DESCRIPTION
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`TITLE OF INVENTION: SECONDARYBATTERYPOSITIVE ELECTRODEAND
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`SECONDARYBATTERY
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`TECHNICAL FIELD
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`(6001)
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`The present disclosure relates to a positive electrode for a secondarybatteryard 4
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`secondarybattery.
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`BACKGROUND ART
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`[3002]
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`tfi
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`19
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`A positive electrode for a secondary battery m which an mfermediate layer mainly
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`imcluding an alunupum oxide is formed between acurrent collector anda muxture layer has
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`ws si
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`been known (see Patent Literature 1, and the ke}. The mtermediate layer disclosed in
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`Patent Literature | has a thickness of I pamto 3 pum and includes an ahinunumoxide, a
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`conductive material, and a bimder.
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`Patent Literature 1 has described that it 1s possible fo
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`suppress the heat cenerated by the redox reaction befween a positive electrode active
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`material and an ahuminuimcurrent collector while mamtamme good current collectability.
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`CITATION LIST
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`PATENT LITERATURE
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`{G003]
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`PATENT LITERATURE1: Japanese Unexanuned Patent Apphcation Publication No.
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`ba Lf
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`2016-127000
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`SUMMARY
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`[004]
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`

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`iis important to suppress heat generation when an abnormality such as an mtermal
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`short circuit cecurs in a secondarybattery such as a ithina: ion battery. The technology
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`disclosed in Patent Literature | is expected to have the above effect, butthere 1s roomfor
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`mprovement in the suppression ofheat generation when an mternal short circuit occurs.
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`tfi
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`Th addition,if is an important subject fo suppress gas generation during high temperature
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`storage in a secondarybattery.
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`{G005]
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`The positive electrode for a secondarybattery according to one aspect of the present
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`disclosure comprises a current collector, an intermediate layer formed on at least one
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`surface of the current collector, and a mixture layer formed on the intermediate layer.
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`The intermediate layer includes metal compoundparticles, a conductive agent, and a
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`binder, and the metal compound particles are composed of at least one selected froma
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`sulfate, hydroxide, and oxide ofan alkaline earth metal or alkah metal.
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`{G006]
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`si
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`The secondarybattery according to one aspect of the present disclosure comprises
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`the above positive electrode, a negative electrode, and an electrolyte.
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`{O007]
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`The positive electrode for a secondary battery accarding to one aspect of the present
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`disclosure can suppress heat generation when an internal short circuit of the battery occurs
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`and gax generation during hioh temperature storage.
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`BRIEF DESCRIPTION OF DRAWINGS
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`{G008]
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`FIG, 1 is a sectional viewof a secondarybattery according to an example ofthe
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`enrbodimient.
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`FIG, 2 1s a sectional view ofa positive electrode according to an exanyde of the
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`embodiment.
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`ko
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`

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`FIG. 3 1s a sectional viewofa positive electrode according io another example of the
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`embodiment,
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`DESCRIPTION OF EMBODIMENTS
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`tfi
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`{G009]
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`As described above, if ix an important issue to suppress heat generation when an
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`imternal short circuit of the battery occurs and gas generation durme high temperature
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`storage uta secondarybattery such as a lithium ion battery.
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`In order to salve such
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`problems, the present mventors have focused on the mitermediate layer of the positive
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`19
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`electrode interposed between the positive electrode current collector and the positive
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`electrode nuxture layer and have performedintensive investigations. As a resnif, it was
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`found that the above heat ceneration and gas generation are suppressed by providing an
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`intermediate layer mainly incladme metal compoundparticles that are composedofat least
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`one selected from a sulfate, hydroxide, and oxide of an alkalime earth metal or alkali metal.
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`ws si
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`{G010]
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`Whenan internal short circuit of the secondarybattery occurs, it is considered that
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`the intermediate layer mainly mchiding the above metal compound particles will suppress
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`the redox reaction between the positive electrode current collector and the positive
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`electrode active material to suppress heat generation of the battery.
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`In addition, when the
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`secondarybatteryis left in a high temperature environment for along time, fluoric acid
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`produced in the battery promotes decomposition of an electrolyte to cause gas generation,
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`but #is considered that the above metal compound particles efficiently capture the fluoric
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`acid fo suppress gas generation.
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`fG012]
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`Hereinafter an example of the embodiment of the positive electrode for a secondary
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`battery and the secondarybattery according to the present disclosure wul be describest in
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`detail. Hereinafter, a cylindrical battery m which a wound electrode body 14 is housed m
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`a cylindrical battery case is exemplified, and the electrode assembly is not limited to the
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`1
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`'
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`“abd
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`

