WO2020003846A1 - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

Info

Publication number
WO2020003846A1
WO2020003846A1 PCT/JP2019/020847 JP2019020847W WO2020003846A1 WO 2020003846 A1 WO2020003846 A1 WO 2020003846A1 JP 2019020847 W JP2019020847 W JP 2019020847W WO 2020003846 A1 WO2020003846 A1 WO 2020003846A1
Authority
WO
WIPO (PCT)
Prior art keywords
lithium ion
ion secondary
secondary battery
separator
negative electrode
Prior art date
Application number
PCT/JP2019/020847
Other languages
French (fr)
Japanese (ja)
Inventor
良太 柳澤
Original Assignee
株式会社エンビジョンＡｅｓｃエナジーデバイス
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社エンビジョンＡｅｓｃエナジーデバイス filed Critical 株式会社エンビジョンＡｅｓｃエナジーデバイス
Priority to CN201980041983.4A priority Critical patent/CN112335091B/en
Priority to JP2020527295A priority patent/JP7027648B2/en
Publication of WO2020003846A1 publication Critical patent/WO2020003846A1/en

Links

Images

Classifications

    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0583—Construction or manufacture of accumulators with folded construction elements except wound ones, i.e. folded positive or negative electrodes or separators, e.g. with "Z"-shaped electrodes or separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
    • H01M50/102—Primary casings, jackets or wrappings of a single cell or a single battery characterised by their shape or physical structure
    • H01M50/105—Pouches or flexible bags
    • 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 have the feature of high energy density, and are widely used as power sources for mobile phones, notebook computers, electric vehicles, and the like.
  • a self-folding structure lithium ion secondary battery is known.
  • Patent Literature 1 Japanese Patent Application Laid-Open No. 2009-218105
  • Patent Literature 2 Japanese Patent Application Laid-Open No. 2016-143550
  • Patent Document 1 has a rectangular battery element in which a flat positive electrode, a separator, and a flat negative electrode are stacked, and one surface of the battery element is provided in each of the positive electrode and the negative electrode.
  • the positive electrode terminal connection part and the plate-shaped negative electrode terminal connection part are both drawn out terminal connection part extraction surfaces, and the projection in which the positive electrode terminal connection part and the negative electrode terminal connection part are respectively projected perpendicularly to the extending surface of the positive electrode and the negative electrode
  • the surfaces do not intersect with each other, and the positive electrode and the negative electrode have different areas of the surfaces facing each other, and all the projection portions projecting the electrode having the smaller area on the facing surface of the electrode having the larger area are on the larger side.
  • Each electrode is arranged so as to be located on the electrode surface of the separator, the separator is provided with an abutting portion that abuts the positive electrode end surface and the negative electrode end surface and regulates the movement of the positive electrode and the negative electrode.
  • the portion is formed by a fold or a joint between adjacent separators among the separators arranged on each electrode surface, and all the separators laminated on the electrode surface are joined by the fold or the joint.
  • Patent Literature 2 discloses a secondary battery in which a plurality of positive plates including a positive electrode active material and a plurality of negative plates including a negative electrode active material are sandwiched between separators folded in a zigzag manner. Wherein the separator has a plurality of protrusions protruding from the positive electrode plate and the negative electrode plate, and at least a portion of the protrusions has a tensile strength at break smaller than the remaining portion. A folded structure of a secondary battery having a break portion is described.
  • the conventional outermost layer separator of a lithium ion secondary battery having a meandering structure may be altered (discoloration, embrittlement, etc.).
  • the present invention has been made in view of the above circumstances, and provides a self-folding structure lithium-ion secondary battery in which the deterioration of the outermost layer separator is suppressed.
  • the inventor of the present invention has conducted intensive studies to solve the above-described problems, and has found that the separator located on the surface of the outermost negative electrode on which the SEI film is not formed is easily decomposed by the reaction with the electrolytic solution.
  • the present inventor has further studied diligently based on the above findings, and found that by controlling the separator on the outermost negative electrode to be located on the SEI film formed on the surface of the outermost negative electrode, the quality of the separator of the outermost layer was deteriorated. (Discoloration, embrittlement, etc.) can be suppressed, and the present invention has been completed.
  • the present invention has been made based on such knowledge.
  • a battery body including at least one power generating element composed of at least a positive electrode, an electrolytic solution, a separator and a negative electrode, An exterior body for enclosing the battery body therein; A pair of electrode terminals electrically connected to the battery body, and at least a part of which is exposed outside the exterior body;
  • a lithium ion secondary battery comprising:
  • the battery body has a structure in which the positive electrode and the negative electrode are respectively arranged between the separators folded in a zigzag manner, A solid electrolyte interface (SEI) film is formed on at least a peripheral portion of a surface of the outermost negative electrode, which is located on the outermost side of the electrode including the positive electrode and the negative electrode in the battery body, and does not face the positive electrode.
  • SEI solid electrolyte interface
  • the length L 1 of the outermost negative electrode of the SEI layer, said outermost negative electrode of the separator and the length L 2 is provided a lithium ion secondary battery which satisfies the relationship L 1 ⁇ L 2> 0 Is done. (Where the length L 1 of the SEI film, the end of the SEI film at the center of one side of the side where the electrode terminals are not exposed in the lithium ion secondary cell, the other of the SEI film the length of the end portion, and a length in a direction perpendicular to said one side.
  • the separator length L 2 is, on the side where the electrode terminals of the lithium ion secondary battery is not exposed (The length from the end of the separator on the outermost negative electrode at the center of one side to the other end of the separator, and the length in the direction perpendicular to the one side.)
  • FIG. 2 is an exploded perspective view schematically showing an example of the structure of the battery body according to the embodiment of the present invention. It is the perspective view which showed typically an example of the structure of the battery main body of embodiment which concerns on this invention.
  • FIG. 3 is a cross-sectional view schematically illustrating an example of the structure of a battery main body according to an embodiment of the present invention, and is a cross-sectional view in the A-A ′ direction illustrated in FIG. 2. It is the top view which showed typically an example of the structure of the battery main body of embodiment which concerns on this invention.
  • 1 is a perspective view schematically showing an example of the structure of a lithium ion secondary battery according to an embodiment of the present invention.
  • FIG. 1 is an exploded perspective view schematically showing an example of the structure of the battery main body 10 according to the embodiment of the present invention.
  • FIG. 2 is a perspective view schematically showing an example of the structure of the battery main body 10 of the embodiment according to the present invention.
  • FIG. 3 is a cross-sectional view schematically illustrating an example of the structure of the battery main body 10 according to the embodiment of the present invention, and is a cross-sectional view in the A-A ′ direction illustrated in FIG.
  • FIG. 4 is a plan view schematically showing an example of the structure of the battery main body 10 of the embodiment according to the present invention.
  • FIG. 5 is a perspective view schematically showing an example of the structure of the lithium ion secondary battery 100 of the embodiment according to the present invention.
  • a lithium ion secondary battery 100 includes a battery main body 10 including at least one power generating element including at least a positive electrode 15, an electrolytic solution, a separator 18, and a negative electrode 20,
  • the battery pack includes an exterior body for enclosing the battery body therein, and a pair of electrode terminals electrically connected to the battery body and at least partially exposed to the outside of the exterior body.
  • the battery main body 10 has a structure in which the positive electrode 15 and the negative electrode 20 are respectively arranged between the separators 18 folded in a zigzag manner, and is located at the outermost position among the electrodes composed of the positive electrode 15 and the negative electrode 20 in the battery main body 10.
  • the length L 1 of the SEI film 25 on the outermost negative electrode 20A and the length L 2 of the separator 18 on the outermost negative electrode 20A is, satisfy the relationship of L 1 ⁇ L 2> 0.
  • the length L 1 of the SEI film, as shown in FIG. 4, from the end of the SEI film 25 at the center of the side of one side 28 of the electrode terminal 30 in a lithium ion secondary battery 100 is not exposed, The length is the length to the other end of the SEI film 25 and the length in the direction perpendicular to one side 28.
  • the length L 2 of the separator, the end portion of the separator 18 on the outermost negative electrode 20A at the center of the side of one side 28 of the electrode terminal 30 in a lithium ion secondary battery 100 is not exposed, the other end of the separator 18 It is the length to the part and the length in the direction perpendicular to one side 28.
  • the conventional outermost layer separator of a lithium ion secondary battery having a zigzag structure may be altered (discoloration, embrittlement, etc.).
  • the inventors of the present invention have made intensive studies to realize a lithium ion secondary battery having a meandering structure in which deterioration of the outermost layer of the separator is suppressed. As a result, it was found that the separator located on the surface of the outermost negative electrode where the SEI film was not formed was easily decomposed by the reaction with the electrolytic solution.
  • the present inventor has further studied diligently based on the above findings, and found that by controlling the separator on the outermost negative electrode to be located on the SEI film formed on the surface of the outermost negative electrode, the quality of the separator of the outermost layer was deteriorated. (Discoloration, embrittlement, etc.) can be suppressed for the first time. That is, according to the present embodiment, the solid electrolyte interface (SEI) film 25 is formed on at least the peripheral portion of the surface of the outermost negative electrode 20 ⁇ / b> A located on the outermost side of the electrodes including the positive electrode 15 and the negative electrode 20 in the battery body 10.
  • SEI solid electrolyte interface
  • the length L 2 of the separator 18 on the outermost negative electrode 20A is the relationship of L 1 ⁇ L 2> 0
  • the separator located on the outermost negative electrode is decomposed by the reaction with the electrolytic solution, and is likely to deteriorate.
  • the ester bond is easily decomposed by the reaction with the electrolytic solution, when the separator contains a polyester resin, the quality of the outermost separator tends to be remarkable.
  • the separator located on the portion where the SEI film is formed does not directly contact the outermost negative electrode, a decomposition reaction hardly occurs.
  • the length L 1 of the SEI film 25 on the outermost negative electrode 20A, the length L 2 of the separator 18 on the outermost negative electrode 20A is, by satisfying the relationship of L 1 ⁇ L 2> 0, the outermost Since the ratio of the separator in direct contact with the negative electrode decreases, decomposition of the separator is suppressed. As a result, it is considered that the lithium ion secondary battery 100 having the meandering structure in which the deterioration of the outermost layer of the separator is suppressed can be obtained.
  • the SEI film is usually formed on the surface facing the positive electrode, but lithium ions for forming the SEI film also go around the surface not facing the positive electrode.
  • the SEI film 25 is also formed on at least the peripheral portion 20B of the surface not facing the positive electrode 15.
  • the length L 1 of the SEI film 25 on the outermost negative electrode 20A can be measured by XPS analysis. Specifically, since the ratio of Li is large in the portion where the SEI film is formed, the presence or absence of the SEI film can be checked by the ratio of Li. By examining whether or not the SEI film is formed in the portion, it can be determined whether or not the relationship of L 1 ⁇ L 2 > 0 is satisfied.
  • the length L 2 of the separator 18, the more the viewpoint of suppressing deterioration of the outermost layer of the separator is preferably less than 15.0 mm, more preferably 10. 0 mm or less, further preferably 8.0 mm or less, still more preferably 5.0 mm or less, and particularly preferably 4.0 mm or less.
  • the lower limit of the length L 2 of the separator 18 is not particularly limited, it is preferably at 0.1mm or more, more preferably 0.5mm or more.
  • the average length L 3 of the SEI film 25 on the outermost negative electrode 20A, on the outermost negative electrode 20A It is preferable that the average length L 4 of the separator 18 satisfies the relationship of L 3 ⁇ L 4 > 0.
  • the length of the SEI film 25 in the direction perpendicular to the side 28 was measured at 10 points, and the obtained 10 points were measured.
  • the average length and the average length L 3 of the SEI film was measured 10 points the vertical length of the separator to an edge 28, the average length of 10 points obtained average of the separator 18 the length L 4.
  • the average length and the average length L 3 of the SEI film was measured 10 points the vertical length of the separator to an edge 28, the average length of 10 points obtained average of the separator 18 the length L 4.
  • one side 28 is divided into ten pieces at equal intervals, and each central part (a total of ten points) can be selected.
  • the average length L 4 of the separator 18 is preferably less than 15.0 mm, more preferably 10 0.0 mm or less, more preferably 8.0 mm or less, still more preferably 5.0 mm or less, particularly preferably 4.0 mm or less.
  • lower limit of the average length L 4 of the separator 18 is not particularly limited, it is preferably at 0.1mm or more, more preferably 0.5mm or more.
  • the lithium ion secondary battery according to the present embodiment preferably has a cell rated capacity of 7 Ah or more.
  • the number of laminations or the number of windings of the positive electrode in the central portion is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. .
  • the capacity of the lithium ion secondary battery according to the present embodiment can be increased.
  • the lithium ion secondary battery according to the present embodiment has excellent short circuit resistance and can suppress thermal runaway of the battery.
  • the battery body according to the present embodiment includes, for example, one or more power generating elements in which a positive electrode and a negative electrode are alternately stacked via a separator folded in a zigzag manner. These power generating elements are housed in a container formed of an exterior body together with an electrolytic solution (not shown). Electrode terminals (a positive electrode terminal and a negative electrode terminal) are electrically connected to the power generating element, and part or all of the electrode terminals are drawn out of the exterior body.
  • the positive electrode is provided with a coated portion of the positive electrode active material (positive electrode active material layer) and an uncoated portion on the front and back of the positive electrode current collector layer
  • the negative electrode is provided with a negative electrode active material on the front and back of the negative electrode current collector layer. (A negative electrode active material layer) and an uncoated portion are provided.
  • An uncoated portion of the positive electrode active material in the positive electrode current collector layer is used as a positive electrode tab for connecting to the positive electrode terminal, and an uncoated portion of the negative electrode active material in the negative electrode current collector layer is used as a negative electrode tab for connecting to the negative electrode terminal.
  • the positive electrode tabs are assembled on the positive electrode terminal and connected together with the positive electrode terminal by ultrasonic welding or the like, and the negative electrode tabs are assembled on the negative electrode terminal and connected with the negative electrode terminal by ultrasonic welding or the like. Then, one end of the positive electrode terminal is drawn out of the exterior body, and one end of the negative electrode terminal is also drawn out of the exterior body.
  • the battery main body according to the present embodiment can be manufactured according to a known method.
  • the positive electrode can be appropriately selected from the positive electrodes that can be used in known lithium ion secondary batteries, depending on the application and the like.
  • the positive electrode active material used for the positive electrode a material having high electron conductivity that can reversibly release and occlude lithium ions and facilitate electron transport is preferable.
  • the positive electrode active material used for the positive electrode is not particularly limited.
  • a lithium composite oxide having a layered rock salt structure or a spinel structure, or lithium iron phosphate having an olivine structure is used.
  • the lithium composite oxide include lithium manganate (LiMn 2 O 4 ); lithium cobalt oxide (LiCoO 2 ); lithium nickelate (LiNiO 2 ); and at least a part of the manganese, cobalt, and nickel portions of these lithium compounds.
  • One of these positive electrode active materials may be used alone, or two or more thereof may be used in combination.
  • a lithium-containing composite oxide having a layered crystal structure a lithium-nickel-containing composite oxide is exemplified.
  • this lithium-nickel-containing composite oxide an oxide in which part of nickel at nickel sites is replaced with another metal can be used.
  • the metal other than Ni occupying nickel sites 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. More preferably, the lithium nickel-containing composite oxide 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 composite oxide (NCA) or a mixture thereof can be suitably used.
  • NCM lithium nickel cobalt manganese composite oxide
  • NCA Cobalt aluminum composite oxide
  • lithium nickel-containing composite oxide having a layered crystal structure for example, an oxide 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, and In (excluding 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 from 0.1 to 50 ⁇ m, more preferably from 1 to 30 ⁇ m, and still more preferably from 2 to 25 ⁇ m, from the viewpoint of reactivity with the electrolytic solution and rate characteristics.
  • the average particle diameter means a particle diameter (median diameter: D 50 ) at an integrated value of 50% in a particle size distribution (by volume) by a laser diffraction scattering method.
  • the positive electrode includes, for example, a positive electrode current collector layer and a positive electrode active material layer on the positive electrode current collector layer.
  • the positive electrode is arranged such that the positive electrode active material layer faces the negative electrode active material layer on the negative electrode current collector layer via the separator.
  • the positive electrode according to the present embodiment can be manufactured by a known method. For example, by dispersing a positive electrode active material, a binder resin, and a conductive additive in an organic solvent to obtain a positive electrode slurry, applying and drying the positive electrode slurry on a positive electrode current collector layer, and pressing if necessary.
  • a method of forming a positive electrode active material layer on a positive electrode current collector layer can be employed.
  • the slurry solvent used for producing the positive electrode for example, N-methyl-2-pyrrolidone (NMP) can be used.
  • a resin generally used as a binder resin for a positive electrode such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) can be used.
  • PTFE polytetrafluoroethylene
  • PVDF polyvinylidene fluoride
  • the content of the binder resin in the positive electrode active material layer is preferably 0.1 part by mass or more and 10.0 parts by mass or less when the whole of the positive electrode active material layer is 100 parts by mass, and is 0.5 part by mass. It is more preferably at least 5.0 parts by mass and even more preferably at least 1.0 part by mass and not more than 5.0 parts by mass.
  • the content of the binder resin is within the above range, the balance between the coating properties of the positive electrode slurry, the binding properties of the binder, and the battery characteristics is further improved.
  • the content of the binder resin is equal to or less than the above upper limit, the ratio of the positive electrode active material increases, and the capacity per positive electrode mass increases, which is preferable. It is preferable that the content of the binder resin be equal to or more than the lower limit, because the electrode peeling is suppressed.
  • the positive electrode active material layer can include a conductive auxiliary in addition to the positive electrode active material and the binder resin.
  • the conductive assistant 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, and carbon fiber. 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 is preferably 1.0 part by mass or more and 4.0 parts by mass or less, when the whole positive electrode active material layer is 100 parts by mass, and is 1.2 parts by mass. It is more preferably not less than 3.5 parts by mass, more preferably not less than 1.5 parts by mass and not more than 3.5 parts by mass, and more preferably not less than 2.0 parts by mass and not more than 3.5 parts by mass. Particularly preferred. When the content of the conductive additive is within the above range, the balance between the coating properties of the positive electrode slurry, the binding properties of the binder resin, and the battery characteristics is further improved.
  • the content of the conductive auxiliary agent be equal to or less than the above upper limit, because the ratio of the positive electrode active material increases and the capacity per positive electrode mass increases. It is preferable that the content of the conductive auxiliary agent be equal to or more than the above lower limit, because the conductivity of the positive electrode is further improved and the battery characteristics of the lithium ion secondary battery are improved.
