be made smaller and lighter as high-voltage, high-energy density batteries. Information-related mobile communications such as mobile phones and laptop computers Widely used in electronic equipment and power tools. In the future, as one of the means to solve environmental problems, it is expected that the use will be expanded to in-vehicle applications mounted on electric vehicles / hybrid electric vehicles, etc., and power storage applications such as home and industrial use. Therefore, further increase in capacity of the battery is eagerly desired.
リチウムイオン電池の容量を更に向上させる際の課題は、正極活物質の高容量化である。次世代のリチウムイオン電池に検討されている酸化物正極活物質の容量密度は、１７０〜２００Ａｈ／ｋｇ程度であるが、電気自動車の航続距離拡大やバックアップ電力の貯蔵量増大のために、更に高容量の材料の開発が期待されている。 A problem in further improving the capacity of the lithium ion battery is to increase the capacity of the positive electrode active material. The capacity density of the oxide positive electrode active material being studied for the next-generation lithium ion battery is about 170 to 200 Ah / kg. However, the capacity density of the oxide positive electrode active material is further increased in order to expand the cruising distance of electric vehicles and increase the amount of backup power stored. The development of capacity materials is expected.
単体硫黄を電極として用いた場合の理論容量は１６７５Ａｈ／ｋｇで、極めて大きな容量を有している。しかしながら、硫黄正極には以下の２つの大きな課題がある。１つめは、硫黄は抵抗率が２×１０の１５乗Ωｍの絶縁体であるため、実用的な充放電レートが確保できないこと、２つめは、充放電過程に生成した多硫化物が電解液中に溶出するため、電池のサイクル特性が著しく低いことである。これらの課題により、硫黄は正極活物質として高いポテンシャルを持っているにも関わらず、未だ実用化されていない。 When single sulfur is used as an electrode, the theoretical capacity is 1675 Ah / kg, which is extremely large. However, the sulfur positive electrode has the following two major problems. First, since sulfur is an insulator with a resistivity of 2 × 10 15 Ωm, a practical charge / discharge rate cannot be secured, and second, polysulfide generated during the charge / discharge process is an electrolyte. The cycle characteristics of the battery are remarkably low due to elution. Due to these problems, sulfur has not yet been put into practical use even though it has a high potential as a positive electrode active material.
硫黄正極を実用化するためには、上述の２つの課題を量産可能な方法で解決する必要がある。今まで様々な方法が提案されているが、２つの課題を同時に解決できる技術として、種々のカーボン材料と硫黄を複合化する方法が開示されている（特許文献１、非特許文献１−３）。 In order to put the sulfur positive electrode into practical use, it is necessary to solve the above two problems by a method capable of mass production. Various methods have been proposed so far, but as a technique capable of simultaneously solving the two problems, a method of combining various carbon materials and sulfur is disclosed (Patent Document 1, Non-Patent Documents 1-3). .
これらは、カーボンの空孔内に硫黄を保持することにより、電子伝導性を向上させつつ、電解液への溶出を抑制しようとするものである。 These are intended to suppress elution into the electrolyte while improving the electron conductivity by retaining sulfur in the carbon vacancies.
特許文献１および非特許文献１には、メソポーラスカーボンと硫黄とを複合化する技術が開示されている。メソポーラスカーボンは規則性のある５ｎｍ未満の空隙を有し、硫黄の充填・保持に適した構造を有している。また、非特許文献２には、硫黄を合成しながら酸化グラフェンと複合化する技術が開示されている。また、非特許文献３には、薄層グラファイトと硫黄を溶解させた溶液とを混合することで薄層グラファイトの空隙間に硫黄を複合化させる技術が開示されている。 Patent Document 1 and Non-Patent Document 1 disclose a technique for combining mesoporous carbon and sulfur. Mesoporous carbon has regular pores of less than 5 nm and has a structure suitable for filling and holding sulfur. Non-Patent Document 2 discloses a technique of combining with graphene oxide while synthesizing sulfur. Non-Patent Document 3 discloses a technique of combining sulfur between voids of thin-layer graphite by mixing thin-layer graphite and a solution in which sulfur is dissolved.
上述のとおり、単体硫黄が本来持つ正極活物質としてのポテンシャルを引き出し実用化に繋げるために、各種カーボン材料との複合化が試みられている（特許文献１、非特許文献１−３）。しかしながら、これらによっても、十分な充放電性能を達成していないか、あるいは複雑なプロセスが必要なために、工業的な量産が困難であった。 As described above, in order to draw out the potential as a positive electrode active material inherent in elemental sulfur and put it to practical use, compounding with various carbon materials has been attempted (Patent Literature 1, Non-Patent Literature 1-3). However, due to these, sufficient charge / discharge performance has not been achieved, or a complicated process is required, and industrial mass production has been difficult.
本発明者らは、以下のように考察した。特許文献１および非特許文献１のカーボン硫黄複合体は、カーボン材料としてメソポーラスカーボンを用いているが、これはシリカの鋳型にカーボン源を導入・焼成してから、シリカを溶解することにより作製するものである。この手法で作製したカーボンは、アモルファスカーボンであるため導電性が低く、また、そもそも製法が複雑であるため低コスト化が難しく、量産には適さないものである。非特許文献２では、空隙の大きさが制御されていないため、大きい空隙が多くあると考えられ、そのために十分な充放電特性が得られていないのではないかと考えた。また、非特許文献３では、薄層グラファイトの空隙が５ｎｍ程度と大きいために、硫黄が十分に保持されておらず、充放電サイクルでの硫黄溶出による容量低下が発生しているのではないかと考えた。 The present inventors considered as follows. The carbon-sulfur composites of Patent Document 1 and Non-Patent Document 1 use mesoporous carbon as a carbon material, which is prepared by introducing and firing a carbon source into a silica mold and then dissolving the silica. Is. The carbon produced by this method is amorphous carbon and therefore has low conductivity, and since the production method is complicated in the first place, it is difficult to reduce the cost and is not suitable for mass production. In Non-Patent Document 2, since the size of the gap is not controlled, it is considered that there are many large gaps, and therefore, it was considered that sufficient charge / discharge characteristics were not obtained. Further, in Non-Patent Document 3, since the voids of the thin-layer graphite are as large as about 5 nm, sulfur is not sufficiently retained, and capacity reduction due to sulfur elution in the charge / discharge cycle may have occurred. Thought.
以上のように、硫黄正極の課題である導電性付与、電解液への溶出抑制を量産可能な方法で解決した例はなく、実用化のための技術創出が求められていた。そして、本発明者らは、空隙に着目し、鋭意努力を重ねた。 As described above, there has been no example of solving the problem of the sulfur positive electrode by imparting conductivity and suppressing elution to the electrolytic solution by a method capable of mass production, and the creation of a technology for practical use has been demanded. And the present inventors paid their attention to the gap and made intensive efforts.
本発明者は、薄層グラファイト構造間に極めて狭い空隙を設け、これに硫黄を充填することにより、上記した従来技術の欠点を解消し、単体硫黄が本来持つ正極活物質としてのポテンシャルを発現できることを見出したものである。 The present inventor can solve the above-mentioned drawbacks of the prior art by providing a very narrow void between thin-layer graphite structures and filling it with sulfur, and can express the potential as a positive electrode active material inherent in simple sulfur. Is found.
