JP5230117B2 - Method for producing graphite particles - Google Patents
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- JP5230117B2 JP5230117B2 JP2007088593A JP2007088593A JP5230117B2 JP 5230117 B2 JP5230117 B2 JP 5230117B2 JP 2007088593 A JP2007088593 A JP 2007088593A JP 2007088593 A JP2007088593 A JP 2007088593A JP 5230117 B2 JP5230117 B2 JP 5230117B2
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims description 235
- 229910002804 graphite Inorganic materials 0.000 title claims description 118
- 239000010439 graphite Substances 0.000 title claims description 118
- 239000002245 particle Substances 0.000 title claims description 76
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 239000013078 crystal Substances 0.000 claims description 31
- 238000000034 method Methods 0.000 claims description 26
- 238000010438 heat treatment Methods 0.000 claims description 24
- 230000004913 activation Effects 0.000 claims description 19
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 15
- 229910052799 carbon Inorganic materials 0.000 claims description 15
- 229910001416 lithium ion Inorganic materials 0.000 claims description 15
- 230000003213 activating effect Effects 0.000 claims description 9
- 229910021469 graphitizable carbon Inorganic materials 0.000 claims description 9
- 238000010030 laminating Methods 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- 239000011261 inert gas Substances 0.000 claims description 7
- 239000007773 negative electrode material Substances 0.000 claims description 7
- 125000004432 carbon atom Chemical group C* 0.000 claims description 6
- 239000002006 petroleum coke Substances 0.000 claims description 4
- 239000011335 coal coke Substances 0.000 claims description 2
- 238000001994 activation Methods 0.000 description 21
- 238000004140 cleaning Methods 0.000 description 12
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 9
- 229910000000 metal hydroxide Inorganic materials 0.000 description 9
- 150000004692 metal hydroxides Chemical class 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- 239000011229 interlayer Substances 0.000 description 8
- 239000000571 coke Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- 239000010410 layer Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 239000003208 petroleum Substances 0.000 description 5
- 230000000704 physical effect Effects 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 238000003917 TEM image Methods 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 230000009257 reactivity Effects 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000001354 calcination Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000011889 copper foil Substances 0.000 description 3
- 229910001873 dinitrogen Inorganic materials 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 239000007770 graphite material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- BMYNFMYTOJXKLE-UHFFFAOYSA-N 3-azaniumyl-2-hydroxypropanoate Chemical compound NCC(O)C(O)=O BMYNFMYTOJXKLE-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 1
- 239000011260 aqueous acid Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical compound [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 description 1
- 229910001863 barium hydroxide Inorganic materials 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000010000 carbonizing Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000011333 coal pitch coke Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 238000004231 fluid catalytic cracking Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 description 1
- 229940071870 hydroiodic acid Drugs 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
- 239000011302 mesophase pitch Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 229910052756 noble gas Inorganic materials 0.000 description 1
- 150000002835 noble gases Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000004525 petroleum distillation Methods 0.000 description 1
- 239000011301 petroleum pitch Substances 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229920001059 synthetic polymer Polymers 0.000 description 1
- 239000011271 tar pitch Substances 0.000 description 1
- 238000004736 wide-angle X-ray diffraction Methods 0.000 description 1
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Description
本発明は、黒鉛粒子及びその製造方法に関する。 The present invention relates to graphite particles and a method for producing the same.
黒鉛は導電性に優れ、また滑性を有していることから、これらの特性を利用した塗料や潤滑剤などが開発されている。また、黒鉛は結晶性や電気化学的な安定性にも優れていることから、リチウムイオン二次電池、電気二重層キャパシタなどの電極材料あるいは水素吸蔵材料などにも利用されている。 Since graphite is excellent in conductivity and has slipperiness, paints and lubricants using these properties have been developed. In addition, graphite is excellent in crystallinity and electrochemical stability, so that it is also used for electrode materials such as lithium ion secondary batteries and electric double layer capacitors, or hydrogen storage materials.
黒鉛は、炭素原子が配列してなる六方網目構造を有する黒鉛結晶シートが積み重なって形成される層状構造を有している。それぞれの黒鉛結晶シートは、炭素原子が平面状に配列したＡＢ面（ベーサル面）と、このＡＢ面に垂直な断面であるエッジ面とを備える。黒鉛結晶シートのエッジ面は、ベーサル面と比較すると反応性が高いことが知られている。したがって、黒鉛の電気化学的な安定性を更に高めるためには、このエッジ面を何らかの方法で処理して、その反応性を低くすることが必要である。 Graphite has a layered structure formed by stacking graphite crystal sheets having a hexagonal network structure in which carbon atoms are arranged. Each graphite crystal sheet includes an AB plane (basal plane) in which carbon atoms are arranged in a plane, and an edge plane that is a cross section perpendicular to the AB plane. It is known that the edge surface of the graphite crystal sheet is more reactive than the basal surface. Therefore, in order to further increase the electrochemical stability of graphite, it is necessary to treat this edge surface by some method to reduce its reactivity.
黒鉛結晶シートのエッジ面の反応性を低くする方法として、黒鉛結晶シートの末端をループ状に閉じた閉塞構造にしてエッジ面が露出しないようにすることが挙げられる。例えば、特許文献１には、ハンマークラッシャーとディスククラッシャーにより粉砕処理した炭素材を２５００℃以上の温度で熱処理することで、グラファイトｃ面末端をループ状に閉じた構造とすることが記載されている。また、特許文献２には、ホウ素を０．０１〜５．０質量％含有する炭素材を高速粉砕処理した後、１５００℃以上の温度で熱処理することで、同様にグラファイトｃ面末端をループ状に閉じた構造とすることが記載されている。
ところで、負極材料として黒鉛が使用されたリチウムイオン二次電池は、リチウムイオンが以下のように挙動することによって充放電が繰り返される。すなわち、リチウムイオン二次電池の充電時には、電解液中のリチウムイオンが黒鉛の層間に取り込まれる。他方、放電時には、黒鉛の層間のリチウムイオンが電解液中に放出される。したがって、リチウムイオン二次電池の負極材料を構成する黒鉛としては、電気化学的な安定性に優れると共に、比表面積がある程度大きく、電解液との間で溶媒和したリチウムイオンを効率的に出し入れできるものが望ましいといえる。 By the way, the lithium ion secondary battery in which graphite is used as the negative electrode material is repeatedly charged and discharged when the lithium ions behave as follows. That is, when the lithium ion secondary battery is charged, lithium ions in the electrolytic solution are taken in between the graphite layers. On the other hand, during discharge, lithium ions between graphite layers are released into the electrolyte. Therefore, the graphite constituting the negative electrode material of the lithium ion secondary battery is excellent in electrochemical stability, has a large specific surface area, and can efficiently take in and out lithium ions solvated with the electrolyte. Things are desirable.
