WO2022210443A1 - Lithium secondary battery - Google Patents

Lithium secondary battery Download PDF

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Publication number
WO2022210443A1
WO2022210443A1 PCT/JP2022/014729 JP2022014729W WO2022210443A1 WO 2022210443 A1 WO2022210443 A1 WO 2022210443A1 JP 2022014729 W JP2022014729 W JP 2022014729W WO 2022210443 A1 WO2022210443 A1 WO 2022210443A1
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Prior art keywords
secondary battery
lithium secondary
positive electrode
aluminum
negative electrode
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PCT/JP2022/014729
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French (fr)
Japanese (ja)
Inventor
慎吾 松本
滝太郎 山口
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住友化学株式会社
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Publication of WO2022210443A1 publication Critical patent/WO2022210443A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys

Definitions

  • the present invention relates to lithium secondary batteries. This application claims priority based on Japanese Patent Application No. 2021-059724 filed in Japan on March 31, 2021, the content of which is incorporated herein.
  • Patent Document 1 describes a negative electrode composed of a negative electrode active material for a secondary battery, which is a porous aluminum alloy and contains at least one of silicon and tin. ing.
  • the metal negative electrode described in Patent Document 1 generally has a problem that the cycle retention rate tends to decrease.
  • the present invention has been made in view of the above circumstances, and an object thereof is to provide a lithium secondary battery in which the cycle retention rate is less likely to decrease.
  • the present invention includes the following [1] to [6].
  • a lithium secondary battery having an electrode group including a negative electrode, an electrolyte, and a positive electrode, wherein the negative electrode is a laminate in which a plurality of metal foils are laminated, and the metal foil is composed of lithium and A lithium secondary battery consisting of metals capable of forming alloys.
  • the metal foil contains one or more metals selected from the group consisting of Al, Sn, Si, Ge and Pb.
  • the metal foil is made of aluminum or an alloy thereof with a purity of 99% by mass or more.
  • FIG. 1 is a schematic cross-sectional view showing an example of a lithium secondary battery
  • FIG. 1 is a schematic cross-sectional view showing an example of a lithium secondary battery
  • FIG. 1 is a schematic cross-sectional view showing an example of a lithium secondary battery
  • Lithium secondary battery A lithium secondary battery according to the present embodiment will be described.
  • the lithium secondary battery of this embodiment has an electrode group including a negative electrode, an electrolyte, and a positive electrode.
  • Lithium secondary batteries include non-aqueous electrolyte secondary batteries using an electrolytic solution as an electrolyte. Further, a solid electrolyte type secondary battery using a solid electrolyte as the electrolyte can be mentioned.
  • FIG. 1 shows a schematic diagram of a cross section of a lithium secondary battery 1.
  • a lithium secondary battery 1 has an electrode group 14 having a positive electrode 11 , a negative electrode 12 , and an electrolytic solution 13 .
  • the positive electrode 11 has a positive electrode lead 21 and the negative electrode 12 has a negative electrode lead 22 .
  • the electrode group 14 is housed in the exterior body 30 .
  • the lithium secondary battery 1 may have a separator 16 between the positive electrode 11 and the negative electrode 12 .
  • the negative electrode 12 is a laminate having a two-layer structure in which metal foils 12a and 12b, which are a plurality of metal foils, are laminated.
  • the metal foil 12a and the metal foil 12b are in close contact with each other and can be electrically connected.
  • the metal foil 12a and the metal foil 12b are not glued or joined but are directly superimposed.
  • the metal foil 12a and the metal foil 12b are preferably the same metal foil.
  • the same metal foil means that the metal composition and the thickness are the same.
  • the thickness of the negative electrode 12 is preferably 5 ⁇ m or more, more preferably 6 ⁇ m or more, and even more preferably 7 ⁇ m or more. Moreover, it is preferably 200 ⁇ m or less, more preferably 190 ⁇ m or less, and particularly preferably 180 ⁇ m or less.
  • the above upper limit and lower limit can be combined arbitrarily.
  • the thickness of the negative electrode 12 is preferably 5 ⁇ m or more and 200 ⁇ m or less, more preferably 6 ⁇ m or more and 190 ⁇ m or less, and particularly preferably 7 ⁇ m or more and 180 ⁇ m or less.
  • the number of metal foils forming the laminate may be increased within the range in which the thickness of the negative electrode 12 is the thickness described above.
  • the negative electrode 12 may be a laminate having a three-layer structure further including a metal foil 12c (not shown).
  • the negative electrode 12 is, for example, a laminate of 2 to 5 layers, a laminate of 2 to 4 layers, or a laminate of 2 to 3 layers.
  • the thickness of the negative electrode may be measured using a thickness gauge or vernier calipers.
  • the thickness of the negative electrode means the average value when the thickness of the negative electrode is measured at five points.
  • the negative electrode 12 expands and contracts with charging and discharging. The stress generated at this time may cause the negative electrode 12 to break, resulting in poor conduction. Once broken, it becomes impossible to conduct.
  • the negative electrode 12 is a laminate in which a plurality of metal foils are laminated, even if the metal foil 12a is broken, for example, the metal foil 12b can compensate for current collection. Since the plurality of metal foils are not adhered or joined, for example, breakage occurring in the metal foil 12a is less likely to be transmitted to the metal foil 12b.
  • FIG. 2 shows a schematic diagram of a cross section of the lithium secondary battery 2 .
  • the lithium secondary battery 2 has an electrode group 15 including a positive electrode 11a, a positive electrode 11b, a negative electrode 12, and an electrolytic solution 13. As shown in FIG.
  • the positive electrode 11a and the positive electrode 11b are provided with a positive electrode lead 21, and the negative electrode 12 is provided with a negative electrode lead 22, respectively.
  • the electrode group 15 is housed in the exterior body 30 .
  • the lithium secondary battery 2 may include a separator 16a between the positive electrode 11a and the metal foil 12a, and a separator 16b between the positive electrode 11b and the metal foil 12b.
  • This embodiment is the same as the first embodiment except that a negative electrode 12 is provided between a pair of positive electrodes 11a and 11b.
  • stress is applied to the negative electrode 12 from the respective directions of the positive electrode 11a and the positive electrode 11b due to charging and discharging.
  • the negative electrode 12 is a laminate of a plurality of metal foils, the metal foils 12a and 12b can be independently deformed to relieve stress. Therefore, breakage is less likely to occur.
  • the metal foil consists of a metal capable of forming an alloy with lithium.
  • the metal foil preferably contains one or more metals selected from the group consisting of Al, Sn, Si, Ge and Pb.
  • metal foils include high-purity aluminum foil, high-purity tin foil, high-purity silicon foil, high-purity germanium foil, and high-purity lead foil.
  • the metal foil is preferably made of aluminum or its alloy with a purity of 99% or more.
  • Al metal foil an aluminum foil with a purity of 99% or more and a metal foil made of an alloy of aluminum with a purity of 99% or more may be referred to as "Al metal foil”.
  • the term "aluminum alloy with a purity of 99% or higher” means an alloy with an aluminum content of 99% or higher.
  • Aluminum used for Al metal foil is demonstrated.
  • Aluminum has a purity of 99% by mass or more, preferably 99.9% by mass or more, more preferably 99.95% by mass or more, and particularly preferably 99.99% by mass or more.
  • refining methods for purifying aluminum to the above purity include a segregation method and a three-layer electrolysis method.
  • the segregation method is a purification method that utilizes the segregation phenomenon during solidification of molten aluminum, and a plurality of methods have been put into practical use.
  • the segregation method there is a method of pouring molten aluminum into a container, heating the upper molten aluminum while rotating the container, and solidifying refined aluminum from the bottom while stirring. Aluminum with a purity of 99% by mass or more can be obtained by the segregation method.
  • Three-Layer Electrolysis Method As one form of the three-layer electrolysis method, first, aluminum or the like (for example, a grade of about 1 according to JIS-H2102 with a purity of 99% by mass) is put into the Al—Cu alloy layer. Thereafter, the molten state is used as an anode, and an electrolytic bath containing, for example, aluminum fluoride and barium fluoride is placed thereon to deposit high-purity aluminum on the cathode. High-purity aluminum with a purity of 99.999% by mass or more can be obtained by the three-layer electrolysis method.
  • aluminum or the like for example, a grade of about 1 according to JIS-H2102 with a purity of 99% by mass
  • an electrolytic bath containing, for example, aluminum fluoride and barium fluoride is placed thereon to deposit high-purity aluminum on the cathode.
  • High-purity aluminum with a purity of 99.999% by mass or more can be obtained by the three-layer electrolysis method.
  • the refining method for purifying aluminum is not limited to the segregation method and the three-layer electrolysis method, but other known methods such as the zone melting refining method and the ultra-high vacuum dissolution method may be used.
  • Aluminum alloy Al metal foil may be an aluminum alloy containing aluminum.
  • Elements to be added to aluminum for alloying are selected from the group consisting of Ca, Sr, Ba, Ra, Ni, Mn, Zn, Cd, Pb, Si, Ge, Sn, Ag, Sb, Bi, In and Mg. One or more selected are preferred.
  • Metals of Group 14 of the periodic table are particularly preferable, silicon or tin is preferable, and silicon is more preferable.
  • the content of the metal of Group 14 of the periodic table contained in the total amount of the aluminum alloy is preferably 0.1% by mass or more, and 0.2% by mass or more. is more preferable, and 0.3% by mass or more is even more preferable.
  • the content of metals of Group 14 of the periodic table contained in the total amount of the aluminum alloy is 1.0% by mass or less, more preferably 0.9% by mass or less, and even more preferably 0.8% by mass or less.
  • the above upper limit and lower limit can be arbitrarily combined.
  • the content of the group 14 metal of the periodic table contained in the total amount of the aluminum alloy is preferably 0.1% by mass or more and 1.0% by mass or less, more preferably 0.2% by mass or more and 0.9% by mass or less, 0.3% by mass or more and 0.8% by mass or less is particularly preferable.
