WO2013088929A1 - 二次電池 - Google Patents
二次電池 Download PDFInfo
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- WO2013088929A1 WO2013088929A1 PCT/JP2012/080189 JP2012080189W WO2013088929A1 WO 2013088929 A1 WO2013088929 A1 WO 2013088929A1 JP 2012080189 W JP2012080189 W JP 2012080189W WO 2013088929 A1 WO2013088929 A1 WO 2013088929A1
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- secondary battery
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- graphite
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- 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
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H01M4/04—Processes of manufacture in general
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- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0416—Methods of deposition of the material involving impregnation with a solution, dispersion, paste or dry powder
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- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- 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
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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- H01M2220/00—Batteries for particular applications
- H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
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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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- 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
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- 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
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- Embodiments according to the present invention relate to a secondary battery.
- lithium ion secondary batteries Since lithium ion secondary batteries have a small volume, a large mass capacity density, and a high voltage can be taken out, they are widely used as power sources for small devices. For example, it is used as a power source for mobile devices such as mobile phones and notebook computers. Also, in recent years, in addition to small mobile device applications, large secondary devices that require a long life with a large capacity, such as electric vehicles (EV) and power storage fields, are being considered due to consideration for environmental issues and increased awareness of energy conservation. Application to batteries is expected.
- EV electric vehicles
- a carbon-based material is used as the negative electrode active material used for the negative electrode of the secondary battery.
- the binder used for the electrode of a secondary battery plays the role which couple
- the binder is required to have high adhesiveness, high resistance to an electrolytic solution, electrochemical stability, a simple manufacturing process, and low cost.
- a typical binder is polyvinylidene fluoride (PVDF).
- PVDF polyvinylidene fluoride
- an imide resin typified by polyimide as a binder is disclosed (Patent Documents 1 to 3).
- An object of the present embodiment is to provide a secondary battery negative electrode capable of providing a secondary battery having high charge / discharge efficiency and a high capacity retention rate in a charge / discharge cycle.
- the negative electrode for a secondary battery according to the present embodiment includes scaly graphite, a fluorine resin, and an imide resin.
- the secondary battery according to the present embodiment includes the secondary battery negative electrode according to the present embodiment.
- a method for manufacturing a negative electrode for a secondary battery according to the present embodiment includes a negative electrode slurry containing scaly graphite, a fluorine resin, an imide resin, and a solvent that dissolves the fluorine resin and the imide resin.
- a negative electrode for a secondary battery that can provide a secondary battery with high charge / discharge efficiency and a high capacity retention rate in a charge / discharge cycle.
- the negative electrode for a secondary battery includes scaly graphite, a fluorine-based resin, and an imide-based resin.
- the graphite When graphite is used as the negative electrode active material for the negative electrode for secondary batteries, the graphite is usually coated with amorphous carbon from the viewpoint of low reactivity with the electrolyte and low orientation of the graphite particles, Graphite with a small aspect ratio processed into a spherical shape or a block shape is used.
- these graphites are high in cost because it is necessary to process particles into a spherical shape or to coat the surface with amorphous carbon.
- graphite coated with amorphous carbon generates irreversible capacity derived from amorphous carbon, and the charge / discharge efficiency of the secondary battery decreases.
- flaky graphite which is relatively inexpensive, is easily oriented on the negative electrode and has high activity on the edge surface, so that it has high reactivity with the electrolytic solution, and has low charge / discharge efficiency and capacity maintenance rate in the charge / discharge cycle.
- a fluorine resin and an imide resin are used as a binder in the negative electrode.
- a resin it is possible to provide a negative electrode for a secondary battery that has high charge / discharge efficiency and a high capacity retention rate in a charge / discharge cycle when used in a secondary battery.
- the adhesion of the negative electrode active material layer can be improved, and the reactivity between the electrolyte and the scaly graphite can be reduced. Conceivable.
- the surface of the scaly graphite is coated with an imide resin to form a kind of lithium ion-permeable film such as SEI, and the reactivity of the scaly graphite to the electrolyte solution is reduced. Is guessed.
- Patent Document 3 describes the use of a fluorine-based resin and an imide-based resin as a binder, but the example of Patent Document 3 describes an example in which the binder is used only in a positive electrode. Yes. Patent Document 3 does not describe scaly graphite.
- fluorine-based resin and imide-based resin are used as a negative electrode binder, and the negative electrode active material has a low charge-discharge efficiency and a low capacity retention rate in the charge-discharge cycle.
- the negative electrode for secondary batteries which can provide a secondary battery with low cost, high charge / discharge efficiency, and a high capacity retention rate in the charge / discharge cycle can be provided.
- the negative electrode for a secondary battery according to this embodiment includes flaky graphite as a negative electrode active material.
- Graphite materials include naturally occurring natural graphite and artificially produced artificial graphite. These have various particle forms such as block graphite, flake graphite, and spherical graphite depending on the manufacturing method and processing method. As described above, although it is inexpensive in this embodiment, it is easily oriented on the electrode, and the activity of the edge surface is high, so the reactivity with the electrolytic solution is high, the charge / discharge efficiency, and the capacity retention rate in the charge / discharge cycle. Is used as the negative electrode active material.
- “flaky graphite” refers to graphite particles having a flat shape.
- the “flaky graphite” is preferably graphite particles having a flat plate shape.
- the shape of the “flaky graphite” is not particularly limited as long as it has the above form, and may be, for example, a cylindrical shape or a rectangular parallelepiped shape.
- the aspect ratio of scaly graphite is preferably 2 or more, and more preferably 4 or more. Further, the aspect ratio is preferably 10 or less, and more preferably 8 or less.
- the aspect ratio is represented by A / B, where A is the length in the maximum major axis direction of the graphite particles and B is the length in the minor axis direction orthogonal thereto.
