WO2016056374A1 - リチウムイオン二次電池用正極活物質およびその製造方法、並びにリチウムイオン二次電池 - Google Patents
リチウムイオン二次電池用正極活物質およびその製造方法、並びにリチウムイオン二次電池 Download PDFInfo
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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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
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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
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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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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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
- H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
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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
- 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
- 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
- the present embodiment relates to a positive electrode active material for a lithium ion secondary battery, a manufacturing method thereof, and a lithium ion secondary battery.
- Lithium ion secondary batteries have been put to practical use as batteries for small electronic devices such as notebook computers and mobile phones due to advantages such as high energy density, small self-discharge, and excellent long-term reliability.
- the application of the lithium ion secondary battery to electric vehicles, household storage batteries, and power storage is progressing.
- a decomposition product of a solvent in the electrolytic solution reduced and decomposed on the negative electrode surface accumulates on the negative electrode surface, and resistance increases.
- the battery swells due to the gas generated by the decomposition.
- the decomposition product of the oxidatively decomposed solvent on the surface of the positive electrode accumulates on the surface of the positive electrode to increase the resistance, or the battery swells due to the gas generated by the decomposition of the solvent.
- the storage characteristics of the battery and the cycle characteristics of the secondary battery are deteriorated, and the battery characteristics are deteriorated.
- a method of adding a compound having a protective film generating function in a nonaqueous electrolytic solution there is a method of adding a compound having a protective film generating function in a nonaqueous electrolytic solution.
- SEI Solid Electrolyte Interface
- Non-Patent Document 1 describes that by forming a protective film on the negative electrode surface with an additive, the chemical reaction or decomposition of the solvent on the electrode surface is appropriately suppressed, and the battery characteristics of the secondary battery are maintained. Has been. Patent Document 1 describes an electrode surface film forming agent for protecting the negative electrode surface. However, these techniques do not sufficiently suppress gas generation due to oxidative decomposition of the solvent in the positive electrode.
- Patent Documents 2 and 3 describe a lithium ion secondary battery using a positive electrode having a high potential, and the lithium ion secondary battery has a potential of 4.5 V or more. Therefore, gas generation due to oxidative decomposition of the solvent is more likely to occur at the positive electrode than the voltage (3.5 to 4.2 V) of a general lithium ion secondary battery. Therefore, there is a need for a technique for suppressing gas generation at the positive electrode in a high potential lithium ion secondary battery.
- Patent Document 4 discloses a method of suppressing gas generation from the positive electrode by forming a protective film on the positive electrode surface by using a silane coupling agent and an epoxy resin.
- Patent Document 5 discloses a method for suppressing gas generation from the positive electrode by depositing a boric acid compound on the positive electrode active material.
- An object of the present embodiment is to provide a positive electrode active material for a lithium ion secondary battery that can suppress gas generation and can provide a lithium ion secondary battery having a high capacity retention rate in a charge / discharge cycle.
- the positive electrode active material for a lithium ion secondary battery according to the present embodiment has a layered rock salt structure, and has the following formula (1) Li x Fe s M 1 (z ⁇ s) M 2 y O ⁇ (1) (In the formula (1), 1.05 ⁇ x ⁇ 1.90, 0.05 ⁇ s ⁇ 0.50, 0.05 ⁇ z ⁇ 0.50, 0.33 ⁇ y ⁇ 0.90, 1.20. ⁇ ⁇ ⁇ 3.10, z ⁇ s ⁇ 0, M 1 is at least one element selected from the group consisting of Co and Ni, and M 2 is selected from the group consisting of Mn, Ti and Zr At least one element.) A compound represented by A 1,3-propanedione derivative represented by the following formula (2); including.
- R1 and R2 are each independently a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group;
- R3 is a hydrogen atom or a substituted or unsubstituted aryl group.
- the lithium ion secondary battery according to the present embodiment includes a positive electrode including the positive electrode active material for the lithium ion secondary battery.
- particles having a layered rock salt structure and containing a compound represented by the formula (1) are represented by the formula (2).
- a 1,3-propanedione derivative represented by the formula (2) is immersed on at least a part of the surface of the particle containing the compound represented by the formula (1) by immersing in a solution in which the 1,3-propanedione derivative is dissolved. Coating.
- a positive electrode active material for a lithium ion secondary battery that can suppress gas generation and can provide a lithium ion secondary battery having a high capacity retention rate in a charge / discharge cycle.
- the positive electrode active material for a lithium ion secondary battery according to the present embodiment has a layered rock salt structure, and the following formula (1) Li x Fe s M 1 (z ⁇ s) M 2 y O ⁇ (1) (In the formula (1), 1.05 ⁇ x ⁇ 1.90, 0.05 ⁇ s ⁇ 0.50, 0.05 ⁇ z ⁇ 0.50, 0.33 ⁇ y ⁇ 0.90, 1.20. ⁇ ⁇ ⁇ 3.10, z ⁇ s ⁇ 0, M 1 is at least one element selected from the group consisting of Co and Ni, and M 2 is selected from the group consisting of Mn, Ti and Zr At least one element.) A compound represented by A 1,3-propanedione derivative represented by the following formula (2); including.
- R1 and R2 are each independently a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group;
- R3 is a hydrogen atom or a substituted or unsubstituted aryl group.
- M 1 is at least one element selected from the group consisting of Co and Ni, and preferably contains Ni.
- M 2 is at least one element selected from the group consisting of Mn, Ti and Zr, preferably contains Mn or Ti, and more preferably contains Mn from the viewpoint of cost reduction.
- x satisfies 1.05 ⁇ x ⁇ 1.90, preferably satisfies 1.10 ⁇ x ⁇ 1.80, and more preferably satisfies 1.15 ⁇ x ⁇ 1.70.
- s satisfies 0.05 ⁇ s ⁇ 0.50, preferably satisfies 0.08 ⁇ s ⁇ 0.40, more preferably satisfies 0.10 ⁇ s ⁇ 0.30, and 0.15 ⁇ s More preferably, ⁇ 0.25 is satisfied.
