JPH11329434A - Carbon material for lithium ion secondary battery negative electrode and its manufacture - Google Patents
Carbon material for lithium ion secondary battery negative electrode and its manufactureInfo
- Publication number
- JPH11329434A JPH11329434A JP10150790A JP15079098A JPH11329434A JP H11329434 A JPH11329434 A JP H11329434A JP 10150790 A JP10150790 A JP 10150790A JP 15079098 A JP15079098 A JP 15079098A JP H11329434 A JPH11329434 A JP H11329434A
- Authority
- JP
- Japan
- Prior art keywords
- negative electrode
- carbon fiber
- secondary battery
- metal
- ion secondary
- 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
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、有機溶媒系のリチ
ウムイオン二次電池負極に適した電気伝導度が高く、高
容量の炭素材に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon material having a high electric conductivity and a high capacity suitable for a negative electrode of an organic solvent-based lithium ion secondary battery.
【０００２】[0002]
【従来の技術】近年、電子機器は小型化・軽量化・高性
能化を目指して急速な技術発展を遂げ、それによりセル
ラー、ＰＨＳ、カムコーダー、パソコンに代表される携
帯用電子機器の普及が一段と進んだ。これらの新しい機
器の発展に伴い、新たな二次電池として登場したのがニ
ッケル水素電池やリチウムイオン二次電池である。特
に、リチウムイオン二次電池は、高エネルギー密度及び
高起電力である他、非水電解液を用いるため作動温度範
囲が広く、長期保存に優れ、さらに軽量小型である等の
多くの利点を有している。従って、このようなリチウム
イオン二次電池は、携帯用電子機器電源をはじめとし
て、電気自動車、電力貯蔵用などの高性能電池としての
実用化が期待されている。2. Description of the Related Art In recent years, electronic devices have undergone rapid technological development with the aim of miniaturization, weight reduction, and high performance. As a result, portable electronic devices such as cellular phones, PHSs, camcorders, and personal computers have become more widespread. Advanced. With the development of these new devices, nickel-metal hydride batteries and lithium-ion secondary batteries have emerged as new secondary batteries. In particular, a lithium ion secondary battery has many advantages such as a high energy density and a high electromotive force, a wide operating temperature range due to the use of a non-aqueous electrolyte, excellent long-term storage, and light weight and small size. doing. Therefore, such a lithium ion secondary battery is expected to be put to practical use as a high-performance battery for a power source of a portable electronic device, an electric vehicle, a power storage device, and the like.
【０００３】このリチウムイオン二次電池の負極とし
て、金属リチウムに代わって炭素系材料を用いることが
研究され実用化に至っている。このような炭素系材料用
として炭素繊維を使用することが研究されており、特
に、熱処理温度の高いピッチ系黒鉛繊維を粉砕（ミルド
化）した黒鉛繊維ミルドを使用することが、特開平５−
３２５９６７号、６−３６８０２号、７−９０７２５号
等各公報に開示され実用化されている。The use of a carbon-based material instead of metallic lithium as the negative electrode of this lithium ion secondary battery has been studied and has been put to practical use. The use of carbon fibers for such a carbon-based material has been studied, and in particular, the use of graphite fiber mills obtained by pulverizing (milling) pitch-based graphite fibers having a high heat treatment temperature has been disclosed in Japanese Unexamined Patent Application Publication No. Hei.
Nos. 325967, 6-36802, 7-90725 and the like are disclosed and put to practical use.
【０００４】一方、低温焼成の炭素繊維については、特
開平７−６７５４号公報等に開示はあるものの、未だ実
用化には至っていない。これは、黒鉛繊維に比較して、
低温焼成の炭素繊維は、負極材として初期充電容量は大
きいものの、サイクル特性が劣り、また導電性が低いと
いう欠点があるためと考えられる。この導電性の改善の
方法として、炭素材を導電材で被覆したり、導電材と混
合使用することが研究されており、例えば、導電材とし
て金属を使用することが特開平７−３３５２６３号公報
に開示されている。しかし、特開平７−３３５２６３号
公報においては、金属の添加量が炭素材に対して９５／
２から４０／６０と比較的に多く、本方法を低温焼成の
ピッチ系炭素繊維に適用しても、初期容量が大きく低下
することも見られ、サイクル特性の改善効果はあまり見
られなかった。On the other hand, low-temperature fired carbon fibers have been disclosed in Japanese Patent Application Laid-Open No. 7-6754, but have not yet been put to practical use. This is compared to graphite fiber,
It is considered that the low-temperature fired carbon fiber has a drawback that although the initial charge capacity is large as a negative electrode material, the cycle characteristics are poor and the conductivity is low. As a method of improving the conductivity, it has been studied to coat a carbon material with a conductive material or to mix and use the carbon material with the conductive material. For example, Japanese Patent Application Laid-Open No. 7-335263 discloses the use of a metal as the conductive material. Is disclosed. However, in JP-A-7-335263, the amount of metal added is 95 /
2 to 40/60, which is relatively large, and even when this method was applied to pitch-based carbon fibers fired at a low temperature, the initial capacity was also significantly reduced, and the effect of improving the cycle characteristics was not so much observed.