すなわち本発明は
（１）薄層グラファイト構造間の空隙に硫黄が充填されてなるカーボン硫黄複合体であって、該空隙の平均距離が3nm未満であり、硫黄の含有量がカーボン硫黄複合体総重量の5%以上であることを特徴とするカーボン硫黄複合体。
（２）２次形状として、平均厚さ30nm〜1μmの板状構造と空隙を持つ（１）記載のカーボン硫黄複合体。
（３）（１）または（２）に記載のカーボン硫黄複合体を含有する電気化学素子。
（４）（１）または（２）に記載のカーボン硫黄複合体を含有するリチウムイオン電池。
である。
That is, the present invention is (1) a carbon sulfur composite in which voids between thin graphite structures are filled with sulfur, the average distance of the voids is less than 3 nm, and the sulfur content is A carbon-sulfur composite characterized by being 5% or more by weight.
(2) The carbon-sulfur composite according to (1) having a plate-like structure having an average thickness of 30 nm to 1 μm and voids as a secondary shape.
(3) An electrochemical element containing the carbon-sulfur composite according to (1) or (2).
(4) A lithium ion battery containing the carbon-sulfur composite according to (1) or (2).
It is.
本発明のカーボン硫黄複合体は、量産可能な容易なプロセスで作製することができ、これを電極材料に用いることにより、高い容量を有する電極を得ることが可能である。このため、電気化学素子、特に、リチウムイオン電池等の非水電解液二次電池に好適に使用でき、また、キャパシター、燃料電池用の電極にも使用でき、本発明は工業的に極めて有用である。 The carbon-sulfur composite of the present invention can be produced by an easy process that can be mass-produced. By using this as an electrode material, an electrode having a high capacity can be obtained. For this reason, it can be suitably used for electrochemical devices, particularly non-aqueous electrolyte secondary batteries such as lithium ion batteries, and can also be used for electrodes for capacitors and fuel cells. The present invention is extremely useful industrially. is there.
本発明のカーボン硫黄複合体は、薄層グラファイト構造間の空隙に硫黄が充填されている構造を持つ。薄層グラファイト構造間の空隙に硫黄を充填することにより、好適に電子伝導することが可能になり、硫黄の溶出を防ぐことも同時に可能になる。また、薄層グラファイトは結晶性の黒鉛を原料とするため、アモルファスカーボンを基材とするメソポーラスカーボンと比較して導電性が高く、良好な電子伝導が得られる。 The carbon-sulfur composite of the present invention has a structure in which voids between thin graphite structures are filled with sulfur. By filling the gaps between the thin-layer graphite structures with sulfur, it becomes possible to conduct electrons suitably, and at the same time, it is possible to prevent the elution of sulfur. In addition, since thin-layer graphite uses crystalline graphite as a raw material, it has higher conductivity than mesoporous carbon based on amorphous carbon, and good electron conduction can be obtained.
本発明のカーボン硫黄複合体における薄層グラファイト構造間の空隙は、薄層グラファイト構造の層間部分である。薄層グラファイト構造間の空隙には、硫黄が充填されている部分と、後述の空隙中の硫黄充填率が１００％でない場合は、硫黄が充填されてない部分がある。 The gap between the thin-layer graphite structures in the carbon-sulfur composite of the present invention is an interlayer portion of the thin-layer graphite structure. In the gaps between the thin-layer graphite structures, there are a part filled with sulfur and a part not filled with sulfur when the sulfur filling rate in the gaps described later is not 100%.
ここで、硫黄が充填されている空隙の距離（層間距離）は平均で3nm未満であることが必要である。本発明者は、厚みをこの領域に制御することにより充放電特性が大幅に向上することを見出した。これは、厚みが3nm未満の領域では、硫黄と薄層グラファイト間で電子がホッピング伝導し良好な電子伝導が得られるようになること、及び電解液の空隙への浸入が大幅に抑制され、硫黄が溶出しなくなるためであると推定している。特に限定されないが、厚みとしては、2.5nm未満が好ましく、2nm未満であることがより好ましい。なお、ここでいう空隙の距離（層間距離）とは、カーボン材料の異なる粒子間に生じる空隙ではなく、同一粒子内で薄層グラファイト構造が平行に相対してなる空隙の距離である。硫黄が充填されている空隙の距離は透過電子顕微鏡により測定することが可能である。 Here, the distance between the voids filled with sulfur (interlayer distance) needs to be less than 3 nm on average. The inventor has found that the charge / discharge characteristics are greatly improved by controlling the thickness in this region. This is because, in the region where the thickness is less than 3 nm, electrons hop and conduct between sulfur and the thin graphite, and good electron conduction can be obtained. It is estimated that this is because no longer elutes. Although not particularly limited, the thickness is preferably less than 2.5 nm, and more preferably less than 2 nm. Here, the distance between the voids (interlayer distance) is not a void generated between different particles of the carbon material, but a distance between voids in which the thin-layer graphite structure is opposed in parallel within the same particle. The distance of the void filled with sulfur can be measured with a transmission electron microscope.
本発明のカーボン硫黄複合体は、２次形状として平均厚さ30nm〜1μmの板状構造と空隙を持つと、電解液が浸透しやすくなり電池性能をさらに向上することが可能となる。ここで、２次形状として、と言う意味は、板状構造内にカーボンと硫黄が両方含有しているということであり、カーボン単独の構造や硫黄のみの構造を指すのではない。 When the carbon-sulfur composite of the present invention has a plate-like structure having an average thickness of 30 nm to 1 μm and voids as the secondary shape, the electrolyte solution can easily penetrate and the battery performance can be further improved. Here, as the secondary shape, the meaning is that both carbon and sulfur are contained in the plate-like structure, and does not indicate a structure of carbon alone or a structure of only sulfur.
板状構造と空隙は断面SEMによって測定することが可能である。板状構造の平均厚さはランダムに20箇所カーボン硫黄複合体の厚さを測定した時の平均値である。板状構造と空隙の断面SEM写真の代表例としては、実施例８のカーボン硫黄複合体の板状構造と空隙の断面SEM写真である図１が挙げられる。 Plate-like structures and voids can be measured by cross-sectional SEM. The average thickness of the plate-like structure is an average value when the thickness of 20 carbon sulfur composites is randomly measured. As a typical example of the plate-like structure and the cross-sectional SEM photograph of the void, FIG. 1 is a cross-sectional SEM photograph of the plate-like structure and void of the carbon-sulfur composite of Example 8.
本発明のカーボン硫黄複合体の製造方法としては、特に限定はないが、薄層グラファイト構造を有するカーボン材料と硫黄とを複合化させる方法が好適に用いられる。複合化は、カーボン材料と硫黄を公知の混練方法により混練することで可能になる。混練するには溶媒を用いる湿式でも、溶媒を用いない乾式でも良く、湿式で用いる溶媒としては、エタノール、メタノール、水、ジメチルアセトアミド、ヘキサン、N-メチルピロリドン、γブチロラクトンなどが挙げられる。混練方法としては、自動乳鉢・三本ロール・ビーズミル・遊星ボールミル・自公転ミキサー・湿式ジェットミル・ホモジェナイザー・プラネタリーミキサーなどを利用した方法が挙げられる。 The method for producing the carbon-sulfur composite of the present invention is not particularly limited, but a method of combining a carbon material having a thin graphite structure and sulfur is preferably used. Compounding is possible by kneading the carbon material and sulfur by a known kneading method. The kneading may be a wet process using a solvent or a dry process using no solvent. Examples of the solvent used in the wet process include ethanol, methanol, water, dimethylacetamide, hexane, N-methylpyrrolidone, and γ-butyrolactone. Examples of the kneading method include a method using an automatic mortar, a triple roll, a bead mill, a planetary ball mill, a self-revolving mixer, a wet jet mill, a homogenizer, and a planetary mixer.