- z satisfies 0.05 ⁇ z ⁇ 0.50, preferably satisfies 0.15 ⁇ z ⁇ 0.48, more preferably satisfies 0.25 ⁇ z ⁇ 0.46, and 0.35 ⁇ z More preferably, ⁇ 0.45 is satisfied.
- y satisfies 0.33 ⁇ y ⁇ 0.90, preferably satisfies 0.40 ⁇ y ⁇ 0.85, more preferably satisfies 0.45 ⁇ y ⁇ 0.80, and 0.50 ⁇ y. More preferably, ⁇ 0.70 is satisfied.
- ⁇ satisfies 1.20 ⁇ ⁇ ⁇ 3.10, preferably satisfies 1.50 ⁇ ⁇ ⁇ 3.00, more preferably satisfies 1.80 ⁇ ⁇ ⁇ 2.80, and 2.20 ⁇ ⁇ More preferably, ⁇ 2.60 is satisfied. Note that z and s satisfy z ⁇ s ⁇ 0.
- Li 1.4 Fe 0.2 Ni 0.2 Mn 0.6 O 2.4 Li 1.55 Fe 0.15 Ni 0 .15 Mn 0.7 O 2.55 , Li 1.2 Fe 0.20 Ni 0.20 Mn 0.40 O 2.00 , Li 1.23 Fe 0.15 Ni 0.15 Mn 0.46 O 2 .00 , Li 1.26 Fe 0.11 Ni 0.11 Mn 0.52 O 2.00 , Li 1.29 Fe 0.07 Ni 0.14 Mn 0.57 O 2.00 , Li 1.26 Fe 0.22 Mn 0.37 Ti 0.15 O 2.00 , Li 1.8 Fe 0.1 Ni 0.1 Mn 0.8 O 2.8 , Li 1.85 Fe 0.05 Ni 0.1 Mn 0.85 O 2.85, Li 1.9 Fe 0.05 Ni 0 05 Mn 0.9 O 3.1, and the like.
- the method for synthesizing the compound represented by the formula (1) is not particularly limited, and a general method for synthesizing an oxide having a layered rock salt structure can be applied.
- R1 and R2 each independently represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.
- R3 represents a hydrogen atom or a substituted or unsubstituted aryl group.
- Examples of the substituted or unsubstituted alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, pentyl group, and n-hexyl group. Can be mentioned.
- the alkyl group may have a substituent.
- one or more hydrogen atoms independently represent a fluorine atom, a cyano group, an ester group, an alkoxy group having 1 to 5 carbon atoms, an aryl group, a hetero group. It may be substituted with an aryl group or the like.
- Examples of the substituted alkyl group include a trifluoromethyl group, a pentafluoroethyl group, a trifluoroethyl group, a heptafluoropropyl group, a cyanomethyl group, a benzyl group, and a 2-thienylmethyl group.
- Examples of the substituted or unsubstituted aryl group include a phenyl group, a naphthyl group, a tolyl group, a 4-cyanophenyl group, a 2-fluorophenyl group, a 3-fluorophenyl group, a 4-fluorophenyl group, and a 2,3-difluorophenyl group.
- 2,4-difluorophenyl group 2,5-difluorophenyl group, 2,6-difluorophenyl group, 3,4-difluorophenyl group, 3,5-difluorophenyl group, 3,6-difluorophenyl group, 2 , 4,6-trifluorophenyl group, a fluorophenyl group such as a pentafluorophenyl group, a 4-methoxyphenyl group, and the like.
- substituted or unsubstituted heteroaryl group examples include 2-thienyl group, 3-thienyl group, 2-furanyl group, 4-methyl-2-thienyl group, 3-fluoro-2-thienyl group and the like.
- R1 and R2 are methyl, trifluoromethyl, pentafluoroethyl, phenyl, 2-thienyl, 2-furanyl, 2-fluorophenyl, pentafluorophenyl, 4-fluorophenyl
- 2 Preferred are fluorophenyl groups such as 1,4-difluorophenyl group, 3,4-difluorophenyl group, 3,5-difluorophenyl group, 2,4,6-trifluorophenyl group, and 4-cyanophenyl group. From this viewpoint, a 2-thienyl group, a 2-furanyl group, or a fluorophenyl group is more preferable.
- R3 is preferably a hydrogen atom, a phenyl group, a 4-fluorophenyl group, a 2,4-difluorophenyl group, a pentafluorophenyl group, or the like.
- 1,3-propanedione derivative represented by the formula (2) are shown in Table 1.
- the 1,3-propanedione derivative represented by the formula (2) according to the present embodiment is not limited to the compounds in Table 1.
- the 1,3-propanedione derivative represented by the formula (2) preferably covers at least a part of the surface of the particle containing the compound represented by the formula (1).
- grains containing the compound shown by said Formula (1) are particles which consist of a compound shown by said Formula (1).
- the coating ratio is not particularly limited as long as at least a part of the surface of the particle containing the compound represented by the formula (1) is coated with the 1,3-propanedione derivative represented by the formula (2). It is preferable that most or all of the surface of the particle containing the compound represented by the formula (1) is coated with the 1,3-propanedione derivative represented by the formula (2).
- the 1,3-propanedione derivative represented by the formula (2) exists in the solution as a keto form represented by the formula (2) or an enol form (isomer) represented by the following formula (3). .
- the enol body represented by the following formula (3) binds to a metal ion (M n + ) as shown in the following formula (4) on the surface of the particle containing the compound represented by the above formula (1) to form a complex. Form.
- the surface of the particle containing the compound represented by the formula (1) is coated with the 1,3-propanedione derivative represented by the formula (2).
- the 1,3-propanedione derivative represented by the formula (2) may be attached to the surface of the particle containing the compound represented by the formula (1).
- the surface of the particle containing the compound represented by) need not necessarily be coated. That is, the positive electrode active material according to the present embodiment only needs to contain the compound represented by the formula (1) and the 1,3-propanedione derivative represented by the formula (2).
- the surface of the particle containing the compound represented by the formula (1) is initially coated with the 1,3-propanedione derivative represented by the formula (2), a process for producing a lithium ion secondary battery
- the case where the 1,3-propanedione derivative represented by the formula (2) is detached from the surface during the use process is also included in this embodiment.
