JP2007265915A - Reformed graphite for nonaqueous electrolyte secondary battery - Google Patents
Reformed graphite for nonaqueous electrolyte secondary battery Download PDFInfo
- Publication number
- JP2007265915A JP2007265915A JP2006092126A JP2006092126A JP2007265915A JP 2007265915 A JP2007265915 A JP 2007265915A JP 2006092126 A JP2006092126 A JP 2006092126A JP 2006092126 A JP2006092126 A JP 2006092126A JP 2007265915 A JP2007265915 A JP 2007265915A
- Authority
- JP
- Japan
- Prior art keywords
- graphite
- electrolyte secondary
- secondary battery
- hydrogen plasma
- negative electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Description
本発明は、黒鉛の改質に関し、より詳しくは非水電解質二次電池の構成材料である黒鉛のリチウムイオン吸蔵放出特性を改善する技術に関する。 The present invention relates to graphite modification, and more particularly to a technique for improving lithium ion storage / release characteristics of graphite, which is a constituent material of a non-aqueous electrolyte secondary battery.
黒鉛負極を用いる非水電解質二次電池は、高容量で高いエネルギー密度を有し、かつ安全性やサイクル特性に優れることから、携帯電話、ノートパソコン、ＰＤＡ等の移動情報端末の駆動電源として広く利用されている。しかし、移動情報端末の急速な小型化・高機能化の進展に伴い、今日では益々高性能な非水電解質二次電池が求められるようになっている。 Non-aqueous electrolyte secondary batteries using graphite negative electrodes are widely used as driving power sources for mobile information terminals such as mobile phones, notebook computers and PDAs because they have high capacity, high energy density, and excellent safety and cycle characteristics. It's being used. However, with the rapid progress of miniaturization and higher functionality of mobile information terminals, there is an increasing demand for high-performance nonaqueous electrolyte secondary batteries today.
このような背景にあって、天然黒鉛を酸化処理することにより、その層間を広げ、リチウムイオンの吸蔵量を増やす試みがなされている。天然黒鉛を酸化処理すると、リチウムイオンの吸蔵量が増え、見掛け上の充電容量が向上する。しかし、吸蔵されたリチウムの一部は黒鉛結晶内に留まり放出されないために、十分に放電容量が向上しないと共に、酸化処理により黒鉛の結晶構造が不安定化するために充放電サイクル寿命が短くなるという問題がある。 Against this backdrop, attempts have been made to increase the amount of lithium ions occluded by oxidizing the natural graphite to expand the interlayer. When natural graphite is oxidized, the amount of occluded lithium ions increases and the apparent charge capacity improves. However, since some of the occluded lithium remains in the graphite crystal and is not released, the discharge capacity is not sufficiently improved, and the charge / discharge cycle life is shortened because the crystal structure of the graphite is destabilized by the oxidation treatment. There is a problem.
このような問題に関する技術としては、特許文献１〜４がある。 As technologies related to such a problem, there are Patent Documents 1 to 4.
特許文献１は、酸化黒鉛とスズ化合物とを混合したのち非酸化性雰囲気下で焼成して金属スズ担持酸化黒鉛となす技術である。この技術によると放電容量が高い上に、サイクル特性にすぐれた負極材料が得られるとされる。 Patent Document 1 is a technique in which graphite oxide and a tin compound are mixed and then fired in a non-oxidizing atmosphere to form metal tin-supported graphite oxide. According to this technique, a negative electrode material having a high discharge capacity and excellent cycle characteristics is obtained.
特許文献２は、酸化黒鉛の層間に導電性高分子を存在させた層間化合物となす技術に関し、この技術によると放電容量が大きく充放電サイクル寿命が長い非水電解質二次電池用の電極材料が得られるとされる。 Patent Document 2 relates to a technique for forming an intercalation compound in which a conductive polymer is present between graphite oxide layers. According to this technique, an electrode material for a nonaqueous electrolyte secondary battery having a large discharge capacity and a long charge / discharge cycle life is disclosed. It is supposed to be obtained.
特許文献３は、酸化黒鉛と脂肪酸金属塩との混合物が、熱処理されて、酸化黒鉛の層間間隔が小さくされて熱分解酸化黒鉛が形成されるとともに、熱分解酸化黒鉛の表面の少なくとも一部に、脂肪酸金属塩が熱分解されて非晶質な金属化合物が被覆形成されたものを非水電解質二次電池用負極材料とする技術である。この技術によると、非晶質な金属化合物が熱分解酸化黒鉛の表面に被覆されているので、金属化合物の長所と熱分解酸化黒鉛の長所を併せ持った負極材料を形成でき、金属化合物により高い充放電容量が得られるのと同時に、熱分解酸化黒鉛により高い充放電効率や高いサイクル特性といった優れた特性が得られる等とされる。 In Patent Document 3, a mixture of graphite oxide and a fatty acid metal salt is heat-treated to reduce the interlayer spacing of the graphite oxide to form pyrolytic graphite oxide, and at least part of the surface of the pyrolytic graphite oxide. This is a technique in which a fatty acid metal salt is thermally decomposed to form an amorphous metal compound as a negative electrode material for a non-aqueous electrolyte secondary battery. According to this technique, since the surface of the pyrolytic graphite oxide is coated with an amorphous metal compound, a negative electrode material having both the advantages of the metal compound and the pyrolytic graphite oxide can be formed. At the same time that the discharge capacity is obtained, excellent properties such as high charge / discharge efficiency and high cycle characteristics are obtained by pyrolytic graphite oxide.
