WO2015025207A1 - Manufacturing method of nonaqueous electrolytic solution secondary battery - Google Patents

Manufacturing method of nonaqueous electrolytic solution secondary battery Download PDF

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Publication number
WO2015025207A1
WO2015025207A1 PCT/IB2014/001519 IB2014001519W WO2015025207A1 WO 2015025207 A1 WO2015025207 A1 WO 2015025207A1 IB 2014001519 W IB2014001519 W IB 2014001519W WO 2015025207 A1 WO2015025207 A1 WO 2015025207A1
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Prior art keywords
electrolytic solution
negative electrode
nonaqueous electrolytic
copper
outer package
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PCT/IB2014/001519
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French (fr)
Inventor
Yo Kato
Ryuta Morishima
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Toyota Jidosha Kabushiki Kaisha
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Publication of WO2015025207A1 publication Critical patent/WO2015025207A1/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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/049—Processes for forming or storing electrodes in the battery container
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0438—Processes of manufacture in general by electrochemical processing
    • H01M4/044—Activating, forming or electrochemical attack of the supporting material
    • H01M4/0442—Anodisation, Oxidation
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0438—Processes of manufacture in general by electrochemical processing
    • H01M4/044—Activating, forming or electrochemical attack of the supporting material
    • H01M4/0445—Forming after manufacture of the electrode, e.g. first charge, cycling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a manufacturing method of a nonaqueous electrolytic solution secondary battery.
  • nonaqueous electrolytic solution secondary batteries including a lithium ion battery are widely in use.
  • the nonaqueous electrolytic solution secondary battery since it does not use water in an electrolytic solution that plays a role of transporting ions between positive and negative electrodes, can have a high battery voltage exceeding a water electrolysis voltage.
  • the battery after the nonaqueous electrolytic solution is injected is in a non-charged state and a negative electrode potential exceeds an elution potential of copper. Therefore, when a time (infiltration time) for infiltrating the nonaqueous electrolytic solution is set longer, copper is eluted from the copper foil that is a current collector into the nonaqueous electrolytic solution. When copper is eluted, not only a current collection function is degraded but also eluted copper precipitates again, and various performance degradations are caused thereby. Therefore, for the battery after injection, it is required to set a potential of the negative electrode to less than the elution potential of copper by performing a predetermined amount of charging in an early stage. That is, in order to prevent copper from being eluted, the infiltration time of the nonaqueous electrolytic solution has to be limited.
  • the nonaqueous electrolytic solution secondary battery is demanded to have a higher capacity, and higher densification of the positive electrode, the negative electrode and the electrode body is in progress.
  • an infiltration passage of the nonaqueous electrolytic solution is narrowed, and there is a tendency that the nonaqueous electrolytic solution becomes difficult to infiltrate thereby. That is, in order to obtain a high capacity and high performance nonaqueous electrolytic solution secondary battery, a corresponding infiltration time is necessary.
  • the present invention provides a high capacity and high performance nonaqueous electrolytic solution secondary battery by preventing copper from being eluted.
  • a manufacturing method of a nonaqueous electrolytic solution secondary battery of the present invention includes the following structure.
  • the manufacturing method comprises: forming a negative electrode mixture layer on a copper foil and obtaining a negative electrode having the negative electrode mixture layer and a copper exposed part thereby; oxidizing the copper exposed part; inserting an electrode body including the negative electrode into a battery outer package; injecting a nonaqueous electrolytic solution into the battery outer package; infiltrating the nonaqueous electrolytic solution into the electrode body; and making an atmosphere inside the battery outer package a reducing gas atmosphere.
  • the exposed surface of the copper foil (copper exposed part) is oxidized, and an oxide film is formed on the exposed surface. Therefore, even when a sufficient infiltration time is set, copper can be prevented from being eluted. Further, usually, when the copper foil is oxidized, electric resistance increases. However, according to the manufacturing method described above, by making the atmosphere inside the battery outer package the reducing gas atmosphere, the oxide film is reduced and returned to copper, therefore, an increase in the electric resistance can be suppressed. Therefore, while suppressing copper from being eluted, by setting a sufficient infiltration time, a high capacity and high performance nonaqueous electrolytic solution secondary battery can be manufactured.
  • the "copper exposed part” here shows not only a site in which the negative electrode mixture layer is not formed on the copper foil (that is, intermittently coated part) but also a site in which the negative electrode mixture layer is formed. This ⁇ is because since the negative electrode mixture layer is porous, also a site that is coated with the negative electrode mixture layer of the copper foil is substantially equivalent to be exposed.
  • the nonaqueous electrolytic solution described above may contain a component that generates a reducing gas by an electrochemical reaction. And the reducing gas that derived from the component, may generated by applying an electric current to the electrode body.
  • the atmosphere inside the battery outer package is not necessary to be substituted with the reducing gas in order to make the inside of the battery outer package a reducing gas atmosphere. That is, compared with conventional ones, without increasing process load, the manufacturing method of the present invention can be performed.
  • the component that generates the reducing gas by the electrochemical reaction described above may be lithium difluorobisoxalatophosphate (hereinafter, abbreviated as "LiFOP" in some cases).
  • LiFOP lithium difluorobisoxalatophosphate
  • LiFOP is reduced during charging and generates carbon monoxide (CO) that is the reducing gas.
  • CO is strong in a reduction action and can return the oxide film to copper by reduction.
  • LiFOP forms an excellent SEI (Solid Electrolyte Interface) on a surface of the negative electrode during initial charging, the battery performance can be also improved.
  • a nonaqueous electrolytic solution secondary battery of the present invention while suppressing copper from being eluted, a high capacity and high performance nonaqueous electrolytic solution secondary battery can be provided.
  • FIG. 1 is a graph that shows an example of a relationship between a infiltration time of a nonaqueous electrolytic solution and a copper elution amount in a nonaqueous electrolytic solution secondary battery according to an embodiment of the present invention
  • FIG. 2 is a graph that shows an example of a direct current resistance of the nonaqueous electrolytic solution secondary battery according to the embodiment of the present invention.
  • FIG. 3 is a flowchart that shows an outline of the manufacturing method of the nonaqueous electrolytic solution secondary battery of the embodiment of the present invention.
  • the present inventors studied hard to solve the problems described above and obtained knowledge that when an oxide film is formed by oxidizing copper foil, copper can be suppressed from being eluted. Further, a method of resolving an increase in electric resistance due to the oxide film by reducing the oxide film was found, and the present invention came to completion thereby.
  • a manufacturing method of a nonaqueous electrolytic solution secondary battery includes the following steps.
  • the manufacturing method comprise: a step a of obtaining a negative electrode haying a negative electrode mixture layer and a copper exposed part by forming the negative electrode mixture layer on copper foil; a step ⁇ of oxidizing the copper exposed part of the negative electrode; a step ⁇ of inserting an electrode body including the negative electrode into a battery outer package; a step ⁇ of injecting a nonaqueous electrolytic solution in the battery outer package; a step ⁇ of infiltrating the nonaqueous electrolytic solution into the electrode body; and a step ⁇ of making an atmosphere inside the battery outer package a reducing gas atmosphere.
