WO2019073595A1 - Lithium-ion secondary battery - Google Patents

Lithium-ion secondary battery Download PDF

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Publication number
WO2019073595A1
WO2019073595A1 PCT/JP2017/037184 JP2017037184W WO2019073595A1 WO 2019073595 A1 WO2019073595 A1 WO 2019073595A1 JP 2017037184 W JP2017037184 W JP 2017037184W WO 2019073595 A1 WO2019073595 A1 WO 2019073595A1
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Prior art keywords
ion secondary
secondary battery
lithium ion
positive electrode
active material
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PCT/JP2017/037184
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French (fr)
Japanese (ja)
Inventor
良太 ▲柳▼澤
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Ｎｅｃエナジーデバイス株式会社
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Priority to PCT/JP2017/037184 priority Critical patent/WO2019073595A1/en
Priority to JP2019547880A priority patent/JPWO2019073595A1/en
Priority to CN201780095520.7A priority patent/CN111164817B/en
Publication of WO2019073595A1 publication Critical patent/WO2019073595A1/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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/494—Tensile strength
    • 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
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • 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.
  • Lithium ion secondary batteries are characterized by high energy density, and are widely used as power sources for mobile phones, notebook computers, electric cars and the like. In lithium ion secondary batteries, since a flammable organic solvent is used as a main solvent of the electrolyte, safety against ignition and explosion is required.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2013-251281.
  • Patent Document 1 Japanese Patent Laid-Open No. 2013-251281 discloses a positive electrode having a positive electrode active material layer containing a positive electrode active material on the surface of a positive electrode current collector, and a negative electrode active containing a negative electrode active material on the surface of the negative electrode current collector.
  • An electrode assembly comprising a negative electrode having a material layer, a separator disposed between the positive electrode and the negative electrode, and a battery case for containing the electrode assembly together with an electrolytic solution;
  • a lithium secondary battery is described in which the value of the ratio to the energy capacity at the time of charging is 4.5 cm 2 / Wh or more, and the electrical resistivity of the positive electrode is 10 ⁇ ⁇ cm to 450 ⁇ ⁇ cm. .
  • lithium ion secondary batteries With the increase in size and energy density of lithium ion secondary batteries, further improvement in safety of lithium ion secondary batteries is required.
  • a high capacity type positive electrode active material such as lithium nickel-containing composite oxide is used, or a positive electrode
  • the thickness of the current collector layer of the negative electrode is reduced or the density of the positive electrode active material layer is increased, the thermal stability of the lithium ion secondary battery may be reduced, and the safety of the battery may be deteriorated. It became clear.
  • the present invention has been made in view of the above circumstances, and provides a lithium ion secondary battery having excellent battery characteristics such as cycle characteristics and battery safety.
  • the present inventors diligently studied to achieve the above object. As a result, by setting the direct current resistance between the positive and negative electrodes in the lithium ion secondary battery after the nail penetration test under specific conditions to a specific range, a trade-off exists between battery characteristics such as cycle characteristics and battery safety. It has been revealed that a lithium ion secondary battery can be obtained which can improve the off relationship and has both battery characteristics such as cycle characteristics and battery safety characteristics. That is, the scale of direct current resistance between positive and negative electrodes in a lithium ion secondary battery after a nail penetration test performed under a specific condition is a lithium ion secondary battery excellent in the balance of battery characteristics such as cycle characteristics and battery safety. The inventors have found that the present invention is effective as a design guideline for realization.
  • the present invention was devised based on such knowledge. That is, according to the present invention, the following lithium ion secondary battery is provided.
  • a positive electrode having a positive electrode current collector layer and a positive electrode active material layer a negative electrode having a negative electrode current collector layer and a negative electrode active material layer, a non-aqueous electrolyte containing a lithium salt, and between the positive electrode and the negative electrode
  • a lithium ion secondary battery in which a sandwiched separator is contained in a container In a fully charged state under a 25 ° C. environment, a SUS304 nail with a diameter of 3 mm and a length of 70 mm is pierced at the center of the lithium ion secondary battery at a speed of 80 mm / sec to short the lithium ion secondary battery.
  • the lithium ion secondary battery When the nail penetration test was conducted, After the nail penetration test, the lithium ion secondary battery is short-circuit discharged, and when the voltage is in the range of 0.001 V to 0.100 V, the direct current resistance between the positive and negative electrodes in the lithium ion secondary battery is 0.
  • a lithium ion secondary battery having 1 ⁇ or more and 300 ⁇ or less.
  • the present invention it is possible to provide a lithium ion secondary battery which is excellent in battery characteristics such as cycle characteristics and battery safety.
  • the lithium ion secondary battery according to the present embodiment includes a positive electrode having a positive electrode current collector layer and a positive electrode active material layer, a negative electrode having a negative electrode current collector layer and a negative electrode active material layer, and a non-aqueous electrolysis containing a lithium salt.
  • a liquid and a separator sandwiched between the positive electrode and the negative electrode are accommodated in a container. Then, in a fully charged state under a 25 ° C.
  • a nail made of SUS304 with a diameter of 3 mm and a length of 70 mm is pierced at the center of the lithium ion secondary battery at a speed of 80 mm / sec to complete the lithium ion secondary battery
  • the lithium ion secondary battery is short-circuit discharged after the nail penetration test when the nail penetration test is performed to short-circuit the lithium ion secondary battery, and when the voltage is in the range of 0.001 V or more and 0.100 V or less
  • the direct current resistance between positive and negative electrodes in the battery is 0.1 ⁇ or more and 300 ⁇ or less.
  • a high capacity type positive electrode active material such as a lithium nickel-containing composite oxide is used, or It is apparent that if the thickness of the current collector layer is reduced or the density of the positive electrode active material layer is increased, the thermal stability of the lithium ion secondary battery may be reduced and the safety of the battery may be deteriorated. Became. Also, according to the study of the present inventor, it has become clear that if the electrical resistance of the electrode is increased to improve the safety of the battery, then the battery characteristics such as cycle characteristics may be deteriorated.
  • the present inventor has found that there is a trade-off relationship between battery characteristics such as cycle characteristics and battery safety in the conventional lithium ion secondary battery. Therefore, the present inventors diligently studied to achieve the above object. As a result, by setting the direct current resistance between positive and negative electrodes in the lithium ion secondary battery after the nail penetration test performed under the above conditions to the above range, a trade-off between battery characteristics such as cycle characteristics and battery safety It has been revealed that a lithium ion secondary battery can be obtained which can improve the relationship of (1) and have both battery characteristics such as cycle characteristics and battery safety characteristics.
  • the scale of direct current resistance between positive and negative electrodes in a lithium ion secondary battery after a nail penetration test performed under a specific condition is a lithium ion secondary battery excellent in the balance of battery characteristics such as cycle characteristics and battery safety. It was found for the first time that it was effective as a design guideline to realize it.
  • the lower limit of the direct current resistance between the positive and negative electrodes after the nail penetration test is 0.1 ⁇ or more, preferably 1 ⁇ or more, more preferably 2 ⁇ or more, further preferably 10 ⁇
  • the resistance is more preferably 40 ⁇ or more, still more preferably 60 ⁇ or more, and particularly preferably 80 ⁇ or more.
  • the safety of the lithium ion secondary battery can be effectively improved by setting the direct current resistance between the positive and negative electrodes after the nail penetration test to the above lower limit value or more. it can.
  • the upper limit of the direct current resistance between the positive and negative electrodes after the nail penetration test is 300 ⁇ or less, preferably 250 ⁇ or less, more preferably 200 ⁇ or less, still more preferably 150 ⁇ . The following is particularly preferable: 130 ⁇ or less.
  • the fully charged state is a voltage of 4.2 V at a constant current of 1 C with respect to a lithium ion secondary battery at 25 ° C. using a constant current constant voltage (CC-CV) method. Constant current charging up to a constant voltage, and then a constant voltage charging to a charge termination current of 0.015 C at a constant voltage of 4.2 V.
  • the direct current resistance between the positive and negative electrodes after the above-mentioned nailing test of the lithium ion secondary battery according to the present embodiment is: (A) the compounding ratio of the positive electrode active material layer and the negative electrode active material layer; ) It is possible to realize by appropriately selecting the type of the current collector layer and the like. Among these, for example, the amount of the conductive additive in the positive electrode active material layer is in a specific range, the separator having high heat resistance and high elongation is used, the positive electrode current collector layer, the negative electrode current collector The use of a separator having a tensile elongation greater than that of the layer, etc. is mentioned as a factor for setting the direct current resistance between the positive and negative electrodes in the lithium ion secondary battery after the above-mentioned nail penetration test to a desired numerical range.
  • the lithium ion secondary battery according to the present embodiment is excellent in battery safety is not necessarily clear, such a lithium ion secondary battery has high battery resistance even if foreign matter enters the battery and shorts, for example. Since the range can be maintained, it is possible to suppress the flow of a large current, and as a result, it is possible to suppress the thermal runaway of the battery.
  • the lithium ion secondary battery according to this embodiment preferably has a cell rated capacity of 5 Ah or more, more preferably 7 Ah or more. Moreover, in the lithium ion secondary battery according to the present embodiment, the number of laminations or the number of laminations of the positive electrode in the central portion is preferably 10 or more, more preferably 15 or more, and still more preferably 20 or more . Thus, the capacity of the lithium ion secondary battery according to the present embodiment can be increased. Further, even with such a high capacity, the lithium ion secondary battery according to the present embodiment is excellent in the short circuit resistance, and it is possible to suppress the thermal runaway of the battery.
  • the form and type of the lithium ion secondary battery of the present embodiment are not particularly limited, but, for example, the following configuration can be made.
  • FIG. 1 schematically shows the structure of a laminated battery.
  • Stacked battery 100 includes battery elements in which positive electrode 1 and negative electrode 6 are alternately laminated in multiple layers with separator 20 interposed therebetween, and these battery elements are a flexible film together with an electrolytic solution (not shown). It is housed in a 30 container.
  • the positive electrode terminal 11 and the negative electrode terminal 16 are electrically connected to the battery element, and a part or all of the positive electrode terminal 11 and the negative electrode terminal 16 are drawn out of the flexible film 30. .
  • the positive electrode 1 is provided with the coated part (positive electrode active material layer 2) and the uncoated part of the positive electrode active material on the front and back of the positive electrode collector layer 3, and the negative electrode 6 is on the front and back of the negative electrode collector layer 8.
  • the coated part of the negative electrode active material (negative electrode active material layer 7) and the uncoated part are provided.
  • the uncoated portion of the positive electrode active material in the positive electrode current collector layer 3 is used as a positive electrode tab 10 for connecting to the positive electrode terminal 11, and the uncoated portion of the negative electrode active material in the negative electrode current collector layer 8 is connected to the negative electrode terminal 16.
  • the negative electrode tab 5 of FIG. The positive electrode tabs 10 are assembled on the positive electrode terminal 11 and connected together by ultrasonic welding etc. together with the positive electrode terminal 11, and the negative electrode tabs 5 are assembled on the negative electrode terminal 16 connected together by ultrasonic welding etc. together with the negative electrode terminal 16. Be done.
  • one end of the positive electrode terminal 11 is drawn out of the flexible film 30, and one end of the negative electrode terminal 16 is also drawn out of the flexible film 30.
  • an insulating member can be formed at the boundary 4 between the coated part (positive electrode active material layer 2) and the non-coated part of the positive electrode active material, and the insulating member is not only the boundary 4 but also the positive electrode tab. 10 and near the boundary between the positive electrode active material.
  • an insulating member can be formed on the boundary portion 9 between the coated portion (negative electrode active material layer 7) and the non-coated portion of the negative electrode active material as required, and the boundary between both the negative electrode tab 5 and the negative electrode active material It can be formed near the part.
  • the outer dimension of the negative electrode active material layer 7 is larger than the outer dimension of the positive electrode active material layer 2 and smaller than the outer dimension of the separator 20.
  • FIG. 2 schematically shows the configuration of a wound battery, and the container etc. are not shown.
  • the wound battery 101 includes a battery element in which a positive electrode 1 and a negative electrode 6 are stacked via a separator 20 and wound, and this battery element is made of a flexible film together with an electrolytic solution (not shown). Contained in the The positive electrode terminal and the negative electrode terminal are also electrically connected to the battery element of the wound battery 101, and the other configuration is substantially the same as that of the laminated battery 100, and thus further description is omitted here.
  • the positive electrode 1 used in the present embodiment can be appropriately selected from among positive electrodes that can be used for known lithium ion secondary batteries, according to the application and the like.
  • the active material used for the positive electrode 1 is preferably a material having high electron conductivity so that lithium ions can be reversibly released and stored, and electron transport can be easily performed.
  • the positive electrode active material used for the positive electrode 1 is not particularly limited.
  • lithium composite oxide having a layered rock salt structure or spinel structure, lithium iron phosphate having an olivine structure, etc. are used. be able to.
  • lithium complex oxide lithium manganate (LiMn 2 O 4 ); lithium cobaltate (LiCoO 2 ); lithium nickelate (LiNiO 2 ); at least a part of manganese, cobalt and nickel of these lithium compounds Those substituted with other metal elements such as aluminum, magnesium, titanium, zinc, etc .; Nickel-substituted lithium manganate in which at least part of manganese in lithium manganate is substituted with nickel; at least part of nickel in lithium nickel nickelate Substituted cobalt-substituted lithium nickelate; part of manganese of lithium-substituted lithium manganate substituted with another metal (eg, at least one of aluminum, magnesium, titanium, zinc); nickel of cobalt-substituted lithium nickelate; Other metal
  • lithium-containing composite oxides having a layered crystal structure examples include lithium-nickel-containing composite oxides.
  • this lithium nickel-containing composite oxide one in which a part of nickel at the nickel site is replaced with another metal can be used.
  • metals other than Ni that occupy the nickel site include at least one metal selected from Mn, Co, Al, Mg, Fe, Cr, Ti, and In.
  • the lithium nickel-containing composite oxide preferably contains Co as a metal other than Ni occupying nickel sites.
  • the lithium-nickel-containing composite oxide more preferably contains Mn or Al in addition to Co, that is, lithium-nickel-cobalt-manganese composite oxide (NCM) having a layered crystal structure, lithium-nickel having a layered crystal structure Cobalt aluminum complex oxide (NCA) or a mixture thereof can be suitably used.
  • NCM lithium-nickel-cobalt-manganese composite oxide
  • NCA Cobalt aluminum complex oxide
  • lithium nickel-containing composite oxide having a layered crystal structure for example, one represented by the following formula (1) can be used.
  • Me1 is Mn or Al
  • Me2 is at least one selected from the group consisting of Mn, Al, Mg, Fe, Cr, Ti, In (except metals of the same type as Me1), ⁇ 0.5 ⁇ a ⁇ 0.1, 0.1 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 0.5, 0 ⁇ d ⁇ 0.5)
  • the average particle diameter of the positive electrode active material is, for example, preferably 0.1 to 50 ⁇ m, more preferably 1 to 30 ⁇ m, and still more preferably 2 to 25 ⁇ m, from the viewpoint of reactivity with the electrolytic solution, rate characteristics, and the like.
  • the average particle diameter means a particle diameter (median diameter: D 50 ) at an integrated value of 50% in a particle size distribution (volume basis) by a laser diffraction scattering method.
  • the positive electrode 1 includes a positive electrode current collector layer 3 and a positive electrode active material layer 2 on the positive electrode current collector layer 3.
  • the positive electrode 1 is disposed such that the positive electrode active material layer 2 faces the negative electrode active material layer 7 on the negative electrode current collector layer 8 with the separator interposed therebetween.
  • the positive electrode 1 in the present embodiment can be manufactured by a known method. For example, after a positive electrode active material, a binder resin, and a conductive additive are dispersed in an organic solvent to obtain a positive electrode slurry, this positive electrode slurry is applied to the positive electrode current collector layer 3 and dried, and pressed as necessary. Thus, the method of forming the positive electrode active material layer 2 on the positive electrode current collector layer 3 can be adopted.
  • NMP N-methyl-2-pyrrolidone
  • NMP N-methyl-2-pyrrolidone
  • binder resin what is generally used as binder resin for positive electrodes, such as a polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), can be used, for example.
  • PTFE polytetrafluoroethylene
  • PVDF polyvinylidene fluoride
  • the content of the binder resin in the positive electrode active material layer 2 is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, based on 100 parts by mass of the entire positive electrode active material layer 2. It is more preferable that it is mass part or more and 5.0 mass parts or less, and it is further more preferable that it is 1.0 mass part or more and 5.0 mass parts or less.
  • the balance of the coating property of a positive electrode slurry, the binding property of a binder, and the battery characteristic as the content of binder resin is in the said range is much more excellent.
  • the ratio of a positive electrode active material becomes large as content of binder resin is below the said upper limit, and since the capacity
  • the positive electrode active material layer 2 can contain a conductive support agent in addition to the positive electrode active material and the binder resin.
  • the conductive aid is not particularly limited as long as it improves the conductivity of the positive electrode, and examples thereof include carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, carbon fiber and the like. These conductive aids may be used alone or in combination of two or more.
  • the content of the conductive additive in the positive electrode active material layer 2 is preferably more than 1.0 parts by mass and less than 4.0 parts by mass, based on 100 parts by mass of the whole of the positive electrode active material layer 2. It is more preferably 2 parts by mass or more and 3.5 parts by mass or less, still more preferably 1.5 parts by mass or more and 3.5 parts by mass or less and 2.0 parts by mass or more and 3.5 parts by mass or less Is particularly preferred.
  • the balance of the coating property of a positive electrode slurry, the binding property of binder resin, and battery characteristics as the content of the conductive support agent is within the above range is further excellent.
  • the ratio of a positive electrode active material becomes large as content of a conductive support agent is less than or less than the said upper limit, and the capacity
  • the positive electrode current collector layer 3 aluminum, stainless steel, nickel, titanium, an alloy of these, or the like can be used. As the shape, foil, flat form, mesh form etc. are mentioned, for example. In particular, an aluminum foil can be suitably used.
  • the thickness of the positive electrode collector layer 3 is not particularly limited, it is, for example, 1 ⁇ m or more and 30 ⁇ m or less.
  • the thickness of the positive electrode current collector layer 3 is smaller, the positive electrode current collector layer 3 is more easily deformed or broken, so that the safety of the lithium ion secondary battery is easily deteriorated.
  • the thickness of the positive electrode current collector layer 3 is thin, the deterioration of the safety of the battery can be suppressed.
  • the positive electrode current collection is preferably less than 25 ⁇ m, more preferably less than 20 ⁇ m, and particularly preferably less than 18 ⁇ m.
  • the tensile elongation of the positive electrode collector layer 3 measured according to 6.3 of JISL1913: 2010 is less than 10%, and it is more preferable that it is less than 8%.
  • the separator 20 is torn by a sharp metal such as lithium dendrite, for example, the expansion of the positive electrode current collector layer 3 can be suppressed, so the contact between the metal that has broken the separator 20 and the positive and negative electrodes is suppressed. be able to. As a result, thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
  • the density of the positive electrode active material layer 2 is not particularly limited, for example, it is preferably not more than 2.0 g / cm 3 or more 4.0g / cm 3, 2.4g / cm 3 or more 3.8 g / cm 3 or less Some are more preferable, and 2.8 g / cm 3 or more and 3.6 g / cm 3 or less are more preferable.
  • the density of the positive electrode active material layer 2 is higher, battery characteristics such as cycle characteristics of the lithium ion secondary battery are likely to be deteriorated.
  • the lithium ion secondary battery according to the present embodiment can suppress the deterioration of the battery characteristics such as the cycle characteristics.
  • the density of the positive electrode active material layer 2 is 3.0 g / cm 3 or more from the viewpoint of further improving the energy density of the obtained lithium ion secondary battery while making battery characteristics such as cycle characteristics better.