特許文献４は、黒鉛構造の発達した結晶部と未発達の非晶質部が混在する炭素材料を用いる技術であり、この技術によると、高電気容量を有し、サイクル寿命も長い、充放電効率も良好な非水電解質二次電池の作製が可能になるとされる。 Patent Document 4 is a technique using a carbon material in which a crystal part having a developed graphite structure and an undeveloped amorphous part are mixed. According to this technique, charge / discharge has a high electric capacity and a long cycle life. It is said that it is possible to produce a non-aqueous electrolyte secondary battery with good efficiency.
本発明は、黒鉛を酸化処理した場合における、充放電効率の低下、サイクル寿命の低下などの問題点を解消し、放電容量が大きく、サイクル寿命に優れた非水電解質二次電池用の改質黒鉛を簡易に製造することのできる製造方法を提供することを目的とする。また、放電容量が大きく、サイクル寿命に優れた非水電解質二次電池を生産性よく製造することのできる非水電解質二次電池の製造方法を提供することを目的とする。 The present invention eliminates problems such as reduced charge / discharge efficiency and cycle life when graphite is oxidized, and has a large discharge capacity and improved cycle life for nonaqueous electrolyte secondary batteries. It aims at providing the manufacturing method which can manufacture graphite easily. It is another object of the present invention to provide a method for producing a nonaqueous electrolyte secondary battery that can produce a nonaqueous electrolyte secondary battery having a large discharge capacity and excellent cycle life with high productivity.
上記課題を解決するための発明は、次のように構成されている。
原料黒鉛を酸化処理して酸化黒鉛となす酸化処理工程と、前記酸化黒鉛を、１０００℃以上の水素プラズマ雰囲気中で熱処理することにより、前記原料黒鉛に対する膨張率が１.１以上、１.４以下である改質黒鉛を作製する水素プラズマ処理工程と、を備える非水電解質二次電池用改質黒鉛の製造方法。
The invention for solving the above problems is configured as follows.
An oxidation treatment step of oxidizing raw material graphite into graphite oxide, and heat-treating the graphite oxide in a hydrogen plasma atmosphere at 1000 ° C. or higher, the expansion coefficient of the raw material graphite is 1.1 or more and 1.4. A method for producing modified graphite for a non-aqueous electrolyte secondary battery, comprising: a hydrogen plasma treatment step for producing modified graphite as described below.
上記構成では、酸化処理工程で原料黒鉛に対し酸化処理を施すが、この酸化処理によりリチウムイオンを吸蔵し得る結晶層間隙を広げることができる。しかし、酸化処理済み黒鉛はダングリングボンドを有し、また層間に酸が残留しているので、物理的・化学的に不安定な状態にある。 In the above configuration, the raw graphite is subjected to an oxidation treatment in the oxidation treatment step, and this oxidation treatment can widen the crystal layer gap that can occlude lithium ions. However, oxidized graphite has dangling bonds, and acid remains between the layers, so that it is physically and chemically unstable.
この状態は、酸化処理工程に続いて行う、１０００℃以上の水素プラズマ雰囲気中で熱処理する水素プラズマ処理により取り除かれる。すなわち、酸化処理済み黒鉛（酸化黒鉛）に対し１０００℃以上の水素プラズマ処理を行うと、結晶層間等に入り込んでいた酸が除去されると共に、ダングリングボンドが水素終端されるので、結晶構造が化学的・物理的に安定化する。 This state is removed by a hydrogen plasma treatment performed in a hydrogen plasma atmosphere at 1000 ° C. or higher, which is performed following the oxidation treatment step. That is, when hydrogen plasma treatment at 1000 ° C. or higher is performed on oxidized graphite (graphite oxide), the acid that has entered the crystal layers and the like is removed, and the dangling bonds are terminated with hydrogen. Stabilize chemically and physically.
ここで上記構成ではこの水素プラズマ処理を、改質黒鉛の原料黒鉛に対する膨張率が１.１以上、１.４以下となるように行う。この条件での処理であると、リチウムイオンの吸蔵放出にとって好都合な黒鉛結晶構造が形成できる。すなわち、より多くのリチウムイオンを吸蔵でき、かつ吸蔵したリチウムイオンを効率よく放出でき、しかも化学的物理的に安定な結晶構造に改質できる。この改質黒鉛は、充放電容量、充放電効率、およびサイクル特性に優れる。 Here, in the above configuration, the hydrogen plasma treatment is performed so that the expansion coefficient of the modified graphite with respect to the raw graphite is 1.1 or more and 1.4 or less. When the treatment is performed under these conditions, a graphite crystal structure that is convenient for the storage and release of lithium ions can be formed. That is, more lithium ions can be occluded, occluded lithium ions can be efficiently released, and the crystal structure can be modified into a chemically and physically stable crystal structure. This modified graphite is excellent in charge / discharge capacity, charge / discharge efficiency, and cycle characteristics.
上記構成においては、水素プラズマ処理温度を１０００℃以上とするが、水素プラズマ処理における温度が１０００℃未満であると、結晶層間に残留する酸を十分に除去できない等のため、水素プラズマ処理効果が低減する。他方、水素プラズマ処理温度が高すぎると、熱による結晶構造の破壊が生じると共に、無駄なエネルギーコストがかかる。２８００℃以下の温度であれば、結晶構造の破壊の恐れがない。よって、水素プラズマ処理温度は１０００℃以上２８００℃以下とするのが好ましい。 In the above configuration, the hydrogen plasma treatment temperature is set to 1000 ° C. or more. However, if the temperature in the hydrogen plasma treatment is less than 1000 ° C., the acid remaining between the crystal layers cannot be sufficiently removed. To reduce. On the other hand, if the hydrogen plasma treatment temperature is too high, the crystal structure is destroyed by heat and wasteful energy costs are required. If the temperature is 2800 ° C. or lower, there is no fear of destruction of the crystal structure. Therefore, the hydrogen plasma treatment temperature is preferably 1000 ° C. or higher and 2800 ° C. or lower.
