JP4102848B2 - Method for producing composite material for positive electrode of lithium battery - Google Patents
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- JP4102848B2 JP4102848B2 JP2007169148A JP2007169148A JP4102848B2 JP 4102848 B2 JP4102848 B2 JP 4102848B2 JP 2007169148 A JP2007169148 A JP 2007169148A JP 2007169148 A JP2007169148 A JP 2007169148A JP 4102848 B2 JP4102848 B2 JP 4102848B2
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- 239000002131 composite material Substances 0.000 title claims description 66
- 238000004519 manufacturing process Methods 0.000 title claims description 32
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims description 24
- 229910052744 lithium Inorganic materials 0.000 title claims description 24
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- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 18
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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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率１５％以上で被覆した正極材料が提案されている。また、これを用いて正極を作製する際に、粒径１〜２０μｍの黒鉛（グラファイト）を添加することが開示されている。 For these reasons, several attempts have been made to improve the fine composite structure related to the positive electrode. For example, Patent Document 1 discloses a positive electrode material in which a positive electrode active material and a conductive material are mixed and a surface of the positive electrode active material is coated at a coverage of 15% or more by a dry method of applying compressive shear stress. Proposed. Further, it is disclosed that graphite having a particle diameter of 1 to 20 μm is added when a positive electrode is produced using this.
また、特許文献２では、炭素繊維を正極活物質に添加して導電経路を改善する試みがなされている。 In Patent Document 2, an attempt is made to improve the conductive path by adding carbon fiber to the positive electrode active material.
更に、特許文献３では、カーボンブラックと炭素繊維の両者を正極活物質に添加・混合した複合材料で形成された正極が提案されている。 Further, Patent Document 3 proposes a positive electrode formed of a composite material obtained by adding and mixing both carbon black and carbon fiber to a positive electrode active material.
しかしながら、特許文献１に開示される正極材料では、被覆率の制御が困難であり、導電性物質が正極活物質の表面に緻密に被覆され易いため、Ｌｉイオンの経路が遮断され、その結果、高速放電性能が向上しにくくなる。また、被覆により正極活物質の導電性は向上するものの、得られる正極の導電性は十分とは言えず、黒鉛を併用した場合でも、導電性の改善効果はさほど大きくないことが判明した。 However, in the positive electrode material disclosed in Patent Document 1, it is difficult to control the coverage, and the conductive material is likely to be densely coated on the surface of the positive electrode active material, so that the Li ion path is blocked. High-speed discharge performance is difficult to improve. Moreover, although the electroconductivity of the positive electrode active material is improved by the coating, the electroconductivity of the positive electrode obtained is not sufficient, and it has been found that the effect of improving the electroconductivity is not so great even when graphite is used in combination.
また、特許文献２に記載される炭素繊維は、一般に正極活物質との接触効率が悪いことから、正極の導電性等に関して十分な性能が得られない。 Moreover, since the carbon fiber described in Patent Document 2 generally has poor contact efficiency with the positive electrode active material, sufficient performance cannot be obtained with respect to the conductivity of the positive electrode.
更に、特許文献３に開示される正極は、カーボンブラック、炭素繊維、正極活物質、バインダを乾式混合した後に、溶媒を添加して溶媒に分散したスラリーを用いて形成されるため、正極活物質と導電性物質が必ずしも適切な配置をもった微細複合構造を形成できず、得られる正極は、高速放電性能に関して、十分な性能を発現しないことが判明した。 Furthermore, since the positive electrode disclosed in Patent Document 3 is formed using a slurry in which carbon black, carbon fiber, a positive electrode active material, and a binder are dry mixed and then a solvent is added and dispersed in the solvent, the positive electrode active material It has been found that the fine composite structure in which the conductive material and the conductive material are not properly arranged cannot be formed, and the obtained positive electrode does not exhibit sufficient performance with respect to the high-speed discharge performance.
そこで、本発明の目的は、特に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。 Accordingly, an object of the present invention is to provide a method for producing a composite material for a lithium battery positive electrode that is particularly excellent in high-speed discharge performance of a battery.
本発明者らは、上記目的を達成すべく、正極の形成に用いる正極用複合材料の微細複合構造について鋭意研究したところ、正極活物質と導電性物質とが強制分散したスラリーの溶媒を除去して得られた複合粒子に、特定のアスペクト比を有する導電性物質を混合することによって、正極で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微細複合構造が得られ、特に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。 In order to achieve the above object, the present inventors have intensively studied the fine composite structure of the positive electrode composite material used for forming the positive electrode, and have removed the solvent of the slurry in which the positive electrode active material and the conductive material are forcibly dispersed. By mixing the obtained composite particles with a conductive material having a specific aspect ratio, a fine composite structure that can move electrons and lithium ions smoothly at the positive electrode can be obtained. The inventors have found that the performance is improved and have completed the present invention.
即ち、本発明のリチウム電池正極用複合材料の第１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、溶媒中で、少なくとも正極活物質と導電性物質１とが、強制分散した状態まで分散して得られるスラリーから溶媒を除去して、前記正極活物質と前記導電性物質１とを含有する複合粒子を得る複合粒子化工程と、少なくとも、前記複合粒子、及びアスペクト比が２〜１０の導電性物質２を混合する混合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。 That is, a first method for producing a composite material for a lithium battery positive electrode according to 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 a positive electrode active material in a solvent. A composite particle forming step of obtaining a composite particle containing the positive electrode active material and the conductive material 1 by removing the solvent from the slurry obtained by dispersing the material and the conductive material 1 to a state where the material and the conductive material 1 are forcibly dispersed; And at least a mixing step of mixing the composite particles and the conductive material 2 having an aspect ratio of 2 to 10. In addition, the various physical-property values in this invention are values specifically measured by the method as described in an Example.
また、本発明のリチウム電池正極用複合材料の第２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、溶媒中で、少なくとも正極活物質と導電性物質１とが、強制分散した状態まで分散して得られるスラリーから溶媒を除去して、前記正極活物質と前記導電性物質１とを含有する複合粒子を得る複合粒子化工程と、少なくとも、前記複合粒子、及びＤＢＰ吸収量１００〜５００ｃｍ３／１００ｇの導電性物質２を混合する混合工程とを含むものである。 A second method for producing a composite material for a lithium battery positive electrode according to 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 a positive electrode active material in a solvent. A composite particle forming step of obtaining a composite particle containing the positive electrode active material and the conductive material 1 by removing the solvent from the slurry obtained by dispersing the material and the conductive material 1 to a state where the material and the conductive material 1 are forcibly dispersed; at least said those containing composite particles, and a mixing step of mixing a DBP absorption 100~500cm 3 / 100g of conductive material 2.