  • it is 3.2 g / cm 3 or more, more preferably 3.3 g / cm 3 or more.
  • the density of the positive electrode active material layer 2 is 4.0 g / cm 3 or less, more preferably 3.8 g / cm 3 or less More preferably, it is 3.6 g / cm 3 or less.
  • the thickness (the sum of the thicknesses on both sides) of the positive electrode active material layer 2 is not particularly limited, and can be appropriately set according to the desired characteristics. For example, it can be set thick in terms of energy density, and can be set thin in terms of output characteristics.
  • the thickness (total of the thickness on both sides) of the positive electrode active material layer 2 can be appropriately set, for example, in the range of 20 ⁇ m to 500 ⁇ m, preferably 40 ⁇ m to 400 ⁇ m, and more preferably 60 ⁇ m to 300 ⁇ m.
  • the thickness (thickness of one side) of the positive electrode active material layer 2 is not particularly limited, and can be appropriately set according to the desired characteristics.
  • the positive electrode active material layer 2 can be appropriately set, for example, in the range of 10 ⁇ m to 250 ⁇ m, preferably 20 ⁇ m to 200 ⁇ m, and more preferably 30 ⁇ m to 150 ⁇ m.
  • the negative electrode 6 which concerns on this embodiment can be suitably selected from the negative electrodes which can be used for a well-known lithium ion secondary battery according to a use etc.
  • the negative electrode active material used for the negative electrode 6 can be appropriately set according to the application etc. as long as it can be used for the negative electrode.
  • the negative electrode 6 has a structure including a negative electrode current collector layer 8 and a negative electrode active material layer 7 formed on the negative electrode current collector layer 8.
  • the negative electrode active material layer 7 preferably contains a negative electrode active material and a binder resin, and preferably further contains a conductive auxiliary agent in order to enhance the conductivity.
  • the negative electrode active material is not particularly limited as long as it is an active material for a negative electrode capable of inserting and extracting lithium ions, but a carbonaceous material can be used.
  • the carbonaceous material include graphite, amorphous carbon (for example, graphitizable carbon, non-graphitizable carbon), diamond-like carbon, fullerene, carbon nanotube, carbon nanohorn and the like.
  • graphite natural graphite and artificial graphite can be used, and inexpensive natural graphite is preferable from the viewpoint of material cost.
  • Examples of amorphous carbon include those obtained by heat-treating coal pitch coke, petroleum pitch coke, acetylene pitch coke and the like.
  • lithium metal materials, alloy materials such as silicon and tin, oxide materials such as Nb 2 O 5 and TiO 2 , or a composite thereof can be used.
  • the negative electrode active material may be used alone or in combination of two or more.
  • the average particle diameter of the negative electrode active material is preferably 2 ⁇ m or more, more preferably 5 ⁇ m or more, from the viewpoint of suppressing side reactions during charge and discharge to suppress a decrease in charge and discharge efficiency From (Smoothness of the negative electrode surface, etc.), 40 ⁇ m or less is preferable and 30 ⁇ m or less is more preferable.
  • the average particle diameter means a particle diameter (median diameter: D 50 ) at an integrated value of 50% in a particle size distribution (volume basis) by a laser diffraction scattering method.
  • the negative electrode 6 in the present embodiment can be manufactured by a known method.
  • this slurry is applied to the negative electrode current collector layer 8 and dried, and pressed as necessary to form the negative electrode active material layer 7 A method etc. can be adopted.
  • the method of applying the negative electrode slurry include a doctor blade method, a die coater method, and a dip coating method. If necessary, additives such as an antifoaming agent and a surfactant may be added to the slurry.
  • the content of the binder resin in the negative electrode active material layer 7 is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, based on 100 parts by mass of the entire negative electrode active material layer 7. It is more preferable that it is mass part or more and 8.0 mass parts or less, it is more preferable that it is 1.0 mass part or more and 5.0 mass parts or less, and it is 1.0 mass part or more and 3.0 mass parts or less Is particularly preferred.
  • the content of the binder resin is in the above range, the balance between the coatability of the negative electrode slurry, the binding property of the binder resin, and the battery characteristics is more excellent.
  • the ratio of a negative electrode active material becomes large as content of binder resin is below the said upper limit, and the capacity
  • an organic solvent such as N-methyl-2-pyrrolidone (NMP) or water
  • NMP N-methyl-2-pyrrolidone
  • a binder resin for an organic solvent such as polyvinylidene fluoride (PVDF)
  • PVDF polyvinylidene fluoride
  • rubber binders for example, SBR (styrene-butadiene rubber)
  • acrylic binder resins can be used.
  • aqueous binder resin can be used in the form of an emulsion.
  • water it is preferable to use an aqueous binder and a thickener such as CMC (carboxymethyl cellulose) in combination.
  • the negative electrode active material layer 7 may contain a conductive auxiliary, as necessary.
  • a conductive aid conductive materials generally used as a conductive aid for a negative electrode, such as carbonaceous materials such as carbon black, ketjen black and acetylene black can be used.
  • the content of the conductive additive in the negative electrode active material layer 7 is preferably 0.1 parts by mass or more and 3.0 parts by mass or less, based on 100 parts by mass of the whole of the negative electrode active material layer 7. The content is more preferably 1 part by mass or more and 2.0 parts by mass or less, and particularly preferably 0.2 parts by mass or more and 1.0 parts by mass or less.
  • the balance of the coating property of negative electrode slurry, the binding property of binder resin, and the battery characteristic as the content of a conductive support agent is in the above-mentioned range is much more excellent. Moreover, since the ratio of a negative electrode active material becomes large as content of a conductive support agent is below the said upper limit, and the capacity
  • the average particle size (primary particle size) of the conductive additive used for the positive electrode active material layer 2 and the negative electrode active material layer 7 is preferably in the range of 10 to 100 nm.
  • the average particle size (primary particle size) of the conductive aid is preferably 10 nm or more, more preferably 30 nm or more, and a sufficient number of contact points from the viewpoint of suppressing excessive aggregation of the conductive aid and uniformly dispersing in the negative electrode. From the viewpoint of forming a good conductive path, and is preferably 100 nm or less, more preferably 80 nm or less.
  • the conductive aid is in the form of fibers, those having an average diameter of 2 to 200 nm and an average fiber length of 0.1 to 20 ⁇ m can be mentioned.
  • the average particle diameter of the conductive additive is the median diameter (D 50 ), which means the particle diameter at an integrated value of 50% in the particle size distribution (volume basis) by the laser diffraction scattering method.
  • the thickness (total of the thickness on both sides) of the negative electrode active material layer 7 is not particularly limited, and can be appropriately set according to the desired characteristics. For example, it can be set thick in terms of energy density, and can be set thin in terms of output characteristics.
  • the thickness (total of the thickness on both sides) of the negative electrode active material layer 7 can be appropriately set, for example, in the range of 40 ⁇ m to 1000 ⁇ m, preferably 80 ⁇ m to 800 ⁇ m, and more preferably 120 ⁇ m to 600 ⁇ m.
  • the thickness (thickness of one side) of the negative electrode active material layer 7 is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thick in terms of energy density, and can be set thin in terms of output characteristics.
  • the thickness (thickness of one side) of the negative electrode active material layer 7 can be appropriately set, for example, in the range of 20 ⁇ m to 500 ⁇ m, preferably 40 ⁇ m to 400 ⁇ m, and more preferably 60 ⁇ m to 300 ⁇ m.
  • the density of the negative electrode active material layer 7 is not particularly limited, it is preferably, for example, 1.2 g / cm 3 or more and 2.0 g / cm 3 or less, and 1.3 g / cm 3 or more and 1.9 g / cm 3 or less Some are more preferable, and 1.4 g / cm 3 or more and 1.8 g / cm 3 or less are more preferable.
  • the negative electrode current collector layer 8 copper, stainless steel, nickel, titanium or an alloy thereof can be used. As the shape, foil, flat form, mesh form is mentioned.
  • the thickness of the negative electrode current collector layer 8 is not particularly limited, and is, for example, 1 ⁇ m or more and 20 ⁇ m or less.
  • the thickness of the negative electrode current collector layer 8 is thinner, the negative electrode current collector layer 8 is more easily deformed or broken, so that the safety of the lithium ion secondary battery is easily deteriorated.
  • the thickness of the negative electrode current collector layer 8 is thin, the deterioration of the safety of the battery can be suppressed.
  • the negative electrode current collection is preferably less than 15 ⁇ m, more preferably less than 12 ⁇ m, and particularly preferably less than 10 ⁇ m.
  • the tensile elongation of the negative electrode current collector layer 8 is preferably less than 10%, more preferably less than 5%, which is measured according to 6.3 of JIS L1913: 2010.
  • the expansion of the negative electrode current collector layer 8 can be suppressed, so the contact between the metal that has broken the separator 20 and the positive and negative electrodes is suppressed. be able to.
  • thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
  • Non-aqueous electrolyte containing lithium salt The non-aqueous electrolytic solution containing a lithium salt used in the present embodiment can be appropriately selected from known ones depending on the type of electrode active material, the use of the lithium ion secondary battery, and the like.
  • lithium salt 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 Examples include (C 2 H 5 ) 4 , CF 3 SO 3 Li, CH 3 SO 3 Li, LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 2 N, and lower fatty acid carboxylate lithium.
  • the solvent for dissolving the lithium salt is not particularly limited as long as it is generally used as a liquid for dissolving the electrolyte, and ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), carbonates such as vinylene carbonate (VC); lactones such as ⁇ -butyrolactone and ⁇ -valerolactone; trimethoxymethane Ethers such as 1,2-dimethoxyethane, diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, etc.
  • EC ethylene carbonate
  • PC propylene carbonate
  • BC butylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbon
  • Sulfoxides such as dimethylsulfoxide, etc. 1,3-Dioxolane, 4-methyl-1,3-dioxola
  • Nitrogenous solvents such as acetonitrile, nitromethane, formamide and dimethylformamide; methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate and the like; organic acid esters such as phosphoric acid triester And diglymes; triglymes; sulfolanes such as sulfolane and methyl sulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; and sultones such as 1,3-propane sultone, 1,4-butane sultone and naphtha sultone. . These may be used singly or in combination of two or more.
  • a well-known member can be used for a container in this embodiment, and it is preferable to use the flexible film 30 from a viewpoint of weight reduction of a battery.
  • the flexible film 30 can use what provided the resin layer in front and back of the metal layer used as a base material.
  • the metal layer can be selected to have a barrier property to prevent leakage of the electrolytic solution and entry of moisture from the outside, and aluminum, stainless steel, etc. can be used.
  • a heat-sealable resin layer such as modified polyolefin is provided on at least one surface of the metal layer, and the heat-sealable resin layers of the flexible film 30 are opposed to each other through the battery element to make the battery element
  • the sheath is formed by heat-sealing the periphery of the part to be stored.
  • a resin layer such as a nylon film or a polyester film can be provided on the surface of the exterior body opposite to the surface on which the heat-fusible resin layer is formed.
  • the positive electrode terminal 11 may be made of aluminum or an aluminum alloy
  • the negative electrode terminal 16 may be copper or a copper alloy, or those plated with nickel.
  • Each terminal is drawn to the outside of the container, but a heat fusible resin can be provided in advance in a portion located at a portion of the respective terminal where the periphery of the package is heat welded.
  • Insulating member In the case of forming the insulating member at the boundary portions 4 and 9 between the coated portion and the non-coated portion of the active material, polyimide, glass fiber, polyester, polypropylene or those containing these in the structure can be used. Heat can be applied to these members to weld them to the boundaries 4 and 9, or a gel-like resin can be applied to the boundaries 4 and 9 and dried to form an insulating member.
  • the separator 20 according to the present embodiment preferably includes a resin layer containing a heat resistant resin as a main component.
  • the resin layer is formed of a heat resistant resin which is a main component.
  • the term "main component" means that the proportion in the resin layer is 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more, and 100% by mass. It means that you may.
  • the resin layer constituting the separator 20 according to the present embodiment may be a single layer or two or more layers.
  • Examples of the heat resistant resin forming the above resin layer include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polycarbonate, polyester carbonate, aliphatic polyamide, all Aromatic polyamide, semiaromatic polyamide, wholly aromatic polyester, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyimide, polyarylate, polyetherimide, polyamideimide, polyacetal, polyetheretherketone, polysulfone, polyethersulfone, One or more selected from fluorine resins, polyether nitriles, modified polyphenylene ethers and the like can be mentioned.
  • polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, aliphatic polyamide, wholly aromatic polyamide, semiaromatic polyamide and all aromatic from the viewpoint of excellent balance of heat resistance, mechanical strength, stretchability, price and the like.
  • Family of polyesters one or more selected from polyethylene terephthalates, polybutylene terephthalates, aliphatic polyamides, wholly aromatic polyamides and semiaromatic polyamides are more preferred, and polyethylene terephthalates are preferred.
  • One or more selected from wholly aromatic polyamides are more preferable, and polyethylene terephthalate is more preferable.
  • the melting point of the separator 20 according to the present embodiment is preferably 220 ° C. or higher, more preferably 230 ° C. or higher, and 240 ° C. or higher from the viewpoint of improving the safety of the lithium ion secondary battery. Is more preferred.
  • the separator 20 according to the present embodiment preferably does not have a melting point, preferably has a decomposition temperature of 220 ° C. or higher, and 230 ° C. It is more preferable that it is the above, It is more preferable that it is 240 degreeC or more, It is especially preferable that it is 250 degreeC or more.
  • the battery By setting the melting point or decomposition temperature of the separator 20 according to the present embodiment to the above lower limit value or more, the battery generates heat and heat contraction of the separator 20 can be suppressed even when the temperature is high.
  • the contact area with the negative electrode can be suppressed.
  • thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
  • the upper limit of the melting point of the separator 20 according to the present embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of stretchability.
  • the upper limit of the decomposition temperature of the separator according to the present embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of stretchability.
  • the average value of the tensile elongation in the MD direction and the tensile elongation in the TD direction of the separator according to this embodiment, which is measured according to 6.3 of JIS L 1913: 2010, is the positive electrode current collector layer 3 and the negative electrode current collector. It is preferable that the tensile elongation of the body layer 8 be larger than that of the body layer 8. Thus, even if the separator 20 is torn by a sharp metal such as lithium dendrite, for example, the positive and negative electrodes are easily covered by the separator 20 because the separator 20 extends more than the positive and negative electrode current collectors.
  • the contact between the metal that has broken through the separator 20 and the positive and negative electrodes can be suppressed by the extended separator 20.
  • thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
  • the positive and negative electrodes are effectively covered, it is possible to suppress the contact between the metal that has broken through the separator 20 and the positive and negative electrodes. As a result, thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
  • the upper limit value of the tensile elongation in the MD direction of the separator 20 and the tensile elongation in the TD direction measured according to 6.3 of JIS L 1913: 2010 is not particularly limited, the heat resistance viewpoint of the separator 20 Therefore, 100% or less is preferable, 70% or less is more preferable, and 50% or less is more preferable.
  • the tensile elongation in the MD direction of the separator 20 which is measured according to 6.3 of JIS L1913: 2010, is preferably 10% or more, and more preferably 12% or more.
  • the upper limit value of the tensile elongation in the MD direction of the separator 20 measured according to 6.3 of JIS L 1913: 2010 is not particularly limited, but 100% or less is preferable, 70% or less is more preferable, and 50% or less More preferable.
  • the resin layer which comprises the separator 20 which concerns on this embodiment is a porous resin layer.
  • the resin layer which comprises the separator 20 which concerns on this embodiment is a porous resin layer.
  • the porosity of the porous resin layer is preferably 20% to 80%, more preferably 30% to 70%, and still more preferably 40% to 60%. Is particularly preferred.
  • ⁇ porosity (%)
  • Ws basis weight (g / m 2 )
  • ds true density (g / cm 3 )
  • t film thickness ( ⁇ m).
  • the planar shape of the separator 20 according to the present embodiment is not particularly limited, and can be appropriately selected according to the shapes of the electrode and the current collector, and can be, for example, rectangular.
  • the thickness of the separator 20 according to the present embodiment is preferably 5 ⁇ m or more and 50 ⁇ m or less, more preferably 10 ⁇ m or more and 40 ⁇ m or less, and further preferably 10 ⁇ m or more and 30 ⁇ m from the viewpoint of balance of mechanical strength and lithium ion conductivity. It is below.
  • the separator 20 according to the present embodiment preferably further includes a ceramic layer on at least one surface of the resin layer from the viewpoint of further improving heat resistance.
  • the ceramic layer is preferably provided only on one side of the resin layer from the viewpoint of the handleability, productivity, etc. of the separator 20 according to the present embodiment, but the heat resistance of the separator 20 is further enhanced. From the viewpoint of further improving, it may be provided on both sides of the resin layer.
  • the separator 20 according to the present embodiment can further reduce the thermal contraction of the separator 20 by further including the ceramic layer, and can further prevent a short circuit between the electrodes.
  • the said ceramic layer can be formed by, for example, apply
  • the ceramic layer forming material for example, a material obtained by dissolving or dispersing an inorganic filler and a binder resin in a suitable solvent can be used.
  • the inorganic filler used for this ceramic layer can be suitably selected from the well-known materials used for the separator of a lithium ion secondary battery.
  • oxides, nitrides, sulfides, carbides and the like having high insulating properties are preferable, and are selected from aluminum oxide, boehmite, titanium oxide, silicon oxide, magnesium oxide, barium oxide, zirconium oxide, zinc oxide and iron oxide etc. It is more preferable to adjust one or two or more kinds of ceramics into particles. Among these, aluminum oxide, boehmite and titanium oxide are preferable.
  • the binder resin is not particularly limited, and examples thereof include cellulose resins such as carboxymethyl cellulose (CMC); acrylic resins; fluorine resins such as polyvinylidene fluoride (PVDF); and the like.
  • a binder resin may be used individually by 1 type, and may be used in combination of 2 or more types.
  • the solvent for dissolving or dispersing these components is not particularly limited, and is appropriately selected from, for example, water, alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. Can be used.
  • alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc.
  • NMP N-methylpyrrolidone
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • the thickness of the ceramic layer is preferably 0.1 ⁇ m or more and 50 ⁇ m or less, more preferably 0.5 ⁇ m or more and 30 ⁇ m or less, from the viewpoint of the balance between heat resistance, mechanical strength, handleability and lithium ion conductivity. Preferably they are 1 micrometer or more and 15 micrometers or less.
  • Example 1 ⁇ Fabrication of positive electrode> 94.0 parts by mass of lithium nickel-containing composite oxide (chemical formula: LiNi 0.8 Co 0.15 Al 0.05 O 2 , average particle diameter: 6 ⁇ m) as a positive electrode active material, and carbon black as a conductive additive 3. 0 parts by mass, and 3.0 parts by mass of polyvinylidene fluoride (PVDF) as a binder resin were used. These were dispersed in an organic solvent to prepare a positive electrode slurry.
  • lithium nickel-containing composite oxide chemical formula: LiNi 0.8 Co 0.15 Al 0.05 O 2 , average particle diameter: 6 ⁇ m
  • PVDF polyvinylidene fluoride
  • This positive electrode slurry is continuously applied and dried on a 15 ⁇ m thick aluminum foil (tensile elongation: 6%) which is a positive electrode current collector, and then pressed to obtain a coated portion of the positive electrode current collector (positive electrode Active material layer: A positive electrode roll comprising a thickness of 60 ⁇ m on one side, a density of 3.35 g / cm 3 ) and an uncoated portion not coated was prepared. The positive electrode roll was punched out to leave a non-coated portion to be a tab for connecting to the positive electrode terminal, and was used as a positive electrode.