  • the aluminum alloy has a total content of aluminum, metals of Group 14 of the periodic table, and metal components other than Ca, Sr, Ba, Ra, Ni, Mn, Zn, Cd, Ag, Sb, Bi, In, and Mg. It is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.01% by mass or less, relative to the total amount of the alloy.
  • the Al metal foil can be manufactured by a manufacturing method including a casting process, a foil processing process, and a heat treatment process in this order.
  • ⁇ Casting process In the casting process, for example, aluminum is melted at about 680 ° C. or higher and 800 ° C. or lower, and a generally known cleaning process (for example, vacuum treatment of molten alloy) is performed to remove gas and non-metallic inclusions. .
  • a generally known cleaning process for example, vacuum treatment of molten alloy
  • the vacuum treatment is performed, for example, at a temperature of 700° C. to 800° C., 1 hour to 10 hours, and a degree of vacuum of 0.1 Pa to 100 Pa.
  • a treatment for cleaning the alloy a treatment of blowing flux, inert gas, or chlorine gas into the molten aluminum can also be used.
  • the molten alloy that has been cleaned by vacuum treatment or the like is usually cast in a mold to obtain an aluminum ingot.
  • a mold made of iron or graphite heated to 50° C. or more and 200° C. or less is used.
  • Aluminum is cast by a method of pouring molten alloy at a temperature of 680° C. or more and 800° C. or less into a mold.
  • An ingot can also be obtained by continuous casting, which is generally used.
  • An aluminum alloy can be obtained by adding a predetermined amount of a metal element such as a metal of Group 14 of the periodic table during melting in the casting process described above.
  • the obtained aluminum ingot or aluminum alloy ingot is subjected to rolling, extrusion, forging, or the like to be processed into a foil-shaped raw material for Al metal foil.
  • hot rolling and cold rolling are performed to process the aluminum ingot or aluminum alloy ingot into a foil shape.
  • the temperature conditions for hot rolling include, for example, setting the temperature of an aluminum ingot or an aluminum alloy ingot to 350° C. or higher and 450° C. or lower.
  • the aluminum ingot or aluminum alloy ingot is repeatedly processed until it reaches the target thickness under the condition that the processing rate r is 2% or more and 20% or less.
  • an intermediate annealing treatment may be performed before cold rolling.
  • a hot-rolled aluminum ingot or aluminum alloy ingot may be heated to 350° C. or higher and 450° C. or lower, and immediately allowed to cool after the temperature rise.
  • the aluminum ingot or aluminum alloy ingot may be allowed to cool after being held for about 1 to 5 hours.
  • Cold rolling is performed, for example, at a temperature below the recrystallization temperature of an aluminum ingot or an aluminum alloy ingot, usually from room temperature to 80°C or less, and with a single-pass die, the working rate r is 1% or more and 10% or less. The condition is repeated until the aluminum ingot reaches the desired thickness.
  • the metal foil raw material obtained in the foil processing process is heat-treated to obtain a metal foil having an oxide film on its surface.
  • the heat treatment step can be performed under an air atmosphere or an oxygen atmosphere.
  • the oxygen concentration may be controlled to 0.1% or more and 3% or less in a nitrogen atmosphere.
  • the heat treatment temperature in the heat treatment step is preferably 200° C. or higher and 600° C. or lower, more preferably 250° C. or higher and 550° C. or lower, and particularly preferably 350° C. or higher and 500° C. or lower.
  • the heat treatment time of the heat treatment step is preferably 60 minutes or more and 1200 minutes or less, more preferably 120 minutes or more and 600 minutes or less, and particularly preferably 180 minutes or more and 480 minutes or less.
  • the positive electrode can be manufactured by first preparing a positive electrode mixture containing a positive electrode active material, a conductive material, and a binder, and supporting the positive electrode mixture on a positive electrode current collector.
  • lithium-containing compound or other metal compound As the positive electrode active material, a lithium-containing compound or other metal compound can be used.
  • lithium-containing compounds include lithium-cobalt composite oxides having a layered structure, lithium-nickel composite oxides having a layered structure, lithium-manganese composite oxides having a spinel structure, and lithium iron phosphate having an olivine structure.
  • Other metal compounds include, for example, oxides such as titanium oxide, vanadium oxide or manganese dioxide, or sulfides such as titanium sulfide or molybdenum sulfide.
  • a carbon material can be used as the conductive material of the positive electrode.
  • Examples of carbon materials include graphite powder, carbon black (eg, acetylene black), and fibrous carbon materials. Carbon black is fine and has a large surface area. Therefore, by adding a small amount to the positive electrode mixture, the conductivity inside the positive electrode can be increased, and the charge/discharge efficiency and output characteristics can be improved. On the other hand, if too much carbon black is added, both the binding force between the positive electrode mixture and the positive electrode current collector and the binding force inside the positive electrode mixture due to the binder are lowered, causing an increase in internal resistance.
  • the ratio of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.
  • a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, it is possible to reduce the proportion of the conductive material in the positive electrode mixture.
  • thermoplastic resin can be used as the binder of the positive electrode.
  • thermoplastic resins include polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), ethylene tetrafluoride/propylene hexafluoride/vinylidene fluoride. fluororesins such as copolymers, propylene hexafluoride/vinylidene fluoride copolymers and tetrafluoroethylene/perfluorovinyl ether copolymers; and polyolefin resins such as polyethylene and polypropylene.
  • thermoplastic resins may be used in combination of two or more.
  • a fluororesin and a polyolefin resin are used as a binder, and the ratio of the fluororesin to the entire positive electrode mixture is 1% by mass or more and 10% by mass or less, and the ratio of the polyolefin resin is 0.1% by mass or more and 2% by mass or less. It is possible to obtain a positive electrode mixture having both high adhesion to the current collector and high bonding strength inside the positive electrode mixture.
  • a strip-shaped member made of a metal material such as Al, Ni, or stainless steel can be used as the positive electrode current collector of the positive electrode.
  • a metal material such as Al, Ni, or stainless steel
  • As the current collector it is preferable to use Al as a forming material and process it into a thin film because it is easy to process and inexpensive.
  • the positive electrode mixture As a method of supporting the positive electrode mixture on the positive electrode current collector, there is a method of pressure-molding the positive electrode mixture on the positive electrode current collector.
  • the positive electrode mixture is made into a paste using an organic solvent, and the obtained positive electrode mixture paste is applied to at least one side of a positive electrode current collector, dried, and pressed to adhere, thereby forming a positive electrode on the positive electrode current collector.
  • a mixture may be supported.
  • organic solvents that can be used include amine-based solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether-based solvents such as tetrahydrofuran; ketone-based solvents such as methyl ethyl ketone; ester solvents such as dimethylacetamide, amide solvents such as N-methyl-2-pyrrolidone;
  • Examples of methods for applying the positive electrode mixture paste to the positive electrode current collector include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spraying.
  • a positive electrode can be manufactured by the method described above.
  • separator for example, a material having a form such as a porous film, nonwoven fabric, or woven fabric made of polyolefin resin such as polyethylene or polypropylene, fluororesin, nitrogen-containing aromatic polymer, or the like can be used. Moreover, the separator may be formed using two or more of these materials, or the separator may be formed by laminating these materials.
  • the air permeability resistance according to the Gurley method defined in JIS P 8117 must be 50 seconds/100 cc or more and 300 seconds/100 cc or less. It is preferably 50 seconds/100 cc or more and more preferably 200 seconds/100 cc or less.
  • the porosity of the separator is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less.
  • the separator may be a laminate of separators with different porosities.
  • the electrolytic solution contains an electrolyte and an organic solvent.
  • Electrolytes contained in the electrolytic solution include LiClO 4 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiN ( SO2CF3 )( COCF3 ) , Li ( C4F9SO3 ), LiC(SO2CF3)3 , Li2B10Cl10 , LiBOB ( where BOB is bis(oxalato)borate ), LiFSI (where FSI is bis(fluorosulfonyl)imide), lower aliphatic carboxylic acid lithium salts, LiAlCl4 and other lithium salts, and mixtures of two or more thereof may be used.
  • the electrolyte is at least selected from the group consisting of LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 and LiC(SO 2 CF 3 ) 3 containing fluorine. It is preferred to use one containing one.
  • organic solvent contained in the electrolytic solution examples include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one and 1,2-dioxolan-2-one.
  • Carbonates such as (methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran and 2- ethers such as methyltetrahydrofuran; esters such as methyl formate, methyl acetate, propyl propionate and ⁇ -butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide.
  • Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propanesultone, or those obtained by further introducing a fluoro group into these organic solvents (hydrogen contained in organic solvents one or more atoms of which are substituted with fluorine atoms) can be used.
  • the electrolyte may contain additives such as tris (trimethylsilyl) phosphate and tris (trimethylsilyl) borate.
  • the organic solvent it is preferable to use a mixture of two or more of these.
  • a mixed solvent containing carbonates is preferable, and a mixed solvent of a cyclic carbonate and a non-cyclic carbonate and a mixed solvent of a cyclic carbonate and an ether are more preferable.
  • a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable as the mixed solvent of the cyclic carbonate and the non-cyclic carbonate.
  • An electrolytic solution using such a mixed solvent has a wide operating temperature range, does not easily deteriorate even when charged and discharged at a high current rate, and does not easily deteriorate even when used for a long time.
  • an electrolytic solution containing a fluorine-containing lithium salt such as LiPF 6 and an organic solvent having a fluorine substituent from the viewpoint of enhancing the safety of the resulting lithium secondary battery.
  • Mixed solvents containing fluorine-substituted ethers such as pentafluoropropylmethyl ether and 2,2,3,3-tetrafluoropropyldifluoromethyl ether and dimethyl carbonate retain their capacity even when charged and discharged at a high current rate. It is more preferable because of its high retention rate.
  • the cycle retention rate is less likely to decrease means that the value of the cycle retention rate measured by the method below is in the range of 90% or more and 100% or less.