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`wound type, and may be a lammate in which a plurality of positive electrodes anda
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`plurality of negative electrodes are alternately laminated one by ove via a separator.
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`Tn
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`addition, ihe secondary battery according to the present disclosure may be a rectangular
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`battery having a rectangular metal case, acoin battery having a coin-shaped metal case, or
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`the hke, and a laminated battery including an extenor body being composed of a laminate
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`sheet mceluding a metal layer and a resin layer.
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`{O012]
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`FG. 1 is a sectional viewof a secondary battery 10 according to an example of
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`the embodiment. As dhuistrated m FIG. 1, the secondarybattery 10 mechudes an electrode
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`assembly 14. aelectrolyte, and a battery case 15 that houses the electrode assembly 14
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`and the electrolyte. The electrode assembly 14 includes a positive electrode 11, a
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`negative electrode 12, and a separator 13, and has a wound stricture in which the positive
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`electrode 11 and the negative electrode 12 are wound via the separator 13. A battery
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`case 15 ix composed of a bottomed cylindrical exterior can 16 and a sealing assembly 17
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`si
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`that closes the openme of the exterior can 16. The secondary baftery 10 may be a
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`secondary battery using an aqueous electrolyte, or may be a secondary battery using 2
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`non-aqueous electrolyte. Heremafter, the secondary battery 10 will be described as a
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`bon-aqueous electrolyte secondary battery such as @ lithium ton battery using a non-
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`aqueous electrolyte.
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`[0013]
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`A non-aqueous electrolyte mchudes a non-aqueous solvent and an electrolyte salt
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`dissolved m the non-aqueous solvent.
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`For example, esters, ethers, nitriles, amudes, and a
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`nuxed solvent of fwo or more thereof mav be used as the non-aqueous solvent.
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`The non-aqueous solvent may contam a halogen substitute such as a fluorcethylene
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`carbonate in whichat least a part of hydrogen of these solvents is substituted with a
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`halogen atom such as fluaerme. The non-aqueous electrolyte is not linuted to a liquid
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`electrolyte, and may be a solid electrolyte. A lithrumsalt such as LiPFs is usedas the
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`electrolyte salt.
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`

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`{O01 4]
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`The secondary battery 10 includes insulating plates 18 and 19 arranged above and
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`below the electrode assembly I4, respectively.
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`in the example shown in FIG. 1, a
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`positive electrode lead 20 attached ta the positive electrode 11] extends to the side of the
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`sealing assembly 17 through the through hole of the msulating plate 18. and a negative
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`electrode lead 21 attached to the negative electrode 12 extends to the bottom: side ofthe
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`exterior can 16 through the outside of the msulating plate 19. The positive electrode
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`lead 20 is connected to the lowersurface of a bottom plate 23 ofthe sealing assembly17,
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`by weldme or fhe ke, and a cap 27, which is a top plate of the sealing assembly 17
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`19
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`electrically connected fo the bottom plate 23, serves as a positive electrode termunal,
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`The negative electrode lead 21 is connected to the mner surface of botiomof the exterior
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`can 16 by welding or the like, and the exterior can 16 serves as a begative electrode
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`termmial.
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`{G015]
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`ws si
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`The exterior can 16 18, for example, a mefal confamer with a bottomed cylindrical
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`shape. A gasket 28 1s provided between the exterior can 16 and the sealing assembly 17
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`to ensure the sealability inside the battery. The exterior can 16 has a projecting portion
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`22 for supporting the sealing assembly 17, m which a part of the side surface of the
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`exterior can 16 protrudes mpvard. The projectmg portion 22 is preferably formed in an
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`annular shape along the circumferential direction of the exterior can 16, and the sealing
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`assembly17 is supported on the upper surface thereof.
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`{G016]
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`The sealing assembly 17 has a structure in which a bottomplate 23, a lower vent
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`member 24, an isulating member 25, an upper vent member 26, and a cap 27 are
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`lsmmnated in this order from the electrode assembly 14 side. Each member constituting
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`the sealing assembly 17 has a disk shape or rmg shape, for example, and each member
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`except the msulatmea member 25 is electrically connected each other The lower vent
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`member 24 and the upper vent member 26 are connected together at then respectrve
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`1
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`'
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`LAT
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`

