WO2010082261A1 - 非水電解質二次電池用正極の製造方法および非水電解質二次電池 - Google Patents
非水電解質二次電池用正極の製造方法および非水電解質二次電池 Download PDFInfo
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- WO2010082261A1 WO2010082261A1 PCT/JP2009/006230 JP2009006230W WO2010082261A1 WO 2010082261 A1 WO2010082261 A1 WO 2010082261A1 JP 2009006230 W JP2009006230 W JP 2009006230W WO 2010082261 A1 WO2010082261 A1 WO 2010082261A1
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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
- H01M10/052—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
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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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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- 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 invention relates to a non-aqueous electrolyte secondary battery and a positive electrode thereof, and more particularly, to an improvement in a method for removing impurities from a positive electrode active material for a non-aqueous electrolyte secondary battery.
- a lithium ion battery has a high capacity, a high energy density, and can be easily reduced in size and weight. For this reason, it is widely used as a power source for portable electronic devices such as mobile phones, personal digital assistants (PDAs), notebook personal computers, digital cameras, and portable game machines.
- PDAs personal digital assistants
- portable game machines Portable game machines
- application development as an in-vehicle power source such as an electric vehicle and a hybrid vehicle, an uninterruptible power source, and the like is also in progress.
- a lithium ion battery includes a positive electrode including a positive electrode active material such as a lithium-containing composite oxide, a negative electrode including a negative electrode active material capable of inserting and extracting lithium, a separator separating the positive electrode and the negative electrode, and an electrolyte.
- a positive electrode active material such as a lithium-containing composite oxide
- a negative electrode including a negative electrode active material capable of inserting and extracting lithium a separator separating the positive electrode and the negative electrode
- an electrolyte LiCoO 2 is generally used as the lithium-containing composite oxide used as the positive electrode active material.
- LiCoO 2 is generally used as the lithium-containing composite oxide used as the positive electrode active material.
- LiNiO 2 and a lithium nickel-based composite represented by LiMNiCoO 2 described in Patent Document 1 (M represents Al, Mn, Cu, Fe, etc.) Oxides have been proposed.
- lithium-containing composite oxides particularly lithium nickel composite oxides
- by-products such as lithium hydroxide and lithium carbonate during firing.
- Lithium hydroxide reacts with an electrolyte such as ethylene carbonate to generate gas.
- Lithium carbonate is oxidized and decomposed in a high temperature environment to generate gas.
- the battery may expand or the electrode may be deformed as the gas is generated.
- Such expansion of the battery and deformation of the electrode deteriorate cycle characteristics and storage characteristics, and further cause damage to the battery and liquid leakage, thereby reducing the reliability of the battery.
- Patent Documents 2 to 4 disclose techniques for removing lithium hydroxide and lithium carbonate by washing the lithium-containing composite oxide after firing with water and drying.
- the present invention suppresses the mixing of lithium hydroxide and lithium carbonate during the production of a positive electrode for a nonaqueous electrolyte secondary battery, thereby improving the cycle characteristics, storage characteristics, and reliability of the nonaqueous electrolyte secondary battery. For the purpose.
- the manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries of one aspect of the present invention is represented by the general formula (1): Li x M y Me 1-y O 2 + ⁇ (1) (M represents at least one element selected from the group consisting of Ni, Co and Mn, Me represents a metal element different from M, x satisfied 0.98 ⁇ x ⁇ 1.10.
- the nonaqueous electrolyte secondary battery according to another aspect of the present invention is represented by the general formula (1): Li x M y Me 1-y O 2 + ⁇ (1) (M, Me, x, y and ⁇ are the same as above)
- lithium hydroxide and lithium carbonate can be efficiently removed from the positive electrode including the lithium-containing composite oxide represented by the general formula (1). Therefore, according to the present invention, it is possible to highly suppress the mixing of lithium hydroxide and lithium carbonate into the positive electrode and the battery, and to provide a nonaqueous electrolyte secondary battery excellent in cycle characteristics, storage characteristics and reliability. Obtainable.
- the method for producing the positive electrode for the nonaqueous electrolyte secondary battery of the present embodiment is as follows: General formula (1): Li x M y Me 1-y O 2 + ⁇ (1) (M represents at least one element selected from the group consisting of Ni, Co and Mn, Me represents a metal element different from M, x satisfied 0.98 ⁇ x ⁇ 1.10.
- the positive electrode obtained in the positive electrode forming step is represented by the general formula (2): BR 1 R 2 R 3 (2) (Wherein R 1 , R 2 and R 3 each independently represents an aryl group having a fluorine atom or an alkyl group having a fluorine atom), and an aprotic solvent Cleaning with a cleaning liquid containing.
- organic boranes (2) organic boranes represented by the general formula (2)
- organic boranes (2) by washing the positive electrode with a cleaning liquid in which the organic boranes (2) are dissolved or dispersed in an aprotic solvent, lithium hydroxide remaining in the positive electrode or Lithium carbonate can be incorporated into the organic borane (2) as an adduct.
- cleaning liquid from a positive electrode lithium hydroxide and lithium carbonate can be efficiently removed from a positive electrode as an adduct of organic boranes (2).
- the method for manufacturing a positive electrode for a non-aqueous electrolyte secondary battery of the present embodiment mixing of lithium hydroxide and lithium carbonate into the positive electrode and the battery can be highly suppressed, and the non-aqueous electrolyte secondary battery can be suppressed.
- the cycle characteristics, storage characteristics and reliability of the battery can be improved.
- the organic boranes (2) may remain in the positive electrode without being removed by washing of the positive electrode for the nonaqueous electrolyte secondary battery, and may be mixed into the battery.
- the organic boranes (2) mixed in the battery are considered to be reduced at the negative electrode to form a stable film on the surface of the negative electrode, and the film thus formed strongly protects the negative electrode surface. For this reason, a side reaction between the nonaqueous electrolyte and the negative electrode active material, which causes cycle deterioration, can be suppressed, and the cycle characteristics of the battery can be further improved.
- lithium-containing composite oxide (1) is represented by the general formula (3): Li x Ni w M 'z Me ' 1- (w + z) O 2 + ⁇ (3) (M ′ represents at least one element of Co and Mn, Me ′ represents a metal element different from M ′, w satisfies 0.3 ⁇ w ⁇ 1.0, and z satisfies 0 ⁇ z ⁇ 0.7, w + z satisfies 0.9 ⁇ (w + z) ⁇ 1.0, and x and ⁇ are the same as described above) (hereinafter referred to as “lithium nickel composite”) Oxide (3) ”is preferred.
- the positive electrode active material is the lithium nickel composite oxide (3)
- the cycle of the nonaqueous electrolyte secondary battery can be obtained by applying the method for manufacturing the positive electrode for the nonaqueous electrolyte secondary battery according to this embodiment. The effect of improving the characteristics, storage characteristics, reliability, etc. is more remarkably exhibited.
