WO2016060253A1 - リチウムイオン電池 - Google Patents
リチウムイオン電池 Download PDFInfo
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- WO2016060253A1 WO2016060253A1 PCT/JP2015/079340 JP2015079340W WO2016060253A1 WO 2016060253 A1 WO2016060253 A1 WO 2016060253A1 JP 2015079340 W JP2015079340 W JP 2015079340W WO 2016060253 A1 WO2016060253 A1 WO 2016060253A1
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/02—Magnesia
- C01F5/04—Magnesia by oxidation of metallic magnesium
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/003—Titanates
- C01G23/005—Alkali titanates
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G45/00—Compounds of manganese
- C01G45/006—Compounds containing, besides manganese, two or more other elements, with the exception of oxygen or hydrogen
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G51/00—Compounds of cobalt
- C01G51/006—Compounds containing, besides cobalt, two or more other elements, with the exception of oxygen or hydrogen
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
- C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic System
- C07F5/02—Boron compounds
- C07F5/04—Esters of boric acids
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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
- H01M10/0567—Liquid materials characterised by the additives
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
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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
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
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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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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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
Definitions
- the present invention relates to a lithium ion battery.
- Lithium ion batteries are high energy density secondary batteries, and are used as power sources for portable devices such as notebook computers and mobile phones, taking advantage of their characteristics.
- a technique relating to a lithium ion battery using a spinel-structure lithium-titanium composite oxide having a specific specific surface area as a negative electrode active material is disclosed (for example, Japanese Patent Application Laid-Open No. 2005-2005). -317512).
- a technique related to a lithium ion battery containing tris (trimethylsilyl) borate in a nonaqueous electrolyte is disclosed. (For example, see International Publication No. 2009/110490).
- the lithium ion battery using the non-aqueous electrolyte containing tris (trimethylsilyl) borate described in Patent Document 2 still has room for improvement in terms of storage characteristics and cycle characteristics at high temperatures. It became clear by examination of inventors.
- This invention is made
- Means for solving the above problems include the following embodiments.
- a positive electrode, a negative electrode, and a nonaqueous electrolytic solution The positive electrode has a current collector and a positive electrode mixture applied to at least one surface of the current collector, The positive electrode mixture includes a lithium transition metal oxide as a positive electrode active material, The negative electrode includes a lithium titanium composite oxide as a negative electrode active material, The nonaqueous electrolytic solution is a lithium ion battery containing a fluorine-containing borate ester.
- R 1 , R 2 and R 3 each independently represents a hydrocarbon group having 1 to 10 carbon atoms, and at least one of R 1 , R 2 and R 3 is a fluorine atom. including.
- a lithium ion battery having excellent charge / discharge cycle characteristics and excellent storage characteristics at high temperatures is provided.
- the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.
- numerical values indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
- the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. Good. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
- the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. It means the content rate of.
- the particle diameter of each component in the composition is a mixture of the plurality of types of particles present in the composition unless there is a specific indication when there are a plurality of types of particles corresponding to each component in the composition. Means the value of.
- the term “layer” or “film” refers to a part of the region in addition to the case where the layer or the film is formed when the region where the layer or film exists is observed. It is also included when it is formed only.
- the term “lamination” indicates that layers are stacked, and two or more layers may be combined, or two or more layers may be detachable.
- the lithium ion battery of this embodiment is a lithium ion battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode is applied to at least one surface of the current collector and the current collector.
- the positive electrode mixture includes a lithium transition metal oxide as a positive electrode active material
- the negative electrode includes a lithium titanium composite oxide as a negative electrode active material
- the non-aqueous electrolyte includes a fluorine-containing boron. Contains acid ester.
- the lithium ion battery of this embodiment includes a lithium transition metal oxide as a positive electrode active material and a lithium titanium composite oxide as a negative electrode active material, so that the lithium titanium composite oxide inserts and desorbs lithium ions.
- the potential is 1.55 V with respect to the lithium electrode. For this reason, reductive decomposition of the electrolytic solution and precipitation of metal Li hardly occur, and the safety is excellent.
- the nonaqueous electrolytic solution contains a fluorine-containing borate ester, the charge / discharge cycle characteristics and the storage characteristics at high temperatures are excellent. The reason is not clear, but is presumed as follows.
- a lithium salt (LiPF 6 or the like) contained as an electrolyte is decomposed by reaction with a trace amount of water contained in the electrolytic solution, reduction on the negative electrode, or the like to generate an inorganic substance such as LiF or Li 2 O.
- These inorganic substances are generated on the surface of the LTO negative electrode and may cause an increase in resistance or a decrease in capacity.
- the fluorine-containing boric acid ester contained in the nonaqueous electrolytic solution stabilizes the lithium salt and suppresses the above decomposition.
- the positive electrode includes a positive electrode active material containing a lithium transition metal oxide and a conductive material. If necessary, a positive electrode mixture containing a binder and a solvent is applied to the surface of the current collector, and pressed as necessary. It is formed by increasing the density of the positive electrode mixture by, for example.
- x value which shows the molar ratio of lithium increases / decreases by charging / discharging.
- the lithium transition metal oxide is preferably a lithium transition metal oxide containing manganese from the viewpoints of safety, energy density, and high capacity.
- the lithium transition metal oxide containing manganese spinel type lithium manganese oxide (sp-Mn) is preferable from the viewpoint of further improving safety.
- layered lithium / nickel / manganese / cobalt composite oxide (NMC) is preferable.
- spinel type lithium / manganese oxide (sp-Mn) and layered type lithium / nickel / manganese / cobalt composite oxide (NMC) in combination.
- lithium manganese nickel composite oxide (LNMO) that can increase the potential of the positive electrode is preferable.
- spinel type lithium manganese oxide those represented by the following composition formula (1) are preferable.
- (1 + ⁇ ) represents the composition ratio of Li
- (2- ⁇ ) represents the composition ratio of Mn
- ⁇ represents the composition ratio of the element M ′.
- the composition ratio of O (oxygen) is 4.
- the element M ′ is at least one selected from the group consisting of Mg (magnesium), Ca (calcium), Sr (strontium), Al, Ga, Zn (zinc), Ti, Cr, Fe, Co, and Cu (copper). It is a seed element.