特に比表面積が大きいカーボン材料を用いる場合は、硫黄の融点である１１５℃以上で加熱する工程を含めると、表面張力により複合化が進みやすくなり良好に複合化できる。特に硫黄の粘度が最小となる１５５℃付近で加熱することが好ましい。 In particular, when a carbon material having a large specific surface area is used, if a step of heating at 115 ° C. or higher, which is the melting point of sulfur, is included, the composite can easily proceed due to the surface tension, and the composite can be performed well. In particular, it is preferable to heat at around 155 ° C. where the viscosity of sulfur is minimized.
複合化に使用する薄層グラファイト構造を有するカーボン材料としては、特に限定されないが、天然黒鉛あるいは人造黒鉛などの黒鉛（グラファイト）系材料の層間を部分的に広げた材料が好ましく用いられる。黒鉛（グラファイト）は、グラフェン層が層間距離0.335ｎｍで積層した構造を有しているが、超音波処理や、グラフェン層間に他の物質をインターカレーションした後に熱処理または機械的処理（磨砕など）をすることにより、層間を広げることができ、処理条件を制御することにより、層間距離を制御できる。 The carbon material having a thin-layer graphite structure used for the composite is not particularly limited, but a material in which a layer of a graphite (graphite) material such as natural graphite or artificial graphite is partially expanded is preferably used. Graphite (graphite) has a structure in which graphene layers are stacked with an interlayer distance of 0.335 nm. However, ultrasonic treatment, or heat treatment or mechanical treatment (such as grinding) after intercalation of other substances between graphene layers ), The interlayer can be widened, and the interlayer distance can be controlled by controlling the processing conditions.
上述のような薄層グラファイト構造を有するカーボン材料としては、例えば膨張化黒鉛、あるいは酸化黒鉛の還元体を好適に用いることが出来る。膨張化黒鉛は、黒鉛のグラフェン層間に硫酸をインターカレートした材料（膨張黒鉛）を熱処理することによりグラフェン層間を広げた材料であり、インターカレートする硫酸の量や熱処理温度、熱処理速度で層の厚みや数を制御することができる。酸化黒鉛の還元体は、還元時に脱ガス等でグラファイト層間を広げた材料であり、酸化黒鉛の酸化度や大きさ、還元条件で層間距離や層数を制御することができる。ここで、酸化黒鉛の製造方法としては特に限定はなく、Hummers法、Staudenmaier法などの公知の方法を用いることができ、原料黒鉛の種類、酸化剤の量や反応温度などで酸化度を制御できる。酸化黒鉛の還元方法としては、特に限定はないが、熱還元またはヒドラジンなどによる化学還元などを用いることができ、熱還元の方が熱処理温度、熱処理速度などの比較的簡単な条件変更で層間距離や層数を制御しやすいので、好ましい。 As the carbon material having a thin-layer graphite structure as described above, for example, expanded graphite or a reduced form of graphite oxide can be suitably used. Expanded graphite is a material in which the graphene layer is expanded by heat-treating a material in which sulfuric acid is intercalated between the graphene layers of graphite (expanded graphite). It is possible to control the thickness and the number of the glass. The reduced form of graphite oxide is a material in which the graphite layer is expanded by degassing or the like at the time of reduction, and the interlayer distance and the number of layers can be controlled by the oxidation degree and size of the graphite oxide and the reducing conditions. Here, the method for producing graphite oxide is not particularly limited, and known methods such as the Hummers method and the Staudenmaier method can be used, and the degree of oxidation can be controlled by the type of raw material graphite, the amount of oxidizing agent, the reaction temperature, and the like. . There is no particular limitation on the method for reducing graphite oxide, but thermal reduction or chemical reduction with hydrazine can be used. Thermal reduction is a relatively simple change in conditions such as heat treatment temperature and heat treatment rate. And the number of layers is easy to control, which is preferable.
また、酸化黒鉛を硫黄により還元することも可能である。酸化黒鉛を硫黄により還元することで、酸化黒鉛の還元と複合化を同時に行うことができるため、カーボン硫黄複合体の製造方法としては好適である。特に酸化黒鉛と硫黄を良く混合してから還元を行うと、硫黄酸化物の気体発生により複合体内に空隙が生成され、その結果前述の板状構造を形成しやすい。そのため、酸化黒鉛を硫黄により還元する手法は板状構造形成の手段としても好適である。 It is also possible to reduce graphite oxide with sulfur. By reducing graphite oxide with sulfur, graphite oxide can be reduced and combined at the same time, which is suitable as a method for producing a carbon-sulfur composite. In particular, when reduction is performed after thoroughly mixing graphite oxide and sulfur, voids are generated in the composite due to the generation of sulfur oxide gas, and as a result, the aforementioned plate-like structure is easily formed. Therefore, the technique of reducing graphite oxide with sulfur is suitable as a means for forming a plate-like structure.
本発明のカーボン硫黄複合体における、硫黄の含有量は、例えばリチウムイオン電池用正極材料として用いる場合は、硫黄が少なすぎると重量あたりの電池容量が小さくなり、硫黄が多すぎると導電性が低くなり充放電特性が悪化する場合があるので、適度な含有量であることが好ましい。具体的には、硫黄含有量はカーボン硫黄複合体総重量の5%以上であることが必要である。中でも30％以上が好ましく、50％以上がより好ましく、70％以上が更に好ましい。また、95％以下が好ましく、90％以下がより好ましい。硫黄の含有量は、カーボン材料と複合化する際の硫黄の使用量を変えることにより制御できる。 When the sulfur content in the carbon-sulfur composite of the present invention is used, for example, as a positive electrode material for a lithium ion battery, if the amount of sulfur is too small, the battery capacity per weight becomes small, and if the amount of sulfur is too large, the conductivity is low. Since charge / discharge characteristics may deteriorate, it is preferable that the content is appropriate. Specifically, the sulfur content needs to be 5% or more of the total weight of the carbon-sulfur composite. Among these, 30% or more is preferable, 50% or more is more preferable, and 70% or more is more preferable. Moreover, 95% or less is preferable and 90% or less is more preferable. The sulfur content can be controlled by changing the amount of sulfur used in the composite with the carbon material.
本発明のカーボン硫黄複合体において、空隙中の硫黄の充填率は、例えばリチウムイオン電池用正極材料として用いる場合は、70%以上であることが好ましく、80%以上であることがより好ましく、更には90％以上が好ましい。空隙中の硫黄の充填率が小さすぎると、電池容量が小さくなるので好ましくない。 In the carbon-sulfur composite of the present invention, the filling rate of sulfur in the voids is preferably 70% or more, more preferably 80% or more, for example, when used as a positive electrode material for a lithium ion battery. Is preferably 90% or more. If the sulfur filling rate in the voids is too small, the battery capacity becomes small, which is not preferable.
本発明のカーボン硫黄複合体は、特に電気化学素子に好適に用いられる。電気化学素子としては例えばリチウムイオン電池用正極として、好適に用いられる。 The carbon-sulfur composite of the present invention is particularly suitably used for electrochemical devices. As an electrochemical element, it is used suitably, for example as a positive electrode for lithium ion batteries.