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`central portions, and the imsulating member 25 is mterposed between the respective
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`peripheral portions. When the internal pressure of the batteryrises due to abnormal heat
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`generation, the lower vent member 24 is deformed and broken so as to push the upper
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`vent member 26 toward the cap 27 side, and the current path between the lower vent
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`member 24 and the upper vent member 26 1s blocked. When the mternal pressure
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`further rises, the upper vent member 26 is broken and gas is discharged from the opening
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`of the cap 27.
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`[G017]
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`Hereinafter, the pasifive electrode 11, the negative electrode 12, and the separator
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`19
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`13 constituting the electrode assembly 14, particularly the positive electrode 1 will be
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`described m detail.
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`[G018]
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`{Positive Electrode}
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`FIG.2 is a sectional view of the positive electrode 11 according to an example of
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`ws si
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`the embodiment. As exemplified m FIG. 2, the positive electrode 1] comprises: a
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`positive electrode current collector 30; an mtermediate layer 32 formed on at least one
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`surface of the positive electrode current collector 30; and a positive electrode nuxture layer
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`31 formed on the utermediate layer 32. The intermediate layer 32 1s preferably formed
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`on both sides of the positive electrode current collector 30. The positive electrode
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`mixture layer 31 mehides a positive electrode active material, a conductive agent, and a
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`binder, and is formed on both sides of the positive electrode current collector 30 via the
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`intermediate layer 32. The surface of the positive electrode current collector 30 may have
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`an area im which the intermediate layer 32 is not formed, and imthis area, the positive
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`electrode mrxture layer 31 1s formed directly on the positive electrode current collector 30,
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`{OO19]
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`The positive electrode 11 is produced by applying the intermediate Jayer shinry on
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`both sides of the pasitive electrode current collector 30, drymg the coating filmto formthe
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`intermediate layer 32, and then formung a positive electrode mixture layer 31 on the
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`

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`uermediate layer 32. The positive electrode mixture laver 31 is formed on both sides of
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`the positive electrode current collector 30 via the mtermeciate layer 32 by applying onto
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`the intermediate layer 32 a posttive electrode nuxtie slurrymichiding a positive electrade
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`active material, a conductive agent, a binder, and the like, drying the coating film, and then
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`tfi
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`conipressing the coating film.
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`[GG20]
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`A foil of a metal stable in the potential range of the positive electrode 11 such as
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`aliminuni or ahimununi alloy, a film im which the metal is disposed on the surface, or the
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`like can be used as the postirve electrode current collecfor 30. The content of ahumumin
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`im the positive electrode current collector 30 is 50% or more, preferably 70% or more,
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`and more preferably 80%or more with respect to fhe mass of the current collector The
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`preferable positive electrode current collector 30 is a metal foil consisting of alumunum or
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`an alummumalloy and has a thickness of 5 pamto 20 uum.
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`{0021}
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`si
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`A lithtum-contamung transifion metal composite oxide containing transition metal
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`elements such as Co, Mn, and Ni
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`is used as the positive electrode active material.
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`Examples of the lithram-contaiing transition metal composite oxide mehide Li.CoOh,
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`LixNiOo, LixMnOQ», LiCosNirdb, LisCoyMis, LisNiaMyO:, LiineOs, LiMo.
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`yM,O4, LiMPOs., and LioMPOgF (M: at least one of the group consisting of Na, Mg, Se, Y,
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`~
`Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and BhQ <x < 12, 0<y<00 202
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`lA be Nad3).
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`These maybe used singly or m combmation of two or more.
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`(0022)
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`Examples of the conductive agent meluded in the positive electrode mixture layer
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`31 inchide carbon materials such as carbon black (CB), acetvlene black {AB}, ketyen black,
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`and graphite. Examples ofthe binder inchided in the positive electrode mixture layer 31
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`include fluorme resms such as polytetrafluoroethylene {PTFE} and polyvinylidene fluoride
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`(PVdF), polyacrylonitniie (PAN), polyimide resins, acrylic resins, and polyolefin resins.
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`In addition, these resms may be used in combination with carboxvmethylicellulose (CMC)
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`vd
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`

