JPWO2015119084A1 - Lithium ion secondary battery electrode forming composition, lithium ion secondary battery electrode and lithium ion secondary battery, and method for producing lithium ion secondary battery electrode forming composition - Google Patents
Lithium ion secondary battery electrode forming composition, lithium ion secondary battery electrode and lithium ion secondary battery, and method for producing lithium ion secondary battery electrode forming composition Download PDFInfo
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- JPWO2015119084A1 JPWO2015119084A1 JP2015560974A JP2015560974A JPWO2015119084A1 JP WO2015119084 A1 JPWO2015119084 A1 JP WO2015119084A1 JP 2015560974 A JP2015560974 A JP 2015560974A JP 2015560974 A JP2015560974 A JP 2015560974A JP WO2015119084 A1 JPWO2015119084 A1 JP WO2015119084A1
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- lithium ion
- ion secondary
- secondary battery
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- 239000011668 ascorbic acid Substances 0.000 description 1
- 125000001797 benzyl group Chemical group [H]C1=C([H])C([H])=C(C([H])=C1[H])C([H])([H])* 0.000 description 1
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 description 1
- 238000007724 calendar pressing method Methods 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000002482 conductive additive Substances 0.000 description 1
- LDHQCZJRKDOVOX-NSCUHMNNSA-N crotonic acid Chemical compound C\C=C\C(O)=O LDHQCZJRKDOVOX-NSCUHMNNSA-N 0.000 description 1
- 125000000113 cyclohexyl group Chemical group [H]C1([H])C([H])([H])C([H])([H])C([H])(*)C([H])([H])C1([H])[H] 0.000 description 1
- 229960004132 diethyl ether Drugs 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000010556 emulsion polymerization method Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- UIWXSTHGICQLQT-UHFFFAOYSA-N ethenyl propanoate Chemical compound CCC(=O)OC=C UIWXSTHGICQLQT-UHFFFAOYSA-N 0.000 description 1
- FWDBOZPQNFPOLF-UHFFFAOYSA-N ethenyl(triethoxy)silane Chemical compound CCO[Si](OCC)(OCC)C=C FWDBOZPQNFPOLF-UHFFFAOYSA-N 0.000 description 1
- NKSJNEHGWDZZQF-UHFFFAOYSA-N ethenyl(trimethoxy)silane Chemical compound CO[Si](OC)(OC)C=C NKSJNEHGWDZZQF-UHFFFAOYSA-N 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 229940052303 ethers for general anesthesia Drugs 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 239000005038 ethylene vinyl acetate Substances 0.000 description 1
- 229920006226 ethylene-acrylic acid Polymers 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000001530 fumaric acid Substances 0.000 description 1
- 125000003055 glycidyl group Chemical group C(C1CO1)* 0.000 description 1
- FUZZWVXGSFPDMH-UHFFFAOYSA-N hexanoic acid Chemical compound CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 125000000959 isobutyl group Chemical group [H]C([H])([H])C([H])(C([H])([H])[H])C([H])([H])* 0.000 description 1
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 1
- 150000002596 lactones Chemical class 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 1
- 239000011976 maleic acid Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 229940017219 methyl propionate Drugs 0.000 description 1
- 238000007721 mold pressing method Methods 0.000 description 1
- 150000002763 monocarboxylic acids Chemical class 0.000 description 1
- 125000004108 n-butyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 125000001280 n-hexyl group Chemical group C(CCCCC)* 0.000 description 1
- 125000004123 n-propyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 125000002560 nitrile group Chemical group 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- LYGJENNIWJXYER-UHFFFAOYSA-N nitromethane Chemical compound C[N+]([O-])=O LYGJENNIWJXYER-UHFFFAOYSA-N 0.000 description 1
- MHYFEEDKONKGEB-UHFFFAOYSA-N oxathiane 2,2-dioxide Chemical compound O=S1(=O)CCCCO1 MHYFEEDKONKGEB-UHFFFAOYSA-N 0.000 description 1
- RPQRDASANLAFCM-UHFFFAOYSA-N oxiran-2-ylmethyl prop-2-enoate Chemical compound C=CC(=O)OCC1CO1 RPQRDASANLAFCM-UHFFFAOYSA-N 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 description 1
- 229920001197 polyacetylene Polymers 0.000 description 1
- 125000003367 polycyclic group Chemical group 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000007870 radical polymerization initiator Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000007717 redox polymerization reaction Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical class [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 description 1
- 235000011121 sodium hydroxide Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 125000004079 stearyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 150000003462 sulfoxides Chemical class 0.000 description 1
- 125000000999 tert-butyl group Chemical group [H]C([H])([H])C(*)(C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- CIHOLLKRGTVIJN-UHFFFAOYSA-N tert‐butyl hydroperoxide Chemical compound CC(C)(C)OO CIHOLLKRGTVIJN-UHFFFAOYSA-N 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- LDHQCZJRKDOVOX-UHFFFAOYSA-N trans-crotonic acid Natural products CC=CC(O)=O LDHQCZJRKDOVOX-UHFFFAOYSA-N 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
活物質とバインダー樹脂との結着性を良好にできるリチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池用電極及びリチウムイオン二次電池を提供する。活物質と、バインダー樹脂とを含有してなり、前記活物質は、下記条件１により測定される分散液の水プロトンの横緩和時間が１０秒以上であり、前記バインダー樹脂は、下記条件２により測定される水系エマルジョンの水プロトンの横緩和時間が２００秒以上であるリチウムイオン二次電池電極形成用組成物。条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。Provided are a composition for forming a lithium ion secondary battery electrode, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery that can improve the binding property between an active material and a binder resin. The active material contains a binder resin, and the active material has a transverse relaxation time of water protons of the dispersion measured under the following condition 1 of 10 seconds or more. A composition for forming a lithium ion secondary battery electrode, wherein the transverse relaxation time of water protons of the aqueous emulsion to be measured is 200 seconds or more. Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method. Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
Description
本発明は、リチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池用電極及びリチウムイオン二次電池、並びにリチウムイオン二次電池電極形成用組成物の製造方法に関する。 The present invention relates to a composition for forming a lithium ion secondary battery electrode, an electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a method for producing a composition for forming a lithium ion secondary battery electrode.
近年、ノートパソコン、携帯電話、電動工具、電子機器及び通信機器等の小型化、軽量化の面からリチウムイオン二次電池が注目されている。また、最近では環境適用の観点から電気自動車、ハイブリッド自動車用のリチウムイオン二次電池、特に高電圧、高容量、高エネルギー密度化したリチウムイオン二次電池が強く求められてきている。 In recent years, lithium ion secondary batteries have attracted attention in terms of downsizing and weight reduction of notebook computers, mobile phones, electric tools, electronic devices, communication devices, and the like. In recent years, lithium ion secondary batteries for electric vehicles and hybrid vehicles, particularly high voltage, high capacity, and high energy density lithium ion secondary batteries have been strongly demanded from the viewpoint of environmental applications.
リチウムイオン二次電池は、コバルト酸リチウム等の金属酸化物を活物質とした正極と黒鉛等の炭素材料を活物質とした負極およびカーボネート類を中心した電解液から構成されており、リチウムイオンが正極と負極間を移動することにより電池の充放電が行われる二次電池である。
より詳細には、正極は、アルミ箔等の正極集電体表面に、金属酸化物等の正極活物質及びバインダーを含む組成物から正極層を形成することにより得ることができ、負極は、銅箔等の負極集電体表面に、黒鉛等の負極活物質及びバインダーを含む組成物から負極層を形成することにより得られる。したがって、各バインダーは、活物質とバインダーとを結着させ、正極層及び負極層の凝集破壊を防ぐ役割がある。A lithium ion secondary battery is composed of a positive electrode using a metal oxide such as lithium cobaltate as an active material, a negative electrode using a carbon material such as graphite as an active material, and an electrolyte mainly composed of carbonates. It is a secondary battery in which the battery is charged and discharged by moving between the positive electrode and the negative electrode.
More specifically, the positive electrode can be obtained by forming a positive electrode layer from a composition containing a positive electrode active material such as a metal oxide and a binder on the surface of a positive electrode current collector such as an aluminum foil. It is obtained by forming a negative electrode layer on a negative electrode current collector surface such as a foil from a composition containing a negative electrode active material such as graphite and a binder. Accordingly, each binder has a role of binding the active material and the binder and preventing cohesive failure of the positive electrode layer and the negative electrode layer.
従来、正極層及び負極層用のバインダーとしては、電解液に対する樹脂自体の耐膨潤性の観点から、有機溶剤系のＮ−メチルピロリドン（ＮＭＰ）を溶剤としたポリフッ化ビニリデン（ＰＶＤＦ）が用いられ、工業的に多くの機種に使用されてきた。しかしながら、このバインダーは活物質との結着性が低く、実際に使用するには多量のバインダーを必要とし、結果としてリチウムイオン二次電池の容量、エネルギー密度が低下する欠点がある。また、バインダーに高価な有機溶剤であるＮＭＰを使用しているため、最終製品の価格およびスラリーまたは集電体作製時の作業環境保全にも問題があった。 Conventionally, as a binder for the positive electrode layer and the negative electrode layer, polyvinylidene fluoride (PVDF) using an organic solvent-based N-methylpyrrolidone (NMP) as a solvent is used from the viewpoint of the swelling resistance of the resin itself with respect to the electrolytic solution. Has been used industrially in many models. However, since this binder has a low binding property with an active material, a large amount of binder is required for actual use, and as a result, there is a drawback that the capacity and energy density of the lithium ion secondary battery are lowered. In addition, since NMP, which is an expensive organic solvent, is used for the binder, there is a problem in the price of the final product and the maintenance of the working environment when the slurry or current collector is produced.
これらの問題を解決するものとして、特許文献１では、全エチレン性不飽和単量体に対して、特定量のスチレン、エチレン性不飽和カルボン酸エステル、エチレン性不飽和カルボン酸及び内部架橋剤を必須成分として含有するエチレン性不飽和単量体を乳化剤の存在下、乳化重合して得られるガラス転移温度が３０℃以下のリチウムイオン二次電池電極用バインダーが提案されている。 In order to solve these problems, in Patent Document 1, a specific amount of styrene, an ethylenically unsaturated carboxylic acid ester, an ethylenically unsaturated carboxylic acid and an internal crosslinking agent are added to all ethylenically unsaturated monomers. A binder for lithium ion secondary battery electrodes having a glass transition temperature of 30 ° C. or less obtained by emulsion polymerization of an ethylenically unsaturated monomer containing an essential component in the presence of an emulsifier has been proposed.
しかし、特許文献１のバインダーは、負極活物質として多く用いられている天然黒鉛の結着性は良好にできるものの、人造黒鉛等の他の活物質の結着性を必ずしも良好にできるものではなかった。他の活物質の中でも人造黒鉛は、高価であるものの、不純物が少なく電気抵抗を小さくでき、電池性能を向上できるため、近年は人造黒鉛に適するバインダーが求められている。
本発明は、天然黒鉛以外の活物質であっても、活物質とバインダー樹脂との結着性を良好にできるリチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池用電極及びリチウムイオン二次電池を提供することを目的とする。また、本発明は、天然黒鉛以外の活物質であっても、活物質とバインダー樹脂との結着性が良好であるリチウムイオン二次電池電極形成用組成物を効率よく製造する方法を提供することを目的とする。However, the binder of Patent Document 1 can improve the binding property of natural graphite, which is often used as a negative electrode active material, but does not necessarily improve the binding property of other active materials such as artificial graphite. It was. Among other active materials, artificial graphite is expensive, but has few impurities, can reduce electric resistance, and can improve battery performance. In recent years, a binder suitable for artificial graphite has been demanded.
