JP2002141062A - Graphite/carbon complex material for lithium secondary battery anode, its manufacturing method and lithium secondary battery - Google Patents
Graphite/carbon complex material for lithium secondary battery anode, its manufacturing method and lithium secondary batteryInfo
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- JP2002141062A JP2002141062A JP2000335837A JP2000335837A JP2002141062A JP 2002141062 A JP2002141062 A JP 2002141062A JP 2000335837 A JP2000335837 A JP 2000335837A JP 2000335837 A JP2000335837 A JP 2000335837A JP 2002141062 A JP2002141062 A JP 2002141062A
- Authority
- JP
- Japan
- Prior art keywords
- graphite
- carbon
- secondary battery
- composite material
- 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.)
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- 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
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、大容量で、高電位
で、充放電サイクル特性に優れ、且つ電解液の分解を防
止したリチウム二次電池負極用黒鉛―炭素複合材料、そ
の製造方法、及び同複合材料を備えたリチウム二次電池
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphite-carbon composite material for a negative electrode of a lithium secondary battery, which has a large capacity, a high potential, excellent charge-discharge cycle characteristics, and prevents decomposition of an electrolytic solution. And a lithium secondary battery including the composite material.
【０００２】[0002]
【従来の技術】電子機器の小型軽量化に伴い、電池の高
エネルギー密度化が要求されている。また、省資源の観
点からも、繰り返し充放電が可能な高性能の二次電池の
開発が要求されている。このような要求に応えることを
目的として、リチウム二次電池が提案され、開発が続け
られている。リチウム二次電池は、電解質の種類によっ
て、リチウムイオン二次電池、リチウムポリマー二次電
池、全固体リチウム二次電池等に分類される。2. Description of the Related Art As electronic devices become smaller and lighter, batteries are required to have higher energy density. Also, from the viewpoint of resource saving, development of a high-performance secondary battery capable of repeatedly charging and discharging is demanded. To meet such demands, lithium secondary batteries have been proposed and are being developed. Lithium secondary batteries are classified into lithium ion secondary batteries, lithium polymer secondary batteries, all-solid lithium secondary batteries, and the like, depending on the type of electrolyte.
【０００３】これらの二次電池のうち、リチウムイオン
二次電池はリチウム化合物で正極を構成し、炭素材料で
負極を構成するものである。この電池を充電すると、負
極においてはリチウムイオンが炭素材料にドーピングさ
れ、いわゆる炭素−リチウム層間化合物が形成される。
一方、放電時には、炭素材料の層間からリチウムイオン
が脱ドーピングされ、リチウムイオンは再び正極に移動
してリチウム化合物に戻る。このような機構で、リチウ
ムイオン二次電池は充放電を繰り返すことができる。[0003] Among these secondary batteries, a lithium ion secondary battery has a positive electrode composed of a lithium compound and a negative electrode composed of a carbon material. When the battery is charged, lithium ions are doped into the carbon material in the negative electrode, so that a so-called carbon-lithium intercalation compound is formed.
On the other hand, at the time of discharging, lithium ions are dedoped from between layers of the carbon material, and the lithium ions move to the positive electrode again and return to the lithium compound. With such a mechanism, the lithium ion secondary battery can repeat charging and discharging.
【０００４】リチウムイオン二次電池の負極としては、
黒鉛系負極と炭素系負極とがある。炭素系負極の放電容
量は、実用性を無視して長時間の放電を行なう場合には
６００ｍＡｈ／ｇ以上であるが、実用的な使用条件では
２５０〜３００ｍＡｈ／ｇ程度である。これに対して、
黒鉛系負極の放電容量は、実用的な使用条件においても
３５０〜３７０ｍＡｈ／ｇと優れている。[0004] As a negative electrode of a lithium ion secondary battery,
There are graphite-based negative electrodes and carbon-based negative electrodes. The discharge capacity of the carbon-based negative electrode is 600 mAh / g or more when discharging for a long time ignoring practicality, but is about 250 to 300 mAh / g under practical use conditions. On the contrary,
The discharge capacity of the graphite-based negative electrode is excellent at 350 to 370 mAh / g even under practical use conditions.
【０００５】また、炭素系負極は、黒鉛系負極と比較し
て炭素材料の密度が低く、放電圧も低い。従って、エネ
ルギー密度の高い電池を製造するためには、黒鉛系負極
を採用することが好ましい。[0005] The carbon-based negative electrode has a lower carbon material density and a lower discharge voltage than a graphite-based negative electrode. Therefore, in order to manufacture a battery having a high energy density, it is preferable to employ a graphite-based negative electrode.
【０００６】しかしながら、黒鉛系負極を使用する場
合、電池の電解液を構成する溶媒と黒鉛とが反応し、電
池のクーロン効率が低下すると共に、溶媒が分解してガ
スを発生する。密閉された電池内にガスが発生すると、
電池の内部圧が上昇して電池が爆発する危険性がある。[0006] However, when a graphite-based negative electrode is used, the solvent constituting the electrolyte of the battery reacts with the graphite to reduce the Coulomb efficiency of the battery and to decompose the solvent to generate gas. When gas is generated in the sealed battery,
There is a danger that the battery will explode due to an increase in the internal pressure of the battery.
【０００７】リチウムイオン二次電池に用いる電解液の
主溶媒としては、エチレンカーボネード（以下ＥＣと略
す）、プロピレンカーボネード（以下ＰＣと略す）等の
炭酸エステル類が多い。これらの主溶媒に、ＬｉＰＦ6
或はＬｉＢＦ4等の電解質を添加混合して電解液として
いる。ＥＣやＰＣ等の溶媒が、電解液の主溶媒として多
く使用されている理由は、これらの溶媒は高い比誘電
率、広い作用温度範囲等の好ましい溶媒特性を有するか
らである。中でもＰＣは低温で使用できる溶媒である。[0007] As a main solvent of an electrolytic solution used for a lithium ion secondary battery, there are many carbonates such as ethylene carbonate (hereinafter abbreviated as EC) and propylene carbonate (hereinafter abbreviated as PC). LiPF 6
Alternatively, an electrolyte such as LiBF 4 is added and mixed to form an electrolyte. Solvents such as EC and PC are often used as the main solvent of the electrolytic solution because these solvents have preferable solvent characteristics such as a high dielectric constant and a wide operating temperature range. Among them, PC is a solvent that can be used at low temperatures.
【０００８】しかし、ＰＣを含む電解液と黒鉛系負極と
を電池中で共存させると、ＰＣが分解してガスを発生す
る。ＰＣの分解は、電池の負極に黒鉛を用いる場合にの
み見られる現象であり、炭素系負極を用いる場合には見
られない現象である。However, if an electrolyte containing PC and a graphite-based negative electrode coexist in a battery, the PC is decomposed to generate gas. The decomposition of PC is a phenomenon that is observed only when graphite is used for the negative electrode of a battery, and is a phenomenon that is not observed when a carbon-based negative electrode is used.
【０００９】従来は、この問題を解決するために、黒鉛
粒子の表面をＰＣを分解しない低結晶性炭素又は非晶質
性炭素で被覆する方法が提案されている。これに対し、
本発明者らは、黒鉛粒子の全表面を結晶性の炭素で均一
に被覆することにより、上記の問題を解決することがで
きることを発見し、特許出願を行なった。（特開２００
０−１０６１８２号公報）。即ち、化学蒸着法を用いて
黒鉛粒子の表面を結晶性炭素で均一、かつ完全に被覆し
た黒鉛−炭素複合材料をリチウムイオン二次電池の負極
として用いる場合、この負極はＰＣ等の分解を確実に抑
制する。これは、形成される被覆層が結晶性炭素であっ
ても黒鉛ではないので溶媒を分解しないこと、及び黒鉛
の表面を結晶性炭素の００２面で被覆しているため、複
合材料粒子の内部に溶媒が浸透しない事がその理由であ
ると考えられる。更に、この負極材を用いて得られる電
池は放電容量が高く、高速充電が可能であり、従来の低
結晶性炭素で被覆された負極材料よりも優れた電極性能
を有している。Hitherto, in order to solve this problem, there has been proposed a method of coating the surface of graphite particles with low crystalline carbon or amorphous carbon which does not decompose PC. In contrast,
The present inventors have discovered that the above problem can be solved by uniformly coating the entire surface of the graphite particles with crystalline carbon, and have filed a patent application. (Japanese Patent Laid-Open No. 200
0-106182). That is, when a graphite-carbon composite material in which the surface of graphite particles is uniformly and completely coated with crystalline carbon by using a chemical vapor deposition method is used as a negative electrode of a lithium ion secondary battery, this negative electrode ensures decomposition of PC and the like. To suppress. This is because even if the coating layer to be formed is crystalline carbon, it is not graphite, so it does not decompose the solvent. Further, since the surface of graphite is coated with the 002 surface of crystalline carbon, the inside of the composite material particles It is considered that the reason is that the solvent does not penetrate. Further, a battery obtained using this negative electrode material has a high discharge capacity, can be charged at high speed, and has better electrode performance than a conventional negative electrode material coated with low crystalline carbon.
【００１０】[0010]
【発明が解決しようとする課題】しかしながら、黒鉛粒
子を結晶性炭素又は低結晶性炭素で被覆した複合材料
は、その被覆層の機械的強度が高いため、電池のエネル
ギー密度を高くすることができないという新たな問題が
発生した。黒鉛−炭素複合材料に少量のバインダーを加
え、集電体と共に成形して電極とする際に、成形体にお
ける複合材料の密度（電極密度と略す）は、電池のエネ
ルギー密度及び充放電速度を決定する因子となる。電極
密度が高いほどエネルギー密度が高くなるが、充放電速
度を高くするためには成形体の内部に電解液を保持する
空隙が必要である。このため、電極密度は１．４〜１．
７ｇ／ｃｍ3とすることが最も好ましい。黒鉛粒子自体
は比較的柔らかい粒子であるが、黒鉛粒子の表面を炭素
で被覆した複合材料は、その被覆層が低結晶性炭素であ
る場合も、高結晶性炭素である場合も被覆量に比例して
剛性が高くなる。このため、加圧しても複合材料粒子が
変形して高密度になり難く、その結果電極密度が１．２
５〜１．３５ｇ／ｃｍ3と低下する。従って、上記の好
ましい電極密度を達成することができず、 黒鉛系負極
が本来備えている、高エネルギー密度という特性を十分
に発揮することができなくなっている。However, a composite material in which graphite particles are coated with crystalline carbon or low-crystalline carbon cannot increase the energy density of the battery because the coating layer has high mechanical strength. A new problem has arisen. When a small amount of a binder is added to a graphite-carbon composite material and molded together with a current collector to form an electrode, the density of the composite material in the molded body (abbreviated as electrode density) determines the energy density and charge / discharge rate of the battery. Factor. The higher the electrode density, the higher the energy density. However, in order to increase the charge / discharge rate, a void for holding the electrolyte is required inside the molded body. For this reason, the electrode density is 1.4 to 1.