  • the nonaqueous electrolytic solution secondary battery manufactured according to such a manufacturing method typically has a structure as shown below. That is, the nonaqueous electrolytic solution secondary battery is formed by housing the electrode body and the nonaqueous electrolytic solution in the battery outer package. The electrode body is formed by winding a positive electrode and the negative electrode so as to face each other via a separator. The nonaqueous electrolytic solution is obtained by dissolving a lithium salt in an organic solvent. The positive electrode is obtained by forming a positive electrode mixture layer containing a positive electrode active material that can store and emit lithium ions on a current collector.
  • the negative electrode is obtained by forming a negative electrode mixture layer containing a negative electrode active material that can store and emit lithium ions on copper foil that is a current collector.
  • a separator is made of, for example, a microporous polyolefin film.
  • the electrode body described here is a wound type. However, the electrode body may be a stack type electrode body formed by stacking the positive electrode, the separator and the negative electrode.
  • FIG. 3 is a flowchart that shows an outline of the manufacturing method of a nonaqueous electrolytic solution secondary battery of the present embodiment.
  • the manufacturing method of a nonaqueous electrolytic solution secondary battery of the present embodiment includes a step a, a step ⁇ , a step ⁇ , a step ⁇ , a step ⁇ , and a step ⁇ , and preferably includes the step a to step ⁇ in this order.
  • the step ⁇ may be performed preceding the step a.
  • the step a is a step of obtaining the negative electrode having the negative electrode mixture layer and a copper exposed part by forming the negative electrode mixture layer on the copper foil.
  • a method of forming the negative electrode mixture layer on the copper foil is not particularly limited. For example, the following method can be illustrated. That is, a negative electrode mixture slurry obtained by kneading the negative electrode active material, a thickener, a binder and a solvent (for example, water) is coated on the copper foil and dried, the negative electrode mixture layer can be formed oh the copper foil. At this time, the negative electrode mixture slurry may be intermittently coated on the copper foil such that the copper exposed part for welding later a negative electrode current collector tab may be formed. However, as described above, the copper exposed part does not show only such an intermittent coated part.
  • the negative electrode mixture layer is preferably compressed to a predetermined thickness.
  • the thickness of the negative electrode mixture layer can be compressed such that the density of the negative electrode mixture layer becomes about 0.5 to 2.5 g/cm 3 .
  • the density of the negative electrode mixture layer can be calculated according to "mass of the negative electrode mixture layer” ⁇ "volume of the negative electrode mixture layer”.
  • the negative electrode active material for example, carbonaceous materials such as graphite and cokes, silicon (Si), tin oxide (Sn0 2 ) or the like can be used.
  • a content of the negative electrode active material in the negative electrode mixture is, for example, about 90 to 99% by mass.
  • the binder for example, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVdF), and polytetrafluoroethylene (PTFE) can be used.
  • SBR styrene butadiene rubber
  • PVdF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • the solvent when water is used, in order to improve the coatability, for example, a thickener such as carboxymethylcellulose (CMC) or the like is preferably used.
  • the copper foil that is the negative electrode current collector any of electrolytic copper foil and rolled copper foil may be used. Further, in place of pure copper foil, copper alloy foil containing impurity elements can be used as well. This is because as long as metal foil containing copper is used as the negative electrode current collector, an effect of the present invention is exhibited. That is, the copper foil of the present embodiment includes also copper alloy foil. From the viewpoint of strength and. electric conductivity, a thickness of the copper foil is preferably about 5 to 30 ⁇ .
  • the step ⁇ is a step of oxidizing the copper exposed part of the negative electrode. That is, the step ⁇ is a step of oxidizing a surface of the copper foil.
  • a method of oxidizing a surface of the copper foil for example, a method of heat treating a simple substance of copper foil, and a method of treating the simple substance of copper foil with a chemical such as acid or the like can be used.
  • the simple substance of copper foil is treated with a chemical such as acid or the like
  • the step ⁇ is performed preceding the step a.
  • the negative electrode mixture slurry is coated on the copper foil and dried, also the copper foil can be heat treated at the same time.
  • the negative electrode on which the negative electrode mixture layer was formed can also be heat treated.
  • the method of oxidizing according to heat treatment is less in process load and preferable.
  • a heat treatment temperature is preferably set to 100°C or more and 200°C or less. This is because when the heat treatment temperature exceeds 200°C, the binder is denatured and the binding force is degraded thereby in some cases, and when the heat treatment temperature is less than 100°C, the oxide film is insufficiently formed in some cases. From the same reason, the heat treatment time is preferably set to 30 minutes or more and 24 hours or less.
  • the oxide film can be formed on a surface of the copper foil.
  • copper inside the copper foil can be suppressed from being eluted in the nonaqueous electrolytic solution. Therefore,, in accordance with a specification of the battery, the infiltration time of the nonaqueous electrolytic solution can be set.
  • the manufacturing method of the present embodiment is applied to a high capacity battery designed such that the positive electrode, the negative electrode and the electrode body have high density, a high capacity and high performance battery can be obtained.
  • the step ⁇ is a step of inserting the electrode body containing the negative electrode into the battery outer package.
  • the electrode body containing the negative electrode can be manufactured, for example, by welding a current collector tab to the positive electrode and the negative electrode, and by winding such that the positive electrode and the negative electrode face with each other via the separator. All of the positive electrode, the negative electrode and the separator are formed in sheet.
  • the electrode body is, after being inserted in the battery outer package, electrically connected with the battery outer package via the positive electrode current collector tab and the negative electrode current collector tab.
  • the positive electrode can be manufactured, for example, in such a manner that a positive electrode mixture slurry is coated on the current collector and dried and the positive electrode mixture layer is formed on the current collector thereby, thereafter, the positive electrode mixture layer is compressed to a predetermined thickness.
  • the positive electrode mixture slurry is obtained by kneading, for example, the positive electrode active material, a conductive auxiliary agent, the binder and the organic solvent (for example, N-methyl-2-pyrrolidone (NMP)).
  • a content of the positive electrode active material in the positive electrode mixture is, for example, about 90 to 99% by mass.
  • the conductive auxiliary agent for example, carbonaceous material such as Acetylene Black (AB) or the like can be used, and as the binder, for example, PVdF and the like can be used.
  • the positive electrode current collector for example, aluminum (Al) foil or aluminum alloy foil can be used, Further, the density of the positive electrode mixture layer (mass of positive electrode mixture layer ⁇ volume of
  • positive electrode mixture layer is, for example, about 2.0 to 4.0 g/cm .
  • a microporous film made of a polyolefm-based material is preferable.
  • the polyolefin-based material polyethylene (PE), polypropylene (PP) and the like can be used, and these can be used also by combining. Further, a plurality of microporous films may be laminated. A thickness of the separator can be set to, for example, about 5 to 40 ⁇ .
  • the battery outer package for example, there are a cylindrical shape, a rectangular shape and the like.
  • the battery outer package includes usually an outer packaging can and a cap.
  • the cap is provided with a positive electrode or negative electrode terminal part, and the terminal part is insulated from a counter electrode with a resin material, for example.