- A is the length in the maximum major axis direction of the graphite particles and B is the length in the minor axis direction orthogonal thereto.
- the cross-section of the negative electrode mixture containing graphite particles and a binder is observed with an SEM, and at the midpoint between the maximum long axis length (A) and the maximum long axis of 10 arbitrarily selected graphite particles.
- An average value of A / B is calculated from the length (B) of the orthogonal short axis. Let this average value be an aspect ratio.
- the average particle diameter (D50) of the flaky graphite in the present embodiment is preferably 5 ⁇ m or more and 50 ⁇ m or less, and more preferably 10 ⁇ m or more and 30 ⁇ m or less.
- the specific surface area of the scaly graphite in the present embodiment is preferably 0.5 m 2 / g or more and 5 m 2 / g or less, and more preferably 1 m 2 / g or more and 3 m 2 / g or less. .
- the average particle diameter (D50) of scaly graphite be the value measured by the laser diffraction and the scattering method.
- the specific surface area of the scaly graphite is a value measured and calculated by the BET method.
- the ratio of the flaky graphite to the total of the flaky graphite contained in the negative electrode for secondary battery according to the present embodiment and the binder of the negative electrode described later is preferably 85% by mass or more and 99% by mass or less, 90 More preferably, it is at least 98% by mass.
- the negative electrode for a secondary battery according to this embodiment includes a fluorine resin and an imide resin as a binder.
- PVDF polyvinylidene fluoride
- SBR styrene butadiene rubber
- CMC carboxymethylcellulose
- the imide resin since the imide resin has high adhesiveness, high resin strength, and high resistance to the electrolyte, it is considered that the physical properties of the resin are suitable for the binder of the negative electrode, and improvement in cycle characteristics is expected.
- the imide-based resin is expensive and has a property of trapping lithium, so that the irreversible capacity increases, the charge / discharge efficiency (battery capacity) decreases, and the imide ring is closed at 300 ° C. or higher in order to close the ring. It is difficult to put it into practical use because of the necessity of heat treatment.
- a fluorine resin and an imide resin are used in combination as a binder used for the negative electrode.
- the fluorine-based resin and the imide-based resin in combination, it is possible to impart the adhesiveness and electrolyte resistance required for the negative electrode binder while reducing the amount of the imide-based resin used. Thereby, cycling characteristics can be improved and the fall of the charging / discharging efficiency resulting from the lithium trap of imide resin can be suppressed.
- Fluorine resin according to the present embodiment is not particularly limited, but PVDF, polytetrafluoroethylene (PTFE), or the like can be used.
- a polymer or copolymer containing at least one selected from the group consisting of vinylidene fluoride (VDF), tetrafluoroethylene (TFE) and hexafluoropropane (HFP) as a constituent unit can be used.
- VDF vinylidene fluoride
- TFE tetrafluoroethylene
- HFP hexafluoropropane
- PVDF KF polymer (trade name, manufactured by Kureha Co., Ltd.) and the like can be mentioned.
- VDF vinylidene fluoride
- TFE tetrafluoroethylene
- HFP hexafluoropropane
- VDF / TFE / HFP ternary copolymer examples thereof include Neoflon VT470 (trade name, manufactured by Daikin Industries, Ltd.). These may use only 1 type and may use 2 or more types together.
- the weight average molecular weight of the fluororesin according to the present embodiment is preferably 200,000 or more and 1,200,000 or less, and more preferably 300,000 or more and 800,000 or less.
- the imide resin according to the present embodiment is not particularly limited, but is preferably polyimide or polyamideimide.
- the polyimide include aromatic polyimide and polyetherimide.
- the polyamideimide include aromatic polyamideimide.
- imide resin which concerns on this embodiment has hydrophilic groups, such as a carboxyl group and a hydroxyl group. These may use only 1 type and may use 2 or more types together.
- the imide ring closure rate of the imide resin used in preparing the negative electrode slurry before the heat treatment step is preferably 80% or more, and the imide ring closure rate is more than 90%. preferable.
- the weight average molecular weight of the imide resin according to this embodiment is preferably 5,000 or more and 50,000 or less, and more preferably 10,000 or more and 30,000 or less.
- the mass ratio (IP / (FP + IP)) of the imide resin (IP) to the total of the fluorine resin (FP) and the imide resin (IP) included in the negative electrode for a secondary battery according to the present embodiment is 0. It is preferably 1 or more and 0.5 or less.
- IP / (FP + IP) is 0.1 or more, the adhesive strength is sufficient and the cycle characteristics are improved.
- IP / (FP + IP) is 0.5 or less, a decrease in initial capacity due to a decrease in charge / discharge efficiency can be suppressed.
- IP / (FP + IP) is more preferably 0.15 or more and 0.4 or less, and further preferably 0.2 or more and 0.3 or less.
- the mass ratio (FP / SG) of the fluororesin (FP) to the scaly graphite (SG) included in the negative electrode for a secondary battery according to this embodiment is 0.01 or more and 0.05 or less. From the viewpoint of improving charge / discharge efficiency and capacity retention rate, it is preferable.
- FP / SG is more preferably 0.02 or more and 0.047 or less, and further preferably 0.025 or more and 0.045 or less.
- the mass ratio (IP / SG) of the imide resin (IP) to the flaky graphite (SG) contained in the secondary battery negative electrode according to the present embodiment is 0.005 or more and 0.05 or less. From the viewpoint of improving charge / discharge efficiency and capacity retention rate, it is preferable. IP / SG is more preferably 0.01 or more and 0.04 or less, and further preferably 0.016 or more and 0.03 or less.