上記の特許文献１には、原料の粉砕条件を適宜制御することでグラファイト粉末の間隙面の密度や結晶子径を制御することが記載されている（特許文献１の段落［００３０］を参照）。しかしながら、具体的な制御方法は明らかでなく、また黒鉛材料の比表面積については、一切記載されていない。他方、特許文献２の段落［００５３］には、電解液との反応性を低くする観点から、グラファイト粉末の比表面積は１．０ｍ２／ｇ以下であることが好ましい旨、記載されている。つまり、従来のグラファイト粉末では、比表面積を１．０ｍ２／ｇよりも大きくすると電気化学的な安定性を十分に確保できず、この点について改善の余地があった。 In the above-mentioned Patent Document 1, it is described that the density of the gap surface and the crystallite diameter of the graphite powder are controlled by appropriately controlling the pulverization conditions of the raw material (see paragraph [0030] of Patent Document 1). . However, a specific control method is not clear, and no specific surface area of the graphite material is described. On the other hand, paragraph [0053] of Patent Document 2 describes that the specific surface area of the graphite powder is preferably 1.0 m 2 / g or less from the viewpoint of reducing the reactivity with the electrolytic solution. That is, in the conventional graphite powder, if the specific surface area is larger than 1.0 m 2 / g, the electrochemical stability cannot be sufficiently secured, and there is room for improvement in this respect.
本発明は、このような実情に鑑みてなされたものであり、比表面積が十分に大きく、かつ、電気化学的な安定性に優れた黒鉛粒子及びその製造方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and an object of the present invention is to provide graphite particles having a sufficiently large specific surface area and excellent electrochemical stability and a method for producing the same.
本発明者らは、コークスなどの易黒鉛化性炭素を賦活処理して活性炭を製造すると、活性炭の炭素網面が褶曲した構造となることに着目した。そして、炭素網面が褶曲した構造の活性炭に対して、熱処理を更に施して黒鉛結晶を発達させると、比表面積を十分に維持しつつ電気化学的に安定な黒鉛粒子を容易に製造できることを見出し、本発明を完成させた。 The inventors of the present invention have focused on the fact that when activated carbon is produced by activating a graphitizable carbon such as coke, the carbon network surface of the activated carbon has a curved structure. It was also found that when activated carbon having a curved carbon network surface is further subjected to heat treatment to develop graphite crystals, it is possible to easily produce electrochemically stable graphite particles while maintaining sufficient specific surface area. The present invention has been completed.
すなわち、本発明の黒鉛粒子の製造方法は、リチウムイオン二次電池の負極材料用黒鉛粒子を製造するためのものであり、易黒鉛化性炭素を含有する原料炭素組成物を賦活処理して活性炭を製造する賦活処理工程と、この活性炭を不活性ガス雰囲気下、２０００〜３０００℃の温度で熱処理して黒鉛の結晶を成長させて黒鉛粒子を得る熱処理工程と、を備え、上記黒鉛粒子は炭素原子が平面状に配列した黒鉛結晶シートが複数積層してなる積層構造体を備え、当該積層構造体の端部がループ状に閉じた構造を有することを特徴とする。 That is, the method for producing graphite particles of the present invention is for producing graphite particles for a negative electrode material of a lithium ion secondary battery, and activated carbon obtained by activating a raw material carbon composition containing graphitizable carbon. and activation treatment step of producing the inert gas atmosphere the activated carbon, and a resulting Ru heat treatment step the temperature and heat-treated by growing crystals of graphite graphite particles 2000 to 3000 ° C., the graphite particles comprising a laminated structure of graphite crystal sheet in which carbon atoms are arranged in a plane is formed by stacking a plurality, characterized in Rukoto the end of the laminate structure having a closed structure in a loop.
本発明の黒鉛粒子の製造方法によれば、易黒鉛化性炭素を含有する原料炭素組成物を賦活処理した活性炭を更に熱処理することによって、比表面積が十分に大きく、かつ、電気化学的な安定性に優れた黒鉛粒子を容易に製造することができる。 According to the method for producing graphite particles of the present invention, the activated carbon obtained by activating the raw carbon composition containing graphitizable carbon is further heat-treated, so that the specific surface area is sufficiently large and electrochemically stable. Graphite particles having excellent properties can be easily produced.
本発明において、熱処理工程における黒鉛結晶の優れた成長性の観点から、易黒鉛化性炭素は石油コークス、石炭コークス及び炭素質メソフェーズからなる群から選ばれる１種又は２種以上であることが好ましい。 In the present invention, the graphitizable carbon is preferably one or more selected from the group consisting of petroleum coke, coal coke and carbonaceous mesophase, from the viewpoint of excellent growth of graphite crystals in the heat treatment step. .