  • the positive electrode current collector layer aluminum, stainless steel, nickel, titanium, an alloy thereof, or the like can be used.
  • Examples of the shape include a foil, a flat plate, and a mesh.
  • an aluminum foil can be suitably used.
  • the thickness of the positive electrode current collector layer is not particularly limited, but is, for example, 1 ⁇ m or more and 30 ⁇ m or less.
  • the density of the positive electrode active material layer is not particularly limited, for example, it is preferably, 2.4 g / cm 3 or more 3.8 g / cm 3 or less or less 2.0 g / cm 3 or more 4.0 g / cm 3 More preferably, it is 2.8 g / cm 3 or more and 3.6 g / cm 3 or less.
  • the thickness of the positive electrode active material layer (the sum of the thicknesses of both surfaces) is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thicker from the viewpoint of energy density, and can be set thinner from the viewpoint of output characteristics.
  • the thickness of the positive electrode active material layer (the sum of the thicknesses of both surfaces) can be appropriately set, for example, in the range of 20 ⁇ m or more and 500 ⁇ m or less, preferably 40 ⁇ m or more and 400 ⁇ m or less, more preferably 60 ⁇ m or more and 300 ⁇ m or less.
  • the thickness of the positive electrode active material layer (one-side thickness) is not particularly limited, and can be appropriately set according to desired characteristics.
  • the thickness (one-sided thickness) of the positive electrode active material layer 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 can be appropriately selected from the negative electrodes that can be used in known lithium ion secondary batteries, depending on the application and the like.
  • the negative electrode active material used for the negative electrode can be appropriately set depending on the use and the like as long as it can be used for the negative electrode.
  • the negative electrode includes, for example, a negative electrode current collector layer and a negative electrode active material layer formed on the negative electrode current collector layer.
  • the negative electrode active material layer preferably contains, for example, a negative electrode active material and a binder resin, and further contains a conductive auxiliary from the viewpoint of increasing 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 and non-graphitizable carbon), diamond-like carbon, fullerene, carbon nanotube, and carbon nanohorn.
  • graphite natural graphite and artificial graphite can be used, and in terms of material cost, inexpensive natural graphite is preferable.
  • the amorphous carbon include those obtained by heat-treating coal pitch coke, petroleum pitch coke, acetylene pitch coke, and the like.
  • a lithium metal material an alloy material such as silicon or tin, an oxide material such as Nb 2 O 5 or TiO 2 , or a composite thereof can be used.
  • the negative electrode active material only one kind may be used alone, or two or more kinds may be used in combination.
  • the average particle size of the negative electrode active material is preferably 2 ⁇ m or more, more preferably 5 ⁇ m or more, from the viewpoint of suppressing a side reaction during charge and discharge and suppressing a decrease in charge and discharge efficiency.
  • the thickness is preferably 40 ⁇ m or less, and more preferably 30 ⁇ m or less.
  • 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 in the present embodiment can be manufactured by a known method.
  • a method in which a negative electrode active material and a binder resin are dispersed in a solvent to obtain a slurry, the slurry is applied to a negative electrode current collector layer, dried, and pressed as necessary to form a negative electrode active material layer can be adopted.
  • the method for 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 is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, when the whole of the negative electrode active material layer is 100 parts by mass, and is 0.5 part by mass. It is more preferably at least 8.0 parts by mass, more preferably at least 1.0 parts by mass and at most 5.0 parts by mass, particularly preferably at least 1.0 part by mass and at most 3.0 parts by mass. preferable.
  • the content of the binder resin is within the above range, the balance between the coating properties of the negative electrode slurry, the binding properties of the binder resin, and the battery characteristics is further improved.
  • the content of the binder resin is equal to or less than the above upper limit, the ratio of the negative electrode active material is increased, and the capacity per mass of the negative electrode is preferably increased. It is preferable that the content of the binder resin be equal to or more than the lower limit, because the electrode peeling is suppressed.
  • 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
  • a rubber-based binder for example, SBR (styrene-butadiene rubber)
  • acrylic-based binder resin can be used.
  • Such an aqueous binder resin may be 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 may contain a conductive aid as needed.
  • a conductive material generally used as a conductive aid for a negative electrode such as a carbonaceous material 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 is preferably 0.1 part by mass or more and 3.0 parts by mass or less, when the whole of the negative electrode active material layer is 100 parts by mass, It is more preferable that the amount is from 2.0 parts by mass to 2.0 parts by mass, and particularly preferable is from 0.2 parts by mass to 1.0 parts by mass.
  • the content of the conductive assistant is within the above range, the balance between the coating properties of the negative electrode slurry, the binding properties of the binder resin, and the battery characteristics is further improved.
  • the content of the conductive auxiliary agent be equal to or less than the above upper limit, because the proportion of the negative electrode active material increases and the capacity per mass of the negative electrode increases. It is preferable that the content of the conductive auxiliary agent be equal to or more than the above lower limit, because the conductivity of the negative electrode is further improved.
  • the average particle size (primary particle size) of the conductive additive used in the positive electrode active material layer and the negative electrode active material layer is preferably in the range of 10 to 100 nm.
  • the average particle size (primary particle size) of the conductive additive 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 additive and uniformly dispersing it in the negative electrode. Is preferably 100 nm or less, and more preferably 80 nm or less, from the viewpoint of forming a good conductive path.
  • the conductive additive When the conductive additive is in a fibrous form, examples thereof include those having an average diameter of 2 to 200 nm and an average fiber length of 0.1 to 20 ⁇ m.
  • the average particle diameter of the conductive additive is a median diameter (D 50 ), which means a particle diameter at an integrated value of 50% in a particle size distribution (volume basis) by a laser diffraction scattering method.
  • the thickness of the negative electrode active material layer (the sum of the thicknesses of both surfaces) is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thicker from the viewpoint of energy density, and can be set thinner from the viewpoint of output characteristics.
  • the thickness of the negative electrode active material layer (total thickness of both surfaces) can be appropriately set, for example, in the range of 40 ⁇ m or more and 1000 ⁇ m or less, preferably 80 ⁇ m or more and 800 ⁇ m or less, and more preferably 120 ⁇ m or more and 600 ⁇ m or less.
  • the thickness of the negative electrode active material layer (one-side thickness) is not particularly limited, and can be appropriately set according to desired characteristics.
  • the thickness of the negative electrode active material layer can be appropriately set, for example, in the range of 20 ⁇ m or more and 500 ⁇ m or less, preferably 40 ⁇ m or more and 400 ⁇ m or less, and more preferably 60 ⁇ m or more and 300 ⁇ m or less.
  • the density of the negative electrode active material layer is not particularly limited, but is preferably, for example, 1.2 g / cm 3 or more and 2.0 g / cm 3 or less, and is 1.3 g / cm 3 or more and 1.9 g / cm 3 or less. More preferably, it is 1.4 g / cm 3 or more and 1.8 g / cm 3 or less.
  • the negative electrode current collector layer copper, stainless steel, nickel, titanium, or an alloy thereof can be used.
  • the shape include a foil, a flat plate, and a mesh.
  • the thickness of the negative electrode current collector layer is not particularly limited, but is, for example, 1 ⁇ m or more and 20 ⁇ m or less.
  • the electrolytic solution according to the present embodiment is obtained by dissolving an electrolyte in a solvent.
  • the electrolytic solution used in the present embodiment is, for example, a non-aqueous electrolytic solution containing a lithium salt, and may be appropriately selected from known ones according to the type of the electrode active material and the use of the lithium ion secondary battery. it can.
  • 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 (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, lithium lower fatty acid carboxylate, and the like can be given.
  • 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.
  • the separator according to this embodiment is not particularly limited as long as it has a function of electrically insulating the positive electrode and the negative electrode and transmitting lithium ions.
  • a porous separator can be used.
  • the separator 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 as a main component.
  • the “main component” means that the proportion in the resin layer is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and 100% by mass. Means that you may.
  • the resin layer constituting the separator according to this embodiment may be a single layer or two or more layers.
  • heat-resistant resin forming the resin layer examples include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polycarbonate, polyester carbonate, aliphatic polyamide, Aromatic polyamide, semi-aromatic polyamide, wholly aromatic polyester, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyimide, polyarylate, polyetherimide, polyamideimide, polyacetal, polyetheretherketone, polysulfone, polyethersulfone, One type or two or more types selected from a fluorine-based resin, polyether nitrile, modified polyphenylene ether, and the like can be given.
  • polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, wholly aromatic polyester, aliphatic polyamide, and wholly aromatic, from the viewpoint of excellent balance among heat resistance, mechanical strength, elasticity, and price.
  • polyamide resins such as aromatic polyamides and semi-aromatic polyamides
  • polyesters selected from polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and wholly aromatic polyester A system resin is more preferred, and polyethylene terephthalate is even more preferred.
  • the melting point of the separator according to this embodiment is preferably 220 ° C. or higher, more preferably 230 ° C. or higher, and more preferably 240 ° C. or higher, from the viewpoint of improving the safety of the lithium ion secondary battery. More preferred.
  • the separator according to the present embodiment preferably does not show a melting point, and preferably has a decomposition temperature of 220 ° C or higher, and 230 ° C or higher. Is more preferably 240 ° C. or higher, and particularly preferably 250 ° C. or higher.
  • the melting point or the decomposition temperature of the separator according to the present embodiment By setting the melting point or the decomposition temperature of the separator according to the present embodiment to the above lower limit or more, the battery generates heat, and even when the battery becomes hot, it is possible to suppress thermal contraction of the separator, and as a result, the positive electrode and the negative electrode Can be suppressed. Thereby, thermal runaway of the lithium ion secondary battery and the like can be suppressed, and safety can be further improved.
  • the upper limit of the melting point of the separator according to this embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of elasticity.
  • the upper limit of the decomposition temperature of the separator according to this embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of elasticity.
  • the resin layer constituting the separator according to the present embodiment is preferably a porous resin layer.
  • the porosity of the porous resin layer is preferably from 20% to 80%, more preferably from 30% to 70%, and more preferably from 40% to 60%, from the viewpoint of balance between mechanical strength and lithium ion conductivity. 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 according to this embodiment is not particularly limited, and can be appropriately selected according to the shape of the electrode or the current collector, and may be, for example, a rectangle.
  • the thickness of the separator 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 still more preferably 10 ⁇ m or more and 30 ⁇ m or less, from the viewpoint of balance between mechanical strength and lithium ion conductivity. It is.
  • the separator according to the embodiment 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 surface of the resin layer from the viewpoint of handleability of the separator according to the present embodiment and productivity, but further improves the heat resistance of the separator. From the viewpoint of causing the resin layer to be provided, the resin layer may be provided on both surfaces. Since the separator according to the present embodiment further includes the ceramic layer, the heat shrinkage of the separator can be further reduced, and the short circuit between the electrodes can be further prevented.
  • the ceramic layer can be formed, for example, by applying and drying a ceramic layer forming material on the resin layer.
  • a ceramic layer forming material for example, a material obtained by dissolving or dispersing an inorganic filler and a binder resin in an appropriate solvent can be used.
  • the inorganic filler used for the ceramic layer can be appropriately selected from known materials used for a separator of a lithium ion secondary battery.
  • highly insulating oxides, nitrides, sulfides, carbides, and the like are preferable, and are selected from aluminum oxide, boehmite, titanium oxide, silicon oxide, magnesium oxide, barium oxide, zirconium oxide, zinc oxide, iron oxide, and the like. More preferably, one or two or more types of ceramics are adjusted to particles.
  • aluminum oxide, boehmite and titanium oxide are preferred.
  • the binder resin is not particularly limited, and examples thereof include a cellulosic resin such as carboxymethylcellulose (CMC); an acrylic resin; and a fluororesin such as polyvinylidene fluoride (PVDF).
  • a cellulosic resin such as carboxymethylcellulose (CMC); an acrylic resin; and a fluororesin such as polyvinylidene fluoride (PVDF).
  • PVDF polyvinylidene fluoride
  • the binder resin only one kind may be used alone, or two or more kinds may be used in combination.
  • 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), and ethyl methyl carbonate (EMC). Can be used.
  • alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).
  • 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 it is 1 ⁇ m or more and 15 ⁇ m or less.
  • the electrolyte layer is a layer disposed so as to be interposed between the positive electrode and the negative electrode.
  • the electrolyte layer contains a separator and an electrolyte, and examples thereof include a porous separator in which a non-aqueous electrolyte is impregnated.
  • the exterior body according to the present embodiment has, for example, a substantially rectangular planar shape.
  • the exterior body according to the present embodiment includes, for example, a housing portion for housing the battery body, and a joint portion in which the heat-fusible resin layers located on the peripheral edge of the housing portion are directly or via electrode terminals.
  • the exterior body according to the present embodiment has at least a heat-fusible resin layer and a barrier layer, and is capable of enclosing the battery body therein.
  • a laminated film having at least a heat-fusible resin layer and a barrier layer may be selected from those having a barrier property such as preventing leakage of electrolyte and intrusion of moisture from the outside.
  • stainless steel (SUS) foil, aluminum foil, aluminum alloy foil, copper foil, titanium foil A barrier layer made of a metal such as a foil can be used.
  • the thickness of the barrier layer is, for example, 10 ⁇ m or more and 100 ⁇ m or less, preferably 20 ⁇ m or more and 80 ⁇ m or less, and more preferably 30 ⁇ m or more and 50 ⁇ m or less.
  • the resin material constituting the heat-fusible resin layer is not particularly limited, for example, polyethylene, polypropylene, nylon, polyethylene terephthalate (PET) and the like can be used.
  • the thickness of the heat-fusible resin layer is, for example, 20 ⁇ m or more and 200 ⁇ m or less, preferably 30 ⁇ m or more and 150 ⁇ m or less, and more preferably 50 ⁇ m or more and 100 ⁇ m or less.
  • the heat-fusible resin layer and the barrier layer of the laminated film according to the present embodiment are not limited to one layer each, and may be two or more layers.
  • the exterior body can be formed by causing the heat-fusible resin layers to face each other with the battery body interposed therebetween and heat-sealing the periphery of the portion housing the battery body.
  • a resin layer such as a nylon film or a polyester film can be provided on the outer surface of the exterior body, which is the surface opposite to the surface on which the heat-fusible resin layer is formed.
  • the heating temperature at the time of performing heat fusion between the heat-fusible resin layers depends on the melting point of the resin material constituting the heat-fusible resin layer. In this case, the temperature is preferably from 140 ° C. to 185 ° C., and more preferably from 150 ° C. to 180 ° C. In addition, the heat sealing time when performing heat fusion between the heat-fusible resin layers is, for example, 10 seconds to 50 seconds, preferably 12 seconds to 30 seconds.
  • Electrode terminal In the present embodiment, known members can be used for the pair of electrode terminals 30 (the positive electrode terminal and the negative electrode terminal).
  • the positive electrode terminal for example, one made of aluminum or an aluminum alloy can be used
  • the negative electrode terminal for example, copper or a copper alloy or one obtained by plating them with nickel can be used.
  • Each terminal is drawn out of the container, and a heat-fusible resin layer is provided in advance at a portion of each terminal located at a portion where the periphery of the outer package is thermally welded.
  • the positive electrode terminal and the negative electrode terminal are drawn from the same side of the package, but the positive terminal and the negative terminal may be drawn from different sides of the package.
  • Example 1 ⁇ Preparation of positive electrode> 93.9 parts by mass of a lithium nickel-containing composite oxide (chemical formula: LiNi 0.8 Co 0.15 Al 0.05 O 2 , average particle size: 6 ⁇ m) as a positive electrode active material, and carbon black as a conductive auxiliary agent. 0 parts by mass, 3.0 parts by mass of polyvinylidene fluoride (PVDF) as a binder resin, and 0.1 parts by mass of oxalic anhydride as an additive were used. These were dispersed in an organic solvent to prepare a positive electrode slurry.
  • PVDF polyvinylidene fluoride
  • This positive electrode slurry is continuously applied to a 15 ⁇ m-thick aluminum foil (tensile elongation: 6%), which is a positive electrode current collector, dried, and then pressed to form a coated portion of the positive electrode current collector (positive electrode).
  • An active material layer a positive electrode roll having a thickness of 60 ⁇ m on one side, a density of 3.35 g / cm 3 ) and an uncoated portion not coated was prepared. This positive electrode roll was punched out so that an uncoated portion serving as a tab for connecting to the positive electrode terminal was left, thereby forming a positive electrode.
  • An active material layer a negative electrode roll having a thickness of 90 ⁇ m on one side, a density of 1.55 g / cm 3 ) and an uncoated portion not coated was prepared. This negative electrode roll was punched out such that an uncoated portion serving as a tab for connecting to the negative electrode terminal was left to form a negative electrode.
  • a positive electrode and a negative electrode were laminated in a zigzag structure with a separator interposed therebetween, and a negative electrode terminal and a positive electrode terminal were provided thereon, thereby obtaining a laminate.
  • an electrolyte solution in which 1M LiPF 6 was dissolved in a solvent composed of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, and the obtained laminate were accommodated in a flexible film, thereby forming a laminate type laminated battery. Obtained.
  • the rated capacity of this laminated battery was 9.2 Ah, the positive electrode had 28 layers, and the negative electrode had 29 layers.
  • a separator 1 (thickness: 25 ⁇ m, porosity: 56%, resin layer melting point: 250 ° C.) including a porous resin layer made of polyethylene terephthalate (PET) and a ceramic layer made of boehmite particles was used. . Further, the average length L 4 and the length L 2 of the outermost negative electrode of the separator was adjusted to a value shown in Table 1.
  • ⁇ porosity (%)
  • Ws basis weight (g / m 2 )
  • ds true density (g / cm 3 )
  • t film thickness ( ⁇ m).
  • the obtained lithium ion secondary battery was subjected to a constant current constant voltage (CC-CV) method at 25 ° C. and a constant current of 0.2 C.
  • the battery was charged at a constant current up to 2 V, then charged at a constant voltage of 4.2 V at a constant voltage up to a charge termination current of 0.015 C, and then subjected to CC discharge at a discharge rate of 0.2 C and a discharge termination voltage of 2.5 V.
  • the lithium ion secondary battery after the first charge / discharge was allowed to stand at 45 ° C. for 168 hours to perform an aging treatment.
  • the obtained lithium ion secondary battery was disassembled, the deterioration of the outermost layer separator was visually observed, and each was evaluated according to the following criteria.
  • ⁇ No discolored portion is observed on the outermost layer of the separator surface. :: One or two discolored portions having a diameter of about 1 to 5 mm are observed, but deterioration of the entire separator is suppressed. :: Length One or two light brown discolored portions having a size of 5 mm to 20 mm and a width of about 1 to 5 mm are observed, but deterioration of the entire separator is suppressed.
  • ⁇ Light brown discolored portion over the entire outermost layer separator surface Are observed, but deterioration is suppressed in the entire separator.
  • ⁇ A dark brown discolored portion is observed over the entire outermost surface of the separator, and the entire separator is deteriorated.
  • Example 1 (Examples 2 to 4 and Comparative Example 1) L 2 and L 4 was replaced with the values shown in Table 1 were prepared with different lithium ion secondary battery in the same manner as in Example 1, was subjected to the same evaluation as in Example 1, respectively. Table 1 shows the obtained evaluation results.

