WO2015011965A1 - Lithium-ion secondary battery - Google Patents

Lithium-ion secondary battery Download PDF

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Publication number
WO2015011965A1
WO2015011965A1 PCT/JP2014/062519 JP2014062519W WO2015011965A1 WO 2015011965 A1 WO2015011965 A1 WO 2015011965A1 JP 2014062519 W JP2014062519 W JP 2014062519W WO 2015011965 A1 WO2015011965 A1 WO 2015011965A1
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negative electrode
active material
positive electrode
electrode
separator
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PCT/JP2014/062519
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French (fr)
Japanese (ja)
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英二 水谷
英明 篠田
祐樹 杉本
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株式会社豊田自動織機
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Publication of WO2015011965A1 publication Critical patent/WO2015011965A1/en

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    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a lithium ion secondary battery.
  • a lithium ion secondary battery in which an electrode protective layer is provided between an electrode and a separator is known. It is also known to use N-methylpyrrolidone when forming an electrode or an electrode protective layer.
  • the conventional method does not have sufficient high-speed charge / discharge characteristics.
  • This invention is made
  • the lithium ion secondary battery according to the present invention includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, the positive electrode and / or the negative electrode, and the separator.
  • the high-speed charge / discharge characteristics are excellent as compared with a conventional lithium ion secondary battery using N-methylpyrrolidone (NMP). It can be considered that since the amount of residual NMP is small, a film formed on the negative electrode surface due to N-methylpyrrolidone is reduced. This film becomes an electric resistance component and affects the charge / discharge characteristics of the lithium ion secondary battery.
  • NMP N-methylpyrrolidone
  • the N-methylpyrrolidone is preferably derived from the solvent in the slurry used for the production of the electrode protective layer.
  • a lithium ion secondary battery having excellent high-speed charge / discharge characteristics is provided.
  • FIG. 1 is a schematic cross-sectional view of a lithium ion secondary battery according to an embodiment of the present invention.
  • FIG. 2 is a graph showing the relationship of 2s discharge power to A / B in the lithium ion secondary battery according to the example.
  • FIG. 3 is a graph showing a relationship of 2s charging power with respect to A / B in the lithium ion secondary battery according to the example.
  • the lithium ion secondary battery 100 (power storage device) according to the present embodiment mainly includes an electrode assembly 50, a container 70, and leads 7 and 8 connected to the electrode assembly 50. Yes.
  • the electrode assembly 50 includes a plurality of negative electrodes 10, positive electrodes 20, separators 30, and electrode protection layers 40.
  • the negative electrodes 10 and the positive electrodes 20 are alternately stacked with the separators 30 disposed between them.
  • the electrode protective layer 40 is arrange
  • the negative electrode 10 has a negative electrode metal foil 12 and a negative electrode active material layer 14 formed on both surfaces of the negative electrode metal foil 12.
  • the negative electrode metal foil 12 has a tab portion 12a where the negative electrode active material layer 14 is not formed.
  • the negative electrode metal foil 12 is made of a conductive material.
  • An example of the material of the negative electrode metal foil 12 is a metal material such as stainless steel, titanium, nickel, aluminum, or copper, or a conductive resin.
  • copper is suitable as the material for the negative electrode metal foil 12.
  • the thickness of the negative electrode metal foil 12 is not particularly limited, but can be, for example, 5 to 25 ⁇ m. Further, the thickness of the negative electrode active material layer 14 is not particularly limited, but may be, for example, 40 to 100 ⁇ m.
  • the negative electrode active material layer 14 includes a negative electrode active material and a binder, and may include a conductive aid as necessary.
  • Examples of the negative electrode active material are a carbonaceous material that can occlude and release lithium, an element that can be alloyed with lithium, an elemental compound that has an element that can be alloyed with lithium, or a polymer material.
  • Examples of the carbonaceous material are non-graphitizable carbon, artificial graphite, coke, graphite, glassy carbon, organic polymer compound fired body, carbon fiber, activated carbon, or carbon black.
  • the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.
  • elements that can be alloyed with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, 1n, Si, Ge. , Sn, Pb, Sb, Bi.
  • the element that can be alloyed with lithium is preferably silicon (Si) or tin (Sn).
  • Examples of element compound having lithium can be alloyed elements, ZnLiAl, AlSb, SiB 4, SiB 6, Mg 2 Si, Mg 2 Sn, Ni 2 Si, TiSi 2, MoSi 2, CoSi 2, NiSi 2, CaSi 2, CrSi 2, Cu 5 Si , FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N4, Si 2 N 2 O, SiO v (0 ⁇ v ⁇ 2 ), SnO w (0 ⁇ w ⁇ 2), SnSiO 3 , LiSiO or LiSnO.
  • An example of the elemental compound having an element capable of alloying with lithium is preferably a silicon compound or a tin compound.
  • An example of the silicon compound is SiO x (0.5 ⁇ x ⁇ 1.5).
  • a tin alloy Cu—Sn alloy, Co—Sn alloy, etc.
  • the polymer material are polyacetylene and polypyrrole.
  • binders are fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, and styrene-butadiene rubber And synthetic rubbers such as carboxymethylcellulose.
  • the amount of the binder can be 1 to 30 parts by mass with respect to 100 parts by mass of the active material.
  • Examples of the conductive aid are carbon-based particles such as carbon black, graphite, acetylene black (AB), ketjen black (registered trademark), KB, and vapor grown carbon fiber (Vapor, Grown, Carbon, Fiber: VGCF). These can be added alone or in combination of two or more.
  • the amount of the conductive aid used is not particularly limited, but for example, it can be 1 to 30 parts by mass with respect to 100 parts by mass of the active material.
  • the negative electrode active material layer 14 prepares a slurry in which a negative electrode active material, a conductive auxiliary (if necessary), a binder, and a binder solvent are mixed, and is applied onto the negative electrode metal foil 12, and then the solvent is dried Can be formed.
  • the solvent are N-methylpyrrolidone, acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, tetrahydrofuran and dioxane.
  • the positive electrode 20 includes a positive electrode metal foil 22 and a positive electrode active material layer 24 formed on both surfaces of the positive electrode metal foil 22. At the end of the positive electrode metal foil 22, there is a tab portion 22 a where the positive electrode active material layer 24 is not formed.
  • the positive metal foil 22 is made of a conductive material. An example of the material of the positive electrode metal foil 22 is a metal such as aluminum.
  • the positive electrode active material layer 24 includes a positive electrode active material and a binder, and may include a conductive aid as necessary. Examples and blending amounts of the binder and the conductive additive can be the same as those described for the negative electrode 10.
  • the positive electrode active material is not particularly limited as long as it is a positive electrode active material for a lithium secondary battery.
  • An example of the positive electrode active material is a lithium compound.