本発明に係るリチウムイオン二次電池の負極材料用黒鉛粒子は、上記本発明に係る黒鉛粒子の製造方法によって製造される。本発明の黒鉛粒子は、炭素原子が平面状に配列して形成される黒鉛結晶シートが複数積層してなる積層構造体を備え、当該積層構造体の端部がループ状に閉じた構造を有し、比表面積が１ｍ２／ｇより大きく１０ｍ２／ｇ以下であることを特徴とする。なお、本発明でいう「比表面積」とは、窒素ガス吸着法（吸着温度条件：−１９６℃）により得られるＢＥＴプロットにおける相対圧０．０５〜０．３の範囲での近似直線の傾きと切片とから求められる比表面積を意味する。 The graphite particles for the negative electrode material of the lithium ion secondary battery according to the present invention are produced by the method for producing graphite particles according to the present invention. The graphite particles of the present invention comprise a laminated structure formed by laminating a plurality of graphite crystal sheets formed by arranging carbon atoms in a planar shape, and have a structure in which the end of the laminated structure is closed in a loop shape. The specific surface area is greater than 1 m 2 / g and 10 m 2 / g or less. The “specific surface area” as used in the present invention is the slope of an approximate line in the range of relative pressure 0.05 to 0.3 in a BET plot obtained by the nitrogen gas adsorption method (adsorption temperature condition: −196 ° C.). It means the specific surface area obtained from the section.
本発明の黒鉛粒子は、複数の黒鉛結晶シートが積層してなる積層構造体の端部がループ状に閉じた構造となっているため、エッジ面の反応性が十分に低くなっている。したがって、本発明の黒鉛粒子は、従来の黒鉛粒子と比較し、大きい比表面積が有していながら、電気化学的な安定性に優れる。 Since the graphite particle of the present invention has a structure in which the end of a laminated structure formed by laminating a plurality of graphite crystal sheets is closed in a loop shape, the reactivity of the edge surface is sufficiently low. Therefore, the graphite particles of the present invention are excellent in electrochemical stability while having a large specific surface area as compared with conventional graphite particles.
本発明の黒鉛粒子は、Ｘ線回折によって求められる黒鉛結晶の平均層間距離ｄ００２が０．３４３ｎｍ以下であることが好ましい。なお、本発明でいう「Ｘ線回折によって求められる黒鉛結晶の平均層間距離ｄ００２」とは、以下のようにしてＸ線回折法により測定した、微結晶炭素の格子面（００２）に対応する層の平均層間距離（ｄ００２）を意味する。すなわち、試料（活性炭又は黒鉛粒子）に対して１５質量％のシリコン粉末を混合して測定用セルに充填し、ＣｕＫα線を線源として反射式ディフラクトメーター法によって広角Ｘ線回折線を測定し、学振法に基づき（００２）面の平均層間距離（ｄ００２）を求めたものである。 The graphite particles of the present invention preferably have an average interlayer distance d 002 of graphite crystals determined by X-ray diffraction of 0.343 nm or less. The “average interlayer distance d 002 of graphite crystals determined by X-ray diffraction” referred to in the present invention corresponds to the lattice plane (002) of microcrystalline carbon measured by the X-ray diffraction method as follows. Means the average interlayer distance (d002) of the layers. That is, 15% by mass of silicon powder is mixed with a sample (activated carbon or graphite particles), filled in a measurement cell, and a wide angle X-ray diffraction line is measured by a reflective diffractometer method using a CuKα ray as a radiation source. The average interlayer distance (d002) of the (002) plane is obtained based on the Gakushin method.
また、本発明の黒鉛粒子は、真密度が２．１０ｇ／ｃｍ３以上であることが好ましい。なお、本発明でいう「真密度」とは、１−ブタノール液相置換法（ピクノメータ法）により求められる真密度（測定温度条件：２０〜３０℃）を意味する。 The true density of the graphite particles of the present invention is preferably 2.10 g / cm 3 or more. In addition, "true density" as used in the field of this invention means the true density (measurement temperature conditions: 20-30 degreeC) calculated | required by the 1-butanol liquid phase substitution method (pycnometer method).
平均層間距離ｄ００２及び真密度が上記数値範囲内の黒鉛粒子によって電極を構成した場合、単位体積あたりの炭素量を十分に多くすることができ、電極の炭素密度を十分に高くすることができる。 When the electrode is composed of graphite particles having an average interlayer distance d 002 and a true density within the above numerical range, the amount of carbon per unit volume can be sufficiently increased, and the carbon density of the electrode can be sufficiently increased. .
本発明によれば、比表面積が十分に大きく、かつ、電気化学的な安定性に優れた黒鉛粒子及びその製造方法を提供することができる。 According to the present invention, it is possible to provide graphite particles having a sufficiently large specific surface area and excellent electrochemical stability, and a method for producing the same.
本発明の好適な実施形態について説明する。 A preferred embodiment of the present invention will be described.
本実施形態に係る黒鉛粒子の製造方法は、原料炭素組成物を賦活処理して活性炭を製造する賦活処理工程と、活性炭を不活性ガス雰囲気下、２０００〜３０００℃の温度で熱処理して黒鉛の結晶を成長させる熱処理工程と、を備える。 The method for producing graphite particles according to the present embodiment includes an activation treatment step of activating a raw material carbon composition to produce activated carbon, and heat treatment of the activated carbon at a temperature of 2000 to 3000 ° C. in an inert gas atmosphere. And a heat treatment step for growing crystals.
原料炭素組成物としては、易黒鉛化性炭素であれば特に限定されず、メソフェーズピッチやそれを紡糸したメソフェーズ系炭素繊維を不融化・炭素化して得られるもの、石油コークスや石炭ピッチコークス等を炭素化して得られるもの、石油の蒸留残渣油、ナフサの熱分解時に副生するナフサタールピッチ、ナフサ等の流動接触分解法（ＦＣＣ法）で副生するＦＣＣデカントオイル等の石油系ピッチ、ＰＶＣ等の合成高分子の熱分解で得られるピッチ等の炭素化物が挙げられる。これらの炭化物のうち、炭素質メソフェーズ、石油生コークス及び石炭生コークスが好適な例として挙げられる。 The raw material carbon composition is not particularly limited as long as it is graphitizable carbon, such as mesophase pitch or mesophase carbon fiber spun from it, obtained by infusibilizing and carbonizing, petroleum coke, coal pitch coke, etc. Products obtained by carbonization, petroleum distillation residue oil, naphtha tar pitch by-produced during thermal decomposition of naphtha, petroleum pitch such as FCC decant oil by-produced by fluid catalytic cracking method (FCC method) such as naphtha, PVC And carbonized products such as pitch obtained by thermal decomposition of synthetic polymers such as Among these carbides, carbonaceous mesophase, petroleum raw coke and coal raw coke are preferable examples.