The present invention provides a composition for forming a lithium ion secondary battery electrode, an electrode for a lithium ion secondary battery, and a lithium ion capable of improving the binding property between the active material and the binder resin even if the active material is other than natural graphite. An object is to provide a secondary battery. In addition, the present invention provides a method for efficiently producing a composition for forming a lithium ion secondary battery electrode that has good binding properties between an active material and a binder resin even if it is an active material other than natural graphite. For the purpose.
本発明者らは、上記課題を解決すべく鋭意研究し、まず、活物質とバインダー樹脂との結着性には、活物質の表面の性質が大きな影響を与えていると推定した。しかし、活物質の表面の性質は分析が困難であった。特に、人造黒鉛は焼成により表面の官能基が消失しており、表面の性質の分析が極めて困難であり、実際に活物質層を形成しなければ、結着性の良否を判断できなかった。そこで、本発明者らはさらに鋭意研究を重ね、活物質の表面の性質を特定する手段として、パルスＮＭＲ法による水プロトンの横緩和時間に着目し、上記課題を解決するに至った。
すなわち、本発明は、下記［１］〜［７］のリチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池用電極及びリチウムイオン二次電池、並びにリチウムイオン二次電池電極形成用組成物の製造方法を提供する。The present inventors have intensively studied to solve the above problems, and firstly estimated that the surface properties of the active material have a great influence on the binding property between the active material and the binder resin. However, the surface properties of the active material have been difficult to analyze. In particular, artificial graphite has surface functional groups disappeared by firing, and analysis of surface properties is extremely difficult, and it was impossible to judge whether the binding property was good or not unless an active material layer was actually formed. Accordingly, the present inventors have further conducted intensive studies and focused on the transverse relaxation time of water protons by the pulse NMR method as means for specifying the surface properties of the active material, and have solved the above problems.
That is, the present invention provides the following lithium ion secondary battery electrode forming composition, lithium ion secondary battery electrode and lithium ion secondary battery, and lithium ion secondary battery electrode forming composition of [1] to [7] below. A method for manufacturing a product is provided.
［１］活物質と、バインダー樹脂とを含有してなり、前記活物質は、下記条件１により測定される分散液の水プロトンの横緩和時間が１０秒以上であり、前記バインダー樹脂は、下記条件２により測定される水系エマルジョンの水プロトンの横緩和時間が２００秒以上であるリチウムイオン二次電池電極形成用組成物。
条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。
条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。
［２］前記活物質が人造黒鉛である上記［１］に記載のリチウムイオン二次電池電極形成用組成物。
［３］前記バインダー樹脂の酸価が２０ｍｇＫＯＨ／ｇ以下である上記［１］又は［２］に記載のリチウムイオン二次電池電極形成用組成物。
［４］前記バインダー樹脂が、スチレンとエチレン性不飽和カルボン酸エステルとの共重合体である上記［１］〜［３］の何れかに記載のリチウムイオン二次電池電極形成用組成物。
［５］集電体上に、上記［１］〜［４］の何れかに記載のリチウムイオン二次電池電極形成用組成物から形成されてなる活物質含有層を有するリチウムイオン二次電池電極。
［６］上記［５］に記載のリチウムイオン二次電池電極を用いてなるリチウムイオン二次電池。
［７］活物質と、バインダー樹脂とを混合する工程を含むリチウムイオン二次電池電極形成用組成物の製造方法であって、
活物質が、下記条件１により測定される分散液の水プロトンの横緩和時間が１０秒以上である場合に、バインダー樹脂として、下記条件２により測定される水系エマルジョンの水プロトンの横緩和時間が２００秒以上であるものを用いる、リチウムイオン二次電池電極形成用組成物の製造方法。
条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。
条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。[1] An active material and a binder resin are contained, and the active material has a lateral relaxation time of water protons of the dispersion measured by the following condition 1 of 10 seconds or more. A composition for forming a lithium ion secondary battery electrode, wherein the transverse relaxation time of water protons in an aqueous emulsion measured under Condition 2 is 200 seconds or more.
Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method.
Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
[2] The composition for forming a lithium ion secondary battery electrode according to the above [1], wherein the active material is artificial graphite.
[3] The composition for forming a lithium ion secondary battery electrode according to the above [1] or [2], wherein the acid value of the binder resin is 20 mgKOH / g or less.
[4] The composition for forming a lithium ion secondary battery electrode according to any one of [1] to [3], wherein the binder resin is a copolymer of styrene and an ethylenically unsaturated carboxylic acid ester.
[5] A lithium ion secondary battery electrode having an active material-containing layer formed from the composition for forming a lithium ion secondary battery electrode according to any one of [1] to [4] on a current collector .
[6] A lithium ion secondary battery using the lithium ion secondary battery electrode according to [5].
[7] A method for producing a composition for forming a lithium ion secondary battery electrode comprising a step of mixing an active material and a binder resin,
When the active material has a transverse relaxation time of water protons of the dispersion measured under the following condition 1 of 10 seconds or more, the transverse relaxation time of water protons of the aqueous emulsion measured under the following condition 2 is used as a binder resin. The manufacturing method of the composition for lithium ion secondary battery electrode formation using what is 200 seconds or more.
Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method.
Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
本発明のリチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池用電極及びリチウムイオン二次電池によれば、天然黒鉛以外の活物質であっても、活物質とバインダー樹脂との結着性を良好にすることができる。
また、従来は活物質含有層を実際に形成しなければ、活物質とバインダー樹脂との結着性を判断できなかったところ、本発明のリチウムイオン二次電池電極形成用組成物の製造方法によれば、実際に活物質含有層を形成しなくても、結着性に優れる活物質とバインダー樹脂とを選択することができ、リチウムイオン二次電池電極形成用組成物の製造効率を高めることができる。According to the composition for forming a lithium ion secondary battery electrode, the electrode for a lithium ion secondary battery, and the lithium ion secondary battery of the present invention, the active material and the binder resin are bonded even if the active material is other than natural graphite. Wearability can be improved.
Further, conventionally, unless the active material-containing layer was actually formed, the binding property between the active material and the binder resin could not be determined. Thus, the method for producing a composition for forming a lithium ion secondary battery electrode of the present invention was used. According to the present invention, it is possible to select an active material and a binder resin that have excellent binding properties without actually forming an active material-containing layer, and to increase the production efficiency of the composition for forming a lithium ion secondary battery electrode. Can do.
［リチウムイオン二次電池電極形成用組成物］
本発明のリチウムイオン二次電池電極形成用組成物（以下、「本発明の組成物」と称する場合がある。）は、活物質と、バインダー樹脂とを含有してなり、前記活物質は、下記条件１により測定される分散液の水プロトンの横緩和時間が１０秒以上であり、前記バインダー樹脂は、下記条件２により測定される水系エマルジョンの水プロトンの横緩和時間が２００秒以上であるものである。
条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。
条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。[Composition for forming lithium ion secondary battery electrode]
The composition for forming a lithium ion secondary battery electrode of the present invention (hereinafter sometimes referred to as “the composition of the present invention”) contains an active material and a binder resin. The transverse relaxation time of water protons of the dispersion measured under the following condition 1 is 10 seconds or more, and the binder resin has a transverse relaxation time of water protons of the aqueous emulsion measured by the following condition 2 of 200 seconds or more. Is.
Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method.
Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
本発明の組成物は、活物質として条件１により測定される分散液の水プロトン（水素原子核）の横緩和時間が１０秒以上であるものを用い、かつ、バインダー樹脂として条件２により測定される水系エマルジョンの水プロトンの横緩和時間が２００秒以上であるものを用いる。
本発明では、パルスＮＭＲ法によって測定した水プロトンの横緩和時間（以下、「横緩和時間」と称する場合がある。）は、活物質及びバインダー樹脂の水への濡れやすさを示すことに着目した。つまり、横緩和時間が長ければ水に濡れにくく（親水性の程度が低い）、横緩和時間が短ければ水に濡れやすい（親水性の程度が高い）ことを意味する。
従来、活物質の表面の性質は分析が困難であり、特に、人造黒鉛は焼成により表面の官能基が消失しており、表面の性質の分析が困難であった。本発明では、活物質及びバインダー樹脂の親水性の強弱を判断する指標として、パルスＮＭＲ法によって測定した水プロトンの横緩和時間を着目し、さらには、活物質の横緩和時間とバインダー樹脂の横緩和時間とを特定の関係にすることにより、天然黒鉛以外の活物質であっても、活物質とバインダー樹脂との結着性を良好にすることを可能としたものである。また、条件１及び条件２を満たす本発明の組成物は、後述する集電体との結着性も良好にしやすくできる点で良好である。
本発明の組成物は、リチウムイオン二次電池電極の正極形成組成物としても、負極形成組成物としても用いることができるが、負極形成組成物として用いた場合に、特に効果を発揮できる。The composition of the present invention uses a dispersion whose water proton (hydrogen nucleus) has a lateral relaxation time of 10 seconds or more as an active material and is measured under condition 2 as a binder resin. An aqueous emulsion having a water proton lateral relaxation time of 200 seconds or more is used.
In the present invention, attention is paid to the fact that the lateral relaxation time of water protons (hereinafter sometimes referred to as “lateral relaxation time”) measured by the pulse NMR method indicates the wettability of the active material and the binder resin to water. did. That is, if the transverse relaxation time is long, it is difficult to get wet with water (low degree of hydrophilicity), and if the transverse relaxation time is short, it means that it is easy to get wet with water (highly hydrophilic).
Conventionally, it has been difficult to analyze the surface properties of the active material, and in particular, artificial graphite has lost surface functional groups due to firing, making it difficult to analyze the surface properties. In the present invention, as an index for determining the hydrophilicity of the active material and the binder resin, the transverse relaxation time of water protons measured by a pulse NMR method is focused. Further, the lateral relaxation time of the active material and the transverse relaxation time of the binder resin are focused. By making the relaxation time into a specific relationship, it is possible to improve the binding property between the active material and the binder resin even for an active material other than natural graphite. In addition, the composition of the present invention that satisfies the conditions 1 and 2 is favorable in that it can easily improve the binding property with the current collector described later.
The composition of the present invention can be used both as a positive electrode forming composition for a lithium ion secondary battery electrode and as a negative electrode forming composition. However, when the composition is used as a negative electrode forming composition, it is particularly effective.
（活物質）
活物質は、下記条件１により測定される分散液の水プロトンの横緩和時間が１０秒以上であるものを用いる。
条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。(Active material)
As the active material, a material in which the lateral relaxation time of water protons in the dispersion measured under the following condition 1 is 10 seconds or more is used.
Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method.
