JP4299608B2 - Method for producing graphite material, negative electrode material for lithium ion secondary battery, and lithium ion secondary battery - Google Patents
Method for producing graphite material, negative electrode material for lithium ion secondary battery, and lithium ion secondary battery Download PDFInfo
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- JP4299608B2 JP4299608B2 JP2003290720A JP2003290720A JP4299608B2 JP 4299608 B2 JP4299608 B2 JP 4299608B2 JP 2003290720 A JP2003290720 A JP 2003290720A JP 2003290720 A JP2003290720 A JP 2003290720A JP 4299608 B2 JP4299608 B2 JP 4299608B2
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- Prior art keywords
- graphite material
- precursor
- graphite
- negative electrode
- fibrous
- 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.)
- Expired - Lifetime
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- 239000007770 graphite material Substances 0.000 title claims description 246
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 47
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 47
- 239000007773 negative electrode material Substances 0.000 title claims description 41
- 238000004519 manufacturing process Methods 0.000 title claims description 34
- 239000002243 precursor Substances 0.000 claims description 142
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 77
- 229910002804 graphite Inorganic materials 0.000 claims description 66
- 239000010439 graphite Substances 0.000 claims description 66
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 9
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Images
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
Description
本発明は、黒鉛質材料の製造方法、およびリチウムイオン二次電池用負極材料、ならびに該負極材料を用いた、初期充放電効率と放電容量が高く、かつ急速充放電効率とサイクル特性に優れるリチウムイオン二次電池に関する。 The present invention relates to a method for producing a graphite material, a negative electrode material for a lithium ion secondary battery, and lithium using the negative electrode material, which has high initial charge / discharge efficiency and high discharge capacity, and excellent rapid charge / discharge efficiency and cycle characteristics. The present invention relates to an ion secondary battery.
近年、電子機器の小型化あるいは高性能化に伴い、電池の高エネルギー密度化に対する要望はますます高まっている。特に、リチウムイオン二次電池は、他の二次電池に比べて高電圧化が可能であり、エネルギー密度を高められるため注目されている。リチウムイオン二次電池は、負極、正極および非水電解質を主たる構成要素とする。非水電解質を介して、リチウムイオンは放電過程および充電過程で負極と正極との間を移動し、二次電池となる。通常、上記のリチウムイオン二次電池の負極材料には炭素材料が使用される。このような炭素材料として、特に、充放電特性に優れ、高い放電容量と電位平坦性とを示す黒鉛（特許文献１など）が有望視されている。 In recent years, with the miniaturization or high performance of electronic devices, there is an increasing demand for higher energy density of batteries. In particular, lithium ion secondary batteries are attracting attention because they are capable of higher voltages than other secondary batteries and can increase energy density. A lithium ion secondary battery has a negative electrode, a positive electrode, and a non-aqueous electrolyte as main components. Through the non-aqueous electrolyte, lithium ions move between the negative electrode and the positive electrode in the discharging process and charging process, and become a secondary battery. Usually, a carbon material is used for the negative electrode material of the lithium ion secondary battery. As such a carbon material, graphite (eg, Patent Document 1) that is excellent in charge / discharge characteristics and exhibits high discharge capacity and potential flatness is particularly promising.
負極材料として使用される黒鉛（黒鉛質粒子）としては、天然黒鉛、人造黒鉛などの黒鉛粒子、さらにはタールやピッチを原料としたメソフェーズピッチやメソフェーズ小球体を熱処理して得られるバルクメソフェーズ黒鉛質粒子やメソフェーズ小球体黒鉛質粒子、粒子状や繊維状のメソフェーズピッチを酸化不融化した後に熱処理して得られるメソフェーズ黒鉛質粒子やメソフェーズ黒鉛質繊維、天然黒鉛や人造黒鉛をタールやピッチなどで被覆した後に熱処理して得られる複合黒鉛質粒子などが挙げられる。 The graphite (graphite particles) used as the negative electrode material includes natural graphite, artificial graphite and other bulk particles, as well as bulk mesophase graphite obtained by heat treatment of mesophase pitch and mesophase spherules made from tar and pitch. Particles, mesophase small spherical graphite particles, mesophase graphite particles and mesophase graphite fibers obtained by heat-treating particulate or fibrous mesophase pitch after oxidation infusibilization, natural graphite and artificial graphite are coated with tar, pitch, etc. And composite graphite particles obtained by heat treatment.
さらに、急速充放電特性やサイクル特性の向上を目的として、上記黒鉛質粒子に導電助材を配合、複合することが検討されている。例えば、球状粒子よりなる黒鉛材料と炭素繊維とからなる複合炭素材（特許文献２）、メソフェーズ小球体黒鉛質粒子に気相成長炭素繊維を３〜３０質量％混合したもの（特許文献３）、球状黒鉛または鱗片状黒鉛に繊維状黒鉛を含有させたもの（特許文献４）、炭素材料の表面に分散させた金属触媒により、気相成長炭素繊維または炭素ナノチューブを生成させ、その炭素材料をそのまま負極活物質として使用するもの（特許文献５）、黒鉛母粒子にアモルファスカーボンからなる粒状の子粒子３〜５重量％を一体化させたもの（特許文献６）が挙げられる。 Furthermore, for the purpose of improving rapid charge / discharge characteristics and cycle characteristics, it has been studied to mix and combine a conductive additive with the graphite particles. For example, a composite carbon material composed of a graphite material composed of spherical particles and carbon fibers (Patent Document 2), a mesophase small spherical graphite particle mixed with 3 to 30% by mass of vapor-grown carbon fibers (Patent Document 3), Vapor-grown graphite or scale-like graphite containing fibrous graphite (Patent Document 4), a metal catalyst dispersed on the surface of a carbon material is used to produce vapor-grown carbon fiber or carbon nanotube, and the carbon material is used as it is. Examples include those used as a negative electrode active material (Patent Document 5) and those obtained by integrating 3 to 5% by weight of granular child particles made of amorphous carbon into graphite mother particles (Patent Document 6).
前記従来のリチウムイオン二次電池用負極材料は、リチウムイオン二次電池の放電容量や初期充放電効率を大きく劣化させることなく、急速充放電特性やサイクル特性をそれなりに向上させることができるが、下記のような課題も有している。 The negative electrode material for the conventional lithium ion secondary battery can improve the rapid charge / discharge characteristics and cycle characteristics as it is without greatly degrading the discharge capacity and initial charge / discharge efficiency of the lithium ion secondary battery, It also has the following problems.
特許文献３に記載された、黒鉛質粒子に気相成長炭素繊維を混合しただけの負極材料の場合、黒鉛化した気相成長炭素繊維自体の放電容量や初期充放電効率が、母体のメソフェーズ黒鉛よりも低いため、負極材料としての放電容量や初期充放電効率が低下する問題がある。また気相成長炭素繊維が母体のメソフェーズ黒鉛と接触する機会が少なく、導電性の向上に寄与しないものが多い。その結果、急速充放電特性やサイクル特性の改良効果が充分なレベルにあるとは言えない。さらに、気相成長炭素繊維は比較的高価であり、３〜２０質量％という多量の混合を必要とすることから、コストアップの問題もある。加えて、負極を製造する場合、一般に、負極材料、溶媒、結合剤を混合して負極合剤ペーストを調製し、これを集電体に塗布する方法が採られるが、気相成長炭素繊維の混合量が多いため、負極合剤ペーストの粘度が不安定になるなどの問題もある。 In the case of the negative electrode material described in Patent Document 3 in which the vapor-grown carbon fiber is simply mixed with the graphite particles, the discharge capacity and the initial charge / discharge efficiency of the graphitized vapor-grown carbon fiber itself are the main mesophase graphite. Therefore, there is a problem that the discharge capacity as the negative electrode material and the initial charge / discharge efficiency are lowered. In addition, there are few opportunities for vapor-grown carbon fibers to come into contact with the base mesophase graphite, and many of them do not contribute to improvement of conductivity. As a result, it cannot be said that the effect of improving rapid charge / discharge characteristics and cycle characteristics is at a sufficient level. Furthermore, the vapor grown carbon fiber is relatively expensive and requires a large amount of mixing of 3 to 20% by mass, which causes a problem of cost increase. In addition, when manufacturing a negative electrode, generally, a method of preparing a negative electrode mixture paste by mixing a negative electrode material, a solvent and a binder and applying this to a current collector is adopted. Since the mixing amount is large, there is a problem that the viscosity of the negative electrode mixture paste becomes unstable.
特許文献５に記載された、炭素材料の表面に気相成長炭素繊維または炭素ナノチューブを生成させた負極材料の場合、黒鉛質材料に直接または非晶質炭素前駆体とともに、金属触媒をドーピングし、該触媒を起点にして炭素ナノチューブを形成することにより、黒鉛質材料間の導電性を改善している。しかし、形成された炭素ナノチューブは、黒鉛質材料の基材または表面の非晶質炭素膜の表面に存在する触媒金属から成長しているため、黒鉛質材料から脱離または破損しやすく、初期充放電効率やサイクル特性の向上効果が小さくなることがある。また、得られる負極材料中に触媒金属が残存するため、電池特性に悪影響を及ぼすことがある。さらに、製造工程が煩雑で、かつ収率が低く、工業的にはコストアップの問題がある。 In the case of the negative electrode material in which vapor-grown carbon fibers or carbon nanotubes are formed on the surface of the carbon material described in Patent Document 5, the metal material is doped directly or together with the amorphous carbon precursor in the graphite material, The conductivity between the graphite materials is improved by forming carbon nanotubes starting from the catalyst. However, since the formed carbon nanotubes are grown from the catalytic metal existing on the surface of the base material of the graphite material or the amorphous carbon film on the surface, the carbon nanotubes are easily detached or damaged from the graphite material and are initially charged. The effect of improving discharge efficiency and cycle characteristics may be reduced. In addition, since the catalytic metal remains in the obtained negative electrode material, the battery characteristics may be adversely affected. Further, the manufacturing process is complicated and the yield is low, and there is a problem of cost increase industrially.
特許文献６に記載された、黒鉛母粒子にアモルファスカーボンからなる粒状の子粒子３〜５質量％を一体化させた負極材料の場合、導電助材であるアモルファスカーボンが粒状であるため、黒鉛母粒子間の導電性の改善効果が乏しい。また、アモルファスカーボン自体の放電容量や初期充放電効率が母体の黒鉛より低いため、負極材料としての放電容量や初期充放電効率が低下する問題がある。さらに、黒鉛母粒子間にアモルファスカーボンをメカノケミカル処理によって一体化するが、比較的硬質な黒鉛母粒子にアモルファスカーボンを一体化させるには強力な機械的エネルギーの付与が必要であるため、黒鉛母粒子の一部が破壊することがあり、この場合、初期充放電効率が低下するという問題がある。 In the case of a negative electrode material in which 3 to 5 mass% of granular child particles made of amorphous carbon are integrated with graphite mother particles described in Patent Document 6, since amorphous carbon which is a conductive additive is granular, the graphite mother The effect of improving conductivity between particles is poor. Moreover, since the discharge capacity and initial charge / discharge efficiency of the amorphous carbon itself are lower than that of the base graphite, there is a problem that the discharge capacity and the initial charge / discharge efficiency as the negative electrode material are lowered. Furthermore, amorphous carbon is integrated between graphite base particles by mechanochemical treatment, but it is necessary to apply strong mechanical energy to integrate amorphous carbon with relatively hard graphite base particles. Part of the particles may be destroyed. In this case, there is a problem that the initial charge / discharge efficiency is lowered.
本発明は、上記のような状況を鑑みてなされたものであり、高い放電容量および高い初期充放電効率が得られ、さらに優れた急速充放電特性および優れたサイクル特性が得られ、加えて、工業的観点からも簡便かつ安価にリチウムイオン二次電池用負極材料を製造することが可能な黒鉛質材料の製造方法を提供することを目的とする。また、そのような黒鉛質材料を含むリチウムイオン二次電池用負極材料およびそのような負極材料を用いてなるリチウムイオン二次電池を提供することが目的である。 The present invention has been made in view of the situation as described above, and high discharge capacity and high initial charge / discharge efficiency are obtained, and further excellent rapid charge / discharge characteristics and excellent cycle characteristics are obtained. It aims at providing the manufacturing method of the graphite material which can manufacture the negative electrode material for lithium ion secondary batteries simply and cheaply also from an industrial viewpoint. It is another object of the present invention to provide a negative electrode material for a lithium ion secondary battery containing such a graphite material and a lithium ion secondary battery using such a negative electrode material.
本発明は、黒鉛質材料Ａの前駆体と繊維状黒鉛材料Ｂの前駆体に、機械的エネルギーを付与して、該黒鉛質材料Ａの前駆体に該繊維状黒鉛材料Ｂの前駆体を付着させたのち、黒鉛化する黒鉛質材料の製造方法において、該繊維状黒鉛材料Ｂの前駆体の配合量が、該黒鉛質材料Ａの前駆体と該繊維状黒鉛材料Ｂの前駆体の総量に対して、０．０５質量％以上、３質量％未満であることを特徴とする黒鉛質材料の製造方法である。 In the present invention, mechanical energy is applied to the precursor of the graphite material A and the precursor of the fibrous graphite material B, and the precursor of the fibrous graphite material B is attached to the precursor of the graphite material A. Then, in the method for producing graphitized material to be graphitized, the compounding amount of the precursor of the fibrous graphite material B is the total amount of the precursor of the graphite material A and the precursor of the fibrous graphite material B. On the other hand, it is a manufacturing method of a graphite material, which is 0.05% by mass or more and less than 3% by mass .
本発明の黒鉛質材料の製造方法において、前記黒鉛質材料Ａの前駆体は、該黒鉛質材料Ａの前駆体の総量に対して、２．０質量％以上２０質量％未満の揮発分を含有することが好ましい。 In the method for producing a graphite material of the present invention, the precursor of the graphite material A contains a volatile content of 2.0% by mass or more and less than 20% by mass with respect to the total amount of the precursor of the graphite material A. It is preferable to do.