  • lithium metal composite oxides such as lithium cobalt composite oxide, lithium nickel composite oxide, and lithium manganese composite oxide can be used.
  • Other metal compounds or polymer materials can also be used as the positive electrode active material.
  • examples of other metal compounds include oxides such as titanium oxide, vanadium oxide, and manganese dioxide, or disulfides such as titanium sulfide and molybdenum sulfide.
  • Examples of the polymer material include conductive polymers such as polyaniline and polythiophene.
  • the composite metal oxide include LiCo 1/3 Ni 1/3 Mn 1/3 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.5 CO 0.2 Mn 0.3 O 2 , LiCoO 2 , LiNi 0.8 Co 0.2 O 2 , and LiCoMnO 2 can be used.
  • the positive electrode active material layer 24 prepares a slurry in which a positive electrode active material, a conductive additive (if necessary), a binder, and a binder solvent are mixed, and is applied onto the positive electrode metal foil 22 to dry the solvent. Can be formed.
  • a solvent is the same as that of manufacture of a negative electrode active material layer.
  • the separator 30 separates the positive electrode 20 and the negative electrode 10 and allows lithium ions to pass through while preventing a short circuit of current due to contact between both electrodes.
  • An example of the separator 30 is a porous film made of synthetic resin such as polytetrafluoroethylene (PEFE), polypropylene (PP), polyethylene terephthalate (PET), or polyethylene (PE), or a porous film made of ceramics.
  • the end portion of the separator 30 preferably extends outward from the end surfaces of the positive electrode active material layer 24 and the negative electrode active material layer 14.
  • a pair of separators 30 may form a bag so as to surround the negative electrode 10.
  • the thickness of the separator 30 can be 10 to 50 ⁇ m.
  • the electrode protective layer 40 is provided between the negative electrode 10 and the separator 30 and between the positive electrode 20 and the separator.
  • the electrode protective layer 40 is a porous layer having ceramic particles and a binder that bonds the ceramic particles.
  • ceramics are alumina, silica and titania.
  • the particle size of the ceramic particles can be 0.2 to 2.0 ⁇ m.
  • the kind of binder can be made the same as the binder mentioned by the negative electrode.
  • the amount of the binder can be, for example, 1 to 30 parts by mass with respect to 100 parts by mass of the ceramic particles.
  • the thickness of the electrode protective layer 40 can be set to 0.5 to 30 ⁇ m, for example.
  • the electrode protective layer 40 may be fixed to the negative electrode 10 or the positive electrode 20 in advance, or may be fixed to the separator 30, and is not fixed to the positive electrode 20 and the negative electrode 10 and is not fixed to the separator 30. An aspect may be sufficient.
  • the electrode protective layer 40 is prepared by preparing a slurry in which ceramic particles, a binder, and a solvent for the binder are mixed, and applying the slurry to the positive electrode 20, the negative electrode 10, the separator 30, or another substrate, and drying the solvent. Can be formed.
  • the example of a solvent is the same as that of manufacture of a negative electrode active material layer.
  • the container 70 accommodates the electrode assembly 50 and an electrolytic solution (not shown).
  • the material and form of the container 70 are not particularly limited, and various known materials such as resins and metals can be used.
  • the electrolytic solution includes an electrolyte and a solvent that dissolves the electrolyte.
  • the electrolytic solution is impregnated in the negative electrode active material layer 14, the separator 30, and the positive electrode active material layer 24.
  • Examples of the electrolyte are lithium salts such as LiBF 4 , LiPF 6 , LiClO 4 , LiAsF 6 , LiCF 3 SO 3 , and LiN (CF 3 SO 2 ) 2 .
  • Examples of the solvent are cyclic esters, chain esters, and ethers. Two or more of these solvents can be mixed.
  • Examples of cyclic esters are ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma ptyrolactone, gamma valerolactone.
  • Examples of the chain esters are methyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester.
  • ethers examples include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane.
  • the concentration of the electrolyte in the electrolytic solution can be, for example, 0.5 to 1.7 mol / L.
  • the electrolytic solution may contain a gelling agent.
  • the lead 7 is connected to the tab portion 12 a of each negative electrode metal foil 12.
  • the lead 8 is connected to the tab portion 22 a of each positive metal foil 22. The ends of the leads 7 and 8 are outside the container 70.
  • the N-methylpyrrolidone in the container 70 is derived from the solvent in the slurry used for the production of the negative electrode active material layer 14, the positive electrode active material layer 24, and / or the electrode protective layer 40. Most of the N-methylpyrrolidone is removed when the slurry is dried, but a part of it remains in the layer and is contained in the container of the completed lithium ion secondary battery 100.
  • the drying temperature of the slurry containing N-methylpyrrolidone may be increased and / or the drying time may be lengthened.
  • the drying temperature is preferably 100 ° C. or higher and preferably 125 ° C. or lower.
  • the drying time is preferably 2 hours or more.
  • the total mass of N-methylpyrrolidone in the container 70 can be measured by a gas chromatography fluff mass spectrometer (GCMS).
  • GCMS gas chromatography fluff mass spectrometer
  • the electrolytic solution may be supplied to the GCMS as it is.
  • the concentration in the solid matter such as the negative electrode, the positive electrode, the electrode protective layer, and the separator
  • the remaining N-methylpyrrolidone is transferred to acetone by applying ultrasonic waves, and then acetone is supplied to the GCMS.
  • the lithium ion secondary battery 100 compared with the conventional lithium ion secondary battery in which N-methylpyrrolidone is used as a solvent during the production of the electrode and / or the electrode protective layer, the high-speed charge / discharge characteristics. Excellent. The reason for this is not clear, but it is conceivable that, for example, since the amount of residual N-methylpyrrolidone is small, a film formed on the negative electrode surface due to N-methylpyrrolidone is reduced.
  • the present invention is not limited to the above embodiment, and various modifications can be made.
  • the electrode protection layer 40 is provided between both the negative electrode 10 and the separator 30 and between the negative electrode 10 and the separator 30, but electrode protection is provided only between either one. It can be implemented even if the layer 40 is provided.
  • Example 1 Manufacture of negative electrode
  • Graphite powder negative electrode active material: particle size D50: 20 ⁇ m
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • LiNi 0.5 Co 0.2 Mn 0.3 O 2 particle diameter D50: 10 ⁇ m
  • acetylene black acetylene black
  • PVDF polyvinylidene fluoride
  • This slurry was applied to one side of an aluminum foil, the solvent was dried on a hot plate at 80 ° C. for 30 minutes, pressed, and further heated at 120 ° C. for 3 hours.
  • Electrode protective layer thickness 5 ⁇ m
  • Alumina particles D50: 0.5 ⁇ m
  • PVDF polyvinylidene fluoride
  • a solvent N-methylpyrrolidone
  • a polyethylene porous sheet was sandwiched between the positive electrode and the negative electrode to obtain a laminate.