- the content of the fluorine-based resin and the imide-based resin as the binder contained in the secondary battery negative electrode according to this embodiment is preferably 2% by mass or more and 10% by mass or less, and preferably 3% by mass or more and 6% by mass. % Or less is more preferable.
- the content of the fluorine-based resin and the imide-based resin is 2% by mass or more, the adhesive strength is improved and the cycle characteristics are improved.
- content of a fluorine resin and an imide resin is 10 mass% or less, the reduction
- a method for manufacturing a negative electrode for a secondary battery according to the present embodiment includes a negative electrode slurry containing scaly graphite, a fluorine resin, an imide resin, and a solvent that dissolves the fluorine resin and the imide resin.
- the negative electrode slurry according to the present embodiment includes scaly graphite, a fluorine resin, an imide resin, and a solvent that dissolves the fluorine resin and the imide resin.
- the imide resin contained in the negative electrode slurry preferably has an imide ring closing rate of 80% or more, more preferably 90% or more.
- an imide resin having an imide ring closure rate of 80% or higher heat treatment at a high temperature of 300 ° C. or higher is not necessary in the heat treatment step described later, and therefore a fluorine resin having a heat resistance of 150 ° C. or lower is also used. It becomes possible to do.
- adhesive strength improves and it can suppress the fall of cycling characteristics by presence of an unreacted precursor.
- imide-based resins having an imide ring closure rate of 80% or more include, as commercial products, polyamide-imide Bilomax (trade name, manufactured by Toyobo Co., Ltd.), polyimide Rika Coat (trade name, New Nippon Rika Co., Ltd.), Sokuseal (trade name, manufactured by Nippon Kogyo Paper Industries Co., Ltd.), and the like. These are soluble in N-methylpyrrolidone (NMP).
- NMP N-methylpyrrolidone
- the ring closure rate of the imide ring of the imide resin can be measured by FT-IR. That is, the IR spectrum of 604 cm ⁇ 1 (absorption spectrum derived from an imide group) and 880 cm ⁇ 1 (absorption spectrum derived from vibration of a benzene ring) are used.
- ⁇ absorbance of subject (604 cm ⁇ 1 ) / absorbance of subject (880 cm ⁇ 1 )
- ⁇ ′ absorbance of 100% closed ring (604 cm ⁇ 1 ) / absorbance of 100% ring closed (880 cm ⁇ 1 ) It is.
- Solvents for dissolving the fluorine-based resin and the imide-based resin include, for example, NMP, N-ethyl-2-pyrrolidone (NEP), N, N-dimethylformamide, N, depending on the type of the fluorine-based resin and the imide-based resin. , N-dimethylacetamide, N, N-dimethylpropionamide, methyl ethyl ketone, ⁇ -butyrolactone, xylene and the like. These may use only 1 type and may use 2 or more types together.
- the negative electrode slurry can contain a conductive additive in addition to the flaky graphite, the fluorine resin, the imide resin and the solvent. Carbon black, carbon fiber, etc. can be used as the conductive additive used for the negative electrode slurry.
- the negative electrode current collector copper, stainless steel, nickel, titanium, or an alloy thereof can be used.
- a negative electrode slurry is applied to the negative electrode current collector to form a coating film of the negative electrode slurry on the negative electrode current collector.
- the method for applying the negative electrode slurry to the negative electrode current collector is not particularly limited.
- the coating film of the negative electrode slurry may be formed only on one side of the negative electrode current collector, or may be formed on both sides.
- heat treatment is performed at a temperature of 100 ° C. or higher and 150 ° C. or lower in order to remove the solvent of the coating film formed on the negative electrode current collector.
- the heat treatment is sufficiently performed by performing the heat treatment at a temperature of 100 ° C. or higher.
- by performing heat treatment at a temperature of 150 ° C. or lower it becomes possible to use a fluorine resin having a heat resistance of 150 ° C. or lower in combination.
- a negative electrode active material layer is formed on the negative electrode current collector by the heat treatment step.
- the secondary battery according to the present embodiment includes the secondary battery negative electrode according to the present embodiment.
- the configuration of the secondary battery according to this embodiment is not particularly limited as long as the secondary battery includes the secondary battery negative electrode according to this embodiment.
- a laminated secondary battery is shown in FIG.
- the secondary battery shown in FIG. 1 is a negative electrode for a secondary battery according to this embodiment including a positive electrode composed of a positive electrode active material layer 1 and a positive electrode current collector 3, and a negative electrode active material layer 2 and a negative electrode current collector 4.
- a separator 5 is sandwiched between the two.
- the positive electrode current collector 3 is connected to the positive electrode tab 8
- the negative electrode current collector 4 is connected to the negative electrode tab 7.
- a laminate film 6 is used for the exterior body, and the inside of the secondary battery is filled with a non-aqueous electrolyte.
- the secondary battery according to the present embodiment may be a lithium secondary battery or a lithium ion secondary battery.
- Lithium containing complex oxide can be used as the lithium-containing composite oxide.
- LiM1O 2 is at least one element selected from the group consisting of Mn, Fe, Co, and Ni, and a part of M1 is substituted with Mg, Al, or Ti.
- LiMn 2 ⁇ x M2 x O 4 is at least one element selected from the group consisting of Mg, Al, Co, Ni, Fe and B, and 0 ⁇ x ⁇ 2).
- An olivine type material represented by LiFePO 4 can also be used.
- lithium manganate represented by LiMn 2 ⁇ x M2 x O 4 in particular has a lower capacity than lithium cobaltate (LiCoO 2 ) and lithium nickelate (LiNiO 2 ), but compared with Ni and Co. Therefore, since the production amount of Mn is large, the material cost is low. For this reason, it is preferable as a positive electrode active material for large-sized secondary batteries such as electric vehicles and power storage.