本発明の黒鉛質材料の製造方法において、前記黒鉛質材料Ａの前駆体は、黒鉛Ｃを含有し、前記繊維状黒鉛材料Ｂの前駆体の配合量が、前記黒鉛質材料Ａの前駆体と前記繊維状黒鉛材料Ｂの前駆体と該黒鉛Ｃの総量に対して、０．０５質量％以上、３質量％未満であることが好ましい。 In the method for producing a graphite material of the present invention, the precursor of the graphite material A contains graphite C, and the compounding amount of the precursor of the fibrous graphite material B is the same as that of the precursor of the graphite material A. The total amount of the precursor of the fibrous graphite material B and the graphite C is preferably 0.05% by mass or more and less than 3% by mass .
本発明の黒鉛質材料の製造方法において、前記黒鉛質材料Ａの前駆体は、タールピッチ類の熱処理生成物であることが好ましい。 In the method for producing a graphite material of the present invention, the precursor of the graphite material A is preferably a heat treatment product of tar pitches.
本発明の黒鉛質材料の製造方法において、前記繊維状黒鉛材料Ｂの前駆体は、短軸長が１〜５００ｎｍであり、かつアスペクト比が５〜１０００であることが好ましい。 In the method for producing a graphite material of the present invention, the precursor of the fibrous graphite material B preferably has a minor axis length of 1 to 500 nm and an aspect ratio of 5 to 1000.
また、本発明は、前記のいずれかの製造方法によって得られる黒鉛質材料と結合剤を混合して、リチウムイオン二次電池負極材料用負極合剤を製造することを特徴とするリチウムイオン二次電池負極材料用負極合剤の製造方法である。また、本発明は、前記のいずれかの黒鉛質材料の製造方法によって得られる黒鉛質材料を含むリチウムイオン二次電池用負極材料である。 The present invention also provides a lithium ion secondary battery characterized in that a negative electrode mixture for a lithium ion secondary battery negative electrode material is produced by mixing a graphite material obtained by any of the above production methods and a binder. It is a manufacturing method of the negative mix for battery negative electrode materials. Moreover, this invention is a negative electrode material for lithium ion secondary batteries containing the graphite material obtained by the manufacturing method of one of the said graphite materials.
本発明は、前記のリチウムイオン二次電池用負極材料を用いたリチウムイオン二次電池である。 The present invention is a lithium ion secondary battery using the negative electrode material for a lithium ion secondary battery.
本発明の黒鉛質材料からなる負極材料を用いて作製した負極を用いてなるリチウムイオン二次電池は、高い急速充放電効率を有し、初期充放電効率およびサイクル特性にも優れ、かつ放電容量にも優れるばかりでなく、負極材料自体の製造コストも低い。
そのため、本発明の負極材料を用いてなるリチウムイオン二次電池は、近年の電池の高エネルギー密度化に対する要望を満たし、搭載する機器の小型化および高性能化に有効である。
The lithium ion secondary battery using the negative electrode produced using the negative electrode material made of the graphite material of the present invention has high rapid charge / discharge efficiency, excellent initial charge / discharge efficiency and cycle characteristics, and discharge capacity. In addition, the production cost of the negative electrode material itself is low.
Therefore, the lithium ion secondary battery using the negative electrode material of the present invention satisfies the recent demand for higher energy density of the battery, and is effective in reducing the size and performance of the mounted device.
以下、本発明をより具体的に説明する。
（黒鉛質材料の製造方法）
本発明の黒鉛質材料の製造方法は、黒鉛質材料Ａの前駆体と繊維状黒鉛材料Ｂの前駆体に、つまり、黒鉛質材料Ａの前駆体を、繊維状黒鉛材料Ｂの前駆体の共存下に、機械的エネルギーを付与して、該黒鉛質材料Ａの前駆体に該繊維状黒鉛材料Ｂを付着させたのち、黒鉛化処理し、黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂを付着させた付着物を黒鉛化する方法である。
機械的エネルギーの付与によって、繊維状黒鉛材料Ｂの前駆体が黒鉛質材料Ａの前駆体の表面に押し付けられ、一部が埋没し、黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂの前駆体が付着した状態になる。また、この場合の機械的エネルギーの付与は、繊維状黒鉛材料Ｂの前駆体を解繊し、単繊維化する効果も有し、表面が起毛した黒鉛質材料を得ることができる。したがって、黒鉛質材料Ａの前駆体に、繊維状黒鉛材料Ｂの前駆体を付着させるための付着剤が不要となり、該付着剤に由来する充放電特性の変化を排除することもできる。
Hereinafter, the present invention will be described more specifically.
(Method for producing graphite material)
In the method for producing a graphite material of the present invention, the precursor of the graphite material A and the precursor of the fibrous graphite material B, that is, the precursor of the graphite material A and the precursor of the fibrous graphite material B are coexistent. Below, mechanical energy is applied, and the fibrous graphite material B is attached to the precursor of the graphite material A, and then graphitized to give the fibrous graphite material B to the precursor of the graphite material A. This is a method of graphitizing the deposit on which is adhered.
By applying mechanical energy, the precursor of the fibrous graphite material B is pressed against the surface of the precursor of the graphite material A, and part of the precursor is buried, and the precursor of the fibrous graphite material B is applied to the precursor of the graphite material A. The body becomes attached. In addition, the application of mechanical energy in this case also has the effect of defibrating the precursor of the fibrous graphite material B to form a single fiber, and a graphite material having a raised surface can be obtained. Therefore, an adhesive for attaching the precursor of the fibrous graphite material B to the precursor of the graphite material A becomes unnecessary, and the change in charge / discharge characteristics derived from the adhesive can also be eliminated.
すなわち、機械的エネルギーの付与によって、最終的に得られる黒鉛質材料の表面の結晶構造を適度に乱すことができ、これから作製したリチウムイオン二次電池は、優れた初期充放電効率を発現することができる。また、結晶構造の乱れが黒鉛質材料の最表層のみに発現するため、高い放電容量を維持することもできる。 In other words, by applying mechanical energy, it is possible to moderately disturb the crystal structure of the surface of the finally obtained graphite material, and the lithium ion secondary battery produced from this will exhibit excellent initial charge / discharge efficiency. Can do. In addition, since the disorder of the crystal structure appears only in the outermost layer of the graphite material, a high discharge capacity can be maintained.
（黒鉛質材料Ａの前駆体の調製）
黒鉛質材料Ａの前駆体としては、石油系、石炭系のタールピッチ類の熱処理生成物であることが好ましい。例えば、コールタール、タール軽油、タール中油、タール重油、ナフタリン油、アントラセン油、コールタールピッチ、ピッチ油、メソフェーズピッチ、酸素架橋石油ピッチ、ベビーオイルなどを最終的なメトラー法による軟化点が３６０〜６００℃程度となるように熱処理した生成物である。この熱処理により、前記タールピッチ類は重縮合し、メソフェーズ焼成体、メソフェーズ小球体、コークス類（生コークス、グリーンコークス、ピッチコークス、ニードルコークス、石油コークス）などを生成させる。この黒鉛質材料Ａの前駆体は、その総量に対して２．０質量％以上２０質量％未満、特に３．０質量％以上１０質量％未満の揮発分を含有することが好ましい。
(Preparation of precursor of graphite material A)
The precursor of the graphite material A is preferably a heat treatment product of petroleum-based or coal-based tar pitches. For example, coal tar, tar light oil, tar medium oil, tar heavy oil, naphthalene oil, anthracene oil, coal tar pitch, pitch oil, mesophase pitch, oxygen-crosslinked petroleum pitch, baby oil, etc. have a final softening point of 360 to 360 It is a product that has been heat-treated to a temperature of about 600 ° C. By this heat treatment, the tar pitches are polycondensed to produce mesophase fired bodies, mesophase spherules, cokes (raw coke, green coke, pitch coke, needle coke, petroleum coke) and the like. The precursor of the graphite material A preferably contains 2.0% by mass or more and less than 20% by mass, particularly 3.0% by mass or more and less than 10% by mass, based on the total amount.
揮発分量はＪＩＳ Ｋ２４２５−１９８３の固定炭素分定量方法に準拠して下記の方法に従い測定される。すなわち、試料（黒鉛質材料Ａの前駆体）１ｇを坩堝に量り取り、蓋をしないで４３０℃で３０分間加熱する。その後、二重坩堝とし、８００℃で３０分間加熱して揮発分を除き、試料の減量率を揮発分量とする。 The amount of volatile matter is measured according to the following method based on the fixed carbon content determination method of JIS K2425-1983. That is, 1 g of a sample (precursor of graphite material A) is weighed in a crucible and heated at 430 ° C. for 30 minutes without a lid. Thereafter, a double crucible is formed and heated at 800 ° C. for 30 minutes to remove volatile matter, and the weight loss rate of the sample is taken as the volatile matter amount.
揮発分量が２０質量％以上の場合は、黒鉛質材料Ａの前駆体の黒鉛化処理時に溶融性を示し、形状が変化したり、黒鉛質材料Ａの前駆体同士の融着を起こすことがあり、好ましくない。一方、揮発分量が２．０質量％未満の場合は、機械的エネルギーの付与による、繊維状黒鉛材料Ｂの前駆体の付着が不十分となり、該繊維状黒鉛材料Ｂの脱落や破壊を生じることがあり、また、最終的に得られる黒鉛質材料の表面の結晶構造の乱れが不十分となり、初期充放電効率の向上が不十分となることがある。 When the volatile content is 20% by mass or more, meltability is exhibited during graphitization of the precursor of the graphite material A, and the shape may change or the precursors of the graphite material A may be fused together. It is not preferable. On the other hand, when the volatile content is less than 2.0% by mass, the adhesion of the precursor of the fibrous graphite material B due to the application of mechanical energy becomes insufficient, and the fibrous graphite material B falls off or breaks down. In addition, the disorder of the crystal structure of the surface of the finally obtained graphite material may be insufficient, and the initial charge / discharge efficiency may be insufficiently improved.
また、黒鉛質材料Ａの前駆体は、キノリン不溶分（ＱＩ）が５０質量％以上９９．５質量％未満、特に８５．０質量％以上９８．０質量％未満であることが好ましい。ＱＩはＪＩＳ Ｋ２４２５−１９８３に準拠して下記の方法に従い測定される。すなわち、黒鉛質材料Ａの前駆体をキノリンに溶解させ、７５℃で３０分間加熱した後、濾過器を用いて熱いうちに吸引濾過する。残分をキノリン、アセトンの順に、それぞれ濾液が無色になるまで洗浄した後、乾燥して質量を量り、ＱＩを算出する。なお濾過助剤として珪藻土を用いる。濾過器はＪＩＳ Ｒ３５０３−１９９４に規定するるつぼ型ガラス濾過器１Ｇ４を用いる。 The precursor of the graphite material A preferably has a quinoline insoluble content (QI) of 50% by mass or more and less than 99.5% by mass, particularly 85.0% by mass or more and less than 98.0% by mass. QI is measured according to the following method based on JIS K2425-1983. That is, the precursor of the graphite material A is dissolved in quinoline, heated at 75 ° C. for 30 minutes, and then suction filtered while hot using a filter. The residue is washed in the order of quinoline and acetone until the filtrate becomes colorless, and then dried and weighed to calculate QI. Diatomaceous earth is used as a filter aid. A crucible type glass filter 1G4 prescribed | regulated to JISR3503-1994 is used for a filter.
黒鉛質材料Ａの前駆体の軟化点が３６０℃未満、またはＱＩが５０質量％未満の場合には、黒鉛化処理時に溶融性を示し、形状が変化したり、黒鉛質材料Ａの前駆体同士の融着を起こすこともあり好ましくない。
一方、黒鉛質材料Ａの前駆体の軟化点が３６０℃以上であっても、ＱＩが９９．５質量％以上になるまで重縮合が過度に進行すると、機械的エネルギーの付与によって最終的に得られる黒鉛質材料の表面の結晶構造を乱すことが困難となり、初期充放電効率の向上が不充分となることがある。さらに黒鉛質材料Ａの前駆体と繊維状黒鉛材料Ｂの前駆体との付着が不充分となることがあり、好ましくない。
When the softening point of the precursor of the graphitic material A is less than 360 ° C. or the QI is less than 50% by mass, the graphitization treatment shows meltability, the shape changes, or the precursors of the graphite material A It is not preferable because it may cause fusion.
On the other hand, even if the softening point of the precursor of the graphite material A is 360 ° C. or higher, if the polycondensation proceeds excessively until the QI reaches 99.5% by mass or higher, the final result is obtained by applying mechanical energy. It may be difficult to disturb the crystal structure of the surface of the graphite material to be obtained, and the initial charge / discharge efficiency may be insufficiently improved. Furthermore, adhesion between the precursor of the graphite material A and the precursor of the fibrous graphite material B may be insufficient, which is not preferable.
本発明においては、黒鉛化処理時に、溶融変形または固体同士の融着などを生じないので、若干収縮はするものの黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂが付着した付着物の形状のままで黒鉛質材料が得られる。このため、該付着物を所望する黒鉛質材料の形状で黒鉛化処理に供すれば、黒鉛化後に粉砕や成形する必要がなく、工程が簡略化される。さらに、機械的エネルギーの付与により導入した最表層の結晶構造の乱れも、該付着物を黒鉛化処理した後において、そのまま保持できる。 In the present invention, no melt deformation or fusion between solids occurs at the time of graphitization treatment, so that the shape of the adhering material in which the fibrous graphite material B adheres to the precursor of the graphite material A is slightly shrunk. A graphite material can be obtained as it is. For this reason, if the deposit is subjected to graphitization treatment in the form of a desired graphitic material, there is no need to pulverize or form after graphitization, and the process is simplified. Furthermore, the disorder of the crystal structure of the outermost layer introduced by applying mechanical energy can be maintained as it is after the deposit is graphitized.