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`or a salt thereof, or polyethylene oxide (PEOQ}. These maybe used singly or in
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`combination of hwo or miare.
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`[0023]
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`As described above, the intermediate layer 32 1s interposed between the positrve
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`electrode current collector 30) and the positive electrode mrxture layer 31. The
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`untermediate laver 32 meludes the metal compound particles 35, the conductive agent 36,
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`and a bimder, and is composed of fhe metal compound particles 35 as the maim component.
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`The main component means a conmpanent with the highest mass among the constituent
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`materials of the intermediate layer 32. When only metal compound particles 35 are used
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`19
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`as inorganic particles, the content of the metal compoundparticles 35 1s preferably 70 to
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`99% by mass, more preferably 80 to 95%by mass, and particularly preferably 90 to 97%
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`bymass, with respect to the mass ofthe mtermeciate layer 32. The thickness of the
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`intermediate layer 32 1s not particularlylinuted, but is preferably | um to 10 pm or | pm
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`to 3 pan.
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`ws si
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`[6024]
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`The metal compound particles 35 are particles that are composed of at least one
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`selected from a sulfate, hydroxide, and oxide of an alkaline earth metal (Be, Mg. Ca, Sr, Ba,
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`Ra} or an alkaline metal (Li, Na, K. Rb, Sc, Fr}. Provision of the imtermediate layer 32
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`mamily including the metal compoundparticles 33 can significantly suppress heat
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`generation when an internal short circuit occurs and gas generation durmg high
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`temperature storage or durmg the charge-and-discharge cycle. When a positive electrode
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`curent collector 30 mainly including aluminum is used, the redox reaction between the
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`positive electrode current collector 30 and the hthnun-contaming metal composite oxide
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`maycause significant heat generation, but the mtermeciate layer 32 separates the positive
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`electrode current collector 30 fromthe positive electrode mixture layer 31, thereby
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`suppressing the heat generated by the redox reaction.
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`Inaddition, the metal compound
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`particles 35 are considered to efficiently capture the fhioneacid that causes gas generation.
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`[3023]
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`

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`The alkaline earth metal and alkalme metal contamed m the metal compound
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`particles 35 are preferably Mg. Ca, Sr, Ba, and Li, andparticularly preferably Mz, Ba, and
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`Li. Examples of the preferable metal compound particles 34 miclude at least one selected
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`from barrum sulfate particles (BaSOxparticles}, magnesium hydroxide particles (Me(OH)2
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`tfi
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`parlicles), magnesnunoxide particles (gO particles), and lthrumoxide particles (LicO
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`particles}.
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`In the mtermediate laver 32, one type of metal compound particles 35 may be
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`used singly or two or more types of mefal compound particles 35 maybe used in
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`combination.
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`[0026]
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`The volume-based median diameter (D50) of the metal compound particles 35 is,
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`for exarnple, 0.05 umto 2 pm, ands preferably O.1 pmto lum. The median diameter of
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`the metal compound particles 35is a particle size at which the vohune integratedvalue ix
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`50%in the particle size distribution measured byfhe laser diffraction scaffermg method.
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`In addition, the aspect ratio of metal compound particles 35 is 2 or more, for example.
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`si
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`The aspect ratio of the metal conmpoundparticle 35 1s calenlated by observing the crass
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`section of a negative electrode with a scanning electron microscope (SEM) and averaging
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`the geometryanalysis results of 100 particles randomly selected from the resultant SEM
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`image.
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`[0027]
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`The Mohs hardness of the metal compound particles 35 1s, for example, 7 ar less, or
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`Sorless.
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`Flexible particles with low Mohs hardness may increase the flexibility of the
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`intermediate layer 32 and improve the bending resistance of the positive electrode 11.
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`The method of measuring Mohs hardness 1s as follows {the same applies fo metal
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`phosphate particles 37 described below}.
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`{O028]
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`iMethod of Measuring Mchs Hardness}
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`The metal compound particles 35 are rubbed with each of mmerals used as a class
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`ip the 10-stage Mohs hardness meter MH-10 manufactured by YAGAMI INC., and then
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`