Most preferably, it is 7 g / cm 3 . Graphite particles themselves are relatively soft particles.However, the composite material in which the surface of the graphite particles is coated with carbon is proportional to the coating amount regardless of whether the coating layer is low-crystalline carbon or high-crystalline carbon. This increases the rigidity. For this reason, even if pressure is applied, the composite material particles are unlikely to be deformed and become high in density, and as a result, the electrode density becomes
It decreases to 5 to 1.35 g / cm 3 . Therefore, the above-mentioned preferable electrode density cannot be achieved, and the characteristic of a high energy density inherently provided in the graphite-based negative electrode cannot be sufficiently exhibited.
【００１１】複合材料の被覆炭素量を少なくすれば、電
極密度は高くなる。しかしこの場合は黒鉛粒子の被覆が
不完全になるため、溶媒の分解を抑制する機能が不完全
となり、その結果クーロン効率が低下したり、電池の安
全性の確保が困難になる。逆に、被覆炭素量を多くすれ
ば、溶媒の分解を抑制する機能は確保できるが、黒鉛粒
子の存在割合が減少するのでエネルギー密度を高くする
ことができない。When the amount of carbon coated on the composite material is reduced, the electrode density increases. However, in this case, the coating of the graphite particles is incomplete, so that the function of suppressing the decomposition of the solvent is incomplete, and as a result, the Coulomb efficiency is reduced and it is difficult to ensure the safety of the battery. Conversely, if the amount of coated carbon is increased, the function of suppressing the decomposition of the solvent can be ensured, but the energy density cannot be increased because the proportion of the graphite particles decreases.
【００１２】本発明者等はこれらの点について研究を重
ねた結果、黒鉛粒子に被覆層を形成する化学蒸着処理を
行なう前に、黒鉛粒子を一旦酸化処理すると、炭素被覆
層による溶媒の分解抑制効果が増強されることを発見し
た。即ち、酸化処理した黒鉛粒子を核として用いて、そ
の表面に化学蒸着により炭素被覆層を形成すると、溶媒
の分解を抑制する効果が飛躍的に向上し、従来と比較し
て被覆炭素量を大幅に減少させることができること、被
覆炭素量を少なくできれば、得られる複合材料の剛性が
低下して高密度化しやすくなり、これによって負極材の
電極密度を最適な値にすることができると共に、同じ放
電容量の場合は電池の体積を減少させて小型化できるこ
と等を知得した。As a result of repeated studies on these points, the present inventors have found that if the graphite particles are once oxidized before the chemical vapor deposition process for forming a coating layer on the graphite particles, the decomposition of the solvent by the carbon coating layer is suppressed. The effect was found to be enhanced. That is, when a carbon coating layer is formed on the surface of the oxidized graphite particles by chemical vapor deposition using the graphite particles as nuclei, the effect of suppressing the decomposition of the solvent is dramatically improved, and the amount of coated carbon is significantly increased as compared with the conventional case. If the amount of coated carbon can be reduced, the rigidity of the obtained composite material will be reduced, and it will be easy to increase the density. In the case of capacity, it has been found that the size of the battery can be reduced by reducing the volume of the battery.
【００１３】本発明は上記知見に基づいて完成するに至
ったもので、その目的とするところは、大容量で、高電
位で、充放電サイクル特性に優れ、更に電解液の分解を
防止したリチウム二次電池負極用炭素−黒鉛複合材料、
その製造方法、及び同複合材料を用いたリチウム二次電
池を提供することにある。The present invention has been completed on the basis of the above findings, and it is an object of the present invention to provide a lithium battery having a large capacity, a high potential, excellent charge / discharge cycle characteristics, and further preventing decomposition of an electrolytic solution. Carbon-graphite composite material for secondary battery negative electrode,
It is an object of the present invention to provide a manufacturing method thereof and a lithium secondary battery using the composite material.
【００１４】[0014]
【課題を解決する手段】上記目的を達成する本発明は以
下に示す物である。The present invention to achieve the above object is as follows.
【００１５】〔１〕 酸化処理した黒鉛粒子に、流動床
反応炉を用いて炭素を化学蒸着することを特徴とする黒
鉛粒子の表面に結晶性炭素の被覆層を有してなるリチウ
ム二次電池負極用黒鉛―炭素複合材料の製造方法。[1] A lithium secondary battery comprising a graphite particle having a coating layer of crystalline carbon on the surface of the graphite particle, wherein carbon is chemically deposited on the oxidized graphite particle using a fluidized bed reactor. Manufacturing method of graphite-carbon composite material for negative electrode.
【００１６】〔２〕 酸化処理が、黒鉛粒子を６００〜
８００℃の温度で行う空気酸化処理である〔１〕に記載
のリチウム二次電池負極用黒鉛―炭素複合材料の製造方
法。[2] The oxidation treatment reduces the graphite particles to 600 to
The method for producing a graphite-carbon composite material for a negative electrode of a lithium secondary battery according to [1], which is an air oxidation treatment performed at a temperature of 800 ° C.
【００１７】〔３〕 酸化処理が、黒鉛粒子を酸化する
ことにより黒鉛粒子の質量を０．１〜２０質量％減少さ
せる〔１〕又は〔２〕に記載のリチウム二次電池負極用
黒鉛―炭素複合材料の製造方法。[3] The graphite-carbon for negative electrode of a lithium secondary battery according to [1] or [2], wherein the oxidation treatment reduces the mass of the graphite particles by 0.1 to 20% by mass by oxidizing the graphite particles. Manufacturing method of composite material.
【００１８】〔４〕 炭素の化学蒸着を９００〜１２０
０℃で行なう〔１〕乃至〔３〕の何れかに記載のリチウ
ム二次電池負極用黒鉛―炭素複合材料の製造方法。[4] Chemical vapor deposition of carbon at 900 to 120
The method for producing a graphite-carbon composite material for a negative electrode of a lithium secondary battery according to any one of [1] to [3], which is performed at 0 ° C.
【００１９】〔５〕 炭素の化学蒸着により、黒鉛粒子
に被覆層を２〜１０質量％形成する〔１〕乃至〔４〕の
何れかに記載のリチウム二次電池負極用黒鉛―炭素複合
材料の製造方法。[5] The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to any one of [1] to [4], wherein a coating layer is formed on graphite particles by 2 to 10% by mass by chemical vapor deposition of carbon. Production method.
【００２０】〔６〕 酸化処理した黒鉛粒子と、前記黒
鉛粒子の表面を被覆する結晶性炭素からなる被覆層とか
らなり、前記被覆層の割合が２〜１０質量％であるリチ
ウム二次電池負極用黒鉛―炭素複合材料。[6] A negative electrode for a lithium secondary battery comprising oxidized graphite particles and a coating layer made of crystalline carbon coating the surface of the graphite particles, wherein the ratio of the coating layer is 2 to 10% by mass. Graphite-carbon composite material.
【００２１】〔７〕 黒鉛粒子の全表面が、黒鉛粒子表
面と被覆層の結晶性炭素の００２面とを平行にして結晶
性炭素で被覆されている〔６〕に記載のリチウム二次電
池負極用黒鉛―炭素複合材料。[7] The negative electrode for a lithium secondary battery according to [6], wherein the entire surface of the graphite particles is coated with crystalline carbon such that the surface of the graphite particles and the 002 plane of crystalline carbon of the coating layer are parallel to each other. Graphite-carbon composite material.
【００２２】〔８〕 リチウムイオンをインターカレー
ションした複合材料の7Ｌｉ−ＮＭＲスペクトルが、塩
化リチウム基準ケミカルシフトの４０〜５０ｐｐｍの位
置に黒鉛にインターカレーションしたリチウムの吸収ス
ペクトルと、１０〜２０ｐｐｍの位置に結晶性炭素にイ
ンターカレーションしたリチウムの吸収スペクトルとか
らなる複合スペクトルを有する〔６〕又は〔７〕に記載
のリチウム二次電池負極用黒鉛―炭素複合材料。[8] The 7 Li-NMR spectrum of the composite material in which lithium ions are intercalated shows the absorption spectrum of lithium intercalated into graphite at a position of 40 to 50 ppm of the chemical shift based on lithium chloride, and 10 to 20 ppm. The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to [6] or [7], having a composite spectrum consisting of an absorption spectrum of lithium intercalated into crystalline carbon at the position of (6).
【００２３】[0023]
〔９〕 １００〜４００ｋｇ／ｃｍ2の圧
力で加圧して得られる成形体の密度が１．４ ０〜１．
７０ｇ／ｃｍ3である〔６〕乃至〔８〕の何れかに記載
のリチウム二次電池負極用黒鉛―炭素複合材料 。[9] The density of a molded product obtained by pressing at a pressure of 100 to 400 kg / cm 2 is 1.40 to 1.
The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to any one of [6] to [8], which has a weight of 70 g / cm 3 .
【００２４】〔１０〕 黒鉛粒子が天然黒鉛である
〔６〕乃至[10] The graphite particles are natural graphite [6] to
〔９〕の何れかに記載のリチウム二次電池負
極用黒鉛―炭素複合材料。The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to any one of [9].
