WO2005057690A1 - 非水系電解液二次電池 - Google Patents
非水系電解液二次電池 Download PDFInfo
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- WO2005057690A1 WO2005057690A1 PCT/JP2004/018985 JP2004018985W WO2005057690A1 WO 2005057690 A1 WO2005057690 A1 WO 2005057690A1 JP 2004018985 W JP2004018985 W JP 2004018985W WO 2005057690 A1 WO2005057690 A1 WO 2005057690A1
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- secondary battery
- aqueous electrolyte
- active material
- separator
- battery
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0568—Liquid materials characterised by the solutes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0569—Liquid materials characterised by the solvents
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
- H01M2300/0037—Mixture of solvents
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a non-aqueous electrolyte secondary battery, and more specifically, comprises a negative electrode and a positive electrode capable of inserting and extracting lithium, a separator, and a non-aqueous electrolyte containing a non-aqueous solvent and a lithium salt.
- the present invention relates to a non-aqueous electrolyte secondary battery comprising a high capacity and excellent cycle characteristics.
- the battery has excellent rate characteristics in a low-temperature environment, has a small amount of gas generated during repeated charging and discharging, and ensures the safety of the battery during overcharging without impairing the high-temperature storage characteristics.
- An excellent non-aqueous electrolyte secondary battery that can be provided.
- the present invention relates to the above-mentioned non-aqueous electrolyte secondary battery, which has a stable and good load characteristic, and a so-called trickle charge used for compensating for a decrease in capacity due to self-discharge of a battery such as a personal computer.
- the present invention relates to a non-aqueous electrolyte secondary battery capable of preventing deterioration due to heat. Background technology>
- Lithium secondary batteries which are high-density and lightweight non-aqueous electrolyte secondary batteries, are being used in a wide range of fields as electric appliances become lighter and smaller.
- Lithium secondary batteries generally have a positive electrode in which an active material layer containing a positive electrode active material such as a lithium compound represented by lithium cobalt oxide is formed on a current collector, and a lithium storage represented by graphite or the like.
- a negative electrode active material layer is formed on the current collector containing a negative electrode active material, such as release available carbon materials, non-aqueous electrolyte conventional non pro tons of such lithium salts such as L i PF 6 It is mainly composed of a non-aqueous electrolyte dissolved in a solvent and a separator composed of a polymer porous membrane.
- Patent Document 1 discloses that a negative electrode active material such as flaky graphite is squared by a mechanochemical action to increase the active material. It is described that high capacity is achieved by filling at a high density.
- Patent Document 2 discloses that a secondary particle is a spherical or elliptical lithium nickel cobaltate positive electrode active material particle, which improves heavy load characteristics and low-temperature high-rate discharge characteristics.
- Separators used in lithium secondary batteries are required to satisfy requirements such as not obstructing ionic conduction between the two electrodes, capable of holding an electrolyte, and having resistance to the electrolyte.
- a polymer porous membrane mainly made of a thermoplastic resin such as polyethylene or polypropylene is used.
- the following method is known as a known technique.
- Patent Document 4 A stretching method in which a crystalline polymer material is molded, and then a structurally weak amorphous portion is selectively extended to form micropores.
- the extraction method (1) needs to treat a large amount of waste liquid, and has problems in both environment and economy. Further, it is difficult to obtain a uniform film due to shrinkage of the film generated in the extraction step, and there is a problem in productivity such as yield.
- the elongation method of (2) requires a long heat treatment to control the pore size distribution by controlling the structure of the crystalline phase and the amorphous phase before elongation, and thus has a problem in productivity.
- the interfacial peeling method (3) has no waste liquid and is excellent in terms of both environment and economy.
- the interface between the polymer material and the filler can be easily separated by a stretching operation, a porous membrane can be obtained without the need for a pretreatment such as heat treatment, and the productivity is also excellent. It is a technique.
- separators containing fillers have poor adhesion to the electrodes due to the presence of the filler protruding from the surface, causing non-uniform resistance between the electrodes due to non-uniform inter-electrode distance, and the use of lithium dendrites, etc. It is common sense to think that it is easy to occur and it is inferior in safety. For this reason, there has been no example in which the separator including the filler produced by the method (3) has been put to practical use.
- Patent Document 1 only the separator is simply described in the [004] paragraph, and in Patent Document 2, the polypropylene is made of polypropylene in the [004] paragraph, It is only described as a microporous film made of polyethylene or a copolymer / nonwoven fabric. These microporous polyolefin separators are generally manufactured industrially by the extraction method (1) or the stretching method (2). Moreover, Patent Documents 1 and 2 do not mention at all the influence of the separator when the specific active material as described above is used.
- This side reaction is a reaction in which the electrolytic solution and the electrode mixture composition (the active material and the binder further contain a conductive agent as necessary) are electrochemically decomposed to produce organic and inorganic substances.
- the by-products accumulate on the surface of the separator or inside the pores of the separator from the electrode surface, causing clogging and reducing the diffusion of lithium ions. As a result, the internal resistance of the battery increases, The cycle characteristics tend to deteriorate.
- an object of the present invention is to improve the cycle characteristics of a high-capacity secondary battery in which an active material is densely filled with a particulate active material having a small aspect ratio.
- a porous membrane made of a thermoplastic resin containing an inorganic filler is used as a separator. It has been found that the cycle characteristics can be improved by combining the above, and the present invention has been completed.
- the present invention has the following configurations.
- a non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of inserting and extracting lithium, a separator, and a non-aqueous electrolyte containing a non-aqueous solvent and a lithium salt.
- the separator has a porous film made of a thermoplastic resin containing an inorganic filler, and the active material contained in the negative electrode is a particulate active material having an aspect ratio of 1.02 or more and 3 or less.
- a non-aqueous electrolyte secondary battery wherein the active material contained in the positive electrode satisfies at least one of a particulate active material having an aspect ratio of 1.02 or more and 2.2 or less.
- the tap density of the positive electrode active material is 1.4 g / cm 3 or more.
- the separator has a thickness of 5 pm or more and 10 ⁇ m or less and a porosity of 30% or more. 80% or less, average pore size defined by ASTM F 3 16-86 is 0.05 ⁇ m or more ⁇ ⁇ or less, Gurley air permeability defined by JISP 8 117 is 20 seconds / .100 cc or more 700 seconds / A non-aqueous electrolyte secondary battery having a flow rate of 100 cc or less and an average rate of change in liquid retention of 15% or less.
- the details of the mechanism of improving the cycle characteristics by combining a specific separator with a secondary battery using a particulate active material having a small aspect ratio are not clear, but are as follows. Is estimated.
- the cycle characteristics are reduced due to high-density filling of the particulate active material with a small aspect ratio. Clogging of the pores of the separator by side reaction products generated by It is also considered that the uneven distribution of the electrolyte and the increase in the internal resistance of the battery due to the expansion and contraction of the active material.
- Patent Literature 1 does not discuss a separator at all, and Patent Literature 2 uses a microporous film obtained by an extraction method or a stretching method as a separator.
- Patent Literature 2 uses a microporous film obtained by an extraction method or a stretching method as a separator.
- it is difficult to increase the pore diameter as described later, and clogging by side reaction products is likely to occur.
- the rate of change in the amount of liquid retained is large, and the ability to retain the electrolyte in the separator is low.
- adhesion between the electrode surface and the separator surface is caused by the by-products, and the active material expands and contracts due to the charge-discharge reaction. This reduced the interparticle coupling, increased the internal resistance of the battery, and reduced the cycle characteristics.
- the separator containing the inorganic filler used in the present invention can easily make the pore size sufficiently larger than those obtained by the extraction method or the stretching method, and the size of the separator due to the by-products is small. Less likely to clog. In addition, since the liquid retaining property is good, uneven distribution of the electrolytic solution can be prevented.
- the reason why the separator used in the present invention is excellent in liquid retaining properties is considered as follows. That is, the movement of the electrolyte in the separator can be regarded as a so-called capillary flow in which the liquid permeates through the fine pores. In capillary flow, the smaller the pore size, the longer the permeation distance is, so the liquid is likely to penetrate.However, when the liquid comes out due to external pressure, etc., the liquid retention is low due to the ease of permeation. it is conceivable that.
- the separator containing the filler used in the present invention has a larger pore diameter than the separator used in Patent Document 2 manufactured by the methods (1) and (2), and has a liquid permeable property.
- the inclusion of the filler increases the dielectric constant of the entire separator, thereby improving the chemical affinity between the filler and the electrolyte due to the interaction with the electrolyte, which is a polar solvent. This may have the effect of increasing the ability of the separator to hold the electrolytic solution.
- the separator used in the present invention is characterized by unevenness on the separator surface formed by the presence of the filler. Therefore, since a gap is formed between the electrode plate and the separator in the battery, it is possible to hold a larger amount of the electrolyte in the gap, thereby preventing uneven distribution and lack of the electrolyte. It is considered.
- the separator used in the present invention has an effect of the inorganic filler partially exposed on the surface, which alleviates the adhesive action of the by-products, and the repetitive action of the expansion / contraction movement of the active material accompanying the charge / discharge reaction.
- the separator used in the present invention has an effect of the inorganic filler partially exposed on the surface, which alleviates the adhesive action of the by-products, and the repetitive action of the expansion / contraction movement of the active material accompanying the charge / discharge reaction.
- Patent Document 2 also uses such a porous film containing no filler as a separator. A separator made of such a microporous film cannot achieve the physical properties of the separator of the present invention, and cannot obtain the effects of the present invention.
- the above-described action mechanism has excellent effects. Obtainable.
- the non-aqueous electrolyte secondary battery further has a configuration selected from the following 1 to 4.
- Non-aqueous electrolyte contains film-forming agent
- a non-aqueous electrolyte secondary battery characterized in that the non-aqueous electrolyte contains at least one kind of a chain carbonate represented by the following general formula (I).
- R represents a methyl group or an ethyl group.
- the non-aqueous electrolyte contains an aromatic compound with a heat build-up of 1.5 or more
- the water content in the battery must be 200 to 500 ppm as the concentration in the electrolyte in the battery.
- the film-forming agent is at least one selected from the group consisting of a carbonate having an ethylenically unsaturated bond and a carboxylic anhydride.
- Non-aqueous electrolyte secondary battery characterized by the following.
- the details of the mechanism of action by combining with a non-aqueous electrolyte containing a film forming agent are not clear, but are presumed as follows.
- a passivation film is formed on the negative electrode surface to prevent decomposition of the non-aqueous electrolyte, thereby improving the cycle characteristics of the secondary battery.
- the remarkable increase in the resistance inside the battery at a low temperature due to the film on the negative electrode surface formed by this film forming agent is considered to be the cause of the deterioration of the rate characteristics.
- the use of a film-forming agent effective for improving the cycle characteristics of a secondary battery, a combination of a specific separator, and the effect of reducing the internal resistance of the battery of the separator result in the battery caused by the film-forming agent. This offsets the increase in the internal resistance and maintains the rate characteristics in a low-temperature environment.
- the separator used in the present invention is effective in reducing the internal resistance of the battery is as follows. That is, among the above-mentioned methods (1) to (3) for producing the separator, the extraction method (1) requires the selection of a plasticizer having good compatibility with the polymer material. However, there is a drawback that a sufficiently large hole cannot be formed even when the film is stretched, and the electrical resistance of the obtained separator increases. Further, a method of adding a plasticizer having poor compatibility to increase the pore size is also known as a known technique. However, in this method, molding becomes unstable and it is difficult to obtain a film having good properties. Either method requires a large amount of waste liquid to be treated in the extraction step, and is not economically preferable.
- a multi-layer made of a thermoplastic resin containing an inorganic filler used in the present invention As described later, a separator made of a porous membrane can be easily produced as a porous membrane having a relatively large pore diameter, for example, by an interfacial peeling method. The separator having such a large hole diameter has high continuity of the holes, and is effective in lowering the internal resistance of the battery.
- Patent Document 7 describes that a non-aqueous electrolyte containing vinylene carbonate is used.
- a passivation layer is formed on the surface of the negative electrode by reduction of vinylene carbonate, and this layer constitutes a physical barrier that prevents decomposition of the electrolyte.
