WO2011021644A1 - 非水系電解液二次電池用セパレータ及び非水系電解液二次電池 - Google Patents
非水系電解液二次電池用セパレータ及び非水系電解液二次電池 Download PDFInfo
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- H01M10/052—Li-accumulators
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- 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
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- 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
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/423—Polyamide resins
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
- H01M50/434—Ceramics
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/463—Separators, membranes or diaphragms characterised by their shape
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
- H01M50/509—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing characterised by the type of connection, e.g. mixed connections
- H01M50/51—Connection only in series
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- 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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- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
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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
- lithium secondary batteries have been used in a wide range of fields such as mobile phones, notebook personal computers, and power tools, as electric products have become lighter and smaller in recent years.
- EV electric vehicles
- HEV hybrid electric vehicles
- a module battery is usually constructed by connecting several to 10 single cells in series, and a plurality of module batteries are combined to form an overall battery system. Is building. Since battery input / output control is normally performed in module battery units, a voltage of several tens of volts is applied to the module battery. However, if there are defective cells in the module battery, From the extreme overcharged state in which a voltage of several tens of volts of the entire module battery is applied to one single cell, a situation from short circuit to explosion is assumed. The most effective way to prevent this situation is to individually monitor and control a single cell, but it is not a practical method due to the complexity and cost of control, and it is resistant to overcharged conditions. There is a strong demand for such a material system.
- Patent Document 1 As a countermeasure against the overcharged state, as shown in Patent Document 1, a method of adding an overcharge inhibitor into the electrolytic solution has been conventionally used.
- a compound having an oxidation potential equal to or higher than the upper limit voltage value of the battery is added to the electrolyte as an overcharge inhibitor, and when the overcharged state is reached, the compound is oxidized and polymerized to increase the active material surface.
- the overcharge current is suppressed by forming a resistance film to stop the progress of overcharge.
- many of the compounds used as overcharge inhibitors are electrochemically and chemically active for that purpose, and when added in large amounts in the electrolyte, they can react even under normal battery usage conditions.
- Patent Documents 2 to 5 and the like disclose techniques for improving cycle characteristics by imparting conductivity to a separator.
- Patent Document 8 discloses a technique for preventing winding slippage by applying an acrylic pressure-sensitive adhesive material in which graphite or the like is dispersed to a separator so as to improve adhesion with an electrode.
- Patent Document 9 discloses a technique for improving safety by applying metal particles to a separator and adsorbing a gas generated by overcharging.
- Patent Document 2 an antistatic agent is mixed or applied or sprayed on the separator surface to make the separator antistatic and prevent the adhesion of conductive fine particles such as active materials in the battery manufacturing process due to static electricity.
- conductive fine particles such as active materials in the battery manufacturing process due to static electricity.
- Patent Document 3 discloses a technique for improving the irreversible characteristics by forming an alkali metal powder layer made of Li, Na, or K on the separator surface.
- Patent Document 4 discloses a separator formed by stretching a resin composition containing a thermoplastic resin and a conductive filler.
- Patent Document 5 discloses a multilayer porous membrane having an electrically conductive layer containing conductive particles and an electrically insulating layer containing non-conductive particles as one method for increasing the thermal conductivity in the thickness direction of the separator. It is disclosed.
- the separator surface has conductivity, and the conductive layer on the separator surface acts as a positive electrode conductor (current collector) when the conductivity performance of the positive electrode conductor (current collector) deteriorates.
- a separator having a function of extending the cycle life of the battery.
- Patent Document 7 the active material is applied onto the conductive film provided on the separator surface and the separator and the electrode are integrated, so that the electrode is thinned and the opposing area between the electrodes is widened, thereby reducing the current density.
- a technique for improving the cycle life by suppressing the consumption rate of the negative electrode is disclosed.
- Patent Document 8 discloses a technique for preventing winding slippage by applying graphite or an acrylic pressure-sensitive adhesive in which graphite is dispersed on the separator surface to improve the adhesion between the separator and the electrode.
- Patent Document 9 oxygen is generated in an overcharged state by using a separator whose surface is opposite to the positive electrode and coated with Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, Mo, or the like.
- a technique for suppressing ignition and explosion by absorbing gas is disclosed.
- Japanese Unexamined Patent Publication No. 2003-297423 Japanese Patent Laid-Open No. 10-154499 Japanese Unexamined Patent Publication No. 2005-317551 Japanese Patent No. 4145087 Japanese Unexamined Patent Publication No. 2006-269358 Japanese Unexamined Patent Publication No. 2008-84866 Japanese Laid-Open Patent Publication No. 5-21069 Japanese Laid-Open Patent Publication No. 11-213980 Japanese Unexamined Patent Publication No. 11-16656
- the antistatic agent generally performs antistatic using ions released by adsorbing moisture in the air, and basically non-aqueous electrolysis that eliminates moisture. In a liquid secondary battery, the effect cannot be exhibited. That is, even if the separator obtained by this method is used for a non-aqueous electrolyte secondary battery, it does not function as a separator having conductivity on the surface.
- an alkali metal is a highly reactive metal, and easily reacts with oxygen and moisture in the air. Therefore, such a metal powder layer is formed on the separator surface. Forming has a big problem on safety. Even in Patent Document 3, a problem regarding safety is pointed out, and as a means for solving the problem, an alkali metal polymer coating or the like is mentioned, but if the polymer coating is performed, the conductivity of the metal is inhibited, A conductive separator cannot be formed on the surface.
- the technique disclosed in Patent Document 4 is that the separator is non-conductive because the distance between the conductive fillers in the separator is sufficiently large under the conditions in which a battery is normally used. The heat shrinks and the conductive fillers come into contact with each other to form a conductive path (shutdown effect), and the remaining capacity of the battery is quickly discharged to make it safe. That is, the separator of Patent Document 4 does not have conductivity as a whole as well as the surface when a normal battery is used.
- Patent Document 5 in order to increase the thermal conductivity of the separator, it is necessary for these particles to form percolation with each other. For this reason, Patent Document 5 describes the necessity of adding a large amount of filler, In general, a polymer film containing a large amount of a filler tends to be fragile due to reduced flexibility. On the other hand, as is well known, the active material of a non-aqueous electrolyte secondary battery, in particular, the negative electrode active material expands in volume due to occlusion of lithium, and thus a large pressure is applied to the separator.
- Patent Document 7 when a conductive film is formed on one surface of a separator and a paste mainly composed of an active material is applied thereon as a current collector, the paste solvent is applied to the separator. Since it permeates, the binder resin dissolved in the solvent also permeates the separator and closes the micropores of the separator, thereby degrading the battery performance. Further, when a non-woven fabric or a woven fabric is used as the substrate instead of the microporous film, there is a risk that the active material penetrates the substrate and penetrates in the thickness direction.
- Non-Patent Document 1 a normal electrode is applied and dried and then compressed by a roll press to make the thickness uniform, smooth the surface, and prevent peeling from the current collector.
- it is difficult to perform pressing because there is a risk of deformation of the separator, crushing of fine holes, or breakage of the separator by an active material. There is a problem that the yield is lowered as described in.
- the lithium transition metal composite oxide used as the positive electrode active material has high electrical resistance.
- Patent Document 9 in order to sufficiently absorb the oxygen gas generated from the positive electrode, it is necessary to coat with a metal in the same amount as the positive electrode active material, and the metal oxidation reaction generally generates heat. Since this is a reaction, there is a problem in that there is a high risk of heat shrinkage or meltdown of the separator. In Patent Document 9, this problem is avoided by taking a relatively low charging speed of 1.5 to 2.5 C. However, it cannot sufficiently cope with a higher discharging speed. . In the technology disclosed in Patent Document 9, when the safety is taken into consideration, the thickness of the metal coating layer is important as described above, but there is no description about these, and the safety improvement of the battery is insufficient.
- the present inventors have found that the overcharge resistance can be greatly improved by providing a specific conductive layer on the separator, and the present invention has been completed.
- the gist of the present invention is as follows. ⁇ 1> A separator used for a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium, a separator, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte, wherein the separator is A non-aqueous electrolyte having a conductive layer, the apparent volume resistivity of the conductive layer being 1 ⁇ 10 ⁇ 4 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, and the thickness of the conductive layer being less than 5 ⁇ m Secondary battery separator.
- a separator used for a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium, a separator, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte, wherein the separator is A non-aqueous electrolyte solution having a conductive layer, a volume resistivity of the conductive layer of 1 ⁇ 10 ⁇ 6 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, and a thickness of the conductive layer of less than 5 ⁇ m; Secondary battery separator.
- ⁇ 4> The separator for a non-aqueous electrolyte secondary battery according to any one of ⁇ 1> to ⁇ 3>, wherein the separator has a meltdown temperature of 170 ° C. or higher.
- ⁇ 5> The separator for a non-aqueous electrolyte secondary battery according to any one of ⁇ 1> to ⁇ 4>, wherein the puncture strength of the separator is 250 g or more and 800 g or less.
- ⁇ 6> The separator for a non-aqueous electrolyte secondary battery according to any one of ⁇ 1> to ⁇ 5>, wherein the conductive layer is provided on at least one surface of the separator.
- ⁇ 7> The separator for a non-aqueous electrolyte secondary battery according to any one of ⁇ 1> to ⁇ 6>, wherein the conductive layer contains at least one of a metal element and a carbonaceous material.
- the metal element is at least one selected from the group consisting of aluminum, molybdenum, copper, and titanium.
- the carbonaceous material is at least one selected from the group consisting of graphite, carbon black, and amorphous carbon fine particles.
- a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium, a separator, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte, wherein the separator is the above ⁇ 1>
- the nonaqueous electrolyte secondary battery which is a separator for nonaqueous electrolyte secondary batteries as described in any one of thru
- R 1 and R 2 are each an alkyl group having 1 or 2 carbon atoms, and at least one of R 1 and R 2 has one or more fluorine atoms
- Next battery. ⁇ 19> The non-aqueous electrolyte secondary battery according to any one of ⁇ 16> to ⁇ 18>, wherein the content of the fluorinated carbonate is 20% or less as a volume ratio in the electrolyte.
- Electrolyte secondary battery is the group consisting of lithium tetrafluoroborate, bis (fluorosulfonyl) imide, and lithium bis (trifluorosulfonyl) imide lithium.
- the separator for a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes referred to as “the separator of the present invention”) is A separator used for a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium, a separator, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte, (1)
- the separator has a conductive layer, the apparent volume resistivity of the conductive layer is 1 ⁇ 10 ⁇ 4 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, and the thickness of the conductive layer is less than 5 ⁇ m It is characterized by being, Or (2) the separator has a conductive layer, the volume resistivity of the conductive layer is 1 ⁇ 10 ⁇ 6 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, and the thickness of the conductive layer is less
- the separator of the present invention has, for example, a separator used in a normal non-aqueous electrolyte secondary battery, a porous film or a nonwoven fabric obtained by a conventionally known method as a base material, and is electrically conductive on at least one surface of the base material. It can be manufactured by forming a layer or sandwiching a conductive layer between base materials, and there are no particular limitations on the constituent materials and manufacturing method of the base materials.
- a method for obtaining a separator main body (conventional separator) or a porous film as a base material of the separator of the present invention include the following methods.
- a low molecular weight material that is compatible with the polyolefin resin and extractable in a later step is added to the polyolefin resin to perform melt kneading and sheeting, and the low molecular weight material is extracted after stretching or before stretching.
- a stretching method in which a low-temperature stretch and a high-temperature stretch are added to a highly elastic sheet prepared by forming a crystalline resin into a sheet with a high draft ratio.
- the thermoplastic resin is inorganic or organic.
- Interfacial exfoliation method in which filler is added to melt knead and sheet, and the interface between resin and filler is exfoliated by stretching to make it porous.
- ⁇ crystal nucleating agent additive to polypropylene resin, melt knead and sheet
- the ⁇ crystal nucleating agent method which stretches the sheet on which the ⁇ crystal is formed and makes it porous using the crystal transition
- the base material of the separator for a non-aqueous electrolyte secondary battery of the present invention is a conventional three-layer separator (polypropylene / polyethylene / polypropylene) used in Examples described later, or a single layer by an extraction method.
- a separator polyethylene etc. are mentioned, it is not limited to these at all.
- conductive material The material constituting the conductive layer according to the present invention (hereinafter sometimes referred to as “conductive material”) is not particularly limited as long as it has conductivity, and examples thereof include metals and carbonaceous materials. Can be used.
- the criteria for selecting a suitable metal material are different between the conductive layer facing the positive electrode and the conductive layer facing the negative electrode when the non-aqueous electrolyte secondary battery is assembled. That is, when the conductive layer faces the positive electrode, the conductive layer is exposed to a high potential, so gold, platinum, or an alloy thereof having a high oxidation potential is preferably used.
- the valve metal which produces a passive film by anodization can also be used suitably. Examples of the valve metal include aluminum, tungsten, molybdenum, titanium, and tantalum. Further, stainless steel having a chromium oxide film can also be suitably used.
- a metal material that does not form an alloy with lithium.
- examples of such a metal include copper, nickel, titanium, iron, molybdenum, chromium, and the like, and any of them can be suitably used.
- the conductive material is a carbonaceous material
- amorphous carbon fine particles such as graphite, carbon black and needle coke, or nanocarbon materials such as carbon nanotubes Any of these can be suitably used.
- the carbonaceous material is not particularly limited by its production method, and any natural graphite or artificial graphite can be suitably used as long as it is graphite.
- ketjen black, channel black, furnace black are black carbon powders obtained by incomplete combustion of natural gas, acetylene, anthracene, naphthalene, coal tar, aromatic petroleum fractions, etc.
- Acetylene black, thermal black, lamp black and the like are all preferably used.
- the conductive material may be used alone or in combination of two or more.
- the solvent, binder, etc. used for the preparation of the slurry can be arbitrarily selected according to the conductive material and the resin constituting the base material, but as an example on the surface of the polyolefin base material
- the binder one or more water-soluble compounds such as polyvinyl alcohol and sodium carboxymethyl cellulose can be used.
- water water is preferably used. Therefore, in this case, the conductive layer is formed by applying a slurry in which carbon black is dispersed in an aqueous polyvinyl alcohol solution or an aqueous solution of sodium carboxymethyl cellulose to the separator surface and drying.