- NMC layered lithium / nickel / manganese / cobalt composite oxide
- (1 + ⁇ ) is a composition ratio of Li (lithium), x is a composition ratio of Mn (manganese), y is a composition ratio of Ni (nickel), and (1-xyz) is Co.
- the composition ratio of (cobalt) is shown respectively.
- z represents the composition ratio of the element M.
- the composition ratio of O (oxygen) is 2.
- the elements M are Ti (titanium), Zr (zirconium), Nb (niobium), Mo (molybdenum), W (tungsten), Al (aluminum), Si (silicon), Ga (gallium), Ge (germanium), and Sn. It is at least one element selected from the group consisting of (tin). Examples thereof include LiNi 0.5 Mn 0.3 Co 0.2 O 2 and LiNi 1/3 Mn 1/3 Co 1/3 O 2 .
- the lithium manganese nickel composite oxide is preferably a spinel structure lithium manganese nickel composite oxide.
- the spinel type lithium manganese nickel composite oxide is a compound represented by a composition formula of LiNi X Mn 2-X O 4 (0.1 ⁇ X ⁇ 1.1).
- LiNi 0.5 Mn 1.5 O 4 is more preferable.
- a part of the Mn / Ni site of the spinel structure lithium manganese nickel composite oxide may be substituted with another metal atom, It is also possible to use a material in which lithium is present in the crystal or a defect is generated at the O site.
- Examples of other metal atoms that can substitute the Mn / Ni site include Ti, V, Cr, Fe, Co, Zn, Cu, W, Mg, Al, and Ru. These metal atoms may be only one kind or two or more kinds. Of these replaceable metal elements, Ti is preferable from the viewpoint of stabilizing the crystal structure.
- the above lithium manganese nickel composite oxide is preferably used at a charged potential of 4.5 V to 5 V with respect to Li / Li + at 4.6 to 4.9 V or less. More preferably, it is used.
- the layered lithium / nickel / manganese / cobalt composite oxide (NMC) and the spinel lithium / manganese oxide (sp-Mn) are preferably in the form of particles.
- the range of the BET specific surface area of the particles may be for example 0.2 m 2 / g or more, preferably 0.3 m 2 / g or more, more preferably 0 4 m 2 / g or more.
- it may be 4.0 m 2 / g or less, preferably 2.5 m 2 / g or less, and more preferably 1.5 m 2 / g or less.
- the lithium manganese nickel composite oxide (LNMO) is preferably in the form of particles.
- the BET specific surface area of the particles is preferably less than 1 m 2 / g, more preferably less than 0.5 m 2 / g, from the viewpoint of further improving storage characteristics at high temperatures. Is more preferable, and it is still more preferable that it is less than 0.3 m ⁇ 2 > / g.
- BET specific surface area is preferably at 0.05 m 2 / g or more, more not less 0.08 m 2 / g or more Preferably, it is more preferably 0.1 m 2 / g or more.
- the BET specific surface area can be measured from, for example, nitrogen adsorption capacity according to JIS Z 8830.
- the evaluation device for example, AUTOSORB-1 (trade name) manufactured by QUANTACHROME can be used.
- AUTOSORB-1 trade name manufactured by QUANTACHROME
- a measurement cell charged with 0.05 g of a measurement sample is depressurized to 10 Pa or less with a vacuum pump, heated at 110 ° C. and held for 3 hours or more, and then kept at a normal temperature ( It is preferable to naturally cool to 25 ° C.
- the evaluation temperature is preferably 77K ( ⁇ 196.15 ° C.) and the evaluation pressure range is preferably less than 1 in relative pressure (equilibrium pressure with respect to saturated vapor pressure).
- the median diameter D50 (when the primary particles are aggregated to form secondary particles, the median diameter D50 of the secondary particles) is: From the viewpoint of dispersibility in the positive electrode mixture, the thickness is preferably 0.5 ⁇ m to 100 ⁇ m, and more preferably 1 ⁇ m to 50 ⁇ m.
- the median diameter D50 can be obtained from the particle size distribution obtained by the laser diffraction / scattering method.
- the content in the case of using the lithium transition metal oxide is preferably 50% by mass to 100% by mass, and preferably 60% by mass to 100% by mass in the total amount of the positive electrode active material from the viewpoint of improving battery capacity. More preferably, it is more preferably 80% by mass to 100% by mass.
- the content when the lithium manganese nickel composite oxide (LNMO) is used is 60% by mass to 100% by mass in the total amount of the positive electrode active material from the viewpoint of improving the battery capacity. It is preferably 70% by mass to 100% by mass, more preferably 85% by mass to 100% by mass.
- the conductive material may be one or more of carbon blacks such as acetylene black and ketjen black, and carbon material powders such as graphite.
- carbon blacks such as acetylene black and ketjen black
- carbon material powders such as graphite.
- a small amount of carbon nanotubes, graphene, or the like can be added as a conductive material to increase the electrical conductivity of the positive electrode.
- the conductive material is preferably acetylene black from the viewpoint of further improving the rate characteristics.
- the content of the conductive material is preferably 4% by mass or more, more preferably 5% by mass or more, and still more preferably 5.5% by mass or more, based on the total amount of the positive electrode mixture.
- the upper limit is preferably 10% by mass or less, more preferably 9% by mass or less, and still more preferably 8.5% by mass or less from the viewpoint of battery capacity.
- the binder is not particularly limited, and a material having good solubility or dispersibility in the dispersion solvent is selected.
- resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine Rubbery polymers such as rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or its hydrogenated product, EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymer such as ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or
- binders may be used individually by 1 type, and may use 2 or more types together. From the viewpoint of high adhesion of the positive electrode, it is preferable to use a copolymer obtained by adding acrylic acid and a linear ether group to polyvinylidene fluoride (PVdF) or a polyacrylonitrile skeleton.
- PVdF polyvinylidene fluoride
- the range of the binder content with respect to the mass of the positive electrode mixture is as follows.
- the lower limit of the range is preferably 0.1% by mass or more from the viewpoint of sufficiently binding the positive electrode active material to obtain sufficient mechanical strength of the positive electrode and stabilizing battery performance such as cycle characteristics,
- the content is more preferably 1% by mass or more, and further preferably 2% by mass or more.