- the effect of the vinylene carbonate is intended to improve the charge / discharge efficiency and cycle characteristics of the battery.
- Non-Patent Document 1 the technology of Patent Document 7 is characterized in that the discharge capacity (hereinafter referred to as “rate characteristics”) when performing a large current discharge in a low-temperature environment is reduced. There was a problem. This is also proved in Comparative Examples 2-1 and 2-2 described later. This is thought to be because the passive resistance formed on the negative electrode surface significantly increased the internal resistance of the battery, especially at low temperatures.
- rate characteristics the discharge capacity
- the content of the chain carbonate represented by the general formula (I) in the nonaqueous electrolyte is 5 to 5.
- the details of the action mechanism by combining a non-aqueous electrolyte containing at least one kind of the linear carbonate represented by the above general formula (I) are not clear, but are as follows. Is estimated.
- the chain carbonate represented by the general formula (I) forms a high-quality film on the surface of the negative electrode, and has an excellent effect of improving cycle characteristics.
- the chain carbonate has a methyl group. somewhat weak in terms of oxidation resistance because it contains a gas such as co 2 prone in contact with oxidized separator.
- the separator used in the present invention contains an inorganic filler, a large number of fillers are present on the separator surface, which greatly increases the direct contact area between the base resin of the separator and the positive electrode layer. To reduce. Therefore, it is presumed that oxidation by the positive electrode of the separator is prevented, and the effect of suppressing gas generation is obtained.
- Non-Patent Document 2 when a non-aqueous electrolytic solution is a non-aqueous solvent component of methyl alkyl carbonate represented by the general formula ROCOOCH 3 (R is an alkyl group), a stable film is formed on the negative electrode surface.
- R represents a methyl group (that is, ROCOOCH 3 is dimethyl carbonate, hereinafter referred to as “DMC”) or an ethyl group (that is, ROCOOCH 3 is ethyl methyl carbonate, hereinafter, referred to as “EMC”). ) Is used.
- DMC dimethyl carbonate
- EMC ethyl group
- the separator is a laminated film of two or more layers of a polyethylene layer and a polypropylene layer, and that the separator is applied to a nonaqueous electrolyte secondary battery of a mixed solvent of ethylene carbonate and ethyl carbonate. ing.
- the production of a laminated film by multi-layering is not a preferable method in terms of cost because the process is complicated as compared with the production of a single-layer film.
- the porous structure of the separator may be deformed (perforated holes), and the separator may not function properly.
- Patent Document 8 there is no specific description of a method for manufacturing a separator composed of a laminated film, and a monolayer film formed by biaxially stretching at least one layer in a multilayer film. It is merely described that a film composed of: or a film composed of at least two or more uniaxially stretched single-layer films so that their stretching directions intersect with each other is described. However, this Patent Document 8 only describes “polypropylene layer” and “polyethylene layer”, but does not describe the filler at all, nor does it mention the filler. Therefore, it can be said that the separator described in Patent Document 8 is manufactured at least by a method other than the interfacial peeling method.
- aromatic compounds are at least one member selected from the group consisting of cyclohexylbenzene, cyclohexylfluorene benzene, bipheninole, funorolobiphenyl, and dipheninoleatenole.
- Characteristic non-aqueous electrolyte secondary battery are at least one member selected from the group consisting of cyclohexylbenzene, cyclohexylfluorene benzene, bipheninole, funorolobiphenyl, and dipheninoleatenole.
- the aromatic compound having a heat build-up of 1.5 or more is contained in the non-aqueous electrolyte in an amount of from 0.1 to 0.1.
- the details of the mechanism of action by combining a non-aqueous electrolyte containing an aromatic compound having a heat build-up of 1.5 or more are not clear, but are presumed as follows.
- a polymer film is formed on the positive electrode surface during overcharging to greatly increase the internal resistance of the battery.
- the safety of the secondary battery can be improved.However, this polymerized film partially forms even when the charged battery is stored at high temperature. It is thought that the blocking of the pores of the separator increases the internal resistance of the battery, and as a result, the discharge capacity of the battery is reduced and the rate characteristics are deteriorated. This tendency is particularly remarkable when an overcharge inhibitor composed of an aromatic compound having a heat build-up of 1.5 or more is used.
- a porous film made of a thermoplastic resin containing an inorganic filler used as a separator in the present invention can be easily produced as a porous film having a relatively large pore size by, for example, an interface peeling method as described later. can do.
- the large hole diameter The separator has high pore continuity, is unlikely to be clogged by the polymer of the overcharge inhibitor, and is effective in suppressing an increase in the internal resistance of the battery.
- the presence of the inorganic filler makes it possible to reduce the contact area between the positive electrode active material and the separator and to provide a slight distance between the positive electrode active material and the separator. This also indicates that clogging of the separator is unlikely to occur.
- the overcharge prevention agent when the overcharge prevention agent is not in the overcharged state, a part of the overcharge prevention agent is polymerized.
- the separator is oxidized by the positive electrode active material, and the overcharge prevention agent comes into contact with the oxidized separator.
- the agent may be oxidized and a part of the polymerization reaction may have progressed.However, such a small contact area between the separator and the positive electrode active material is also effective in suppressing the oxidation of the separator. .
- Patent Document 9 also uses such a microporous polyolefin membrane containing no filler as a separator.
- a microporous polyolefin membrane separator cannot achieve the physical properties of the separator of the present invention, and cannot obtain the effects of the present invention.
- Patent Document 9 only describes the use of a microporous polyolefin membrane as a separator, and only describes polypropylene and polyethylene as its material, which is specifically described in Patent Document 9.
- Each of the separators is different from a porous membrane containing a filler.
- This microporous polyolefin membrane is generally produced industrially by the extraction method of (1) or the stretching method of (2).
- the surface of the overcharge inhibitor is very smooth and easily adheres to the electrode active material, and as described later, the polymerization of the overcharge inhibitor is more likely to be promoted by the oxidation of the separator.
- the secondary battery using such a microporous polyolefin membrane separator deteriorates battery characteristics after storage at high temperatures.
- Comparative Examples 4-1 and 4-2 below when a non-aqueous electrolyte containing an overcharge inhibitor composed of an aromatic compound having a heat build-up of 1.5 or more is used, In a secondary battery using a polyolefin membrane as a separator, good rate characteristics cannot be obtained after high-temperature storage.
- the fifth mode of the present application can be summarized as follows.
- the water contained in the battery has a concentration of 200 to 500 ppm as an electrolyte in the battery.
- a non-aqueous electrolyte secondary battery characterized by the following.
- the present inventors further conclude that water taken into the battery mainly through the separator and the electrode during the assembly of the battery has a great effect on the electrode interface resistance, and that the water range is within a specific range. It has been found that by doing so, a battery having stable and good load characteristics can be obtained.
- Patent Literature 6 discloses that the reaction between water in a battery and a fluorine-containing electrolyte generates fluorine, and that the generated fluorine deteriorates the electrolyte and the electrode plate to reduce the battery capacity.
- the amount of water in the battery is not the water concentration of the electrolytic solution used for assembling the battery, but is included in the separator, electrode material, the electrolytic solution, the atmosphere for assembling the battery, and the like at the time of assembling the battery. This is the total amount of all moisture carried into the battery as a product. Therefore, the amount of water in the battery can be determined from the total amount of water that is attached to or contained in the material used for assembling the battery and that is brought into the battery as a product as moisture in the assembly atmosphere. Since most of the water brought into the battery as a product in this way is concentrated in the electrolyte, the assembled battery is disassembled, the electrolyte is taken out, and the water concentration is measured. Can be obtained by
- the water introduced into the battery is mainly due to the separator and the electrode material.
- the water in the electrolyte is usually suppressed to several tens of ppm or less in order to prevent the decomposition of the salt contained therein, so that the water is generally contained in the electrolyte and taken into the battery as a product. There is almost no water content.
- the electrode interfacial resistance decreases due to the presence of a specific amount of water in the battery, but some by-products (hereinafter referred to as “contributing substances”) generated by the reaction of the water with the salt in the electrolytic solution. It may be referred to as ".”).
- the reason that this effect is limited to a specific water content range is that such contributing substances are usually produced compared to the hydrofluoric acid produced by the reaction between water and salts in the electrolyte. Due to the low ratio, it is presumed that, with a water content of less than 200 ppm, there is no contributing substance that produces a sufficient effect.
- the trickle current is defined as a charge current value when 4.2 V-CCV continuous charge is performed for a battery for 672 hours in an atmosphere of 60 ° C.
- Patent Document 3 Patent Document 3
- Patent Document 4 Patent Document 4
- Patent Document 5 (Patent Document 5)
- Patent Document 6 (Patent Document 6)
- Patent Document 7 Patent Document 7
- Patent Document 8 (Patent Document 8)
- Patent Document 9 (Patent Document 9)
- the non-aqueous electrolyte secondary battery of the present invention comprises a non-aqueous electrolyte containing a negative electrode and a positive electrode capable of inserting and extracting lithium, a specific separator described in detail below, a non-aqueous solvent, and a lithium salt.
- An electrolytic solution is used, and a particulate active material having a small specific ratio is used as an active material of the positive electrode and the anode or the negative electrode.
- thermoplastic resin as the base resin of the porous film constituting the separator of the present invention is not particularly limited as long as the inorganic filler described below can be uniformly dispersed, for example, polyolefin resin, Examples include fluorocarbon resins, styrene resins such as polystyrene, ABS resins, vinyl chloride resins, vinyl acetate resins, acrylic resins, polyamide resins, acetal resins, and polycarbonate resins.
- the thermoplastic resins such as the above-mentioned polyolefin resins may be used alone or as a mixture of two or more.
- polyolefin resins are particularly preferred because of their excellent balance of heat resistance, solvent resistance and flexibility.
- the polyolefin resin include monoolefin polymers such as ethylene, propylene, 1-butene, 1-hexene, 1-octene and 1-decene, and ethylene, propylene, 1-butene, 1-hexene, 1-octene and 1-octene.
- Examples include those mainly containing a copolymer of 1-decene and another monomer such as 4-methyl-11-pentene or vinyl acetate. Specific examples thereof include low-density polyethylene, linear low-density polyethylene, and high-density polyethylene.
- Density polyethylene, PO Examples include propylene, crystalline ethylene-propylene block copolymer, polybutene, and ethylene-vinyl acetate copolymer.
- polyethylene or polypropylene among the above-mentioned polyolefin resins.
- the weight-average molecular weight of such a thermoplastic resin has a lower limit of usually 50,000 or more, especially 100,000 or more, and an upper limit of usually 500,000 or less, preferably 400,000 or less, more preferably 300,000 or less, and especially 200,000 or less. What is necessary is just about 100,000 or less.
- the melt molding becomes difficult because the melt viscosity of the resin increases in addition to the decrease in the fluidity due to the addition of the filler. Further, even when a molded product is obtained, the filler is not uniformly dispersed in the resin, and the formation of pores due to interfacial separation is not uniform, which is not preferable. Below this lower limit, the mechanical strength is undesirably reduced.
- Examples of the inorganic filler contained in the polymer porous membrane according to the present invention include calcium carbonate, magnesium carbonate, barium carbonate, tanolek, clay, myriki, kaolin, silica, hydrotalcite, diatomaceous earth, calcium sulfate, and sulfuric acid.
- the inorganic filler contained in the polymer porous membrane according to the present invention those having a property of not decomposing a carbonate organic electrolyte used in a lithium secondary battery are preferable.
- examples of such a filler include sparingly water-soluble sulfates and alumina. Among them, barium sulfate is particularly preferably used.
- the term “poorly water-soluble” means that the solubility in water at 25 ° C is 5 ml or less.
- 0.5 g was added and kept at 85 ° C for 72 hours It is defined that the concentration of lithium ions in the subsequent electrolyte decreases to 0.75 mmol / g or less.
- the amount of lithium ions is measured by an ion chromatography method.
- the electrolyte solution in a holding of 72 hours c needs to put in a closed container so as not to be in contact with ambient air which is to advance the decomposition of the water and react with the electrolyte components in the air.
- Electrolyte in the table below (1M L i PF 6 / ( EC + EMC) (3: 7, volume ratio) shows the results held by the addition of the seed filler under the conditions described above.