【０００５】[0005]
【発明が解決しようとする課題】低温焼成の炭素繊維を
使用したリチウム二次電池負極のサイクル特性を、初期
容量の低下を抑え改善することを課題とする。SUMMARY OF THE INVENTION It is an object of the present invention to improve the cycle characteristics of a negative electrode of a lithium secondary battery using carbon fibers fired at a low temperature while suppressing a decrease in initial capacity.
【０００６】[0006]
【課題を解決するための手段】本発明者は、低温焼成の
炭素繊維の導電性と表面改質に着目し、金属の被覆にお
ける炭素繊維と被覆条件の最適化について種々検討した
結果、低温の特定の温度範囲で焼成されたピッチ系炭素
繊維を、特定の金属で、特に特定の方法で適度な厚さで
被覆することにより、電気伝導度が或る範囲以上とな
り、初期容量の低下を抑えつつ、リチウム二次電池負極
のサイクル特性を改善できることを見出し本発明を完成
するに至った。即ち、本発明は： ６００〜１５００℃で炭化処理された、平均粒径が
５〜５０μｍのピッチ系炭素繊維ミルドの表面を、銀、
白金または銅で被覆したリチウムイオン二次電池負極用
炭素材を提供する。また、 銀、白金または銅の被覆の厚さが０．５〜３０ｎｍ
である点にも特徴を有する。また、 銀、白金または銅の被覆を蒸着法で行うリチウムイ
オン二次電池負極用炭素材の製造方法を提供する。Means for Solving the Problems The present inventor focused on the conductivity and surface modification of carbon fibers fired at a low temperature, and as a result of various studies on the optimization of the carbon fibers and coating conditions in metal coating, as a result, By coating a pitch-based carbon fiber fired in a specific temperature range with a specific metal, in particular with an appropriate thickness by a specific method, the electric conductivity becomes a certain range or more, and a decrease in the initial capacity is suppressed. While finding that the cycle characteristics of the lithium secondary battery negative electrode can be improved, the present invention has been completed. That is, the present invention provides: A surface of a pitch-based carbon fiber milled carbonized at 600 to 1500 ° C. and having an average particle size of 5 to 50 μm is coated with silver,
Provided is a carbon material for a negative electrode of a lithium ion secondary battery coated with platinum or copper. In addition, the thickness of the coating of silver, platinum or copper is 0.5 to 30 nm.
Is also characteristic. Further, the present invention provides a method for producing a carbon material for a negative electrode of a lithium ion secondary battery, in which silver, platinum or copper is coated by a vapor deposition method.
【０００７】[0007]
【発明の実施の形態】以下に本発明を更に詳細に説明す
る。 (A) ＜低温焼成の炭素繊維＞ 炭素繊維としては、電池用負極材としての性能面から、
ピッチ系炭素繊維を適当な温度範囲で炭化したものが好
ましい。また、負極材としては、炭化後に粉砕したもの
（以下炭素繊維ミルドという）が好ましく用いられる。
この炭素繊維ミルドは、通常、ピッチを原料とし、常法
によって紡糸、不融化、及び炭化し炭素繊維とし、次い
で該炭素繊維を粉砕（ミルド化）することで製造されて
いる。以下に、その各々の工程等について簡単に説明す
る。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. (A) <Low-temperature fired carbon fiber> From the viewpoint of performance as a negative electrode material for a battery,
It is preferable that the pitch-based carbon fiber is carbonized in an appropriate temperature range. Further, as the negative electrode material, one obtained by pulverizing after carbonization (hereinafter referred to as carbon fiber mill) is preferably used.
This milled carbon fiber is usually produced by using a pitch as a raw material, spinning, infusibilizing, and carbonizing into a carbon fiber by a conventional method, and then pulverizing (milling) the carbon fiber. Hereinafter, each of the steps will be briefly described.
【０００８】1)原料ピッチ 出発原料ピッチは、樹脂系、石油系、石炭系、触媒など
を用いた合成系の各ピッチのいずれに限定されるもので
はない。原料ピッチの軟化点も特に限定されるものでは
ないが、紡糸温度との関係から、軟化点が低くて且つ不
融化反応速度の速いものが、製造コスト及び安定性の面
から有利である。従って、原料ピッチの軟化点は一般に
２３０℃以上３５０℃以下、好ましくは２８０℃以上３
３０℃以下である。1) Raw material pitch The starting raw material pitch is not limited to any of resin-based, petroleum-based, coal-based, and synthetic pitches using a catalyst or the like. Although the softening point of the raw material pitch is not particularly limited, a material having a low softening point and a high infusibilization reaction rate is advantageous from the viewpoint of production cost and stability in view of the spinning temperature. Therefore, the softening point of the raw material pitch is generally from 230 ° C to 350 ° C, preferably from 280 ° C to 3 ° C.