また、上記構成においては、前記原料黒鉛として、好ましくは天然黒鉛を用いるのがよい。天然黒鉛は結晶性が高いので、酸化処理と水素プラズマ処理とを施す効果が一層顕著に発揮される。 In the above configuration, natural graphite is preferably used as the raw graphite. Since natural graphite has high crystallinity, the effect of performing oxidation treatment and hydrogen plasma treatment is more remarkable.
非水電解質二次電池の製造方法にかかる発明は、上記した改質黒鉛を負極活物質とし負極集電体に結着し黒鉛負極となす黒鉛負極作製工程と、リチウムイオンを吸蔵放出可能なリチウム遷移金属複合酸化物を、正極活物質として正極集電体に結着し正極となす正極作製工程と、セパレータを介在させて前記黒鉛負極と前記正極とを対向させる電極体作製工程と、を備える。 The invention relating to the manufacturing method of the non-aqueous electrolyte secondary battery includes a graphite negative electrode preparation step in which the above modified graphite is used as a negative electrode active material and bound to a negative electrode current collector to form a graphite negative electrode, and lithium capable of occluding and releasing lithium ions. A positive electrode preparation step in which a transition metal composite oxide is bound to a positive electrode current collector as a positive electrode active material to form a positive electrode; and an electrode body preparation step in which the graphite negative electrode and the positive electrode face each other with a separator interposed therebetween. .
この構成によると、充放電容量が大きく、サイクル寿命に優れた非水電解質二次電池を生産性よく製造することができる。 According to this configuration, a nonaqueous electrolyte secondary battery having a large charge / discharge capacity and excellent cycle life can be produced with high productivity.
本発明にかかる改質黒鉛の製造方法によると、酸化処理により黒鉛結晶の結晶層間を広げることができ、水素プラズマ処理により結晶層間に残留する酸を除去できると共に、黒鉛結晶のダングリングボンドを水素終端させ結晶構造を安定化させることができる。よって、本発明にかかる改質黒鉛の製造方法によると、リチウムイオンに対する吸蔵放出能力が高く、吸蔵放出サイクル寿命に優れた改質黒鉛を生産性よく製造することができる。 According to the method for producing modified graphite according to the present invention, it is possible to widen the crystal layers of graphite crystals by oxidation treatment, to remove the acid remaining between the crystal layers by hydrogen plasma treatment, and to dangling bonds of graphite crystals to hydrogen. It can be terminated to stabilize the crystal structure. Therefore, according to the method for producing modified graphite according to the present invention, it is possible to produce modified graphite having a high ability to occlude and release lithium ions and an excellent occlusion / release cycle life with high productivity.
また、このような改質黒鉛を負極活物質として用い非水電解質二次電池を製造する本発明製造方法によると、充放電容量が大きく、充放電効率やサイクル寿命に優れた非水電解質二次電池を生産性よく製造することができる。 Further, according to the production method of the present invention for producing a non-aqueous electrolyte secondary battery using such modified graphite as a negative electrode active material, the non-aqueous electrolyte secondary having a large charge / discharge capacity and excellent charge / discharge efficiency and cycle life. The battery can be manufactured with high productivity.
本発明を実施するための最良の形態を、実施例に基づいて説明する。 The best mode for carrying out the present invention will be described based on examples.
（実施例１）
[正極の作製]
コバルト酸リチウムと導電材としての黒鉛と結着材としてのポリフッ化ビニリデン（ＰＶｄＦ）とを、コバルト酸リチウム：黒鉛：ＰＶｄＦ＝９０：５：５（質量比）の割合で混合した。この混合末スラリーを厚さ１５μmのアルミニウムからなる正極集電体に塗布し、乾燥した後、圧延して厚さ１４０μmの正極を作製した。
Example 1
[Preparation of positive electrode]
Lithium cobaltate, graphite as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed in a ratio of lithium cobaltate: graphite: PVdF = 90: 5: 5 (mass ratio). This mixed powder slurry was applied to a positive electrode current collector made of aluminum having a thickness of 15 μm, dried, and then rolled to produce a positive electrode having a thickness of 140 μm.
[負極の作製]
原料黒鉛として天然黒鉛（ｄ002値：３．３５Å、Ｌｃ００２値：３０００Å、平均粒径：２１μｍ）を用い、この１００質量部を、濃硫酸／濃硝酸＝９／１（体積比）で混合した酸溶液４００質量部に添加し混合して黒鉛-酸溶液となした。天然黒鉛が酸に浸かった状態（浸漬状態）を２時間保持したのち、この黒鉛-酸溶液をろ過し、ろ液pHが６〜７となるまで天然黒鉛をメタノールで洗浄した。なお、この工程を酸化処理工程と称する。
[Preparation of negative electrode]
Natural graphite (d 002 value: 3.35 Ｌ, Lc002 value: 3000 平均, average particle size: 21 μm) was used as raw material graphite, and 100 parts by mass thereof were mixed with concentrated sulfuric acid / concentrated nitric acid = 9/1 (volume ratio). It was added to 400 parts by mass of the acid solution and mixed to obtain a graphite-acid solution. After maintaining the state in which natural graphite was immersed in an acid (immersion state) for 2 hours, this graphite-acid solution was filtered, and the natural graphite was washed with methanol until the filtrate pH became 6-7. This process is referred to as an oxidation treatment process.