Abstract

This lithium ion secondary battery (100) comprises: a battery main body (10) including at least one power generating element comprising at least positive electrodes (15), an electrolyte, a separator (18), and negative electrodes (20); an outer case (40) for inserting the battery main body (10) therein; and a pair of electrode terminals (30) electrically connected to the battery main body (10) and having at least part thereof exposed to the outside of the case (40). The battery main body (10) has: a structure whereby the positive electrodes (15) and the negative electrodes (20) are each arranged between the folds of a separator (18) folded in a zigzag shape; has a solid electrolyte interface (SEI) membrane (25) formed in at least a peripheral section (20B) of a surface of an outermost negative electrode (20A) on a side not facing the positive electrodes (15), said outermost negative electrode being positioned outermost among the electrodes comprising the positive electrodes (15) and the negative electrodes (20) in the battery main body (10); and the length L1 of the SEI membrane (25) upon the outermost negative electrode (20A) and the length L2 of the separator (18) upon the outermost negative electrode (20A) fulfilling the relationship L1 ≥ L2 > 0.

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の構造の一例として、つづら折り構造のリチウムイオン二次電池が知られている。 Lithium ion secondary batteries have the feature of high energy density, and are widely used as power sources for mobile phones, notebook computers, electric vehicles, and the like. As an example of the structure of a lithium ion secondary battery, a self-folding structure lithium ion secondary battery is known.
　つづら折り構造のリチウムイオン二次電池に関する技術としては、例えば、特許文献１（特開２００９－２１８１０５号公報）および特許文献２（特開２０１６－１４３５５０号公報）に記載のものが挙げられる。 技術 Techniques relating to a zigzag structure lithium ion secondary battery include, for example, those described in Patent Literature 1 (Japanese Patent Application Laid-Open No. 2009-218105) and Patent Literature 2 (Japanese Patent Application Laid-Open No. 2016-143550).
　特許文献１には、平板状の正極、セパレータ、平板状の負極が積層された角形の電池要素を有し、該電池要素の一面は、上記正極および負極の各々に設けられた、板状の正極端子接続部および板状の負極端子接続部がともに引き出された端子接続部引出面であり、正極端子接続部と負極端子接続部のそれぞれを正極および負極の延長する面に垂直に投影した投影面は相互に交わらず、上記正極と負極は相互に対向する面の面積が異なり、上記面積が小さな側の電極を面積が大きな側の電極の対向面に投影した投影部は、すべて上記大きな側の電極面に位置するようにそれぞれの電極が配置されており、セパレータには、正極端面および負極端面が突き当たって正極および負極の移動を規制する突き当たり部が設けられており、上記突き当たり部は、各電極面に配置されたセパレータのうち隣接するセパレータ同士の折り目、あるいは接合部によって形成されるとともに、電極面に積層されたすべてのセパレータは、上記折り目あるいは接合部によって結合されたものであることを特徴とする積層型電池が記載されている。 Patent Document 1 has a rectangular battery element in which a flat positive electrode, a separator, and a flat negative electrode are stacked, and one surface of the battery element is provided in each of the positive electrode and the negative electrode. The positive electrode terminal connection part and the plate-shaped negative electrode terminal connection part are both drawn out terminal connection part extraction surfaces, and the projection in which the positive electrode terminal connection part and the negative electrode terminal connection part are respectively projected perpendicularly to the extending surface of the positive electrode and the negative electrode The surfaces do not intersect with each other, and the positive electrode and the negative electrode have different areas of the surfaces facing each other, and all the projection portions projecting the electrode having the smaller area on the facing surface of the electrode having the larger area are on the larger side. Each electrode is arranged so as to be located on the electrode surface of the separator, the separator is provided with an abutting portion that abuts the positive electrode end surface and the negative electrode end surface and regulates the movement of the positive electrode and the negative electrode. The portion is formed by a fold or a joint between adjacent separators among the separators arranged on each electrode surface, and all the separators laminated on the electrode surface are joined by the fold or the joint. A stacked battery is described.
　特許文献２には、正極活物質を含む複数の正極板と負極活物質を含む複数の負極板を、つづら折り状に折り返されたセパレータに、上記正極板及び上記負極板を挟み込んでなる二次電池のつづら折り積層体構造であって、上記セパレータは、上記正極板及び上記負極板から突出した複数の突出部を有し、上記突出部の少なくとも一部には、残部よりも引張破断強度が小さい応力破断部を有する二次電池のつづら折り積層体構造が記載されている。 Patent Literature 2 discloses a secondary battery in which a plurality of positive plates including a positive electrode active material and a plurality of negative plates including a negative electrode active material are sandwiched between separators folded in a zigzag manner. Wherein the separator has a plurality of protrusions protruding from the positive electrode plate and the negative electrode plate, and at least a portion of the protrusions has a tensile strength at break smaller than the remaining portion. A folded structure of a secondary battery having a break portion is described.
特開２００９－２１８１０５号公報JP 2009-218105 A 特開２０１６－１４３５５０号公報JP 2016-143550 A
　本発明者の検討によれば、従来のつづら折り構造のリチウムイオン二次電池は最外層のセパレータが変質（変色や脆化等）してしまう場合があることが明らかになった。 According to the study of the present inventor, it has been clarified that the conventional outermost layer separator of a lithium ion secondary battery having a meandering structure may be altered (discoloration, embrittlement, etc.).
　本発明は上記事情に鑑みてなされたものであり、最外層のセパレータの変質が抑制された、つづら折り構造の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 self-folding structure lithium-ion secondary battery in which the deterioration of the outermost layer separator is suppressed.
　本発明者は上記課題を解決するために鋭意検討したところ、最外負極においてＳＥＩ膜が形成されていない表面上に位置するセパレータが、電解液との反応によって分解しやすいことを知見した。本発明者は上記知見を元にさらに鋭意検討したところ、最外負極上のセパレータが最外負極の表面に形成されたＳＥＩ膜上に位置するように制御することにより、最外層のセパレータの変質（変色や脆化等）を抑制できることを見出し、本発明を完成させた。 The inventor of the present invention has conducted intensive studies to solve the above-described problems, and has found that the separator located on the surface of the outermost negative electrode on which the SEI film is not formed is easily decomposed by the reaction with the electrolytic solution. The present inventor has further studied diligently based on the above findings, and found that by controlling the separator on the outermost negative electrode to be located on the SEI film formed on the surface of the outermost negative electrode, the quality of the separator of the outermost layer was deteriorated. (Discoloration, embrittlement, etc.) can be suppressed, and the present invention has been completed.
　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。 The present invention has been made based on such knowledge.
　本発明によれば、
　少なくとも正極、電解液、セパレータおよび負極により構成された発電素子を１つ以上含む電池本体と、
　上記電池本体を内部に封入するための外装体と、
　上記電池本体と電気的に接続され、かつ、少なくとも一部が上記外装体の外側に露出した一対の電極端子と、
を備えるリチウムイオン二次電池であって、
　上記電池本体は、つづら折りに折り曲げられた上記セパレータの間に上記正極および上記負極がそれぞれ配置された構造を有し、
　上記電池本体における上記正極および上記負極からなる電極の中で最も外側に位置する最外負極の上記正極と対向していない側の表面の少なくとも周縁部に固体電解質界面（ＳＥＩ）膜が形成されており、
　上記最外負極上の上記ＳＥＩ膜の長さＬ１と、上記最外負極上の上記セパレータの長さＬ２とが、Ｌ１≧Ｌ２＞０の関係を満たすリチウムイオン二次電池が提供される。
（ここで、上記ＳＥＩ膜の長さＬ１は、当該リチウムイオン二次電池における上記電極端子が露出していない側の一辺の中心部における上記ＳＥＩ膜の端部から、上記ＳＥＩ膜の他方の端部までの長さであり、かつ、上記一辺に対して垂直方向の長さである。上記セパレータの長さＬ２は、当該リチウムイオン二次電池における上記電極端子が露出していない側の一辺の中心部における上記最外負極上の上記セパレータの端部から、上記セパレータの他方の端部までの長さであり、かつ、上記一辺に対して垂直方向の長さである。） According to the present invention,
A battery body including at least one power generating element composed of at least a positive electrode, an electrolytic solution, a separator and a negative electrode,
An exterior body for enclosing the battery body therein;
A pair of electrode terminals electrically connected to the battery body, and at least a part of which is exposed outside the exterior body;
A lithium ion secondary battery comprising:
The battery body has a structure in which the positive electrode and the negative electrode are respectively arranged between the separators folded in a zigzag manner,
A solid electrolyte interface (SEI) film is formed on at least a peripheral portion of a surface of the outermost negative electrode, which is located on the outermost side of the electrode including the positive electrode and the negative electrode in the battery body, and does not face the positive electrode. Yes,
The length L 1 of the outermost negative electrode of the SEI layer, said outermost negative electrode of the separator and the length L 2 is provided a lithium ion secondary battery which satisfies the relationship L 1 ≧ L 2> 0 Is done.
(Where the length L 1 of the SEI film, the end of the SEI film at the center of one side of the side where the electrode terminals are not exposed in the lithium ion secondary cell, the other of the SEI film the length of the end portion, and a length in a direction perpendicular to said one side. of the separator length L 2 is, on the side where the electrode terminals of the lithium ion secondary battery is not exposed (The length from the end of the separator on the outermost negative electrode at the center of one side to the other end of the separator, and the length in the direction perpendicular to the one side.)
　本発明によれば、最外層のセパレータの変質が抑制された、つづら折り構造の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 self-folding structure lithium ion secondary battery in which deterioration of the outermost layer of the separator is suppressed.
　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 above and other objects, features and advantages will become more apparent from the preferred embodiments described below and the accompanying drawings.
本発明に係る実施形態の電池本体の構造の一例を模式的に示した分解斜視図である。FIG. 2 is an exploded perspective view schematically showing an example of the structure of the battery body according to the embodiment of the present invention. 本発明に係る実施形態の電池本体の構造の一例を模式的に示した斜視図である。It is the perspective view which showed typically an example of the structure of the battery main body of embodiment which concerns on this invention. 本発明に係る実施形態の電池本体の構造の一例を模式的に示した断面図であり、図２に示すＡ－Ａ’方向の断面図である。FIG. 3 is a cross-sectional view schematically illustrating an example of the structure of a battery main body according to an embodiment of the present invention, and is a cross-sectional view in the A-A ′ direction illustrated in FIG. 2. 本発明に係る実施形態の電池本体の構造の一例を模式的に示した平面図である。It is the top view which showed typically an example of the structure of the battery main body of embodiment which concerns on this invention. 本発明に係る実施形態のリチウムイオン二次電池の構造の一例を模式的に示した斜視図である。1 is a perspective view schematically showing an example of the structure of a lithium ion secondary battery according to an embodiment of the present invention.
　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、数値範囲の「～」は特に断りがなければ、以上から以下を表す。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and description thereof will not be repeated. Also, in the drawings, each component schematically shows a shape, size, and arrangement relationship that can be understood by the present invention, and is different from an actual size. Unless otherwise specified, “to” in the numerical range represents the following from the above.
　図１は、本発明に係る実施形態の電池本体１０の構造の一例を模式的に示した分解斜視図である。図２は、本発明に係る実施形態の電池本体１０の構造の一例を模式的に示した斜視図である。図３は、本発明に係る実施形態の電池本体１０の構造の一例を模式的に示した断面図であり、図２に示すＡ－Ａ’方向の断面図である。図４は、本発明に係る実施形態の電池本体１０の構造の一例を模式的に示した平面図である。図５は、本発明に係る実施形態のリチウムイオン二次電池１００の構造の一例を模式的に示した斜視図である。 FIG. 1 is an exploded perspective view schematically showing an example of the structure of the battery main body 10 according to the embodiment of the present invention. FIG. 2 is a perspective view schematically showing an example of the structure of the battery main body 10 of the embodiment according to the present invention. FIG. 3 is a cross-sectional view schematically illustrating an example of the structure of the battery main body 10 according to the embodiment of the present invention, and is a cross-sectional view in the A-A ′ direction illustrated in FIG. FIG. 4 is a plan view schematically showing an example of the structure of the battery main body 10 of the embodiment according to the present invention. FIG. 5 is a perspective view schematically showing an example of the structure of the lithium ion secondary battery 100 of the embodiment according to the present invention.
　図１～５に示すように、本実施形態に係るリチウムイオン二次電池１００は、少なくとも正極１５、電解液、セパレータ１８および負極２０により構成された発電素子を１つ以上含む電池本体１０と、電池本体１０を内部に封入するための外装体４０と、電池本体１０と電気的に接続され、かつ、少なくとも一部が外装体４０の外側に露出した一対の電極端子３０と、を備える。電池本体１０は、つづら折りに折り曲げられたセパレータ１８の間に正極１５および負極２０がそれぞれ配置された構造を有し、電池本体１０における正極１５および負極２０からなる電極の中で最も外側に位置する最外負極２０Ａの正極１５と対向していない側の表面の少なくとも周縁部２０Ｂに固体電解質界面（ＳＥＩ）膜２５が形成されており、最外負極２０Ａ上のＳＥＩ膜２５の長さＬ１と、最外負極２０Ａ上のセパレータ１８の長さＬ２とが、Ｌ１≧Ｌ２＞０の関係を満たす。
　ここで、ＳＥＩ膜の長さＬ１は、図４に示すように、リチウムイオン二次電池１００における電極端子３０が露出していない側の一辺２８の中心部におけるＳＥＩ膜２５の端部から、ＳＥＩ膜２５の他方の端部までの長さであり、かつ、一辺２８に対して垂直方向の長さである。セパレータの長さＬ２は、リチウムイオン二次電池１００における電極端子３０が露出していない側の一辺２８の中心部における最外負極２０Ａ上のセパレータ１８の端部から、セパレータ１８の他方の端部までの長さであり、かつ、一辺２８に対して垂直方向の長さである。 As shown in FIGS. 1 to 5, a lithium ion secondary battery 100 according to the present embodiment includes a battery main body 10 including at least one power generating element including at least a positive electrode 15, an electrolytic solution, a separator 18, and a negative electrode 20, The battery pack includes an exterior body for enclosing the battery body therein, and a pair of electrode terminals electrically connected to the battery body and at least partially exposed to the outside of the exterior body. The battery main body 10 has a structure in which the positive electrode 15 and the negative electrode 20 are respectively arranged between the separators 18 folded in a zigzag manner, and is located at the outermost position among the electrodes composed of the positive electrode 15 and the negative electrode 20 in the battery main body 10. and solid electrolyte interface (SEI) film 25 is formed at least on the peripheral edge portion 20B of the positive electrode 15 and not facing the side surface of the outermost negative electrode 20A, the length L 1 of the SEI film 25 on the outermost negative electrode 20A and the length L 2 of the separator 18 on the outermost negative electrode 20A is, satisfy the relationship of L 1 ≧ L 2> 0.
Here, the length L 1 of the SEI film, as shown in FIG. 4, from the end of the SEI film 25 at the center of the side of one side 28 of the electrode terminal 30 in a lithium ion secondary battery 100 is not exposed, The length is the length to the other end of the SEI film 25 and the length in the direction perpendicular to one side 28. The length L 2 of the separator, the end portion of the separator 18 on the outermost negative electrode 20A at the center of the side of one side 28 of the electrode terminal 30 in a lithium ion secondary battery 100 is not exposed, the other end of the separator 18 It is the length to the part and the length in the direction perpendicular to one side 28.
　本発明者の検討によれば、従来のつづら折り構造のリチウムイオン二次電池は最外層のセパレータが変質（変色や脆化等）してしまう場合があることが明らかになった。
　本発明者は最外層のセパレータの変質が抑制された、つづら折り構造のリチウムイオン二次電池を実現するために鋭意検討した。その結果、最外負極においてＳＥＩ膜が形成されていない表面上に位置するセパレータが、電解液との反応によって分解しやすいことを知見した。本発明者は上記知見を元にさらに鋭意検討したところ、最外負極上のセパレータが最外負極の表面に形成されたＳＥＩ膜上に位置するように制御することにより、最外層のセパレータの変質（変色や脆化等）を抑制できることを初めて見出した。
　すなわち、本実施形態によれば、電池本体１０における正極１５および負極２０からなる電極の中で最も外側に位置する最外負極２０Ａの表面の少なくとも周縁部に固体電解質界面（ＳＥＩ）膜２５が形成されており、最外負極２０Ａ上のＳＥＩ膜２５の長さＬ１と、最外負極２０Ａ上のセパレータ１８の長さＬ２とが、Ｌ１≧Ｌ２＞０の関係を満たすように構成することで、最外層のセパレータの変質が抑制された、つづら折り構造のリチウムイオン二次電池１００を得ることができる。 According to the study by the present inventors, it has been clarified that the conventional outermost layer separator of a lithium ion secondary battery having a zigzag structure may be altered (discoloration, embrittlement, etc.).
The inventors of the present invention have made intensive studies to realize a lithium ion secondary battery having a meandering structure in which deterioration of the outermost layer of the separator is suppressed. As a result, it was found that the separator located on the surface of the outermost negative electrode where the SEI film was not formed was easily decomposed by the reaction with the electrolytic solution. The present inventor has further studied diligently based on the above findings, and found that by controlling the separator on the outermost negative electrode to be located on the SEI film formed on the surface of the outermost negative electrode, the quality of the separator of the outermost layer was deteriorated. (Discoloration, embrittlement, etc.) can be suppressed for the first time.