【００２５】〔１１〕 〔６〕乃至〔１０〕の何れかに
記載のリチウム二次電池負極用黒鉛―炭素複合材料を用
いて形成したリチウム二次電池。[11] A lithium secondary battery formed using the graphite-carbon composite material for a negative electrode of a lithium secondary battery according to any one of [6] to [10].
【００２６】[0026]
【作用】酸化処理と溶媒の分解抑制効果とを結び付ける
機構は明らかではない。本発明においては、化学蒸着処
理により黒鉛粒子の表面に形成される被覆層が、結晶性
炭素であり、また、黒鉛粒子の全表面が結晶性炭素の０
０２面で被覆されている。 このような被覆層の特徴に
よって、電解液溶媒の分解を抑制する優れた効果が得ら
れるものと推測される。酸化処理は、それ自身は、溶媒
の分解を抑制する効果を与えるものではない。即ち、単
に黒鉛粒子に酸化処理を行うだけでは、黒鉛粒子に溶媒
の分解抑制効果を与えるものではなく、酸化処理の効果
は発現しない。酸化処理の効果は、予め酸化処理した黒
鉛粒子に化学蒸着処理をしてその表面に被覆層を形成す
る場合に発現し、被覆層の溶媒分解阻止作用を飛躍的に
向上させるという潜在的な効果である。The mechanism linking the oxidation treatment with the effect of suppressing the decomposition of the solvent is not clear. In the present invention, the coating layer formed on the surface of the graphite particles by the chemical vapor deposition treatment is made of crystalline carbon, and the entire surface of the graphite particles is made of crystalline carbon.
02 surface. It is presumed that such a feature of the coating layer provides an excellent effect of suppressing the decomposition of the electrolyte solvent. The oxidation treatment itself does not have the effect of suppressing the decomposition of the solvent. That is, simply performing the oxidation treatment on the graphite particles does not provide the graphite particles with the effect of suppressing the decomposition of the solvent, and does not exhibit the effect of the oxidation treatment. The effect of the oxidation treatment is manifested in the case where a coating layer is formed on the surface of a previously oxidized graphite particle by chemical vapor deposition, and the potential effect of dramatically improving the solvent decomposition inhibiting action of the coating layer. It is.
【００２７】酸化処理を施すことにより黒鉛粒子に与え
られた潜在的な効果が、後述するように、被覆層の結晶
性炭素の００２面で黒鉛粒子の全表面を被覆することに
より発現し、その結果少ない被覆炭素量で溶媒の分解を
充分抑制するという効果を発揮する。The potential effect given to the graphite particles by performing the oxidation treatment is exhibited by coating the entire surface of the graphite particles with the 002 plane of the crystalline carbon of the coating layer, as described later. As a result, the effect of sufficiently suppressing the decomposition of the solvent can be exhibited with a small amount of coated carbon.
【００２８】本発明は、被覆炭素量を少なくするため
に、流動床反応炉を用いて被覆層を形成する。少ない被
覆炭素量で十分な電解液溶媒の分解抑制効果を発揮させ
るためには、黒鉛粒子の表面に形成する被覆層は均一
で、かつ黒鉛粒子表面の露出部分がないように黒鉛粒子
の全表面が完全に覆われているものでなければならな
い。この様な被覆層は、流動床反応炉を用いた化学蒸着
処理方法によってのみ実現でき、他の方法では困難であ
る。In the present invention, a coating layer is formed using a fluidized bed reactor in order to reduce the amount of coated carbon. In order to exhibit a sufficient effect of suppressing the decomposition of the electrolyte solvent with a small amount of carbon coating, the coating layer formed on the surface of the graphite particles should be uniform and the entire surface of the graphite particles should be free of exposed parts of the graphite particles. Must be completely covered. Such a coating layer can be realized only by a chemical vapor deposition method using a fluidized bed reactor, and is difficult with other methods.
【００２９】従って、本発明は、黒鉛の酸化処理と流動
床反応炉を用いる化学蒸着処理とを結合することにより
相乗的な作用効果を発揮させることを特徴とするもので
ある。Accordingly, the present invention is characterized in that a synergistic effect is exhibited by combining the oxidation treatment of graphite with the chemical vapor deposition treatment using a fluidized bed reactor.
【００３０】[0030]
【発明の実施の形態】本発明のリチウム二次電池負極用
黒鉛−炭素複合材料は、酸化処理した黒鉛粒子と、その
表面を覆う炭素被覆層とからなる黒鉛−炭素複合材料で
ある。前記被覆層は、化学蒸着処理により形成する、所
定の分子配向を有する結晶性炭素である。DETAILED DESCRIPTION OF THE INVENTION The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to the present invention is a graphite-carbon composite material comprising oxidized graphite particles and a carbon coating layer covering the surface thereof. The coating layer is crystalline carbon having a predetermined molecular orientation and formed by a chemical vapor deposition process.
【００３１】ここで、リチウム二次電池の「負極材料」
としては、主材料である炭素系又は黒鉛系の負極材料以
外にも、ペーストや導電材等の副材料もあるが、本発明
において、リチウム二次電池の「負極材料」という場合
には、特に断りがない限り、主材料である炭素系又は黒
鉛系の負極材料を指すものとする。Here, the "negative electrode material" of the lithium secondary battery
As, in addition to the carbon-based or graphite-based negative electrode material that is the main material, there are also sub-materials such as pastes and conductive materials, but in the present invention, when referred to as `` anode material '' of a lithium secondary battery, Unless otherwise noted, the term refers to a carbon-based or graphite-based negative electrode material that is a main material.
【００３２】黒鉛粒子の製造原料の黒鉛は、天然黒鉛で
も人造黒鉛でもよいが、平均面間隔ｄ002は０．３３６
ｎｍ以下の、高結晶性のものであることが望ましい。
原料の黒鉛は、最大粒子径が１００μｍ以下に粉砕して
あるものが望ましい。平均粒子径は５〜３０μｍが好ま
しく、より好ましくは１０〜２０μｍである。黒鉛の粉
砕方法としては、公知の衝撃粉砕方法や磨砕方法等の何
れの方法でも良い。粉砕後の黒鉛粒子の嵩密度は、取扱
いの容易さを考慮すると、０．７ｇ／ｃｍ3以上が好ま
しいが、通常１．３ｇ／ｃｍ3以上とすることは困難を
伴う。The graphite used as a raw material for producing graphite particles may be natural graphite or artificial graphite, but the average spacing d 002 is 0.336.
It is desirable that the material has high crystallinity of not more than nm.
Desirably, the raw material graphite is pulverized to a maximum particle diameter of 100 μm or less. The average particle size is preferably from 5 to 30 μm, more preferably from 10 to 20 μm. As a method of pulverizing graphite, any known method such as an impact pulverization method or a grinding method may be used. The bulk density of the pulverized graphite particles is preferably 0.7 g / cm 3 or more in consideration of the ease of handling, but it is usually difficult to make the bulk density 1.3 g / cm 3 or more.
【００３３】なお、粉砕後の黒鉛粒子の嵩密度が０．７
ｇ／ｃｍ3未満の場合は、コンパクター、ローラーミ
ル、デ ィスクミル、又は振動ミル等でこの黒鉛粒子を
嵩密度が０．７ｇ／ｃｍ3以 上になるように圧密化処理
をすることにより、取扱いを容易にすることができる。
この、圧密化処理は、次に説明する酸化処理の前に行な
っても良いし、酸化処理の後に行なっても良い。Incidentally, the bulk density of the pulverized graphite particles is 0.7
If it is less than g / cm 3 , it is handled by compacting the graphite particles with a compactor, roller mill, disk mill, vibrating mill or the like so that the bulk density becomes 0.7 g / cm 3 or more. Can be facilitated.
This consolidation treatment may be performed before the oxidation treatment described below, or may be performed after the oxidation treatment.
【００３４】本発明においては、上記黒鉛粒子を酸化処
理する。酸化処理は、湿式でも乾式でも行なうことがで
きる。In the present invention, the graphite particles are oxidized. The oxidation treatment can be performed by either a wet method or a dry method.
【００３５】湿式酸化処理方法としては、硝酸と硫酸の
混酸を用いて室温〜９０℃程度の温度で２〜４時間処理
する方法や、過酸化水素にアルカリ触媒を加えて室温〜
９０℃程度の温度で２〜２０時間処理する方法等が挙げ
られる。また、オゾン水、沃素又は次亜塩素酸水溶液等
で処理することもできる。湿式酸化処理方法では、酸化
した後に酸化剤を充分に除去することが必要である。湿
式酸化処理に用いる反応装置としては、撹拌機を備えた
反応器が好ましい。Examples of the wet oxidation treatment include a treatment using a mixed acid of nitric acid and sulfuric acid at a temperature of room temperature to about 90 ° C. for 2 to 4 hours, or a method of adding an alkali catalyst to hydrogen peroxide to reduce the temperature to room temperature.
For example, a method of treating at a temperature of about 90 ° C. for 2 to 20 hours may be used. Further, treatment with ozone water, iodine or an aqueous solution of hypochlorous acid or the like can also be performed. In the wet oxidation treatment method, it is necessary to sufficiently remove the oxidizing agent after the oxidation. A reactor equipped with a stirrer is preferable as a reactor used for the wet oxidation treatment.
【００３６】乾式酸化処理方法として、最も簡単な方法
は黒鉛粒子を空気中で加熱する空気酸化処理方法であ
る。黒鉛の酸化開始温度である６００〜８００℃で黒鉛
の酸化を行なう。結晶性の高い黒鉛は６５０℃前後の温
度で、結晶性の低い黒鉛は６００℃前後で、酸化燃焼が
開始する。酸化に充分な酸素が存在する雰囲気下では、
反応温度６５０℃における反応時間は５〜１５分が好ま
しい。酸化による黒鉛の質量減少は、０．１〜２０質量
％が好ましい。The simplest dry oxidation method is an air oxidation method in which graphite particles are heated in air. The graphite is oxidized at 600 to 800 ° C., which is the temperature at which graphite starts to oxidize. Oxidative combustion starts at a temperature of around 650 ° C. for highly crystalline graphite and around 600 ° C. for low crystalline graphite. In an atmosphere where there is sufficient oxygen for oxidation,
The reaction time at a reaction temperature of 650 ° C. is preferably 5 to 15 minutes. The mass reduction of graphite by oxidation is preferably 0.1 to 20% by mass.