リチウムイオン電池は正極と、それに対向した負極、及び該正極と負極の間に配置された電解質を少なくとも含む
（正極）
リチウムイオン電池用正極は、導電助剤、正極活物質、バインダーポリマーからなる。本発明のカーボン硫黄複合体では導電性のカーボン材料を用いるので、カーボン硫黄複合体のほかに導電助剤を添加する必要は必ずしもない。他に導電助剤を添加しても良く、導電助剤を添加する場合、添加する導電助剤としては、特に限定されないが、例えば、ファーネスブラック、ケッチェンブラック、アセチレンブラック等のカーボンブラック類、天然黒鉛（鱗片状黒鉛等）、人造黒鉛等のグラファイト類、炭素繊維及び金属繊維等の導電性繊維類、銅、ニッケル、アルミニウム及び銀等の金属粉末類などが挙げられる。
The lithium ion battery includes at least a positive electrode, a negative electrode facing the positive electrode, and an electrolyte disposed between the positive electrode and the negative electrode (positive electrode)
The positive electrode for a lithium ion battery includes a conductive additive, a positive electrode active material, and a binder polymer. Since the carbon-sulfur composite of the present invention uses a conductive carbon material, it is not always necessary to add a conductive additive in addition to the carbon-sulfur composite. Other conductive assistants may be added. In the case of adding a conductive assistant, the conductive assistant to be added is not particularly limited. For example, carbon blacks such as furnace black, ketjen black, acetylene black, Examples thereof include graphites such as natural graphite (eg, scaly graphite) and artificial graphite, conductive fibers such as carbon fibers and metal fibers, and metal powders such as copper, nickel, aluminum and silver.
本発明のカーボン硫黄複合体では硫黄が正極活物質として働く。放電過程において硫黄は還元され、硫化物イオンとなり、さらに還元されると硫化(II)リチウムとなる。逆に、充電過程においては硫化(II)リチウムの硫黄が酸化されて硫化物イオンとなり、さらに酸化が進んで硫黄となる。この過程においては、充放電がスムーズに進むためには硫黄にリチウムイオン、電子が供給されやすいことが重要である。硫黄はきわめて絶縁性が高いため電子供給が困難であるが、本発明では硫黄が小さいサイズであり、カーボン材料が周囲を囲んでいるので電子供給がしやすく、充放電反応がすすみやすい。そのため良好な放電容量が得られる。 In the carbon-sulfur composite of the present invention, sulfur serves as a positive electrode active material. In the discharge process, sulfur is reduced to sulfide ions, and further reduced to lithium (II) sulfide. Conversely, in the charging process, sulfur of lithium (II) sulfide is oxidized to sulfide ions, and further oxidation proceeds to sulfur. In this process, it is important that lithium ions and electrons are easily supplied to sulfur in order for charge / discharge to proceed smoothly. Sulfur has a very high insulating property, so it is difficult to supply electrons. However, in the present invention, sulfur has a small size, and since the carbon material surrounds the surroundings, it is easy to supply electrons and the charge / discharge reaction is facilitated. Therefore, a good discharge capacity can be obtained.
パインダーポリマーとしては、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）などのフッ素系重合体、スチレンブタジエンゴム（ＳＢＲ）、天然ゴムなどのゴムから選択することができる。 The binder polymer may be selected from fluorine polymers such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), and rubbers such as natural rubber.
溶剤としては特に限定されないが、N-メチルピロリドン、γ-ブチロラクトン、水、n-ブチルセロソルブ、エチルセロソルブ、などが上げられる。 Although it does not specifically limit as a solvent, N-methylpyrrolidone, (gamma) -butyrolactone, water, n-butyl cellosolve, ethyl cellosolve, etc. are raised.
電極を作製する手法は特に限定されないが、上記バインダーポリマー、電極活物質、導電助剤、及び溶剤を各種分散・混練機で混練してペーストとし、集電体に塗布・乾燥することで作製する。電流集電体としては、ステンレススチール・アルミニウム、カーボンペーパー、銅などを用いることができ、中でもアルミニウムが好適に用いられる。 The method for producing the electrode is not particularly limited, but it is produced by kneading the binder polymer, electrode active material, conductive additive, and solvent with various dispersing and kneading machines to form a paste, and applying and drying the current collector. . As the current collector, stainless steel / aluminum, carbon paper, copper, or the like can be used, and aluminum is preferably used.
分散・混練手法としては、自動乳鉢・三本ロール・ビーズミル・遊星ボールミル・自公転ミキサー・湿式ジェットミル・ホモジェナイザー・プラネタリーミキサー・二軸混練機などを利用した手法などが挙げられる。 Examples of the dispersion / kneading technique include a technique using an automatic mortar, three rolls, a bead mill, a planetary ball mill, a self-revolving mixer, a wet jet mill, a homogenizer, a planetary mixer, a twin-screw kneader, and the like.
分散・混練して得られたペーストを集電体に塗布する手法としては、バーコータ・ドクターブレードによる塗布、スリットコーター、ダイコーター、ブレードコーターなどが挙げられる。 Examples of the method of applying the paste obtained by dispersing and kneading to the current collector include application by a bar coater / doctor blade, slit coater, die coater, blade coater and the like.
（負極）
負極としてはリチウムイオンを脱挿入可能な材料を含有する合剤を銅箔などの集電体に担持したものを用いることができ、リチウム金属・リチウム合金などを用いることもできる。
(Negative electrode)
As the negative electrode, a material in which a mixture containing a material capable of removing and inserting lithium ions is supported on a current collector such as a copper foil can be used, and lithium metal / lithium alloy can also be used.
リチウムイオンを脱挿入可能な材料としては、ＳｉＯやＳｉＣ、ＳｉＯＣ等を基本構成元素とするケイ素化合物、ポリアセチレンやポリピロール等のリチウムをドープした導電性高分子、リチウムイオンを結晶中に取り込んだ層間化合物や天然黒鉛、人造黒鉛、ハードカーボンなどの炭素材料等が用いられている
本発明のカーボン硫黄複合体を正極材料として用いる場合、正極にリチウム源がないので負極材料にリチウム元素が含まれて居ない場合は予めドープする必要がある。
Examples of materials capable of removing and inserting lithium ions include silicon compounds having SiO, SiC, SiOC and the like as basic constituent elements, conductive polymers doped with lithium such as polyacetylene and polypyrrole, and intercalation compounds in which lithium ions are incorporated into crystals. When the carbon-sulfur composite of the present invention is used as a positive electrode material, there is no lithium source in the positive electrode, so that the negative electrode material contains lithium element. If not, it is necessary to dope in advance.
（リチウムイオン電池用電解質）
正極・負極の間に配置される電解質は固体電解質でも良く、液体電解質であっても良い。液体電解質を用いる場合は、通常セパレーターフィルムを使用する。
(Electrolyte for lithium ion battery)
The electrolyte disposed between the positive electrode and the negative electrode may be a solid electrolyte or a liquid electrolyte. When using a liquid electrolyte, a separator film is usually used.
セパレーターフィルムとしてはポリオレフィン樹脂・フッ素含有樹脂・アクリル樹脂などが用いられ、不織布・多孔質膜などの形態のものを用いることができる。 As the separator film, a polyolefin resin, a fluorine-containing resin, an acrylic resin, or the like is used, and a non-woven fabric, a porous film, or the like can be used.
以下、実施例により本発明を具体的かつより詳細に説明するが、本発明はこれらの実施例のみに制限されるものではない。実施例中の空隙の平均距離、空隙中の硫黄充填率、放電容量は、下記の方法によって測定した。 EXAMPLES Hereinafter, although an Example demonstrates this invention concretely and in detail, this invention is not restrict | limited only to these Examples. The average distance of the voids in the examples, the sulfur filling rate in the voids, and the discharge capacity were measured by the following methods.
［測定例１］ 空隙の平均距離
カーボン材料を透過電子顕微鏡にて断面観察し、同一粒子内で薄層グラファイト構造が略平行に相対してなる空隙の距離（層間厚み）を３０箇所測定し、その平均値を空隙の平均距離とした。
[Measurement Example 1] Average distance of voids Cross-sectional observation of the carbon material was performed with a transmission electron microscope, and 30 distances (interlayer thickness) of voids in which the thin-layer graphite structure was opposed substantially parallel to each other in the same particle were measured. The average value was defined as the average distance of the voids.