- the upper limit is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less.
- the solvent for dispersing the positive electrode active material, the conductive material, the binder and the like is not particularly limited, and an organic solvent such as N-methyl-2pyrrolidone can be used.
- the material of the current collector is not particularly limited, and examples thereof include aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, and conductive glass. Further, a surface of a metal foil such as aluminum or copper that has been treated with carbon, nickel, titanium, silver, or the like for the purpose of improving adhesiveness, conductivity, and oxidation resistance can be used.
- the thickness of the current collector is not particularly limited, and is preferably 1 ⁇ m to 50 ⁇ m from the viewpoint of electrode strength and energy density.
- the coating amount of the current collector of positive electrode is preferably from the viewpoint of energy density and output characteristic, a 10g / m 2 ⁇ 250g / m 2, 50g / m 2 ⁇ 200g / m 2 It is more preferable that
- the density of positive electrode from the viewpoint of energy density and rate characteristics, preferably 1.8g / cm 3 ⁇ 3.2g / cm 3, 2.0g / cm 3 ⁇ 3.0g / cm 3 is more preferable.
- the negative electrode includes a negative electrode active material containing a lithium-titanium composite oxide and a conductive material, and if necessary, a negative electrode mixture containing a binder and a solvent is applied to the surface of the current collector. It is formed by increasing the density of the negative electrode mixture by pressing or the like.
- the negative electrode active material can be composed of the lithium titanium composite oxide alone, but may contain other negative electrode active material such as a carbon material for the purpose of improving the characteristics of the lithium ion battery. .
- the lithium titanium composite oxide (LTO) is preferably a lithium titanium composite oxide having a spinel structure.
- the basic composition formula of the spinel structure lithium titanium composite oxide is represented by Li [Li 1/3 Ti 5/3 ] O 4 .
- a part of the Li or Ti site of the spinel structure lithium-titanium composite oxide is replaced with another metal atom, excess lithium is present in the crystal, or one of the O sites. It is also possible to use those in which the part is replaced with other elements.
- Examples of other metal atoms that can be substituted include F, B, Nb, V, Mn, Ni, Cu, Co, Zn, Sn, Pb, Al, Mo, Ba, Sr, Ta, Mg, and Ca. it can. These metal atoms may be only one kind or two or more kinds.
- the content of the lithium titanium composite oxide is preferably 70% by mass to 100% by mass, and preferably 80% by mass to 100% by mass, based on the total amount of the negative electrode active material, from the viewpoint of improving safety and cycle characteristics. More preferably, the content is 90% by mass to 100% by mass.
- the conductive material examples include those similar to the conductive material used for the positive electrode, and preferred conductive materials are also the same. From the viewpoint of further improving the rate characteristics, acetylene black is preferable. From the viewpoint of rate characteristics, the content of the conductive material is preferably 1% by mass or more, more preferably 4% by mass or more, and more preferably 6% by mass or more based on the total amount of the negative electrode mixture. Is more preferable. From the viewpoint of battery capacity, the upper limit is preferably 15% by mass or less, more preferably 12% by mass or less, and still more preferably 10% by mass or less.
- binder examples include the same binders used for the positive electrode.
- the content of the binder with respect to the total amount of the negative electrode mixture is as follows.
- the lower limit of the range is preferably 0.1% by mass or more from the viewpoint of sufficiently binding the negative electrode active material to obtain sufficient mechanical strength of the negative electrode and stabilizing battery performance such as cycle characteristics. More preferably, it is more preferably 1% by mass or more.
- the upper limit is preferably 40% by mass or less, more preferably 25% by mass or less, and still more preferably 15% by mass or less from the viewpoint of improving battery capacity and conductivity.
- the solvent for dispersing the negative electrode active material, the conductive material, the binder and the like is not particularly limited, and an organic solvent such as N-methyl-2pyrrolidone can be used.
- the material of the current collector is not particularly limited, and examples thereof include copper, stainless steel, nickel, aluminum, titanium, baked carbon, conductive polymer, conductive glass, and aluminum-cadmium alloy. Furthermore, for the purpose of improving adhesiveness, conductivity, and reduction resistance, the surface of a metal foil such as copper or aluminum that has been treated with carbon, nickel, titanium, silver or the like can be used.
- the thickness of the current collector is not particularly limited, and is preferably 1 ⁇ m to 50 ⁇ m from the viewpoint of electrode strength and energy density.
- the coating amount of the current collector of negative electrode mixture (one side) is preferably from the viewpoint of energy density and output characteristic, a 10g / m 2 ⁇ 200g / m 2, 50g / m 2 ⁇ 150g / m 2 It is more preferable that The density of the negative electrode mixture is preferably 1.0 g / cm 3 to 2.8 g / cm 3 and 1.2 g / cm 3 to 2.6 g / cm 3 from the viewpoint of energy density and rate characteristics. It is more preferable.
- the nonaqueous electrolytic solution is a solution in which an electrolyte is dissolved in a nonaqueous solvent.
- the nonaqueous electrolytic solution of the present embodiment contains a fluorinated boric acid ester.
- a fluorine-containing boric acid ester may be used individually by 1 type, or may be used in combination of 2 or more type.
- fluorinated boric acid ester for example, a compound represented by the following general formula (a) is preferable.
- R 1 , R 2 and R 3 each independently represents a hydrocarbon group having 1 to 10 carbon atoms, and at least one of R 1 , R 2 and R 3 is a fluorine atom. including.
- the hydrocarbon groups represented by R 1 , R 2 and R 3 in formula (a) preferably each independently have 1 to 6 carbon atoms, A number of 1 to 5 is more preferred, and a carbon number of 1 to 3 is still more preferred.
- the number of fluorine atoms contained in the hydrocarbon group represented by R 1 , R 2 and R 3 in the formula (a) is preferably independently 0 to 21, It is more preferably 13, more preferably 0 to 11, and still more preferably 0 to 7.
- two or more of the hydrocarbon groups represented by R 1 , R 2 and R 3 in the formula (a) contain a fluorine atom, More preferably, all three contain fluorine atoms.
- an alkyl group having a linear, cyclic or branched structure, an aryl group, an alkyl group and an aryl group are bonded.