本発明の製造方法によると、正極活物質と導電性物質が分散したスラリーの溶媒を除去して得られた複合粒子に、特定のアスペクト比を有する導電性物質を混合することによって、正極活物質の表面に導電性物質が確実に付着（部分的に被着）し、その複合粒子間に特定のアスペクト比を有する導電性物質が介在する微細複合構造を呈すると考えられる。このため、付着した導電性物質を介して正極活物質の表面に電子が十分導電され、導電性が向上する。また、正極活物質の表面への付着量をコントロールすることができ、特定のアスペクト比を有する導電性物質が介在することによって、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になると考えられる。その結果、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と考えられる。 According to the manufacturing method of the present invention, the positive electrode active material is mixed with the composite particles obtained by removing the solvent of the slurry in which the positive electrode active material and the conductive material are dispersed, by mixing the conductive material having a specific aspect ratio. It is considered that the conductive material adheres (partially adheres) to the surface of the film and exhibits a fine composite structure in which a conductive material having a specific aspect ratio is interposed between the composite particles. For this reason, electrons are sufficiently conducted to the surface of the positive electrode active material through the attached conductive material, and the conductivity is improved. In addition, the amount of positive electrode active material adhering to the surface can be controlled, and by interposing a conductive material having a specific aspect ratio, the penetration of the electrolyte is smooth and the structure has excellent Li ion ion diffusion. It is considered to be. As a result, it is considered that a higher current can be passed during discharge than in a conventional Li ion secondary battery, and a Li ion battery excellent in high-speed discharge characteristics 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。
本発明の第１の製造方法（以下、「本発明の製造方法」ともいう）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。
Hereinafter, embodiments of the present invention will be described in detail.
The first production method of the present invention (hereinafter also referred to as “the production method 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. The material can be used for manufacturing a positive electrode such as a lithium ion secondary battery.
本発明の製造方法は、溶媒中で少なくとも正極活物質と導電性物質１とが強制分散した状態まで分散して得られるスラリーから溶媒を除去して、前記正極活物質と前記導電性物質１とを含有する複合粒子を得る複合粒子化工程を含むものである。本発明の製造方法で使用する導電性物質１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 removes the solvent from the slurry obtained by dispersing until at least the positive electrode active material and the conductive material 1 are forcibly dispersed in the solvent, and the positive electrode active material, the conductive material 1 and And a composite particle forming step for obtaining composite particles containing. The conductive material 1 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 considered that the particles are dispersed to a state close to unit particles by forced dispersion with ultrasonic waves having an output of 100 to 500 W. This unit particle is referred to as “primary particle” in the present invention.
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。 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.
導電性物質１、正極活物質などの強制分散を行う際、導電性物質１と正極活物質とを溶媒中に添加して、同時に強制分散させるものでもよいが、導電性物質１又は正極活物質の一方を溶媒中に添加して強制分散させた後、これに他方を添加してさらに強制分散させるものでもよい。また、導電性物質１が強制分散したスラリーを得るために、湿式粉砕等の粉砕工程を別途又は強制分散と同時に実施してもよい。 In conducting forced dispersion of the conductive material 1, the positive electrode active material, etc., the conductive material 1 and the positive electrode active material may be added to a solvent and forcedly dispersed at the same time. One of the above may be added to a solvent and forcedly dispersed, and then the other may be added and further forcedly dispersed. Further, in order to obtain a slurry in which the conductive material 1 is forcibly dispersed, a pulverization step such as wet pulverization may be performed separately or simultaneously with the forced dispersion.
導電性物質１としては、炭素質材料が好ましく、例えば、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の繊維状カーボンなどが挙げられる。なかでも、強制分散後の正極活物質への付着性、接触性、若しくは導電性などの観点から、カーボンブラックが好ましい。 The conductive substance 1 is preferably a carbonaceous material, and examples thereof include fibrous carbon such as carbon black, carbon fiber, and carbon nanotube. Among these, carbon black is preferable from the viewpoint of adhesion to the positive electrode active material after forced dispersion, contact property, conductivity, and the like.
導電性物質１として用いる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が好ましく用いられる。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。 Carbon black used as the conductive material 1 includes incomplete combustion methods such as 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. Any of these methods can be used, but furnace black and acetylene black are preferably used from the viewpoint of conductivity. These may be used alone or in combination of two or more.
正極活物質の表面に導電性物質１を効果的に付着させるには、導電性物質１の一次粒子径が正極活物質の一次粒子径より小さいことが好ましく、正極活物質の一次粒子径の１／５以下が好ましく、１／１０以下がより好ましく、１／１５以下が更に好ましい。特に、カーボンブラックを用いる場合、その一次粒子径が、正極活物質の一次粒子径の１／５以下が好ましく、１／１０以下がより好ましく、１／１５以下が更に好ましい。 In order to effectively attach the conductive material 1 to the surface of the positive electrode active material, the primary particle size of the conductive material 1 is preferably smaller than the primary particle size of the positive electrode active material. / 5 or less is preferable, 1/10 or less is more preferable, and 1/15 or less is still more preferable. In particular, when carbon black is used, the primary particle diameter is preferably 1/5 or less, more preferably 1/10 or less, and even more preferably 1/15 or less of the primary particle diameter of the positive electrode active material.
また、導電性物質１、好ましくはカーボンブラックの一次粒子径は、強制分散のしやすさと正極活物質への付着性の観点から、好ましくは１０〜１００ｎｍ、より好ましくは１５〜８０ｎｍ、さらに好ましくは２０〜５０ｎｍである。このような一次粒子径のカーボンブラックは、微粒子化されることで、正極活物質の表面により確実に付着させることができ、体積抵抗率をより低減することができる。 The primary particle size of the conductive material 1, preferably carbon black, is preferably 10 to 100 nm, more preferably 15 to 80 nm, and still more preferably from the viewpoint of ease of forced dispersion and adhesion to the positive electrode active material. 20-50 nm. Carbon black having such a primary particle diameter can be more reliably attached to the surface of the positive electrode active material by being finely divided, and the volume resistivity can be further reduced.
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.
導電性物質１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０．２〜８重量部が好ましい。即ち、正極材料の体積抵抗の低減の観点から、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８重量部以下、より好ましくは５重量部以下、更に好ましくは３重量部以下である。 As content of the electroconductive substance 1, 0.2-8 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 reducing the volume resistance 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 or more with respect to 100 parts by weight of the positive electrode active material. It is. Moreover, from a viewpoint of the coating | cover property to the positive electrode active material surface, Preferably it is 8 weight part or less, More preferably, it is 5 weight part or less, More preferably, it is 3 weight part 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、正極活物質の安全性や安定性、サイクル特性、反応性、高速放電性の観点から、好ましくは０．５〜１０μｍ、より好ましくは０．６〜５μｍ、さらに好ましくは、０．７〜２μｍである。 The primary particle size of the positive electrode active material is preferably 0.5 to 10 μm, more preferably 0.6 to 5 μm, from the viewpoints of safety and stability of the positive electrode active material, cycle characteristics, reactivity, and fast discharge properties. Preferably, it is 0.7-2 micrometers.
分散に用いる溶媒としては、種々の溶媒を用いることができるが、溶媒の沸点は、乾燥の容易さの観点から、好ましくは１００℃以下、より好ましくは９０℃以下、さらに好ましくは８０℃以下である。このような溶媒の具体的なものとして、水、エタノール、アセトン、メチルエチルケトン、トルエン、テトラヒドロフランなどが例示される。このうち、乾燥の容易さやハンドリング性の観点から、エタノールやメチルエチルケトンが好ましい。 As the solvent used for dispersion, various solvents can be used, and the boiling point of the solvent is preferably 100 ° C. or less, more preferably 90 ° C. or less, and still more preferably 80 ° C. or less, from the viewpoint of ease of drying. is there. Specific examples of such a solvent include water, ethanol, acetone, methyl ethyl ketone, toluene, and tetrahydrofuran. Among these, ethanol and methyl ethyl ketone are preferable from the viewpoint of easy drying and handling properties.