- the content of the 1,3-propanedione derivative represented by the formula (2) in the positive electrode active material for a lithium ion secondary battery according to this embodiment is preferably 0.01 to 10% by mass, More preferably, the content is 0.1 to 5% by mass.
- the content is a value measured by an unreacted amount in a reaction in which a positive electrode is coated with a 1,3-propanedione derivative.
- the solution in which the 1,3-propanedione derivative represented by the formula (2) is dissolved may be obtained by, for example, converting the 1,3-propanedione derivative represented by the formula (2) into a chain carbonate or a chain ester. , Lactones, ethers, nitriles and other non-aqueous solvents.
- Examples of the chain carbonates include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and ethyl methyl carbonate.
- Examples of the chain esters include methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate.
- Examples of the lactones include ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -methyl- ⁇ -butyrolactone, and the like.
- Examples of the ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1, Examples include 2-dibutoxyethane.
- Examples of the nitriles include acetonitrile and propionitrile. These non-aqueous solvents may be used alone or in combination of two or more.
- the content of the 1,3-propanedione derivative represented by the formula (2) in the solution in which the 1,3-propanedione derivative represented by the formula (2) is dissolved is 0.05 to 10% by mass.
- the content is 0.1 to 5% by mass.
- the particles containing the compound represented by the formula (1) are added to the solution in which the 1,3-propanedione derivative represented by the formula (2) is dissolved. Thereafter, the mixture is stirred at room temperature to 60 ° C. for 1 to 24 hours, the positive electrode active material is filtered off, washed with a non-aqueous solvent, and then vacuum-dried at room temperature to 100 ° C., whereby the compound represented by the above formula (1) is obtained.
- a positive electrode active material for a lithium ion secondary battery in which at least a part of the surface of the particles containing bismuth is coated with a 1,3-propanedione derivative represented by the above formula (2) is obtained.
- the lithium ion secondary battery according to the present embodiment includes a positive electrode including the positive electrode active material for the lithium ion secondary battery.
- the lithium ion secondary battery can include a negative electrode including a material capable of occluding and releasing lithium ions, and an electrolytic solution.
- the structure of the lithium ion secondary battery is not particularly limited, and examples thereof include a coin battery, a cylindrical battery, and a laminate battery having a single-layer or multiple-layer separator.
- FIG. 1 shows an example of a lithium ion secondary battery according to this embodiment.
- the positive electrode active material layer 1 containing the positive electrode active material for a lithium ion secondary battery according to this embodiment is formed on the positive electrode current collector 1 ⁇ / b> A, whereby the positive electrode is configured.
- the negative electrode is comprised by forming the negative electrode active material layer 2 on the negative electrode collector 2A.
- These positive electrode and negative electrode are disposed so as to face each other through the separator 3 while being immersed in an electrolytic solution.
- the positive electrode is connected to the positive electrode tab 1B, and the negative electrode is connected to the negative electrode tab 2B.
- This battery element is accommodated in the exterior body 4, and the positive electrode tab 1B and the negative electrode tab 2B are exposed to the outside.
- the positive electrode can include, for example, a positive electrode active material including a positive electrode active material, a positive electrode binder, and a positive electrode current collector.
- the positive electrode active material includes the positive electrode active material for a lithium ion secondary battery according to the present embodiment, and can be used alone or in combination of two or more.
- the binder for the positive electrode is not particularly limited.
- polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber, Tetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide and the like can be mentioned.
- polyvinylidene fluoride as the binder for the positive electrode.
- the amount of the positive electrode binder used is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoints of “sufficient binding force” and “high energy” which are in a trade-off relationship. .
- the positive electrode current collector for example, an aluminum foil, a stainless lath plate, or the like can be used.
- the positive electrode active material layer may contain a conductive auxiliary agent for the purpose of reducing impedance.
- the conductive auxiliary agent include graphites such as natural graphite and artificial graphite, and carbon blacks such as acetylene black, ketjen black, furnace black, channel black, and thermal black.
- the conductive auxiliary agent may be used by appropriately mixing a plurality of types.
- the addition amount of the conductive auxiliary agent is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material.
- the positive electrode is, for example, a doctor blade method or a die coater method in which a mixture such as the positive electrode active material, the conductive auxiliary agent, and the positive electrode binder is mixed and kneaded with a solvent such as N-methylpyrrolidone. It can be produced by applying on the positive electrode current collector and drying by the above.
- the negative electrode can include, for example, a negative electrode active material layer including a negative electrode active material and a negative electrode binder, and a negative electrode current collector.
- Examples of the negative electrode active material include lithium metal, metal or alloy that can be alloyed with lithium, oxide that can occlude and release lithium, and carbon.
- Examples of the metal or alloy that can be alloyed with lithium include lithium-silicon and lithium-tin.
- Examples of the oxide capable of inserting and extracting lithium include niobium pentoxide (Nb 2 O 5 ), lithium titanium composite oxide (Li 4/3 Ti 5/3 O 4 ), and titanium dioxide (TiO 2 ).
- Examples of the carbon include graphite material, carbon black, coke, mesocarbon microbeads, hard carbon, and graphite.
- Examples of the graphite material include artificial graphite and natural graphite.
- Examples of the carbon black include acetylene black and furnace black. Among these, carbon is preferable from the viewpoints of excellent cycle characteristics and safety and excellent continuous charge characteristics.
- a negative electrode active material containing silicon may be used.
- the negative electrode active material containing silicon include silicon and silicon compounds.
- the silicon compound include a compound of a transition metal such as silicon oxide, silicate, nickel silicide, and cobalt silicide and silicon. These may use 1 type and may use 2 or more types together.
- At least one selected from the group consisting of silicon, silicon oxide and carbon is preferable to use at least one selected from the group consisting of silicon, silicon oxide and carbon as the negative electrode active material from the viewpoint of battery capacity and stable operation.