30 ° C. or less.
【０００９】2)紡糸 原料ピッチを溶融紡糸する方法は特に限定されるもので
はなく、メルトスピニング、メルトブロー、遠心紡糸等
種々の方法を使用することが出来るが、紡糸時の生産性
や得られる繊維の品質の観点から、メルトブロー法が好
ましい。この時の紡糸孔の大きさは、０．１ｍｍΦ以上
０．５ｍｍΦ以下、好ましくは０．１５ｍｍΦ以上０．
３ｍｍΦ以下である。また、紡糸速度は毎分５００ｍ以
上、好ましくは毎分１５００ｍ以上である。紡糸温度は
使用する原料ピッチにより幾分変更されるが、原料ピッ
チの軟化点以上でピッチが変質しない温度であれば良
く、３００℃以上４００℃以下、好ましくは３００℃以
上３８０℃以下である。2) Spinning The method for melt-spinning the raw material pitch is not particularly limited, and various methods such as melt spinning, melt blowing and centrifugal spinning can be used. From the viewpoint of the quality of the resin, the melt blow method is preferred. The size of the spinning hole at this time is from 0.1 mmΦ to 0.5 mmΦ, preferably from 0.15 mmΦ to 0.
3 mmΦ or less. The spinning speed is 500 m / min or more, preferably 1500 m / min or more. The spinning temperature is somewhat changed depending on the raw material pitch to be used, but may be any temperature above the softening point of the raw material pitch and at which the pitch does not deteriorate, and is 300 ° C to 400 ° C, preferably 300 ° C to 380 ° C.
【００１０】3)不融化 不融化方法としては、特に制限されないが、常法により
二酸化窒素や酸素等の酸化性ガス雰囲気中で加熱処理す
る方法や、硝酸やクロム酸等の酸化性水溶液中で処理す
る方法、さらには、光やγ線等による重合処理方法も可
能である。より簡便な不融化方法は、空気中で２００〜
３５０℃で一定時間加熱処理する方法であり、その時の
平均昇温速度は３℃／分以上、好ましくは４℃／分以上
である。3) Infusibilization The infusibilization method is not particularly limited, but may be a heat treatment in an oxidizing gas atmosphere such as nitrogen dioxide or oxygen by a conventional method, or an oxidizing aqueous solution such as nitric acid or chromic acid. A treatment method, and a polymerization treatment method using light, γ-rays, or the like are also possible. A simpler infusibilization method is 200-
This is a method of performing heat treatment at 350 ° C. for a certain period of time, at which time the average temperature rise rate is 3 ° C./min or more, preferably 4 ° C./min or more.
【００１１】4)炭化 不融化繊維は、常法により酸化性ガスの非存在下、例え
ば不活性ガス中で加熱処理（炭化）することにより炭素
繊維とすることができる。通常、ピッチ系炭素繊維の炭
化は、黒鉛構造が発達しないように２０００℃以下の温
度で行われるが、低温焼成の炭素繊維を電池の負極材用
として用いるには、６００℃以上１５００℃以下、好ま
しくは６５０℃以上１３００℃以下の温度で炭化を行う
ことが好ましい。本発明の炭素繊維をリチウム二次電池
の負極とした場合、電池の初期容量は炭化温度が７００
℃程度までは、炭化温度の上昇に伴い増加する傾向にあ
り、７００℃から１３００℃程度までは、原因は不明で
あるが、炭化温度の上昇とあまり相関が見られず比較的
に高容量となり、１３００℃を越えると炭素繊維の構造
が黒鉛構造に近ずくため、炭化温度の上昇に伴い急激に
低下する傾向が見られる。4) Carbonization The infusible fiber can be converted into a carbon fiber by heat treatment (carbonization) in the absence of an oxidizing gas, for example, in an inert gas, by a conventional method. Normally, carbonization of pitch-based carbon fiber is performed at a temperature of 2000 ° C. or less so that a graphite structure does not develop. However, in order to use a low-temperature fired carbon fiber for a negative electrode material of a battery, 600 ° C. to 1500 ° C. Preferably, carbonization is performed at a temperature of 650 ° C. or more and 1300 ° C. or less. When the carbon fiber of the present invention is used as a negative electrode of a lithium secondary battery, the initial capacity of the battery is a carbonization temperature of 700.
Up to about ℃, there is a tendency to increase with the rise of carbonization temperature, and from 700 ℃ to about 1300 ℃, the cause is unknown, but there is not much correlation with the rise of carbonization temperature and relatively high capacity When the temperature exceeds 1,300 ° C., the structure of the carbon fiber approaches the graphite structure, and therefore, the tendency of the carbon fiber to rapidly decrease as the carbonization temperature increases is observed.