- the organic borane (2) is particularly preferably tris (pentafluorophenyl) borane. In this case, the adduct formed by adding the organic borane (2) to lithium hydroxide or lithium carbonate becomes more stable.
- the content of the organic boranes (2) is sufficient for the non-aqueous electrolyte secondary battery.
- the mass ratio is preferably 50 ppm or more with respect to the nonaqueous electrolyte.
- a positive electrode mixture layer containing a lithium-containing composite oxide (1) is supported on a positive electrode current collector to form a positive electrode (positive electrode forming step).
- the positive electrode obtained through the positive electrode forming step is washed with a washing liquid containing organic boranes (2) and an aprotic solvent (washing step).
- the atomic ratio of Li represented by x is 0.98 to 1.10, preferably 0.98 to 0. .99 or less.
- M examples include Ni, Co, and Mn.
- M may contain these elements independently, and may contain 2 or 3 types in mixture.
- M preferably contains Ni, and a combination of Ni and Co is particularly preferred.
- the atomic ratio of M represented by y is 0.9 or more and 1.0 or less, preferably 0.95 or more and 0.98 or less.
- the element represented by Me is a metal element, specifically, an element belonging to any group from Group 1 to Group 14 of the Periodic Table (IUPAC, 1989), and these metal elements And Ni, Co and Mn are removed. Me may contain these elements independently, and may contain 2 or more types in mixture. Among the above examples, Me is preferably Al, Cr, Fe, Mg or Zn, more preferably Mg or Al, and particularly preferably Al.
- the atomic ratio of Me represented by 1-y is 0 or more and 0.1 or less, and preferably 0.02 or more and 0.05 or less.
- the oxygen defect or oxygen excess represented by ⁇ is usually ⁇ 1% of the stoichiometric composition. That is, ⁇ is preferably ⁇ 0.01 or more and +0.01 or less.
- the lithium-containing composite oxide (1) in the present embodiment is preferably a lithium nickel composite oxide represented by the general formula (3).
- the atomic ratio of Li represented by x and the range of oxygen defects or excess oxygen represented by ⁇ are the same as those of the lithium-containing composite oxide (1). is there.
- the atomic ratio of Ni represented by w is 0.3 or more and 1.0 or less, preferably 0.7 or more and 0.9 or less.
- the effect of adding nickel to the lithium-containing composite oxide that is, the effect of further improving the capacity of the lithium-containing composite oxide cannot be obtained sufficiently.
- M ′ examples include Co or Mn.
- M ′ may contain either Co or Mn alone, or may contain both Co and Mn.
- the atomic ratio of M ′ represented by z is 0 or more and 0.7 or less, preferably 0.05 or more and 0.25 or less.
- Me ′ examples include those exemplified as Me in the lithium-containing composite oxide (1).
- Me ′ may contain the above element alone, or may contain a mixture of two or more.
- Me ′ is preferably Al, Cr, Fe, Mg or Zn, more preferably Mg or Al, and particularly preferably Al.
- the atomic ratio of Me ′ represented by 1-wz is 0 or more and 0.7 or less, preferably 0 or more and 0.1 or less, and more preferably 0.02 or more and 0.05 or less.
- lithium-containing composite oxide (1) examples include, but are not limited to, compounds represented by the following formulas (1-1) to (1-6). LiNi 0.8 Co 0.15 Al 0.05 O 2 (1-1) LiNi 0.5 Co 0.2 Mn 0.3 O 2 (1-2) LiNi 1/3 Co 1/3 Mn 1/3 O 2 (1-3) LiMn 2 O 4 (1-4) LiCoO 2 (1-5) LiCo 0.98 Mg 0.02 O 2 (1-6) Of the above compounds, the formulas (1-1) to (1-3) also belong to the lithium nickel composite oxide (3).
- the lithium-containing composite oxide (1) can be produced by various known methods.
- the lithium-containing composite oxide (1) can be produced by firing a compound containing an element represented by M and Me in the general formula (1) and a lithium compound.
- Examples of the compound containing an element represented by M and Me include hydroxides, oxides, carbonates, and shu containing elements represented by Ni, Co, Mn, Al, Cr, Fe, Mg, Zn, and the like. Examples include acid salts.
- the elements represented by M and Me may be included singly or in combination of two or more.
- these compounds can be obtained as a commercial item, or can be manufactured according to a well-known various method.
- Examples of the lithium compound include lithium hydroxide, lithium carbonate, lithium nitrate, and lithium peroxide.
- lithium hydroxide or lithium carbonate is particularly suitable among the lithium compounds exemplified above.
- these lithium compounds can be obtained as commercial products, or can be produced according to various known methods.
- the firing conditions of the compound containing the element represented by M and Me and the lithium compound are not particularly limited, and known firing conditions can be employed.
- the firing temperature can be set in a range of about 650 to 900 ° C.
- the firing of the compound containing the element represented by M and Me and the lithium compound may be performed by multi-stage firing.
- the atmosphere during firing include an air atmosphere and an oxygen atmosphere. At the time of synthesizing the lithium nickel composite oxide, it is preferable to increase the oxygen partial pressure in the firing atmosphere as the nickel content increases.
- the atmosphere during firing is preferably substantially free of carbon dioxide, and more preferably has a dew point of ⁇ 20 ° C. or lower.
- Examples of the positive electrode current collector for supporting the positive electrode mixture layer include various current collectors used for the positive electrode of a lithium ion battery. Therefore, although not particularly limited, for example, a current collector formed of aluminum, an aluminum alloy, or the like is preferable.
- the thickness of the positive electrode current collector is not particularly limited, but is generally 5 to 100 ⁇ m.
- the positive electrode includes the positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector.
- the positive electrode mixture layer includes a positive electrode active material containing the lithium-containing composite oxide (1), a positive electrode binder, and, if necessary, a positive electrode conductive agent.
- Examples of the positive electrode binder include various known binders such as polyvinylidene fluoride, polytetrafluoroethylene, styrene butadiene rubber, and carboxymethyl cellulose.
- Examples of the conductive agent for the positive electrode include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, and conductive fibers such as carbon fibers and metal fibers.
- the positive electrode mixture layer can be produced by various known methods. For example, first, a positive electrode active material containing a lithium-containing composite oxide (1) is mixed with a conductive agent for positive electrode or a binder for positive electrode, if necessary, and the resulting mixture is dispersed or dissolved in a liquid component. Let Next, the obtained dispersion or solution is applied to the surface of the positive electrode current collector and dried, whereby a positive electrode mixture layer can be produced.
- the liquid component include N-methyl-2-pyrrolidone, acetone, methyl ethyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, tetramethylurea, and trimethyl phosphate.
- the cleaning liquid used in the cleaning process contains organic boranes (2) and an aprotic solvent.