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`the presence or absence of scratches is observed for the metal compound particles 35 and
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`each of the minerals ua particular class. When both the metal compound particles 35
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`and the minerals m a particular class are scratched or not scratched, the Mohs hardness of
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`the metal compound particles 35 is determuned ta be the same class as the minerals inthe
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`particular class.
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`In addition, mthe minerals in all classes, when either the metal
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`ccunpound particles 35 or the minerals in a particular class is scratched, the Mohs hardness
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`of the metal conypound particles 35 1s determmed to be the vahie 0.3 higher than the class
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`afthe mimeral ofthe highest class that did not scratch the metal compoundparticles 35
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`aniong all minerals.
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`{G029]
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`One that is the same as the conductive agent apphed fo the positrve electrode
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`mixture layer 31 can be used as the conductive agent 36 mcluded in the intermediate layer
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`32, for example, conducting particles such as CB, AB, ketjen black, and graphite. The
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`conductive agent 36 attaches to the surface of the metal compound particles 35 by the
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`si
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`bmder and forms a conductrve path in the mtermediate layer 32. The content of the
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`conductive agent 36 ix preferably 0.5 to 10%5 by mass, and more preferably | to 3%by
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`mass, with respect to the mass of the intennediate layer 32. When the content of the
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`conductive agent 36 1s within this range, a good conductive path will be formed imthe
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`intermediate layer 32.
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`0030]
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`One that is fhe same as the conductive agent applied to the postfrve electrode
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`nuxture layer 31 can be used as the binder mcluded m the intermediate layer 32, for
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`example flnonne resms such as PTFEand PVdF, PAN, polyimide resim, acrylic resin, and
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`polyolefin resin. Ofthese, PVdF is preferable. The content of the binder is preferably
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`0.1 to 10% by mass, and more preferably | to 3%5 by mass, with respect to the mass ofthe
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`unfermediate layer 32. The contents ofthe metal compound particles 35, the conductive
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`agent 36, and the binderin the mtermediate laver 32 are determined by observing the crass
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`- }G-
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`

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`section of the intermediate Inyer 32 with a scanning electron microscope (SEM) ora
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`transmission electron microscope (TEM) and element mapping.
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`16031]
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`FRG. 3 35 asectional view of another example ofthe embodiment. The
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`unfermediate layer 32 exeniplified in FIG. 3 differs from the form exemplified m FIG. 2 m
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`that the metal compound particles 35 and metal phosphate particles 37 are inchided as
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`morganic parhcles. The combination of the metal compound particles 35 and the metal
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`phosphate particles 37 improves the effect of suppressing heat generation when an mternal
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`short circuat occurs m fhe battery and the effect of suppressing gas generation durmeg high
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`19
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`temperature storage. The mass ratio of the metal conmpound particles 35 to the metal
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`phosphate particles 37 is not particularly limited. An example of such mass ratios 1s 1]
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`: 9
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`to9:toard:6te6:4. The contents of the metal compound particles 35 and metal
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`phosphate particles 37 may be the same as each other. When the intermediate layer 32
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`icludes the metal phosphate particles 37, the content is, for example, 5 to 90% by mass
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`si
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`with respect to fhe mass of the mtermediate layer 32.
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`In FIG. 3, the metal phosphate
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`particles 37 are shown m a smaller size than the metal compound particles 35, but the
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`relationship between both particle sizes is not particularly limited.
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`{G032]
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`The metal phosphate particles 37 included in the intermediate layer 32 are
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`preferably nonferrous metal phosphates.
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`Specific examples ofthe nonferrous metal
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`phosphates include LisPOs, LIPON, LeHPOs, LiHaPOs, NazPOs, NasHPOs, NaHzPOg,
`
`47xPOahs, ZPCAPOQs}s, HrPO4)3, KsPOs, KSHPOg, KHgPOg, Cas(POd)o, CaHPOs,
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`Mas(POwh, MeHPOs, LICLLisPaQhe, LiCl-LiyPsOre, LiCh-LiPOs, LiC}-Lin0-P205, LpO-
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`P2OQs, Agl-AgPOs, Cul-CuPOQs, PbFo-MnF2-AlPOs)3, Agi-AprO-P25, AIPOs, and
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`ba Lf
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`Mi(POgh)-30.
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`{G033]
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`Preferable examples of the metal phosphate particles 37 include at least one selected
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`irom Inhiamphosphate particles (Lis PO. particles), lnhium hydrogen phosphate particles
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`-}}-
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`