  • ⁇ Fabrication of negative electrode 96.7 parts by mass of natural graphite (average particle diameter: 16 ⁇ m) as a negative electrode active material, 0.3 parts by mass of carbon black as a conductive additive, 2.0 parts by mass of styrene butadiene rubber as a binder resin, thickener 1.0 mass part of carboxymethylcellulose was used as this. These were dispersed in water to prepare a negative electrode slurry.
  • the negative electrode slurry is continuously coated and dried on a copper foil (tensile elongation: 4%) having a thickness of 8 ⁇ m, which is a negative electrode current collector, and then pressed to form a coated portion of the negative electrode current collector (negative electrode Active material layer: A negative electrode roll provided with a thickness of 90 ⁇ m on one side, a density of 1.55 g / cm 3 ) and an uncoated portion not coated. The negative electrode roll was punched out to leave a non-coated portion to be a tab for connecting to the negative electrode terminal.
  • ⁇ Fabrication of Laminated Laminated Battery> The positive electrode and the negative electrode were stacked in a serpentine structure via a separator, and a negative electrode terminal and a positive electrode terminal were provided thereon to obtain a laminate.
  • a laminate type laminate battery is obtained by housing an electrolyte solution in which 1 M LiPF 6 is dissolved in a solvent composed of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, and the obtained laminate in a flexible film. Obtained.
  • the rated capacity of this laminate type laminate battery was 9.2 Ah, the positive electrode was 28 layers, and the negative electrode was 29 layers.
  • separator 1 As a separator, separator 1 (thickness: 25 ⁇ m, porosity 56%) including a porous resin layer made of polyethylene terephthalate (PET) and a ceramic layer made of boehmite particles was used.
  • PET polyethylene terephthalate
  • the physical properties of the separator 1 are as follows. Tensile elongation in the MD direction: 20% Tensile elongation in the TD direction: 19% Average value of tensile elongation in MD direction and tensile elongation in TD direction: 19.5% Melting point: 250 ° C
  • Constant current charge to 4.2 V Constant current charge to 4.2 V, and then constant voltage charge to a charge termination current of 0.015 C at a constant voltage of 4.2 V to make a full charge state.
  • an SUS304 nail manufactured by Hakusui Mfg. Co., Ltd.
  • a nailing test was conducted in which the sheet was pierced in a direction perpendicular to the surface to short the laminated type laminated battery.
  • the laminate battery is short-circuit discharged, and the voltage is in the range of 0.001 V or more and 0.100 V or less, compared with a laminated type laminate battery manufactured by Yokogawa Meter & Instruments.
  • a resistance measuring instrument product name: Digital Multimeter 7544-01
  • a tester was applied to the positive electrode terminal and the negative electrode terminal at 25 ° C. to measure the direct current resistance between the positive and negative electrodes at room temperature (25 ° C.).
  • Cycle Test The cycle characteristics of the obtained laminate type laminated battery were evaluated.
  • the capacity retention rate (%) is a value obtained by dividing the discharge capacity (mAh) after 300 cycles by the discharge capacity (mAh) at the 10th cycle. Those with a capacity retention rate (%) of 80% or more were rated as ⁇ , and those with less than 80% were rated as ⁇ .
  • Safety test A SUS304 nail (manufactured by Hakusui Mfg. Co., Ltd.) with a diameter of 3 mm and a length of 70 mm is made at 80 mm / sec under an environment of 25 ° C. against the central part of a fully charged laminate type laminated battery. The laminate was pierced in a direction perpendicular to the electrode surface at a speed of 1 to short the laminated type laminate battery. Next, the condition of the battery after 6 hours was observed, and the safety of the battery was evaluated based on the following criteria. ⁇ : Both smoke and ignition did not occur from lithium ion battery. ⁇ : At least one of smoke and ignition occurred from lithium ion battery.
  • Example 1 the voltage of the laminate battery when the DC resistance between the positive and negative electrodes was measured was 0.0582 V.
  • Example 2 As the separator, lamination was performed in the same manner as in Example 1 except that a separator 2 made of a porous resin layer (thickness: 15 ⁇ m, porosity 65%) composed of a wholly aromatic polyamide (also referred to as aramid) was used. Type laminated battery was produced and each evaluation was performed.
  • the physical properties of the separator 2 are as follows.
  • Example 3 A laminated laminate battery was prepared in the same manner as in Example 2 except that the composition ratio of the positive electrode was changed to 95.0 parts by mass of the positive electrode active material, 2.0 parts by mass of the conductive additive, and 3.0 parts by mass of the binder resin. It produced and performed each evaluation.
  • the voltage of the laminate battery when the DC resistance between the positive and negative electrodes was measured was 0.0582 V.
  • Example 1 A laminated laminate battery was prepared in the same manner as in Example 1 except that the composition ratio of the positive electrode was changed to 93.0 parts by mass of the positive electrode active material, 4.0 parts by mass of the conductive additive, and 3.0 parts by mass of the binder resin. It produced and performed each evaluation.
  • Example 2 A laminate type laminate battery is prepared in the same manner as in Example 1 except that a separator 3 (thickness: 25 ⁇ m, porosity 54%) including a porous resin layer made of polypropylene and a ceramic layer (alumina) is used as a separator. Were made, and each evaluation was performed.
  • the physical properties of the separator 3 are as follows. Tensile elongation in the MD direction: 125% Tensile elongation in the TD direction: 630% Average value of tensile elongation in MD direction and tensile elongation in TD direction: 377.5% Melting point: 160 ° C
  • Example 3 A laminated laminate battery is produced in the same manner as in Example 1 except that a separator 4 made of a porous resin layer (thickness: 25 ⁇ m, porosity: 55%) made of polypropylene is used as a separator, and each evaluation is shown went.
  • the physical properties of the separator 4 are as follows. Tensile elongation in the MD direction: 50% Tensile elongation in the TD direction: 400% Average value of tensile elongation in MD direction and tensile elongation in TD direction: 225% Melting point: 160 ° C
  • Example 4 Example 1 except that a separator 5 comprising a porous resin layer made of polypropylene (thickness: 18 ⁇ m, porosity: 54%) and a ceramic layer made of alumina (thickness: 7 ⁇ m) was used as a separator
  • a laminated laminate battery was produced in the same manner as in the above, and each evaluation was performed.
  • the physical properties of the separator 5 are as follows. Tensile elongation in the MD direction: 50% Tensile elongation in the TD direction: 400% Average value of tensile elongation in MD direction and tensile elongation in TD direction: 225% Melting point: 160 ° C
  • Example 5 Lamination was carried out in the same manner as in Example 1 except that a separator 6 comprising a non-woven fabric layer made of glass fiber and a layer made of ceramics (magnesium oxide) (thickness: 30 ⁇ m, porosity: 76%) was used as a separator.
  • Type laminated battery was produced and each evaluation was performed.
  • the physical properties of the separator 6 are as follows. Tensile elongation in the MD direction: 8.9% Tensile elongation in the TD direction: 14.3% Average value of tensile elongation in MD direction and tensile elongation in TD direction: 11.6%
  • Example 6 A laminated laminate battery was prepared in the same manner as in Example 1 except that the compounding ratio of the positive electrode was changed to 96.0 parts by mass of the positive electrode active material, 1.0 part by mass of the conductive additive, and 3.0 parts by mass of the binder resin. It produced and performed each evaluation.

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Abstract

A lithium-ion secondary battery according to the present invention comprises a housing that stores: a positive electrode having a positive-electrode collector layer and a positive-electrode active material layer; a negative electrode having a negative-electrode collector layer and a negative-electrode active material layer; a nonaqueous electrolyte solution containing a lithium salt; and a separator interposed between the positive electrode and the negative electrode. The lithium-ion secondary battery is subjected to short-circuit discharge following a nail penetration test, which is conducted to short-circuit the lithium-ion secondary battery in a fully charged state at a temperature of 25°C by causing a nail made of SUS 304 with a diameter φ of 3 mm and a length of 70 mm to penetrate the center of the lithium-ion secondary battery at a speed of 80 mm/sec. When the voltage is 0.001 V-100 V inclusive, the DC resistance between the positive and negative electrodes in the lithium-ion secondary battery is 0.1 Ω-300 Ω inclusive.

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.
　リチウムイオン二次電池は高エネルギー密度という特徴を有しており、携帯電話やノート型パソコン、電気自動車等の電源として広く用いられている。
　リチウムイオン二次電池は、電解液の主溶媒として引火性の有機溶媒が使用されるため、発火や爆発に対する安全性が要求される。 Lithium ion secondary batteries are characterized by high energy density, and are widely used as power sources for mobile phones, notebook computers, electric cars and the like.
In lithium ion secondary batteries, since a flammable organic solvent is used as a main solvent of the electrolyte, safety against ignition and explosion is required.
　このようなリチウムイオン二次電池の安全性に関する技術としては、例えば、特許文献１（特開２０１３－２５１２８１号公報）に記載のものが挙げられる。 Examples of the technology relating to the safety of such a lithium ion secondary battery include those described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-251281).
　特許文献１（特開２０１３－２５１２８１号公報）には、正極集電体の表面に正極活物質を含む正極活物質層を有する正極と、負極集電体の表面に負極活物質を含む負極活物質層を有する負極と、該正極及び負極間に配置されたセパレータとから構成された電極体と、上記電極体を電解液とともに収容する電池ケースとを備え、上記電池ケースの表面積と電池の満充電時におけるエネルギー容量との比の値が４．５ｃｍ２／Ｗｈ以上であり、かつ、上記正極の電気抵抗率が１０Ω・ｃｍ以上４５０Ω・ｃｍ以下である、リチウム二次電池が記載されている。 Patent Document 1 (Japanese Patent Laid-Open No. 2013-251281) discloses a positive electrode having a positive electrode active material layer containing a positive electrode active material on the surface of a positive electrode current collector, and a negative electrode active containing a negative electrode active material on the surface of the negative electrode current collector. An electrode assembly comprising a negative electrode having a material layer, a separator disposed between the positive electrode and the negative electrode, and a battery case for containing the electrode assembly together with an electrolytic solution; A lithium secondary battery is described in which the value of the ratio to the energy capacity at the time of charging is 4.5 cm 2 / Wh or more, and the electrical resistivity of the positive electrode is 10 Ω · cm to 450 Ω · cm. .
特開２０１３－２５１２８１号公報JP, 2013-251281, A
　リチウムイオン二次電池の大型化や高エネルギー密度化に伴い、リチウムイオン二次電池の安全性についてさらなる向上が求められている。
　ここで、本発明者の検討によれば、リチウムイオン二次電池の高エネルギー密度化を実現するために、例えば、リチウムニッケル含有複合酸化物等の高容量タイプの正極活物質を用いたり、正極や負極の集電体層の厚みを薄くしたり、正極活物質層の密度を高めたりすると、リチウムイオン二次電池の熱安定性が低下し、電池の安全性が悪化してしまう場合があることが明らかになった。
　また、本発明者の検討によれば、電池の安全性を向上させるために、電極の電気抵抗を上げると、今度はサイクル特性等の電池特性が悪化してしまう場合があることが明らかになった。
　すなわち、本発明者は、従来のリチウムイオン二次電池には、サイクル特性等の電池特性および電池の安全性の間にトレードオフの関係があることを見出した。 With the increase in size and energy density of lithium ion secondary batteries, further improvement in safety of lithium ion secondary batteries is required.
Here, according to the study of the present inventor, in order to realize high energy density of a lithium ion secondary battery, for example, a high capacity type positive electrode active material such as lithium nickel-containing composite oxide is used, or a positive electrode When the thickness of the current collector layer of the negative electrode is reduced or the density of the positive electrode active material layer is increased, the thermal stability of the lithium ion secondary battery may be reduced, and the safety of the battery may be deteriorated. It became clear.
Also, according to the study of the present inventor, it has become clear that if the electrical resistance of the electrode is increased to improve the safety of the battery, then the battery characteristics such as cycle characteristics may be deteriorated. The
That is, the present inventor has found that there is a trade-off relationship between battery characteristics such as cycle characteristics and battery safety in the conventional lithium ion secondary battery.
　本発明は上記事情に鑑みてなされたものであり、サイクル特性等の電池特性および電池の安全性が良好なリチウムイオン二次電池を提供するものである。 The present invention has been made in view of the above circumstances, and provides a lithium ion secondary battery having excellent battery characteristics such as cycle characteristics and battery safety.
　本発明者らは上記課題を達成すべく鋭意検討を重ねた。その結果、特定の条件でおこなう釘刺し試験後のリチウムイオン二次電池における正負極間の直流抵抗を特定の範囲にすることにより、サイクル特性等の電池特性および電池の安全性の間にあるトレードオフの関係を改善でき、サイクル特性等の電池特性および電池の安全性の両方の特性が良好なリチウムイオン二次電池が得られることが明らかになった。
　すなわち、特定の条件でおこなう釘刺し試験後のリチウムイオン二次電池における正負極間の直流抵抗という尺度が、サイクル特性等の電池特性および電池の安全性のバランスに優れたリチウムイオン二次電池を実現するための設計指針として有効であることを見出し、本発明に到達した。 The present inventors diligently studied to achieve the above object. As a result, by setting the direct current resistance between the positive and negative electrodes in the lithium ion secondary battery after the nail penetration test under specific conditions to a specific range, a trade-off exists between battery characteristics such as cycle characteristics and battery safety. It has been revealed that a lithium ion secondary battery can be obtained which can improve the off relationship and has both battery characteristics such as cycle characteristics and battery safety characteristics.
That is, the scale of direct current resistance between positive and negative electrodes in a lithium ion secondary battery after a nail penetration test performed under a specific condition is a lithium ion secondary battery excellent in the balance of battery characteristics such as cycle characteristics and battery safety. The inventors have found that the present invention is effective as a design guideline for realization.
　本発明はこのような知見に基づいて発案されたものである。
　すなわち、本発明によれば、以下に示すリチウムイオン二次電池が提供される。 The present invention was devised based on such knowledge.
That is, according to the present invention, the following lithium ion secondary battery is provided.
　本発明によれば、
　正極集電体層および正極活物質層を有する正極と、負極集電体層および負極活物質層を有する負極と、リチウム塩を含有する非水電解液と、上記正極と上記負極との間に挟まれたセパレータと、が容器に収容されたリチウムイオン二次電池であって、
　２５℃の環境下で、満充電状態において、直径φ３ｍｍ、長さ７０ｍｍのＳＵＳ３０４製の釘を上記リチウムイオン二次電池の中央部に８０ｍｍ／ｓｅｃの速度で刺し、上記リチウムイオン二次電池をショートさせる釘刺し試験をおこなったとき、
　上記釘刺し試験後、当該リチウムイオン二次電池を短絡放電させ、電圧が０．００１Ｖ以上０．１００Ｖ以下の範囲になったときの上記リチウムイオン二次電池における正負極間の直流抵抗が０．１Ω以上３００Ω以下であるリチウムイオン二次電池が提供される。 According to the invention
Between a positive electrode having a positive electrode current collector layer and a positive electrode active material layer, a negative electrode having a negative electrode current collector layer and a negative electrode active material layer, a non-aqueous electrolyte containing a lithium salt, and between the positive electrode and the negative electrode A lithium ion secondary battery in which a sandwiched separator is contained in a container,
In a fully charged state under a 25 ° C. environment, a SUS304 nail with a diameter of 3 mm and a length of 70 mm is pierced at the center of the lithium ion secondary battery at a speed of 80 mm / sec to short the lithium ion secondary battery. When the nail penetration test was conducted,
After the nail penetration test, the lithium ion secondary battery is short-circuit discharged, and when the voltage is in the range of 0.001 V to 0.100 V, the direct current resistance between the positive and negative electrodes in the lithium ion secondary battery is 0. Provided is a lithium ion secondary battery having 1 Ω or more and 300 Ω or less.
　本発明によれば、サイクル特性等の電池特性および電池の安全性が良好なリチウムイオン二次電池を提供することができる。 According to the present invention, it is possible to provide a lithium ion secondary battery which is excellent in battery characteristics such as cycle characteristics and battery safety.
　上述した目的、およびその他の目的、特徴および利点は、以下に述べる好適な実施の形態、およびそれに付随する以下の図面によってさらに明らかになる。 The objects described above, and other objects, features and advantages will become more apparent from the preferred embodiments described below and the following drawings associated therewith.
本実施形態における積層型電池の一例を示す概略図である。It is the schematic which shows an example of the laminated type battery in this embodiment. 本実施形態における捲回型電池の一例を示す概略図である。It is a schematic diagram showing an example of a winding type battery in this embodiment.
　以下に、本発明の実施形態について、図面を用いて説明する。なお、すべての図面において、同様な構成要素には同様の符号を付し、適宜説明を省略する。また、図において各構成要素は本発明が理解できる程度の形状、大きさおよび配置関係を概略的に示したものであり、実寸とは異なっている。また、本実施形態では数値範囲の「Ａ～Ｂ」は特に断りがなければ、Ａ以上Ｂ以下を表す。 Hereinafter, embodiments of the present invention will be described using the drawings. In all the drawings, similar components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. Further, in the drawings, each component schematically shows the shape, size and arrangement relationship to the extent that the present invention can be understood, and is different from the actual size. Further, in the present embodiment, “A to B” in the numerical value range represent A or more and B or less unless otherwise specified.
＜リチウムイオン二次電池＞
　本実施形態に係るリチウムイオン二次電池は、正極集電体層および正極活物質層を有する正極と、負極集電体層および負極活物質層を有する負極と、リチウム塩を含有する非水電解液と、上記正極と上記負極との間に挟まれたセパレータと、が容器に収容されたものである。そして、２５℃の環境下で、満充電状態において、直径φ３ｍｍ、長さ７０ｍｍのＳＵＳ３０４製の釘を上記リチウムイオン二次電池の中央部に８０ｍｍ／ｓｅｃの速度で刺し、上記リチウムイオン二次電池をショートさせる釘刺し試験をおこなったとき、上記釘刺し試験後、当該リチウムイオン二次電池を短絡放電させ、電圧が０．００１Ｖ以上０．１００Ｖ以下の範囲になったときの上記リチウムイオン二次電池における正負極間の直流抵抗が０．１Ω以上３００Ω以下である。 <Lithium ion secondary battery>
The lithium ion secondary battery according to the present embodiment includes a positive electrode having a positive electrode current collector layer and a positive electrode active material layer, a negative electrode having a negative electrode current collector layer and a negative electrode active material layer, and a non-aqueous electrolysis containing a lithium salt. A liquid and a separator sandwiched between the positive electrode and the negative electrode are accommodated in a container. Then, in a fully charged state under a 25 ° C. environment, a nail made of SUS304 with a diameter of 3 mm and a length of 70 mm is pierced at the center of the lithium ion secondary battery at a speed of 80 mm / sec to complete the lithium ion secondary battery The lithium ion secondary battery is short-circuit discharged after the nail penetration test when the nail penetration test is performed to short-circuit the lithium ion secondary battery, and when the voltage is in the range of 0.001 V or more and 0.100 V or less The direct current resistance between positive and negative electrodes in the battery is 0.1 Ω or more and 300 Ω or less.