【００１２】一方、炭化温度の上昇に伴い黒鉛構造が発
達し、また導電性も良くなるためか、電池のサイクル効
率は、炭化温度の上昇に伴い高くなる傾向が見られる。
このため、炭化温度が６００℃未満の炭素繊維では、サ
イクル効率が悪く、１５００℃を越えた炭素繊維では、
初期容量が黒鉛材に近いレベルまで低下するのでリチウ
ム二次電池用炭素材としてはあまり好ましくない。ま
た、この炭化温度範囲は、以下のミルド化を効率良く行
う上でも好ましい範囲である。なお、この時の昇温速度
や保持時間は特に限定されるものでない。On the other hand, the cycle efficiency of the battery tends to increase as the carbonization temperature increases, probably because the graphite structure develops and the conductivity improves as the carbonization temperature increases.
For this reason, the carbon fiber whose carbonization temperature is lower than 600 ° C. has poor cycle efficiency, and the carbon fiber whose temperature exceeds 1500 ° C.
Since the initial capacity is reduced to a level close to that of the graphite material, it is not preferable as a carbon material for a lithium secondary battery. Further, this carbonization temperature range is a preferable range in terms of efficiently performing the following milling. The rate of temperature rise and the holding time at this time are not particularly limited.
【００１３】5)ミルド化 本発明においては、上記のような温度範囲で炭化された
炭素繊維をミルド化する。リチウムイオンの出入りを容
易にするためには、繊維長を短く、即ち容積（重量）当
たりの繊維表面積を出来るだけ大きくすることが要求さ
れる。また、繊維形態を保持したまま表面積を大きくす
るようミルド化することが、電池の性能を向上させる要
因となっている。しかしながら、繊維をいたずらに微粉
化すると、粉砕後の収率の低下を招き、また、金属の被
覆の面から見て、同じ厚さでも炭素材が小粒径になるほ
ど、炭素材に対する金属の重量比が増加し、電池の初期
容量の低下を生じる等のデメリットが発生するので、適
度な粒度分布及び平均粒径とすることが要求され、平均
粒径が５〜５０μｍ、好ましくは８〜３０μｍの範囲に
ミルド化することが好ましい。5) Milling In the present invention, carbonized carbon fibers in the above temperature range are milled. In order to facilitate the entry and exit of lithium ions, it is required that the fiber length be short, that is, the fiber surface area per volume (weight) be as large as possible. Milling so as to increase the surface area while maintaining the fiber form is a factor for improving the performance of the battery. However, if the fibers are unnecessarily pulverized, the yield after pulverization is reduced, and the weight of the metal relative to the carbon material becomes smaller as the carbon material has a smaller particle size even with the same thickness in view of the metal coating. The ratio increases, and disadvantages such as a decrease in the initial capacity of the battery occur. Therefore, it is required to have an appropriate particle size distribution and an average particle size, and the average particle size is 5 to 50 μm, preferably 8 to 30 μm. It is preferable to mill in the range.
【００１４】なお、本発明の粒度分布は、レーザ回折式
粒度分布測定装置によって測定される値とする。本発明
の方法に使用するミルド化機には、ボールミル、擂潰
機、ビクトリーミル、ジェットミル、ターボミル、クロ
スフローミル、高速回転ミル等任意の装置を使用でき
る。特に、ブレードを取り付けたローターを高速に回転
する機械、例えば高速回転ミルの使用が最も好適であ
る。この場合に、ローターの回転数、ブレードの角度、
ローターの周辺に取り付けられたフィルターの目の大き
さ等を調整することにより、炭素繊維ミルドの繊維長を
コントロールできる。また、ミルド化が炭素繊維と粉砕
機との機械的衝突によってなされているもの（高速回転
ミル等）では、金属の摩耗が特に生じ易いため、粉砕部
の材質を摩耗しにくいものにする必要がある。例えば、
衝突部分を摩耗しにくい窒化処理金属とすると良い。粉
砕が主として機械的衝突以外によってなされているもの
（ジェツトミル等）でも、粉砕機の摩砕又は切断又は衝
突部分を構成する金属の酸化物等の混入を避けるため内
部ライニング等の処理やチタンなど高硬度金属の被膜に
よる金属部の補強が好ましい。The particle size distribution of the present invention is a value measured by a laser diffraction type particle size distribution measuring device. As the milling machine used in the method of the present invention, any device such as a ball mill, a crusher, a Victory mill, a jet mill, a turbo mill, a cross flow mill, a high-speed rotation mill, and the like can be used. In particular, it is most preferable to use a machine that rotates the rotor with the blade attached thereto at a high speed, for example, a high-speed rotating mill. In this case, the rotor speed, blade angle,
The fiber length of the milled carbon fiber can be controlled by adjusting the size of the mesh of the filter attached around the rotor. In the case where the milling is performed by mechanical collision between the carbon fiber and the crusher (such as a high-speed rotating mill), the metal is particularly liable to be abraded. is there. For example,
It is preferable that the collision portion is made of a nitrided metal that is hard to wear. Even in the case where grinding is mainly performed by means other than mechanical collision (jet mill, etc.), internal lining treatment or titanium or other processing such as internal lining or the like is used to avoid the grinding or cutting of the grinding machine or the incorporation of metal oxides forming the collision part. Reinforcement of the metal part by a hard metal coating is preferred.