前記黒鉛質材料Ａの前駆体は、黒鉛Ｃを含有していることが、放電容量をより高める観点から好ましい。この場合、黒鉛Ｃ粒子を１個または複数個、黒鉛質材料Ａの前駆体の各粒子中に含有していればよい。すなわち、黒鉛質材料Ａの前駆体は天然黒鉛を内包する複合体とすることが好ましい。具体的には、天然黒鉛を予め球状に加工または造粒し、これに前記タールピッチ類を含浸または被覆した後に熱処理する方法、天然黒鉛とタールピッチ類を均一に混合した後に熱処理し粉砕する方法が例示される。これらの方法により、黒鉛Ｃを含有した黒鉛質材料Ａの前駆体を得ることができる。 It is preferable that the precursor of the graphite material A contains graphite C from the viewpoint of further increasing the discharge capacity. In this case, one or more graphite C particles may be contained in each particle of the precursor of the graphite material A. That is, the precursor of the graphite material A is preferably a composite containing natural graphite. Specifically, natural graphite is processed or granulated into a spherical shape in advance and then heat-treated after impregnating or coating the tar-pitch, and a method in which natural graphite and tar-pitch are uniformly mixed and then heat-treated and pulverized. Is exemplified. By these methods, a precursor of graphite material A containing graphite C can be obtained.
黒鉛Ｃを含有する場合にも、黒鉛Ｃを除いた黒鉛質材料Ａの前駆体の総量の２．０質量％以上２０質量％未満、特に３．０質量％以上１０質量％未満の揮発分を含有することが好ましい。黒鉛Ｃは該黒鉛質材料Ａの前駆体中で均一に分散していても、偏って分散していてもよいが、表面の少なくとも一部に存在していることが好ましい。 Even when graphite C is contained, a volatile content of 2.0% by mass or more and less than 20% by mass, particularly 3.0% by mass or more and less than 10% by mass, of the total amount of the precursor of the graphite material A excluding graphite C is contained. It is preferable to contain. The graphite C may be uniformly dispersed in the precursor of the graphite material A or may be unevenly dispersed, but is preferably present on at least a part of the surface.
黒鉛Ｃは黒鉛質材料Ａの前駆体より小さいことが好ましく、その平均粒子径は１〜３０μｍ、好ましくは２〜１５μｍである。黒鉛Ｃは黒鉛質材料Ａの前駆体に少なくとも１個含有させれば充分であるが、好ましくは黒鉛質材料Ａの前駆体１００質量部に対し、黒鉛Ｃが５０〜１００００質量部、好ましくは１００〜１０００質量部の割合で含有される。 The graphite C is preferably smaller than the precursor of the graphite material A, and the average particle size is 1 to 30 μm, preferably 2 to 15 μm. Although it is sufficient that at least one graphite C is contained in the precursor of the graphite material A, the graphite C is preferably 50 to 10,000 parts by weight, preferably 100 parts by weight with respect to 100 parts by weight of the precursor of the graphite material A. It is contained at a ratio of ˜1000 parts by mass.
（繊維状黒鉛材料Ｂの前駆体の調製）
繊維状黒鉛材料Ｂの前駆体は、その形状が繊維状であることが必要である。例えば、カーボンナノファイバー、カーボンナノチューブや気相成長炭素繊維などが好ましい。繊維状黒鉛材料Ｂの前駆体は、黒鉛化処理時に溶融性を示さず、最終的に得られる繊維状黒鉛材料Ｂと同じ形状を有するものが好ましい。繊維状黒鉛材料Ｂの前駆体については、繊維の直径にあたる平均短軸長は好ましくは１〜５００ｎｍ、より好ましくは５〜２００ｎｍ、繊維長と繊維直径の比にあたる平均アスペクト比は好ましくは５〜１０００、より好ましくは２０〜５００である。
(Preparation of precursor of fibrous graphite material B)
The precursor of the fibrous graphite material B needs to have a fibrous shape. For example, carbon nanofibers, carbon nanotubes, vapor grown carbon fibers, and the like are preferable. The precursor of the fibrous graphite material B preferably has the same shape as that of the finally obtained fibrous graphite material B without showing meltability during the graphitization treatment. For the precursor of the fibrous graphite material B, the average minor axis length corresponding to the fiber diameter is preferably 1 to 500 nm, more preferably 5 to 200 nm, and the average aspect ratio corresponding to the ratio of the fiber length to the fiber diameter is preferably 5 to 1000. More preferably, it is 20-500.
繊維状黒鉛材料Ｂの前駆体の配合割合は、黒鉛質材料Ａの前駆体と繊維状黒鉛材料Ｂの前駆体の総量、また黒鉛質材料Ａの前駆体が黒鉛Ｃを含有する場合には、黒鉛質材料Ａの前駆体と繊維状黒鉛材料Ｂの前駆体と黒鉛Ｃの総量に対して、０．０５質量％以上３質量％未満である。繊維状黒鉛材料Ｂの前駆体が０．０５質量％未満の場合は、急速充放電効率、サイクル特性の改善効果が小さくなる。３質量％以上の場合は、急速充放電効率、サイクル特性の改善効果が飽和するとともに、負極合剤ペーストを調製する際に粘度が不安定になるなど負極の安定製造に支障を来たすことがあるほか、比較的高価な繊維状黒鉛材料Ｂの前駆体の割合が増えることによりコストアップになる。 The mixing ratio of the precursor of the fibrous graphite material B, the total amount of the precursor and a fibrous graphite material B of the precursor of the graphitic material A, also in the case where the precursor of the graphite material A contains graphite C is It is 0.05 mass% or more and less than 3 mass% with respect to the total amount of the precursor of the graphite material A, the precursor of the fibrous graphite material B, and the graphite C. When the precursor of the fibrous graphite material B is less than 0.05% by mass, the effect of improving rapid charge / discharge efficiency and cycle characteristics is reduced. In the case of 3% by mass or more, the effect of improving rapid charge / discharge efficiency and cycle characteristics is saturated, and the viscosity may become unstable when preparing the negative electrode mixture paste, which may hinder stable production of the negative electrode. In addition, the cost increases due to an increase in the proportion of the precursor of the relatively expensive fibrous graphite material B.
本発明の黒鉛質材料の製造においては、黒鉛化することによって、黒鉛質材料Ａの表面にも導電性を有する繊維状黒鉛材料Ｂを得ることができる。したがって、繊維状黒鉛材料Ｂの前駆体としては、黒鉛化前の状態のものを用いることができる。当然ながら、予め黒鉛化して黒鉛構造を形成した繊維状黒鉛材料Ｂを前駆体として用いてもよい。 In the production of the graphite material of the present invention, a fibrous graphite material B having conductivity also on the surface of the graphite material A can be obtained by graphitization. Therefore, as the precursor of the fibrous graphite material B, the precursor before graphitization can be used. Of course, the fibrous graphite material B that has been graphitized in advance to form a graphite structure may be used as a precursor.
（機械的エネルギーの付与方法）
前述した黒鉛質材料Ａの前駆体と繊維状黒鉛材料Ｂの前駆体に機械的エネルギーを付与する。機械的エネルギーの付与によって、黒鉛質材料Ａの前駆体を粉砕し、形状を調整することができる。しかしながら、黒鉛質材料Ａの前駆体を予め所定形状に調整しておき、これを実質的に粉砕することなく、その表面に機械的エネルギーを付与することが好ましい。黒鉛質材料Ａの前駆体が機械的エネルギーの付与時に過度に破壊されると、初期充放電効率の低下などを生じるおそれがある。本発明で言う機械的エネルギーとは、圧縮、剪断、衝突、摩擦などの各種応力を意味する。この操作は一般にメカノケミカル処理とも呼ばれ、加えられる機械的エネルギーは通常一般の攪拌により付与される力より大きい。
(Mechanical energy application method)
Mechanical energy is applied to the precursor of the graphite material A and the precursor of the fibrous graphite material B described above. By applying mechanical energy, the precursor of the graphite material A can be pulverized and the shape can be adjusted. However, it is preferable to adjust the precursor of the graphite material A to a predetermined shape in advance, and to apply mechanical energy to the surface without substantially crushing the precursor. If the precursor of the graphite material A is excessively destroyed at the time of applying mechanical energy, the initial charge / discharge efficiency may be lowered. The mechanical energy referred to in the present invention means various stresses such as compression, shear, collision, friction and the like. This operation is generally referred to as mechanochemical treatment, and the mechanical energy applied is usually greater than the force imparted by general agitation.
機械的エネルギーを付与するための装置としては、例えば、加圧ニーダー、二本ロールなどの混練機、回転ボールミル、ハイブリダイゼーションシステム（（株）奈良機械製作所製）、メカノマイクロス（（株）奈良機械製作所製）、メカノフュージョンシステム（ホソカワミクロン（株）製）などが挙げられる。前記の装置の中でも、回転速度差を利用した剪断力と圧縮力を同時に付加する装置が好ましい。例えば、図１（Ａ）および（Ｂ）に模式的機構を示すメカノフュージョンシステムが好ましい。 Examples of the apparatus for applying mechanical energy include a kneader such as a pressure kneader and two rolls, a rotating ball mill, a hybridization system (manufactured by Nara Machinery Co., Ltd.), and Mechano Micros (Nara Co., Ltd.). Machine Seisakusho), Mechano Fusion System (manufactured by Hosokawa Micron Corporation), and the like. Among the above-mentioned apparatuses, an apparatus that simultaneously applies a shearing force and a compressive force using a rotational speed difference is preferable. For example, a mechanofusion system having a schematic mechanism shown in FIGS. 1A and 1B is preferable.
すなわち、図１（Ｂ）に示すように、回転ドラム１１と、該回転ドラム１１と回転速度が異なる内部部材（インナーピース）１２と、原料（黒鉛質材料Ａの前駆体および繊維状黒鉛材料Ｂの前駆体の混合物）１３の循環機構１４と排出機構１５を有する装置を用いて行うことができる。この装置において、図１（Ａ）に示すように、回転ドラム１１と内部部材１２との間に遠心力を付加しながら、内部部材１２により回転ドラム１１との速度差に起因する圧縮力と剪断力とを同時に繰り返し付加することにより機械的エネルギーを原料１３に付与することができる。
That is, as shown in FIG. 1B, a
また、例えば、図２に模式的に示すハイブリダイゼーションシステムを用いることもできる。すなわち、固定ドラム２１、高速回転するローター２２、原料２３の循環機構２４と排出機構２５、ブレード２６、ステーター２７およびジャケット２８を有する装置を用い、原料２３を固定ドラム２１とローター２２の間に供給し、固定ドラム２１とローター２２の速度差に起因する圧縮力と剪断力とを原料２３に付加する装置を用いて機械的エネルギーを付与してもよい。
Further, for example, a hybridization system schematically shown in FIG. 2 can be used. That is, using a device having a fixed
機械的エネルギーを付与する条件は、使用する装置によっても異なり、一概に言えないが、機械的エネルギーの付与による黒鉛質材料Ａの前駆体の平均粒子径の低下率が２０％以下となるように設定するのが好ましい。例えば、回転ドラムと内部部材を備えた図１の装置を用いる場合には、回転ドラムと内部部材との周速度差を５〜５０m/s 、両者間の距離を１〜１００ｍｍ、処理時間を５〜６０分の条件下で行うことが好ましい。また、固定ドラムと高速回転ローターを備えた図２の装置を用いる場合には、固定ドラムとローターとの周速度差を５〜５０m/s 、両者間の距離を１〜１００ｍｍ、処理時間を５〜６０分の条件下で行うことが好ましい。 The conditions for applying mechanical energy differ depending on the apparatus used and cannot be generally specified, but the reduction rate of the average particle size of the precursor of the graphite material A by applying mechanical energy is 20% or less. It is preferable to set. For example, when using the apparatus of FIG. 1 equipped with a rotating drum and an internal member, the peripheral speed difference between the rotating drum and the internal member is 5 to 50 m / s, the distance between the two is 1 to 100 mm, and the processing time is 5 It is preferable to carry out under the condition of ~ 60 minutes. When the apparatus of FIG. 2 having a fixed drum and a high-speed rotor is used, the peripheral speed difference between the fixed drum and the rotor is 5 to 50 m / s, the distance between the two is 1 to 100 mm, and the processing time is 5 It is preferable to carry out under the condition of ~ 60 minutes.
黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂの前駆体を付着させた付着物の形状は特に限定されず、球状、楕円体状、塊状、鱗片状、板状、粒状など繊維状以外の形状であればいかなるものであってもよいが、球状もしくは球状に近い形状とすることが好ましい。球状もしくは球状に近い形状のうちで特に好ましいのは、アスペクト比（長軸方向最長部の長さ／直交する短軸方向の長さの比）が５以下、好ましくは３以下の形状である。なお、アスペクト比は、走査型電子顕微鏡観察で各材料の形状が認識できる倍率で１００個について計測し、その平均値として求めることができる。好ましい平均粒子径は体積換算で１〜１００μｍ、より好ましくは５〜５０μｍである。なお、本発明の平均粒子径の好適範囲はレーザー回折式粒度分布計を用いて測定した累積度数が体積百分率で５０％となる粒径値である。
また、粉砕、分級などにより、所定の粒子形状に調整する際には、公知の各種方法を採用することができる。粉砕には、例えば、ローラー方式、衝撃式、摩擦式、圧縮式、石臼式、動体衝突式、渦流（気流）式、剪断式、振動式などの各種市販粉砕機を使用することができる。
The shape of the adhering material in which the precursor of the fibrous graphite material B is adhered to the precursor of the graphite material A is not particularly limited, and other than fibrous shapes such as a spherical shape, an ellipsoidal shape, a lump shape, a scale shape, a plate shape, and a granular shape are used. Any shape may be used, but a spherical shape or a nearly spherical shape is preferable. Particularly preferred among the spherical or nearly spherical shapes is an aspect ratio (ratio of the length of the longest part in the long axis direction / the length in the direction of the short axis perpendicular) of 5 or less, preferably 3 or less. In addition, an aspect ratio can be calculated | required as an average value measured about 100 pieces with the magnification which can recognize the shape of each material by scanning electron microscope observation. A preferable average particle diameter is 1-100 micrometers in volume conversion, More preferably, it is 5-50 micrometers. In addition, the suitable range of the average particle diameter of this invention is a particle size value from which the cumulative frequency measured using the laser diffraction type particle size distribution meter becomes 50% by volume percentage.