- Barium sulfate-alumina shows almost no change in composition as compared with the ionic composition of the electrolyte without the filler, indicating that it is suitable as the filler in the present invention.
- carbonates such as calcium carbonate, lithium carbonate, and silica and titanium oxide show a remarkable decrease in lithium ion and an increase in fluorine ions due to the generation of hydrofluoric acid, which is not preferable as a filler in the present invention. I understand.
- the lower limit of the number-based average particle size is usually at least 0.0 ⁇ cijO ⁇ , preferably at least 0.1 ⁇ , especially at least 0.2 ⁇ , and the upper limit is usually at most ⁇ , preferably Is preferably 5 ⁇ or less, more preferably 3 ⁇ or less, and particularly preferably ⁇ or less. If the number-based average particle size of the inorganic filler exceeds 1 ⁇ , the pore size becomes too large, and the permeability of the electrolyte is deteriorated, which is not preferable. If the diameter of the hole formed by stretching is too large, stretching breakage and a decrease in film strength are likely to occur.
- the number-based average particle size exceeds 1 ⁇ , the number of particles on the surface of the separator becomes too small, so that adhesion between the electrode plate and the separator and formation of a gap are not sufficiently achieved, which is not preferable.
- the number-based average particle size is less than 0.0 ⁇ , the filler is likely to agglomerate, making it difficult to evenly disperse the filler in the base resin. Even if they can be dispersed evenly, the diameter of the pores formed by stretching is too small, so that there is no large difference from the pore diameters of (1) the extraction method and (2) the stretching method described above, and clogging is reduced. Undesirably, the liquid property does not sufficiently increase.
- the particle size is too small to prevent adhesion between the electrode plate and the separator. And the formation of gaps is not sufficient, which is not preferable.
- one type may be used alone, or two or more types may be used in combination.
- the lower limit of the amount of the inorganic filler in the polymer porous membrane according to the present invention is usually 40 parts by weight or more, preferably 50 parts by weight or more, based on 100 parts by weight of the thermoplastic resin. It is at least 600 parts by weight, more preferably at least 100 parts by weight, and the upper limit is usually at most 300 parts by weight, preferably at most 200 parts by weight, more preferably at most 200 parts by weight, based on 100 parts by weight of the thermoplastic resin. Is not more than 150 parts by weight. If the amount of the inorganic filler is less than 40 parts by weight per 100 parts by weight of the thermoplastic resin in the polymer porous membrane, it is difficult to form the communication hole, and the function as a separator may be exhibited. It will be difficult.
- the amount exceeds 300 parts by weight, the viscosity at the time of forming the film is increased and the processability is deteriorated.
- the compounding amount range of the above-mentioned filler is The filler content is in the range.
- thermoplastic resin examples of the surface treatment include a treatment with a fatty acid such as stearic acid or a metal salt thereof, or a polysiloxane / silane coupling agent.
- a low molecular weight compound having compatibility with the thermoplastic resin may be added. This low molecular weight compound enters between the molecules of the thermoplastic resin, reduces the interaction between the molecules and inhibits crystallization, and as a result, improves the stretchability of the resin composition during sheet molding.
- the low molecular weight compound has a function of appropriately increasing the interfacial adhesive strength between the thermoplastic resin and the inorganic filler to prevent the pores from becoming coarse due to stretching. It has the effect of preventing the inorganic filler from falling off from the film by increasing the film thickness.
- this low molecular weight compound those having a molecular weight of 200 to 300 are preferably used. If the molecular weight of the low molecular weight compound exceeds 300, it becomes difficult for the low molecular weight compound to enter between the molecules of the thermoplastic resin, and the effect of improving stretchability becomes insufficient. Also, If the molecular weight is less than 200, the compatibility increases, but the low molecular weight compound precipitates on the surface of the polymer porous membrane, so-called blooming is liable to occur, and the film properties are deteriorated. .
- thermoplastic resin is a polyolefin resin
- aliphatic hydrocarbons or glycerides are preferably used as the low molecular weight compound.
- polyolefin resin is polyethylene
- liquid paraffin / low melting point wax is preferably used.
- the lower limit of the compounding amount of the low-molecular-weight compound is usually at least 1 part by weight, preferably at least 5 parts by weight, per 100 parts by weight of the thermoplastic resin.
- the upper limit is usually at most 20 parts by weight, preferably at most 15 parts by weight, based on 100 parts by weight of the thermoplastic resin. If the compounding amount of the low molecular weight compound is less than 1 part by weight based on 100 parts by weight of the thermoplastic resin, the above-mentioned effect due to the compounding of the low molecular weight compound cannot be sufficiently obtained, and also exceeds 20 parts by weight.
- the interaction between the molecules of the resin and the thermoplastic resin is excessively reduced, so that sufficient strength cannot be obtained.
- smoke is generated at the time of sheet forming, and slipping occurs at a screw portion, which makes stable sheet forming difficult.
- additives such as a heat stabilizer can be added to the resin composition as the film-forming material of the polymer porous membrane according to the present invention.
- Any known additives can be used without particular limitation.
- the amount of these additives is usually 0.05 to 1% by weight based on the total amount of the resin composition.
- the porosity of the polymer porous membrane according to the present invention is usually 30% or more, preferably 40% or more, more preferably 50% or more, as the lower limit of the porosity of the polymer porous membrane,
- the upper limit is usually at most 80%, preferably at most 70%, more preferably at most 65%. If the porosity is less than 30%, the permeability of ions is not sufficient, and the porosity cannot function as a separator, which is not preferable. On the other hand, if the porosity exceeds 80%, the actual strength of the film becomes low, so that it is not preferable because breakage occurs at the time of producing the battery, penetration occurs due to the active material, and short-circuit occurs.
- the porosity of the polymer porous membrane is a value calculated by the following formula.
- Porosity P v (%) 10 Ox (1 -w. [P ⁇ S ⁇ t])
- the upper limit of the thickness of the polymer porous membrane according to the present invention is generally ⁇ ⁇ ⁇ or less, preferably 40 pm or less, and the lower limit is It is usually at least 5 ⁇ , preferably at least ⁇ .
- the thickness is less than 5 ⁇ , the actual strength is low, so that a breakthrough active material at the time of producing the battery may cause penetration and short circuit, which is not preferable.
- the thickness exceeds l O Opm, the electrical resistance of the separator increases, which is not preferable because the capacity of the battery decreases.
- the thickness exceeds 10 ⁇ , the amount of active material that can be put into the battery decreases, and the capacity of the entire battery also decreases, which is not preferable.
- the lower limit of the average pore size of the polymer porous membrane according to the present invention is at least 0.05 ⁇ , preferably at least 0.1 ⁇ , and more preferably at least 0.2 ⁇ .
- the upper limit is 1
- the pore size of the polymer porous membrane can be determined by selecting the characteristics (particle size, etc.) of the non-filled filler and the filling amount as necessary, as described later. Can be changed to Here, the average pore size of the polymer porous membrane is determined by ASTM F316-86.
- the lower limit of the Gurley air permeability is 20 seconds Z 100 cc or more, particularly 100 seconds 100 cc or more, and the upper limit is 700 seconds Z 100 cc or less. In particular, it is preferably 300 seconds / 100 cc or less. If the Gurley air permeability is below this lower limit, the porosity is often too high or too thin, and as described above, the actual strength of the film becomes low, causing breakage during battery fabrication and penetration by active materials. And a short circuit is not preferred. If the upper limit is exceeded, the ion permeability is not sufficient and the function as a separator cannot be achieved, which is not preferable.
- the Gurley air permeability is measured in accordance with JISP 8117, and indicates the number of seconds that 100 cc of air permeates the membrane at a pressure of 1.22 kPa.
- the average rate of change in the amount of retained liquid determined as follows is usually 15% or less, preferably 12% or less, more preferably 10% or less. It is as follows. If the average rate of change in liquid retention exceeds 15%, sufficient liquid retention will not be obtained, and cycle characteristics will be improved by reducing the lack of electrolyte in the battery element by using a specific separator. The effect cannot be obtained sufficiently. It should be noted that the lower the rate of change of the average liquid retention amount, the higher the liquid retention property, which is preferable. However, a lower limit of about 5% Z is sufficient.
- the weight of the separator cut out to a size of 4 cm x 4 cm is measured.
- the separator is immersed in the electrolytic solution, and after the electrolytic solution has sufficiently penetrated, the separator is pulled up, the electrolytic solution attached to the surface is wiped off, and the weight is measured.
- the difference from the weight before immersion is defined as the weight of the permeated electrolyte.
- the change in weight is measured for 2 minutes, and the average liquid retention change rate is calculated as shown in the table below. Table 2
- Separators used in lithium secondary batteries are required to satisfy requirements such as not hindering ionic conduction between the two electrodes, being able to hold the electrolyte, and being resistant to the electrolyte.
- a polymer porous membrane mainly composed of a thermoplastic resin such as polyethylene or polypropylene is used.
- (1) extraction method (2) stretching method and (3) interfacial peeling method is used as a method for producing these polymer porous membranes.
- the interface between the polymer material and the filler can be easily peeled by a stretching operation as compared with the methods (1) and (2).
- a porous membrane having a large pore size can be easily manufactured without requiring pretreatment such as heat treatment.
- the separator having a large pore diameter has a good electrolyte retaining property as described above, and is liable to prevent the electrolyte solution from being depleted in the battery element, and is effective in preventing a decrease in cycle characteristics.
- there is no generation of waste liquid and this method is excellent in terms of both environment and economy.
- the separator of the present invention is preferably manufactured by the interfacial peeling method, and more specifically, manufactured by the following method.
- the above-mentioned resin composition is preliminarily mixed by a Henschel mixer or the like, and then may be prepared by using a commonly used single-screw extruder, twin-screw extruder, mixing roll, or twin-screw kneader.
- the resin composition may be prepared directly by the above extruder or the like without pre-mixing.
- the resin composition is formed into a sheet.
- the sheet can be formed by a commonly used T-die method using a T-die or an inflation method using a circular die.
- the formed sheet is stretched.
- the stretching includes uniaxial stretching in the machine direction (MD), uniaxial stretching in the transverse direction (TD) using a tenter stretching machine, and uniaxial stretching in the MD.
- Delay There is a sequential biaxial stretching method in which stretching is performed, or a simultaneous biaxial stretching method in which stretching is performed simultaneously in the machine direction and the transverse direction.
- the uniaxial stretching can be performed by roll stretching.
- the stretching can be performed at any temperature at which the resin composition constituting the sheet can be easily stretched to a predetermined stretching ratio, and the resin composition does not melt to close the pores and lose communication.
- the stretching is performed in a temperature range from the melting point of the resin to 170 ° C to the melting point of the resin to 15 ° C.
- the stretching ratio is arbitrarily set according to the required pore diameter / strength, but preferably stretching is performed at least 1.2 times or more in one axis direction.
- the upper limit of the stretching ratio is not particularly limited, but is usually 7 times or less in the uniaxial direction. If the stretching exceeds the upper limit, the porosity of the obtained porous membrane becomes too high, the strength is reduced, and there is a possibility that the porous membrane cannot withstand practical use.
- the non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention contains a non-aqueous solvent and a lithium salt.
- any known solvent for a non-aqueous electrolyte secondary battery can be used.
- cyclic carbonates such as alkylene carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate (preferably alkylene carbonates having 3 to 5 carbon atoms); dimethyl carbonate, getyl carbonate, di-n-propyl carbonate, Chain carbonates such as dialkyl carbonates (preferably dialkyl carbonates having an alkyl group having 1 to 4 carbon atoms); cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; dimethoxetane, dimethoxymethane and the like Chain ethers; cyclic carboxylic esters such as ⁇ -butyrolataton, ⁇ -valerolatatone; chain carboxylic esters such as methyl acetate, methyl propylene carbonates and butylene carbonate (preferably alkylene carbonates having 3 to 5 carbon atoms); dimethyl carbonate, gety
- Non-aqueous solvents are preferred from the viewpoint of improving the overall battery performance such as charge / discharge characteristics and battery life.
