JP4104645B2 - Method for producing composite material for positive electrode of lithium battery - Google Patents
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- JP4104645B2 JP4104645B2 JP2007169139A JP2007169139A JP4104645B2 JP 4104645 B2 JP4104645 B2 JP 4104645B2 JP 2007169139 A JP2007169139 A JP 2007169139A JP 2007169139 A JP2007169139 A JP 2007169139A JP 4104645 B2 JP4104645 B2 JP 4104645B2
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- 239000002131 composite material Substances 0.000 title claims description 94
- 238000004519 manufacturing process Methods 0.000 title claims description 29
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims description 28
- 229910052744 lithium Inorganic materials 0.000 title claims description 28
- 239000007774 positive electrode material Substances 0.000 claims description 94
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- JQMFQLVAJGZSQS-UHFFFAOYSA-N 2-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-N-(2-oxo-3H-1,3-benzoxazol-6-yl)acetamide Chemical group C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)CC(=O)NC1=CC2=C(NC(O2)=O)C=C1 JQMFQLVAJGZSQS-UHFFFAOYSA-N 0.000 description 1
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- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical group O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
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- 125000003368 amide group Chemical group 0.000 description 1
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- 229910052742 iron Inorganic materials 0.000 description 1
- UXKNCQDLMPVIFP-UHFFFAOYSA-H iron(2+) diphosphate hydrate Chemical compound O.[Fe++].[Fe++].[Fe++].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O UXKNCQDLMPVIFP-UHFFFAOYSA-H 0.000 description 1
- 239000006233 lamp black Substances 0.000 description 1
- 229910001386 lithium phosphate Inorganic materials 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
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- 229910052727 yttrium Inorganic materials 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、正極活物質及び導電性物質を含有するリチウム電池正極用複合材料の製造方法に関する。本発明で得られるリチウム電池正極用複合材料は、リチウムイオン二次電池等の正極の形成に好適に使用することができる。 The present invention relates to a method for producing a composite material for a lithium battery positive electrode containing a positive electrode active material and a conductive material. The composite material for a lithium battery positive electrode obtained in the present invention can be suitably used for forming a positive electrode such as a lithium ion secondary battery.
近年、石油資源の高騰、国際的な地球環境保護運動の高まりを背景として、電気自動車、ハイブリッド自動車、燃料電池自動車などが注目されており、その一部が実用化されている。これらの駆動システムには、補助用電源等として二次電池が不可欠であり、しかも自動車の急発進・急加速に対応できる高出力な二次電池が望まれている。また、車への重量負荷、燃費向上の観点から、エネルギー密度の高い二次電池が望まれる。このような背景から、二次電池の中で最もエネルギー密度が高く、かつ高出力を発現できるリチウムイオン二次電池が有望視されている。 In recent years, electric vehicles, hybrid vehicles, fuel cell vehicles, and the like have attracted attention against the background of soaring petroleum resources and the growing global environmental protection movement, and some of them have been put into practical use. In these drive systems, a secondary battery is indispensable as an auxiliary power source and the like, and a high-power secondary battery that can cope with sudden start / acceleration of an automobile is desired. Moreover, a secondary battery with a high energy density is desired from the viewpoint of weight load on the vehicle and improvement in fuel consumption. From such a background, a lithium ion secondary battery that has the highest energy density among the secondary batteries and can exhibit high output is promising.
リチウムイオン二次電池では、リチウム塩を非水溶媒中に含有する電解液が用いられ、セパレータを介して正極活物質を備える正極と負極活物質を備える負極とが隔てられた構造となっている。また、正極では、正極活物質自体の導電性が低いことから、導電性を向上させるために、カーボンブラック等の導電性物質が添加されている。 In a lithium ion secondary battery, an electrolytic solution containing a lithium salt in a non-aqueous solvent is used, and a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material are separated via a separator. . In the positive electrode, since the conductivity of the positive electrode active material itself is low, a conductive material such as carbon black is added to improve the conductivity.
一般に、上記のような正極は、ＬｉＭｎ2Ｏ4等の活物質、カーボンブラック等の導電性物質、バインダ、及び溶剤を混合したスラリーを集電体となる金属箔に塗布・乾燥することにより製造される。その結果、正極の微細構造は、導電性の低い正極活物質の粒子と、これより粒径の小さい導電性物質の粒子とが分散・結合した構造となる。 Generally, the positive electrode as described above is manufactured by applying and drying a slurry obtained by mixing an active material such as LiMn 2 O 4, a conductive material such as carbon black, a binder, and a solvent onto a metal foil as a current collector. Is done. As a result, the fine structure of the positive electrode has a structure in which particles of a positive electrode active material having low conductivity and particles of a conductive material having a smaller particle diameter are dispersed and bonded.
リチウムイオン二次電池の正極では、放電時にリチウムが正極活物質内に吸蔵されるが、その際、正極側へ拡散するリチウムイオンと正極集電体から導電した電子との作用によって放電が進行する。また、充電時には、正極活物質から、電子とイオン化したリチウムとが放出される。このため、電池の特性、特に高速放電性能（高出力化）に影響を与える因子として、導電性の高い導電材料を選択することや、正極活物質と導電性物質の微細複合構造が非常に重要となる。 In the positive electrode of a lithium ion secondary battery, lithium is occluded in the positive electrode active material at the time of discharge. At that time, discharge proceeds by the action of lithium ions diffusing to the positive electrode side and electrons conducted from the positive electrode current collector. . Further, at the time of charging, electrons and ionized lithium are released from the positive electrode active material. For this reason, it is very important to select a conductive material with high conductivity and a fine composite structure of a positive electrode active material and a conductive material as factors affecting battery characteristics, particularly high-speed discharge performance (high output). It becomes.
このような理由から、正極に関する微細複合構造の改良が幾つか試みられている。例えば特許文献１には、正極活物質と導電性物質とを混合して、乾式で圧縮せん断応力を加える方法により、正極活物質表面に導電性物質を被覆した正極材料が提案されている。 For these reasons, several attempts have been made to improve the fine composite structure related to the positive electrode. For example, Patent Document 1 proposes a positive electrode material in which a positive electrode active material surface is coated with a conductive material by a method in which a positive electrode active material and a conductive material are mixed and compressive shear stress is applied in a dry manner.
また、湿式混合により正極複合材料を製造する方法も知られており、例えば特許文献２には、リン酸第一鉄含水塩、リン酸リチウム及び炭素質物質前駆体を湿式混合した後、溶媒を除去して混合物を得た後、これを粉砕、焼成等して炭素複合材料を製造する製造方法が提案されている。 In addition, a method for producing a positive electrode composite material by wet mixing is also known. For example, in Patent Document 2, a ferrous phosphate hydrate, lithium phosphate and a carbonaceous material precursor are wet mixed, and then a solvent is added. There has been proposed a production method for producing a carbon composite material by removing the mixture to obtain a mixture and then pulverizing and firing the mixture.
しかしながら、特許文献１に記載の正極材料では、導電性が向上するものの、導電性物質が正極活物質の表面に緻密に被覆されるため、Ｌｉイオンの経路が遮断され、その結果、高速放電性能はそれほど向上しないことが判明した。 However, in the positive electrode material described in Patent Document 1, although the conductivity is improved, since the conductive material is densely coated on the surface of the positive electrode active material, the Li ion path is blocked, resulting in high-speed discharge performance. Turned out not to improve much.
また、特許文献２に記載された炭素複合材料の製造方法では、カーボンブラック等の導電性物質を用いるのではなく、ポリエチレングリコール等の炭素質物質前駆体を用いて混合物を得た後、これを粉砕、焼成等している。このため、得られる炭素複合材料の微細複合構造を制御するのが困難であり、これを用いて得られる正極の高速放電性能は、特許文献１に記載の正極材料より優れるとは考えにくい。 In addition, in the method for producing a carbon composite material described in Patent Document 2, a mixture is obtained using a carbonaceous material precursor such as polyethylene glycol, instead of using a conductive material such as carbon black. It is pulverized and fired. For this reason, it is difficult to control the fine composite structure of the obtained carbon composite material, and the high-speed discharge performance of the positive electrode obtained using the carbon composite material is unlikely to be superior to the positive electrode material described in Patent Document 1.
そこで、本発明の目的は、電池の高速放電性能に優れるリチウム電池正極用複合材料の製造方法を提供することにある。 Then, the objective of this invention is providing the manufacturing method of the composite material for lithium battery positive electrodes which is excellent in the high-speed discharge performance of a battery.
本発明者らは、溶媒中で自己凝集性を有する導電性物質及び正極活物質を溶媒中に強制分散させた後、溶媒中で凝集させることによって、電池の高速放電性能が向上することを見出し、本発明を完成するに至った。 The present inventors have found that the high-speed discharge performance of a battery is improved by forcibly dispersing a conductive material having a self-aggregating property and a positive electrode active material in a solvent and then aggregating them in the solvent. The present invention has been completed.
即ち、本発明のリチウム電池正極用複合材料の製造方法は、正極活物質、及び導電性物質を含有するリチウム電池正極用複合材料の製造方法であって、少なくとも溶媒中で自己凝集性を有する導電性物質及び正極活物質を、溶媒中に分散させて強制分散した状態とする分散工程と、前記導電性物質を前記正極活物質と共に溶媒中で凝集させて凝集粒子を得る凝集工程とを含むものである。ここで、「溶媒中で自己凝集性を有する」とは、用いる溶媒中に強制分散させた後、放置することで凝集により平均粒径が大きくなる性質をいい、具体的には実施例に記載の測定方法で定義される。 That is, the method for producing a composite material for a lithium battery positive electrode of the present invention is a method for producing a composite material for a lithium battery positive electrode containing a positive electrode active material and a conductive material, and is a conductive material having self-aggregation properties at least in a solvent. A dispersion step of forcibly dispersing the active material and the positive electrode active material in a solvent, and an agglomeration step of aggregating the conductive material together with the positive electrode active material in the solvent to obtain agglomerated particles. . Here, “having self-aggregation in a solvent” refers to the property that the average particle size becomes larger due to aggregation by forcibly dispersing in a solvent to be used and then allowing to stand, and specifically described in the Examples. Defined by the measurement method.
また、本発明のリチウム電池正極用複合材料の製造方法は、正極活物質、及び導電性物質を含有するリチウム電池正極用複合材料の製造方法であって、少なくとも、ＤＢＰ（フタル酸ジブチル）吸収量が２００〜８００ｃｍ３／１００ｇであるカーボンブラック及び／又はアスペクト比が５０〜１０００の繊維状カーボンを含有する導電性物質及び正極活物質を溶媒中に分散させて強制分散した状態とする分散工程と、前記導電性物質を前記正極活物質と共に溶媒中で凝集させて凝集粒子を得る凝集工程とを含むものである。なお、本発明における各種の物性値は、具体的には実施例に記載の方法で測定される値である。 The method for producing a composite material for a lithium battery positive electrode of the present invention is a method for producing a composite material for a lithium battery positive electrode containing a positive electrode active material and a conductive material, and at least DBP (dibutyl phthalate) absorption amount a dispersion step but to a state where the carbon black and / or aspect ratio is 200~800cm 3 / 100g is a conductive material and a positive electrode active material containing a fibrous carbon 50-1000 forced dispersion is dispersed in a solvent And an aggregating step of aggregating the conductive material together with the positive electrode active material in a solvent to obtain aggregated particles. In addition, the various physical-property values in this invention are values specifically measured by the method as described in an Example.