条件１の測定は、パルスＮＭＲ法により行う。より具体的には、パルス核磁気共鳴装置を用い、測定核を水素原子核とし、測定温度２５℃、周波数１３ＭＨｚ、９０°パルス幅２μｓの測定条件で、ＣＰＭＧ法（Ｃａｒｒ−ＰｕｒｃｅｌｌＭｅｉｂｏｏｍ−Ｇｉｌｌ法）により、水プロトンの横緩和時間（スピン−スピン緩和時間）を測定する。なお、条件１の測定の際、活物質分散液のｐＨは７．０に調製することが好ましい。
また、条件１の測定では、活物質の表面に接触している水プロトンの横緩和時間、及び活物質の表面に接触していない自由な状態の水プロトンの横緩和時間の２つ成分の平均が、水プロトンの横緩和時間として算出される。
条件１の横緩和時間は１１秒以上であることが好ましく、１２秒以上であることがより好ましい。また、条件１の横緩和時間の上限は特に制限されないが、５０秒以下であることが好ましく、４０秒以下であることがより好ましく、３０秒以下であることがさらに好ましい。
なお、カルボキシメチルセルロース（ＣＭＣ）は、増粘作用により、活物質分散液の分散安定性を向上する役割を奏するものである。The measurement under Condition 1 is performed by a pulse NMR method. More specifically, a pulse nuclear magnetic resonance apparatus is used, the measurement nucleus is a hydrogen nucleus, and measurement is performed at a measurement temperature of 25 ° C., a frequency of 13 MHz, and a 90 ° pulse width of 2 μs by the CPMG method (Carr-PurcellMeiboom-Gill method). The transverse relaxation time (spin-spin relaxation time) of water protons is measured. In the measurement under condition 1, it is preferable to adjust the pH of the active material dispersion to 7.0.
In the measurement under Condition 1, the average of the two components of the lateral relaxation time of the water proton in contact with the surface of the active material and the lateral relaxation time of the water proton in a free state not in contact with the surface of the active material Is calculated as the lateral relaxation time of water protons.
The lateral relaxation time of Condition 1 is preferably 11 seconds or longer, and more preferably 12 seconds or longer. Further, the upper limit of the lateral relaxation time in Condition 1 is not particularly limited, but is preferably 50 seconds or less, more preferably 40 seconds or less, and further preferably 30 seconds or less.
Carboxymethylcellulose (CMC) plays a role of improving the dispersion stability of the active material dispersion by a thickening action.
活物質は、条件１を満たすものであれば特に制限されることなく使用できる。活物質としては、リチウムイオンを吸蔵及び放出することができるものが好ましく用いられる。活物質には正極活物質と負極活物質とがある。本発明は、活物質として負極活物質を用いた場合に効果を発揮しやすく、負極活物質の中でも炭素質材料又は人造黒鉛を用いた場合により効果を発揮しやすく、特に表面の性質の分析が困難である人造黒鉛を用いた場合に極めて顕著な効果を発揮できる。 The active material can be used without particular limitation as long as it satisfies the condition 1. As the active material, those capable of occluding and releasing lithium ions are preferably used. The active material includes a positive electrode active material and a negative electrode active material. The present invention is more effective when a negative electrode active material is used as an active material, and more effective when a carbonaceous material or artificial graphite is used among negative electrode active materials. When artificial graphite, which is difficult, is used, an extremely remarkable effect can be exhibited.
活物質の形状は、特に限定されず、球状、燐片状等のものを用いることができる。これらの中でも、電子伝導性の観点から球状のものが好適である。
活物質の平均粒子径は、活物質の分散性の観点から、５〜１００μｍであることが好ましく、１０〜５０μｍであることがより好ましく、１５〜３０μｍであることがさらに好ましい。なお、平均粒子径はレーザー回折法により算出できる。
活物質の平均比表面積は、活物質の分散性の観点から、０．１〜１００ｍ２／ｇであることが好ましく、０．１〜５０ｍ２／ｇであることがより好ましく、０．１〜３０ｍ２／ｇであることがさらに好ましい。なお、平均比表面積は、ＢＥＴ窒素吸着法による比表面積測定(ＪＩＳ Ｚ８８３０に準じる)から得ることができる。The shape of the active material is not particularly limited, and a spherical shape, a flake shape, or the like can be used. Among these, spherical ones are preferable from the viewpoint of electron conductivity.
The average particle diameter of the active material is preferably 5 to 100 μm, more preferably 10 to 50 μm, and still more preferably 15 to 30 μm, from the viewpoint of dispersibility of the active material. The average particle diameter can be calculated by a laser diffraction method.
Average specific surface area of the active material, from the viewpoint of the dispersibility of the active material is preferably 0.1 to 100 m 2 / g, more preferably 0.1 to 50 m 2 / g, 0.1 to More preferably, it is 30 m 2 / g. In addition, an average specific surface area can be obtained from the specific surface area measurement (according to JIS Z8830) by the BET nitrogen adsorption method.
正極活物質としては、金属複合酸化物、特にリチウム及び鉄、コバルト、ニッケル、マンガンの少なくとも１種類以上の金属を含有する金属複合酸化物等が挙げられ、好ましくは、ＬｉｘＭｙ1Ｏ２（但し、Ｍは１種以上の遷移金属、好ましくはＣｏ、ＭｎまたはＮｉの少なくとも一種を表し、１．１０＞ｘ＞０．０５、１≧ｙ１＞０である）、または、ＬｉｘＭｙ２Ｏ４（但し、Ｍは１種以上の遷移金属、好ましくはＭｎまたはＮｉを表し、１．１０＞ｘ＞０．０５、２≧ｙ２＞０である。）または、ＬｉｘＭｙ１ＰＯ４（但し、Ｍは１種以上の遷移金属、好ましくはＦｅ、Ｃｏ、ＭｎまたはＮｉの少なくとも一種を表し、１．１０＞ｘ＞０．０５、１≧ｙ１＞０である）を含んだ活物質が挙げられ、例えばＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉｘＮｉｙ３ＭｎｚＣｏaＯ２（式中、１．１０＞ｘ＞０．０５、１＞ｙ３＞０、１＞z＞０、１＞ａ＞０である。）、ＬｉＭｎ２Ｏ４、ＬｉＦｅＰＯ４で表される複合酸化物等が挙げられる。Examples of the positive electrode active material include metal composite oxides, particularly metal composite oxides containing at least one metal selected from lithium and iron, cobalt, nickel, and manganese. Preferably, Li x M y1 O 2 ( M represents one or more transition metals, preferably at least one of Co, Mn or Ni, and 1.10>x> 0.05, 1 ≧ y1> 0), or Li x M y2 O 4 (where M represents one or more transition metals, preferably Mn or Ni, and 1.10>x> 0.05, 2 ≧ y2> 0) or Li x M y1 PO 4 (provided that , M represents one or more transition metals, preferably at least one of Fe, Co, Mn, or Ni, and 1.10>x> 0.05, 1 ≧ y1> 0). is, for example LiCoO 2, L NiO 2, Li x Ni y3 Mn z Co a O 2 ( wherein, 1.10>x>0.05,1> y3 >0,1>z>0,1>a> is 0.), LiMn Examples thereof include composite oxides represented by 2 O 4 and LiFePO 4 .
負極活物質としては、各種の珪素酸化物（ＳｉＯ２等）；炭素質物質；Ｌｉ４Ｔｉ５Ｏ１２等の金属複合酸化物等が挙げられ、人造黒鉛が好適である。
人造黒鉛は、アモルファスカーボン、グラファイト、天然黒鉛、ピッチ系炭素繊維、ポリアセチレン等の炭素質材料を３０００℃程度の温度で焼成してなるものであり、炭素質材料とは結晶構造が異なる。なお、人造黒鉛は、原子結合の形状は六角形の板状結晶であり、構造は亀の甲状の層状物質である。Examples of the negative electrode active material include various silicon oxides (SiO 2 and the like); carbonaceous materials; metal composite oxides such as Li 4 Ti 5 O 12 and the like, and artificial graphite is preferable.
Artificial graphite is obtained by firing a carbonaceous material such as amorphous carbon, graphite, natural graphite, pitch-based carbon fiber, and polyacetylene at a temperature of about 3000 ° C., and has a crystal structure different from that of the carbonaceous material. Artificial graphite is a hexagonal plate-like crystal with atomic bonds and a turtle shell-like layered material.
（バインダー樹脂）
バインダー樹脂は、下記条件２により測定される水系エマルジョンの水プロトン（水素原子核）の横緩和時間が２００秒以上であるものを用いる。
条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。(Binder resin)
As the binder resin, one having a lateral relaxation time of water protons (hydrogen nuclei) of the aqueous emulsion measured under the following condition 2 of 200 seconds or more is used.
Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
条件２の測定は、パルスＮＭＲ法により行う。より具体的には、パルス核磁気共鳴装置を用い、測定核を水素原子核とし、測定温度２５℃、周波数１３ＭＨｚ、９０°パルス幅２μｓの測定条件で、ＣＰＭＧ法（Ｃａｒｒ−ＰｕｒｃｅｌｌＭｅｉｂｏｏｍ−Ｇｉｌｌ法）により、水プロトンの横緩和時間（スピン−スピン緩和時間）を測定した。なお、条件２の測定の際、アニオン性水系エマルジョンのｐＨは７．０に調製することが好ましい。
また、条件２の測定では、バインダー樹脂粒子の表面に接触している水プロトンの横緩和時間、及びバインダー樹脂粒子の表面に接触していない自由な状態の水プロトンの横緩和時間の２つ成分の平均が、水プロトンの横緩和時間として算出される。
条件２の横緩和時間は２２０秒以上であることが好ましく、３００秒以上であることがより好ましい。また、条件２の横緩和時間の上限は特に制限されないが、７５０秒以下であることが好ましく、６００秒以下であることがより好ましく、４５０秒以下であることがさらに好ましい。The measurement of Condition 2 is performed by a pulse NMR method. More specifically, a pulse nuclear magnetic resonance apparatus is used, the measurement nucleus is a hydrogen nucleus, and measurement is performed at a measurement temperature of 25 ° C., a frequency of 13 MHz, and a 90 ° pulse width of 2 μs. The transverse relaxation time (spin-spin relaxation time) of water protons was measured. In the measurement under Condition 2, it is preferable to adjust the pH of the anionic aqueous emulsion to 7.0.
In the measurement under Condition 2, the two components of the lateral relaxation time of water protons in contact with the surface of the binder resin particles and the lateral relaxation time of water protons in a free state not in contact with the surface of the binder resin particles are used. Is calculated as the transverse relaxation time of water protons.
The lateral relaxation time of Condition 2 is preferably 220 seconds or more, and more preferably 300 seconds or more. Further, the upper limit of the lateral relaxation time in Condition 2 is not particularly limited, but is preferably 750 seconds or less, more preferably 600 seconds or less, and further preferably 450 seconds or less.
条件２の測定に用いるアニオン性水系エマルジョンは、例えば、以下（１）、（２）の方法により調製できる。
（１）アニオン性乳化剤を用いてバインダー樹脂を４０質量％含む水系エマルジョンに調製する。
（２）バインダー樹脂を生成する重合性モノマーとして反応性のアニオン性乳化剤を用い、重合したバインダー樹脂を４０質量％含む水系エマルジョンに調製する。
水系エマルジョン中のバインダー樹脂粒子の平均粒子径は、水プロトンの横緩和時間に特に影響を与えないが、５０〜５００ｎｍとすることが好ましく、１００〜２５０ｎｍとすることがより好ましい。なお、水系エマルジョン中のバインダー樹脂粒子の平均粒子径は、レーザー回折法により測定できる。The anionic water-based emulsion used for the measurement under Condition 2 can be prepared, for example, by the following methods (1) and (2).
(1) An aqueous emulsion containing 40% by mass of a binder resin is prepared using an anionic emulsifier.
(2) A reactive anionic emulsifier is used as a polymerizable monomer for forming a binder resin, and an aqueous emulsion containing 40% by mass of the polymerized binder resin is prepared.