That is, according to the present embodiment, the solid electrolyte interface (SEI) film 25 is formed on at least the peripheral portion of the surface of the outermost negative electrode 20 </ b> A located on the outermost side of the electrodes including the positive electrode 15 and the negative electrode 20 in the battery body 10. are, configured so as to satisfy the length L 1 of the SEI film 25 on the outermost negative electrode 20A, the length L 2 of the separator 18 on the outermost negative electrode 20A is the relationship of L 1 ≧ L 2> 0 By doing so, it is possible to obtain the self-folding structure lithium-ion secondary battery 100 in which the deterioration of the outermost layer of the separator is suppressed.
　本実施形態に係るリチウムイオン二次電池１００の最外層のセパレータ１８の変質が抑制される理由は必ずしも明らかではないが、以下の理由が考えられる。
　まず、最外負極上に位置するセパレータは、電解液との反応によって分解され、変質が起きやすい。特にエステル結合は電解液との反応によって分解されやすいため、セパレータがポリエステル系樹脂を含む場合に最外層のセパレータの変質が顕著になりやすい。
　ここで、ＳＥＩ膜が形成された部分の上に位置するセパレータは、最外負極と直接接しないため、分解反応が起きにくい。そのため、最外負極２０Ａ上のＳＥＩ膜２５の長さＬ１と、最外負極２０Ａ上のセパレータ１８の長さＬ２とが、Ｌ１≧Ｌ２＞０の関係を満たすことにより、最外負極と直接接するセパレータの割合が低くなるため、セパレータの分解は抑制される。その結果、最外層のセパレータの変質が抑制された、つづら折り構造のリチウムイオン二次電池１００を得ることができると考えられる。 The reason why the deterioration of the outermost layer separator 18 of the lithium ion secondary battery 100 according to the present embodiment is suppressed is not necessarily clear, but the following reasons are considered.
First, the separator located on the outermost negative electrode is decomposed by the reaction with the electrolytic solution, and is likely to deteriorate. In particular, since the ester bond is easily decomposed by the reaction with the electrolytic solution, when the separator contains a polyester resin, the quality of the outermost separator tends to be remarkable.
Here, since the separator located on the portion where the SEI film is formed does not directly contact the outermost negative electrode, a decomposition reaction hardly occurs. Therefore, the length L 1 of the SEI film 25 on the outermost negative electrode 20A, the length L 2 of the separator 18 on the outermost negative electrode 20A is, by satisfying the relationship of L 1 ≧ L 2> 0, the outermost Since the ratio of the separator in direct contact with the negative electrode decreases, decomposition of the separator is suppressed. As a result, it is considered that the lithium ion secondary battery 100 having the meandering structure in which the deterioration of the outermost layer of the separator is suppressed can be obtained.
　ここで、ＳＥＩ膜は正極と対向する側の面に通常は形成されるが、ＳＥＩ膜を形成するためのリチウムイオンは正極と対向していない側の面にも回り込むため、最外負極２０Ａの正極１５と対向していない側の表面の少なくとも周縁部２０ＢにもＳＥＩ膜２５が形成されている。
　また、最外負極２０Ａ上のＳＥＩ膜２５の長さＬ１は、例えば、ＸＰＳ分析で測定することができる。具体的には、ＳＥＩ膜が形成されている箇所はＬｉの比率が大きいため、Ｌｉの比率によってＳＥＩ膜の形成の有無を調べることができ、例えばＸＰＳ分析によって、セパレータの電池中心部側の端部におけるＳＥＩ膜の形成の有無を調べることによって、Ｌ１≧Ｌ２＞０の関係を満たすか否かを判断することができる。 Here, the SEI film is usually formed on the surface facing the positive electrode, but lithium ions for forming the SEI film also go around the surface not facing the positive electrode. The SEI film 25 is also formed on at least the peripheral portion 20B of the surface not facing the positive electrode 15.
The length L 1 of the SEI film 25 on the outermost negative electrode 20A, for example, can be measured by XPS analysis. Specifically, since the ratio of Li is large in the portion where the SEI film is formed, the presence or absence of the SEI film can be checked by the ratio of Li. By examining whether or not the SEI film is formed in the portion, it can be determined whether or not the relationship of L 1 ≧ L 2 > 0 is satisfied.
　本実施形態に係るリチウムイオン二次電池１００において、セパレータ１８の長さＬ２は、最外層のセパレータの変質をより一層抑制する観点から、好ましくは１５．０ｍｍ未満であり、より好ましくは１０．０ｍｍ以下であり、さらに好ましくは８．０ｍｍ以下であり、さらにより好ましくは５．０ｍｍ以下であり、特に好ましくは４．０ｍｍ以下である。
　また、セパレータ１８の長さＬ２の下限は特に限定されないが、好ましくは０．１ｍｍ以上であり、さらに好ましくは０．５ｍｍ以上である。 In the lithium ion secondary battery 100 according to the present embodiment, the length L 2 of the separator 18, the more the viewpoint of suppressing deterioration of the outermost layer of the separator, is preferably less than 15.0 mm, more preferably 10. 0 mm or less, further preferably 8.0 mm or less, still more preferably 5.0 mm or less, and particularly preferably 4.0 mm or less.
Although the lower limit of the length L 2 of the separator 18 is not particularly limited, it is preferably at 0.1mm or more, more preferably 0.5mm or more.
　本実施形態に係るリチウムイオン二次電池１００において、最外層のセパレータの変質をより一層抑制する観点から、最外負極２０Ａ上のＳＥＩ膜２５の平均長さＬ３と、最外負極２０Ａ上のセパレータ１８の平均長さＬ４とが、Ｌ３≧Ｌ４＞０の関係を満たすことが好ましい。
　ここで、リチウムイオン二次電池１００における電極端子３０が露出していない側の一辺２８において、一辺２８に対して垂直方向のＳＥＩ膜２５の長さを１０点測定し、得られた１０点の長さの平均値をＳＥＩ膜の平均長さＬ３とし、一辺２８に対して垂直方向のセパレータの長さを１０点測定し、得られた１０点の長さの平均値をセパレータ１８の平均長さＬ４とする。上記１０点は、例えば、一辺２８を等間隔に１０個に分割し、それぞれの中心部分（合計１０点）を選択することができる。 In the lithium ion secondary battery 100 according to the present embodiment, a further inhibition of the deterioration of the outermost layer of the separator, the average length L 3 of the SEI film 25 on the outermost negative electrode 20A, on the outermost negative electrode 20A It is preferable that the average length L 4 of the separator 18 satisfies the relationship of L 3 ≧ L 4 > 0.
Here, on one side 28 of the lithium ion secondary battery 100 on which the electrode terminal 30 is not exposed, the length of the SEI film 25 in the direction perpendicular to the side 28 was measured at 10 points, and the obtained 10 points were measured. the average length and the average length L 3 of the SEI film was measured 10 points the vertical length of the separator to an edge 28, the average length of 10 points obtained average of the separator 18 the length L 4. As for the above-mentioned ten points, for example, one side 28 is divided into ten pieces at equal intervals, and each central part (a total of ten points) can be selected.
　本実施形態に係るリチウムイオン二次電池１００において、最外層のセパレータの変質をより一層抑制する観点から、セパレータ１８の平均長さＬ４は、好ましくは１５．０ｍｍ未満であり、より好ましくは１０．０ｍｍ以下であり、さらに好ましくは８．０ｍｍ以下であり、さらにより好ましくは５．０ｍｍ以下であり、特に好ましくは４．０ｍｍ以下である。
　また、セパレータ１８の平均長さＬ４の下限は特に限定されないが、好ましくは０．１ｍｍ以上であり、さらに好ましくは０．５ｍｍ以上である。 In the lithium ion secondary battery 100 according to the present embodiment, a further inhibition of the deterioration of the outermost layer of the separator, the average length L 4 of the separator 18 is preferably less than 15.0 mm, more preferably 10 0.0 mm or less, more preferably 8.0 mm or less, still more preferably 5.0 mm or less, particularly preferably 4.0 mm or less.
Although lower limit of the average length L 4 of the separator 18 is not particularly limited, it is preferably at 0.1mm or more, more preferably 0.5mm or more.
　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。 Further, the lithium ion secondary battery according to the present embodiment preferably has a cell rated capacity of 7 Ah or more.
In addition, in the lithium ion secondary battery according to the present embodiment, the number of laminations or the number of windings of the positive electrode in the central portion is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. .
Thereby, the capacity of the lithium ion secondary battery according to the present embodiment can be increased. In addition, even with such a high capacity, the lithium ion secondary battery according to the present embodiment has excellent short circuit resistance and can suppress thermal runaway of the battery.
　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。 Next, each configuration used in the lithium ion secondary battery of the present embodiment will be described.
＜電池本体＞
　本実施形態に係る電池本体は、例えば、正極と負極とが、つづら折りに折り曲げられたセパレータを介して交互に積層された発電素子を１つ以上含む。これらの発電素子は電解液（図示せず）とともに外装体からなる容器に収納されている。発電素子には電極端子（正極端子および負極端子）が電気的に接続されており、電極端子の一部または全部が外装体の外部に引き出されている構成になっている。 <Battery body>
The battery body according to the present embodiment includes, for example, one or more power generating elements in which a positive electrode and a negative electrode are alternately stacked via a separator folded in a zigzag manner. These power generating elements are housed in a container formed of an exterior body together with an electrolytic solution (not shown). Electrode terminals (a positive electrode terminal and a negative electrode terminal) are electrically connected to the power generating element, and part or all of the electrode terminals are drawn out of the exterior body.
　正極には正極集電体層の表裏に、正極活物質の塗布部（正極活物質層）と未塗布部がそれぞれ設けられており、負極には負極集電体層の表裏に、負極活物質の塗布部（負極活物質層）と未塗布部が設けられている。 The positive electrode is provided with a coated portion of the positive electrode active material (positive electrode active material layer) and an uncoated portion on the front and back of the positive electrode current collector layer, and the negative electrode is provided with a negative electrode active material on the front and back of the negative electrode current collector layer. (A negative electrode active material layer) and an uncoated portion are provided.
　正極集電体層における正極活物質の未塗布部を正極端子と接続するための正極タブとし、負極集電体層における負極活物質の未塗布部を負極端子と接続するための負極タブとする。
　正極タブ同士は正極端子上にまとめられ、正極端子とともに超音波溶接等で互いに接続され、負極タブ同士は負極端子上にまとめられ、負極端子とともに超音波溶接等で互いに接続される。そのうえで、正極端子の一端は外装体の外部に引き出され、負極端子の一端も外装体の外部に引き出されている。
　本実施形態に係る電池本体は公知の方法に準じて作製することができる。 An uncoated portion of the positive electrode active material in the positive electrode current collector layer is used as a positive electrode tab for connecting to the positive electrode terminal, and an uncoated portion of the negative electrode active material in the negative electrode current collector layer is used as a negative electrode tab for connecting to the negative electrode terminal. .
The positive electrode tabs are assembled on the positive electrode terminal and connected together with the positive electrode terminal by ultrasonic welding or the like, and the negative electrode tabs are assembled on the negative electrode terminal and connected with the negative electrode terminal by ultrasonic welding or the like. Then, one end of the positive electrode terminal is drawn out of the exterior body, and one end of the negative electrode terminal is also drawn out of the exterior body.
The battery main body according to the present embodiment can be manufactured according to a known method.
（正極）
　正極は、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。正極に用いられる正極活物質としては、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)
The positive electrode can be appropriately selected from the positive electrodes that can be used in known lithium ion secondary batteries, depending on the application and the like. As the positive electrode active material used for the positive electrode, a material having high electron conductivity that can reversibly release and occlude lithium ions and facilitate electron transport is preferable.
　正極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。
　これらの正極活物質は、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 positive electrode active material used for the positive electrode is not particularly limited. For example, a lithium composite oxide having a layered rock salt structure or a spinel structure, or lithium iron phosphate having an olivine structure is used. Can be. Examples of the lithium composite oxide include lithium manganate (LiMn 2 O 4 ); lithium cobalt oxide (LiCoO 2 ); lithium nickelate (LiNiO 2 ); and at least a part of the manganese, cobalt, and nickel portions of these lithium compounds. Aluminum, magnesium, titanium, zinc, and other metal elements; nickel-substituted lithium manganate in which at least part of manganese of lithium manganate is substituted with nickel; at least part of nickel of lithium nickelate with at least cobalt Substituted cobalt-substituted lithium nickelate; nickel-substituted lithium manganate in which part of manganese is substituted with another metal (for example, at least one of aluminum, magnesium, titanium, and zinc); Other metal elements (e.g. aluminum, magnesium, titanium, zinc, at least one manganese) include those substituted with.
One of these positive electrode active materials may be used alone, or two or more thereof may be used in combination.
　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。 リ チ ウ ム As a lithium-containing composite oxide having a layered crystal structure, a lithium-nickel-containing composite oxide is exemplified. As this lithium-nickel-containing composite oxide, an oxide in which part of nickel at nickel sites is replaced with another metal can be used. Examples of the metal other than Ni occupying nickel sites 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. More preferably, the lithium nickel-containing composite oxide 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 composite 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, an oxide represented by the following formula (1) can be used.
Li 1 + a (Ni b Co c Me1 d Me2 1- bcd) O 2 (1)
(In the formula, Me1 is Mn or Al, Me2 is at least one selected from the group consisting of Mn, Al, Mg, Fe, Cr, Ti, and In (excluding 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 from 0.1 to 50 μm, more preferably from 1 to 30 μm, and still more preferably from 2 to 25 μm, from the viewpoint of reactivity with the electrolytic solution and rate characteristics. Here, the average particle diameter means a particle diameter (median diameter: D 50 ) at an integrated value of 50% in a particle size distribution (by volume) by a laser diffraction scattering method.
　正極は、例えば、正極集電体層と、正極集電体層上の正極活物質層から構成されている。この正極は、正極活物質層がセパレータを介して、負極集電体層上の負極活物質層と対向するように配置される。 The positive electrode includes, for example, a positive electrode current collector layer and a positive electrode active material layer on the positive electrode current collector layer. The positive electrode is arranged such that the positive electrode active material layer faces the negative electrode active material layer on the negative electrode current collector layer via the separator.
　また、本実施形態に係る正極は、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上に正極活物質層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。 Further, the positive electrode according to the present embodiment can be manufactured by a known method. For example, by dispersing a positive electrode active material, a binder resin, and a conductive additive in an organic solvent to obtain a positive electrode slurry, applying and drying the positive electrode slurry on a positive electrode current collector layer, and pressing if necessary. A method of forming a positive electrode active material layer on a positive electrode current collector layer can be employed.
As the slurry solvent used for producing the positive electrode, for example, N-methyl-2-pyrrolidone (NMP) can be used.
　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 the binder resin, for example, a resin generally used as a binder resin for a positive electrode such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) can be used.
　正極活物質層中のバインダー樹脂の含有量は、正極活物質層の全体を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 is preferably 0.1 part by mass or more and 10.0 parts by mass or less when the whole of the positive electrode active material layer is 100 parts by mass, and is 0.5 part by mass. It is more preferably at least 5.0 parts by mass and even more preferably at least 1.0 part by mass and not more than 5.0 parts by mass. When the content of the binder resin is within the above range, the balance between the coating properties of the positive electrode slurry, the binding properties of the binder, and the battery characteristics is further improved.
Further, when the content of the binder resin is equal to or less than the above upper limit, the ratio of the positive electrode active material increases, and the capacity per positive electrode mass increases, which is preferable. It is preferable that the content of the binder resin be equal to or more than the lower limit, because the electrode peeling is suppressed.
　正極活物質層は、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 can include a conductive auxiliary in addition to the positive electrode active material and the binder resin. The conductive assistant 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, and carbon fiber. These conductive aids may be used alone or in combination of two or more.
　正極活物質層中の導電助剤の含有量は、正極活物質層の全体を１００質量部としたとき、１．０質量部以上４．０質量部以下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 is preferably 1.0 part by mass or more and 4.0 parts by mass or less, when the whole positive electrode active material layer is 100 parts by mass, and is 1.2 parts by mass. It is more preferably not less than 3.5 parts by mass, more preferably not less than 1.5 parts by mass and not more than 3.5 parts by mass, and more preferably not less than 2.0 parts by mass and not more than 3.5 parts by mass. Particularly preferred. When the content of the conductive additive is within the above range, the balance between the coating properties of the positive electrode slurry, the binding properties of the binder resin, and the battery characteristics is further improved.