- the solid content concentration of the conductive material in the slurry is usually 1 to 50% by weight, preferably 3 to 40% by weight, more preferably 5 to 30% by weight. If the solid content concentration of the conductive material is not less than the above lower limit, the viscosity of the slurry will not be too low and uneven coating will not easily occur. If the solid content concentration of the conductive material is less than or equal to the above upper limit, the slurry can be applied easily without the viscosity of the slurry being too high.
- the binder content such as polyvinyl alcohol in the slurry is usually 1 to 50 parts by weight, preferably 3 to 35 parts by weight, more preferably 5 to 20 parts by weight with respect to 100 parts by weight of the conductive material.
- the amount of the binder used is too small, the binding force between the conductive materials becomes low, the mechanical strength of the formed conductive layer is insufficient, and the conductive layer may be destroyed due to expansion and contraction of the active material due to charge and discharge.
- the amount of binder used is too large, the binder will form a film on the surface of the conductive material or the base separator, impairing the air permeability of the separator, or the conductivity of the formed conductive layer will be insufficient. .
- the thickness of the conductive layer is less than 5 ⁇ m, and the lower limit is preferably 0.001 ⁇ m or more, more preferably 0.003 ⁇ m or more, and further preferably 0.005 ⁇ m or more.
- the thickness of the conductive layer is not less than the above lower limit value, the effect of improving the overcharge resistance is more sufficiently exhibited.
- the thickness of the conductive layer is 5 ⁇ m or more, the airflow resistance of the conductive layer portion, and consequently the ion permeation resistance becomes too large, and the battery performance such as output decreases.
- the thickness of the formed conductive layer and the conductive material used may be different or the same on both surfaces of the separator.
- a metal suitable for the negative electrode facing surface side may be used for one surface of the separator, and a metal suitable for the positive electrode facing surface side may be used for the other surface of the separator.
- the thickness of the conductive layer is measured by the method described in the Examples section below.
- the separator of the present invention is (1) Apparent volume resistivity is 1 ⁇ 10 ⁇ 4 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, or (2) Volume resistivity is 1 ⁇ 10 ⁇ 6 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, Or (3) a conductive layer having a surface electrical resistance of 1 ⁇ 10 ⁇ 2 ⁇ to 1 ⁇ 10 9 ⁇ .
- the apparent volume resistivity of the conductive layer is 1 ⁇ 10 ⁇ 4 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, preferably 1 ⁇ 10 ⁇ 4 to 1 ⁇ 10 5 ⁇ ⁇ cm, more preferably 1 ⁇ 10 ⁇ 4 to 1 ⁇ 10 4 ⁇ ⁇ cm.
- the volume resistivity of the conductive layer is 1 ⁇ 10 ⁇ 6 ⁇ ⁇ cm to 1 ⁇ 10 6 ⁇ ⁇ cm, preferably 1 ⁇ 10 ⁇ 3 to 1 ⁇ 10 3 ⁇ ⁇ cm, more preferably 1 ⁇ 10 ⁇ 2 to 1 ⁇ 10 2 ⁇ ⁇ cm.
- the volume resistivity is a value specific to the material forming the conductive layer.
- the volume resistivity inherent in the conductive material is affected by the influence of the voids and the contact resistance between the conductive materials.
- the apparent volume resistivity has a higher value. If the apparent volume resistivity or volume resistivity of the conductive layer exceeds the above upper limit, details of the reason are unclear, but it is difficult to obtain a sufficient overcharge resistance improving effect according to the present invention.
- the ventilation resistance due to the conductive layer is increased, and the characteristics of the separator as a lithium ion movement path may be impaired.
- the conductive layer may function as a current collector, and the separator may be thermally deteriorated due to Joule heat generation.
- the surface electrical resistance of the conductive layer is 1 ⁇ 10 ⁇ 2 to 1 ⁇ 10 9 ⁇ , preferably 1 ⁇ 10 ⁇ 1 to 1 ⁇ 10 8 ⁇ , more preferably 1 to 1 ⁇ 10 7 ⁇ . is there.
- the surface resistivity of the conductive layer is preferably 4 ⁇ 10 ⁇ 2 to 1 ⁇ 10 9 ⁇ / ⁇ , more preferably 1 ⁇ 10 ⁇ 1 to 1 ⁇ 10 8 ⁇ / ⁇ , and still more preferably 1 to 1 ⁇ 10 7 ⁇ / ⁇ . If the surface electrical resistance of the conductive layer exceeds the above upper limit, the details of the reason are unclear, but it is difficult to obtain a sufficient overcharge resistance improving effect according to the present invention.
- the ventilation resistance by the conductive layer is increased, and the characteristics of the separator as a lithium ion transfer path may be impaired. If the surface electrical resistance is less than the lower limit, the conductive layer may function as a current collector, and the separator may be thermally deteriorated due to Joule heat generation.
- the alkali metal is a highly reactive metal and can easily be combined with oxygen and moisture in the air.
- the conductive layer according to the present invention is not reactive like an alkali metal, and is in a normal environment. It can be handled and has excellent handleability.
- the separator containing a conductive filler in the thermoplastic resin described in Patent Document 4 has no conductivity when the battery is used normally. Since the conductive layer according to the present invention is present on the surface or intermediate layer of the separator, there is no short circuit between the positive and negative electrodes during normal battery use, and sufficient conductivity can be imparted as necessary.
- the separator described in Patent Document 5 is brittle in strength and has a high possibility of causing an internal short circuit in an overcharged state.
- the conductive layer according to the present invention is formed on the surface or intermediate layer of the separator. Because it is less than 5 ⁇ m, there is little or no effect on the strength of the separator, it can sufficiently withstand the expansion of the active material during overcharge, and problems such as internal short circuit It does not occur.
- the separator described in Patent Document 5 contains a large amount of filler having high thermal conductivity, the thermal conductivity in the thickness direction is 0%. Although it is ⁇ 5 W / ( ⁇ ⁇ m0.2 ⁇ K) or more, the thermal conductivity in the thickness direction of the separator of the present application is about 0.2W / (m ⁇ K).
- the increase rate of the Gurley air permeability when the conductive layer is formed on the porous substrate is preferably within 10%.
- the Gurley air permeability was measured using a B-type Gurley densometer (manufactured by Toyo Seiki Seisakusho) according to JISP8117.
- the present inventors have found that the overcharge resistance is further improved by setting the meltdown temperature of the separator of the present invention to 170 ° C. or higher. That is, since the separator has a conductive layer and the meltdown temperature is 170 ° C. or higher, defective cells are mixed in the module battery, and a voltage of several tens of volts of the entire module battery is applied to one or a few single cells.
- a highly safe non-aqueous electrolyte secondary battery that can further prevent a short circuit and an explosion even when an overcharged state is applied.
- Non-Patent Document 3 the non-aqueous electrolyte solution undergoes thermal decomposition and reaction with the positive electrode at 150 to 160 ° C. It is thought that the by-product of this product has some influence.
- carbonates such as calcium carbonate, magnesium carbonate and barium carbonate
- sulfates such as calcium sulfate, magnesium sulfate and barium sulfate
- chlorides such as sodium chloride, calcium chloride and magnesium chloride
- aluminum oxide In addition to oxides such as calcium oxide, magnesium oxide, zinc oxide, titanium oxide, and silica, silicates such as talc, clay, and mica can be used.
- oxides such as aluminum oxide, magnesium oxide, and titanium oxide, and sulfates such as magnesium sulfate and barium sulfate are preferable, and aluminum oxide, magnesium oxide, titanium oxide, and barium sulfate are particularly preferable.
- the heat-resistant organic filler includes polymethylpentene, polyamide, polyimide, polyamideimide, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, polysulfone, polyphenylene sulfide, polyether ketone, polyether sulfone.
- the particle size of the filler is 0.001 ⁇ m or more, it is possible to form a heat-resistant layer having a uniform structure in which the filler is less likely to aggregate during formation of the heat-resistant layer. If the particle size of the filler is 3 ⁇ m or less, the heat-resistant layer can be thinned, and the heat-resistant layer can be prevented from being reduced in air permeability and, in turn, ion permeability. When the aspect ratio of the filler is 10 or less, the heat-resistant layer can be densely configured.
- a non-aqueous electrolyte secondary battery of the present invention includes a positive electrode and a negative electrode capable of inserting and extracting lithium, a separator, and a non-aqueous electrolyte comprising a non-aqueous electrolyte obtained by dissolving an electrolyte in a non-aqueous solvent.
- the separator is the separator for a non-aqueous electrolyte secondary battery of the present invention.
- Non-aqueous electrolyte solution ⁇ Non-aqueous solvent>
- any known solvent can be used as the solvent for the non-aqueous electrolyte secondary battery.
- a lithium salt is usually used as the electrolyte that is the solute of the nonaqueous electrolytic solution.
- Any lithium salt can be used, for example, an inorganic lithium salt such as LiClO 4 , LiPF 6 , LiBF 4 ; LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 F 5 ) 2 , LiPF 4 (CF 3 SO 2 ) 2 , LiPF 4 (C 2 F 5 SO 2 ) 2 , LiBF 2 (CF 3 ) 2 , LiBF 2 (C 2 F 5 ) 2 , LiBF 2 (CF 3 SO 2 ) 2 , LiBF Fluorine-containing organic lithium salts such as 2 (C 2 F 5 SO 2 ) 2 are included.
- LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , and LiN (C 2 F 5 SO 2 ) 2 are preferable, and LiPF 6 and LiBF 4 are particularly preferable.
- LiPF 6 and LiBF 4 are particularly preferable.
- 1 type may be used independently and 2 or more types may be used together.
- the non-aqueous electrolyte solution according to the present invention includes other useful components as required in addition to the non-aqueous solvent and the electrolyte, such as conventionally known overcharge inhibitors, dehydrating agents, deoxidizing agents, capacity maintenance after high-temperature storage.
- Various additives such as an auxiliary agent for improving characteristics and cycle characteristics may be contained.
- Nitrogen-containing compounds hydrocarbon compounds such as heptane, octane, cycloheptane and the like.
- concentration in the non-aqueous electrolyte is usually 0.1 to 5% by weight.
- the present inventors have further improved overcharge resistance by using a non-aqueous electrolyte secondary battery in combination with an electrolyte that satisfies the following requirement (1) or (2). I found out that I can do it.
- Patent Document 15 Japanese Patent Application Laid-Open No. 2004-241339 (Patent Document 15)
- the high potential here is 4.8 V, which is used for EV or HEV.
- the battery module for EV or HEV there is a demand for a new technology that reacts under a voltage of several tens of volts or more to suppress an overcharge reaction, but a technology that satisfies this is still available. Not found.
- the conductive layer provided on the surface of the separator is in an overcharged state. It is related to the fact that the presence of fluorinated carbonate significantly promotes or densifies the passivation of the current collector surface in an overcharged state, while causing some influence on the electric field inside the battery and making it difficult to cause a short circuit. It is guessed. In particular, since the formation reaction of the passive film is accelerated under high voltage and high temperature environment, it is presumed that the increase in voltage and temperature due to overcharging has a great influence.
- dimethyl carbonate derivatives include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoro) methyl carbonate and the like. Can be mentioned.
- ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2, Examples include 2-trifluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.
- a typical example of the fluorinated cyclic carbonate is a derivative of a cyclic carbonate having an alkylene group having 2 to 6 carbon atoms.
- one or two hydrogen atoms constituting ethylene carbonate are fluorine atoms.
- / or an ethylene carbonate derivative substituted with a fluorinated alkyl group is usually 1 to 4, and the number of fluorine atoms constituting the fluorinated cyclic carbonate is usually 1 or more and 8 or less, preferably 3 or less.
- fluorinated unsaturated cyclic carbonate examples include vinylene carbonate derivatives, ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, and the like.
- Examples of the ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4,4-difluoro-4 -Vinylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4-fluoro-4-phenyl Examples thereof include ethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, and the like.
- the molecular weight of the fluorinated cyclic carbonate is not particularly limited, and is preferably 50 or more, more preferably 80 or more, and preferably 250 or less, more preferably 150 or less. When the molecular weight is 250 or less, the solubility of the fluorinated cyclic carbonate in the nonaqueous electrolytic solution is good, and the effects of the present invention are easily exhibited. Moreover, there is no restriction
- the use amount of the fluorinated carbonate is, as a volume ratio in the electrolytic solution, the upper limit is preferably 20% or less, more preferably 15% or less, and the lower limit is preferably 1% or more, more preferably 5%. That's it. Within the above range, the electrical conductivity is not lowered, the battery performance of the large battery is not hindered, and the effect on overcharge is improved.
- a non-aqueous electrolyte solution obtained by dissolving an electrolyte in a non-aqueous solvent is further used as a sub-electrolyte, in addition to lithium borate salts, lithium phosphate salts, lithium fluorophosphate salts, lithium carboxylate salts, lithium sulfonate salts, Containing at least one compound selected from the group consisting of lithium imide salts, lithium oxalatoborate salts, lithium oxalatophosphate salts and lithium methide salts, the concentration of all sub-electrolytes in the electrolyte is 0.01 mol / liter or more, When it is 0.3 mol / liter or less
- Patent Document 16 discloses a technique of adding an oxygen-containing lithium salt as a sub-electrolyte.
- an oxygen-containing lithium salt is added to a non-aqueous electrolyte, a side reaction proceeds during battery use, and the irreversible capacity increases. Therefore, it is difficult to obtain satisfactory battery characteristics even though it is effective for protecting the current collector. Further, the proper combination and concentration of the sub-electrolytes have not been sufficiently studied, and it has been insufficient as a countermeasure against overcharging of batteries for automobiles having high capacity and high output.
- Patent Document 17 discloses a technique of adding lithium tetrafluoroborate to a nonaqueous electrolytic solution
- Patent Document 18 discloses an electrolytic solution in which a compound having BF 4 ⁇ as an anion is added.
- the present inventors have found that the overcharge resistance can be further greatly improved by combining the separator of the present invention with an electrolyte containing a specific amount of a specific subelectrolyte. I found it. As a result, even if an overcharged state occurs in which defective cells are mixed in the module battery and a voltage of several tens of volts of the entire module battery is applied to one or a few single cells, the short circuit and the explosion are further increased. A highly safe non-aqueous electrolyte secondary battery that can be prevented can be provided.