- the positive electrode of the secondary battery according to the present embodiment is not particularly limited, for example, a positive electrode active material layer is formed on at least one surface of the positive electrode current collector.
- a positive electrode active material layer is not specifically limited, for example, the said positive electrode active material, a binder, and a conductive support agent are included.
- binder used for the positive electrode examples include fluorine resins such as PVDF and acrylic resins. These may use only 1 type and may use 2 or more types together.
- Examples of the conductive aid used for the positive electrode include carbon black and carbon fiber. These may use only 1 type and may use 2 or more types together. In particular, it is preferable to use carbon black having low crystallinity as a conductive additive used for the positive electrode.
- the positive electrode current collector aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used.
- the method for producing the positive electrode is not particularly limited.
- the positive electrode active material, the binder, and the conductive additive are dispersed and kneaded in a predetermined amount in a solvent such as NMP, and the obtained positive electrode slurry is used as the positive electrode.
- the positive electrode slurry can be appropriately dried and heat-treated, whereby a positive electrode active material layer can be formed on the positive electrode current collector.
- Non-aqueous electrolyte Although it does not specifically limit as a non-aqueous electrolyte, for example, the solution which melt
- lithium salt examples include LiPF 6 , lithium imide salt, LiAsF 6 , LiAlCl 4 , LiClO 4 , LiBF 4 , LiSbF 6, and the like.
- At least one solvent selected from the group consisting of cyclic carbonates, chain carbonates, aliphatic carboxylic acid esters, ⁇ -lactones, cyclic ethers and chain ethers can be used.
- the cyclic carbonate include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and derivatives thereof (including fluorinated products).
- the chain carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and derivatives thereof (including fluorinated products).
- Examples of the aliphatic carboxylic acid ester include methyl formate, methyl acetate, ethyl propionate, and derivatives thereof (including fluorinated products).
- Examples of ⁇ -lactone include ⁇ -butyrolactone and its derivatives (including fluorinated products).
- Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran and derivatives thereof (including fluorinated products).
- Examples of the chain ether include 1,2-diethoxyethane (DEE), ethoxymethoxyethane (EME), ethyl ether, diethyl ether, and derivatives thereof (including fluorinated compounds).
- non-aqueous solvents include dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propyl nitrile, nitromethane, ethyl monoglyme, phosphate triester, trimethoxymethane, Dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, 1,3-propane sultone, anisole, N-methylpyrrolidone, and derivatives thereof (fluorinated compounds) Can also be used. These may use only 1 type and may use 2 or more types together.
- the concentration of the lithium salt in the nonaqueous electrolytic solution is preferably 0.7 mol / L or more and 1.5 mol / L or less.
- concentration of the lithium salt By setting the concentration of the lithium salt to 0.7 mol / L or more, sufficient ionic conductivity can be obtained.
- concentration of lithium salt 1.5 mol / L or less a viscosity can be made low and the movement of lithium ion is not prevented.
- the non-aqueous electrolyte may contain an additive in order to form a high-quality SEI (Solid Electrolyte Interface) film on the negative electrode surface.
- SEI Solid Electrolyte Interface
- the SEI film functions to suppress the reactivity with the electrolytic solution or to smooth the desolvation reaction accompanying the insertion and desorption of lithium ions to prevent structural deterioration of the negative electrode active material.
- examples of such additives include propane sultone, vinylene carbonate, and cyclic disulfonic acid esters. These may use only 1 type and may use 2 or more types together.
- the concentration of the additive in the nonaqueous electrolytic solution is preferably 0.2% by mass or more and 5% by mass or less.
- concentration of the additive is 0.2% by mass or more, a sufficient SEI film is formed.
- resistance can be made low because the density
- Positive electrode tab negative electrode tab
- at least 1 type selected from the group which consists of Al, Cu, phosphor bronze, Ni, Ti, Fe, brass, stainless steel can be used as a material.
- Separator Although it does not specifically limit as a separator, The porous film which consists of polyolefin, such as a polypropylene and polyethylene, a fluorine resin, etc. can be used. In addition, inorganic separators such as cellulose and glass separators can also be used.
- Exterior body Although it does not specifically limit as an exterior body, Cans, such as a coin shape, a square shape, and a cylindrical shape, and a laminate exterior body can be used. Among these, a laminate outer package which is a flexible film made of a laminate of a synthetic resin and a metal foil is preferable from the viewpoint of being able to reduce the weight and improving the energy density of the secondary battery.
- a laminate-type secondary battery including a laminate outer package is excellent in heat dissipation, and thus is suitable as a vehicle-mounted battery such as an electric vehicle.
- a positive electrode tab and a negative electrode tab are connected to the positive electrode and the negative electrode for a secondary battery according to the present embodiment via a positive electrode current collector and a negative electrode current collector, respectively.
- the positive electrode and the negative electrode are arranged opposite to each other with the separator interposed therebetween, and an electrode laminate is produced in which the positive electrode and the negative electrode are laminated.
- the electrode laminate is accommodated in an exterior body and immersed in an electrolytic solution.
- a secondary battery is manufactured by sealing the exterior body so that a part of the positive electrode tab and the negative electrode tab protrudes to the outside.
- Example 1 (Preparation of negative electrode) As flaky graphite (SG) which is a negative electrode active material, flaky artificial graphite powder (average particle diameter (D50): 13 ⁇ m, specific surface area: 2.0 m 2 / g, aspect ratio: 4.3) was prepared. As a binder, VDF / TFE / HFP ternary copolymer (trade name: NEOFLON VT470, manufactured by Daikin Industries, Ltd.), which is a fluororesin (FP), was prepared. In addition, polyamideimide (trade name: Viromax HR11NN, manufactured by Toyobo Co., Ltd.), which is an imide resin (IP), was prepared as a binder.