- R 1 , R 2, and R 3 of the organic boranes (2) include an aryl group that may have a fluorine atom or an alkyl group that may have a fluorine atom.
- R 1 , R 2 and R 3 may all be the same substituent or may be different from each other.
- the aryl group that may have a fluorine atom preferably has 6 to 12 carbon atoms.
- the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, cumenyl group, and naphthyl group. Among these, a phenyl group is particularly preferable.
- the alkyl group which may have a fluorine atom preferably has 1 to 4 carbon atoms.
- Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a t-butyl group. Among these, a methyl group, an ethyl group, an n-propyl group, and an isopropyl group are particularly preferable.
- organic boranes (2) when R 1 , R 2 and R 3 are alkyl groups or aryl groups include triphenylborane, ethyldiphenylborane, methyldiphenylborane, diethylphenylborane, tri (p- Tolyl) borane, tri ( ⁇ -naphthyl) borane and the like.
- At least one of R 1 , R 2 and R 3 is preferably a fluoroaryl group or a fluoroalkyl group. That is, the organic borane (2) is preferably a fluorinated organic borane.
- the fluoroaryl group is preferably a fluorophenyl group such as pentafluorophenyl, 2,4,6-trifluorophenyl, 2-fluorophenyl, 4-fluorophenyl.
- the fluoroalkyl group is preferably trifluoromethyl, pentafluoroethyl, hexafluoroisopropyl or the like.
- Preferred embodiments of the fluorinated organic boranes include tris (fluorophenyl) borane represented by general formula (21), bis (fluorophenyl) phenylborane represented by general formula (22), and general formula (23).
- k represents an integer of 1 to 5
- R represents an alkyl group having 1 to 4 carbon atoms
- m represents an integer of 1 to 4
- n represents 0 to 2 m.
- K ′ represents an integer from 0 to 5
- n ′ represents an integer from 0 to 2m + 1
- a represents 1 or 2.
- tris (fluoroaryl) borane of the general formula (21) examples include tris (pentafluorophenyl) borane (TPFPB; [21-1]), tris (2-fluorophenyl) borane [21-2], tris (4- Fluorophenyl) borane [21-3], tris (2,6-difluorophenyl) borane, tris (2,4,6-trifluorophenyl) borane [21-4], bis (2-fluorophenyl) -4- And fluorophenylborane.
- TPFPB penentafluorophenyl borane
- 21-2 examples include tris (2-fluorophenyl) borane [21-2], tris (4- Fluorophenyl) borane [21-3], tris (2,6-difluorophenyl) borane, tris (2,4,6-trifluorophenyl) borane [21-4], bis (2-fluoroph
- Examples of the bis (fluoroaryl) phenylborane of the general formula (22) include bis (2-fluorophenyl) phenylborane [22-1], bis (4-fluorophenyl) phenylborane [22-2], and bis (pentafluoro Phenyl) phenylborane [22-3] and the like.
- diphenyl (fluoroaryl) borane of the general formula (23) examples include diphenyl (2-fluorophenyl) borane [23-1], diphenyl (4-fluorophenyl) borane [23-2], diphenyl (2,6-difluoro Phenyl) borane, diphenyl (2,4,6-trifluorophenyl) borane, diphenyl (pentafluorophenyl) borane [23-3] and the like.
- tris (fluoroalkyl) borane of the general formula (24) examples include tris (trifluoromethyl) borane [24-1], tris (pentafluoroethyl) borane [24-2], and tris (hexafluoropropyl) borane [24. -3], tris (hexafluoroisopropyl) borane [24-4], tris (heptafluoroisopropyl) borane, bis (trifluoromethyl) -fluoromethylborane, bis (trifluoromethyl) -pentafluoroethylborane, etc. It is done.
- Examples of the bis (fluoroalkyl) alkylborane of the general formula (25) include bis (trifluoromethyl) methylborane [25-1], bis (pentafluoroethyl) methylborane [25-2], and pentafluoroethyl- (trifluoromethyl). And methylborane [25-3].
- dialkyl (fluoroalkyl) borane of the general formula (26) examples include dimethyl (trifluoromethyl) borane [26-1], diethyl (trifluoroethyl) borane [26-2], and the like.
- fluorinated organic borane of the general formula (27) examples include dimethyl (pentafluorophenyl) borane [27-1], diethyl (pentafluorophenyl) borane [27-2], and the like.
- TPFPB [21-1] is particularly preferable.
- TPFPB is particularly suitable for use in cleaning lithium-containing composite oxides because it has a very high ability to form a stable adduct by adding to lithium hydroxide or lithium carbonate on the positive electrode surface.
- the organic boranes (2) may be used alone or in combination of two or more from the above examples.
- aprotic solvents examples include N-substituted amides, N-substituted ureas, sulfoxides, sulfolanes, nitriles, carbonates, and cyclic ethers.
- N-substituted amides include N-methylformamide, N-methylacetamide, N-methylpropionamide, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2 -Pyrrolidone, N-cyclohexylpyrrolidone, N-methylcaprolactam and the like.
- N-substituted ureas include N, N, N ′, N′-tetramethylurea, N, N′-dimethylimidazolidinone, N, N′-dimethylethyleneurea, N, N′-dimethylpropyleneurea, etc. Is mentioned.
- Examples of the sulfoxides include dimethyl sulfoxide and tetramethylene sulfoxide.
- sulfolanes include sulfolane and dimethyl sulfolane.
- nitriles include acetonitrile and propiononitrile.
- carbonate esters include propylene carbonate and ethylene carbonate.
- Examples of the cyclic ethers include dioxane (1,4-, 1,2-, or 1,3-dioxane).
- the aprotic solvent is particularly preferably propylene carbonate among the above examples.
- the concentration of the organic boranes (2) in the cleaning liquid is preferably 0.01 to 0.2 mol / L, more preferably 0.05 as the molar amount of the organic boranes (2) with respect to 1 L of the cleaning liquid. ⁇ 0.1 mol / L.
- concentration of the organic boranes (2) is below the above range, the effect of removing lithium hydroxide and lithium carbonate from the positive electrode may be insufficient.
- an amount of the organic borane (2) exceeding the above concentration is added to the cleaning solution, the effect of removing lithium hydroxide and lithium carbonate from the positive electrode is not observed. Rather, the organic boranes (2) are precipitated in the cleaning liquid and the cost is increased.
- the positive electrode for example, a positive electrode provided with a positive electrode current collector and a positive electrode mixture layer containing a lithium-containing composite oxide (1) is immersed in a cleaning liquid, and the cleaning liquid is stirred as necessary, for 0.5 to 2 It is cleaned by leaving it for a period of time.
- the temperature of the cleaning liquid is preferably 10 to 45 ° C, more preferably 20 to 30 ° C.
- the positive electrode is subjected to a second cleaning for rinsing the cleaning liquid as necessary after the cleaning with the cleaning liquid.