The average particle diameter of the binder resin particles in the aqueous emulsion does not particularly affect the lateral relaxation time of water protons, but is preferably 50 to 500 nm, and more preferably 100 to 250 nm. The average particle diameter of the binder resin particles in the aqueous emulsion can be measured by a laser diffraction method.
バインダー樹脂は、条件２を満たすものであれば特に制限されることなく使用できる。条件２を満たすバインダー樹脂としては、酸価が低いものが好適であり、具体的には、酸価が２０ｍｇＫＯＨ／ｇ以下のものが好ましく、１５ｍｇＫＯＨ／ｇ以下のものがより好ましく、１０ｍｇＫＯＨ／ｇ以下のものがさらに好ましい。 The binder resin can be used without particular limitation as long as it satisfies the condition 2. As the binder resin satisfying the condition 2, those having a low acid value are suitable. Specifically, those having an acid value of 20 mgKOH / g or less are preferred, those having a value of 15 mgKOH / g or less are more preferred, and those having a acid value of 10 mgKOH / g or less are preferred. Are more preferred.
バインダー樹脂は、本発明の組成物から形成した電極を割れにくくする観点から、ガラス転移温度を３０℃以下とすることが好ましく、２０℃以下とすることがより好ましく、１５℃以下とすることがさらに好ましい。なお、取り扱い性の観点から、バインダー樹脂のガラス転移温度は、−２０℃以上とすることが好ましい。
バインダー樹脂のガラス転移温度は、バインダー樹脂の乳化重合に使用されるエチレン性不飽和単量体Ｍｉ（ｉ＝１，２，．．．，ｉ）の各ホモポリマーのガラス転移温度Ｔｇｉ（ｉ＝１，２，．．．，ｉ）と、エチレン性不飽和単量体Ｍｉの各重量分率Ｘｉ（ｉ＝１，２，．．．，ｉ）とから、下記式（Ｉ）により理論値として算出できる。
１／Ｔｇ＝Σ（Ｘｉ／Ｔｇｉ） ‥（Ｉ）From the viewpoint of making the electrode formed from the composition of the present invention difficult to break, the binder resin preferably has a glass transition temperature of 30 ° C. or lower, more preferably 20 ° C. or lower, and preferably 15 ° C. or lower. Further preferred. In addition, it is preferable that the glass transition temperature of binder resin shall be -20 degreeC or more from a viewpoint of handleability.
The glass transition temperature of the binder resin is the glass transition temperature Tgi (i = i = n) of each homopolymer of the ethylenically unsaturated monomer Mi (i = 1, 2,..., I) used in the emulsion polymerization of the binder resin. 1, 2), and the respective weight fractions Xi (i = 1, 2,..., I) of the ethylenically unsaturated monomer Mi from the following formula (I). Can be calculated as
1 / Tg = Σ (Xi / Tgi) (I)
バインダー樹脂としては、例えば、スチレン−ブタジエンゴム；スチレンとエチレン性不飽和カルボン酸エステルとの共重合体；エチレン−酢酸ビニル共重合体、エチレン−バーサチック酸ビニル共重合体、エチレン−アクリル酸エステル共重合体等のエチレン−エチレン性不飽和カルボン酸エステル共重合体等が挙げられる。これらの中でも、スチレンとエチレン性不飽和カルボン酸エステルとの共重合体は、活物質とバインダー樹脂との結着性を良好にできるとともに、電解液に対する耐膨潤性に優れ、充放電サイクル特性に優れる点で好適である。また、スチレンとエチレン性不飽和カルボン酸エステルとの共重合体は、集電体との結着性にも優れる点で良好である。 Examples of the binder resin include styrene-butadiene rubber; a copolymer of styrene and an ethylenically unsaturated carboxylic acid ester; an ethylene-vinyl acetate copolymer, an ethylene-vinyl versatate copolymer, and an ethylene-acrylic acid ester copolymer. Examples include ethylene-ethylenically unsaturated carboxylic acid ester copolymers such as polymers. Among these, a copolymer of styrene and an ethylenically unsaturated carboxylic acid ester can improve the binding property between the active material and the binder resin, and is excellent in swelling resistance to the electrolytic solution, and in charge / discharge cycle characteristics. It is preferable in terms of superiority. A copolymer of styrene and an ethylenically unsaturated carboxylic acid ester is good in that it has excellent binding properties with the current collector.
スチレンとエチレン性不飽和カルボン酸エステルとの共重合体（以下、単に「共重合体」と称する場合がある。）は、スチレンとエチレン性不飽和カルボン酸エステルとを併用することにより、上記効果を奏するものである。該共重合体は、例えば、水性媒質中、スチレン、エチレン性不飽和カルボン酸エステル及び内部架橋剤を含有する原料組成物を、乳化剤の存在下、乳化重合することで得ることができる。 A copolymer of styrene and an ethylenically unsaturated carboxylic acid ester (hereinafter sometimes simply referred to as “copolymer”) can be obtained by using styrene and an ethylenically unsaturated carboxylic acid ester in combination. It plays. The copolymer can be obtained, for example, by emulsion polymerization of a raw material composition containing styrene, an ethylenically unsaturated carboxylic acid ester and an internal crosslinking agent in an aqueous medium in the presence of an emulsifier.
スチレンは、主として、活物質とバインダー樹脂との結着性、及び活物質含有層と集電体との結着性を良好にする役割を有する。特に、活物質として人造黒鉛を用いた場合、より一層その効果を発揮できる。
スチレンの使用量は、上記共重合体を形成する全モノマー成分の１５〜７０質量％であることが好ましく、３０〜６０質量％であることがより好ましく、３５〜５５質量％であることがさらに好ましい。
スチレンの使用量を１５質量％以上とすることにより、活物質とバインダー樹脂との結着性、及び活物質含有層と集電体との結着性を良好にしやすくできる。また、スチレンの使用量を７０質量％以下とすることにより、本発明の組成物から形成した電極を割れにくくすることができる。Styrene mainly has a role of improving the binding property between the active material and the binder resin and the binding property between the active material-containing layer and the current collector. In particular, when artificial graphite is used as the active material, the effect can be further exhibited.
The amount of styrene used is preferably 15 to 70% by mass, more preferably 30 to 60% by mass, and further preferably 35 to 55% by mass of the total monomer components forming the copolymer. preferable.
By making the amount of styrene used 15% by mass or more, the binding property between the active material and the binder resin and the binding property between the active material-containing layer and the current collector can be easily improved. Moreover, the electrode formed from the composition of this invention can be made hard to be cracked by the usage-amount of styrene being 70 mass% or less.
エチレン性不飽和カルボン酸エステルは、官能基を有さないものと、官能基を有するものとに分けることができる。
官能基を有さないエチレン性不飽和カルボン酸エステルとしては、例えば、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸ｎ−プロピル、（メタ）アクリル酸イソプロピル、（メタ）アクリル酸ｎ−ブチル、（メタ）アクリル酸ｉｓｏ−ブチル、（メタ）アクリル酸ｔｅｒｔ−ブチル、（メタ）アクリル酸ｎ−ヘキシル、（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸ラウリル、（メタ）アクリル酸ステアリル、（メタ）アクリル酸シクロヘキシル、(メタ)アクリル酸イソノニル、（メタ）アクリル酸イソボロニル、(メタ)アクリル酸ベンジル等の（メタ）アクリル酸エステル類等が挙げられる。これらの中でも、乳化重合の容易さや耐久性の観点から、（メタ）アクリル酸ｎ−ブチル、（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸ラウリル、（メタ）アクリル酸イソボロニルが好ましい。Ethylenically unsaturated carboxylic acid esters can be divided into those having no functional group and those having a functional group.
Examples of the ethylenically unsaturated carboxylic acid ester having no functional group include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (meth ) N-butyl acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, Examples include (meth) acrylic acid esters such as stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isononyl (meth) acrylate, isobornyl (meth) acrylate, and benzyl (meth) acrylate. Among these, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and isobornyl (meth) acrylate are preferable from the viewpoint of ease of emulsion polymerization and durability.
官能基を有さないエチレン性不飽和カルボン酸エステルの使用量としては、上記共重合体を形成する全モノマー成分の２５〜８５質量％であることが好ましく、３０〜６５質量％であることがより好ましく、４０〜５５質量％であることがさらに好ましい。
官能基を有さないエチレン性不飽和カルボン酸エステルの使用量を２５質量％以上とすることにより、形成した電極の柔軟性や耐熱性を良好にしやすくでき、８５質量％以下とすることにより、活物質とバインダー樹脂との結着性、及び活物質含有層と集電体との結着性を良好にしやすくできる。The use amount of the ethylenically unsaturated carboxylic acid ester having no functional group is preferably 25 to 85% by mass, and preferably 30 to 65% by mass, based on all monomer components forming the copolymer. More preferably, the content is 40 to 55% by mass.
By making the use amount of the ethylenically unsaturated carboxylic acid ester having no functional group 25% by mass or more, flexibility and heat resistance of the formed electrode can be easily improved, and by making it 85% by mass or less, The binding property between the active material and the binder resin and the binding property between the active material-containing layer and the current collector can be easily improved.
官能基を有するエチレン性不飽和カルボン酸エステルとしては、ヒドロキシ基、グリシジル基等を有するエチレン性不飽和カルボン酸エステルが挙げられる。例えば、（メタ）アクリル酸２−ヒドロキシエチル、（メタ）アクリル酸２−ヒドロキシプロピル等の（メタ）アクリル酸２−ヒドロキシアルキル、アクリル酸グリシジル等が挙げられる。これらの中でも、（メタ）アクリル酸２−ヒドロキシエチルが好ましい。 Examples of the ethylenically unsaturated carboxylic acid ester having a functional group include ethylenically unsaturated carboxylic acid esters having a hydroxy group, a glycidyl group, and the like. Examples thereof include 2-hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, glycidyl acrylate, and the like. Among these, 2-hydroxyethyl (meth) acrylate is preferable.
官能基を有するエチレン性不飽和カルボン酸エステルの使用量としては、上記共重合体を形成する全モノマー成分の０．１〜１０質量％であることが好ましく、０．５〜５質量％であることがより好ましく、１〜３質量％であることがさらに好ましい。
官能性基を有するエチレン性不飽和カルボン酸の使用量を０．１質量％以上とすることにより、乳化重合安定性や機械的安定性を良好にしやすくでき、また、電解液に対する乾燥皮膜の耐膨潤性を良好にしやすくできる。また、官能基を有するエチレン性不飽和カルボン酸の使用量が多くなると横緩和時間が短くなり、逆に使用量が少ないと横緩和時間が長くなる傾向がある。このため、官能基を有するエチレン性不飽和カルボン酸の使用量を１０質量％以下とすることにより、横緩和時間を本発明の範囲としやすくでき、活物質とバインダー樹脂との結着性、及び活物質含有層と集電体との結着性を良好にしやすくできる。As the usage-amount of the ethylenically unsaturated carboxylic acid ester which has a functional group, it is preferable that it is 0.1-10 mass% of all the monomer components which form the said copolymer, and is 0.5-5 mass%. Is more preferable, and it is still more preferable that it is 1-3 mass%.