- the mixed non-aqueous solvent contains cyclic carbonate and chain carbonate in an amount of 15% by volume or more of the entire non-aqueous solvent, and the total volume thereof is 70% by volume or more of the entire non-aqueous solvent. Is preferably mixed.
- alkylene carbonate having an alkylene group having 2 to 4 carbon atoms is preferable.
- Specific examples thereof include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Among them, ethylene carbonate and propylene carbonate are preferred.
- the chain carbonate used in the mixed non-aqueous solvent obtained by mixing the cyclic carbonate and the chain carbonate is preferably a dialkyl carbonate having an alkyl group having 1 to 4 carbon atoms. Specific examples thereof include dimethyl carbonate, getyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methynole-n-propyl carbonate, ethyl-n-propynole carbonate and the like. Among them, dimethyl carbonate, getyl carbonate and ethyl methyl carbonate are preferred.
- cyclic carbonates and chain carbonates may be used independently alone, or a plurality of them may be used in any combination and in any ratio.
- the proportion of cyclic carbonate in the mixed non-aqueous solvent is 15% by volume or more, especially 20 to 50% by volume, and the proportion of chain carbonate is 30% by volume or more, particularly 40 to 80% by volume.
- the mixed non-aqueous solvent may contain a solvent other than the cyclic carbonate and the chain carbonate as long as the battery performance of the manufactured lithium battery is not deteriorated.
- the proportion of the solvent other than the cyclic carbonate and the chain carbonate in the mixed nonaqueous solvent is usually 30% by volume or less, preferably 10% by volume or less.
- the non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention contains a non-aqueous solvent and a lithium salt, and is represented by ROCOOCH 3 (R is a methyl group or ethyl group). It is preferable to contain at least one kind of chain carbonate, that is, dimethyl carbonate (DMC) and / or ethyl methyl carbonate (EMC).
- DMC dimethyl carbonate
- EMC ethyl methyl carbonate
- the non-aqueous electrolyte according to the present invention can be used by mixing any known solvent for a non-aqueous electrolyte secondary battery in addition to the specific chain carbonate described above. Is desirably used in combination.
- non-aqueous solvents that can be used in combination include, for example, cyclic carbonates (preferably alkylene carbonates having 3 to 5 carbon atoms) such as alkylene carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; getyl carbonate; Chain carbonates such as dialkyl carbonates such as n-propyl carbonate (preferably dialkyl carbonates having an alkyl group having 4 or less carbon atoms and 5 or more carbon atoms); cyclic rings such as tetrahydrofuran and 2-methyltetrahydrofuran Ethers; linear ethers such as dimethoxetane and dimethoxymethane; linear carboxylic esters such as ⁇ -butyrolactone and ⁇ -valerolactone; linear carboxylic esters such as methyl acetate, methyl propionate and ethyl propionate; And the like.
- cyclic carbonates preferably alkylene carbonates having 3 to 5 carbon atoms
- the content of the specific chain carbonate, that is, DMC and / or EMC of the nonaqueous electrolyte is preferably 5% by volume or more, more preferably 10% by volume or more, by volume ratio. Most preferably, it is 30% by volume or more. Further, it is preferably at most 95% by volume, more preferably at most 90% by volume, most preferably at most 85%. Further, the content of the specific chain carbonate, that is, DMC and NO or EMC in the nonaqueous electrolyte is preferably 4% by weight or more, more preferably 10% by weight or more. Most preferably, it is at least 20% by weight. It is preferably at most 85% by weight, more preferably at most 80% by weight, most preferably at most 75% by weight. Outside this range, sufficient cycle characteristics may not be obtained, and the conductivity of the electrolyte may be reduced.
- the mixing ratio of DMC and EMC is not particularly limited, and any ratio can be adopted.
- a mixed non-aqueous solvent in which cyclic carbonate is mixed with DMC and / or EMC can improve the overall battery performance such as charge / discharge characteristics and battery life.
- the content of the cyclic carbonate at that time is preferably 5% by volume or more, more preferably 10% by volume or more, and most preferably 15% by volume or more of the whole non-aqueous solvent. Further, it is preferably at most 70% by volume, more preferably at most 60% by volume, most preferably at most 50% by volume.
- an alkylene carbonate having an alkylene group having 2 to 4 carbon atoms is preferable.
- Specific examples thereof include one or two of ethylene carbonate, propylene carbonate, butylene carbonate, etc., and among them, ethylene carbonate and / or propylene carbonate are preferred, and at least ethylene carbonate is particularly preferred. preferable.
- the chain carbonate is preferably a dialkyl carbonate having 5 or more carbon atoms, and a dialkyl carbonate having 4 or less carbon atoms in the alkyl group. Specific examples thereof include one or two or more of getyl carbonate, di-n-propyl carbonate, methyl-n-propyl propyl carbonate, and ethyl-n-propyl carbonate. preferable.
- the content of this other chain carbonate is preferably 40% by volume or less, more preferably 30% by volume or less of the whole non-aqueous solvent. Most preferably, it is not more than 25% by volume. If the upper limit is exceeded, the cycle characteristics may be degraded.
- the lysis solution may contain a solvent other than the cyclic carbonate and the chain carbonate as long as the battery performance of the manufactured lithium battery is not deteriorated.
- the proportion of the solvent other than the cyclic carbonate and the chain carbonate in the mixed non-aqueous solvent is usually 30% by volume or less, preferably 10% by volume or less.
- any lithium salt which is a solute of the non-aqueous electrolyte, can be used.
- L i C 10 4, L i PF 6, inorganic lithium salts such as L i BF 4; L i CF 3 SO 3, L i N (CF a S 0 2) 2, L i N (C 2 F 5 S0 2 ) 2 , L i N (CF 3 S 0 2 ) C 4 F 9 SO 2 ), L i C (CF 3 S 0 2 ) 3 , L i PF 4 (CF 3 ) 2 , L i PF 4 (C 2 F 5 ) 2 , L i PF 4 (CF 3 S 0 2 ) 2 , L i PF 4 (C 2 F 5 S 0 2 ) 2 , L i BF 2 (CF 3 ) 2 , L i BF 2 (C 2 F 5) 2, L i BF 2 (CF 3 S0 2) 2, L i BF 2 ( such as C 2 F 5 S0 2)
- One lithium salt may be used alone, or two or more lithium salts may be used in combination.
- the lower limit of the concentration of these lithium salts in the non-aqueous electrolyte is usually 0.5 mo 1/1 or more, especially 0.75 m o 1/1 or more, and the upper limit is usually 2 mol 1 Zl or less, Above all, it is less than 1.5mol Zl. If the concentration of the lithium salt exceeds this upper limit, the viscosity of the non-aqueous electrolyte increases, and the electric conductivity decreases. Further, when the value is below the lower limit, the electric conductivity becomes low. Therefore, it is preferable to prepare the non-aqueous electrolyte within the above concentration range.
- the non-aqueous electrolytic solution of the present invention preferably contains a film forming agent.
- a film-forming agent that forms a resistive film on the surface of the negative electrode and has a moderately large temperature dependence in the resistance of the formed film has been previously described.
- the specific separator used in the present invention described above particularly in a low temperature environment. This is preferable in that the effect of preventing the deterioration of the characteristics can be effectively obtained.
- the film-forming agent used in the present invention includes vinylene carbonate, vinyl / ethylene carbonate, phenolic ethylene carbonate, trifluoropropylene carbonate, phenylethylene carbonate and erythritan carbonate.
- Carbonate compounds having an ethylenically unsaturated bond such as succinic anhydride, dartartic anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride And carboxylic acid anhydrides such as cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride.
- vinylene carbonate, vinylethylene carbonate, and succinic anhydride are preferred as the film-forming agent from the viewpoints of good cycle characteristics improvement effect and temperature dependency of film-forming resistance, because they can form a good-quality film. It is more preferable to use vinylene carbonate.
- These film-forming agents may be used alone or in a combination of two or more. '
- the content of the film-forming agent in the non-aqueous electrolyte is at least 0.1% by weight, preferably at least 0.1% by weight, more preferably at least 0.3% by weight. % Or less, preferably 8% by weight or less, more preferably 7% by weight or less. If the content of the film-forming agent is below the lower limit of the above range, it is difficult to obtain the effect of improving the cycle characteristics of the battery, while if it exceeds the upper limit, the rate characteristics at low temperatures may be reduced.
- the non-aqueous electrolyte solution of the present invention preferably contains an aromatic compound having a heat build-up of 1.5 or more.
- the exothermicity of the aromatic compound is defined by the following method. Measurement method of heat generation>
- the measurement is performed by preparing a battery for measurement in the following procedure and performing an exothermic test.
- Ethylene carbonate and ethyl methyl carbonate are mixed in a ratio of 3: 7 (volume ratio), and Li PF 6 is mixed as a Li salt at a concentration of l mo 1 / L, and the aromatic compound of the sample is added to the electrolyte. Add and mix at a concentration of 3% by weight to prepare a non-aqueous electrolyte.
- L i C o O 2 As the positive electrode active material, L i C o 0 2 90 parts by weight carbon black click 5 parts by weight of polyvinylidene fluoride (Kureha Chemical Co., trade name "KF 1 000 j) 5 wt Then, the mixture is dispersed in N-methyl-2-pyrrolidone to form a slurry, which is uniformly applied to both sides of a 2- ⁇ -thick aluminum foil serving as a positive electrode current collector, and dried. A positive electrode is pressed by a press so that the density of the positive electrode active material layer becomes 3. O g / cm 3 .
- natural graphite powder as the negative electrode active material, 94 parts by weight of natural graphite powder and 6 parts by weight of polyvinylidene fluoride are mixed and dispersed with N-methyl-2-pyrrolidone to form a slurry. This was uniformly applied to one surface of a copper foil having a thickness of 1 8Myupaiiota a negative electrode current collector, dried and then press and pressed such that the density of the negative electrode active material layer becomes 1. 5 gZc m 3 A negative electrode.
- polyethylene having a weight-average molecular weight in the range of 300,000 to 1,000,000
- physical properties in the range of 15 to 25 ⁇ and porosity of 30 to 50%.
- the above positive electrode, negative electrode, and separator are laminated in the order of negative electrode, separator, positive electrode, separator, and negative electrode, and the battery element thus obtained is first sandwiched between PET films, and then both sides of the aluminum layer are covered with resin layers. Positive and negative terminals on the laminated film Is inserted while protruding, and the above-mentioned electrolytic solution of 0.5 CC is added thereto, followed by vacuum sealing to produce a sheet-shaped lithium secondary battery (laminated battery). Further, in order to enhance the adhesion between the electrodes, a sheet-shaped battery is sandwiched between silicon rubber and a glass plate, and then pressed at 0.35 kgcm 2 .
- Charge end voltage at constant current equivalent to 0.2 C (1 C is the current value that discharges in 1 hour at the rated capacity based on the discharge capacity of 1 hour rate) 5 cycles of charge and discharge at 2 V and discharge end voltage of 3 V are performed for 5 cycles to stabilize.
- the fourth cycle is charged to a charge end voltage of 4.2 V with a current equivalent to 0.5 C, and the charge current value is 0.0 Charge until the current value becomes equivalent to 5 C.
- T J the temperature at the center of the aluminum surface outside the laminated battery.
- the above fully charged battery is further charged (overcharged) at a current value equivalent to 2 C. 21 minutes after the start of charging, that is, when the full charge is set to 100%, the temperature (T f ) of the center of the aluminum surface outside the laminated battery when the overcharge state of 170% is reached is measured.
- T f the temperature of the center of the aluminum surface outside the laminated battery when the overcharge state of 170% is reached is measured.
- the above temperature units are all Celsius temperatures (° C).
- an aromatic compound having an exothermicity of 1.5 or more is used.
- This heat generating property is usually 1.5 or more, preferably 1.8 or more, and more preferably 2.0 or more. It is usually 6.0 or less, preferably 5.5 or less, and more preferably 5.2 or less. If the heat build-up exceeds the upper limit, the temperature of the battery tends to increase, which is dangerous. If the heat build-up is lower than the lower limit, it becomes difficult to obtain the battery safety intended in the present invention.