【００３７】他の乾式酸化処理方法としては、酸化剤と
してオゾン、塩素、沃素、水蒸気、二酸化窒素、又は二
酸化炭素を用いる方法もある。As another dry oxidation treatment method, there is a method using ozone, chlorine, iodine, water vapor, nitrogen dioxide, or carbon dioxide as an oxidizing agent.
【００３８】乾式酸化処理方法に用いるの反応装置とし
ては、ロータリーキルン、撹拌流動床反応装置、振動流
動床反応装置等が例示できる。酸化処理後の質量の減少
が少ない場合でも質量の減少が多い場合と同じ様に、得
られる複合材料が充分電解液の分解抑制効果を発現させ
ることから、酸化処理の効果は、黒鉛にカルボニル基、
或はラクトン基を生成させることにより、黒鉛の活性ラ
ジカルを固定する効果ではないかと推測している。Examples of the reactor used in the dry oxidation treatment method include a rotary kiln, a stirred fluidized bed reactor, a vibrating fluidized bed reactor and the like. Even when the mass loss after the oxidation treatment is small, as in the case where the mass loss is large, the obtained composite material sufficiently exhibits the effect of suppressing the decomposition of the electrolytic solution. ,
Alternatively, it is speculated that the formation of a lactone group may have the effect of fixing the active radical of graphite.
【００３９】酸化処理した黒鉛粒子の表面に結晶性炭素
の被覆層を形成する方法としては、流動床式の反応炉を
用いた化学蒸着処理方法が優れている。この方法によ
り、黒鉛粒子の表面を完全に炭素で被覆することがで
き、しかも結晶性の炭素が蒸着する（以下、被覆炭素又
は蒸着炭素と略す）。また、この方法は簡単であり、効
率良く大量の化学蒸着処理を行なうことができる。As a method for forming a coating layer of crystalline carbon on the surface of the oxidized graphite particles, a chemical vapor deposition method using a fluidized bed type reaction furnace is excellent. By this method, the surface of the graphite particles can be completely covered with carbon, and crystalline carbon is deposited (hereinafter, abbreviated as coated carbon or deposited carbon). In addition, this method is simple, and a large amount of chemical vapor deposition can be efficiently performed.
【００４０】流動床式の反応炉においては、反応炉の下
部から供給する流動化ガスによって黒鉛粒子に浮力を与
え、粒子が激しく不規則な運動をする黒鉛の流動床を形
成する。流動化は、ガスの流れのみによって行うことも
できるが、反応炉の内部に撹拌機を設けて流動床内を撹
拌する方法や、振動機を用いて反応炉を振動する方法等
を併用することにより、一層安定した流動床を得ること
ができる。流動床における黒鉛粒子の体積は、静置して
いる場合の体積の１．２〜１．６倍程度に膨張した状態
となる。黒鉛粒子を流動化した場合の嵩密度は、０．１
〜０．５ｇ／ｃｍ3が望ましい。In a fluidized bed type reactor, a fluidizing gas supplied from the lower part of the reactor gives buoyancy to graphite particles to form a fluidized bed of graphite in which the particles move violently and irregularly. Fluidization can be performed only by the flow of gas.However, a method in which a stirrer is provided inside the reaction furnace to stir the inside of the fluidized bed, or a method in which the reaction furnace is vibrated using a vibrator, etc., are also used. Thereby, a more stable fluidized bed can be obtained. The volume of the graphite particles in the fluidized bed is expanded to about 1.2 to 1.6 times the volume when the graphite bed is left still. The bulk density when the graphite particles are fluidized is 0.1
~0.5g / cm 3 is desirable.
【００４１】流動床は熱伝達が非常に良いので、流動床
を所定の化学蒸着処理温度に昇温するには、反応炉の外
部から電気ヒーター等で加熱すれば充分である。しか
し、必要により流動化ガスを予熱しても良い。また、化
学蒸着処理は回分式でも連続式でも行うことができる。
化学蒸着処理温度は、処理をする際に用いる炭素源とし
ての有機物の種類により異なるが、通常８５０〜１２０
０℃が好ましく、より好ましい温度は９００〜１２００
℃、更により好ましい温度は９５０〜１１５０℃であ
る。化学蒸着処理温度が８５０℃未満の場合は、熱分解
炭素の析出速度が小さく、化学蒸着処理に長時間を要す
るので好ましくない。化学蒸着処理温度が高くなるに従
って、有機物の炭素への変換率は高くなる。しかし、化
学蒸着処理温度が１２００℃を越えると、蒸着炭素が繊
維状、或は不定形のスス状に成長し、膜状に成長し難く
なる。このため、均一な膜状の被膜の形成を目的とする
本発明においては、化学蒸着処理を１２００℃を越える
温度で行なうことは好ましくない。Since the fluidized bed has a very good heat transfer, it is sufficient to heat the fluidized bed from the outside of the reactor with an electric heater or the like in order to raise the temperature of the fluidized bed to a predetermined chemical vapor deposition treatment temperature. However, if necessary, the fluidizing gas may be preheated. Further, the chemical vapor deposition can be performed in a batch system or a continuous system.
The chemical vapor deposition temperature varies depending on the type of organic substance as a carbon source used in the treatment, but is usually 850 to 120.
0 ° C. is preferable, and a more preferable temperature is 900 to 1200.
C., an even more preferred temperature is 950 to 1150.degree. If the chemical vapor deposition temperature is lower than 850 ° C., the deposition rate of pyrolytic carbon is low, and the chemical vapor deposition requires a long time, which is not preferable. The higher the temperature of the chemical vapor deposition process, the higher the conversion of organic substances to carbon. However, when the temperature of the chemical vapor deposition exceeds 1200 ° C., the deposited carbon grows in a fibrous or irregular soot shape, and becomes difficult to grow in a film shape. Therefore, in the present invention for forming a uniform film-like film, it is not preferable to perform the chemical vapor deposition at a temperature exceeding 1200 ° C.
【００４２】化学蒸着処理の炭素源として好ましい有機
物としては、ベンゼン、トルエン、キシレン、スチレ
ン、エチルベンゼン、ジフェニルメタン、ジフェニル、
ナフタレン、フェノール、クレゾール、ニトロベンゼ
ン、クロルベンゼン、インデン、クマロン、ピリジン、
アントラセン、フェナントレン等の１環乃至３環の芳香
族炭化水素、又はその誘導体、或はこれらの混合物が挙
げられる。中でも、芳香族環が１個のベンゼン、トルエ
ン、キシレン、スチレン等の誘導体が化学蒸着処理時に
タールを生成し難いので好ましい。また、石炭系のター
ルの蒸留工程で得られるガス軽油、クレオソート油、ア
ントラセン油、石油系の分解油、ナフサ分解タール油、
メタン、エタン、プロパン、ブタン、ペンタン、ヘキサ
ン等の脂肪族炭化水素、及び前記脂肪族炭化水素の誘導
体であるアルコールも単独で、或は混合物として用いる
ことができる。更に、アセチレン、エチレン、プロピレ
ン、イソプロピレン、ブタジエン等の二重結合を有する
有機物も用いることができる。Preferred organic substances as a carbon source for the chemical vapor deposition include benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, diphenyl, and the like.
Naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, cumarone, pyridine,
Examples thereof include monocyclic to tricyclic aromatic hydrocarbons such as anthracene and phenanthrene, derivatives thereof, and mixtures thereof. Among them, derivatives having one aromatic ring, such as benzene, toluene, xylene, and styrene, are preferable because tar is not easily generated during chemical vapor deposition. In addition, gas diesel oil, creosote oil, anthracene oil, petroleum cracked oil, naphtha cracked tar oil obtained in the coal-based tar distillation process,
Aliphatic hydrocarbons such as methane, ethane, propane, butane, pentane and hexane, and alcohols which are derivatives of the aliphatic hydrocarbons can be used alone or as a mixture. Further, organic substances having a double bond such as acetylene, ethylene, propylene, isopropylene, and butadiene can also be used.
【００４３】化学蒸着処理において、炭素源としての有
機物は、不活性ガスで希釈した混合ガスの形態で流動床
反応炉に供給する。In the chemical vapor deposition process, an organic substance as a carbon source is supplied to a fluidized bed reactor in the form of a mixed gas diluted with an inert gas.
【００４４】不活性ガスとしては、窒素、アルゴン等が
挙げられる。入手や取扱いのしやすさから窒素が特に好
ましい。不活性ガスは、反応系内から酸素や未反応の残
存有機物を排出させると共に、黒鉛粒子の流動床を形成
する流動化ガスとしても重要な役割を果す。Examples of the inert gas include nitrogen, argon and the like. Nitrogen is particularly preferred because of its availability and ease of handling. The inert gas plays a significant role as a fluidizing gas that forms a fluidized bed of graphite particles while discharging oxygen and unreacted residual organic matter from the reaction system.
【００４５】混合ガス中の有機物濃度は、生成する被覆
層の結晶性及び分子配向に大きな影響を与える。混合ガ
ス中の好ましい有機物の濃度は、２〜５０モル％、更に
好ましくは５〜３３モル％である。上記濃度範囲に調節
することにより、簡単に所定の結晶性及び分子配向性を
有する蒸着炭素の被覆層を形成することができる。混合
ガス中の有機物の濃度が２モル％未満の場合は、被覆層
の結晶性は高くなるが、炭素蒸着速度が小さく、蒸着処
理に長時間を要するので好ましくない。一方、有機物の
濃度が５０モル％を越える場合は、炭素蒸着速度は大き
い。しかし、得られる被覆層の結晶性が低下し、更に蒸
着炭素の形態が膜状にならず、繊維状、或はスス状に成
長する。このため、黒鉛粒子の表面に均一な被覆層を形
成することを目的とする本発明の黒鉛−炭素複合材料の
製造には好ましくない。The concentration of the organic substance in the mixed gas has a great influence on the crystallinity and molecular orientation of the formed coating layer. The preferred concentration of the organic substance in the mixed gas is 2 to 50 mol%, more preferably 5 to 33 mol%. By adjusting the concentration within the above range, a coating layer of deposited carbon having predetermined crystallinity and molecular orientation can be easily formed. When the concentration of the organic substance in the mixed gas is less than 2 mol%, the crystallinity of the coating layer is high, but the carbon deposition rate is low, and the vapor deposition process is not long, which is not preferable. On the other hand, when the concentration of the organic substance exceeds 50 mol%, the carbon deposition rate is high. However, the crystallinity of the obtained coating layer is reduced, and the form of the deposited carbon does not form a film but grows in a fibrous or soot form. Therefore, it is not preferable for the production of the graphite-carbon composite material of the present invention for the purpose of forming a uniform coating layer on the surface of the graphite particles.