By making the use amount of the ethylenically unsaturated carboxylic acid having a functional group 0.1% by mass or more, emulsion polymerization stability and mechanical stability can be easily improved, and the resistance of the dry film to the electrolytic solution can be improved. Swellability can be easily improved. Further, when the amount of the ethylenically unsaturated carboxylic acid having a functional group is increased, the lateral relaxation time is shortened. Conversely, when the amount is small, the lateral relaxation time tends to be longer. For this reason, by setting the amount of the ethylenically unsaturated carboxylic acid having a functional group to 10% by mass or less, the transverse relaxation time can be easily set within the range of the present invention, and the binding property between the active material and the binder resin, and It is possible to easily improve the binding between the active material-containing layer and the current collector.
上記共重合体を形成するモノマーとして、さらにエチレン性不飽和カルボン酸を用いてもよい。
エチレン性不飽和カルボン酸としては、アクリル酸、メタクリル酸、クロトン酸等の不飽和モノカルボン酸、マレイン酸、フマル酸、イタコン酸等の不飽和ジカルボン酸またはこれら不飽和ジカルボン酸のハーフエステル等が挙げられ、これらの中でも、アクリル酸、イタコン酸が好ましい。これらのエチレン性不飽和カルボン酸は１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。An ethylenically unsaturated carboxylic acid may be further used as a monomer for forming the copolymer.
Examples of ethylenically unsaturated carboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, and half esters of these unsaturated dicarboxylic acids. Among these, acrylic acid and itaconic acid are preferable. These ethylenically unsaturated carboxylic acids may be used individually by 1 type, and may be used in combination of 2 or more type.
エチレン性不飽和カルボン酸は、少量添加すると、乳化重合安定性や機械的安定性の向上に寄与し得るが、多量に添加すると、横緩和時間が短くなりやすく、活物質とバインダー樹脂との結着性、及び活物質含有層と集電体との結着性が低下する傾向にある。このため、エチレン性不飽和カルボン酸の使用量としては、上記共重合体を形成する全モノマー成分の３質量％以下であることが好ましく、２質量％以下であることがより好ましく、１質量％以下であることがさらに好ましい。 When a small amount of ethylenically unsaturated carboxylic acid is added, it can contribute to the improvement of emulsion polymerization stability and mechanical stability. However, when added in a large amount, lateral relaxation time tends to be short, and the binding between the active material and the binder resin is likely to occur. Adhesiveness and binding properties between the active material-containing layer and the current collector tend to decrease. For this reason, the amount of the ethylenically unsaturated carboxylic acid used is preferably 3% by mass or less, more preferably 2% by mass or less, more preferably 1% by mass based on the total monomer components forming the copolymer. More preferably, it is as follows.
上記共重合体を形成するモノマーとして、さらに、少なくとも１つの重合可能なエチレン性不飽和基を有する上述した以外のモノマーを用いてもよい。このようなモノマーとしては、（メタ）アクリルアミド、Ｎ−メチロール（メタ）アクリルアミド、（メタ）アクリロニトリル、酢酸ビニル、プロピオン酸ビニル等のアミド基、ニトリル基等の官能基を有するエチレン性不飽和カルボン酸エステル以外の化合物、パラスチレンスルホン酸ソーダ等が挙げられる。
また、上記共重合体を形成するモノマーとして、分子量を調整するために、メルカプタン、チオグリコール酸及びそのエステル、β−メルカプトプロピオン酸及びそのエステルなどを用いてもよい。
また、上記共重合体を形成するモノマーとして、さらに、後述する反応性の乳化剤を用いても良い。As the monomer for forming the copolymer, a monomer other than those described above having at least one polymerizable ethylenically unsaturated group may be used. Examples of such monomers include (meth) acrylamide, N-methylol (meth) acrylamide, (meth) acrylonitrile, vinyl acetate, vinyl propionate and other functional groups such as amide groups and nitrile groups. Examples include compounds other than esters, sodium parastyrene sulfonate, and the like.
Further, as a monomer for forming the copolymer, mercaptan, thioglycolic acid and its ester, β-mercaptopropionic acid and its ester may be used in order to adjust the molecular weight.
Moreover, you may use the reactive emulsifier mentioned later further as a monomer which forms the said copolymer.
スチレンとエチレン性不飽和カルボン酸エステルとの共重合体の原料組成物中には、乾燥皮膜の電解液に対する耐膨潤性をより向上させるために、さらに内部架橋剤（内部架橋性モノマー）を含むことが好ましい。
内部架橋剤としては、少なくとも１つのエチレン性不飽和結合を有し、上述したモノマーが有する官能基と反応性を有する反応性基を有するもの、或いは、２つ以上のエチレン性不飽和結合を有するものを用いることができる。
このような内部架橋剤としては、ジビニルベンゼン、エチレングリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、トリアリルシアヌレート等の不飽和基を２個以上有する架橋性多官能単量体、ビニルトリメトキシシラン、ビニルトリエトキシシラン、γ−メタクリオキシプロピルトリメトキシシラン、γ−メタクリオキシプロピルトリエトキシシラン等のシランカップリング剤等が挙げられ、これらの中でも、ジビニルベンゼン、トリメチロールプロパントリ（メタ）アクリレート及びγ−メタクリオキシプロピルトリメトキシシランが好ましい。これらの内部架橋剤は１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。The raw material composition of the copolymer of styrene and ethylenically unsaturated carboxylic acid ester further contains an internal cross-linking agent (internal cross-linkable monomer) in order to further improve the swelling resistance of the dry film to the electrolyte. It is preferable.
The internal cross-linking agent has at least one ethylenically unsaturated bond, has a reactive group reactive with the functional group of the above-mentioned monomer, or has two or more ethylenically unsaturated bonds Things can be used.
As such an internal crosslinking agent, a crosslinkable polyfunctional monomer having two or more unsaturated groups such as divinylbenzene, ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, triallyl cyanurate, etc. Silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropyltriethoxysilane. Among these, divinylbenzene, trimethylolpropanetri (Meth) acrylate and γ-methacryloxypropyltrimethoxysilane are preferred. These internal cross-linking agents may be used alone or in combination of two or more.
内部架橋剤の使用量としては、上記共重合体を形成する全モノマー成分の０．１〜５質量％であることが好ましく、０．１〜３質量％であることがより好ましく、０．２〜２質量％であることがさらに好ましい。内部架橋剤の使用量を０．１質量％以上とすることにより、電解液に対する乾燥皮膜の耐膨潤性を良好にしやすくでき、５質量％以下とすることにより、乳化重合安定性の低下を防止できる。 The amount of the internal crosslinking agent used is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, based on all monomer components forming the copolymer. More preferably, it is -2 mass%. By making the amount of the internal crosslinking agent used 0.1% by mass or more, it is easy to improve the swelling resistance of the dry film against the electrolytic solution, and by making it 5% by mass or less, a decrease in emulsion polymerization stability is prevented. it can.
スチレンとエチレン性不飽和カルボン酸エステルとの共重合体の横緩和時間を条件２の範囲とするには、該共重合体中を形成するモノマーのうち、スチレンと官能基を有さないエチレン性不飽和カルボン酸エステルとの合計量を多くした上で、内部架橋剤を用いることが好ましい。具体的には、スチレンと官能基を有さないエチレン性不飽和カルボン酸エステルとの合計量を９０質量％以上とすることが好ましく、９３質量％以上とすることがより好ましく、９４質量％以上とすることがさらに好ましい。 In order to set the transverse relaxation time of the copolymer of styrene and ethylenically unsaturated carboxylic acid ester within the range of Condition 2, among the monomers forming the copolymer, styrene and ethylenic group having no functional group It is preferable to use an internal crosslinking agent after increasing the total amount with the unsaturated carboxylic acid ester. Specifically, the total amount of styrene and ethylenically unsaturated carboxylic acid ester having no functional group is preferably 90% by mass or more, more preferably 93% by mass or more, and 94% by mass or more. More preferably.
乳化重合の際に用いられる乳化剤としては、通常のアニオン性乳化剤、ノニオン性乳化剤が用いられる。
アニオン性乳化剤としては、例えば、アルキルベンゼンスルホン酸塩、アルキル硫酸エステル塩、ポリオキシエチレンアルキルエーテル硫酸エステル塩、脂肪酸塩等が挙げられる。ノニオン性乳化剤としては、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレン多環フィニルエーテル、ポリオキシアルキレンアルキルエーテル、ソルビタン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸アステル等が挙げられる。これらは１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。
また、乳化剤として反応性の乳化剤を用いれば、乳化剤のブリードアウトが防止され、本発明の組成物から形成した電極の機械的安定性を向上できる点で好適である。反応性の乳化剤としては、例えば、以下の一般式（１）〜（５）に示すものが挙げられる。As an emulsifier used in the emulsion polymerization, a normal anionic emulsifier and a nonionic emulsifier are used.
Examples of the anionic emulsifier include alkylbenzene sulfonate, alkyl sulfate ester salt, polyoxyethylene alkyl ether sulfate ester salt, fatty acid salt and the like. Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polycyclic finyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid aster. These may be used individually by 1 type and may be used in combination of 2 or more type.
In addition, if a reactive emulsifier is used as the emulsifier, the bleed-out of the emulsifier is prevented, which is preferable in that the mechanical stability of the electrode formed from the composition of the present invention can be improved. Examples of the reactive emulsifier include those represented by the following general formulas (1) to (5).
式中、Ｒはアルキル基、ｍは１０〜４０の整数を示す。
In the formula, R represents an alkyl group, and m represents an integer of 10 to 40.
式中、ｎは１０〜１２の整数、ｍは１０〜４０の整数を示す。
In the formula, n represents an integer of 10 to 12, and m represents an integer of 10 to 40.
式中、Ｒはアルキル基、ＭはＮＨ４又はＮａを示す。
In the formula, R represents an alkyl group, and M represents NH 4 or Na.
式中、Ｒはアルキル基を示す。
In the formula, R represents an alkyl group.
式中、ＡＯは炭素数２又は３のアルキレンオキシド、ｍは１０〜４０の整数を示す。
In the formula, AO represents an alkylene oxide having 2 or 3 carbon atoms, and m represents an integer of 10 to 40.
乳化剤の好適な使用量は、非反応性の乳化剤の場合、上記共重合体を形成する全モノマー成分１００質量部に対して、０．１〜３質量部であることが好ましく、０．１〜２質量部であることがより好ましく、０．２〜１質量部であることがさらに好ましい。反応性の乳化剤の場合、上記共重合体を形成する全モノマー成分の０．３〜５質量％であることが好ましく、０．５〜４質量％であることがより好ましく、０．５〜２質量部であることがさらに好ましい。また、非反応性の乳化剤、反応性の乳化剤はそれぞれ単独で用いてもよいが、混合して用いることが好ましい。 In the case of a non-reactive emulsifier, the preferred amount of the emulsifier is preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of all monomer components forming the copolymer. The amount is more preferably 2 parts by mass, and further preferably 0.2 to 1 part by mass. In the case of a reactive emulsifier, it is preferably 0.3 to 5% by mass, more preferably 0.5 to 4% by mass, and more preferably 0.5 to 2% by mass of all the monomer components forming the copolymer. More preferably, it is part by mass. Moreover, although a non-reactive emulsifier and a reactive emulsifier may each be used independently, it is preferable to mix and use.