  • a material of the battery outer package may be properly selected from various metals, alloy materials and the like, by considering the withstand voltage and the strength. For example, aluminum and alloys thereof, iron (Fe), stainless materials and the like can be used.
  • the step ⁇ is a step of injecting the nonaqueous electrolytic solution in the battery outer package in which the electrode body was inserted.
  • a method of injecting the nonaqueous electrolytic solution is not particularly limited. However, it is preferable to sufficiently dry the electrode body and the battery outer package before injection in order to avoid mixing of water.
  • the step ⁇ is preferably performed under an inert gas 1 atmosphere (for example, argon (Ar)).
  • an organic solvent in which a solute (lithium salt) is dissolved can be used.
  • the organic solvent for example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ⁇ -butyrolactone (GBL) and vinylene carbonate (VC), and chain carbonates such as dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) can be used.
  • cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ⁇ -butyrolactone (GBL) and vinylene carbonate (VC)
  • chain carbonates such as dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC)
  • DMC dimethyl carbonate
  • EMC ethylmethyl carbonate
  • DEC diethyl carbonate
  • a mixture of the cyclic carbonate and the chain carbonate and a volume ratio of the cyclic carbonate and the chain carbonate is preferable to be about 1 :9 to 5:5.
  • three kinds of EC, DMC and EMC can be mixed and used.
  • lithium salt that is a solute for example, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiC10 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(trifluoromethanesulfonyl)imide (Li(CF 3 S0 2 ) 2 N), lithium trifluoromethanesulfonate (Li(CF 3 S0 3 ) and the like can be used. Further, also these solutes may be used in combination of two or more kinds thereof. A concentration of the solute in the nonaqueous electrolytic solution is not particularly limited.
  • the nonaqueous electrolytic solution of the present embodiment preferably contains a component that generates the reducing gas by the electrochemical reaction as an additive.
  • the nonaqueous electrolytic solution contains the component like this, at the time of initial charging, the reducing gas is generated on a surface of the negative electrode, and the oxide film formed by the step ⁇ is reduced thereby. Thus, an increase in the resistance due to the oxide film can be resolved.
  • the component like this is preferable to be able to form a high quality SEI on the surface of the negative electrode at the time of the initial charging.
  • lithium salts that have an oxalate complex as an anion are preferred. This is because the lithium salts having the oxalate complex as an anion can emit carbon monoxide having a stronger reduction action at the time of reduction and decomposition.
  • lithium difluorobisoxalatophosphate Li [P(C 2 0 4 ) 2 F 2 ]
  • lithium tetrafluorobisoxalatophosphate Li[P(C 2 0 4 ) 2 F 4 ]
  • lithium difluorobisoxalatoborate Li[B(C 2 0 4 ) 2 F 2 ]
  • lithium bisoxalatoborate Li[B(C 2 0 4 ) 2 ]
  • lithium difluorobisoxalatophosphate LiFOP
  • LiFOP lithium difluorobisoxalatophosphate
  • An addition amount of the component described above in the nonaqueous electrolytic solution is preferably 0.1% by mole or more and 1.0% by mole or less. This is because when the addition amount is 0.1% by mole or less, in some cases, a generation amount of the reducing gas is small, and the oxide film is insufficiently reduced thereby, and when the addition amount exceeds 1.0% by mole, in some cases, the reducing gas is excessively generated.
  • the addition amount of the component described above is preferable to be 0.3% by mole or more and 0.7% by mole or less.
  • the step ⁇ is a step of infiltrating the nonaqueous electrolytic solution in the electrode body.
  • the oxide film is formed on a surface of the copper foil. Therefore, in accordance with the battery specification, a desired infiltration time can be set.
  • the battery specification includes, for example, the densities of the positive electrode mixture layer and the negative electrode mixture layer, the retention amount of the nonaqueous electrolytic solution, a battery capacity and so on.
  • depressurization, pressurization or heating may be accompanied.
  • the step ⁇ is a step of making the inside of the battery outer package the reducing gas atmosphere after the nonaqueous electrolytic solution being thoroughly infiltrated into the electrode body.
  • the oxide film formed on the copper foil in the step ⁇ is reduced, and an increase in a direct current resistance of the battery can be evaded thereby.
  • the step ⁇ is performed to prevent copper from being eluted after the initial charging. "After the initial charging” includes the same time with the initial charging or after the initial charging.
  • the reducing gas atmosphere indicates that the reducing gas occupies 30% by volume or more of a gas composition in the battery outer package.
  • the reducing gas preferably occupies 40% by volume or more and more preferably 50% by volume or more of the gas composition in the battery outer package.
  • the reducing gas that can be used in the step ⁇ hydrogen (H 2 ), carbon monoxide (CO), hydrogen sulfide (H 2 S), sulfur dioxide (S0 2 ) and the like can be used.
  • a method of making the inside of the battery outer package the reducing gas atmosphere is not particularly limited. For example, after the inside of the battery outer package is depressurized, the reducing gas may be injected, or a gas is introduced in a chamber in which the battery outer package is left at rest and the inside of the battery outer package may be substituted with the reducing gas.
  • the component that generates the reducing gas when the component that generates the reducing gas is added in the nonaqueous electrolytic solution, by applying an electric current to the electrode body (that is, by charging), the reducing gas is generated inside the battery outer package, and the inside of the battery outer package can be made the reducing gas atmosphere. That is, by introducing the electric current to the electrode body, a step of generating the reducing gas derived from the additive can be contained in the step ⁇ . This method is preferable because it does not accompany a gas substitution operation and is less in process load thereby. In this case, the initial charging and the step ⁇ can be combined.
  • a nonaqueous electrolytic solution secondary battery After undergoing the steps described above, when an opening part of the battery outer package is sealed by a predetermined method, a nonaqueous electrolytic solution secondary battery according to the present embodiment can be manufactured.
  • step ⁇ was performed and the copper exposed part of the negative electrode was oxidized, and it was confirmed that copper could be suppressed from being eluted hereby.
  • the positive electrode active material a powder made of a lithium-containing transition metal composite oxide that contains Li and three kinds of transition metal elements (Co, Ni and Mn) was prepared.
  • This positive electrode active material, AB as the conductive auxiliary agent, and a solution in which PVdF as the binder is dissolved in NMP were kneaded, and the positive electrode mixture slurry was obtained.
  • the positive electrode mixture slurry was coated on both surfaces of Al foil that is the positive electrode current collector and dried, and the positive electrode mixture layer was formed on the Al foil. Subsequently, by use of a roll machine, the positive electrode mixture layer and the Al foil were rolled and a positive electrode was obtained thereby.
  • the negative electrode active material a carbonaceous material with natural graphite as a core material was prepared. Then, the negative electrode active material, CMC as the thickener, and SBR as the binder were kneaded in water, and the negative electrode mixture slurry was obtained. Then, the negative electrode mixture slurry was coated on both surfaces of Cu foil and dried, and a negative electrode mixture layer was formed on the Cu foil. Subsequently, by use of the roll machine, the negative electrode active material layer and the Cu foil were rolled and a negative electrode X was obtained thereby. [0054] The negative electrode X was charged in a thermostat set at 180°C and left for 1 hour. Thereby, a negative electrode Y in which the oxide film was formed on the copper exposed part was obtained.