本実施形態においては、上記炭化物を賦活処理して活性炭を製造する（賦活処理工程）。この賦活処理は、従来公知の方法を採用することができる。炭化物を賦活処理する方法としては、例えば、二酸化炭素や水蒸気を含有する酸化性ガス中で炭化物を５００〜１０００℃程度に加熱する方法、及び、炭化物と金属水酸化物とを混合して熱処理する方法が知られている。これらの方法のうち、炭化物と金属水酸化物とを混合して熱処理する方法が好ましく採用される。 In the present embodiment, activated carbon is produced by activating the carbides (activation process step). For this activation treatment, a conventionally known method can be adopted. As a method for activating the carbide, for example, a method in which the carbide is heated to about 500 to 1000 ° C. in an oxidizing gas containing carbon dioxide or water vapor, and a heat treatment is performed by mixing the carbide and the metal hydroxide. The method is known. Among these methods, a method in which a carbide and a metal hydroxide are mixed and heat-treated is preferably employed.
賦活処理に使用する金属水酸化物としては、水酸化カリウム、水酸化ナトリウム及び水酸化リチウム等のアルカリ金属水酸化物、水酸化マグネシウム及び水酸化バリウム等のアルカリ土類金属水酸化物を挙げることができる。これらの金属水酸化物は、１種を単独で使用してもよく、２種以上を組み合わせて使用してもよい。活性炭の微細孔を効率よく形成できる点から、金属水酸化物として水酸化カリウムを使用することが特に好ましい。 Examples of metal hydroxides used for activation treatment include alkali metal hydroxides such as potassium hydroxide, sodium hydroxide and lithium hydroxide, and alkaline earth metal hydroxides such as magnesium hydroxide and barium hydroxide. Can do. These metal hydroxides may be used individually by 1 type, and may be used in combination of 2 or more type. It is particularly preferable to use potassium hydroxide as the metal hydroxide from the viewpoint that the fine pores of the activated carbon can be efficiently formed.
上記炭化物と金属水酸化物との混合比率（質量比）は、炭化物の質量をＷｃ、金属水酸化物の質量をＷｍとすると、Ｗｃ／Ｗｍの値は、０．１〜２であることが好ましく、０．２〜１であることがより好ましい。当該混合比率が０．１未満であると、賦活反応の効率が低下しやすいと共に、製造される活性炭のかさ密度が不十分となりやすい。他方、当該混合比率が２を超えると、活性炭に形成される微細孔が不十分となり、製造される活性炭の比表面積が不十分となりやすい。 The mixing ratio (mass ratio) of the carbide and the metal hydroxide is such that the value of W c / W m is 0.1 to 2 when the mass of the carbide is W c and the mass of the metal hydroxide is W m. It is preferable that it is, and it is more preferable that it is 0.2-1. When the mixing ratio is less than 0.1, the efficiency of the activation reaction tends to decrease, and the bulk density of the activated carbon that is produced tends to be insufficient. On the other hand, when the mixing ratio exceeds 2, the fine pores formed in the activated carbon are insufficient, and the specific surface area of the produced activated carbon tends to be insufficient.
炭化物を賦活処理するにあたっては、賦活炉を用いることができる。賦活炉内を不活性ガス雰囲気に置換した後、炭化物と金属水酸化物との混合物を５００〜１２００℃で加熱することによって活性炭を製造することができる。賦活処理の温度条件は、十分な微細孔を有する活性炭を効率的に製造する観点から、６００〜１０００℃であることがより好ましく、６００〜８００℃であることが更に好ましい。賦活処理の処理時間は、温度条件等との関連において適宜設定すればよいが、例えば３〜６時間に設定することができる。 In activating the carbide, an activation furnace can be used. After replacing the inside of the activation furnace with an inert gas atmosphere, activated carbon can be produced by heating a mixture of carbide and metal hydroxide at 500 to 1200 ° C. From the viewpoint of efficiently producing activated carbon having sufficient fine pores, the temperature condition for the activation treatment is more preferably 600 to 1000 ° C, and further preferably 600 to 800 ° C. The treatment time of the activation treatment may be set as appropriate in relation to the temperature condition or the like, but can be set to 3 to 6 hours, for example.
賦活処理を行う賦活炉内を置換する不活性ガスとしては、例えば、窒素ガス又はヘリウム、ネオン、アルゴンなどの希ガスを挙げることができる。賦活処理を行う賦活炉内は、酸素濃度を１００容量ｐｐｍ以下に保持することが好ましい。ただし、賦活反応においては、炭化物及び金属水酸化物の他に、水等が共存していてもよい。 As an inert gas which substitutes the inside of the activation furnace which performs an activation process, noble gases, such as nitrogen gas or helium, neon, and argon, can be mentioned, for example. In the activation furnace for performing the activation treatment, the oxygen concentration is preferably maintained at 100 ppm by volume or less. However, in the activation reaction, water or the like may coexist in addition to the carbide and the metal hydroxide.
賦活処理工程を経て得られる活性炭に対して、洗浄液を用いた洗浄処理を行うことが好ましい（洗浄処理工程）。この洗浄処理を行うことによって、賦活処理後の活性炭の微細孔に残留するアルカリ金属などを除去することができる。活性炭を洗浄液中に浸漬して必要に応じて攪拌及び／又は加熱などを行った後、洗浄液と活性炭とを固液分離する。 It is preferable to perform a cleaning process using a cleaning liquid on the activated carbon obtained through the activation process (cleaning process). By performing this washing treatment, it is possible to remove alkali metals remaining in the fine pores of the activated carbon after the activation treatment. After the activated carbon is immersed in the cleaning liquid and stirred and / or heated as necessary, the cleaning liquid and the activated carbon are separated into solid and liquid.