  • Cycle retention rate (%) Discharge capacity at 80th cycle (mAh/g)/Discharge capacity at 2nd cycle (mAh/g) x 100
  • Example 1 [Preparation of negative electrode]
  • the silicon-aluminum alloy used in Example 1 was produced by the following method. High-purity aluminum (purity: 99.99% by mass or more) and high-purity chemical silicon (purity: 99.999% by mass or more) are heated to 760 ° C. and held to reduce the silicon content to 1.0 mass. % aluminum-silicon alloy melt. Next, the molten alloy was held at a temperature of 740° C. and a degree of vacuum of 50 Pa for 2 hours for cleaning. The molten alloy was cast in a cast iron mold (22 mm ⁇ 150 mm ⁇ 200 mm) dried at 150° C. to obtain an ingot.
  • Rolling was performed under the following conditions. After both surfaces of the ingot were chamfered by 2 mm, cold rolling was performed from a thickness of 18 mm at a reduction ratio of 99.6%. The thickness of the obtained rolled material was 100 ⁇ m.
  • the negative electrode 12 was manufactured by laminating the aluminum negative electrode 12a and the aluminum negative electrode 12b. Negative electrode leads were connected to the aluminum negative electrode 12a and the aluminum negative electrode 12b, respectively. The negative electrode lead is drawn out of the outer package 30 and combined together outside.
  • lithium cobalt oxide product name: Cellseed, manufactured by Nippon Kagaku Kogyo Co., Ltd., average particle size (D50): 10 ⁇ m
  • 5 parts by mass of polyvinylidene fluoride manufactured by Kureha Co., Ltd.
  • a conductive material 5 parts by mass of acet
  • the obtained electrode mixture is coated in a sheet, and the coated electrode mixture is dried at 60° C. for 2 hours and further vacuum-dried at 150° C. for 10 hours to obtain N-methyl-2- Pyrrolidone was volatilized.
  • the coating amount of the positive electrode active material after drying was 21.5 mg/cm 2 .
  • the sheet thickness was 50 ⁇ m.
  • the obtained sheet was cut out to manufacture positive electrodes 11a and 11b each having a length of 50 mm and a width of 50 mm.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • a negative electrode 12 was placed between a pair of positive electrodes 11a and 11b with a polyethylene porous separator interposed therebetween, and housed in a laminate film package. After that, the above electrolytic solution was injected, and the laminate film of the outer package was sealed to produce a film laminate type lithium secondary battery 10 .
  • Example 2 A lithium secondary battery 11 was produced in the same manner as in Example 1, except that the positive electrode 11a and the negative electrode 12 were arranged via a polyethylene porous separator.
  • a lithium secondary battery 12 was fabricated in the same manner as in Example 1, except that a single-layer aluminum negative electrode having a thickness of 100 ⁇ m was used as the negative electrode 12 .

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Abstract

Provided is a lithium secondary battery having an electrode group including an anode, an electrolyte, and a cathode, wherein the anode is a laminated body formed by laminating multiple sheets of metal foil, and the metal foil is made of a metal that can form an alloy together with lithium.

Description

リチウム二次電池lithium secondary battery
　本発明は、リチウム二次電池に関する。
　本願は、２０２１年３月３１日に、日本に出願された特願２０２１－０５９７２４号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to lithium secondary batteries.
This application claims priority based on Japanese Patent Application No. 2021-059724 filed in Japan on March 31, 2021, the content of which is incorporated herein.
　リチウム二次電池を構成する負極について、従来の負極材料である黒鉛よりも理論容量が大きい材料を用い、電池性能を向上させる検討が行われている。このような材料として、黒鉛と同様に、例えばリチウムイオンを吸蔵可能及び放出可能な金属材料が注目されている。 　Concerning the negative electrode that constitutes the lithium secondary battery, studies are being conducted to improve battery performance by using a material that has a larger theoretical capacity than graphite, which is the conventional negative electrode material. As such materials, similar to graphite, metallic materials capable of intercalating and deintercalating lithium ions, for example, have attracted attention.
　金属材料から形成された負極の例として、例えば特許文献１には、多孔質のアルミニウム合金であり、シリコン又はスズの少なくとも１種を含む二次電池用負極活物質から構成される負極が記載されている。 As an example of a negative electrode made of a metal material, for example, Patent Document 1 describes a negative electrode composed of a negative electrode active material for a secondary battery, which is a porous aluminum alloy and contains at least one of silicon and tin. ing.
特開２０１１－２２８０５８号公報JP 2011-228058 A
　特許文献１に記載されている金属負極は、一般的にサイクル維持率が低下しやすいという課題がある。
　本発明は上記事情に鑑みてなされたものであって、サイクル維持率が低下しにくいリチウム二次電池を提供することを目的とする。 The metal negative electrode described in Patent Document 1 generally has a problem that the cycle retention rate tends to decrease.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a lithium secondary battery in which the cycle retention rate is less likely to decrease.
　本発明は以下の［１］～［６］を包含する。
［１］負極と、電解質と、正極とが備えられた電極群を有するリチウム二次電池であって、前記負極は複数の金属箔を重ね合わせた積層体であり、前記金属箔は、リチウムと合金を形成することが可能である金属からなる、リチウム二次電池。
［２］前記金属箔は、Ａｌ、Ｓｎ、Ｓｉ、Ｇｅ及びＰｂからなる群より選択される１種以上の金属を含む、［１］に記載のリチウム二次電池。
［３］前記金属箔は純度が９９質量％以上のアルミニウム又はその合金からなる、［１］に記載のリチウム二次電池。
［４］前記複数の金属箔は同一の金属箔である、［１］～［３］のいずれか１つに記載のリチウム二次電池。
［５］前記負極と前記正極との間にセパレータを備える、［１］～［４］のいずれか１つに記載のリチウム二次電池。
［６］前記負極の両面に、セパレータを介して前記正極がそれぞれ配置されている、［５］に記載のリチウム二次電池。 The present invention includes the following [1] to [6].
[1] A lithium secondary battery having an electrode group including a negative electrode, an electrolyte, and a positive electrode, wherein the negative electrode is a laminate in which a plurality of metal foils are laminated, and the metal foil is composed of lithium and A lithium secondary battery consisting of metals capable of forming alloys.
[2] The lithium secondary battery according to [1], wherein the metal foil contains one or more metals selected from the group consisting of Al, Sn, Si, Ge and Pb.
[3] The lithium secondary battery according to [1], wherein the metal foil is made of aluminum or an alloy thereof with a purity of 99% by mass or more.
[4] The lithium secondary battery according to any one of [1] to [3], wherein the plurality of metal foils are the same metal foil.
[5] The lithium secondary battery according to any one of [1] to [4], comprising a separator between the negative electrode and the positive electrode.
[6] The lithium secondary battery according to [5], wherein the positive electrodes are arranged on both sides of the negative electrode with separators interposed therebetween.
　本発明によれば、サイクル維持率が低下しにくいリチウム二次電池を提供することができる。 According to the present invention, it is possible to provide a lithium secondary battery whose cycle retention rate is less likely to decrease.
リチウム二次電池の一例を示す断面の模式図である。1 is a schematic cross-sectional view showing an example of a lithium secondary battery; FIG. リチウム二次電池の一例を示す断面の模式図である。1 is a schematic cross-sectional view showing an example of a lithium secondary battery; FIG.
＜リチウム二次電池＞
　本実施形態のリチウム二次電池について説明する。 <Lithium secondary battery>
A lithium secondary battery according to the present embodiment will be described.
［全体構成］
　本実施形態のリチウム二次電池は、負極と、電解質と、正極とが備えられた電極群を有する。
　リチウム二次電池としては、電解質として電解液を用いた非水電解液型二次電池が挙げられる。また、電解質として固体電解質を用いた固体電解質型二次電池が挙げられる。 [overall structure]
The lithium secondary battery of this embodiment has an electrode group including a negative electrode, an electrolyte, and a positive electrode.
Lithium secondary batteries include non-aqueous electrolyte secondary batteries using an electrolytic solution as an electrolyte. Further, a solid electrolyte type secondary battery using a solid electrolyte as the electrolyte can be mentioned.
≪第１実施形態≫
　図１に、リチウム二次電池１の断面の模式図を示す。
　リチウム二次電池１は、正極１１、負極１２、及び電解液１３を備える電極群１４を有する。正極１１は、正極リード２１を、負極１２は負極リード２２をそれぞれ備える。
　電極群１４は外装体３０に収容されている。 <<First embodiment>>
FIG. 1 shows a schematic diagram of a cross section of a lithium secondary battery 1. As shown in FIG.
A lithium secondary battery 1 has an electrode group 14 having a positive electrode 11 , a negative electrode 12 , and an electrolytic solution 13 . The positive electrode 11 has a positive electrode lead 21 and the negative electrode 12 has a negative electrode lead 22 .
The electrode group 14 is housed in the exterior body 30 .
　リチウム二次電池１は、正極１１と負極１２との間にセパレータ１６を備えていてもよい。 The lithium secondary battery 1 may have a separator 16 between the positive electrode 11 and the negative electrode 12 .
　負極１２は、複数の金属箔である金属箔１２ａと金属箔１２ｂとを重ね合わせた２層構造の積層体である。金属箔１２ａと金属箔１２ｂとは、密着しており、導通が可能である。金属箔１２ａと金属箔１２ｂとは、接着又は接合されておらず、直接重ね合わされている。 The negative electrode 12 is a laminate having a two-layer structure in which metal foils 12a and 12b, which are a plurality of metal foils, are laminated. The metal foil 12a and the metal foil 12b are in close contact with each other and can be electrically connected. The metal foil 12a and the metal foil 12b are not glued or joined but are directly superimposed.
　金属箔１２ａと、金属箔１２ｂとは同一の金属箔であることが好ましい。ここで、「同一の金属箔」とは、金属の組成と、厚みがそれぞれ同一であることを意味する。 The metal foil 12a and the metal foil 12b are preferably the same metal foil. Here, "the same metal foil" means that the metal composition and the thickness are the same.
　負極１２の厚みは、５μｍ以上が好ましく、６μｍ以上がより好ましく、７μｍ以上がさらに好ましい。また、２００μｍ以下が好ましく、１９０μｍ以下がより好ましく、１８０μｍ以下が特に好ましい。 The thickness of the negative electrode 12 is preferably 5 µm or more, more preferably 6 µm or more, and even more preferably 7 µm or more. Moreover, it is preferably 200 μm or less, more preferably 190 μm or less, and particularly preferably 180 μm or less.