溶媒の使用量は、以下の観点から正極活物質１００重量部に対して５０〜１０００重量部が好ましい。即ち、導電性物質１、正極活物質などを効果的に分散させる観点から、正極活物質１００重量部に対して、５０重量部以上が好ましく、１００重量部以上がより好ましい。また、溶媒の乾燥の煩雑さなどの観点から、１０００重量部以下が好ましく、８００重量部以下がより好ましい。 The amount of the solvent used is preferably 50 to 1000 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 dispersing the conductive material 1 and the positive electrode active material, the amount is preferably 50 parts by weight or more, more preferably 100 parts by weight or more with respect to 100 parts by weight of the positive electrode active material. Moreover, 1000 weight part or less is preferable from viewpoints of the complexity of drying of a solvent, etc., and 800 weight part or less is more preferable.
導電性物質１および正極活物質を強制分散させる方法としては、溶媒中で分散機により強制分散させる方法や、分散剤により分散させる方法、両者を併用する方法などが用いられる。特に、導電性物質１が強制分散したスラリーを効果的に得るためには、粉砕作用（カーボンブラックの場合は一次粒子化）を伴う分散機を用いるのが好ましい。 As a method for forcibly dispersing the conductive material 1 and the positive electrode active material, a method for forcibly dispersing in a solvent by a disperser, a method for dispersing by a dispersing agent, a method for using both in combination, and the like are used. In particular, in order to effectively obtain a slurry in which the conductive material 1 is forcibly dispersed, it is preferable to use a disperser with a pulverizing action (in the case of carbon black, primary particles).
また、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く、導電性物質１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。このような分散状態は、例えば、走査型電子顕微鏡（ＳＥＭ）を用いて、得られた正極用複合材料を観察する際に、正極活物質の表面に付着した導電性物質の一次粒子の数をカウント（例えば正極活物質の1個の粒子に対して平均値で１０個以上の一次粒子が観察される）することによって、確認することができる。 In the forced dispersion state, the positive electrode active material is preferably dispersed to primary particles, and the conductive material 1 is also preferably dispersed to primary particles or a state close to primary particles. For example, when the obtained composite material for a positive electrode is observed using a scanning electron microscope (SEM), such a dispersed state indicates the number of primary particles of the conductive material attached to the surface of the positive electrode active material. This can be confirmed by counting (for example, 10 or more primary particles are observed in average for one particle of the positive electrode active material).
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。また、粉砕作用を伴う分散機としては、ミル型分散機が好適に用いられる。なお、予め湿式粉砕や乾式粉砕によって、導電性物質１を調製し、これを溶媒に分散させてもよい。 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. A mill type disperser is preferably used as a disperser with a pulverizing action. Note that the conductive substance 1 may be prepared in advance by wet pulverization or dry pulverization and dispersed in a solvent.
分散剤を使用する方法は、特に導電性物質１を好適に分散させるのに有効である。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。 The method using the dispersant is particularly effective for suitably dispersing the conductive material 1. 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。 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.
ポリアミン系高分子分散剤としてはポリアルキレンアミン、ポリアリルアミンやN,N-ジメチルアミノエチルメタクリレートなどのポリアミンにポリエステルをグラフトさせたくし型ポリマー等を挙げることができる。 Examples of the polyamine polymer dispersant include comb polymers in which a polyester is grafted to a polyamine such as polyalkyleneamine, polyallylamine, and N, N-dimethylaminoethyl methacrylate.
ポリカルボン酸系高分子分散剤としては（メタ）アクリル酸と（メタ）アクリル酸エステルとの共重合体、無水マレイン酸共重合体とアルキルアミンなどの各種アミンやアルコールのアミド化およびエステル化物、およびポリ（メタ）アクリル酸共重合体などのポリカルボン酸のポリエステルやポリアルキレングリコールをグラフトさせたくし型ポリマー等を挙げることができる。なお、本明細書において、（メタ）アクリル酸は、アクリル酸又はメタクリル酸を指す。 Examples of polycarboxylic acid-based polymer dispersants include copolymers of (meth) acrylic acid and (meth) acrylic acid esters, various amines such as maleic anhydride copolymer and alkylamine, and amidated and esterified products of alcohols, Examples thereof include polycarboxylic acid polyesters such as poly (meth) acrylic acid copolymers and comb polymers grafted with polyalkylene glycol. In the present specification, (meth) acrylic acid refers to acrylic acid or methacrylic acid.
分子内に複数のアミド基を有する高分子分散剤としては縮合反応によって得られるポリアミドやポリビニルピロリドンやポリN,N-ジメチルアクリルアミドの共重合体やこれにポリエステルやポリアルキレングリコールをグラフトさせたくし型ポリマー等を挙げることができる。 Polymer dispersants with multiple amide groups in the molecule include polyamides obtained by condensation reactions, polyvinylpyrrolidone, poly N, N-dimethylacrylamide copolymers, and comb polymers in which polyesters or polyalkylene glycols are grafted. Etc.
多環式芳香族化合物を含有する高分子分散剤としてはピレンやキナクリドン骨格を有するビニルモノマーと各種モノマーとの共重合体を挙げることが出来る。以上の分散剤は単独で、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。 Examples of the polymer dispersant containing a polycyclic aromatic compound include copolymers of vinyl monomers having a pyrene or quinacridone skeleton and various monomers. The above dispersants can be used alone or in admixture of two or more dispersants.
分散剤を使用する場合、分散剤の添加量は、分散を好適に行う観点から、分散対象物（本発明では正極活物質＋導電性物質１）１００重量部に対して、０．１〜２０重量部が好ましく、０．５〜１０重量部がより好ましい。 In the case of using a dispersant, the amount of the dispersant added is 0.1 to 20 with respect to 100 parts by weight of the object to be dispersed (positive electrode active material + conductive material 1 in the present invention) from the viewpoint of suitably dispersing. Part by weight is preferable, and 0.5 to 10 parts by weight is more preferable.
本発明における複合粒子化工程は、上記のような分散によって得られたスラリーから溶媒を除去して複合粒子を得るものである。スラリーからの溶媒の除去は、加熱蒸発、減圧留去、スプレードライ、凍結乾燥などによって行うことができる。 In the composite particle forming step in the present invention, the solvent is removed from the slurry obtained by the dispersion as described above to obtain composite particles. The removal of the solvent from the slurry can be performed by heat evaporation, distillation under reduced pressure, spray drying, freeze drying, or the like.
このようにして得られた複合粒子は、導電性物質１が正極活物質に付着した構造となるが、導電性物質１による正極活物質表面に対する被覆率は、導電性物質１と正極活物質の含有量比、粒子のサイズ比などによって、容易にコントロールすることができる。この被覆率は、体積抵抗率を低減させる観点から、好ましくは５％以上、より好ましくは１０％以上であり、リチウムイオンの拡散経路を好適に確保する観点から、８０％以下が好ましく、７０％以下がより好ましい。 The composite particles thus obtained have a structure in which the conductive material 1 adheres to the positive electrode active material. The coverage of the conductive material 1 on the surface of the positive electrode active material is determined by the ratio between the conductive material 1 and the positive electrode active material. It can be easily controlled by the content ratio, the particle size ratio, and the like. This coverage is preferably 5% or more, more preferably 10% or more from the viewpoint of reducing the volume resistivity, and preferably 80% or less, preferably 70% from the viewpoint of suitably securing a lithium ion diffusion path. The following is more preferable.