  • This laminated body was accommodated in a case in which both surfaces of an aluminum foil were laminated with a resin. Further, an electrolyte solution was supplied into the case, and then the case was sealed to obtain a plurality of lithium ion secondary batteries.
  • the electrolytic solution contained a solvent and an electrolyte (1 mol / dm 3 LiPF 6 ), and the solvent contained ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and fluoroethylene carbonate at a mass ratio of 30:30:40. .
  • the total mass B of the negative electrode active material in each battery was 84.9 mg.
  • Example 2 The drying conditions after pressing the positive electrode, the negative electrode, and the electrode protective layer were the same as in Example 1 except that the drying conditions were 120 ° C. and 6 hours. Moreover, the total mass B of the negative electrode active material in each battery was 84.1 mg.
  • Example 1 The drying conditions after pressing the positive electrode, the negative electrode, and the electrode protective layer were the same as in Example 1 except that the drying conditions were 100 ° C. and 3 hours. Moreover, the total mass B of the negative electrode active material in each battery was 84.4 mg.

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Abstract

A lithium-ion secondary battery (100) comprises: a positive electrode (20) having a positive electrode active material; a negative electrode (10) having a negative electrode active material; a separator (30) disposed between the positive electrode (20) and the negative electrode (10); an electrode protective layer (40) disposed between the positive electrode (20) and the separator (30) and/or between the negative electrode (10) and the separator (30); an electrolyte; and a container (70) for housing the positive electrode (20), the negative electrode (10), the separator (30), the electrode protective layer (40), and the electrolyte. 50 ppm ≤ A/B ≤ 150 ppm, where A is the total mass of N-methylpyrrolidone in the container (70) and B is the total mass of the negative electrode active material in the container (70).

Description

リチウムイオン二次電池Lithium ion secondary battery
　本発明は、リチウムイオン二次電池に関する。 The present invention relates to a lithium ion secondary battery.
　従来より、電極とセパレータとの間に、電極保護層を設けたリチウムイオン二次電池が知られている。また、電極や電極保護層の形成時にはＮ－メチルピロリドンを用いることが知られている。 Conventionally, a lithium ion secondary battery in which an electrode protective layer is provided between an electrode and a separator is known. It is also known to use N-methylpyrrolidone when forming an electrode or an electrode protective layer.
特開２００６－４８９４２号公報JP 2006-48842 A
　しかしながら、従来の方法では、高速充放電特性が十分ではない。本発明は上記課題に鑑みてなされたものであり、高速充放電特性に優れたリチウムイオン二次電池を提供することを目的とする。 However, the conventional method does not have sufficient high-speed charge / discharge characteristics. This invention is made | formed in view of the said subject, and it aims at providing the lithium ion secondary battery excellent in the high-speed charge / discharge characteristic.
　本発明に係るリチウムイオン二次電池は、正極活物質を含む正極、負極活物質を含む負極、前記正極と前記負極との間に配置されたセパレータ、前記正極及び／又は前記負極と、前記セパレータとの間に配置された電極保護層、電解液、及び、前記正極、前記負極、前記セパレータ、前記電極保護層、及び前記電解液を収容する容器を備える。
　そして、前記容器内におけるＮ－メチルピロリドンの全質量をＡ、前記負極活物質の質量をＢとしたときに、５０ｐｐｍ≦Ａ／Ｂ≦１５０ｐｐｍである。 The lithium ion secondary battery according to the present invention includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, the positive electrode and / or the negative electrode, and the separator. An electrode protective layer, an electrolytic solution, and a container for accommodating the positive electrode, the negative electrode, the separator, the electrode protective layer, and the electrolytic solution.
When the total mass of N-methylpyrrolidone in the container is A and the mass of the negative electrode active material is B, 50 ppm ≦ A / B ≦ 150 ppm.
　本発明によれば、従来のＮ－メチルピロリドン（ＮＭＰ）を用いたリチウムイオン二次電池に比して、高速充放電特性に優れる。残存ＮＭＰ量が少ないために、Ｎ－メチルピロリドンに起因して負極表面に形成される膜が少なくなることが考えられる。この膜は電気抵抗成分となり、リチウムイオン二次電池の充放電特性に影響がある。 According to the present invention, the high-speed charge / discharge characteristics are excellent as compared with a conventional lithium ion secondary battery using N-methylpyrrolidone (NMP). It can be considered that since the amount of residual NMP is small, a film formed on the negative electrode surface due to N-methylpyrrolidone is reduced. This film becomes an electric resistance component and affects the charge / discharge characteristics of the lithium ion secondary battery.
　また、前記Ｎ－メチルピロリドンは、前記電極保護層の製造に用いるスラリー中の溶媒に由来することが好ましい。 The N-methylpyrrolidone is preferably derived from the solvent in the slurry used for the production of the electrode protective layer.
　本発明によれば、高速充放電特性に優れたリチウムイオン二次電池が提供される。 According to the present invention, a lithium ion secondary battery having excellent high-speed charge / discharge characteristics is provided.
図１は、本発明の一実施形態に係るリチウムイオン二次電池の概略断面図である。FIG. 1 is a schematic cross-sectional view of a lithium ion secondary battery according to an embodiment of the present invention. 図２は、実施例に係るリチウムイオン二次電池において、Ａ／Ｂに対する２ｓ放電電力の関係を示すグラフである。FIG. 2 is a graph showing the relationship of 2s discharge power to A / B in the lithium ion secondary battery according to the example. 図３は、実施例に係るリチウムイオン二次電池において、Ａ／Ｂに対する２ｓ充電電力の関係を示すグラフである。FIG. 3 is a graph showing a relationship of 2s charging power with respect to A / B in the lithium ion secondary battery according to the example.
　本発明に掛かる実施形態の一例を、図面を参照して説明する。図１に示すように、本実施形態に掛かるリチウムイオン二次電池１００（蓄電装置）は、電極組立体５０、容器７０、及び、電極組立体５０に接続されたリード７、８を主として備えている。 An example of an embodiment according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the lithium ion secondary battery 100 (power storage device) according to the present embodiment mainly includes an electrode assembly 50, a container 70, and leads 7 and 8 connected to the electrode assembly 50. Yes.
　（電極組立体５０）
　電極組立体５０は、負極１０、正極２０、セパレータ３０、及び、電極保護層４０をそれぞれ複数有している。負極１０及び正極２０が、これらの間にそれぞれセパレータ３０が配置されつつ、交互に積層されている。また、負極１０とセパレータ３０との間、及び、正極２０とセパレータ３０との間に、それぞれ、電極保護層４０が配置されている。 (Electrode assembly 50)
The electrode assembly 50 includes a plurality of negative electrodes 10, positive electrodes 20, separators 30, and electrode protection layers 40. The negative electrodes 10 and the positive electrodes 20 are alternately stacked with the separators 30 disposed between them. Moreover, the electrode protective layer 40 is arrange | positioned between the negative electrode 10 and the separator 30, and between the positive electrode 20 and the separator 30, respectively.