  • a positive electrode current collector tab was welded to the positive electrode, and a negative electrode current collector tab was welded to the negative electrode X. Subsequently, the positive electrode, the negative electrode X and a separator made of a polyolefin microporous film were wound such that the positive electrode and the negative electrode X face each other via the separator, and an electrode body X was obtained. Further, in the same manner except that in place of the negative electrode X, the negative electrode Y was used, an electrode body Y was obtained.
  • the electrode body X was inserted in the battery outer package (outer package can) and the negative electrode current collector and the outer package can were welded, and the positive electrode current collector tab and the battery outer package (cap) were welded. Thus, a test cell X was obtained. Further, in the same manner except that in place of the electrode body X, the electrode body Y was used, a test cell Y was obtained.
  • the nonaqueous electrolytic solution A was injected in each of the test cell X and the test cell Y, and a test cell XA and a test cell YA were obtained.
  • test cell XA and the test cell YA were left at rest to make the nonaqueous electrolytic solution infiltrate into the electrode body. Then, every time when a predetermined time passed, the nonaqueous electrolytic solutions were sampled from the test cell XA and the test cell YA, and by means of an inductively-coupled plasma emission spectrometer (type name: ICP-V8100, manufactured by Shimadzu Corporation), concentrations of copper eluted in the nonaqueous electrolytic solutions were measured. Results are shown in FIG. 1.
  • FIG. 1 is a graph that shows a relationship between the infiltration time of the nonaqueous electrolytic solution and a copper elution amount.
  • a horizontal axis shows the infiltration time of the nonaqueous electrolytic solution and a vertical axis shows a concentration of copper ions eluted in the electrolytic solution.
  • Curves in FIG. 1 are supplementarily drawn to make it easy to understand a tendency.
  • the Cu elution amount of the test cell YA that underwent the step ⁇ is small from the start of infiltration and continues to be nearly flat even after the elapse of 50 hours.
  • the Cu elution amount of the test cell XA that did not undergo the step ⁇ rapidly increases from immediately after the start of infiltration and continues to increase after that.
  • the test cell YA that underwent the step ⁇ was remarkably reduced in the copper elution amount compared with that of the test cell XA that did not undergo the step ⁇ . This is considered because in the test cell YA, by undergoing the step ⁇ , the oxide film was formed on the copper exposed part of the negative electrode, and by the oxide film, copper was suppressed from being eluted.
  • step ⁇ the step of infiltrating the nonaqueous electrolytic solution by performing the step ⁇ that oxidizes the copper exposed part of the negative electrode.
  • test cell YB By injecting the nonaqueous electrolytic solution B in the test cell Y (copper foil was oxidized) and by fixing the cap and the outer package can by a predetermined method, a test cell YB according to the example was obtained. Further, in the same manner except that the nonaqueous electrolytic solution A was injected in the test cell Y, a test cell YA according to comparative example was obtained.
  • test cells of example and comparative example were left at rest for 24 hours to make the nonaqueous electrolytic solution infiltrate into the electrode body.
  • the initial charging was performed.
  • a gas composition inside each of the test cells was analyzed with a gas chromatograph analyzer (type "G1530A", manufactured by Agilent Technology) and found that while, in the test cell YA of the comparative example, carbon monoxide (CO) was less than 1% by volume, in the test cell YB of the example, CO was 50% by volume or more. That is, in the example, the inside of the battery outer package was the reducing gas (CO gas) atmosphere. This CO is considered generated at the time of initial charging by reduction and decomposition of the LiFOP added to the nonaqueous electrolytic solution. Further, from the result of this gas analysis, it is found that in the test cell YB of the example, the step ⁇ was performed by the initial charging, and in the test cell YA of the comparative example, the step ⁇ was not performed by the initial charging.
  • I-V characteristics was measured by using a commercially available electronic load device, and the direct current resistances of the test cells after charging of the example and the comparative example were obtained thereby. Results are shown in FIG. 2.
  • FIG. 2 is a graph that shows direct current resistances of the test cells of the example and the comparative example.
  • the test cell YB of the example had the direct current resistance lower than that of the test cell YA of the comparative example and was a battery excellent in the performance. This is considered because CO that has a strong reduction action reduced the oxide film formed on the surface of the copper foil.

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Abstract

A manufacturing method of a nonaqueous electrolytic solution secondary battery, the manufacturing method comprising: obtaining a negative electrode having a negative electrode, mixture layer and a copper exposed part by forming the negative electrode mixture layer on copper foil; oxidizing the copper exposed part; inserting an electrode body containing the negative electrode in a battery outer package; injecting a nonaqueous electrolytic solution in the battery outer package; infiltrating the nonaqueous electrolytic solution into the electrode body; and making an atmosphere inside the battery outer package a reducing gas atmosphere. The amount of copper dissolved into the electrolyte is thereby decreased.

Description

MANUFACTURING METHOD OF NONAQUEOUS ELECTROLYTIC SOLUTION
SECONDARY BATTERY
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a manufacturing method of a nonaqueous electrolytic solution secondary battery. 2. Description of Related Art
[0002] At present time, nonaqueous electrolytic solution secondary batteries including a lithium ion battery are widely in use. The nonaqueous electrolytic solution secondary battery, since it does not use water in an electrolytic solution that plays a role of transporting ions between positive and negative electrodes, can have a high battery voltage exceeding a water electrolysis voltage.
[0003] In such a nonaqueous electrolytic solution secondary battery, a retention amount and a distribution of the nonaqueous electrolytic solution in the battery largely affect a battery performance. So far, various approaches have been carried out to efficiently infiltrate the nonaqueous electrolytic solution into the battery (see Japanese Patent Application Publication No. 2007-335181 (JP 2007-335181 A), for example).
[0004] In general, in a negative electrode of the nonaqueous electrolytic solution secondary battery, copper (Cu) foil is used as a current collector. In a process of manufacturing the nonaqueous electrolytic solution secondary battery, after an electrode body including a positive electrode, the negative electrode and a separator is inserted in a battery outer package, the nonaqueous electrolytic solution is injected in the battery outer package.
[0005] Here, from the viewpoint of the battery performance, it is desirable to perform charging of a battery after the injected nonaqueous electrolytic solution is sufficiently infiltrated inside the electrode body. This is because when the charging of the battery is performed in a state in which the nonaqueous electrolytic solution is insufficiently infiltrated, there is a risk that an overvoltage is locally generated, the nonaqueous electrolytic solution causes an undesired decomposition reaction, or an active material is degraded.
[0006] However, the battery after the nonaqueous electrolytic solution is injected is in a non-charged state and a negative electrode potential exceeds an elution potential of copper. Therefore, when a time (infiltration time) for infiltrating the nonaqueous electrolytic solution is set longer, copper is eluted from the copper foil that is a current collector into the nonaqueous electrolytic solution. When copper is eluted, not only a current collection function is degraded but also eluted copper precipitates again, and various performance degradations are caused thereby. Therefore, for the battery after injection, it is required to set a potential of the negative electrode to less than the elution potential of copper by performing a predetermined amount of charging in an early stage. That is, in order to prevent copper from being eluted, the infiltration time of the nonaqueous electrolytic solution has to be limited.