　本発明者の検討によれば、リチウムイオン二次電池の高エネルギー密度化を実現するために、例えば、リチウムニッケル含有複合酸化物等の高容量タイプの正極活物質を用いたり、正極や負極の集電体層の厚みを薄くしたり、正極活物質層の密度を高めたりすると、リチウムイオン二次電池の熱安定性が低下し、電池の安全性が悪化してしまう場合があることが明らかになった。
　また、本発明者の検討によれば、電池の安全性を向上させるために、電極の電気抵抗を上げると、今度はサイクル特性等の電池特性が悪化してしまう場合があることが明らかになった。
　すなわち、本発明者は、従来のリチウムイオン二次電池には、サイクル特性等の電池特性および電池の安全性の間にトレードオフの関係があることを見出した。
　そこで、本発明者らは上記課題を達成すべく鋭意検討を重ねた。その結果、上記の条件でおこなう釘刺し試験後のリチウムイオン二次電池における正負極間の直流抵抗を上記範囲にすることにより、サイクル特性等の電池特性および電池の安全性の間にあるトレードオフの関係を改善でき、サイクル特性等の電池特性および電池の安全性の両方の特性が良好なリチウムイオン二次電池が得られることが明らかになった。
　すなわち、特定の条件でおこなう釘刺し試験後のリチウムイオン二次電池における正負極間の直流抵抗という尺度が、サイクル特性等の電池特性および電池の安全性のバランスに優れたリチウムイオン二次電池を実現するための設計指針として有効であることを初めて見出した。 According to the study of the present inventor, in order to realize high energy density of a lithium ion secondary battery, for example, a high capacity type positive electrode active material such as a lithium nickel-containing composite oxide is used, or It is apparent that if the thickness of the current collector layer is reduced or the density of the positive electrode active material layer is increased, the thermal stability of the lithium ion secondary battery may be reduced and the safety of the battery may be deteriorated. Became.
Also, according to the study of the present inventor, it has become clear that if the electrical resistance of the electrode is increased to improve the safety of the battery, then the battery characteristics such as cycle characteristics may be deteriorated. The
That is, the present inventor has found that there is a trade-off relationship between battery characteristics such as cycle characteristics and battery safety in the conventional lithium ion secondary battery.
Therefore, the present inventors diligently studied to achieve the above object. As a result, by setting the direct current resistance between positive and negative electrodes in the lithium ion secondary battery after the nail penetration test performed under the above conditions to the above range, a trade-off between battery characteristics such as cycle characteristics and battery safety It has been revealed that a lithium ion secondary battery can be obtained which can improve the relationship of (1) and have both battery characteristics such as cycle characteristics and battery safety characteristics.
That is, the scale of direct current resistance between positive and negative electrodes in a lithium ion secondary battery after a nail penetration test performed under a specific condition is a lithium ion secondary battery excellent in the balance of battery characteristics such as cycle characteristics and battery safety. It was found for the first time that it was effective as a design guideline to realize it.
　本実施形態に係るリチウムイオン二次電池において、上記釘刺し試験後の正負極間の直流抵抗の下限は０．１Ω以上であるが、好ましくは１Ω以上、より好ましくは２Ω以上、さらに好ましくは１０Ω以上、さらにより好ましくは４０Ω以上、さらにより好ましくは６０Ω以上、特に好ましくは８０Ω以上である。
　本実施形態に係るリチウムイオン二次電池において、上記釘刺し試験後の正負極間の直流抵抗を上記下限値以上とすることにより、リチウムイオン二次電池の安全性を効果的に向上させることができる。
　また、本実施形態に係るリチウムイオン二次電池において、上記釘刺し試験後の正負極間の直流抵抗の上限は３００Ω以下であるが、好ましくは２５０Ω以下、より好ましくは２００Ω以下、さらに好ましくは１５０Ω以下、特に好ましくは１３０Ω以下である。
　本実施形態に係るリチウムイオン二次電池において、上記釘刺し試験後の正負極間の直流抵抗を上記上限値以下とすることにより、リチウムイオン二次電池のサイクル特性等の電池特性を効果的に向上させることができる。
　ここで、本実施形態において、満充電状態とは、定電流定電圧（ＣＣ－ＣＶ）法を用いて、２５℃で、リチウムイオン二次電池に対して、１Ｃの定電流で電圧４．２Ｖまで定電流充電し、次いで、４．２Ｖの定電圧で充電終止電流０．０１５Ｃまで定電圧充電したときの状態をいう。 In the lithium ion secondary battery according to the present embodiment, the lower limit of the direct current resistance between the positive and negative electrodes after the nail penetration test is 0.1 Ω or more, preferably 1 Ω or more, more preferably 2 Ω or more, further preferably 10 Ω The resistance is more preferably 40 Ω or more, still more preferably 60 Ω or more, and particularly preferably 80 Ω or more.
In the lithium ion secondary battery according to the present embodiment, the safety of the lithium ion secondary battery can be effectively improved by setting the direct current resistance between the positive and negative electrodes after the nail penetration test to the above lower limit value or more. it can.
In the lithium ion secondary battery according to the present embodiment, the upper limit of the direct current resistance between the positive and negative electrodes after the nail penetration test is 300 Ω or less, preferably 250 Ω or less, more preferably 200 Ω or less, still more preferably 150 Ω. The following is particularly preferable: 130 Ω or less.
In the lithium ion secondary battery according to the present embodiment, by setting the direct current resistance between the positive and negative electrodes after the nail penetration test to the upper limit value or less, battery characteristics such as cycle characteristics of the lithium ion secondary battery are effectively made. It can be improved.
Here, in the present embodiment, the fully charged state is a voltage of 4.2 V at a constant current of 1 C with respect to a lithium ion secondary battery at 25 ° C. using a constant current constant voltage (CC-CV) method. Constant current charging up to a constant voltage, and then a constant voltage charging to a charge termination current of 0.015 C at a constant voltage of 4.2 V.
　本実施形態に係るリチウムイオン二次電池の上記釘刺し試験後の正負極間の直流抵抗は、（Ａ）正極活物質層や負極活物質層の配合比率、（Ｂ）セパレータの種類、（Ｃ）集電体層の種類等を適切に選択することにより実現することが可能である。
　これらの中でも、例えば正極活物質層において導電助剤の量を特定の範囲とすること、高耐熱で、かつ、高伸度であるセパレータを使用すること、正極集電体層や負極集電体層よりも引張伸度が大きいセパレータを用いること等が、上記釘刺し試験後のリチウムイオン二次電池における正負極間の直流抵抗を所望の数値範囲とするための要素として挙げられる。 The direct current resistance between the positive and negative electrodes after the above-mentioned nailing test of the lithium ion secondary battery according to the present embodiment is: (A) the compounding ratio of the positive electrode active material layer and the negative electrode active material layer; ) It is possible to realize by appropriately selecting the type of the current collector layer and the like.
Among these, for example, the amount of the conductive additive in the positive electrode active material layer is in a specific range, the separator having high heat resistance and high elongation is used, the positive electrode current collector layer, the negative electrode current collector The use of a separator having a tensile elongation greater than that of the layer, etc. is mentioned as a factor for setting the direct current resistance between the positive and negative electrodes in the lithium ion secondary battery after the above-mentioned nail penetration test to a desired numerical range.
　本実施形態に係るリチウムイオン二次電池が電池の安全性に優れる理由は必ずしも明らかではないが、このようなリチウムイオン二次電池は、例えば電池に異物が入りショートしたとしても電池の抵抗を高い範囲に維持できるため大電流が流れることを抑制でき、その結果、電池の熱暴走を抑制できるからだと考えられる。 Although the reason why the lithium ion secondary battery according to the present embodiment is excellent in battery safety is not necessarily clear, such a lithium ion secondary battery has high battery resistance even if foreign matter enters the battery and shorts, for example. Since the range can be maintained, it is possible to suppress the flow of a large current, and as a result, it is possible to suppress the thermal runaway of the battery.
　また、本実施形態に係るリチウムイオン二次電池は、セル定格容量が好ましくは５Ａｈ以上であり、より好ましくは７Ａｈ以上である。
　また、本実施形態に係るリチウムイオン二次電池は、中央部における正極の積層数または捲回数が１０以上であることが好ましく、１５以上であることがより好ましく、２０以上であることがさらに好ましい。
　これにより、本実施形態に係るリチウムイオン二次電池の高容量化を図ることができる。また、このような高容量であっても、本実施形態に係るリチウムイオン二次電池は、耐短絡性に優れ、電池の熱暴走を抑制することが可能となる。 The lithium ion secondary battery according to this embodiment preferably has a cell rated capacity of 5 Ah or more, more preferably 7 Ah or more.
Moreover, in the lithium ion secondary battery according to the present embodiment, the number of laminations or the number of laminations of the positive electrode in the central portion is preferably 10 or more, more preferably 15 or more, and still more preferably 20 or more .
Thus, the capacity of the lithium ion secondary battery according to the present embodiment can be increased. Further, even with such a high capacity, the lithium ion secondary battery according to the present embodiment is excellent in the short circuit resistance, and it is possible to suppress the thermal runaway of the battery.
　本実施形態のリチウムイオン二次電池は特にその形態や種類が限定されるものではないが、例えば、以下のような構成とすることができる。 The form and type of the lithium ion secondary battery of the present embodiment are not particularly limited, but, for example, the following configuration can be made.
［積層型電池］
　図１は積層型電池の構成を模式的に示したものである。積層型電池１００は、正極１と負極６とが、セパレータ２０を介して交互に複数層積層された電池要素を備えており、これらの電池要素は電解液（図示せず）とともに可撓性フィルム３０からなる容器に収納されている。電池要素には正極端子１１および負極端子１６が電気的に接続されており、正極端子１１および負極端子１６の一部または全部が可撓性フィルム３０の外部に引き出されている構成になっている。 [Stacked battery]
FIG. 1 schematically shows the structure of a laminated battery. Stacked battery 100 includes battery elements in which positive electrode 1 and negative electrode 6 are alternately laminated in multiple layers with separator 20 interposed therebetween, and these battery elements are a flexible film together with an electrolytic solution (not shown). It is housed in a 30 container. The positive electrode terminal 11 and the negative electrode terminal 16 are electrically connected to the battery element, and a part or all of the positive electrode terminal 11 and the negative electrode terminal 16 are drawn out of the flexible film 30. .
　正極１には正極集電体層３の表裏に、正極活物質の塗布部（正極活物質層２）と未塗布部がそれぞれ設けられており、負極６には負極集電体層８の表裏に、負極活物質の塗布部（負極活物質層７）と未塗布部が設けられている。 The positive electrode 1 is provided with the coated part (positive electrode active material layer 2) and the uncoated part of the positive electrode active material on the front and back of the positive electrode collector layer 3, and the negative electrode 6 is on the front and back of the negative electrode collector layer 8. In addition, the coated part of the negative electrode active material (negative electrode active material layer 7) and the uncoated part are provided.
　正極集電体層３における正極活物質の未塗布部を正極端子１１と接続するための正極タブ１０とし、負極集電体層８における負極活物質の未塗布部を負極端子１６と接続するための負極タブ５とする。
　正極タブ１０同士は正極端子１１上にまとめられ、正極端子１１とともに超音波溶接等で互いに接続され、負極タブ５同士は負極端子１６上にまとめられ、負極端子１６とともに超音波溶接等で互いに接続される。そのうえで、正極端子１１の一端は可撓性フィルム３０の外部に引き出され、負極端子１６の一端も可撓性フィルム３０の外部に引き出されている。 The uncoated portion of the positive electrode active material in the positive electrode current collector layer 3 is used as a positive electrode tab 10 for connecting to the positive electrode terminal 11, and the uncoated portion of the negative electrode active material in the negative electrode current collector layer 8 is connected to the negative electrode terminal 16. The negative electrode tab 5 of FIG.
The positive electrode tabs 10 are assembled on the positive electrode terminal 11 and connected together by ultrasonic welding etc. together with the positive electrode terminal 11, and the negative electrode tabs 5 are assembled on the negative electrode terminal 16 connected together by ultrasonic welding etc. together with the negative electrode terminal 16. Be done. In addition, one end of the positive electrode terminal 11 is drawn out of the flexible film 30, and one end of the negative electrode terminal 16 is also drawn out of the flexible film 30.
　正極活物質の塗布部（正極活物質層２）と未塗布部の境界部４には、必要に応じて絶縁部材を形成することができ、当該絶縁部材は境界部４だけでなく、正極タブ１０と正極活物質の双方の境界部付近に形成することができる。 If necessary, an insulating member can be formed at the boundary 4 between the coated part (positive electrode active material layer 2) and the non-coated part of the positive electrode active material, and the insulating member is not only the boundary 4 but also the positive electrode tab. 10 and near the boundary between the positive electrode active material.
　負極活物質の塗布部（負極活物質層７）と未塗布部の境界部９にも同様に、必要に応じて絶縁部材を形成することができ、負極タブ５と負極活物質の双方の境界部付近に形成することができる。 Similarly, an insulating member can be formed on the boundary portion 9 between the coated portion (negative electrode active material layer 7) and the non-coated portion of the negative electrode active material as required, and the boundary between both the negative electrode tab 5 and the negative electrode active material It can be formed near the part.
　通常、負極活物質層７の外形寸法は正極活物質層２の外形寸法よりも大きく、セパレータ２０の外形寸法よりも小さい。 Usually, the outer dimension of the negative electrode active material layer 7 is larger than the outer dimension of the positive electrode active material layer 2 and smaller than the outer dimension of the separator 20.
［捲回型電池］
　図２は捲回型電池の構成を模式的に示したものであり、容器等の図示を省略したものである。捲回型電池１０１は正極１と負極６とがセパレータ２０を介して積層され、捲回された電池要素を備えており、この電池要素は電解液（図示せず）とともに可撓性のフィルムからなる容器に収納されている。
　捲回型電池１０１の電池要素にも正極端子や負極端子が電気的に接続されている等、その他の構成は積層型電池１００と概ね一致するため、ここでのこれ以上の説明は省略する。 [Wound battery]
FIG. 2 schematically shows the configuration of a wound battery, and the container etc. are not shown. The wound battery 101 includes a battery element in which a positive electrode 1 and a negative electrode 6 are stacked via a separator 20 and wound, and this battery element is made of a flexible film together with an electrolytic solution (not shown). Contained in the
The positive electrode terminal and the negative electrode terminal are also electrically connected to the battery element of the wound battery 101, and the other configuration is substantially the same as that of the laminated battery 100, and thus further description is omitted here.
　つづいて、本実施形態のリチウムイオン二次電池に用いられる各構成について説明する。 It continues and demonstrates each structure used for the lithium ion secondary battery of this embodiment.
（リチウムを吸蔵放出する正極）
　本実施形態に用いる正極１は、用途等に応じて、公知のリチウムイオン二次電池に使用することのできる正極の中から適宜選択することができる。正極１に用いられる活物質としては、リチウムイオンを可逆に放出・吸蔵でき、電子輸送が容易に行えるように電子伝導度の高い材料が好ましい。 (Positive electrode for absorbing and desorbing lithium)
The positive electrode 1 used in the present embodiment can be appropriately selected from among positive electrodes that can be used for known lithium ion secondary batteries, according to the application and the like. The active material used for the positive electrode 1 is preferably a material having high electron conductivity so that lithium ions can be reversibly released and stored, and electron transport can be easily performed.
　正極１に用いられる正極活物質としては、特に制限されるものではないが、例えば、層状岩塩型構造又はスピネル型構造を有するリチウム複合酸化物や、オリビン型構造を有するリン酸鉄リチウム等を用いることができる。リチウム複合酸化物としては、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）；コバルト酸リチウム（ＬｉＣｏＯ２）；ニッケル酸リチウム（ＬｉＮｉＯ２）；これらのリチウム化合物のマンガン、コバルト、ニッケルの部分の少なくとも一部をアルミニウム、マグネシウム、チタン、亜鉛等の他の金属元素で置換したもの；マンガン酸リチウムのマンガンの一部を少なくともニッケルで置換したニッケル置換マンガン酸リチウム；ニッケル酸リチウムのニッケルの一部を少なくともコバルトで置換したコバルト置換ニッケル酸リチウム；ニッケル置換マンガン酸リチウムのマンガンの一部を他の金属（例えばアルミニウム、マグネシウム、チタン、亜鉛の少なくとも一種）で置換したもの；コバルト置換ニッケル酸リチウムのニッケルの一部を他の金属元素（例えばアルミニウム、マグネシウム、チタン、亜鉛、マンガンの少なくとも一種）で置換したものが挙げられる。これらのリチウム複合酸化物は一種を単独で使用してもよいし、二種以上を混合して用いてもよい。 The positive electrode active material used for the positive electrode 1 is not particularly limited. For example, lithium composite oxide having a layered rock salt structure or spinel structure, lithium iron phosphate having an olivine structure, etc. are used. be able to. As lithium complex oxide, lithium manganate (LiMn 2 O 4 ); lithium cobaltate (LiCoO 2 ); lithium nickelate (LiNiO 2 ); at least a part of manganese, cobalt and nickel of these lithium compounds Those substituted with other metal elements such as aluminum, magnesium, titanium, zinc, etc .; Nickel-substituted lithium manganate in which at least part of manganese in lithium manganate is substituted with nickel; at least part of nickel in lithium nickel nickelate Substituted cobalt-substituted lithium nickelate; part of manganese of lithium-substituted lithium manganate substituted with another metal (eg, at least one of aluminum, magnesium, titanium, zinc); nickel of cobalt-substituted lithium nickelate; Other metal elements (e.g. aluminum, magnesium, titanium, zinc, at least one manganese) include those substituted with. These lithium composite oxides may be used alone or in combination of two or more.
　層状結晶構造を有するリチウム含有複合酸化物として、リチウムニッケル含有複合酸化物が挙げられる。このリチウムニッケル含有複合酸化物は、ニッケルサイトのニッケルの一部が他の金属で置換されたものを用いることができる。ニッケルサイトを占めるＮｉ以外の金属としては、例えば、Ｍｎ、Ｃｏ、Ａｌ、Ｍｇ、Ｆｅ、Ｃｒ，Ｔｉ、Ｉｎから選ばれる少なくとも一種の金属が挙げられる。 Examples of lithium-containing composite oxides having a layered crystal structure include lithium-nickel-containing composite oxides. As this lithium nickel-containing composite oxide, one in which a part of nickel at the nickel site is replaced with another metal can be used. Examples of metals other than Ni that occupy the nickel site include at least one metal selected from Mn, Co, Al, Mg, Fe, Cr, Ti, and In.
　このリチウムニッケル含有複合酸化物は、ニッケルサイトを占めるＮｉ以外の金属としてＣｏを含むことが好ましい。また、このリチウムニッケル含有複合酸化物は、Ｃｏに加えてＭｎ又はＡｌを含むことがより好ましく、すなわち、層状結晶構造を有するリチウムニッケルコバルトマンガン複合酸化物（ＮＣＭ）、層状結晶構造を有するリチウムニッケルコバルトアルミニウム複合酸化物（ＮＣＡ）、又はこれらの混合物を好適に用いることができる。 The lithium nickel-containing composite oxide preferably contains Co as a metal other than Ni occupying nickel sites. The lithium-nickel-containing composite oxide more preferably contains Mn or Al in addition to Co, that is, lithium-nickel-cobalt-manganese composite oxide (NCM) having a layered crystal structure, lithium-nickel having a layered crystal structure Cobalt aluminum complex oxide (NCA) or a mixture thereof can be suitably used.
　層状結晶構造を有するリチウムニッケル含有複合酸化物は、例えば、下記式（１）で示されるものを用いることができる。
　Ｌｉ１＋ａ（ＮｉｂＣｏｃＭｅ１ｄＭｅ２１－ｂ－ｃ－ｄ）Ｏ２　　　　　　　（１）
（式中、Ｍｅ１はＭｎ又はＡｌであり、Ｍｅ２は、Ｍｎ、Ａｌ、Ｍｇ、Ｆｅ、Ｃｒ、Ｔｉ、Ｉｎからなる群から選択される少なくとも１種であり（Ｍｅ１と同種の金属を除く）、－０．５≦ａ＜０．１、０．１≦ｂ＜１、０＜ｃ＜０．５、０＜ｄ＜０．５） As the lithium nickel-containing composite oxide having a layered crystal structure, for example, one represented by the following formula (1) can be used.