洗浄液としては、水又は酸水溶液を用いることが好ましい。酸水溶液としては、例えば、塩酸、ヨウ化水素酸及び臭化水素酸などのハロゲン化水素酸、硫酸及び炭酸などの無機酸を挙げることができる。酸水溶液の濃度は、０．０１〜３Ｎであることが好ましい。洗浄処理は、複数の洗浄液を使用して繰り返し実施してもよい。例えば、まず水による洗浄処理を行い、その後、酸水溶液による洗浄処理を行い、更に水による洗浄処理を行ってもよい。洗浄処理が施された活性炭を回収し、適宜加熱又は風乾などを行って水分を除去することによって、乾燥した活性炭を得ることができる。 As the cleaning liquid, it is preferable to use water or an aqueous acid solution. Examples of the acid aqueous solution include hydrohalic acids such as hydrochloric acid, hydroiodic acid and hydrobromic acid, and inorganic acids such as sulfuric acid and carbonic acid. The concentration of the acid aqueous solution is preferably 0.01 to 3N. The cleaning process may be repeatedly performed using a plurality of cleaning liquids. For example, a cleaning process with water may be performed first, followed by a cleaning process with an acid aqueous solution, and then a cleaning process with water. Dry activated carbon can be obtained by collecting the activated carbon that has been subjected to the washing treatment and removing moisture by appropriately heating or air drying.
洗浄処理工程を経て得られた活性炭は、比表面積が５００〜３０００ｍ２／ｇであることが好ましく、２０００〜３０００ｍ２／ｇであることがより好ましい。活性炭の比表面積が上記範囲内であると、この活性炭を更に熱処理することによって、比表面積が好適な黒鉛粒子を得ることができる。なお、製造した活性炭の比表面積が上記の範囲外であった場合は、賦活処理の温度及び／又は処理時間を適宜調整して、再度、活性炭を製造すればよい。 Activated carbon obtained through the cleaning process is preferably a specific surface area of 500~3000m 2 / g, more preferably 2000~3000m 2 / g. When the specific surface area of the activated carbon is within the above range, graphite particles having a suitable specific surface area can be obtained by further heat-treating the activated carbon. In addition, when the specific surface area of the manufactured activated carbon is outside the above range, the activated carbon may be manufactured again by appropriately adjusting the temperature and / or processing time of the activation treatment.
比表面積が上記数値範囲内の活性炭を不活性ガス雰囲気下で熱処理して黒鉛の結晶を成長させ、目的の黒鉛粒子を製造する（熱処理工程）。結晶が十分に成長した黒鉛粒子を効率的且つ経済的に製造する観点から、熱処理工程において活性炭の熱処理温度は、２０００〜３０００℃である。熱処理温度が２０００℃未満であると、黒鉛の結晶化の進行が不十分となり、３０００℃を超えると、経済性の面で不利となる。 Activated carbon having a specific surface area within the above numerical range is heat-treated in an inert gas atmosphere to grow graphite crystals to produce target graphite particles (heat treatment step). From the viewpoint of efficiently and economically producing graphite particles with sufficiently grown crystals, the heat treatment temperature of the activated carbon is 2000 to 3000 ° C. in the heat treatment step. If the heat treatment temperature is less than 2000 ° C, the progress of crystallization of graphite is insufficient, and if it exceeds 3000 ° C, it is disadvantageous in terms of economy.
活性炭の熱処理温度の下限は、２２００℃であることが好ましく、２４００℃であることがより好ましい。他方、当該熱処理温度の上限は、２８００℃であることが好ましく、２６００℃であることがより好ましい。熱処理時間は、特に限定されないが、通常１０分間〜１時間である。熱処理工程で使用する不活性ガスとしては、例えば、アルゴンなどの希ガスが好ましい。 The lower limit of the heat treatment temperature of the activated carbon is preferably 2200 ° C, and more preferably 2400 ° C. On the other hand, the upper limit of the heat treatment temperature is preferably 2800 ° C, and more preferably 2600 ° C. The heat treatment time is not particularly limited, but is usually 10 minutes to 1 hour. As the inert gas used in the heat treatment step, for example, a rare gas such as argon is preferable.
熱処理工程を経て得られた黒鉛粒子は、比表面積が１ｍ２／ｇより大きく１０ｍ２／ｇ以下である。なお、製造した黒鉛粒子の比表面積がこの範囲外であった場合は、熱処理の温度及び／又は処理時間を適宜調整して、再度、黒鉛粒子を製造すればよい。 The graphite particles obtained through the heat treatment step have a specific surface area of more than 1 m 2 / g and 10 m 2 / g or less. In addition, when the specific surface area of the manufactured graphite particle is outside this range, the temperature and / or processing time of the heat treatment may be adjusted as appropriate, and the graphite particle may be manufactured again.
黒鉛粒子は、比表面積が１ｍ２／ｇより大きく１０ｍ２／ｇ以下であるが、比表面積の下限は２ｍ２／ｇであることが好ましく、他方、上限は５ｍ２／ｇであることが好ましい。比表面積が１ｍ２／ｇ以下であると、黒鉛粒子の微細孔の形成が不十分で電解液などの浸透が不十分となりやすく、他方、比表面積が１０ｍ２／ｇを超えると黒鉛粒子のかさ密度が低下して、単位体積あたりの炭素量が不十分となりやすい。 The graphite particles have a specific surface area of more than 1 m 2 / g and 10 m 2 / g or less, but the lower limit of the specific surface area is preferably 2 m 2 / g, while the upper limit is preferably 5 m 2 / g. . When the specific surface area is 1 m 2 / g or less, the formation of fine pores in the graphite particles is insufficient, and the penetration of the electrolyte and the like tends to be insufficient. On the other hand, when the specific surface area exceeds 10 m 2 / g, the bulk of the graphite particles The density tends to decrease, and the amount of carbon per unit volume tends to be insufficient.
Ｘ線回折法によって求められる黒鉛結晶の平均層間距離ｄ００２は０．３４３ｎｍ以下であることが好ましく、０．３４０ｎｍ以下であることがより好ましい。黒鉛粒子の平均層間距離ｄ００２が０．３４３ｎｍを超える場合は、黒鉛粒子を更に熱処理して黒鉛結晶を成長させることが好ましい。 The average interlayer distance d 002 of the graphite crystals determined by the X-ray diffraction method is preferably 0.343 nm or less, and more preferably 0.340 nm or less. When the average interlayer distance d 002 of the graphite particles exceeds 0.343 nm, it is preferable to further heat treat the graphite particles to grow graphite crystals.