［測定例２］ 空隙中の硫黄充填率
カーボン硫黄複合体を透過電子顕微鏡による電子エネルギー損失分光法にて断面観察し、カーボン部分を検出し硫黄部分と区別した。続いて、測定例１記載のカーボン材料の空隙に相当する部分において、硫黄部分の面積比率を測定した。この測定を３０箇所測定し、その平均値を空隙中の硫黄充填率とした。
[Measurement Example 2] Sulfur filling rate in voids A cross section of the carbon-sulfur composite was observed by electron energy loss spectroscopy using a transmission electron microscope, and the carbon portion was detected and distinguished from the sulfur portion. Subsequently, the area ratio of the sulfur portion was measured in the portion corresponding to the voids of the carbon material described in Measurement Example 1. This measurement was performed at 30 locations, and the average value was taken as the sulfur filling rate in the voids.
［測定例３］ 放電容量
直径16.1mm厚さ０．２mmに切り出したリチウム箔を負極とし、直径17mmに切り出したセルガード＃2400（セルガード社製）セパレータとして、下記実施例で作製した電極を直径１５．９mmに打ち抜いて正極とし、電解液としてＬｉＴＦＳＩ（リチウムビス（トリフルオロメタンスルホニル）イミド）を１Ｍ含有するポリエチレングリコールジメチルエーテル（Mn=500、アルドリッチ社）の溶媒を電解液として、2042型コイン電池を作製し、電気化学評価を行った。レート０．５Ｃ（840mA/g）、上限電圧３．０Ｖ、下限電圧１．５Ｖで充放電測定を３回行い、三回目の放電時の容量を放電容量とした。
[Measurement Example 3] Discharge capacity A lithium foil cut to a diameter of 16.1 mm and a thickness of 0.2 mm was used as a negative electrode, and a cell guard # 2400 (manufactured by Celgard) separator cut to a diameter of 17 mm was used. A 2042 type coin battery was manufactured using a solvent of polyethylene glycol dimethyl ether (Mn = 500, Aldrich) containing 1M LiTFSI (lithium bis (trifluoromethanesulfonyl) imide) as the electrolyte. Then, electrochemical evaluation was performed. Charge / discharge measurement was performed three times at a rate of 0.5 C (840 mA / g), an upper limit voltage of 3.0 V, and a lower limit voltage of 1.5 V, and the capacity at the third discharge was defined as the discharge capacity.
［測定例４］ 硫黄の含有量
カーボン硫黄複合体を元素分析により測定した。CHN元素分析はvarioMicrocube(Elementar社)により行いC元素、H元素、N元素の比を分析した。また、varioEL-III(Elementar社)のCHN-O(Oモード)によりO元素に比を分析した。さらにカーボン硫黄複合体をフラスコ燃焼法-イオンクロマトグラフィーにより、S元素含有比を分析した。以上の3つの分析により、C,H,N,O,Sの5元素の含有比を決定した。
[Measurement Example 4] Sulfur content The carbon-sulfur composite was measured by elemental analysis. CHN elemental analysis was performed by varioMicrocube (Elementar) to analyze the ratio of C element, H element and N element. Further, the ratio of O element was analyzed by CHN-O (O mode) of varioEL-III (Elementar). Further, the sulfur content of the carbon-sulfur composite was analyzed by flask combustion method-ion chromatography. The content ratio of the five elements C, H, N, O, and S was determined by the above three analyses.
［測定例５］ 板状構造と空隙の観察
カーボン硫黄複合体の板状構造と空隙は断面SEMにより観察することが可能である。カーボン硫黄複合体を樹脂包埋し、イオンミリング装置により断面を出し、SEM観察を行った。
[Measurement Example 5] Observation of plate-like structure and voids The plate-like structure and voids of the carbon-sulfur composite can be observed by cross-sectional SEM. A carbon sulfur composite was embedded in a resin, a cross section was taken out by an ion milling apparatus, and SEM observation was performed.
［合成例１］
酸化グラフェン粉末の作製方法：粒子径４５マイクロメートルの天然黒鉛粉末（和光純薬）を原料として、氷浴中の5ｇの天然黒鉛粉末に、88ｍｌの98％濃硫酸、45mlの発煙硝酸を入れ、スターラーで十分攪拌する。攪拌しながら、55ｇの塩素酸カリウムを、20℃以上に発熱しないように少しずつ入れる。入れ終わってから攪拌を続けながら96時間反応を行う。反応液を4リットルのイオン交換水に投入し、分散液を濾過する。得られた固体を5％塩酸で繰り返し洗浄し、充分硫酸イオンを除去した後に、イオン交換水で中性になるまで洗浄する。得られた酸化グラフェンゲルをスプレードライ法により乾燥し、酸化グラフェン粉末を得た。
[Synthesis Example 1]
Preparation method of graphene oxide powder: Using natural graphite powder (Wako Pure Chemical) with a particle size of 45 micrometers as raw material, put 88 ml of 98% concentrated sulfuric acid and 45 ml of fuming nitric acid into 5 g of natural graphite powder in an ice bath, Stir well with a stirrer. While stirring, 55 g of potassium chlorate is added little by little so as not to generate heat above 20 ° C. After completion of the addition, the reaction is continued for 96 hours with continued stirring. The reaction solution is poured into 4 liters of ion exchange water, and the dispersion is filtered. The obtained solid is repeatedly washed with 5% hydrochloric acid to sufficiently remove sulfate ions, and then washed with ion-exchanged water until neutral. The obtained graphene oxide gel was dried by a spray drying method to obtain graphene oxide powder.
［合成例２］
酸化グラフェンの作製方法：粒子径４５マイクロメートルの天然黒鉛粉末（和光純薬）を原料として、氷浴中の10ｇの天然黒鉛粉末に、220ｍｌの98％濃硫酸、5ｇの硝酸ナトリウム、30ｇの過マンガン酸カリウムを入れ、1時間機械攪拌し、混合液の温度は20℃以下で保持した。上述混合液を氷浴から取り出し、35℃水浴中で４時間攪拌反応し、その後イオン交換水500ｍｌを入れて得られた懸濁液を90℃で更に15分反応を行った。最後に600ｍｌのイオン交換水と50ｍｌの過酸化水素を入れ、5分間の反応を行い、酸化グラフェン分散液を得た。これを濾過し、希塩酸溶液で金属イオンを洗浄し、イオン交換水で酸を洗浄し、pHが７になるまで洗浄を繰り返し、酸化グラフェンゲルを作製した。得られた酸化グラフェンゲルをスプレードライ法により乾燥し、酸化グラフェン粉末を得た。
[Synthesis Example 2]
Preparation of graphene oxide: Using natural graphite powder (Wako Pure Chemical) with a particle size of 45 micrometers as raw material, 10 g natural graphite powder in an ice bath, 220 ml 98% concentrated sulfuric acid, 5 g sodium nitrate, 30 g excess Potassium manganate was added and mechanically stirred for 1 hour, and the temperature of the mixed solution was kept at 20 ° C. or lower. The above mixed solution was taken out from the ice bath and reacted with stirring in a 35 ° C. water bath for 4 hours. After that, a suspension obtained by adding 500 ml of ion-exchanged water was further reacted at 90 ° C. for 15 minutes. Finally, 600 ml of ion exchange water and 50 ml of hydrogen peroxide were added and the reaction was performed for 5 minutes to obtain a graphene oxide dispersion. This was filtered, the metal ions were washed with a diluted hydrochloric acid solution, the acid was washed with ion-exchanged water, and the washing was repeated until the pH became 7, thereby producing a graphene oxide gel. The obtained graphene oxide gel was dried by a spray drying method to obtain graphene oxide powder.