　（負極１０）
　負極１０は、負極金属箔１２と、この負極金属箔１２の両面に形成された負極活物質層１４とを有している。負極金属箔１２は、負極活物質層１４が形成されていないタブ部１２ａを有する。 (Negative electrode 10)
The negative electrode 10 has a negative electrode metal foil 12 and a negative electrode active material layer 14 formed on both surfaces of the negative electrode metal foil 12. The negative electrode metal foil 12 has a tab portion 12a where the negative electrode active material layer 14 is not formed.
　負極金属箔１２は導電材料からなる。負極金属箔１２の材料の例は、ステンレス鋼、チタン、ニッケル、アルミニウム、銅などの金属材料または導電性樹脂である。特に、負極金属箔１２の材料として、銅が好適である。負極金属箔１２の厚みは特に限定されないが、例えば、５～２５μｍとすることができる。また、負極活物質層１４の厚みも特に限定されないが、例えば、４０～１００μｍとすることができる。 The negative electrode metal foil 12 is made of a conductive material. An example of the material of the negative electrode metal foil 12 is a metal material such as stainless steel, titanium, nickel, aluminum, or copper, or a conductive resin. In particular, copper is suitable as the material for the negative electrode metal foil 12. The thickness of the negative electrode metal foil 12 is not particularly limited, but can be, for example, 5 to 25 μm. Further, the thickness of the negative electrode active material layer 14 is not particularly limited, but may be, for example, 40 to 100 μm.
　負極活物質層１４は、負極活物質、バインダを含み、必用に応じて導電助剤を含むことができる。 The negative electrode active material layer 14 includes a negative electrode active material and a binder, and may include a conductive aid as necessary.
　負極活物質の例は、リチウムを吸蔵、放出可能な炭素質材料、リチウムと合金化可能な元素、リチウムと合金化可能な元素を有する元素化合物、あるいは高分子材料である。
　炭素質材料の例は、難黒鉛化性炭素、人造黒鉛、コークス類、グラファイト類、ガラス状炭素類、有機高分子化合物焼成体、炭素繊維、活性炭あるいはカーボンブラック類である。ここで、有機高分子化合物焼成体とは、フェノール類やフラン類などの高分子材料を適当な温度で焼成して炭素化したものをいう。
　リチウムと合金化可能な元素の例は、Ｎａ、Ｋ、Ｒｂ、Ｃｓ、Ｆｒ、Ｂｅ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａ、Ｒａ、Ｔｉ、Ａｇ、Ｚｎ、Ｃｄ、Ａｌ、Ｇａ、１ｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｐｂ、Ｓｂ、Ｂｉである。中でも、リチウムと合金化可能な元素は、珪素（Ｓｉ）または錫（Ｓｎ）であるとよい。
　リチウムと合金化可能な元素を有する元素化合物の例は、ＺｎＬｉＡｌ、ＡｌＳｂ、ＳｉＢ４、ＳｉＢ６、Ｍｇ２Ｓｉ、Ｍｇ２Ｓｎ、Ｎｉ２Ｓｉ、ＴｉＳｉ２、ＭｏＳｉ２、ＣｏＳｉ２、ＮｉＳｉ２、ＣａＳｉ２、ＣｒＳｉ２、Ｃｕ５Ｓｉ、ＦｅＳｉ２、ＭｎＳｉ２、ＮｂＳｉ２、ＴａＳｉ２、ＶＳｉ２、ＷＳｉ２、ＺｎＳｉ２、ＳｉＣ、Ｓｉ３Ｎ４、Ｓｉ２Ｎ２Ｏ、ＳｉＯｖ（０＜ｖ≦２）、ＳｎＯｗ（０＜ｗ≦２）、ＳｎＳｉＯ３、ＬｉＳｉＯあるいはＬｉＳｎＯである。リチウムと合金化反応可能な元素を有する元素化合物の例は、珪素化合物または錫化合物であることがよい。珪素化合物の例は、ＳｉＯｘ（０．５≦ｘ≦１．５）である。錫化合物は、例えば、スズ合金（Ｃｕ－Ｓｎ合金、Ｃｏ－Ｓｎ合金等）などが使用できる。高分子材料の例は、ポリアセチレン、ポリピロールである。 Examples of the negative electrode active material are a carbonaceous material that can occlude and release lithium, an element that can be alloyed with lithium, an elemental compound that has an element that can be alloyed with lithium, or a polymer material.
Examples of the carbonaceous material are non-graphitizable carbon, artificial graphite, coke, graphite, glassy carbon, organic polymer compound fired body, carbon fiber, activated carbon, or carbon black. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.
Examples of elements that can be alloyed with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, 1n, Si, Ge. , Sn, Pb, Sb, Bi. Among them, the element that can be alloyed with lithium is preferably silicon (Si) or tin (Sn).
Examples of element compound having lithium can be alloyed elements, ZnLiAl, AlSb, SiB 4, SiB 6, Mg 2 Si, Mg 2 Sn, Ni 2 Si, TiSi 2, MoSi 2, CoSi 2, NiSi 2, CaSi 2, CrSi 2, Cu 5 Si , FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N4, Si 2 N 2 O, SiO v (0 <v ≦ 2 ), SnO w (0 <w ≦ 2), SnSiO 3 , LiSiO or LiSnO. An example of the elemental compound having an element capable of alloying with lithium is preferably a silicon compound or a tin compound. An example of the silicon compound is SiO x (0.5 ≦ x ≦ 1.5). As the tin compound, for example, a tin alloy (Cu—Sn alloy, Co—Sn alloy, etc.) can be used. Examples of the polymer material are polyacetylene and polypyrrole.
　バインダの例は、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、フッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチレン等の熱可塑性樹脂、ポリイミド、ポリアミドイミド等のイミド系樹脂、アルコキシシリル基含有樹脂、スチレンブタジエンゴム等の合成ゴム、カルボキシメチルセルロース等である。バインダの量は、活物質１００質量部に対して、１～３０質量部とすることができる。 Examples of binders are fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, and styrene-butadiene rubber And synthetic rubbers such as carboxymethylcellulose. The amount of the binder can be 1 to 30 parts by mass with respect to 100 parts by mass of the active material.
　導電助剤の例は、カーボンブラック、黒鉛、アセチレンブラック(ＡＢ) 、ケッチェンブラック(登録商標) (ＫＢ) 、気相法炭素繊維(Vapor Grown Carbon Fiber：ＶＧＣＦ) 等の炭素系粒子である。これらは、単独で、または二種以上組み合わせて添加することができる。導電助剤の使用量については、特に限定されないが、例えば、１００質量部の活物質に対して、１～３０質量部とすることができる。 Examples of the conductive aid are carbon-based particles such as carbon black, graphite, acetylene black (AB), ketjen black (registered trademark), KB, and vapor grown carbon fiber (Vapor, Grown, Carbon, Fiber: VGCF). These can be added alone or in combination of two or more. The amount of the conductive aid used is not particularly limited, but for example, it can be 1 to 30 parts by mass with respect to 100 parts by mass of the active material.