更に、本発明の製造方法は、少なくとも、以上のような複合粒子、及びアスペクト比が２〜１０の導電性物質２を混合する混合工程を含むものである。この工程によって、導電性物質１が正極活物質に付着した複合粒子間に、アスペクト比が２〜１０の導電性物質２が介在する微細複合構造となる。従って、この混合工程では、複合粒子の構造をできるだけ維持可能な混合方法を採用することが好ましい。 Furthermore, the production method of the present invention includes at least a mixing step of mixing the composite particles as described above and the conductive material 2 having an aspect ratio of 2 to 10. By this step, a fine composite structure in which the conductive material 2 having an aspect ratio of 2 to 10 is interposed between the composite particles in which the conductive material 1 is attached to the positive electrode active material. Therefore, in this mixing step, it is preferable to employ a mixing method that can maintain the structure of the composite particles as much as possible.
混合方法としては、湿式混合、乾式混合のいずれの方法でも可能であるが、均一混合の観点から湿式混合が好ましい。乾式混合としては、Ｖ型混合機、リボン型混合機などの粉体混合機や、ニーダーやヘンシェルミキサーなどの混合機を使用できる。また、湿式混合としては、バタフライ型、錨型、リボン型、枠型などの撹拌板で混合する構造の撹拌型混合機や、ハイスピードディスパーサーやホモミキサーなどの混合装置が使用できる。 As a mixing method, either wet mixing or dry mixing is possible, but wet mixing is preferable from the viewpoint of uniform mixing. As dry mixing, a powder mixer such as a V-type mixer or a ribbon-type mixer, or a mixer such as a kneader or a Henschel mixer can be used. In addition, as the wet mixing, a stirring type mixer having a structure in which mixing is performed with a stirring plate such as a butterfly type, a bowl type, a ribbon type, or a frame type, or a mixing device such as a high speed disperser or a homomixer can be used.
アスペクト比が２〜１０の導電性物質２としては、ストラクチャ構造を有するカーボンブラックが好ましい。このような範囲のアスペクト比を持つカーボンブラックは、ストラクチャ構造の発達によりＬｉイオンの拡散のための空隙を好適に形成できると共に、複合粒子間に介在して、好適に導電経路を形成することができると考えられる。 As the conductive material 2 having an aspect ratio of 2 to 10, carbon black having a structure structure is preferable. Carbon black having an aspect ratio in such a range can suitably form voids for the diffusion of Li ions due to the development of the structure structure, and can form a conductive path between the composite particles. It is considered possible.
このようなカーボンブラックとしては、次のようなものが使用できる。カーボンブラックは、一次粒子が数珠繋ぎになった不規則な鎖状に枝分かれした凝集構造を呈している場合がある。走査型電子顕微鏡でこのような粒子を観察した際に、最長径（Ｌ）と最短径（Ｗ）のアスペクト比、すなわちＬ／Ｗが重要になる。 The following can be used as such carbon black. Carbon black may have an agglomerated structure in which the primary particles are branched in an irregular chain in which a number of primary particles are connected. When such particles are observed with a scanning electron microscope, the aspect ratio of the longest diameter (L) and the shortest diameter (W), that is, L / W becomes important.
導電性物質２のアスペクト比は、正極用複合材料の導電性の観点から、２以上、好ましくは３以上、より好ましくは３．５以上であり、リチウムイオンの拡散経路を確保する観点から、１０以下、好ましくは５以下である。 The aspect ratio of the conductive substance 2 is 2 or more, preferably 3 or more, more preferably 3.5 or more from the viewpoint of the conductivity of the positive electrode composite material. From the viewpoint of securing a lithium ion diffusion path, 10 10 Hereinafter, it is preferably 5 or less.
高アスペクト比のカーボンブラックは、凝集構造をとっていることから、一般にＤＢＰ（フタル酸ジブチル）吸収量が大きい。このため、ストラクチャ構造を有するカーボンブラックのＤＢＰ吸収量は、好ましくは１００ｃｍ３／１００ｇ以上、より好ましくは１２０ｃｍ３／１００ｇ以上、さらに好ましくは１５０ｃｍ３／１００ｇ以上である。また、電極密度を低下させない観点から、５００ｃｍ３／１００ｇ以下が好ましく、４００ｃｍ３／１００ｇ以下がより好ましく、３００ｃｍ３／１００ｇ以下がさらに好ましく、２００ｃｍ３／１００ｇ以下がさらにより好ましい。前記観点を総合すると、１００〜５００ｃｍ３／１００ｇが好ましく、１００〜４００ｃｍ３／１００ｇがより好ましく、１２０〜３００ｃｍ３／１００ｇがさらに好ましく、１５０〜２００ｃｍ３／１００ｇがさらにより好ましい。 Since carbon black having a high aspect ratio has an aggregated structure, it generally has a large DBP (dibutyl phthalate) absorption. Therefore, DBP absorption amount of carbon black having a structure structure is preferably 100 cm 3/100 g or more, more preferably 120 cm 3/100 g or more, more preferably 150 cm 3/100 g or more. Further, from the viewpoint of not lowering the electrode density is preferably not more than 500 cm 3/100 g, more preferably not more than 400cm 3 / 100g, 300cm 3 / 100g and more preferably less, still more preferably 200 cm 3/100 g or less. When the said viewpoint is put together, 100-500 cm < 3 > / 100g is preferable, 100-400 cm < 3 > / 100g is more preferable, 120-300 cm < 3 > / 100g is further more preferable, 150-200 cm < 3 > / 100g is still more preferable.
また、カーボンブラックの比表面積は、２０ｍ３／ｇ以上が好ましく、３０ｍ３／ｇ以上がより好ましく、４０ｍ３／ｇ以上が更に好ましく、正極の容積を適度に抑え、コンパクトさを確保する観点から、２０００ｍ３／ｇ以下が好ましく、５００ｍ３／ｇ以下がより好ましく、１００ｍ３／ｇ以下が更に好ましい。前記観点を総合すると、２０〜２０００ｍ３／ｇが好ましく、３０〜５００ｍ３／ｇがより好ましく、４０〜１００ｍ３／ｇが更に好ましい。 Further, the specific surface area of carbon black is preferably 20 m 3 / g or more, more preferably 30 m 3 / g or more, further preferably 40 m 3 / g or more, from the viewpoint of appropriately suppressing the volume of the positive electrode and ensuring compactness. 2000 m 3 / g or less is preferable, 500 m 3 / g or less is more preferable, and 100 m 3 / g or less is more preferable. When the said viewpoint is put together, 20-2000 m < 3 > / g is preferable, 30-500 m < 3 > / g is more preferable, 40-100 m < 3 > / g is still more preferable.