【００１５】(B) ＜金属被覆＞ 1)被覆金属 導電性の高い金属であれば、金属単体、もしくは合金、
酸化物等使用可能であるが、本発明においては、銀、白
金または銅がより効果的で好ましい。これは、これらの
金属が導電性に優れると共に、炭素繊維ミルドに適当な
厚さで被覆することが比較的に容易であり、また、電解
液との反応性が低い面からも好ましい。(B) <Metal coating> 1) Coated metal As long as the metal has high conductivity, a simple metal or an alloy,
Although an oxide or the like can be used, in the present invention, silver, platinum or copper is more effective and preferable. This is preferable because these metals have excellent conductivity, it is relatively easy to coat the carbon fiber mill with an appropriate thickness, and the reactivity with the electrolytic solution is low.
【００１６】2)金属の被覆厚 使用炭素材の種類、粒径等の形状、及び被覆する金属の
電気伝導度や比重により金属の被覆厚は幾分変化する
が、本発明においては、０．５〜３０ｎｍ、好ましくは
０．７〜１０ｎｍの厚さで白金、銅または銀を炭素繊維
ミルドに被覆することが望ましい。被覆厚が０．５ｎｍ
以下では、導電性の改善効果が低いためか、電池特性の
改善効果が見られない。また、被覆厚が３０ｎｍを越え
ると、サイクル特性の改善はみられるものの、被覆金属
分の重量比が増加するため、単位重量当たりの初期容量
の低下が著しく、また、充放電時にＬｉイオンの移動性
が低下し、さらに初期容量を低下させる恐れもあり好ま
しくない。なお、本発明において、被覆厚の測定は、Ｓ
ＩＭＳ（二次イオン質量分析）法により実施した。この
測定は、ＳＩＭＳ装置としてＡ−ＤＩＤＡ３０００（Ａ
ＴＯＭＩＫＡ社製）を使用し、一次イオン源にＯ2 + を
用いて１２ＫｅＶのエネルギーで６０×６０μｍの範囲
をスパッタリングを行い、標準試料を用いて時間補正し
算定した。2) Metal coating thickness The metal coating thickness varies somewhat depending on the type of carbon material used, the shape of the particle size, etc., and the electrical conductivity and specific gravity of the metal to be coated. It is desirable to coat the carbon fiber mill with platinum, copper or silver in a thickness of 5 to 30 nm, preferably 0.7 to 10 nm. 0.5nm coating thickness
Below, the effect of improving the battery characteristics is not seen, probably because the effect of improving the conductivity is low. When the coating thickness exceeds 30 nm, although the cycle characteristics are improved, the weight ratio of the coating metal is increased, so that the initial capacity per unit weight is remarkably reduced. This is not preferable because the properties may be reduced and the initial capacity may be further reduced. In the present invention, the measurement of the coating thickness is performed by S
The measurement was performed by the IMS (secondary ion mass spectrometry) method. This measurement was performed using an A-DIDA3000 (A
(TOMIKA), using O 2 + as the primary ion source, sputtering at an energy of 12 KeV in a range of 60 × 60 μm, and performing time correction using a standard sample to calculate.
【００１７】3)金属の被覆方法 金属の被覆方法としては、通常用いられる蒸着法、無電
解メッキ法、浸漬法、スパッタリング法等の使用が可能
であるが、簡便さ、本発明の被覆厚における炭素繊維と
金属の均一な被覆性、後処理が不要である等から、蒸着
法が特に好ましい。また、蒸着装置としては汎用の装置
を使用することができる面も好ましい。3) Metal Coating Method As the metal coating method, a commonly used vapor deposition method, electroless plating method, immersion method, sputtering method and the like can be used. The vapor deposition method is particularly preferred because the carbon fiber and the metal can be uniformly covered and no post-treatment is required. In addition, it is preferable that a general-purpose device can be used as the vapor deposition device.
【００１８】(C) ＜二次電池用負極＞ 本発明の金属被覆炭素繊維ミルドは、通常の手法により
負極とすることが出来る。即ち、ポリエチレンやポリテ
トラフルオロエチレン等のバインダーを添加し、有機溶
媒あるいは水溶媒を用いスラリー状とし、厚さ１０〜５
０μｍの銅、ニッケル等からなる金属箔上の片面または
両面に塗布し、圧延、乾燥を行い、厚さ１００μｍ程度
のシート状物とする方法が広く用いられている。その
後、所定の幅・長さにスリットし、正極及びセパレータ
ーと共に巻取り製缶する方法が一般的である。本発明の
金属被覆炭素繊維ミルドを負極に用い、リチウムイオン
二次電池を作製する場合には、電解液としてはリチウム
塩を溶解し得るものであればよいが、特に非プロトン性
の誘電率が大きい有機溶媒が好ましい。(C) <Negative electrode for secondary battery> The metal-coated carbon fiber mill of the present invention can be made into a negative electrode by a usual method. That is, a binder such as polyethylene or polytetrafluoroethylene is added, and a slurry is formed using an organic solvent or an aqueous solvent.