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`(LeHPdOy particles), aluminum phosphate particles (AIPOg particles), and manganese
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`phosphate hydrate particles (Vins(PO4)>-3H20 particles}.
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`In the uvtermediate layer 32, one
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`mietal phosphate particles 37 may be used smaly, or hwo or more metal phosphate particles
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`37 maybe used in combination.
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`tfi
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`{0034]
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`An example of the vofume-based median diameter (D0) of the metal phosphate
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`particles 37 1s 0.05 pmto 2 um, and is preferably O.1 mito i jen.
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`In addrtion, the aspect
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`ratio of the metal phosphate particles 37 is 2 or more, for example. The Mohs hardness of
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`the metal phosphate particles 37 1s, for exanyple, 7 or less, or Sor idess. The metal
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`19
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`phosphate particles 37 may have the same median diameter, aspect ratio, and Mohs
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`hardness as the metal conmpoundparticles 35.
`
`{G035
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`Asdescribed above, the intermediate laver 32 can be formed by applyme onto the
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`surface of the positive electrode current collector 30 an mtermediate lever shury inchiding
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`ws si
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`the metal compound particles 35, the metal phosphate particles 37, the conductive agent 36,
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`and a binder, and then drying the coating film. The dispersion medinun of the
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`intermediate layer slurry is not particularly limited, but a preferable example ts N-methy1-
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`2-pyrrolidone (NMP). The intermediate layer 32 1s formed on the surface of the positive
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`electrode current collector 30 ai a surface density of, for example, 0.1 o/m* to 20 afm”.
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`[3036]
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`The mtermediate layer 32 may melude morgamic particles other than the metal
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`compound particles 35 and the metal phosphate particles 37, as lang as the cbyect of the
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`present disclosure is not impaired. Examples of the morganic particles mclide morgamic
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`compmuids with lower oxidizing power than Iithnm-contamung transition metal oxides,
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`specifically a manganese oxide, silicon dioxide, titanium dioxide, and aluminumoxide.
`
`{G037]
`
`{Negative Electrode]
`
`A negative electrode 12 comprises a negative electrode current collector and a
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`-}?-
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`

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`negative electrode mixture layer formed on at least one surface of the negatrve electrode
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`current collector. A foil of a metal stable in the potential range ofthe negative electrode
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`12 such as copper or copper alloy, a film in which the metal is disposed onthe surface, or
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`the like can be usedas the negative electrode current collector.
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`Preferably, the negative
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`electrode mixture layer includes a negative electrode active material snd a binder, and is
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`formed on both sides of the negative electrode current collector. The negative electrode
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`[2 can be produced by applyime a negative electrode mixfure shury incindme a negative
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`electrode actrve material and a bmder onto a negative electrode current collector, drymeg
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`the coating film, and then compressing fo form the negative electrode nuxture layer on
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`19
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`both sides of the negative electrode current collector.
`
`{G038]
`
`The negative electrode active material ix not particularly limited as long as it can
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`reversibly infercalate and demtercalate lithram:
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`ions, and a carbon material such as
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`eraphite is generally used. The graphite may be any of natural graphite such as flake
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`ws si
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`craphite, lump craphite, and earth graphite and artrficial graphite such as lumpartificial
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`graphite and oraphrtized mesophase carbon microbeads.
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`In addition, as the negative
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`electrode active material, metals such as Si and Sn that are alloyed with Li, metal
`
`compounds meluding Si and Sn, and Iithnim titanium composite oxides may be used
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`The Si-containmgs compound represented by S10, (0.5 < x < 1.6} may be used in
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`combination with a carbon material such as graphite.
`
`[0039]
`
`As a binder mchnled in the negative electrode nuxture laver, fluorme-contaming
`
`resin such as PYFE and PVdF, PAN, polyimide, acrylic resin, and polyolefins may be
`
`used as in the case of the positive electrode 11, but stvrene-butadiene rubber (SBR} is
`
`preferably used.
`
`In addition, the negative electrode mixture layer mayinclude CMCor
`
`a salt thereof, palvacrylic acid (PAA)or a4 salt thereof, PVA, or the hke. The negative
`
`electrode nuxture layer 41 meludes, for example, SBR and CMCora salt thereof.
`
`[O04]
`
`V
`
`i
`
`pee Lod
`
`