- VDF / TFE / HFP ternary copolymer trade name: NEOFLON VT470, manufactured by Daikin Industries, Ltd.
- FP fluororesin
- polyamideimide trade name: Viromax HR11NN, manufactured by Toyobo Co., Ltd
- the ring closure rate of the polyamideimide is 100%.
- NMP nitrogen-pentane
- the negative electrode slurry was applied on a copper foil having a thickness of 15 ⁇ m as a negative electrode current collector. Then, it was made to dry at 125 degreeC for 10 minute (s), and NMP was evaporated, and the negative electrode active material layer was formed. A negative electrode was produced by pressing the negative electrode active material layer. In addition, the mass of the negative electrode active material layer per unit area after drying was 0.008 g / cm 2 .
- LiMn 2 O 4 powder (average particle diameter (D50): 15 ⁇ m, specific surface area: 0.5 m 2 / g) was prepared as a positive electrode active material.
- the positive electrode active material, PVDF as a binder, and carbon black as a conductive additive were uniformly dispersed in NMP at a mass ratio of 91: 4: 5 to prepare a positive electrode slurry.
- the positive electrode slurry was applied on a 20 ⁇ m thick aluminum foil as a positive electrode current collector. Then, it dried at 125 degreeC for 10 minute (s), the NMP was evaporated, the positive electrode active material layer was formed, and it was set as the positive electrode.
- the mass of the positive electrode active material layer per unit area after drying was set to 0.024 g / cm 2 .
- the produced positive electrode and negative electrode were each cut into 5 cm ⁇ 6 cm. Of these, a side of 5 cm ⁇ 1 cm was a portion where the electrode active material layer was not formed (uncoated portion) in order to connect the tab, and a portion where the electrode active material layer was formed was 5 cm ⁇ 5 cm.
- a positive electrode tab made of aluminum having a width of 5 mm, a length of 3 cm, and a thickness of 0.1 mm was ultrasonically welded to the uncoated portion of the positive electrode with a length of 1 cm. Also, a nickel negative electrode tab having the same size as the positive electrode tab was ultrasonically welded to the uncoated portion of the negative electrode.
- the negative electrode and the positive electrode were arranged on both sides of a 6 cm ⁇ 6 cm polyethylene / polypropylene separator so that the electrode active material layers overlapped with the separator interposed therebetween to obtain an electrode laminate.
- Three sides of the two 7 cm ⁇ 10 cm aluminum laminate films except one of the long sides were bonded to each other with a width of 5 mm by thermal fusion to produce a bag-shaped laminate outer package.
- the electrode laminate was inserted into the bag-shaped laminate outer package so that the distance from the short side of the laminate outer package was 1 cm. Further, 0.2 g of the non-aqueous electrolyte was injected and vacuum impregnated, and then the opening was sealed with a width of 5 mm by thermal fusion under reduced pressure. Thus, a laminate type secondary battery was produced.
- FP fluorine-based resin
- FP fluorine-based resin
- Comparative Examples 2 and 3 the effect of heat treatment at a high temperature in the case of using an imide resin (IP) having a high imide ring closing rate was examined.
- the charge / discharge efficiency and the capacity retention rate were not significantly different depending on the presence or absence of the heat treatment at 250 ° C.
- Comparative Examples 4 and 5 the effect of heat treatment at a high temperature when using a polyamic acid which is a polyimide precursor whose imide ring is not closed was examined. Since the capacity retention rate of Comparative Example 4 was significantly lower than that of Comparative Example 5, it was confirmed that heat treatment at 300 ° C. was necessary in this case.
- Fluorine resin (FP) has a heat treatment temperature limited to 150 ° C.
- Example 3 showing the highest charge / discharge efficiency and capacity retention rate among the examples in order to further examine the effects of using a fluorine resin (FP) and an imide resin (IP) in combination as a binder for the negative electrode; Comparative Examples 1 and 2 were evaluated as follows.
- FP fluorine resin
- IP imide resin
- Example 3 and Comparative Examples 1 and 2 Only the negative electrode produced in Example 3 and Comparative Examples 1 and 2 was placed in an aluminum laminate film sealed on three sides, and a non-aqueous electrolyte was injected as in Example 3 and Comparative Examples 1 and 2 to seal one side. Stopped. After leaving this at 20 ° C., 45 ° C. and 60 ° C. for 20 hours, the negative electrode was taken out and the presence or absence of peeling of the negative electrode active material layer was visually confirmed. The results are shown in Table 2.
- Example 1 In Comparative Example 1 in which only the fluororesin (FP) was used as the binder for the negative electrode, the negative electrode active material layer was significantly peeled off as the temperature increased. On the other hand, in Example 3 and Comparative Example 2, no peeling was observed even at 60 ° C. From this, it was confirmed that the adhesiveness of the negative electrode active material layer is improved by adding the imide resin (IP) to the fluorine resin (FP) as the binder of the negative electrode.
- IP imide resin
- Initial charge / discharge was performed on the coin cell, and an initial charge / discharge curve was measured with the horizontal axis representing the capacity per mass of the negative electrode active material (mAh / g) and the vertical axis representing the voltage (mV).
- the initial charging condition was CC-CV charging at 0.16 mA (CV time: 20 hours, lower limit voltage: 5 mV).
- the initial discharge conditions were CC discharge at 0.16 mA (upper limit voltage: 2000 mV).
- FIG. 2 shows the measurement results of the initial charge / discharge curves in Example 3 and Comparative Examples 1 and 2.