次に、酸化処理工程で得た酸化処理済み黒鉛（酸化黒鉛）を平面上に広げ軽く押さえて板状とし、これを１０００℃の水素プラズマ雰囲気中に２５分間保持した。この操作を水素プラズマ処理と称し、この工程を水素プラズマ処理工程と称する。 Next, the oxidized graphite (graphite oxide) obtained in the oxidation treatment step was spread on a flat surface and pressed lightly into a plate shape, which was held in a hydrogen plasma atmosphere at 1000 ° C. for 25 minutes. This operation is referred to as hydrogen plasma treatment, and this step is referred to as a hydrogen plasma treatment step.
水素プラズマ処理した黒鉛を、窒素不活性雰囲気中で粉砕し、平均粒径が２３μmの改質黒鉛粒子を得た。この改質黒鉛の原料黒鉛に対する膨張率は１．２であった。
原料黒鉛および改質黒鉛の平均粒径は、２１μmであった。なお、平均粒径はレーザー回折法で測定したまた、膨張率は、下記数１に従って算出した。更に、嵩比重はJIS-K1469の方法により測定した。
The graphite treated with hydrogen plasma was pulverized in a nitrogen inert atmosphere to obtain modified graphite particles having an average particle size of 23 μm. The expansion coefficient of the modified graphite relative to the raw material graphite was 1.2.
The average particle diameter of the raw material graphite and the modified graphite was 21 μm. The average particle diameter was measured by a laser diffraction method, and the expansion coefficient was calculated according to the following formula 1. Furthermore, the bulk specific gravity was measured by the method of JIS-K1469.
膨張率＝1／（改質黒鉛の嵩比重／原料黒鉛（出発物質）の嵩比重）・・・数１
Expansion coefficient = 1 / (bulk specific gravity of modified graphite / bulk specific gravity of raw graphite (starting material))
上記で作製した改質黒鉛を用い、改質黒鉛／カルボキシメチルセルロース（ＣＭＣ）／スチレン-ブタジエンゴム（ＳＢＲ）＝９５／３／２（質量比）の割合で混合し、このスラリーを厚さ１０μｍの銅箔からなる負極集電体に塗布し，乾燥した後、圧延して厚み１２５μmの負極を作製した。正負集電体への活物質の塗布量は、設計基準となる充電電圧４．２Ｖにおいて、正極と負極の対向する部分での充電容量比（負極充電容量／正極充電容量）が１．１となるように調整した。 Using the modified graphite produced above, the mixture was mixed at a ratio of modified graphite / carboxymethyl cellulose (CMC) / styrene-butadiene rubber (SBR) = 95/3/2 (mass ratio), and this slurry was mixed with a thickness of 10 μm. It was applied to a negative electrode current collector made of copper foil, dried, and then rolled to prepare a negative electrode having a thickness of 125 μm. The amount of the active material applied to the positive and negative current collectors is 1.1 at a charging capacity ratio (negative electrode charging capacity / positive electrode charging capacity) at the portion where the positive electrode and the negative electrode face each other at a charging voltage of 4.2 V, which is a design standard. It adjusted so that it might become.
[電解質の作製]
エチレンカーボネート２０体積％、エチレンカルボネート５０体積％、ジエチルカーボネート３０体積％の比率で混合した混合溶媒に、ＬｉＰＦ6を１mol／Ｌの割合で溶解し、この溶液を非水電解質とした。
[Preparation of electrolyte]
LiPF6 was dissolved at a rate of 1 mol / L in a mixed solvent in which 20% by volume of ethylene carbonate, 50% by volume of ethylene carbonate, and 30% by volume of diethyl carbonate were mixed, and this solution was used as a nonaqueous electrolyte.
[電池の作製]
上記の正極と負極とを、両者の間にポリエチレン製微多孔膜からなるセパレータを介して巻回して電極体となし、これと上記電解質を角形電池缶に収容し電池缶の開口をカシメ封口することにより、理論容量７００ｍｈＡの角形非水電解質二次電池を作製した。
[Production of battery]
The positive electrode and the negative electrode are wound with a separator made of a polyethylene microporous film between them to form an electrode body, and the electrolyte and the electrolyte are accommodated in a rectangular battery can and the opening of the battery can is sealed. Thus, a prismatic nonaqueous electrolyte secondary battery having a theoretical capacity of 700 mhA was produced.
（実施例２）
改質黒鉛の作製に際して、水素プラズマ雰囲気中に保持する時間を４５分間とし、原料黒鉛に対する膨張率を１.４としたこと以外はすべて上記実施例１と同様にして、実施例２に係る非水電解質二次電池を作製した。
(Example 2)
In the production of the modified graphite, the same as in Example 1 except that the time for maintaining in the hydrogen plasma atmosphere was 45 minutes and the coefficient of expansion relative to the raw material graphite was 1.4. A water electrolyte secondary battery was produced.
（実施例３）
負極活物質の作製に際して、水素プラズマ雰囲気中に保持する時間を１０分間とし、原料黒鉛に対する膨張率を１.１としたこと以外はすべて上記実施例１と同様にして、実施例３に係る非水電解質二次電池を作製した。
(Example 3)
In producing the negative electrode active material, the same as in Example 1 above except that the time in the hydrogen plasma atmosphere was kept for 10 minutes and the coefficient of expansion relative to the raw material graphite was 1.1. A water electrolyte secondary battery was produced.