In addition, it is preferable that the content of the conductive auxiliary agent be equal to or less than the above upper limit, because the ratio of the positive electrode active material increases and the capacity per positive electrode mass increases. It is preferable that the content of the conductive auxiliary agent be equal to or more than the above lower limit, because the conductivity of the positive electrode is further improved and the battery characteristics of the lithium ion secondary battery are improved.
　正極集電体層としては、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。
　正極集電体層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。 As the positive electrode current collector layer, aluminum, stainless steel, nickel, titanium, an alloy thereof, or the like can be used. Examples of the shape include a foil, a flat plate, and a mesh. In particular, an aluminum foil can be suitably used.
The thickness of the positive electrode current collector layer is not particularly limited, but is, for example, 1 μm or more and 30 μm or less.
　正極活物質層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。 Although the density of the positive electrode active material layer is not particularly limited, for example, it is preferably, 2.4 g / cm 3 or more 3.8 g / cm 3 or less or less 2.0 g / cm 3 or more 4.0 g / cm 3 More preferably, it is 2.8 g / cm 3 or more and 3.6 g / cm 3 or less.
　正極活物質層の厚み（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 of the positive electrode active material layer (the sum of the thicknesses of both surfaces) is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thicker from the viewpoint of energy density, and can be set thinner from the viewpoint of output characteristics. The thickness of the positive electrode active material layer (the sum of the thicknesses of both surfaces) can be appropriately set, for example, in the range of 20 μm or more and 500 μm or less, preferably 40 μm or more and 400 μm or less, more preferably 60 μm or more and 300 μm or less.
Further, the thickness of the positive electrode active material layer (one-side thickness) is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thicker from the viewpoint of energy density, and can be set thinner from the viewpoint of output characteristics. The thickness (one-sided thickness) of the positive electrode active material layer 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.
（負極）
　負極は、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。
　負極は、例えば、負極集電体層と、負極集電体層上に形成された負極活物質層から構成されている。負極活物質層は、例えば、負極活物質および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。 (Negative electrode)
The negative electrode can be appropriately selected from the negative electrodes that can be used in known lithium ion secondary batteries, depending on the application and the like. The negative electrode active material used for the negative electrode can be appropriately set depending on the use and the like as long as it can be used for the negative electrode.
The negative electrode includes, for example, a negative electrode current collector layer and a negative electrode active material layer formed on the negative electrode current collector layer. The negative electrode active material layer preferably contains, for example, a negative electrode active material and a binder resin, and further contains a conductive auxiliary from the viewpoint of increasing 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 and non-graphitizable carbon), diamond-like carbon, fullerene, carbon nanotube, and carbon nanohorn. As the graphite, natural graphite and artificial graphite can be used, and in terms of material cost, inexpensive natural graphite is preferable. Examples of the 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, a lithium metal material, an alloy material such as silicon or tin, an oxide material such as Nb 2 O 5 or TiO 2 , or a composite thereof can be used.
As the negative electrode active material, only one kind may be used alone, or two or more kinds may be used in combination.
　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 size of the negative electrode active material is preferably 2 μm or more, more preferably 5 μm or more, from the viewpoint of suppressing a side reaction during charge and discharge and suppressing a decrease in charge and discharge efficiency. From the viewpoint of (eg, smoothness of the negative electrode surface), the thickness is preferably 40 μm or less, and more preferably 30 μm or less. 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に塗布・乾燥し、必要に応じてプレスして負極活物質層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。 Further, the negative electrode in the present embodiment can be manufactured by a known method. For example, a method in which a negative electrode active material and a binder resin are dispersed in a solvent to obtain a slurry, the slurry is applied to a negative electrode current collector layer, dried, and pressed as necessary to form a negative electrode active material layer Can be adopted.
Examples of the method for 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.
　負極活物質層中のバインダー樹脂の含有量は、負極活物質層の全体を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 is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, when the whole of the negative electrode active material layer is 100 parts by mass, and is 0.5 part by mass. It is more preferably at least 8.0 parts by mass, more preferably at least 1.0 parts by mass and at most 5.0 parts by mass, particularly preferably at least 1.0 part by mass and at most 3.0 parts by mass. preferable. When the content of the binder resin is within the above range, the balance between the coating properties of the negative electrode slurry, the binding properties of the binder resin, and the battery characteristics is further improved.
Further, when the content of the binder resin is equal to or less than the above upper limit, the ratio of the negative electrode active material is increased, and the capacity per mass of the negative electrode is preferably increased. It is preferable that the content of the binder resin be equal to or more than the lower limit, because the electrode peeling is suppressed.
　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, a rubber-based binder (for example, SBR (styrene-butadiene rubber)) or an acrylic-based binder resin can be used. Such an aqueous binder resin may be 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。
　負極活物質層中の導電助剤の含有量は、負極活物質層の全体を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 may contain a conductive aid as needed. As the conductive aid, a conductive material generally used as a conductive aid for a negative electrode, such as a carbonaceous material 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 is preferably 0.1 part by mass or more and 3.0 parts by mass or less, when the whole of the negative electrode active material layer is 100 parts by mass, It is more preferable that the amount is from 2.0 parts by mass to 2.0 parts by mass, and particularly preferable is from 0.2 parts by mass to 1.0 parts by mass. When the content of the conductive assistant is within the above range, the balance between the coating properties of the negative electrode slurry, the binding properties of the binder resin, and the battery characteristics is further improved.
In addition, it is preferable that the content of the conductive auxiliary agent be equal to or less than the above upper limit, because the proportion of the negative electrode active material increases and the capacity per mass of the negative electrode increases. It is preferable that the content of the conductive auxiliary agent be equal to or more than the above lower limit, because the conductivity of the negative electrode is further improved.
　正極活物質層や負極活物質層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 in the positive electrode active material layer and the negative electrode active material layer is preferably in the range of 10 to 100 nm. The average particle size (primary particle size) of the conductive additive 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 additive and uniformly dispersing it in the negative electrode. Is preferably 100 nm or less, and more preferably 80 nm or less, from the viewpoint of forming a good conductive path. When the conductive additive is in a fibrous form, examples thereof include those having an average diameter of 2 to 200 nm and an average fiber length of 0.1 to 20 μm.
Here, the average particle diameter of the conductive additive is a median diameter (D 50 ), which means a particle diameter at an integrated value of 50% in a particle size distribution (volume basis) by a laser diffraction scattering method.
　負極活物質層の厚み（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 of the negative electrode active material layer (the sum of the thicknesses of both surfaces) is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thicker from the viewpoint of energy density, and can be set thinner from the viewpoint of output characteristics. The thickness of the negative electrode active material layer (total thickness of both surfaces) can be appropriately set, for example, in the range of 40 μm or more and 1000 μm or less, preferably 80 μm or more and 800 μm or less, and more preferably 120 μm or more and 600 μm or less.
In addition, the thickness of the negative electrode active material layer (one-side thickness) is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thicker from the viewpoint of energy density, and can be set thinner from the viewpoint of output characteristics. The thickness of the negative electrode active material layer (one-side thickness) can be appropriately set, for example, in the range of 20 μm or more and 500 μm or less, preferably 40 μm or more and 400 μm or less, and more preferably 60 μm or more and 300 μm or less.
　負極活物質層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。 The density of the negative electrode active material layer is not particularly limited, but is preferably, for example, 1.2 g / cm 3 or more and 2.0 g / cm 3 or less, and is 1.3 g / cm 3 or more and 1.9 g / cm 3 or less. More preferably, it is 1.4 g / cm 3 or more and 1.8 g / cm 3 or less.
　負極集電体層としては、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。
　負極集電体層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。 As the negative electrode current collector layer, copper, stainless steel, nickel, titanium, or an alloy thereof can be used. Examples of the shape include a foil, a flat plate, and a mesh.
The thickness of the negative electrode current collector layer is not particularly limited, but is, for example, 1 μm or more and 20 μm or less.
（電解液）
　本実施形態に係る電解液は電解質を溶媒に溶解させたものである。
　本実施形態に用いる電解液は、例えば、リチウム塩を含有する非水電解液であり、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。 (Electrolyte)
The electrolytic solution according to the present embodiment is obtained by dissolving an electrolyte in a solvent.
The electrolytic solution used in the present embodiment is, for example, a non-aqueous electrolytic solution containing a lithium salt, and may be appropriately selected from known ones according to the type of the electrode active material and the use of the lithium ion secondary battery. it can.
　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 (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, lithium lower fatty acid carboxylate, and the like can be given.
　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. Ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), carbonates such as ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC) and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; trimethoxymethane Ethers such as 1,2-dimethoxyethane, diethyl ether, tetrahydrofuran and 2-methyltetrahydrofuran; sulfoxides such as dimethylsulfoxide; 1,3-dioxolane, 4-methyl-1,3-dioxola Nitrous solvents such as acetonitrile, nitromethane, formamide, dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate; phosphate triester And diglymes; triglymes; sulfolane such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propanesultone, 1,4-butanesultone and naphthasultone. . These may be used alone or in combination of two or more.
（セパレータ）
　本実施形態に係るセパレータは、正極と負極を電気的に絶縁させ、リチウムイオンを透過する機能を有するものであれば特に限定されないが、例えば、多孔性セパレータを用いることができる。 (Separator)
The separator according to this embodiment is not particularly limited as long as it has a function of electrically insulating the positive electrode and the negative electrode and transmitting lithium ions. For example, a porous separator can be used.
　本実施形態に係るセパレータは、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。 The separator 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 as a main component. Here, the “main component” means that the proportion in the resin layer is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and 100% by mass. Means that you may.
The resin layer constituting the separator according to this 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 resin layer include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polycarbonate, polyester carbonate, aliphatic polyamide, Aromatic polyamide, semi-aromatic polyamide, wholly aromatic polyester, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyimide, polyarylate, polyetherimide, polyamideimide, polyacetal, polyetheretherketone, polysulfone, polyethersulfone, One type or two or more types selected from a fluorine-based resin, polyether nitrile, modified polyphenylene ether, and the like can be given.
　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、全芳香族ポリエステル等のポリエステル系樹脂、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等のポリアミド系樹脂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、ポリエチレンナフタレート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のポリエステル系樹脂がより好ましく、ポリエチレンテレフタレートがさらに好ましい。 Among them, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, wholly aromatic polyester, aliphatic polyamide, and wholly aromatic, from the viewpoint of excellent balance among heat resistance, mechanical strength, elasticity, and price. One or two or more selected from polyamide resins such as aromatic polyamides and semi-aromatic polyamides, and one or more polyesters selected from polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and wholly aromatic polyester A system resin is more preferred, and polyethylene terephthalate is even more preferred.
　本実施形態に係るセパレータの融点は、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 according to this embodiment is preferably 220 ° C. or higher, more preferably 230 ° C. or higher, and more preferably 240 ° C. or higher, from the viewpoint of improving the safety of the lithium ion secondary battery. More preferred. Alternatively, from the viewpoint of improving the safety of the lithium ion secondary battery, the separator according to the present embodiment preferably does not show a melting point, and preferably has a decomposition temperature of 220 ° C or higher, and 230 ° C or higher. Is more preferably 240 ° C. or higher, and particularly preferably 250 ° C. or higher.
By setting the melting point or the decomposition temperature of the separator according to the present embodiment to the above lower limit or more, the battery generates heat, and even when the battery becomes hot, it is possible to suppress thermal contraction of the separator, and as a result, the positive electrode and the negative electrode Can be suppressed. Thereby, thermal runaway of the lithium ion secondary battery and the like can be suppressed, and safety can be further improved.
The upper limit of the melting point of the separator according to this embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of elasticity. Alternatively, the upper limit of the decomposition temperature of the separator according to this embodiment is not particularly limited, but is, for example, 500 ° C. or less, and preferably 400 ° C. or less from the viewpoint of elasticity.
　本実施形態に係るセパレータ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。 樹脂 The resin layer constituting the separator according to the present embodiment is preferably a porous resin layer. As a result, when an abnormal current is generated in the lithium ion secondary battery and the temperature of the battery rises, the micropores of the porous resin layer are closed and the flow of current can be interrupted. 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。 The porosity of the porous resin layer is preferably from 20% to 80%, more preferably from 30% to 70%, and more preferably from 40% to 60%, from the viewpoint of balance between mechanical strength and lithium ion conductivity. Is particularly preferred.