- a cleaning liquid in the second cleaning an aprotic solvent not containing the organic borane (2) is used.
- an aprotic solvent used as a non-aqueous solvent for the non-aqueous electrolyte is used as a washing liquid for the second washing.
- the organic boranes (2) remain without being removed from the positive electrode, and even when mixed in the battery, there is a low possibility that the physical properties of the nonaqueous electrolyte secondary battery will be reduced. Rather, the organic borane (2) is reduced at the negative electrode to form a film on the surface of the negative electrode, thereby improving the cycle characteristics of the battery. For this reason, the organic boranes (2) in the cleaning liquid used for the positive electrode cleaning process may be positively left in the positive electrode.
- the amount of organic boranes (2) remaining on the positive electrode after washing is a predetermined ratio in the nonaqueous electrolyte of the nonaqueous electrolyte secondary battery. It is adjusted so that it may be contained.
- the content ratio of the organic borane (2) in the nonaqueous electrolyte will be described later.
- the nonaqueous electrolyte secondary battery of this embodiment contains a lithium-containing composite oxide obtained by using the manufacturing method of this embodiment as a positive electrode active material.
- FIG. 1 is a partially cutaway perspective view of a nonaqueous electrolyte secondary battery according to the present embodiment.
- the nonaqueous electrolyte secondary battery includes an electrode group 1 formed by winding a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode.
- the electrode group 1 is housed in a battery case 2 together with a non-aqueous electrolyte (not shown).
- a positive electrode lead 3 connected to the positive electrode is provided at one end in the winding axis direction (longitudinal direction) of the electrode group 1, and a negative electrode lead connected to the negative electrode at the other end. 4 is provided.
- the positive electrode lead 3 is connected to a sealing plate 5 that seals the battery case 2 on the opening end side of the battery case 2.
- the sealing plate 5 is also used as a positive electrode side external connection terminal.
- the negative electrode lead 4 is connected to the negative electrode side external connection terminal 6 on the opening end side of the battery case 2.
- an insulating plate 7 that separates the electrode group 1 from the sealing plate 5 and separates the positive electrode lead 3 and the negative electrode lead 4 is disposed.
- the negative electrode side external connection terminal 6 is arrange
- the sealing plate 5 further includes a nonaqueous electrolyte injection port, a cap 9 for sealing the injection port, and a battery safety valve 10.
- the positive electrode includes a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector.
- As the positive electrode one that has been cleaned by the cleaning method of the present embodiment is used.
- the positive electrode current collector and the positive electrode mixture layer are as described above.
- the negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector.
- the negative electrode current collector various current collectors used for the negative electrode of a lithium ion battery can be used without limitation. Specific examples include a metal foil made of a metal such as stainless steel, nickel, copper, and titanium, a thin film made of carbon, a conductive resin, and the like. These negative electrode current collectors may be further subjected to surface treatment with carbon, nickel, titanium or the like. The thickness of the negative electrode current collector is generally 5 to 100 ⁇ m.
- the negative electrode mixture layer includes a negative electrode active material capable of occluding and releasing lithium ions, and, if necessary, a negative electrode conductive agent and a negative electrode binder.
- the negative electrode active material include various negative electrode active materials used in nonaqueous electrolyte secondary batteries. Therefore, it is not particularly limited, and examples thereof include carbon materials such as graphite and amorphous carbon, silicon or tin alone, alloys containing silicon or tin, solid solutions, or composite materials thereof.
- Examples of the negative electrode conductive agent include those exemplified as the positive electrode conductive agent.
- Examples of the negative electrode binder include those exemplified as the positive electrode binder.
- the separator examples include a microporous thin film, a woven fabric or a non-woven fabric, and a material having a high ion permeability and a predetermined mechanical strength and insulation.
- a polyolefin microporous film such as polypropylene and polyethylene having excellent durability and a shutdown function is preferable from the viewpoint of improving the reliability of the nonaqueous electrolyte secondary battery.
- the thickness of the separator is generally 10 ⁇ m or more and 300 ⁇ m or less, preferably 10 ⁇ m or more and 40 ⁇ m or less.
- the nonaqueous electrolyte includes, for example, a lithium salt, a nonaqueous solvent, and organic boranes (2).
- Non-aqueous solvents include aprotic organic solvents such as carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, ethers such as tetrahydrofuran and 1,3-dioxolane, and carboxylic acid esters such as ⁇ -butyrolactone. It is done. These non-aqueous solvents may be used alone or in combination of two or more.
- Examples of the lithium salt include various lithium salts such as LiPF 6 .
- Organic boranes (2) are contained in the non-aqueous electrolyte by producing the positive electrode by the production method of the present embodiment.
- the positive electrode is cleaned with a cleaning liquid containing organic boranes (2) and an aprotic solvent. After this washing step, the organic borane (2) remains in the positive electrode.
- the organic borane (2) remaining in the positive electrode is dissolved or dispersed in the nonaqueous electrolyte when the nonaqueous electrolyte secondary battery is assembled.
- the organic boranes (2) form a film on the surface of the negative electrode, thereby improving the cycle characteristics of the nonaqueous electrolyte secondary battery. Therefore, in order to sufficiently exhibit the effect of improving the cycle characteristics, the amount of the organic boranes (2) derived from the washing step and contained in the non-aqueous electrolyte is 1500 ppm or less, preferably 50 to 500 ppm. When the amount of the organic boranes (2) in the nonaqueous electrolyte is less than 50 ppm, the coating film may not be formed on the surface of the negative electrode.
- the nonaqueous electrolyte secondary battery includes a negative electrode, a positive electrode, a separator, and a nonaqueous electrolyte, together with a positive electrode lead 3, a negative electrode lead 4, an insulating plate 7, and the like, in a battery case 2. It is obtained by air-sealing with a plate (external connection terminal for positive electrode) 5, an external connection terminal for negative electrode 6 and an insulating packing 8. Specifically, first, a positive electrode, a negative electrode, and a separator that separates both electrodes are wound to obtain a spiral electrode group 1.
- the electrode group 1 is accommodated in the battery case 4 so that the positive electrode lead 2 attached to the positive electrode and the negative electrode lead 3 attached to the negative electrode respectively extend toward the opening side of the battery case 4.
- the opening of the battery case 4 is sealed with the sealing plate 5.
- the positive electrode lead 2 is brought into contact with the inside surface of the battery case 4 of the sealing plate 5, and the negative electrode lead 3 is connected to the negative electrode external connection terminal 6 disposed through the gasket 7 in the through hole on the sealing plate 5.
- Contact is made from the inside of the case 4.
- a nonaqueous electrolyte is injected from a liquid injection port provided on the sealing plate 5, and then the liquid injection port is sealed with a sealing material 8.