[0007] On the other hand, the nonaqueous electrolytic solution secondary battery is demanded to have a higher capacity, and higher densification of the positive electrode, the negative electrode and the electrode body is in progress. Accompanying this, an infiltration passage of the nonaqueous electrolytic solution is narrowed, and there is a tendency that the nonaqueous electrolytic solution becomes difficult to infiltrate thereby. That is, in order to obtain a high capacity and high performance nonaqueous electrolytic solution secondary battery, a corresponding infiltration time is necessary.
[0008] From the situations described above, in the existing technologies, it was very difficult to manufacture a high capacity and high performance nonaqueous electrolytic solution secondary battery while preventing copper from being eluted.
SUMMARY OF THE INVENTION
[0009] The present invention provides a high capacity and high performance nonaqueous electrolytic solution secondary battery by preventing copper from being eluted.
[0010] A manufacturing method of a nonaqueous electrolytic solution secondary battery of the present invention includes the following structure. The manufacturing method comprises: forming a negative electrode mixture layer on a copper foil and obtaining a negative electrode having the negative electrode mixture layer and a copper exposed part thereby; oxidizing the copper exposed part; inserting an electrode body including the negative electrode into a battery outer package; injecting a nonaqueous electrolytic solution into the battery outer package; infiltrating the nonaqueous electrolytic solution into the electrode body; and making an atmosphere inside the battery outer package a reducing gas atmosphere.
[0011] According to the manufacturing method described above, the exposed surface of the copper foil (copper exposed part) is oxidized, and an oxide film is formed on the exposed surface. Therefore, even when a sufficient infiltration time is set, copper can be prevented from being eluted. Further, usually, when the copper foil is oxidized, electric resistance increases. However, according to the manufacturing method described above, by making the atmosphere inside the battery outer package the reducing gas atmosphere, the oxide film is reduced and returned to copper, therefore, an increase in the electric resistance can be suppressed. Therefore, while suppressing copper from being eluted, by setting a sufficient infiltration time, a high capacity and high performance nonaqueous electrolytic solution secondary battery can be manufactured.
[0012] The "copper exposed part" here shows not only a site in which the negative electrode mixture layer is not formed on the copper foil (that is, intermittently coated part) but also a site in which the negative electrode mixture layer is formed. This ■ is because since the negative electrode mixture layer is porous, also a site that is coated with the negative electrode mixture layer of the copper foil is substantially equivalent to be exposed.
[0013] In the manufacturing method described above, the nonaqueous electrolytic solution described above may contain a component that generates a reducing gas by an electrochemical reaction. And the reducing gas that derived from the component, may generated by applying an electric current to the electrode body.
[0014] According to such an aspect, the atmosphere inside the battery outer package is not necessary to be substituted with the reducing gas in order to make the inside of the battery outer package a reducing gas atmosphere. That is, compared with conventional ones, without increasing process load, the manufacturing method of the present invention can be performed.
[0015] The component that generates the reducing gas by the electrochemical reaction described above may be lithium difluorobisoxalatophosphate (hereinafter, abbreviated as "LiFOP" in some cases).
[0016] LiFOP is reduced during charging and generates carbon monoxide (CO) that is the reducing gas. CO is strong in a reduction action and can return the oxide film to copper by reduction. Further, since LiFOP forms an excellent SEI (Solid Electrolyte Interface) on a surface of the negative electrode during initial charging, the battery performance can be also improved.
[0017] According to the manufacturing method a nonaqueous electrolytic solution secondary battery of the present invention, while suppressing copper from being eluted, a high capacity and high performance nonaqueous electrolytic solution secondary battery can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
FIG. 1 is a graph that shows an example of a relationship between a infiltration time of a nonaqueous electrolytic solution and a copper elution amount in a nonaqueous electrolytic solution secondary battery according to an embodiment of the present invention; FIG. 2 is a graph that shows an example of a direct current resistance of the nonaqueous electrolytic solution secondary battery according to the embodiment of the present invention; and
FIG. 3 is a flowchart that shows an outline of the manufacturing method of the nonaqueous electrolytic solution secondary battery of the embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0019] Hereinafter, embodiments related to the present invention will be described in more detail. However, the present invention is not limited to these.
[0020] The present inventors studied hard to solve the problems described above and obtained knowledge that when an oxide film is formed by oxidizing copper foil, copper can be suppressed from being eluted. Further, a method of resolving an increase in electric resistance due to the oxide film by reducing the oxide film was found, and the present invention came to completion thereby.
[0021] That is, a manufacturing method of a nonaqueous electrolytic solution secondary battery according to the present embodiment includes the following steps. The manufacturing method comprise: a step a of obtaining a negative electrode haying a negative electrode mixture layer and a copper exposed part by forming the negative electrode mixture layer on copper foil; a step β of oxidizing the copper exposed part of the negative electrode; a step γ of inserting an electrode body including the negative electrode into a battery outer package; a step δ of injecting a nonaqueous electrolytic solution in the battery outer package; a step ε of infiltrating the nonaqueous electrolytic solution into the electrode body; and a step ζ of making an atmosphere inside the battery outer package a reducing gas atmosphere.
[0022] The nonaqueous electrolytic solution secondary battery manufactured according to such a manufacturing method typically has a structure as shown below. That is, the nonaqueous electrolytic solution secondary battery is formed by housing the electrode body and the nonaqueous electrolytic solution in the battery outer package. The electrode body is formed by winding a positive electrode and the negative electrode so as to face each other via a separator. The nonaqueous electrolytic solution is obtained by dissolving a lithium salt in an organic solvent. The positive electrode is obtained by forming a positive electrode mixture layer containing a positive electrode active material that can store and emit lithium ions on a current collector. The negative electrode is obtained by forming a negative electrode mixture layer containing a negative electrode active material that can store and emit lithium ions on copper foil that is a current collector. A separator is made of, for example, a microporous polyolefin film. The electrode body described here is a wound type. However, the electrode body may be a stack type electrode body formed by stacking the positive electrode, the separator and the negative electrode.
[0023] That is, in the nonaqueous electrolytic solution secondary battery manufactured according to the manufacturing method of the present embodiment, except that the copper foil is used in the negative electrode current collector, all so far known materials and structures can be adopted.
[0024] Hereinafter, each of steps of the manufacturing methodof the present embodiment will be described. FIG. 3 is a flowchart that shows an outline of the manufacturing method of a nonaqueous electrolytic solution secondary battery of the present embodiment. As shown in FIG. 3, the manufacturing method of a nonaqueous electrolytic solution secondary battery of the present embodiment includes a step a, a step β, a step γ, a step δ, a step ε, and a step ζ, and preferably includes the step a to step ζ in this order. The step β may be performed preceding the step a.