The porosity can be obtained 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 ), and t: film thickness (μm).
　本実施形態に係るセパレータの平面形状は、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。 平面 The planar shape of the separator according to this embodiment is not particularly limited, and can be appropriately selected according to the shape of the electrode or the current collector, and may be, for example, a rectangle.
　本実施形態に係るセパレータの厚みは、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 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 still more preferably 10 μm or more and 30 μm or less, from the viewpoint of balance between mechanical strength and lithium ion conductivity. It is.
　本実施形態に係るセパレータは、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。 It is preferable that the separator according to the embodiment 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 surface of the resin layer from the viewpoint of handleability of the separator according to the present embodiment and productivity, but further improves the heat resistance of the separator. From the viewpoint of causing the resin layer to be provided, the resin layer may be provided on both surfaces.
Since the separator according to the present embodiment further includes the ceramic layer, the heat shrinkage of the separator can be further reduced, and the short circuit between the electrodes can be further prevented.
　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 ceramic layer can be formed, for example, by applying and drying a ceramic layer forming material on the 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 an appropriate solvent can be used.
The inorganic filler used for the ceramic layer can be appropriately selected from known materials used for a separator of a lithium ion secondary battery. For example, highly insulating oxides, nitrides, sulfides, carbides, and the like are preferable, and are selected from aluminum oxide, boehmite, titanium oxide, silicon oxide, magnesium oxide, barium oxide, zirconium oxide, zinc oxide, iron oxide, and the like. More preferably, one or two or more types of ceramics are adjusted to particles. Among these, aluminum oxide, boehmite and titanium oxide are preferred.
　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 a cellulosic resin such as carboxymethylcellulose (CMC); an acrylic resin; and a fluororesin such as polyvinylidene fluoride (PVDF). As the binder resin, only one kind may be used alone, or two or more kinds may be used in combination.
　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), and ethyl methyl carbonate (EMC). 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 it is 1 μm or more and 15 μm or less.
（電解質層）
　電解質層は、正極と負極との間に介在するように配置される層である。電解質層はセパレータおよび電解液を含み、例えば、多孔性セパレータに非水電解液を含浸させたものが挙げられる。 (Electrolyte layer)
The electrolyte layer is a layer disposed so as to be interposed between the positive electrode and the negative electrode. The electrolyte layer contains a separator and an electrolyte, and examples thereof include a porous separator in which a non-aqueous electrolyte is impregnated.
＜外装体＞
　本実施形態に係る外装体は、例えば、略四角形の平面形状を有する。そして、本実施形態に係る外装体は、例えば、電池本体を収容する収容部と、収容部の周縁部に位置する熱融着性樹脂層同士が直接または電極端子を介して接合した接合部と、を有する。 <Outer body>
The exterior body according to the present embodiment has, for example, a substantially rectangular planar shape. The exterior body according to the present embodiment includes, for example, a housing portion for housing the battery body, and a joint portion in which the heat-fusible resin layers located on the peripheral edge of the housing portion are directly or via electrode terminals. And
　本実施形態に係る外装体は少なくとも熱融着性樹脂層とバリア層とを有し、かつ、電池本体を内部に封入できるものが好ましい。
　電池の軽量化の観点からは少なくとも熱融着性樹脂層とバリア層とを有する積層フィルムを用いることが好ましい。バリア層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、例えば、ステンレス（ＳＵＳ）箔、アルミニウム箔、アルミニウム合金箔、銅箔、チタン箔等の金属により構成されたバリア層を用いることができる。バリア層の厚みは、例えば、１０μｍ以上１００μｍ以下であり、好ましくは２０μｍ以上８０μｍ以下、より好ましくは３０μｍ以上５０μｍ以下である。
　熱融着性樹脂層を構成する樹脂材料は、特に限定されないが、例えば、ポリエチレン、ポリプロピレン、ナイロン、ポリエチレンテレフタレート（ＰＥＴ）等を用いることができる。熱融着性樹脂層の厚みは、例えば、２０μｍ以上２００μｍ以下であり、好ましくは３０μｍ以上１５０μｍ以下、より好ましくは５０μｍ以上１００μｍ以下である。
　また、本実施形態に係る積層フィルムの熱融着性樹脂層やバリア層は、それぞれ１層に限定されるものではなく、２層以上であってもよい。 It is preferable that the exterior body according to the present embodiment has at least a heat-fusible resin layer and a barrier layer, and is capable of enclosing the battery body therein.
From the viewpoint of reducing the weight of the battery, it is preferable to use a laminated film having at least a heat-fusible resin layer and a barrier layer. The barrier layer may be selected from those having a barrier property such as preventing leakage of electrolyte and intrusion of moisture from the outside. For example, stainless steel (SUS) foil, aluminum foil, aluminum alloy foil, copper foil, titanium foil A barrier layer made of a metal such as a foil can be used. The thickness of the barrier layer is, for example, 10 μm or more and 100 μm or less, preferably 20 μm or more and 80 μm or less, and more preferably 30 μm or more and 50 μm or less.
Although the resin material constituting the heat-fusible resin layer is not particularly limited, for example, polyethylene, polypropylene, nylon, polyethylene terephthalate (PET) and the like can be used. The thickness of the heat-fusible resin layer is, for example, 20 μm or more and 200 μm or less, preferably 30 μm or more and 150 μm or less, and more preferably 50 μm or more and 100 μm or less.
Further, the heat-fusible resin layer and the barrier layer of the laminated film according to the present embodiment are not limited to one layer each, and may be two or more layers.
　本実施形態において、熱融着性樹脂層同士を電池本体を介して対向させ、電池本体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ことができる。熱融着性樹脂層が形成された面と反対側の面となる外装体の外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。 In the present embodiment, the exterior body can be formed by causing the heat-fusible resin layers to face each other with the battery body interposed therebetween and heat-sealing the periphery of the portion housing the battery body. A resin layer such as a nylon film or a polyester film can be provided on the outer surface of the exterior body, which is the surface opposite to the surface on which the heat-fusible resin layer is formed.
　熱融着性樹脂層同士の熱融着をおこなう際の加熱温度は熱融着性樹脂層を構成する樹脂材料の融点によって異なるが、例えば、熱融着性樹脂層を構成する樹脂材料がポリプロピレンの場合、好ましくは１４０℃～１８５℃であり、より好ましくは１５０℃～１８０℃である。
　また、熱融着性樹脂層同士の熱融着をおこなう際の熱シール時間は、例えば、１０秒～５０秒、好ましくは１２秒～３０秒である。 The heating temperature at the time of performing heat fusion between the heat-fusible resin layers depends on the melting point of the resin material constituting the heat-fusible resin layer. In this case, the temperature is preferably from 140 ° C. to 185 ° C., and more preferably from 150 ° C. to 180 ° C.
In addition, the heat sealing time when performing heat fusion between the heat-fusible resin layers is, for example, 10 seconds to 50 seconds, preferably 12 seconds to 30 seconds.
（電極端子）
　本実施形態において、一対の電極端子３０（正極端子および負極端子）には公知の部材を用いることができる。正極端子には、例えば、アルミニウムやアルミニウム合金で構成されたもの、負極端子には、例えば、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樹脂層をあらかじめ設ける。 (Electrode terminal)
In the present embodiment, known members can be used for the pair of electrode terminals 30 (the positive electrode terminal and the negative electrode terminal). For the positive electrode terminal, for example, one made of aluminum or an aluminum alloy can be used, and for the negative electrode terminal, for example, copper or a copper alloy or one obtained by plating them with nickel can be used. Each terminal is drawn out of the container, and a heat-fusible resin layer is provided in advance at a portion of each terminal located at a portion where the periphery of the outer package is thermally welded.
　なお、図１においては、正極端子および負極端子は、外装体の同一辺から引き出されているが、正極端子および負極端子は外装体の異なる辺から引き出されていてもよい。 In FIG. 1, the positive electrode terminal and the negative electrode terminal are drawn from the same side of the package, but the positive terminal and the negative terminal may be drawn from different sides of the package.
　以上、本発明の実施形態について述べたが、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。
　なお、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。 Although the embodiments of the present invention have been described above, these are only examples of the present invention, and various configurations other than the above can be adopted.
It should be noted that the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.
（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９３．９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、添加剤として無水蓚酸を０．１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)
<Preparation of positive electrode>
93.9 parts by mass of a lithium nickel-containing composite oxide (chemical formula: LiNi 0.8 Co 0.15 Al 0.05 O 2 , average particle size: 6 μm) as a positive electrode active material, and carbon black as a conductive auxiliary agent. 0 parts by mass, 3.0 parts by mass of polyvinylidene fluoride (PVDF) as a binder resin, and 0.1 parts by mass of oxalic anhydride as an additive were used. These were dispersed in an organic solvent to prepare a positive electrode slurry. This positive electrode slurry is continuously applied to a 15 μm-thick aluminum foil (tensile elongation: 6%), which is a positive electrode current collector, dried, and then pressed to form a coated portion of the positive electrode current collector (positive electrode). An active material layer: a positive electrode roll having a thickness of 60 μm on one side, a density of 3.35 g / cm 3 ) and an uncoated portion not coated was prepared.
This positive electrode roll was punched out so that an uncoated portion serving as a tab for connecting to the positive electrode terminal was left, thereby forming 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。 <Preparation of negative electrode>
96.7 parts by mass of natural graphite (average particle size: 16 μm) as a negative electrode active material, 0.3 parts by mass of carbon black as a conductive aid, 2.0 parts by mass of styrene-butadiene rubber as a binder resin, a thickener Carboxymethyl cellulose was used in an amount of 1.0 part by mass. These were dispersed in water to prepare a negative electrode slurry. The negative electrode slurry is continuously applied to an 8 μm-thick copper foil (tensile elongation: 4%), which is a negative electrode current collector, dried, and then pressed to form a coated portion of the negative electrode current collector (negative electrode). An active material layer: a negative electrode roll having a thickness of 90 μm on one side, a density of 1.55 g / cm 3 ) and an uncoated portion not coated was prepared.
This negative electrode roll was punched out such that an uncoated portion serving as a tab for connecting to the negative electrode terminal was left to form a negative electrode.
＜リチウムイオン二次電池の作製＞
　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％、樹脂層融点：２５０℃）を用いた。
　また、最外負極上のセパレータの長さＬ２と平均長さＬ４を表１に記載の値に調整した。 <Production of lithium ion secondary battery>
A positive electrode and a negative electrode were laminated in a zigzag structure with a separator interposed therebetween, and a negative electrode terminal and a positive electrode terminal were provided thereon, thereby obtaining a laminate. Next, an electrolyte solution in which 1M LiPF 6 was dissolved in a solvent composed of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, and the obtained laminate were accommodated in a flexible film, thereby forming a laminate type laminated battery. Obtained. The rated capacity of this laminated battery was 9.2 Ah, the positive electrode had 28 layers, and the negative electrode had 29 layers.
As the separator, a separator 1 (thickness: 25 μm, porosity: 56%, resin layer melting point: 250 ° C.) including a porous resin layer made of polyethylene terephthalate (PET) and a ceramic layer made of boehmite particles was used. .
Further, the average length L 4 and the length L 2 of the outermost negative electrode of the separator was adjusted to a value shown in Table 1.
＜評価＞
（１）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。 <Evaluation>
(1) Porosity of porous resin layer It was 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 ), and t: film thickness (μm).
（２）ＳＥＩ膜の長さの測定
　電極端子が露出していない側の一辺の中心部におけるセパレータの電池中心部側の端部の直下において、ＳＥＩ膜の形成の有無をＸＰＳ分析により調べた。ＳＥＩ膜が形成されている場合はＬ１≧Ｌ２＞０の関係およびＬ３≧Ｌ４＞０の関係を満たすとした。表１において、上記式を満足する場合をそれぞれ○とし、満足しない場合をそれぞれ×とした。
　また、ＳＥＩ膜の形成の有無は、ＸＰＳ分析で調べた。具体的にはＳＥＩ膜が形成されている箇所はＬｉの比率が大きいため、Ｌｉの比率によってＳＥＩ膜の形成の有無を調べることができる。 (2) Measurement of length of SEI film The presence or absence of the SEI film was examined by XPS analysis immediately below the end of the separator on the side of the battery center at the center of one side where the electrode terminals were not exposed. When the SEI film is formed, the relationship of L 1 ≧ L 2 > 0 and the relationship of L 3 ≧ L 4 > 0 are satisfied. In Table 1, a case where the above formula was satisfied was evaluated as O, and a case where it was not satisfied was evaluated as x.
The presence or absence of the SEI film was checked by XPS analysis. Specifically, since the ratio of Li is large in the portion where the SEI film is formed, the presence or absence of the SEI film can be checked based on the Li ratio.
（３）最外層のセパレータの変質評価
　得られたリチウムイオン二次電池に対して、定電流定電圧（ＣＣ－ＣＶ）法を用いて、２５℃で、０．２Ｃ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、次いで、放電レート０．２Ｃ、放電終止電圧２．５ＶでＣＣ放電をおこなった。
　次いで、初回の充放電が終わったリチウムイオン二次電池に対して、４５℃で１６８時間静置し、エージング処理をおこなった。
　得られたリチウムイオン二次電池を解体し、最外層のセパレータの変質を目視で観察し、以下の基準でそれぞれ評価した。
　◎◎：最外層のセパレータ表面には変色部位が観察されない
　◎：直径が１～５ｍｍ程度の変色部位が１～２個観察されるが、セパレータ全体としては変質が抑制されている
　○：長さ５ｍｍ～２０ｍｍ、幅１～５ｍｍ程度の薄褐色の変色部位が１～２個観察されるが、セパレータ全体としては変質が抑制されている
　△：最外層のセパレータ表面の全体にわたって薄い褐色の変色部位が観察されるが、セパレータ全体としては変質が抑制されている
　×：最外層のセパレータ表面の全体にわたって濃い褐色の変色部位が観察され、セパレータ全体が変質している
　得られた評価結果を表１に示す。 (3) Deterioration evaluation of the outermost layer separator The obtained lithium ion secondary battery was subjected to a constant current constant voltage (CC-CV) method at 25 ° C. and a constant current of 0.2 C. The battery was charged at a constant current up to 2 V, then charged at a constant voltage of 4.2 V at a constant voltage up to a charge termination current of 0.015 C, and then subjected to CC discharge at a discharge rate of 0.2 C and a discharge termination voltage of 2.5 V.
Next, the lithium ion secondary battery after the first charge / discharge was allowed to stand at 45 ° C. for 168 hours to perform an aging treatment.
The obtained lithium ion secondary battery was disassembled, the deterioration of the outermost layer separator was visually observed, and each was evaluated according to the following criteria.
◎: No discolored portion is observed on the outermost layer of the separator surface. ：: One or two discolored portions having a diameter of about 1 to 5 mm are observed, but deterioration of the entire separator is suppressed. ：: Length One or two light brown discolored portions having a size of 5 mm to 20 mm and a width of about 1 to 5 mm are observed, but deterioration of the entire separator is suppressed. Δ: Light brown discolored portion over the entire outermost layer separator surface Are observed, but deterioration is suppressed in the entire separator. ×: A dark brown discolored portion is observed over the entire outermost surface of the separator, and the entire separator is deteriorated. The obtained evaluation results are shown in Table 1. Shown in
（実施例２～４および比較例１）
　Ｌ２およびＬ４を表１に示す値に変えた以外は実施例１と同様にしてリチウムイオン二次電池をそれぞれ作製し、実施例１と同様の評価をそれぞれおこなった。
　得られた評価結果を表１にそれぞれ示す。 (Examples 2 to 4 and Comparative Example 1)
L 2 and L 4 was replaced with the values shown in Table 1 were prepared with different lithium ion secondary battery in the same manner as in Example 1, was subjected to the same evaluation as in Example 1, respectively.
Table 1 shows the obtained evaluation results.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１から、Ｌ１≧Ｌ２＞０の関係を満たす実施例のリチウムイオン二次電池は最外層のセパレータの変質が抑制されていた。これに対し、Ｌ１≧Ｌ２＞０の関係を満たさない比較例のリチウムイオン二次電池は最外層のセパレータ表面が変質していた。 According to Table 1, in the lithium ion secondary battery of the example satisfying the relationship of L 1 ≧ L 2 > 0, deterioration of the outermost layer of the separator was suppressed. On the other hand, in the lithium ion secondary battery of the comparative example that did not satisfy the relationship of L 1 ≧ L 2 > 0, the surface of the outermost layer of the separator was deteriorated.
　この出願は、２０１８年６月２９日に出願された日本出願特願２０１８－１２５０１６号を基礎とする優先権を主張し、その開示の全てをここに取り込む。 This application claims priority based on Japanese Patent Application No. 2018-125016 filed on June 29, 2018, the entire disclosure of which is incorporated herein.