- non-aqueous electrolyte secondary battery an example of application to a wound-type square non-aqueous electrolyte secondary battery is shown, but the shape of the non-aqueous electrolyte secondary battery is not limited to this.
- Various shapes such as a coin type, a cylindrical type, a sheet type, a button type, a flat type, and a laminated type can be appropriately selected depending on the use of the nonaqueous electrolyte secondary battery.
- Example 1 Fabrication of positive electrode 1 kg of lithium-containing composite oxide (LiNi 0.80 Co 0.15 Al 0.05 O 2 ) powder and N-methyl-2-pyropidone (NMP) solution of polyvinylidene fluoride (manufactured by Kureha Chemical Co., Ltd., # 1320, solid content concentration 12 wt%) 0.5 kg and acetylene black 40 g together with an appropriate amount of NMP are put into a double-arm kneader and stirred at 30 ° C. for 30 minutes to obtain a positive electrode mixture paste. Prepared. The obtained positive electrode mixture paste was applied to both surfaces of a 20 ⁇ m thick aluminum foil as a positive electrode current collector and dried at 120 ° C.
- NMP N-methyl-2-pyropidone
- the positive electrode thus obtained was cut and formed into a size suitable for being accommodated in a rectangular battery case having a height of 50 mm, a width of 34 mm, and a thickness of 5 mm.
- a positive electrode lead was attached to a part of the positive electrode.
- the positive electrode plate was rolled up and put into a 50 mL beaker, and about 50 mL of the above-described cleaning solution (TPFPB / PC electrolyte solution) was further poured. And it was left to stand for 1 hour in the state (room temperature 25 degreeC) in which the positive electrode plate was immersed in cleaning liquid. After standing, the positive electrode plate was taken out from the cleaning solution. Next, the washed positive electrode plate was rolled into a 50 mL beaker, and about 50 mL of propylene carbonate (PC) was poured. And in the state which the positive electrode plate was immersed in PC, it was left for 5 minutes, stirring a little, and PC was removed after that.
- PC propylene carbonate
- TPFPB was rinsed off from the positive electrode plate. Furthermore, the PC solvent was removed by vacuum-drying the positive electrode plate subjected to the rinsing treatment in an environment of a temperature of 85 ° C. and an atmospheric pressure of 1 mmHg for 10 minutes. Thus, cleaning of the positive electrode was completed.
- nonaqueous electrolyte Ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 3 to prepare a nonaqueous solvent.
- a non-aqueous electrolyte non-aqueous electrolyte having a LiPF 6 concentration of 1.4 mol / m 3 was obtained.
- vinylene carbonate as an additive was added to the nonaqueous electrolyte for the purpose of increasing the charge / discharge efficiency of the battery.
- the content ratio of vinylene carbonate was adjusted so as to be 5% by weight of the whole non-aqueous solvent.
- Examples 2 to 21 A nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the cleaning liquid used for the cleaning treatment of the positive electrode plate was different.
- the cleaning liquid an electrolytic solution in which organic boranes were dissolved in 100 mL of propylene carbonate (PC) and stirred was used.
- PC propylene carbonate
- Example 2 Tris (2-fluorophenyl) borane [21-2]
- Example 3 Tris (4-fluorophenyl) borane [21-3]
- Example 4 Tris (2,4,6-trifluorophenyl) borane [21-4]
- Example 5 Bis (2-fluorophenyl) phenylborane [22-1]
- Example 6 Bis (4-fluorophenyl) phenylborane [22-2]
- Example 7 Bis (pentafluorophenyl) phenylborane [22-3]
- Example 8 Diphenyl (2-fluorophenyl) borane [23-1]
- Example 9 Diphenyl (4-fluorophenyl) borane [23-2]
- Example 10 Diphenyl (pentafluorophenyl) borane [23-3]
- Example 11 Tris (trifluoromethyl) borane [24-1]
- Example 12 Tris (pentafluoroeth
- Comparative Example 1 A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode plate was not washed. Comparative Example 2 A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the cleaning liquid used for the cleaning treatment of the positive electrode plate was 100 mL of propylene carbonate.
- the thickness of the central portion of the maximum plane (vertical 50 mm, horizontal 34 mm) of the rectangular battery is measured between the state after charging at the third cycle and the state after charging at the 501st cycle, and the difference in the battery thickness From this, the amount of battery swelling [mm] after the charge / discharge cycle at 45 ° C. was determined.
- the measurement results are shown in the “Battery after cycle” column of Table 1.
- the maximum current was 630 mA
- the upper limit voltage was 4.2 V
- constant current / constant voltage charging was performed for 2 hours 30 minutes.
- the rest time after charging was 10 minutes.
- a constant current discharge was performed with a discharge current of 900 mA and a discharge end voltage of 2.5V.
- the rest time after discharge was 10 minutes.
- the content of boron in the extracted measurement sample is quantified by ICP emission spectroscopic analysis (VISTA-RL manufactured by VARIAN), and based on the quantification result, the remaining organic boranes in the non-aqueous electrolyte solution The amount [ppm] was calculated.
- the calculation results are shown in the column “Organic boranes in electrolyte” in Table 1.
- the charge / discharge conditions were the same as those used for evaluating the capacity maintenance rate.
- the cleaning liquid of Comparative Example 2 does not contain organic boranes (2).
- Organic boranes column of Table 1, the compound numbers assigned to the organic boranes (2) are shown.
- the capacity of the nonaqueous electrolyte secondary battery The maintenance rate was improved and the amount of battery swelling after the cycle could be reduced.
- the organic boranes (2) remained in the nonaqueous electrolytic solution at a ratio of 50 ppm or more after the battery was assembled.
- the present invention is suitable for application to non-aqueous electrolyte secondary batteries such as lithium ion batteries and polymer electrolyte secondary batteries. Further, the present invention is not limited to non-aqueous electrolyte secondary batteries for small devices, and is also effective for large-sized and large-capacity secondary batteries such as electric vehicle power supplies and power storage power supplies.