[0025] The step a is a step of obtaining the negative electrode having the negative electrode mixture layer and a copper exposed part by forming the negative electrode mixture layer on the copper foil. A method of forming the negative electrode mixture layer on the copper foil is not particularly limited. For example, the following method can be illustrated. That is, a negative electrode mixture slurry obtained by kneading the negative electrode active material, a thickener, a binder and a solvent (for example, water) is coated on the copper foil and dried, the negative electrode mixture layer can be formed oh the copper foil. At this time, the negative electrode mixture slurry may be intermittently coated on the copper foil such that the copper exposed part for welding later a negative electrode current collector tab may be formed. However, as described above, the copper exposed part does not show only such an intermittent coated part.
[0026] In order to prevent the negative electrode mixture from falling, the negative electrode mixture layer is preferably compressed to a predetermined thickness. For example, the thickness of the negative electrode mixture layer can be compressed such that the density of the negative electrode mixture layer becomes about 0.5 to 2.5 g/cm3. The density of the negative electrode mixture layer can be calculated according to "mass of the negative electrode mixture layer" ÷ "volume of the negative electrode mixture layer".
[0027] As the negative electrode active material, for example, carbonaceous materials such as graphite and cokes, silicon (Si), tin oxide (Sn02) or the like can be used. A content of the negative electrode active material in the negative electrode mixture is, for example, about 90 to 99% by mass. Further, as the binder, for example, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVdF), and polytetrafluoroethylene (PTFE) can be used. As the solvent, when water is used, in order to improve the coatability, for example, a thickener such as carboxymethylcellulose (CMC) or the like is preferably used.
[0028] As the copper foil that is the negative electrode current collector, any of electrolytic copper foil and rolled copper foil may be used. Further, in place of pure copper foil, copper alloy foil containing impurity elements can be used as well. This is because as long as metal foil containing copper is used as the negative electrode current collector, an effect of the present invention is exhibited. That is, the copper foil of the present embodiment includes also copper alloy foil. From the viewpoint of strength and. electric conductivity, a thickness of the copper foil is preferably about 5 to 30 μηι.
[0029] The step β is a step of oxidizing the copper exposed part of the negative electrode. That is, the step β is a step of oxidizing a surface of the copper foil. As a method of oxidizing a surface of the copper foil, for example, a method of heat treating a simple substance of copper foil, and a method of treating the simple substance of copper foil with a chemical such as acid or the like can be used. When the simple substance of copper foil is treated with a chemical such as acid or the like, the step β is performed preceding the step a. Further, when the negative electrode mixture slurry is coated on the copper foil and dried, also the copper foil can be heat treated at the same time. Furthermore, the negative electrode on which the negative electrode mixture layer was formed can also be heat treated. Among these, the method of oxidizing according to heat treatment is less in process load and preferable.
[0030] Here, for example, when the negative electrode on which the negative electrode mixture layer was formed is heat treated, a heat treatment temperature is preferably set to 100°C or more and 200°C or less. This is because when the heat treatment temperature exceeds 200°C, the binder is denatured and the binding force is degraded thereby in some cases, and when the heat treatment temperature is less than 100°C, the oxide film is insufficiently formed in some cases. From the same reason, the heat treatment time is preferably set to 30 minutes or more and 24 hours or less.
[0031] According to the present embodiment, by oxidizing a surface of the copper foil, the oxide film can be formed on a surface of the copper foil. Thus, copper inside the copper foil can be suppressed from being eluted in the nonaqueous electrolytic solution. Therefore,, in accordance with a specification of the battery, the infiltration time of the nonaqueous electrolytic solution can be set. In particular, when the manufacturing method of the present embodiment is applied to a high capacity battery designed such that the positive electrode, the negative electrode and the electrode body have high density, a high capacity and high performance battery can be obtained.
[0032] The step γ is a step of inserting the electrode body containing the negative electrode into the battery outer package. The electrode body containing the negative electrode can be manufactured, for example, by welding a current collector tab to the positive electrode and the negative electrode, and by winding such that the positive electrode and the negative electrode face with each other via the separator. All of the positive electrode, the negative electrode and the separator are formed in sheet. The electrode body is, after being inserted in the battery outer package, electrically connected with the battery outer package via the positive electrode current collector tab and the negative electrode current collector tab.
[0033] The positive electrode can be manufactured, for example, in such a manner that a positive electrode mixture slurry is coated on the current collector and dried and the positive electrode mixture layer is formed on the current collector thereby, thereafter, the positive electrode mixture layer is compressed to a predetermined thickness. The positive electrode mixture slurry is obtained by kneading, for example, the positive electrode active material, a conductive auxiliary agent, the binder and the organic solvent (for example, N-methyl-2-pyrrolidone (NMP)).
[0034] As the positive electrode active material, lithium-containing transition metal oxides such as LiCo02, LiNi02, LiNiaCob02 (a + b = 1, 0<a<l, 0<b<l), LiMn02, LiMn204, LiNiaCobMnc02 (a + b + c = 1, 0<a<l, 0<b<l, 0<c<l), LiFeP04 and the like can be used. A content of the positive electrode active material in the positive electrode mixture is, for example, about 90 to 99% by mass.
[0035] Further, as the conductive auxiliary agent, for example, carbonaceous material such as Acetylene Black (AB) or the like can be used, and as the binder, for example, PVdF and the like can be used. As the positive electrode current collector, for example, aluminum (Al) foil or aluminum alloy foil can be used, Further, the density of the positive electrode mixture layer (mass of positive electrode mixture layer ÷ volume of
* 3
positive electrode mixture layer) is, for example, about 2.0 to 4.0 g/cm .
[0036] As the separator, a microporous film made of a polyolefm-based material is preferable. Here, as the polyolefin-based material, polyethylene (PE), polypropylene (PP) and the like can be used, and these can be used also by combining. Further, a plurality of microporous films may be laminated. A thickness of the separator can be set to, for example, about 5 to 40 μπι.
[0037] As shape of the battery outer package, for example, there are a cylindrical shape, a rectangular shape and the like. The battery outer package includes usually an outer packaging can and a cap. The cap is provided with a positive electrode or negative electrode terminal part, and the terminal part is insulated from a counter electrode with a resin material, for example. A material of the battery outer package may be properly selected from various metals, alloy materials and the like, by considering the withstand voltage and the strength. For example, aluminum and alloys thereof, iron (Fe), stainless materials and the like can be used.
[0038] The step δ is a step of injecting the nonaqueous electrolytic solution in the battery outer package in which the electrode body was inserted. A method of injecting the nonaqueous electrolytic solution is not particularly limited. However, it is preferable to sufficiently dry the electrode body and the battery outer package before injection in order to avoid mixing of water. And the step δ is preferably performed under an inert gas 1 atmosphere (for example, argon (Ar)).
[0039] As the nonaqueous electrolytic solution, an organic solvent in which a solute (lithium salt) is dissolved can be used. Here, as the organic solvent, for example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (GBL) and vinylene carbonate (VC), and chain carbonates such as dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) can be used. These organic solvents can be used by properly combining two or more kinds thereof from the viewpoint of the electric conductivity and the electrochemical stability. It is particularly preferable to use a mixture of the cyclic carbonate and the chain carbonate and a volume ratio of the cyclic carbonate and the chain carbonate is preferable to be about 1 :9 to 5:5. When a specific example is cited, for example, three kinds of EC, DMC and EMC can be mixed and used.