　負極活物質層１４は、負極活物質、導電助剤（必要であれば）、バインダ、及び、バインダ用の溶媒を混合したスラリーを準備し、負極金属箔１２上に塗布し、その後溶媒を乾燥させることにより形成できる。溶媒の例は、Ｎ－メチルピロリドン、アセトン、メチルエチルケトン、シクロヘキサノン、メチルイソブチルケトン、酢酸エチル、酢酸ブチル、テトラヒドロフラン、ジオキサンである。 The negative electrode active material layer 14 prepares a slurry in which a negative electrode active material, a conductive auxiliary (if necessary), a binder, and a binder solvent are mixed, and is applied onto the negative electrode metal foil 12, and then the solvent is dried Can be formed. Examples of the solvent are N-methylpyrrolidone, acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, tetrahydrofuran and dioxane.
　（正極２０）
　正極２０は、正極金属箔２２と、この正極金属箔２２の両面に形成された正極活物質層２４とを有している。正極金属箔２２の端には、正極活物質層２４が形成されていないタブ部２２ａを有する。正極金属箔２２は導電材料からなる。正極金属箔２２の材料の例は、アルミニウムなどの金属である。 (Positive electrode 20)
The positive electrode 20 includes a positive electrode metal foil 22 and a positive electrode active material layer 24 formed on both surfaces of the positive electrode metal foil 22. At the end of the positive electrode metal foil 22, there is a tab portion 22 a where the positive electrode active material layer 24 is not formed. The positive metal foil 22 is made of a conductive material. An example of the material of the positive electrode metal foil 22 is a metal such as aluminum.
　正極活物質層２４は、正極活物質、バインダを含み、必用に応じて導電助剤を含むことができる。バインダや導電助剤の例及び配合量は、負極１０で記載したのと同様とすることができる。 The positive electrode active material layer 24 includes a positive electrode active material and a binder, and may include a conductive aid as necessary. Examples and blending amounts of the binder and the conductive additive can be the same as those described for the negative electrode 10.
　正極活物質は、リチウム二次電池用の正極活物質であれば特に限定されない。正極活物質の例は、リチウム化合物である。例えばリチウムコバルト複合酸化物、リチウムニッケル複合酸化物、リチウムマンガン複合酸化物などのリチウム金属複合酸化物などを用いることができる。また正極活物質として他の金属化合物あるいは高分子材料を用いることもできる。他の金属化合物としては、例えば酸化チタン、酸化バナジウムあるいは二酸化マンガンなどの酸化物、または硫化チタンあるいは硫化モリブデンなどの二硫化物が挙げられる。高分子材料としては例えばポリアニリンあるいはポリチオフェンなどの導電性高分子が挙げられる。 The positive electrode active material is not particularly limited as long as it is a positive electrode active material for a lithium secondary battery. An example of the positive electrode active material is a lithium compound. For example, lithium metal composite oxides such as lithium cobalt composite oxide, lithium nickel composite oxide, and lithium manganese composite oxide can be used. Other metal compounds or polymer materials can also be used as the positive electrode active material. Examples of other metal compounds include oxides such as titanium oxide, vanadium oxide, and manganese dioxide, or disulfides such as titanium sulfide and molybdenum sulfide. Examples of the polymer material include conductive polymers such as polyaniline and polythiophene.
　特に正極活物質は、一般式：ＬｉＣｏｐＮｉｑＭｎｒＯ２（ｐ＋ｑ＋ｒ＝１、０＜ｐ≦１、０≦ｑ＜１、０≦ｒ＜１）で表されるリチウム金属複合酸化物を含むことが好ましい。上記複合金属酸化物として、例えばＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２、ＬｉＮｉ０．６Ｃｏ０．２Ｍｎ０．２Ｏ２、ＬｉＮｉ０．５ＣＯ０．２Ｍｎ０．３Ｏ２、ＬｉＣｏＯ２、ＬｉＮｉ０．８Ｃｏ０．２Ｏ２、ＬｉＣｏＭｎＯ２を用いることができる。
　また、正極活物質は、一般式：ＬｉＣｏｐＮｉｑＭｎｒＤｓＯ２（ｐ＋ｑ＋ｒ＋ｓ＝１、０＜ｐ≦１、０≦ｑ＜１、０≦ｒ＜１、０＜ｓ＜１）で表されるリチウム金属複合酸化物を含むことも好ましい。Ｄは、Ａｌ，Ｍｇ，Ｔｉ，Ｓｎ，Ｚｎ，Ｗ，Ｚｒ，Ｍｏ，Ｆｅ，Ｎａから成る群から選択される少なくとも１つの元素である。 In particular, the positive electrode active material is a lithium metal composite oxide represented by the general formula: LiCo p Ni q Mn r O 2 (p + q + r = 1, 0 <p ≦ 1, 0 ≦ q <1, 0 ≦ r <1). It is preferable to include. Examples of the composite metal oxide include LiCo 1/3 Ni 1/3 Mn 1/3 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.5 CO 0.2 Mn 0.3 O 2 , LiCoO 2 , LiNi 0.8 Co 0.2 O 2 , and LiCoMnO 2 can be used.
The positive electrode active material has a general formula: LiCo p Ni q Mn r D S O 2 (p + q + r + s = 1, 0 <p ≦ 1, 0 ≦ q <1, 0 ≦ r <1, 0 <s <1) It is also preferable to contain the lithium metal complex oxide represented. D is at least one element selected from the group consisting of Al, Mg, Ti, Sn, Zn, W, Zr, Mo, Fe, and Na.
　正極活物質層２４は、正極活物質、導電助剤（必要であれば）、バインダ、及び、バインダ用の溶媒を混合したスラリーを準備し、正極金属箔２２上に塗布し、溶媒を乾燥させることにより形成できる。溶媒の例は、負極活物質層の製造と同様である。 The positive electrode active material layer 24 prepares a slurry in which a positive electrode active material, a conductive additive (if necessary), a binder, and a binder solvent are mixed, and is applied onto the positive electrode metal foil 22 to dry the solvent. Can be formed. The example of a solvent is the same as that of manufacture of a negative electrode active material layer.