- the conductive layer provided on the surface of the separator It has some influence on the electric field inside the battery in the overcharged state, making it difficult to cause a short circuit, and at the same time, the presence of the secondary electrolyte significantly promotes or densifies the passivation of the current collector surface in the overcharged state. Presumed to be. In particular, since the formation reaction of the passive film is accelerated under high voltage and high temperature environment, it is presumed that the increase in voltage and temperature due to overcharging has a great influence.
- the conductive layer provided on the separator surface is thought to have some influence on the electric field inside the battery, it has some effect on the generation of passive film, and as a result, it produces a synergistic effect. It is guessed that. Since the formation of the passive film increases the internal resistance of the battery and suppresses the charging current, it is presumed that the safety of the battery in an overcharged state is enhanced.
- lithium salt is usually used.
- the lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples include the following.
- Lithium borate salts such as lithium tetrafluoroborate; Lithium fluorophosphates such as lithium fluorophosphate and lithium difluorophosphate; Lithium carboxylates such as lithium formate, lithium acetate, lithium monofluoroacetate, lithium difluoroacetate, lithium trifluoroacetate; Lithium sulfonates such as lithium fluorosulfonate, lithium methanesulfonate, lithium monofluoromethanesulfonate, lithium difluoromethanesulfonate, lithium trifluoromethanesulfonate; LiN (FCO 2 ) 2 , LiN (FCO) (FSO 2 ), LiN (FSO 2 ) 2 , LiN (FSO 2 ) (CF 3 SO 2 ), LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium
- lithium fluorophosphates lithium borates, and lithium imide salts are preferable in that they do not deteriorate battery performance.
- Specific compounds include lithium tetrafluoroborate, lithium perchlorate, bis (trifluoromethanesulfonyl) imide lithium, bis (pentafluoroethanesulfonyl) imide lithium, lithium trifluoromethanesulfonate, and bis (fluorosulfonyl) imide lithium.
- LiBF4 lithium tetrafluoroborate
- LiFSI bis (fluorosulfonyl) imide lithium
- LiTFSI bis (trifluorosulfonyl) imide lithium
- the total concentration of all sub-electrolytes in the electrolytic solution is preferably 0.01 mol / liter or more, more preferably 0.015 mol / lit or more as a lower limit.
- the upper limit is preferably 0.3 mol / liter or less, more preferably 0.2 mol / liter or less. If the total concentration of all sub-electrolytes is in the above range, the electrical conductivity is not lowered and the battery performance of the large battery is not hindered, and the effect on overcharge is improved.
- the positive electrode used for the non-aqueous electrolyte secondary battery of the present invention is usually one in which an active material layer containing a positive electrode active material and a binder is formed on a current collector.
- the positive electrode active material examples include materials capable of inserting and extracting lithium, such as lithium transition metal composite oxide materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide, and preferably contain a NiMnCo alloy. It is preferable. These may be used individually by 1 type, or may use multiple types together.
- the binder is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode manufacture and other materials used during battery use.
- Specific examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, EPDM (ethylene-propylene-diene terpolymer), SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), Examples thereof include SBS (styrene-butadiene-styrene elastomer), fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, and nitrocellulose. These may be used individually by 1 type, or may use multiple types together.
- the lower limit is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and the upper limit is usually 80% by weight or less, preferably 60% by weight or less, more preferably 40% by weight or less, and still more preferably 10% by weight or less. If the ratio of the binder is not less than the above lower limit, the active material can be sufficiently retained, the mechanical strength of the positive electrode can be obtained, and the battery performance such as cycle characteristics can be improved. There is no risk of lowering electrical conductivity.
- the positive electrode active material layer usually contains a conductive agent to improve conductivity.
- the conductive agent include carbonaceous materials such as graphite fine particles such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon fine particles such as needle coke. These may be used individually by 1 type, or may use multiple types together.
- the ratio of the conductive agent in the positive electrode active material layer is such that the lower limit is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and the upper limit is usually 50% by weight or less. , Preferably 30% by weight or less, more preferably 15% by weight or less. If the ratio of the conductive agent is equal to or higher than the lower limit, the conductivity is sufficient, and if it is equal to or lower than the upper limit, the battery capacity does not decrease.
- the positive electrode active material layer may contain other additives for a normal active material layer such as a thickener.
- the thickener is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode manufacture and other materials used during battery use. Specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type, or may use multiple types together.
- the thickness of the positive electrode current collector is arbitrary, it is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and usually 100 ⁇ m or less, preferably 50 ⁇ m or less, more preferably 20 ⁇ m or less. If the thickness of the positive electrode current collector is not less than the above lower limit, the strength required for the current collector can be obtained. Further, if the thickness of the current collector is not more than the above upper limit value, the volume ratio of the active material put in the battery is not lowered, and the necessary battery capacity can be obtained.
- the surface current resistance of the positive electrode current collector is 6 ⁇ 10 ⁇ 3 to 6 ⁇ 10 ⁇ 5 ⁇ with respect to the thickness of 1 ⁇ m to 100 ⁇ m, although it varies depending on the thickness.
- the positive electrode can be formed by applying a slurry obtained by slurrying the above-described positive electrode active material, a binder, a conductive agent, and other additives added as necessary with a solvent onto a current collector, and drying the positive electrode active material. .
- an organic solvent that dissolves the binder is usually used.
- N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like are used, but not limited thereto. These may be used individually by 1 type, or may use multiple types together.
- a dispersing agent, a thickener, etc. can be added to water, and an active material can also be slurried with latex, such as SBR.
- the thickness of the positive electrode active material layer thus formed is usually about 10 to 200 ⁇ m.
- the active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the active material.
- the negative electrode used in the non-aqueous electrolyte secondary battery of the present invention is usually one in which an active material layer containing a negative electrode active material and a binder is formed on a current collector.
- a negative electrode active material a carbonaceous material capable of occluding and releasing lithium such as organic pyrolysate, artificial graphite and natural graphite under various pyrolysis conditions; capable of occluding and releasing lithium such as tin oxide and silicon oxide Metal oxide material; lithium metal; various lithium alloys can be used.
- These negative electrode active materials may be used individually by 1 type, and may mix and use 2 or more types.
- the binder is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode manufacture and other materials used during battery use. Specific examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, styrene / butadiene rubber, isoprene rubber, and butadiene rubber. These may be used individually by 1 type, or may use multiple types together.
- the ratio of the binder in the negative electrode active material layer is such that the lower limit is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and the upper limit is usually 80% by weight or less. Preferably it is 60 weight% or less, More preferably, it is 40 weight% or less, More preferably, it is 10 weight% or less. If the ratio of the binder is equal to or higher than the above lower limit value, the active material can be sufficiently retained, so that the mechanical strength of the negative electrode can be sufficiently obtained, and the battery performance such as cycle characteristics can be improved. If so, there is no risk of lowering battery capacity or conductivity.
- the negative electrode active material layer may contain a conductive agent in order to further increase the conductivity.
- the conductive agent include carbonaceous materials such as carbon black such as acetylene black and amorphous carbon fine particles such as needle coke. These may be used individually by 1 type, or may use multiple types together.
- the ratio of the conductive agent in the negative electrode active material layer the lower limit is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and the upper limit is usually 50% by weight or less. , Preferably 30% by weight or less, more preferably 15% by weight or less.
- the proportion of the conductive agent is equal to or higher than the above lower limit, the necessary conductivity improvement effect is obtained, and if the proportion of the conductive agent is equal to or lower than the upper limit, the necessary conductivity is obtained without decreasing the ratio of the active material. .
- the negative electrode active material layer may contain other additives for a normal active material layer such as a thickener.
- the thickener is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode production and other materials used during battery use. Specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type, or may use multiple types together.
- the thickness of the negative electrode current collector is arbitrary, but is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and usually 100 ⁇ m or less, preferably 50 ⁇ m or less, more preferably 20 ⁇ m or less. If the thickness of the negative electrode current collector is thicker than the lower limit, the strength required for the current collector can be obtained. Further, if the thickness of the current collector is thinner than the above upper limit value, there is no possibility that the volume ratio of the active material put in the battery is lowered, and a necessary battery capacity can be obtained.
- the surface electrical resistance of the negative electrode current collector is 4 ⁇ 10 ⁇ 3 to 4 ⁇ 10 ⁇ 5 ⁇ with respect to the thickness of 1 ⁇ m to 100 ⁇ m, although it varies depending on the thickness in the case of the most commonly used copper foil.
- the negative electrode can be formed by applying a slurry obtained by slurrying the above-described negative electrode active material, a binder, a conductive agent, and other additives added as necessary with a solvent onto a current collector, and then drying the negative electrode active material. .
- an organic solvent that dissolves the binder is usually used.
- N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like are used, but not limited thereto. These may be used individually by 1 type, or may use multiple types together.
- a dispersing agent, a thickener, etc. can be added to water, and an active material can also be slurried with latex, such as SBR.
- the thickness of the negative electrode active material layer thus formed is usually about 10 to 200 ⁇ m.
- the active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the active material.
- the battery shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be appropriately selected from various shapes generally employed according to the application.
- Examples of commonly used battery shapes include a cylinder type with a sheet electrode and separator in a spiral shape, a cylinder type with an inside-out structure combining a pellet electrode and a separator, a coin type with stacked pellet electrodes and a separator, Examples include a laminate type in which a sheet electrode and a separator are laminated.
- the method for assembling the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery.
- the separator of the present invention having a conductive layer on at least one surface, the above-described non-aqueous electrolyte, the positive electrode and the negative electrode are laminated, and the non-aqueous electrolyte is injected between the positive and negative electrodes to assemble in an appropriate shape.
- other components such as an outer case can be used as necessary.
- the separator of the present invention when assembling the non-aqueous electrolyte secondary battery, when the separator of the present invention has a conductive layer only on one surface, this conductive layer faces the negative electrode side even if it is laminated facing the positive electrode side. May be laminated.
- the conductive material constituting the conductive layer is a metal material suitable for facing the positive electrode, it faces the positive electrode side, and when it is a metal material suitable for facing the negative electrode, it faces the negative electrode side.
- a vigorous reaction such as decomposition of the electrolyte occurs on the positive electrode side, which is at a high potential, so the details of the reason are unknown. Therefore, it is preferable to dispose the separator so that the conductive layer of the separator faces at least the positive electrode side.
- the application of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various conventionally known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. , Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting fixtures, toys, game devices, watches, strobes, cameras, and other small devices.
- the non-aqueous electrolyte secondary battery of the present invention is particularly suitable for use in large equipment such as electric vehicles and hybrid vehicles, that is, as a lithium secondary battery for EV or HEV.
- the measuring method of the surface electrical resistance and thickness of the conductive layer of the separator in the following examples and comparative examples is as follows.
- ⁇ Method for measuring surface electrical resistance of conductive layer> The surface electrical resistance was measured using Lorester EP and Hirester UP manufactured by Dia Instruments (currently Mitsubishi Chemical Analytech). When the surface electrical resistance is 10 6 ⁇ or less, a four-probe method using a combination of Lorester EP and an ASP probe (correction coefficient 4.2353), and when the surface electrical resistance is 10 6 ⁇ or more, the Hirester UP and UA probes ( Measurement was performed by a two-probe method using a combination of correction coefficients of 1.050).
- ⁇ Method for measuring thickness of conductive layer The thicknesses of the sputtering film and the deposited film were measured using a step / surface roughness / fine shape measuring device P-15 manufactured by KLA-Tencor. The thickness of the coating film was measured using an upright dial gauge manufactured by Ozaki Seisakusho.
- the separator of the present invention is cut out, and the four sides are fixed by being sandwiched by two aluminum plates having an outer dimension of 60 ⁇ 60 mm with a 30 ⁇ 30 mm rectangular hole. Place in a windowed oven with thermocouple to monitor temperature. The temperature at which the temperature inside the oven was increased at a rate of 5 ° C./min and the separator was visually observed and the occurrence of holes penetrating from the front to the back of the separator was recognized as the meltdown temperature.
- Example 1 ⁇ Preparation of non-aqueous electrolyte solution>
- a well-dried lithium hexafluorophosphate (LiPF 6 ) dissolved in a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed in a volume ratio of 3/7 to a ratio of 1.0 mol / l was used as a non-aqueous electrolyte.
- LiNi 1/3 Mn 1/3 Co 1/3 O 2 is used as the positive electrode active material
- 90 parts by weight of LiNi 1/3 Mn 1/3 Co 1/3 O 2 5 parts by weight of acetylene black and polyvinylidene fluoride (Kureha) 5 parts by weight of a product name “KF-1000” manufactured by Kagaku Co., Ltd. was added and mixed, and the mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry.
- the obtained slurry was uniformly applied to both surfaces of a 15 ⁇ m-thick aluminum foil as a positive electrode current collector, dried, and then rolled to a thickness of 81 ⁇ m by a press machine.
- a positive electrode was cut into a shape having an uncoated part with a thickness of 100 mm and a width of 30 mm.
- the density of the positive electrode active material layer was 2.35 g / cm 3 .
- the active material layer had a width of 104 mm and a length of A negative electrode was cut into a shape having an uncoated part with a width of 104 mm and a width of 30 mm.
- the density of the negative electrode active material layer was 1.35 g / cm 3 .
- ⁇ Create separator> Using a commercially available three-layer separator (polypropylene / polyethylene / polypropylene) having a thickness of 25 ⁇ m, a piercing strength of 380 g, and a porosity of 39%, one surface thereof was subjected to Al sputtering treatment to provide a conductive layer.
- the thickness of the Al layer was 25 nm and the surface electrical resistance was 26 ⁇ .
- the piercing strength of the separator on which the Al layer was formed was 350 g, and the porosity was 39%.
- a battery can having a positive and negative current collecting terminal, a pressure release valve, and a non-aqueous electrolyte injection port at the lid portion was used.
- the current collecting tab and the current collecting terminal were connected by spot welding. Then, 20 mL of nonaqueous electrolyte solution was inject
- valve operation represents a phenomenon in which a gas discharge valve is activated and a non-aqueous electrolyte component is released
- rupture is a case where the battery container is torn violently and the contents are forcibly released. Represents a phenomenon.