（比較例１）
改質黒鉛の作製に際して、水素プラズマ雰囲気中に保持する時間を６０分間とし、原料黒鉛に対する膨張率を１.５としたこと以外はすべて上記実施例１と同様にして、比較例１に係る非水電解質二次電池を作製した。
(Comparative Example 1)
In producing the modified graphite, the same as in Example 1 except that the time in the hydrogen plasma atmosphere was maintained for 60 minutes and the expansion coefficient for the raw material graphite was 1.5. A water electrolyte secondary battery was produced.
（比較例２）
改質黒鉛の作製に際して、水素プラズマ雰囲気中に保持する時間を９５分間とし、原料黒鉛に対する膨張率を１.７としたこと以外はすべて上記実施例１と同様にして、比較例２に係る非水電解質二次電池を作製した。
(Comparative Example 2)
In the production of the modified graphite, the same as in Example 1 except that the time in the hydrogen plasma atmosphere was maintained for 95 minutes and the coefficient of expansion relative to the raw material graphite was 1.7. A water electrolyte secondary battery was produced.
（比較例３）
改質黒鉛の作製に際して、水素プラズマ雰囲気の温度を９００℃とし、水素プラズマ雰囲気中に保持する時間を５５分間とし、原料黒鉛に対する膨張率を１.４としたこと以外はすべて上記実施例１と同様にして、比較例３に係る非水電解質二次電池を作製した。
(Comparative Example 3)
In the production of the modified graphite, the temperature of the hydrogen plasma atmosphere was set to 900 ° C., the time for holding in the hydrogen plasma atmosphere was set to 55 minutes, and the expansion coefficient for the raw material graphite was set to 1.4. Similarly, a nonaqueous electrolyte secondary battery according to Comparative Example 3 was produced.
（比較例４）
改質黒鉛の作製に際して、水素プラズマ雰囲気中に保持する時間を８分間とし、原料黒鉛に対する膨張率を１.０５としたこと以外はすべて上記実施例１と同様にして、比較例４に係る非水電解質二次電池を作製した。
(Comparative Example 4)
In producing the modified graphite, the same as in Example 1 except that the time for maintaining in the hydrogen plasma atmosphere was 8 minutes and the expansion coefficient for the raw material graphite was 1.05. A water electrolyte secondary battery was produced.
（比較例５）
改質黒鉛の作製に際して、水素プラズマ雰囲気中に保持する水素プラズマ処理を全く行わなかったこと以外はすべて上記実施例１と同様にして、比較例５に係る非水電解質二次電池を作製した。なお、この比較例５は、天然黒鉛に対し酸化処理を行ったが、水素プラズマ処理を行わなかったものである。
(Comparative Example 5)
A non-aqueous electrolyte secondary battery according to Comparative Example 5 was produced in the same manner as in Example 1 except that the modified graphite was not subjected to any hydrogen plasma treatment held in a hydrogen plasma atmosphere. In Comparative Example 5, the natural graphite was oxidized, but the hydrogen plasma treatment was not performed.
（比較例６）
原料の天然黒鉛に対し酸化処理および水素プラズマ処理の双方を行うことなく、天然黒鉛をそのまま用いて負極を作製したこと以外はすべて上記実施例１と同様にして、比較例６に係る非水電解質二次電池を作製した。
(Comparative Example 6)
The non-aqueous electrolyte according to Comparative Example 6 was the same as Example 1 except that the negative electrode was produced using natural graphite as it was without performing both oxidation treatment and hydrogen plasma treatment on the raw natural graphite. A secondary battery was produced.
（比較例７）
天然黒鉛に対し酸化処理を行わないで、１０００℃の水素プラズマ雰囲気中に４５分間保持する水素プラズマ処理のみを行い、この処理済み黒鉛を負極活物質としたこと以外はすべて上記実施例１と同様にして、比較例７に係る非水電解質二次電池を作製した。なお、比較例７は、天然黒鉛に対し水素プラズマ処理のみを行ったものである。
(Comparative Example 7)
All the same as Example 1 except that natural graphite was not oxidized, only hydrogen plasma treatment was performed for 45 minutes in a hydrogen plasma atmosphere at 1000 ° C., and this treated graphite was used as the negative electrode active material. Thus, a nonaqueous electrolyte secondary battery according to Comparative Example 7 was produced. In Comparative Example 7, only natural hydrogen plasma treatment was performed on natural graphite.
[処理済黒鉛の電気化学特性]
上記で作製した各電池の充電容量および放電容量を測定し充放電効率を調べた。また、３００サイクル特性を調べた。具体的には、各電池に対して、２５℃において７００ｍAで電池電圧４．２Ｖまで定電流充電し、更に電池電圧４．２Vで充電電流が３５mAになるまで定電圧充電した。次いで、７００ｍAで２．７５Vまで定電流放電して１サイクル目の放電容量を測定し、再び上記と同様な条件で２サイクル目の充電と放電を行うという繰り返しを３００サイクル続けた。１サイクル目の充電容量と放電容量の比を充放電効率とし、１サイクル目の放電容量（初期放電容量）に対する３００サイクル目の放電容量率を３００サイクル特性とした。これらの測定結果を表１，２に示す。
[Electrochemical properties of treated graphite]
The charge capacity and discharge capacity of each of the batteries prepared above were measured to investigate the charge / discharge efficiency. In addition, 300 cycle characteristics were examined. Specifically, each battery was charged at a constant current of 700 mA at 25 ° C. to a battery voltage of 4.2 V, and further charged at a battery voltage of 4.2 V until the charging current reached 35 mA. Next, a constant current was discharged at 700 mA to 2.75 V, the discharge capacity of the first cycle was measured, and the second cycle of charging and discharging was repeated again under the same conditions as described above for 300 cycles. The ratio between the charge capacity and the discharge capacity at the first cycle was defined as charge / discharge efficiency, and the discharge capacity ratio at the 300th cycle relative to the discharge capacity (initial discharge capacity) at the first cycle was defined as 300 cycle characteristics. The measurement results are shown in Tables 1 and 2.