Claims (11)

  1. 　少なくとも正極、電解液、セパレータおよび負極により構成された発電素子を１つ以上含む電池本体と、
    　前記電池本体を内部に封入するための外装体と、
    　前記電池本体と電気的に接続され、かつ、少なくとも一部が前記外装体の外側に露出した一対の電極端子と、
    を備えるリチウムイオン二次電池であって、
    　前記電池本体は、つづら折りに折り曲げられた前記セパレータの間に前記正極および前記負極がそれぞれ配置された構造を有し、
    　前記電池本体における前記正極および前記負極からなる電極の中で最も外側に位置する最外負極の前記正極と対向していない側の表面の少なくとも周縁部に固体電解質界面（ＳＥＩ）膜が形成されており、
    　前記最外負極上の前記ＳＥＩ膜の長さＬ１と、前記最外負極上の前記セパレータの長さＬ２とが、Ｌ１≧Ｌ２＞０の関係を満たすリチウムイオン二次電池。
    （ここで、前記ＳＥＩ膜の長さＬ１は、当該リチウムイオン二次電池における前記電極端子が露出していない側の一辺の中心部における前記ＳＥＩ膜の端部から、前記ＳＥＩ膜の他方の端部までの長さであり、かつ、前記一辺に対して垂直方向の長さである。前記セパレータの長さＬ２は、当該リチウムイオン二次電池における前記電極端子が露出していない側の一辺の中心部における前記最外負極上の前記セパレータの端部から、前記セパレータの他方の端部までの長さであり、かつ、前記一辺に対して垂直方向の長さである。）     A battery body including at least one power generating element composed of at least a positive electrode, an electrolytic solution, a separator and a negative electrode,
    An exterior body for enclosing the battery body therein,
    A pair of electrode terminals electrically connected to the battery body, and at least a part of which is exposed outside the exterior body;
    A lithium ion secondary battery comprising:
    The battery body has a structure in which the positive electrode and the negative electrode are respectively arranged between the separators folded in a zigzag manner,
    A solid electrolyte interface (SEI) film is formed on at least a peripheral portion of a surface of the outermost negative electrode, which is located on the outermost side among the electrodes formed of the positive electrode and the negative electrode in the battery body, and does not face the positive electrode. Yes,
    Wherein the length L 1 of the outermost negative electrode of the SEI film, the the length L 2 of the outermost negative electrode of the separator, a lithium ion secondary battery which satisfies the relationship L 1 ≧ L 2> 0.
    (Where the length L 1 of the SEI film, from the end of the SEI film at the center portion of the electrode terminals are not exposed side side of the lithium ion secondary cell, the other of the SEI film the length of the end portion, and a length in the direction perpendicular to the one side. the length L 2 of the separator, the side where the electrode terminals of the lithium ion secondary battery is not exposed (The length from the end of the separator on the outermost negative electrode at the center of one side to the other end of the separator, and the length in the direction perpendicular to the one side.)
  2. 　請求項１に記載のリチウムイオン二次電池において、
    　前記セパレータはポリエステル系樹脂を含むリチウムイオン二次電池。     The lithium ion secondary battery according to claim 1,
    The separator is a lithium ion secondary battery including a polyester resin.
  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、
    　前記セパレータの長さＬ２が１５．０ｍｍ未満であるリチウムイオン二次電池。     The lithium ion secondary battery according to claim 1,
    Length lithium ion secondary battery L 2 is less than 15.0mm of the separator.
  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、
    　前記最外負極上の前記ＳＥＩ膜の平均長さＬ３と、前記最外負極上の前記セパレータの平均長さＬ４とが、Ｌ３≧Ｌ４＞０の関係を満たすリチウムイオン二次電池。
    （ここで、当該リチウムイオン二次電池における前記電極端子が露出していない側の一辺において、前記一辺に対して垂直方向の前記ＳＥＩ膜の長さを１０点測定し、得られた１０点の長さの平均値を前記ＳＥＩ膜の平均長さＬ３とし、前記一辺に対して垂直方向の前記セパレータの長さを１０点測定し、得られた１０点の長さの平均値を前記セパレータの平均長さＬ４とする。）     The lithium ion secondary battery according to any one of claims 1 to 3,
    Wherein the average length L 3 of the outermost negative electrode of the SEI film, the average length L 4 of the outermost negative electrode of the separator, lithium ion secondary batteries satisfy the relationship of L 3 ≧ L 4> 0 .
    (Here, on one side of the lithium ion secondary battery where the electrode terminals are not exposed, the length of the SEI film in a direction perpendicular to the one side was measured at 10 points, and the obtained 10 points were measured. the average length and the average length L 3 of the SEI film was measured 10 points the length of the vertical direction of the separator with respect to said one side, said average length of 10 points obtained separator the average length L 4 of the.)
  5. 　請求項４に記載のリチウムイオン二次電池において、
    　前記セパレータの平均長さＬ４が１５．０ｍｍ未満であるリチウムイオン二次電池。     The lithium ion secondary battery according to claim 4,
    Lithium ion secondary batteries mean length L 4 is less than 15.0mm of the separator.
  6. 　請求項１乃至５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、
    　前記外装体が少なくとも熱融着性樹脂層とバリア層とを有する積層フィルム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 5,
    A lithium ion secondary battery in which the outer package is a laminated film having at least a heat-fusible resin layer and a barrier layer.
  7. 　請求項１乃至６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、
    　前記正極が正極活物質として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 1 to 6,
    A lithium ion secondary battery in which the positive electrode contains a lithium nickel-containing composite oxide as a positive electrode active material.
  8. 　請求項７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）     The lithium ion secondary battery according to claim 7,
    A lithium ion secondary battery in which the lithium nickel-containing composite oxide is represented by the following formula (1).
    Li 1 + a (Ni b Co c Me1 d Me2 1- bcd) O 2 (1)
    (In the formula, Me1 is Mn or Al, Me2 is at least one selected from the group consisting of Mn, Al, Mg, Fe, Cr, Ti, and In (excluding metals of the same type as Me1); −0.5 ≦ a <0.1, 0.1 ≦ b <1, 0 <c <0.5, 0 <d <0.5)
  9. 　請求項１乃至８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７Ａｈ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 8,
    A lithium ion secondary battery in which the lithium ion secondary battery has a cell rated capacity of 7 Ah or more.
  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、
    　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 9,
    A lithium ion secondary battery in which the number of laminations or the number of windings of the positive electrode at the center of the lithium ion secondary battery is 10 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、
    　前記セパレータは樹脂層およびセラミック層を有す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 separator is a lithium ion secondary battery having a resin layer and a ceramic layer.
PCT/JP2019/020847 2018-06-29 2019-05-27 Lithium ion secondary battery WO2020003846A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN201980041983.4A CN112335091B (en) 2018-06-29 2019-05-27 Lithium ion secondary battery
JP2020527295A JP7027648B2 (en) 2018-06-29 2019-05-27 Lithium ion secondary battery