【００４６】化学蒸着処理により黒鉛粒子表面に被覆す
る結晶性炭素からなる被覆層の量は、得られる黒鉛−炭
素複合材料に対して２〜１０質量％とすることが好まし
く、更に好ましくは３〜７質量％である。被覆層の量を
を２質量％以上とすることにより、溶媒の分解抑制作用
が発現する。被覆炭素量が１０質量％を越えると、次第
に個々の粒子の剛性が高くなって高密度化が困難にな
り、負極を調製する際にロールプレスを行なっても電極
密度を高くしにくくなり、その結果エネルギー密度の高
い電池を製造し難くなる。The amount of the coating layer made of crystalline carbon which coats the graphite particles by chemical vapor deposition is preferably 2 to 10% by mass, more preferably 3 to 10% by mass, based on the obtained graphite-carbon composite material. 7% by mass. By setting the amount of the coating layer to 2% by mass or more, the effect of suppressing the decomposition of the solvent is exhibited. When the coating carbon amount exceeds 10% by mass, the rigidity of each particle gradually increases, making it difficult to increase the density. Even when a negative electrode is prepared by roll pressing, it is difficult to increase the electrode density. As a result, it becomes difficult to manufacture a battery having a high energy density.
【００４７】次に、上記複合材料を透過型電子顕微鏡等
を用いて観察して得られた結果について図面を参照して
説明する。Next, the results obtained by observing the above composite material using a transmission electron microscope or the like will be described with reference to the drawings.
【００４８】図１は、本発明の複合材料の一例を示すも
のである。この模式的断面図に示す負極材料６は、略平
板状の黒鉛粒子２と、その表面を均一に被覆する被覆層
４とからなる。図２は、図１中の境界線Ａで示される部
分の拡大図である。黒鉛粒子２及び被覆層４の分子配向
を図２を参照して詳細に検討すると以下の知見を得る。
図２に示されるように、略平板状の黒鉛粒子２は、側面
８（１１０面）を側面被覆層１４で被覆され、また、上
面１０（００２面）を上面被覆層１６で被覆されてい
る。FIG. 1 shows an example of the composite material of the present invention. A negative electrode material 6 shown in this schematic cross-sectional view is composed of a substantially flat graphite particle 2 and a coating layer 4 that uniformly covers the surface. FIG. 2 is an enlarged view of a portion indicated by a boundary line A in FIG. When the molecular orientation of the graphite particles 2 and the coating layer 4 is examined in detail with reference to FIG.
As shown in FIG. 2, the substantially flat graphite particles 2 have a side surface 8 (110 surface) covered with a side surface coating layer 14 and an upper surface 10 (002 surface) with an upper surface coating layer 16. .
【００４９】図２において、上方から下方に向かって透
過型電子顕微鏡の電子線Ｘを照射して上面被覆層１６を
観察すると、炭素００２面の明瞭な格子像を観察するこ
とはできない。しかし、電子線回折法によると、炭素０
０２面が観察される。一方、上方から下方に向かって透
過型電子顕微鏡の電子線Ｙを照射して側面被覆層１４を
観察すると、炭素１１０面の明瞭な格子像を観察するこ
とができる。従って、側面被覆層１４は結晶構造をなし
ており、しかも側面被覆層１４の炭素００２面は黒鉛粒
子表面（側面８）に平行であることが理論的に結論され
る。In FIG. 2, when the upper coating layer 16 is observed by irradiating the electron beam X of the transmission electron microscope from above to below, a clear lattice image of the carbon 002 plane cannot be observed. However, according to the electron diffraction method, carbon 0
Surface 02 is observed. On the other hand, when the side surface coating layer 14 is observed by irradiating the electron beam Y of the transmission electron microscope from above to below, a clear lattice image of the carbon 110 surface can be observed. Accordingly, it is theoretically concluded that the side surface coating layer 14 has a crystal structure, and that the carbon 002 plane of the side surface coating layer 14 is parallel to the graphite particle surface (side surface 8).
【００５０】この観察結果は、黒鉛粒子表面（上面１
０）の炭素００２面は被覆層の炭素００２面で被覆され
ていること、更に黒鉛粒子表面（側面８）の炭素１１０
面も同様に被覆層の炭素００２面で被覆されていること
を意味する。よって、本発明の複合材料は、被覆層の炭
素００２面を黒鉛粒子の表面と平行にして、被覆層の炭
素００２面で黒鉛粒子の全表面を被覆した構造のもので
あることが分かる。This observation result indicates that the surface of the graphite particles (upper surface 1)
0) that the carbon 002 face of the coating layer is covered with the carbon 002 face of the coating layer,
Similarly, the surface is also covered with the carbon 002 surface of the coating layer. Therefore, it can be seen that the composite material of the present invention has a structure in which the carbon 002 surface of the coating layer is parallel to the surface of the graphite particles, and the entire surface of the graphite particles is coated with the carbon 002 surface of the coating layer.
【００５１】更に、リチウムイオンをインターカレーシ
ョンした上記の複合材料を試料に用いて、7Ｌｉ−ＮＭ
Ｒを測定したデータを黒鉛−炭素複合材料の構造評価に
用いることができる。具体的には、この黒鉛−炭素複合
材料と金属リチウムで電池を構成し、複合材料にリチウ
ムイオンをインターカレーションした状態で7Ｌｉ−Ｎ
ＭＲを測定する。塩化リチウム基準（０ｐｐｍ）で、ケ
ミカルシフト が４０〜５０ｐｐｍの位置の吸収スペク
トルと、１０〜２０ｐｐｍの位置の吸収スペクトルとか
らなる複合スペクトルを有するものは、リチウム二次電
池負極材料として好ましいものである。ここで、４０〜
５０ｐｐｍの位置の吸収スペクトルは、高結晶性黒鉛粒
子にインターカレーションしたリチウムイオンに由来す
る吸収スペクトルである。また、１０〜２０ｐｐｍの位
置の吸収スペクトルは、結晶性炭素からなる被覆層にイ
ンターカレーションしたリチウムイオンに由来する吸収
スペクトルである。これら２つの吸収スペクトルの存
在、及びその存在の位置、並びに９０〜１２０ｐｐｍの
位置に吸収スペクトルが存在しないことは、本発明の複
合材料を特徴づけるもので、特に被覆層が結晶性炭素で
あることを示すものとして重要である。Further, using the above-mentioned composite material intercalated with lithium ions as a sample, 7 Li-NM
The data obtained by measuring R can be used for evaluating the structure of the graphite-carbon composite material. Specifically, a battery is composed of the graphite-carbon composite material and metallic lithium, and 7 Li-N
Measure MR. Those having a composite spectrum consisting of an absorption spectrum at a position of 40 to 50 ppm and an absorption spectrum at a position of 10 to 20 ppm based on lithium chloride (0 ppm) are preferable as a negative electrode material for a lithium secondary battery. . Here, 40 ~
The absorption spectrum at the position of 50 ppm is an absorption spectrum derived from lithium ions intercalated into the highly crystalline graphite particles. The absorption spectrum at a position of 10 to 20 ppm is an absorption spectrum derived from lithium ions intercalated in the coating layer made of crystalline carbon. The presence of these two absorption spectra, and the location of their presence, and the absence of an absorption spectrum at 90 to 120 ppm, characterize the composite material of the present invention, and particularly the fact that the coating layer is made of crystalline carbon. It is important as an indicator.
【００５２】一方、黒鉛粒子に非晶質炭素を被覆した複
合材料にリチウムイオンをインターカレーションした場
合、その7Ｌｉ−ＮＭＲ吸収スペクトルには、１０ 〜２
０ｐｐｍの吸収スペクトルは認められず、９０〜１２０
ｐｐｍの位置に吸収スペクトルが観察される。On the other hand, when lithium ions were intercalated into a composite material in which graphite particles were coated with amorphous carbon, its 7 Li-NMR absorption spectrum showed 10 to 2
No absorption spectrum at 0 ppm was observed,
An absorption spectrum is observed at the ppm position.
【００５３】更に、黒鉛粒子に低結晶性炭素を被覆した
複合材料にリチウムイオンをインターカレーションした
場合、その7Ｌｉ−ＮＭＲ吸収 スペクトルには、１０〜
２０ｐｐｍの位置と、９０〜１２０ｐｐｍの位置にそれ
ぞれ吸収スペクトルが観察されることがある。Furthermore, when lithium ions were intercalated into a composite material in which graphite particles were coated with low-crystalline carbon, the 7 Li-NMR absorption spectrum showed 10 to 10
Absorption spectra may be observed at a position of 20 ppm and at a position of 90 to 120 ppm, respectively.
【００５４】黒鉛粒子表面上に析出する炭素層の平均面
間隔ｄ002は、０．３４ｎｍ未満が好ましく、０．３３
７ｎｍ未満 が更に望ましく、より好ましい被覆炭素層
の平均面間隔ｄ002は 、０．３３５２〜０．３３６９ｎ
ｍ、更により好ましい平均面間隔ｄ002は、０ ．３３５
２〜０．３３５９ｎｍである。しかし、炭素層の平均面
間隔は必ずしも上記範囲に有ることを必要とするもので
は無い。The average spacing d 002 of the carbon layer deposited on the graphite particle surface is preferably less than 0.34 nm, and 0.33 nm.