上記表１、２において、黒鉛の膨張率が大きくなるに従って充電容量が大きくなる傾向が認められた。しかし、膨張率が１.４を超える比較例１および２では、充放電効率７７.２％〜７９.９％と低く、かつ300サイクル特性が１２％〜５６％と低かった。これに対し、膨張率が１.１〜１.４である実施例１〜３は充放電効率が８８.９％〜９０.2％と高く、また300サイクル特性も、７８％〜８０％と高かった。 In the said Table 1, 2, the tendency for charge capacity to become large was recognized as the expansion coefficient of graphite became large. However, in Comparative Examples 1 and 2 having an expansion coefficient exceeding 1.4, the charge / discharge efficiency was as low as 77.2% to 79.9%, and the 300 cycle characteristics were as low as 12% to 56%. In contrast, Examples 1 to 3 having an expansion coefficient of 1.1 to 1.4 have a high charge / discharge efficiency of 88.9% to 90.2%, and a 300 cycle characteristic of 78% to 80%. it was high.
他方、水素プラズマ処理温度が９００℃であった比較例３は、膨張率が１.４であるにもかかわらず、充放電効率が６８.９％と低く、また300サイクル特性も６０％と低かった。この原因は水素プラズマ処理温度が９００℃と低かったため、黒鉛結晶層間に入り込んだ酸を十分に除去できなかったためと考えられる。また、膨張率が１.４を超える比較例１および２において、充放電効率が低く、300サイクル特性が悪かったのは、膨張率が１.４を超えると結晶構造の安定性が悪くなるためではないかと考えられる。 On the other hand, in Comparative Example 3 in which the hydrogen plasma treatment temperature was 900 ° C., the charge / discharge efficiency was as low as 68.9% and the 300 cycle characteristics were also as low as 60% despite the expansion coefficient being 1.4. It was. This is presumably because the hydrogen plasma treatment temperature was as low as 900 ° C., so that the acid that entered the graphite crystal layer could not be sufficiently removed. In Comparative Examples 1 and 2 with an expansion coefficient exceeding 1.4, the charge / discharge efficiency was low and the 300 cycle characteristics were poor because the crystal structure stability deteriorated when the expansion coefficient exceeded 1.4. It is thought that.
また、水素プラズマ処理温度が１０００℃であったが、膨張率が１.０５であった比較例４は、充電容量が低かった。これはリチウム層間が狭いために、そこに入り込めるリチウムイオン量が少ないためと考えられる。 Moreover, although the hydrogen plasma processing temperature was 1000 degreeC, the comparative example 4 whose expansion coefficient was 1.05 had low charge capacity. This is presumably because the amount of lithium ions that can enter the lithium layer is small because the lithium layer is narrow.
また、酸化処理を行ったが、水素プラズマ処理を行わない比較例５は、充放電効率が６０.４％と低く、サイクル特性が１２９サイクルで５％（表２参照）と極端に低下した。この原因は、黒鉛結晶中に酸が残存し、かつダングリングボンドが存在するため、結晶構造が物理化学的に不安定であるためであると考えられる。 Further, in Comparative Example 5 in which the oxidation treatment was performed but the hydrogen plasma treatment was not performed, the charge / discharge efficiency was as low as 60.4%, and the cycle characteristics were extremely reduced to 5% (see Table 2) at 129 cycles. This is considered to be because the crystal structure is unstable physicochemically because acid remains in the graphite crystal and dangling bonds exist.
また、酸化処理および水素プラズマ処理の双方を行わなかった比較例６の結果から、未処理の天然黒鉛は充電容量が小さいので、当然なこととして放電電容量も小さいことが認められた。また酸化処理および水素プラズマ処理の双方を行わなかった比較例６と、水素プラズマ処理のみを行った比較例７との比較から、水素プラズマ処理のみを行っても、充電容量や放電容量の向上がないことが認められた。 Further, from the result of Comparative Example 6 in which neither the oxidation treatment nor the hydrogen plasma treatment was performed, it was recognized that the untreated natural graphite had a small charge capacity, and therefore, the discharge capacity was also small. Further, from comparison between Comparative Example 6 in which neither the oxidation treatment nor the hydrogen plasma treatment was performed and Comparative Example 7 in which only the hydrogen plasma treatment was performed, even when only the hydrogen plasma treatment was performed, the charge capacity and the discharge capacity were improved. It was recognized that there was no.
以上の結果により、原料黒鉛に対し、酸化処理と１０００℃以上の温度での水素プラズマ処理とを共に行うと、充電容量が高まると共に、充放電効率が高まるため、放電容量を向上させることができる。また、１０００℃以上の温度での水素プラズマ処理は、サイクル特性を顕著に向上させることが明らかになった。また、酸化処理と水素プラズマ処理後の膨張率は、１.１以上、１.４以下とする必要があることが明らかとなった。なお、１０００℃以上の温度での水素プラズマ処理は黒鉛の結晶構造を安定化させる効果があるものと推察される。 Based on the above results, when both the oxidation treatment and the hydrogen plasma treatment at a temperature of 1000 ° C. or higher are performed on the raw graphite, the charge capacity is increased and the charge / discharge efficiency is increased, so that the discharge capacity can be improved. . It has also been clarified that hydrogen plasma treatment at a temperature of 1000 ° C. or higher significantly improves cycle characteristics. Moreover, it became clear that the expansion coefficient after oxidation treatment and hydrogen plasma treatment needs to be 1.1 or more and 1.4 or less. It is assumed that hydrogen plasma treatment at a temperature of 1000 ° C. or higher has an effect of stabilizing the crystal structure of graphite.