`

`{Separator}
`
`As a separator 13, a porous sheet having ion permeability and insulating property
`
`isused.
`
`Specific examples of the porous sheet inchide a nueroporous thin film, a woven
`
`fabric, and a non-woven fabric. As the material of the separator, polyolefins such as
`
`tfi
`
`polyethylene and polypropylene, cellulose, and the bke are suitable. The separator 13
`
`may have asingle-layer structure or a lamunated structure.
`
`In addition, on the surface of
`
`the separator 13, a resm layer havme high heat resistance such as an aramid resm ora
`
`iller layer meluding a filler of an morgaruc compound maybe provided.
`
`EXAMPLES
`
`{G041]
`
`Hereinafter,
`
`the present disclosure will be further described with reference to
`
`examples, but the present disclosure is not lunited to these examples.
`
`{e042}
`
`si
`
`<Exanmiple b>
`
`{Production of Positive Electrode]
`
`95 parts by mass of barium sulfate (BaSQ,) with a D50 of 0.2 pam and an aspect
`
`ratio of 2, 2 parts by mass of acetylene black (AB}, and 3 parts by mass ofpolyvinylidene
`
`fuoride (PVdF) were nuxed to prepare a particle mixture. Therealter, the particle
`
`mixture was added to N-methyl-2-pyrolidone (NMP} and was stirred fo prepare an
`
`intermediate layer slurry. The shurry was applied onto both sides of the positive electrade
`
`current collector consisting of aluminum foil having a thickness of 15 pum and the coating
`
`film was dned to form an mtermediate laver having a thickness of 3 um.
`
`0043]
`
`A Ithram-contaimine fransition metal oxide represented by LiNigsCog2Mne302 was
`
`used a8 a positive electrode active material. A positive electrode active material, AB, and
`
`PVdF were nuxed ma solid content mass ratio of 97 : 2 : 1 to prepare a positive electrode
`
`mixture slurry with NMP as a dispersion mednun. Thereafter, the positive electrode
`
`-]4-
`
`

`

`mixture slurry was applied onto both sides of the postive electrode current collector on
`
`which the intermediate laver was formed, the coating film was dried, and the cnatuie film
`
`was conipressed to forma positive electrode nuxhire layer on both sides ofthe current
`
`collector via the intermediate layer. The current collector was cut into apredetermined
`
`tfi
`
`electrode size io produce a positive electrode.
`
`[e044]
`
`{Production of Negative Electrode}
`
`Graphite powder, sodium salt of CMC, and dispersion of SBR were mumed at a solid
`=:-
`
`: 0.7 : 0.6 to prepare a negative electrode nuxture shury with
`
`content mass ratio of 98.7
`
`19
`
`water as a dispersion medium. Thereafter, the negative electrode mixture slurry was
`
`applied onto both sides of the negative electrode current collector consisting of copper foul,
`
`the coating film was dried, and the coating film was eampressed to form a negative
`
`electrode mixture layer on both sides of the current collector. The current collector was
`
`ct into a predetermined electrode size to produce a negative electrode.
`
`ws si
`
`{G045]
`
`{Preparation of Non-Aqueous Electrolyte]
`
`Ethylene carbonate (EC), efhyl methyl carbonate (EMC), and dimethyl carbonate
`
`(DMC) were nuxed in a volume ratio of 3: 3:4. LiPFs was dissolved m the nuxed
`
`solvent so as to obtarma concentration of 1.2 mol/L to prepare a non-aqueons electrolyte.
`
`[O046]
`
`{Production of Battery]
`
`An alumimun lead was attached to the above pasttive electrode, a nickel lead was
`
`attached fo fhe above negative electrode, and fhe positive electrode and the negative
`
`electrode were spirally wound via a polyethylene separatorto produce a woundelectrode
`
`assembly. The electrode assembly was accommodated m a bottomed cylindrical battery
`
`case body having an outer diameter of 18.2 nun and a height of 65 mm, the above non-
`
`aqueons electrolyte solution was myected therein, the openma of the battery case body was
`
`1
`
`rl
`
`pee ai
`
`