［合成例３］
［合成例１］で得られた酸化グラフェン粉末を石英チューブに入れ、予め1050℃に加熱してあるアルゴン雰囲気下の電気炉に、その石英チューブごと導入し、酸化グラフェン粉末を急加熱した。その結果、酸化グラフェン粉末が熱還元され、グラフェン粉末を得た。得られたグラフェン粉末を透過電子顕微鏡により空隙の平均距離を測定したところ、5.3nmであった。
[Synthesis Example 3]
The graphene oxide powder obtained in [Synthesis Example 1] was placed in a quartz tube, and the quartz tube was introduced into an electric furnace under an argon atmosphere that had been heated to 1050 ° C. in advance, and the graphene oxide powder was rapidly heated. As a result, the graphene oxide powder was thermally reduced to obtain graphene powder. It was 5.3 nm when the average distance of the space | gap was measured for the obtained graphene powder with the transmission electron microscope.
［合成例４］
［合成例１］で得られた酸化グラフェン粉末を、電気炉に入れてアルゴン雰囲気下で10℃/分で昇温して700℃まで加熱し、700℃で30分保持した。これにより酸化グラフェン粉末を熱還元し、グラフェン粉末を得た。得られたグラフェン粉末を透過電子顕微鏡により空隙の平均距離を測定したところ、2.9nmであった。
[Synthesis Example 4]
The graphene oxide powder obtained in [Synthesis Example 1] was placed in an electric furnace, heated at 10 ° C./min in an argon atmosphere, heated to 700 ° C., and held at 700 ° C. for 30 minutes. Thus, the graphene oxide powder was thermally reduced to obtain graphene powder. It was 2.9 nm when the average distance of the space | gap was measured for the obtained graphene powder with the transmission electron microscope.
［合成例５］
［合成例１］で得られた酸化グラフェン粉末を、電気炉に入れてアルゴン雰囲気下で10℃/分で昇温して550℃まで加熱し、550℃で30分保持した。これにより酸化グラフェン粉末を熱還元し、グラフェン粉末を得た。得られたグラフェン粉末を透過電子顕微鏡により空隙の平均距離を測定したところ、2.2nmであった。
[Synthesis Example 5]
The graphene oxide powder obtained in [Synthesis Example 1] was placed in an electric furnace, heated at 10 ° C./min in an argon atmosphere, heated to 550 ° C., and held at 550 ° C. for 30 minutes. Thus, the graphene oxide powder was thermally reduced to obtain graphene powder. It was 2.2 nm when the average distance of the space | gap was measured for the obtained graphene powder with the transmission electron microscope.
［合成例６］
［合成例１］で得られた酸化グラフェン粉末を、電気炉に入れてアルゴン雰囲気下で10℃/分で昇温して300℃まで加熱し、300℃で30分保持した。これにより酸化グラフェン粉末を熱還元し、グラフェン粉末を得た。得られたグラフェン粉末を透過電子顕微鏡により空隙の平均距離を測定したところ、1.5nmであった。
[Synthesis Example 6]
The graphene oxide powder obtained in [Synthesis Example 1] was placed in an electric furnace, heated at 10 ° C./min in an argon atmosphere, heated to 300 ° C., and held at 300 ° C. for 30 minutes. Thus, the graphene oxide powder was thermally reduced to obtain graphene powder. It was 1.5 nm when the average distance of the space | gap was measured for the obtained graphene powder with the transmission electron microscope.
［合成例７］
膨張黒鉛（伊藤黒鉛工業、品番95100150）を、電気炉に入れてアルゴン雰囲気下で10℃/分で昇温して300℃まで加熱し、300℃で30分保持し、膨張化黒鉛粉末を得た。得られた膨張化黒鉛粉末を透過電子顕微鏡により空隙の平均距離を測定したところ、2.5nmであった。
[Synthesis Example 7]
Expanded graphite (Ito Graphite Industry, product number 95100150) is placed in an electric furnace, heated to 10 ° C / min in an argon atmosphere, heated to 300 ° C, and held at 300 ° C for 30 minutes to obtain expanded graphite powder It was. It was 2.5 nm when the average distance of the space | gap was measured for the obtained expanded graphite powder with the transmission electron microscope.
［合成例８］
膨張黒鉛（伊藤黒鉛工業、品番95100150）を、石英チューブに入れ、予め500℃に加熱してあるアルゴン雰囲気下の電気炉に、その石英チューブごと導入し、膨張黒鉛を急加熱した。これにより、膨張化黒鉛粉末を得た。得られた膨張化黒鉛粉末を透過電子顕微鏡により空隙の平均距離を測定したところ、20nmであった。
[Synthesis Example 8]
Expanded graphite (Ito Graphite Industry, product number 95100150) was put into a quartz tube, and the quartz tube was introduced into an electric furnace under an argon atmosphere that had been heated to 500 ° C. in advance, and the expanded graphite was rapidly heated. Thereby, expanded graphite powder was obtained. It was 20 nm when the average distance of the space | gap was measured for the obtained expanded graphite powder with the transmission electron microscope.
［実施例１］
市販の硫黄粉末（Alfa Aeser,325mesh）4重量部と［合成例４］で作製した空隙の平均距離が2.9nmのグラフェン粉末１重量部を遊星ボールミルで300rpmで2時間混合し、カーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は８０％、空隙の平均距離は２．８ｎｍ、充填率は８２％であった。［測定例５］によりカーボン硫黄複合体を観察したところ、平均厚さ80nmの板状構造と空隙がみられた。
[Example 1]
4 parts by weight of commercially available sulfur powder (Alfa Aeser, 325mesh) and 1 part by weight of graphene powder with an average gap distance of 2.9 nm prepared in [Synthesis Example 4] were mixed for 2 hours at 300 rpm with a planetary ball mill to obtain a carbon sulfur composite. Was made. The sulfur content of the carbon-sulfur composite was 80%, the average gap distance was 2.8 nm, and the filling rate was 82%. When the carbon-sulfur composite was observed according to [Measurement Example 5], a plate-like structure having an average thickness of 80 nm and voids were observed.
該カーボン硫黄複合体を80重量部、導電助剤としてアセチレンブラックを8重量部、バインダーとしてポリ弗化ビニリデン10重量部、溶剤としてN-メチルピロリドンを、200重量部加えて、プラネタリーミキサーで混合して電極ペーストを得た。電極ペーストをアルミニウム箔（厚さ18μｍ）にアプリケータ（80μm）を用いて塗布し、80℃30分間乾燥して電極板を得た。該電極板を用いて、電極の放電容量を測定したところ、８９５ｍAh/gであった。 Add 80 parts by weight of the carbon-sulfur composite, 8 parts by weight of acetylene black as a conductive additive, 10 parts by weight of polyvinylidene fluoride as a binder, and 200 parts by weight of N-methylpyrrolidone as a solvent, and mix with a planetary mixer. Thus, an electrode paste was obtained. The electrode paste was applied to an aluminum foil (thickness 18 μm) using an applicator (80 μm) and dried at 80 ° C. for 30 minutes to obtain an electrode plate. When the discharge capacity of the electrode was measured using the electrode plate, it was 895 mAh / g.