- State hydrocarbon groups and the like include methyl group, ethyl group, n-propyl group, isopropyl group, 2-methylpropyl group, phenyl group, 2-phenylpropyl and the like.
- hydrocarbon group containing a fluorine atom represented by R 1 , R 2 and R 3 in the formula (a) include a trifluoroethyl group, a tetrafluoroethyl group, a monofluoroethyl group, and a pentafluoropropyl group.
- a fluoropropyl group, a tetrafluorophenyl group, a pentafluorophenyl group, etc. are mentioned.
- Examples of the compound represented by the formula (a) include tris borate (trifluoroethyl), methyl bis (trifluoroethyl) borate, tris (tetrafluoroethyl) borate, and tris (monofluoroethyl) borate. , Tris borate (pentafluoropropyl), tris borate (hexafluoropropyl), tris borate (hexafluoroisopropyl), tris borate (2-methyl-1,1,1,3,3,3-hexafluoro Propyl) tris borate (2-phenyl-1,1,1,3,3,3-hexafluoropropyl) and tris borate (pentafluorophenyl). These compounds may be used alone or in combination of two or more.
- tris borate hexafluoroisopropyl
- tris borate 2,2,2-trifluoroethyl
- tris borate trifluoroethyl
- tris borate penentafluorophenyl
- tris borate hexafluoroisopropyl
- the content of the fluorinated boric acid ester in the non-aqueous electrolyte is 0.02% by mass to 10% by mass from the viewpoint of cycle characteristics and high temperature storage characteristics, based on the total amount of the non-aqueous electrolyte. It is preferably 0.05% by mass to 5% by mass, more preferably 0.05% by mass to 4% by mass, and particularly preferably 0.1% by mass to 3% by mass. .
- Examples of the electrolyte contained in the nonaqueous electrolytic solution include lithium salts.
- Lithium salts include LiPF 6 , LiBF 4 , LiFSI (lithium bisfluorosulfonylimide), LiTFSI (lithium bistrifluoromethanesulfonylimide), LiClO 4 , LiB (C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN (SO 2 F) 2 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 CF 2 CF 3 ) 2 and the like. These lithium salts may be used alone or in combination of two or more.
- lithium hexafluorophosphate (LiPF 6 ) is preferable when comprehensively judging the solubility in a solvent, charge / discharge characteristics in the case of a lithium ion battery, input / output characteristics, cycle characteristics, and the like.
- the concentration of the electrolyte is preferably 0.5 mol / L to 1.5 mol / L, more preferably 0.7 mol / L to 1.3 mol / L with respect to the nonaqueous solvent, and 0.8 mol / L. More preferably, it is L to 1.2 mol / L.
- Non-aqueous solvents are not particularly limited, and cyclic carbonates (ethylene carbonate, propylene carbonate, etc.), chain carbonates (methyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc.), ⁇ -butyrolactone, acetonitrile, 1,2-dimethoxyethane, dimethoxy Examples include methane, tetrahydrofuran, dioxolane, methylene chloride, and methyl acetate. These nonaqueous solvents may be used alone or in combination of two or more, but it is preferable to use a cyclic carbonate and a chain carbonate in combination.
- the content of the cyclic carbonate is preferably 10% by volume to 70% by volume, and preferably 15% by volume to 60% by volume with respect to the total amount of the non-aqueous solvent. More preferably, it is 20% by volume to 55% by volume.
- the non-aqueous electrolytic solution may contain additives other than the fluorinated boric acid ester in order to improve storage characteristics at high temperatures, cycle characteristics, input / output characteristics, and the like.
- the kind of additive is not particularly limited, and can be selected according to the purpose. Examples thereof include heterocyclic compounds containing at least one selected from the group consisting of nitrogen atoms and sulfur atoms, cyclic carboxylic acid esters, fluorine-containing cyclic carbonates, and other compounds having an unsaturated bond in the molecule.
- the non-aqueous electrolyte may use other additives such as an overcharge preventing material, a negative electrode film forming material, a positive electrode protective material, and a high input / output material in addition to the above-mentioned additives depending on the required function.
- additives such as an overcharge preventing material, a negative electrode film forming material, a positive electrode protective material, and a high input / output material in addition to the above-mentioned additives depending on the required function.
- the lithium ion battery of this embodiment preferably includes a separator disposed between the positive electrode and the negative electrode in addition to the positive electrode, the negative electrode, and the non-aqueous electrolyte.
- the separator is not particularly limited as long as it has ion permeability while electronically insulating the positive electrode and the negative electrode and has resistance to oxidation on the positive electrode side and reducibility on the negative electrode side.
- a material (material) of the separator satisfying such characteristics a resin, an inorganic material, glass fiber, or the like is used.
- the resin examples include olefin polymer, fluoropolymer, cellulose polymer, polyimide, and nylon. From the viewpoint of being chemically stable and excellent in liquid retention, porous sheets, nonwoven fabrics, and the like made from polyolefins such as polyethylene and polypropylene are preferred.
- inorganic substances examples include oxides (alumina, silicon dioxide, etc.), nitrides (aluminum nitride, silicon nitride, etc.), sulfates (barium sulfate, calcium sulfate, etc.), and the like.
- oxides alumina, silicon dioxide, etc.
- nitrides aluminum nitride, silicon nitride, etc.
- sulfates barium sulfate, calcium sulfate, etc.
- thin film-shaped substrate those having a pore diameter of 0.01 ⁇ m to 1 ⁇ m and a thickness of 5 ⁇ m to 50 ⁇ m are preferably used.
- a separator in which a composite porous layer is formed using the above-described inorganic material in a fiber shape or a particle shape by using a binder such as a resin can be used as a separator.
- this composite porous layer may be formed on the surface of the positive electrode or the negative electrode to form a separator.
- a composite porous layer in which alumina particles having a 90% average particle diameter (D90) of less than 1 ⁇ m are bound with a fluororesin as a binder is formed on the surface of the positive electrode or negative electrode or the surface facing the positive electrode or negative electrode of the separator. It may be formed.
- the shape of the lithium ion battery of this embodiment is not particularly limited, and can be selected from various shapes such as a cylindrical shape, a stacked shape, and a coin shape.