　上記上限値及び下限値は任意に組み合わせることができる。
　負極１２の厚みは、５μｍ以上２００μｍ以下が好ましく、６μｍ以上１９０μｍ以下がより好ましく、７μｍ以上１８０μｍ以下が特に好ましい。 The above upper limit and lower limit can be combined arbitrarily.
The thickness of the negative electrode 12 is preferably 5 μm or more and 200 μm or less, more preferably 6 μm or more and 190 μm or less, and particularly preferably 7 μm or more and 180 μm or less.
　積層体を構成する金属箔の数は、負極１２の厚みが上記の厚みとなる範囲内において、増加させてもよい。
　例えば、負極１２は、さらに不図示の金属箔１２ｃを備える３層構造の積層体であってもよい。 The number of metal foils forming the laminate may be increased within the range in which the thickness of the negative electrode 12 is the thickness described above.
For example, the negative electrode 12 may be a laminate having a three-layer structure further including a metal foil 12c (not shown).
　負極１２は、例えば２層以上５層以下の積層体、２層以上４層以下の積層体、２層以上３層以下の積層体である。 The negative electrode 12 is, for example, a laminate of 2 to 5 layers, a laminate of 2 to 4 layers, or a laminate of 2 to 3 layers.
　負極の厚みは、シックネスゲージ又はノギスを用いて測定すればよい。
　負極の厚みとは、負極について、厚みを５点測定したときの平均値を意味する。 The thickness of the negative electrode may be measured using a thickness gauge or vernier calipers.
The thickness of the negative electrode means the average value when the thickness of the negative electrode is measured at five points.
　充電及び放電に伴い、負極１２は膨張及び収縮する。このときに生じる応力により、負極１２は破断し、導電不良が生じうる。一度破断してしまうと導通不能となってしまう。 The negative electrode 12 expands and contracts with charging and discharging. The stress generated at this time may cause the negative electrode 12 to break, resulting in poor conduction. Once broken, it becomes impossible to conduct.
　リチウム二次電池１は、負極１２が複数の金属箔を重ね合わせた積層体であるため、例えば金属箔１２ａに破断が生じたとしても金属箔１２ｂにより集電を補うことができる。複数の金属箔は接着又は接合されていないため、例えば金属箔１２ａに生じた破断が金属箔１２ｂに伝わりにくい。 In the lithium secondary battery 1, since the negative electrode 12 is a laminate in which a plurality of metal foils are laminated, even if the metal foil 12a is broken, for example, the metal foil 12b can compensate for current collection. Since the plurality of metal foils are not adhered or joined, for example, breakage occurring in the metal foil 12a is less likely to be transmitted to the metal foil 12b.
≪第２実施形態≫
　図２に、リチウム二次電池２の断面の模式図を示す。
　リチウム二次電池２は、正極１１ａ、正極１１ｂ、負極１２、電解液１３を備える電極群１５を有する。正極１１ａと正極１１ｂは正極リード２１を、負極１２は負極リード２２をそれぞれ備える。
　電極群１５は外装体３０に収容されている。 <<Second embodiment>>
FIG. 2 shows a schematic diagram of a cross section of the lithium secondary battery 2 .
The lithium secondary battery 2 has an electrode group 15 including a positive electrode 11a, a positive electrode 11b, a negative electrode 12, and an electrolytic solution 13. As shown in FIG. The positive electrode 11a and the positive electrode 11b are provided with a positive electrode lead 21, and the negative electrode 12 is provided with a negative electrode lead 22, respectively.
The electrode group 15 is housed in the exterior body 30 .
　リチウム二次電池２は、正極１１ａと金属箔１２ａとの間にセパレータ１６ａを、正極１１ｂと金属箔１２ｂとの間にセパレータ１６ｂをそれぞれ備えていてもよい。 The lithium secondary battery 2 may include a separator 16a between the positive electrode 11a and the metal foil 12a, and a separator 16b between the positive electrode 11b and the metal foil 12b.
　一対の正極１１ａ及び正極１１ｂの間に、負極１２を備える点が相違する以外は、第１実施形態と同様である。 This embodiment is the same as the first embodiment except that a negative electrode 12 is provided between a pair of positive electrodes 11a and 11b.
　第２実施形態の場合、充電及び放電に伴い、負極１２には、正極１１ａ及び正極１１ｂのそれぞれの方向から応力がかかる。この場合、負極１２が複数の金属箔の積層体であると、金属箔１２ａ及び１２ｂが独立して変形して応力を緩和できる。このため破断が生じにくくなる。 In the case of the second embodiment, stress is applied to the negative electrode 12 from the respective directions of the positive electrode 11a and the positive electrode 11b due to charging and discharging. In this case, if the negative electrode 12 is a laminate of a plurality of metal foils, the metal foils 12a and 12b can be independently deformed to relieve stress. Therefore, breakage is less likely to occur.
（金属箔）
　金属箔は、リチウムと合金を形成することが可能である金属からなる。
　金属箔は、Ａｌ、Ｓｎ、Ｓｉ、Ｇｅ及びＰｂからなる群より選択される１種以上の金属を含むことが好ましい。具体的には、金属箔は高純度アルミニウム箔、高純度スズ箔、高純度シリコン箔、高純度ゲルマニウム箔、及び高純度鉛箔が挙げられる。 (metal foil)
The metal foil consists of a metal capable of forming an alloy with lithium.
The metal foil preferably contains one or more metals selected from the group consisting of Al, Sn, Si, Ge and Pb. Specifically, metal foils include high-purity aluminum foil, high-purity tin foil, high-purity silicon foil, high-purity germanium foil, and high-purity lead foil.
　本実施形態において、金属箔は純度が９９％以上のアルミニウム又はその合金からなる金属箔であることが好ましい。以下において、純度９９％以上のアルミニウム箔及び純度９９％以上のアルミニウムの合金からなる金属箔を「Ａｌ金属箔」と記載する場合がある。
　本明細書において、「純度９９％以上のアルミニウムの合金」とは、アルミニウムの含有率が９９％以上である合金を意味する。 In this embodiment, the metal foil is preferably made of aluminum or its alloy with a purity of 99% or more. Hereinafter, an aluminum foil with a purity of 99% or more and a metal foil made of an alloy of aluminum with a purity of 99% or more may be referred to as "Al metal foil".
As used herein, the term "aluminum alloy with a purity of 99% or higher" means an alloy with an aluminum content of 99% or higher.
・アルミニウム
　Ａｌ金属箔に用いるアルミニウムについて説明する。
　アルミニウムは、純度が９９質量％以上であり、９９．９質量％以上が好ましく、９９．９５質量％以上がより好ましく、９９．９９質量％以上が特に好ましい。
　アルミニウムを上記の純度まで高純度化する精錬方法として、例えば偏析法および三層電解法を例示できる。 - Aluminum Aluminum used for Al metal foil is demonstrated.
Aluminum has a purity of 99% by mass or more, preferably 99.9% by mass or more, more preferably 99.95% by mass or more, and particularly preferably 99.99% by mass or more.
Examples of refining methods for purifying aluminum to the above purity include a segregation method and a three-layer electrolysis method.
・・偏析法
　偏析法は、アルミニウム溶湯の凝固の際の偏析現象を利用した純化法であり、複数の手法が実用化されている。偏析法の一つの形態としては、容器の中に溶湯アルミニウムを注ぎ、容器を回転させながら上部の溶湯アルミニウムを加熱、撹拌しつつ底部より精製アルミニウムを凝固させる方法がある。偏析法により、純度９９質量％以上のアルミニウムを得ることができる。 Segregation method The segregation method is a purification method that utilizes the segregation phenomenon during solidification of molten aluminum, and a plurality of methods have been put into practical use. As one form of the segregation method, there is a method of pouring molten aluminum into a container, heating the upper molten aluminum while rotating the container, and solidifying refined aluminum from the bottom while stirring. Aluminum with a purity of 99% by mass or more can be obtained by the segregation method.
・・三層電解法
　三層電解法の一つの形態としては、まず、Ａｌ－Ｃｕ合金層に、アルミニウム等（例えば純度９９質量％のＪＩＳ－Ｈ２１０２の時１種程度のグレード）を投入する。その後、溶融状態で陽極とし、その上に例えばフッ化アルミニウムおよびフッ化バリウム等を含む電解浴を配置し、陰極に高純度のアルミニウムを析出させる方法である。
　三層電解法では純度９９．９９９質量％以上の高純度アルミニウムを得ることができる。 Three-Layer Electrolysis Method As one form of the three-layer electrolysis method, first, aluminum or the like (for example, a grade of about 1 according to JIS-H2102 with a purity of 99% by mass) is put into the Al—Cu alloy layer. Thereafter, the molten state is used as an anode, and an electrolytic bath containing, for example, aluminum fluoride and barium fluoride is placed thereon to deposit high-purity aluminum on the cathode.
High-purity aluminum with a purity of 99.999% by mass or more can be obtained by the three-layer electrolysis method.
　アルミニウムを高純度化する精錬方法は、偏析法、三層電解法に限定されるものではなく、帯溶融精製法、超高真空溶解性製法等、既に知られている他の方法でもよい。 The refining method for purifying aluminum is not limited to the segregation method and the three-layer electrolysis method, but other known methods such as the zone melting refining method and the ultra-high vacuum dissolution method may be used.
・アルミニウム合金
　Ａｌ金属箔はアルミニウムを含むアルミニウム合金であってもよい。合金とするためにアルミニウムに添加する元素としては、Ｃａ、Ｓｒ、Ｂａ、Ｒａ、Ｎｉ、Ｍｎ、Ｚｎ、Ｃｄ、Ｐｂ、Ｓｉ、Ｇｅ、Ｓｎ、Ａｇ、Ｓｂ、Ｂｉ、ＩｎおよびＭｇからなる群より選択される１種以上が好ましい。
　特に周期表１４族の金属が好ましく、ケイ素又はスズが好ましく、ケイ素がより好ましい。 - Aluminum alloy Al metal foil may be an aluminum alloy containing aluminum. Elements to be added to aluminum for alloying are selected from the group consisting of Ca, Sr, Ba, Ra, Ni, Mn, Zn, Cd, Pb, Si, Ge, Sn, Ag, Sb, Bi, In and Mg. One or more selected are preferred.