上記のようなストラクチャ構造を有するカーボンブラックとしては、導電性物質１として用いられる、微粒子化前のカーボンブラックなどが使用可能である。より具体的には、原油やガスの燃焼熱によって原料炭化水素を熱分解させカーボンブラックを生成させるファーネス法導電性カーボンブラック、重質油のガス化プロセスによって得られるケッチェンブラック（登録商標）、アセチレンガスを熱分解して得られるアセチレンブラック等を挙げることができ、例えば、ライオン社製ケッチェンブラックＥＣ、キャボット社製バルカンＸＣ−７２、デグサ社製Ｐｒｉｎｔｅｘ Ｌ６やＰｒｉｎｔｅｘ ＸＥ２等が市販されている。 As the carbon black having the structure as described above, carbon black before being used as the conductive material 1 before being finely divided can be used. More specifically, a furnace method conductive carbon black in which raw material hydrocarbons are pyrolyzed by the heat of combustion of crude oil or gas to produce carbon black, ketjen black (registered trademark) obtained by a heavy oil gasification process, Examples include acetylene black obtained by pyrolyzing acetylene gas, such as Lion Ketjen Black EC, Cabot Vulcan XC-72, Degussa Printex L6, Printex XE2, and the like. .
ストラクチャ構造を有するカーボンブラックの粒径は、一次粒子がつながって構成される凝集体の平均粒径（凝集粒径）で表され、レーザー回折／散乱式粒度分布測定装置ＬＡ７５０（堀場製作所製）を用いた粒度分布の測定によって求められる。この平均粒径は、正極の導電性の観点、及び、正極材料を塗工して、塗膜を形成する際の塗膜の平滑性の観点から、０．０５〜１０μｍが好ましく、０．０８〜５μｍがより好ましく、０．１〜２μｍが更に好ましい。 The particle size of the carbon black having a structure structure is represented by the average particle size (aggregated particle size) of aggregates formed by connecting primary particles, and a laser diffraction / scattering type particle size distribution analyzer LA750 (manufactured by Horiba) is used. It is determined by measuring the particle size distribution used. The average particle size is preferably 0.05 to 10 μm from the viewpoint of the conductivity of the positive electrode and the smoothness of the coating film when the positive electrode material is applied to form a coating film, and is preferably 0.08. ˜5 μm is more preferable, and 0.1 to 2 μm is still more preferable.
導電性物質２の配合量としては、得られる正極の導電経路の形成による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２重量部以上、より好ましくは、４重量部以上、更に好ましくは８重量部以上である。また、正極用複合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 blending amount of the conductive material 2 is preferably 2 parts by weight or more, more preferably 4 parts by weight with respect to 100 parts by weight of the positive electrode active material from the viewpoint of reducing volume resistivity by forming a conductive path of the positive electrode to be obtained. Part or more, more preferably 8 parts by weight or more. Moreover, from a viewpoint of raising the energy density of the composite material for positive electrodes, Preferably it is 50 weight part or less, More preferably, it is 30 weight part or less, More preferably, it is 15 weight part or less.
導電性物質１と導電性物質２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３〜５０重量部が好ましい。即ち、複合正極材料の体積抵抗低減の観点から、正極活物質１００重量部に対して、好ましくは３重量部以上、より好ましくは５重量部以上、更に好ましくは１０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。 As for the total compounding quantity of the electroconductive substance 1 and the electroconductive substance 2, 3-50 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 reducing the volume resistance of the composite positive electrode material, the amount is preferably 3 parts by weight or more, more preferably 5 parts by weight or more, and still more preferably 10 parts by weight or more with respect to 100 parts by weight of the positive electrode active material. 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.
得られる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、５Ω・ｃｍ以下であることが好ましく、より好ましくは３Ω・ｃｍ以下、更に好ましくは２Ω・ｃｍ以下である。 The volume resistivity of the obtained positive electrode composite material is preferably 5 Ω · cm or less, more preferably 3 Ω · cm or less, and still more preferably 2 Ω · cm or less, from the viewpoint of improving high-speed discharge characteristics.
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。 Although the composite material for positive electrodes of this invention can be obtained as a slurry or powder, formation of positive electrodes, such as a lithium ion secondary battery, can be performed using these. 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.
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。 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.
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Ｎ−メチル−２−ピロリドン（ＮＭＰ）、ジメチルホルムアミド（ＤＭＦ）、ジメチルアセトアミド、メチルエチルケトン、テトラヒドロフラン、アセトン、エタノール、酢酸エチルなどが好適に用いられる。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 solvent, any conventional solvent used for forming a positive electrode can be used. For example, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetone, ethanol, Ethyl acetate or the like is preferably 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５５％以上、より好ましくは６０％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 60C to 55C is preferably 55% or more, and more preferably 60% or more.
上記のように、本発明の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正極用複合材料を得る工程と、その正極用複合材料、溶媒及びバインダを含有する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。 As described above, the method for producing a positive electrode for a lithium battery according to the present invention includes a step of obtaining a composite material for a positive electrode by the method for producing a composite material for a lithium battery positive electrode according to the present invention, and a composite material for the positive electrode, a solvent, and a binder. And applying a slurry to the current collector and drying.
また、本発明のリチウム電池正極用複合材料の第２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、溶媒中で少なくとも正極活物質と導電性物質１とが強制分散した状態まで分散して得られるスラリーから溶媒を除去して、前記正極活物質と前記導電性物質１とを含有する複合粒子を得る複合粒子化工程と、少なくとも、前記複合粒子、及びＤＢＰ吸収量１００〜５００ｃｍ３／１００ｇの導電性物質２を混合する混合工程とを含むものである。この第２の製造方法によっても上述した第１の製造方法と同様の効果を奏する。なお、前記ＤＢＰ吸収量は、実施例に記載の方法で測定される。また、上記第２の製造方法における構成要件の好ましい例については、上述した第１の製造方法と同様である。 A second method for producing a composite material for a lithium battery positive electrode according to 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, wherein the positive electrode active material is at least in a solvent. And a composite particle forming step of obtaining composite particles containing the positive electrode active material and the conductive material 1 by removing the solvent from the slurry obtained by dispersing the conductive material 1 and the conductive material 1 to a state where they are forcibly dispersed, the those containing composite particles and a mixing step of mixing a DBP absorption 100~500cm 3 / 100g of conductive material 2. This second manufacturing method also has the same effect as the first manufacturing method described above. In addition, the said DBP absorption amount is measured by the method as described in an Example. Further, preferred examples of the configuration requirements in the second manufacturing method are the same as those in the first manufacturing method described above.
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）複合粒子の表面被覆率
電界放出型走査電子顕微鏡（日立製Ｓ−４０００）により、ＳＥＭ−ＥＤＳ分析を行い、カーボンの表面被覆率を求めた。
(4) Surface coverage of composite particles SEM-EDS analysis was performed using a field emission scanning electron microscope (S-4000 manufactured by Hitachi) to determine the surface coverage of carbon.