- Comparative Example 1 in which only the fluororesin (FP) was used as the negative electrode binder, a shoulder presumed to be due to the reaction with the non-aqueous electrolyte was observed around 0.5 V during the initial charge. Therefore, it was suggested that when only the fluororesin (FP) was used as the binder for the negative electrode, not only the adhesion of the negative electrode active material layer was low but also the reactivity with the non-aqueous electrolyte was high. On the other hand, in Example 3 and Comparative Example 2, a shoulder near 0.5 V was not observed, and it was confirmed that the reactivity with the nonaqueous electrolytic solution was low.
- Example 3 has a smaller irreversible capacity than Comparative Examples 1 and 2, it is preferable to use both a fluororesin (FP) and an imide resin (IP) as a binder for the negative electrode. It was confirmed that the charge / discharge characteristics were improved as compared with the case of using alone. This is because the addition of the imide resin (IP) suppresses the reaction with the non-aqueous electrolyte, and the lithium trap by the imide resin (IP) is also suppressed by controlling the amount of the imide resin (IP) added. Therefore, it is estimated that the entire irreversible capacity is reduced.
- FP fluororesin
- IP imide resin
- the secondary battery could not be evaluated because the negative electrode active material layer was peeled off from the negative electrode current collector. It was confirmed that the amount of the imide resin (IP) used can be significantly reduced by using not only the imide resin (IP) but also the fluorine resin (FP) as a binder for the negative electrode.
- IP imide resin
- FP fluorine resin
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Abstract
Description
本実施形態に係る二次電池用負極は、鱗片状黒鉛と、フッ素系樹脂と、イミド系樹脂とを含む。
本実施形態に係る二次電池用負極は、負極活物質として鱗片状黒鉛を含む。
本実施形態に係る二次電池用負極は、バインダーとしてフッ素系樹脂およびイミド系樹脂を含む。
本実施形態に係る二次電池用負極の製造方法は、鱗片状黒鉛と、フッ素系樹脂と、イミド系樹脂と、前記フッ素系樹脂および前記イミド系樹脂を溶解する溶媒と、を含む負極スラリーを負極集電体に塗布する工程と、前記負極集電体を100℃以上、150℃以下の温度で熱処理する工程と、を含む。
本実施形態に係る二次電池は、本実施形態に係る二次電池用負極を備える。
本実施形態に係る二次電池の正極に含まれる正極活物質としては、特に限定されないが、リチウム含有複合酸化物を用いることができる。リチウム含有複合酸化物としては、LiM1O2(M1はMn、Fe、CoおよびNiからなる群から選択される少なくとも1種の元素であり、M1の一部がMg、AlまたはTiで置換されていてもよい)、LiMn2-xM2xO4(M2はMg、Al、Co、Ni、FeおよびBからなる群から選択される少なくとも一種の元素であり、0≦x<2である。)などを用いることができる。また、LiFePO4で表されるオリビン型材料を用いることもできる。これらは、例えばLi過剰組成など非化学量論組成であっても良い。また、これらは一種のみを用いてもよく、二種以上を併用することもできる。これらの中でも、特に前記LiMn2-xM2xO4で表されるマンガン酸リチウムは、コバルト酸リチウム(LiCoO2)やニッケル酸リチウム(LiNiO2)より容量は低いものの、NiやCoと比較してMnの産出量が多いため材料コストが低く、スピネル構造を有するため熱的安定性が高い。このため、電気自動車や電力貯蔵用などの大型二次電池向けの正極活物質材料として好ましい。
本実施形態に係る二次電池の正極は特に限定されないが、例えば、正極集電体の少なくとも一方の面に正極活物質層が形成されてなる。正極活物質層は特に限定されないが、例えば、前記正極活物質と、バインダーと、導電助剤とを含む。
非水電解液としては特に限定されないが、例えばリチウム塩を非水溶媒に溶解した溶液を用いることができる。
正極タブ、負極タブとしては、特に限定されないが、例えばAl、Cu、燐青銅、Ni、Ti、Fe、真鍮、ステンレスからなる群から選択される少なくとも一種を材料として用いることができる。
セパレータとしては、特に限定されないが、ポリプロピレン、ポリエチレン等のポリオレフィンや、フッ素系樹脂等からなる多孔性フィルムを用いることができる。また、セルロースやガラスセパレータなどの無機系セパレータを用いることもできる。