- the molecular weight of the aromatic compound is usually at least 80, preferably at least 100, more preferably at least 120, and usually at most 300, preferably at most 250, more preferably at most 230. It is 0 or less. If the molecular weight exceeds this upper limit, it will be difficult to dissolve in a non-aqueous solvent, and if it is below the lower limit, it will be difficult to obtain an overcharge prevention effect.
- aromatic compound having a heat build-up of 1.5 or more examples include aromatic compounds such as cyclohexylbenzene, cyclohexinolephnoleobenzene, bipheninole, fenoleolobifeninole, and diphenyl ether. These aromatic compounds may be used alone or in a combination of two or more.
- the content of the aromatic compound having a heat build-up of 1.5 or more in the non-aqueous electrolyte is usually 0.1% by weight or more, preferably 0.3% by weight or more, and more preferably 0.5% by weight. % Or more, usually 8 weight. / 0 or less, preferably 6% by weight or less, more preferably 5% by weight or less. If the content of the aromatic compound exceeds the upper limit, the storage characteristics / cycle characteristics may be deteriorated. If the content is lower than the lower limit, the effect of preventing overcharge is hardly obtained.
- the non-aqueous electrolyte according to the present invention contains, in addition to the non-aqueous solvent and the lithium salt, other useful components as necessary, for example, conventionally known vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, phenylethylene carbonate, Negative electrode film forming agents such as succinic anhydride, ethylene sulfite, propylene sulfite, dimethyl sulfite, propane sultone, butane sultone, methyl methanesulfonate, methyl toluenesulfonate, dimethinole sulfate, ethylene sulfate, snoreholane, dimethinoresnoreon, Positive electrode protecting agents such as cetinoresolefon, dimethinoresulfoxide, getyl sulfoxide, tetramethylene sulfoxide, diphenylenoresolefide, thioanisole, dipheninoresinole
- the present invention relates to an active material, wherein the active material contained in the negative electrode is a particulate active material having an aspect ratio of 1.02 or more and 3 or less, or the active material contained in the positive electrode is At least one of the particulate active materials having a ratio of 1.02 to 2.2 is satisfied.
- the definition of this aspect ratio is as follows.
- the particulate active material was dispersed on a flat plate, the resin-embedded material was polished in parallel with the flat plate, and a cross-sectional photograph was taken using a scanning electron microscope (SEM).
- SEM scanning electron microscope
- the cross section of the electrode was polished in parallel to a current collector (metal foil, etc.), and a cross-sectional photograph of the electrode powder present on the electrode cross section was taken with a scanning electron microscope (SEM).
- SEM scanning electron microscope
- the major and minor diameters of the cross section of the particle are measured at 20 points by image analysis of the photographed SEM photograph, and the aspect ratio (hereinafter referred to as “two-dimensional aspect ratio”) is determined from the average value.
- the particulate active material was dispersed on a flat plate, and the resin-embedded material was polished in parallel with the flat plate, and both the cross-sectional photograph and the vertical cross-section were taken.
- the electrode cross section was polished parallel to the current collector (metal foil, etc.), and the electrode cross section (parallel to the current collector).
- a cross section perpendicular to the cross section is cut out and polished, and a cross-sectional photograph of the electrode powder present in the electrode vertical cross section (a cross section perpendicular to the current collector) is taken.
- the major and minor diameters of the horizontal and vertical cross-sections of each particle were measured at 20 points or more by image analysis of the SEM photograph, and the average value was used as the aspect ratio (hereinafter referred to as the “three-dimensional aspect ratio”). ), The shape of the more particulate active material becomes three-dimensional. Caught in
- a particulate active material having a two-dimensional aspect ratio, preferably a three-dimensional aspect ratio of 1.02 or more and 2.2 or less is used as the positive electrode active material.
- a particulate active material having a two-dimensional peak ratio, preferably a three-dimensional peak ratio of 1.02 or more and 3 or less is used. Active material aspect ratio>
- the upper limit of the two-dimensional aspect ratio of the positive electrode active material is usually 2.2 or less, especially 1.6 or less, especially 1.2 or less, and the lower limit is usually 1.02 or more, especially 1. 05 or more, especially 1.1 or more.
- the upper limit of the three-dimensional aspect ratio is usually 2.2 or less, especially 1.5 or less, especially 1.2 or less, and the lower limit is usually 1.02 or more, especially 1.05 or more, especially 1 1 or more.
- the peak ratio of the positive electrode active material exceeds this upper limit, the particle shape becomes flat, so that the tap density becomes too large and the deposition of by-products accompanying the high density becomes difficult to occur.
- the effect of improving the cycle characteristics of the invention is not so large.
- those having a lower limit than the above-mentioned lower limit have extremely high circularity, so that it is difficult to produce with high industrial yield.
- the upper limit of the two-dimensional aspect ratio of the negative electrode active material is usually 3.0 or less, especially 2.4 or less, particularly 1.7 or less, particularly 1.4 or less, and the lower limit is usually 1. 02 or higher, especially 1.05 or higher, especially 1: 1 or higher.
- the upper limit of the three-dimensional aspect ratio is usually 3 or less, especially 2.5 or less, especially 1.9 or less, especially 1.4 or less.
- the lower limit is usually 1.02 or more, especially 1.05 or more, Especially 1.1 or more.
- the particles have a flat particle shape, so the tap density does not increase so much that the accumulation of by-products due to the high density becomes difficult to occur. Therefore, the effect of improving the cycle characteristics of the present invention is not so large.
- those having a lower limit than the above-mentioned lower limit have extremely high circularity, so that it is difficult to produce with high industrial yield.
- the method for forming the negative electrode active material particles having a predetermined aspect ratio into a predetermined shape is not particularly limited.
- a negative electrode active material made of a carbon material the following methods are exemplified.
- the carbon material a naturally occurring carbon material or an artificially produced carbon material may be used.
- the method for producing the carbon material for the negative electrode is not particularly limited. Therefore, it is also possible to select and obtain a carbon material for a negative electrode having the above-described aspect ratio by using a separation means such as sieving or air classification.
- carbon produced in the natural world, graphite material or artificially produced carbonized or graphitized material may be subjected to mechanical energy treatment such as surface grinding to form spheroids, and the carbon for the negative electrode may be formed. It can also be obtained by the method of manufacturing the material.
- An example of the mechanical energy treatment can be obtained by subjecting a carbonaceous material to surface grinding as is well known.
- a pulverizer equipped with a high-speed rotating rotor with a large number of blades installed in the casing ⁇
- mechanical treatment such as impact compression, friction, and shearing is applied to the carbonaceous material to perform surface treatment while pulverizing.
- the peripheral speed of the rotor is preferably 30 to 10 OmZ seconds, particularly preferably 50 to 10 OmZ seconds.
- Classification after pulverization is generally carried out using a pneumatic classifier such as a micron separator, a forced vortex centrifugal classifier such as Turboplex, or an inertial classifier such as El Posiette, but wet sedimentation or centrifugal sedimentation. A disembarkation or the like can also be used.
- carbon and graphite materials and artificially manufactured carbonized and graphitized materials are mixed with a carbon precursor and then heated to adjust the degree of crystallinity. It can also be obtained through carbonization and graphitization of powder and through powder processing. At this time, carbon powder or graphite powder mixed with the carbon precursor or a mixture thereof is preliminarily spheroidized by mechanical energy processing so that particles having a predetermined shape are obtained in the final powder processing.
- a method of selecting a carbon material such as selecting a non-needle-like coatus having poor graphitization property so that a predetermined shape is easily formed in a pulverization process after carbonization and graphitization.
- the active material particles finally obtained can be formed into a predetermined shape by bonding a large number of fine particles via a carbonized or graphitized material starting from a carbon precursor.
- so-called mesocarbon microbeads obtained by dissolving an underdeveloped tissue with a solvent at the stage of a carbon precursor and extracting developed spherulites can be used as carbonized or graphitized ones.
- these methods can be used alone or in combination of two or more.
- lithium transition metal composite oxide As the negative electrode active material, active material particles obtained by these methods and the like may be used alone or in combination of two or more.
- examples of the positive electrode active material include lithium cobaltate, lithium nickelate, spinel-type lithium manganate, and materials using a plurality of these transition metals such as lithium nickel cobaltate and lithium nickel manganate.
- a composite oxide of lithium and a transition metal hereinafter, referred to as “lithium transition metal composite oxide” is suitably used.
- the positive electrode active material For the synthesis of the positive electrode active material, a mixture of different elements and control of the powder shape are performed by using a kind of coprecipitation method such as spray drying method, hydroxide method, complex carbonate method, etc. By baking in the above method, a spherical or elliptical spherical positive electrode active material powder can be obtained. That is, the lithium compound (L i 2 C0 3, etc.) powder and a transition metal of compound (Mn0 2, C0 2 0 4 , N i O , etc.) powder were mixed, and lithium-transition metals compound oxide by firing The method has been widely adopted.
- a kind of coprecipitation method such as spray drying method, hydroxide method, complex carbonate method, etc.
- Transition metal compound as the respective oxides by calcination as raw materials for example, cobalt, nickel, manganese compounds, more specifically, C o 3 0 4, C oO, C o (OH) 2, N i O, Mn0 2 , and Mn 3 0 4, Mn 2 0 3, Mn C_ ⁇ 3, etc.
- a dispersion medium eg, water
- the mixture is further wet-mixed to form a slurry, which is spray-dried with a spray drier.
- oxides such as Cr, Al, Co, Ni, Mo, and W can be added to the raw materials as additional elements. It is preferable to add a polymer solution such as PVA to the slurry.
- Spray drying is a method in which atomized slurry is supplied to a drying chamber using an atomizer and dried to obtain spherical particles. Examples of the atomization method include a disk method, a pressure nozzle method, a two-fluid nozzle method, and a four-fluid nozzle method.
- the fine particles obtained by spray drying become lithium transition metal composite oxides in the firing step.
- the maximum temperature during firing is usually 500 ° C or higher, preferably 600 ° C or higher, more preferably 800 ° C or higher.
- the temperature is too low, the treatment time will be too long to obtain the desired crystallinity, and if the temperature is too high, the power to generate a crystal phase other than the target lithium transition metal composite oxide, or lithium with many defects Because a transition metal composite oxide is produced, Usually, it is 1100 ° C or lower, preferably 1050 ° C or lower, more preferably 950 ° C or lower.
- This firing can be performed all at once in a constant atmosphere, but it is also possible to perform the firing process in at least two stages.
- the firing gas atmosphere may be an air atmosphere or an oxygen atmosphere, but is preferably performed in at least two stages: a first stage in a low oxygen concentration atmosphere and a second stage in a high oxygen concentration atmosphere.
- the oxygen content is 10% by volume to 0% by volume.
- the oxygen content is 80% by volume or less, preferably 50% by volume or less, 15% by volume or more, preferably 20% by volume. % Or more.
- the timing of switching from the low-oxygen-concentration atmosphere to the high-oxygen-concentration atmosphere is preferably in the middle of raising the temperature to the maximum temperature from the start of firing.
- the switching temperature is set to 900 ° C or lower, preferably 800 ° C or lower.
- the particles are crushed with a raikai or the like, and then classified using a sieve or the like to obtain a predetermined particle size.
- the aspect ratio can be controlled by performing a mechanical treatment or a mechanochemical treatment to adjust the particle shape.
- active material particles obtained by these methods and the like may be used alone or in combination of two or more. Active material tap density>
- the upper limit of the tap density of the positive electrode active material used in the present invention is usually 3.5 g / cm 3 or less, among them 3.0 gZcm 3 or less, especially 2.5 g / cm 3 or less, especially 2.3 g / cm 3 or less. 3 or less, the lower limit is usually 1. 4 GZC m 3 or more, among them 1 ⁇ 7 gZc m 3 or more on, especially 2. 0 GZC m 3 or more.
- the upper limit of the tap density of the negative electrode active material typically 1. 5 g / cm 3 or less, preferably 1. 3 gZcm 3 or less, particularly 1. 2 gZc m 3 or less
- the lower limit is usually 0. 7 g Roh cm 3 or more, especially 0.8 gZcm 3 or more, especially 0.9 g / cm 3 or more.