Li 1 + a (Ni b Co c Me 1 d Me 2 1-b c d ) O 2 (1)
(Wherein, Me1 is Mn or Al, Me2 is at least one selected from the group consisting of Mn, Al, Mg, Fe, Cr, Ti, In (except metals of the same type as Me1), −0.5 ≦ a <0.1, 0.1 ≦ b <1, 0 <c <0.5, 0 <d <0.5)
　正極活物質の平均粒径は、電解液との反応性やレート特性等の観点から、例えば０．１～５０μｍが好ましく、１～３０μｍがより好ましく、２～２５μｍがさらに好ましい。ここで、平均粒径は、レーザー回折散乱法による粒度分布（体積基準）における積算値５０％での粒径（メジアン径：Ｄ５０）を意味する。 The average particle diameter of the positive electrode active material is, for example, preferably 0.1 to 50 μm, more preferably 1 to 30 μm, and still more preferably 2 to 25 μm, from the viewpoint of reactivity with the electrolytic solution, rate characteristics, and the like. Here, the average particle diameter means a particle diameter (median diameter: D 50 ) at an integrated value of 50% in a particle size distribution (volume basis) by a laser diffraction scattering method.
　正極１は、正極集電体層３と、正極集電体層３上の正極活物質層２から構成されている。この正極１は、正極活物質層２がセパレータを介して、負極集電体層８上の負極活物質層７と対向するように配置される。 The positive electrode 1 includes a positive electrode current collector layer 3 and a positive electrode active material layer 2 on the positive electrode current collector layer 3. The positive electrode 1 is disposed such that the positive electrode active material layer 2 faces the negative electrode active material layer 7 on the negative electrode current collector layer 8 with the separator interposed therebetween.
　また、本実施形態における正極１は、公知の方法により製造することができる。例えば、正極活物質、バインダー樹脂、および導電助剤を有機溶媒中に分散させ正極スラリーを得た後、この正極スラリーを正極集電体層３に塗布・乾燥し、必要に応じてプレスすることにより正極集電体層３上に正極活物質層２を形成する方法等を採用することができる。
　正極作製時に用いるスラリー溶媒としては、例えば、Ｎ－メチル－２－ピロリドン（ＮＭＰ）を用いることができる。 In addition, the positive electrode 1 in the present embodiment can be manufactured by a known method. For example, after a positive electrode active material, a binder resin, and a conductive additive are dispersed in an organic solvent to obtain a positive electrode slurry, this positive electrode slurry is applied to the positive electrode current collector layer 3 and dried, and pressed as necessary. Thus, the method of forming the positive electrode active material layer 2 on the positive electrode current collector layer 3 can be adopted.
For example, N-methyl-2-pyrrolidone (NMP) can be used as a slurry solvent used at the time of preparation of the positive electrode.
　バインダー樹脂としては、例えば、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）等の正極用バインダー樹脂として一般的に用いられるものを使用できる。 As a binder resin, what is generally used as binder resin for positive electrodes, such as a polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), can be used, for example.
　正極活物質層２中のバインダー樹脂の含有量は、正極活物質層２の全体を１００質量部としたとき、０．１質量部以上１０．０質量部以下であることが好ましく、０．５質量部以上５．０質量部以下であることがより好ましく、１．０質量部以上５．０質量部以下であることがさらに好ましい。バインダー樹脂の含有量が上記範囲内であると、正極スラリーの塗工性、バインダーの結着性および電池特性のバランスがより一層優れる。
　また、バインダー樹脂の含有量が上記上限値以下であると、正極活物質の割合が大きくなり、正極質量当たりの容量が大きくなるため好ましい。バインダー樹脂の含有量が上記下限値以上であると、電極剥離が抑制されるため好ましい。 The content of the binder resin in the positive electrode active material layer 2 is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, based on 100 parts by mass of the entire positive electrode active material layer 2. It is more preferable that it is mass part or more and 5.0 mass parts or less, and it is further more preferable that it is 1.0 mass part or more and 5.0 mass parts or less. The balance of the coating property of a positive electrode slurry, the binding property of a binder, and the battery characteristic as the content of binder resin is in the said range is much more excellent.
Moreover, the ratio of a positive electrode active material becomes large as content of binder resin is below the said upper limit, and since the capacity | capacitance per positive electrode mass becomes large, it is preferable. It is preferable in order that electrode peeling may be suppressed as content of binder resin is more than the said lower limit.
　正極活物質層２は、正極活物質とバインダー樹脂の他に導電助剤を含むことができる。導電助剤としては正極の導電性を向上させるものであれば特に限定されないが、例えば、カーボンブラック、ケッチェンブラック、アセチレンブラック、天然黒鉛、人工黒鉛、炭素繊維等が挙げられる。これらの導電助剤は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 positive electrode active material layer 2 can contain a conductive support agent in addition to the positive electrode active material and the binder resin. The conductive aid is not particularly limited as long as it improves the conductivity of the positive electrode, and examples thereof include carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, carbon fiber and the like. These conductive aids may be used alone or in combination of two or more.
　正極活物質層２中の導電助剤の含有量は、正極活物質層２の全体を１００質量部としたとき、１．０質量部超過４．０質量部未満であることが好ましく、１．２質量部以上３．５質量部以下であることがより好ましく、１．５質量部以上３．５質量部以下であることがさらに好ましく、２．０質量部以上３．５質量部以下であることが特に好ましい。導電助剤の含有量が上記範囲内であると、正極スラリーの塗工性、バインダー樹脂の結着性および電池特性のバランスがより一層優れる。
　また、導電助剤の含有量が上記上限値未満または以下であると、正極活物質の割合が大きくなり、正極質量当たりの容量が大きくなるため好ましい。導電助剤の含有量が上記下限値以上であると、正極の導電性がより良好になり、リチウムイオン二次電池の電池特性が向上するため好ましい。 The content of the conductive additive in the positive electrode active material layer 2 is preferably more than 1.0 parts by mass and less than 4.0 parts by mass, based on 100 parts by mass of the whole of the positive electrode active material layer 2. It is more preferably 2 parts by mass or more and 3.5 parts by mass or less, still more preferably 1.5 parts by mass or more and 3.5 parts by mass or less and 2.0 parts by mass or more and 3.5 parts by mass or less Is particularly preferred. The balance of the coating property of a positive electrode slurry, the binding property of binder resin, and battery characteristics as the content of the conductive support agent is within the above range is further excellent.
Moreover, since the ratio of a positive electrode active material becomes large as content of a conductive support agent is less than or less than the said upper limit, and the capacity | capacitance per positive electrode mass becomes large, it is preferable. It is preferable for the content of the conductive additive to be not less than the above lower limit value, since the conductivity of the positive electrode becomes better and the battery characteristics of the lithium ion secondary battery are improved.
　正極集電体層３としては、アルミニウム、ステンレス鋼、ニッケル、チタンまたはこれらの合金等を用いることができる。その形状としては、例えば、箔、平板状、メッシュ状等が挙げられる。特にアルミニウム箔を好適に用いることができる。 As the positive electrode current collector layer 3, aluminum, stainless steel, nickel, titanium, an alloy of these, or the like can be used. As the shape, foil, flat form, mesh form etc. are mentioned, for example. In particular, an aluminum foil can be suitably used.
　正極集電体層３の厚みは特に限定されないが、例えば１μｍ以上３０μｍ以下である。
　ここで、正極集電体層３の厚みが薄いほど、正極集電体層３が変形したり、破れたりしやすくなるため、リチウムイオン二次電池の安全性が悪化しやすい。しかし、本実施形態に係るリチウムイオン二次電池は正極集電体層３の厚みが薄くても電池の安全性の悪化を抑制することができる。そのため、リチウムイオン二次電池の安全性を良好にしつつ、リチウムイオン二次電池における正極集電体層３の割合を減らし、リチウムイオン二次電池をより高エネルギー密度化する観点から、正極集電体層３の厚みは２５μｍ未満が好ましく、２０μｍ未満がより好ましく、１８μｍ未満が特に好ましい。 Although the thickness of the positive electrode collector layer 3 is not particularly limited, it is, for example, 1 μm or more and 30 μm or less.
Here, as the thickness of the positive electrode current collector layer 3 is smaller, the positive electrode current collector layer 3 is more easily deformed or broken, so that the safety of the lithium ion secondary battery is easily deteriorated. However, in the lithium ion secondary battery according to the present embodiment, even if the thickness of the positive electrode current collector layer 3 is thin, the deterioration of the safety of the battery can be suppressed. Therefore, from the viewpoint of increasing the energy density of the lithium ion secondary battery by reducing the proportion of the positive electrode current collector layer 3 in the lithium ion secondary battery while improving the safety of the lithium ion secondary battery, the positive electrode current collection The thickness of the body layer 3 is preferably less than 25 μm, more preferably less than 20 μm, and particularly preferably less than 18 μm.
　また、ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、正極集電体層３の引張伸度が１０％未満であることが好ましく、８％未満であることがより好ましい。これにより、例えばリチウムデンドライド等の鋭利な金属によってセパレータ２０が破れたとしても、正極集電体層３の伸びを抑制できるため、セパレータ２０を突き破った金属と、正負極との接触を抑制することができる。その結果、リチウムイオン二次電池の熱暴走等を抑制でき、安全性をより向上させることができる。 Moreover, it is preferable that the tensile elongation of the positive electrode collector layer 3 measured according to 6.3 of JISL1913: 2010 is less than 10%, and it is more preferable that it is less than 8%. Thus, even if the separator 20 is torn by a sharp metal such as lithium dendrite, for example, the expansion of the positive electrode current collector layer 3 can be suppressed, so the contact between the metal that has broken the separator 20 and the positive and negative electrodes is suppressed. be able to. As a result, thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
　正極活物質層２の密度は特に限定されないが、例えば、２．０ｇ／ｃｍ３以上４．０ｇ／ｃｍ３以下であることが好ましく、２．４ｇ／ｃｍ３以上３．８ｇ／ｃｍ３以下であることがより好ましく、２．８ｇ／ｃｍ３以上３．６ｇ／ｃｍ３以下であることがさらに好ましい。
　ここで、正極活物質層２の密度が高いほど、リチウムイオン二次電池のサイクル特性等の電池特性が悪化しやすい。しかし、本実施形態に係るリチウムイオン二次電池はこのサイクル特性等の電池特性の悪化を抑制することができる。そのため、サイクル特性等の電池特性を良好にしつつ、得られるリチウムイオン二次電池のエネルギー密度をより一層向上させる観点から、正極活物質層２の密度は３．０ｇ／ｃｍ３以上であることが好ましく、３．２ｇ／ｃｍ３以上であることがより好ましく、３．３ｇ／ｃｍ３以上であることが特に好ましい。また、高温でのサイクル特性の悪化をより抑制する観点から、正極活物質層２の密度は４．０ｇ／ｃｍ３以下であることが好ましく、３．８ｇ／ｃｍ３以下であることがより好ましく、３．６ｇ／ｃｍ３以下であることがさらに好ましい。 Although the density of the positive electrode active material layer 2 is not particularly limited, for example, it is preferably not more than 2.0 g / cm 3 or more 4.0g / cm 3, 2.4g / cm 3 or more 3.8 g / cm 3 or less Some are more preferable, and 2.8 g / cm 3 or more and 3.6 g / cm 3 or less are more preferable.
Here, as the density of the positive electrode active material layer 2 is higher, battery characteristics such as cycle characteristics of the lithium ion secondary battery are likely to be deteriorated. However, the lithium ion secondary battery according to the present embodiment can suppress the deterioration of the battery characteristics such as the cycle characteristics. Therefore, the density of the positive electrode active material layer 2 is 3.0 g / cm 3 or more from the viewpoint of further improving the energy density of the obtained lithium ion secondary battery while making battery characteristics such as cycle characteristics better. Preferably, it is 3.2 g / cm 3 or more, more preferably 3.3 g / cm 3 or more. Further, from a more suppressing the deterioration of the cycle characteristics at high temperatures, it is preferable that the density of the positive electrode active material layer 2 is 4.0 g / cm 3 or less, more preferably 3.8 g / cm 3 or less More preferably, it is 3.6 g / cm 3 or less.
　正極活物質層２の厚み（両面の厚みの合計）は特に限定されるものではなく、所望の特性に応じて適宜設定することができる。例えば、エネルギー密度の観点からは厚く設定することができ、また出力特性の観点からは薄く設定することができる。正極活物質層２の厚み（両面の厚みの合計）は、例えば２０μｍ以上５００μｍ以下の範囲で適宜設定でき、４０μｍ以上４００μｍ以下が好ましく、６０μｍ以上３００μｍ以下がより好ましい。
　また、正極活物質層２の厚み（片面の厚み）は特に限定されるものではなく、所望の特性に応じて適宜設定することができる。例えば、エネルギー密度の観点からは厚く設定することができ、また出力特性の観点からは薄く設定することができる。正極活物質層２の厚み（片面の厚み）は、例えば、１０μｍ以上２５０μｍ以下の範囲で適宜設定でき、２０μｍ以上２００μｍ以下が好ましく、３０μｍ以上１５０μｍ以下がより好ましい。 The thickness (the sum of the thicknesses on both sides) of the positive electrode active material layer 2 is not particularly limited, and can be appropriately set according to the desired characteristics. For example, it can be set thick in terms of energy density, and can be set thin in terms of output characteristics. The thickness (total of the thickness on both sides) of the positive electrode active material layer 2 can be appropriately set, for example, in the range of 20 μm to 500 μm, preferably 40 μm to 400 μm, and more preferably 60 μm to 300 μm.
In addition, the thickness (thickness of one side) of the positive electrode active material layer 2 is not particularly limited, and can be appropriately set according to the desired characteristics. For example, it can be set thick in terms of energy density, and can be set thin in terms of output characteristics. The thickness (thickness on one side) of the positive electrode active material layer 2 can be appropriately set, for example, in the range of 10 μm to 250 μm, preferably 20 μm to 200 μm, and more preferably 30 μm to 150 μm.
（リチウムを吸蔵放出する負極）
　本実施形態に係る負極６は、用途等に応じて、公知のリチウムイオン二次電池に使用することのできる負極の中から適宜選択することができる。負極６に用いられる負極活物質についても負極に使用可能なものであれば用途等に応じて適宜設定することができる。
　負極６は、負極集電体層８と、負極集電体層８上に形成された負極活物質層７を含む構造を有する。負極活物質層７は、負極活物質とバインダー樹脂を含み、導電性を高める点から導電助剤をさらに含むことが好ましい。 (Anode that occludes and releases lithium)
The negative electrode 6 which concerns on this embodiment can be suitably selected from the negative electrodes which can be used for a well-known lithium ion secondary battery according to a use etc. The negative electrode active material used for the negative electrode 6 can be appropriately set according to the application etc. as long as it can be used for the negative electrode.
The negative electrode 6 has a structure including a negative electrode current collector layer 8 and a negative electrode active material layer 7 formed on the negative electrode current collector layer 8. The negative electrode active material layer 7 preferably contains a negative electrode active material and a binder resin, and preferably further contains a conductive auxiliary agent in order to enhance the conductivity.
　負極活物質としては、リチウムイオンを吸蔵、放出可能な負極用の活物質材料であれば特に限定されないが、炭素質材料を用いることができる。炭素質材料としては、黒鉛、非晶質炭素（例えば易黒鉛化性炭素、難黒鉛化性炭素）、ダイヤモンド状炭素、フラーレン、カーボンナノチューブ、カーボンナノホーン等が挙げられる。黒鉛としては、天然黒鉛、人造黒鉛を用いることができ、材料コストの観点から安価な天然黒鉛が好ましい。非晶質炭素としては、例えば、石炭ピッチコークス、石油ピッチコークス、アセチレンピッチコークス等を熱処理して得られるものが挙げられる。その他の負極活物質として、リチウム金属材料、シリコンやスズ等の合金系材料、Ｎｂ２Ｏ５やＴｉＯ２等の酸化物系材料、あるいはこれらの複合物を用いることができる。
　負極活物質は、一種のみを単独で用いてもよく、二種以上を組み合わせて用いてもよい。 The negative electrode active material is not particularly limited as long as it is an active material for a negative electrode capable of inserting and extracting lithium ions, but a carbonaceous material can be used. Examples of the carbonaceous material include graphite, amorphous carbon (for example, graphitizable carbon, non-graphitizable carbon), diamond-like carbon, fullerene, carbon nanotube, carbon nanohorn and the like. As graphite, natural graphite and artificial graphite can be used, and inexpensive natural graphite is preferable from the viewpoint of material cost. Examples of amorphous carbon include those obtained by heat-treating coal pitch coke, petroleum pitch coke, acetylene pitch coke and the like. As other negative electrode active materials, lithium metal materials, alloy materials such as silicon and tin, oxide materials such as Nb 2 O 5 and TiO 2 , or a composite thereof can be used.
The negative electrode active material may be used alone or in combination of two or more.
　負極活物質の平均粒径は、充放電時の副反応を抑えて充放電効率の低下を抑える点から、２μｍ以上が好ましく、５μｍ以上がより好ましく、入出力特性の観点や負極作製上の観点（負極表面の平滑性等）から、４０μｍ以下が好ましく、３０μｍ以下がより好ましい。ここで平均粒径は、レーザー回折散乱法による粒度分布（体積基準）における積算値５０％での粒子径（メジアン径：Ｄ５０）を意味する。 The average particle diameter of the negative electrode active material is preferably 2 μm or more, more preferably 5 μm or more, from the viewpoint of suppressing side reactions during charge and discharge to suppress a decrease in charge and discharge efficiency From (Smoothness of the negative electrode surface, etc.), 40 μm or less is preferable and 30 μm or less is more preferable. Here, the average particle diameter means a particle diameter (median diameter: D 50 ) at an integrated value of 50% in a particle size distribution (volume basis) by a laser diffraction scattering method.
　また、本実施形態における負極６は、公知の方法により製造することができる。例えば負極活物質とバインダー樹脂とを溶媒中に分散させスラリーを得た後、このスラリーを負極集電体層８に塗布・乾燥し、必要に応じてプレスして負極活物質層７を形成する方法等を採用することができる。
　負極スラリーの塗布方法としては、ドクターブレード法、ダイコーター法、ディップコーティング法が挙げられる。スラリーには、必要に応じて、消泡剤や界面活性剤等の添加剤を加えてもよい。 In addition, the negative electrode 6 in the present embodiment can be manufactured by a known method. For example, after the negative electrode active material and the binder resin are dispersed in a solvent to obtain a slurry, this slurry is applied to the negative electrode current collector layer 8 and dried, and pressed as necessary to form the negative electrode active material layer 7 A method etc. can be adopted.
Examples of the method of applying the negative electrode slurry include a doctor blade method, a die coater method, and a dip coating method. If necessary, additives such as an antifoaming agent and a surfactant may be added to the slurry.
　負極活物質層７中のバインダー樹脂の含有量は、負極活物質層７の全体を１００質量部としたとき、０．１質量部以上１０．０質量部以下であることが好ましく、０．５質量部以上８．０質量部以下であることがより好ましく、１．０質量部以上５．０質量部以下であることがさらに好ましく、１．０質量部以上３．０質量部以下であることが特に好ましい。バインダー樹脂の含有量が上記範囲内であると、負極スラリーの塗工性、バインダー樹脂の結着性および電池特性のバランスがより一層優れる。
　また、バインダー樹脂の含有量が上記上限値以下であると、負極活物質の割合が大きくなり、負極質量当たりの容量が大きくなるため好ましい。バインダー樹脂の含有量が上記下限値以上であると、電極剥離が抑制されるため好ましい。 The content of the binder resin in the negative electrode active material layer 7 is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, based on 100 parts by mass of the entire negative electrode active material layer 7. It is more preferable that it is mass part or more and 8.0 mass parts or less, it is more preferable that it is 1.0 mass part or more and 5.0 mass parts or less, and it is 1.0 mass part or more and 3.0 mass parts or less Is particularly preferred. When the content of the binder resin is in the above range, the balance between the coatability of the negative electrode slurry, the binding property of the binder resin, and the battery characteristics is more excellent.