- Table 1 The results of the overcharge test are shown in Table 1.
- Example 2 A commercially available three-layer separator having a thickness of 25 ⁇ m similar to that used in Example 1 was used as a base material, and Mo sputtering treatment was performed on one surface thereof to provide a conductive layer.
- the thickness of the Mo layer was 147 nm and the surface electrical resistance was 11 ⁇ .
- the puncture strength of the separator was 310 g, and the porosity was 38%.
- a battery was prepared in the same manner as in Example 1, and an overcharge test was performed. The results are shown in Table 1.
- Example 3 A battery was prepared in the same manner as in Example 2 except that the conductive layer of the separator obtained in Example 2 was opposed to the negative electrode, and an overcharge test was performed. The results are shown in Table 1.
- Example 4 Using a commercially available three-layer separator having a thickness of 25 ⁇ m similar to that used in Example 1 as a base material, Mo sputtering treatment was performed on both surfaces to provide a conductive layer. The thickness of the Mo layer was 147 nm in both layers, and the surface electrical resistance was 11 ⁇ . Further, the puncture strength of the separator was 280 g, and the porosity was 36%. Using the obtained separator, a battery was prepared in the same manner as in Example 1, and an overcharge test was performed. The results are shown in Table 1.
- Example 5 Using a commercially available three-layer separator having a thickness of 25 ⁇ m as used in Example 1 as a base material, graphite was vapor-deposited on one surface thereof to provide a conductive layer. The thickness of the graphite layer was 5 nm, and the surface electrical resistance was 2 ⁇ 10 7 ⁇ . The puncture strength was 350 g, and the porosity was 39%. Using the obtained separator, a battery was prepared in the same manner as in Example 1, and an overcharge test was performed. The results are shown in Table 1.
- Example 6 Uniformly disperse 15 parts by weight of acetylene black “Denka Black HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd., 2.7 parts by weight of polyvinyl alcohol (average polymerization degree 1700, saponification degree 99% or more) and 82.3 parts by weight of water. A slurry was prepared, and this slurry was applied to one surface of a commercially available three-layer separator having a thickness of 25 ⁇ m similar to that used in Example 1, and then dried at 60 ° C. to obtain a conductive material having a thickness of 4.5 ⁇ m. A layer was provided. The conductive layer had a surface electrical resistance of 664 ⁇ . Further, the puncture strength of the separator was 380 g, and the porosity was 39%. Using the obtained separator, a battery was prepared in the same manner as in Example 1, and an overcharge test was performed. The results are shown in Table 1.
- Example 1 Using the same commercially available three-layer separator (polypropylene / polyethylene / polypropylene) as used in Example 1, a battery was prepared in the same manner as in Example 1 and an overcharge test was performed. The results are shown in Table 1.
- Example 7 A slurry was prepared by uniformly dispersing 15 parts by weight of graphite used in Example 4, 0.85 part by weight of polyvinyl alcohol (average polymerization degree 1700, saponification degree 99% or more) and 84.15 parts by weight of water, This slurry was applied to one surface of a commercially available three-layer separator having a thickness of 20 ⁇ m and a Gurley air permeability of 400 seconds / 100 cc, and then dried at 60 ° C. to provide a conductive layer having a thickness of 4.5 ⁇ m. The surface electrical resistance of this conductive layer was 0.9 ⁇ .
- the piercing strength of the separator was 350 g, the porosity was 39%, the Gurley air permeability was 435 seconds / 100 cc, and the rate of increase in air permeability was 8.8%.
- a conductive layer was formed on one surface of a commercially available three-layer separator having a thickness of 20 ⁇ m and a Gurley air permeability of 400 seconds / 100 cc, except that the thickness was 6 ⁇ m.
- the surface electrical resistance of this conductive layer was 0.6 ⁇ .
- the piercing strength of the separator was 350 g, the porosity was 39%, the Gurley air permeability was 450 seconds / 100 cc, and the rate of increase in air permeability was 12.5%.
- Example 8 A battery was prepared and an overcharge test was performed in the same manner as in Example 1 except that the constant current charge rate from the discharge state (3 V) in the overcharge test was set to 5C. The results are shown in Table 1.
- Example 9 Uniformly disperse 15 parts by weight of acetylene black “Denka Black HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd., 2.7 parts by weight of polyvinyl alcohol (average polymerization degree 1700, saponification degree 99% or more) and 82.3 parts by weight of water. A slurry was prepared, and this slurry was applied to one surface of a commercially available polyethylene separator having a thickness of 9 ⁇ m, and then dried at 60 ° C. to provide a conductive layer having a thickness of 3 ⁇ m. The surface electrical resistance of this conductive layer was 1.1 ⁇ 10 3 ⁇ .
- a separator having a conductive layer inside was formed by laminating the obtained separator and a commercially available polyethylene separator having a thickness of 9 ⁇ m in a shape sandwiching the conductive layer. Using this separator, a battery was prepared in the same manner as in Example 1 and an overcharge test was conducted. The results are shown in Table 1.
- Example 10 Using the electrolytic solution prepared in Example 1, the positive electrode, the negative electrode, and the separator, the conductive layer was opposed to the positive electrode to prepare an 18650 type cylindrical battery, and then a voltage range of 4.1 to 3.0 V at 25 ° C., current Initial charge / discharge of 5 cycles was performed at a value of 0.2C. Next, this battery was charged and discharged for 350 cycles in a voltage range of 4.1 to 3.0 V and a current value of 2 C in an environment of 60 ° C. The discharge capacity retention rate at the end of 350 cycles with respect to the initial discharge capacity was 75%.
- Example 4 A 18650 cylindrical battery was prepared in the same manner as in Example 6 except that the commercially available three-layer separator (polypropylene / polyethylene / polypropylene) used as the base material in Example 1 was used, and a cycle test was performed. The discharge capacity retention rate at the end of 350 cycles with respect to the initial discharge capacity was 65%.
- Example 11 A 18650 cylindrical battery was prepared in the same manner as in Example 10 except that the graphite vapor-deposited separator prepared in Example 5 was opposed to the positive electrode, and the voltage range was 4.1 to 3.0 V at 25 ° C. and the current value was 0.2 C. Five cycles of initial charge / discharge were performed. Next, this battery was charged at a current value of 0.2 C to 4.3 V in an environment of 60 ° C., then stored for 2 weeks while maintaining the voltage at 4.3 V, and then discharged to 3.0 V. The battery was disassembled and the separator was observed. No color change was observed in the separator, and there was no change.
- Example 5 A 18650 cylindrical battery was prepared and subjected to a storage test in the same manner as in Example 7 except that the commercially available three-layer separator (polypropylene / polyethylene / polypropylene) used as the base material in Example 1 was used. When the battery was disassembled and the separator was observed in the same manner as in Example 7, the separator was discolored and deteriorated.
- the commercially available three-layer separator polypropylene / polyethylene / polypropylene
- Example 12 Under a dry argon atmosphere, a mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3/7 was mixed with LiPF 6 sufficiently dried as a Li salt at 1.0 mol / liter and LiBF 4 at 0.2 mol / liter. A battery was prepared and an overcharge test was conducted in the same manner as in Example 1 except that the non-aqueous electrolyte solution was used so that it was dissolved so as to have the above ratio. The results are shown in Table 2.
- Example 13 Under a dry argon atmosphere, a mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3/7 was mixed with LiPF 6 sufficiently dried as a Li salt at 1.0 mol / liter and LiBF 4 at 0.01 mol / liter. A battery was prepared and an overcharge test was conducted in the same manner as in Example 1 except that the non-aqueous electrolyte was dissolved to give a ratio of The results are shown in Table 2.
- Example 14 A battery was prepared and an overcharge test was performed in the same manner as in Example 1 except that the electrolytic solution obtained in Example 12 and the separator obtained in Example 2 were used. The results are shown in Table 2.
- Example 15 A battery was prepared and an overcharge test was performed in the same manner as in Example 1 except that the electrolytic solution obtained in Example 13 and the separator obtained in Example 2 were used. The results are shown in Table 2.
- Example 16 A battery was prepared and an overcharge test was conducted in the same manner as in Example 14 except that the separator conductive layer obtained in Example 2 was opposed to the negative electrode. The results are shown in Table 2.
- Example 17 A battery was prepared and an overcharge test was performed in the same manner as in Example 4 except that the electrolytic solution obtained in Example 12 was used. The results are shown in Table 2.
- Example 18 A battery was prepared and an overcharge test was conducted in the same manner as in Example 1 except that the electrolytic solution obtained in Example 12 and the separator obtained in Example 5 were used. The results are shown in Table 2.
- Example 19 A battery was prepared and an overcharge test was performed in the same manner as in Example 1 except that the electrolytic solution obtained in Example 13 and the separator obtained in Example 5 were used. The results are shown in Table 2.
- Example 22 Under a dry argon atmosphere, a solvent prepared by mixing ethylene carbonate and ethyl methyl carbonate at a volume ratio of 3/7, LiPF 6 sufficiently dried as a Li salt was 1.0 mol / liter, and LiFSI was 0.1 mol / liter. A battery was prepared and an overcharge test was performed in the same manner as in Example 5 except that the nonaqueous electrolyte solution was dissolved to obtain a ratio. The results are shown in Table 2.
- the batteries were charged with a constant current at a current value of 5 C from the fully charged state (open end voltage of each battery 4.1 V, assumed open end voltage of the battery module was 41 V), and the behavior was observed. A voltage of 50 V was applied to the battery module, but only a battery with a low capacity was opened.
- Example 25 A battery was prepared in the same manner as in Example 1 except that ethylene solvent, ethyl methyl carbonate, and trifluoroethyl methyl carbonate (hereinafter referred to as TFEMC) were mixed at a volume ratio of 3/6/1. Charge evaluation was performed. The results are shown in Table 3.
- Example 29 A battery was prepared in the same manner as in Example 25 except that the conductive layer of the separator obtained in Example 2 was opposed to the negative electrode, and an overcharge test was performed. The results are shown in Table 3.
- Example 31 A battery was prepared and an overcharge test was performed in the same manner as in Example 1 except that the electrolytic solution obtained in Example 25 and the separator obtained in Example 5 were used. The results are shown in Table 3.
- Example 33 A battery was prepared and an overcharge test was performed in the same manner as in Example 1 except that the electrolytic solution obtained in Example 25 and the separator obtained in Example 6 were used. The results are shown in Table 3.
- Example 34 A battery was prepared and an overcharge test was conducted in the same manner as in Example 1 except that the electrolytic solution obtained in Example 26 and the separator obtained in Example 6 were used. The results are shown in Table 3.
- Example 36 A battery was prepared in the same manner as in Example 5 except that the solvent was a mixture of ethylene carbonate, ethyl methyl carbonate and cis-4,5-difluoroethylene carbonate (hereinafter c-DFEC) at a volume ratio of 2/7/1. An overcharge evaluation was made. The results are shown in Table 3.
- Example 37 A battery was prepared in the same manner as in Example 5 except that the solvent was a mixture of ethylene carbonate, ethyl methyl carbonate and trans-4,5-difluoroethylene carbonate (hereinafter t-DFEC) at a volume ratio of 2/7/1. An overcharge evaluation was made. The results are shown in Table 3.
- the batteries were charged with a constant current at a current value of 5 C from the fully charged state (open end voltage of each battery 4.1 V, assumed open end voltage of the battery module was 41 V), and the behavior was observed. A voltage of 50 V was applied to the battery module, but only a battery with a low capacity was opened.
- Example 39 6.6 parts by weight of acetylene black “Denka Black HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd., 1.3 parts by weight of polyvinyl alcohol (average polymerization degree 1700, saponification degree 99% or more), alumina particles (particle size 0.2 ⁇ m, Aspect ratio 1.1) 23.4 parts by weight and 68.7 parts by weight of water were uniformly dispersed to prepare a slurry.
- a commercially available three-layer separator polypropylene / polypropylene having a thickness of 25 ⁇ m, a piercing strength of 380 g, and a porosity of 39%.
- Polyethylene / polypropylene was applied to one surface as a base material, and then dried at 60 ° C. to provide a heat resistant conductive layer having a thickness of 4.8 ⁇ m.
- the surface electrical resistance of this conductive layer was 1.7 ⁇ 10 4 ⁇ .
- the puncture strength of the separator was 380 g, the porosity was 39%, and the meltdown temperature was 190 ° C.
- a battery was prepared in the same manner as in Example 1 except that this separator was used, and overcharge evaluation was performed. The results are shown in Table 4.
- Example 40 Polymetaphenylene isophthalamide was dissolved in N, N-dimethylacetamide to prepare a 10% by weight solution as a spinning solution.
- the commercially available three-layer separator used in Example 1 was used as the base material, the voltage was 17 kV, the distance to the collector was 20 cm, the nozzle inner diameter was 0.59 mm, the three-layer separator was fixed on the collector, and the polyspinning was performed by electrospinning. Metaphenylene isophthalamide nanofibers were laminated. Lamination of nanofibers was performed on both sides of the separator, and lamination was performed until the thickness became 2 ⁇ m.
- acetylene black “Denka Black HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd., 2.7 parts by weight of polyvinyl alcohol (average polymerization degree 1700, saponification degree 99% or more) and 82.3 parts by weight of water were uniformly added.
- a slurry is prepared by dispersing the slurry on the surface of the separator on which the nanofibers of polymetaphenylene isophthalamide are laminated, and then dried at 60 ° C. to form a conductive layer having a thickness of 4 ⁇ m.
- the conductive layer had a surface electrical resistance of 712 ⁇ .
- the puncture strength of the separator was 380 g, the porosity was 41%, and the meltdown temperature was 220 ° C.
- a battery was prepared and an overcharge test was performed in the same manner as in Example 1 except that the obtained separator was used. The results are shown in Table 4.
- Composition 1 Mixture of 80% by weight of poly-4 methylpentene-1 and 20% by weight of paraffin wax
- Composition 2 Mixture of ultrahigh molecular weight PE with a molecular weight of 1 million 30% by weight and 70% by weight of paraffin wax Mixture of Composition 1 and Composition 2
- the mixture was melt-kneaded and sheet-molded to produce a multilayer sheet having a composition of 1 / composition 2 / composition 1 and a thickness ratio of 2/6/2 and a thickness of 200 ⁇ m.