- the tap density of the active material exceeds this upper limit, other physical properties other than the tap density are maintained. If it is less than the lower limit, the electrode packing density is low and the battery capacity does not increase so much, so that the effect of improving the cycle characteristics of the present invention cannot be obtained so much.
- tap density used in this specification refers to the bulk density (pi 000) at the time of filling taps into a 20 cm 3 cell 1,000 times, as the final bulk density p.
- the average secondary particle size (average particle size of secondary particles) of the positive electrode active material particles is usually lpm or more, preferably 3 ⁇ or more, and more preferably 6 ⁇ or more, as measured by a laser diffraction type particle size distribution meter. Is most preferred. If the average particle size is too small, it is difficult to form a high-density active material layer. On the other hand, if the average particle size is too large, it may protrude from the surface of the active material layer, penetrate the separator, and cause a short circuit. Therefore, the upper limit is preferably 3 ⁇ or less, particularly preferably 26 pm or less. In addition, it is preferable that particles having a particle size of 50 ⁇ or more, particularly 10 ⁇ or more, do not substantially exist.
- the BET specific surface area of the positive electrode active material particles measured by a nitrogen adsorption method is usually 0.3 m 2 / g or more, preferably 0.3 Sn ⁇ Zg or more, more preferably 1.0 m 2 Zg or more, and further preferably 2. Above, most preferably 3. Om 2 ng or more. If the specific surface area is too small, it means that the primary particle size becomes large, that is, the rate characteristics and capacity tend to decrease, which is not preferable.However, if it is too large, the side reaction in the battery proceeds. and cycle characteristics, as it reduces the durability of the storage characteristics such as a battery, the upper limit of the specific surface area is usually 1 0. 0 m 2 Zg less, preferably 8. Om 2 / g or less, more preferably 5. Om 2 ⁇ Or less, most preferably 4.0 m 2 / g or less.
- the average secondary particle size (average particle size of secondary particles) of the negative electrode active material particles is usually preferably 3 ⁇ or more, more preferably 6 ⁇ or more, particularly 8 ⁇ m or more, as measured by a laser diffraction type particle size distribution analyzer. Is most preferred. If the average particle size is too small, it is difficult to form a high-density active material layer. Conversely, if the average particle size is too large, the surface of the active material layer The upper limit is preferably 3 ⁇ or less, particularly preferably 26 ⁇ or less, since it may protrude and penetrate the separator to cause a short circuit. Further, it is preferable that particles having a particle size of 50 ⁇ or more, particularly 10 Opm or more, do not substantially exist.
- the BET specific surface area of the negative electrode active material particles by a nitrogen adsorption method is generally preferably 0.5 to 2 Om 2 Zg.
- the upper limit of the BET specific surface area is preferably 10 m 2 / g or less, more preferably 5 m 2 Zg or less.
- the lower limit varies depending on the characteristics required for the battery, in applications that emphasize the storage characteristics such as a wait or a 0. 5 m 2 Roh g or more, but home appliances both the storage stability and the current release is required, such as It is preferably at least 1. Om 2 / g for consumer use and at least 2. Om 2 ng for vehicle applications that require large current emission.
- the average circularity of the negative electrode active material particles is preferably 0.85 or more, more preferably 0.89 or more, and particularly preferably 0.92 or more. If a carbonaceous material having a small average circularity is used, it is generally difficult to produce a negative electrode having excellent rapid charge / discharge characteristics. On the other hand, if the average circularity is too large, the adhesive strength with the binder during the preparation of the negative electrode is reduced, so that the strength of the negative electrode is weakened and the long-term charge / discharge cycle characteristics of the battery are deteriorated. Therefore, the upper limit of the average circularity of the negative electrode active material is preferably 0.99 or less, particularly preferably 0.997 or less.
- the circularity is an index defined as a ratio of the circumference of a perfect circle (equivalent circle) having the same projected area as the particle as a numerator and the circumference of the particle as a denominator. Therefore, when the projected image of a particle is a perfect circle, the circularity is 1, and the smaller the particle is, the smaller the circularity is.
- Average circularity in this specification is a value calculated as an arithmetic average of the circularity obtained by imaging the shape of 9,000 to 11,000 particles using a flow-type particle image angle analyzer. is there.
- the carbon material to be measured and a surfactant (polyoxyethylene (20) sorbitan monolaurate) were added to ion-exchanged water as a dispersion medium, stirred, and ultrasonically dispersed for 30 minutes. Is used as a sample.
- the upper limit of the measured values by pycnometer method typically 2. 40 gZc m 3 or less, preferably 2. 30 g / cm 3 or less, particularly 2.28 g / cm 3 or less, usually 1. 7 0 gZc m 3 or more on the lower limit, among them 1. 80 gZc m 3 or more, especially 2. good that 1 is 0 g / cm 3 or more Good. If the true density of the negative electrode active material exceeds the upper limit, the cycle deterioration of the active material becomes large, which is not preferable.If the lower limit is less than the lower limit, the active material capacity is small and the effect of improving the cycle characteristics of the present invention cannot be obtained so much. .
- Spacing of graphitic carbon material used as the negative electrode active material (d 0. 2) is preferably equal to or less than 0. 348 ⁇ m, 0. 338 1 1111 or less, der lever particular 0. 3 37 nm or less More preferred.
- the thickness (L c) of the crystallite in the C-axis direction can be generally used as long as it is 2 nm or more, preferably 20 nm or more, more preferably 40 nm or more, particularly preferably 90 nm or more.
- the peak intensity at 1580 to 1620 cm- 1 is defined as I A
- the half width is defined as ⁇ .
- the peak intensity ratio R is further preferably 0.6 or less, particularly preferably 0.4 or less, but preferably not less than 0.2.
- it is preferred half-value width ⁇ is 40 cm- 1 or less, more preferably in the range from 36 c ⁇ 1 below.
- the half width ⁇ is generally preferably as small as possible, but is usually 20 cm- 1 or more.
- the theoretical capacity value per gram of graphite is 372 mAh based on C 6 Li, which is an intercalation compound formed by storing lithium ions between graphite layers.
- a graphitic carbon material that is preferably used as a material, a material having a capacity of 32 OmAhr / g or more when measured with a half-cell using a lithium metal counter electrode with a charge / discharge rate of 0.1 SmAZcm 2 is preferable.
- the capacity is more preferably at least 34 OmAhr / g, particularly preferably at least 350 mAhr / g.
- the positive electrode one obtained by forming an active material layer containing the above-described positive electrode active material and a binder on a current collector is usually used.
- the type of the positive electrode active material is not limited as long as it can electrochemically store and release lithium ions.
- Preferred examples include lithium transition metal composite oxides. Specific examples of the lithium-transition metal composite oxide, L i C o 0 2 lithium. Cobalt composite oxide such as, L i N i 0 2 Lithium 'nickel composite oxide such as such as L i Mn O 2 Lithium-manganese composite oxide; In these lithium transition metal composite oxides, some of the main transition metal atoms are A1, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Z It is preferable to replace the metal with another metal such as n, Mg, Ga, Zr, Si or the like because the metal can be stabilized. Any one of these positive electrode active materials may be used alone, or two or more thereof may be used in any combination and in any ratio.
- the binder is not particularly limited as long as it is a material that is stable with respect to the solvent and the electrolyte used in the production of the electrode and other materials used in the use of the battery.
- Specific examples include polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, EPDM (ethylene-propylene / 1-gen terpolymer), SBR (styrene-butadiene rubber), NBR (Acrylonitrile-butadiene rubber), fluorine rubber, polyacetate biel, polymethyl methacrylate, polyethylene, nitrocellulose and the like. These may be used alone or in combination of two or more.
- the lower limit of the proportion of the binder in the positive electrode active material layer 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. It is preferably at most 60% by weight, more preferably at most 40% by weight, even more preferably at most 10% by weight. If the ratio of the binder is small, the active material cannot be sufficiently retained, so that the mechanical strength of the positive electrode is insufficient and the battery performance such as cycle characteristics may be deteriorated.On the other hand, if the ratio is too large, the battery capacity and conductivity are reduced. Will be.
- the positive electrode active material layer usually contains a conductive agent to increase conductivity.
- Examples of 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 a needle coater. These may be used alone or in combination of two or more.
- the proportion of the conductive agent in the positive electrode active material layer is, the lower limit is usually 0.01 wt% or more, preferably rather is 0.1 wt 0/0 or more, more preferably 1 wt% or more, the upper limit is usually Five
- the positive electrode active material layer may contain additives of a normal active material layer such as a thickener.
- the viscosity agent is not particularly limited as long as it is a material that is stable with respect to the solvent and the electrolyte used in the manufacture of the electrode and other materials used in the use of the battery.
- Specific examples thereof include carboxy sinoremethinoresenorelose, methinoresenorelose, hydroxymethinoresenorelose, ethylcellulose, polyvinylinolenolechol, oxidized starch, phosphorylated starch, casein, and the like.
- Can be These may be used alone or in combination of two or more.
- Aluminum, stainless steel, nickel plating steel, etc. are used for the current collector of the positive electrode.
- the positive electrode is formed by applying a slurry of the above-described positive electrode active material, a binder, a conductive agent, and other optional additives to a current collector and drying the slurry. can do.
- a solvent used for slurrying an organic solvent that dissolves the binder is usually used.
- N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, getyltriamine, N, N-dimethylaminopropylamine , Ethylene oxide, tetrahydrofuran and the like are used, but not limited thereto. These may be used alone or in combination of two or more.
- a slurry of the active material can be prepared by adding a dispersing agent, a thickening agent and the like to water and using a latex such as SBR.
- the thickness of the positive electrode active material layer thus formed is usually about 10 to 20 ⁇ .
- the active material layer obtained by coating and drying is preferably compacted by a roller press or the like in order to increase the packing density of the active material.
- the negative electrode one obtained by forming an active material layer containing the above-described negative electrode active material and a binder on a current collector is usually used.
- Negative electrode active materials include thermally decomposed organic substances under various pyrolysis conditions, artificial graphite, and natural Carbonaceous materials capable of occluding and releasing lithium such as graphite; metal oxide materials capable of occluding and releasing lithium such as tin oxide and silicon oxide; lithium metal; various lithium alloys,
- a metal material capable of forming an alloy with lithium such as Si and Sn, can be used.
- These negative electrode active materials may be used alone or in a combination of two or more.
- the resistance of the film formed by the film-forming agent in the non-aqueous electrolyte and its temperature dependency are considered to be appropriate when the carbonaceous material is used. Therefore, the effect of the present invention can be more easily obtained, which is preferable.
- the chain carbonate represented by the general formula (I) when the carbonaceous material is used in the above, the general formula in a non-aqueous electrolyte is used.
- the chain carbonate represented by (I) is preferable because a stable film is easily formed, and the effect of improving cycle characteristics according to the present invention is more easily obtained.
- the effect of the present invention is more likely to be obtained because the positive electrode potential does not easily increase when the battery is used at a high voltage. And preferred.
- the binder is not particularly limited as long as it is a material that is stable with respect to the solvent and the electrolyte used in the production of the electrode and other materials used in the use of the battery.
- Specific examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, styrene'butadiene rubber, isoprene rubber, and butadiene rubber. These may be used alone or in combination of two or more.
- the lower limit of the proportion of the binder in the negative electrode active material layer 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.
- the content is preferably 60% by weight or less, more preferably 40% by weight or less, and further preferably 10% by weight or less. If the proportion of the binder is small, the active material cannot be sufficiently retained, so that the mechanical strength of the negative electrode becomes insufficient and battery performance such as cycle characteristics may be deteriorated.On the other hand, if the proportion is too large, the battery capacity and conductivity may be reduced. become.
- the negative electrode active material layer may further contain a usual additive for the active material layer such as a thickener.
- Thickeners are used in solvents and electrolytes used in electrode manufacturing, and in other materials used in batteries.
- the material is not particularly limited as long as it is a stable material. Specific examples thereof include carboxycinolemethinolenorelose, methinoresenolelolose, hydroxymethylinoresenorelose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and the like. . These may be used alone or in combination of two or more. Copper, nickel, stainless steel, nickel plating steel, etc. are used as the current collector of the negative electrode.