（５）カーボンブラックのアスペクト比
電界放出型走査電子顕微鏡（日立製Ｓ−４０００）により撮影したＳＥＭ像から、一次粒子が数珠繋ぎとなった形状で、かつ最長径が平均粒径±（平均粒径×０．２）のカーボンブラック二次凝集体を３０個抽出し、その最長径（Ｌ）と最短径（Ｗ）の比、すなわちＬ／Ｗの平均値をアスペクト比として求めた。なお、最長径とは、前記二次凝集体のＳＥＭ像の二次凝集体域（以下、凝集体画像という）を通過（接することを含む）する直線Ｌが、凝集体画像に切り取られる線分のうち、最長の線分の長さをいう。また、最短径とは、直線Ｌの中で、最長径に対応する直線に平行な直線群の中で、最も距離の離れた２本の平行線の間の距離をいう。ただし、２本の平行線の間の距離とは、当該２本の平行線に垂直な直線が、当該２本の平行線に切り取られる線分の長さをいう。
(5) Aspect ratio of carbon black From a SEM image taken with a field emission scanning electron microscope (Hitachi S-4000), the primary particles are connected in a daisy chain, and the longest diameter is the average particle diameter ± (average particle diameter) 30 x 0.2) carbon black secondary aggregates were extracted, and the ratio of the longest diameter (L) to the shortest diameter (W), that is, the average value of L / W was determined as the aspect ratio. The longest diameter is a line segment where a straight line L passing through (including contacting with) a secondary aggregate region (hereinafter referred to as an aggregate image) of the SEM image of the secondary aggregate is cut into the aggregate image. The length of the longest line segment. The shortest diameter is a distance between two parallel lines that are the farthest apart from each other in the straight line group parallel to the straight line corresponding to the longest diameter. However, the distance between the two parallel lines refers to the length of a line segment that is cut by the two parallel lines from a straight line perpendicular to the two parallel lines.
（６）体積抵抗率
ＪＩＳ Ｋ １４６９にもとづき、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 Based on JIS K 1469, the amount of the powder sample was changed to 0.3 g, the pressure at the time of powder compression was changed to 100 kg / cm 2, and the electric resistance value of the compressed powder sample compressed into a cylindrical shape was 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２７重量部に対して、ポリフッ化ビニリデン粉末（呉羽化学社製、♯１３００）３重量部、ＮＭＰ４５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) Production of Battery A coating paste was prepared by uniformly mixing 3 parts by weight of polyvinylidene fluoride powder (Kureha Chemical Co., Ltd., # 1300) and 45 parts by weight of NMP with respect to 27 parts by weight of the powder sample. 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
実施例１
エタノール１００重量部に平均粒径０．６μｍ（一次粒子径２１ｎｍ）の微粒子カーボンブラック（東海カーボン社製、♯７５５０）０．４重量部を添加し、超音波型分散機を用いて超音波による分散を行った。この分散液に、一次粒子径０．８μｍのマンガン酸リチウム２０重量部を添加し、更に超音波による分散を行った。得られたスラリーを蒸発させて乾燥固化し、マンガン酸リチウム表面に微粒子カーボンブラックを付着させた粉末（ＣＢ付着マンガン酸リチウム、表面被覆率２４％）を得た。ついで、エタノール１００重量部に平均粒径１μｍ、アスペクト比３．８のカーボンブラック（電気化学工業社製、ＨＳ−１００、ＤＢＰ吸収量１４０ｃｍ３／１００ｇ）２．１重量部を加え、Ｔ．Ｋ．ホモディスパーで撹拌した。次に、ＣＢ付着マンガン酸リチウム２０．４重量部を加えＴ．Ｋ．ホモディスパーで混合し、得られたスラリーを蒸発させて乾燥固化し、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１に示す。
Example 1
To 100 parts by weight of ethanol, 0.4 part by weight of fine particle carbon black (manufactured by Tokai Carbon Co., # 7550) having an average particle diameter of 0.6 μm (primary particle diameter of 21 nm) is added, and ultrasonically using an ultrasonic disperser. Dispersion was performed. To this dispersion, 20 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and dispersion by ultrasonic waves was further performed. The obtained slurry was evaporated to dryness and solidified to obtain a powder (CB-attached lithium manganate, surface coverage 24%) in which fine particle carbon black was adhered to the surface of the lithium manganate. Then, the average particle diameter of 1μm to 100 parts by weight of ethanol, the carbon black having an aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo, a HS-100, DBP absorption amount 140cm 3 /100g)2.1 parts by weight of, T. K. Stir with homodispers. Next, 20.4 parts by weight of CB-attached lithium manganate was added and T.P. K. Mixing with a homodisper, the resulting slurry was evaporated to dryness and solidified to obtain a composite material for positive electrode. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例２
２−ブタノン１００重量部に、ポリアクリル酸系分散剤（イソブチレン−マレイン酸ステアリルアミド）０．５６重量部を添加し、そこに平均粒径１μｍ（一次粒子径４５ｎｍ）、アスペクト比３．８のカーボンブラック（電気化学工業社製、ＨＳ−１００、ＤＢＰ吸収量１４０ｃｍ３／１００ｇ）１１．１重量部を加え、スラリーを得た。このスラリーをダイノーミルを用いて湿式粉砕し、平均粒径０．３μｍ（一次粒子径４５ｎｍ）の微粒子カーボンブラックスラリーを得た。次に、２−ブタノン１００重量部に、得られた微粒子カーボンブラックスラリー４重量部を添加し、超音波型分散機を用いて超音波による分散を行った。この分散液に、一次粒子径０．８μｍのマンガン酸リチウム２０重量部を添加し、更に超音波による分散を行った。得られたスラリーを蒸発させて乾燥固化し、マンガン酸リチウム表面に微粒子カーボンブラックを付着させた粉末（ＣＢ付着マンガン酸リチウム、表面被覆率３２％）を得た。ついで、エタノール１００重量部に平均粒径１μｍ、アスペクト比３．８のカーボンブラック（電気化学工業社製、ＨＳ−１００）２．１重量部を加えＴ．Ｋ．ホモディスパーで撹拌した。次に、ＣＢ付着マンガン酸リチウム２０．４重量部を加えＴ．Ｋ．ホモディスパーで混合し、得られたスラリーを蒸発させて乾燥固化し、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１に示す。
Example 2
0.56 parts by weight of polyacrylic acid dispersant (isobutylene-maleic stearylamide) is added to 100 parts by weight of 2-butanone, and there is an average particle diameter of 1 μm (primary particle diameter of 45 nm) and an aspect ratio of 3.8. carbon black (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm 3 /100g)11.1 parts by weight was added to obtain a slurry. This slurry was wet pulverized using a dyno mill to obtain a fine particle carbon black slurry having an average particle size of 0.3 μm (primary particle size: 45 nm). Next, 4 parts by weight of the obtained fine particle carbon black slurry was added to 100 parts by weight of 2-butanone, and dispersion by ultrasonic waves was performed using an ultrasonic disperser. To this dispersion, 20 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and dispersion by ultrasonic waves was further performed. The obtained slurry was evaporated to dryness and solidified to obtain a powder (CB-attached lithium manganate, surface coverage 32%) having fine carbon black adhered to the lithium manganate surface. Next, 2.1 parts by weight of carbon black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) having an average particle diameter of 1 μm and an aspect ratio of 3.8 was added to 100 parts by weight of ethanol. K. Stir with homodispers. Next, 20.4 parts by weight of CB-attached lithium manganate was added and T.P. K. Mixing with a homodisper, the resulting slurry was evaporated to dryness and solidified to obtain a composite material for positive electrode. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例３