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Abstract
Description
LixMyMe1-yO2+δ (1)
(MはNi、CoおよびMnからなる群より選ばれる少なくとも1の元素を示し、MeはMとは異なる金属元素を示し、xは0.98≦x≦1.10を満たし、yは0.9≦y≦1.0を満たし、δは酸素欠陥分または酸素過剰分を示す)
で表されるリチウム含有複合酸化物を含む正極合剤層を正極集電体に支持させて正極を形成する正極形成工程と、上記正極を、有機ボラン類と、非プロトン性溶媒とを含む洗浄液で洗浄する洗浄工程と、を含み、上記有機ボラン類が、下記一般式(2):
BR1R2R3 (2)
(R1、R2およびR3は互いに独立して、フッ素原子を有することのあるアリール基またはフッ素原子を有することのあるアルキル基を示す)
で表されることを特徴とする。
LixMyMe1-yO2+δ (1)
(M、Me、x、yおよびδは上記と同じである)
で表されるリチウム含有複合酸化物を含む正極と、負極と、上記正極および負極の間に介在されるセパレータと、非水電解質と、を備え、上記非水電解質が、一般式(2):
BR1R2R3 (2)
(R1、R2およびR3は上記と同じである)
で表される有機ボラン類を含むことを特徴とする。
一般式(1):
LixMyMe1-yO2+δ (1)
(MはNi、CoおよびMnからなる群より選ばれる少なくとも1の元素を示し、MeはMとは異なる金属元素を示し、xは0.98≦x≦1.10を満たし、yは0.9≦y≦1.0を満たし、δは酸素欠陥分または酸素過剰分を示す)で表されるリチウム含有複合酸化物を含む正極合剤層を正極集電体に支持させて正極を形成する正極形成工程と、
正極形成工程で得られた正極を、一般式(2):
BR1R2R3 (2)
(R1、R2およびR3は互いに独立して、フッ素原子を有することのあるアリール基またはフッ素原子を有することのあるアルキル基を示す)で表される有機ボラン類と、非プロトン性溶媒とを含む洗浄液で洗浄する洗浄工程と、を含む。
LixNiwM’zMe’1-(w+z)O2+δ (3)
(M’はCoおよびMnの少なくともいずれか1の元素を示し、Me’はM’とは異なる金属元素を示し、wは0.3≦w≦1.0を満たし、zは0≦z≦0.7を満たし、w+zは0.9≦(w+z)≦1.0を満たし、xおよびδは上記と同じである)で表されるリチウムニッケル系複合酸化物(以下、「リチウムニッケル系複合酸化物(3)」という)であることが好適である。
本実施形態の非水電解質二次電池用正極の製造方法では、まず、リチウム含有複合酸化物(1)を含む正極合剤層を正極集電体に支持させて正極を形成する(正極形成工程)。さらに、上記正極形成工程を経ることにより得られた正極を、有機ボラン類(2)と、非プロトン性溶媒とを含む洗浄液で洗浄する(洗浄工程)。
正極形成工程に用いられるリチウム含有複合酸化物(1)において、xで表されるLiの原子割合は0.98以上1.10以下であり、好ましくは0.98以上0.99以下である。
yで表されるMの原子割合は0.9以上1.0以下であり、好ましくは0.95以上0.98以下である。
1-yで表されるMeの原子割合は0以上0.1以下であり、好ましくは、0.02以上0.05以下である。
リチウムニッケル系複合酸化物(3)において、xで表されるLiの原子割合およびδで表される酸素欠陥分または酸素過剰分の範囲は、リチウム含有複合酸化物(1)の場合と同じである。
zで表されるM’の原子割合は0以上0.7以下であり、好ましくは0.05以上0.25以下である。
1-w-zで表されるMe’の原子割合は0以上0.7以下であり、好ましくは0以上0.1以下であり、さらに好ましくは0.02以上0.05以下である。
LiNi0.8Co0.15Al0.05O2 …(1-1)
LiNi0.5Co0.2Mn0.3O2 …(1-2)
LiNi1/3Co1/3Mn1/3O2 …(1-3)
LiMn2O4 …(1-4)
LiCoO2 …(1-5)
LiCo0.98Mg0.02O2 …(1-6)
上記化合物のうち式(1-1)~(1-3)は、リチウムニッケル系複合酸化物(3)にも属している。
リチウム化合物としては、例えば、水酸化リチウム、炭酸リチウム、硝酸リチウム、過酸化リチウムなどが挙げられる。リチウムニッケル系複合酸化物(3)を製造する場合には、上記例示のリチウム化合物のなかでも特に、水酸化リチウムまたは炭酸リチウムが好適である。また、これらリチウム化合物は、市販品として得ることができ、または、公知の各種の方法に従って製造することができる。
焼成時の雰囲気としては、大気雰囲気、酸素雰囲気などが挙げられる。リチウムニッケル系複合酸化物の合成時には、ニッケルの含有割合が多いほど、焼成時の雰囲気の酸素分圧を高くすることが好ましい。また、焼成時の雰囲気は、二酸化炭素を実質的に含まないことが好ましく、露点が-20℃以下であることがさらに好ましい。
正極用導電剤としては、例えば、天然黒鉛、人造黒鉛などのグラファイト類、アセチレンブラックなどのカーボンブラック類、炭素繊維、金属繊維などの導電性繊維類などが挙げられる。
液状成分としては、例えば、N-メチル-2-ピロリドン、アセトン、メチルエチルケトン、テトラヒドロフラン、ジメチルホルムアミド、ジメチルアセタミド、テトラメチル尿素、リン酸トリメチルなどが挙げられる。
洗浄工程に用いられる洗浄液は、有機ボラン類(2)と、非プロトン性溶媒とを含んでいる。
フッ素原子を有することのあるアルキル基の炭素数は1~4が好ましい。炭素数1~4のアルキル基としては、メチル基、エチル基、n-プロピル基、イソプロピル基、n-ブチル基、t-ブチル基などが挙げられる。これらの中でもメチル基、エチル基、n-プロピル基およびイソプロピル基が特に好ましい。
一般式(23)のジフェニル(フルオロアリール)ボランとしては、ジフェニル(2-フルオロフェニル)ボラン[23-1]、ジフェニル(4-フルオロフェニル)ボラン[23-2]、ジフェニル(2,6-ジフルオロフェニル)ボラン、ジフェニル(2,4,6-トリフルオロフェニル)ボラン、ジフェニル(ペンタフルオロフェニル)ボラン[23-3]などが挙げられる。
一般式(25)のビス(フルオロアルキル)アルキルボランとしては、ビス(トリフルオロメチル)メチルボラン[25-1]、ビス(ペンタフルオロエチル)メチルボラン[25-2]、ペンタフルオロエチル-(トリフルオロメチル)メチルボラン[25-3]などが挙げられる。
一般式(27)のフッ化有機ボランとしては、ジメチル(ペンタフルオロフェニル)ボラン[27-1]、ジエチル(ペンタフルオロフェニル)ボラン[27-2]などが挙げられる。
有機ボラン類(2)は、上記例示のなかから、1種を単独で使用してもよく、2種以上を混合して使用してもよい。
本実施形態の非水電解質二次電池は、本実施形態の製造方法を用いて得られたリチウム含有複合酸化物を正極活物質として含有する。
電池ケース2内には、電極群1と封口板5とを隔離し、かつ、正極リード3と負極リード4とを隔離する絶縁板7が配置されている。また、負極側外部接続端子6は、正極側外部接続端子としての封口板5に設けられた貫通孔内に配置されており、封口板5と負極側外部接続端子6との間は、絶縁パッキン8によって隔離されている。封口板5は、さらに非水電解質の注液口およびその注液口を封鎖するキャップ9と、電池の安全弁10とを備えている。