- the multilayer sheet was biaxially stretched at a temperature of 130 ° C. and a stretching ratio of 4 ⁇ 4 using a biaxial stretching machine.
- the batteries were charged with a constant current at a current value of 5 C from the fully charged state (open end voltage of each battery 4.1 V, assumed open end voltage of the battery module was 41 V), and the behavior was observed. A voltage of 50 V was applied to the battery module, but only a battery with a low capacity was opened.
- the separator since the separator has a specific conductive layer, defective cells are mixed in the module battery, and a voltage of several tens of volts of the entire module battery is applied to one or a few single cells.
- a highly safe non-aqueous electrolyte secondary battery that can prevent a short circuit and an explosion even if it reaches an overcharged state is provided.
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Abstract
Description
特許文献3でも、安全性に関する問題が指摘されており、その解決手段としてアルカリ金属の高分子コーティング等が挙げられているが、高分子コーティングを行えば金属の持つ導電性は阻害されるため、表面に導電性を有するセパレータを形成し得ない。
<1>
リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池に用いられるセパレータであって、該セパレータが導電層を有し、該導電層の見掛け体積抵抗率が1×10-4Ω・cm乃至1×106Ω・cmであり、かつ該導電層の膜厚が5μm未満である非水系電解液二次電池用セパレータ。
<2>
リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池に用いられるセパレータであって、該セパレータが導電層を有し、該導電層の体積抵抗率が1×10-6Ω・cm乃至1×106Ω・cmであり、かつ該導電層の膜厚が5μm未満である非水系電解液二次電池用セパレータ。
<3>
リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池に用いられるセパレータであって、該セパレータが導電層を有し、該導電層の表面電気抵抗が1×10-2Ω乃至1×109Ωであり、かつ該導電層の膜厚が5μm未満である非水系電解液二次電池用セパレータ。
<4>
前記セパレータのメルトダウン温度が170℃以上である上記<1>乃至<3>の何れか1に記載の非水系電解液二次電池用セパレータ。
<5>
前記セパレータの突き刺し強度が250g以上800g以下である上記<1>乃至<4>の何れか1に記載の非水系電解液二次電池用セパレータ。
<6>
前記導電層がセパレータの少なくとも一方の表面に設けられている上記<1>乃至<5>の何れか1に記載の非水系電解液二次電池用セパレータ。
<7>
前記導電層が金属元素及び炭素質材料のうち少なくとも一方を含有する上記<1>乃至<6>の何れか1に記載の非水系電解液二次電池用セパレータ。
<8>
前記金属元素が、アルミニウム、モリブデン、銅、及びチタンよりなる群から選ばれる少なくとも1種である上記<7>に記載の非水系電解液二次電池用セパレータ。
<9>
前記炭素質材料が、黒鉛、カーボンブラック、及び無定形炭素微粒子よりなる群から選ばれる少なくとも1種である上記<7>に記載の非水系電解液二次電池用セパレータ。
<10>
前記セパレータが耐熱層を有しており、該耐熱層が融点またはガラス転移温度が170℃以上の樹脂を含有する上記<1>乃至<9>の何れか1に記載の非水系電解液二次電池用セパレータ。
<11>
前記耐熱層が無機フィラーを含有する上記<10>に記載の非水系電解液二次電池用セパレータ。
<12>
前記耐熱層がポリメチルペンテン、ポリアミド、ポリイミド、及びポリアミドイミドからなる群から選ばれる少なくとも1つの樹脂を含有する上記<10>または<11>に記載の非水系電解液二次電池用セパレータ。
<13>
前記無機フィラーが酸化アルミニウム、酸化マグネシウム、酸化チタン、及び硫酸バリウムからなる群から選ばれる少なくとも1つである上記<11>に記載の非水系電解液二次電池用セパレータ。
<14>
リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池であって、該セパレータが上記<1>乃至<13>の何れか1に記載の非水系電解液二次電池用セパレータである非水系電解液二次電池。
<15>
前記正極が、NiMnCo合金を含有する上記<14>に記載の非水系電解液二次電池。
<16>
前記非水系電解液が、フッ素化カーボネートを含有するものである上記<14>または<15>に記載の非水系電解液二次電池。
<17>
前記フッ素化カーボネートが、一般式C=O(OR1)(OR2)で表されるものである上記<16>に記載の非水系電解液二次電池。
(前記一般式中、R1及びR2は、それぞれ炭素数1または2のアルキル基であり、R1及びR2のうち少なくとも1方が1個以上のフッ素原子を有する)
<18>
前記フッ素化カーボネートが、エチレンカーボネートを構成する水素原子のうち1個または2個をフッ素原子及びフッ素化アルキル基のうち少なくとも一方で置換したものである上記<16>に記載の非水系電解液二次電池。
<19>
前記フッ素化カーボネートの含有量が、電解液中の体積割合として20%以下である、上記<16>乃至<18>の何れか1に記載の非水系電解液二次電池。
<20>
前記電解質が、LiPF6を含有し、かつその電解液中の濃度が0.5モル/リットル以上2モル/リットル以下である、上記<14>乃至<19>の何れか1に記載の非水系電解液二次電池。
<21>
前記非水系電解液が、副電解質として更に、ホウ酸リチウム塩類、リン酸リチウム塩類、フルオロリン酸リチウム塩類、カルボン酸リチウム塩類、スルホン酸リチウム塩類、リチウムイミド塩類、リチウムオキサラトボレート塩類、リチウムオキサラトフォスフェート塩類及びリチウムメチド塩類からなる群から選ばれる少なくとも一種の化合物を含有し、全副電解質の電解液中の濃度が0.01モル/リットル以上0.3モル/リットル以下である、上記<14>乃至<20>の何れか1に記載の非水系電解液二次電池。
<22>
前記副電解質が、テトラフルオロホウ酸リチウム、ビス(フルオロスルホニル)イミド、及びリチウムビス(トリフルオロスルホニル)イミドリチウムからなる群より選ばれる少なくとも1種の化合物である上記<21>に記載の非水系電解液二次電池。
<23>
上記<14>乃至<22>の何れか1に記載の非水系電解液二次電池を5個以上直列に連結して有し、満充電に20V以上の電圧を必要とする非水系電解液二次電池モジュール。
本発明の非水系電解液二次電池用セパレータ(以下「本発明のセパレータ」と称す場合がある。)は、
リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池に用いられるセパレータであって、
(1)該セパレータが導電層を有し、該導電層の見掛け体積抵抗率が1×10-4Ω・cm乃至1×106Ω・cmであり、かつ該導電層の膜厚が5μm未満であることを特徴とするものであり、
または(2)該セパレータが導電層を有し、該導電層の体積抵抗率が1×10-6Ω・cm乃至1×106Ω・cmであり、かつ該導電層の膜厚が5μm未満であることを特徴とするものであり、
または(3)該セパレータが導電層を有し、該導電層の表面電気抵抗が1×10-2Ω乃至1×109Ωである導電層を有しており、かつ該導電層の膜厚が5μm未満であることを特徴とするものである。
本発明のセパレータは、例えば、通常の非水系電解液二次電池で用いられるセパレータや、従来公知の方法で得られる多孔質フィルムや不織布を基材とし、この基材の少なくとも一方の表面に導電層を形成する、或いは、導電層を基材で挟み込むことにより製造することができ、この基材の構成材料や製法には特に制限はない。
(1) ポリオレフィン樹脂に、ポリオレフィン樹脂に対して相溶性があり後工程で抽出可能な低分子量物を加えて溶融混練、シート化を行い、延伸後又は延伸前に該低分子量物の抽出を行って多孔化する抽出法
(2) 結晶性樹脂を高ドラフト比でシート化して作成した高弾性シートに低温延伸と高温延伸を加えて多孔化する延伸法
(3) 熱可塑性樹脂に無機又は有機の充填剤を加えて溶融混練、シート化を行い、延伸により樹脂と充填剤の界面を剥離させて多孔化する界面剥離法
(4) ポリプロピレン樹脂にβ晶核剤を添加して溶融混練、シート化を行い、β晶を生成させたシートを延伸して結晶転移を利用して多孔化するβ晶核剤法
<導電材>
本発明に係る導電層を構成する材料(以下、「導電材」と称す場合がある。)としては、導電性を有するものであれば良く、特に制限はないが、例えば、金属、炭素質材料を用いることができる。
即ち、導電層が正極に対向する場合、導電層は高電位に曝されるため、酸化電位の高い金や白金又はその合金類が好ましく使用される。また、陽極酸化により不働態皮膜を生じるバルブ金属も好適に使うことができる。バルブ金属の例としてはアルミニウムやタングステン、モリブデン、チタン、タンタルなどが挙げられる。また、酸化クロムの皮膜を持つステンレス鋼も好適に用いることができる。
導電層の形成方法は特に制限されず公知の方法が用いられる。
一例を挙げれば、スパッタリングやイオンプレーティング、真空蒸着等の方法で前述の基材の少なくとも一方の表面に導電層を形成する方法が挙げられる。また、他の例としては、導電材をバインダー等と共に溶媒中に混合したスラリーを調製し、このスラリーをドクターブレード又はロールコータ、ダイコータ、その他ディッピングやスプレー法等などの公知の手法で基材の少なくとも一方の表面に塗布、乾燥して導電層を形成する方法が挙げられる。
導電層の厚みは、5μm未満であり、下限値としては好ましくは0.001μm以上、より好ましくは0.003μm以上、更に好ましくは0.005μm以上である。導電層の厚みが上記下限値以上であると耐過充電性の改善効果がより十分に発揮される。一方で導電層の厚みが5μm以上だと、導電層部分の通気抵抗、ひいてはイオン透過抵抗が大きくなりすぎて出力等の電池性能が低下する。
導電層が金属材料からなる場合、導電層の厚みは、好ましくは0.001乃至1μm、より好ましくは0.003乃至0.5μm、更に好ましくは0.005乃至0.3μm、特に好ましくは0.005乃至0.1μmである。導電層の厚みが上記下限値以上であると耐過充電性の改善効果がより十分に発揮される。導電層の厚みが5μm以上だと、前述のように過充電によって発生する酸素の吸収による発熱が大きくセパレータの熱収縮やメルトダウン等が生じる危険性が高いので好ましくない。
セパレータの両表面に導電層を形成する場合は、セパレータ全体の厚みを抑える上でも、両表面の導電層の合計の厚みは10μm未満である。また、導電層が炭素質材料を用いる場合は、好ましくは0.002μm以上、より好ましくは0.01μm以上である。また導電層が金属材料よりなる場合については、好ましくは0.002乃至1μmであり、より好ましくは0.01乃至0.6μmであり、さらに好ましくは0.01乃至0.2μmである。
またセパレータの両表面に導電層を形成する場合、セパレータの両表面で、形成された導電層の厚みや用いた導電材が異なるものであっても、同一であってもよく、例えば、前述の如く、セパレータの一方の表面には、負極対向面側として好適な金属を用い、セパレータの他方の表面には、正極対向面側として好適な金属を用いるようにしてもよい。
本発明のセパレータは、
(1)見掛け体積抵抗率が1×10-4Ω・cm乃至1×106Ω・cm、または(2)体積抵抗率が1×10-6Ω・cm乃至1×106Ω・cm、または(3)表面電気抵抗が1×10-2Ω乃至1×109Ω、の導電層を有するものである。
そして、
(1)導電層の見掛け体積抵抗率は、1×10―4Ω・cm乃至1×106Ω・cmであり、好ましくは1×10-4乃至1×105Ω・cm、より好ましくは1×10-4乃至1×104Ω・cmである。
(2)導電層の体積抵抗率は、1×10-6Ω・cm乃至1×106Ω・cmであり、好ましくは1×10-3乃至1×103Ω・cm、より好ましくは1×10-2乃至1×102Ω・cmである。
ここで、体積抵抗率とは導電層を形成する材料固有の値である。そして、導電層はリチウムイオン等のイオンの透過経路が必要なことから多孔質であるため、その空隙の影響や導電性材料同士の接触抵抗などの影響により、導電性材料が本来持つ体積抵抗率よりも見掛け体積抵抗率は高い値を有する。
導電層の見掛け体積抵抗率ないしは体積抵抗率が上記上限を超えると、その理由の詳細は不明であるが、本発明による充分な耐過充電性改善効果を得ることが難しい。見掛け体積抵抗率ないしは体積抵抗率が上記下限未満では、導電層による通気抵抗が高くなり、リチウムイオンの移動経路としてのセパレータの特性を損なうことがある。また見掛け体積抵抗率ないしは体積抵抗率が上記下限未満では、導電層が集電体として働く場合がありジュール発熱によりセパレータが熱劣化を生じる恐れがある。
また導電層の表面抵抗率としては、好ましくは4×10-2乃至1×109Ω/□であり、より好ましくは1×10-1乃至1×108Ω/□、更に好ましくは1乃至1×107Ω/□である。
導電層の表面電気抵抗が上記上限を超えると、その理由の詳細は不明であるが、本発明による充分な耐過充電性改善効果を得ることが難しい。表面電気抵抗が上記下限未満では、導電層による通気抵抗が高くなり、リチウムイオンの移動経路としてのセパレータの特性を損なうことがある。また表面電気抵抗が上記下限未満では、導電層が集電体として働く場合がありジュール発熱によりセパレータが熱劣化を生じる恐れがある。
表面電気抵抗は、ダイアインスツルメンツ社(現三菱化学アナリテック社)製の測定装置ロレスターEPおよびハイレスターUPにより測定できる。
表面抵抗率は、上記表面電気抵抗と三菱化学アナリテック社が公開するプローブごとの補正係数を用いて下記式により算出できる。
表面抵抗率=表面電気抵抗×補正係数
見掛けの体積抵抗率は下記式により算出できる。
見掛けの体積抵抗率=表面抵抗率×導電層の厚み