エタノール１００重量部に平均粒径０．８μｍ（一次粒子径２５ｎｍ）の微粒子カーボンブラック（東海カーボン社製、♯５５００）０．４重量部を添加し、超音波型分散機を用いて超音波による分散を行った。この分散液に、一次粒子径０．８μｍのマンガン酸リチウム２０重量部を添加し、更に超音波による分散を行った。得られたスラリーを蒸発させて乾燥固化し、マンガン酸リチウム表面に微粒子カーボンブラックを付着させた粉末（ＣＢ付着マンガン酸リチウム、表面被覆率４８％）を得た。ついで、エタノール１００重量部に平均粒径１μｍ、アスペクト比３．８のカーボンブラック（電気化学工業社製、ＨＳ−１００、ＤＢＰ吸収量１４０ｃｍ３／１００ｇ）２．１重量部を加えＴ．Ｋ．ホモディスパーで撹拌した。次に、ＣＢ付着マンガン酸リチウム２０．４重量部を加えＴ．Ｋ．ホモディスパーで混合し、得られたスラリーを蒸発させて乾燥固化し、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１に示す。
Example 3
To 100 parts by weight of ethanol, 0.4 part by weight of fine particle carbon black (manufactured by Tokai Carbon Co., # 5500) having an average particle diameter of 0.8 μm (primary particle diameter of 25 nm) is added, and ultrasonically using an ultrasonic disperser. Dispersion was performed. To this dispersion, 20 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and dispersion by ultrasonic waves was further performed. The obtained slurry was evaporated to dryness and solidified to obtain a powder (CB-attached lithium manganate, surface coverage of 48%) in which fine particle carbon black was adhered to the surface of the lithium manganate. Then, the average particle diameter of 1μm to 100 parts by weight of ethanol, the carbon black having an aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm 3 /100g)2.1 parts by weight of a T. K. Stir with homodispers. Next, 20.4 parts by weight of CB-attached lithium manganate was added and T.P. K. Mixing with a homodisper, the resulting slurry was evaporated to dryness and solidified to obtain a composite material for positive electrode. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例４
実施例３において、エタノールに添加するカーボンブラックとして平均粒径２μｍの東海カーボン社製♯５５００を用いたことと、一次粒子径が１．２μmのマンガン酸リチウムを用いたこと以外は同様の方法で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１に示す。
Example 4
In Example 3, the same method was used except that # 5500 manufactured by Tokai Carbon Co., Ltd. having an average particle diameter of 2 μm was used as carbon black added to ethanol, and lithium manganate having a primary particle diameter of 1.2 μm was used. A composite material for positive electrode was obtained. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例５
実施例３において、エタノールに添加するカーボンブラックとして平均粒径２μｍの東海カーボン社製♯５５００を用いたことと、一次粒子径が１０μmのマンガン酸リチウムを用いたこと以外は同様の方法で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１に示す。
Example 5
In Example 3, the same method was used for the positive electrode except that # 5500 manufactured by Tokai Carbon Co., Ltd. having an average particle diameter of 2 μm was used as carbon black to be added to ethanol, and lithium manganate having a primary particle diameter of 10 μm was used. A composite material was obtained. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例６
実施例３において、エタノールに添加するカーボンブラックとして東海カーボン社製＃３８００（一次粒子径７０ｎｍ）を用いたことと、一次粒子径が１．２μmのマンガン酸リチウムを用いたこと以外は同様の方法で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１に示す。
Example 6
In Example 3, the same method except that # 3800 (primary particle diameter 70 nm) manufactured by Tokai Carbon Co., Ltd. was used as the carbon black to be added to ethanol, and lithium manganate having a primary particle diameter of 1.2 μm was used. Thus, a composite material for positive electrode was obtained. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例７
実施例４において、ＨＳ−１００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同様の方法で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１に示す。
Example 7
In Example 4, a composite material for a positive electrode was obtained in the same manner except that FX-35 (carbon black manufactured by Denki Kagaku Kogyo Co., Ltd.) was used instead of HS-100. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例８
実施例４において、ＨＳ−１００の代わりにケッチェンブラック（ライオン社製カーボンブラック）を用いたこと以外は同様の方法で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１に示す。
Example 8
In Example 4, a composite material for a positive electrode was obtained in the same manner except that ketjen black (Lion Corporation carbon black) was used instead of HS-100. Table 1 shows the physical properties of the obtained composite material for positive electrode.
実施例９
実施例４において、ＨＳ−１００の代わりにＦＷ１（デグッサ社製カーボンブラック）を用いたこと以外は同様の方法で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１に示す。
Example 9
A composite material for a positive electrode was obtained in the same manner as in Example 4 except that FW1 (carbon black manufactured by Degussa) was used instead of HS-100. Table 1 shows the physical properties of the obtained composite material for positive electrode.
比較例１
２−ブタノン１００重量部に、ポリアクリル酸系分散剤（イソブチレン−マレイン酸ステアリルアミド）０．５６重量部を添加し、そこに平均粒径１μｍ（一次粒子径４５ｎｍ）、アスペクト比３．８のカーボンブラック（電気化学工業社製、ＨＳ−１００、ＤＢＰ吸収量１４０ｃｍ３／１００ｇ）１１．１重量部を加え、スラリーを得た。このスラリーをダイノーミルを用いて湿式粉砕し、平均粒径０．３μｍ（一次粒子径４５ｎｍ）のカーボンブラックスラリーを得た。次に、２−ブタノン８０重量部に、得られた微粒子カーボンブラックスラリー２５重量部を添加し、超音波型分散機を用いて超音波による分散を行った。この分散液に、一次粒子径０．８μｍのマンガン酸リチウム２０重量部を添加し、更に超音波による分散を行った。得られたスラリーを蒸発させて乾燥固化し、カーボンブラックと正極活物質とが複合した比較正極材料を得た。得られた材料の物性を表１に示す。
Comparative Example 1
0.56 parts by weight of polyacrylic acid dispersant (isobutylene-maleic stearylamide) is added to 100 parts by weight of 2-butanone, and there is an average particle diameter of 1 μm (primary particle diameter of 45 nm) and an aspect ratio of 3.8. carbon black (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, HS-100, DBP absorption amount 140cm 3 /100g)11.1 parts by weight was added to obtain a slurry. This slurry was wet pulverized using a dyno mill to obtain a carbon black slurry having an average particle size of 0.3 μm (primary particle size of 45 nm). Next, 25 parts by weight of the obtained fine particle carbon black slurry was added to 80 parts by weight of 2-butanone, and dispersion by ultrasonic waves was performed using an ultrasonic disperser. To this dispersion, 20 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm was added, and dispersion by ultrasonic waves was further performed. The obtained slurry was evaporated and dried and solidified to obtain a comparative positive electrode material in which carbon black and a positive electrode active material were combined. Table 1 shows the physical properties of the obtained material.