Moreover, when adjusting to a predetermined particle shape by grinding | pulverization, classification, etc., well-known various methods are employable. For the pulverization, various commercially available pulverizers such as a roller system, an impact system, a friction system, a compression system, a stone mill system, a moving object collision system, a vortex (airflow) system, a shear system, and a vibration system can be used.
また、機械的エネルギーを付与する処理前、処理の途中、処理後のいずれかにおいて、本発明の効果を損なわない範囲において、公知の導電性材料、イオン伝導性材料、界面活性剤、金属化合物、結合剤などの各種添加剤を併用することもできる。 Moreover, in the range which does not impair the effect of this invention in the range which does not impair the effect of this invention in the process before giving the mechanical energy, in the middle of a process, or after a process, a well-known electroconductive material, an ion conductive material, surfactant, a metal compound, Various additives such as a binder may be used in combination.
（黒鉛化処理方法）
機械的エネルギーの付与によって、黒鉛質材料Ａの前駆体または黒鉛Ｃを含有する黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂの前駆体を付着させたのち、該付着物を黒鉛化処理する。黒鉛化処理は、例えば、坩堝などの容器に該付着物を充填し、非酸化性雰囲気下で行うことが好ましい。黒鉛の結晶構造の結晶性、すなわち、放電容量を高める観点から、黒鉛化処理温度は高温であるほど好ましい。１５００℃超が好ましく、２５００℃以上がより好ましい。上限は、装置の耐熱性や黒鉛の昇華を防ぐ観点から３３００℃程度であり、最も好ましいのは２８００〜３２００℃である。このような高温に０．５〜５０時間、好ましくは２〜２０時間加熱することにより該付着物を構成する黒鉛質材料Ａの前駆体と繊維状黒鉛材料Ｂの前駆体は黒鉛化する。
(Graphitization method)
By applying mechanical energy, the precursor of the fibrous graphite material B is attached to the precursor of the graphite material A or the precursor of the graphite material A containing the graphite C, and then the deposit is graphitized. . The graphitization treatment is preferably performed in a non-oxidizing atmosphere, for example, by filling the deposit in a container such as a crucible. From the viewpoint of increasing the crystallinity of the crystal structure of graphite, that is, the discharge capacity, the graphitization temperature is preferably as high as possible. More than 1500 degreeC is preferable and 2500 degreeC or more is more preferable. The upper limit is about 3300 ° C. from the viewpoint of preventing heat resistance of the apparatus and sublimation of graphite, and most preferably 2800 to 3200 ° C. By heating at such a high temperature for 0.5 to 50 hours, preferably 2 to 20 hours, the precursor of the graphite material A and the precursor of the fibrous graphite material B constituting the deposit are graphitized.
（黒鉛質材料）
本発明の製造方法によって得られる黒鉛質材料の走査型電子顕微鏡写真（倍率１０００倍）の一例を図４に示す。図４から明らかなように、本発明の黒鉛質材料は、黒鉛質材料Ａに繊維状黒鉛材料Ｂが付着し、該繊維状黒鉛材料Ｂが起毛している。特に、繊維状黒鉛材料Ｂは機械的エネルギーの付与過程で解繊されて単繊維の状態で付着していることが好ましい。
最終的に得られる黒鉛質材料の結晶性の平均値は、Ｘ線広角回折法における炭素網面層の格子面間隔（ｄ002 ）で０．３３６５ｎｍ以下であることが好ましい。なお、格子面間隔の測定は、ＣｕＫα線をＸ線源、高純度シリコンを標準物質に使用して、黒鉛質材料の（００２）回折ピークを測定し、そのピーク位置よりｄ002 を算出する。算出方法は学振法（日本学術振興会第１１７委員会が定めた測定法）に従うものであり、具体的には、「炭素繊維」（大谷杉郎著、７３３−７４２頁（１９８６年３月）、近代編集社）などに記載された方法によって測定した値である。
(Graphite material)
An example of a scanning electron micrograph (magnification 1000 times) of the graphite material obtained by the production method of the present invention is shown in FIG. As is clear from FIG. 4, in the graphite material of the present invention, the fibrous graphite material B adheres to the graphite material A, and the fibrous graphite material B is raised. In particular, it is preferable that the fibrous graphite material B is defibrated in the process of applying mechanical energy and adhered in a single fiber state.
The average value of the crystallinity of the finally obtained graphite material is preferably 0.3365 nm or less in terms of the lattice spacing (d 002 ) of the carbon network layer in the X-ray wide angle diffraction method. The lattice spacing is measured by measuring the (002) diffraction peak of the graphite material using CuKα rays as an X-ray source and high-purity silicon as a standard substance, and calculating d 002 from the peak position. The calculation method follows the Japan Science and Technology Act (measurement method defined by the 117th Committee of the Japan Society for the Promotion of Science). Specifically, “Carbon Fiber” (Suguro Otani, pages 733-742 (March 1986) ), Modern Editing Co.) and the like.
本発明の製造方法によって得られる黒鉛質材料は、最表層の結晶構造が適度に乱れており、リチウムイオン二次電池用負極材料として優れた初期充放電効率を発現する。表面の結晶性を確認する方法としては、アルゴンレーザーを用いたラマンスペクトル法が挙げられる。すなわち、黒鉛構造に基づく９種の格子振動のうち、炭素網面内の格子振動に相当するＥ２ｇ型振動に対応した１５８０ｃｍ-1近傍のラマンスペクトルと、主に表層での結晶欠陥や積層不整などの結晶構造の乱れを反映した１３６０ｃｍ-1近傍のラマンスペクトルを、５１４．５ｎｍの波長を有するアルゴンレーザーを用いたラマン分光分析器（日本分光（株）製、ＮＲ１１００）により測定する。それぞれのラマンスペクトルのピーク強度からその強度比Ｒ＝Ｉ1360／Ｉ1580を算出し、Ｒが大きいものほど表面の結晶性が低いと評価する。強度比Ｒは初期充放電効率を大きくする観点から、Ｒ≧０．０５であるのが好ましい。これは最表層の結晶性が適度に乱され、黒鉛質材料の表面での電解液の分解反応が抑制されるためと考えられる。また、強度比Ｒは放電容量の低下を最小に抑える観点からＲ＜０．３であることが好ましい。 The graphitic material obtained by the production method of the present invention has a moderate disorder in the crystal structure of the outermost layer, and exhibits excellent initial charge / discharge efficiency as a negative electrode material for a lithium ion secondary battery. As a method for confirming the crystallinity of the surface, there is a Raman spectrum method using an argon laser. That is, among the nine types of lattice vibrations based on the graphite structure, the Raman spectrum near 1580 cm −1 corresponding to the E2g type vibration corresponding to the lattice vibration in the carbon network surface, crystal defects and stacking irregularities mainly on the surface layer, etc. The Raman spectrum in the vicinity of 1360 cm −1 reflecting the disorder of the crystal structure is measured with a Raman spectroscopic analyzer (NR1100, manufactured by JASCO Corporation) using an argon laser having a wavelength of 514.5 nm. The intensity ratio R = I 1360 / I 1580 is calculated from the peak intensity of each Raman spectrum, and the larger R, the lower the surface crystallinity. The intensity ratio R is preferably R ≧ 0.05 from the viewpoint of increasing the initial charge / discharge efficiency. This is presumably because the crystallinity of the outermost layer is moderately disturbed and the decomposition reaction of the electrolytic solution on the surface of the graphite material is suppressed. Further, the intensity ratio R is preferably R <0.3 from the viewpoint of minimizing the decrease in discharge capacity.
本発明の製造方法によって得られる黒鉛質材料の強度比Ｒは、初期充放電効率の改善を目的として炭素材料を酸化や低温焼成（非黒鉛構造）処理する従来技術（例えば、特許第２６４３０３５号明細書、特許第３１３９７９０号明細書）の強度比Ｒに比べると小さい値を示すが、優れた初期充放電効率を有する。このメカニズムは明らかでないが、黒鉛質材料Ａの前駆体の表面に機械的エネルギーを付与したのちに黒鉛化処理するという本発明の製造方法によって達成される現象である。 The strength ratio R of the graphite material obtained by the production method of the present invention is a conventional technique (for example, Japanese Patent No. 2643035) in which a carbon material is oxidized or low-temperature fired (non-graphite structure) for the purpose of improving the initial charge / discharge efficiency. Although it shows a small value as compared with the intensity ratio R in Japanese Patent No. 3139790, it has excellent initial charge / discharge efficiency. Although this mechanism is not clear, it is a phenomenon achieved by the manufacturing method of the present invention in which mechanical energy is applied to the surface of the precursor of the graphite material A and then graphitization is performed.
本発明は、前述の黒鉛質材料を含有するリチウムイオン二次電池用負極材料も提供する。
本発明の黒鉛質材料は、その特徴を活かして、例えば、燃料電池セパレーター用の導電材料や耐火物用黒鉛などにも使用することができるが、リチウムイオン二次電池用負極材料としての使用が好適である。すなわち、本発明のリチウムイオン二次電池用負極材料は、少なくとも前述の黒鉛質材料を含有する結果、放電容量、初期充放電効率、急速充放電特性およびサイクル特性に優れたリチウムイオン二次電池用負極となる。
The present invention also provides a negative electrode material for a lithium ion secondary battery containing the aforementioned graphite material.
The graphite material of the present invention can be used as, for example, a conductive material for a fuel cell separator or a graphite for a refractory, taking advantage of its characteristics, but it can be used as a negative electrode material for a lithium ion secondary battery. Is preferred. That is, the negative electrode material for a lithium ion secondary battery according to the present invention contains at least the above-mentioned graphite material, and as a result, the lithium ion secondary battery is excellent in discharge capacity, initial charge / discharge efficiency, rapid charge / discharge characteristics, and cycle characteristics. It becomes the negative electrode.
以下、本発明の黒鉛質材料を含む負極材料を用いたリチウムイオン二次電池について説明する。
（リチウムイオン二次電池用負極）
本発明の負極は、前述の本発明の黒鉛質材料を含有する負極材料を固化および／または賦形して得られる。該負極の製造は、通常の賦形方法に準じて行うことができるが、黒鉛質材料の性能を十分に引き出し、かつ粉末に対する賦形性が高く、化学的、電気化学的に安定な負極を得ることができる方法であれば特に制限されない。
Hereinafter, a lithium ion secondary battery using a negative electrode material containing the graphite material of the present invention will be described.
(Anode for lithium ion secondary battery)
The negative electrode of the present invention is obtained by solidifying and / or shaping the negative electrode material containing the above-described graphite material of the present invention. The negative electrode can be produced in accordance with a normal shaping method. However, a negative electrode that is sufficiently chemically and electrochemically stable and that sufficiently draws out the performance of the graphite material and has high shapeability to powder. The method is not particularly limited as long as it can be obtained.
負極製造時には、黒鉛質材料に結合剤を加えた負極合剤を用いることができる。結合剤としては、電解質や電解液溶媒に対して化学的安定性、電気化学的安定性を有するものを用いることが好ましい。例えば、ポリフッ化ビニリデン、ポリテトラフルオロエチレンなどのフッ素系樹脂、ポリエチレン、ポリビニルアルコール、スチレン−ブタジエンゴム、さらにはカルボキシメチルセルロースなどが用いられる。これらを併用することもできる。
結合剤の含有量は、通常、負極合剤の全量中１〜２０質量％程度であるのが好ましい。
At the time of producing the negative electrode, a negative electrode mixture obtained by adding a binder to a graphite material can be used. As the binder, it is preferable to use a binder having chemical stability and electrochemical stability with respect to the electrolyte and the electrolyte solvent. For example, fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene, polyethylene, polyvinyl alcohol, styrene-butadiene rubber, and carboxymethyl cellulose are used. These can also be used together.
Usually, the content of the binder is preferably about 1 to 20% by mass in the total amount of the negative electrode mixture.
負極合剤層は、具体的には、分級などにより適当な粒径に調整した黒鉛質材料を、結合剤と混合することによって負極合剤を調製し、この負極合剤を、通常、集電体の片面または両面に塗布することにより形成することができる。この際、通常の溶媒を用いることができ、負極合剤を溶媒中に分散させてペースト状とした後、集電体に塗布、乾燥すれば、負極合剤層が均一かつ強固に集電体に接着された負極を得ることができる。ペーストは各種ミキサーで攪拌することにより調製することができる。 Specifically, the negative electrode mixture layer is prepared by mixing a graphite material adjusted to an appropriate particle size by classification or the like with a binder, and this negative electrode mixture is usually collected as a current collector. It can be formed by applying to one or both sides of the body. In this case, a normal solvent can be used. If the negative electrode mixture is dispersed in a solvent to form a paste, and then applied to the current collector and dried, the negative electrode mixture layer is uniformly and firmly formed. A negative electrode adhered to the substrate can be obtained. The paste can be prepared by stirring with various mixers.
例えば、本発明の黒鉛質材料と、ポリテトラフルオロエチレンなどのフッ素系樹脂粉末を、イソプロピルアルコールなどの溶媒中で混合、混練した後、塗布して負極合剤層を形成することもできる。また、本発明の黒鉛質材料と、ポリフッ化ビニリデンなどのフッ素系樹脂粉末またはカルボキシメチルセルロースなどの水溶性粘結剤を、Ｎ−メチルピロリドン、ジメチルホルムアミドまたは水、アルコールなどの溶媒と混合してスラリーとした後、塗布して負極合剤層を形成することもできる。
本発明の黒鉛質材料と結合剤との混合物からなる負極合剤を集電体に塗布する際の塗布厚は１０〜３００μｍ、好ましくは３０〜１００μｍである。
負極合剤層を形成した後、プレス加圧などの圧着を行うと、負極合剤層と集電体との接着強度をさらに高めることができる。
For example, the graphite material of the present invention and a fluorine resin powder such as polytetrafluoroethylene may be mixed and kneaded in a solvent such as isopropyl alcohol, and then applied to form a negative electrode mixture layer. Further, a slurry obtained by mixing the graphite material of the present invention, a fluorine resin powder such as polyvinylidene fluoride, or a water-soluble binder such as carboxymethyl cellulose with a solvent such as N-methylpyrrolidone, dimethylformamide, water or alcohol. Then, it can be applied to form a negative electrode mixture layer.