- an electrode body having a structure in which a positive electrode and a negative electrode are laminated (a separator is disposed between the positive electrode and the negative electrode as necessary) is sealed in a battery case together with a non-aqueous electrolyte. It has a structure.
- the positive current collector and the negative current collector are connected to the positive electrode terminal and the negative electrode terminal connected to the outside by using a current collecting lead or the like.
- a stacked lithium ion battery having an electrode body in which a positive electrode and a negative electrode are stacked via a separator will be described with reference to the drawings.
- the size, shape, and the like of each member shown in FIGS. 1 and 2 can be arbitrarily selected, and are not limited to the specific examples shown in FIGS.
- the present embodiment is not limited to the mode shown in the drawings, and is, for example, a wound lithium ion battery in which an electrode body in which a positive electrode and a negative electrode are stacked via a separator is wound in a roll shape. Also good.
- FIG. 1 is a perspective view schematically showing the overall structure of a stacked lithium ion battery.
- the lithium ion battery 10 includes an electrode body and a non-aqueous electrolyte contained in a battery container formed from a laminate film 6, and a positive electrode current collecting tab 2 connected to the positive electrode and a negative electrode current collecting tab connected to the negative electrode 4 has a structure extending to the outside of the battery container.
- FIG. 2 is a perspective view schematically showing the structure of the electrode body.
- the electrode body 20 is formed by laminating the positive electrode 1 with the positive electrode current collecting tab 2, the separator 5, and the negative electrode plate 3 with the negative electrode current collecting tab 4 attached in this order.
- the capacity ratio of the negative electrode to the positive electrode is preferably 0.7 or more and less than 1.5 from the viewpoint of safety and energy density, and 0.75 to 1. 2 is more preferable, and 0.90 to 1.1 is still more preferable.
- the capacity ratio of the positive electrode to the negative electrode is preferably 0.7 or more and less than 1.
- the capacity ratio of the positive electrode to the negative electrode is less than 1, the decomposition reaction of the fluorinated boric acid ester due to the positive electrode becoming high potential is unlikely to occur, and the cycle characteristics of the lithium ion battery tend to be good. It is in.
- the above-mentioned “positive electrode capacity” and “negative electrode capacity” are used reversibly, which are obtained when a constant-current-constant-voltage charge-constant-current discharge is performed by forming an electrochemical cell having a counter electrode made of metallic lithium. Means the maximum capacity possible.
- the “positive electrode capacity” and “negative electrode capacity” have a voltage range of 4.95 V to 3 in the electrochemical cell. 5 V and 2 V to 1 V, and the capacity obtained when the above charge / discharge is evaluated under the condition that the current density during constant current charge and constant current discharge is 0.1 mA / cm 2 .
- the “positive electrode capacity” and the “negative electrode capacity” have a voltage range of 3.0 V in the electrochemical cell, respectively.
- the capacity is obtained when the above charging / discharging is performed and evaluated under the conditions of -4.3V and 2V-1V, and the current density during constant current charging and constant current discharging is 0.1 mA / cm 2 .
- a paste-like positive electrode mixture was prepared by adding 2-pyrrolidone and kneading. This positive electrode mixture was applied in an amount of 195 g / m 2 to one surface of a 20 ⁇ m-thick aluminum foil which is a positive electrode current collector. Thereafter, drying treatment was performed, and consolidation was performed by press treatment until the density reached 2.55 g / cm 3 to produce a sheet-like positive electrode.
- the produced positive electrode was cut into a rectangle having a width of 31 mm and a length of 46 mm, and a positive electrode current collecting tab was attached at a position as shown in FIG.
- the produced negative electrode was cut into a rectangle having a width of 30 mm and a length of 45 mm, and a negative electrode current collecting tab was attached at a position as shown in FIG.
- the produced positive electrode, a polyethylene microporous membrane having a thickness of 30 ⁇ m, a width of 35 mm, and a length of 50 mm as a separator and the produced negative electrode were laminated in this order to produce an electrode body.
- the positive electrode and the negative electrode were arranged such that the surface of the positive electrode coated with the positive electrode active material and the surface of the negative electrode coated with the negative electrode active material were opposed to each other with a separator interposed therebetween.
- the electrode body produced above was accommodated in a battery container as shown in FIG. 1, and 1 ml of the non-aqueous electrolyte prepared above was injected. Then, the opening part of the battery container was closed in the state in which the edge part of the positive electrode current collection tab and negative electrode current collection tab of an electrode body had come out of the battery container, and the lithium ion battery was produced.
- a battery container what was formed from the laminated film which is a laminated body of a polyethylene terephthalate (PET) film / aluminum foil / sealant layer (polypropylene etc.) was used. Two lithium ion batteries were prepared for each example and comparative example for cycle characteristic evaluation and high temperature storage characteristic evaluation described later.
- Example 5 A lithium ion battery was produced in the same manner as in Example 1 except that the production of the positive electrode and the preparation of the nonaqueous electrolytic solution were performed as follows. Thereafter, the cycle characteristics and the storage characteristics at high temperatures were evaluated by the method described later.
- This positive electrode mixture was applied in an amount of 140 g / m 2 to one side of a 20 ⁇ m-thick aluminum foil, which is a positive electrode current collector. Thereafter, drying treatment was performed, and consolidation was performed by press treatment until the density became 2.3 g / cm 3 , thereby producing a sheet-like positive electrode.
- the produced positive electrode was cut into a rectangle having a width of 31 mm and a length of 46 mm, and a positive electrode current collecting tab was attached at a position as shown in FIG.