- the negative electrode can be formed by applying a slurry of the above-described negative electrode active material, a binder, and other optional additives to a current collector, and drying the slurry.
- a solvent used for slurrying an organic solvent that dissolves a binder is usually used.
- N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, getyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran Etc. are used, but are not limited to these. These may be used alone or in combination of two or more.
- a dispersant, a thickener and the like can be added to water to form a slurry of the active material with a latex such as SBR.
- the thickness of the negative electrode active material layer thus formed is usually about 10 to 200 ⁇ .
- the active material layer obtained by coating and drying is preferably compacted by a roller press or the like in order to increase the packing density of the active material.
- the lithium secondary battery of the present invention is manufactured by assembling the above-described positive electrode, negative electrode, non-aqueous electrolyte, and separator into an appropriate shape. Further, if necessary, other components such as an outer case can be used.
- the shape of the battery is not particularly limited, and can be appropriately selected from various generally employed shapes according to the application.
- Examples of commonly used shapes include a cylinder type with a sheet electrode and a separator in a spiral shape, a cylinder type with an inside-out structure combining a pellet electrode and a separator, and a coin with a stacked pellet electrode and a separator.
- Type, sheet electrode and Examples include a laminate type in which separators are laminated.
- the method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the intended battery.
- the amount of water contained in the battery is preferably in a specific range with respect to the electrolyte.
- the water content is usually at least 200 ppm, preferably at least 250 ppm, and usually at most 500 ppm, preferably at most 300 ppm.
- the amount of water in the battery is less than the above range, the amount of the contributing substance effective for lowering the electrode interface resistance described above is small, and the interface resistance cannot be reduced. If the amount of water in the battery is larger than the above range, the capacity decreases due to the deterioration of the electrode active material due to hydrofluoric acid generated by the reaction between the water and the salt in the electrolytic solution, which is not preferable.
- any known method can be used to measure the water content in the battery. Before the battery is assembled, the water content of each component may be measured and the sum thereof may be obtained. Also, after the battery is assembled, the water content in the battery is immediately collected in the electrolyte solution as described above, so that the water content in the electrolyte solution in the battery may be measured.
- the water content of the electrode material and the separator used for assembling the battery is measured as follows.
- the measurement sample Place the measurement sample in a 130 ° C heating furnace with nitrogen gas flow and hold it for 20 minutes.
- the flowed nitrogen gas is introduced into the measurement cell of the Karl Fischer moisture meter and the water content is measured.
- the integrated value for 20 minutes is defined as the total water content.
- the measurement is performed in a glove box with a dew point of 75 ° C to prevent the ingress of moisture.
- the amount of water in the electrolyte is measured as follows.
- HF can be quantified by acid measurement, and the water content can be calculated from the value.
- the method of measuring the water content of the electrolytic solution in the battery is not limited, but the battery may be disassembled in a sealed container free of water, the electrolytic solution may be taken out, and the above-mentioned water content may be measured.
- the method of measuring the water content of the electrolytic solution in the battery is not limited, but the battery may be disassembled in a closed container, the electrolytic solution may be taken out, and the above-mentioned water content may be measured.
- the present invention in order to keep the amount of water in the battery within a specific range, it is important to control the moisture conditions such as the moisture brought in from each member and the assembly atmosphere in assembling the battery of the present invention. It is. That is, for the members to be used, for example, in accordance with the total amount of water in the battery, appropriate measures are taken such as controlling the water in the storage atmosphere and protecting the material with a material that does not damp. Also, when assembling batteries, it is necessary to take measures such as paying attention to moisture management in the atmosphere such as dry air.
- the total amount of water contained in the positive electrode material, the negative electrode material, and the separator is usually 200 ppm or more, preferably '250 ppm or more, usually 500 ppm or less, even 300 ppm in the electrolyte.
- the battery of the present invention can be manufactured.
- the general embodiment of the lithium secondary battery of the present invention has been described above.
- the lithium secondary battery of the present invention is not limited to the above embodiment, and various modifications may be made without departing from the gist thereof. Can be added. Examples>
- High-density polyethylene ““HI-Z EX 7000 FP” manufactured by Mitsui Chemicals, weight average molecular weight: 200,000, density: 0.0 SS e gZcm 3 , melt flow rate: 0.04 g
- R 110 E weight average molecular weight: 330,000
- 8.8 parts by weight hardened castor oil [Toyokuni Oil ⁇ HY-CASTOR 01 '', molecular weight 938) 8.8 parts by weight, barium sulfate (number-average average particle size 0.1 8 ⁇ ) 176.5 parts by weight as an inorganic filler, and melt-knead.
- the obtained resin composition was subjected to inflation molding at a temperature of 210 ° C. to obtain a raw sheet.
- the thickness of the raw sheet was 105 ⁇ on average.
- the obtained raw sheet was successively stretched 4 times in the sheet longitudinal direction (MD) at 90 ° C, and then 2.9 times in the width direction (TD) at 120 ° C to obtain a film thickness of 26 ⁇ .
- Porosity 64% average pore size (average pore size defined by ASTM F 3 16-86) 0.2 7 ⁇ , gas permeability (Gurley permeability defined by JISP 8 117) 44 Seconds /
- a polymer porous membrane of 100 cc was obtained.
- This polymer porous membrane is referred to as a separator A.
- the inorganic filler was not dropped off from the polymer porous membrane.
- the average liquid retention rate change rate obtained by the measurement method described above is 9.
- Li CoO 2 having the physical properties shown in Table 3 as the positive electrode active material
- 85 parts by weight of Li Co 0 2 and 6 parts by weight of carbon black and polyvinylidene fluoride (trade name “KF-1 000 ”), 9 parts by weight were added, mixed, and dispersed with N-methyl-2-pyrrolidone to form a slurry.
- This is uniformly applied to one side of a 2 ⁇ thick aluminum foil as a positive electrode current collector, dried, and then pressed by a press machine so that the density of the positive electrode active material layer becomes 3.0 gZcm 3.
- the positive electrode was used.
- a negative electrode active material As a negative electrode active material, 94 parts by weight of natural graphite powder having the physical properties shown in Table 3 Six parts by weight of twolidenes were mixed and dispersed with N-methyl-2-pyrrolidone to form a slurry. This was uniformly applied to one surface of a copper foil having a thickness of 1 8Myupaiiota a negative electrode current collector, dried, and flop-less as the density of the negative electrode active material layer becomes 1. 5 g cm 3 by press A negative electrode was used. Battery assembly>
- a 18650 type cylindrical battery was fabricated using the separator A, the nonaqueous electrolyte, the positive electrode and the negative electrode (the lithium secondary battery of Example 11-11). That is, the positive electrode and the negative electrode were wound through the separator A to form an electrode group, which was sealed in a battery can. After that, 5 ml of the above electrolyte solution was injected into the battery can loaded with the electrode group, and was sufficiently permeated into the electrodes.
- the end-of-charge voltage at a constant current equivalent to 0.2 C (the current value for discharging the rated capacity per hour with a discharge capacity of 1 hour is 1 C, the same applies hereinafter) at a constant current of 4.2 V, Stabilize by performing charge / discharge 3 cycles at a discharge end voltage of 3 V, and charge the 4th cycle to a charge end voltage of 4.2 V with a current equivalent to 0.5 C, with a charge current value of 0.05 C Charge until the current value is reached.
- the charge / discharge cycle for discharging at a constant current of C was defined as one cycle, and this cycle was repeated 500 times.
- the cycle test was performed at 25 ° C. After this cycle test, the same charge / discharge as in 1) Initial charge / discharge was performed, and the ratio of the last discharge capacity to the initial capacity at this time is shown in Table 3 as the cycle durability. (Example 11-2)
- the natural graphite having the physical properties shown in Table 3 was used as the negative electrode active material, and the physical properties shown in Table 3 were spheroidized by spray dryer treatment using a four-fluid nozzle method as the positive electrode active material.
- a secondary battery was fabricated and evaluated in the same manner. The results are shown in Table 3.
- a 5850 type cylindrical battery (the lithium secondary battery of Examples 1-3) was prepared in the same procedure as in Example 1-1 except that 5: 0.50: 0.50 (molar ratio) was used. The evaluation was performed in the same manner, and the results are shown in Table 3. '
- High-density polyethylene ““HI-ZEX 7000 FP” manufactured by Mitsui Chemicals, weight average molecular weight: 200,000, density: 0.956 gZcm 3 , menoleto flow rate: 0.04 g
- R110E weight average molecular weight: 330,000] 8.8 parts by weight, hardened castor oil [HY-CASTORO IL, manufactured by Toyokuni Oil Co., molecular weight 938] 8.8 parts by weight, barium sulfate as an inorganic filler [Numerical average particle size 0.17 ⁇ ] 11.7.6 parts by weight were blended and melt-kneaded, and the obtained resin composition was subjected to inflation molding at a temperature of 210 ° C to obtain a raw sheet. . The thickness of the raw sheet was 11 1 ⁇ on average.
- the obtained raw sheet was sequentially stretched 4 times in the sheet longitudinal direction (MD) at 90 ° C, and then 2.9 times in the width direction (TD) at 120 ° C, and the film thickness was 25 ⁇
- a polymer porous membrane having a porosity of 61%, an average pore diameter of 0.19 ⁇ , and a Gurley air permeability of 85 s / 100 cc was obtained.
- This polymer porous membrane is referred to as a separator B.
- no inorganic filler was dropped from the polymer porous membrane.
- the average rate of change in the amount of liquid retention determined by the above-described measurement method was 1.3%.
- An 18650 type cylindrical battery (lithium secondary battery of Examples 1 to 4) was fabricated in the same procedure as in Example 3 except that separator B was used as the separator, and the evaluation was performed in the same manner. The results are shown in Table 3.
- Example 11 The procedure of Example 11 was repeated except that natural graphite having the physical properties shown in Table 3 was used as the negative electrode active material, and LiCoO 2 having the physical properties shown in Table 3 was used as the positive electrode active material.
- a 0-type cylindrical battery (the lithium secondary battery of Comparative Example 11) was fabricated and evaluated in the same manner. The results are shown in Table 2.
- a mixture of 25 parts by weight of poly earth styrene having a viscosity average molecular weight of 100,000 and 25 parts by weight of paraffin wax (average molecular weight of 389) was extruded using a twin screw extruder with a diameter of 4 Omm at a temperature of 170 °.
- An original film was prepared by extrusion inflation at a temperature of ° C.
- the obtained raw film was immersed in isopropanol at 60 ° C to extract and remove paraffin wax.
- the obtained film was longitudinally stretched 2.0 times at a temperature of 90 ° C using a roll stretching machine, and then stretched 6.0 times at a temperature of 100 ° C with a tenter stretching machine.
- a porous membrane having a thickness of 22 ⁇ , a porosity of 50%, an average pore diameter of 0.04 ⁇ , and a Gurley air permeability of 450 seconds 100 cc was obtained.
- This polymer porous membrane is referred to as a separator C.
- the average liquid retention amount change rate determined by the above-described measurement method was 17.2% / min.
- An 18650 type cylindrical battery (lithium secondary battery of Comparative Example 1-2) was fabricated in the same procedure as in Example 1-3 except that separator C was used as the separator, and the evaluation was performed in the same manner. Table 3 shows the results.
- the separator C of Comparative Example 1-2 has the same area stretching ratio as that of the separators 8 and ⁇ of Examples 13 and 1-4. About 12 times).
- a particulate active material having a small aspect ratio is used as the negative electrode active material and / or the positive electrode active material, and a separator having an inorganic filler in a thermoplastic resin is provided.
- the lithium secondary batteries of Examples 11 to 11 were obtained by Comparative Example 1-1 or the extraction method in which neither the negative electrode active material nor the positive electrode active material was a particulate active material having a small aspect ratio. It shows better cycle characteristics than Comparative Examples 1-2 using a small pore size separator containing no inorganic filler.
- Examples 13 and 1-4 and Comparative Examples 1 and 2 the same negative electrode active material and the same positive electrode active material were used, the same density of the negative electrode and the positive electrode were formed, and only the separator was different. I have.