More preferably, the average interplanar spacing d 002 of the coated carbon layer is 0.3352 to 0.3369 n.
m, and an even more preferred average surface distance d 002 is 0. 335
2 to 0.3359 nm. However, the average plane spacing of the carbon layer does not necessarily need to be in the above range.
【００５５】本発明の黒鉛−炭素複合材料を負極材料と
して、リチウムイオン二次電池用負極を調製する方法
は、特に限定されないが、以下にその好ましい一例を示
す。A method for preparing a negative electrode for a lithium ion secondary battery using the graphite-carbon composite material of the present invention as a negative electrode material is not particularly limited, but a preferred example is shown below.
【００５６】本複合材料に、バインダー（例えば、ＰＶ
ＤＦ：ポリビニリデンフルオライド）を溶解した溶剤
（例えば、１−メチル−２−ピロリドン）を加え、十分
に混練する。この操作により、４０％以上の複合材料を
含む高濃度の複合材料スラリーを調製することができ
る。この複合材料スラリーを、金属箔（例えば銅箔）か
らなる集電体にドクターブレード等を用いて２０〜１０
０μｍの厚みにコーティングする。これを乾燥させるこ
とにより、複合材料粒子が金属箔集電体に密着する。更
に、ロールプレス等により加圧して密着性を高めると共
に、電極密度を高める。バインダーには公知の材料、例
えば、各種のピッチ、ラバー、合成樹脂等を用いること
ができる。これらの中でもＰＶＤＦやカルボキシメチル
セルロース（ＣＭＣ）やＳＢＲラテックスゴムが最適で
ある。A binder (for example, PV) is added to the composite material.
A solvent (for example, 1-methyl-2-pyrrolidone) in which DF: polyvinylidene fluoride) is dissolved, and the mixture is sufficiently kneaded. By this operation, a high-concentration composite material slurry containing 40% or more of the composite material can be prepared. This composite material slurry is applied to a current collector made of a metal foil (for example, a copper foil) for 20 to 10 using a doctor blade or the like.
Coat to a thickness of 0 μm. By drying this, the composite material particles adhere to the metal foil current collector. Further, the pressure is increased by a roll press or the like to increase the adhesion and the electrode density. As the binder, known materials, for example, various pitches, rubbers, synthetic resins, and the like can be used. Among them, PVDF, carboxymethylcellulose (CMC) and SBR latex rubber are most suitable.
【００５７】複合材料とバインダーの混合比（質量比）
は１００：２〜１００：２０とすることが望ましい。Mixing ratio (mass ratio) of composite material and binder
Is preferably 100: 2 to 100: 20.
【００５８】電極密度は、１．４〜１．７ｇ／ｃｍ3に
調整される。この密度は、電極中に２２〜３６ｖｏｌ％
の空隙率に相当する空間を作ることになり、この空隙率
が、電解液の保持に最適な空間容量となる。黒鉛−炭素
複合材料においては、複合材料中の被覆層の割合が１０
質量％以下の場合に、この電極密度を達成することが可
能である。The electrode density is adjusted to 1.4 to 1.7 g / cm 3 . This density is 22-36 vol% in the electrode.
A space corresponding to the porosity is created, and this porosity is an optimal space capacity for holding the electrolyte. In the graphite-carbon composite material, the ratio of the coating layer in the composite material is 10%.
In the case of not more than mass%, it is possible to achieve this electrode density.
【００５９】酸化処理を施していない黒鉛粒子を化学蒸
着処理して被覆層を形成する場合、被覆層を１０質量％
以下にすると、被覆層形成の主目的である電解液の分解
抑制効果が不十分となったり、クーロン効率が低下する
等、電気的な特性を充分に満足することができない。し
かし、酸化処理した黒鉛粒子に被覆層を形成する本発明
の方法によれば、酸化処理の効果により電解液の分解抑
制効果が著しく向上し、被覆層を１０質量％以下とする
ことが可能となる。この結果、電極密度を１．４〜１．
７ｇ／ｃｍ3に調整することが可能となるものである。When a coating layer is formed by chemically vapor-depositing graphite particles that have not been subjected to an oxidizing treatment, the coating layer is formed in an amount of 10% by mass.
If it is less than the above, electrical characteristics cannot be sufficiently satisfied, such as an insufficient effect of suppressing the decomposition of the electrolytic solution, which is a main purpose of forming the coating layer, and a decrease in Coulomb efficiency. However, according to the method of the present invention in which the coating layer is formed on the oxidized graphite particles, the effect of the oxidation treatment significantly suppresses the decomposition of the electrolytic solution, and the coating layer can be reduced to 10% by mass or less. Become. As a result, the electrode density was 1.4 to 1.
It can be adjusted to 7 g / cm 3 .
【００６０】二次電池の実用生産ラインにおいては、電
極密度の調整にロールプレスを多用しており、複合材料
はロールの線圧によって加圧されるが、複合材料の評価
は、通常の平板加圧で行なうことができる。即ち、ロー
ルプレスによる加圧は、１００〜４００ｋｇ／ｃｍ2の
面圧による加圧に相当すると見なすことができる。従っ
て、１００〜４００ｋｇ／ｃｍ2の圧力で加圧したとき
に電極密度が、１．４〜１．７ｇ／ｃｍ3となること
が、黒鉛−炭素複合材料の最も好ましい条件である。In a practical production line for a secondary battery, a roll press is frequently used to adjust the electrode density, and the composite material is pressed by the linear pressure of the roll. It can be done with pressure. That is, pressurization by a roll press can be considered to correspond to pressurization by a surface pressure of 100 to 400 kg / cm 2 . Therefore, the most preferable condition of the graphite-carbon composite material is that the electrode density becomes 1.4 to 1.7 g / cm 3 when pressed at a pressure of 100 to 400 kg / cm 2 .
【００６１】正極材料は特に限定されないが、当業者に
公知のＬｉＣｏＯ2、Ｌｉ ＮｉＯ2又はＬｉＭｎ2Ｏ4等
のリチウム含有化合物、或はこれらの混合物が好適であ
る。粉末状の正極材料は、必要があれば導電剤を加え、
バインダーを溶解した溶剤などと十分に混練後、集電体
と共に成形して調製できる。また、セパレーターについ
ても特に限定はなく、ポリプロピレンやポリエチレン等
の公知の材料を用いることができる。The cathode material is not particularly limited, but lithium-containing compounds such as LiCoO 2 , Li NiO 2 or LiMn 2 O 4 known to those skilled in the art, or a mixture thereof are preferred. Powdered cathode material, if necessary, add a conductive agent,
After sufficiently kneading with a solvent or the like in which a binder is dissolved, it can be formed by molding with a current collector. The separator is not particularly limited, and a known material such as polypropylene or polyethylene can be used.
【００６２】電解液の主溶媒である非水溶媒としては、
リチウム塩を溶解する非プロトン性低誘電率の公知の溶
媒が挙げられる。The non-aqueous solvent which is the main solvent of the electrolytic solution includes
Examples of the solvent include a known aprotic solvent having a low dielectric constant that dissolves a lithium salt.
【００６３】例えば、エチレンカーボネート、ジメチル
カーボネート（以下ＤＭＣと略す）、メチルエチルカー
ボネート（以下ＭＥＣと略す）、プロピレンカーボネー
ト、ジエチレンカーボネート、アセトニトリル、プロピ
オニトリル、テトラヒドロフラン、ｒ−ブチロラクト
ン、２−メチルテトラヒドロフラン、１、３−ジオキソ
ラン、４−メチル−１、３−ジオキソラン、１、２−ジ
メトキシエタン、１、２−ジエトキシエタン、ジエチル
エーテル、スルホラン、メチルスルホラン、ニトロメタ
ン、Ｎ、Ｎ−ジメチルホルムアミド、ジメチルスルホキ
シド等の溶媒を単独で、又は２種以上の溶媒を混合して
用いることができる。For example, ethylene carbonate, dimethyl carbonate (hereinafter abbreviated as DMC), methyl ethyl carbonate (hereinafter abbreviated as MEC), propylene carbonate, diethylene carbonate, acetonitrile, propionitrile, tetrahydrofuran, r-butyrolactone, 2-methyltetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3-dioxolan, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether, sulfolane, methylsulfolane, nitromethane, N, N-dimethylformamide, dimethylsulfoxide Or a mixture of two or more solvents.
【００６４】電解質として用いられるリチウム塩として
は、ＬｉＣｌＯ4、ＬｉＡｓＦ6、ＬｉＰＦ6、ＬｉＢ
Ｆ4、ＬｉＢ（Ｃ6Ｈ5）4、ＬｉＣｌ、ＬｉＢｒ、ＣＨ3
ＳＯ3Ｌｉ、ＣＦ3ＳＯ3Ｌｉ等を例示でき、これらの塩
を単独、又は２種類以上を混合して用いることができ
る。The lithium salt used as the electrolyte includes LiClO 4 , LiAsF 6 , LiPF 6 , LiB
F 4 , LiB (C 6 H 5 ) 4 , LiCl, LiBr, CH 3
Examples thereof include SO 3 Li and CF 3 SO 3 Li, and these salts may be used alone or in combination of two or more.
【００６５】なお、上記電解液の主溶媒である非水溶媒
と電解質とをゲル化したゲル電解質、又はポリエチレン
オキサイド、ポリアクリロニトリル等の高分子電解質等
を用いてリチウムポリマー二次電池とすることもでき
る。It is to be noted that a lithium polymer secondary battery may be formed by using a gel electrolyte obtained by gelling an electrolyte with a non-aqueous solvent which is a main solvent of the electrolytic solution, or a polymer electrolyte such as polyethylene oxide and polyacrylonitrile. it can.
【００６６】更には、固体電解質を用いて全固体リチウ
ム二次電池を製造することもできる。 これら二次電池
の構成自体は公知のものである。Furthermore, an all-solid lithium secondary battery can be manufactured using a solid electrolyte. The configuration itself of these secondary batteries is known.