本発明のリチウム電池正極用複合材料の製造方法によると、自己凝集性を有する導電性物質等を用いて、正極活物質と共に溶媒中に強制分散させることによって、凝集後に導電性物質が正極活物質を包み込む微細複合構造を構成すると考えられる。このため、正極活物質と導電性物質の接触点が多くなり、導電性が向上すると考えられ、電解液の浸透がスムーズでＬｉイオンのイオン拡散に優れた構造を呈すると考えられる。 According to the method for producing a composite material for a lithium battery positive electrode of the present invention, by using a conductive material having self-aggregation property or the like and forcibly dispersing it in a solvent together with the positive electrode active material, the conductive material becomes positive electrode active material after aggregation. It is thought that it constitutes a fine composite structure that wraps around. For this reason, it is thought that the contact point of a positive electrode active material and an electroconductive substance increases, and electroconductivity improves, It is thought that the osmosis | permeation of electrolyte solution is smooth and exhibits the structure excellent in the ion diffusion of Li ion.
また、ＤＢＰ吸収量の高いカーボンや繊維径の細い繊維状カーボンを含有する導電性物質を用いる場合にも、凝集後に導電性物質が正極活物質を包み込む微細複合構造を構成できると考えられ、正極活物質と導電性物質の接触点が多くなり、導電性が向上すると考えられる。しかも、微細な隙間を有する多孔のカーボンネットワークを構築できるため、電解液の浸透がスムーズでＬｉイオンのイオン拡散により優れた構造を呈すると考えられる。 In addition, even when a conductive material containing carbon having a high DBP absorption amount or fibrous carbon having a small fiber diameter is used, it is considered that a fine composite structure in which the conductive material wraps the positive electrode active material after aggregation can be formed. It is considered that the contact point between the active material and the conductive material increases, and the conductivity is improved. Moreover, since a porous carbon network having fine gaps can be constructed, it is considered that the electrolyte solution is smoothly permeated and exhibits an excellent structure due to ion diffusion of Li ions.
本発明では、上記の結果、電子及びリチウムイオンの移動がスムーズに行えると考えられる複合構造によって、従来のＬｉイオン二次電池にくらべ、放電時に高い電流を流すことができ、高速放電特性に優れたＬｉイオン電池を得ることができる。 In the present invention, as a result of the above, the composite structure, which is thought to be able to move electrons and lithium ions smoothly, allows a higher current to flow during discharge than the conventional Li ion secondary battery, and is excellent in high-speed discharge characteristics. Li-ion battery can be obtained.
以下、本発明の実施の形態について詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail.
本発明の製造方法は、正極活物質、及び導電性物質を含有するリチウム電池正極用複合材料の製造方法であり、当該正極用複合材料は、リチウムイオン二次電池等の正極の製造に用いることができる。本発明の製造方法で使用する導電性物質と正極活物質は、溶媒中で化学的に安定な単位粒子の集合物であり、溶媒中で超音波等で、好ましくは、周波数１５〜２５ｋＨｚ、出力１００〜５００Ｗの超音波で強制分散させることで、単位粒子に近い状態まで分散されると考えられる。この単位粒子を本発明では「一次粒子」という。 The production method of the present invention is a production method of a positive electrode active material and a composite material for a lithium battery positive electrode containing a conductive substance, and the positive electrode composite material is used for production of a positive electrode such as a lithium ion secondary battery. Can do. The conductive material and the positive electrode active material used in the production method of the present invention are aggregates of unit particles that are chemically stable in a solvent, and are ultrasonic waves in the solvent, preferably a frequency of 15 to 25 kHz. It is thought that it is dispersed to a state close to unit particles by forced dispersion with ultrasonic waves of 100 to 500 W. This unit particle is referred to as “primary particle” in the present invention.
本発明の製造方法は、少なくとも、溶媒中で自己凝集性を有する導電性物質及び正極活物質を溶媒中に分散させて強制分散した状態とする分散工程を含むものである。本発明において「強制分散した状態」とは、スラリーをサンプリングして所定濃度に希釈し、遅滞なく粒度分布測定装置で平均粒径を測定した際に、当該平均粒径が正極活物質の一次粒子径の１３０％以内になるような分散状態を指す（正極活物質の一次粒子径と比較する観点から、具体的な測定方法は、正極活物質の一次粒子径の測定方法にて後述する）。つまり、この状態では、初期の凝集状態から強制分散した状態に移行することによって、測定される平均粒径が正極活物質の一次粒子径に近づき（導電性物質の分散状態もこの測定値に反映される）、この現象から強制分散した状態を把握することができる。 The production method of the present invention includes at least a dispersion step in which a conductive material having self-aggregation property and a positive electrode active material are dispersed in a solvent and forcedly dispersed. In the present invention, the “forced dispersion state” means that when the slurry is sampled and diluted to a predetermined concentration and the average particle size is measured with a particle size distribution measurement device without delay, the average particle size is the primary particle of the positive electrode active material. The dispersion state is within 130% of the diameter (from the viewpoint of comparison with the primary particle diameter of the positive electrode active material, a specific measurement method will be described later in the measurement method of the primary particle diameter of the positive electrode active material). That is, in this state, the measured average particle size approaches the primary particle size of the positive electrode active material by shifting from the initial aggregated state to the forcedly dispersed state (the dispersion state of the conductive material is also reflected in this measured value). It is possible to grasp the state of forced dispersion from this phenomenon.
上記の分散工程は、自己凝集性の導電性物質と正極活物質とを溶媒中に添加して、同時に分散させるものでもよいが、導電性物質又は正極活物質の一方を溶媒中に添加して分散させた後、これに他方を添加して分散させるものでもよい。 In the dispersion step, the self-aggregating conductive material and the positive electrode active material may be added to the solvent and dispersed simultaneously, but one of the conductive material and the positive electrode active material is added to the solvent. After the dispersion, the other may be added and dispersed.
本発明では、特に、自己凝集性の導電性物質を効果的に強制分散させ、その分散状態を維持しながら正極活物質を効果的に分散させる観点から、当該導電性物質を溶媒中に添加して分散させた後、これに正極活物質を添加して分散させる方法が好ましい。後から正極活物質を添加して分散させる方法では、導電性物質と正極活物質を均一に混合させることが好ましく、分散機で分散を行いながら正極活物質を添加することがより好ましい。 In the present invention, in particular, from the viewpoint of effectively forcibly dispersing the self-aggregating conductive material and effectively dispersing the positive electrode active material while maintaining the dispersion state, the conductive material is added to the solvent. A method in which the positive electrode active material is added and dispersed after the dispersion is preferable. In the method of adding and dispersing the positive electrode active material later, it is preferable to uniformly mix the conductive material and the positive electrode active material, and it is more preferable to add the positive electrode active material while dispersing with a disperser.
自己凝集性を有する導電性物質としては、分散に用いる溶媒中に強制分散させた後、放置することで自己凝集する性質を有する導電性物質であればよく、例えば、自己凝集性を有するカーボンブラックや、自己凝集性を有するカーボンファイバー、カーボンナノチューブ（ＣＮＴ）等の繊維状カーボンなどが挙げられる。 The conductive material having self-aggregating property may be any conductive material having a property of self-aggregating by being forced to disperse in a solvent used for dispersion and then standing, for example, carbon black having self-aggregating property. And carbon fiber having self-aggregating property, fibrous carbon such as carbon nanotube (CNT), and the like.
本発明では、自己凝集性を有しない導電性物質を、分散工程で添加することも可能である。その場合、自己凝集性の導電性物質を効果的に強制分散させ、その分散状態を維持しながら追加の導電性物質を効果的に分散させる観点から、自己凝集性の導電性物質を溶媒中に添加して分散させた後、これに追加の導電性物質（好ましくは凝集性を有しない導電性物質、より好ましくは凝集性を有しないカーボンブラック）を添加して分散させることが好ましい。追加の導電性物質と正極活物質とは、予め混合するか、同時に混合してもよく、順次添加して分散させる場合は、その順序はいずれでもよい。 In the present invention, it is also possible to add a conductive substance having no self-aggregation property in the dispersion step. In that case, the self-aggregating conductive material is effectively forcedly dispersed, and the additional conductive material is effectively dispersed while maintaining the dispersion state. After adding and dispersing, it is preferable to add and disperse an additional conductive material (preferably a conductive material having no cohesiveness, more preferably carbon black having no cohesive property). The additional conductive material and the positive electrode active material may be mixed in advance or may be mixed at the same time. When sequentially added and dispersed, the order may be any.
予め混合する場合は、粉末同士の乾式混合でもよいが、できるだけ均一に混合する観点から、溶媒中で湿式混合することが好ましい。その際、まず追加の導電性物質を分散させた後に、正極活物質を添加して、分散、混合させることが好ましい。 When mixing in advance, dry mixing of powders may be performed, but wet mixing in a solvent is preferable from the viewpoint of mixing as uniformly as possible. At that time, it is preferable to first disperse the additional conductive material and then add the positive electrode active material to disperse and mix.
カーボンブラックとしては、サーマルブラック法、アセチレンブラック法等の分解法、チャンネルブラック法、ガスファーネスブラック法、オイルファーネスブラック法、松煙法、ランプブラック法等の不完全燃焼法のいずれの製法で製造されたものも使用できるが、導電性の観点からファーネスブラック、アセチレンブラック、ケッチェンブラック（登録商標）が好ましく用いられ、このうちケッチェンブラックがより好ましい。これらは単独で用いても良いし、２種以上を混合しても良い。ケッチェンブラックとしては、溶媒中での自己凝集性や得られる微細複合構造の観点から、ＤＢＰ吸収量が２００〜８００ｃｍ３／１００ｇのものが好ましい。 Carbon black is produced by any of the following methods: thermal black method, decomposition method such as acetylene black method, channel black method, gas furnace black method, oil furnace black method, pine smoke method, lamp black method, etc. However, furnace black, acetylene black, and ketjen black (registered trademark) are preferably used from the viewpoint of conductivity, and ketjen black is more preferable. These may be used alone or in combination of two or more. The Ketjen black, from the viewpoint of the self-aggregating properties and resulting fine composite structure in a solvent, DBP absorption amount is preferably from 200~800cm 3 / 100g.
自己凝集性を有するカーボンブラックは、正極活物質を包含して凝集できるような、ストラクチャーの大きなものが好ましい。カーボンブラックのストラクチャーの大きさは、ＤＢＰ吸収量から判断でき、電解液のしみ込みを良好にし、Ｌｉイオンの拡散経路を確保させる観点から、用いるカーボンブラックのＤＢＰ吸収量は、好ましくは２００ｃｍ３／１００ｇ以上、より好ましくは２５０ｃｍ３／１００ｇ以上、さらに好ましくは３００ｃｍ３／１００ｇ以上である。また、電極密度を低下させない観点から、ＤＢＰ吸収量は８００ｃｍ３／１００ｇ以下が好ましく、７００ｃｍ３／１００ｇ以下がより好ましく、６００ｃｍ３／１００ｇ以下が更に好ましい。 The carbon black having a self-aggregating property is preferably a carbon black having a large structure that can be aggregated by including the positive electrode active material. The size of the carbon black structure can be determined from the DBP absorption amount. From the viewpoint of improving the penetration of the electrolytic solution and ensuring the diffusion path of Li ions, the DBP absorption amount of the carbon black used is preferably 200 cm 3 / 100g or more, more preferably 250 cm 3 / 100g or more, still more preferably 300 cm 3 / 100g or more. Further, from the viewpoint of not lowering the electrode density, DBP absorption amount is preferably from 800 cm 3/100 g, more preferably not more than 700 cm 3/100 g, more preferably less 600 cm 3/100 g.