- a silicon compound is preferably used from the viewpoint of charge / discharge cycle characteristics because the silicon compound relaxes expansion and contraction due to repeated charge / discharge of the negative electrode active material itself. Further, depending on the type of silicon compound, there is a function of ensuring conduction between silicon. From such a viewpoint, as the silicon compound, silicon oxide is preferable.
- the silicon oxide is not particularly limited, for example, oxide represented by SiO x (0 ⁇ x ⁇ 2 ) and the like.
- the silicon oxide may contain Li.
- the silicon oxide containing Li is represented by, for example, SiLi y O z (0 ⁇ y, 0 ⁇ z ⁇ 2).
- the silicon oxide may contain a small amount of other metal elements and non-metal elements.
- the silicon oxide can contain, for example, 0.1 to 5% by mass of one or more elements selected from nitrogen, boron and sulfur.
- silicon oxide may be crystalline or amorphous.
- the negative electrode active material when the negative electrode active material contains silicon or silicon oxide, the negative electrode active material preferably further contains carbon capable of inserting and extracting lithium ions. Carbon may be combined with silicon or silicon oxide. Carbon, like silicon oxide, has a function of relaxing expansion and contraction due to repeated charge and discharge of the negative electrode active material itself and ensuring conduction between silicon. In particular, when the negative electrode active material contains silicon, silicon oxide, and carbon, better cycle characteristics can be obtained.
- the carbon graphite, amorphous carbon, diamond-like carbon, carbon nanotube, or the like can be used.
- Graphite with high crystallinity has high electrical conductivity, and is excellent in adhesion to a positive electrode current collector made of a metal such as copper and voltage flatness.
- amorphous carbon having low crystallinity has a relatively small volume expansion, the volume expansion of the entire negative electrode can be relaxed, and deterioration due to non-uniformity such as crystal grain boundaries and defects hardly occurs. 2 mass% or more and 50 mass% or less are preferable, and, as for content of carbon in a negative electrode active material, 2 mass% or more and 30 mass% or less are more preferable.
- the negative electrode active material containing silicon and silicon compound is prepared, for example, by mixing silicon and silicon oxide and sintering under high temperature and reduced pressure. Can do.
- the negative electrode active material is melted by mixing silicon and transition metal, or the transition metal is coated on the surface of silicon by vapor deposition or the like. It is possible to make it.
- the nucleus of silicon and silicon oxide is introduced.
- a coating layer containing carbon can be formed around the substrate.
- a mixture containing silicon and silicon oxide is mixed with a precursor resin of carbon to coat the silicon and silicon oxide around the core.
- a layer can be formed.
- the negative electrode active material is preferably a composite containing silicon, silicon oxide and carbon (hereinafter also referred to as Si / SiO / C composite).
- the silicon oxide has an amorphous structure.
- the silicon oxide having an amorphous structure can suppress the volume expansion of carbon and silicon. Although this mechanism is not clear, it is presumed that the formation of a film at the interface between carbon and the electrolyte has some influence due to the amorphous structure of silicon oxide.
- the amorphous structure is considered to have relatively few elements due to non-uniformity such as crystal grain boundaries and defects.
- all or part of silicon is preferably dispersed in silicon oxide.
- silicon oxide By dispersing at least a part of silicon in silicon oxide, volume expansion as a whole of the negative electrode can be further suppressed, and decomposition of the electrolytic solution can also be suppressed.
- silicone is disperse
- the Si / SiO / C composite for example, all or part of silicon oxide has an amorphous structure, and all or part of silicon is dispersed in silicon oxide.
- a Si / SiO / C composite can be produced, for example, by a method disclosed in Japanese Patent Application Laid-Open No. 2004-47404. That is, the Si / SiO / C composite can be obtained, for example, by performing a CVD process on silicon oxide in an atmosphere containing an organic gas such as methane gas. In the Si / SiO / C composite obtained by such a method, the surfaces of particles made of silicon oxide containing silicon are coated with carbon. Silicon is nanoclustered in silicon oxide.
- the ratio of silicon, silicon oxide and carbon is not particularly limited, but is preferably the following ratio.
- Silicon is preferably contained in an amount of 5% by mass to 90% by mass and more preferably 20% by mass to 50% by mass with respect to the Si / SiO / C composite.
- the silicon oxide is preferably contained in an amount of 5% by mass to 90% by mass and more preferably 40% by mass to 70% by mass with respect to the Si / SiO / C composite.
- Carbon is contained in an amount of 2% by mass or more and 50% by mass or less, and more preferably 2% by mass or more and 30% by mass or less, relative to the Si / SiO / C composite.
- the Si / SiO / C composite may be a mixture of silicon, silicon oxide and carbon.
- it can be produced by mixing particulate silicon, particulate silicon oxide, and particulate carbon by mechanical milling.
- the average particle diameter of silicon is preferably smaller than the average particle diameter of carbon and silicon oxide.
- silicon with a large volume change during charge / discharge has a relatively small particle size
- carbon and silicon oxide with a small volume change have a relatively large particle size. Is suppressed.
- lithium is occluded and released in the order of large particle size, small particle size, and large particle size. From this point, residual stress and residual strain are generated. It is suppressed.
- the average particle diameter of silicon is preferably 20 ⁇ m or less, and more preferably 15 ⁇ m or less.
- the average particle diameter of silicon oxide is preferably 1/2 or less of the average particle diameter of carbon.
- the average particle diameter of silicon is preferably 1 ⁇ 2 or less of the average particle diameter of silicon oxide. More preferably, the average particle diameter of silicon oxide is 1 ⁇ 2 or less of the average particle diameter of carbon, and the average particle diameter of silicon is 1 ⁇ 2 or less of the average particle diameter of silicon oxide. If the average particle diameter is controlled within the above range, the effect of relaxing the volume expansion can be obtained more effectively, so that a secondary battery excellent in the balance of energy density, cycle life and efficiency can be obtained.
- the average particle diameter of silicon oxide is 1/2 or less of the average particle diameter of graphite
- the average particle diameter of silicon is 1/2 of the average particle diameter of silicon oxide.
- the average particle diameter is measured by a laser diffraction scattering method or a dynamic light scattering method.
- the negative electrode active material a material obtained by treating the surface of the aforementioned Si / SiO / C composite with a silane coupling agent or the like may be used.