Metals of Group 14 of the periodic table are particularly preferable, silicon or tin is preferable, and silicon is more preferable.
　アルミニウムと周期表１４族の金属との合金とする場合には、アルミニウム合金の全量中に含まれる周期表１４族の金属の含有量は０．１質量％以上が好ましく、０．２質量％以上がより好ましく、０．３質量％以上がさらに好ましい。 In the case of an alloy of aluminum and a metal of Group 14 of the periodic table, the content of the metal of Group 14 of the periodic table contained in the total amount of the aluminum alloy is preferably 0.1% by mass or more, and 0.2% by mass or more. is more preferable, and 0.3% by mass or more is even more preferable.
　また、アルミニウム合金の全量中に含まれる周期表１４族の金属の含有量は１．０質量％以下であり、０．９質量％以下がより好ましく、０．８質量％以下がさらに好ましい。 In addition, the content of metals of Group 14 of the periodic table contained in the total amount of the aluminum alloy is 1.0% by mass or less, more preferably 0.9% by mass or less, and even more preferably 0.8% by mass or less.
　上記上限値及び下限値は任意に組み合わせることができる。アルミニウム合金の全量中に含まれる周期表１４族の金属の含有量は、０．１質量％以上１．０質量％以下が好ましく、０．２質量％以上０．９質量％以下がより好ましく、０．３質量％以上０．８質量％以下が特に好ましい。 The above upper limit and lower limit can be arbitrarily combined. The content of the group 14 metal of the periodic table contained in the total amount of the aluminum alloy is preferably 0.1% by mass or more and 1.0% by mass or less, more preferably 0.2% by mass or more and 0.9% by mass or less, 0.3% by mass or more and 0.8% by mass or less is particularly preferable.
　アルミニウム合金は、アルミニウムと、周期表１４族の金属とＣａ、Ｓｒ、Ｂａ、Ｒａ、Ｎｉ、Ｍｎ、Ｚｎ、Ｃｄ、Ａｇ、Ｓｂ、Ｂｉ、ＩｎおよびＭｇを除く金属成分の合計含有率が、アルミニウム合金の全量に対して０．１質量％以下であることが好ましく、０．０５質量％以下がより好ましく、０．０１質量％以下がさらに好ましい。 The aluminum alloy has a total content of aluminum, metals of Group 14 of the periodic table, and metal components other than Ca, Sr, Ba, Ra, Ni, Mn, Zn, Cd, Ag, Sb, Bi, In, and Mg. It is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.01% by mass or less, relative to the total amount of the alloy.
［Ａｌ金属箔の製造方法］
　Ａｌ金属箔は、鋳造工程、箔状加工工程、熱処理工程をこの順で備える製造方法により製造できる。 [Manufacturing method of Al metal foil]
The Al metal foil can be manufactured by a manufacturing method including a casting process, a foil processing process, and a heat treatment process in this order.
・鋳造工程
　鋳造工程は、例えばアルミニウムを約６８０℃以上８００℃以下で溶融し、通常知られたガスや非金属介在物を除去して清浄にする処理（例えば、合金溶湯の真空処理）を行う。 ・Casting process In the casting process, for example, aluminum is melted at about 680 ° C. or higher and 800 ° C. or lower, and a generally known cleaning process (for example, vacuum treatment of molten alloy) is performed to remove gas and non-metallic inclusions. .
　真空処理は、例えば７００℃以上８００℃以下で、１時間以上１０時間以下、真空度０．１Ｐａ以上１００Ｐａ以下の条件で行われる。 The vacuum treatment is performed, for example, at a temperature of 700° C. to 800° C., 1 hour to 10 hours, and a degree of vacuum of 0.1 Pa to 100 Pa.
　合金を清浄にする処理としては、フラックス、不活性ガスや塩素ガスを溶湯アルミニウムに吹き込む処理も利用できる。真空処理などで清浄にされた合金溶湯は、通常、鋳型にて鋳造され、アルミニウム鋳塊が得られる。
　鋳型は５０℃以上２００℃以下に加熱した鉄や黒鉛製を用いる。アルミニウムは、６８０℃以上８００℃以下の合金溶湯を鋳型に流し込む方法で鋳造する。また、一般的に利用されている連続鋳造により鋳塊を得ることもできる。 As a treatment for cleaning the alloy, a treatment of blowing flux, inert gas, or chlorine gas into the molten aluminum can also be used. The molten alloy that has been cleaned by vacuum treatment or the like is usually cast in a mold to obtain an aluminum ingot.
A mold made of iron or graphite heated to 50° C. or more and 200° C. or less is used. Aluminum is cast by a method of pouring molten alloy at a temperature of 680° C. or more and 800° C. or less into a mold. An ingot can also be obtained by continuous casting, which is generally used.
　上述の鋳造工程での溶融の際に、周期表１４族の金属等の金属元素を所定量添加することで、アルミニウム合金を得ることができる。 An aluminum alloy can be obtained by adding a predetermined amount of a metal element such as a metal of Group 14 of the periodic table during melting in the casting process described above.
・箔状加工工程
　得られたアルミニウム鋳塊又はアルミニウム合金鋳塊は、圧延加工、押出加工、鍛造加工などを施して箔状に加工することで、Ａｌ金属箔原料となる。 - Foil-shaped processing step The obtained aluminum ingot or aluminum alloy ingot is subjected to rolling, extrusion, forging, or the like to be processed into a foil-shaped raw material for Al metal foil.
　鋳塊の圧延加工においては、例えば、熱間圧延と冷間圧延とを行い、アルミニウム鋳塊又はアルミニウム合金鋳塊を箔状に加工する。
　熱間圧延を実施する温度条件は、例えば、アルミニウム鋳塊又はアルミニウム合金鋳塊を温度３５０℃以上４５０℃以下とすることが挙げられる。 In the rolling process of the ingot, for example, hot rolling and cold rolling are performed to process the aluminum ingot or aluminum alloy ingot into a foil shape.
The temperature conditions for hot rolling include, for example, setting the temperature of an aluminum ingot or an aluminum alloy ingot to 350° C. or higher and 450° C. or lower.
　圧延加工では、一対の圧延ロール間に材料を繰り返し通過させ、目標の板厚に仕上げてゆく。一対の圧延ロール間に通過させることを「パス」と記載する。
　１回のパス（１パス）当たりの加工率ｒは、圧延ロールを１回通過したときの板厚減少率であり、下記の式で算出される。
　　ｒ＝（Ｔ０－Ｔ）／Ｔ０×１００
　（Ｔ０：圧延ロール通過前の厚み、Ｔ：圧延ロール通過後の厚み） In the rolling process, the material is repeatedly passed between a pair of rolling rolls to finish it to the target thickness. Passage between a pair of rolling rolls is described as "pass".
The reduction rate r per one pass (one pass) is the thickness reduction rate when passing through the rolling rolls once, and is calculated by the following formula.
r=(T 0 −T)/T 0 ×100
(T 0 : thickness before passing through rolling rolls, T: thickness after passing through rolling rolls)
　加工率ｒが２％以上２０％以下の条件で、アルミニウム鋳塊又はアルミニウム合金鋳塊を目的の厚さとなるまで繰り返し行うことが好ましい。 It is preferable that the aluminum ingot or aluminum alloy ingot is repeatedly processed until it reaches the target thickness under the condition that the processing rate r is 2% or more and 20% or less.
　熱間圧延後、必要に応じ、冷間圧延の前に中間焼鈍処理を行ってもよい。
　中間焼鈍処理は、例えば、熱間圧延したアルミニウム鋳塊又はアルミニウム合金鋳塊を、３５０℃以上４５０℃以下に加熱、昇温後直ちに放冷してもよい。
　また、アルミニウム鋳塊又はアルミニウム合金鋳塊を１時間以上５時間以下程度保持後に放冷してもよい。 After hot rolling, if necessary, an intermediate annealing treatment may be performed before cold rolling.
In the intermediate annealing treatment, for example, a hot-rolled aluminum ingot or aluminum alloy ingot may be heated to 350° C. or higher and 450° C. or lower, and immediately allowed to cool after the temperature rise.
Alternatively, the aluminum ingot or aluminum alloy ingot may be allowed to cool after being held for about 1 to 5 hours.
　冷間圧延は、例えば、アルミニウム鋳塊又はアルミニウム合金鋳塊の再結晶温度未満の温度、通常、室温から８０℃以下で、１パスのダイスにおいては、加工率ｒが１％以上１０％以下の条件で、アルミニウム鋳塊を目的の厚さとなるまで繰り返し行われる。 Cold rolling is performed, for example, at a temperature below the recrystallization temperature of an aluminum ingot or an aluminum alloy ingot, usually from room temperature to 80°C or less, and with a single-pass die, the working rate r is 1% or more and 10% or less. The condition is repeated until the aluminum ingot reaches the desired thickness.
・熱処理工程
　箔状加工工程で得られた金属箔原料を熱処理し、表面に酸化被膜を備えた金属箔を得る。
　熱処理工程は、大気雰囲気下、酸素雰囲気下で実施できる。また、窒素雰囲気下において酸素濃度を０．１％以上３％以下に制御して実施してもよい。本実施形態においては、酸化被膜を均一に形成する観点から、大気雰囲気下で実施することが好ましく、乾燥大気であることがより好ましい。 - Heat treatment process The metal foil raw material obtained in the foil processing process is heat-treated to obtain a metal foil having an oxide film on its surface.
The heat treatment step can be performed under an air atmosphere or an oxygen atmosphere. Alternatively, the oxygen concentration may be controlled to 0.1% or more and 3% or less in a nitrogen atmosphere. In the present embodiment, from the viewpoint of forming a uniform oxide film, it is preferable to carry out the process under an air atmosphere, and more preferably a dry atmosphere.