つまり、ＤＢＰ吸収量が２００〜８００ｃｍ３／１００ｇであるカーボンブラックは、一般に自己凝集性が高く、溶媒中に強制分散させた後、放置することで自己凝集して凝集粒子を生成する能力が高いため、本発明に好適に用いることができる。 That is, the carbon black DBP absorption is 200~800cm 3 / 100g is generally self-aggregation property is high, after forcibly dispersed in the solvent, a high ability to produce a self-aggregate into agglomerated particles by standing Therefore, it can be suitably used in the present invention.
自己凝集性を有しないカーボンブラックとしては、ＤＢＰ吸収量が２００ｃｍ３／１００ｇ未満のものが好ましく使用できる。このようなカーボンブラックは、ストラクチャーがあまり発達しておらず、比較的容易に溶媒中に微分散させることができるため、正極活物質と自己凝集性を有するカーボンブラックとの間に介在して、導電性をより向上させることができると考えられる。同様の理由から、自己凝集性を有するカーボンブラックについても、ＤＢＰ吸収量が比較的小さいものと、比較的大きいものとを併用することが、凝集性を維持しながら導電性を向上させる上で好ましい。 The carbon black having no self-aggregation properties, as the DBP absorption is less than 200 cm 3/100 g is preferably used. Since such a carbon black has a less developed structure and can be relatively easily dispersed in a solvent, it is interposed between the positive electrode active material and the self-aggregating carbon black, It is considered that the conductivity can be further improved. For the same reason, it is preferable to use a carbon black having a relatively small DBP absorption amount and a relatively large carbon black in order to improve conductivity while maintaining the aggregation property. .
また、自己凝集性のカーボンブラックの一次粒子径は、以下の観点から１０〜１００ｎｍが好ましい。即ち、走査型電子顕微鏡で測定した一次粒子径が、一次分散のしやすさの観点から、好ましくは１０ｎｍ以上、より好ましくは１５ｎｍ以上、さらに好ましくは２０ｎｍ以上である。また、分散後の再凝集のしやすさの観点から、好ましくは１００ｎｍ以下、より好ましくは８０ｎｍ以下、５０ｎｍ以下がさらに好ましい。 The primary particle diameter of the self-aggregating carbon black is preferably 10 to 100 nm from the following viewpoints. That is, the primary particle diameter measured with a scanning electron microscope is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more, from the viewpoint of ease of primary dispersion. Further, from the viewpoint of ease of reaggregation after dispersion, it is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 50 nm or less.
自己凝集性を有するカーボンブラックの凝集粒径は、以下の観点から１〜５０μｍが好ましい。即ち、本発明ではカーボンブラックと正極活物質を均一に混合分散したのち、カーボンブラックの自己凝集力を利用して、正極活物質を包含させた複合粒子を形成させることができる。このような観点から、自己凝集性を有するカーボンブラックの凝集粒径は、好ましくは、１μｍ以上、より好ましくは５μｍ以上、更に好ましくは１０μｍ以上である。また、本発明の複合正極材料を用いて作製された、正極電極表面の平滑性の観点から、好ましくは、５０μｍ以下、より好ましくは３０μｍ以下、さらに好ましくは２０μｍ以下である。 The aggregated particle diameter of the carbon black having self-aggregation property is preferably 1 to 50 μm from the following viewpoints. That is, in the present invention, after carbon black and the positive electrode active material are uniformly mixed and dispersed, composite particles including the positive electrode active material can be formed by utilizing the self-aggregating force of carbon black. From such a viewpoint, the aggregated particle size of the carbon black having self-aggregation property is preferably 1 μm or more, more preferably 5 μm or more, and further preferably 10 μm or more. Moreover, from the viewpoint of the smoothness of the surface of the positive electrode produced using the composite positive electrode material of the present invention, it is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.
自己凝集性を有するカーボンブラックの含有量としては、以下の観点から正極活物質１００重量部に対して０．２〜２０重量部が好ましい。即ち、凝集工程において自己凝集力を効果的に発現させる観点から、正極活物質１００重量部に対して、好ましくは０．２重量部以上、より好ましくは、０．５重量部以上、更に好ましくは１重量部以上である。また、体積抵抗率と全孔容積率とのバランスの観点から、好ましくは２０重量部以下、より好ましくは１０重量部以下、更に好ましくは５重量部以下である。 The content of the carbon black having self-aggregating property is preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the positive electrode active material from the following viewpoints. That is, from the viewpoint of effectively expressing the self-aggregation force in the aggregation step, it is preferably 0.2 parts by weight or more, more preferably 0.5 parts by weight or more, further preferably 100 parts by weight of the positive electrode active material. 1 part by weight or more. Further, from the viewpoint of the balance between the volume resistivity and the total pore volume ratio, it is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and still more preferably 5 parts by weight or less.
自己凝集性を有しないカーボンブラックを併用する場合、その含有量としては、以下の観点から正極活物質１００重量部に対して０．２〜２０重量部が好ましい。即ち、正極材料の体積抵抗率の低減の観点から、正極活物質１００重量部に対して、好ましくは０．２重量部以上、より好ましくは、０．５重量部以上、更に好ましくは１重量部以上である。また、正極活物質表面への被覆性の観点から、好ましくは２０重量部以下、より好ましくは１０重量部以下、更に好ましくは５重量部以下である。 When carbon black having no self-aggregation property is used in combination, the content is preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the positive electrode active material from the following viewpoints. That is, from the viewpoint of reducing the volume resistivity of the positive electrode material, it is preferably 0.2 parts by weight or more, more preferably 0.5 parts by weight or more, and further preferably 1 part by weight with respect to 100 parts by weight of the positive electrode active material. That's it. In addition, from the viewpoint of coverage on the surface of the positive electrode active material, it is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and still more preferably 5 parts by weight or less.
一方、繊維状カーボンとしては、ポリアクリロニトリル（ＰＡＮ）に代表される高分子を原料としたカーボンファイバー、ピッチを原料としたピッチ系カーボンファイバー、カーボンナノチューブ（グラファイトの１枚面つまりグラフェンシートを巻いて筒状にした形状物（微粒子工学大系第Ｉ巻P651、株式会社フジ・テクノシステム））であって、炭化水素ガスを原料とする気相成長系のカーボンファイバー（例えば、ＶＧＣＦ：登録商標）、アーク放電法、レーザー蒸発法、化学気相成長法などで得られる、いわゆる狭義のカーボンナノチューブ（以下、狭義のカーボンナノチューブを単にカーボンナノチューブという）などが好適に用いられる。より多くの導電経路を構築させる観点から、繊維径の細い繊維状カーボンが好ましく、ＶＧＣＦやカーボンナノチューブが好適に用いられ、中でもカーボンナノチューブを用いることが好ましい。カーボンナノチューブは、例えば、ＨｅやＡｒ、ＣＨ４、Ｈ２などの雰囲気ガスのもとで、黒鉛電極をアーク放電で蒸発させるアーク放電法、ＮｉやＣｏ、Ｙ、Ｆｅなどの金属触媒を含む黒鉛電極をアーク放電で蒸発させるアーク放電法、Ｎｉ−Ｃｏ、Ｐｄ−Ｒｄなどの金属触媒を混ぜた黒鉛にＹＡＧレーザーを当て蒸発させ、Ａｒの気流で１２００℃程度に加熱された電気炉に送り出すレーザー蒸発法、触媒にペンタカルボニル鉄（Ｆｅ（ＣＯ）５）を用い、一酸化炭素を高圧で熱分解するＨｉＰＣＯ法等で得ることができる。カーボンナノチューブのアスペクト比については、例えば、炭化水素（ベンゼン等）と水素ガス等の雰囲気ガスの濃度比が小さいほど、生成するカーボンナノチューブの直径が細くなり、アスペクト比が大きくなる。また、反応時間が短いほど、生成するカーボンナノチューブの直径が細くなり、やはりアスペクト比が大きくなる。 On the other hand, as carbon fiber, carbon fiber made from a polymer represented by polyacrylonitrile (PAN), pitch-based carbon fiber made from pitch, carbon nanotube (one surface of graphite, that is, a graphene sheet is wound. A cylindrical shaped product (Particulate Engineering University Volume I, P651, Fuji Techno System Co., Ltd.), a vapor-grown carbon fiber (for example, VGCF: registered trademark) using hydrocarbon gas as a raw material So-called carbon nanotubes in a narrow sense (hereinafter, the carbon nanotubes in a narrow sense are simply referred to as carbon nanotubes) obtained by an arc discharge method, a laser evaporation method, a chemical vapor deposition method, or the like are preferably used. From the viewpoint of constructing more conductive paths, fibrous carbon having a small fiber diameter is preferable, and VGCF and carbon nanotubes are preferably used. Among them, carbon nanotubes are preferably used. The carbon nanotube is, for example, an arc discharge method in which a graphite electrode is evaporated by arc discharge under an atmospheric gas such as He, Ar, CH 4 , or H 2 , and graphite containing a metal catalyst such as Ni, Co, Y, or Fe. Arc discharge method in which electrodes are evaporated by arc discharge, YAG laser is applied to graphite mixed with a metal catalyst such as Ni—Co, Pd—Rd, and evaporated, and then sent to an electric furnace heated to about 1200 ° C. with an Ar air flow It can be obtained by an evaporation method, a HiPCO method in which pentacarbonyl iron (Fe (CO) 5 ) is used as a catalyst, and carbon monoxide is thermally decomposed at high pressure. As for the aspect ratio of the carbon nanotube, for example, the smaller the concentration ratio of the hydrocarbon (benzene or the like) and the atmospheric gas such as hydrogen gas, the smaller the diameter of the generated carbon nanotube and the larger the aspect ratio. In addition, the shorter the reaction time, the thinner the carbon nanotubes that are produced, and the higher the aspect ratio.
本発明では、繊維が絡み合って糸玉状に凝集している繊維状カーボンを、正極活物質の存在下で分散剤や機械的な応力を加えて分散せしめ、その後分散を止めることによって再凝集させることにより、正極活物質を包含させた複合粒子を形成させることができると考えられる。このような観点から、繊維状カーボンの繊維長（Ｌ）に対する繊維径（Ｗ）のアスペクト比、すなわちＬ／Ｗが重要になる。繊維状カーボンのアスペクト比は、更に導電性の観点から、好ましくは５０以上、より好ましくは１００以上、更に好ましくは２００以上であり、繊維状カーボンの分散性の観点から、好ましくは２万以下、より好ましくは５０００以下、さらに好ましくは１０００以下、さらにより好ましくは６００以下である。 In the present invention, fibrous carbon in which fibers are entangled and aggregated in a yarn ball shape is dispersed by applying a dispersing agent or mechanical stress in the presence of a positive electrode active material, and then re-aggregated by stopping the dispersion. Thus, it is considered that composite particles including the positive electrode active material can be formed. From such a viewpoint, the aspect ratio of the fiber diameter (W) to the fiber length (L) of the fibrous carbon, that is, L / W is important. The aspect ratio of the fibrous carbon is preferably 50 or more, more preferably 100 or more, further preferably 200 or more from the viewpoint of conductivity, and preferably 20,000 or less from the viewpoint of the dispersibility of the fibrous carbon. More preferably, it is 5000 or less, More preferably, it is 1000 or less, More preferably, it is 600 or less.