- the negative electrode active material layer preferably contains 55% by mass or more of the negative electrode active material, and more preferably contains 65% by mass or more.
- the binder for the negative electrode is not particularly limited.
- polyimide, polyamideimide, SBR, alkali-neutralized lithium salt, sodium salt or potassium salt containing polyacrylic acid or carboxymethylcellulose are preferred because of their high binding properties.
- the amount of the binder for the negative electrode to be used is preferably 5 to 25 parts by mass with respect to 100 parts by mass of the negative electrode active material from the viewpoints of “sufficient binding force” and “high energy” which are in a trade-off relationship. .
- the material of the negative electrode current collector for example, a metal material such as copper, nickel, and stainless steel is used. Among these, copper is preferable from the viewpoint of ease of processing and cost. Moreover, it is preferable that the surface of the negative electrode current collector is roughened in advance. Examples of the shape of the negative electrode current collector include a foil shape, a flat plate shape, and a mesh shape. Also, a perforated current collector such as expanded metal or punching metal can be used.
- the negative electrode can be produced in the same manner as the positive electrode. For example, a slurry obtained by adding a solvent to a mixture of a negative electrode active material, a negative electrode binder, and various auxiliary agents as necessary, and kneading the mixture can be applied to the negative electrode current collector and dried. .
- the electrolytic solution according to the present embodiment can include a nonaqueous solvent and an electrolyte salt.
- the non-aqueous solvent include cyclic carbonates, chain carbonates, chain esters, lactones, ethers, sulfones, nitriles, phosphate esters, and the like.
- cyclic carbonates include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, and the like.
- chain carbonates include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, and methyl butyl carbonate.
- chain esters include methyl formate, methyl acetate, methyl propionate, ethyl propionate, methyl pivalate, ethyl pivalate and the like.
- lactones include ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -methyl- ⁇ -butyrolactone, and the like.
- ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, , 2-dibutoxyethane and the like.
- sulfones include sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane and the like.
- nitriles include acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile and the like.
- phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, and trioctyl phosphate.
- non-aqueous solvents can be used singly or in combination of two or more.
- combinations of a plurality of types of non-aqueous solvents include a combination of cyclic carbonates and chain carbonates.
- fluorinated ethers, chain esters, lactones, ethers, nitriles, sulfones, phosphate esters and the like may be added to the combination of cyclic carbonates and chain carbonates.
- the nonaqueous solvent contains at least one of a chain carbonate solvent and a cyclic carbonate solvent from the viewpoint of realizing excellent battery characteristics.
- electrolyte salt examples include LiPF 6 , LiBF 4 , LiClO 4 , LiN (SO 2 F) 2 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 , CF 3 SO 3.
- LiPF 6 , LiBF 4 , LiN (SO 2 F) 2 , LiN (SO 2 CF 3 ) 2 , and LiN (SO 2 C 2 F 5 ) 2 are preferable.
- These electrolyte salts can be used individually by 1 type or in combination of 2 or more types.
- the concentration of the electrolyte salt in the electrolytic solution is preferably 0.1 to 3 mol / L, and more preferably 0.5 to 2 mol / L.
- the electrolyte solution can optionally contain general components as other components.
- the other components include maleic anhydride, ethylene sulfite, and boronic acid ester, 1,3-propane sultone, 1,5,2,4-dioxadithian-2,2,4,4-tetraoxide Etc.
- the separator is not particularly limited, but for example, a single layer or multiple layers porous film made of polyolefin such as polypropylene or polyethylene, a nonwoven fabric, a polyolefin coated with a different material, a laminated film or the like may be used. it can.
- a polyolefin coated with a different material a polyolefin base material coated with a fluorine compound or inorganic fine particles can be mentioned.
- An example of the laminated film is a film in which a polyolefin base material and an aramid layer are laminated.
- the thickness of the separator is preferably 5 to 50 ⁇ m and more preferably 10 to 40 ⁇ m from the viewpoint of the energy density of the secondary battery and the mechanical strength of the separator.
- a laminate film As the exterior body, for example, a laminate film can be used.
- the laminate film can be appropriately selected as long as it is stable to the electrolyte and has a sufficient water vapor barrier property.
- a laminate film made of polypropylene, polyethylene or the like coated with aluminum, silica, or alumina can be used.
- a structure in which a metal thin film layer and a heat-fusible resin layer are laminated can be mentioned.
- a protective layer made of a film of polyester or polyamide such as polyethylene terephthalate may be further laminated on the surface of the metal thin film layer opposite to the surface in contact with the heat sealing resin layer.
- the battery element when sealing the battery element, the battery element is surrounded with the heat-fusible resin layer facing the battery element.
- the metal thin film layer for example, a foil made of Al, Ti, Ti alloy, Fe, stainless steel, or Mg alloy having a thickness of 10 to 100 ⁇ m is used.
- the resin contained in the heat-fusible resin layer is not particularly limited as long as it can be heat-sealed.
- the resin include polypropylene, polyethylene, polypropylene or an acid-modified product of polyethylene, polyester such as polyphenylene sulfide and polyethylene terephthalate, polyamide, and ethylene-vinyl acetate copolymer.
- an ionomer resin in which an ethylene-methacrylic acid copolymer or an ethylene-acrylic acid copolymer is intermolecularly bonded with metal ions can also be used.
- the thickness of the heat-fusible resin layer is preferably 10 to 200 ⁇ m, and more preferably 30 to 100 ⁇ m.
- Example 1 ⁇ Positive electrode> A slurry containing 92 parts by mass of the lithium oxide coated with the 1,3-propanedione derivative PD1 obtained in Synthesis Example 1, 4 parts by mass of ketjen black, and 4 parts by mass of polyvinylidene fluoride was prepared. The slurry was applied onto a positive electrode current collector made of aluminum foil (thickness 20 ⁇ m) and dried to prepare a positive electrode having a thickness of 175 ⁇ m. Moreover, the double-sided electrode obtained by apply
- ⁇ Negative electrode> A slurry containing 85 parts by mass of SiO having an average particle size of 15 ⁇ m and 15 parts by mass of polyamic acid was prepared. The slurry was applied onto a negative electrode current collector made of copper foil (thickness 10 ⁇ m) and dried to prepare a negative electrode having a thickness of 46 ⁇ m. The negative electrode was annealed at 350 ° C. for 3 hours in a nitrogen atmosphere to cure the polyamic acid as a binder.