乳化重合の際に用いられるラジカル重合開始剤としては公知慣用のものを用いることができ、例えば、過硫酸アンモニウム、過硫酸カリウム、過酸化水素、ｔ−ブチルハイドロパーオキサイド等が挙げられる。また、必要に応じて、これらの重合開始剤を重亜硫酸ナトリウム、ロンガリット（ヒドロキシメタンスルフィン酸ナトリウム）、アスコルビン酸等の還元剤と併用してレドックス重合としてもよい。 As the radical polymerization initiator used in the emulsion polymerization, known ones can be used, and examples thereof include ammonium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide and the like. Further, if necessary, these polymerization initiators may be used in combination with a reducing agent such as sodium bisulfite, Rongalite (sodium hydroxymethanesulfinate), ascorbic acid, or the like for redox polymerization.
乳化重合法としては、一括して仕込む重合方法、各成分を連続供給しながら重合する方法等が適用される。重合は通常３０〜９０℃の温度で攪拌下に行われる。なお、上記共重合体の重合中または重合終了後に塩基性物質を加えてｐＨを調整することにより、乳化重合時の重合安定性、機械的安定性、化学的安定性を向上させることができる。この場合に使用される塩基性物質としては、アンモニア、トリエチルアミン、エタノールアミン、苛性ソーダ等を使用する事ができる。これらは１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 As the emulsion polymerization method, a polymerization method charged in a lump, a method of polymerization while continuously supplying each component, and the like are applied. The polymerization is usually carried out at a temperature of 30 to 90 ° C. with stirring. The polymerization stability, mechanical stability, and chemical stability during emulsion polymerization can be improved by adding a basic substance during the polymerization of the copolymer or after completion of the polymerization to adjust the pH. As the basic substance used in this case, ammonia, triethylamine, ethanolamine, caustic soda and the like can be used. These may be used individually by 1 type and may be used in combination of 2 or more type.
本発明の組成物は、水、又は、水と親水性の高い溶媒との混合物に、活物質及びバインダー樹脂を分散または溶解させて用いることが好ましい。本発明の組成物の調製は、例えば、バインダー樹脂を溶媒に分散、溶解または混練させた後に、活物質及び必要に応じて用いる添加剤を加えて、さらに、分散、溶解または混練する方法が挙げられる。
本発明の組成物中における活物質及びバインダー樹脂の含有割合は、固形分基準で、活物質が９５．０〜９９．５質量％、バインダー樹脂が０．５〜５．０質量％であることが好ましく、活物質が９８．０〜９９．５質量％、バインダー樹脂が０．５〜２．０質量％であることがより好ましく、活物質が９９．０〜９９．５質量％、バインダー樹脂が０．５〜１．０質量％であることがさらに好ましい。The composition of the present invention is preferably used by dispersing or dissolving an active material and a binder resin in water or a mixture of water and a highly hydrophilic solvent. Preparation of the composition of the present invention includes, for example, a method in which a binder resin is dispersed, dissolved or kneaded in a solvent, and then an active material and additives used as necessary are added, and further dispersed, dissolved or kneaded. It is done.
The content ratio of the active material and the binder resin in the composition of the present invention is 95.0 to 99.5% by mass of the active material and 0.5 to 5.0% by mass of the binder resin on a solid basis. More preferably, the active material is 98.0 to 99.5% by mass, the binder resin is more preferably 0.5 to 2.0% by mass, the active material is 99.0 to 99.5% by mass, and the binder resin. Is more preferably 0.5 to 1.0% by mass.
［リチウムイオン二次電池電極］
本発明のリチウムイオン二次電池電極（以下、「本発明の電極」と称する場合がある。）は、集電体上に、上述した本発明のリチウムイオン二次電池電極形成用組成物から形成されてなる活物質含有層を有するものである。
本発明の電極は、リチウムイオン二次電池の正極としても、負極としても用いることができるが、負極として用いた場合に、特に効果を発揮できる。[Lithium ion secondary battery electrode]
The lithium ion secondary battery electrode of the present invention (hereinafter sometimes referred to as “the electrode of the present invention”) is formed on the current collector from the above-described composition for forming a lithium ion secondary battery electrode of the present invention. It has an active material content layer formed.
The electrode of the present invention can be used as both a positive electrode and a negative electrode of a lithium ion secondary battery, but can be particularly effective when used as a negative electrode.
集電体としては、鉄、銅、アルミニウム、ニッケル、ステンレスなどの金属性のものであれば、特に限定されない。これらの中でも、正極用の集電体としてはアルミニウムが好ましく、負極用の集電体としては銅が好ましい。
集電体の形状についても、特に限定されないが、通常、厚さ０．００１〜０．５ｍｍのシート状のものを用いることが好ましい。The current collector is not particularly limited as long as it is metallic such as iron, copper, aluminum, nickel, and stainless steel. Among these, aluminum is preferable as the current collector for the positive electrode, and copper is preferable as the current collector for the negative electrode.
The shape of the current collector is not particularly limited, but it is usually preferable to use a sheet having a thickness of 0.001 to 0.5 mm.
本発明の電極は、例えば、集電体上に、上述した本発明のリチウムイオン二次電池電極形成用組成物を塗布し、乾燥することにより得ることができる。
塗布方法は、一般的な方法を用いることができ、例えば、リバースロール法、ダイレクトロール法、ドクターブレード法、ナイフ法、エクストルージョン法、カーテン法、グラビア法、バー法、ディップ法およびスクイーズ法をあげることができる。これらの中でも、本発明の組成物の粘性等の諸物性及び乾燥性に合わせて塗布方法を選定することにより、活物質含有層の表面状態を良好にし得るという観点から、ドクターブレード法、ナイフ法、又はエクストルージョン法が好ましい。
また、本発明の電極は、活物質含有層の形成後、必要に応じてプレスすることができる。プレスの方法としては、一般的な方法を用いることができるが、特に金型プレス法やカレンダープレス法が好ましい。プレス圧は、特に限定されないが、０．２〜３ｔ／ｃｍ２が好ましい。The electrode of the present invention can be obtained, for example, by applying the above-described composition for forming a lithium ion secondary battery electrode of the present invention on a current collector and drying it.
As a coating method, general methods can be used, for example, reverse roll method, direct roll method, doctor blade method, knife method, extrusion method, curtain method, gravure method, bar method, dip method and squeeze method. I can give you. Among these, from the viewpoint that the surface state of the active material-containing layer can be improved by selecting a coating method in accordance with various physical properties such as viscosity and drying properties of the composition of the present invention, the doctor blade method, the knife method Or an extrusion method is preferred.
Moreover, the electrode of this invention can be pressed as needed after formation of an active material content layer. As a pressing method, a general method can be used, but a mold pressing method and a calendar pressing method are particularly preferable. Although a press pressure is not specifically limited, 0.2-3 t / cm < 2 > is preferable.
本発明の電極は、活物質とバインダー樹脂との結着性が良好であり、活物質含有層の凝集破壊を防止することができる。また、本発明の電極は、活物質含有層と集電体との結着性を良好にすることができる。該効果は、特に、集電体として銅を用いた場合に、極めて良好にすることができる。 The electrode of the present invention has good binding properties between the active material and the binder resin, and can prevent cohesive failure of the active material-containing layer. Moreover, the electrode of this invention can make favorable binding property of an active material content layer and a collector. This effect can be made very good especially when copper is used as the current collector.
［リチウムイオン二次電池］
本発明のリチウムイオン二次電池（以下、「本発明の電池」と称する場合がある。）は、上述した本発明のリチウムイオン二次電池電極を用いてなるものである。[Lithium ion secondary battery]
The lithium ion secondary battery of the present invention (hereinafter sometimes referred to as “the battery of the present invention”) is formed using the above-described lithium ion secondary battery electrode of the present invention.
本発明の電池は、正極及び／又は負極と、電解液と、必要に応じてセパレータ等の部品を用い、公知の方法にしたがって製造できる。電極としては、正極及び負極ともに上述した本発明の電極を用いてもよく、正極又は負極の一方に上述した本発明の電極を用いてもよいが、負極に上述した本発明の電極を用いた場合に特に効果を発揮できる。
電池の外装体としては、金属外装体やアルミラミネート外装体を使用できる。電池の形状は、コイン型、ボタン型、シート型、円筒型、角型、扁平型等いずれの形状であってもよい。電池の電解液中の電解質としては、公知のリチウム塩がいずれも使用でき、活物質の種類に応じて選択すればよい。例えば、ＬｉＣｌＯ４、ＬｉＢＦ６、ＬｉＰＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢ１０Ｃｌ１０、ＬｉＡｌＣｌ４、ＬｉＣｌ、ＬｉＢｒ、ＬｉＢ（Ｃ２Ｈ５）４、ＣＦ３ＳＯ３Ｌｉ、ＣＨ３ＳＯ３Ｌｉ、ＬｉＣＦ３ＳＯ３、ＬｉＣ４Ｆ９ＳＯ３、Ｌｉ（ＣＦ３ＳＯ２）２Ｎ、低級脂肪酸カルボン酸リチウム等が挙げられる。The battery of the present invention can be produced according to a known method using a positive electrode and / or a negative electrode, an electrolytic solution, and parts such as a separator as necessary. As the electrode, the electrode of the present invention described above may be used for both the positive electrode and the negative electrode, and the electrode of the present invention described above may be used for one of the positive electrode and the negative electrode, but the electrode of the present invention described above is used for the negative electrode. In particular, it can be effective.
As a battery exterior body, a metal exterior body or an aluminum laminate exterior body can be used. The shape of the battery may be any shape such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, and a flat shape. Any known lithium salt may be used as the electrolyte in the battery electrolyte, and may be selected according to the type of active material. For example, LiClO 4, LiBF 6, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, CF 3 Examples include SO 3 Li, CH 3 SO 3 Li, LiCF 3 SO 3 , LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 2 N, and lower fatty acid carboxylate lithium.
電解質を溶解する溶媒としては、電解質を溶解させる液体として通常用いられるものであれば特に限定されるものではなく、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルエチルカーボネート（ＭＥＣ）、ビニレンカーボネート（ＶＣ）などのカーボネート類；γ−ブチロラクトン、γ−バレロラクトンなどのラクトン類；トリメトキシメタン、１，２−ジメトキシエタン、ジエチルエーテル、２−エトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフランなどのエーテル類；ジメチルスルホキシドなどのスルホキシド類；１，３−ジオキソラン、４−メチル−１，３−ジオキソランなどのオキソラン類；アセトニトリル、ニトロメタン、ホルムアミド、ジメチルホルムアミドなどの含窒素類；ギ酸メチル、酢酸メチル、酢酸エチル、酢酸ブチル、プロピオン酸メチル、プロピオン酸エチルなどの有機酸エステル類；リン酸トリエステルやジグライム類；トリグライム類；スルホラン、メチルスルホランなどのスルホラン類；３−メチル−２−オキサゾリジノンなどのオキサゾリジノン類；１，３−プロパンスルトン、１，４−ブタンスルトン、ナフタスルトンなどのスルトン類；等が挙げられる。これらは、１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 The solvent for dissolving the electrolyte is not particularly limited as long as it is usually used as a liquid for dissolving the electrolyte. Ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate ( DMC), carbonates such as diethyl carbonate (DEC), methyl ethyl carbonate (MEC), vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; trimethoxymethane, 1,2-dimethoxyethane, Ethers such as diethyl ether, 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxo such as 1,3-dioxolane and 4-methyl-1,3-dioxolane Orchids; nitrogen-containing compounds such as acetonitrile, nitromethane, formamide, dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate; phosphate triesters and diglymes Triglymes; sulfolanes such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propane sultone, 1,4-butane sultone and naphtha sultone; These may be used individually by 1 type and may be used in combination of 2 or more type.