つまり、アスペクト比が５０〜２００００の繊維状カーボンは、一般に自己凝集性が高く、溶媒中に強制分散させた後、放置することで自己凝集して凝集粒子を生成する能力が高いため、本発明に好適に用いることができる。 That is, the fibrous carbon having an aspect ratio of 50 to 20000 generally has high self-aggregation property, and has a high ability to self-aggregate and produce aggregated particles by being forcedly dispersed in a solvent and then left standing. Can be suitably used.
その際、繊維状カーボンの繊維長は、以下の観点から５０ｎｍ以上５０μｍ以下が好ましい。即ち、正極活物質表面とより多く接触し、導電経路を確立する観点から、好ましくは、５０ｎｍ以上、より好ましくは５００ｎｍ以上、更に好ましくは１μｍ以上である。また、本発明の複合正極材料を用いて作製された、正極電極表面の平滑性の観点から、好ましくは、５０μｍ以下、より好ましくは３０μｍ以下、さらに好ましくは１０μｍ以下である。 At that time, the fiber length of the fibrous carbon is preferably 50 nm or more and 50 μm or less from the following viewpoints. That is, it is preferably 50 nm or more, more preferably 500 nm or more, and further preferably 1 μm or more from the viewpoint of making more contact with the surface of the positive electrode active material and establishing a conductive path. Moreover, from the viewpoint of the smoothness of the surface of the positive electrode produced using the composite positive electrode material of the present invention, it is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less.
また、繊維状カーボンの繊維径は、正極活物質表面とより多く接触し、導電経路を確立させる観点から、１ｎｍ〜１μｍが好ましく、１〜５００ｎｍがより好ましく、１〜３００ｎｍが更に好ましい。 The fiber diameter of the fibrous carbon is preferably 1 nm to 1 μm, more preferably 1 to 500 nm, and still more preferably 1 to 300 nm from the viewpoint of making more contact with the surface of the positive electrode active material and establishing a conductive path.
繊維状カーボンの含有量としては、以下の観点から正極活物質１００重量部に対して０．２〜２０重量部が好ましい。即ち、凝集工程において自己凝集力を効果的に発現させる観点から、正極活物質１００重量部に対して、好ましくは０．２重量部以上、より好ましくは、０．５重量部以上、更に好ましくは１重量部以上である。また、体積抵抗率と全孔容積率とのバランスの観点から、好ましくは２０重量部以下、より好ましくは１０重量部以下、更に好ましくは５重量部以下である。 As content of fibrous carbon, 0.2-20 weight part is preferable with respect to 100 weight part of positive electrode active materials from the following viewpoints. That is, from the viewpoint of effectively expressing the self-aggregation force in the aggregation step, it is preferably 0.2 parts by weight or more, more preferably 0.5 parts by weight or more, further preferably 100 parts by weight of the positive electrode active material. 1 part by weight or more. Further, from the viewpoint of the balance between the volume resistivity and the total pore volume ratio, it is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and still more preferably 5 parts by weight or less.
カーボンの総配合量は、以下の観点から正極活物質１００重量部に対して０．２〜５０重量部が好ましい。即ち、複合正極材料の体積抵抗率低減の観点から、正極活物質１００重量部に対して、好ましくは０．２重量部以上、より好ましくは０．５重量部以上、更に好ましくは３重量部以上である。また、複合正極材料のエネルギー密度を高める観点から、好ましくは５０重量部以下、より好ましくは３０重量部以下、更に好ましくは１５重量部以下である。 The total amount of carbon is preferably 0.2 to 50 parts by weight with respect to 100 parts by weight of the positive electrode active material from the following viewpoints. That is, from the viewpoint of reducing the volume resistivity of the composite positive electrode material, it is preferably 0.2 parts by weight or more, more preferably 0.5 parts by weight or more, still more preferably 3 parts by weight or more with respect to 100 parts by weight of the positive electrode active material. It is. Further, from the viewpoint of increasing the energy density of the composite positive electrode material, it is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 15 parts by weight or less.
本発明に用いられる正極活物質としては、従来公知の何れの材料も使用でき、例えば、ＬｉＭｎ2Ｏ4などのＬｉ・Ｍｎ系複合酸化物、ＬｉＣｏＯ2などのＬｉ・Ｃｏ系複合酸化物、ＬｉＮｉＯ2などのＬｉ・Ｎｉ系複合酸化物、ＬｉＦｅＯ2などのＬｉ・Ｆｅ系複合酸化物などが挙げられ、ＬｉxＣｏＯ2，ＬｉxＮｉＯ2，ＭｎＯ2，ＬｉＭｎＯ2，ＬｉxＭｎ2Ｏ4，ＬｉxＭｎ2-yＯ4，α−Ｖ2Ｏ5，ＴｉＳ2等が挙げられる。なかでも、熱的安定性、及び容量、出力特性に優れるという観点から、ＬｉＭｎ2Ｏ4，ＬｉＣｏＯ2，ＬｉＮｉＯ2が好ましく、ＬｉＭｎ2Ｏ4がより好ましい。 As the positive electrode active material used in the present invention, any conventionally known material can be used. For example, a Li · Mn composite oxide such as LiMn 2 O 4, a Li · Co composite oxide such as LiCoO 2 , LiNiO Li · Ni-based composite oxide such as 2, is like Li · Fe-based composite oxides such as LiFeO 2, Li x CoO 2, Li x NiO 2, MnO 2, LiMnO 2, Li x Mn 2 O 4, li x Mn 2-y O 4 , α-V 2 O 5, TiS 2 and the like. Of these, LiMn 2 O 4 , LiCoO 2 , and LiNiO 2 are preferable and LiMn 2 O 4 is more preferable from the viewpoint of excellent thermal stability, capacity, and output characteristics.
正極活物質の一次粒子径は、以下の観点から０．１〜１０μｍが好ましい。即ち、正極活物質の安全性や安定性、サイクル特性の観点から、好ましくは０．１μｍ以上、より好ましくは０．２μｍ以上、さらに好ましくは、０．３μｍ以上であり、また、凝集工程における複合凝集性や、反応性、高速放電性の観点から１０μｍ以下が好ましく、より好ましくは５μｍ以下、さらに好ましくは２μｍ以下である。 The primary particle diameter of the positive electrode active material is preferably 0.1 to 10 μm from the following viewpoints. That is, from the viewpoint of safety and stability of the positive electrode active material, and cycle characteristics, it is preferably 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm or more. The thickness is preferably 10 μm or less, more preferably 5 μm or less, and still more preferably 2 μm or less from the viewpoints of cohesion, reactivity, and fast discharge.
分散に用いる溶媒としては、Ｎ−メチル−２−ピロリドン（ＮＭＰ、沸点２０２℃）、ジメチルホルムアミド（ＤＭＦ、沸点１５３℃）、ジメチルアセトアミド（沸点１６５℃）、メチルエチルケトン（沸点７９．５℃）、テトラヒドロフラン（沸点６６℃）、アセトン（沸点５６．３℃）、エタノール（沸点７８．３℃）、酢酸エチル（沸点７６．８℃）などが好適に用いられる。このうち複合粒子をスラリー状態で得る場合は、沸点の高いＮＭＰを溶媒とすることが好ましく、また、乾燥粒子の状態で得る場合には、沸点の低いメチルエチルケトンやエタノールが好ましい。 As a solvent used for dispersion, N-methyl-2-pyrrolidone (NMP, boiling point 202 ° C.), dimethylformamide (DMF, boiling point 153 ° C.), dimethylacetamide (boiling point 165 ° C.), methyl ethyl ketone (boiling point 79.5 ° C.), tetrahydrofuran (Boiling point 66 ° C.), acetone (boiling point 56.3 ° C.), ethanol (boiling point 78.3 ° C.), ethyl acetate (boiling point 76.8 ° C.) and the like are preferably used. Among these, when obtaining composite particles in a slurry state, NMP having a high boiling point is preferably used as a solvent, and when obtaining in a dry particle state, methyl ethyl ketone or ethanol having a low boiling point is preferred.
なお、溶媒の沸点は、乾燥の容易さの観点から、好ましくは２５０℃以下、より好ましくは１００℃以下、さらに好ましくは８０℃以下である。 The boiling point of the solvent is preferably 250 ° C. or lower, more preferably 100 ° C. or lower, and further preferably 80 ° C. or lower, from the viewpoint of ease of drying.
溶媒の使用量は、自己凝集性の導電性物質、正極活物質などを均一に分散させる観点から、正極活物質１００重量部に対して、１００重量部以上が好ましく、２００重量部以上がより好ましい。また、溶媒の乾燥の煩雑さや、得られるスラリーの濃度の観点から、１０００重量部以下が好ましく、８００重量部以下がより好ましい。以上を総合した観点から、１００〜１０００重量部が好ましく、２００〜８００重量部がより好ましい。 The amount of the solvent used is preferably 100 parts by weight or more, more preferably 200 parts by weight or more with respect to 100 parts by weight of the positive electrode active material, from the viewpoint of uniformly dispersing the self-aggregating conductive material, the positive electrode active material, and the like. . Moreover, 1000 weight part or less is preferable from a viewpoint of the complexity of drying of a solvent, and the density | concentration of the slurry obtained, and 800 weight part or less is more preferable. From the viewpoint of integrating the above, 100 to 1000 parts by weight is preferable, and 200 to 800 parts by weight is more preferable.
分散工程において、導電性物質および正極活物質を分散させる方法としては、溶媒中で分散機により分散させる方法や、分散剤により分散させる方法などが用いられるが、いずれの場合も、自己凝集性を有する導電性物質及び正極活物質を溶媒中に分散させて強制分散した状態とする分散工程が含まれる。強制分散した状態では、正極活物質が一次粒子まで分散していることが好ましい。また、導電性物質が好ましくは２００ｃｍ３／１００ｇ以上のＤＢＰ吸収量を有するカーボンブラックである場合、導電性物質も一次粒子又は一次粒子に近い状態まで分散していることが好ましい。 In the dispersion step, as a method for dispersing the conductive material and the positive electrode active material, a method of dispersing with a disperser in a solvent, a method of dispersing with a dispersing agent, or the like is used. A dispersion step is included in which the conductive material and the positive electrode active material are dispersed in a solvent and forcedly dispersed. In the forcibly dispersed state, the positive electrode active material is preferably dispersed to the primary particles. Also, when the conductive material is preferably a carbon black having a 200 cm 3/100 g or more DBP absorption, it is preferable that the conductive material is also dispersed to a state close to primary particles or primary particles.
分散機としては、例えば超音波型分散機、攪拌型分散機、高速回転せん断型分散機、ミル型分散機、高圧噴射型分散機などが挙げられるが、強制分散させる工程に使用する場合、超音波型分散機、高圧噴射型分散機が好適に用いられる。 Examples of the disperser include an ultrasonic disperser, a stirring disperser, a high-speed rotary shear disperser, a mill disperser, a high-pressure jet disperser, and the like. Sonic dispersers and high-pressure jet dispersers are preferably used.