（その他の事項）
（１）上記ではリチウムイオンを吸蔵放出することのできるリチウム遷移金属複合酸化物として、コバルト酸リチウムを用いたが、これに限られるものではない。リチウムイオンを吸蔵放出することのできるリチウム遷移金属複合酸化物としては、例えばＬｉＮｉＯ２、ＬｉＭｎ２Ｏ４、ＬｉＭｎＯ２、ＬｉＦｅＯ２、ＬｉＭｎ１／３Ｎｉ１／３Ｃｏ１／３Ｏ２などや、これらの遷移金属を他の元素で置換したものなどが例示でき、これらを単独で用いたり、２種類以上を混合して用いることができる。
(Other matters)
(1) Although lithium cobaltate was used as the lithium transition metal composite oxide capable of occluding and releasing lithium ions in the above, it is not limited to this. Examples of the lithium transition metal composite oxide capable of occluding and releasing lithium ions include LiNiO 2 , LiMn 2 O 4 , LiMnO 2 , LiFeO 2 , LiMn 1/3 Ni 1/3 Co 1/3 O 2, etc. The thing which substituted these transition metals with the other element etc. can be illustrated, These can be used individually or can be used in mixture of 2 or more types.
（２）また、上記では原料黒鉛として、天然黒鉛を用いたが、本発明の適用は天然黒鉛に限られない。結晶性を有する黒鉛であれば天然黒鉛、人工黒鉛を問わず本発明を適用でき、充放電効率の改善等の効果が得られる。 (2) Moreover, although natural graphite was used as raw material graphite in the above, application of this invention is not restricted to natural graphite. The present invention can be applied to any graphite having crystallinity regardless of natural graphite or artificial graphite, and effects such as improvement of charge / discharge efficiency can be obtained.
（３）また、上記実施例では、酸化処理を濃硫酸と濃硝酸の９/１質量比混合液で行ったが、混合比率はこれに限定されるものではない。また、濃硫酸や濃硝酸以外の酸を用いてもよい。例えば、過酸化水素、塩素酸カリウム、無水クロム酸などが使用できる。 (3) Moreover, in the said Example, although the oxidation process was performed with the 9/1 mass ratio liquid mixture of concentrated sulfuric acid and concentrated nitric acid, a mixing ratio is not limited to this. An acid other than concentrated sulfuric acid or concentrated nitric acid may be used. For example, hydrogen peroxide, potassium chlorate, chromic anhydride, etc. can be used.
本発明によると、黒鉛の持つリチウムイオンを吸蔵放出することのできる能力を増強しつつ、従来問題となっていた黒鉛を酸化処理した場合における諸問題点を解消できる。このような本発明によると、放電容量が大きく、サイクル寿命に優れたリチウム二次電池を生産性よく製造することができるので、その産業上の利用可能性は大きい。
According to the present invention, while the ability of graphite to absorb and release lithium ions is enhanced, various problems in the case of oxidizing graphite, which has been a problem in the past, can be solved. According to the present invention as described above, a lithium secondary battery having a large discharge capacity and an excellent cycle life can be manufactured with high productivity, so that its industrial applicability is great.
Claims (3)
前記酸化黒鉛を、１０００℃以上の水素プラズマ雰囲気中で熱処理することにより、前記原料黒鉛に対する膨張率が１.１以上、１.４以下である改質黒鉛を作製する水素プラズマ処理工程と、
を備える非水電解質二次電池用改質黒鉛の製造方法。 An oxidation treatment step of oxidizing raw material graphite into graphite oxide;
A hydrogen plasma treatment step of producing a modified graphite having an expansion coefficient of 1.1 to 1.4 with respect to the raw graphite by heat-treating the graphite oxide in a hydrogen plasma atmosphere at 1000 ° C. or higher;
A method for producing modified graphite for a non-aqueous electrolyte secondary battery.
前記原料黒鉛が天然黒鉛である、非水電解質二次電池用の改質黒鉛の製造方法。 In the manufacturing method of the modified graphite for nonaqueous electrolyte secondary batteries according to claim 1,
A method for producing modified graphite for a non-aqueous electrolyte secondary battery, wherein the raw graphite is natural graphite.