外装体としては、特に限定されないが、コイン型、角型、円筒型等の缶や、ラミネート外装体を用いることができる。この中でも、軽量化が可能であり、二次電池のエネルギー密度の向上を図る観点から、合成樹脂と金属箔との積層体からなる可撓性フィルムであるラミネート外装体が好ましい。ラミネート外装体を備えるラミネート型の二次電池は、放熱性にも優れているため、電気自動車などの車載用電池として好適である。
本実施形態に係る二次電池の製造方法は特に限定されないが、例えば、以下に示す方法が挙げられる。前記正極および本実施形態に係る二次電池用負極にそれぞれ正極集電体及び負極集電体を介して正極タブ、負極タブを接続する。前記正極と前記負極とを前記セパレータを挟んで対向配置させ、積層させた電極積層体を作製する。該電極積層体を外装体内に収容し、電解液に浸す。正極タブ、負極タブの一部を外部に突出するようにして外装体を封止することで、二次電池を作製する。
(負極の作製)
負極活物質である鱗片状黒鉛(SG)として、鱗片状人造黒鉛粉末(平均粒径(D50):13μm、比表面積:2.0m2/g、アスペクト比:4.3)を用意した。バインダーとして、フッ素系樹脂(FP)であるVDF/TFE/HFP3元共重合体(商品名:ネオフロンVT470、ダイキン工業(株)製)を用意した。また、バインダーとして、イミド系樹脂(IP)であるポリアミドイミド(商品名:バイロマックスHR11NN、東洋紡製)を用意した。該ポリアミドイミドの閉環率は100%である。鱗片状黒鉛(SG)、フッ素系樹脂(FP)およびイミド系樹脂(IP)を、それぞれの固形分の質量比がSG:FP:IP=95.0:2.5:2.5となるようにNMP中に均一に分散させて、負極スラリーを調製した。該負極スラリーを負極集電体である厚み15μmの銅箔上に塗布した。その後、125℃にて10分間乾燥させてNMPを蒸発させることにより、負極活物質層を形成した。該負極活物質層をプレスすることにより、負極を作製した。なお、乾燥後の単位面積当たりの負極活物質層の質量は0.008g/cm2とした。
正極活物質として、LiMn2O4粉末(平均粒径(D50):15μm、比表面積:0.5m2/g)を用意した。該正極活物質と、バインダーとしてのPVDFと、導電助剤としてのカーボンブラックとを、質量比91:4:5でNMP中に均一に分散させて、正極スラリーを調製した。該正極スラリーを正極集電体である厚み20μmのアルミニウム箔上に塗布した。その後、125℃にて10分間乾燥させてNMPを蒸発させることにより正極活物質層を形成し、正極とした。なお、乾燥後の単位面積当たりの正極活物質層の質量は0.024g/cm2とした。
EC:DEC=30:70(体積%)の比率で混合した非水溶媒に、電解質としてLiPF6を1mol/Lとなるように溶解させた非水電解液を用意した。この非水電解液に、添加剤としてビニレンカーボネートを1.5質量%添加した。
作製した正極および負極を各々5cm×6cmに切り出した。このうち、一辺5cm×1cmはタブを接続するために電極活物質層を形成していない部分(未塗布部)とし、電極活物質層が形成された部分は5cm×5cmとした。幅5mm×長さ3cm×厚み0.1mmのアルミニウム製の正極タブを、正極の未塗布部に長さ1cmで超音波溶接した。また、正極タブと同サイズのニッケル製の負極タブを、負極の未塗布部に超音波溶接した。6cm×6cmのポリエチレンおよびポリプロピレンからなるセパレータの両面に前記負極と前記正極とを電極活物質層同士がセパレータを隔てて重なるように配置して、電極積層体を得た。2枚の7cm×10cmのアルミニウムラミネートフィルムの長辺の一方を除いて三辺を熱融着により幅5mmで接着して、袋状のラミネート外装体を作製した。該袋状のラミネート外装体に、ラミネート外装体の一方の短辺より1cmの距離となるように前記電極積層体を挿入した。さらに前記非水電解液を0.2g注液して真空含浸させた後、減圧下にて開口部を熱融着により幅5mmで封止した。これにより、ラミネート型の二次電池を作製した。
作製した二次電池に対して、初回充放電を行った。まず、20℃にて5時間率(0.2C)相当の10mAの定電流で4.2Vまで充電した。その後、合計で8時間4.2V定電圧充電を行った。その後、10mAで3.0Vまで定電流放電した。初回充電容量に対する初回放電容量の比率((初回放電容量/初回充電容量)×100(%))を充放電効率(%)として算出した。結果を表1に示す。
前記初回充放電を行った二次電池を、1C(50mA)で4.2Vまで充電した。その後、合計で2.5時間4.2V定電圧充電を行った。その後、1Cで3.0Vまで定電流放電を行った。この充放電サイクルを45℃で500回繰り返した。初回放電容量に対する500サイクル後の放電容量の比率を容量維持率(%)として算出した。結果を表1に示す。
負極スラリーの調製において、SG、FPおよびIPの質量比をSG:FP:IP=95.0:3.5:1.5とした以外は実施例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、SG、FPおよびIPの質量比をSG:FP:IP=95.0:4.0:1.0とした以外は実施例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、SG、FPおよびIPの質量比をSG:FP:IP=95.0:4.5:0.5とした以外は実施例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、イミド系樹脂(IP)を添加せず、SGおよびFPの質量比をSG:FP=95.0:5.0とした以外は実施例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、フッ素系樹脂(FP)を添加せず、SGおよびIPの質量比をSG:IP=95.0:5.0とした以外は実施例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極の作製において、125℃にて10分間乾燥させた後、窒素気流中で250℃にて10分間熱処理を行った以外は比較例2と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、イミド系樹脂(IP)としてポリイミド前駆体であるポリアミック酸溶液(商品名:U-ワニスA、宇部興産(株)製、イミド環の閉環率0%)を用いた以外は比較例2と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極の作製において、125℃にて10分間乾燥させた後、窒素気流中で300℃にて10分間熱処理を行った以外は比較例4と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、フッ素系樹脂(FP)を添加せず、SGおよびIPの質量比をSG:IP=98.5:1.5とした以外は実施例1と同様の方法で二次電池を作製し、評価した。しかし、比較例6では、負極活物質層が集電体から剥離したため前記評価を行うことが出来なかった。