A method is widely used in which a sheet is coated on one or both sides of a metal foil made of 0 μm copper, nickel or the like, rolled and dried to form a sheet having a thickness of about 100 μm. After that, a method of slitting to a predetermined width and length and winding and forming the can together with the positive electrode and the separator is general. When a metal-coated carbon fiber mill of the present invention is used for a negative electrode to produce a lithium ion secondary battery, any electrolytic solution may be used as long as it can dissolve a lithium salt. Larger organic solvents are preferred.
【００１９】上記有機溶媒としては、例えば、プロピレ
ンカーボネート、エチレンカーボネート、テトラヒドロ
フラン、２−メチルテトラヒドロフラン、ジオキソラ
ン、４−メチル−ジオキソラン、アセトニトリル、ジメ
チルカーボネート、メチルエチルカーボネート、ジエチ
ルカーボネート等を挙げることができる。これらの溶媒
を単独あるいは適宜混合して用いることが可能である。
電解質としては、安定なアニオンを生成するリチウム
塩、例えば、過塩素酸リチウム、ホウフッ化リチウム、
六塩化アンチモン酸リチウム、六フッ化アンチモン酸リ
チウム等が好適である。Examples of the organic solvent include propylene carbonate, ethylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, 4-methyl-dioxolan, acetonitrile, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and the like. These solvents can be used alone or in a suitable mixture.
As the electrolyte, a lithium salt that generates a stable anion, for example, lithium perchlorate, lithium borofluoride,
Lithium antimonate hexachloride, lithium hexafluoroantimonate and the like are preferred.
【００２０】リチウムイオン二次電池の正極としては、
例えば、酸化クロム、酸化チタン、酸化コバルト、五酸
化バナジウム等の金属酸化物や、リチウムマンガン酸化
物（ＬｉＭｎ2 Ｏ4 ）、リチウムコバルト酸化物（Ｌｉ
ＣｏＯ2 ）、リチウムニッケル酸化物（ＬｉＮｉＯ2 ）
等のリチウム金属酸化物；硫化チタン、硫化モリブデン
等の遷移金属のカルコゲン化合物；及びポリアセチレ
ン、ポリパラフェニレン、ポリピロール等の導電性を有
する共役系高分子物質等を用いることが出来る。これら
の正極と負極との間に合成繊維製又はガラス繊維製の不
織布、織布やポリオレフィン系多孔質膜、ポリテトラフ
ルオロエチレンの不織布等のセパレータを設ける。本発
明の二次電池は、前記セパレータ、集電体、ガスケッ
ト、封口板、ケース等の電池構成要素と本発明の特定の
負極を用い、常法に従って円筒型、角型或いはボタン型
等の形態のリチウムイオン二次電池に組立てることがで
きる。As the positive electrode of the lithium ion secondary battery,
For example, metal oxides such as chromium oxide, titanium oxide, cobalt oxide, and vanadium pentoxide, lithium manganese oxide (LiMn 2 O 4 ), lithium cobalt oxide (Li
CoO 2 ), lithium nickel oxide (LiNiO 2 )
Lithium metal oxides; chalcogen compounds of transition metals such as titanium sulfide and molybdenum sulfide; and conductive conjugated polymers such as polyacetylene, polyparaphenylene, and polypyrrole. A separator such as a nonwoven fabric made of synthetic fiber or glass fiber, a woven fabric, a polyolefin-based porous membrane, or a nonwoven fabric made of polytetrafluoroethylene is provided between the positive electrode and the negative electrode. The secondary battery of the present invention uses the above-mentioned battery components such as the separator, current collector, gasket, sealing plate, and case and the specific negative electrode of the present invention, and has a form such as a cylindrical type, a square type, or a button type according to a conventional method. Can be assembled into a lithium ion secondary battery.
【００２１】[0021]
【実施例】以下に、本発明を実施例により更に具体的に
説明するが、本発明はこれらの例によってなんら限定さ
れるものではない。 （実施例１）軟化点２８０℃の光学的異方性の石油系メ
ソフェーズピッチを原料とし、幅３ｍｍのスリットの中
に直径０．２ｍｍφの紡糸孔を一列に１，５００個有す
る口金を用い、スリットから加熱空気を噴出させて、溶
融ピッチを牽引してピッチ繊維を製造した。この時の紡
糸ピッチ粘度は１２ポイズであった。紡出されたピッチ
繊維を、捕集部分が２０メッシュのステンレス製金網で
出来たベルトの背面から吸引しつつ、ベルト上にマット
状に捕集した。この捕集マットを空気中、室温から３０
０℃までの平均昇温速度６℃／分で昇温して不融化処理
をした。このようにして得られたメソフェーズピッチ不
融化繊維を９００℃で炭化処理し炭素繊維を得た。EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. (Example 1) An optically anisotropic petroleum-based mesophase pitch having a softening point of 280 ° C was used as a raw material, and a spinneret having 1,500 spinning holes with a diameter of 0.2 mm in a 3 mm wide slit was used. Hot air was ejected from the slits to pull the molten pitch to produce pitch fibers. The spinning pitch viscosity at this time was 12 poise. The spun pitch fibers were collected in a mat shape on the belt while being sucked from the back surface of a belt made of a stainless steel wire mesh having a collecting portion of 20 mesh. Place this collection mat in air at room temperature to 30
The temperature was raised at an average temperature rising rate of 6 ° C./min up to 0 ° C. to perform infusibility treatment. The thus obtained mesophase pitch infusible fiber was carbonized at 900 ° C. to obtain a carbon fiber.