【００６７】[0067]
【実施例】各物性値は以下の方法で測定した。EXAMPLES Each physical property value was measured by the following methods.
【００６８】嵩密度： １００ｍｌのガラス製メスシリ
ンダーに試料を入れてタッピングし、試料の容積が変化
しなくなったところで試料容積を測定し、試料質量を試
料容積で除した値を嵩密度とした。Bulk density: A sample was placed in a 100-ml glass measuring cylinder and tapped. When the sample volume stopped changing, the sample volume was measured, and the value obtained by dividing the sample mass by the sample volume was defined as the bulk density.
【００６９】電極密度： 呉羽化学製ＰＶＤＦ１１００
をバインダーとし、溶剤をＮＭＰ（１−メチル−２−ピ
ロリドン）とし、６．６質量％のバインダー溶液に黒鉛
−炭素複合材料を加えて混錬し、濃度４０質量％のスラ
リーを調製した。乾燥後のバインダー量は９．０質量％
である。得られたスラリーを、ドクターブレードを用い
て銅箔上に約２００μｍの厚みに塗布し、乾燥した後、
一軸プレスを用いて所定の圧力で加圧することにより高
密度化した。これを２．５ｃｍ2になるように切り出
し、試料厚み（銅箔を除く）をマイクロメータで測定し
た。試料質量を面積と厚みで除して電極密度とした。Electrode density: PVDF1100 manufactured by Kureha Chemical
Was used as a binder, the solvent was NMP (1-methyl-2-pyrrolidone), and a graphite-carbon composite material was added to a 6.6% by mass binder solution and kneaded to prepare a slurry having a concentration of 40% by mass. The amount of the binder after drying is 9.0% by mass.
It is. The obtained slurry was applied to a thickness of about 200 μm on a copper foil using a doctor blade, and dried,
Densification was achieved by applying pressure at a predetermined pressure using a uniaxial press. This was cut out to a size of 2.5 cm 2 , and the sample thickness (excluding the copper foil) was measured with a micrometer. The mass of the sample was divided by the area and thickness to obtain the electrode density.
【００７０】結晶格子定数Ｃｏ（００２）： 理学製Ｘ
線回折装置ＬＩＮＴ１１１を用い、Ｃｕ−Ｋα線をＮｉ
で単色化し、高純度シリコンを標準物質として学振法で
測定した。Crystal lattice constant Co (002): Rigaku X
Using a line diffractometer LINT111, the Cu-Kα
And measured by Gakushin method using high-purity silicon as a standard substance.
【００７１】透過型電子顕微鏡及び電子線回折： 日本
電子製透過型電子顕微鏡２０００ＦＸを用い、明視野像
撮影及び電子線回折測定を行った。Transmission Electron Microscope and Electron Diffraction: A bright field image photographing and electron diffraction measurement were performed using a transmission electron microscope 2000FX manufactured by JEOL.
【００７２】7Ｌｉ固体ＮＭＲ： ブルカー社製固体核
磁気共鳴装置ＤＳＸ３００ｗｂに多核種広幅プローブヘ
ッドを装着し、塩化リチウム水溶液を標準として測定し
た。 7 Li Solid NMR: A multi-nuclide wide probe head was attached to a solid nuclear magnetic resonance apparatus DSX300wb manufactured by Bruker, and measurement was performed using a lithium chloride aqueous solution as a standard.
【００７３】表面積： 日本ベル社製高精度自動ガス吸
着装置ＢＥＬＳＯＲＢ２８を用い、液体窒素温度で窒素
吸着量を多点法で測定し、ＢＥＴ法により表面積を算出
した。Surface area: Using a high-precision automatic gas adsorption apparatus BELSORB28 manufactured by Bell Japan, the nitrogen adsorption amount was measured at a liquid nitrogen temperature by a multipoint method, and the surface area was calculated by the BET method.
【００７４】蒸着炭素量： 島津製作所製熱重量分析装
置ＴＧＡ−５０を用い、空気気流下で質量減少量を測定
し、黒鉛成分と明確に異なる質量減少分を炭素量とし
た。Amount of evaporated carbon: The amount of mass loss was measured in a stream of air using a thermogravimetric analyzer TGA-50 manufactured by Shimadzu Corporation, and the amount of mass reduction clearly different from the graphite component was taken as the amount of carbon.
【００７５】実施例１ ブラジル産天然黒鉛を振動ロッドミルで圧密化した後、
５３μｍで篩い分けを行い、その篩い下である嵩密度
０．８００ｇ／ｃｍ3の黒鉛粒子に、空気酸化処理を施
した。Example 1 Brazilian natural graphite was compacted by a vibrating rod mill.
The mixture was sieved at 53 μm, and the graphite particles having a bulk density of 0.800 g / cm 3 under the sieve were subjected to an air oxidation treatment.
【００７６】空気酸化処理はロータリーキルンを用い、
黒鉛１ｋｇ当り２５ ｌ／ｍｉｎの空気を送りながら、
温度６５０℃で、滞留時間５分とした。酸化による燃焼
損失は、２．１質量％であった。The air oxidation treatment uses a rotary kiln,
While sending 25 l / min air per kg of graphite,
The temperature was 650 ° C. and the residence time was 5 minutes. The combustion loss due to oxidation was 2.1% by mass.
【００７７】酸化処理した黒鉛６０ｋｇを流動床反応炉
に仕込み、窒素を５０ １／ｍｉｎで流しながら、反応
炉内温度を１０００℃まで昇温した後、炭素源としてト
ルエンを４０モル％含有する窒素ガスを８０ ｌ／ｍｉ
ｎで供給して流動状態を保ちながら２５分間化学蒸着処
理を行った。60 kg of the oxidized graphite was charged into a fluidized-bed reactor, and the temperature in the reactor was raised to 1000 ° C. while flowing nitrogen at a rate of 50 1 / min. Then, nitrogen containing 40 mol% of toluene as a carbon source was added. 80 l / mi of gas
n, and a chemical vapor deposition process was performed for 25 minutes while maintaining a fluid state.
【００７８】得られた黒鉛−炭素複合材料の５３μｍ篩
下試料を用いて、表１の条件で電池を構成し、負極材料
としての評価試験を行った。その結果を表２に示す。Using the obtained graphite-carbon composite material under a sieve of 53 μm, a battery was constructed under the conditions shown in Table 1, and an evaluation test as a negative electrode material was performed. Table 2 shows the results.
【００７９】また、得られた複合材料を透過型電子顕微
鏡及び電子線回折により観察した結果は、先に述べた通
りであった。The results of observation of the obtained composite material with a transmission electron microscope and an electron beam diffraction were as described above.
【００８０】実施例２ 空気流量を黒鉛１ｋｇ当り５０ ｌ／ｍｉｎ、滞留時間
１２分間で酸化処理を行い、酸化による燃焼損失が１
０．８質量％であった以外は、実施例１と同様に操作し
た。Example 2 Oxidation treatment was performed at an air flow rate of 50 l / min per kg of graphite and a residence time of 12 minutes.
The same operation as in Example 1 was performed except that the content was 0.8% by mass.
【００８１】実施例１と同様にして、表１の条件で電池
を構成し、負極材料としての評価試験を行った。その結
果を表２に示す。In the same manner as in Example 1, a battery was constructed under the conditions shown in Table 1, and an evaluation test as a negative electrode material was performed. Table 2 shows the results.
【００８２】実施例３ 化学蒸着時間を１５分間とする以外は実施例と同様に操
作し、実施例１と同様にして表１の条件で電池を構成
し、負極材料としての評価試験を行った。その結果を表
２に示す。Example 3 A battery was constructed in the same manner as in Example 1 except that the chemical vapor deposition time was changed to 15 minutes, and a battery was constructed under the conditions shown in Table 1, and an evaluation test as a negative electrode material was performed. . Table 2 shows the results.
【００８３】比較例１ 実施例１で用いた圧密化処理及び空気酸化処理を施した
黒鉛粒子の５３μｍ篩下試料についてに、化学蒸着処理
を行わずに、表１の条件で負極材料としての評価試験を
行った。その結果を表３に示す。Comparative Example 1 A 53 μm sieve sample of the graphite particles subjected to the consolidation treatment and the air oxidation treatment used in Example 1 was evaluated as a negative electrode material under the conditions shown in Table 1 without chemical vapor deposition treatment. The test was performed. Table 3 shows the results.
【００８４】この結果から、酸化処理のみでは、溶媒の
分解を抑制することができないことが分かる。From the results, it is understood that the decomposition of the solvent cannot be suppressed only by the oxidation treatment.
【００８５】比較例２ 実施例１で用いた圧密化処理を行った黒鉛粒子に、空気
酸化処理を施すことなく、実施例１と同一条件で化学蒸
着処理を行った。Comparative Example 2 The compacted graphite particles used in Example 1 were subjected to a chemical vapor deposition treatment under the same conditions as in Example 1 without being subjected to an air oxidation treatment.
【００８６】得られた黒鉛−炭素複合材料の５３μｍ篩
下試料について、表１の条件で負極材料としての評価試
験を行った。その結果を表３に示す。An evaluation test as a negative electrode material was performed on the obtained graphite-carbon composite material under a sieve of 53 μm under the conditions shown in Table 1. Table 3 shows the results.
【００８７】この結果から、酸化処理を行っていない複
合材料は、被覆層が少ない場合は充分な電極密度が得ら
れるが、被覆層が少ないため電解液の分解抑制効果が低
下していることが分かる。From these results, it can be seen that in the case of a composite material which has not been subjected to oxidation treatment, a sufficient electrode density can be obtained when the coating layer is small, but the effect of suppressing the decomposition of the electrolytic solution is reduced due to the small coating layer. I understand.
【００８８】比較例３ 実施例１で用いた圧密化処理を行った黒鉛粒子に、空気
酸化処理を施すことなく、実施例１と同一条件で化学蒸
着処理を行った。ただし、化学蒸着処理時間は１２０分
とした。Comparative Example 3 The compacted graphite particles used in Example 1 were subjected to chemical vapor deposition under the same conditions as in Example 1 without being subjected to an air oxidation treatment. However, the chemical vapor deposition processing time was 120 minutes.