分散剤により分散させる方法は、正極活物質や自己凝集性の低い導電性物質を分散させる方法として有効であるが、凝集工程において凝集粒子の生成を妨げない添加量の範囲で使用することが好ましい。 The method of dispersing with a dispersing agent is effective as a method of dispersing a positive electrode active material or a low self-aggregating conductive material, but is preferably used within a range of addition amount that does not hinder the formation of aggregated particles in the aggregation process. .
分散剤を使用する場合、分散剤としてはアニオン性、ノニオン性もしくはカチオン性界面活性剤、または高分子分散剤を用いることが出来るが、分散性能の点から高分子分散剤の使用が好ましい。 When a dispersant is used, an anionic, nonionic or cationic surfactant, or a polymer dispersant can be used as the dispersant, but a polymer dispersant is preferably used from the viewpoint of dispersion performance.
高分子分散剤としては種々の化合物を使用することができるが、分子内に複数のカルボキシル基を有するポリカルボン酸系高分子分散剤、分子内に複数のアミノ基を有するポリアミン系高分子分散剤、分子内に複数のアミド基を有する高分子分散剤や分子内に複数の多環式芳香族化合物を含有する高分子分散剤が好ましい。これらの分散剤は単独で、あるいは二種以上の分散剤を混合して用いることができる。 Although various compounds can be used as the polymer dispersant, a polycarboxylic acid polymer dispersant having a plurality of carboxyl groups in the molecule and a polyamine polymer dispersant having a plurality of amino groups in the molecule A polymer dispersant having a plurality of amide groups in the molecule and a polymer dispersant containing a plurality of polycyclic aromatic compounds in the molecule are preferred. These dispersing agents can be used alone or in admixture of two or more kinds of dispersing agents.
更に、本発明の製造方法は、前記導電性物質を前記正極活物質と共に溶媒中で凝集させて凝集粒子を得る凝集工程を含むものである。この凝集工程は、自己凝集性の導電性物質が自己凝集しやすいため、分散機を停止することで、自己凝集を促進させ、凝集粒子を含んだスラリーを得る手法や、溶媒中での凝集力を更に高めるべく、溶媒を留去して強制的に凝集させて凝集粒子の粉末を得る手法を用いることができる。 Furthermore, the production method of the present invention includes an aggregating step of aggregating the conductive material together with the positive electrode active material in a solvent to obtain aggregated particles. In this agglomeration process, self-aggregating conductive materials are likely to self-aggregate. Therefore, by stopping the disperser, self-aggregation is promoted, and a slurry containing aggregated particles is obtained. In order to further increase the ratio, a method of obtaining a powder of aggregated particles by distilling off the solvent and forcibly aggregating can be used.
得られる凝集粒子は、好ましくは正極活物質を導電性物質で取り巻いた形状をしている。得られる凝集粒子の平均粒径は、以下の観点から１〜２０μｍが好ましい。即ち、このような凝集粒子の粉末状又は溶媒中での平均粒径は、１μｍ以上が好ましく、３μｍ以上がより好ましく、５μｍ以上が更に好ましい。また、本複合粒子を用いて得られる正極電極の表面性の観点から、好ましくは、２０μｍ以下、より好ましくは１５μｍ以下、１０μｍ以下が更に好ましい。 The obtained aggregated particles preferably have a shape in which a positive electrode active material is surrounded by a conductive material. The average particle diameter of the obtained aggregated particles is preferably 1 to 20 μm from the following viewpoints. That is, the average particle diameter of such agglomerated particles in a powder form or in a solvent is preferably 1 μm or more, more preferably 3 μm or more, and still more preferably 5 μm or more. In addition, from the viewpoint of the surface properties of the positive electrode obtained using the composite particles, it is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.
凝集工程における凝集粒子の濃度としては、凝集粒子を好適に得る観点から、スラリー中、２〜１００重量％が好ましく、５〜５０重量％がより好ましく、１０〜４０重量％が更に好ましい。 The concentration of the aggregated particles in the aggregation process is preferably 2 to 100% by weight, more preferably 5 to 50% by weight, and still more preferably 10 to 40% by weight in the slurry from the viewpoint of suitably obtaining the aggregated particles.
溶媒を留去した後の正極用複合材料は、従来の正極用複合材料よりも少ない導電性物質の配合量で体積抵抗率を低減でき、その分、正極活物質を多く配合できるため、正極のエネルギー密度を向上できる。その場合、正極用複合材料の体積抵抗率は、高速放電特性向上の観点から、３Ω・ｃｍ以下であることが好ましく、より好ましくは２Ω・ｃｍ以下、更に好ましくは１．８Ω・ｃｍ以下である。 The positive electrode composite material after distilling off the solvent can reduce the volume resistivity with a smaller amount of conductive material than the conventional positive electrode composite material, and can add more positive electrode active material accordingly, Energy density can be improved. In that case, the volume resistivity of the positive electrode composite material is preferably 3 Ω · cm or less, more preferably 2 Ω · cm or less, and even more preferably 1.8 Ω · cm or less, from the viewpoint of improving high-speed discharge characteristics. .
また、溶媒を留去した後の正極用複合材料の全細孔容量は、以下の観点から０．８〜２５ｃｃ／ｇが好ましい。即ち、高速放電性向上の観点から、好ましくは０．８ｃｃ／ｇ以上、より好ましくは０．９ｃｃ／ｇ以上、さらに好ましくは１ｃｃ／ｇ以上であり、正極のエネルギー密度を適切に確保する観点から、好ましくは２５ｃｃ／ｇ以下、より好ましくは１０ｃｃ／ｇ以下、さらに好ましくは５ｃｃ／ｇ以下である。前記観点を総合すると、好ましくは０．８〜２５ｃｃ／ｇ、より好ましくは０．９〜１０ｃｃ／ｇ、さらに好ましくは１〜５ｃｃ／ｇである。このような全細孔容量とすることで、Ｌｉイオンの拡散をスムーズにすることができると考えられる本発明の正極用複合材料は、スラリー又は粉末として得ることができるが、これらを用いて、リチウムイオン二次電池等の正極の形成を行うことができる。一般的に、正極の形成は、正極活物質、導電性物質、バインダ、及び溶剤を混合したスラリーを集電体となる金属箔に塗布・乾燥することにより行われる。従って、本発明の正極用複合材料は、スラリー状態のままで、必要に応じてバインダを添加して、正極の形成に使用できる。あるいは、粉末状の正極用複合材料は、必要に応じてバインダ、及び溶剤を添加して、正極の形成に使用できる。 Further, the total pore volume of the positive electrode composite material after distilling off the solvent is preferably 0.8 to 25 cc / g from the following viewpoints. That is, from the viewpoint of improving fast discharge performance, it is preferably 0.8 cc / g or more, more preferably 0.9 cc / g or more, and further preferably 1 cc / g or more, from the viewpoint of appropriately ensuring the energy density of the positive electrode. Preferably, it is 25 cc / g or less, More preferably, it is 10 cc / g or less, More preferably, it is 5 cc / g or less. When the said viewpoint is put together, Preferably it is 0.8-25 cc / g, More preferably, it is 0.9-10 cc / g, More preferably, it is 1-5 cc / g. The composite material for positive electrode of the present invention considered to be able to smooth the diffusion of Li ions can be obtained as a slurry or a powder by using such a total pore volume. A positive electrode such as a lithium ion secondary battery can be formed. In general, the positive electrode is formed by applying and drying a slurry obtained by mixing a positive electrode active material, a conductive material, a binder, and a solvent onto a metal foil serving as a current collector. Therefore, the composite material for a positive electrode of the present invention can be used for forming a positive electrode by adding a binder as necessary in a slurry state. Alternatively, the powdery composite material for positive electrode can be used for forming a positive electrode by adding a binder and a solvent as necessary.
その際、正極としての導電性を高める観点から、導電性物質を更に添加してもよい。このような導電性物質としては、正極用複合材料の形成に用いるカーボンブラック、カーボンファイバー、カーボンナノチューブ等が何れも使用可能であるが、正極としての導電性を高める観点から、ＤＢＰ吸収量が１００〜８００ｃｍ３／１００ｇのカーボンブラック、特にケッチェンブラック、アセチレンブラックが好ましい。 At that time, a conductive substance may be further added from the viewpoint of enhancing the conductivity as the positive electrode. As such a conductive substance, carbon black, carbon fiber, carbon nanotube, and the like used for forming the composite material for the positive electrode can be used. However, from the viewpoint of improving the conductivity as the positive electrode, the DBP absorption amount is 100. ~800cm 3 / 100g of carbon black, especially ketjen black, acetylene black preferred.
バインダとしては、正極の形成用に使用される従来のバインダが何れも使用できるが、ポリフッ化ビニリデン、ポリアミドイミド、ポリテトラフルオロエチレン、ポリエチレン、ポリプロピレン、ポリメタクリル酸メチルなどが好適に使用できる。溶媒としては、正極の形成用に使用される従来の溶媒が何れも使用でき、例えば正極用複合材料の形成に用いたものなどが使用できる。集電体としては、正極の形成用に使用される従来の金属箔等が何れも使用できる。また、正極の形成に使用される従来公知の添加剤を何れもスラリーに添加することができる。 As the binder, any conventional binder used for forming a positive electrode can be used, but polyvinylidene fluoride, polyamideimide, polytetrafluoroethylene, polyethylene, polypropylene, polymethyl methacrylate, and the like can be preferably used. As the solvent, any conventional solvent used for forming a positive electrode can be used. For example, a solvent used for forming a composite material for positive electrode can be used. As the current collector, any of conventional metal foils used for forming a positive electrode can be used. Any conventionally known additive used for forming the positive electrode can be added to the slurry.
本発明における正極用複合材料は、正極材料として使用する場合、Ｌｉイオン二次電池の高速放電特性が優れたものとなる。高速放電特性は、後述する電池特性評価において、１Ｃに対して、６０Ｃの放電量の割合が、好ましくは７０％以上、より好ましくは８０％以上である。 When the positive electrode composite material in the present invention is used as a positive electrode material, the high-speed discharge characteristics of the Li ion secondary battery are excellent. In the battery characteristics evaluation described later, the ratio of the discharge amount of 60 C to 70 C is preferably 70% or more, and more preferably 80% or more in the high-speed discharge characteristics.
つまり、以上の正極用複合材料を用いたリチウム電池用正極の製造方法は、本発明のリチウム電池正極用複合材料の製造方法によって、溶媒中で凝集させた凝集粒子を得る工程と、前記溶媒を留去して乾燥粒子を得る工程と、この乾燥粒子に溶媒及びバインダを添加したスラリーを集電体に塗布して乾燥させる工程とを含むものである。また、本発明のリチウム電池正極用複合材料の製造方法によって、溶媒中で凝集させた凝集粒子を得る工程と、前記凝集粒子を含むスラリーにバインダを添加したスラリーを集電体に塗布して乾燥させる工程とを含むものである。 That is, the method for producing a positive electrode for a lithium battery using the above composite material for a positive electrode includes a step of obtaining aggregated particles aggregated in a solvent by the method for producing a composite material for a lithium battery positive electrode of the present invention, The method includes a step of distilling off to obtain dry particles, and a step of applying a slurry obtained by adding a solvent and a binder to the dry particles and drying the current collector. Further, according to the method for producing a composite material for a lithium battery positive electrode of the present invention, a step of obtaining aggregated particles aggregated in a solvent, and a slurry obtained by adding a binder to the slurry containing the aggregated particles are applied to a current collector and dried. And a step of causing
本発明の正極用複合材料を用いた電池の用途は、特に限定されないが、例えばノートパソコン、電子ブックプレーヤー、ＤＶＤプレーヤー、携帯オーディオプレーヤー、ビデオムービー、携帯テレビ、携帯電話などの電子機器に使用できるほか、コードレス掃除機やコードレス電動工具、電気自動車、ハイブリッドカーなどのバッテリー、燃料電池車の補助電源などの民生用機器に使用できる。このうち特に高出力が求められる自動車用バッテリーとして好適に用いられる。 The use of the battery using the positive electrode composite material of the present invention is not particularly limited, but can be used for electronic devices such as notebook computers, electronic book players, DVD players, portable audio players, video movies, portable TVs, and mobile phones. In addition, it can be used for consumer devices such as cordless vacuum cleaners, cordless electric tools, batteries for electric vehicles, hybrid cars, etc., and auxiliary power sources for fuel cell vehicles. Among these, it is suitably used as a battery for automobiles that require particularly high output.