【００２２】次いで、該炭素繊維を、高速回転タイプの
粉砕機によりミルド化し炭素繊維ミルドを得た。該炭素
繊維ミルドの粒径を、レ−ザ−回折式粒度分布測定装置
で測定した結果、平均粒径が１８μｍであった。該炭素
繊維ミルドに汎用の真空蒸着装置を使用し、白金を２ｗ
ｔ％蒸着し、金属被覆炭素繊維ミルドを作製した。被覆
厚は、ＳＩＭＳで測定した結果、平均で約１ｎｍであっ
た。該金属被覆炭素繊維ミルドを使用し、充放電容量等
の電池性能確認した結果を表１に示す。なお、電池性能
は、陽極及び参照電極に金属リチウムを用い、エチレン
カーボネート（ＥＣ）／ジメチルカーボネート（ＤＭ
Ｃ）を体積比で１／１に調整した混合炭酸エステル溶媒
に、電解質として過塩素酸リチウム（ＬｉＣｌＯ4）を
１モルの濃度で溶解させた電解液中で、１００ｍＡ／ｇ
の定電流充放電下、測定電位範囲は対参照電極（０〜
１．５Ｖ／Ｌｉ／Ｌｉ+ ）で、１０回繰返し測定とし
た。この結果を表１に示す。Next, the carbon fiber was milled with a high-speed rotation type pulverizer to obtain a carbon fiber mill. As a result of measuring the particle size of the carbon fiber mill by a laser diffraction type particle size distribution analyzer, the average particle size was 18 μm. Using a general-purpose vacuum deposition apparatus for the carbon fiber mill, platinum
t% was deposited to produce a metal-coated carbon fiber mill. The coating thickness was about 1 nm on average as measured by SIMS. Table 1 shows the results of battery performance confirmation such as charge / discharge capacity using the metal-coated carbon fiber mill. The battery performance was measured using ethylene lithium (EC) / dimethyl carbonate (DM) using lithium metal for the anode and the reference electrode.
100 mA / g in an electrolytic solution in which lithium perchlorate (LiClO 4 ) was dissolved at a concentration of 1 mol as an electrolyte in a mixed carbonate solvent in which C) was adjusted to 1/1 by volume ratio.
Under the constant current charge / discharge of
(1.5 V / Li / Li + ) and the measurement was repeated 10 times. Table 1 shows the results.
【００２３】（比較例１）実施例１で得た炭素繊維ミル
ドを用い実施例１と同様に電池性能を測定した。この結
果を合わせて表１に示す。 （実施例２）実施例１で得た炭素繊維ミルドを用い、金
属を白金から銅に代えた以外実施例１と同様にして、銅
を５ｗｔ％蒸着した炭素繊維ミルドを得た。被覆厚は平
均で約１ｎｍであった。 該金属被覆炭素繊維ミルドを
用い実施例１と同様に電池性能を測定した結果を合わせ
て表１に示す。 （実施例３）実施例１で得た炭素繊維ミルドを用い、金
属を白金から銀に代えた以外実施例１と同様にして、銀
を４ｗｔ％蒸着した炭素繊維ミルドを得た。被覆厚は平
均で約１ｎｍであった。 該金属被覆炭素繊維ミルドを
用い実施例１と同様に電池性能を測定した結果を合わせ
て表１に示す。Comparative Example 1 Battery performance was measured in the same manner as in Example 1 using the milled carbon fiber obtained in Example 1. The results are shown in Table 1. (Example 2) The carbon fiber mill obtained by vapor-depositing 5 wt% of copper was obtained in the same manner as in Example 1 except that the metal was changed from platinum to copper, using the carbon fiber mill obtained in Example 1. The coating thickness was on average about 1 nm. Table 1 also shows the results of measuring the battery performance in the same manner as in Example 1 using the metal-coated carbon fiber mill. (Example 3) A carbon fiber mill obtained by depositing 4 wt% of silver was obtained in the same manner as in Example 1 except that the metal was changed from platinum to silver, using the carbon fiber mill obtained in Example 1. The coating thickness was on average about 1 nm. Table 1 also shows the results of measuring the battery performance in the same manner as in Example 1 using the metal-coated carbon fiber mill.