Abstract
Description
一方、リチウムチタン複合酸化物を負極活物質に用いたリチウムイオン電池の高温での保存特性を向上させる手段として、非水電解質にホウ酸トリス(トリメチルシリル)を含有するリチウムイオン電池に関する技術が開示されている(例えば、国際公開第2009/110490号参照)。
本発明は、上記事情を鑑みてなされたものであり、充放電サイクル特性に優れ、且つ、高温での保存特性に優れるリチウムイオン電池を提供することを課題とする。
<1>正極と、負極と、非水電解液と、を備え、
前記正極は、集電体と前記集電体の少なくとも片面に塗布された正極合材とを有し、
前記正極合材は、正極活物質としてリチウム遷移金属酸化物を含み、
前記負極は、負極活物質としてリチウムチタン複合酸化物を含み、
前記非水電解液は含フッ素ホウ酸エステルを含有する、リチウムイオン電池。
<2>前記含フッ素ホウ酸エステルが下記一般式(a)で示される化合物を含む、<1>に記載のリチウムイオン電池。
(式(a)中、R1、R2及びR3は、それぞれ独立に、炭素数が1~10の炭化水素基を表し、R1、R2及びR3のうち少なくとも1つはフッ素原子を含む。)
本明細書において「~」を用いて示された数値範囲には、「~」の前後に記載される数値がそれぞれ最小値及び最大値として含まれる。
本明細書中に段階的に記載されている数値範囲において、一つの数値範囲で記載された上限値又は下限値は、他の段階的な記載の数値範囲の上限値又は下限値に置き換えてもよい。また、本明細書中に記載されている数値範囲において、その数値範囲の上限値又は下限値は、実施例に示されている値に置き換えてもよい。
本明細書において組成物中の各成分の含有率は、組成物中に各成分に該当する物質が複数種存在する場合、特に断らない限り、組成物中に存在する当該複数種の物質の合計の含有率を意味する。
本明細書において組成物中の各成分の粒子径は、組成物中に各成分に該当する粒子が複数種存在する場合、特に断らない限り、組成物中に存在する当該複数種の粒子の混合物についての値を意味する。
本明細書において「層」又は「膜」との語には、当該層又は膜が存在する領域を観察したときに、当該領域の全体に形成されている場合に加え、当該領域の一部にのみ形成されている場合も含まれる。
本明細書において「積層」との語は、層を積み重ねることを示し、二以上の層が結合されていてもよく、二以上の層が着脱可能であってもよい。
さらに、非水電解液が含フッ素ホウ酸エステルを含有することにより、充放電サイクル特性と高温での保存特性に優れている。その理由は明らかではないが、以下のように推測される。電解質として含まれるリチウム塩(LiPF6等)は、電解液に含まれる微量水分との反応、負極上での還元等により分解され、LiF、Li2O等の無機物を生成する。これらの無機物はLTO負極の表面に生成し、抵抗の増大や容量の低下の原因となる場合がある。しかし、非水電解液中に含まれる含フッ素ホウ酸エステルがリチウム塩を安定化させ、上記の分解が抑制されるためと考えられる。
正極は、リチウム遷移金属酸化物を含む正極活物質と、導電材とを含み、必要に応じて結着材及び溶剤を含む正極合材を集電体の表面に塗布し、必要に応じてプレス等によって正極合材の密度を高めることによって形成する。
マンガンを含むリチウム遷移金属酸化物としては、安全性をより向上できる観点からは、スピネル型リチウム・マンガン酸化物(sp-Mn)が好ましい。また、高容量化の観点からは、層状型リチウム・ニッケル・マンガン・コバルト複合酸化物(NMC)が好ましい。
安全性及び高容量化の両方の観点からは、スピネル型リチウム・マンガン酸化物(sp-Mn)と層状型リチウム・ニッケル・マンガン・コバルト複合酸化物(NMC)を併用して用いることが好ましい。
高エネルギー密度化の観点からは、正極の電位を高くすることが可能であるリチウムマンガンニッケル複合酸化物(LNMO)が好ましい。
組成式(1)中、-0.2≦η≦0.2、0≦λ≦1である。
元素M’は、Mg(マグネシウム)、Ca(カルシウム)、Sr(ストロンチウム)、Al、Ga、Zn(亜鉛)、Ti、Cr、Fe、Co及びCu(銅)よりなる群から選択される少なくとも1種の元素である。
組成式(2)中、-0.15<δ<0.15、0.1<x≦0.5、0.6<x+y+z≦1.0、0≦z≦0.1である。
元素Mは、Ti(チタン)、Zr(ジルコニウム)、Nb(ニオブ)、Mo(モリブデン)、W(タングステン)、Al(アルミニウム)、Si(シリコン)、Ga(ガリウム)、Ge(ゲルマニウム)及びSn(錫)よりなる群から選択される少なくとも1種の元素である。例えば、LiNi0.5Mn0.3Co0.2O2、LiNi1/3Mn1/3Co1/3O2等が挙げられる。
上記リチウム遷移金属酸化物の中でも、上記リチウムマンガンニッケル複合酸化物(LNMO)を用いる場合の含有量は、電池容量を向上できる観点から、正極活物質の総量中、60質量%~100質量%であることが好ましく、70質量%~100質量%であることがより好ましく、85質量%~100質量%であることが更に好ましい。
負極は、リチウムチタン複合酸化物を含む負極活物質と、導電材とを含み、必要に応じて結着材及び溶剤を含む負極合材を、集電体の表面に塗布し、必要に応じてプレス等によって負極合材の密度を高めることによって形成する。
負極活物質は、リチウムチタン複合酸化物だけで負極活物質を構成することもできるが、リチウムイオン電池の特性改善等を目的として、炭素材料等のその他の負極活物質となる物質を含んでもよい。
非水電解液は、非水溶媒に電解質が溶解したものである。本実施形態の非水電解液は、含フッ素ホウ酸エステルを含有する。含フッ素ホウ酸エステルは、1種を単独で用いても、2種以上を組み合わせて用いてもよい。
本実施形態のリチウムイオン電池は、正極、負極及び非水電解液に加えて、正極と負極の間に配置されるセパレータを有することが好ましい。
本実施形態のリチウムイオン電池の形状は特に制限されず、円筒型、積層型、コイン型等、種々の形状から選択できる。いずれの形状のリチウムイオン電池も、正極と負極とが積層(必要に応じて正極と負極との間にセパレータを配置する)した構造を有する電極体が非水電解液とともに電池ケースに密閉された構造を有している。なお、正極の集電体及び負極の集電体から外部に通ずる正極端子及び負極端子までの間は、集電用リード等を用いて接続されている。
本実施形態において、負極と正極の容量比(負極容量/正極容量)は、安全性とエネルギー密度の観点から、0.7以上、1.5未満であることが好ましく、0.75~1.2であることがより好ましく、0.90~1.1であることが更に好ましい。