Moreover, since the ratio of a negative electrode active material becomes large as content of binder resin is below the said upper limit, and the capacity | capacitance per negative electrode mass becomes large, it is preferable. It is preferable in order that electrode peeling may be suppressed as content of binder resin is more than the said lower limit.
　溶媒としては、Ｎ－メチル－２－ピロリドン（ＮＭＰ）等の有機溶媒や、水を用いることができる。溶媒として有機溶媒を用いた場合は、ポリフッ化ビニリデン（ＰＶＤＦ）等の有機溶媒用のバインダー樹脂を用いることができる。溶媒として水を用いた場合は、ゴム系バインダー（例えばＳＢＲ（スチレン・ブタジエンゴム））やアクリル系バインダー樹脂を用いることができる。このような水系バインダー樹脂はエマルジョンの形態のものを用いることができる。溶媒として水を用いる場合は、水系バインダーとＣＭＣ（カルボキシメチルセルロース）等の増粘剤とを併用することが好ましい。 As the solvent, an organic solvent such as N-methyl-2-pyrrolidone (NMP) or water can be used. When an organic solvent is used as the solvent, a binder resin for an organic solvent such as polyvinylidene fluoride (PVDF) can be used. When water is used as the solvent, rubber binders (for example, SBR (styrene-butadiene rubber)) and acrylic binder resins can be used. Such aqueous binder resin can be used in the form of an emulsion. When water is used as the solvent, it is preferable to use an aqueous binder and a thickener such as CMC (carboxymethyl cellulose) in combination.
　負極活物質層７は、必要に応じて導電助剤を含有してもよい。この導電助剤としては、カーボンブラック、ケッチェンブラック、アセチレンブラック等の炭素質材料等の一般的に負極の導電助剤として使用されている導電性材料を用いることができる。
　負極活物質層７中の導電助剤の含有量は、負極活物質層７の全体を１００質量部としたとき、０．１質量部以上３．０質量部以下であることが好ましく、０．１質量部以上２．０質量部以下であることがより好ましく、０．２質量部以上１．０質量部以下であることが特に好ましい。導電助剤の含有量が上記範囲内であると、負極スラリーの塗工性、バインダー樹脂の結着性および電池特性のバランスがより一層優れる。
　また、導電助剤の含有量が上記上限値以下であると、負極活物質の割合が大きくなり、負極質量当たりの容量が大きくなるため好ましい。導電助剤の含有量が上記下限値以上であると、負極の導電性がより良好になるため好ましい。 The negative electrode active material layer 7 may contain a conductive auxiliary, as necessary. As the conductive aid, conductive materials generally used as a conductive aid for a negative electrode, such as carbonaceous materials such as carbon black, ketjen black and acetylene black can be used.
The content of the conductive additive in the negative electrode active material layer 7 is preferably 0.1 parts by mass or more and 3.0 parts by mass or less, based on 100 parts by mass of the whole of the negative electrode active material layer 7. The content is more preferably 1 part by mass or more and 2.0 parts by mass or less, and particularly preferably 0.2 parts by mass or more and 1.0 parts by mass or less. The balance of the coating property of negative electrode slurry, the binding property of binder resin, and the battery characteristic as the content of a conductive support agent is in the above-mentioned range is much more excellent.
Moreover, since the ratio of a negative electrode active material becomes large as content of a conductive support agent is below the said upper limit, and the capacity | capacitance per negative electrode mass becomes large, it is preferable. It is preferable for the content of the conductive additive to be not less than the above lower limit value because the conductivity of the negative electrode is further improved.
　正極活物質層２や負極活物質層７に用いられる導電助剤の平均粒子径（一次粒子径）は１０～１００ｎｍの範囲にあることが好ましい。導電助剤の平均粒子径（一次粒子径）は、導電助剤の過度な凝集を抑えて負極中に均一に分散させる観点から１０ｎｍ以上が好ましく、３０ｎｍ以上がより好ましく、十分な数の接触点が形成でき、良好な導電経路を形成する観点から１００ｎｍ以下が好ましく、８０ｎｍ以下がより好ましい。導電助剤が繊維状の場合は、平均直径が２～２００ｎｍ、平均繊維長が０．１～２０μｍのものが挙げられる。
　ここで、導電助剤の平均粒子径は、メジアン径（Ｄ５０）であり、レーザー回折散乱法による粒度分布（体積基準）における積算値５０％での粒子径を意味する。 The average particle size (primary particle size) of the conductive additive used for the positive electrode active material layer 2 and the negative electrode active material layer 7 is preferably in the range of 10 to 100 nm. The average particle size (primary particle size) of the conductive aid is preferably 10 nm or more, more preferably 30 nm or more, and a sufficient number of contact points from the viewpoint of suppressing excessive aggregation of the conductive aid and uniformly dispersing in the negative electrode. From the viewpoint of forming a good conductive path, and is preferably 100 nm or less, more preferably 80 nm or less. When the conductive aid is in the form of fibers, those having an average diameter of 2 to 200 nm and an average fiber length of 0.1 to 20 μm can be mentioned.
Here, the average particle diameter of the conductive additive is the median diameter (D 50 ), which means the particle diameter at an integrated value of 50% in the particle size distribution (volume basis) by the laser diffraction scattering method.
　負極活物質層７の厚み（両面の厚みの合計）は特に限定されるものではなく、所望の特性に応じて適宜設定することができる。例えば、エネルギー密度の観点からは厚く設定することができ、また出力特性の観点からは薄く設定することができる。負極活物質層７の厚み（両面の厚みの合計）は、例えば４０μｍ以上１０００μｍ以下の範囲で適宜設定でき、８０μｍ以上８００μｍ以下が好ましく、１２０μｍ以上６００μｍ以下がより好ましい。
　また、負極活物質層７の厚み（片面の厚み）は特に限定されるものではなく、所望の特性に応じて適宜設定することができる。例えば、エネルギー密度の観点からは厚く設定することができ、また出力特性の観点からは薄く設定することができる。負極活物質層７の厚み（片面の厚み）は、例えば、２０μｍ以上５００μｍ以下の範囲で適宜設定でき、４０μｍ以上４００μｍ以下が好ましく、６０μｍ以上３００μｍ以下がより好ましい。 The thickness (total of the thickness on both sides) of the negative electrode active material layer 7 is not particularly limited, and can be appropriately set according to the desired characteristics. For example, it can be set thick in terms of energy density, and can be set thin in terms of output characteristics. The thickness (total of the thickness on both sides) of the negative electrode active material layer 7 can be appropriately set, for example, in the range of 40 μm to 1000 μm, preferably 80 μm to 800 μm, and more preferably 120 μm to 600 μm.
Further, the thickness (thickness of one side) of the negative electrode active material layer 7 is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thick in terms of energy density, and can be set thin in terms of output characteristics. The thickness (thickness of one side) of the negative electrode active material layer 7 can be appropriately set, for example, in the range of 20 μm to 500 μm, preferably 40 μm to 400 μm, and more preferably 60 μm to 300 μm.
　負極活物質層７の密度は特に限定されないが、例えば、１．２ｇ／ｃｍ３以上２．０ｇ／ｃｍ３以下であることが好ましく、１．３ｇ／ｃｍ３以上１．９ｇ／ｃｍ３以下であることがより好ましく、１．４ｇ／ｃｍ３以上１．８ｇ／ｃｍ３以下であることがさらに好ましい。 Although the density of the negative electrode active material layer 7 is not particularly limited, it is preferably, for example, 1.2 g / cm 3 or more and 2.0 g / cm 3 or less, and 1.3 g / cm 3 or more and 1.9 g / cm 3 or less Some are more preferable, and 1.4 g / cm 3 or more and 1.8 g / cm 3 or less are more preferable.
　負極集電体層８としては、銅、ステンレス鋼、ニッケル、チタンまたはこれらの合金を用いることができる。その形状としては、箔、平板状、メッシュ状が挙げられる。 As the negative electrode current collector layer 8, copper, stainless steel, nickel, titanium or an alloy thereof can be used. As the shape, foil, flat form, mesh form is mentioned.
　負極集電体層８の厚みは特に限定されないが、例えば１μｍ以上２０μｍ以下である。
　ここで、負極集電体層８の厚みが薄いほど、負極集電体層８が変形したり、破れたりしやすくなるため、リチウムイオン二次電池の安全性が悪化しやすい。しかし、本実施形態に係るリチウムイオン二次電池は負極集電体層８の厚みが薄くても電池の安全性の悪化を抑制することができる。そのため、リチウムイオン二次電池の安全性を良好にしつつ、リチウムイオン二次電池における負極集電体層８の割合を減らし、リチウムイオン二次電池をより高エネルギー密度化する観点から、負極集電体層８の厚みは１５μｍ未満が好ましく、１２μｍ未満がより好ましく、１０μｍ未満が特に好ましい。 The thickness of the negative electrode current collector layer 8 is not particularly limited, and is, for example, 1 μm or more and 20 μm or less.
Here, as the thickness of the negative electrode current collector layer 8 is thinner, the negative electrode current collector layer 8 is more easily deformed or broken, so that the safety of the lithium ion secondary battery is easily deteriorated. However, in the lithium ion secondary battery according to the present embodiment, even if the thickness of the negative electrode current collector layer 8 is thin, the deterioration of the safety of the battery can be suppressed. Therefore, from the viewpoint of increasing the energy density of the lithium ion secondary battery by reducing the proportion of the negative electrode current collector layer 8 in the lithium ion secondary battery while improving the safety of the lithium ion secondary battery, the negative electrode current collection The thickness of the body layer 8 is preferably less than 15 μm, more preferably less than 12 μm, and particularly preferably less than 10 μm.
　また、ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、負極集電体層８の引張伸度が１０％未満であることが好ましく、５％未満であることがより好ましい。これにより、例えばリチウムデンドライド等の鋭利な金属によってセパレータ２０が破れたとしても、負極集電体層８の伸びを抑制できるため、セパレータ２０を突き破った金属と、正負極との接触を抑制することができる。その結果、リチウムイオン二次電池の熱暴走等を抑制でき、安全性をより向上させることができる。 In addition, the tensile elongation of the negative electrode current collector layer 8 is preferably less than 10%, more preferably less than 5%, which is measured according to 6.3 of JIS L1913: 2010. Thus, even if the separator 20 is torn by a sharp metal such as lithium dendrite, for example, the expansion of the negative electrode current collector layer 8 can be suppressed, so the contact between the metal that has broken the separator 20 and the positive and negative electrodes is suppressed. be able to. As a result, thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
（リチウム塩を含有する非水電解液）
　本実施形態に用いるリチウム塩を含有する非水電解液は、電極活物質の種類やリチウムイオン二次電池の用途等に応じて公知のものの中から適宜選択することができる。 (Non-aqueous electrolyte containing lithium salt)
The non-aqueous electrolytic solution containing a lithium salt used in the present embodiment can be appropriately selected from known ones depending on the type of electrode active material, the use of the lithium ion secondary battery, and the like.
　具体的なリチウム塩の例としては、例えば、ＬｉＣｌＯ４、ＬｉＢＦ６、ＬｉＰＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢ１０Ｃｌ１０、ＬｉＡｌＣｌ４、ＬｉＣｌ、ＬｉＢｒ、ＬｉＢ（Ｃ２Ｈ５）４、ＣＦ３ＳＯ３Ｌｉ、ＣＨ３ＳＯ３Ｌｉ、ＬｉＣ４Ｆ９ＳＯ３、Ｌｉ（ＣＦ３ＳＯ２）２Ｎ、低級脂肪酸カルボン酸リチウム等を挙げることができる。 Specific examples of the lithium salt, 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 Examples include (C 2 H 5 ) 4 , CF 3 SO 3 Li, CH 3 SO 3 Li, LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 2 N, and lower fatty acid carboxylate lithium.
　リチウム塩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）、エチルメチルカーボネート（ＥＭＣ），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）等のカーボネート類；γ－ブチロラクトン、γ－バレロラクトン等のラクトン類；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、テトラヒドロフラン、２－メチルテトラヒドロフラン等のエーテル類；ジメチルスルホキシド等のスルホキシド類；１，３－ジオキソラン、４－メチル－１，３－ジオキソラン等のオキソラン類；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等の含窒素溶媒；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等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、メチルスルホラン等のスルホラン類；３－メチル－２－オキサゾリジノン等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、ナフタスルトン等のスルトン類等が挙げられる。これらは、一種単独で使用してもよいし、二種以上を組み合わせて使用してもよい。 The solvent for dissolving the lithium salt is not particularly limited as long as it is generally used as a liquid for dissolving the electrolyte, and ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), carbonates such as vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; trimethoxymethane Ethers such as 1,2-dimethoxyethane, diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, etc. Sulfoxides such as dimethylsulfoxide, etc. 1,3-Dioxolane, 4-methyl-1,3-dioxola Nitrogenous solvents such as acetonitrile, nitromethane, formamide and dimethylformamide; methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate and the like; organic acid esters such as phosphoric acid triester And diglymes; triglymes; sulfolanes such as sulfolane and methyl sulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; and sultones such as 1,3-propane sultone, 1,4-butane sultone and naphtha sultone. . These may be used singly or in combination of two or more.
（容器）
　本実施形態において容器には公知の部材を用いることができ、電池の軽量化の観点からは可撓性フィルム３０を用いることが好ましい。可撓性フィルム３０は、基材となる金属層の表裏面に樹脂層が設けられたものを用いることができる。金属層には電解液の漏出や外部からの水分の侵入を防止する等のバリア性を有するものを選択することができ、アルミニウム、ステンレス鋼等を用いることができる。金属層の少なくとも一方の面には変性ポリオレフィン等の熱融着性の樹脂層が設けられ、可撓性フィルム３０の熱融着性の樹脂層同士を電池要素を介して対向させ、電池要素を収納する部分の周囲を熱融着することで外装体を形成する。熱融着性の樹脂層が形成された面と反対側の面となる外装体表面にはナイロンフィルム、ポリエステルフィルム等の樹脂層を設けることができる。 (container)
A well-known member can be used for a container in this embodiment, and it is preferable to use the flexible film 30 from a viewpoint of weight reduction of a battery. The flexible film 30 can use what provided the resin layer in front and back of the metal layer used as a base material. The metal layer can be selected to have a barrier property to prevent leakage of the electrolytic solution and entry of moisture from the outside, and aluminum, stainless steel, etc. can be used. A heat-sealable resin layer such as modified polyolefin is provided on at least one surface of the metal layer, and the heat-sealable resin layers of the flexible film 30 are opposed to each other through the battery element to make the battery element The sheath is formed by heat-sealing the periphery of the part to be stored. A resin layer such as a nylon film or a polyester film can be provided on the surface of the exterior body opposite to the surface on which the heat-fusible resin layer is formed.
（端子）
　本実施形態において、正極端子１１にはアルミニウムやアルミニウム合金で構成されたもの、負極端子１６には銅や銅合金あるいはそれらにニッケルメッキを施したもの等を用いることができる。それぞれの端子は容器の外部に引き出されるが、それぞれの端子における外装体の周囲を熱溶着する部分に位置する箇所には熱融着性の樹脂をあらかじめ設けることができる。 (Terminal)
In the present embodiment, the positive electrode terminal 11 may be made of aluminum or an aluminum alloy, and the negative electrode terminal 16 may be copper or a copper alloy, or those plated with nickel. Each terminal is drawn to the outside of the container, but a heat fusible resin can be provided in advance in a portion located at a portion of the respective terminal where the periphery of the package is heat welded.
（絶縁部材）
　活物質の塗布部と未塗布部の境界部４、９に絶縁部材を形成する場合には、ポリイミド、ガラス繊維、ポリエステル、ポリプロピレンあるいはこれらを構成中に含むものを用いることができる。これらの部材に熱を加えて境界部４、９に溶着させるか、または、ゲル状の樹脂を境界部４、９に塗布、乾燥させることで絶縁部材を形成することができる。 (Insulation member)
In the case of forming the insulating member at the boundary portions 4 and 9 between the coated portion and the non-coated portion of the active material, polyimide, glass fiber, polyester, polypropylene or those containing these in the structure can be used. Heat can be applied to these members to weld them to the boundaries 4 and 9, or a gel-like resin can be applied to the boundaries 4 and 9 and dried to form an insulating member.
（セパレータ）
　本実施形態に係るセパレータ２０は、耐熱性樹脂を主成分として含む樹脂層を備えることが好ましい。
　ここで、上記樹脂層は主成分である耐熱性樹脂により形成されている。ここで、「主成分」とは、樹脂層中における割合が５０質量％以上であることをいい、好ましくは７０質量％以上であり、さらに好ましくは９０質量％以上であり、１００質量％であってもよいことを意味する。
　本実施形態に係るセパレータ２０を構成する樹脂層は、単層であっても、二種以上の層であってもよい。 (Separator)
The separator 20 according to the present embodiment preferably includes a resin layer containing a heat resistant resin as a main component.
Here, the resin layer is formed of a heat resistant resin which is a main component. Here, the term "main component" means that the proportion in the resin layer is 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more, and 100% by mass. It means that you may.
The resin layer constituting the separator 20 according to the present embodiment may be a single layer or two or more layers.
　上記樹脂層を形成する耐熱性樹脂としては、例えば、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート、ポリ－ｍ－フェニレンテレフタレート、ポリ－ｐ－フェニレンイソフタレート、ポリカーボネート、ポリエステルカーボネート、脂肪族ポリアミド、全芳香族ポリアミド、半芳香族ポリアミド、全芳香族ポリエステル、ポリフェニレンサルファイド、ポリパラフェニレンベンゾビスオキサゾール、ポリイミド、ポリアリレート、ポリエーテルイミド、ポリアミドイミド、ポリアセタール、ポリエーテルエーテルケトン、ポリサルホン、ポリエーテルサルホン、フッ素系樹脂、ポリエーテルニトリル、変性ポリフェニレンエーテル等から選択される一種または二種以上を挙げることができる。 Examples of the heat resistant resin forming the above resin layer include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polycarbonate, polyester carbonate, aliphatic polyamide, all Aromatic polyamide, semiaromatic polyamide, wholly aromatic polyester, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyimide, polyarylate, polyetherimide, polyamideimide, polyacetal, polyetheretherketone, polysulfone, polyethersulfone, One or more selected from fluorine resins, polyether nitriles, modified polyphenylene ethers and the like can be mentioned.
　これらの中でも、耐熱性や機械的強度、伸縮性、価格等のバランスに優れる観点から、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート、脂肪族ポリアミド、全芳香族ポリアミド、半芳香族ポリアミドおよび全芳香族ポリエステルから選択される一種または二種以上が好ましく、ポリエチレンテレフタレート、ポリブチレンテレフタレート、脂肪族ポリアミド、全芳香族ポリアミドおよび半芳香族ポリアミドから選択される一種または二種以上がより好ましく、ポリエチレンテレフタレートおよび全芳香族ポリアミドから選択される一種または二種以上がさらに好ましく、ポリエチレンテレフタレートがより好ましい。 Among them, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, aliphatic polyamide, wholly aromatic polyamide, semiaromatic polyamide and all aromatic from the viewpoint of excellent balance of heat resistance, mechanical strength, stretchability, price and the like. Family of polyesters, one or more selected from polyethylene terephthalates, polybutylene terephthalates, aliphatic polyamides, wholly aromatic polyamides and semiaromatic polyamides are more preferred, and polyethylene terephthalates are preferred. One or more selected from wholly aromatic polyamides are more preferable, and polyethylene terephthalate is more preferable.