`

`sealed with a gasket and a sealme assembly to produce a cylindrical non-aqueous
`
`electrolyte secondarybattery.
`
`[0047]
`
`<Example 2>
`
`tfi
`
`Apositive electrode and a secondarybattery were produced mi the same manneras
`
`im Example 1, except that magnesium hydroxide (Mo{OH}2) with a DS6 of 0.05 am and an
`
`aspect ratio of 3 was used instead of BaSO, m preparation of the intermediate layer sharry.
`
`[O048]
`
`<Example 3>
`
`A positive electrode and a secondarybattery were produced in the sare mamner as
`
`im Example 1, except that magnesiumoxide (MoO) with a D40of 0.5 um and an aspect
`
`ratio of 5 was used instead of BaSOs in preparation of the intermediate layer shirrv.
`
`{O049]
`
`<Exaniple 4>
`
`si
`
`A positive electrode and a secondarybattery were produced in the same mammeras
`
`in Example 1, except that lithtum oxide (LigO) with a DSO of 2 pun and an aspect ratia of 2
`
`was used mstead of BaSOs in preparation of the intermediate layer slurrv.
`
`{C050}
`
`<Exaniple 53>
`
`A positive electrode and a secondarybattery were produced im the same manneras
`
`in Example 1, except that BaSOs used in Example | andlithram phosphate (LisPOs) with a
`
`DS50 of 0.5 pam and an aspect ratio af 2 were mixed in a mass ratic of 1: 9 and the resultant
`
`nuxtire was used as morganic particles m preparation of the mtermediate layerslurry.
`
`[0051]
`
`<Example 6>
`
`A positive electrode and a secondarybattery were produced in the same maimmer as
`
`in Example 2, except that MeO used in Example 2 and lithrumhydrogen phosphate
`
`(LpeHPO,) with a DSO of 0.5 pumand an aspect ratio of 2 were mixed im a mass ratio of 9:
`
`-}6-
`
`

`

`i and the resultant? mixture was used as morganic particles m preparation of the
`
`unermediate laver slurry.
`
`{0082]
`
`<Example 7>
`
`tfi
`
`Apositive electrode and a secondarybattery were produced mi the same manneras
`
`uz Example 1, except that BaSO, used in Example 1 and aluminum phosphate (AiPOs}
`
`with a D50 of 0.5 pumand an aspect ratio of 3 were mixed in a mass ratio of 1: I and the
`
`resultant mixture was used as imorgzanic particles im preparation of the mtermeciiate layer
`
`slurry.
`
`19
`
`{C053}
`
`<Exaniple §>
`
`A positive electrode and a secondarybattery were produced in the same manneras
`
`in Example 1, except that BaSQ, used in Example | and manganese phosphate hydrate
`
`(Mans{POs)>-3H2O} with a DS0 of 0.5 jum and an aspect ratio of 2 were mixed in a mass
`
`ws si
`
`ratio of 8: 1 andthe resultant mixture was used as morganicparticles m preparation of the
`
`intermediate layer shurry.
`
`(0054)
`
`<Comparative Example I>
`
`A positive electrode and a secondarybattery were produced in the same mammeras
`
`in Example 1, except that no intermediate layer was formed in production of the positive
`
`electrode.
`
`{e055}
`
`<Comparative Example 2>
`
`A positive electrode and a secondary battery were produced im the same manneras
`
`in Example 1, except that aluminumoxide (AbOs} with s D50 of 0.1 pmand an aspect
`
`ratio of ] was used instead of BaSO, mm preperation of the intermediate layer shury.
`
`{G0S6]
`
`{Nating Test (Measurement of Battery Termperature}|
`
`-j7-
`
`

`

`Rachofthe batteries mthe examples and comparative examples was charged to the
`
`end-of-charge voliage of 4.2with a constant current of 0.3C, and then charged to the
`
`current value of 0.05C with a consiant vollage of4.2V. Under the 25°C environment, a
`
`round nail pierced to the center of the side of the chargedbattery, the round nail was
`
`tfi
`
`stopped piereme at the moment when the round nail completely penetrated the battery, and
`
`the temperature on the side of the battery was measured after one numute.
`
`{G0S7]
`
`iTest of High Temperature Storage (Measurement of Amount of Gas Generated}]
`
`Eachofthe batteries m the examples and comparat