　熱処理工程の熱処理温度は、２００℃以上６００℃以下が好ましく、２５０℃以上５５０℃以下がより好ましく、３５０℃以上５００℃以下が特に好ましい。
　熱処理工程の熱処理時間は、６０分間以上１２００分間以下が好ましく、１２０分間以上６００分間以下がより好ましく、１８０分間以上４８０分間以下が特に好ましい。 The heat treatment temperature in the heat treatment step is preferably 200° C. or higher and 600° C. or lower, more preferably 250° C. or higher and 550° C. or lower, and particularly preferably 350° C. or higher and 500° C. or lower.
The heat treatment time of the heat treatment step is preferably 60 minutes or more and 1200 minutes or less, more preferably 120 minutes or more and 600 minutes or less, and particularly preferably 180 minutes or more and 480 minutes or less.
［正極］
　正極は、まず正極活物質、導電材およびバインダーを含む正極合剤を調整し、正極合剤を正極集電体に担持させることで製造することができる。 [Positive electrode]
The positive electrode can be manufactured by first preparing a positive electrode mixture containing a positive electrode active material, a conductive material, and a binder, and supporting the positive electrode mixture on a positive electrode current collector.
（正極活物質）
　正極活物質には、リチウム含有化合物又は他の金属化合物からなるものを用いることができる。リチウム含有化合物としては、例えば、層状構造を有するリチウムコバルト複合酸化物、層状構造を有するリチウムニッケル複合酸化物、スピネル構造を有するリチウムマンガン複合酸化物及びオリビン型構造を有するリン酸鉄リチウムが挙げられる。
　また他の金属化合物としては、例えば、酸化チタン、酸化バナジウム若しくは二酸化マンガンなどの酸化物、または硫化チタン若しくは硫化モリブデンなどの硫化物が挙げられる。 (Positive electrode active material)
As the positive electrode active material, a lithium-containing compound or other metal compound can be used. Examples of lithium-containing compounds include lithium-cobalt composite oxides having a layered structure, lithium-nickel composite oxides having a layered structure, lithium-manganese composite oxides having a spinel structure, and lithium iron phosphate having an olivine structure. .
Other metal compounds include, for example, oxides such as titanium oxide, vanadium oxide or manganese dioxide, or sulfides such as titanium sulfide or molybdenum sulfide.
（導電材）
　正極が有する導電材としては、炭素材料を用いることができる。炭素材料として黒鉛粉末、カーボンブラック（例えばアセチレンブラック）、繊維状炭素材料などを挙げることができる。カーボンブラックは、微粒で表面積が大きい。このため、少量を正極合剤中に添加することにより正極内部の導電性を高め、充放電効率および出力特性を向上させることができる。一方、カーボンブラックを多く入れすぎるとバインダーによる正極合剤と正極集電体との結着力、および正極合剤内部の結着力がいずれも低下し、かえって内部抵抗を増加させる原因となる。 (Conductive material)
A carbon material can be used as the conductive material of the positive electrode. Examples of carbon materials include graphite powder, carbon black (eg, acetylene black), and fibrous carbon materials. Carbon black is fine and has a large surface area. Therefore, by adding a small amount to the positive electrode mixture, the conductivity inside the positive electrode can be increased, and the charge/discharge efficiency and output characteristics can be improved. On the other hand, if too much carbon black is added, both the binding force between the positive electrode mixture and the positive electrode current collector and the binding force inside the positive electrode mixture due to the binder are lowered, causing an increase in internal resistance.
　正極合剤中の導電材の割合は、正極活物質１００質量部に対して５質量部以上２０質量部以下であると好ましい。導電材として黒鉛化炭素繊維、カーボンナノチューブなどの繊維状炭素材料を用いる場合には、正極合剤中の導電材の割合を下げることも可能である。 The ratio of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, it is possible to reduce the proportion of the conductive material in the positive electrode mixture.
（バインダー）
　正極が有するバインダーとしては、熱可塑性樹脂を用いることができる。この熱可塑性樹脂としては、ポリフッ化ビニリデン（以下、ＰＶｄＦということがある。）、ポリテトラフルオロエチレン（以下、ＰＴＦＥということがある。）、四フッ化エチレン・六フッ化プロピレン・フッ化ビニリデン系共重合体、六フッ化プロピレン・フッ化ビニリデン系共重合体、四フッ化エチレン・パーフルオロビニルエーテル系共重合体などのフッ素樹脂；ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂；を挙げることができる。 (binder)
A thermoplastic resin can be used as the binder of the positive electrode. Examples of thermoplastic resins include polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), ethylene tetrafluoride/propylene hexafluoride/vinylidene fluoride. fluororesins such as copolymers, propylene hexafluoride/vinylidene fluoride copolymers and tetrafluoroethylene/perfluorovinyl ether copolymers; and polyolefin resins such as polyethylene and polypropylene.
　これらの熱可塑性樹脂は、２種以上を混合して用いてもよい。バインダーとしてフッ素樹脂およびポリオレフィン樹脂を用い、正極合剤全体に対するフッ素樹脂の割合を１質量％以上１０質量％以下、ポリオレフィン樹脂の割合を０．１質量％以上２質量％以下とすることによって、正極集電体との密着力および正極合剤内部の結合力がいずれも高い正極合剤を得ることができる。 These thermoplastic resins may be used in combination of two or more. A fluororesin and a polyolefin resin are used as a binder, and the ratio of the fluororesin to the entire positive electrode mixture is 1% by mass or more and 10% by mass or less, and the ratio of the polyolefin resin is 0.1% by mass or more and 2% by mass or less. It is possible to obtain a positive electrode mixture having both high adhesion to the current collector and high bonding strength inside the positive electrode mixture.
（正極集電体）
　正極が有する正極集電体としては、Ａｌ、Ｎｉ、ステンレスなどの金属材料を形成材料とする帯状の部材を用いることができる。なかでも、集電体としては、加工しやすく、安価であるという点でＡｌを形成材料とし、薄膜状に加工したものが好ましい。 (Positive electrode current collector)
A strip-shaped member made of a metal material such as Al, Ni, or stainless steel can be used as the positive electrode current collector of the positive electrode. Among them, as the current collector, it is preferable to use Al as a forming material and process it into a thin film because it is easy to process and inexpensive.
　正極集電体に正極合剤を担持させる方法としては、正極合剤を正極集電体上で加圧成型する方法が挙げられる。また、有機溶媒を用いて正極合剤をペースト化し、得られる正極合剤のペーストを正極集電体の少なくとも一面側に塗布して乾燥させ、プレスし固着することで、正極集電体に正極合剤を担持させてもよい。 As a method of supporting the positive electrode mixture on the positive electrode current collector, there is a method of pressure-molding the positive electrode mixture on the positive electrode current collector. In addition, the positive electrode mixture is made into a paste using an organic solvent, and the obtained positive electrode mixture paste is applied to at least one side of a positive electrode current collector, dried, and pressed to adhere, thereby forming a positive electrode on the positive electrode current collector. A mixture may be supported.
　正極合剤をペースト化する場合、用いることができる有機溶媒としては、Ｎ，Ｎ－ジメチルアミノプロピルアミン、ジエチレントリアミンなどのアミン系溶媒；テトラヒドロフランなどのエーテル系溶媒；メチルエチルケトンなどのケトン系溶媒；酢酸メチルなどのエステル系溶媒；ジメチルアセトアミド、Ｎ－メチル－２－ピロリドンなどのアミド系溶媒；が挙げられる。 When the positive electrode mixture is made into a paste, organic solvents that can be used include amine-based solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether-based solvents such as tetrahydrofuran; ketone-based solvents such as methyl ethyl ketone; ester solvents such as dimethylacetamide, amide solvents such as N-methyl-2-pyrrolidone;
　正極合剤のペーストを正極集電体へ塗布する方法としては、例えば、スリットダイ塗工法、スクリーン塗工法、カーテン塗工法、ナイフ塗工法、グラビア塗工法および静電スプレー法が挙げられる。 Examples of methods for applying the positive electrode mixture paste to the positive electrode current collector include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spraying.
　以上に挙げられた方法により、正極を製造することができる。 A positive electrode can be manufactured by the method described above.
［セパレータ］
　セパレータとしては、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂、フッ素樹脂、含窒素芳香族重合体などの材質からなる、多孔質膜、不織布、織布などの形態を有する材料を用いることができる。また、これらの材質を２種以上用いてセパレータを形成してもよいし、これらの材料を積層してセパレータを形成してもよい。 [Separator]
As the separator, for example, a material having a form such as a porous film, nonwoven fabric, or woven fabric made of polyolefin resin such as polyethylene or polypropylene, fluororesin, nitrogen-containing aromatic polymer, or the like can be used. Moreover, the separator may be formed using two or more of these materials, or the separator may be formed by laminating these materials.
　セパレータは、電池使用時（充放電時）に電解質を良好に透過させるため、ＪＩＳ　Ｐ　８１１７で定められるガーレー法による透気抵抗度が、５０秒／１００ｃｃ以上、３００秒／１００ｃｃ以下であることが好ましく、５０秒／１００ｃｃ以上、２００秒／１００ｃｃ以下であることがより好ましい。 In order for the separator to allow the electrolyte to pass satisfactorily when the battery is in use (during charging and discharging), the air permeability resistance according to the Gurley method defined in JIS P 8117 must be 50 seconds/100 cc or more and 300 seconds/100 cc or less. It is preferably 50 seconds/100 cc or more and more preferably 200 seconds/100 cc or less.
　また、セパレータの空孔率は、好ましくは３０体積％以上８０体積％以下、より好ましくは４０体積％以上７０体積％以下である。セパレータは空孔率の異なるセパレータを積層したものであってもよい。 In addition, the porosity of the separator is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less. The separator may be a laminate of separators with different porosities.
［電解液］
　電解液は、電解質および有機溶媒を含有する。 [Electrolyte]
The electrolytic solution contains an electrolyte and an organic solvent.