比較例２
エタノール１００重量部に平均粒径１μｍ（一次粒子径４５ｎｍ）、アスペクト比３．８のカーボンブラック（電気化学工業社製、ＨＳ−１００、ＤＢＰ吸収量１４０ｃｍ３／１００ｇ）２．５重量部を加えて撹拌した。この液に、一次粒子径０．８μｍのマンガン酸リチウム２０重量部を添加し、更にＴ．Ｋ．ホモディスパーで撹拌した。得られたスラリーを蒸発させて乾燥固化し、正極活物質と高アスペクト比カーボンブラックが複合した比較正極材料を得た。得られた材料の物性を表１に示す。
Comparative Example 2
The average particle diameter of 1μm to 100 parts by weight of ethanol (primary particle diameter 45 nm), carbon black having an aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo, a HS-100, DBP absorption amount 140cm 3 /100g)2.5 parts by weight of And stirred. To this solution, 20 parts by weight of lithium manganate having a primary particle size of 0.8 μm was added. K. Stir with homodispers. The obtained slurry was evaporated and dried and solidified to obtain a comparative positive electrode material in which the positive electrode active material and high aspect ratio carbon black were combined. The physical properties of the obtained material are shown in Table 1.
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、平均粒径０．８μｍ（一次粒子径２５ｎｍ）の微粒子カーボンブラック（東海カーボン社製、♯５５００）２重量部、平均粒径１μｍ（一次粒子径４５ｎｍ）、アスペクト比３．８のカーボンブラック（電気化学工業社製、ＨＳ−１００、ＤＢＰ吸収量１４０ｃｍ３／１００ｇ）１０．５重量部をヘンシェルミキサーで乾式混合し、比較正極材料を得た。得られた材料の物性を表１に示す。
Comparative Example 3
100 parts by weight of lithium manganate having a primary particle diameter of 0.8 μm, 2 parts by weight of fine particle carbon black (# 5500, manufactured by Tokai Carbon Co., Ltd.) having an average particle diameter of 0.8 μm (primary particle diameter of 25 nm), an average particle diameter of 1 μm (primary particles) diameter 45 nm), carbon black having an aspect ratio 3.8 (manufactured by Denki Kagaku Kogyo KK, was dry mixed HS-100, DBP absorption amount 140cm 3 /100g)10.5 parts in a Henschel mixer to obtain a comparative positive electrode material . Table 1 shows the physical properties of the obtained material.
比較例４
実施例３において、ＨＳ−１００の代わりに♯７５５０（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同様の方法で、比較正極材料を得た。得られた材料の物性を表１に示す。
Comparative Example 4
A comparative positive electrode material was obtained in the same manner as in Example 3 except that # 75550 (carbon black produced by Tokai Carbon Co.) was used instead of HS-100. Table 1 shows the physical properties of the obtained material.
表１の結果が示すように、正極活物質に導電性物質１が付着した複合粒子に、ストラクチャ構造を有するカーボンブラックを混合した実施例の複合材料は、いずれも低い体積抵抗率であり、優れた高速放電特性を有している。これに対して、導電性物質１又はストラクチャ構造のカーボンブラックを単独で用いた比較例１〜２では体積抵抗率が高く、高速放電特性が不十分であった。また、両者を単に混合した比較例３でも、体積抵抗率や高速放電特性の改善効果は小さかった。 As shown in the results of Table 1, the composite materials of the examples in which the carbon black having a structure structure is mixed with the composite particles in which the conductive material 1 is attached to the positive electrode active material have low volume resistivity and are excellent. It has high-speed discharge characteristics. On the other hand, in Comparative Examples 1 and 2 in which the conductive material 1 or carbon black having a structure structure was used alone, the volume resistivity was high and the high-speed discharge characteristics were insufficient. Further, even in Comparative Example 3 in which both were simply mixed, the effect of improving the volume resistivity and high-speed discharge characteristics was small.
Claims (6)
溶媒中で、少なくとも正極活物質と導電性物質１とが、強制分散した状態まで分散して得られるスラリーから溶媒を除去して、前記正極活物質と前記導電性物質１とを含有する複合粒子を得る複合粒子化工程と、
少なくとも、前記複合粒子、及びアスペクト比が２〜１０の導電性物質２を混合する混合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,
A composite particle containing the positive electrode active material and the conductive material 1 by removing the solvent from a slurry obtained by dispersing the positive electrode active material and the conductive material 1 in a solvent to a state where the positive active material and the conductive material 1 are forcibly dispersed. A composite particle forming step to obtain
The manufacturing method of the composite material for lithium battery positive electrodes including the mixing process which mixes the said composite particle and the electroconductive substance 2 whose aspect ratio is 2-10 at least.
溶媒中で、少なくとも正極活物質と導電性物質１とが、強制分散した状態まで分散して得られるスラリーから溶媒を除去して、前記正極活物質と前記導電性物質１とを含有する複合粒子を得る複合粒子化工程と、
少なくとも、前記複合粒子、及びＤＢＰ吸収量１００〜５００ｃｍ３／１００ｇの導電性物質２を混合する混合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,
A composite particle containing the positive electrode active material and the conductive material 1 by removing the solvent from a slurry obtained by dispersing the positive electrode active material and the conductive material 1 in a solvent to a state where the positive active material and the conductive material 1 are forcibly dispersed. A composite particle forming step to obtain
At least, the composite particles, and DBP absorption 100~500cm 3 / 100g mixing step in the method of manufacturing the lithium battery positive electrode composite material comprising mixing a conductive material 2.
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| KR101337365B1 (en) | 2010-09-20 | 2013-12-05 | 주식회사 엘지화학 | Cathode Active Material with High Capacity and Improved Conductivity and Non-aqueous Electrolyte Secondary Battery Comprising the Same |
| PL2621003T3 (en) * | 2010-09-20 | 2019-10-31 | Lg Chemical Ltd | Positive electrode active material comprising lithium manganese oxide and non-aqueous electrolyte secondary battery |
| JP5839221B2 (en) | 2011-08-26 | 2016-01-06 | トヨタ自動車株式会社 | Lithium secondary battery |
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| JP5561559B2 (en) * | 2011-10-06 | 2014-07-30 | トヨタ自動車株式会社 | Method for manufacturing lithium secondary battery |
| JP5962956B2 (en) * | 2012-02-03 | 2016-08-03 | トヨタ自動車株式会社 | Lithium secondary battery |
| JP6136765B2 (en) | 2013-08-28 | 2017-05-31 | 住友金属鉱山株式会社 | Method for producing positive electrode active material for non-aqueous electrolyte secondary battery, positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery |
| KR20160020237A (en) * | 2014-08-13 | 2016-02-23 | 삼성에스디아이 주식회사 | Cathode material, cathode including the same, and lithium battery including the cathode |
| JP7031278B2 (en) * | 2017-12-18 | 2022-03-08 | 荒川化学工業株式会社 | Binder aqueous solution for lithium ion battery, electrode slurry for lithium ion battery and its manufacturing method, electrode for lithium ion battery, and lithium ion battery |
| JP7109512B2 (en) * | 2020-08-31 | 2022-07-29 | 三洋化成工業株式会社 | Coated cathode active material particles for lithium-ion batteries |
| WO2023204215A1 (en) * | 2022-04-18 | 2023-10-26 | Ａｐｂ株式会社 | Electrode composition for lithium ion batteries, coated negative electrode active material particles for lithium ion batteries, method for producing coated negative electrode active material particles for lithium ion batteries, negative electrode for lithium ion batteries, and lithium ion battery |
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