　本実施形態に係るセパレータ２０の融点は、リチウムイオン二次電池の安全性を向上させる観点から、２２０℃以上であることが好ましく、２３０℃以上であることがより好ましく、２４０℃以上であることがさらに好ましい。あるいは、本実施形態に係るセパレータ２０は、リチウムイオン二次電池の安全性を向上させる観点から、融点を示さないものであることが好ましく、分解温度が２２０℃以上であることが好ましく、２３０℃以上であることがより好ましく、２４０℃以上であることがさらに好ましく、２５０℃以上であることが特に好ましい。
　本実施形態に係るセパレータ２０の融点または分解温度を上記下限値以上とすることにより、電池が発熱し、高温になったとしてもセパレータ２０の熱収縮を抑制することができ、その結果、正極と負極との接触面積を抑制することができる。これにより、リチウムイオン二次電池の熱暴走等を抑制でき、安全性をより向上させることができる。
　本実施形態に係るセパレータ２０の融点の上限は特に限定されないが、例えば５００℃以下であり、伸縮性の観点から、好ましくは４００℃以下である。あるいは、本実施形態に係るセパレータの分解温度の上限は特に限定されないが、例えば５００℃以下であり、伸縮性の観点から、好ましくは４００℃以下である。 The melting point of the separator 20 according to the present embodiment is preferably 220 ° C. or higher, more preferably 230 ° C. or higher, and 240 ° C. or higher from the viewpoint of improving the safety of the lithium ion secondary battery. Is more preferred. Alternatively, from the viewpoint of improving the safety of the lithium ion secondary battery, the separator 20 according to the present embodiment preferably does not have a melting point, preferably has a decomposition temperature of 220 ° C. or higher, and 230 ° C. It is more preferable that it is the above, It is more preferable that it is 240 degreeC or more, It is especially preferable that it is 250 degreeC or more.
By setting the melting point or decomposition temperature of the separator 20 according to the present embodiment to the above lower limit value or more, the battery generates heat and heat contraction of the separator 20 can be suppressed even when the temperature is high. The contact area with the negative electrode can be suppressed. Thus, thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
The upper limit of the melting point of the separator 20 according to the present embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of stretchability. Alternatively, the upper limit of the decomposition temperature of the separator according to the present embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of stretchability.
　ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、本実施形態に係るセパレータのＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値は、正極集電体層３および負極集電体層８の引張伸度よりもそれぞれ大きいことが好ましい。これにより、例えばリチウムデンドライド等の鋭利な金属によってセパレータ２０が破れたとしても、セパレータ２０が正負極集電体よりも伸びるため、セパレータ２０によって正負極が覆われやすくなる。そのため、セパレータ２０を突き破った金属と正負極との接触を、伸びたセパレータ２０によって抑制することができる。その結果、リチウムイオン二次電池の熱暴走等を抑制でき、安全性をより向上させることができる。 The average value of the tensile elongation in the MD direction and the tensile elongation in the TD direction of the separator according to this embodiment, which is measured according to 6.3 of JIS L 1913: 2010, is the positive electrode current collector layer 3 and the negative electrode current collector. It is preferable that the tensile elongation of the body layer 8 be larger than that of the body layer 8. Thus, even if the separator 20 is torn by a sharp metal such as lithium dendrite, for example, the positive and negative electrodes are easily covered by the separator 20 because the separator 20 extends more than the positive and negative electrode current collectors. Therefore, the contact between the metal that has broken through the separator 20 and the positive and negative electrodes can be suppressed by the extended separator 20. As a result, thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
　また、ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、セパレータ２０のＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値が１０％以上であることが好ましく、１２％以上であることがより好ましく、１３％以上であることが特に好ましい。セパレータ２０のＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値が上記下限値以上であると、例えばリチウムデンドライド等の鋭利な金属によってセパレータ２０が破れたとしても、セパレータ２０が伸びて正負極を効果的に覆うため、セパレータ２０を突き破った金属と、正負極との接触を抑制することができる。その結果、リチウムイオン二次電池の熱暴走等を抑制でき、安全性をより向上させることができる。
　ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、セパレータ２０のＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値の上限値は特に限定されないが、セパレータ２０の耐熱性の観点から、１００％以下が好ましく、７０％以下がより好ましく、５０％以下がさらに好ましい。 In addition, it is preferable that the average value of the tensile elongation in the MD direction and the tensile elongation in the TD direction of the separator 20, which is measured in accordance with 6.3 of JIS L 1913: 2010, be 10% or more, and 12% or more. It is more preferably present, and particularly preferably 13% or more. If the average value of the tensile elongation in the MD direction and the tensile elongation in the TD direction of the separator 20 is equal to or more than the above lower limit, the separator 20 stretches even if the separator 20 is torn by a sharp metal such as lithium dendrite. Since the positive and negative electrodes are effectively covered, it is possible to suppress the contact between the metal that has broken through the separator 20 and the positive and negative electrodes. As a result, thermal runaway or the like of the lithium ion secondary battery can be suppressed, and safety can be further improved.
Although the upper limit value of the tensile elongation in the MD direction of the separator 20 and the tensile elongation in the TD direction measured according to 6.3 of JIS L 1913: 2010 is not particularly limited, the heat resistance viewpoint of the separator 20 Therefore, 100% or less is preferable, 70% or less is more preferable, and 50% or less is more preferable.
　また、ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、セパレータ２０のＭＤ方向の引張伸度が１０％以上であることが好ましく、１２％以上であることがより好ましい。
　ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、セパレータ２０のＭＤ方向の引張伸度の上限値は特に限定されないが、１００％以下が好ましく、７０％以下がより好ましく、５０％以下がさらに好ましい。 In addition, the tensile elongation in the MD direction of the separator 20, which is measured according to 6.3 of JIS L1913: 2010, is preferably 10% or more, and more preferably 12% or more.
The upper limit value of the tensile elongation in the MD direction of the separator 20 measured according to 6.3 of JIS L 1913: 2010 is not particularly limited, but 100% or less is preferable, 70% or less is more preferable, and 50% or less More preferable.
　本実施形態に係るセパレータ２０を構成する樹脂層は多孔性樹脂層であることが好ましい。これにより、リチウムイオン二次電池に異常電流が発生し、電池の温度が上昇した場合等に多孔性樹脂層の微細孔が閉塞して電流の流れを遮断することができ、電池の熱暴走を回避することができる。 It is preferable that the resin layer which comprises the separator 20 which concerns on this embodiment is a porous resin layer. As a result, abnormal current is generated in the lithium ion secondary battery, and when the temperature of the battery rises, etc., the fine pores of the porous resin layer can be blocked and the flow of current can be blocked, thereby causing thermal runaway of the battery. It can be avoided.
　上記多孔性樹脂層の空孔率は、機械的強度およびリチウムイオン伝導性のバランスの観点から、２０％以上８０％以下が好ましく、３０％以上７０％以下がより好ましく、４０％以上６０％以下が特に好ましい。
　空孔率は、下記式から求めることができる。
　ε＝｛１－Ｗｓ／（ｄｓ・ｔ）｝×１００
　ここで、ε：空孔率（％）、Ｗｓ：目付（ｇ／ｍ２）、ｄｓ：真密度（ｇ／ｃｍ３）、ｔ：膜厚（μｍ）である。 From the viewpoint of the balance between mechanical strength and lithium ion conductivity, the porosity of the porous resin layer is preferably 20% to 80%, more preferably 30% to 70%, and still more preferably 40% to 60%. Is particularly preferred.
The porosity can be determined from the following equation.
ε = {1-Ws / (ds · t)} × 100
Here, ε: porosity (%), Ws: basis weight (g / m 2 ), ds: true density (g / cm 3 ), t: film thickness (μm).
　本実施形態に係るセパレータ２０の平面形状は、特に限定されず、電極や集電体の形状に合わせて適宜選択することが可能であり、例えば、矩形とすることができる。 The planar shape of the separator 20 according to the present embodiment is not particularly limited, and can be appropriately selected according to the shapes of the electrode and the current collector, and can be, for example, rectangular.
　本実施形態に係るセパレータ２０の厚みは、機械的強度およびリチウムイオン伝導性のバランスの観点から、好ましくは５μｍ以上５０μｍ以下であり、より好ましくは１０μｍ以上４０μｍ以下であり、さらに好ましくは１０μｍ以上３０μｍ以下である。 The thickness of the separator 20 according to the present embodiment is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less, and further preferably 10 μm or more and 30 μm from the viewpoint of balance of mechanical strength and lithium ion conductivity. It is below.
　本実施形態に係るセパレータ２０は、耐熱性をさらに向上させる観点から、上記樹脂層の少なくとも一方の面にセラミック層をさらに備えることが好ましい。ここで、セラミックス層は、本実施形態に係るセパレータ２０の取り扱い性や、生産性等の観点から、樹脂層の一方の面のみに設けられていることが好ましいが、セパレータ２０の耐熱性をより一層向上させる観点から、樹脂層の両面に設けられていてもよい。
　本実施形態に係るセパレータ２０は、上記セラミック層をさらに備えることにより、セパレータ２０の熱収縮をより小さくすることができ、電極間の短絡をより一層防止することができる。 The separator 20 according to the present embodiment preferably further includes a ceramic layer on at least one surface of the resin layer from the viewpoint of further improving heat resistance. Here, the ceramic layer is preferably provided only on one side of the resin layer from the viewpoint of the handleability, productivity, etc. of the separator 20 according to the present embodiment, but the heat resistance of the separator 20 is further enhanced. From the viewpoint of further improving, it may be provided on both sides of the resin layer.
The separator 20 according to the present embodiment can further reduce the thermal contraction of the separator 20 by further including the ceramic layer, and can further prevent a short circuit between the electrodes.
　上記セラミック層は、例えば、上記樹脂層上に、セラミック層形成材料を塗布して乾燥させることにより形成することができる。セラミック層形成材料としては、例えば、無機フィラーとバインダー樹脂とを適当な溶媒に溶解または分散させたものを用いることができる。
　このセラミック層に用いられる無機フィラーは、リチウムイオン二次電池のセパレータに使用される公知の材料の中から適宜選択することができる。例えば、絶縁性の高い酸化物、窒化物、硫化物、炭化物等が好ましく、酸化アルミニウム、ベーマイト、酸化チタン、酸化ケイ素、酸化マグネシウム、酸化バリウム、酸化ジルコニウム、酸化亜鉛および酸化鉄等から選択される一種または二種以上のセラミックスを粒子状に調整したものがより好ましい。これらの中でも、酸化アルミニウム、ベーマイトおよび酸化チタンが好ましい。 The said ceramic layer can be formed by, for example, apply | coating and drying a ceramic layer forming material on the said resin layer. As the ceramic layer forming material, for example, a material obtained by dissolving or dispersing an inorganic filler and a binder resin in a suitable solvent can be used.
The inorganic filler used for this ceramic layer can be suitably selected from the well-known materials used for the separator of a lithium ion secondary battery. For example, oxides, nitrides, sulfides, carbides and the like having high insulating properties are preferable, and are selected from aluminum oxide, boehmite, titanium oxide, silicon oxide, magnesium oxide, barium oxide, zirconium oxide, zinc oxide and iron oxide etc. It is more preferable to adjust one or two or more kinds of ceramics into particles. Among these, aluminum oxide, boehmite and titanium oxide are preferable.
　上記バインダー樹脂は特に限定されず、例えば、カルボキシメチルセルロース（ＣＭＣ）等のセルロース系樹脂；アクリル系樹脂；ポリビニリデンフロライド（ＰＶＤＦ）等のフッ素系樹脂；等が挙げられる。バインダー樹脂は、一種のみを単独で用いてもよく、二種以上を組み合わせて用いてもよい。 The binder resin is not particularly limited, and examples thereof include cellulose resins such as carboxymethyl cellulose (CMC); acrylic resins; fluorine resins such as polyvinylidene fluoride (PVDF); and the like. A binder resin may be used individually by 1 type, and may be used in combination of 2 or more types.
　これら成分を溶解または分散させる溶媒は特に限定されず、例えば、水、エタノール等のアルコール類、Ｎ－メチルピロリドン（ＮＭＰ）、トルエン、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）等から適宜選択して用いることができる。 The solvent for dissolving or dispersing these components is not particularly limited, and is appropriately selected from, for example, water, alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. Can be used.
　セラミックス層の厚みは、耐熱性、機械的強度、取扱い性およびリチウムイオン伝導性のバランスの観点から、好ましくは０．１μｍ以上５０μｍ以下であり、より好ましくは０．５μｍ以上３０μｍ以下であり、さらに好ましくは１μｍ以上１５μｍ以下である。 The thickness of the ceramic layer is preferably 0.1 μm or more and 50 μm or less, more preferably 0.5 μm or more and 30 μm or less, from the viewpoint of the balance between heat resistance, mechanical strength, handleability and lithium ion conductivity. Preferably they are 1 micrometer or more and 15 micrometers or less.
　以上、実施形態に基づいて本発明を説明したが、これらは本発明の例示であり、上記以外の様々な構成を採用することもできる。
　また、本発明は前述の実施形態に限定されるものではなく、本発明の目的を達成できる範囲での変形、改良等は本発明に含まれるものである。 As mentioned above, although this invention was demonstrated based on embodiment, these are the illustrations of this invention, and various structures other than the above can also be employ | adopted.
Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the range in which the object of the present invention can be achieved are included in the present invention.
　以下、本発明を実施例および比較例により説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be described by way of Examples and Comparative Examples, but the present invention is not limited thereto.
（実施例１）
＜正極の作製＞
　正極活物質としてリチウムニッケル含有複合酸化物（化学式：ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２、平均粒径：６μｍ）を９４．０質量部、導電助剤としてカーボンブラックを３．０質量部、バインダー樹脂としてポリフッ化ビニリデン（ＰＶＤＦ）を３．０質量部用いた。これらを有機溶媒に分散させ、正極スラリーを調製した。この正極スラリーを、正極集電体である厚さ１５μｍのアルミニウム箔（引張伸度：６％）に連続的に塗布・乾燥し、次いで、プレスすることによって、正極集電体の塗布部（正極活物質層：片面の厚み６０μｍ、密度：３．３５ｇ／ｃｍ３）と塗布しない未塗布部とを備える正極ロールを作製した。
　この正極ロールを、正極端子と接続するためのタブとなる未塗布部が残るように打ち抜いて、正極とした。 Example 1
<Fabrication of positive electrode>
94.0 parts by mass of lithium nickel-containing composite oxide (chemical formula: LiNi 0.8 Co 0.15 Al 0.05 O 2 , average particle diameter: 6 μm) as a positive electrode active material, and carbon black as a conductive additive 3. 0 parts by mass, and 3.0 parts by mass of polyvinylidene fluoride (PVDF) as a binder resin were used. These were dispersed in an organic solvent to prepare a positive electrode slurry. This positive electrode slurry is continuously applied and dried on a 15 μm thick aluminum foil (tensile elongation: 6%) which is a positive electrode current collector, and then pressed to obtain a coated portion of the positive electrode current collector (positive electrode Active material layer: A positive electrode roll comprising a thickness of 60 μm on one side, a density of 3.35 g / cm 3 ) and an uncoated portion not coated was prepared.
The positive electrode roll was punched out to leave a non-coated portion to be a tab for connecting to the positive electrode terminal, and was used as a positive electrode.
＜負極の作製＞
　負極活物質として天然黒鉛（平均粒径：１６μｍ）を９６．７質量部、導電助剤としてカーボンブラックを０．３質量部、バインダー樹脂としてスチレン・ブタジエンゴムを２．０質量部、増粘剤としてカルボキシメチルセルロースを１．０質量部用いた。これらを水に分散させ、負極スラリーを調製した。この負極スラリーを、負極集電体である厚さ８μｍの銅箔（引張伸度：４％）に連続的に塗布・乾燥し、次いで、プレスすることによって、負極集電体の塗布部（負極活物質層：片面の厚み９０μｍ、密度：１．５５ｇ／ｃｍ３）と塗布しない未塗布部とを備える負極ロールを作製した。
　この負極ロールを、負極端子と接続するためのタブとなる未塗布部が残るように打ち抜いて負極とした。 <Fabrication of negative electrode>
96.7 parts by mass of natural graphite (average particle diameter: 16 μm) as a negative electrode active material, 0.3 parts by mass of carbon black as a conductive additive, 2.0 parts by mass of styrene butadiene rubber as a binder resin, thickener 1.0 mass part of carboxymethylcellulose was used as this. These were dispersed in water to prepare a negative electrode slurry. The negative electrode slurry is continuously coated and dried on a copper foil (tensile elongation: 4%) having a thickness of 8 μm, which is a negative electrode current collector, and then pressed to form a coated portion of the negative electrode current collector (negative electrode Active material layer: A negative electrode roll provided with a thickness of 90 μm on one side, a density of 1.55 g / cm 3 ) and an uncoated portion not coated.
The negative electrode roll was punched out to leave a non-coated portion to be a tab for connecting to the negative electrode terminal.
＜積層型ラミネート電池の作製＞
　正極と負極とをセパレータを介してつづら折り構造で積層し、これに負極端子や正極端子を設け、積層体を得た。次いで、エチレンカーボネートとジエチルカーボネートとエチルメチルカーボネートとからなる溶媒に、１ＭのＬｉＰＦ６を溶かした電解液と、得られた積層体を可撓性フィルムに収容することで、積層型のラミネート電池を得た。この積層型のラミネート電池の定格容量を９．２Ａｈ、正極を２８層、負極を２９層とした。
　セパレータとしては、ポリエチレンテレフタレート（ＰＥＴ）からなる多孔性樹脂層と、ベーマイト粒子からなるセラミックス層とを備えるセパレータ１（厚さ：２５μｍ、空孔率５６％）を用いた。ここで、セパレータ１の物性は以下のとおりである。
　ＭＤ方向の引張伸度：２０％
　ＴＤ方向の引張伸度：１９％
　ＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値：１９．５％
　融点：２５０℃ <Fabrication of Laminated Laminated Battery>
The positive electrode and the negative electrode were stacked in a serpentine structure via a separator, and a negative electrode terminal and a positive electrode terminal were provided thereon to obtain a laminate. Next, a laminate type laminate battery is obtained by housing an electrolyte solution in which 1 M LiPF 6 is dissolved in a solvent composed of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, and the obtained laminate in a flexible film. Obtained. The rated capacity of this laminate type laminate battery was 9.2 Ah, the positive electrode was 28 layers, and the negative electrode was 29 layers.
As a separator, separator 1 (thickness: 25 μm, porosity 56%) including a porous resin layer made of polyethylene terephthalate (PET) and a ceramic layer made of boehmite particles was used. Here, the physical properties of the separator 1 are as follows.