- the battery element shown in FIG. 1 was produced.
- a separator 3 which is a porous film, was sandwiched between a positive electrode including the positive electrode active material layer 1 and the positive electrode current collector 1 ⁇ / b> A and a negative electrode including the negative electrode active material layer 2 and the negative electrode current collector 2 ⁇ / b> A.
- a positive electrode tab 1B and a negative electrode tab 2B were welded to the positive electrode current collector 1A and the negative electrode current collector 2A, respectively.
- the produced battery element was wrapped in an outer package 4 that was an aluminum laminate film, and three sides of the outer package 4 were sealed by heat sealing, and then the electrolyte was impregnated at an appropriate degree of vacuum. Then, under reduced pressure, one side of the outer package 4 that was not thermally fused was sealed by thermal fusion to produce a lithium ion secondary battery before activation treatment.
- the produced lithium ion secondary battery before the activation process it charged to 4.5V with the electric current of 20 mA (20 mA / g) per 1 g of positive electrode active materials. Thereafter, the battery was discharged to 1.5 V at a current of 20 mA (20 mA / g) per 1 g of the positive electrode active material. Thereafter, similarly, the battery was charged to 4.5 V with a current of 20 mA / g and then discharged to 1.5 V. That is, the activation process which repeats a charging / discharging cycle twice was performed. Then, the lithium ion secondary battery was produced by once breaking the sealing part and depressurizing to degas the inside of the battery and resealing the broken part.
- Example 2 In place of the lithium oxide coated with the 1,3-propanedione derivative PD1 obtained in Synthesis Example 1, the lithium oxide coated with the 1,3-propanedione derivative PD2 obtained in Synthesis Example 2 was used to form a positive electrode. A lithium ion secondary battery was produced in the same manner as in Example 1 except that was produced.
- Example 3 Instead of the lithium oxide coated with the 1,3-propanedione derivative PD1 obtained in Synthesis Example 1, the lithium oxide coated with the 1,3-propanedione derivative PD4 obtained in Synthesis Example 3 was used to form a positive electrode. A lithium ion secondary battery was produced in the same manner as in Example 1 except that was produced.
- the lithium ion secondary battery after the initial capacity measurement was charged to 4.5 V at a constant current of 40 mA / g in a constant temperature bath at 45 ° C., and then a constant voltage of 4.5 V until a current of 5 mA / g was reached. Continued charging. Thereafter, the battery was discharged to 1.5 V with a current of 40 mA / g. This charge / discharge cycle was repeated 30 times in total. The capacity retention rate after 30 cycles was determined from the ratio between the initial capacity obtained in the first cycle and the discharge capacity obtained in the 30th cycle. Moreover, the gas generation amount after 30 cycles was calculated
- Table 1 shows the 1,3-propanedione derivative, lithium oxide, initial capacity, capacity retention rate after 30 cycles, and gas generation after 30 cycles used in each example and comparative example.
- the gas generation amount it showed by the conversion value when the gas generation amount of the comparative example 1 is set to 100.
- Examples 1 to 3 were improved by 10% or more in comparison with Comparative Example 1 with respect to the capacity retention rate. Further, with respect to the amount of gas generated, it was confirmed that Examples 1 to 3 were reduced to about 65 to 70% as compared with Comparative Example 1. Therefore, from the comparison between Examples 1 to 3 and Comparative Example 1, by using a positive electrode active material in which a specific lithium oxide is coated with a specific 1,3-propanedione derivative, the lithium ion secondary battery can be cycled. It was confirmed that the amount of gas generated can be suppressed and a high capacity can be stably obtained.
- the lithium ion secondary battery using the positive electrode active material in which the specific lithium oxide according to the present embodiment is coated with the specific 1,3-propanedione derivative can suppress gas generation during the cycle, It exhibits excellent characteristics that can stably obtain a high capacity.
- the positive electrode active material for a lithium ion secondary battery and the lithium ion secondary battery according to the present embodiment are used in, for example, all industrial fields that require a power source and industrial fields related to transport, storage, and supply of electrical energy. be able to. Specifically, it can be used as a power source for mobile devices such as mobile phones, notebook computers, tablet terminals, and portable game machines. In addition, it can be used as a power source for moving / transporting media such as electric vehicles, hybrid cars, electric motorcycles, and electric assist bicycles. Further, it can be used for a household power storage system, a backup power source such as a UPS, a power storage facility for storing power generated by solar power generation, wind power generation, or the like.
- a UPS power storage facility for storing power generated by solar power generation, wind power generation, or the like.