The coating thickness when applying the negative electrode mixture comprising the mixture of the graphite material of the present invention and the binder to the current collector is 10 to 300 μm, preferably 30 to 100 μm.
When the negative electrode mixture layer is formed and then pressure bonding such as pressurization is performed, the adhesive strength between the negative electrode mixture layer and the current collector can be further increased.
本発明のリチウムイオン二次電池において、負極に用いる集電体の形状は、特に限定されないが、箔状、メッシュ、エキスパンドメタルなどの網状物などが好ましい。集電体の材質としては、銅、ステンレス、ニッケルなどが好ましい。集電体の厚みは、箔状の場合は好ましくは５〜２０μｍである。 In the lithium ion secondary battery of the present invention, the shape of the current collector used for the negative electrode is not particularly limited, but a net-like material such as a foil shape, a mesh, and an expanded metal is preferable. The material for the current collector is preferably copper, stainless steel, nickel or the like. The thickness of the current collector is preferably 5 to 20 μm in the case of a foil.
本発明では、前述の負極のいずれかを用いたリチウムイオン二次電池が提供される。
（リチウムイオン二次電池）
リチウムイオン二次電池は、通常、負極、正極および非水系電解質を主たる電池構成要素とし、正極および負極はそれぞれリチウムイオンの担持体からなる。充電時には、リチウムイオンが負極中にドープされ、放電時には負極から脱ドープする電池機構である。
本発明のリチウムイオン二次電池は、負極材料として本発明の黒鉛質材料を含有する負極材料を用いること以外は特に限定されず、他の電池構成要素については一般的なリチウムイオン二次電池の要素に準じる。
In the present invention, a lithium ion secondary battery using any of the aforementioned negative electrodes is provided.
(Lithium ion secondary battery)
A lithium ion secondary battery usually includes a negative electrode, a positive electrode, and a non-aqueous electrolyte as main battery components, and each of the positive electrode and the negative electrode includes a lithium ion carrier. This is a battery mechanism in which lithium ions are doped into the negative electrode during charging and are dedoped from the negative electrode during discharging.
The lithium ion secondary battery of the present invention is not particularly limited except that the negative electrode material containing the graphite material of the present invention is used as the negative electrode material, and other battery components are those of a general lithium ion secondary battery. According to the element.
（正極（正極活物質））
正極の材料（正極活物質）としては、十分量のリチウムをドープ／脱ドープし得るものを選択することが好ましい。正極活物質としては、リチウムと遷移金属の複合酸化物が好ましく、リチウムと遷移金属の複合酸化物（リチウム含有遷移金属酸化物とも称す）が特に好ましい。該複合酸化物は、リチウムと２種類以上の遷移金属を固溶したものであってもよい。
リチウム含有遷移金属酸化物は、具体的には、ＬｉＭ1 1-XＭ2 X Ｏ2 （式中Ｘは０≦Ｘ≦１の範囲の数値であり、Ｍ1 、Ｍ2 は少なくとも一種の遷移金属元素である）またはＬｉＭ1 2-YＭ2 Y Ｏ4 （式中Ｙは０≦Ｙ≦１の範囲の数値であり、Ｍ1 、Ｍ2 は少なくとも一種の遷移金属元素である）で示される。Ｍで示される遷移金属元素は、Ｃｏ、Ｎｉ、Ｍｎ、Ｃｒ、Ｔｉ、Ｖ、Ｆｅ、Ｚｎ、Ａｌ、Ｉｎ、Ｓｎなどである。好ましい具体例は、ＬｉＣｏＯ2 、ＬｉＮｉＯ2 、ＬｉＭｎＯ2 、ＬｉＮｉ0.9 Ｃｏ0.1 Ｏ2 、ＬｉＮｉ0.5 Ｍｎ0.5 Ｏ2 などである。
リチウム含有遷移金属酸化物は、例えば、リチウム、遷移金属の酸化物、塩類または水酸化物を出発原料とし、これら出発原料を所定の組成に応じて混合し、酸素雰囲気下６００〜１０００℃の温度で焼成して調製することができる。
(Positive electrode (positive electrode active material))
As the positive electrode material (positive electrode active material), it is preferable to select a material capable of doping / dedoping a sufficient amount of lithium. As the positive electrode active material, a composite oxide of lithium and transition metal is preferable, and a composite oxide of lithium and transition metal (also referred to as lithium-containing transition metal oxide) is particularly preferable. The composite oxide may be a solid solution of lithium and two or more transition metals.
Specifically, the lithium-containing transition metal oxide is LiM 1 1-X M 2 X O 2 (where X is a numerical value in the range of 0 ≦ X ≦ 1, and M 1 and M 2 are at least one kind of transition. A metal element) or LiM 1 2-Y M 2 Y O 4 (where Y is a numerical value in the range of 0 ≦ Y ≦ 1, and M 1 and M 2 are at least one transition metal element) It is. Transition metal elements represented by M are Co, Ni, Mn, Cr, Ti, V, Fe, Zn, Al, In, Sn, and the like. Preferred examples are LiCoO 2 , LiNiO 2 , LiMnO 2 , LiNi 0.9 Co 0.1 O 2 , LiNi 0.5 Mn 0.5 O 2 and the like.
The lithium-containing transition metal oxide is, for example, lithium, a transition metal oxide, salt or hydroxide as a starting material, these starting materials are mixed according to a predetermined composition, and a temperature of 600 to 1000 ° C. in an oxygen atmosphere. Can be prepared by baking.
正極活物質は、前記化合物を単独で使用しても２種類以上併用してもよい。例えば、正極中に炭酸リチウム等の炭酸塩を添加することができる。
このような正極材料によって正極を作製するには、例えば、正極材料と結合剤、および正極に導電性を付与するための導電剤よりなる正極合剤を、集電体の両面に塗布して正極合剤層を形成して作製される。結合剤としては、負極の作製に使用されるものと同じものが使用可能である。導電剤としては、例えば、炭素材料、黒鉛やカーボンブラックなど公知のものが使用される。
集電体の形状は特に限定されないが、箔状またはメッシュ、エキスパンドメタル等の網状などのものが用いられる。集電体の材質は、アルミニウム箔、ステンレス箔、ニッケル箔などである。その厚さは１０〜４０μｍであることが好ましい。
The positive electrode active material may be used alone or in combination of two or more. For example, a carbonate such as lithium carbonate can be added to the positive electrode.
In order to produce a positive electrode using such a positive electrode material, for example, a positive electrode mixture comprising a positive electrode material, a binder, and a conductive agent for imparting conductivity to the positive electrode is applied to both sides of the current collector. It is produced by forming a mixture layer. As the binder, the same one as that used for producing the negative electrode can be used. As the conductive agent, for example, a known material such as a carbon material, graphite, or carbon black is used.
The shape of the current collector is not particularly limited, and a foil shape or a mesh shape such as a mesh or an expanded metal is used. The material of the current collector is aluminum foil, stainless steel foil, nickel foil or the like. The thickness is preferably 10 to 40 μm.
正極も負極と同様に、正極合剤を溶剤中に分散させペースト状にし、このペースト状の正極合剤を集電体に塗布、乾燥して正極合剤層を形成してもよく、正極合剤層を形成した後、さらにプレス加圧等の圧着を行ってもよい。これにより正極合剤層が均一且つ強固に集電材に接着される。 Similarly to the negative electrode, the positive electrode mixture may be formed in a paste by dispersing the positive electrode mixture in a solvent, and the paste-like positive electrode mixture may be applied to a current collector and dried to form a positive electrode mixture layer. After forming the agent layer, pressure bonding such as press pressing may be further performed. As a result, the positive electrode mixture layer is uniformly and firmly bonded to the current collector.
本発明に用いられる電解質は、溶媒と電解質塩からなる有機系電解質や、高分子化合物と電解質塩とからなるポリマー電解質などである。電解質塩としては、例えば、ＬｉＰＦ6 、ＬｉＢＦ4 、ＬｉＡｓＦ6 、ＬｉＣｌＯ4 、ＬｉＢ（Ｃ6 Ｈ5 ）、ＬｉＣｌ、ＬｉＢｒ、ＬｉＣＦ3 ＳＯ3 、ＬｉＣＨ3 ＳＯ3 、ＬｉＮ（ＣＦ3 ＳＯ2 ）2 、ＬｉＣ（ＣＦ3 ＳＯ2 ）3 、ＬｉＮ（ＣＦ3 ＣＨ2 ＯＳＯ2 ）2 、ＬｉＮ（ＣＦ3 ＣＦ2 ＯＳＯ2 ）2 、ＬｉＮ（ＨＣＦ2 ＣＦ2 ＣＨ2 ＯＳＯ2 ）2 、ＬｉＮ［（ＣＦ3 ）2 ＣＨＯＳＯ2 ］2 、ＬｉＢ［Ｃ6 Ｈ3 （ＣＦ3 ）2 ］4 、ＬｉＡｌＣｌ4 、ＬｉＳｉＦ6 などのリチウム塩を用いることができる。特にＬｉＰＦ6 、ＬｉＢＦ4 が酸化安定性の点から好ましく用いられる。
有機系電解質中の電解質塩濃度は０．１〜５ mol/lが好ましく、０．５〜３．０mol/l がより好ましい。
The electrolyte used in the present invention includes an organic electrolyte composed of a solvent and an electrolyte salt, and a polymer electrolyte composed of a polymer compound and an electrolyte salt. Examples of the electrolyte salt include LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB (C 6 H 5 ), LiCl, LiBr, LiCF 3 SO 3 , LiCH 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiN (CF 3 CH 2 OSO 2 ) 2 , LiN (CF 3 CF 2 OSO 2 ) 2 , LiN (HCF 2 CF 2 CH 2 OSO 2 ) 2 , LiN [(CF 3 ) Lithium salts such as 2 CHOSO 2 ] 2 , LiB [C 6 H 3 (CF 3 ) 2 ] 4 , LiAlCl 4 , LiSiF 6 can be used. In particular, LiPF 6 and LiBF 4 are preferably used from the viewpoint of oxidation stability.
The electrolyte salt concentration in the organic electrolyte is preferably 0.1 to 5 mol / l, and more preferably 0.5 to 3.0 mol / l.
有機系電解質の溶媒としては、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、１，1 −または１，2 −ジメトキシエタン、１，2 −ジエトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、γ−ブチロラクトン、1 ，３−ジオキソラン、4 −メチル−1 ，3 −ジオキソラン、アニソール、ジエチルエーテル、スルホラン、メチルスルホラン、アセトニトリル、クロロニトリル、プロピオニトリル、ホウ酸トリメチル、ケイ酸テトラメチル、ニトロメタン、ジメチルホルムアミド、Ｎ−メチルピロリドン、酢酸エチル、トリメチルオルトホルメート、ニトロベンゼン、塩化ベンゾイル、臭化ベンゾイル、テトラヒドロチオフェン、ジメチルスルホキシド、３−メチル−２−オキサゾリドン、エチレングリコール、ジメチルサルファイトなどの非プロトン性有機溶媒を用いることができる。 Solvents for organic electrolytes include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,1- or 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran , Γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, anisole, diethyl ether, sulfolane, methylsulfolane, acetonitrile, chloronitrile, propionitrile, trimethylborate, tetramethylsilicate, nitromethane , Dimethylformamide, N-methylpyrrolidone, ethyl acetate, trimethylorthoformate, nitrobenzene, benzoyl chloride, benzoyl bromide, tetrahydrothiophene, dimethylsulfoxy And aprotic organic solvents such as 3-methyl-2-oxazolidone, ethylene glycol, and dimethyl sulfite can be used.
非水電解質をポリマー電解質とする場合には、可塑剤（非水電解液）でゲル化されたマトリクス高分子化合物を含むが、このマトリクス高分子化合物としては、ポリエチレンオキサイドやその架橋体などのエーテル系重合体、ポリメタクリレート系重合体、ポリアクリレート系重合体、ポリビニリデンフルオライドやビニリデンフルオライド−ヘキサフルオロプロピレン共重合体などのフッ素系重合体などを単独、もしくは混合して用いることができる。
これらの中で、酸化還元安定性の観点などから、ポリビニリデンフルオライドやビニリデンフルオライド−ヘキサフルオロプロピレン共重合体などのフッ素系重合体を用いることが好ましい。
ポリマー電解質に含有される可塑剤を構成する電解質塩や溶媒としては、前述のものが使用可能である。可塑剤である電解液中の電解質塩濃度は、０．１〜５mol/l が好ましく、０．５〜２．０mol/l がより好ましい。
When a non-aqueous electrolyte is used as a polymer electrolyte, it includes a matrix polymer compound gelled with a plasticizer (non-aqueous electrolyte). Examples of the matrix polymer compound include ethers such as polyethylene oxide and cross-linked products thereof. Fluorine polymers such as polymer, polymethacrylate polymer, polyacrylate polymer, polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer can be used alone or in combination.
Among these, it is preferable to use a fluorine-based polymer such as polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer from the viewpoint of redox stability.
As the electrolyte salt and the solvent constituting the plasticizer contained in the polymer electrolyte, those described above can be used. 0.1-5 mol / l is preferable and, as for the electrolyte salt concentration in the electrolyte solution which is a plasticizer, 0.5-2.0 mol / l is more preferable.
ポリマー電解質の作製方法は、特に制限されるものではないが、例えば、マトリクスを構成する高分子化合物、リチウム塩および溶媒を混合し、加熱して溶融・溶解する方法が挙げられる。また、混合用有機溶媒に、高分子化合物、リチウム塩、および溶媒を溶解させた後、混合用有機溶媒を蒸発させる方法、重合性モノマー、リチウム塩および溶媒を混合し、紫外線、電子線または分子線などを照射して、重合性モノマーを重合させ、ポリマーを得る方法などを挙げることができる。
ポリマー電解質中の溶媒の割合は１０〜９０質量％が好ましく、３０〜８０質量％がより好ましい。該範囲であると、導電率が高く、機械的強度が強く、フィルム化しやすい。
The method for producing the polymer electrolyte is not particularly limited, and examples thereof include a method in which a polymer compound constituting a matrix, a lithium salt, and a solvent are mixed, heated, and melted / dissolved. In addition, after dissolving a polymer compound, a lithium salt, and a solvent in an organic solvent for mixing, the organic solvent for mixing is evaporated, a polymerizable monomer, a lithium salt, and a solvent are mixed, and ultraviolet rays, electron beams, or molecules are mixed. Examples include a method of polymerizing a polymerizable monomer by irradiating a line and the like to obtain a polymer.