尚、体積抵抗率とは導電層を形成する材料固有の値であり、例えば、「化学便覧 基礎編 改定5版 II-611ページ 表14.9、丸善株式会社 発行、発行日 平成16年2月20日」に基づき導かれる。ただし、アセチレンブラックに関しては電気化学工業株式会社のホームページの物性一覧より体積抵抗率の値を得た。
本発明に係る導電層は、上述のように、セパレータの少なくとも一方の表面に形成されてもよく、基材で挟み込み中間層として形成されてもよい。そして、前述の特許文献2~5に記載されるような従来のセパレータへの導電性付与技術に対して、以下のように明確に区別され、その特徴的な構成により優れた耐過充電性が得られる。
これに対して、本発明のセパレータに形成される導電層は、例えば金属や炭素質材料からなり、水分が排除された非水系電解液二次電池の環境下においても充分に導電性を発揮するものである。
本発明に係る導電層は、セパレータの表面または中間層に存在するため、通常の電池使用時における正負両極の短絡は生じることはなく、必要に応じて充分な導電性を付与しうる。
本発明のセパレータの多孔性の程度としての空隙率は、通常30乃至90%、好ましくは35乃至80%、より好ましくは38乃至70%である。セパレータの空隙率が上記下限以上であれば、電気抵抗が高くなりすぎず出力などの電池性能が低下するおそれがなく好ましい。空隙率が上記上限以下であれば、機械的強度が高く、高速捲回時の破断、または充放電時の活物質の膨張・収縮による内部短絡を生じるおそれがなく好ましい。
即ち、まずセパレータの厚み(導電層を含めた総厚み)をt0、単位面積あたりの重量(導電層を含めた総重量)をw0、平均比重をρとすると、セパレータの空隙率Pvは次式で得ることができる。
Pv(%)=100×{1-(w0/[ρ・t0])}
(但し、サンプル面積は単位面積。)
なお、平均比重ρは、多孔質フィルム等の基材と導電層の成分の比重および単位面積当たり重量比をそれぞれρi、kiとして、
ρ=1/(Σki/ρi)
で得ることができる。重量比は導電層形成前後の重量を測定することで得ることができる。
本発明のセパレータの厚さ(導電層を含めた総厚み)は、通常5乃至50μm、好ましくは9乃至35μm、より好ましくは15乃至30μmである。セパレータの厚みが上記下限以上であれば、機械的強度が得られ、高速捲回時の破断、あるいは充放電時の活物質の膨張・収縮による内部短絡を生じるおそれがなく好ましい。セパレータの厚みが上記上限以下であれば、電気抵抗が高くなりすぎず、出力などの電池性能が低下するおそれがないため好ましい。
本発明のセパレータの突き刺し強度(導電層を含めたセパレータの突き刺し強度)は通常250g以上、好ましくは300g以上、より好ましくは350g以上である。突き刺し強度が250g以上であれば過充電時の活物質の膨張による圧力に対抗でき、内部短絡を起こる可能性が低いため好ましい。突き刺し強度の好ましい上限は特に存在せず、電気抵抗などのセパレータとしての特性が電池性能から要求される性能を満たしていればいくら大きくても構わないが、通常は800g以下である。
なお、本発明におけるセパレータの突き刺し強度とは、以下に記述する方法で測定された強度を意味する。
ホルダーで固定したサンプル(測定部:直径20mmの円形)に、直径1mm、先端曲率半径0.5mmの金属(SUS440C)製針を厚さ方向に300mm/minの速さで突き刺して、穴が開口する最大荷重を測定する。
本発明のセパレータの基材として用いられる従来公知の方法で得られる多孔質フィルムや不織布のガーレー透気度は10秒/100ccないし800秒/100cc、好ましくは50秒/100ccないし600秒/100cc、より好ましくは100秒/100ccないし400秒/100ccである。多孔質基材に導電層を形成した場合、導電層が通気抵抗となって通気性が低下する場合があるが、多孔質基材の透気度はイオン透過抵抗と密接に関わるため通気性の低下は10%以内が好ましい。すなわち多孔質基材に導電層を形成した場合のガーレー透気度の増加率は10%以内が好ましい。なおガーレー透気度はJISP8117に準じてB型ガーレーデンソーメーター(東洋精機製作所製)を使用して測定を行った。
本発明のセパレータはその基材として、メルトダウン温度が170℃以上であれば従来公知の方法で得られる多孔質フィルムや不織布などを適宜用いることができ、この基材の構成材料や製法には特に制限はなく、この基材に導電層を形成することにより製造することができる。
また基材のメルトダウン温度が170℃未満であってもその少なくとも1つの面に耐熱層を設けることによりセパレータ全体としてメルトダウン温度が170℃以上になるようにしてもよい。耐熱層は樹脂のような有機材料、無機フィラーのような無機材料の何れから構成されてもよく、両者を併用してもよい。
本発明のセパレータに170℃以上のメルトダウン温度を付与する方法の例としては上記の公知の方法で得られたセパレータ基材に耐熱多孔層を形成する方法が挙げられる。耐熱多孔層は少なくとも基材の一方の表面上に形成する必要があり、耐熱層の両表面に基材がきてもよく、基材の両表面に耐熱層が形成されてもよいが、耐熱層を基材の両表面に形成することがより好ましい。耐熱層は、耐熱性を有する無機または有機フィラーまたは耐熱性を有する無機または有機ファイバーから形成されていてもよいし、耐熱性樹脂より形成されてもよい。これらは単独で用いてもよく2種類以上の材料を適宜選択して使用してもよい。
あるいは電界紡糸法(エレクトロスピニング)を用いて耐熱層を形成してもよく、多層成形などの手法を用いて耐熱層を形成することもできる。
耐熱性を有する有機ファイバーとしてはセルロースファイバー、あるいは前述の耐熱性樹脂よりなるファイバーを好適に用いることができる。
耐熱層を形成する樹脂は前述の耐熱性樹脂を好適に用いることができる。溶剤可溶性の樹脂は樹脂溶液を作成して塗布することで耐熱層を形成することができる。溶剤難溶性の樹脂は熱可塑性樹脂であれば多層成形などの手法を用いて耐熱層を形成することができる。
本発明の非水系電解液二次電池は、リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒に電解質を溶解してなる非水系電解液とを備える非水系電解液二次電池において、該セパレータが、上記本発明の非水系電解液二次電池用セパレータであることを特徴とする。
<非水系溶媒>
本発明の非水系電解液二次電池に使用される電解液の非水系溶媒としては、非水系電解液二次電池の溶媒として公知の任意のものを用いることができる。例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート等のアルキレンカーボネート;ジメチルカーボネート、ジエチルカーボネート、ジ-n-プロピルカーボネート、エチルメチルカーボネート等のジアルキルカーボネート(ジアルキルカーボネートのアルキル基は、炭素数1~4のアルキル基が好ましい);テトラヒドロフラン、2-メチルテトラヒドロフラン等の環状エーテル;ジメトキシエタン、ジメトキシメタン等の鎖状エーテル;γ-ブチロラクトン、γ-バレロラクトン等の環状カルボン酸エステル;酢酸メチル、プロピオン酸メチル、プロピオン酸エチル等の鎖状カルボン酸エステルなどが挙げられる。これらは1種を単独で用いてもよく、2種類以上を併用してもよい。
非水系電解液の溶質である電解質としては、通常リチウム塩が用いられる。このリチウム塩としては、任意のものを用いることができ、例えば、LiClO4、LiPF6、LiBF4等の無機リチウム塩;LiCF3SO3、LiN(CF3SO2)2、LiN(C2F5SO2)2、LiN(CF3SO2)(C4F9SO2)、LiC(CF3SO2)3、LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2等の含フッ素有機リチウム塩などが挙げられる。これらのうち、LiPF6、LiBF4、LiCF3SO3、LiN(CF3SO2)2、LiN(C2F5SO2)2が好ましく、特にLiPF6、LiBF4が好ましい。なお、リチウム塩についても1種を単独で用いてもよく、2種以上を併用してもよい。
本発明に係る非水系電解液には、非水系溶媒及び電解質以外に必要に応じて他の有用な成分、例えば従来公知の過充電防止剤、脱水剤、脱酸剤、高温保存後の容量維持特性やサイクル特性を改善するための助剤等の各種の添加剤を含有させてもよい。
電解液にフッ素原子を有するカーボネート類(これを以下、「フッ素化カーボネート」と略記する場合がある)を用いることは知られているが(日本国特開2008-192504号公報(特許文献10)、日本国特開2005-38722号公報(特許文献11)、日本国特開2008-257988号公報(特許文献12)、日本国特開2009-163939号公報(特許文献13)、日本国特開2010-10078号公報(特許文献14))、EV用あるいはHEV用電池モジュールに用いられる充電上限電圧が20V乃至あるいは数百Vとなる場合の過充電に関する検討は行われていない。
上述したように、EV用あるいはHEV用の電池モジュールにおいては数十V以上の電圧下で反応して過充電反応を抑制するような新技術が求められているが、これを満足する技術は未だ見出されていない。
代表的には、一般式C=O(OR1)(OR2)(式中、R1及びR2は、それぞれ炭素数1または2のアルキル基であり、R1及びR2のうち少なくとも1方が1個以上のフッ素原子を有する)で表される化合物が用いられ、ジメチルカーボネート誘導体類、エチルメチルカーボネート誘導体類、ジエチルカーボネート誘導体類等が挙げられる。
これらの中でも、トリフルオロエチルメチルカーボネート、エチルトリフルオロエチルカーボネートが、電池を大型化した際の電導性等の電池特性を維持しつつ、高い耐過充電防止性能を発現できるため好ましい。
特許文献16には、副電解質として含酸素リチウム塩を添加する技術が開示されているが、含酸素リチウム塩を非水電解液に加えると電池使用時に副反応が進行し不可逆容量が大きくなっていくため集電体の保護には有効でも電池の特性として満足なものを得ることは困難であった。また、副電解質の適正な組み合わせや濃度については充分に検討されておらず、高容量、高出力を持つ自動車用途などの電池の過充電への対策としては不充分なものであった。
本発明者らは上記課題を解決すべく鋭意研究した結果、本発明のセパレータに特定の副電解質を特定量含有する電解液と組み合わせることで、耐過充電性をより一層、大幅に改善できることを見出した。これにより、モジュール電池の中に不良セルが混在して1個乃至少数の単セルにモジュール電池全体の数十Vの電圧が印加されるような過充電状態に至っても、短絡、爆発をより一層防止しうる、安全性の高い非水系電解液二次電池が提供できる。
フルオロリン酸リチウム、ジフルオロリン酸リチウム等のフルオロリン酸リチウム塩類;
ギ酸リチウム、酢酸リチウム、モノフルオロ酢酸リチウム、ジフルオロ酢酸リチウム、トリフルオロ酢酸リチウム等のカルボン酸リチウム塩類;
フルオロスルホン酸リチウム、メタンスルホン酸リチウム、モノフルオロメタンスルホン酸リチウム、ジフルオロメタンスルホン酸リチウム、トリフルオロメタンスルホン酸リチウム等のスルホン酸リチウム塩類;
LiN(FCO2)2、LiN(FCO)(FSO2)、LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2、リチウム環状1,2-パーフルオロエタンジスルホニルイミド、リチウム環状1,3-パーフルオロプロパンジスルホニルイミド、LiN(CF3SO2)(C4F9SO2)等のリチウムイミド塩類;
LiC(FSO2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3等のリチウムメチド塩類;
リチウムジフルオロオキサラトボレート等のリチウムオキサラトボレート塩類;
リチウムテトラフルオロオキサラトフォスフェート、リチウムジフルオロオキサラトフォスフェート等のリチウムオキサラトフォスフェート塩類;
その他、LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2等の含フッ素有機リチウム塩類;
等が挙げられる。
本発明の非水系電解液二次電池に使用される正極は、通常、正極活物質とバインダーを含有する活物質層を集電体上に形成させたものである。
正極集電体の表面電気抵抗は最も一般的に使用されるアルミニウム箔の場合、厚みによって異なるが、厚み1μm乃至100μmに対して6×10-3乃至6×10-5Ωである。セパレータ表面の導電層の表面電気抵抗をこれより大きくすることで、導電層が正極集電体として機能することを防止することができ、ジュール発熱によるセパレータの熱劣化を抑制することができる。
本発明の非水系電解液二次電池に使用される負極は、通常、負極活物質とバインダーを含有する活物質層を集電体上に形成させたものである。
本発明の非水系電解液二次電池の電池形状は特に制限されず、一般的に採用されている各種形状の中から、その用途に応じて適宜選択することができる。一般的に採用されている電池形状の例としては、シート電極及びセパレータをスパイラル状にしたシリンダータイプ、ペレット電極及びセパレータを組み合わせたインサイドアウト構造のシリンダータイプ、ペレット電極及びセパレータを積層したコインタイプ、シート電極及びセパレータを積層したラミネートタイプなどが挙げられる。
本発明の非水系電解液二次電池を組み立てる方法は特に制限されず、目的とする電池の形状に合わせて、通常用いられている各種方法の中から適宜選択することができる。例えば、少なくとも一方の表面に導電層を有する本発明のセパレータ、前述の非水系電解液、正極及び負極とを積層し、正負極間に非水系電解液を注入して、適切な形状に組み立てることにより製造される。更に、必要に応じて外装ケース等の他の構成要素を用いることも可能である。
本発明の非水系電解液二次電池の用途は特に限定されず、従来公知の各種の用途に用いることが可能である。具体例としては、ノートパソコン、ペン入力パソコン、モバイルパソコン、電子ブックプレーヤー、携帯電話、携帯ファックス、携帯コピー、携帯プリンター、ヘッドフォンステレオ、ビデオムービー、液晶テレビ、ハンディークリーナー、ポータブルCD、ミニディスク、トランシーバー、電子手帳、電卓、メモリーカード、携帯テープレコーダー、ラジオ、バックアップ電源、モーター、照明器具、玩具、ゲーム機器、時計、ストロボ、カメラ等の小型機器が挙げられるが、過充電下における高い安全性を有するという特長から、本発明の非水系電解液二次電池は特に電気自動車、ハイブリッド自動車等の大型機器への用途、即ち、EV用あるいはHEV用リチウム二次電池として好適である。
ダイアインスツルメンツ社(現三菱化学アナリテック社)製のロレスターEPおよびハイレスターUPを用いて表面電気抵抗を測定した。表面電気抵抗が106Ω以下の場合はロレスターEPとASPプローブ(補正係数4.2353)の組み合わせによる四探針法で、表面電気抵抗が106Ω以上の場合はハイレスターUPとUAプローブ(補正係数1.050)の組み合わせによる二探針法で測定を行った。
<導電層の見掛けの体積抵抗率>
表面抵抗率は三菱化学アナリテック社が公開するプローブごとの補正係数を用いて下式により求めた。