黒鉛粒子の真密度は、２．１０ｇ／ｃｍ３以上であることが好ましく、２．１４ｇ／ｃｍ３以上であることがより好ましい。真密度が２．１０ｇ／ｃｍ３未満であると、これを用いて電池の電極を作製した場合、電極の単位体積あたりの炭素量が不十分となりやすく、その結果、炭素密度の低下を招来する傾向にある。 True density of the graphite particles is preferably 2.10 g / cm 3 or more, and more preferably 2.14 g / cm 3 or more. When the true density is less than 2.10 g / cm 3 , when an electrode of a battery is produced using this, the amount of carbon per unit volume of the electrode tends to be insufficient, resulting in a decrease in the carbon density. There is a tendency.
図１は、本実施形態に係る製造方法で製造された黒鉛粒子の構造を示す透過型電子顕微鏡写真である。同図に部分的に示された黒鉛粒子は、炭素原子が平面状に配列した黒鉛結晶シート１ａが複数積層してなる積層構造体１を有している。この黒鉛粒子は、この積層構造体１が更に複数積層して構成されている。それぞれの積層構造体１の端部２は、ループ状に閉じた構造となっており、通常の黒鉛にみられるエッジ面が消失しているのが特徴である。なお、黒鉛結晶シート１ａ同士又は積層構造体１同士が重なっている部分は、通常の黒鉛と同様の層面が略平行に発達した構造である。 FIG. 1 is a transmission electron micrograph showing the structure of graphite particles produced by the production method according to the present embodiment. The graphite particles partially shown in the figure have a laminated structure 1 formed by laminating a plurality of graphite crystal sheets 1a in which carbon atoms are arranged in a plane. The graphite particles are formed by further laminating a plurality of the laminated structures 1. The end portion 2 of each laminated structure 1 has a closed structure in a loop shape, and is characterized in that the edge surface seen in ordinary graphite has disappeared. In addition, the part where the graphite crystal sheets 1a or the laminated structures 1 overlap each other has a structure in which layer surfaces similar to those of normal graphite are developed substantially in parallel.
黒鉛結晶シート１ａのエッジ面が多数存在すると、イオンや分子はエッジ面に存在する活性点に吸着されて化学反応が生じ、黒鉛粒子の電気化学的安定性が不十分となる傾向にある。したがって、エッジ面が多数存在する黒鉛粒子をリチウムイオン二次電池の負極材料として用いた場合、初期効率（放電容量／充電容量比）が不十分となりやすく、また、充放電を繰り返し行うと、エッジ部分から粉化が生じてサイクル特性が低下する傾向にある。 When there are a large number of edge surfaces of the graphite crystal sheet 1a, ions and molecules are adsorbed by active sites existing on the edge surfaces to cause a chemical reaction, and the electrochemical stability of the graphite particles tends to be insufficient. Therefore, when graphite particles having a large number of edge surfaces are used as a negative electrode material for a lithium ion secondary battery, the initial efficiency (discharge capacity / charge capacity ratio) tends to be insufficient, and if charge / discharge is repeated, the edge There is a tendency that the pulverization occurs from the part and the cycle characteristics are lowered.
これに対し、本実施形態によって製造される黒鉛粒子にあっては、黒鉛結晶シート１ａのエッジ面が積層構造体１の端部２のループ構造によって閉じられている。そのため、この黒鉛粒子をリチウムイオン二次電池の負極材料として用いた場合、電気化学的に安定していることから、初期効率が十分に高く、サイクル特性に優れたリチウムイオン二次電池を作製することができる。 On the other hand, in the graphite particles produced by the present embodiment, the edge surface of the graphite crystal sheet 1 a is closed by the loop structure of the end portion 2 of the laminated structure 1. Therefore, when this graphite particle is used as a negative electrode material for a lithium ion secondary battery, it is electrochemically stable, so that a lithium ion secondary battery with sufficiently high initial efficiency and excellent cycle characteristics is produced. be able to.
本実施形態に係る黒鉛粒子の製造方法では、易黒鉛化性炭素を原料として、これを賦活処理した活性炭を更に熱処理するため、易黒鉛化性炭素から得られる黒鉛としての性質と、比表面積が大きいという活性炭の性質とを併せ持つ黒鉛粒子を製造することができる。本実施形態によれば、炭素網面が褶曲した構造の活性炭を更に熱処理することによって、図１に示すように、端部２がループ状に閉じた構造の積層構造体１を多数備える黒鉛粒子を容易に製造することができる。 In the method for producing graphite particles according to the present embodiment, since the activated carbon obtained by activating the graphitizable carbon as a raw material is further heat-treated, the properties as the graphite obtained from the graphitizable carbon and the specific surface area are Graphite particles having both the properties of activated carbon that are large can be produced. According to the present embodiment, by further heat-treating the activated carbon having a curved carbon network surface, as shown in FIG. 1, the graphite particles including a large number of laminated structures 1 having end portions 2 closed in a loop shape. Can be easily manufactured.
なお、本実施形態においては、本発明に係る黒鉛粒子の用途として、リチウムイオン二次電池の電極材料を例示したが、本発明の黒鉛粒子は、電極材料としての用途に限られるものではない。本発明の黒鉛粒子は、安定性に優れた黒鉛材料が求められる分野において幅広く適用可能である。 In addition, in this embodiment, the electrode material of the lithium ion secondary battery was illustrated as an application of the graphite particle which concerns on this invention, However, The graphite particle of this invention is not restricted to the use as an electrode material. The graphite particles of the present invention can be widely applied in fields where graphite materials having excellent stability are required.
以下、実施例及び比較例に基づき本発明を更に具体的に説明するが、本発明は以下の実施例に何ら限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.