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Abstract
Description
LixFesM1 (z-s)M2 yOδ (1)
(式(1)において、1.05≦x≦1.90、0.05≦s≦0.50、0.05≦z≦0.50、0.33≦y≦0.90、1.20≦δ≦3.10、z-s≧0であり、M1はCo及び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、M2はMn、Ti及びZrからなる群から選択される少なくとも1種の元素である。)
で示される化合物と、
下記式(2)で示される1,3-プロパンジオン誘導体と、
を含む。
本発明者らは、上述の課題を解決するために鋭意研究を重ねた結果、特定のリチウム酸化物と、特定の構造を有する1,3-プロパンジオン誘導体とを含む正極活物質を用いることによって、正極からのガス発生を抑制でき、かつ優れた容量維持率を実現できることを見出した。
LixFesM1 (z-s)M2 yOδ (1)
(式(1)において、1.05≦x≦1.90、0.05≦s≦0.50、0.05≦z≦0.50、0.33≦y≦0.90、1.20≦δ≦3.10、z-s≧0であり、M1はCo及び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、M2はMn、Ti及びZrからなる群から選択される少なくとも1種の元素である。)
で示される化合物と、
下記式(2)で示される1,3-プロパンジオン誘導体と、
を含む。
前記式(1)で示される化合物は、正極活物質として用いた場合に4.5V以上の高電位正極が得られ、層状岩塩型構造を有する。層状岩塩型構造を有するか否かは、X線回折測定により確認する。
前記式(2)において、R1およびR2は、それぞれ独立に、置換または無置換の炭素数1~6のアルキル基、置換または無置換のアリール基、或いは置換または無置換のヘテロアリール基を示す。R3は、水素原子、或いは置換または無置換のアリール基を示す。
本実施形態に係るリチウムイオン二次電池用正極活物質の製造方法は、前記式(1)で示される化合物を含む粒子を、前記式(2)で示される1,3-プロパンジオン誘導体を溶解させた溶液に浸漬し、前記式(1)で示される化合物を含む粒子の表面の少なくとも一部に前記式(2)で示される1,3-プロパンジオン誘導体を被覆する工程を含む。本実施形態に係る方法によれば、前記式(1)で示される化合物を含む粒子の表面の少なくとも一部に前記式(2)で示される1,3-プロパンジオン誘導体を容易に被覆させることができる。
本実施形態に係るリチウムイオン二次電池は、前記リチウムイオン二次電池用正極活物質を含む正極を備える。該リチウムイオン二次電池は、リチウムイオンを吸蔵放出可能な材料を含む負極と、電解液と、を備えることができる。リチウムイオン二次電池の構造には特に限定はなく、例えば、単層または複数層のセパレータを有するコイン電池、円筒型電池、ラミネート型電池等が挙げられる。
本実施形態において正極は、例えば、正極活物質と、正極用結着剤とを含む正極活物質層と、正極集電体とを備えることができる。
本実施形態において負極は、例えば、負極活物質と、負極用結着剤とを含む負極活物質層と、負極集電体とを備えることができる。
本実施形態に係る電解液は、非水溶媒および電解質塩を含むことができる。該非水溶媒としては、例えば、環状カーボネート類、鎖状カーボネート類、鎖状エステル類、ラクトン類、エーテル類、スルホン類、ニトリル類、リン酸エステル類等が挙げられる。
セパレータとしては、特に制限されるものではないが、例えばポリプロピレン、ポリエチレン等のポリオレフィンからなる単層または複数層の多孔性フィルム、不織布、ポリオレフィンへ異種素材をコーティングしたもの、積層フィルム等を用いることができる。ポリオレフィンへ異種素材をコーティングしたものの一例としては、ポリオレフィン基材にフッ素化合物や無機微粒子をコーティングしたものが挙げられる。また、積層フィルムの一例としては、ポリオレフィン基材とアラミド層とを積層したフィルムが挙げられる。セパレータの厚みは、二次電池のエネルギー密度とセパレータの機械的強度との観点から、5~50μmが好ましく、10~40μmがより好ましい。
外装体としては、例えばラミネートフィルムを用いることができる。ラミネートフィルムとしては、電解液に安定でかつ十分な水蒸気バリア性を有するものであれば、適宜選択することができる。例えば、アルミニウム、シリカ、アルミナをコーティングしたポリプロピレン、ポリエチレン等からなるラミネートフィルムを用いることができる。特に、体積膨張を抑制する観点から、アルミニウムを含むラミネートフィルムを用いることが好ましい。
1,3-プロパンジオン誘導体PD1で被覆されたリチウム酸化物の合成
前記表1に示される1,3-プロパンジオン誘導体PD1(2-テノイルトリフルオロアセトン)0.8gを、ジエチルカーボネート(DEC)80mlに溶解した。1,3-プロパンジオン誘導体PD1を溶解させたDEC中に、層状岩塩型構造を有するリチウム酸化物(Li1.4Fe0.2Ni0.2Mn0.6O2.4)を50g加え、室温で17時間撹拌した。溶液中からリチウム酸化物をろ別して、DECで洗浄した後、60℃で8時間真空乾燥させた。これにより、1,3-プロパンジオン誘導体PD1で被覆されたリチウム酸化物を得た。
1,3-プロパンジオン誘導体PD2で被覆されたリチウム酸化物の合成
1,3-プロパンジオン誘導体PD1を用いる代わりに、前記表1に示される1,3-プロパンジオン誘導体PD2(2-フロイルトリフルオロアセトン)を用いた以外は、合成例1と同様の方法で1,3-プロパンジオン誘導体PD2で被覆されたリチウム酸化物を得た。
1,3-プロパンジオン誘導体PD4で被覆されたリチウム酸化物の合成
1,3-プロパンジオン誘導体PD1を用いる代わりに、前記表1に示される1,3-プロパンジオン誘導体PD4(1,3-ビス(4-フルオロフェニル)-1,3-プロパンジオン)を用いた以外は、合成例1と同様の方法で1,3-プロパンジオン誘導体PD4で被覆されたリチウム酸化物を得た。
<正極>
合成例1で得た1,3-プロパンジオン誘導体PD1で被覆されたリチウム酸化物を92質量部、ケッチェンブラックを4質量部、ポリフッ化ビニリデンを4質量部含むスラリーを調製した。該スラリーをアルミニウム箔(厚み20μm)からなる正極集電体上に塗布し、乾燥して、厚み175μmの正極を作製した。また、該正極集電体の両面に該スラリーを塗布し、乾燥して得られる両面電極も、同様の手順で作製した。
平均粒径15μmのSiOを85質量部、ポリアミック酸を15質量部含むスラリーを調製した。該スラリーを銅箔(厚み10μm)からなる負極集電体上に塗布し、乾燥して、厚み46μmの負極を作製した。該負極を窒素雰囲気下350℃で3時間アニールし、バインダであるポリアミック酸を硬化させた。