[0040] Further, as the lithium salt that is a solute, for example, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiC104), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3S02)2N), lithium trifluoromethanesulfonate (Li(CF3S03) and the like can be used. Further, also these solutes may be used in combination of two or more kinds thereof. A concentration of the solute in the nonaqueous electrolytic solution is not particularly limited. However, it is preferable to be about 0.5 to 2.0 mol/L from the viewpoint of the discharge performance and storability. [0041] The nonaqueous electrolytic solution of the present embodiment preferably contains a component that generates the reducing gas by the electrochemical reaction as an additive. When the nonaqueous electrolytic solution contains the component like this, at the time of initial charging, the reducing gas is generated on a surface of the negative electrode, and the oxide film formed by the step β is reduced thereby. Thus, an increase in the resistance due to the oxide film can be resolved. Further,, the component like this is preferable to be able to form a high quality SEI on the surface of the negative electrode at the time of the initial charging.
[0042] As the component that can generate the reducing gas due to a reduction reaction and can form the SEI on the negative electrode, lithium salts that have an oxalate complex as an anion are preferred. This is because the lithium salts having the oxalate complex as an anion can emit carbon monoxide having a stronger reduction action at the time of reduction and decomposition. As the lithium salt having the oxalate complex as an anion, for example, lithium difluorobisoxalatophosphate (Li [P(C204)2F2]), lithium tetrafluorobisoxalatophosphate (Li[P(C204)2F4]), lithium difluorobisoxalatoborate (Li[B(C204)2F2]), and lithium bisoxalatoborate (Li[B(C204)2]) can be used. Among these, lithium difluorobisoxalatophosphate (LiFOP) is particularly preferably used. This is because since LiFOP forms a high quality SEI, also an improvement in the battery performance can be realized.
[0043] An addition amount of the component described above in the nonaqueous electrolytic solution is preferably 0.1% by mole or more and 1.0% by mole or less. This is because when the addition amount is 0.1% by mole or less, in some cases, a generation amount of the reducing gas is small, and the oxide film is insufficiently reduced thereby, and when the addition amount exceeds 1.0% by mole, in some cases, the reducing gas is excessively generated. The addition amount of the component described above is preferable to be 0.3% by mole or more and 0.7% by mole or less.
[0044] The step ε is a step of infiltrating the nonaqueous electrolytic solution in the electrode body. In the present embodiment, by undergoing the step β, the oxide film is formed on a surface of the copper foil. Therefore, in accordance with the battery specification, a desired infiltration time can be set. The battery specification includes, for example, the densities of the positive electrode mixture layer and the negative electrode mixture layer, the retention amount of the nonaqueous electrolytic solution, a battery capacity and so on. In the step ε, in order to facilitate the infiltration of the nonaqueous electrolytic solution, depressurization, pressurization or heating may be accompanied.
[0045] The step ζ is a step of making the inside of the battery outer package the reducing gas atmosphere after the nonaqueous electrolytic solution being thoroughly infiltrated into the electrode body. By undergoing the step ζ, the oxide film formed on the copper foil in the step β is reduced, and an increase in a direct current resistance of the battery can be evaded thereby. The step ζ is performed to prevent copper from being eluted after the initial charging. "After the initial charging" includes the same time with the initial charging or after the initial charging.
[0046] "The reducing gas atmosphere" indicates that the reducing gas occupies 30% by volume or more of a gas composition in the battery outer package. Here, from the viewpoint of making the direct current resistance of the battery further lower, the reducing gas preferably occupies 40% by volume or more and more preferably 50% by volume or more of the gas composition in the battery outer package.
[0047] As the reducing gas that can be used in the step ζ, hydrogen (H2), carbon monoxide (CO), hydrogen sulfide (H2S), sulfur dioxide (S02) and the like can be used. A method of making the inside of the battery outer package the reducing gas atmosphere is not particularly limited. For example, after the inside of the battery outer package is depressurized, the reducing gas may be injected, or a gas is introduced in a chamber in which the battery outer package is left at rest and the inside of the battery outer package may be substituted with the reducing gas.
[0048] Further, as described above, when the component that generates the reducing gas is added in the nonaqueous electrolytic solution, by applying an electric current to the electrode body (that is, by charging), the reducing gas is generated inside the battery outer package, and the inside of the battery outer package can be made the reducing gas atmosphere. That is, by introducing the electric current to the electrode body, a step of generating the reducing gas derived from the additive can be contained in the step ζ. This method is preferable because it does not accompany a gas substitution operation and is less in process load thereby. In this case, the initial charging and the step ζ can be combined.
[0049] After undergoing the steps described above, when an opening part of the battery outer package is sealed by a predetermined method, a nonaqueous electrolytic solution secondary battery according to the present embodiment can be manufactured.
[0050] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited thereto.
[0051] At first, as a preliminary experiment, the step β was performed and the copper exposed part of the negative electrode was oxidized, and it was confirmed that copper could be suppressed from being eluted hereby.
[0052] As the positive electrode active material, a powder made of a lithium-containing transition metal composite oxide that contains Li and three kinds of transition metal elements (Co, Ni and Mn) was prepared. This positive electrode active material, AB as the conductive auxiliary agent, and a solution in which PVdF as the binder is dissolved in NMP were kneaded, and the positive electrode mixture slurry was obtained. Then, the positive electrode mixture slurry was coated on both surfaces of Al foil that is the positive electrode current collector and dried, and the positive electrode mixture layer was formed on the Al foil. Subsequently, by use of a roll machine, the positive electrode mixture layer and the Al foil were rolled and a positive electrode was obtained thereby.
[0053] As the negative electrode active material, a carbonaceous material with natural graphite as a core material was prepared. Then, the negative electrode active material, CMC as the thickener, and SBR as the binder were kneaded in water, and the negative electrode mixture slurry was obtained. Then, the negative electrode mixture slurry was coated on both surfaces of Cu foil and dried, and a negative electrode mixture layer was formed on the Cu foil. Subsequently, by use of the roll machine, the negative electrode active material layer and the Cu foil were rolled and a negative electrode X was obtained thereby. [0054] The negative electrode X was charged in a thermostat set at 180°C and left for 1 hour. Thereby, a negative electrode Y in which the oxide film was formed on the copper exposed part was obtained.
[0055] A positive electrode current collector tab was welded to the positive electrode, and a negative electrode current collector tab was welded to the negative electrode X. Subsequently, the positive electrode, the negative electrode X and a separator made of a polyolefin microporous film were wound such that the positive electrode and the negative electrode X face each other via the separator, and an electrode body X was obtained. Further, in the same manner except that in place of the negative electrode X, the negative electrode Y was used, an electrode body Y was obtained.
[0056] Subsequently, the electrode body X was inserted in the battery outer package (outer package can) and the negative electrode current collector and the outer package can were welded, and the positive electrode current collector tab and the battery outer package (cap) were welded. Thus, a test cell X was obtained. Further, in the same manner except that in place of the electrode body X, the electrode body Y was used, a test cell Y was obtained.
[0057] In an organic solvent obtained by mixing EC, DMC and EMC, LiPF6 was dissolved at 1.1 M (1.1 mol/L) and a nonaqueous electrolytic solution A was obtained.