［リチウムイオン二次電池電極形成用組成物の製造方法］
本発明のリチウムイオン二次電池電極形成用組成物の製造方法は、活物質と、バインダー樹脂とを混合する工程を含むリチウムイオン二次電池電極形成用組成物の製造方法であって、
活物質が、下記条件１により測定される分散液の水プロトンの横緩和時間が１０秒以上である場合に、バインダー樹脂として、下記条件２により測定される水系エマルジョンの水プロトンの横緩和時間が２００秒以上であるものを用いるものである。
条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。
条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。[Method for producing composition for forming lithium ion secondary battery electrode]
The method for producing a composition for forming a lithium ion secondary battery electrode according to the present invention is a method for producing a composition for forming a lithium ion secondary battery electrode comprising a step of mixing an active material and a binder resin,
When the active material has a transverse relaxation time of water protons of the dispersion measured under the following condition 1 of 10 seconds or more, the transverse relaxation time of water protons of the aqueous emulsion measured under the following condition 2 is used as a binder resin. What uses 200 seconds or more is used.
Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method.
Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
従来は、活物質の表面の性質を分析することが困難であったことから、活物質含有層を実際に形成しなければ、活物質とバインダー樹脂との結着性を判断できなかった。一方、本発明のリチウムイオン二次電池電極形成用組成物の製造方法によれば、水プロトンの横緩和時間の概念を用いることにより、実際に活物質含有層を形成することなく、結着性に優れる活物質とバインダー樹脂を選択することができ、リチウムイオン二次電池電極形成用組成物の製造効率を高めることができる。 Conventionally, since it was difficult to analyze the surface properties of the active material, the binding property between the active material and the binder resin could not be determined unless the active material-containing layer was actually formed. On the other hand, according to the method for producing a composition for forming a lithium ion secondary battery electrode of the present invention, by using the concept of the lateral relaxation time of water protons, binding properties can be reduced without actually forming an active material-containing layer. Active material and binder resin can be selected, and the production efficiency of the composition for forming a lithium ion secondary battery electrode can be increased.
以下、実施例及び比較例を示して本発明をさらに詳細に説明するが、本発明はこれらによって限定されるものではない。なお、実施例及び比較例中の「部」および「％」は、特に断りのない場合はそれぞれ質量部、質量％を示す。
また、実施例及び比較例で使用した材料、並びに、実施例及び比較例で得られたリチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池用電極及びリチウムイオン二次電池について、以下の測定及び評価を行った。結果を表１又は２に示す。EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further in detail, this invention is not limited by these. In the examples and comparative examples, “parts” and “%” represent parts by mass and mass%, respectively, unless otherwise specified.
The materials used in Examples and Comparative Examples, and the compositions for forming lithium ion secondary battery electrodes, the electrodes for lithium ion secondary batteries, and the lithium ion secondary batteries obtained in Examples and Comparative Examples are as follows. Measurement and evaluation were performed. The results are shown in Table 1 or 2.
（横緩和時間の測定）
パルス核磁気共鳴装置（ＸＩＧＯ社製、Ａｃｒｏｎａｒｅａ）を用い、測定核を水素原子核とし、測定温度２５℃、周波数１３ＭＨｚ、９０°パルス幅２μｓの測定条件で、ＣＰＭＧ法（Ｃａｒｒ−ＰｕｒｃｅｌｌＭｅｉｂｏｏｍ−Ｇｉｌｌ法）により、バインダー樹脂のアニオン性水系エマルジョンＡ〜Ｆの水プロトンの横緩和時間、及び活物質分散液ｉ〜iiiの水プロトンの横緩和時間を測定した。
なお、活物質分散液ｉ〜iiiは、下記の活物質ｉ〜iiiと、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなるものを用いた。
活物質ｉ；天然黒鉛（球状、平均粒子径１７μｍ、平均比表面積５．９ｍ２／ｇ）
活物質ii；人造黒鉛（球状、平均粒子径１８μｍ、平均比表面積１．３ｍ２／ｇ）
活物質iii；人造黒鉛（鱗片状、平均粒子径２２μｍ、平均比表面積１．３ｍ２／ｇ）(Measurement of lateral relaxation time)
CPMG method (Carr-PurcellMeiboom-Gill method) using a pulse nuclear magnetic resonance apparatus (XIGO, Acronare), measuring nucleus of hydrogen nucleus, measuring temperature 25 ° C, frequency 13MHz, 90 ° pulse width 2μs. The transverse relaxation time of the water protons of the anionic aqueous emulsions A to F of the binder resin and the transverse relaxation time of the water protons of the active material dispersions i to iii were measured.
In addition, the active material dispersion liquids i to iii are the following active materials i to iii, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water: 52.8: 0.5: 46. What mixed by the mass ratio of 6 was used.
Active material i: natural graphite (spherical, average particle diameter 17 μm, average specific surface area 5.9 m 2 / g)
Active material ii; artificial graphite (spherical, average particle size 18 μm, average specific surface area 1.3 m 2 / g)
Active material iii; artificial graphite (scale-like, average particle diameter 22 μm, average specific surface area 1.3 m 2 / g)
（結着性）
集電体である銅箔上に、リチウムイオン二次電池電極（負極）形成用組成物をＷｅｔ厚みが１５０μｍとなるように塗布し、６０℃で３０分加熱乾燥した。続いて１２０℃で１ｈ真空乾燥し、２３℃、５０％ＲＨ下で２４時間放置したものを試験片とした。試験片塗装面とＳＵＳ板とを両面テープを用いて貼り合わせ、１８０°剥離を実施し（剥離幅２５ｍｍ、剥離速度１００ｍｍ／ｍｉｎ）、剥離強度を測定した。剥離強度が小さいものは、活物質含有層が凝集破壊しやすく、活物質とバインダー樹脂との結着性が低いことを意味している。(Binding property)
A composition for forming a lithium ion secondary battery electrode (negative electrode) was applied on a copper foil as a current collector so that the wet thickness was 150 μm, and was heated and dried at 60 ° C. for 30 minutes. Then, it vacuum-dried at 120 degreeC for 1 hour, and what was left to stand under 23 degreeC and 50% RH for 24 hours was used as the test piece. The coated surface of the test piece and the SUS plate were bonded using a double-sided tape, peeled at 180 ° (peel width 25 mm, peel rate 100 mm / min), and peel strength was measured. A material having a small peel strength means that the active material-containing layer tends to cohesively break and the binding property between the active material and the binder resin is low.
（充放電高温サイクル特性）
電池のサイクル試験は、ＣＣ−ＣＶ充電（上限電圧４．２Ｖ、電流１Ｃ、ＣＶ時間１．５時間、ＣＣ放電（下限電圧３．０Ｖ、電流１Ｃ）とし、いずれも４５℃で実施した。容量維持率は、１サイクル目の放電容量に対する２００サイクル目の放電容量の割合とした。(Charge / discharge high temperature cycle characteristics)
The cycle test of the battery was CC-CV charge (upper limit voltage 4.2V, current 1C, CV time 1.5 hours, CC discharge (lower limit voltage 3.0V, current 1C), and all were performed at 45 ° C. The maintenance rate was the ratio of the discharge capacity at the 200th cycle to the discharge capacity at the first cycle.
（バインダー樹脂のアニオン性水系エマルジョンＡの合成）
冷却管、温度計、攪拌機、滴下ロートを有するセパラブルフラスコに、イオン交換水４０部及び上記一般式（４）に示す反応性のアニオン性乳化剤（三洋化成工業株式会社製、商品名エレミノールＪＳ−２０、有効成分４０％）０．２部を仕込み、７５℃に昇温した。
次いで、上記一般式（４）に示す反応性のアニオン性乳化剤（三洋化成工業株式会社製、商品名エレミノールＪＳ−２０、有効成分４０％）を２．３部、非反応性のアニオン性乳化剤（第一工業製薬株式会社製、商品名ハイテノール０８Ｅ、ポリオキシエチレンアルキルエーテル硫酸エステル塩）０．４部、スチレン５０．４部、アクリル酸２−エチルヘキシル４４．１部、メタクリル酸２−ヒドロキシエチル２．０部、アクリル酸１．６部、パラスチレンスルホン酸ソーダ０．４部、トリメチロールプロパンメタクリレート０．５部及びイオン交換水８５部を予め混合してなるモノマー乳化物を３時間かけて滴下した。同時に重合開始剤として過硫酸カリウム０．４３部をイオン交換水２０部に溶解したものを３時間かけて８０℃で滴下重合した。滴下終了後、２時間熟成後冷却し、アンモニア水１．８部を添加して、アニオン性の水系エマルジョンＡを得た。得られたアニオン性水系エマルジョンＡ中のバインダー樹脂の割合は４０％、粘度６０ｍＰａ・ｓ、エマルジョン中の樹脂粒子の平均粒子径は１３０ｎｍ、ｐＨ７．０であった。
なお、粘度は、ブルックフィールド型回転粘度計を用いて、液温２３℃、回転数６０ｒｐｍ、Ｎｏ．２またはＮｏ．３ローターにて測定した。(Synthesis of binder resin anionic aqueous emulsion A)
In a separable flask having a condenser, a thermometer, a stirrer, and a dropping funnel, 40 parts of ion-exchanged water and a reactive anionic emulsifier represented by the above general formula (4) (trade name Eleminol JS- manufactured by Sanyo Chemical Industries, Ltd.) 20, active ingredient 40%) was charged in 0.2 parts, and the temperature was raised to 75 ° C.
Next, 2.3 parts of a reactive anionic emulsifier (manufactured by Sanyo Kasei Kogyo Co., Ltd., trade name Eleminol JS-20, active ingredient 40%) represented by the above general formula (4), a non-reactive anionic emulsifier ( (Daiichi Kogyo Seiyaku Co., Ltd., trade name: Hytenol 08E, polyoxyethylene alkyl ether sulfate ester salt) 0.4 part, styrene 50.4 parts, 2-ethylhexyl acrylate 44.1 parts, 2-hydroxyethyl methacrylate A monomer emulsion prepared by mixing 2.0 parts, 1.6 parts of acrylic acid, 0.4 parts of sodium parastyrene sulfonate, 0.5 parts of trimethylolpropane methacrylate and 85 parts of ion-exchanged water over 3 hours. It was dripped. At the same time, 0.43 part of potassium persulfate dissolved in 20 parts of ion-exchanged water as a polymerization initiator was dropped and polymerized at 80 ° C. over 3 hours. After completion of dropping, the mixture was aged for 2 hours and then cooled, and 1.8 parts of aqueous ammonia was added to obtain an anionic aqueous emulsion A. The ratio of the binder resin in the obtained anionic aqueous emulsion A was 40%, the viscosity was 60 mPa · s, the average particle size of the resin particles in the emulsion was 130 nm, and pH 7.0.
The viscosity was measured using a Brookfield rotational viscometer using a liquid temperature of 23 ° C., a rotational speed of 60 rpm, and a No. 2 or No. Measurements were taken with 3 rotors.
（バインダー樹脂のアニオン性水系エマルジョンＢ〜Ｆの合成）
モノマーの組成を表１の配合に変更した以外は、上記と同様にしてアニオン性水系エマルジョンＢ〜Ｆを得た。(Synthesis of binder resin anionic aqueous emulsions B to F)
Anionic aqueous emulsions B to F were obtained in the same manner as above except that the monomer composition was changed to the formulation shown in Table 1.