　電解液に含まれる電解質としては、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２、ＬｉＮ（ＳＯ２ＣＦ３）（ＣＯＣＦ３）、Ｌｉ（Ｃ４Ｆ９ＳＯ３）、ＬｉＣ（ＳＯ２ＣＦ３）３、Ｌｉ２Ｂ１０Ｃｌ１０、ＬｉＢＯＢ（ここで、ＢＯＢは、ｂｉｓ（ｏｘａｌａｔｏ）ｂｏｒａｔｅのことである。）、ＬｉＦＳＩ（ここで、ＦＳＩはｂｉｓ（ｆｌｕｏｒｏｓｕｌｆｏｎｙｌ）ｉｍｉｄｅのことである）、低級脂肪族カルボン酸リチウム塩、ＬｉＡｌＣｌ４などのリチウム塩が挙げられ、これらの２種以上の混合物を使用してもよい。なかでも電解質としては、フッ素を含むＬｉＰＦ６、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＳＯ２ＣＦ３）２およびＬｉＣ（ＳＯ２ＣＦ３）３からなる群より選ばれる少なくとも１種を含むものを用いることが好ましい。 Electrolytes contained in the electrolytic solution include LiClO 4 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiN ( SO2CF3 )( COCF3 ) , Li ( C4F9SO3 ), LiC(SO2CF3)3 , Li2B10Cl10 , LiBOB ( where BOB is bis(oxalato)borate ), LiFSI (where FSI is bis(fluorosulfonyl)imide), lower aliphatic carboxylic acid lithium salts, LiAlCl4 and other lithium salts, and mixtures of two or more thereof may be used. Among them, the electrolyte is at least selected from the group consisting of LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 and LiC(SO 2 CF 3 ) 3 containing fluorine. It is preferred to use one containing one.
　また前記電解液に含まれる有機溶媒としては、例えばプロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、４－トリフルオロメチル－１，３－ジオキソラン－２－オン及び１，２－ジ（メトキシカルボニルオキシ）エタンなどのカーボネート類；１，２－ジメトキシエタン、１，３－ジメトキシプロパン、ペンタフルオロプロピルメチルエーテル、２，２，３，３－テトラフルオロプロピルジフルオロメチルエーテル、テトラヒドロフラン及び２－メチルテトラヒドロフランなどのエーテル類；ギ酸メチル、酢酸メチル、プロピオン酸プロピル及びγ－ブチロラクトンなどのエステル類；アセトニトリル及びブチロニトリルなどのニトリル類；Ｎ，Ｎ－ジメチルホルムアミド及びＮ，Ｎ－ジメチルアセトアミドなどのアミド類；３－メチル－２－オキサゾリドンなどのカーバメート類；スルホラン、ジメチルスルホキシド及び１，３－プロパンサルトンなどの含硫黄化合物、又はこれらの有機溶媒にさらにフルオロ基を導入したもの（有機溶媒が有する水素原子のうち１以上をフッ素原子で置換したもの）を用いることができる。 Examples of the organic solvent contained in the electrolytic solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one and 1,2-dioxolan-2-one. Carbonates such as (methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran and 2- ethers such as methyltetrahydrofuran; esters such as methyl formate, methyl acetate, propyl propionate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide. Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propanesultone, or those obtained by further introducing a fluoro group into these organic solvents (hydrogen contained in organic solvents one or more atoms of which are substituted with fluorine atoms) can be used.
　電解液は、リン酸トリス（トリメチルシリル）及びホウ酸トリス（トリメチルシリル）等の添加物を含んでいてもよい。 The electrolyte may contain additives such as tris (trimethylsilyl) phosphate and tris (trimethylsilyl) borate.
　有機溶媒としては、これらのうちの２種以上を混合して用いることが好ましい。中でもカーボネート類を含む混合溶媒が好ましく、環状カーボネートと非環状カーボネートとの混合溶媒および環状カーボネートとエーテル類との混合溶媒がさらに好ましい。環状カーボネートと非環状カーボネートとの混合溶媒としては、エチレンカーボネート、ジメチルカーボネートおよびエチルメチルカーボネートを含む混合溶媒が好ましい。このような混合溶媒を用いた電解液は、動作温度範囲が広く、高い電流レートにおける充放電を行っても劣化し難く、長時間使用しても劣化し難い。 As the organic solvent, it is preferable to use a mixture of two or more of these. Among them, a mixed solvent containing carbonates is preferable, and a mixed solvent of a cyclic carbonate and a non-cyclic carbonate and a mixed solvent of a cyclic carbonate and an ether are more preferable. A mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable as the mixed solvent of the cyclic carbonate and the non-cyclic carbonate. An electrolytic solution using such a mixed solvent has a wide operating temperature range, does not easily deteriorate even when charged and discharged at a high current rate, and does not easily deteriorate even when used for a long time.
　また、電解液としては、得られるリチウム二次電池の安全性を高める観点から、ＬｉＰＦ６などのフッ素を含むリチウム塩およびフッ素置換基を有する有機溶媒を含む電解液を用いることが好ましい。ペンタフルオロプロピルメチルエーテル、２，２，３，３－テトラフルオロプロピルジフルオロメチルエーテルなどのフッ素置換基を有するエーテル類とジメチルカーボネートとを含む混合溶媒は、高い電流レートにおける充放電を行っても容量維持率が高いため、さらに好ましい。 As the electrolytic solution, it is preferable to use an electrolytic solution containing a fluorine-containing lithium salt such as LiPF 6 and an organic solvent having a fluorine substituent, from the viewpoint of enhancing the safety of the resulting lithium secondary battery. Mixed solvents containing fluorine-substituted ethers such as pentafluoropropylmethyl ether and 2,2,3,3-tetrafluoropropyldifluoromethyl ether and dimethyl carbonate retain their capacity even when charged and discharged at a high current rate. It is more preferable because of its high retention rate.
　本明細書において「サイクル維持率が低下しにくい」とは、下記の方法により測定するサイクル維持率の値が９０％以上１００％以下の範囲内にあることを意味する。 In the present specification, "the cycle retention rate is less likely to decrease" means that the value of the cycle retention rate measured by the method below is in the range of 90% or more and 100% or less.
［サイクル維持率の測定方法］
　まず、フィルムラミネート型のリチウム二次電池を室温で１０時間静置することでセパレータ及び正極合剤層に充分電解液を含浸させる。
　次に、室温において４．２Ｖまで１６ｍＡで定電流充電してから４．２Ｖで定電圧充電する定電流定電圧充電を５時間行った後、３．４Ｖまで１６ｍＡ放電する定電流放電を行う充放電を２回繰り返す。２サイクル目の放電容量を測定し、得られた値を「２サイクル目の放電容量」（ｍＡｈ／ｇ）とする。
　上記条件と同様に１６ｍＡで充電、１６ｍＡで放電を繰り返し、８０サイクル目の放電容量（ｍＡｈ／ｇ）を測定する。得られた値を「８０サイクル目の放電容量」（ｍＡｈ／ｇ）とする。
　２サイクル目の放電容量と８０サイクル目の放電容量から、下記の式でサイクル維持率を算出する。
　サイクル維持率（％）＝８０サイクル目の放電容量（ｍＡｈ／ｇ）／２サイクル目の放電容量（ｍＡｈ／ｇ）　×１００ [Method for measuring cycle maintenance rate]
First, the film-laminated lithium secondary battery is allowed to stand at room temperature for 10 hours, so that the separator and the positive electrode mixture layer are sufficiently impregnated with the electrolytic solution.
Next, at room temperature, constant current charging at 16 mA to 4.2 V and then constant voltage charging at 4.2 V were performed for 5 hours, followed by constant current discharging at 16 mA to 3.4 V. Repeat the discharge twice. The discharge capacity at the second cycle is measured, and the obtained value is defined as "discharge capacity at the second cycle" (mAh/g).
Charging at 16 mA and discharging at 16 mA are repeated under the same conditions as above, and the discharge capacity (mAh/g) at the 80th cycle is measured. Let the obtained value be "discharge capacity at the 80th cycle" (mAh/g).
From the discharge capacity at the 2nd cycle and the discharge capacity at the 80th cycle, the cycle retention rate is calculated by the following formula.
Cycle retention rate (%) = Discharge capacity at 80th cycle (mAh/g)/Discharge capacity at 2nd cycle (mAh/g) x 100
　次に、本発明を実施例によりさらに詳細に説明する。 Next, the present invention will be described in more detail by way of examples.
＜実施例１＞
［負極の作製］
　実施例１に用いたシリコン－アルミニウム合金は下記の方法により製造した。
　高純度アルミニウム（純度：９９．９９質量％以上）および高純度化学製シリコン（純度：９９．９９９質量％以上）を、７６０℃に加熱し、保持することで、シリコン含有量が１．０質量％であるアルミニウム－シリコン合金溶湯を得た。
　次に、合金溶湯を温度７４０℃で、２時間、真空度５０Ｐａの条件で保持して清浄化した。
　合金溶湯を１５０℃にて乾燥した鋳鉄鋳型（２２ｍｍ×１５０ｍｍ×２００ｍｍ）にて鋳造し、鋳塊を得た。 <Example 1>
[Preparation of negative electrode]
The silicon-aluminum alloy used in Example 1 was produced by the following method.
High-purity aluminum (purity: 99.99% by mass or more) and high-purity chemical silicon (purity: 99.999% by mass or more) are heated to 760 ° C. and held to reduce the silicon content to 1.0 mass. % aluminum-silicon alloy melt.
Next, the molten alloy was held at a temperature of 740° C. and a degree of vacuum of 50 Pa for 2 hours for cleaning.
The molten alloy was cast in a cast iron mold (22 mm×150 mm×200 mm) dried at 150° C. to obtain an ingot.
　圧延は以下の条件で行った。鋳塊の両面を２ｍｍ面削加工した後、厚さ１８ｍｍから加工率９９．６％で冷間圧延を行った。得られた圧延材の厚みは１００μｍであった。
　アルミニウム純度９９．９９９％、シリコン含有量１．０質量％の高純度アルミニウム－シリコン合金箔（厚さ５０μｍ）を切り出し、縦５２ｍｍ、横５２ｍｍのアルミニウム負極１２aを製造した。さらに同一のアルミニウム負極１２ｂを製造した。アルミニウム負極１２a及びアルミニウム負極１２ｂを重ね合わせて積層し、負極１２を製造した。アルミニウム負極１２aとアルミニウム負極１２ｂに負極リードをそれぞれ接続した。負極リードは外装体３０の外部に引き出され、外部で一つにまとめた。 Rolling was performed under the following conditions. After both surfaces of the ingot were chamfered by 2 mm, cold rolling was performed from a thickness of 18 mm at a reduction ratio of 99.6%. The thickness of the obtained rolled material was 100 μm.