　（セパレータ３０）
　セパレータ３０は、正極２０と負極１０とを隔離し、両極の接触による電流の短絡を防止しつつ、リチウムイオンを通過させる。セパレータ３０の例は、ポリテトラフルオロエチレン（ＰＥＦＥ）、ポリプロピレン（ＰＰ）、ポリエチレンテレフタレート（ＰＥＴ）、あるいはポリエチレン（ＰＥ）などの合成樹脂製の多孔質膜、またはセラミックス製の多孔質膜である。 (Separator 30)
The separator 30 separates the positive electrode 20 and the negative electrode 10 and allows lithium ions to pass through while preventing a short circuit of current due to contact between both electrodes. An example of the separator 30 is a porous film made of synthetic resin such as polytetrafluoroethylene (PEFE), polypropylene (PP), polyethylene terephthalate (PET), or polyethylene (PE), or a porous film made of ceramics.
　セパレータ３０の端部は、図１に示すように、正極活物質層２４及び負極活物質層１４の端面よりも外側に延びていることが好ましい。また、一対のセパレータ３０が、負極１０を取り囲むように袋を形成していても良い。セパレータ３０の厚みは、１０～５０μｍとすることができる。 As shown in FIG. 1, the end portion of the separator 30 preferably extends outward from the end surfaces of the positive electrode active material layer 24 and the negative electrode active material layer 14. A pair of separators 30 may form a bag so as to surround the negative electrode 10. The thickness of the separator 30 can be 10 to 50 μm.
　（電極保護層４０）
　電極保護層４０は、負極１０とセパレータ３０との間、及び、正極２０とセパレータとの間にそれぞれ設けられている。電極保護層４０は、セラミクス粒子と、セラミクス粒子同士を結合するバインダとを有する、多孔質層である。セラミクスの例は、アルミナ、シリカ、チタニアである。セラミクス粒子の粒径は、０．２～２．０μｍとすることができる。バインダの種類は、負極で挙げたバインダと同じとすることができる。バインダの量は、セラミクス粒子１００質量部に対して、例えば、１～３０質量部とすることができる。電極保護層４０の厚みは、例えば、０．５～３０μｍとすることができる。 (Electrode protective layer 40)
The electrode protective layer 40 is provided between the negative electrode 10 and the separator 30 and between the positive electrode 20 and the separator. The electrode protective layer 40 is a porous layer having ceramic particles and a binder that bonds the ceramic particles. Examples of ceramics are alumina, silica and titania. The particle size of the ceramic particles can be 0.2 to 2.0 μm. The kind of binder can be made the same as the binder mentioned by the negative electrode. The amount of the binder can be, for example, 1 to 30 parts by mass with respect to 100 parts by mass of the ceramic particles. The thickness of the electrode protective layer 40 can be set to 0.5 to 30 μm, for example.
　電極保護層４０は、予め負極１０又は正極２０に固定されていても良いし、セパレータ３０に固定されていても良いし、正極２０及び負極１０に固定されずかつセパレータ３０にも固定されていない態様でも良い。 The electrode protective layer 40 may be fixed to the negative electrode 10 or the positive electrode 20 in advance, or may be fixed to the separator 30, and is not fixed to the positive electrode 20 and the negative electrode 10 and is not fixed to the separator 30. An aspect may be sufficient.
　電極保護層４０は、セラミック粒子、バインダ、及び、バインダ用の溶媒を混合したスラリーを準備し、正極２０、負極１０、セパレータ３０、あるいは、他の基材等に塗布し、溶媒を乾燥させることにより形成できる。溶媒の例は、負極活物質層の製造と同様である。 The electrode protective layer 40 is prepared by preparing a slurry in which ceramic particles, a binder, and a solvent for the binder are mixed, and applying the slurry to the positive electrode 20, the negative electrode 10, the separator 30, or another substrate, and drying the solvent. Can be formed. The example of a solvent is the same as that of manufacture of a negative electrode active material layer.
　（容器７０）
　容器７０は、電極組立体５０、及び電解液（図示略）を収容する。容器７０の材料や形態は特に限定されず、樹脂、金属などの公知の種々の物を使用できる。 (Container 70)
The container 70 accommodates the electrode assembly 50 and an electrolytic solution (not shown). The material and form of the container 70 are not particularly limited, and various known materials such as resins and metals can be used.
　（電解液）
　電解液は、電解質と、この電解質を溶解する溶媒とを含む。電解液は、負極活物質層１４、セパレータ３０、正極活物質層２４内に含浸されている。 (Electrolyte)
The electrolytic solution includes an electrolyte and a solvent that dissolves the electrolyte. The electrolytic solution is impregnated in the negative electrode active material layer 14, the separator 30, and the positive electrode active material layer 24.
　電解質の例は、ＬｉＢＦ４、ＬｉＰＦ６、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２等のリチウム塩である。 Examples of the electrolyte are lithium salts such as LiBF 4 , LiPF 6 , LiClO 4 , LiAsF 6 , LiCF 3 SO 3 , and LiN (CF 3 SO 2 ) 2 .
　溶媒の例は、環状エステル類、鎖状エステル類、エーテル類である。これらの溶媒を２種以上混合することもできる。環状エステル類の例は、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ガンマブチロラクトン、ビニレンカーボネート、２－メチル－ガンマブチロラクトン、アセチル－ガンマプチロラクトン、ガンマバレロラクトンである。鎖状エステル類の例は、メチルカーボネート、ジエチルカーボネート、ジブチルカーボネート、ジプロピルカーボネート、メチルエチルカーボネート、プロピオン酸アルキルエステル、マロン酸ジアルキルエステル、酢酸アルキルエステルである。エーテル類の例は、テトラヒドロフラン、２－メチルテトラヒドロフラン、１，４－ジオキサン、１，２－ジメトキシエタン、１，２－ジエトキシエタン、１，２－ジブトキシエタンである。 Examples of the solvent are cyclic esters, chain esters, and ethers. Two or more of these solvents can be mixed. Examples of cyclic esters are ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma ptyrolactone, gamma valerolactone. Examples of the chain esters are methyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers are tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane.
　電解液における電解質の濃度は、例えば、０．５～１．７ｍｏｌ／Ｌとすることができる。電解液は、ゲル化剤を含んでいても良い。 The concentration of the electrolyte in the electrolytic solution can be, for example, 0.5 to 1.7 mol / L. The electrolytic solution may contain a gelling agent.
　（リード）
　リード７は各負極金属箔１２のタブ部１２ａに接続されている。リード８は各正極金属箔２２のタブ部２２ａに接続されている。リード７、８の端部は、容器７０の外部に出ている。 (Lead)
The lead 7 is connected to the tab portion 12 a of each negative electrode metal foil 12. The lead 8 is connected to the tab portion 22 a of each positive metal foil 22. The ends of the leads 7 and 8 are outside the container 70.