［実施例２］
用いるグラフェン粉末を［合成例５］で作製した空隙の平均距離が2.2nmのグラフェン粉末とした以外は実施例１と同様にしてカーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は８０％、空隙の平均距離は２．０ｎｍ、充填率は８２％であった。［測定例５］によりカーボン硫黄複合体を観察したところ、平均厚さ76nmの板状構造と空隙がみられた。該カーボン硫黄複合体を用いて、実施例１と同様に電極を作製し、電極の放電容量を測定したところ、９２４ｍAh/gであった。
[Example 2]
A carbon-sulfur composite was produced in the same manner as in Example 1 except that the graphene powder used was a graphene powder having an average gap distance of 2.2 nm produced in [Synthesis Example 5]. The sulfur content of the carbon-sulfur composite was 80%, the average gap distance was 2.0 nm, and the filling rate was 82%. When the carbon-sulfur composite was observed according to [Measurement Example 5], a plate-like structure having an average thickness of 76 nm and voids were observed. Using this carbon-sulfur composite, an electrode was produced in the same manner as in Example 1, and the discharge capacity of the electrode was measured. The result was 924 mAh / g.
［実施例３］
用いるグラフェン粉末を［合成例６］で作製した空隙の平均距離が1.5nmのグラフェン粉末とした以外は実施例１と同様にしてカーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は８０％、空隙の平均距離は１．４ｎｍ、充填率は７６％であった。［測定例５］によりカーボン硫黄複合体中の板状構造と空隙を観察したところ、平均厚さ73nmの板状構造と空隙がみられた。該カーボン硫黄複合体を用いて、実施例１と同様に電極を作製し、電極の放電容量を測定したところ、９８９ｍAh/gであった。
[Example 3]
A carbon-sulfur composite was produced in the same manner as in Example 1 except that the graphene powder used was a graphene powder having an average gap distance of 1.5 nm produced in [Synthesis Example 6]. The sulfur content of the carbon-sulfur composite was 80%, the average distance between the voids was 1.4 nm, and the filling rate was 76%. When the plate-like structure and voids in the carbon-sulfur composite were observed by [Measurement Example 5], a plate-like structure and voids having an average thickness of 73 nm were observed. Using this carbon-sulfur composite, an electrode was produced in the same manner as in Example 1, and the discharge capacity of the electrode was measured. As a result, it was 989 mAh / g.
［実施例４］
グラフェン粉末を用いる替わりに［合成例７］で作製した空隙の平均距離が2.5nmの膨張化黒鉛粉末を用いた以外は実施例１と同様にしてカーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は８１％、空隙の平均距離は２．３ｎｍ、充填率は８１％であった。［測定例５］によりカーボン硫黄複合体を観察したが、明らかな板状構造は見られなかった。該カーボン硫黄複合体を用いて、実施例１と同様に電極を作製し、電極の放電容量を測定したところ、９３２ｍAh/gであった。
[Example 4]
A carbon-sulfur composite was prepared in the same manner as in Example 1 except that expanded graphite powder having an average gap distance of 2.5 nm prepared in [Synthesis Example 7] was used instead of using graphene powder. The sulfur content of the carbon-sulfur composite was 81%, the average distance between the voids was 2.3 nm, and the filling rate was 81%. The carbon-sulfur composite was observed according to [Measurement Example 5], but no obvious plate-like structure was observed. Using this carbon-sulfur composite, an electrode was produced in the same manner as in Example 1, and the discharge capacity of the electrode was measured. The result was 932 mAh / g.
［実施例５］
市販の硫黄粉末（Alfa Aeser,325mesh）4重量部と［合成例４］で作製した空隙の平均距離が2.9nmのグラフェン粉末１重量部を乳鉢で混合した後に、120℃で2時間加熱した。加熱した粉末を再び乳鉢で粉砕した後に、遊星ボールミルで300rpm2時間混合し、カーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は７９％、空隙の平均距離は２．７ｎｍ、充填率は８６％であった。［測定例５］によりカーボン硫黄複合体を観察したところ、平均厚さ78nmの板状構造と空隙がみられた。該カーボン硫黄複合体を実施例１と同様に電極を作製し、電極の放電容量を測定したところ、１００１ｍAh/gであった。
[Example 5]
After mixing 4 parts by weight of commercially available sulfur powder (Alfa Aeser, 325mesh) and 1 part by weight of graphene powder having an average distance of 2.9 nm of gaps produced in [Synthesis Example 4] in a mortar, the mixture was heated at 120 ° C. for 2 hours. The heated powder was pulverized again in a mortar and then mixed with a planetary ball mill at 300 rpm for 2 hours to prepare a carbon sulfur composite. The sulfur content of the carbon-sulfur composite was 79%, the average gap distance was 2.7 nm, and the filling rate was 86%. When the carbon-sulfur composite was observed according to [Measurement Example 5], a plate-like structure having an average thickness of 78 nm and voids were observed. An electrode was produced from the carbon-sulfur composite in the same manner as in Example 1, and the discharge capacity of the electrode was measured. As a result, it was 1001 mAh / g.
［実施例6］
加熱温度を155℃とした以外は実施例5と同様にしてカーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は７８％、空隙の平均距離は２．７ｎｍ、充填率は９１％であった。［測定例５］によりカーボン硫黄複合体を観察したところ、平均厚さ77nmの板状構造と空隙がみられた。該カーボン硫黄複合体を用いて、実施例１と同様に電極を作製し、電極の放電容量を測定したところ、１０１３ｍAh/gであった。
［実施例７］
市販の硫黄粉末（Alfa Aeser,325mesh）4重量部と［合成例１］で得られた酸化グラフェン粉末と、1.5重量部とを、乳鉢で混合した後に、155℃で2時間加熱した。加熱した粉末を再び乳鉢で粉砕した後に、遊星ボールミルで300rpm2時間混合し、さらに155℃で2時間加熱し、カーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は７９％、このカーボン硫黄複合体は透過電子顕微鏡で観察不能なほど小さく、空隙は1nm以下である。充填率は９２％であった。［測定例５］によりカーボン硫黄複合体を観察したところ、平均厚さ54nmの板状構造と空隙がみられた。該カーボン硫黄複合体を実施例１と同様に電極を作製し、電極の放電容量を測定したところ、１１２０ｍAh/gであった。
［実施例8］
市販の硫黄粉末（Alfa Aeser,325mesh）4重量部と［合成例２］で得られた酸化グラフェン粉末と、1.5重量部とを、乳鉢で混合した後に、155℃で2時間加熱した。加熱した粉末を再び乳鉢で粉砕した後に、遊星ボールミルで300rpm2時間混合し、さらに155℃で2時間加熱し、カーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は８０％、このカーボン硫黄複合体は透過電子顕微鏡で観察不能なほど小さく、空隙は1nm以下である。充填率は９３％であった。［測定例５］によりカーボン硫黄複合体を観察したところ、平均厚さ48nmの板状構造と空隙がみられた。観察結果のSEM写真を図１に示す。該カーボン硫黄複合体を実施例１と同様に電極を作製し、電極の放電容量を測定したところ、１１３４ｍAh/gであった。
[Example 6]
A carbon-sulfur composite was produced in the same manner as in Example 5 except that the heating temperature was 155 ° C. The sulfur content of the carbon-sulfur composite was 78%, the average distance between the voids was 2.7 nm, and the filling rate was 91%. When the carbon-sulfur composite was observed by [Measurement Example 5], a plate-like structure having an average thickness of 77 nm and voids were observed. Using the carbon-sulfur composite, an electrode was produced in the same manner as in Example 1, and the discharge capacity of the electrode was measured. As a result, it was 1013 mAh / g.
[Example 7]
4 parts by weight of commercially available sulfur powder (Alfa Aeser, 325mesh) and the graphene oxide powder obtained in [Synthesis Example 1] and 1.5 parts by weight were mixed in a mortar and then heated at 155 ° C. for 2 hours. The heated powder was again pulverized in a mortar, mixed with a planetary ball mill at 300 rpm for 2 hours, and further heated at 155 ° C. for 2 hours to produce a carbon sulfur composite. The sulfur content of the carbon-sulfur composite is 79%, the carbon-sulfur composite is so small that it cannot be observed with a transmission electron microscope, and the voids are 1 nm or less. The filling rate was 92%. When the carbon-sulfur composite was observed according to [Measurement Example 5], a plate-like structure having an average thickness of 54 nm and voids were observed. An electrode was produced from the carbon-sulfur composite in the same manner as in Example 1, and the discharge capacity of the electrode was measured. The result was 1120 mAh / g.