（バインダー樹脂のアニオン性水系エマルジョンＧ）
バインダー樹脂のアニオン性水系エマルジョンＧとして、スチレン−ブタジエンゴム（ガラス転移温度−７℃（ＤＳＣにての実測値））のアニオン性水系エマルジョン（バインダー樹脂の割合４０％、粘度１１ｍＰａ・ｓ、エマルジョン中の樹脂粒子の平均粒子径１９０ｎｍ、ｐＨ７．０）を調整した。(Anionic aqueous emulsion G of binder resin)
As anionic aqueous emulsion G of binder resin, anionic aqueous emulsion of styrene-butadiene rubber (glass transition temperature -7 ° C. (actual value measured by DSC)) (ratio of binder resin 40%, viscosity 11 mPa · s, in emulsion) The average particle diameter of the resin particles was adjusted to 190 nm and pH 7.0).
（実施例１）
１．正極形成用組成物及び正極の作製
ＬｉＮｉ１／３Ｍｎ１／３Ｃｏ１／３Ｏ２を９０部、導電補助剤としてアセチレンブラックを５部、バインダー樹脂としてポリフッ化ビニリデン５部を混合したものに、Ｎ−メチルピロリドンを１００部加えてさらに混合して正極形成用組成物を作製した。
次いで、ドクターブレード法により、集電体となる厚さ２０μｍのアルミニウム箔の片面にロールプレス処理後の厚さが６０μｍになるように該組成物を塗布し、１２０℃で５分乾燥、プレス工程を経て正極活物質含有層を形成した。Example 1
1. Composition for forming positive electrode and preparation of positive electrode 90 parts LiNi 1/3 Mn 1/3 Co 1/3 O 2 , 5 parts acetylene black as a conductive additive, and 5 parts polyvinylidene fluoride as a binder resin , 100 parts of N-methylpyrrolidone was added and further mixed to prepare a positive electrode forming composition.
Next, the doctor blade method is used to apply the composition to one side of a 20 μm thick aluminum foil serving as a current collector so that the thickness after the roll press treatment is 60 μm, followed by drying at 120 ° C. for 5 minutes, pressing step Then, a positive electrode active material-containing layer was formed.
２．負極形成用組成物及び負極の作製
上記活物質iiを１００部、上記エマルジョンＡを３．７５部、及びＣＭＣ（重量平均分子量３００万、置換度０．９）の２％水溶液を５０部混合し、さらに水を２８部添加して、実施例１のリチウムイオン二次電池電極（負極）形成用組成物を得た。
次いで、該組成物を集電体となる厚さ１０μｍの銅箔の片面にロールプレス処理後の厚さが６０μｍとなるように塗布し、８０℃で５分乾燥し、プレス工程を経て負極活物質含有層を形成した。2. Composition for Negative Electrode Formation and Production of Negative Electrode 100 parts of the active material ii, 3.75 parts of the emulsion A, and 50 parts of a 2% aqueous solution of CMC (weight average molecular weight 3 million, substitution degree 0.9) were mixed. Furthermore, 28 parts of water was added to obtain a composition for forming a lithium ion secondary battery electrode (negative electrode) of Example 1.
Next, the composition was applied to one side of a 10 μm thick copper foil serving as a current collector so that the thickness after the roll press treatment was 60 μm, dried at 80 ° C. for 5 minutes, passed through a pressing step, and the negative electrode active A substance-containing layer was formed.
３．電池の作製
得られた正極活物質含有層および負極活物質含有層に導電タブをつけ、正極と負極との間にポリオレフィン系の多孔性フィルムからなるセパレータを介在させて、正極と負極との活物質が互いに対向するようにアルミラミネート外装体（電池パック）の中に収納した。この外装体中にＬｉＰＦ６の１．０ｍｏｌ／Ｌ（リットル）エチレンカーボネート（ＥＣ）／ジエチルカーボネート（ＥＭＣ）＝４０／６０（体積比）電解液を注液し真空含浸を行い、注液部分を熱融着し、実施例１のリチウムイオン二次電池を得た。3. Batteries were prepared by attaching conductive tabs to the obtained positive electrode active material-containing layer and negative electrode active material-containing layer, and interposing a separator made of a polyolefin-based porous film between the positive electrode and the negative electrode. The materials were stored in an aluminum laminate outer package (battery pack) so that the materials face each other. An electrolyte solution of 1.0 mol / L (liter) ethylene carbonate (EC) / diethyl carbonate (EMC) = 40/60 (volume ratio) of LiPF 6 was injected into this outer package, and vacuum impregnation was performed. The lithium ion secondary battery of Example 1 was obtained by heat sealing.
（実施例２〜１０）（比較例１〜９）
負極の作製に用いる活物質及びエマルジョンを表２のエマルジョンに変更した以外は、実施例１と同様にして、リチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池電極及びリチウムイオン二次電池を得た。(Examples 2 to 10) (Comparative Examples 1 to 9)
Except having changed the active material and emulsion used for preparation of a negative electrode into the emulsion of Table 2, it carried out similarly to Example 1, the composition for lithium ion secondary battery electrode formation, a lithium ion secondary battery electrode, and a lithium ion secondary A battery was obtained.
表１から明らかなように、実施例１〜１０のリチウムイオン二次電池電極形成用組成物、リチウムイオン二次電池電極及びリチウムイオン二次電池は、剥離強度が高く、活物質とバインダー樹脂との結着性が良好であることが確認できる。さらに、実施例１〜４及び実施例６〜９のものは、バインダー樹脂がスチレンとエチレン性不飽和カルボン酸エステルとの共重合体であることから、充放電高温リサイクル特性に優れるものであった。
一方、比較例１〜９のものは、活物質の横緩和時間又はバインダー樹脂の横緩和時間の何れかが本願発明の条件を満たさないことから、活物質とバインダー樹脂との結着性を良好にできず、塗膜が凝集破壊してしまい、剥離強度に劣るものであった。As is apparent from Table 1, the compositions for forming lithium ion secondary battery electrodes, lithium ion secondary battery electrodes and lithium ion secondary batteries of Examples 1 to 10 have high peel strength, and the active material and binder resin It can be confirmed that the binding property is good. Furthermore, in Examples 1-4 and Examples 6-9, the binder resin is a copolymer of styrene and an ethylenically unsaturated carboxylic acid ester, and thus has excellent charge / discharge high temperature recycling characteristics. .
On the other hand, those of Comparative Examples 1 to 9 have good binding properties between the active material and the binder resin because either the lateral relaxation time of the active material or the lateral relaxation time of the binder resin does not satisfy the conditions of the present invention. The coating film was agglomerated and broken, and the peel strength was poor.
Claims (7)
条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。
条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。The active material contains a binder resin, and the active material has a transverse relaxation time of water protons of the dispersion measured under the following condition 1 of 10 seconds or more. A composition for forming a lithium ion secondary battery electrode, wherein the transverse relaxation time of water protons of the aqueous emulsion to be measured is 200 seconds or more.
Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method.
Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
活物質が、下記条件１により測定される分散液の水プロトンの横緩和時間が１０秒以上である場合に、バインダー樹脂として、下記条件２により測定される水系エマルジョンの水プロトンの横緩和時間が２００秒以上であるものを用いる、リチウムイオン二次電池電極形成用組成物の製造方法。
条件１：活物質と、重量平均分子量３００万で置換度０．９のカルボキシメチルセルロースと、水とを、５２．８：０．５：４６．６の質量割合で混合してなる活物質分散液をパルスＮＭＲ法によって測定した水プロトンの横緩和時間。
条件２：バインダー樹脂を４０質量％含むアニオン性水系エマルジョンをパルスＮＭＲ法によって測定した水プロトンの横緩和時間。A method for producing a composition for forming a lithium ion secondary battery electrode comprising a step of mixing an active material and a binder resin,
When the active material has a transverse relaxation time of water protons of the dispersion measured under the following condition 1 of 10 seconds or more, the transverse relaxation time of water protons of the aqueous emulsion measured under the following condition 2 is used as a binder resin. The manufacturing method of the composition for lithium ion secondary battery electrode formation using what is 200 seconds or more.
Condition 1: An active material dispersion obtained by mixing an active material, carboxymethyl cellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9, and water in a mass ratio of 52.8: 0.5: 46.6. Is the transverse relaxation time of water proton measured by pulse NMR method.
Condition 2: Transverse relaxation time of water protons measured by pulse NMR method for an anionic aqueous emulsion containing 40% by mass of binder resin.
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| TWI710160B (en) * | 2017-12-26 | 2020-11-11 | 日商昭和電工股份有限公司 | Binder for nonaqueous battery electrode, slurry for nonaqueous battery electrode, nonaqueous battery electrode, and nonaqueous battery |
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| JP2001076731A (en) * | 1999-09-03 | 2001-03-23 | Nippon Zeon Co Ltd | Binder for lithium ion secondary battery electrode, and its utilization |
| JP2011243464A (en) * | 2010-05-19 | 2011-12-01 | Showa Denko Kk | Binder for lithium ion secondary battery electrodes, slurry obtained by using the binder for electrodes, electrodes obtained by using the slurry, and lithium ion secondary battery obtained by using the electrodes |
| JP2012059648A (en) * | 2010-09-13 | 2012-03-22 | Unitika Ltd | Resin for binder of secondary battery electrode, and binder liquid using the same, secondary battery electrode, secondary battery |
| WO2012111425A1 (en) * | 2011-02-14 | 2012-08-23 | 昭和電工株式会社 | Slurries obtained using binder for cell electrodes, electrodes obtained using slurries, and lithium-ion secondary cell obtained using electrodes |
| JP2013062080A (en) * | 2011-09-12 | 2013-04-04 | Nippon Shokubai Co Ltd | Water dispersion for aqueous system electrode composition |
| JP2013110108A (en) * | 2011-10-24 | 2013-06-06 | Toyo Ink Sc Holdings Co Ltd | Emulsion binder for formation of electrodes of secondary batteries, mixture ink for formation of electrodes of secondary batteries, secondary battery electrode, and secondary battery |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001076731A (en) * | 1999-09-03 | 2001-03-23 | Nippon Zeon Co Ltd | Binder for lithium ion secondary battery electrode, and its utilization |
| JP2011243464A (en) * | 2010-05-19 | 2011-12-01 | Showa Denko Kk | Binder for lithium ion secondary battery electrodes, slurry obtained by using the binder for electrodes, electrodes obtained by using the slurry, and lithium ion secondary battery obtained by using the electrodes |
| JP2012059648A (en) * | 2010-09-13 | 2012-03-22 | Unitika Ltd | Resin for binder of secondary battery electrode, and binder liquid using the same, secondary battery electrode, secondary battery |
| WO2012111425A1 (en) * | 2011-02-14 | 2012-08-23 | 昭和電工株式会社 | Slurries obtained using binder for cell electrodes, electrodes obtained using slurries, and lithium-ion secondary cell obtained using electrodes |
| JP2013062080A (en) * | 2011-09-12 | 2013-04-04 | Nippon Shokubai Co Ltd | Water dispersion for aqueous system electrode composition |
| JP2013110108A (en) * | 2011-10-24 | 2013-06-06 | Toyo Ink Sc Holdings Co Ltd | Emulsion binder for formation of electrodes of secondary batteries, mixture ink for formation of electrodes of secondary batteries, secondary battery electrode, and secondary battery |
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