[0058] The nonaqueous electrolytic solution A was injected in each of the test cell X and the test cell Y, and a test cell XA and a test cell YA were obtained.
[0059] The test cell XA and the test cell YA were left at rest to make the nonaqueous electrolytic solution infiltrate into the electrode body. Then, every time when a predetermined time passed, the nonaqueous electrolytic solutions were sampled from the test cell XA and the test cell YA, and by means of an inductively-coupled plasma emission spectrometer (type name: ICP-V8100, manufactured by Shimadzu Corporation), concentrations of copper eluted in the nonaqueous electrolytic solutions were measured. Results are shown in FIG. 1.
[0060] FIG. 1 is a graph that shows a relationship between the infiltration time of the nonaqueous electrolytic solution and a copper elution amount. In FIG. 1, a horizontal axis shows the infiltration time of the nonaqueous electrolytic solution and a vertical axis shows a concentration of copper ions eluted in the electrolytic solution. Curves in FIG. 1 are supplementarily drawn to make it easy to understand a tendency. As shown in FIG. 1 , the Cu elution amount of the test cell YA that underwent the step β is small from the start of infiltration and continues to be nearly flat even after the elapse of 50 hours. On the other hand, the Cu elution amount of the test cell XA that did not undergo the step β rapidly increases from immediately after the start of infiltration and continues to increase after that. Thus, the test cell YA that underwent the step β was remarkably reduced in the copper elution amount compared with that of the test cell XA that did not undergo the step β. This is considered because in the test cell YA, by undergoing the step β, the oxide film was formed on the copper exposed part of the negative electrode, and by the oxide film, copper was suppressed from being eluted.
[0061] As described above, it was confirmed that copper can be suppressed from being eluted in the step (step ε) of infiltrating the nonaqueous electrolytic solution by performing the step β that oxidizes the copper exposed part of the negative electrode.
[0062] In the example, it was confirmed that when the step ζ of making the inside of the battery outer package the reducing gas atmosphere is performed to the test cell Y in which, by undergoing the step β, the oxide film was formed on the copper exposed part of the negative electrode, the direct current resistance of the battery can be reduced.
[0063] By adding 0.5% by mole of LiFOP to the nonaqueous electrolytic solution
A, a nonaqueous electrolytic solution B was obtained.
[0064] By injecting the nonaqueous electrolytic solution B in the test cell Y (copper foil was oxidized) and by fixing the cap and the outer package can by a predetermined method, a test cell YB according to the example was obtained. Further, in the same manner except that the nonaqueous electrolytic solution A was injected in the test cell Y, a test cell YA according to comparative example was obtained.
[0065] The test cells of example and comparative example were left at rest for 24 hours to make the nonaqueous electrolytic solution infiltrate into the electrode body.
[0066] Next, to the test cells of the example and the comparative example, the initial charging was performed. After charging, a gas composition inside each of the test cells was analyzed with a gas chromatograph analyzer (type "G1530A", manufactured by Agilent Technology) and found that while, in the test cell YA of the comparative example, carbon monoxide (CO) was less than 1% by volume, in the test cell YB of the example, CO was 50% by volume or more. That is, in the example, the inside of the battery outer package was the reducing gas (CO gas) atmosphere. This CO is considered generated at the time of initial charging by reduction and decomposition of the LiFOP added to the nonaqueous electrolytic solution. Further, from the result of this gas analysis, it is found that in the test cell YB of the example, the step ζ was performed by the initial charging, and in the test cell YA of the comparative example, the step ζ was not performed by the initial charging.
[0067] Further, I-V characteristics was measured by using a commercially available electronic load device, and the direct current resistances of the test cells after charging of the example and the comparative example were obtained thereby. Results are shown in FIG. 2.
[0068] FIG. 2 is a graph that shows direct current resistances of the test cells of the example and the comparative example. As shown in FIG. 2, the test cell YB of the example had the direct current resistance lower than that of the test cell YA of the comparative example and was a battery excellent in the performance. This is considered because CO that has a strong reduction action reduced the oxide film formed on the surface of the copper foil.
[0069] As described aboye, when the step ζ of making the inside of the battery outer package the reducing gas atmosphere is performed after undergoing the step a to step ε, it was confirmed that, while suppressing copper from being eluted, a high performance nonaqueous electrolytic solution secondary battery having a low direct current resistance can be obtained.
[0070] Further, it was confirmed that whe the component (lithium difluorobisoxalatophosphate) that generates the reducing gas by the electrochemical reaction to the nonaqueous electrolytic solution, the initial charging can combine the step [0071] The embodiment and example disclosed this time are illustrations in all points and should be considered not restrictive; The range of the present invention is shown not by the descriptions described above but by claims, and all modifications in the meaning and range equivalent with claims are intended to be included.

Claims

1. A manufacturing method of a nonaqueous electrolytic solution secondary battery, the manufacturing method comprising:
obtaining a negative electrode having a negative electrode mixture layer and a copper exposed part by forming the negative electrode mixture layer on copper foil;
oxidizing the copper exposed part;
inserting an electrode body containing the negative electrode in a battery outer package;
injecting a nonaqueous electrolytic solution into the battery outer package;
infiltrating the nonaqueous electrolytic solution in the electrode body; and
making an atmosphere inside the battery outer package to be a reducing gas atmosphere.1
2. The manufacturing method according to claim 1 , wherein
the nonaqueous electrolytic solution contains a component that generates the reducing gas by an electrochemical reaction, the reducing gas that derived from the component, is generated by applying an electric current to the electrode body.
3. The manufacturing method according to claim 2, wherein
the component is lithium difluorobisoxalatophosphate.
PCT/IB2014/001519 2013-08-22 2014-08-14 Manufacturing method of nonaqueous electrolytic solution secondary battery WO2015025207A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001196096A (en) * 2000-01-11 2001-07-19 Toyota Central Res & Dev Lab Inc Manufacturing method for non-aqueous lithium secondary battery
JP2007335181A (en) 2006-06-14 2007-12-27 Matsushita Electric Ind Co Ltd Manufacturing method and device for nonaqueous electrolyte secondary battery
WO2013035187A1 (en) * 2011-09-08 2013-03-14 トヨタ自動車株式会社 Lithium secondary battery manufacturing method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001196096A (en) * 2000-01-11 2001-07-19 Toyota Central Res & Dev Lab Inc Manufacturing method for non-aqueous lithium secondary battery
JP2007335181A (en) 2006-06-14 2007-12-27 Matsushita Electric Ind Co Ltd Manufacturing method and device for nonaqueous electrolyte secondary battery
WO2013035187A1 (en) * 2011-09-08 2013-03-14 トヨタ自動車株式会社 Lithium secondary battery manufacturing method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
NOVAK P ET AL: "Advanced in situ methods for the characterization of practical electrodes in lithium-ion batteries", JOURNAL OF POWER SOURCES, ELSEVIER SA, CH, vol. 90, no. 1, 1 September 2000 (2000-09-01), pages 52 - 58, XP004209913, ISSN: 0378-7753, DOI: 10.1016/S0378-7753(00)00447-X *

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