（実施例１）
ディレードコーカーで製造した石油生コークスを５５０℃で１時間焼成し、炭化物（原料炭素組成物）を得た。本実施例で使用した石油生コークスの焼成前及び焼成後の物性を表１に示す。
Petroleum raw coke produced with a delayed coker was fired at 550 ° C. for 1 hour to obtain a carbide (raw material carbon composition). Table 1 shows the physical properties of the petroleum raw coke used in this example before and after firing.
石油生コークスを焼成して得られた炭化物を、ジェットミルを用いて平均粒径１０μｍとなるように粉砕した。粉砕後の炭化物１００質量部と水酸化カリウム２５０質量部とを混合して混合物を調製した。この混合物を窒素ガス雰囲気下、７５０℃で１時間焼成することで、炭化物の賦活処理を行った（賦活処理工程）。賦活処理を経て製造された活性炭に対して、水洗処理及び塩酸による酸洗浄処理を繰り返し行った（洗浄処理工程）。洗浄処理を行うことで、活性炭中に残存する金属カリウムを除去した。金属カリウムを十分に除去した後、水分を蒸発させて熱処理に供する活性炭を得た。図２は、この活性炭の透過型電子顕微鏡写真である。表２に活性炭の物性を示す。 The carbide obtained by calcining petroleum raw coke was pulverized using a jet mill to an average particle size of 10 μm. A mixture was prepared by mixing 100 parts by mass of the ground carbide and 250 parts by mass of potassium hydroxide. The mixture was baked at 750 ° C. for 1 hour in a nitrogen gas atmosphere to perform carbide activation treatment (activation treatment step). The activated carbon produced through the activation treatment was repeatedly subjected to water washing treatment and acid washing treatment with hydrochloric acid (washing treatment step). The metal potassium remaining in the activated carbon was removed by performing a washing treatment. After sufficiently removing potassium metal, activated carbon to be subjected to heat treatment by evaporating water was obtained. FIG. 2 is a transmission electron micrograph of this activated carbon. Table 2 shows the properties of the activated carbon.
上記のようにして製造した活性炭を、アルゴンガス気流中、温度２０００℃にて３０分間熱処理することで黒鉛粒子を製造した。この黒鉛粒子を透過型電子顕微鏡で観察したところ、黒鉛結晶シートが複数積層してなる積層構造体の端部は、ループ状に閉じた構造となっていた。表２に黒鉛粒子の物性を示す。 The activated carbon produced as described above was heat-treated at 2000 ° C. for 30 minutes in an argon gas stream to produce graphite particles. When the graphite particles were observed with a transmission electron microscope, the end of the laminated structure formed by laminating a plurality of graphite crystal sheets was closed in a loop shape. Table 2 shows the physical properties of the graphite particles.
活性炭及び黒鉛粒子の比表面積は、ＢＥＴ法による比表面積測定装置（日本ベル株式会社製、商品名：ＢＥＬＳＯＲＰ−ｍｉｎｉ）を用いて測定した。活性炭及び黒鉛粒子の真密度は、真密度測定装置（株式会社セイシン企業社製、商品名：ＭＡＴ）を用いてＪＩＳ Ｋ２１５１に準拠して測定した。また、格子面間隔（平均層間距離）は、Ｘ線回折装置（理学電機株式会社製、商品名：ＲＩＮＴ１４００ＶＸ）を用いて測定した。 The specific surface areas of the activated carbon and the graphite particles were measured using a specific surface area measuring device (manufactured by Nippon Bell Co., Ltd., trade name: BELSORP-mini) by the BET method. The true density of the activated carbon and the graphite particles was measured according to JIS K2151 using a true density measuring device (manufactured by Seishin Enterprise Co., Ltd., trade name: MAT). The lattice spacing (average interlayer distance) was measured using an X-ray diffractometer (manufactured by Rigaku Corporation, trade name: RINT1400VX).
本実施例で製造した黒鉛粒子を用いて３極セルを以下のようにして作製した。すなわち、容器内に黒鉛粒子９３質量部と、導電材としてアセチレンブラック２質量部と、バインダーとしてポリフッ化ビニリデン５質量部とを投入後、これらを攪拌してスラリーを得た。このときＮ−メチル−２−ピロリドンを加えて電極を塗布するのに適した粘度に調整した。このスラリーを銅箔（厚さ１８μｍ）上に塗布し、ホットプレートで１０分間乾燥させて銅箔と黒鉛含有層との積層体を得た。 Using the graphite particles produced in this example, a triode cell was produced as follows. That is, 93 parts by mass of graphite particles, 2 parts by mass of acetylene black as a conductive material, and 5 parts by mass of polyvinylidene fluoride as a binder were put into a container, and these were stirred to obtain a slurry. At this time, N-methyl-2-pyrrolidone was added to adjust the viscosity to be suitable for coating the electrode. This slurry was applied onto a copper foil (thickness: 18 μm) and dried on a hot plate for 10 minutes to obtain a laminate of the copper foil and the graphite-containing layer.
ロールプレスを用いて銅箔と黒鉛含有層とを圧着させた後、この積層体を打ち抜いて円盤形状（直径１７ｍｍ）の負極を作製した。負極を１７０℃で１０時間減圧乾燥した後、この負極と、金属リチウムからなる対極及び参照極とを用いて３極セルを作製した。なお、電解液として、エチレンカーボネートとジメチルカーボネートとを体積比１：１で混合して得た混合液に濃度１モル／リットルのＬｉＰＦ６を溶解したものを使用した。作製した３極セルの充放電テストを行った。充放電テストは２５℃で初期充放電特性（０．２Ｃ）を測定し、充電容量、放電容量及び充放電効率を求めた。図３は、本実施例で作製した３極セルの充放電曲線のグラフである。また、表２に充放電テストの結果を示す。 After the copper foil and the graphite-containing layer were pressure-bonded using a roll press, this laminate was punched out to produce a disc-shaped negative electrode (diameter 17 mm). After the negative electrode was dried under reduced pressure at 170 ° C. for 10 hours, a three-electrode cell was produced using the negative electrode, a counter electrode made of metallic lithium, and a reference electrode. As the electrolyte, a volume ratio of 1 ethylene carbonate and dimethyl carbonate were used: a solution obtained by dissolving LiPF 6 concentration of 1 mol / liter in a mixed solution obtained by mixing 1. The charge / discharge test of the produced tripolar cell was performed. In the charge / discharge test, initial charge / discharge characteristics (0.2 C) were measured at 25 ° C., and charge capacity, discharge capacity, and charge / discharge efficiency were determined. FIG. 3 is a graph of the charge / discharge curve of the triode cell produced in this example. Table 2 shows the results of the charge / discharge test.