以下、本発明を具体的に示す実施例等について説明する。なお、実施例等における評価項目は下記のようにして測定を行った。 Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.
（１）ＤＢＰ吸収量
ＤＢＰ吸収量は、ＪＩＳＫ６２１７−４に基づいて測定した。
(1) DBP absorption amount DBP absorption amount was measured based on JISK6217-4.
（２）導電性物質の平均粒径及び正極活物質の一次粒子径
レーザー回折／散乱式粒度分布測定装置ＬＡ７５０（堀場製作所製）を用い、エタノールを分散媒とし、超音波１分照射後の粒度分布を、導電性物質では相対屈折率１．５で測定し、正極活物質では相対屈折率１．７で測定したときの体積中位粒径（Ｄ５０）の値を導電性物質の平均粒径、及び正極活物質の一次粒子径とした。
(2) Average particle size of conductive material and primary particle size of positive electrode active material Using laser diffraction / scattering particle size distribution analyzer LA750 (manufactured by Horiba, Ltd.), ethanol as a dispersion medium, particle size after 1 minute of ultrasonic irradiation The distribution was measured at a relative refractive index of 1.5 for the conductive material, and the volume median particle size (D50) measured at a relative refractive index of 1.7 for the positive electrode active material was the average particle size of the conductive material. And the primary particle diameter of the positive electrode active material.
（３）カーボンブラックの一次粒子径
電界放出形走査電子顕微鏡（日立製Ｓ−４０００）により撮影したＳＥＭ像から、一次粒子５０個を抽出し、その直径を測定した平均値を一次粒子径とした。
(3) Primary particle diameter of carbon black 50 primary particles were extracted from an SEM image taken with a field emission scanning electron microscope (Hitachi S-4000), and the average value obtained by measuring the diameter was defined as the primary particle diameter. .
（４）繊維状カーボンの繊維径および繊維長さ
電界放出形走査電子顕微鏡（日立製Ｓ−４０００）により撮影したＳＥＭ像から、繊維３０個を抽出し、その繊維径を測定した平均値を繊維径とした。また、繊維の長さを測定し平均した結果を繊維長とした。
(4) Fiber diameter and fiber length of fibrous carbon 30 fibers were extracted from an SEM image taken with a field emission scanning electron microscope (S-4000 manufactured by Hitachi), and the average value of the measured fiber diameter was determined as the fiber. The diameter. Moreover, the length of the fiber was measured and averaged to obtain the fiber length.
（５）繊維状カーボンのアスペクト比
繊維状カーボンの繊維長を繊維径で除することで求めた。
(5) Aspect ratio of fibrous carbon This was determined by dividing the fiber length of fibrous carbon by the fiber diameter.
（６）体積抵抗率
ＪＩＳ Ｋ １４６９の方法において、粉体試料量を０．３ｇ、粉体圧縮時圧力を１００ｋｇ／ｃｍ２に変更して、円筒状に圧縮した圧縮粉体試料の電気抵抗値を測定し、測定抵抗値より下記の式１により体積抵抗率（電気抵抗率）を算出した。
(6) Volume resistivity In the method of JIS K 1469, the electric resistance value of a compressed powder sample compressed into a cylindrical shape by changing the amount of the powder sample to 0.3 g and changing the pressure during powder compression to 100 kg / cm 2 The volume resistivity (electrical resistivity) was calculated from the measured resistance value according to the following formula 1.
具体的には、絶縁性円筒（ベークライト製、外径２８ｍｍ、内径８ｍｍ）と（−）電極からなる円筒容器に粉体試料を０．３ｇ充填し、試料を詰めた絶縁性円筒容器に（＋）電極を挿入して粉体試料を挟み、プレス機架台上に設置した。プレス機により円筒容器内の試料に１００ｋｇ／ｃｍ２の力を加え、圧縮した。（＋）電極と（−）電極をデジタルマルチメーターの測定用入力ケーブルに接続し、圧縮開始から３分経過後、電気抵抗値を測定した。 Specifically, 0.3 g of a powder sample is filled in a cylindrical container composed of an insulating cylinder (made of Bakelite, outer diameter 28 mm, inner diameter 8 mm) and (−) electrode, and the insulating cylindrical container packed with the sample (+ ) The electrode was inserted and the powder sample was sandwiched, and placed on the press machine base. A force of 100 kg / cm 2 was applied to the sample in the cylindrical container by a press machine and compressed. The (+) electrode and the (−) electrode were connected to the input cable for measurement of a digital multimeter, and the electrical resistance value was measured after 3 minutes from the start of compression.
ρ＝Ｓ／ｈ×Ｒ （式１）
ここで、ρは電気抵抗率（Ω・ｃｍ）、Ｓは試料の断面積（ｃｍ２）、ｈは試料の充填高さ（ｃｍ）、Ｒは電気抵抗値（Ω）である。
ρ = S / h × R (Formula 1)
Here, ρ is the electrical resistivity (Ω · cm), S is the cross-sectional area (cm 2 ) of the sample, h is the filling height (cm) of the sample, and R is the electrical resistance value (Ω).
用いた（−）電極は、黄銅製であり、電極面は７．８±１ｍｍφで、高さ５ｍｍの突起部のある台座上電極であり、（＋）電極は、黄銅製であり、電極面は７．８±１ｍｍφで、長さ６０ｍｍの棒状電極であった。 The (−) electrode used was made of brass, the electrode surface was 7.8 ± 1 mmφ, and was a pedestal-top electrode with a projection of 5 mm in height, and the (+) electrode was made of brass and the electrode surface Was a rod-like electrode having a length of 7.8 ± 1 mmφ and a length of 60 mm.
（７）電池の作製
粉体試料２０．８重量部に対して、市販の導電性カーボンブラック粉末（品名ＨＳ−１００、ＤＢＰ吸収量１４０ｃｍ３／１００ｇ）１．７重量部、ポリフッ化ビニリデン粉末（呉羽化学社製、♯１３００）２．５重量部、ＮＭＰ３７．５重量部を均一に混合し、塗工用ペーストを調製した。当該ペーストをコーターを用いて集電体として用いたアルミニウム箔（厚さ２０μｍ）上に均一に塗工し、１４０℃にて１０分以上かけて乾燥した。乾燥後、プレス機で均一膜厚に成型した後、所定の大きさ（２０ｍｍ×１５ｍｍ）に切断し、試験用正極とした。このときの電極活物質層の厚さは２５μｍであった。
(7) to the prepared powder sample 20.8 parts by weight of the battery, a commercially available conductive carbon black powder (product name HS-100, DBP absorption amount 140cm 3 /100g)1.7 parts, polyvinylidene fluoride powder ( A coating paste was prepared by uniformly mixing 2.5 parts by weight of Kureha Chemical Co., Ltd., # 1300) and 37.5 parts by weight of NMP. The paste was uniformly coated on an aluminum foil (thickness 20 μm) used as a current collector using a coater, and dried at 140 ° C. over 10 minutes. After drying, it was molded into a uniform film thickness with a press machine, and then cut into a predetermined size (20 mm × 15 mm) to obtain a test positive electrode. At this time, the thickness of the electrode active material layer was 25 μm.
上記の試験用正極を用いて試験セルを作製した。負極電極には金属リウチム箔を所定の大きさに切断して使用し、セパレータはセルガード♯２４００（セルガード社製）を使用した。電解液は１ｍｏｌ／ｌのＬｉＰＦ６／エチレンカーボネート（ＥＣ）：ジエチルカーボネート（ＤＥＣ）（ＥＣ：ＤＥＣ＝１：１ｖｏｌ％）を用いた。試験セルの組み立ては、アルゴン雰囲気下のグローブボックス内で行った。試験セルの組み立て後、２５℃にて２４時間放置後、高速放電特性評価を行った。 A test cell was produced using the test positive electrode. A metal lithium foil was cut into a predetermined size for the negative electrode, and Celgard # 2400 (manufactured by Celgard) was used as the separator. As the electrolyte, 1 mol / l LiPF 6 / ethylene carbonate (EC): diethyl carbonate (DEC) (EC: DEC = 1: 1 vol%) was used. The test cell was assembled in a glove box under an argon atmosphere. After the test cell was assembled, it was allowed to stand at 25 ° C. for 24 hours, and then high-speed discharge characteristics were evaluated.
（８）高速放電特性評価
試験セルに０．２Ｃにて定電流充放電を行った後、（１）０．５Ｃで定電流充電した後、１Ｃで定電流放電された放電容量（Ａ）と、さらに（２）０．５Ｃで定電流充電した後、６０Ｃで定電流放電された放電容量（Ｂ）との比を高速放電特性とした。
高速放電特性（％）＝Ｂ／Ａ×１００
(8) Fast discharge characteristics evaluation After performing constant current charge / discharge on the test cell at 0.2C, (1) after charging with constant current at 0.5C, discharge capacity (A) discharged with constant current at 1C Further, (2) the ratio of the discharge capacity (B) discharged at a constant current of 0.5 C and then discharged at a constant current of 60 C was defined as a high-speed discharge characteristic.
High-speed discharge characteristics (%) = B / A × 100
（９）全細孔容積
水銀圧入式細孔分布測定装置（ポアサイザー９３２０、島津製作所製）を用いて、０．００８μｍ〜２００μｍの範囲の細孔容量を測定し、得られた値を全細孔容積とした。
(9) Total pore volume Using a mercury intrusion pore distribution measuring device (pore sizer 9320, manufactured by Shimadzu Corporation), the pore volume in the range of 0.008 μm to 200 μm was measured, and the obtained value was assigned to the total pores. Volume.