請求項１又は２に記載の非水電解質二次電池用の改質黒鉛を、負極活物質として負極集電体に結着し黒鉛負極となす黒鉛負極作製工程と、
リチウムイオンを吸蔵放出可能なリチウム遷移金属複合酸化物を、正極活物質として正極集電体に結着し正極となす正極作製工程と、
セパレータを介在させて前記黒鉛負極と前記正極とを対向させる電極体作製工程と
を備える非水電解質二次電池の製造方法。
In a method for producing a graphite negative electrode for a non-aqueous electrolyte secondary battery,
A graphite negative electrode preparation step in which the modified graphite for a non-aqueous electrolyte secondary battery according to claim 1 or 2 is bound as a negative electrode active material to a negative electrode current collector to become a graphite negative electrode,
A positive electrode preparation step of binding a lithium transition metal composite oxide capable of occluding and releasing lithium ions to a positive electrode current collector as a positive electrode active material;
A method for producing a nonaqueous electrolyte secondary battery, comprising: an electrode body manufacturing step in which a separator is interposed and the graphite negative electrode and the positive electrode are opposed to each other.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006092126A JP2007265915A (en) | 2006-03-29 | 2006-03-29 | Reformed graphite for nonaqueous electrolyte secondary battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006092126A JP2007265915A (en) | 2006-03-29 | 2006-03-29 | Reformed graphite for nonaqueous electrolyte secondary battery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2007265915A true JP2007265915A (en) | 2007-10-11 |
Family
ID=38638693
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2006092126A Pending JP2007265915A (en) | 2006-03-29 | 2006-03-29 | Reformed graphite for nonaqueous electrolyte secondary battery |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2007265915A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011216231A (en) * | 2010-03-31 | 2011-10-27 | Jx Nippon Oil & Energy Corp | Carbon material for lithium ion secondary battery, and electrode using the same |
| KR101098376B1 (en) * | 2010-06-07 | 2011-12-26 | 인하대학교 산학협력단 | Method for manufacturing the anode material for lithium ion capacitor |
| CN102557019A (en) * | 2011-12-27 | 2012-07-11 | 黑龙江科技学院 | Method and device for producing high-purity natural graphite |
| KR20150098548A (en) * | 2014-02-20 | 2015-08-28 | 썬쩐 비티아르 뉴 에너지 머티어리얼스 아이엔씨이 | A graphene-based composite material preparation method, anode materials and lithium ion battery |
| WO2016157508A1 (en) * | 2015-03-27 | 2016-10-06 | Nec Corporation | Boron-doped activated carbon material |
-
2006
- 2006-03-29 JP JP2006092126A patent/JP2007265915A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011216231A (en) * | 2010-03-31 | 2011-10-27 | Jx Nippon Oil & Energy Corp | Carbon material for lithium ion secondary battery, and electrode using the same |
| KR101098376B1 (en) * | 2010-06-07 | 2011-12-26 | 인하대학교 산학협력단 | Method for manufacturing the anode material for lithium ion capacitor |
| CN102557019A (en) * | 2011-12-27 | 2012-07-11 | 黑龙江科技学院 | Method and device for producing high-purity natural graphite |
| CN102557019B (en) * | 2011-12-27 | 2013-07-24 | 黑龙江科技学院 | Method and device for producing high-purity natural graphite |
| KR20150098548A (en) * | 2014-02-20 | 2015-08-28 | 썬쩐 비티아르 뉴 에너지 머티어리얼스 아이엔씨이 | A graphene-based composite material preparation method, anode materials and lithium ion battery |
| KR101631590B1 (en) | 2014-02-20 | 2016-06-20 | 썬쩐 비티아르 뉴 에너지 머티어리얼스 아이엔씨이 | A graphene-based composite material preparation method, anode materials and lithium ion battery |
| WO2016157508A1 (en) * | 2015-03-27 | 2016-10-06 | Nec Corporation | Boron-doped activated carbon material |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP6238251B2 (en) | Porous silicon-based negative electrode active material and lithium secondary battery including the same | |
| CN107615531B (en) | Transition metal-containing composite hydroxide and method for producing same, nonaqueous electrolyte secondary battery and positive electrode active material for same, and method for producing same | |
| JP6037052B2 (en) | Porous silicon-based particles, production method thereof, and negative electrode active material including the same | |
| JP3902611B2 (en) | Negative electrode composition for lithium battery and negative electrode and lithium battery employing the same | |
| US9831500B2 (en) | Porous electrode active material and secondary battery including the same | |
| JP2007335325A (en) | Cathode active material for nonaqueous electrolyte secondary battery and battery | |
| JP2009238659A (en) | Lithium secondary battery, and method of manufacturing the same | |
| JP7128290B2 (en) | Negative electrode active material for lithium secondary battery and lithium secondary battery including the same | |
| JP6269837B2 (en) | Lithium secondary battery | |
| JP2009245917A (en) | Positive electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing same, and positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery | |
| US11677065B2 (en) | Cathode active material of lithium secondary battery | |
| JP2010055777A (en) | Method for manufacturing positive active material and positive active material | |
| JP2007265915A (en) | Reformed graphite for nonaqueous electrolyte secondary battery | |
| JP2010225366A (en) | Nonaqueous electrolyte secondary battery | |
| JP2013110049A (en) | Positive electrode collector foil for lithium ion secondary battery, and lithium ion secondary battery | |
| JP2016503569A (en) | Conductive material for secondary battery and electrode for lithium secondary battery including the same | |
| KR101226107B1 (en) | Anode active material for lithium secondary battery And Lithium secondary battery comprising the same | |
| KR101722960B1 (en) | Negative active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same | |
| JP2005135755A (en) | Method of manufacturing carbon material for negative electrode of nonaqueous secondary battery and nonaqueous secondary battery using same | |
| KR20090103807A (en) | Lithum secondary battery and manufacturing method thereof | |
| JP2010257982A (en) | Anode active material for lithium secondary battery, and lithium secondary battery including the same | |
| EP3852173A1 (en) | Cathode active material, method for preparing same, and lithium secondary battery comprising same | |
| KR101976252B1 (en) | Manufacturing method of graphites for lithium-ion battery anode materials and Manufacturing Method lithium-ion battery electrode using graphites manufactured by the method | |
| KR100991358B1 (en) | Anode active material for lithium secondary battery and Method for preparing thereof and Lithium secondary battery containing the same for anode | |
| JP2003257419A (en) | Nonaqueous secondary battery |