（実施例２）
実施例１と同様にして製造した活性炭の熱処理温度を２６００℃としたことの他は、実施例１と同様にして黒鉛粒子を製造すると共に、３極セルを作製して充放電テストを行った。表２に黒鉛粒子の物性及び充放電テスト結果を示す。なお、本実施例で製造した黒鉛粒子を透過型電子顕微鏡で観察したところ、黒鉛結晶シートが複数積層してなる積層構造体の端部は、ループ状に閉じた構造となっていた。
(Example 2)
Except that the heat treatment temperature of the activated carbon produced in the same manner as in Example 1 was set to 2600 ° C., graphite particles were produced in the same manner as in Example 1, and a triode cell was produced and a charge / discharge test was performed. . Table 2 shows the physical properties of the graphite particles and the charge / discharge test results. When the graphite particles produced in this example were observed with a transmission electron microscope, the end of the laminated structure formed by laminating a plurality of graphite crystal sheets was closed in a loop shape.
（比較例１）
実施例１と同様にして製造した活性炭の熱処理温度を１３００℃としたことの他は、実施例１と同様にして黒鉛粒子を製造し、更に３極セルを作製して充放電テストを行った。表２に黒鉛粒子の物性及び充放電テスト結果を示す。なお、本比較例で製造した黒鉛粒子を透過型電子顕微鏡で観察したところ、黒鉛結晶シートが複数積層してなる積層構造体の端部はループ状に閉じてはいるが、シートの積層枚数が少なく結晶発達が不十分であった。
(Comparative Example 1)
Except that the heat treatment temperature of the activated carbon produced in the same manner as in Example 1 was set to 1300 ° C., graphite particles were produced in the same manner as in Example 1, and further a tripolar cell was produced and a charge / discharge test was performed. . Table 2 shows the physical properties of the graphite particles and the charge / discharge test results. When the graphite particles produced in this comparative example were observed with a transmission electron microscope, the end of the laminated structure formed by laminating a plurality of graphite crystal sheets was closed in a loop shape, but the number of laminated sheets was There was little crystal development.
（比較例２）
実施例１で使用したものと同様の石油生コークスを５５０℃で１時間焼成して得た炭化物（石油コークス）を、２６００℃で３０分間焼成することによって、黒鉛粒子を製造した。得られた黒鉛粒子を用いて、実施例１と同様に３極セルを作製して充放電テストを行った。表２に黒鉛粒子の物性及び充放電テスト結果を示す。なお、本比較例で製造した黒鉛粒子を透過型電子顕微鏡で観察したところ、黒鉛結晶シートが複数積層してなる積層構造体の端部はループ状に閉じた構造が形成されず、エッジ面が残存していた。
Graphite particles were manufactured by calcining a carbide (petroleum coke) obtained by calcining petroleum raw coke similar to that used in Example 1 at 550 ° C. for 1 hour at 2600 ° C. Using the obtained graphite particles, a tripolar cell was produced in the same manner as in Example 1, and a charge / discharge test was performed. Table 2 shows the physical properties of the graphite particles and the charge / discharge test results. When the graphite particles produced in this comparative example were observed with a transmission electron microscope, the end of the laminated structure formed by laminating a plurality of graphite crystal sheets was not formed into a loop-like structure, and the edge surface was not formed. It remained.
表２に示した通り、活性炭を２０００℃及び２６００℃で熱処理して製造した黒鉛粒子を用いた実施例１及び実施例２では、充放電効率がいずれも９０％以上と極めて良好であった。一方、活性炭を１３００℃で熱処理して製造した黒鉛粒子を用いた比較例１及び活性炭を製造する工程を経ることなく製造した黒鉛粒子を用いた比較例２では、実施例１及び２に係る３極セルと比較すると充放電効率がいずれも低かった。 As shown in Table 2, in Examples 1 and 2 using graphite particles produced by heat treatment of activated carbon at 2000 ° C. and 2600 ° C., the charge / discharge efficiency was extremely good at 90% or more. On the other hand, in Comparative Example 1 using graphite particles produced by heat treatment of activated carbon at 1300 ° C. and Comparative Example 2 using graphite particles produced without passing through the step of producing activated carbon, 3 according to Examples 1 and 2 Compared with the polar cell, the charge / discharge efficiency was low.
１…積層構造体、１ａ…黒鉛結晶シート、２…黒鉛結晶シートの端部。 DESCRIPTION OF SYMBOLS 1 ... Laminated structure, 1a ... Graphite crystal sheet, 2 ... End part of graphite crystal sheet.
Claims (3)
易黒鉛化性炭素を含有する原料炭素組成物を賦活処理して活性炭を製造する賦活処理工程と、
前記活性炭を不活性ガス雰囲気下、２０００〜３０００℃の温度で熱処理して黒鉛の結晶を成長させて黒鉛粒子を得る熱処理工程と、
を備え、
前記黒鉛粒子は、炭素原子が平面状に配列した黒鉛結晶シートが複数積層してなる積層構造体を備え、当該積層構造体の端部がループ状に閉じた構造を有することを特徴とする黒鉛粒子の製造方法。 A method for producing graphite particles for a negative electrode material of a lithium ion secondary battery,
An activation treatment process for producing activated carbon by activating the raw carbon composition containing graphitizable carbon;
A heat treatment step in which the activated carbon is heat-treated at a temperature of 2000 to 3000 ° C. in an inert gas atmosphere to grow graphite crystals to obtain graphite particles;
With
The graphite particles are provided with a laminated structure formed by laminating a plurality of graphite crystal sheets in which carbon atoms are arranged in a plane, and the end of the laminated structure is closed in a loop shape. Particle production method.
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