表面抵抗率=表面電気抵抗×補正係数
また、見掛けの体積抵抗率は下式により求めた。
見掛けの体積抵抗率=表面抵抗率×厚み
スパッタリング膜、蒸着膜の厚みは、KLA-Tencor社の段差・表面あらさ・微細形状測定装置P-15を使用して測定した。
塗布膜の厚みは、尾崎製作所のアプライトダイヤルゲージを使用して測定した。
本発明のセパレータを切り出し、30×30mmの矩形状の穴を開けた外寸60×60mmのアルミ板2枚で挟んで4辺を固定する。窓のついたオーブンに熱電対と共に入れて温度をモニターする。5℃/分の昇温速度でオーブン内温度を上げながらセパレータを目視観察してセパレータの表から裏へ貫通する穴の発生が認められた温度をメルトダウン温度とした。
<非水系電解液の調製>
乾燥アルゴン雰囲気下、エチレンカーボネートとエチルメチルカーボネートを体積比3/7混合した溶媒に、十分に乾燥したヘキサフルオロリン酸リチウム(LiPF6)を1.0mol/lの割合となるように溶解したものを非水系電解液とした。
正極活物質としてLiNi1/3Mn1/3Co1/3O2を用い、LiNi1/3Mn1/3Co1/3O290重量部にアセチレンブラック5重量部及びポリフッ化ビニリデン(呉羽化学社製商品名「KF-1000」)5重量部を加えて混合し、混合物をN-メチル-2-ピロリドンに分散させてスラリー状とした。得られたスラリーを正極集電体である厚さ15μmのアルミニウム箔の両面に均一に塗布して乾燥後、プレス機により厚さ81μmに圧延したものを、活物質層のサイズとして幅100mm、長さ100mm、及び幅30mmの未塗工部を有する形状に切り出して正極とした。正極活物質層の密度は2.35g/cm3であった。
負極活物質として天然黒鉛粉末を用い、天然黒鉛粉末98重量部に、増粘剤、バインダーとしてそれぞれ、カルボキシメチルセルロースナトリウムの水溶液(カルボキシメチルセルロースナトリウムの濃度1重量%)100重量部、及び、スチレン・ブタジエンゴムの水性ディスパージョン(スチレン・ブタジエンゴムの濃度50重量%)2重量部を加えて混合してスラリー状とした。得られたスラリーを負極集電体である厚さ10μmの圧延銅箔の両面に塗布して乾燥後、プレス機で厚さ75μmに圧延したものを、活物質層のサイズとして幅104mm、長さ104mm、及び幅30mmの未塗工部を有する形状に切り出し、負極とした。負極活物質層の密度は1.35g/cm3であった。
厚み25μm、突き刺し強度380g、空隙率39%の、市販の三層セパレータ(ポリプロピレン/ポリエチレン/ポリプロピレン)を基材としてその一方の表面にAlスパッタリング処理を行って導電層を設けた。Al層の厚みは25nmであり、表面電気抵抗は26Ωであった。また、Al層を形成したセパレータの突き刺し強度は350g、空隙率は39%であった。
正極32枚と負極33枚を交互となるように配置し、各電極の間に上述のセパレータがAlスパッタリング層が正極に対向して挟まれるよう積層した。この際、正極の正極活物質面が負極の負極活物質面内から外れないよう両活物質層面が互いに対面するように位置させた。この正極と負極それぞれについての未塗工部同士を束ねスポット溶接して集電タブを作製し、電極群としたものを、アルミニウム製の電池缶(外寸:120×110×10mm)に封入した。電池缶としては蓋部分に正極及び負極の集電端子、圧力放出弁、非水系電解液の注入口を備えた電池缶を用いた。集電タブと集電端子はスポット溶接により接続した。その後、電極群を装填した電池缶に非水系電解液を20mL注入して、電極に充分浸透させ、注入口を密閉して電池を作製した。
充放電サイクルを経ていない新たな電池に対して、25℃で電圧範囲4.1~3.0V、電流値0.2C(1時間率の放電容量による定格容量を1時間で放電する電流値を1Cとする、以下同様)にて5サイクル初期充放電を行った。
続いて同じく25℃環境下で過充電試験を行った。放電状態(3V)から3Cの定電流で充電を行い、その挙動を観測した。ここで、「弁作動」は、ガス排出弁が作動し非水系電解液成分が放出される現象を表し、「破裂」は、電池容器が猛烈な勢いで破れ,内容物が強制的に放出される現象を表す。
過充電試験の結果を表1に示す。
実施例1で用いたと同様の厚み25μmの市販の三層セパレータを基材として、その一方の表面にMoスパッタリング処理を行って導電層を設けた。Mo層の厚みは147nmであり、表面電気抵抗は11Ωであった。また、セパレータの突き刺し強度は310g、空隙率は38%であった。
得られたセパレータを用いて実施例1と同様に電池を作成して過充電試験を行った。
結果を表1に示す。
実施例2で得られたセパレータを、その導電層を負極に対向させる以外は実施例2と同様に電池を作成して過充電試験を行った。
結果を表1に示す。
実施例1で用いたと同様の厚み25μmの市販の三層セパレータを基材として、その両方の表面にMoスパッタリング処理を行って導電層を設けた。Mo層の厚みは両層とも147nmであり、表面電気抵抗は共に11Ωであった。また、セパレータの突き刺し強度は280g、空隙率は36%であった。得られたセパレータを用いて実施例1と同様に電池を作成して過充電試験を行った。結果を表1に示す。
実施例1で用いたと同様の厚み25μmの市販の三層セパレータを基材として、その一方の表面に黒鉛を蒸着して導電層を設けた。黒鉛層の厚みは5nmであり、表面電気抵抗は2×107Ωであった。また、突き刺し強度は350g、空隙率は39%であった。
得られたセパレータを用いて実施例1と同様に電池を作成して過充電試験を行った。
結果を表1に示す。
電気化学工業社製アセチレンブラック「デンカブラックHS-100」15重量部、及びポリビニルアルコール(平均重合度1700、ケン化度99%以上)2.7重量部と水82.3重量部を均一に分散させてスラリーを調製し、このスラリーを、実施例1で用いたと同様の厚み25μmの市販の三層セパレータの一方の表面に塗布した後、60℃で乾燥して、厚さ4.5μmの導電層を設けた。この導電層の表面電気抵抗は664Ωであった。また、セパレータの突き刺し強度は380g、空隙率は39%であった。
得られたセパレータを用いて実施例1と同様に電池を作成して過充電試験を行った。
結果を表1に示す。
実施例1で用いたと同様の市販の三層セパレータ(ポリプロピレン/ポリエチレン/ポリプロピレン)をそのまま用いて実施例1と同様に電池を作成して過充電試験を行った。
結果を表1に示す。
実施例4で用いた黒鉛15重量部、及びポリビニルアルコール(平均重合度1700、ケン化度99%以上)0.85重量部と水84.15重量部を均一に分散させてスラリーを調製し、このスラリーを、厚み20μm、ガーレー透気度400秒/100ccの市販の三層セパレータの一方の表面に塗布した後、60℃で乾燥して、厚さ4.5μmの導電層を設けた。この導電層の表面電気抵抗は0.9Ωであった。また、セパレータの突き刺し強度は350g、空隙率は39%、ガーレー透気度は435秒/100ccであり透気度の増加率は8.8%であった。
厚みを6μmにする以外は実施例1と同様にして、厚み20μm、ガーレー透気度400秒/100ccの市販の三層セパレータの一方の表面に導電層を形成した。この導電層の表面電気抵抗は0.6Ωであった。また、セパレータの突き刺し強度は350g、空隙率は39%、ガーレー透気度は450秒/100ccであり透気度の増加率は12.5%であった。
過充電試験における放電状態(3V)からの定電流充電速度を5Cとする以外は実施例1と同様にして電池の作成と過充電試験を行った。結果を表1に示す。
電気化学工業社製アセチレンブラック「デンカブラックHS-100」15重量部、及びポリビニルアルコール(平均重合度1700、ケン化度99%以上)2.7重量部と水82.3重量部を均一に分散させてスラリーを調製し、このスラリーを、厚み9μmの市販のポリエチレンセパレータの一方の表面に塗布した後、60℃で乾燥して、厚さ3μmの導電層を設けた。この導電層の表面電気抵抗は1.1×103Ωであった。導電層をはさむ形で、得られたセパレータと厚み9μmの市販のポリエチレンセパレータを積層して一体として内部に導電層を有するセパレータを作成した。このセパレータを用いて実施例1と同様に電池を作成して過充電試験を行った。結果を表1に示す。
厚み9μmの市販のポリエチレンセパレータを2枚積層して一体とした。このセパレータを用いて実施例1と同様に電池を作成して過充電試験を行った。結果を表1に示す。
実施例1で作成した電解液、正極、負極、およびセパレータを使用して導電層を正極に対向させ、18650型円筒電池を作成した後、25℃で電圧範囲4.1~3.0V 、電流値0.2Cにて5サイクル初期充放電を行った。次にこの電池を60℃の環境下で電圧範囲4.1~3.0V 、電流値2Cにて350サイクルの充放電を行った。初期放電容量に対する350サイクル終了時の放電容量維持率は75%であった。
実施例1における基材として用いた市販の三層セパレータ(ポリプロピレン/ポリエチレン/ポリプロピレン)を用いた以外は実施例6と同様にして18650円筒電池を作成してサイクル試験を行った。初期放電容量に対する350サイクル終了時の放電容量維持率は65%であった。
実施例5で作成した黒鉛蒸着セパレータを正極対向とした以外は実施例10と同様にして18650円筒電池を作成して25℃で電圧範囲4.1~3.0V 、電流値0.2Cにて5サイクル初期充放電を行った。次にこの電池を60℃の環境下で4.3Vまで電流値0.2Cで充電を行った後、そのまま4.3Vに電圧を保ったまま2週間保存して、その後3.0Vまで放電を行い、電池を解体してセパレータの観察を行った。セパレータに変色等は認められず変化はなかった。
実施例1における基材として用いた市販の三層セパレータ(ポリプロピレン/ポリエチレン/ポリプロピレン)を用いた以外は実施例7と同様にして18650円筒電池を作成して保存試験を行った。実施例7と同様に電池を解体してセパレータを観察したところ、セパレータは変色、劣化していた。
乾燥アルゴン雰囲気下、エチレンカーボネートとエチルメチルカーボネートを体積比で3/7で混合した溶媒に、Li塩として十分に乾燥したLiPF6を1.0モル/リットル、LiBF4を0.2モル/リットルの割合となるように溶解したものを非水系電解液とした以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
乾燥アルゴン雰囲気下、エチレンカーボネートとエチルメチルカーボネートを体積比で3/7で混合した溶媒に、Li塩として十分に乾燥したLiPF6を1.0モル/リットル、LiBF4を0.01モル/リットルの割合となるように溶解して非水系電解液とした以外は実施例1と同様にして、電池を作成して過充電試験を行った。結果を表2に示す。
実施例12で得た電解液と実施例2で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
実施例13で得た電解液と実施例2で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
実施例2で得たセパレータの導電層を負極に対向させる以外は実施例14と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
実施例12で得た電解液を用いる以外は実施例4と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
実施例12で得た電解液と実施例5で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
実施例13で得た電解液と実施例5で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
実施例12で得た電解液と実施例6で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
実施例13で得た電解液と実施例6で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表2に示す。
乾燥アルゴン雰囲気下、エチレンカーボネートとエチルメチルカーボネートを体積比で3/7で混合した溶媒に、Li塩として十分に乾燥したLiPF6を1.0モル/リットル、LiFSIを0.1モル/リットルの割合となるように溶解して非水系電解液とした以外は実施例5と同様にして、電池を作成して過充電試験を行った。結果を表2に示す。
[実施例23]
乾燥アルゴン雰囲気下、エチレンカーボネートとエチルメチルカーボネートを体積比で3/7で混合した溶媒に、Li塩として十分に乾燥したLiPF6を1.0モル/リットル、LiTFSIを0.1モル/リットルの割合となるように溶解して非水系電解液とした以外は実施例5と同様にして、電池を作成して過充電試験を行った。結果を表2に示す。
実施例12と同様にして電池を作成した。充放電サイクルを経ていない新たな電池に対して、25℃で電圧範囲4.1~3.0V、電流値0.2C(1時間率の放電容量による定格容量を1時間で放電する電流値を1Cとする、以下同様)にて5サイクル初期充放電を行った。
続いて同じく25℃環境下で以下の手順による過充電試験を行った。初期充放電を行った10個の電池を直列に接続してなる電池モジュールを作成し、仮想的な不良電池モジュールとして他の電池よりも容量が低い電池を1個混在させる。電池が満充電状態(各電池の開放端電圧4.1V、想定される電池モジュールの開放端電圧は41V)から電流値5Cで定電流充電を行い、その挙動を観測した。電池モジュールには50Vの電圧が印加されたが容量の低い電池の開弁しか発生しなかった。
比較例1と同様にして作成した電池を使用した以外は実施例24と同様にして過充電試験を行った。電池モジュールには50Vの電圧が印加され、容量の低い電池が開弁後に破裂した。
溶媒をエチレンカーボネートとエチルメチルカーボネートとトリフルオロエチルメチルカーボネート(以下、以下、TFEMC)を体積比で3/6/1で混合したものにした以外は実施例1と同様に電池を作成して過充電評価を行った。結果を表3に示す。
溶媒をエチレンカーボネートとエチルメチルカーボネートとエチルトリフルオロエチルカーボネート(以下、ETFEC)を体積比で3/6/1で混合したものにした以外は実施例1と同様に電池を作成して過充電評価を行った。結果を表3に示す。
実施例25で得た電解液と実施例2で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
実施例26で得た電解液と実施例2で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
実施例2で得たセパレータの導電層を負極に対向させる以外は実施例25と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
実施例25で得た電解液を用いる以外は実施例4と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
実施例25で得た電解液と実施例5で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