（１０）自己凝集性試験
導電性物質２ｇを、エタノール５００ｇに添加し、超音波ホモジナイザー（日本精機製作所製、ＭＯＤＥＬＵＳ−３００Ｔ）を用いて、周波数１９ｋＨｚ、出力３００Ｗで一分間超音波照射を行った後、超音波照射を停止する。停止した直後に約１ｃｃサンプリングし、遅滞なくレーザー回折／散乱式粒度分布測定装置ＬＡ７５０（堀場製作所製）でエタノールを分散媒とし、相対屈折率１．５で超音波照射をせずにサンプリング液の平均粒径（Ａ）を測定する。次に超音波照射を停止してから３分経過後に導電性物質の分散液をサンプリングし、平均粒径（Ａ）と同様の測定条件にて上記ＬＡ７５０で平均粒径（Ｂ）を測定する。平均粒径（Ｂ）を平均粒径（Ａ）で割った値が２以上のものを自己凝集性を有する導電性物質とした。
(10) Self-aggregation test 2 g of conductive material was added to 500 g of ethanol, and ultrasonic irradiation was carried out for 1 minute at a frequency of 19 kHz and an output of 300 W using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, MODELUS-300T). Then, the ultrasonic irradiation is stopped. Immediately after stopping, about 1 cc was sampled, and without delay, the laser diffraction / scattering particle size distribution analyzer LA750 (manufactured by Horiba) used ethanol as the dispersion medium, and the relative refractive index was 1.5 and the sample solution was not irradiated with ultrasonic waves. The average particle size (A) is measured. Next, after 3 minutes have passed since the ultrasonic irradiation was stopped, the conductive material dispersion was sampled, and the average particle size (B) was measured with the LA750 under the same measurement conditions as the average particle size (A). A substance having a value obtained by dividing the average particle diameter (B) by the average particle diameter (A) was 2 or more was defined as a conductive substance having self-aggregation property.
その際の評価結果を表１に示す。 The evaluation results at that time are shown in Table 1.
実施例１
溶媒としてエタノール５００重量部に、導電性物質として繊維径２０ｎｍ、繊維長さ１０μｍ、アスペクト比５００のカーボンナノチューブを２重量部添加し、超音波型分散機を用いて超音波分散（照射時間３分）した。次に平均粒径２μｍ（一次粒子径２５ｎｍ）、ＤＢＰ吸収量１５５ｃｍ３／１００ｇのカーボンブラック（東海カーボン社製、♯５５００）を２重量部加え超音波分散（照射時間１分）した。このカーボン分散液に超音波照射をしながら、正極活物質として粉砕した一次粒子径０．４μｍのマンガン酸リチウム１００重量部を添加し、更に超音波による分散（照射時間２分）を行い、強制分散した状態にした。その後超音波照射をとめて自己凝集を生じさせたのち、エタノールを留去し、正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 1
2 parts by weight of carbon nanotubes having a fiber diameter of 20 nm, a fiber length of 10 μm, and an aspect ratio of 500 as a conductive substance are added to 500 parts by weight of ethanol as a solvent, and ultrasonic dispersion (irradiation time: 3 minutes) using an ultrasonic disperser )did. Then an average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm 3/100 g carbon black (Tokai Carbon Co., ♯5500) of the 2 parts by weight of ultrasonic dispersion (1 minute irradiation time). While ultrasonically irradiating this carbon dispersion, 100 parts by weight of lithium manganate having a primary particle size of 0.4 μm pulverized as a positive electrode active material was added, and further dispersed by ultrasonic waves (irradiation time: 2 minutes). It was in a distributed state. Thereafter, ultrasonic irradiation was stopped to cause self-aggregation, and then ethanol was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
上記において、超音波照射を停止してから１０秒以内にスラリーを２ｃｃサンプリングし、エタノールを加えてスラリーの透過率が９５％になるまで希釈し、遅滞なくレーザー回折／散乱式粒度分布測定装置ＬＡ７５０（堀場製作所製）で平均粒径を測定する。当該平均粒径が、正極活物質の一次粒子径の１３０％以内になったとき、「強制分散した状態」とみなす（以下の実施例も同様）。 In the above, 2 cc of the slurry is sampled within 10 seconds after the ultrasonic irradiation is stopped, ethanol is added to dilute until the transmittance of the slurry becomes 95%, and the laser diffraction / scattering type particle size distribution measuring apparatus LA750 without delay. The average particle size is measured with (Horiba Seisakusho). When the average particle diameter falls within 130% of the primary particle diameter of the positive electrode active material, it is regarded as “forced dispersion state” (the same applies to the following examples).
実施例２
エタノール５００重量部に繊維径２０ｎｍ、繊維長さ１０μｍ、アスペクト比５００のカーボンナノチューブを２重量部添加し、超音波型分散機を用いて超音波分散（照射時間３分）した。次に平均粒径２μｍ（一次粒子径２５ｎｍ）、ＤＢＰ吸収量１５５ｃｍ３／１００ｇのカーボンブラック（東海カーボン社製、♯５５００）を２重量部加え超音波分散（照射時間１分）した。このカーボン分散液に超音波照射をしながら、一次粒子径０．８μｍのマンガン酸リチウム１００重量部を添加し更に超音波による分散（照射時間２分）を行い、強制分散した状態にした。その後超音波照射をとめて自己凝集を生じさせたのち、エタノールを留去し、正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 2
Two parts by weight of carbon nanotubes having a fiber diameter of 20 nm, a fiber length of 10 μm, and an aspect ratio of 500 were added to 500 parts by weight of ethanol, and ultrasonically dispersed (irradiation time: 3 minutes) using an ultrasonic disperser. Then an average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm 3/100 g carbon black (Tokai Carbon Co., ♯5500) of the 2 parts by weight of ultrasonic dispersion (1 minute irradiation time). While ultrasonically irradiating this carbon dispersion, 100 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and further dispersed by ultrasonic waves (irradiation time: 2 minutes) to make a forced dispersion state. Thereafter, ultrasonic irradiation was stopped to cause self-aggregation, and then ethanol was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例３
ＮＭＰ５００重量部に繊維径２０ｎｍ、繊維長さ１０μｍ、アスペクト比５００のカーボンナノチューブを２重量部添加し、超音波型分散機を用いて超音波分散（照射時間３分）した。次に平均粒径２μｍ（一次粒子径２５ｎｍ）、ＤＢＰ吸収量１５５ｃｍ３／１００ｇのカーボンブラック（東海カーボン社製、♯５５００）を２重量部加え超音波分散（照射時間１分）した。このカーボン分散液に超音波照射をしながら、一次粒子径０．８μｍのマンガン酸リチウム１００重量部を添加し更に超音波による分散（照射時間２分）を行い、強制分散した状態にした。その後超音波照射をとめ、ＮＭＰ中でカーボンナノチューブを自己凝集させ、正極用複合材料を含有する分散液を得た。この分散液は、液体のまま、必要な成分を添加して正極の形成に用いることができるが、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 3
2 parts by weight of carbon nanotubes having a fiber diameter of 20 nm, a fiber length of 10 μm, and an aspect ratio of 500 were added to 500 parts by weight of NMP, and subjected to ultrasonic dispersion (irradiation time: 3 minutes) using an ultrasonic disperser. Then an average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm 3/100 g carbon black (Tokai Carbon Co., ♯5500) of the 2 parts by weight of ultrasonic dispersion (1 minute irradiation time). While ultrasonically irradiating this carbon dispersion, 100 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and further dispersed by ultrasonic waves (irradiation time: 2 minutes) to make a forced dispersion state. Thereafter, the ultrasonic irradiation was stopped, and the carbon nanotubes were self-aggregated in NMP to obtain a dispersion containing the composite material for positive electrode. This dispersion liquid can be used for forming a positive electrode by adding necessary components in a liquid state, but for the physical property evaluation, the solvent was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例４
ＮＭＰ５００重量部に平均粒径１０μｍ（一次粒子径３５ｎｍ）、ＤＢＰ吸収量４９５のケッチェンブラックを２重量部添加し、超音波型分散機を用いて超音波分散（照射時間３分）した。次に平均粒径２μｍ（一次粒子径２５ｎｍ）、ＤＢＰ吸収量１５５ｃｍ３／１００ｇのカーボンブラック（東海カーボン社製、♯５５００）を２重量部加え超音波分散（照射時間１分）した。このカーボン分散液に超音波照射をしながら、一次粒子径０．８μｍのマンガン酸リチウム１００重量部を添加し更に超音波による分散（照射時間２分）を行い、強制分散した状態にした。その後超音波照射をとめ、ＮＭＰ中でケッチェンブラックを自己凝集させ、正極用複合材料を含有する分散液を得た。この分散液は、液体のまま、必要な成分を添加して正極の形成に用いることができるが、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 4
2 parts by weight of ketjen black having an average particle diameter of 10 μm (primary particle diameter of 35 nm) and a DBP absorption amount of 495 was added to 500 parts by weight of NMP, and ultrasonic dispersion (irradiation time: 3 minutes) was performed using an ultrasonic disperser. Then an average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm 3/100 g carbon black (Tokai Carbon Co., ♯5500) of the 2 parts by weight of ultrasonic dispersion (1 minute irradiation time). While ultrasonically irradiating this carbon dispersion, 100 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and further dispersed by ultrasonic waves (irradiation time: 2 minutes) to make a forced dispersion state. Thereafter, the ultrasonic irradiation was stopped, and ketjen black was self-aggregated in NMP to obtain a dispersion containing a composite material for positive electrode. This dispersion liquid can be used for forming a positive electrode by adding necessary components in a liquid state, but for the physical property evaluation, the solvent was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例５
ＮＭＰ５００重量部に繊維径１２０ｎｍ、繊維長さ１０μｍ、アスペクト比８３のＶＧＣＦを２重量部添加し、超音波型分散機を用いて超音波分散（照射時間３分）した。次に平均粒径２μｍ（一次粒子径２５ｎｍ）、ＤＢＰ吸収量１５５ｃｍ３／１００ｇのカーボンブラック（東海カーボン社製、♯５５００）を２重量部加え超音波分散（照射時間１分）した。このカーボン分散液に超音波照射をしながら、一次粒子径０．８μｍのマンガン酸リチウム１００重量部を添加し更に超音波による分散（照射時間２分）を行い、強制分散した状態にした。その後超音波照射をとめ、ＮＭＰ中でＶＧＣＦを自己凝集させ、正極用複合材料を含有する分散液を得た。この分散液は、液体のまま、必要な成分を添加した正極の形成に用いることができるが、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 5
2 parts by weight of VGCF having a fiber diameter of 120 nm, a fiber length of 10 μm, and an aspect ratio of 83 were added to 500 parts by weight of NMP, and subjected to ultrasonic dispersion (irradiation time: 3 minutes) using an ultrasonic disperser. Then an average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm 3/100 g carbon black (Tokai Carbon Co., ♯5500) of the 2 parts by weight of ultrasonic dispersion (1 minute irradiation time). While ultrasonically irradiating this carbon dispersion, 100 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and further dispersed by ultrasonic waves (irradiation time: 2 minutes) to make a forced dispersion state. Thereafter, the ultrasonic wave irradiation was stopped, and VGCF was self-aggregated in NMP to obtain a dispersion containing a composite material for positive electrode. This dispersion liquid can be used for forming a positive electrode to which a necessary component is added as a liquid, but a solvent is distilled off for physical property evaluation to obtain a composite material for a positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例６
実施例４において、ケッチェンブラックの添加量を４重量部とし、追加のカーボンブラックを添加しないこと以外は、実施例４と同じ条件で正極用複合材料を含有する分散液を得た後、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 6
In Example 4, the dispersion amount containing the composite material for positive electrode was obtained under the same conditions as in Example 4 except that the amount of ketjen black added was 4 parts by weight and no additional carbon black was added. For evaluation, the solvent was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例７
実施例４において、カーボン分散液に添加するマンガン酸リチウムとして、一次粒子径が０．５μｍのものを用いたこと以外は、実施例４と同じ条件で正極用複合材料を含有する分散液を得た後、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 7
In Example 4, a dispersion containing the composite material for positive electrode was obtained under the same conditions as in Example 4 except that lithium manganate added to the carbon dispersion was used with a primary particle size of 0.5 μm. Then, the solvent was distilled off for physical property evaluation to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例８
実施例４において、カーボン分散液に添加するマンガン酸リチウムとして、一次粒子径が１．２μｍのものを用いたこと以外は、実施例４と同じ条件で正極用複合材料を含有する分散液を得た後、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 8
In Example 4, a dispersion containing the composite material for positive electrode was obtained under the same conditions as in Example 4 except that lithium manganate added to the carbon dispersion was used with a primary particle diameter of 1.2 μm. Then, the solvent was distilled off for physical property evaluation to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例９
実施例８において、ケッチェンブラックの代わりにＦＸ−３５（電気化学工業社製カーボンブラック）を用いたこと以外は、実施例８と同じ条件で正極用複合材料を含有する分散液を得た後、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 9
In Example 8, after obtaining a dispersion containing the composite material for positive electrode under the same conditions as in Example 8 except that FX-35 (Carbon Black manufactured by Denki Kagaku Kogyo Co., Ltd.) was used instead of Ketjen Black. In order to evaluate the physical properties, the solvent was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例１０
実施例８において、ケッチェンブラックの代わりに＃３０５０Ｂ（東海カーボン社製カーボンブラック）を用いたこと以外は、実施例８と同じ条件で正極用複合材料を含有する分散液を得た後、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 10
In Example 8, except that # 3050B (carbon black manufactured by Tokai Carbon Co., Ltd.) was used instead of ketjen black, a dispersion containing the positive electrode composite material was obtained under the same conditions as in Example 8, and then physical properties were obtained. For evaluation, the solvent was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
実施例１１
実施例４において、カーボン分散液に添加するマンガン酸リチウムとして、一次粒子径が１０μｍのものを用いたこと以外は、実施例４と同じ条件で正極用複合材料を含有する分散液を得た後、物性評価のために溶媒を留去して正極用複合材料を得た。得られた正極用複合材料の物性を表２に示す。
Example 11
In Example 4, after obtaining a dispersion containing the positive electrode composite material under the same conditions as in Example 4 except that lithium manganate added to the carbon dispersion was used with a primary particle diameter of 10 μm. In order to evaluate the physical properties, the solvent was distilled off to obtain a composite material for positive electrode. Table 2 shows the physical properties of the obtained composite material for positive electrode.