エチレンカーボネート(EC)とジエチルカーボネート(DEC)とを体積比30:70で混合した溶媒を調製した。該溶媒に1.0mol/LのLiPF6を溶解させて電解液を調製した。
上記方法で作製した正極および負極を成形した後、図1に示される電池要素を作製した。正極活物質層1と正極集電体1Aとを備える正極と、負極活物質層2と負極集電体2Aとを備える負極との間に多孔質フィルムであるセパレータ3を挟みこんだ。正極集電体1Aおよび負極集電体2Aには、正極タブ1Bおよび負極タブ2Bをそれぞれ溶接した。作製した電池要素をアルミニウムラミネートフィルムである外装体4で包み、外装体4の3方を熱融着により封止した後、前記電解液を適度な真空度において含浸させた。その後、減圧下において、熱融着しなかった外装体4の1方を熱融着により封止し、活性化処理前のリチウムイオン二次電池を作製した。
作製した活性化処理前のリチウムイオン二次電池について、正極活物質1gあたり20mA(20mA/g)の電流で4.5Vまで充電した。その後、正極活物質1gあたり20mA(20mA/g)の電流で1.5Vまで放電した。その後、同様に、20mA/gの電流で4.5Vまで充電した後、1.5Vまで放電した。すなわち、充放電サイクルを2回繰り返す活性化処理を行った。その後、一旦封口部を破って減圧することによって電池内部のガスを抜き、さらに破った箇所を再封口することにより、リチウムイオン二次電池を作製した。
合成例1で得た1,3-プロパンジオン誘導体PD1で被覆されたリチウム酸化物の代わりに、合成例2で得た1,3-プロパンジオン誘導体PD2で被覆されたリチウム酸化物を用いて正極を作製した以外は、実施例1と同様の方法でリチウムイオン二次電池を作製した。
合成例1で得た1,3-プロパンジオン誘導体PD1で被覆されたリチウム酸化物の代わりに、合成例3で得た1,3-プロパンジオン誘導体PD4で被覆されたリチウム酸化物を用いて正極を作製した以外は、実施例1と同様の方法でリチウムイオン二次電池を作製した。
合成例1で得た1,3-プロパンジオン誘導体PD1で被覆されたリチウム酸化物の代わりに、被覆処理していない層状岩塩型構造を有するリチウム酸化物(Li1.4Fe0.2Ni0.2Mn0.6O2.4)を用いて正極を作製した以外は、実施例1と同様の方法でリチウムイオン二次電池を作製した。
上記方法で作製したリチウムイオン二次電池について、45℃の恒温槽中、40mA/gの定電流で4.5Vまで充電し、さらに5mA/gの電流になるまで4.5Vの定電圧で充電を続けた。その後、5mA/gの電流で1.5Vまで放電し、リチウムイオン二次電池の初期容量を求めた。
各実施例および比較例で用いた1,3-プロパンジオン誘導体、リチウム酸化物、初期容量、30サイクル後の容量維持率、30サイクル後のガス発生量を表2に示す。なお、ガス発生量に関しては、比較例1のガス発生量を100とした時の換算値で示した。
1A 正極集電体
1B 正極タブ
2 負極活物質層
2A 負極集電体
2B 負極タブ
3 セパレータ
4 外装体
Claims (10)
- 層状岩塩型構造を有し、かつ下記式(1)
LixFesM1 (z-s)M2 yOδ (1)
(式(1)において、1.05≦x≦1.90、0.05≦s≦0.50、0.05≦z≦0.50、0.33≦y≦0.90、1.20≦δ≦3.10、z-s≧0であり、M1はCo及び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、M2はMn、Ti及びZrからなる群から選択される少なくとも1種の元素である。)
で示される化合物と、
下記式(2)で示される1,3-プロパンジオン誘導体と、
を含むリチウムイオン二次電池用正極活物質。
- 前記式(2)で示される1,3-プロパンジオン誘導体が、前記式(1)で示される化合物を含む粒子の表面の少なくとも一部を被覆している請求項1に記載のリチウムイオン二次電池用正極活物質。
- 前記式(2)において、R1およびR2の少なくとも一方が、2-チエニル基、2-フラニル基またはフルオロフェニル基である請求項1または2に記載のリチウムイオン二次電池用正極活物質。
- 前記式(1)において、M1がNiを含み、M2がMnを含む請求項1乃至3のいずれか一項に記載のリチウムイオン二次電池用正極活物質。
- 前記式(1)で示される化合物が、Li1.4Fe0.2Ni0.2Mn0.6O2.4で示される化合物である請求項1乃至4のいずれか一項に記載のリチウムイオン二次電池用正極活物質。
- 請求項1乃至5のいずれか一項に記載のリチウムイオン二次電池用正極活物質を含む正極を備えるリチウムイオン二次電池。
- リチウムイオンを吸蔵放出可能な材料を含む負極と、電解液と、を備える請求項6に記載のリチウムイオン二次電池。
- 前記負極が、シリコン、シリコン酸化物および炭素からなる群から選択される少なくとも一種を含有する請求項7に記載のリチウムイオン二次電池。
- 前記電解液が、鎖状カーボネート系溶媒および環状カーボネート系溶媒の少なくとも一方を含有する請求項7または8に記載のリチウムイオン二次電池。
- 層状岩塩型構造を有し、かつ下記式(1)
LixFesM1 (z-s)M2 yOδ (1)
(式(1)において、1.05≦x≦1.90、0.05≦s≦0.50、0.05≦z≦0.50、0.33≦y≦0.90、1.20≦δ≦3.10、z-s≧0であり、M1はCo及び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、M2はMn、Ti及びZrからなる群から選択される少なくとも1種の元素である。)
で示される化合物を含む粒子を、下記式(2)で示される1,3-プロパンジオン誘導体を溶解させた溶液に浸漬し、前記式(1)で示される化合物を含む粒子の表面の少なくとも一部に前記式(2)で示される1,3-プロパンジオン誘導体を被覆する工程を含むリチウムイオン二次電池用正極活物質の製造方法。
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JP2006172726A (ja) * | 2004-12-13 | 2006-06-29 | Matsushita Electric Ind Co Ltd | 非水電解液二次電池 |
WO2006070546A1 (ja) * | 2004-12-27 | 2006-07-06 | Ube Industries, Ltd. | 非水電解液及びそれを用いたリチウム二次電池 |
JP2006351242A (ja) * | 2005-06-13 | 2006-12-28 | Matsushita Electric Ind Co Ltd | 非水電解液二次電池 |
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