[Example 8]
4 parts by weight of commercially available sulfur powder (Alfa Aeser, 325mesh) and the graphene oxide powder obtained in [Synthesis Example 2] and 1.5 parts by weight were mixed in a mortar and then heated at 155 ° C. for 2 hours. The heated powder was again pulverized in a mortar, mixed with a planetary ball mill at 300 rpm for 2 hours, and further heated at 155 ° C. for 2 hours to produce a carbon sulfur composite. The sulfur content of the carbon-sulfur composite is 80%, the carbon-sulfur composite is so small that it cannot be observed with a transmission electron microscope, and the voids are 1 nm or less. The filling rate was 93%. When the carbon-sulfur composite was observed according to [Measurement Example 5], a plate-like structure having an average thickness of 48 nm and voids were observed. The SEM photograph of the observation result is shown in FIG. An electrode was produced from the carbon-sulfur composite in the same manner as in Example 1, and the discharge capacity of the electrode was measured. As a result, it was 1134 mAh / g.
［比較例１］
市販の硫黄粉末（Alfa Aeser,325mesh）4重量部と［合成例３］で作製した空隙の平均距離が5.3nmのグラフェン粉末１重量部を遊星ボールミルで300rpm2時間混合し、カーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は８０％、空隙の平均距離は５．０ｎｍ、充填率は８１％であった。［測定例５］によりカーボン硫黄複合体を観察したところ、平均厚さ86nmの板状構造と空隙がみられた。該カーボン硫黄複合体を実施例１と同様に電極にして、電極の放電容量を測定したところ、７６０ｍAh/gであった。
[Comparative Example 1]
4 parts by weight of commercially available sulfur powder (Alfa Aeser, 325mesh) and 1 part by weight of graphene powder with an average gap distance of 5.3 nm prepared in [Synthesis Example 3] are mixed with a planetary ball mill at 300 rpm for 2 hours to produce a carbon sulfur composite. did. The sulfur content of the carbon-sulfur composite was 80%, the average distance between the voids was 5.0 nm, and the filling rate was 81%. When the carbon-sulfur composite was observed according to [Measurement Example 5], a plate-like structure having an average thickness of 86 nm and voids were observed. The carbon-sulfur composite was used as an electrode in the same manner as in Example 1, and the discharge capacity of the electrode was measured and found to be 760 mAh / g.
［比較例２］
市販の硫黄粉末（Alfa Aeser,325mesh）4重量部と［合成例８］で作製した空隙の平均距離が20nmの膨張化黒鉛粉末１重量部を遊星ボールミルで300rpm2時間混合し、カーボン硫黄複合体を作製した。カーボン硫黄複合体の硫黄の含有量は８０％、空隙の平均距離は１８ｎｍ、充填率は８９％であった。［測定例５］によりカーボン硫黄複合体を観察したが、明らかな板状構造は見られなかった。該カーボン硫黄複合体を実施例１と同様に電極にして、電極の放電容量を測定したところ、７２０ｍAh/gであった。
[Comparative Example 2]
4 parts by weight of commercially available sulfur powder (Alfa Aeser, 325mesh) and 1 part by weight of expanded graphite powder with an average gap distance of 20 nm prepared in [Synthesis Example 8] were mixed with a planetary ball mill at 300 rpm for 2 hours to obtain a carbon sulfur composite. Produced. The sulfur content of the carbon-sulfur composite was 80%, the average distance between the voids was 18 nm, and the filling rate was 89%. The carbon-sulfur composite was observed according to [Measurement Example 5], but no obvious plate-like structure was observed. Using the carbon-sulfur composite as an electrode in the same manner as in Example 1, the discharge capacity of the electrode was measured and found to be 720 mAh / g.
［比較例３］
市販の硫黄粉末（Alfa Aeser,325mesh）4重量部とアセチレンブラック（電気化学社）１重量部を遊星ボールミルで300rpm2時間混合し、カーボン硫黄混合体を作製した。カーボン硫黄複合体の硫黄の含有量は８０％であった。［測定例５］によりカーボン硫黄複合体を観察したが、明らかな板状構造は見られなかった。該カーボン硫黄混合体を実施例１と同様に電極にして、電極の放電容量を測定したところ、６６０ｍAh/gであった。
[Comparative Example 3]
4 parts by weight of commercially available sulfur powder (Alfa Aeser, 325mesh) and 1 part by weight of acetylene black (Electrochemical) were mixed in a planetary ball mill at 300 rpm for 2 hours to prepare a carbon sulfur mixture. The sulfur content of the carbon-sulfur composite was 80%. The carbon-sulfur composite was observed according to [Measurement Example 5], but no obvious plate-like structure was observed. The carbon sulfur mixture was used as an electrode in the same manner as in Example 1, and the discharge capacity of the electrode was measured. As a result, it was 660 mAh / g.
本発明のカーボン硫黄複合体は、特に用途は限定されないが、例えばリチウムイオン電池の電極材料として好適に利用することができる。 The use of the carbon-sulfur composite of the present invention is not particularly limited, but it can be suitably used, for example, as an electrode material for a lithium ion battery.
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| JP2013038519A JP6167561B2 (en) | 2012-03-09 | 2013-02-28 | Carbon sulfur composite, electrochemical device using the same, and lithium ion battery |
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| CN103606649A (en) * | 2013-11-21 | 2014-02-26 | 浙江工业大学 | Electrolysis preparation method of sulfur/carbon composite material |
| JPWO2016075916A1 (en) * | 2014-11-13 | 2017-09-28 | 株式会社Ｇｓユアサ | Sulfur-carbon composite, non-aqueous electrolyte battery equipped with electrode containing sulfur-carbon composite, and method for producing sulfur-carbon composite |
| WO2018225619A1 (en) | 2017-06-05 | 2018-12-13 | 積水化学工業株式会社 | Sulfur-carbon material composite body, positive electrode material for lithium sulfur secondary batteries, and lithium sulfur secondary battery |
| CN113823787A (en) * | 2021-08-17 | 2021-12-21 | 华南理工大学 | Porous sulfur composite cathode material and preparation method and application thereof |
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| KR20200014720A (en) | 2017-06-05 | 2020-02-11 | 세키스이가가쿠 고교가부시키가이샤 | Sulfur-carbon material composite, positive electrode material for lithium sulfur secondary battery and lithium sulfur secondary battery |
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| WO2018225619A1 (en) | 2017-06-05 | 2018-12-13 | 積水化学工業株式会社 | Sulfur-carbon material composite body, positive electrode material for lithium sulfur secondary batteries, and lithium sulfur secondary battery |
| JP2022505642A (en) * | 2018-11-14 | 2022-01-14 | エルジー・ケム・リミテッド | Thermally expanded reduced graphene oxide, its production method, sulfur-carbon composite containing it and lithium secondary battery |
| JP7176110B2 (en) | 2018-11-14 | 2022-11-21 | エルジー エナジー ソリューション リミテッド | Thermally expanded reduced graphene oxide, method for producing the same, sulfur-carbon composite containing the same, and lithium secondary battery |
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| JP7307780B2 (en) | 2020-11-25 | 2023-07-12 | ネッチュ トロッケンマールテヒニク ゲーエムベーハー | Method for producing a homogenized mixture of carbon, sulfur and PTFE |
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