比較例１
一次粒子径０．８μｍのマンガン酸リチウム１００重量部に対して、平均粒径１μｍ（一次粒子径５０ｎｍ）、ＤＢＰ吸収量１４０ｃｍ３／１００ｇのカーボンブラック（電気化学工業社製、ＨＳ−１００）４重量部を乾式混合し、比較正極材料を得た。得られた材料の物性を表２に示す。
Comparative Example 1
To the primary particle diameter 0.8μm lithium 100 parts by weight of manganese oxide, the average particle diameter of 1 [mu] m (primary particle diameter 50 nm), DBP absorption 140cm 3/100 g of carbon black (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100) of 4 The weight parts were dry mixed to obtain a comparative positive electrode material. Table 2 shows the physical properties of the obtained material.
比較例２
一次粒子径０．８μｍのマンガン酸リチウム１００重量部に対して、平均粒径２μｍ（一次粒子径５０ｎｍ）、ＤＢＰ吸収量１５５ｃｍ３／１００ｇのカーボンブラック（東海カーボン社製、♯５５００）を２重量部、平均粒径１０μｍ（一次粒子径３５ｎｍ）、ＤＢＰ吸収量４９５のケッチェンブラック２重量部を乾式混合し、比較正極材料を得た。得られた材料の物性を表２に示す。
Comparative Example 2
To the primary particle diameter 0.8μm lithium 100 parts by weight of manganese oxide, the average particle diameter of 2 [mu] m (primary particle diameter 50 nm), DBP absorption 155cm 3/100 g carbon black (Tokai Carbon Co., ♯5500) of 2wt Parts, an average particle diameter of 10 μm (primary particle diameter of 35 nm), and 2 parts by weight of ketjen black having a DBP absorption of 495 were dry-mixed to obtain a comparative positive electrode material. Table 2 shows the physical properties of the obtained material.
比較例３
一次粒子径０．８μｍのマンガン酸リチウム１００重量部に対して、平均粒径２μｍ（一次粒子径２５ｎｍ）、ＤＢＰ吸収量１５５ｃｍ３／１００ｇのカーボンブラック（東海カーボン社製、♯５５００）を２重量部、繊維径２０ｎｍ、繊維長さ１０μｍのアスペクト比５００のカーボンナノチューブ２重量部を乾式混合し、比較正極材料を得た。得られた材料の物性を表２に示す。
Comparative Example 3
To the primary particle diameter 0.8μm lithium 100 parts by weight of manganese oxide, the average particle diameter of 2 [mu] m (primary particle size 25 nm), DBP absorption 155cm 3/100 g carbon black (Tokai Carbon Co., ♯5500) of 2wt 2 parts by weight of carbon nanotubes with an aspect ratio of 500 having a fiber diameter of 20 nm and a fiber length of 10 μm were dry-mixed to obtain a comparative positive electrode material. Table 2 shows the physical properties of the obtained material.
表２の結果が示すように、溶媒中で自己凝集性を有する導電性物質で正極活物質を包含させた実施例の複合材料は、導電性物質と正極活物質を乾式混合したものよりも、低い体積抵抗率でかつ、高い細孔容積を有し、優れた高速放電特性を有している。 As shown in the results of Table 2, the composite material of the example in which the positive electrode active material is included in the conductive material having self-aggregation property in the solvent is more than the dry mixture of the conductive material and the positive electrode active material. It has a low volume resistivity, a high pore volume, and excellent fast discharge characteristics.
一方、図１は、実施例１で得られた正極用複合材料の走査型電子顕微鏡写真を示している。この写真のように、本発明で得られる正極用複合材料は、凝集後に導電性物質（写真中で一次粒子が小さく見えるもの）が正極活物質（写真中で一次粒子が大きく見えるもの）を包み込むような微細複合構造を有している。また、比較例とくらべて全細孔容積が大きいことから、適度な空隙を有する微細複合構造であると考えられる。 On the other hand, FIG. 1 shows a scanning electron micrograph of the composite material for positive electrode obtained in Example 1. As shown in this photograph, in the composite material for positive electrode obtained in the present invention, after aggregation, the conductive material (the primary particles appear to be small in the photograph) wraps the positive electrode active material (the primary particles appear to be large in the photograph). It has such a fine composite structure. Moreover, since the total pore volume is large compared with the comparative example, it is considered that it is a fine composite structure having appropriate voids.
Claims (8)
少なくとも溶媒中で自己凝集性を有する導電性物質及び正極活物質を、溶媒中に分散させて強制分散した状態とする分散工程と、
前記導電性物質を前記正極活物質と共に溶媒中で凝集させて凝集粒子を得る凝集工程とを含み、
前記自己凝集性を有する導電性物質は、当該導電性物質２ｇを、エタノール５００ｇに添加し、超音波ホモジナイザーを用いて、周波数１９ｋＨｚ、出力３００Ｗで一分間超音波照射を行った後、超音波照射を停止し、直後に前記導電性物質の分散液をサンプリングし、遅滞なくレーザー回折／散乱式粒度分布測定装置でエタノールを分散媒とし、相対屈折率１．５で超音波照射をせずにサンプリング液の平均粒径（Ａ）を測定し、次に超音波照射を停止してから３分経過後に前記導電性物質の分散液をサンプリングし、前記平均粒径（Ａ）と同様の測定条件にて前記レーザー回折／散乱式粒度分布測定装置で平均粒径（Ｂ）を測定し、前記平均粒径（Ｂ）を前記平均粒径（Ａ）で割った値が、２以上であるリチウム電池正極用複合材料の製造方法。 A method for producing a positive electrode active material, and a composite material for a lithium battery positive electrode containing a conductive material,
A dispersion step in which a conductive material having a self-aggregating property and a positive electrode active material at least in a solvent are dispersed in a solvent and forcedly dispersed; and
The conductive material is coagulated in a solvent together with the positive electrode active material observed including the aggregation step of obtaining aggregated particles,
The conductive substance having self-aggregation property is obtained by adding 2 g of the conductive substance to 500 g of ethanol, and performing ultrasonic irradiation for 1 minute at a frequency of 19 kHz and an output of 300 W using an ultrasonic homogenizer. Immediately after that, the dispersion liquid of the conductive material is sampled, and ethanol is used as a dispersion medium with a laser diffraction / scattering particle size distribution measurement device without delay, and sampling is performed without irradiating ultrasonic waves with a relative refractive index of 1.5. The average particle size (A) of the liquid is measured, and then the dispersion of the conductive material is sampled after 3 minutes from the termination of ultrasonic irradiation, and the measurement conditions are the same as the average particle size (A). The average particle diameter (B) is measured with the laser diffraction / scattering particle size distribution analyzer, and the value obtained by dividing the average particle diameter (B) by the average particle diameter (A) is 2 or more. Of composite materials Method.
少なくとも、ＤＢＰ吸収量が２００〜８００ｃｍ３／１００ｇであるカーボンブラック及び／又はアスペクト比が５０〜１０００の繊維状カーボンを含有する導電性物質及び正極活物質を溶媒中に分散させて強制分散した状態とする分散工程と、
前記導電性物質を前記正極活物質と共に溶媒中で凝集させて凝集粒子を得る凝集工程とを含むリチウム電池正極用複合材料の製造方法。 A method for producing a positive electrode active material, and a composite material for a lithium battery positive electrode containing a conductive material,
At least, a state where DBP absorption 200~800cm 3 / 100g carbon black and / or aspect ratio is that the conductive material and positive electrode active material containing a fibrous carbon 50-1000 forced dispersion is dispersed in a solvent And a dispersion process
A method for producing a composite material for a lithium battery positive electrode, comprising: an aggregating step of aggregating the conductive material together with the positive electrode active material in a solvent to obtain aggregated particles.
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| EP2765633A1 (en) | 2013-02-12 | 2014-08-13 | Jtekt Corporation | Production apparatus and production method for electric storage material |
| US9662806B2 (en) | 2014-02-26 | 2017-05-30 | Jtekt Corporation | Kneading device |
| US10374217B2 (en) | 2014-02-26 | 2019-08-06 | Jtekt Corporation | Apparatus and process for producing electricity storage material |
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| JP5334506B2 (en) * | 2008-09-08 | 2013-11-06 | 花王株式会社 | Method for producing composition for positive electrode of non-aqueous electrolyte secondary battery |
| CN102142296B (en) * | 2010-05-28 | 2012-07-04 | 南京理工大学 | Preparation method of graphene-loaded nanometre cobalt hydroxide (Co(OH)2) composite material |
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| EP2765633A1 (en) | 2013-02-12 | 2014-08-13 | Jtekt Corporation | Production apparatus and production method for electric storage material |
| US9531007B2 (en) | 2013-02-12 | 2016-12-27 | Jtekt Corporation | Production apparatus and production method for electric storage material |
| US9662806B2 (en) | 2014-02-26 | 2017-05-30 | Jtekt Corporation | Kneading device |
| US10374217B2 (en) | 2014-02-26 | 2019-08-06 | Jtekt Corporation | Apparatus and process for producing electricity storage material |
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