【００２４】[0024]
【表１】 [Table 1]
【００２５】（実施例４）軟化点２７０℃の光学的等方
性の石油系ピッチを原料として、実施例１と同様に紡糸
及び不融化を行い、不融化繊維を得た。該不融化繊維
を、実施例１と炭化温度を６５０℃に変えた以外同様に
して、炭化及びミルド化を行い、平均粒径２０μｍの炭
素繊維ミルドを得た。該炭素繊維ミルドを、実施例１と
同様に白金を用い蒸着量を変化させた５種の白金被覆の
炭素繊維ミルドを作製し、実施例１と同様に電池性能を
測定した結果を表２に示す。 （比較例２）実施例４で得た炭素繊維ミルドを用い実施
例１と同様に電池性能を測定した。この結果を合わせて
表２に示す。Example 4 Using an optically isotropic petroleum pitch having a softening point of 270 ° C. as a raw material, spinning and infusibility were carried out in the same manner as in Example 1 to obtain infusible fibers. The infusible fiber was carbonized and milled in the same manner as in Example 1 except that the carbonization temperature was changed to 650 ° C. to obtain a carbon fiber mill having an average particle diameter of 20 μm. Five kinds of platinum-coated carbon fiber mills were prepared by changing the deposition amount using platinum in the same manner as in Example 1 and the battery performance was measured in the same manner as in Example 1. Show. (Comparative Example 2) Using the milled carbon fiber obtained in Example 4, battery performance was measured in the same manner as in Example 1. The results are shown in Table 2.
【００２６】[0026]
【表２】 [Table 2]
【００２７】[0027]
【発明の効果】以上詳細に述べたように、本発明によ
り、低温焼成の炭素繊維を用いたリチウムイオン二次電
池負極のサイクル特性が大幅に改善される。As described above in detail, according to the present invention, the cycle characteristics of a negative electrode of a lithium ion secondary battery using a low-temperature fired carbon fiber are greatly improved.
Claims (3)
平均粒径が５〜５０μｍのピッチ系炭素繊維ミルドの表
面を、銀、白金または銅で被覆したことを特徴とするリ
チウムイオン二次電池負極用炭素材。1. Carbonized at 600 to 1500 ° C.
A carbon material for a negative electrode of a lithium ion secondary battery, wherein a surface of a milled pitch-based carbon fiber having an average particle size of 5 to 50 μm is coated with silver, platinum or copper.
５〜３０ｎｍであることを特徴とする請求項１記載の炭
素材。2. The coating of silver, platinum or copper having a thickness of 0.
The carbon material according to claim 1, wherein the thickness is 5 to 30 nm.
うことを特徴とする請求項１または２記載の炭素材の製
造方法。3. The method for producing a carbon material according to claim 1, wherein the coating of silver, platinum or copper is performed by a vapor deposition method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10150790A JPH11329434A (en) | 1998-05-15 | 1998-05-15 | Carbon material for lithium ion secondary battery negative electrode and its manufacture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10150790A JPH11329434A (en) | 1998-05-15 | 1998-05-15 | Carbon material for lithium ion secondary battery negative electrode and its manufacture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH11329434A true JPH11329434A (en) | 1999-11-30 |
Family
ID=15504500
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10150790A Pending JPH11329434A (en) | 1998-05-15 | 1998-05-15 | Carbon material for lithium ion secondary battery negative electrode and its manufacture |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH11329434A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001052335A3 (en) * | 2000-01-14 | 2002-03-07 | Comsat Corp | High strength carbon anode for a rechargeable lithium ion electrochemical cell |
| WO2002027822A1 (en) * | 2000-06-06 | 2002-04-04 | Institute Of Physics, Chinese Academy Of Sciences | Nanometer metal or nanometer alloy/carbon composite material, producing method thereof and the application thereof in a secondary lithium battery |
| US6896706B2 (en) | 2002-01-17 | 2005-05-24 | Korea Institute Of Science And Technology | Carbonaceous materials coated with a metal or metal oxide, a preparation method thereof, and a composite electrode and lithium secondary battery comprising the same |
| US8968921B2 (en) | 2005-10-05 | 2015-03-03 | California Institute Of Technology | Fluoride ion electrochemical cell |
-
1998
- 1998-05-15 JP JP10150790A patent/JPH11329434A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001052335A3 (en) * | 2000-01-14 | 2002-03-07 | Comsat Corp | High strength carbon anode for a rechargeable lithium ion electrochemical cell |
| WO2002027822A1 (en) * | 2000-06-06 | 2002-04-04 | Institute Of Physics, Chinese Academy Of Sciences | Nanometer metal or nanometer alloy/carbon composite material, producing method thereof and the application thereof in a secondary lithium battery |
| US6896706B2 (en) | 2002-01-17 | 2005-05-24 | Korea Institute Of Science And Technology | Carbonaceous materials coated with a metal or metal oxide, a preparation method thereof, and a composite electrode and lithium secondary battery comprising the same |
| US8968921B2 (en) | 2005-10-05 | 2015-03-03 | California Institute Of Technology | Fluoride ion electrochemical cell |
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