　（容器内のＮ－メチルピロリドンの濃度）
　本実施形態に係るリチウムイオン二次電池においては、容器７０内におけるＮ－メチルピロリドンの全質量をＡ、容器７０内における負極活物質の全質量をＢとしたときに、５０ｐｐｍ≦Ａ／Ｂ≦１５０ｐｐｍを満たす。７５ｐｐｍ≦Ａ／Ｂであることができる。また、Ａ／Ｂ≦１３０ｐｐｍであることができる。 (Concentration of N-methylpyrrolidone in the container)
In the lithium ion secondary battery according to this embodiment, when the total mass of N-methylpyrrolidone in the container 70 is A and the total mass of the negative electrode active material in the container 70 is B, 50 ppm ≦ A / B ≦ Satisfies 150 ppm. 75 ppm ≦ A / B. Further, A / B ≦ 130 ppm can be satisfied.
　容器７０内のＮ－メチルピロリドンは、負極活物質層１４、正極活物質層２４、及び／又は、電極保護層４０の製造に用いるスラリー中の溶媒に由来する。大部分のＮ－メチルピロリドンはスラリーの乾燥時に除去されるが、一部が層中に残存し、完成したリチウムイオン二次電池１００の容器内に含まれることになる。容器内のＮ－メチルピロリドンの濃度を十分に低くするにはＮ－メチルピロリドンを含むスラリーの乾燥温度を高くし、及び／又は、乾燥時間を長くすればよい。乾燥温度は、１００℃以上が好ましく１２５℃以下が好ましい。乾燥時間は、２時間以上が好ましい。 The N-methylpyrrolidone in the container 70 is derived from the solvent in the slurry used for the production of the negative electrode active material layer 14, the positive electrode active material layer 24, and / or the electrode protective layer 40. Most of the N-methylpyrrolidone is removed when the slurry is dried, but a part of it remains in the layer and is contained in the container of the completed lithium ion secondary battery 100. In order to sufficiently reduce the concentration of N-methylpyrrolidone in the container, the drying temperature of the slurry containing N-methylpyrrolidone may be increased and / or the drying time may be lengthened. The drying temperature is preferably 100 ° C. or higher and preferably 125 ° C. or lower. The drying time is preferably 2 hours or more.
　容器７０内のＮ－メチルピロリドンの全質量量は、ガスクロマトフラフ質量分析計（ＧＣＭＳ）により測定できる。例えば、電解液中の濃度の測定時には電解液をそのままＧＣＭＳに供給すればよいし、負極、正極、電極保護層、及び、セパレータ等の固体物中の濃度の測定時には、これらをアセトンに浸しながら超音波を当てて残存するＮ－メチルピロリドンをアセトンに移行させた後、アセトンをＧＣＭＳに供給すればよい。 The total mass of N-methylpyrrolidone in the container 70 can be measured by a gas chromatography fluff mass spectrometer (GCMS). For example, when measuring the concentration in the electrolytic solution, the electrolytic solution may be supplied to the GCMS as it is. When measuring the concentration in the solid matter such as the negative electrode, the positive electrode, the electrode protective layer, and the separator, The remaining N-methylpyrrolidone is transferred to acetone by applying ultrasonic waves, and then acetone is supplied to the GCMS.
　（作用効果）
　本実施形態にかかるリチウムイオン二次電池１００によれば、Ｎ－メチルピロリドンを電極及び／又は電極保護層製造時の溶媒に用いた従来のリチウムイオン二次電池に比して、高速充放電特性に優れる。その理由は明らかではないが、例えば、残存Ｎ－メチルピロリドン量が少ないために、Ｎ－メチルピロリドンに起因して負極表面に形成される膜が少なくなることが考えられる。 (Function and effect)
According to the lithium ion secondary battery 100 according to the present embodiment, compared with the conventional lithium ion secondary battery in which N-methylpyrrolidone is used as a solvent during the production of the electrode and / or the electrode protective layer, the high-speed charge / discharge characteristics. Excellent. The reason for this is not clear, but it is conceivable that, for example, since the amount of residual N-methylpyrrolidone is small, a film formed on the negative electrode surface due to N-methylpyrrolidone is reduced.
　本発明は上記実施形態に限定されず、様々な変形態様を取ることが出来る。
　例えば、上記実施形態では、負極１０とセパレータ３０との間、及び、負極１０とセパレータ３０との間の両方に、電極保護層４０が設けられているが、いずれか一方の間にのみ電極保護層４０が設けられていても実施可能である。 The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above embodiment, the electrode protection layer 40 is provided between both the negative electrode 10 and the separator 30 and between the negative electrode 10 and the separator 30, but electrode protection is provided only between either one. It can be implemented even if the layer 40 is provided.
　（実施例１）
　（負極の製造）
　黒鉛粉（負極活物質：粒径Ｄ５０：２０μｍ）、スチレンブタジエンゴム（ＳＢＲ）、カルボキシメチルセルロース（ＣＭＣ）を、それぞれ、９８：１：１の質量比で混合し、さらに、溶媒（イオン交換水）を加えてスラリーを得た。このスラリーを、銅箔の片面に成膜し、溶媒をホットプレートにより８０℃で１５分乾燥させ、プレスし、さらに、１２０℃で３時間加熱した。 Example 1
(Manufacture of negative electrode)
Graphite powder (negative electrode active material: particle size D50: 20 μm), styrene butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed at a mass ratio of 98: 1: 1, respectively, and a solvent (ion exchange water) Was added to obtain a slurry. This slurry was formed on one side of a copper foil, the solvent was dried on a hot plate at 80 ° C. for 15 minutes, pressed, and further heated at 120 ° C. for 3 hours.
　（正極の製造）
　ＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２（粒径Ｄ５０：１０μｍ）、アセチレンブラック、及び、ポリフッ化ビニリデン（ＰＶＤＦ）を、９４：３：３の質量比で混合し、さらに、溶媒（Ｎ－メチルピロリドン）を加えてスラリーを得た。このスラリーを、アルミニウム箔の片面に塗布し、溶媒をホットプレートにより８０℃で３０分乾燥させ、プレスし、さらに、１２０℃で３時間加熱した。 (Manufacture of positive electrode)
LiNi 0.5 Co 0.2 Mn 0.3 O 2 (particle diameter D50: 10 μm), acetylene black, and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 94: 3: 3, and the solvent (N-methylpyrrolidone) was added to obtain a slurry. This slurry was applied to one side of an aluminum foil, the solvent was dried on a hot plate at 80 ° C. for 30 minutes, pressed, and further heated at 120 ° C. for 3 hours.