負極スラリーの調製において、鱗片状人造黒鉛粉末の代わりに球状黒鉛(天然黒鉛、平均粒径(D50):20μm、比表面積:0.8m2/g、表面に炭素被覆有)を用いた以外は比較例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、鱗片状人造黒鉛粉末の代わりに球状黒鉛(天然黒鉛、平均粒径(D50):20μm、比表面積:0.8m2/g、表面に炭素被覆有)を用いた以外は実施例3と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、鱗片状人造黒鉛粉末の代わりに球状黒鉛(天然黒鉛、平均粒径(D50):20μm、比表面積:0.8m2/g、表面に炭素被覆有)を用いた以外は実施例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極スラリーの調製において、鱗片状人造黒鉛粉末の代わりに球状黒鉛(天然黒鉛、平均粒径(D50):20μm、比表面積:0.8m2/g、表面に炭素被覆有)を用いた以外は比較例2と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
正極スラリーの調製において、バインダーとして、PVDFの代わりにフッ素系樹脂(FP)とイミド系樹脂(IP)とを、質量比でFP:IP=3.2:0.8として用いた以外は比較例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
正極スラリーの調製において、バインダーとして、PVDFの代わりにフッ素系樹脂(FP)とイミド系樹脂(IP)とを、質量比でFP:IP=2.0:2.0として用いた以外は比較例1と同様の方法で二次電池を作製し、評価した。結果を表1に示す。
負極のバインダーとしてフッ素系樹脂(FP)とイミド系樹脂(IP)を併用することによる効果についてさらに検討するため、実施例の中で最も高い充放電効率および容量維持率を示した実施例3と、比較例1および2について、以下の評価を行った。
実施例3、比較例1および2において作製した負極(12mmΦ)と、対極としてのリチウム金属(15mmΦ、厚さ1.4mm)と、セパレータ(21mmΦ)とを用いて、20mmΦ×3.2mmのコインセルを作製した。非水電解液には実施例1と同様の非水電解液を使用し、負極とセパレータとリチウム金属とをそれぞれ非水電解液に含浸させてからコインセルを組み立てた。該コインセルに対して初回充放電を行い、横軸を負極活物質質量あたりの容量(mAh/g)、縦軸を電圧(mV)とする初回充放電曲線を測定した。なお、初回充電条件は0.16mAでのCC-CV充電(CV時間:20時間、下限電圧:5mV)とした。また、初回放電条件は0.16mAでのCC放電(上限電圧:2000mV)とした。
Claims (19)
- 鱗片状黒鉛と、フッ素系樹脂と、イミド系樹脂とを含む二次電池用負極。
- 前記イミド系樹脂がポリイミドまたはポリアミドイミドである請求項1に記載の二次電池用負極。
- 前記フッ素系樹脂が、ビニリデンフルオライド(VDF)、テトラフルオロエチレン(TFE)およびヘキサフルオロプロパン(HFP)からなる群から選択される少なくとも一種を構成単位として含むポリマーまたはコポリマーである請求項1または2に記載の二次電池用負極。
- 前記フッ素系樹脂(FP)と前記イミド系樹脂(IP)との合計に対する前記イミド系樹脂(IP)の質量比(IP/(FP+IP))が、0.1以上、0.5以下である請求項1から3のいずれか1項に記載の二次電池用負極。
- 前記鱗片状黒鉛(SG)に対する前記フッ素系樹脂(FP)の質量比(FP/SG)が、0.01以上、0.05以下である請求項1から4のいずれか1項に記載の二次電池用負極。
- 前記鱗片状黒鉛(SG)に対する前記イミド系樹脂(IP)の質量比(IP/SG)が、0.005以上、0.05以下である請求項1から5のいずれか1項に記載の二次電池用負極。
- 鱗片状黒鉛と、フッ素系樹脂と、イミド系樹脂と、前記フッ素系樹脂および前記イミド系樹脂を溶解する溶媒と、を含む負極スラリーを負極集電体に塗布する工程と、
前記負極集電体を100℃以上、150℃以下の温度で熱処理する工程と、により製造される請求項1から6のいずれか1項に記載の二次電池用負極。 - 前記負極スラリーに含まれるイミド系樹脂の閉環率が80%以上である請求項7に記載の二次電池用負極。
- 前記鱗片状黒鉛のアスペクト比が2以上、10以下である請求項1から8のいずれか1項に記載の二次電池用負極。
- 請求項1から9のいずれか1項に記載の二次電池用負極を備える二次電池。
- LiMn2-xM2xO4(M2はMg、Al、Co、Ni、FeおよびBからなる群から選択される少なくとも一種の元素であり、0≦x<2である。)を含む正極を備える請求項10に記載の二次電池。
- 鱗片状黒鉛と、フッ素系樹脂と、イミド系樹脂と、前記フッ素系樹脂および前記イミド系樹脂を溶解する溶媒と、を含む負極スラリーを負極集電体に塗布する工程と、
前記負極集電体を100℃以上、150℃以下の温度で熱処理する工程と、を含む二次電池用負極の製造方法。 - 前記負極スラリーに含まれるイミド系樹脂の閉環率が80%以上である請求項12に記載の二次電池用負極の製造方法。
- 前記イミド系樹脂がポリイミドまたはポリアミドイミドである請求項12または13に記載の二次電池用負極の製造方法。
- 前記フッ素系樹脂が、ビニリデンフルオライド(VDF)、テトラフルオロエチレン(TFE)およびヘキサフルオロプロパン(HFP)からなる群から選択される少なくとも一種を構成単位として含むポリマーまたはコポリマーである請求項12から14のいずれか1項に記載の二次電池用負極の製造方法。
- 前記フッ素系樹脂(FP)と前記イミド系樹脂(IP)との合計に対する前記イミド系樹脂(IP)の質量比(IP/(FP+IP))が、0.1以上、0.5以下である請求項12から15のいずれか1項に記載の二次電池用負極の製造方法。
- 前記鱗片状黒鉛(SG)に対する前記フッ素系樹脂(FP)の質量比(FP/SG)が、0.01以上、0.05以下である請求項12から16のいずれか1項に記載の二次電池用負極の製造方法。
- 前記鱗片状黒鉛(SG)に対する前記イミド系樹脂(IP)の質量比(IP/SG)が、0.005以上、0.05以下である請求項12から17のいずれか1項に記載の二次電池用負極の製造方法。
- 前記鱗片状黒鉛のアスペクト比が2以上、10以下である請求項12から18のいずれか1項に記載の二次電池用負極の製造方法。
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