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2018-125016 2018-06-29
JP2018125016 2018-06-29

Publications (1)

Publication Number Publication Date
WO2020003846A1 true WO2020003846A1 (en) 2020-01-02

Family

ID=68986433

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2019/020847 WO2020003846A1 (en) 2018-06-29 2019-05-27 Lithium ion secondary battery

Country Status (3)

Country Link
JP (1) JP7027648B2 (en)
CN (1) CN112335091B (en)
WO (1) WO2020003846A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115832605A (en) * 2021-12-01 2023-03-21 宁德时代新能源科技股份有限公司 Diaphragm, battery module, battery pack, and electric device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008282739A (en) * 2007-05-11 2008-11-20 Tdk Corp Electrochemical device, and its manufacturing method
JP2009218105A (en) * 2008-03-11 2009-09-24 Nec Tokin Corp Stacked battery and manufacturing method therefor
JP2016143550A (en) * 2015-02-02 2016-08-08 株式会社デンソー Zigzag-folded laminate structure of secondary battery and battery module

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009157263A1 (en) * 2008-06-23 2009-12-30 シャープ株式会社 Lithium ion secondary battery
JP5413945B2 (en) * 2008-08-08 2014-02-12 Ｎｅｃエナジーデバイス株式会社 Multilayer laminated nonaqueous electrolyte secondary battery
JP2013211156A (en) * 2012-03-30 2013-10-10 Tdk Corp Lithium ion secondary battery
CN104051792B (en) * 2014-07-03 2016-03-09 宁德新能源科技有限公司 The preparation method of non-rectangle laminated cell
JP6875820B2 (en) * 2016-10-17 2021-05-26 株式会社カネカ Lithium ion secondary battery

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008282739A (en) * 2007-05-11 2008-11-20 Tdk Corp Electrochemical device, and its manufacturing method
JP2009218105A (en) * 2008-03-11 2009-09-24 Nec Tokin Corp Stacked battery and manufacturing method therefor
JP2016143550A (en) * 2015-02-02 2016-08-08 株式会社デンソー Zigzag-folded laminate structure of secondary battery and battery module

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115832605A (en) * 2021-12-01 2023-03-21 宁德时代新能源科技股份有限公司 Diaphragm, battery module, battery pack, and electric device
CN115832605B (en) * 2021-12-01 2023-10-10 宁德时代新能源科技股份有限公司 Separator, battery module, battery pack, and electricity-using device

Also Published As

Publication number Publication date
JPWO2020003846A1 (en) 2021-06-24
CN112335091B (en) 2023-10-27
CN112335091A (en) 2021-02-05
JP7027648B2 (en) 2022-03-02

Similar Documents

Publication Publication Date Title
JP5954674B2 (en) Battery and battery manufacturing method
WO2012042830A1 (en) Nonaqueous electrolyte secondary battery
JP2007335307A (en) Nonaqueous electrolyte battery
JP5441143B2 (en) Lithium secondary battery for mobile devices
WO2017007015A1 (en) Nonaqueous electrolyte battery and battery pack
US20230275208A1 (en) Secondary battery
CN110546809B (en) Battery cell comprising sealing tape for accelerating heat conduction
JP2010097751A (en) Nonaqueous secondary battery
JP5150095B2 (en) Non-aqueous electrolyte battery
JP6279707B2 (en) Nonaqueous electrolyte battery and battery pack
CN111164817B (en) Lithium ion secondary battery
WO2015129376A1 (en) Rolled electrode set and nonaqueous-electrolyte battery
JP7198041B2 (en) battery
JP7027648B2 (en) Lithium ion secondary battery
JP7003775B2 (en) Lithium ion secondary battery
JP2020149920A (en) Lithium secondary battery
JP3700683B2 (en) Non-aqueous electrolyte secondary battery
WO2020003847A1 (en) Lithium ion secondary battery
WO2018155035A1 (en) Lithium ion battery
JP2016085884A (en) battery
JP7350761B2 (en) Nonaqueous electrolyte secondary battery, its manufacturing method, and nonaqueous electrolyte secondary battery system
WO2018135011A1 (en) Wound-type battery
JP2009295489A (en) Battery
JP7348733B2 (en) battery
WO2020184360A1 (en) Battery

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 19826679

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2020527295

Country of ref document: JP

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 19826679

Country of ref document: EP

Kind code of ref document: A1