10-90 mass% is preferable and, as for the ratio of the solvent in a polymer electrolyte, 30-80 mass% is more preferable. Within this range, the electrical conductivity is high, the mechanical strength is strong, and a film is easily formed.
本発明のリチウムイオン二次電池においては、セパレータを使用することもできる。
セパレータは特に限定されるものではないが、例えば織布、不織布、合成樹脂製微多孔膜などが挙げられる。合成樹脂製微多孔膜が好適であるが、なかでもポリオレフィン系微多孔膜が、厚さ、膜強度、膜抵抗の面で好適である。具体的には、ポリエチレンおよびポリプロピレン製微多孔膜、またはこれらを複合した微多孔膜等である。
本発明のリチウムイオン二次電池においては、初期充放電効率が高いことから、ゲル電解質を用いることも可能である。
In the lithium ion secondary battery of the present invention, a separator can also be used.
Although a separator is not specifically limited, For example, a woven fabric, a nonwoven fabric, a synthetic resin microporous film, etc. are mentioned. A synthetic resin microporous membrane is preferred, and among them, a polyolefin microporous membrane is preferred in terms of thickness, membrane strength, and membrane resistance. Specifically, it is a microporous membrane made of polyethylene and polypropylene, or a microporous membrane that combines these.
In the lithium ion secondary battery of the present invention, a gel electrolyte can be used because of the high initial charge / discharge efficiency.
ポリマー電解質を用いたリチウムイオン二次電池は、一般にポリマー電池と呼ばれ、本発明の負極材料を用いてなる負極と、正極およびポリマー電解質から構成される。例えば、負極、ポリマー電解質、正極の順に積層し、電池外装材内に収容することで作製される。なお、これに加えて、さらに、負極と正極の外側にポリマー電解質を配するようにしてもよい。特に、本発明の黒鉛質材料を負極材料として用いるポリマー電池では、ポリマー電解質にプロピレンカーボネートを含有させることができる。一般にプロピレンカーボネートは黒鉛に対して電気的分解反応が激しいが、本発明の黒鉛質材料は分解反応性が低い。 A lithium ion secondary battery using a polymer electrolyte is generally called a polymer battery, and includes a negative electrode using the negative electrode material of the present invention, a positive electrode, and a polymer electrolyte. For example, the negative electrode, the polymer electrolyte, and the positive electrode are laminated in this order, and are housed in a battery outer packaging material. In addition to this, a polymer electrolyte may be further arranged outside the negative electrode and the positive electrode. In particular, in a polymer battery using the graphite material of the present invention as a negative electrode material, propylene carbonate can be contained in the polymer electrolyte. In general, propylene carbonate has a strong electrolysis reaction with respect to graphite, but the graphite material of the present invention has low decomposition reactivity.
さらに、本発明のリチウムイオン二次電池の構造は任意であり、その形状、形態について特に限定されるものではなく、円筒型、角型、コイン型、ボタン型などの中から任意に選択することができる。より安全性の高い密閉型非水電解液電池を得るためには、過充電などの異常時に電池内圧上昇を感知して電流を遮断させる手段を備えたものであることが好ましい。ポリマー電解質を用いたポリマー電池の場合には、ラミネートフィルムに封入した構造とすることもできる。 Furthermore, the structure of the lithium ion secondary battery of the present invention is arbitrary, and the shape and form thereof are not particularly limited, and can be arbitrarily selected from a cylindrical shape, a square shape, a coin shape, a button shape, and the like. Can do. In order to obtain a sealed nonaqueous electrolyte battery with higher safety, it is preferable to include a means for detecting an increase in the internal pressure of the battery and shutting off the current when there is an abnormality such as overcharging. In the case of a polymer battery using a polymer electrolyte, a structure enclosed in a laminate film can also be used.
次に本発明を実施例により具体的に説明するが、本発明はこれら実施例に限定されるものではない。また以下の実施例および比較例では、図３に示すような構成の評価用のボタン型二次電池を作製して黒鉛質材料の評価をした。実電池は、本発明の目的に基づき、公知の方法に準じて作製することができる。該評価用電池においては、作用極を負極、対極を正極と表現した。 EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the following examples and comparative examples, a button-type secondary battery for evaluation having a configuration as shown in FIG. 3 was produced and the graphite material was evaluated. A real battery can be manufactured according to a well-known method based on the objective of this invention. In the evaluation battery, the working electrode was expressed as a negative electrode, and the counter electrode was expressed as a positive electrode.
なお以下の実施例および比較例において、黒鉛質材料Ａの前駆体、および繊維状黒鉛材料Ｂの前駆体の物性、ならびに得られた黒鉛質材料（負極材料）の物性は以下の方法により測定した。
平均アスペクト比は、走査型電子顕微鏡で各材料の形状が認識できる倍率で１００個分を撮影し、最長部の長さと、これに直交する短軸の長さを測り、長軸長／短軸長の平均値を求め、アスペクト比とした。繊維状の材料の場合は、直径を短軸長、最長部の長さを長軸長とした。
平均粒子径はレーザー回折式粒度分布計を用いて測定し、体積換算の５０％累積径を求めた。
格子面間隔ｄ002 は、前述したＸ線広角回折法により求めた。
また、ラマンスペクトルの強度比Ｒ＝Ｉ1360／Ｉ1560は、前述したラマンスペクトル法のピーク強度から算出した。
In the following Examples and Comparative Examples, the physical properties of the precursor of the graphite material A and the precursor of the fibrous graphite material B and the physical properties of the obtained graphite material (negative electrode material) were measured by the following methods. .
For the average aspect ratio, 100 images were taken at a magnification that allows the shape of each material to be recognized with a scanning electron microscope, and the length of the longest part and the length of the short axis perpendicular to this were measured. The average value of the length was obtained and used as the aspect ratio. In the case of a fibrous material, the diameter was the short axis length, and the length of the longest part was the long axis length.
The average particle diameter was measured using a laser diffraction particle size distribution meter, and a 50% cumulative diameter in terms of volume was determined.
The lattice spacing d 002 was determined by the aforementioned X-ray wide angle diffraction method.
The Raman spectrum intensity ratio R = I 1360 / I 1560 was calculated from the peak intensity of the Raman spectrum method described above.
［実施例１］
（黒鉛質材料Ａの前駆体）
揮発分を約４０質量％含有するコールタールピッチ（ＪＦＥケミカル（株）製PK-QL ）を非酸化性雰囲気中、４５０℃で１２時間加熱して、芳香環を重縮合させ、黒鉛質材料Ａの前駆体（揮発分量：６．０質量％、ＱＩ：９６質量％）を得た。該前駆体を衝突式粉砕機を用いて粉砕し、平均粒子径２０μｍの塊状粒子に調整した。
[Example 1]
(Precursor of graphite material A)
Coal tar pitch (PK-QL manufactured by JFE Chemical Co., Ltd.) containing about 40% by mass of volatile matter is heated in a non-oxidizing atmosphere at 450 ° C. for 12 hours to polycondensate the aromatic ring, and the graphite material A Precursor (volatile content: 6.0% by mass, QI: 96% by mass) was obtained. The precursor was pulverized using a collision pulverizer, and adjusted to agglomerated particles having an average particle diameter of 20 μm.
（繊維状黒鉛材料Ｂの前駆体）
高純度酸化第二鉄を固定床流通式反応装置に充填し、常圧、５５０℃で高純度酸化鉄１ｇ当たり３００sccmのＣＯおよび１５sccmの水素を流通して、下記式（Ｉ）に示す反応を生じさせ、高純度酸化第二鉄１ｇ当たり３０ｇの気相成長炭素繊維を得た。この直径は１２０ｎｍ、アスペクト比は３０であった。これを繊維状黒鉛材料Ｂの前駆体とした。
A high-purity ferric oxide is charged into a fixed bed flow type reactor, and 300 sccm of CO and 15 sccm of hydrogen are circulated per gram of high-purity iron oxide at 550 ° C. under normal pressure to carry out the reaction represented by the following formula (I). As a result, 30 g of vapor grown carbon fiber per 1 g of high purity ferric oxide was obtained. This diameter was 120 nm and the aspect ratio was 30. This was used as a precursor of fibrous graphite material B.
（黒鉛質材料）
前記黒鉛質材料Ａの前駆体９９．０質量部と、繊維状黒鉛材料Ｂの前駆体１．０質量部を混合し、図２に示すハイブリダイゼーションシステム（（株）奈良機械製作所製）を用いて、機械的エネルギーを付与した。すなわち、ローターの周速度５０m/s 、処理時間３分の条件で処理することにより、該システム内に投入された材料同士に、衝撃力、圧縮力、摩擦力、剪断力などの機械的エネルギーを繰り返し付与し、黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂの前駆体を付着させた。
得られた付着物は、平均粒子径が１９μｍで、粒子の角が丸められた塊状を呈し、さらに、繊維状黒鉛材料Ｂの前駆体の一部が、黒鉛質材料Ａの前駆体の表面に埋没され、起毛していた。
(Graphite material)
99.0 parts by mass of the precursor of the graphite material A and 1.0 part by mass of the precursor of the fibrous graphite material B are mixed, and a hybridization system shown in FIG. 2 (manufactured by Nara Machinery Co., Ltd.) is used. Mechanical energy was applied. That is, by processing the rotor at a peripheral speed of 50 m / s and a processing time of 3 minutes, mechanical energy such as impact force, compressive force, frictional force, and shear force is applied to the materials put into the system. Repeatedly applied, the precursor of the fibrous graphite material B was adhered to the precursor of the graphite material A.
The obtained deposit has an average particle diameter of 19 μm and a lump shape in which the corners of the particles are rounded. Further, a part of the precursor of the fibrous graphite material B is formed on the surface of the precursor of the graphite material A. It was buried and raised.
引き続き、得られた付着物を黒鉛坩堝に充填し、坩堝の周辺にコークスブリーズを充填して３０００℃で５時間加熱し、黒鉛化処理した。黒鉛化処理後の黒鉛質材料に融着や変形は認められず、粒子形状が保持されていた。その平均粒子径は１８μｍ、平均アスペクト比は２．３であった。
得られた黒鉛質材料の結晶性（黒鉛化度）をＸ線広角回折法およびラマン分光法によって評価した結果を表２に示した。
Subsequently, the obtained deposit was filled into a graphite crucible, coke breeze was filled around the crucible, and heated at 3000 ° C. for 5 hours to graphitize. The graphitic material after the graphitization treatment was not fused or deformed, and the particle shape was maintained. The average particle diameter was 18 μm, and the average aspect ratio was 2.3.
The crystallinity (degree of graphitization) of the obtained graphite material was evaluated by X-ray wide angle diffraction method and Raman spectroscopy.
（負極合剤ペースト）
得られた黒鉛質材料９０質量％と、結合剤としてのポリフッ化ビニリデン１０質量％とを、Ｎ−メチルピロリドン溶媒に入れ、ホモミキサーを用いて２０００rpm で３０分間攪拌混合し、有機溶媒系負極合剤ペーストを調製した。
(Negative electrode mixture paste)
90% by mass of the obtained graphite material and 10% by mass of polyvinylidene fluoride as a binder are placed in an N-methylpyrrolidone solvent, and are stirred and mixed at 2000 rpm for 30 minutes using a homomixer. An agent paste was prepared.
(作用電極（負極））
前記負極合剤ペーストを、銅箔（集電体）上に均一な厚さで塗布し、さらに真空中で９０℃に加熱して、溶媒を揮発させて乾燥した。次に、この銅箔上に塗布された負極合剤をローラープレスによって加圧し、さらに直径１５．５ｍｍの円形状に打抜くことで、集電体に密着した負極合剤層からなる作用電極２を作製した。
(Working electrode (negative electrode))
The negative electrode mixture paste was applied to a copper foil (current collector) with a uniform thickness, and further heated to 90 ° C. in vacuum to evaporate the solvent and dry. Next, the negative electrode mixture applied on the copper foil is pressed by a roller press and punched into a circular shape having a diameter of 15.5 mm, whereby the working electrode 2 composed of the negative electrode mixture layer in close contact with the current collector. Was made.
(対極（正極））
リチウム金属箔を、ニッケルネットに押付け、直径１５．５ｍｍの円形状に打抜いて、ニッケルネットからなる集電体と、該集電体に密着したリチウム金属箔からなる正極を作製した。
(Counter electrode (positive electrode))
The lithium metal foil was pressed against a nickel net and punched into a circular shape with a diameter of 15.5 mm to produce a current collector made of nickel net and a positive electrode made of lithium metal foil in close contact with the current collector.
（電解質・セパレータ）
エチレンカーボネート３３vol%−メチルエチルカーボネート６７vol%の混合溶媒に、ＬｉＰＦ6 を１mol/ｄｍ3 となる濃度で溶解させ、非水電解液を調製した。得られた非水電解液をポリプロピレン微多孔質体に含浸させ、電解質液が含浸されたセパレータを作製した。
(Electrolyte / Separator)
LiPF 6 was dissolved at a concentration of 1 mol / dm 3 in a mixed solvent of ethylene carbonate 33 vol% -methyl ethyl carbonate 67 vol% to prepare a non-aqueous electrolyte. The obtained non-aqueous electrolyte solution was impregnated into a polypropylene microporous material to produce a separator impregnated with the electrolyte solution.
（評価電池）
評価電池として図３に示すボタン型二次電池を作製した。
集電体３７ｂに密着した負極３２と集電体３７ａに密着した正極３４との間に、電解質溶液を含浸させたセパレータ３５を挟んで、積層した。その後、負極集電体３７ｂ側が外装カップ３１内に、正極集電体３７ａ側が外装缶３３内に収容されるように、外装カップ３１と外装缶３３とを合わせた。その際、外装カップ３１と外装缶３３との周縁部に絶縁ガスケット３６を介在させ、両周縁部をかしめて密閉した。
(Evaluation battery)
A button-type secondary battery shown in FIG. 3 was produced as an evaluation battery.