負極集電体としては、リチウムイオン電池の負極に用いられている各種の集電体を限定なく用いることができる。具体的には、ステンレス鋼、ニッケル、銅、チタンなどの金属からなる金属箔、炭素、導電性樹脂などからなる薄膜、などが挙げられる。これら負極集電体は、さらにカーボン、ニッケル、チタンなどによる表面処理が施されていてもよい。負極集電体の厚みは、一般に5~100μmである。
負極活物質としては、非水電解質二次電池に用いられている各種の負極活物質が挙げられる。それゆえ、特に限定されないが、例えば、グラファイト、非晶質カーボンなどの炭素材料、ケイ素またはスズの単体、ケイ素またはスズを含む合金、固溶体またはこれらの複合材料、などが挙げられる。
負極用導電剤としては、正極用導電剤として例示したものが挙げられる。また、負極用結着剤としては、正極用結着剤として例示したものが挙げられる。
非水溶媒としては、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、エチルメチルカーボネートなどの炭酸エステル、テトラヒドロフラン、1,3-ジオキソランなどのエーテル、γ-ブチロラクトンなどのカルボン酸エステルといった非プロトン性有機溶媒が挙げられる。これら非水溶媒は、1種を単独で用いてもよく、2種以上を組み合わせて用いてもよい。
リチウム塩としては、LiPF6などの各種リチウム塩が挙げられる。
そこで、サイクル特性の向上の効果を十分に発揮させるため、上記洗浄工程に由来し、非水電解質中に含有される有機ボラン類(2)の量は、1500ppm以下であり、好ましくは、50~500ppmである。非水電解質中での有機ボラン類(2)の量が50ppmを下回るときは、負極の表面に上記被膜が形成されない場合がある。
(1)正極の作製
リチウム含有複合酸化物(LiNi0.80Co0.15Al0.05O2)の粉末1kgと、ポリフッ化ビニリデンのN-メチル-2-ピロピドン(NMP)溶液(呉羽化学(株)製、#1320、固形分濃度12重量%)0.5kgと、アセチレンブラック40gとを、適量のNMPとともに双腕式練合機に投入して、30℃で30分間攪拌することにより、正極合剤ペーストを調製した。得られた正極合剤ペーストを、正極集電体としての厚さ20μmのアルミニウム箔の両面に塗布して120℃で15分間乾燥させることにより、正極合剤層を作製した。さらに、正極集電体と正極合剤層とを、厚みの合計が160μmとなるようにロールプレスで加圧することにより、正極を得た。こうして得られた正極を切断し、高さ50mm、幅34mmおよび厚さ5mmの角型の電池ケースへ収容するのに適したサイズに成形した。この正極の一部に正極リードを取り付けた。
洗浄液の調製
プロピレンカーボネート(PC)100mLに、有機ボラン類(2)として、トリス(ペンタフルオロフェニル)ボラン[TPFPB;21-1]を5.1g加え、攪拌して溶解させることにより、洗浄液(TPFPB/PC電解液)を調整した。この洗浄液中でのTPFPBの濃度は、0.1mol/Lであった。
50mLのビーカーに正極板を丸めて投入し、さらに、上記洗浄液(TPFPB/PC電解液)約50mLを注いだ。そして、正極板が洗浄液中に浸漬した状態(室温25℃)で1時間放置した。放置後、正極板を洗浄液から取り出した。次に、洗浄処理が施された正極板を50mLビーカーに丸めて投入し、プロピレンカーボネート(PC)を約50mL注いだ。そして、正極板がPC中に浸漬した状態で、少し攪拌しながら5分間放置し、その後、PCを除去した。この操作を3回繰り返すことにより、正極板からTPFPBを濯ぎ落とした。さらに、濯ぎ処理が施された正極板を、温度85℃、気圧1mmHgの環境下で10分間真空乾燥することにより、PC溶媒を除去した。こうして、正極の洗浄を完了した。
人造黒鉛3kgと、変性スチレン-ブタジエンゴムの分散液(日本ゼオン(株)製、BM-400B、固形分40重量%)200gと、カルボキシメチルセルロース50gとを、適量の水とともに双腕式練合機に投入し、攪拌することにより、負極合剤ペーストを調製した。得られた負極合剤ペーストを、負極集電体としての厚さ12μmの銅箔の両面に塗布して120℃で乾燥させた。さらに、負極集電体と負極合剤層とを、厚みの合計が160μmとなるようにロールプレスで圧延した。こうして得られた負極を切断し、上記電池ケースへ収容するのに適したサイズに成形した。この負極の一部に負極リードを取り付けた。
エチレンカーボネートとジメチルカーボネートとを体積比1:3で混合して、非水溶媒を調製した。この非水溶媒にLiPF6を加えて溶解させることにより、LiPF6の濃度が1.4mol/m3の非水電解質(非水電解液)を得た。さらに、電池の充放電効率を高める目的で、非水電解質に添加剤としてのビニレンカーボネートを加えた。ビニレンカーボネートの含有割合は、非水溶媒全体の5重量%となるように調整した。
上述した、正極リードを備える正極と、負極リードを備える負極と、電解質とを用いて、図1に示す角型の非水電解質二次電池を製造した。セパレータとしては、ポリエチレンとポリプロピレンとの複合フィルム(セルガード(株)製、品番「2300」、厚さ25μm)を使用した。この非水電解質二次電池は、高さ50mm、幅34mmおよび厚さ5mmの角型の電池であって、設計容量は900mAhとした。
正極板の洗浄処理に用いた洗浄液が異なること以外は、実施例1と同様にして、非水電解質二次電池を製造した。洗浄液には、プロピレンカーボネート(PC)100mLに、有機ボラン類を溶解させ、攪拌した電解液を使用した。各実施例で用いた有機ボラン類およびその化合物番号は、下記のとおりである。
実施例3:トリス(4-フルオロフェニル)ボラン[21-3]
実施例4:トリス(2,4,6-トリフルオロフェニル)ボラン[21-4]
実施例5:ビス(2-フルオロフェニル)フェニルボラン[22-1]
実施例6:ビス(4-フルオロフェニル)フェニルボラン[22-2]
実施例7:ビス(ペンタフルオロフェニル)フェニルボラン[22-3]
実施例8:ジフェニル(2-フルオロフェニル)ボラン[23-1]
実施例9:ジフェニル(4-フルオロフェニル)ボラン[23-2]
実施例10:ジフェニル(ペンタフルオロフェニル)ボラン[23-3]
実施例11:トリス(トリフルオロメチル)ボラン[24-1]
実施例12:トリス(ペンタフルオロエチル)ボラン[24-2]
実施例13:トリス(ヘキサフルオロプロピル)ボラン[24-3]
実施例14:トリス(ヘキサフルオロイソプロピル)ボラン[24-4]
実施例15:ビス(トリフルオロメチル)メチルボラン[25-1]
実施例16:ビス(ペンタフルオロエチル)メチルボラン[25-2]
実施例17:ペンタフルオロエチル-(トリフルオロメチル)メチルボラン[25-3]
実施例18:ジメチル(トリフルオロメチル)ボラン[26-1]
実施例19:ジエチル(トリフルオロエチル)ボラン[26-2]
実施例20:ジメチル(ペンタフルオロフェニル)ボラン[27-1]
実施例21:ジエチル(ペンタフルオロフェニル)ボラン[27-2]