実施例26で得た電解液と実施例5で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
実施例25で得た電解液と実施例6で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
実施例26で得た電解液と実施例6で得たセパレータを用いた以外は実施例1と同様にして電池を作成して過充電試験を行った。結果を表3に示す。
溶媒をエチレンカーボネートとエチルメチルカーボネートとシス-4,5-ジフルオロ-4,5-ジメチルエチレンカーボネート(以下、A3t)を体積比で2/7/1で混合したものにした以外は実施例5と同様に電池を作成して過充電評価を行った。結果を表3に示す。
溶媒をエチレンカーボネートとエチルメチルカーボネートとシス-4,5-ジフルオロエチレンカーボネート(以下、c-DFEC)を体積比で2/7/1で混合したものにした以外は実施例5と同様に電池を作成して過充電評価を行った。結果を表3に示す。
溶媒をエチレンカーボネートとエチルメチルカーボネートとトランス-4,5-ジフルオロエチレンカーボネート(以下、t-DFEC)を体積比で2/7/1で混合したものにした以外は実施例5と同様に電池を作成して過充電評価を行った。結果を表3に示す。
実施例25と同様にして電池を作成した。充放電サイクルを経ていない新たな電池に対して、25℃で電圧範囲4.1~3.0V、電流値0.2C(1時間率の放電容量による定格容量を1時間で放電する電流値を1Cとする、以下同様)にて5サイクル初期充放電を行った。
続いて同じく25℃環境下で以下の手順による過充電試験を行った。初期充放電を行った10個の電池を直列に接続してなる電池モジュールを作成し、仮想的な不良電池モジュールとして他の電池よりも容量が低い電池を1個混在させる。電池が満充電状態(各電池の開放端電圧4.1V、想定される電池モジュールの開放端電圧は41V)から電流値5Cで定電流充電を行い、その挙動を観測した。電池モジュールには50Vの電圧が印加されたが容量の低い電池の開弁しか発生しなかった。
電気化学工業社製アセチレンブラック「デンカブラックHS-100」6.6重量部、ポリビニルアルコール(平均重合度1700、ケン化度99%以上)1.3重量部、アルミナ粒子(粒径0.2μm、アスペクト比1.1)23.4重量部、水68.7重量部を均一に分散させてスラリーを調製し、厚み25μm、突き刺し強度380g、空隙率39%の、市販の三層セパレータ(ポリプロピレン/ポリエチレン/ポリプロピレン)を基材としてその一方の表面に塗布した後、60℃で乾燥して、厚さ4.8μmの耐熱導電層を設けた。この導電層の表面電気抵抗は1.7×104Ωであった。また、セパレータの突き刺し強度は380g、空隙率は39%、メルトダウン温度は190℃であった。このセパレータを用いた以外は実施例1と同様に電池を作成して過充電評価を行った。結果を表4に示す。
ポリメタフェニレンイソフタルアミドをN,N-ジメチルアセトアミドに溶解させて10重量%の溶液を作成して紡糸溶液とした。実施例1で使用した市販の三層セパレータを基材として、電圧は17kV、コレクターまでの距離を20cm、ノズル内径0.59mmとして、コレクター上に該三層セパレータを固定してエレクトロスピニング法によりポリメタフェニレンイソフタルアミドのナノファイバーを積層した。ナノファイバーの積層はセパレータの両面に行い、それぞれ2μmの厚みとなるまで積層を行った。次に電気化学工業社製アセチレンブラック「デンカブラックHS-100」15重量部、及びポリビニルアルコール(平均重合度1700、ケン化度99%以上)2.7重量部と水82.3重量部を均一に分散させてスラリーを調製し、このスラリーを、ポリメタフェニレンイソフタルアミドのナノファイバーを積層した前述のセパレータの一方の表面に塗布した後、60℃で乾燥して、厚さ4μmの導電層を設けた。この導電層の表面電気抵抗は712Ωであった。また、セパレータの突き刺し強度は380g、空隙率は41%、メルトダウン温度は220℃であった。得られたセパレータを用いた以外は実施例1と同様に電池を作成して過充電試験を行った。結果を表4に示す。
組成1:ポリ-4メチルペンテン-1を80重量%、パラフィンワックス20重量%の混合物
組成2:分子量100万の超高分子量PE30重量%、パラフィンワックス70重量%の混合物
組成1の混合物と組成2の混合物を溶融混練およびシート成形を行い、組成1/組成2/組成1の構成で厚み比2/6/2、厚み200μmの多層シートを作成した。次に二軸延伸機を用いて温度130℃、4×4の延伸倍率で該多層シートの二軸延伸を行った。次に延伸シートを4辺固定した状態で温度60℃の2-プロパノールに30分浸漬してパラフィンワックスを抽出した後、2-プロパノールを60℃で乾燥除去して取り除き多孔質フィルムを得た。該フィルムは厚み20μm、突き刺し強度は400g、空隙率50%、メルトダウン温度は230℃であった。該フィルムの一方の表面にAlスパッタリング処理を行って導電層を設けた。Al層の厚みは30nmであり、表面電気抵抗は20Ωであった。また、Al層を形成したセパレータの突き刺し強度は360g、空隙率は50%、メルトダウン温度は230℃であった。得られたセパレータを用いた以外は実施例1と同様に電池を作成して過充電試験を行った。結果を表4に示す。
ポリビニルアルコール(平均重合度1700、ケン化度99%以上)1.3重量部、アルミナ粒子(粒径0.2μm、アスペクト比1.1)25.1重量部、水73.6重量部を均一に分散させてスラリーを調製し、厚み25μm、突き刺し強度380g、空隙率39%の、市販の三層セパレータ(ポリプロピレン/ポリエチレン/ポリプロピレン)を基材としてその一方の表面に塗布した後、60℃で乾燥して、厚さ3.9μmの耐熱層を設けた。このセパレータの突き刺し強度は380g、空隙率は39%、メルトダウン温度は188℃であった。このセパレータを用いた以外は実施例1と同様に電池を作成して過充電試験を行った。結果を表4に示す。
ポリメタフェニレンイソフタルアミドをN,N-ジメチルアセトアミドに溶解させて10重量%の溶液を作成して紡糸溶液とした。実施例1で使用した市販の三層セパレータを基材として、電圧は17kV、コレクターまでの距離を20cm、ノズル内径0.59mmとして、コレクター上に該三層セパレータを固定してエレクトロスピニング法によりポリメタフェニレンイソフタルアミドのナノファイバーを積層した。ナノファイバーの積層はセパレータの両面に行い、それぞれ2μmの厚みとなるまで積層を行った。得られたセパレータの突き刺し強度は380g、空隙率は41%、メルトダウン温度は220℃であった。このセパレータを用いた以外は実施例1と同様に電池を作成して過充電試験を行った。結果を表4に示す。
実施例39と同様にして電池を作成した。充放電サイクルを経ていない新たな電池に対して、25℃で電圧範囲4.1~3.0V、電流値0.2C(1時間率の放電容量による定格容量を1時間で放電する電流値を1Cとする、以下同様)にて5サイクル初期充放電を行った。
続いて同じく25℃環境下で以下の手順による過充電試験を行った。初期充放電を行った10個の電池を直列に接続してなる電池モジュールを作成し、仮想的な不良電池モジュールとして他の電池よりも容量が低い電池を1個混在させる。電池が満充電状態(各電池の開放端電圧4.1V、想定される電池モジュールの開放端電圧は41V)から電流値5Cで定電流充電を行い、その挙動を観測した。電池モジュールには50Vの電圧が印加されたが容量の低い電池の開弁しか発生しなかった。
比較例7と同様にして作成した電池を使用した以外は実施例42と同様にして過充電試験を行った。電池モジュールには50Vの電圧が印加され、容量の低い電池が開弁後に破裂した。
Claims (23)
- リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池に用いられるセパレータであって、該セパレータが導電層を有し、該導電層の見掛け体積抵抗率が1×10-4Ω・cm乃至1×106Ω・cmであり、かつ該導電層の膜厚が5μm未満である非水系電解液二次電池用セパレータ。
- リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池に用いられるセパレータであって、該セパレータが導電層を有し、該導電層の体積抵抗率が1×10-6Ω・cm乃至1×106 Ω・cmであり、かつ該導電層の膜厚が5μm未満である非水系電解液二次電池用セパレータ。
- リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池に用いられるセパレータであって、該セパレータが導電層を有し、該導電層の表面電気抵抗が1×10-2Ω乃至1×109Ωであり、かつ該導電層の膜厚が5μm未満である非水系電解液二次電池用セパレータ。
- 前記セパレータのメルトダウン温度が170℃以上である請求項1乃至3の何れか1項に記載の非水系電解液二次電池用セパレータ。
- 前記セパレータの突き刺し強度が250g以上800g以下である請求項1乃至4の何れか1項に記載の非水系電解液二次電池用セパレータ。
- 前記導電層がセパレータの少なくとも一方の表面に設けられている請求項1乃至5の何れか1項に記載の非水系電解液二次電池用セパレータ。
- 前記導電層が金属元素及び炭素質材料のうち少なくとも一方を含有する請求項1乃至6の何れか1項に記載の非水系電解液二次電池用セパレータ。
- 前記金属元素が、アルミニウム、モリブデン、銅、及びチタンよりなる群から選ばれる少なくとも1種である請求項7に記載の非水系電解液二次電池用セパレータ。
- 前記炭素質材料が、黒鉛、カーボンブラック、及び無定形炭素微粒子よりなる群から選ばれる少なくとも1種である請求項7に記載の非水系電解液二次電池用セパレータ。
- 前記セパレータが耐熱層を有しており、該耐熱層が融点またはガラス転移温度が170℃以上の樹脂を含有する請求項1乃至9の何れか1項に記載の非水系電解液二次電池用セパレータ。
- 前記耐熱層が無機フィラーを含有する請求項10に記載の非水系電解液二次電池用セパレータ。
- 前記耐熱層がポリメチルペンテン、ポリアミド、ポリイミド、及びポリアミドイミドからなる群から選ばれる少なくとも1つの樹脂を含有する請求項10または11に記載の非水系電解液二次電池用セパレータ。
- 前記無機フィラーが酸化アルミニウム、酸化マグネシウム、酸化チタン、及び硫酸バリウムからなる群から選ばれる少なくとも1つである請求項11に記載の非水系電解液二次電池用セパレータ。
- リチウムを吸蔵・放出することが可能な正極及び負極と、セパレータと、非水系溶媒及び電解質を含む非水系電解液とを備える非水系電解液二次電池であって、該セパレータが請求項1乃至13の何れか1項に記載の非水系電解液二次電池用セパレータである非水系電解液二次電池。
- 前記正極が、NiMnCo合金を含有する請求項14に記載の非水系電解液二次電池。
- 前記非水系電解液が、フッ素化カーボネートを含有するものである請求項14または15に記載の非水系電解液二次電池。
- 前記フッ素化カーボネートが、一般式C=O(OR1)(OR2)で表されるものである請求項16に記載の非水系電解液二次電池。
(前記一般式中、R1及びR2は、それぞれ炭素数1または2のアルキル基であり、R1及びR2のうち少なくとも1方が1個以上のフッ素原子を有する) - 前記フッ素化カーボネートが、エチレンカーボネートを構成する水素原子のうち1個または2個をフッ素原子及びフッ素化アルキル基のうち少なくとも一方で置換したものである請求項16に記載の非水系電解液二次電池。
- 前記フッ素化カーボネートの含有量が、電解液中の体積割合として20%以下である、請求項16乃至18の何れか1項に記載の非水系電解液二次電池。
- 前記電解質が、LiPF6を含有し、かつその電解液中の濃度が0.5モル/リットル以上2モル/リットル以下である、請求項14乃至19の何れか1項に記載の非水系電解液二次電池。
- 前記非水系電解液が、副電解質として更に、ホウ酸リチウム塩類、リン酸リチウム塩類、フルオロリン酸リチウム塩類、カルボン酸リチウム塩類、スルホン酸リチウム塩類、リチウムイミド塩類、リチウムオキサラトボレート塩類、リチウムオキサラトフォスフェート塩類及びリチウムメチド塩類からなる群から選ばれる少なくとも一種の化合物を含有し、全副電解質の電解液中の濃度が0.01モル/リットル以上0.3モル/リットル以下である、請求項14乃至20の何れか1項に記載の非水系電解液二次電池。
- 前記副電解質が、テトラフルオロホウ酸リチウム、ビス(フルオロスルホニル)イミド、及びリチウムビス(トリフルオロスルホニル)イミドリチウムからなる群より選ばれる少なくとも1種の化合物である請求項21に記載の非水系電解液二次電池。
- 請求項14乃至22の何れか1項に記載の非水系電解液二次電池を5個以上直列に連結して有し、満充電に20V以上の電圧を必要とする非水系電解液二次電池モジュール。
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PCT/JP2010/063941 WO2011021644A1 (ja) | 2009-08-19 | 2010-08-18 | 非水系電解液二次電池用セパレータ及び非水系電解液二次電池 |
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US (1) | US20120208070A1 (ja) |
EP (1) | EP2469624A1 (ja) |
JP (1) | JP5640546B2 (ja) |
KR (1) | KR20120062713A (ja) |
CN (1) | CN102498590A (ja) |
WO (1) | WO2011021644A1 (ja) |
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WO2019194094A1 (ja) * | 2018-04-06 | 2019-10-10 | 株式会社大阪ソーダ | 蓄電デバイス用セパレータ、蓄電デバイスおよびそれらの製造方法 |
JPWO2019194094A1 (ja) * | 2018-04-06 | 2021-04-22 | 株式会社大阪ソーダ | 蓄電デバイス用セパレータ、蓄電デバイスおよびそれらの製造方法 |
JP7359137B2 (ja) | 2018-04-06 | 2023-10-11 | 株式会社大阪ソーダ | 蓄電デバイス用セパレータ、蓄電デバイスおよびそれらの製造方法 |
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EP2469624A1 (en) | 2012-06-27 |
JP2011065984A (ja) | 2011-03-31 |
US20120208070A1 (en) | 2012-08-16 |
CN102498590A (zh) | 2012-06-13 |
JP5640546B2 (ja) | 2014-12-17 |
KR20120062713A (ko) | 2012-06-14 |
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