The
前記のように作製された評価電池について、２５℃の温度下で下記のような充放電試験を行い、電池特性を評価した。
（初期充放電効率、放電容量）
０．９ｍＡの電流値で、回路電圧が０ｍＶに達するまで定電流充電を行った後、回路電圧が０ｍＶに達した時点で、定電圧充電に切替え、さらに電流値が２０μＡになるまで充電を続けた。その間の通電量から充電容量を求めた。その後、１２０分間休止した。
次に０．９ｍＡの電流値で、回路電圧が１．５Ｖに達するまで定電流放電を行い、この間の通電量から放電容量を求めた。これを第１サイクルとした。次式（II）から初期充放電効率を計算した。
(Initial charge / discharge efficiency, discharge capacity)
After performing constant current charging until the circuit voltage reaches 0 mV at a current value of 0.9 mA, when the circuit voltage reaches 0 mV, switching to constant voltage charging is continued until the current value reaches 20 μA. It was. The charging capacity was determined from the amount of electricity applied during that time. Then, it rested for 120 minutes.
Next, constant current discharge was performed at a current value of 0.9 mA until the circuit voltage reached 1.5 V, and the discharge capacity was obtained from the energization amount during this period. This was the first cycle. The initial charge / discharge efficiency was calculated from the following formula (II).
なおこの試験では、リチウムイオンを黒鉛質材料中にドープする過程を充電、黒鉛質材料から脱ドープする過程を放電とした。
黒鉛質材料１ｇ当たりの放電容量（mAh/g ）および初期充放電効率（％）を表２に示した。
表１、２に示されるように、負極に本発明の黒鉛質材料を用いたリチウムイオン二次電池は大きい放電容量を示し、かつ高い初期充放電効率を有する。
In this test, the process of doping lithium ions into the graphite material was charged, and the process of dedoping from the graphite material was discharge.
Table 2 shows the discharge capacity per 1 g of the graphite material (mAh / g) and the initial charge / discharge efficiency (%).
As shown in Tables 1 and 2, the lithium ion secondary battery using the graphite material of the present invention for the negative electrode exhibits a large discharge capacity and high initial charge / discharge efficiency.
（急速充電効率）
引き続き、第２サイクルとして、電流値を５倍の４．５ｍＡとして、回路電圧が０ｍＶに達するまで定電流充電を行い、充電容量を求め、次式（III)から急速充電効率を計算した。
Subsequently, as the second cycle, the current value was set to 4.5 mA, which is five times larger, constant current charging was performed until the circuit voltage reached 0 mV, the charging capacity was obtained, and the rapid charging efficiency was calculated from the following formula (III).
（急速放電効率）
初期充放電に引き続き、第２サイクルにて、高速放電を行った。第１サイクルと同様にして充電した後、電流値を２０倍の１８ｍＡとして、回路電圧が１．５Ｖに達するまで定電流放電を行った。得られた放電容量から、次式（IV）により急速放電効率を計算した。
Following the initial charge / discharge, high-speed discharge was performed in the second cycle. After charging in the same way as in the first cycle, the current value was set to 18 mA, which is 20 times, and constant current discharge was performed until the circuit voltage reached 1.5V. From the obtained discharge capacity, the rapid discharge efficiency was calculated by the following formula (IV).
（サイクル特性）
４．０ｍＡの電流値で、回路電圧が０ｍＶに達するまで定電流充電を行った後、回路電圧が０ｍＶに達した時点で、定電圧充電に切替え、さらに電流値が２０μＡになるまで充電を続けた。その後、１２０分間休止した。次に４．０ｍＡの電流値で、回路電圧が１．５Ｖに達するまで定電流放電を行った。２０回充放電を繰り返し、得られた放電容量から、次式（Ｖ）を用いてサイクル特性を計算した。
After constant current charging at a current value of 4.0 mA until the circuit voltage reaches 0 mV, when the circuit voltage reaches 0 mV, switching to constant voltage charging is continued until the current value reaches 20 μA. It was. Then, it rested for 120 minutes. Next, constant current discharge was performed at a current value of 4.0 mA until the circuit voltage reached 1.5V. The charge / discharge was repeated 20 times, and the cycle characteristics were calculated from the obtained discharge capacity using the following formula (V).
急速充電効率（％）、急速放電容量（％）およびサイクル特性を表２に示した。
表１、２に示されるように、作用電極に本発明の黒鉛質材料を含有する負極材料を用いて得られた評価電池は、高い急速充電効率、高い急速放電効率、および優れたサイクル特性を示す。
Table 2 shows the rapid charge efficiency (%), rapid discharge capacity (%), and cycle characteristics.
As shown in Tables 1 and 2, the evaluation battery obtained using the negative electrode material containing the graphite material of the present invention for the working electrode has high rapid charge efficiency, high rapid discharge efficiency, and excellent cycle characteristics. Show.
［実施例２］
（黒鉛Ｃ）
天然黒鉛（（株）中越黒鉛工業所製BF10A 、平均粒子径１０μｍ）を造粒し、緻密な球状〜楕円状の黒鉛造粒物を得た。該黒鉛造粒物は、平均粒子径が２０μｍ、平均アスペクト比が１．８、Ｘ線広角回折法による結晶性が格子面間隔ｄ002 ＝０．３３５５ｎｍであった。
[Example 2]
(Graphite C)
Natural graphite (BF10A manufactured by Chuetsu Graphite Industries Co., Ltd., average particle size: 10 μm) was granulated to obtain dense spherical to elliptical graphite granules. The graphite granulated product had an average particle diameter of 20 μm, an average aspect ratio of 1.8, and crystallinity measured by the X-ray wide angle diffraction method was a lattice spacing d 002 = 0.3355 nm.
（黒鉛質材料Ａの前駆体）
揮発分を約４０質量％含有するコールタールピッチ（ＪＦＥケミカル（株）製PK-QL ）４２質量部をタール中油５８質量部に溶解した溶液を１００質量部準備した。
先に得た黒鉛造粒物１００質量部を前記溶液１００質量部とともに、攪拌機に投入し、１５０℃で３０分間攪拌して、該黒鉛造粒物を該コールタールピッチ溶液に浸漬した後、圧力５mmHg以下、同温度で溶媒であるタール中油を留去した。得られた黒鉛造粒物のピッチ付着体を鋼鉄製容器に充填した。揮発ガスの燃焼処理装置を具備した焼成炉において、不活性ガス流通下に前記付着体を４５０℃で２０時間熱処理し、黒鉛造粒物を含有する黒鉛質材料Ａの前駆体を得た。熱処理後に得られたものは、黒鉛造粒物の表面に介在する黒鉛質材料Ａの前駆体同士がわずかに融着した状態であった。
(Precursor of graphite material A)
100 parts by mass of a solution prepared by dissolving 42 parts by mass of coal tar pitch (PK-QL manufactured by JFE Chemical Co., Ltd.) containing about 40% by mass of volatile matter in 58 parts by mass of oil in tar was prepared.
100 parts by mass of the previously obtained graphite granulated product was put into a stirrer together with 100 parts by mass of the above solution, stirred at 150 ° C. for 30 minutes, and the graphite granulated product was immersed in the coal tar pitch solution. The oil in tar as a solvent was distilled off at 5 mmHg or less and at the same temperature. The obtained graphite agglomerated pitch deposits were filled into a steel container. In a firing furnace equipped with a volatile gas combustion treatment apparatus, the adhering material was heat-treated at 450 ° C. for 20 hours under an inert gas flow to obtain a precursor of a graphitic material A containing graphite granules. What was obtained after the heat treatment was a state in which the precursors of the graphite material A intervening on the surface of the graphite granule were slightly fused.
次いで、衝撃式粉砕機で解砕した。解砕後の形状は、平均粒子径が２２μｍ、平均アスペクト比が１．７の球状〜楕円体であった。解砕後に得られたものは、コールタールピッチの熱処理によって得られた黒鉛質材料Ａの前駆体２０質量％、天然黒鉛造粒物８０質量％から構成されており、コールタールピッチの熱処理生成物の部分は揮発分量を５．０質量％含有していた（黒鉛質材料Ａの前駆体と黒鉛Ｃの造粒物との全体に対して１質量％）。 Subsequently, it was pulverized with an impact pulverizer. The shape after crushing was spherical to ellipsoidal with an average particle diameter of 22 μm and an average aspect ratio of 1.7. What was obtained after crushing was composed of 20% by mass of a precursor of graphitic material A obtained by heat treatment of coal tar pitch and 80% by mass of natural graphite granulated product. This portion contained 5.0% by mass of the volatile content (1% by mass with respect to the whole of the precursor of the graphite material A and the granulated product of graphite C).
（繊維状黒鉛材料Ｂの前駆体）
黒鉛化処理された気相成長炭素繊維（昭和電工（株）製、VGCF、直径１５０ｎｍ、平均アスペクト比約５０）を準備した。
(Precursor of fibrous graphite material B)
A graphitized vapor-grown carbon fiber (manufactured by Showa Denko KK, VGCF, diameter 150 nm, average aspect ratio about 50) was prepared.
（黒鉛質材料）
前記黒鉛Ｃを内包する黒鉛質材料Ａの前駆体９９．０質量部と、繊維状黒鉛材料Ｂの前駆体１．０質量部を混合し、図１Ａおよび図１Ｂに示したメカノフュージョンシステム（ホソカワミクロン（株）製）内に投入し、機械的エネルギーを付与した。すなわち、回転ドラムの周速度２０m/s 、処理時間３０分、回転ドラムと内部部材の距離５ｍｍの条件で、圧縮力、剪断力を繰り返し付加し、黒鉛Ｃを内包する黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂの前駆体を付着させた。
得られた付着物は、平均粒子径が２２μｍで、アスペクト比が１．７であり、機械的エネルギーの付与前後において、平均粒子径とアスペクト比に変化がなかった。さらに、繊維状黒鉛材料Ｂの前駆体の一部が、黒鉛質材料Ａの前駆体の表面に埋没され、起毛していた。
(Graphite material)
99.0 parts by mass of the precursor of the graphite material A containing the graphite C and 1.0 part by mass of the precursor of the fibrous graphite material B are mixed, and the mechano-fusion system (Hosokawa Micron shown in FIGS. 1A and 1B) is mixed. And mechanical energy was applied. That is, a precursor of graphitic material A containing graphite C by repeatedly applying compressive force and shearing force under the conditions of a peripheral speed of the rotating drum of 20 m / s, a processing time of 30 minutes, and a distance of 5 mm between the rotating drum and the internal member. The precursor of the fibrous graphite material B was adhered to.
The obtained deposit had an average particle diameter of 22 μm and an aspect ratio of 1.7, and the average particle diameter and the aspect ratio did not change before and after application of mechanical energy. Furthermore, a part of the precursor of the fibrous graphite material B was buried in the surface of the precursor of the graphite material A and was raised.
次いで、得られた付着物を黒鉛坩堝に充填し、坩堝の周辺にコークスブリーズを充填して３０００℃で５時間加熱し、黒鉛化処理した。黒鉛化処理後の黒鉛質材料Ａに融着や変形は認められず、粒子形状が保持されていた。その平均粒子径は２１μｍ、平均アスペクト比は１．７であった。
得られた黒鉛質材料のＸ線広角回折法による結晶性はｄ002 ＝０．３３５７ｎｍ、ラマン分光法による強度比Ｒは０．０９であった。図４に、製造した黒鉛質材料の走査型電子顕微鏡写真（倍率１０００倍）を示した。
該黒鉛質材料を用いて、実施例１と同様に、評価用電池の作用電極（負極）および評価電池を製造し、電池特性を評価した。結果を表２に示した。
Next, the obtained deposit was filled into a graphite crucible, and coke breeze was filled around the crucible and heated at 3000 ° C. for 5 hours for graphitization. The graphitic material A after the graphitization treatment was not fused or deformed, and the particle shape was maintained. The average particle diameter was 21 μm and the average aspect ratio was 1.7.
The obtained graphite material had a crystallinity of d 002 = 0.3357 nm by an X-ray wide angle diffraction method and an intensity ratio R of 0.09 by Raman spectroscopy. In FIG. 4, the scanning electron micrograph (1000-times multiplication factor) of the manufactured graphite material was shown.
Using the graphite material, a working electrode (negative electrode) and an evaluation battery for an evaluation battery were produced in the same manner as in Example 1, and battery characteristics were evaluated. The results are shown in Table 2.
［実施例３］
（黒鉛Ｃ）
天然黒鉛（（株）中越黒鉛工業所製BF5A、平均粒子径５μｍ）を準備した。該天然黒鉛は、Ｘ線広角回折法による結晶性が格子面間隔ｄ002 ＝０．３３５５ｎｍであった。
[Example 3]
(Graphite C)
Natural graphite (BF5A manufactured by Chuetsu Graphite Industries Co., Ltd., average particle size: 5 μm) was prepared. The natural graphite had crystallinity of lattice spacing d 002 = 0.3355 nm as measured by the X-ray wide angle diffraction method.
（黒鉛質材料Ａの前駆体）
揮発分を約４０質量％含有するコールタールピッチ（ＪＦＥケミカル（株）製PK-QL ）７１質量部をタール中油２９質量部に溶解した溶液を１００質量部準備した。
前記天然黒鉛１００質量部を前記溶液１００質量部とともに、二軸混練機に投入し、１５０℃で３０分間攪拌して、該天然黒鉛を該コールタールピッチ溶液に混合した後、圧力５mmHg以下、同温度で溶媒であるタール中油を留去した。
得られた天然黒鉛とコールタールピッチの混合物を鋼鉄製容器に充填した。揮発ガスの燃焼処理装置を具備した焼成炉において、不活性ガス流通下に前記付着体を４５０℃で２０時間熱処理し、天然黒鉛を含有する黒鉛質材料Ａの前駆体を得た。
(Precursor of graphite material A)
100 parts by mass of a solution prepared by dissolving 71 parts by mass of coal tar pitch (PK-QL manufactured by JFE Chemical Co., Ltd.) containing about 40% by mass of volatile matter in 29 parts by mass of tar oil was prepared.