上記のリチウムマンガンニッケル複合酸化物を正極活物質として用いる場合には、正極と負極の容量比(負極容量/正極容量)が0.7以上1未満とすることが好ましい。正極と負極の容量比が0.7以上である場合は、電池容量が向上し、高エネルギー密度が得られる傾向にある。また、正極と負極の容量比が1未満である場合は、正極が高電位になることに起因する含フッ素ホウ酸エステルの分解反応が生じにくくなり、リチウムイオン電池のサイクル特性が良好となる傾向にある。
例えば、正極活物質にはLNMOを、負極活物質にはLTOをそれぞれ用いた場合には、「正極容量」及び「負極容量」は、上記電気化学セルにおいて、電圧範囲をそれぞれ4.95V~3.5V及び2V~1Vとし、定電流充電及び定電流放電時の電流密度を0.1mA/cm2とする条件で上記充放電を行って評価した場合に得られる容量とする。
正極活物質にsp-Mn及びNMCの混合物を、負極活物質にLTOをそれぞれ用いた場合には、「正極容量」及び「負極容量」は、上記電気化学セルにおいて、電圧範囲をそれぞれ3.0V~4.3V及び2V~1Vとし、定電流充電及び定電流放電時の電流密度を0.1mA/cm2とする条件で上記充放電を行って評価した場合に得られる容量とする。
(正極の作製)
正極活物質である層状型リチウム・ニッケル・マンガン・コバルト複合酸化物(NMC)とスピネル型リチウム・マンガン酸化物(sp-Mn)とを質量比3/7(NMC/sp-Mn)で混合して得た正極活物質混合物を90質量部、導電材としてアセチレンブラック(電気化学工業株式会社製)を5質量部、結着材としてポリフッ化ビニリデンを5質量部混合し、適量のN-メチル-2-ピロリドンを添加して混練することで、ペースト状の正極合材を調製した。この正極合材を、正極用の集電体である厚さ20μmのアルミニウム箔の片面に、195g/m2の量で塗布した。その後、乾燥処理を施し、密度が2.55g/cm3になるまでプレス処理により圧密化し、シート状の正極を作製した。作製した正極を幅31mm、長さ46mmの長方形に切断し、図2に示すような位置に正極集電タブを取り付けた。
負極活物質としてチタン酸リチウム(LTO)を91質量部、導電材としてアセチレンブラック(電気化学工業株式会社製)を4質量部、結着材としてポリフッ化ビニリデンを5質量部混合し、適量のN-メチル-2-ピロリドンを添加して混練することで、ペースト状の負極合材を調製した。この負極合材を、負極用の集電体である厚さ10μmの銅箔の片面に、85g/m2の量で塗布した。その後、乾燥処理を施し、密度が1.9g/cm3になるまでプレス処理により圧密化し、シート状の負極を作製した。作製した負極を幅30mm、長さ45mmの長方形に切断し、図2に示すような位置に負極集電タブを取り付けた。
作製した正極と、セパレータとしての厚さ30μm、幅35mm、長さ50mmのポリエチレン微多孔膜と、作製した負極とをこの順で積層して電極体を作製した。
正極及び負極は、正極の正極活物質が塗布された面と、負極の負極活物質が塗布された面とがセパレータを介して対向するように配置した。
エチレンカーボネートとジメチルカーボネートを体積比(エチレンカーボネート:ジメチルカーボネート)が3:7となる割合で混合して非水溶媒とした。次いで、電解質としてLiPF6を非水溶媒に溶解した。電解質濃度は1.0mol/Lとなるように調節した。これに表1に示す添加剤を添加して、非水電解液を調製した。添加剤の量は、表1に示す含有率(非水電解液全体を100質量%とする)となるように調節した。
上記で作製した電極体を、図1に示すような電池容器に収容し、さらに上記で調製した非水電解液を1ml注入した。その後、電極体の正極集電タブと負極集電タブの端部が電池容器の外部に出ている状態で電池容器の開口部を閉じ、リチウムイオン電池を作製した。電池容器としては、ポリエチレンテレフタレート(PET)フィルム/アルミニウム箔/シーラント層(ポリプロピレン等)の積層体であるラミネートフィルムから形成されたものを使用した。なお、リチウムイオン電池は後述するサイクル特性評価と高温での保存特性評価のために各実施例及び比較例につき2個ずつ作製した。
上記のリチウムイオン電池に対し、充放電装置(BATTERY TEST UNIT、株式会社IEM製)を用いて、25℃において電流値0.2C、充電終止電圧3.1Vで定電流充電を行い、次いで充電電圧3.1Vで電流値が0.01Cになるまで定電圧充電を行った。尚、電流値の単位として用いた「C」は「電流値(A)/電池容量(Ah)」を意味する。15分間の休止後、電流値0.2C、放電終止電圧1.5Vで定電流放電を行った。前記の充放電条件で充放電を3回繰り返した。その後、25℃において電流値1C、充電終止電圧3.1Vで定電流充電を行い、次いで充電電圧3.1Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値1C、放電終止電圧1.5Vで定電流放電を行った。このときの放電容量を初期放電容量とした。さらに、上記の操作を500回繰り返した際の放電容量(500サイクル後の放電容量)を測定した。そして、以下の式からサイクル特性(500サイクル後の劣化率)を算出した。表1に測定結果を示す。
サイクル特性(%)=(500サイクル後の放電容量/初期放電容量)×100
上記のリチウムイオン電池に対し、充放電装置(BATTERY TEST UNIT、株式会社IEM製)を用いて、25℃において電流値0.2C、充電終止電圧3.1Vで定電流充電を行い、次いで充電電圧3.1Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値0.2C、放電終止電圧1.5Vで定電流放電を行った。前記の充放電条件で充放電を3回繰り返した。その後、25℃において電流値1C、充電終止電圧3.1Vで定電流充電を行い、次いで充電電圧3.1Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値1C、放電終止電圧1.5Vで定電流放電を行った。このときの放電容量を初期放電容量とした。
次いで、充電終止電圧3.1Vで電流値が0.01Cになるまで定電圧充電を行った。その後、前記リチウムイオン電池を50℃の恒温槽に70日間保存した。保存後のリチウムイオン電池を、25℃の環境で1時間保存した。その後、25℃において電流値0.2C、終止電圧1.5Vの定電流放電を行った。15分間の休止後、25℃において電流値0.2C、充電終止電圧3.1Vで定電流充電を行い、次いで、充電終止電圧3.1Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、25℃で電流値1C、終止電圧1.5Vの定電流放電を行い、放電容量を測定した(70日間保存後の放電容量)。そして、以下の式から保存特性を算出した。表1に測定結果を示す。
高温での保存特性(%)=(70日保存後の放電容量/初期放電容量)×100