【００８９】得られた黒鉛−炭素複合材料の５３μｍ篩
下試料について、表１の条件で負極材料としての評価試
験を行った。その結果を表３に示す。An evaluation test as a negative electrode material was performed on the obtained graphite-carbon composite material under a sieve of 53 μm under the conditions shown in Table 1. Table 3 shows the results.
【００９０】この結果、酸化処理を行っていないもの
は、被覆炭素量が多い場合には、電解液の分解抑制効果
が充分発現するものの、電極密度が低くなることが分か
る。As a result, it can be seen that in the case where the oxidation treatment was not performed, when the coating carbon amount was large, the effect of suppressing the decomposition of the electrolytic solution was sufficiently exhibited, but the electrode density was low.
【００９１】[0091]
【表１】 [Table 1]
【００９２】[0092]
【表２】 [Table 2]
【００９３】[0093]
【表３】 [Table 3]
【００９４】[0094]
【発明の効果】本発明の黒鉛−炭素複合材料は黒鉛粒子
を予め酸化処理しているので、被覆層の炭素量を電解液
の分解を起こすことなく減少できる。その結果、電極密
度を高くでき、このためこの複合材を負極材として用い
てリチウム二次電池を製造する場合、大容量で、高電位
で、充放電サイクル特性に優れ、小型化でき、しかも電
解液の分解を抑制した電池を得ることが出来る。According to the graphite-carbon composite material of the present invention, since the graphite particles are previously oxidized, the carbon content of the coating layer can be reduced without decomposing the electrolyte. As a result, the electrode density can be increased, and when a lithium secondary battery is manufactured using this composite material as a negative electrode material, a large capacity, high potential, excellent charge / discharge cycle characteristics, miniaturization, and electrolytic A battery in which decomposition of the liquid is suppressed can be obtained.
【図１】本発明黒鉛−炭素複合材料の一例を示す模式的
断面図である。FIG. 1 is a schematic sectional view showing an example of the graphite-carbon composite material of the present invention.
【図２】図１の境界線Ａ内を示す模式的拡大図である。FIG. 2 is a schematic enlarged view showing the inside of a boundary line A in FIG. 1;
【図３】リチウムイオンをインターカレーションした実
施例１の本発明複合材料の7Ｌｉ−ＮＭＲ吸収スペクト
ルである。FIG. 3 is a 7 Li-NMR absorption spectrum of the composite material of the present invention of Example 1 in which lithium ions are intercalated.
２ 黒鉛粒子 ４ 被覆層 ６ 黒鉛−炭素複合材料 ８ 側面 １０ 上面 １４ 側面被覆層 １６ 上面被覆層 Ｘ、Ｙ 電子線 2 Graphite particles 4 Coating layer 6 Graphite-carbon composite material 8 Side surface 10 Top surface 14 Side coating layer 16 Top coating layer X, Y Electron beam
───────────────────────────────────────────────────── フロントページの続き (72)発明者 梅野 達夫 福岡県北九州市若松区響町１丁目３番地 三井鉱山株式会社総合研究所内 (72)発明者 安元 義徳 福岡県北九州市若松区響町１丁目３番地 三井鉱山株式会社総合研究所内 (72)発明者 原 陽一郎 福岡県北九州市若松区響町１丁目３番地 三井鉱山株式会社総合研究所内 Ｆターム(参考） 5H029 AJ02 AJ03 AJ05 AK03 AL07 AM02 AM03 AM04 AM05 AM07 CJ03 CJ14 CJ22 DJ17 HJ01 HJ08 HJ14 HJ15 5H050 AA02 AA07 AA08 BA17 CA08 CA09 CB08 DA03 FA18 FA19 GA03 GA15 HA01 HA08 HA14 HA15 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Tatsuo Umeno 1-3-3 Hibiki-cho, Wakamatsu-ku, Kitakyushu-shi, Fukuoka In-house of Mitsui Mining Co., Ltd. (72) Yoshinori Yasumoto 1 Hibiki-cho, Wakamatsu-ku, Kitakyushu-shi, Fukuoka 3-chome, Mitsui Mining Co., Ltd. (72) Inventor Yoichiro Hara 1-3-3 Hibikicho, Wakamatsu-ku, Kitakyushu-shi, Fukuoka F-term (reference) 5H029 AJ02 AJ03 AJ05 AK03 AL07 AM02 AM03 AM04 AM05 AM07 CJ03 CJ14 CJ22 DJ17 HJ01 HJ08 HJ14 HJ15 5H050 AA02 AA07 AA08 BA17 CA08 CA09 CB08 DA03 FA18 FA19 GA03 GA15 HA01 HA08 HA14 HA15
Claims (11)
を用いて炭素を化学蒸着することを特徴とする黒鉛粒子
の表面に結晶性炭素の被覆層を有してなるリチウム二次
電池負極用黒鉛―炭素複合材料の製造方法。1. A negative electrode for a lithium secondary battery comprising a graphite particle having a coating layer of crystalline carbon on a surface of the graphite particle, wherein carbon is chemically deposited on the oxidized graphite particle using a fluidized bed reactor. For producing graphite-carbon composite materials for industrial use.
℃の温度で行う空気酸化処理である請求項１に記載のリ
チウム二次電池負極用黒鉛―炭素複合材料の製造方法。2. The oxidizing treatment is performed to reduce the graphite particles to 600 to 800.
The method for producing a graphite-carbon composite material for a negative electrode of a lithium secondary battery according to claim 1, which is an air oxidation treatment performed at a temperature of ° C.
より黒鉛粒子の質量を０．１〜２０質量％減少させる請
求項１又は２に記載のリチウム二次電池負極用黒鉛―炭
素複合材料の製造方法。3. The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to claim 1, wherein the oxidation treatment reduces the mass of the graphite particles by 0.1 to 20% by mass by oxidizing the graphite particles. Production method.
行なう請求項１乃至３の何れかに記載のリチウム二次電
池負極用黒鉛―炭素複合材料の製造方法。4. The method for producing a graphite-carbon composite material for a negative electrode of a lithium secondary battery according to claim 1, wherein the chemical vapor deposition of carbon is performed at 900 to 1200 ° C.
層を２〜１０質量％形成する請求項１乃至４の何れかに
記載のリチウム二次電池負極用黒鉛―炭素複合材料の製
造方法。5. The method for producing a graphite-carbon composite material for a negative electrode of a lithium secondary battery according to claim 1, wherein a coating layer is formed on the graphite particles by 2 to 10% by mass by chemical vapor deposition of carbon.
の表面を被覆する結晶性炭素からなる被覆層とからな
り、前記被覆層の割合が２〜１０質量％であるリチウム
二次電池負極用黒鉛―炭素複合材料。6. A negative electrode for a lithium secondary battery, comprising oxidized graphite particles and a coating layer made of crystalline carbon coating the surface of the graphite particles, wherein the ratio of the coating layer is 2 to 10% by mass. Graphite-carbon composite material.
覆層の結晶性炭素の００２面とを平行にして結晶性炭素
で被覆されている請求項６に記載のリチウム二次電池負
極用黒鉛―炭素複合材料。7. The negative electrode for a lithium secondary battery according to claim 6, wherein the entire surface of the graphite particles is coated with crystalline carbon such that the surface of the graphite particles and the 002 plane of the crystalline carbon of the coating layer are parallel to each other. Graphite-carbon composite material.
した複合材料の7Ｌｉ−ＮＭＲスペクトルが、塩化リチ
ウム基準ケミカルシフトの４０〜５０ｐｐｍの位置に黒
鉛にインターカレーションしたリチウムの吸収スペクト
ルと、１０〜２０ｐｐｍの位置に結晶性炭素にインター
カレーションしたリチウムの吸収スペクトルとからなる
複合スペクトルを有する請求項６又は７に記載のリチウ
ム二次電池負極用黒鉛―炭素複合材料。8. The 7 Li-NMR spectrum of the composite material in which lithium ions are intercalated shows the absorption spectrum of lithium intercalated into graphite at a position of 40 to 50 ppm of the lithium chloride-based chemical shift, and the absorption spectrum of 10 to 20 ppm. The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to claim 6 or 7, having a composite spectrum consisting of an absorption spectrum of lithium intercalated into crystalline carbon at a position.
圧して得られる成形体の密度が１．４ ０〜１．７０ｇ
／ｃｍ3である請求項６乃至８の何れかに記載のリチウ
ム二次電池負極用黒鉛―炭素複合材料 。9. A molded product obtained by pressurizing at a pressure of 100 to 400 kg / cm 2 has a density of 1.40 to 1.70 g.
/ Cm 3 lithium secondary battery negative electrode graphite according to any one of claims 6 to 8 - carbon composite.
至９の何れかに記載のリチウム二次電池負極用黒鉛―炭
素複合材料。10. The graphite-carbon composite material for a negative electrode of a lithium secondary battery according to claim 6, wherein the graphite particles are natural graphite.
チウム二次電池負極用黒鉛―炭素複合材料を用いて形成
したリチウム二次電池。11. A lithium secondary battery formed using the graphite-carbon composite material for a negative electrode of a lithium secondary battery according to claim 6.
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| WO2016008951A1 (en) * | 2014-07-15 | 2016-01-21 | Imerys Graphite & Carbon Switzerland Ltd. | Hydrophilic surface-modified carbonaceous particulate material |
| US10707487B2 (en) | 2014-07-15 | 2020-07-07 | Imerys Graphite & Carbon Switzerland Ltd. | Hydrophilic surface-modified carbonaceous particulate material |
| JP2021502687A (en) * | 2017-11-13 | 2021-01-28 | ザ リージェンツ オブ ザ ユニバーシティ オブ コロラド，ア ボディー コーポレイトＴＨＥ ＲＥＧＥＮＴＳ ＯＦ ＴＨＥ ＵＮＩＶＥＲＳＩＴＹ ＯＦ ＣＯＬＯＲＡＤＯ，ａ ｂｏｄｙ ｃｏｒｐｏｒａｔｅ | Thin film coating on mixed metal oxides |
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