正極板の洗浄処理を行わなかったこと以外は、実施例1と同様にして、非水電解質二次電池を製造した。
比較例2
正極板の洗浄処理に用いた洗浄液がプロピレンカーボネート100mLであること以外は、実施例1と同様にして、非水電解質二次電池を製造した。
(i)容量維持率と電池膨れ評価
実施例1~21および比較例1で得られた角型の非水電解質二次電池に対し、それぞれ電池の充放電サイクルを45℃で繰り返した。そして、3サイクル目の放電容量を100%とみなし、500サイクルを経過した時の放電容量を百分率で表し、これを容量維持率[%]とした。算出結果を表1の「容量維持率」欄に示す。
また、3サイクル目の充電後における状態と、501サイクル目の充電後における状態とで、角型電池の最大平面(縦50mm、横34mm)における中央部の厚みを測定し、その電池厚みの差から、45℃での充放電サイクル経過後における電池膨れの量[mm]を求めた。この測定結果を表1の「サイクル後電池膨れ」欄に示す。
実施例1~21および比較例1で得られた角型の非水電解質二次電池に対し、それぞれ電池の充放電サイクルを25℃で3サイクル繰り返した。その後、放電状態にて、角型電池の封口板側端部にニッパーで切り込みを入れて、遠心分離することにより、電池ケース内部から非水電解質(非水電解液)を抽出した。こうして抽出された非水電解質を測定試料とした。
次いで、抽出された測定試料中のホウ素の含有量を、ICP発光分光分析法(VARIAN製のVISTA-RL)により定量し、定量結果に基づいて、非水電解液中での有機ボラン類の残存量[ppm]を算出した。この算出結果を表1の「電解液中の有機ボラン類」欄に示す。なお、充放電条件は、容量維持率の評価時と同じ条件とした。
表1の「有機ボラン類」欄には、有機ボラン類(2)に付した化合物番号を示した。
表1より明らかなように、正極を、有機ボラン類(2)と、非プロトン性溶媒であるPCとを含む洗浄液で洗浄した実施例1~21によれば、非水電解質二次電池の容量維持率を向上させ、かつ、サイクル後における電池の膨れ量を低減させることができた。また、これら実施例1~21では、電池の組立て後において、非水電解液に、50ppm以上の割合で有機ボラン類(2)が残存していた。
Claims (6)
- 一般式(1):
LixMyMe1-yO2+δ (1)
(MはNi、CoおよびMnからなる群より選ばれる少なくとも1の元素を示し、MeはMとは異なる金属元素を示し、xは0.98≦x≦1.10を満たし、yは0.9≦y≦1.0を満たし、δは酸素欠陥分または酸素過剰分を示す)
で表されるリチウム含有複合酸化物を含む正極合剤層を正極集電体に支持させて正極を形成する正極形成工程と、
前記正極を、有機ボラン類と、非プロトン性溶媒とを含む洗浄液で洗浄する洗浄工程と、を含み、
前記有機ボラン類が、一般式(2):
BR1R2R3 (2)
(R1、R2およびR3は互いに独立して、フッ素原子を有することのあるアリール基またはフッ素原子を有することのあるアルキル基を示す)
で表される非水電解質二次電池用正極の製造方法。 - 前記リチウム含有複合酸化物が、一般式(3):
LixNiwM’zMe’1-(w+z)O2+δ (3)
(M’はCoおよびMnの少なくともいずれか1の元素を示し、Me’はM’とは異なる金属元素を示し、xは0.98≦x≦1.10を満たし、wは0.3≦w≦1.0を満たし、zは0≦z≦0.7を満たし、w+zは0.9≦(w+z)≦1.0を満たし、δは酸素欠陥分または酸素過剰分を示す)
で表されるリチウムニッケル系複合酸化物である請求項1に記載の非水電解質二次電池用正極の製造方法。 - 前記一般式(2)におけるR1、R2およびR3の少なくとも1つは、フッ素原子を有する請求項1に記載の非水電解質二次電池用正極の製造方法。
- 前記有機ボラン類が、トリス(ペンタフルオロフェニル)ボランである請求項1に記載の非水電解質二次電池用正極の製造方法。
- 一般式(1):
LixMyMe1-yO2+δ (1)
(MはNi、CoおよびMnからなる群より選ばれる少なくとも1の元素を示し、MeはMとは異なる金属元素を示し、xは0.98≦x≦1.10を満たし、yは0.9≦y≦1.0を満たし、δは酸素欠陥分または酸素過剰分を示す)
で表されるリチウム含有複合酸化物を含む正極と、負極と、前記正極および負極の間に介在されるセパレータと、非水電解質と、を備え、
前記非水電解質が、一般式(2):
BR1R2R3 (2)
(R1、R2およびR3は互いに独立して、フッ素原子を有することのあるアリール基またはフッ素原子を有することのあるアルキル基を示す)
で表される有機ボラン類を含む非水電解質二次電池。 - 前記非水電解質が、重量割合で50ppm以上の前記有機ボラン類を含有する請求項5に記載の非水電解質二次電池。
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CN2009801240086A CN102077394A (zh) | 2009-01-16 | 2009-11-19 | 非水电解质二次电池用正极的制造方法以及非水电解质二次电池 |
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Cited By (4)
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JP2012094459A (ja) * | 2010-10-29 | 2012-05-17 | Hitachi Ltd | リチウムイオン二次電池 |
CN102479951A (zh) * | 2010-11-19 | 2012-05-30 | 日本化学工业株式会社 | 锂二次电池用正极活性物质及其制造方法、及锂二次电池 |
WO2015001871A1 (ja) * | 2013-07-02 | 2015-01-08 | トヨタ自動車株式会社 | 非水電解液二次電池及びその製造方法 |
JP2021503692A (ja) * | 2017-11-17 | 2021-02-12 | マックスウェル テクノロジーズ インコーポレイテッド | エネルギー貯蔵装置のための非水性溶媒電解質組成物 |
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US11430991B2 (en) * | 2018-03-28 | 2022-08-30 | Sumitomo Metal Mining Co., Ltd. | Lithium-nickel composite oxide and method of producing lithium-nickel composite oxide |
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WO2023121838A1 (en) | 2021-11-30 | 2023-06-29 | Quantumscape Battery, Inc. | Catholytes for a solid-state battery |
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