正極の作製と非水電解液の調製を下記のようにして行った以外は実施例1と同様にして、リチウムイオン電池を作製した。その後、後述する方法でサイクル特性と高温での保存特性の評価を行った。
正極活物質であるスピネル型リチウムマンガンニッケル複合酸化物を93質量部、導電材としてアセチレンブラック(電気化学工業株式会社製)を5質量部、結着材としてポリアクリロニトリル骨格にアクリル酸及び直鎖エーテル基を付加した共重合体(日立化成株式会社製、商品名:LSR7)を2質量部混合し、適量のN-メチル-2-ピロリドンを添加して混練することで、ペースト状の正極合材を調製した。この正極合材を、正極用の集電体である厚さ20μmのアルミニウム箔の片面に、140g/m2の量で塗布した。その後、乾燥処理を施し、密度が2.3g/cm3になるまでプレス処理により圧密化し、シート状の正極を作製した。作製した正極を幅31mm、長さ46mmの長方形に切断し、図2に示すような位置に正極集電タブを取り付けた。
エチレンカーボネートとジメチルカーボネートを体積比(エチレンカーボネート:ジメチルカーボネート)が1:3となる割合で混合して非水溶媒とした。次いで、電解質としてLiPF6を非水溶媒に溶解した。電解質濃度は1.0mol/Lとなるように調節した。これに表2に示す添加剤を添加して、非水電解液を調製した。添加剤の量は、表2に示す含有率(非水電解液全体を100質量%とする)となるように調節した。
上記のリチウムイオン電池に対し、充放電装置(BATTERY TEST UNIT、株式会社IEM製)を用いて、25℃において電流値0.2C、充電終止電圧3.4Vで定電流充電を行い、次いで充電電圧3.4Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値0.2C、放電終止電圧2Vで定電流放電を行った。前記の充放電条件で充放電を2回繰り返した。その後、25℃において電流値0.2C、充電終止電圧3.8Vで定電流充電を行い、次いで充電電圧3.8Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値0.2C、放電終止電圧2Vで定電流放電を行った。
次いで、50℃において電流値1C、充電終止電圧3.8Vで定電流充電を行い、次いで充電電圧3.8Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値1C、放電終止電圧2Vで定電流放電を行った。このときの放電容量を初期放電容量とした。さらに、上記の操作を250回繰り返した際の放電容量(250サイクル後の放電容量)を測定した。そして、以下の式からサイクル特性(250サイクル後の劣化率)を算出した。表2に測定結果を示す。
サイクル特性(%)=(250サイクル後の放電容量/初期放電容量)×100
上記のリチウムイオン電池に対し、充放電装置(BATTERY TEST UNIT、株式会社IEM製)を用いて、25℃において電流値0.2C、充電終止電圧3.4Vで定電流充電を行い、次いで充電電圧3.4Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値0.2C、放電終止電圧2Vで定電流放電を行った。前記の充放電条件で充放電を2回繰り返した。その後、25℃において電流値0.2C、充電終止電圧3.8Vで定電流充電を行い、次いで充電電圧3.8Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、電流値0.2C、放電終止電圧2Vで定電流放電を行った。このときの放電容量を初期放電容量とした。
次いで、25℃において電流値0.2C、充電終止電圧3.8Vで定電流充電を行い、充電電圧3.8Vで電流値が0.01Cになるまで定電圧充電を行った。その後、前記リチウムイオン電池を50℃の恒温槽に30日間保存した。保存後のリチウムイオン電池を、25℃の環境で1時間保存した。その後、25℃において電流値0.2C、終止電圧2Vの定電流放電を行った。15分間の休止後、25℃において電流値0.2C、充電終止電圧3.8Vで定電流充電を行い、次いで、充電終止電圧3.8Vで電流値が0.01Cになるまで定電圧充電を行った。15分間の休止後、25℃で電流値1C、終止電圧2Vの定電流放電を行い、放電容量(30日間保存後の放電容量)を測定した。そして、以下の式から保存特性を算出した。表2に測定結果を示す。
保存特性(%)=(30日間保存後の放電容量/初期放電容量)×100
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JP2017091715A (ja) * | 2015-11-06 | 2017-05-25 | 株式会社豊田中央研究所 | リチウム電池及びその製造方法 |
WO2017187707A1 (ja) * | 2016-04-28 | 2017-11-02 | 日立化成株式会社 | リチウムイオン二次電池の充電方法、リチウムイオン二次電池システム、及び電力貯蔵装置 |
US20180183103A1 (en) * | 2016-12-27 | 2018-06-28 | Toyota Jidosha Kabushiki Kaisha | Lithium ion secondary battery |
EP3510649B1 (en) | 2016-09-09 | 2020-10-21 | RAI Strategic Holdings, Inc. | Power source for an aerosol delivery device |
WO2023063303A1 (ja) * | 2021-10-14 | 2023-04-20 | 株式会社カネカ | 正極複合活物質、リチウムイオン二次電池、及びリチウムイオン二次電池の製造方法 |
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JP2017091715A (ja) * | 2015-11-06 | 2017-05-25 | 株式会社豊田中央研究所 | リチウム電池及びその製造方法 |
WO2017187707A1 (ja) * | 2016-04-28 | 2017-11-02 | 日立化成株式会社 | リチウムイオン二次電池の充電方法、リチウムイオン二次電池システム、及び電力貯蔵装置 |
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JPWO2017187707A1 (ja) * | 2016-04-28 | 2019-03-07 | 日立化成株式会社 | リチウムイオン二次電池の充電方法、リチウムイオン二次電池システム、及び電力貯蔵装置 |
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