100 parts by mass of the natural graphite and 100 parts by mass of the solution are put into a twin-screw kneader and stirred at 150 ° C. for 30 minutes to mix the natural graphite with the coal tar pitch solution, and then the pressure is 5 mmHg or less. The oil in tar as solvent was distilled off at temperature.
The obtained mixture of natural graphite and coal tar pitch was filled into a steel container. In a firing furnace equipped with a volatile gas combustion treatment device, the adhering material was heat-treated at 450 ° C. for 20 hours under an inert gas flow to obtain a precursor of a graphitic material A containing natural graphite.
次いで、衝撃式粉砕機で解砕した。解砕後の形状は、平均粒子径が２５μｍ、平均アスペクト比が２．４の突起を有する不定形粒子であった。解砕後に得られたものは、コールタールピッチの熱処理によって得られた黒鉛質材料Ａの前駆体３０質量％、天然黒鉛７０質量％から構成されており、コールタールピッチの熱処理生成物の部分は揮発分を５．０質量％含有していた（黒鉛質材料Ａの前駆体と黒鉛Ｃの造粒物との全体に対して１．５質量％）。 Subsequently, it was pulverized with an impact pulverizer. The shape after pulverization was irregular particles having protrusions having an average particle diameter of 25 μm and an average aspect ratio of 2.4. What was obtained after pulverization was composed of 30% by mass of a precursor of graphitic material A obtained by heat treatment of coal tar pitch, and 70% by mass of natural graphite. The volatile content was 5.0% by mass (1.5% by mass with respect to the whole of the precursor of the graphite material A and the granulated product of graphite C).
（繊維状黒鉛材料Ｂの前駆体）
実施例１で用いた気相成長炭素繊維（昭和電工（株）製、VGCF、直径１５０ｎｍ、平均アスペクト比約５０）を３０００℃で５時間黒鉛化処理したものを準備した。
(Precursor of fibrous graphite material B)
A vapor-grown carbon fiber used in Example 1 (produced by Showa Denko KK, VGCF, diameter 150 nm, average aspect ratio about 50) was graphitized at 3000 ° C. for 5 hours to prepare.
（黒鉛質材料）
前記黒鉛Ｃを内包する黒鉛質材料Ａの前駆体９８．０質量部と、繊維状黒鉛材料Ｂの前駆体２．０質量部を混合し、図１Ａおよび図１Ｂに示したメカノフュージョンシステム（ホソカワミクロン（株）製）内に投入し、機械的エネルギーを付与した。すなわち、回転ドラムの周速度２０m/s 、処理時間３０分、回転ドラムと内部部材の距離５ｍｍの条件で、圧縮力、剪断力を繰り返し付加し、黒鉛Ｃを内包する黒鉛質材料Ａの前駆体に繊維状黒鉛材料Ｂの前駆体を付着させた。
得られた付着物は、平均粒子径が２３μｍで、アスペクト比が２．０であった。機械的エネルギーの付与によって、黒鉛Ｃを内包する黒鉛質材料Ａの前駆体の突起がなくなり、塊状を呈していた。さらに、繊維状黒鉛材料Ｂの前駆体の一部が、黒鉛質材料Ａの前駆体の表面に埋没され、起毛していた。
(Graphite material)
98.0 parts by mass of the precursor of the graphite material A enclosing the graphite C and 2.0 parts by mass of the precursor of the fibrous graphite material B are mixed, and the mechanofusion system (Hosokawa Micron shown in FIGS. 1A and 1B) is mixed. And mechanical energy was applied. That is, a precursor of graphitic material A containing graphite C by repeatedly applying compressive force and shearing force under the conditions of a peripheral speed of the rotating drum of 20 m / s, a processing time of 30 minutes, and a distance of 5 mm between the rotating drum and the internal member. The precursor of the fibrous graphite material B was adhered to.
The obtained deposit had an average particle size of 23 μm and an aspect ratio of 2.0. Due to the application of mechanical energy, the protrusions of the precursor of the graphite material A containing the graphite C disappeared, and a lump was formed. Furthermore, a part of the precursor of the fibrous graphite material B was buried in the surface of the precursor of the graphite material A and was raised.
次いで、得られた付着物を黒鉛坩堝に充填し、坩堝の周辺にコークスブリーズを充填して３２００℃で５時間加熱し、黒鉛化処理して、黒鉛質材料を得た。黒鉛化処理後の黒鉛質材料に融着や変形は認められず、粒子形状が保持されていた。その平均粒子径は２２μｍ、平均アスペクト比は２．０であった。
得られた黒鉛質材料のＸ線広角回折法による結晶性はｄ002 ＝０．３３５８ｎｍ、ラマン分光法による強度比Ｒは０．１１であった。
該黒鉛質材料を用いて、実施例１と同様に、評価用電池の作用電極（負極）および評価電池を製造し、電池特性を評価した。結果を表２に示した。
Next, the obtained deposit was filled in a graphite crucible, and coke breeze was filled around the crucible, heated at 3200 ° C. for 5 hours, and graphitized to obtain a graphite material. The graphitic material after the graphitization treatment was not fused or deformed, and the particle shape was maintained. The average particle diameter was 22 μm and the average aspect ratio was 2.0.
The obtained graphite material had a crystallinity of d 002 = 0.3358 nm by an X-ray wide angle diffraction method, and an intensity ratio R of 0.11 by Raman spectroscopy.
Using the graphite material, a working electrode (negative electrode) and an evaluation battery for an evaluation battery were produced in the same manner as in Example 1, and battery characteristics were evaluated. The results are shown in Table 2.
［実施例４〜７］
実施例２において、黒鉛質材料Ａの前駆体や繊維状黒鉛材料Ｂの前駆体を表１に示すように変更する以外は、実施例２と同様に黒鉛質材料を調製し、負極を製造し、実施例２と同様に電池特性の評価試験を行った。評価結果を表２に示した。
[Examples 4 to 7]
In Example 2, except that the precursor of the graphite material A and the precursor of the fibrous graphite material B are changed as shown in Table 1, a graphite material is prepared in the same manner as in Example 2, and a negative electrode is manufactured. The battery characteristic evaluation test was conducted in the same manner as in Example 2. The evaluation results are shown in Table 2.
［比較例１］
実施例１において、繊維状黒鉛材料Ｂを使用せず、さらに機械的エネルギーを付与しないことを除いて、実施例１と同様に黒鉛質材料を調製した。得られた黒鉛質材料は、黒鉛化処理時に黒鉛質材料同士が融着しており、解砕時の形状を保持できなかった。そこで、融着した黒鉛質材料を再度解砕して平均粒子径１９μｍに調整し、実施例１と同様に負極および評価電池を製造して、実施例１と同様に電池特性の評価試験を行なった。評価結果を表２に示した。
表１、２に示されるように、繊維状黒鉛材料Ｂを含まず、機械的エネルギーを付与しなかった黒鉛質材料の場合には、初期充放電効率が著しく小さいほか、急速充電効率、急速放電効率、サイクル特性も劣る。
[Comparative Example 1]
In Example 1, a graphite material was prepared in the same manner as in Example 1 except that the fibrous graphite material B was not used and no mechanical energy was applied. In the obtained graphite material, the graphite materials were fused together during the graphitization treatment, and the shape at the time of pulverization could not be maintained. Therefore, the fused graphite material is crushed again and adjusted to an average particle diameter of 19 μm, and a negative electrode and an evaluation battery are produced in the same manner as in Example 1. A battery characteristic evaluation test is conducted in the same manner as in Example 1. It was. The evaluation results are shown in Table 2.
As shown in Tables 1 and 2, in the case of a graphite material that does not include the fibrous graphite material B and has not been given mechanical energy, the initial charge / discharge efficiency is remarkably small, and the rapid charge efficiency, rapid discharge Efficiency and cycle characteristics are also inferior.
［比較例２］
実施例１において、繊維状黒鉛材料Ｂを使用しないことを除いて、実施例１と同様に黒鉛質材料を調製した。得られた黒鉛質材料は、黒鉛化処理時の融着がなく、解砕時の形状を保持していた。これを用いて、実施例１と同様に負極および評価電池を作製して、実施例１と同様に電池特性の評価試験を行なった。評価結果を表２に示した。
表１、２に示されるように、繊維状黒鉛材料Ｂを使用しない黒鉛質材料の場合には、高い放電容量と初期充放電効率を有するものの、急速充電効率、急速放電効率およびサイクル特性が相対的に低い。
[Comparative Example 2]
In Example 1, a graphite material was prepared in the same manner as in Example 1 except that the fibrous graphite material B was not used. The obtained graphite material had no fusion at the time of graphitization treatment and retained the shape at the time of pulverization. Using this, a negative electrode and an evaluation battery were produced in the same manner as in Example 1, and a battery characteristic evaluation test was conducted in the same manner as in Example 1. The evaluation results are shown in Table 2.
As shown in Tables 1 and 2, in the case of a graphite material that does not use the fibrous graphite material B, although it has a high discharge capacity and initial charge / discharge efficiency, the rapid charge efficiency, rapid discharge efficiency, and cycle characteristics are relative. Low.
［比較例３］
実施例２において、繊維状黒鉛材料Ｂを使用しないことを除いて、実施例２と同様に黒鉛質材料を調製した。得られた黒鉛質材料は、黒鉛化処理時の融着がなく、解砕時の形状を保持していた。これを用いて、実施例２と同様に負極および評価電池を作製して、実施例１と同様に電池特性の評価試験を行なった。評価結果を表２に示した。
表１、２に示されるように、繊維状黒鉛材料Ｂを使用しない黒鉛質材料の場合には、高い放電容量と初期充放電効率を有するものの、急速充電効率、急速放電効率およびサイクル特性が低い。
[Comparative Example 3]
In Example 2, a graphite material was prepared in the same manner as in Example 2 except that the fibrous graphite material B was not used. The obtained graphite material had no fusion at the time of graphitization treatment and retained the shape at the time of pulverization. Using this, a negative electrode and an evaluation battery were produced in the same manner as in Example 2, and a battery characteristic evaluation test was conducted in the same manner as in Example 1. The evaluation results are shown in Table 2.
As shown in Tables 1 and 2, in the case of a graphite material that does not use the fibrous graphite material B, it has a high discharge capacity and initial charge / discharge efficiency, but has a low rapid charge efficiency, rapid discharge efficiency, and cycle characteristics. .
［比較例４］
比較例３で作製した繊維状黒鉛材料Ｂを含まない黒鉛質材料Ａの前駆体９９．０質量部と、実施例２で用いた繊維状黒鉛材料Ｂ１．０質量部の混合物を用いて、繊維状黒鉛材料Ｂの前駆体を黒鉛質材料Ａの前駆体に付着させないことを除いて、実施例２と同様に黒鉛質材料を調製し、実施例２と同様に負極および評価電池を作製して、実施例１と同様に電池特性の評価試験を行なった。評価結果を表２に示した。
表１、２に示されるように、繊維状黒鉛材料Ｂを単純に混合して負極を作製した場合には、繊維状黒鉛材料Ｂを含まない黒鉛質材料（比較例３）に比べて、急速充電効率、急速放電効率およびサイクル特性が改善されるものの、その効果は小さい。
[Comparative Example 4]
Using a mixture of 99.0 parts by mass of the precursor of the graphite material A not containing the fibrous graphite material B produced in Comparative Example 3 and 1.0 part by mass of the fibrous graphite material B used in Example 2, A graphite material was prepared in the same manner as in Example 2 except that the precursor of the graphite material B was not attached to the precursor of the graphite material A, and a negative electrode and an evaluation battery were prepared in the same manner as in Example 2. In the same manner as in Example 1, an evaluation test of battery characteristics was performed. The evaluation results are shown in Table 2.
As shown in Tables 1 and 2, when the negative electrode was prepared by simply mixing the fibrous graphite material B, it was more rapid than the graphite material not containing the fibrous graphite material B (Comparative Example 3). Although charging efficiency, rapid discharge efficiency and cycle characteristics are improved, the effect is small.
［比較例５］
実施例３において、繊維状黒鉛材料Ｂを使用しないことを除いて、実施例３と同様に黒鉛質材料を調製した。得られた黒鉛質材料を用いて、実施例３と同様に負極および評価電池を作製して、実施例１と同様に電池特性の評価試験を行なった。評価結果を表２に示した。
表１、２に示されるように、繊維状黒鉛材料Ｂを使用しない黒鉛質材料の場合には、高い放電容量と初期充放電効率を有するものの、急速充電効率、急速放電効率およびサイクル特性が低い。
[Comparative Example 5]
In Example 3, a graphite material was prepared in the same manner as in Example 3 except that the fibrous graphite material B was not used. Using the obtained graphite material, a negative electrode and an evaluation battery were produced in the same manner as in Example 3, and a battery characteristic evaluation test was conducted in the same manner as in Example 1. The evaluation results are shown in Table 2.
As shown in Tables 1 and 2, in the case of a graphite material that does not use the fibrous graphite material B, it has a high discharge capacity and initial charge / discharge efficiency, but has a low rapid charge efficiency, rapid discharge efficiency, and cycle characteristics. .
本発明の黒鉛質材料は、その特徴を活かして、燃料電池セパレータ用の導電材や耐火物用黒鉛などに使用することもできる。 The graphite material of the present invention can be used for a conductive material for a fuel cell separator, graphite for a refractory, and the like, taking advantage of the characteristics.
１１ 回転ドラム
１２ 内部部材（インナーピース）
１３ 原料
１４ 循環機構
１５ 排出機構
２１ 固定ドラム
２２ ローター
２３ 原料
２４ 原料の循環機構
２５ 原料の排出機構
２６ ブレード
２７ ステーター
２８ ジャケット
３１ 外装カップ
３２ 作用電極
３３ 外装缶
３４ 対極
３５ 電解質溶液含浸セパレータ
３６ 絶縁ガスケット
３７ａ，３７ｂ 集電体
11
13
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| KR102581549B1 (en) | 2014-07-07 | 2023-09-21 | 미쯔비시 케미컬 주식회사 | Carbon material, method for producing carbon material, and non-aqueous secondary battery using carbon material |
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