A high-purity aluminum-silicon alloy foil (thickness: 50 μm) having an aluminum purity of 99.999% and a silicon content of 1.0% by mass was cut out to manufacture an aluminum negative electrode 12a of 52 mm long and 52 mm wide. Furthermore, the same aluminum negative electrode 12b was manufactured. The negative electrode 12 was manufactured by laminating the aluminum negative electrode 12a and the aluminum negative electrode 12b. Negative electrode leads were connected to the aluminum negative electrode 12a and the aluminum negative electrode 12b, respectively. The negative electrode lead is drawn out of the outer package 30 and combined together outside.
［正極の作製］
　正極活物質としてコバルト酸リチウム（製品名セルシード。日本化学工業株式会社製。平均粒径（Ｄ５０）１０μｍ）９０質量部と、バインダーとしてポリフッ化ビニリデン（株式会社クレハ製）５質量部と、導電材としてアセチレンブラック（製品名デンカブラック。デンカ株式会社製）５質量部とを混合し、更にＮ－メチル－２－ピロリドン７０質量部を混合して正極の電極合剤とした。 [Preparation of positive electrode]
90 parts by mass of lithium cobalt oxide (product name: Cellseed, manufactured by Nippon Kagaku Kogyo Co., Ltd., average particle size (D50): 10 μm) as a positive electrode active material, 5 parts by mass of polyvinylidene fluoride (manufactured by Kureha Co., Ltd.) as a binder, and a conductive material 5 parts by mass of acetylene black (product name: Denka Black, manufactured by Denka Co., Ltd.) was mixed as a material, and 70 parts by mass of N-methyl-2-pyrrolidone was further mixed to prepare a positive electrode mixture.
　得られた電極合剤を、シート状に塗工し、塗工した電極合剤を、６０℃で２時間乾燥させた後、更に１５０℃で１０時間真空乾燥させて、Ｎ－メチル－２－ピロリドンを揮発させた。乾燥後の正極活物質の塗工量は２１．５ｍｇ／ｃｍ２であった。シートの厚さは５０μｍであった。
　得られたシートを切り出し、縦５０ｍｍ、横５０ｍｍの正極１１a及び正極１１ｂをそれぞれ製造した。 The obtained electrode mixture is coated in a sheet, and the coated electrode mixture is dried at 60° C. for 2 hours and further vacuum-dried at 150° C. for 10 hours to obtain N-methyl-2- Pyrrolidone was volatilized. The coating amount of the positive electrode active material after drying was 21.5 mg/cm 2 . The sheet thickness was 50 μm.
The obtained sheet was cut out to manufacture positive electrodes 11a and 11b each having a length of 50 mm and a width of 50 mm.
［電解液の作製］
　エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）とをＥＣ：ＤＥＣ＝３０：７０（体積比）で混合させてなる混合溶媒に、ＬｉＰＦ６を１モル／リットルとなる割合で溶解した電解液を作製した。 [Preparation of electrolytic solution]
An electrolytic solution was prepared by dissolving LiPF6 at a ratio of 1 mol/liter in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at EC:DEC=30:70 (volume ratio). .
［リチウム二次電池の作製］
　一対の正極１１a及び正極１１ｂに間に、ポリエチレン製多孔質セパレータを介して、負極１２を配置し、ラミネートフィルム外装体に収納した。その後、上記の電解液を注液し、外装体のラミネートフィルムを密閉することにより、フィルムラミネート型のリチウム二次電池１０を作製した。 [Production of lithium secondary battery]
A negative electrode 12 was placed between a pair of positive electrodes 11a and 11b with a polyethylene porous separator interposed therebetween, and housed in a laminate film package. After that, the above electrolytic solution was injected, and the laminate film of the outer package was sealed to produce a film laminate type lithium secondary battery 10 .
　リチウム二次電池１０について、上記［サイクル維持率の測定方法］に記載の方法によりサイクル維持率の測定を行ったところ、９８％であった。 When the cycle retention rate of the lithium secondary battery 10 was measured by the method described in [Method for measuring cycle retention rate] above, it was 98%.
＜実施例２＞
　正極１１ａと負極１２とをポリエチレン製多孔質セパレータを介して配置した以外は実施例１と同様の方法により、リチウム二次電池１１を作製した。 <Example 2>
A lithium secondary battery 11 was produced in the same manner as in Example 1, except that the positive electrode 11a and the negative electrode 12 were arranged via a polyethylene porous separator.
　リチウム二次電池１１について、上記［サイクル維持率の測定方法］に記載の方法によりサイクル維持率の測定を行ったところ、９９％であった。 Regarding the lithium secondary battery 11, when the cycle retention rate was measured by the method described in [Method for measuring cycle retention rate] above, it was 99%.
＜比較例１＞
　負極１２として、厚みが１００μｍの単層のアルミニウム負極を用いた以外は実施例１と同様の方法により、リチウム二次電池１２を作製した。 <Comparative Example 1>
A lithium secondary battery 12 was fabricated in the same manner as in Example 1, except that a single-layer aluminum negative electrode having a thickness of 100 μm was used as the negative electrode 12 .
　リチウム二次電池１２について、上記［サイクル維持率の測定方法］に記載の方法によりサイクル維持率の測定を行ったところ、４３％であった。 When the cycle retention rate of the lithium secondary battery 12 was measured by the method described in [Method for measuring cycle retention rate] above, it was 43%.
　複数の金属箔を重ね合わせた積層体である負極を用いた場合には、サイクル維持率が低下しにくいことが確認できた。 It was confirmed that when using a negative electrode that is a laminate in which multiple metal foils are laminated, the cycle retention rate is less likely to decrease.
１，２：リチウム二次電池、１１、１１ａ，１１ｂ：正極、１２：負極、１２ａ：金属箔１、１２ｂ：金属箔２、２１：正極リード、２２：負極リード、３０：外装体、１３：電解液、１４，１５：電極群、１６、１６ａ、１６ｂ：セパレータ 1, 2: lithium secondary battery, 11, 11a, 11b: positive electrode, 12: negative electrode, 12a: metal foil 1, 12b: metal foil 2, 21: positive electrode lead, 22: negative electrode lead, 30: exterior body, 13: Electrolyte solution, 14, 15: electrode group, 16, 16a, 16b: separator

Claims (6)

  1. 　負極と、電解質と、正極とが備えられた電極群を有するリチウム二次電池であって、
    　前記負極は複数の金属箔を重ね合わせた積層体であり、前記金属箔は、リチウムと合金を形成することが可能である金属からなる、リチウム二次電池。     A lithium secondary battery having an electrode group comprising a negative electrode, an electrolyte, and a positive electrode,
    A lithium secondary battery, wherein the negative electrode is a laminate obtained by stacking a plurality of metal foils, and the metal foil is made of a metal capable of forming an alloy with lithium.
  2. 　前記金属箔は、Ａｌ、Ｓｎ、Ｓｉ、Ｇｅ及びＰｂからなる群より選択される１種以上の金属を含む、請求項１に記載のリチウム二次電池。 The lithium secondary battery according to claim 1, wherein the metal foil contains one or more metals selected from the group consisting of Al, Sn, Si, Ge and Pb.
  3. 　前記金属箔は純度が９９質量％以上のアルミニウム又はその合金からなる、請求項１に記載のリチウム二次電池。 The lithium secondary battery according to claim 1, wherein the metal foil is made of aluminum or its alloy with a purity of 99% by mass or more.
  4. 　前記複数の金属箔は同一の金属箔である、請求項１～３のいずれか１項に記載のリチウム二次電池。 The lithium secondary battery according to any one of claims 1 to 3, wherein the plurality of metal foils are the same metal foil.
  5. 　前記負極と前記正極との間にセパレータを備える、請求項１～４のいずれか１項に記載のリチウム二次電池。 The lithium secondary battery according to any one of claims 1 to 4, comprising a separator between said negative electrode and said positive electrode.
  6. 　前記負極の両面に、セパレータを介して前記正極がそれぞれ配置されている、請求項５に記載のリチウム二次電池。 The lithium secondary battery according to claim 5, wherein the positive electrodes are arranged on both sides of the negative electrode with separators interposed therebetween.
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JPH0212761A (en) * 1988-06-29 1990-01-17 Nippon Denso Co Ltd Secondary battery
JPH0434844A (en) * 1990-05-29 1992-02-05 Sanyo Electric Co Ltd Nonaqueous system secondary battery
JPH09129265A (en) * 1995-10-31 1997-05-16 Matsushita Electric Ind Co Ltd Organic electrolyte secondary battery
JP2018120849A (en) * 2017-01-26 2018-08-02 本田技研工業株式会社 Negative electrode for lithium ion secondary battery, manufacturing method of the same, and lithium ion secondary battery
WO2020075616A1 (en) * 2018-10-10 2020-04-16 住友化学株式会社 Negative electrode active material for nonaqueous electrolyte secondary battery, negative electrode, battery, and aluminum clad metal laminate

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0212761A (en) * 1988-06-29 1990-01-17 Nippon Denso Co Ltd Secondary battery
JPH0434844A (en) * 1990-05-29 1992-02-05 Sanyo Electric Co Ltd Nonaqueous system secondary battery
JPH09129265A (en) * 1995-10-31 1997-05-16 Matsushita Electric Ind Co Ltd Organic electrolyte secondary battery
JP2018120849A (en) * 2017-01-26 2018-08-02 本田技研工業株式会社 Negative electrode for lithium ion secondary battery, manufacturing method of the same, and lithium ion secondary battery
WO2020075616A1 (en) * 2018-10-10 2020-04-16 住友化学株式会社 Negative electrode active material for nonaqueous electrolyte secondary battery, negative electrode, battery, and aluminum clad metal laminate

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