Tensile elongation in the MD direction: 20%
Tensile elongation in the TD direction: 19%
Average value of tensile elongation in MD direction and tensile elongation in TD direction: 19.5%
Melting point: 250 ° C
＜評価＞
（１）セパレータおよび集電体の引張伸度
　ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定した。
（２）多孔性樹脂層の空孔率
　下記式から求めた。
　ε＝｛１－Ｗｓ／（ｄｓ・ｔ）｝×１００
　ここで、ε：空孔率（％）、Ｗｓ：目付（ｇ／ｍ２）、ｄｓ：真密度（ｇ／ｃｍ３）、ｔ：膜厚（μｍ）である。
（３）釘刺し試験後の正負極間の直流抵抗
　得られた積層型のラミネート電池に対して、定電流定電圧（ＣＣ－ＣＶ）法を用いて、２５℃で、１Ｃの定電流で電圧４．２Ｖまで定電流充電し、次いで、４．２Ｖの定電圧で充電終止電流０．０１５Ｃまで定電圧充電し、満充電状態とした。
　次いで、満充電状態の積層型のラミネート電池の中央部に対して、２５℃の環境下で、直径φ３ｍｍ、長さ７０ｍｍのＳＵＳ３０４製の釘（白水製作所社製）を８０ｍｍ／ｓｅｃの速度で電極面に対し垂直方向に刺し、積層型のラミネート電池をショートさせる釘刺し試験をおこなった。
　次いで、釘刺し試験をおこなった後、当該ラミネート電池を短絡放電させ、電圧が０．００１Ｖ以上０．１００Ｖ以下の範囲になった積層型のラミネート電池に対して、横河メータ＆インスツルメンツ社製の抵抗測定器（製品名：Digital Multimeter 7544-01）を用いて、２５℃で、正極端子および負極端子にテスターを当てて、室温（２５℃）下で、正負極間の直流抵抗を測定した。
（４）サイクル試験
　得られた積層型のラミネート電池に対して、サイクル特性を評価した。温度２５℃において、０．５Ｃの定電流で電圧４．２Ｖまで定電流充電し、次いで、４．２Ｖの定電圧で充電終止電流０．０１５Ｃまで定電圧充電した。次いで、放電レート３．０Ｃ、放電終止電圧２．５ＶでＣＣ放電をおこなった。この充放電を３００サイクルおこなった。容量維持率（％）は３００サイクル後の放電容量（ｍＡｈ）を、１０サイクル目の放電容量（ｍＡｈ）で割った値である。容量維持率（％）が８０％以上のものを〇、８０％未満のものを×とした。
（５）安全性試験
　満充電状態の積層型のラミネート電池の中央部に対して、２５℃の環境下で、直径φ３ｍｍ、長さ７０ｍｍのＳＵＳ３０４製の釘（白水製作所社製）を８０ｍｍ／ｓｅｃの速度で電極面に対し垂直方向に刺し、積層型のラミネート電池をショートさせた。次いで、６時間経過後の電池の状態を観察し、以下の基準で、電池の安全性を評価した。
　〇：リチウムイオン電池から発煙および発火の両方が生じなかったもの
　×：リチウムイオン電池から発煙および発火の少なくとも一方が生じたもの <Evaluation>
(1) Tensile Elongation of Separator and Current Collector Measured according to 6.3 of JIS L1913: 2010.
(2) Porosity of porous resin layer It calculated | required from the following formula.
ε = {1-Ws / (ds · t)} × 100
Here, ε: porosity (%), Ws: basis weight (g / m 2 ), ds: true density (g / cm 3 ), t: film thickness (μm).
(3) Direct current resistance between positive and negative electrodes after nail penetration test For the obtained laminated type laminated battery, using constant current constant voltage (CC-CV) method, voltage is applied at a constant current of 1 C at 25 ° C. Constant current charge to 4.2 V, and then constant voltage charge to a charge termination current of 0.015 C at a constant voltage of 4.2 V to make a full charge state.
Next, with respect to the central part of a fully charged laminated type laminate battery, an SUS304 nail (manufactured by Hakusui Mfg. Co., Ltd.) with a diameter of 3 mm and a length of 70 mm is electroded at a speed of 80 mm / sec under an environment of 25 ° C. A nailing test was conducted in which the sheet was pierced in a direction perpendicular to the surface to short the laminated type laminated battery.
Next, after a nail penetration test, the laminate battery is short-circuit discharged, and the voltage is in the range of 0.001 V or more and 0.100 V or less, compared with a laminated type laminate battery manufactured by Yokogawa Meter & Instruments. Using a resistance measuring instrument (product name: Digital Multimeter 7544-01), a tester was applied to the positive electrode terminal and the negative electrode terminal at 25 ° C. to measure the direct current resistance between the positive and negative electrodes at room temperature (25 ° C.).
(4) Cycle Test The cycle characteristics of the obtained laminate type laminated battery were evaluated. At a temperature of 25 ° C., constant current charging was performed at a constant current of 0.5 C to a voltage of 4.2 V, and then constant voltage charging was performed at a constant voltage of 4.2 V to a charge termination current of 0.015 C. Next, CC discharge was performed at a discharge rate of 3.0 C and a discharge termination voltage of 2.5 V. This charge and discharge was performed for 300 cycles. The capacity retention rate (%) is a value obtained by dividing the discharge capacity (mAh) after 300 cycles by the discharge capacity (mAh) at the 10th cycle. Those with a capacity retention rate (%) of 80% or more were rated as ○, and those with less than 80% were rated as ×.
(5) Safety test A SUS304 nail (manufactured by Hakusui Mfg. Co., Ltd.) with a diameter of 3 mm and a length of 70 mm is made at 80 mm / sec under an environment of 25 ° C. against the central part of a fully charged laminate type laminated battery. The laminate was pierced in a direction perpendicular to the electrode surface at a speed of 1 to short the laminated type laminate battery. Next, the condition of the battery after 6 hours was observed, and the safety of the battery was evaluated based on the following criteria.
○: Both smoke and ignition did not occur from lithium ion battery. ×: At least one of smoke and ignition occurred from lithium ion battery.
　以上の評価結果を表１に示す。ここで、実施例１において、正負極間の直流抵抗を測定したときのラミネート電池の電圧は、０．０５８２Ｖであった。 The above evaluation results are shown in Table 1. Here, in Example 1, the voltage of the laminate battery when the DC resistance between the positive and negative electrodes was measured was 0.0582 V.
（実施例２）
　セパレータとして、全芳香族ポリアミド（アラミドとも呼ぶ。）により構成された多孔性樹脂層（厚さ：１５μｍ、空孔率６５％）からなるセパレータ２を用いた以外は、実施例１と同様に積層型ラミネート電池を作製し、各評価を行った。ここで、セパレータ２の物性は以下のとおりである。
　ＭＤ方向の引張伸度：４０％
　ＴＤ方向の引張伸度：３５％
　ＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値：３７．５％
　熱分解温度：４００℃
　ここで、実施例２において、正負極間の直流抵抗を測定したときのラミネート電池の電圧は、０．００１１Ｖであった。 (Example 2)
As the separator, lamination was performed in the same manner as in Example 1 except that a separator 2 made of a porous resin layer (thickness: 15 μm, porosity 65%) composed of a wholly aromatic polyamide (also referred to as aramid) was used. Type laminated battery was produced and each evaluation was performed. Here, the physical properties of the separator 2 are as follows.
Tensile elongation in the MD direction: 40%
Tensile elongation in the TD direction: 35%
Average value of tensile elongation in MD direction and tensile elongation in TD direction: 37.5%
Thermal decomposition temperature: 400 ° C
Here, in Example 2, the voltage of the laminate battery was 0.0011 V when the DC resistance between the positive and negative electrodes was measured.
（実施例３）
　正極の配合割合を正極活物質：９５．０質量部、導電助剤：２．０質量部、バインダー樹脂：３．０質量部に変更した以外は、実施例２と同様に積層型ラミネート電池を作製し、各評価を行った。ここで、実施例３において、正負極間の直流抵抗を測定したときのラミネート電池の電圧は、０．０５８２Ｖであった。 (Example 3)
A laminated laminate battery was prepared in the same manner as in Example 2 except that the composition ratio of the positive electrode was changed to 95.0 parts by mass of the positive electrode active material, 2.0 parts by mass of the conductive additive, and 3.0 parts by mass of the binder resin. It produced and performed each evaluation. Here, in Example 3, the voltage of the laminate battery when the DC resistance between the positive and negative electrodes was measured was 0.0582 V.
（比較例１）
　正極の配合割合を正極活物質：９３．０質量部、導電助剤：４．０質量部、バインダー樹脂：３．０質量部に変更した以外は、実施例１と同様に積層型ラミネート電池を作製し、各評価を行った。 (Comparative example 1)
A laminated laminate battery was prepared in the same manner as in Example 1 except that the composition ratio of the positive electrode was changed to 93.0 parts by mass of the positive electrode active material, 4.0 parts by mass of the conductive additive, and 3.0 parts by mass of the binder resin. It produced and performed each evaluation.
（比較例２）
　セパレータとして、ポリプロピレンにより構成された多孔性樹脂層とセラミック層（アルミナ）を含むセパレータ３（厚さ： ２５μｍ、空孔率５４％）を用いた以外は、実施例１と同様に積層型ラミネート電池を作製し、各評価を行った。ここで、セパレータ３の物性は以下のとおりである。
　ＭＤ方向の引張伸度：１２５％
　ＴＤ方向の引張伸度：６３０％
　ＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値：３７７．５％
　融点：１６０℃ (Comparative example 2)
A laminate type laminate battery is prepared in the same manner as in Example 1 except that a separator 3 (thickness: 25 μm, porosity 54%) including a porous resin layer made of polypropylene and a ceramic layer (alumina) is used as a separator. Were made, and each evaluation was performed. Here, the physical properties of the separator 3 are as follows.
Tensile elongation in the MD direction: 125%
Tensile elongation in the TD direction: 630%
Average value of tensile elongation in MD direction and tensile elongation in TD direction: 377.5%
Melting point: 160 ° C
（比較例３）
　セパレータとして、ポリプロピレンからなる多孔性樹脂層（厚さ：２５μｍ、空孔率：５５％）からなるセパレータ４を用いた以外は、実施例１と同様に積層型ラミネート電池を作製し、各評価を行った。ここで、セパレータ４の物性は以下のとおりである。
　ＭＤ方向の引張伸度：５０％
　ＴＤ方向の引張伸度：４００％
　ＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値：２２５％
　融点：１６０℃ (Comparative example 3)
A laminated laminate battery is produced in the same manner as in Example 1 except that a separator 4 made of a porous resin layer (thickness: 25 μm, porosity: 55%) made of polypropylene is used as a separator, and each evaluation is shown went. Here, the physical properties of the separator 4 are as follows.
Tensile elongation in the MD direction: 50%
Tensile elongation in the TD direction: 400%
Average value of tensile elongation in MD direction and tensile elongation in TD direction: 225%
Melting point: 160 ° C
（比較例４）
　セパレータとして、ポリプロピレンからなる多孔性樹脂層（厚さ：１８μｍ、空孔率：５４％）と、アルミナからなるセラミックス層（厚さ：７μｍ）とを備えるセパレータ５を用いた以外は、実施例１と同様に積層型ラミネート電池を作製し、各評価を行った。ここで、セパレータ５の物性は以下のとおりである。
　ＭＤ方向の引張伸度：５０％
　ＴＤ方向の引張伸度：４００％
　ＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値：２２５％
　融点：１６０℃ (Comparative example 4)
Example 1 except that a separator 5 comprising a porous resin layer made of polypropylene (thickness: 18 μm, porosity: 54%) and a ceramic layer made of alumina (thickness: 7 μm) was used as a separator A laminated laminate battery was produced in the same manner as in the above, and each evaluation was performed. Here, the physical properties of the separator 5 are as follows.
Tensile elongation in the MD direction: 50%
Tensile elongation in the TD direction: 400%
Average value of tensile elongation in MD direction and tensile elongation in TD direction: 225%
Melting point: 160 ° C
（比較例５）
　セパレータとして、ガラス繊維からなる不織布層と、セラミックス（酸化マグネシウム)からなる層（厚さ：３０μｍ、空孔率：７６％）とを備えるセパレータ６を用いた以外は、実施例１と同様に積層型ラミネート電池を作製し、各評価を行った。ここで、セパレータ６の物性は以下のとおりである。
　ＭＤ方向の引張伸度：８．９％ 
　ＴＤ方向の引張伸度：１４．３％
　ＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値：１１．６％ (Comparative example 5)
Lamination was carried out in the same manner as in Example 1 except that a separator 6 comprising a non-woven fabric layer made of glass fiber and a layer made of ceramics (magnesium oxide) (thickness: 30 μm, porosity: 76%) was used as a separator. Type laminated battery was produced and each evaluation was performed. Here, the physical properties of the separator 6 are as follows.
Tensile elongation in the MD direction: 8.9%
Tensile elongation in the TD direction: 14.3%
Average value of tensile elongation in MD direction and tensile elongation in TD direction: 11.6%
（比較例６）
　正極の配合割合を正極活物質：９６．０質量部、導電助剤：１．０質量部、バインダー樹脂：３．０質量部に変更した以外は、実施例１と同様に積層型ラミネート電池を作製し、各評価を行った。 (Comparative example 6)
A laminated laminate battery was prepared in the same manner as in Example 1 except that the compounding ratio of the positive electrode was changed to 96.0 parts by mass of the positive electrode active material, 1.0 part by mass of the conductive additive, and 3.0 parts by mass of the binder resin. It produced and performed each evaluation.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

Claims (13)

  1. 　正極集電体層および正極活物質層を有する正極と、負極集電体層および負極活物質層を有する負極と、リチウム塩を含有する非水電解液と、前記正極と前記負極との間に挟まれたセパレータと、が容器に収容されたリチウムイオン二次電池であって、
    　２５℃の環境下で、満充電状態において、直径φ３ｍｍ、長さ７０ｍｍのＳＵＳ３０４製の釘を前記リチウムイオン二次電池の中央部に８０ｍｍ／ｓｅｃの速度で刺し、前記リチウムイオン二次電池をショートさせる釘刺し試験をおこなったとき、
    　前記釘刺し試験後、当該リチウムイオン二次電池を短絡放電させ、電圧が０．００１Ｖ以上０．１００Ｖ以下の範囲になったときの前記リチウムイオン二次電池における正負極間の直流抵抗が０．１Ω以上３００Ω以下であるリチウムイオン二次電池。     Between a positive electrode having a positive electrode current collector layer and a positive electrode active material layer, a negative electrode having a negative electrode current collector layer and a negative electrode active material layer, a non-aqueous electrolyte containing a lithium salt, and between the positive electrode and the negative electrode A lithium ion secondary battery in which a sandwiched separator is contained in a container,
    In a fully charged state under a 25 ° C. environment, a SUS304 nail with a diameter of 3 mm and a length of 70 mm is pierced at the center of the lithium ion secondary battery at a speed of 80 mm / sec to short the lithium ion secondary battery When the nail penetration test was conducted,
    After the nail penetration test, the lithium ion secondary battery is short-circuit discharged, and the direct current resistance between positive and negative electrodes in the lithium ion secondary battery is 0. 0 when the voltage is in the range of 0.001 V or more and 0.100 V or less. Lithium ion secondary battery with 1Ω or more and 300Ω or less.
  2. 　請求項１に記載のリチウムイオン二次電池において、
    　前記セパレータの融点または分解温度が２２０℃以上であるリチウムイオン二次電池。     In the lithium ion secondary battery according to claim 1,
    The lithium ion secondary battery whose melting point or decomposition temperature of the said separator is 220 degreeC or more.
  3. 　請求項１または２に記載のリチウムイオン二次電池において、
    　ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、前記セパレータのＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値が、前記正極集電体層および前記負極集電体層の引張伸度よりもそれぞれ大きいリチウムイオン二次電池。     In the lithium ion secondary battery according to claim 1 or 2,
    The average value of the tensile elongation in the MD direction and the tensile elongation in the TD direction of the separator, measured according to 6.3 of JIS L 1913: 2010, is the same as that of the positive electrode current collector layer and the negative electrode current collector layer. Lithium ion secondary batteries, each of which is larger than the tensile elongation.
  4. 　請求項１乃至３のいずれか一項に記載のリチウムイオン二次電池において、
    　ＪＩＳ　Ｌ１９１３：２０１０の６．３に準じて測定される、前記セパレータのＭＤ方向の引張伸度およびＴＤ方向の引張伸度の平均値が１０％以上であるリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 3.
    The lithium ion secondary battery whose average value of the tensile elongation degree of MD direction of said separator and the tensile elongation degree of TD direction measured according to 6.3 of JISL1913: 2010 is 10% or more.
  5. 　請求項１乃至４のいずれか一項に記載のリチウムイオン二次電池において、
    　前記正極活物質層が正極活物質、バインダー樹脂および導電助剤を含むリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 4.
    The lithium ion secondary battery in which the said positive electrode active material layer contains a positive electrode active material, a binder resin, and a conductive support agent.
  6. 　請求項５に記載のリチウムイオン二次電池において、
    　前記正極活物質層の全体を１００質量部としたとき、前記導電助剤の含有量が１．０質量部超過４．０質量部未満であるリチウムイオン二次電池。     In the lithium ion secondary battery according to claim 5,
    The lithium ion secondary battery whose content of the said conductive support agent is 1.0 mass part or more and less than 4.0 mass parts when the whole of the said positive electrode active material layer is 100 mass parts.
  7. 　請求項５または６に記載のリチウムイオン二次電池において、
    　前記導電助剤がカーボンブラック、ケッチェンブラック、アセチレンブラック、天然黒鉛、人工黒鉛および炭素繊維からなる群から選択される一種または二種以上を含むリチウムイオン二次電池。     In the lithium ion secondary battery according to claim 5 or 6,
    The lithium ion secondary battery in which the said conductive support agent contains 1 type, or 2 or more types selected from the group which consists of carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, and carbon fiber.
  8. 　請求項５乃至７のいずれか一項に記載のリチウムイオン二次電池において、
    　前記正極活物質がリチウムニッケル含有複合酸化物を含むリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 5 to 7, wherein
    The lithium ion secondary battery in which the said positive electrode active material contains lithium nickel containing complex oxide.
  9. 　請求項８に記載のリチウムイオン二次電池において、
    　前記リチウムニッケル含有複合酸化物が下記式（１）で表されるリチウムイオン二次電池。
    　Ｌｉ１＋ａ（ＮｉｂＣｏｃＭｅ１ｄＭｅ２１－ｂ－ｃ－ｄ）Ｏ２　　　　　　　（１）
    （式中、Ｍｅ１はＭｎ又はＡｌであり、Ｍｅ２は、Ｍｎ、Ａｌ、Ｍｇ、Ｆｅ、Ｃｒ、Ｔｉ、Ｉｎからなる群から選択される少なくとも１種であり（Ｍｅ１と同種の金属を除く）、－０．５≦ａ＜０．１、０．１≦ｂ＜１、０＜ｃ＜０．５、０＜ｄ＜０．５）     In the lithium ion secondary battery according to claim 8,
    The lithium ion secondary battery in which the said lithium nickel containing complex oxide is represented by following formula (1).
    Li 1 + a (Ni b Co c Me 1 d Me 2 1-b c d ) O 2 (1)
    (Wherein, Me1 is Mn or Al, Me2 is at least one selected from the group consisting of Mn, Al, Mg, Fe, Cr, Ti, In (except metals of the same type as Me1), −0.5 ≦ a <0.1, 0.1 ≦ b <1, 0 <c <0.5, 0 <d <0.5)
  10. 　請求項１乃至９のいずれか一項に記載のリチウムイオン二次電池において、
    　正極活物質層の密度が３．０ｇ／ｃｍ３以上であるリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 9,
    The lithium ion secondary battery whose density of a positive electrode active material layer is 3.0 g / cm < 3 > or more.
  11. 　請求項１乃至１０のいずれか一項に記載のリチウムイオン二次電池において、
    　前記リチウムイオン二次電池のセル定格容量が５Ａｈ以上であるリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 10.
    The lithium ion secondary battery whose cell rated capacity of the said lithium ion secondary battery is 5 Ah or more.
  12. 　請求項１乃至１１のいずれか一項に記載のリチウムイオン二次電池において、
    　前記リチウムイオン二次電池の中央部における前記正極の積層数または捲回数が１０以上であるリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 11.
    The lithium ion secondary battery in which the number of laminations or the number of winding times of the positive electrode in the central portion of the lithium ion secondary battery is 10 or more.
  13. 　請求項１乃至１２のいずれか一項に記載のリチウムイオン二次電池において、
    　前記セパレータの厚みが５μｍ以上５０μｍ以下であるリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 12.
    The lithium ion secondary battery whose thickness of the said separator is 5 micrometers-50 micrometers.
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