　（電極保護層（厚み５μｍ）の形成）
　アルミナ粒子（Ｄ５０：０．５μｍ）、ポリフッ化ビニリデン（ＰＶＤＦ）をそれぞれ９６：４の質量比で混合し、さらに、溶媒（Ｎ－メチルピロリドン）を加えてスラリーを得た。このスラリーを、正極及び負極の両面に成膜し、溶媒をホットプレートにより８０℃で１５分乾燥させ、プレスし、さらに、１２０℃で３時間加熱し、正極及び負極の両面に電極保護層を設けた。 (Formation of electrode protective layer (thickness 5 μm))
Alumina particles (D50: 0.5 μm) and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 96: 4, respectively, and a solvent (N-methylpyrrolidone) was added to obtain a slurry. This slurry is formed on both surfaces of the positive electrode and the negative electrode, and the solvent is dried on a hot plate at 80 ° C. for 15 minutes, pressed, and further heated at 120 ° C. for 3 hours to form an electrode protective layer on both surfaces of the positive electrode and the negative electrode Provided.
　（電池の製造）
　ポリエチレン多孔質シートを、正極及び負極の間に挟んで、積層体を得た。この積層体を、アルミニウム箔の両面を樹脂でラミネートしたケース内に収容し、さらに、ケース内に電解液を供給し、その後、ケースをシールし、複数のリチウムイオン二次電池を得た。電解液は、溶媒と電解質（１ｍｏｌ／ｄｍ３のＬｉＰＦ６）とを含み、溶媒は、エチレンカーボネート、エチルメチルカーボネート、ジメチルカーボネート、フルオロエチレンカーボネートを、質量比において３０：３０：４０で含んでいた。また、各電池中の負極活物質の全質量Ｂは８４．９ｍｇであった。 (Manufacture of batteries)
A polyethylene porous sheet was sandwiched between the positive electrode and the negative electrode to obtain a laminate. This laminated body was accommodated in a case in which both surfaces of an aluminum foil were laminated with a resin. Further, an electrolyte solution was supplied into the case, and then the case was sealed to obtain a plurality of lithium ion secondary batteries. The electrolytic solution contained a solvent and an electrolyte (1 mol / dm 3 LiPF 6 ), and the solvent contained ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and fluoroethylene carbonate at a mass ratio of 30:30:40. . Moreover, the total mass B of the negative electrode active material in each battery was 84.9 mg.
　（実施例２）
　正極、負極、及び、電極保護層のプレス後の乾燥条件を、１２０℃及び６時間とする以外は実施例１と同様にした。また、各電池中の負極活物質の全質量Ｂは、８４．１ｍｇであった。 (Example 2)
The drying conditions after pressing the positive electrode, the negative electrode, and the electrode protective layer were the same as in Example 1 except that the drying conditions were 120 ° C. and 6 hours. Moreover, the total mass B of the negative electrode active material in each battery was 84.1 mg.
　（比較例１）
　正極、負極、及び、電極保護層のプレス後の乾燥条件を、１００℃及び３時間とする以外は実施例１と同様にした。また、各電池中の負極活物質の全質量Ｂは、８４．４ｍｇであった。 (Comparative Example 1)
The drying conditions after pressing the positive electrode, the negative electrode, and the electrode protective layer were the same as in Example 1 except that the drying conditions were 100 ° C. and 3 hours. Moreover, the total mass B of the negative electrode active material in each battery was 84.4 mg.
　（容器内のＮ－メチルピロリドンの濃度）
　各実施例及び比較例の電池の容器内のＮ－メチルピロリドンの質量Ａを、ＧＣＭＳにて測定した。実施例１、２、比較例１の順に、Ａ／Ｂは、９５ｐｐｍ、１３１ｐｐｍ、４０３ｐｐｍであった。 (Concentration of N-methylpyrrolidone in the container)
The mass A of N-methylpyrrolidone in the container of each example and comparative example was measured by GCMS. In the order of Examples 1 and 2 and Comparative Example 1, A / B was 95 ppm, 131 ppm, and 403 ppm.
　（高速充放電特性の評価）
　充電状態（Ｓｔａｔｅ Ｏｆ Ｃｈａｒｇｅ：ＳＯＣ）が１０％の各電池に対して、２５℃で２秒間に放電できる単位負極活物質質量あたりの電力を測定した。得られた電力を、Ａ／Ｂに対してプロットした結果を図２に示す。
　充電状態（ＳＯＣ）が８０％の各電池に対して、２５℃で２秒間に充電できる単位負極活物質質量あたりの電力を測定した。得られた電力を、Ａ／Ｂに対してプロットした結果を図３に示す。 (Evaluation of high-speed charge / discharge characteristics)
The electric power per unit negative electrode active material mass that can be discharged at 25 ° C. for 2 seconds was measured for each battery having a state of charge (SOC) of 10%. The results of plotting the obtained power against A / B are shown in FIG.
For each battery having a state of charge (SOC) of 80%, the power per unit negative electrode active material mass that can be charged at 25 ° C. for 2 seconds was measured. The results of plotting the obtained power against A / B are shown in FIG.
　５０ｐｐｍ≦Ａ／Ｂ≦１５０ｐｐｍを満たす実施例では、急速充放電特性が優れていることが確認された。 In the examples satisfying 50 ppm ≦ A / B ≦ 150 ppm, it was confirmed that the rapid charge / discharge characteristics were excellent.
　１０…負極、２０…正極、３０…セパレータ、４０…電極保護層、７０…容器、１００…リチウムイオン二次電池。 DESCRIPTION OF SYMBOLS 10 ... Negative electrode, 20 ... Positive electrode, 30 ... Separator, 40 ... Electrode protective layer, 70 ... Container, 100 ... Lithium ion secondary battery.

Claims (2)

  1. 　正極活物質を有する正極、
    　負極活物質を有する負極、
    　前記正極と前記負極との間に配置されたセパレータ、
    　前記正極及び／又は前記負極と、前記セパレータとの間に配置された電極保護層、
    　電解液、及び、
    　前記正極、前記負極、前記セパレータ、前記電極保護層、及び前記電解液を収容する容器を備え、
    　前記容器内におけるＮ－メチルピロリドンの全質量をＡ、前記容器内における前記負極活物質の全質量をＢとしたときに、５０ｐｐｍ≦Ａ／Ｂ≦１５０ｐｐｍを満たす、リチウムイオン二次電池。     A positive electrode having a positive electrode active material,
    A negative electrode having a negative electrode active material,
    A separator disposed between the positive electrode and the negative electrode;
    An electrode protective layer disposed between the positive electrode and / or the negative electrode and the separator;
    Electrolyte, and
    A container containing the positive electrode, the negative electrode, the separator, the electrode protective layer, and the electrolyte;
    A lithium ion secondary battery satisfying 50 ppm ≦ A / B ≦ 150 ppm, where A is the total mass of N-methylpyrrolidone in the container and B is the total mass of the negative electrode active material in the container.
  2. 　前記Ｎ－メチルピロリドンは、前記電極保護層の製造に用いるスラリー中の溶媒に由来する請求項１に記載のリチウムイオン二次電池。 2. The lithium ion secondary battery according to claim 1, wherein the N-methylpyrrolidone is derived from a solvent in a slurry used for producing the electrode protective layer.
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