- the separator C by the extraction method used in Comparative Example 1-2 is the same as the separators 8 and B manufactured by the interfacial peeling method used in Examples 1-3 and 1-4, and has the same area as the raw sheet having the same thickness. It was obtained by stretching at a stretching ratio (about 12 times), but the average pore size was significantly different. The average pore sizes of separators 8 and B were 0.27 ⁇ and 0.19 ⁇ . The separator C is 0.04 pm. Separators 8 and B have excellent liquid retention properties of the electrolyte, with average liquid retention change rates of 9.2% and 11.3% Z, respectively, whereas separator C has an average liquid retention. The rate of change in volume is 17.2% / min.
- the pore size of the obtained porous membrane does not become so large, but rather becomes small even if the stretching ratio is increased, because the film becomes dense (shrinkage in the thickness direction due to stretching). Therefore, it is difficult to realize a separator effective for improving liquid retention.
- High-density polyethylene manufactured by Mitsui Chemicals Inc., "HI- Z EX 7000 FP", a weight average molecular weight: 200,000, density; 0. 9 5 6 gZc m 3 , agate Leto flow rate; 0.
- the obtained raw sheet was successively stretched 4 times in the sheet longitudinal direction (MD) at 90 ° C, and then 2.9 times in the width direction (TD) at 120 ° C. 26 ⁇ , porosity 64%, average pore size (average pore size determined by ASTM F 3 16-86) 0.27 ⁇ , Gurley air permeability (Gurley air permeability specified by JISP 8 117) 44 seconds
- a 100 cc polymer porous membrane was obtained. This polymer porous membrane is referred to as separator A.
- separator A In the process of stretching, the inorganic filler was not dropped off from the polymer porous membrane.
- L i C o O 2 85 parts by weight of carbon black click 6 parts by weight of polyvinylidene fluoride (Kureha Chemical Co., trade name "KF 1000") 9 parts by weight were added, mixed, and dispersed with N-methyl-2-pyrrolidone to form a slurry. This is uniformly applied to one side of a 2 ⁇ thick aluminum foil, which is the positive electrode current collector, dried, and then pressed by a press so that the density of the positive electrode active material layer becomes 3.O gZcm 3. And Production of negative electrode>
- spheroidized natural graphite powder (similar to that in Examples 13 to 13) as a negative electrode active material
- 94 parts by weight of natural graphite powder and 6 parts by weight of polyvinylidene fluoride were mixed, and N-methyl-2- —Dispersed with pyrrolidone to make a slurry.
- This is uniformly coated on one surface of a copper foil having a thickness of 18 ⁇ , which is a negative electrode current collector, dried, and then pressed by a press machine so that the density of the negative electrode active material layer becomes 1.5 gZcm 3.
- a press machine to form a negative electrode.
- a 2032 type coin cell was prepared using the separator A, the nonaqueous electrolyte, the positive electrode and the negative electrode. That is, a stainless steel can body also serving as a positive electrode conductor accommodates a positive electrode impregnated with an electrolytic solution by punching into a disk having a diameter of 12.5 mm and impregnated with an electrolytic solution thereon. A negative electrode impregnated with an electrolytic solution was placed by punching into a disk having a diameter of 12.5 mm through an 8 mm separator. The can body and the sealing plate also serving as the negative electrode conductor were caulked via an insulating gasket and sealed to produce a coin-type battery. Here, the impregnation of the battery member with the electrolytic solution was performed by immersing each member in the electrolytic solution for 2 minutes. Battery evaluation>
- the charge end voltage is 4.2 V
- discharge end Stabilize by performing 3 cycles of charging / discharging at a voltage of 3 V
- charge the 4th cycle with a current equivalent to 0.5 C to the end-of-charge voltage 4.2 V
- charge current value equivalent to 0.05 C Charge until it reaches 4.2 V—constant current, constant voltage charge (CCCV After charging (0.05 C cut), 3 V discharge was performed at a constant current value equivalent to 0.2 C.
- High-density polyethylene manufactured by Mitsui Chemicals Inc., "HI- Z EX 7000 FP", a weight average molecular weight: 200,000, density; 0. 9 56 ⁇ Bruno ⁇ : 11 3, agate Leto flow rate; 0. 04 g
- R110E weight average molecular weight: 330,000] 8.8 parts by weight, hardened castor oil [HY-CASTOR 011, manufactured by Toyokuni Oil Co., molecular weight 938] 8.8 parts by weight, barium sulfate as inorganic filler [Number-based average particle size 0.17 ⁇ ] 11.7.6 parts by weight are blended and melt-kneaded, and the obtained resin composition is subjected to inflation molding at a temperature of 210 ° C to obtain a raw sheet.
- the thickness of the raw sheet was 11 1 ⁇ on average.
- the obtained raw sheet was stretched 4 times in the machine direction (MD) at 90 ° C, and then 2.9 times in the width direction (TD) at 120 ° C.
- This polymer porous membrane is referred to as a separator B.
- no inorganic filler was dropped from the polymer porous membrane.
- a coin-type battery (the lithium secondary battery of Example 2-2) was fabricated in the same procedure as in Example 2-1 except that the separator B was used, and the evaluation was performed in the same manner. The results are shown in Table 4.
- Example 2-1 Same as Example 2-1 except that in preparing the non-aqueous electrolyte, vinyl ethylene carbonate (VEC) was mixed instead of vinylene carbonate so that the concentration in the non-aqueous electrolyte was 2% by weight.
- VEC vinyl ethylene carbonate
- a coin-type battery (the lithium secondary battery of Examples 2-3) was manufactured by the procedure described in Example 2, and the evaluation was similarly performed. The results are shown in Table 4.
- An original film was created.
- the obtained raw film was immersed in isopropanol at 60 ° C to extract and remove paraffin wax.
- the obtained film was longitudinally stretched 2.0 times at a temperature of 90 ° C. using a roll stretching machine, and then stretched 6.0 times at a temperature of 100 ° C. with a tenter stretching machine to obtain a film thickness of 22 pm.
- a porous membrane having a porosity of 50%, an average pore size of 0.04 ⁇ , and a Gurley air permeability of 440 sec / 100 cc was obtained. This polymer porous membrane is referred to as a separator C.
- a coin-type battery (lithium secondary battery of Comparative Example 2-1) was manufactured in the same procedure as in Example 2-1 except that the separator C was used, and the evaluation was performed similarly. The results are shown in Table 4.
- the separator C of Comparative Example 2-1 had the same area stretching ratio (about 12 times) as that of the separators B of Examples 2-1 and 2-2. A comparison of the effect of pore size on resistance can be made. [Example 2-4]
- a coin-type battery (the lithium secondary battery of Example 2-4) was prepared in the same procedure as in Example 2-1 except that vinylene carbonate was not mixed when preparing the electrolyte. The evaluation was performed and the results are shown in Table 4.
- a coin-type battery (lithium secondary battery of Example 2-5) was prepared and evaluated in the same manner as in Example 22 except that vinylene carbonate was not mixed when preparing the electrolyte. Table 4 shows the results.
- a coin-type battery (a lithium secondary battery of Comparative Example 2-2) was produced in the same procedure as in Example 2-3, except that the separator C manufactured in Comparative Example 2-1 was used as the separator. Table 4 shows the results.
- the lithium secondary batteries of Examples 2-1 to 2-3 provided with a non-aqueous electrolytic solution containing a film forming agent and a separator containing an inorganic filler in a thermoplastic resin.
- the battery exhibited better cycle characteristics than those of Examples 2-4 and 2-5 that did not contain a film-forming agent, and used a separator with a small pore size that did not contain an inorganic filler obtained by the extraction method.
- the low-temperature rate characteristics were higher than those of Comparative Examples 2-1 and 2-2.
- Comparative Examples 2-1 and 2-2 using a separator having a small pore diameter obtained by an extraction method as a separator exhibited low-temperature rate characteristics caused by the film-forming agent. There is a problem of decline.
- the separator C obtained by the extraction method used in Comparative Examples 2-1 and 2-2 has the same thickness as the separator manufactured by the interfacial peeling method in Examples 2-1 and 2-2. This was obtained by stretching the raw sheet at the same area stretching ratio (approximately 12 times), but the average pore size was significantly different. Separator C is 0.04 ⁇ while 27 ⁇ and 0.19 ⁇ . The large difference in the average pore diameters in Examples 2-1 to 2-3 using the separators 8 and ⁇ having large pore diameters offset the increase in resistance due to the film forming agent due to the electrical resistance reduction effect of the separators. , Maintain low temperature rate characteristics. On the other hand, in Comparative Examples 2-1 and 2-2 using the separator C having a small pore size, such an effect cannot be obtained, and the low-temperature rate characteristics are deteriorated.
- the pore size of the obtained porous membrane does not become so large, but rather becomes small even if the stretching ratio is increased, because the film becomes dense (shrinkage in the thickness direction due to stretching). Therefore, it is difficult to realize a separator effective for reducing the internal resistance of the battery.
- High-density polyethylene [HI-Z EX 7000 FP, manufactured by Mitsui Chemicals, weight average molecular weight: 200,000, density: 0.956 g / cm 3 , melt flow rate: 0.04 g / 1 Om in 100 parts by weight, soft polypropylene (“PER R 110 E” manufactured by Idemitsu Petrochemical Co., weight average molecular weight: 330000) 8.8 parts by weight, hardened castor oil “HY—CASTOR 01” manufactured by Toyokuni Oil Co., molecular weight 938 8.8 parts by weight, barium sulfate as an inorganic filler [number-based average particle size 0.18 ⁇ ] 176.5 parts by weight is blended and melt-kneaded, and the obtained resin composition is heated at a temperature of 210 ° C.
- L i C o 0 2 85 parts by weight of carbon black click 6 parts by weight of polyvinylidene fluoride (Kureha Chemical Co., trade name "KF 1000") 9 parts by weight was added and mixed, and dispersed with N-methyl-2-pyrrolidone to form a slurry. This is uniformly coated on one side of a 2 ⁇ thick aluminum foil as a positive electrode current collector, dried, and then pressed by a press machine so that the density of the positive electrode active material layer becomes 3.O g / cm 3. To make a positive electrode.
- KF 1000 polyvinylidene fluoride
- spheroidized natural graphite powder (similar to that in Examples 13 to 13) as a negative electrode active material
- 94 parts by weight of natural graphite powder and 6 parts by weight of polyvinylidene fluoride were mixed, and N-methyl-2- —Dispersed with pyrrolidone to make a slurry.
- This is uniformly coated on one side of a 18 pm thick copper foil, which is a negative electrode current collector, dried, and pressed by a press machine so that the density of the negative electrode active material layer becomes 1.5 gZ cm 3.
- a press machine To form a negative electrode.
- An 18650 type cylindrical battery was manufactured using the separator A, the non-aqueous electrolyte, the positive electrode and the negative electrode. That is, the positive electrode and the negative electrode were wound through the separator A to form an electrode group, which was sealed in a battery can. Thereafter, 5 mL of the above-mentioned electrolyte was injected into the battery can in which the electrode group was loaded, and was sufficiently penetrated into the electrodes.
- High-density polyethylene ““HI-Z EX 7000 FP” manufactured by Mitsui Chemicals, weight average molecular weight: 200,000, density: 0.956 g / cm 3 , menoleto flow rate: 0.04 g / 1 Om in 100 parts by weight
- soft polypropylene [PER R110E, manufactured by Idemitsu Petrochemicals Co., Ltd., weight average molecular weight: 330,000] 8.8 parts by weight, hardened castor oil [HY—CASTORO IL, manufactured by Toyokuni Oil Co., Ltd., molecular weight 938] 8.8 parts by weight, barium sulfate as inorganic filler [number-based average particle size 0.17 ⁇ ] 1 17.6 parts by weight, and melt-kneaded.
- An 18650 type cylindrical battery (lithium secondary battery of Example 3-2) was fabricated in the same procedure as in Example 3-1 except that the separator ⁇ was used, and the evaluation was performed in the same manner. The results are shown in Table 5. Indicated.
- An 18650 type cylindrical battery (the lithium secondary battery of Example 3-3) was prepared in the same manner as in Example 3-1 except that ethyl methyl carbonate was used instead of dimethyl carbonate when preparing the nonaqueous electrolyte.
- a secondary battery was fabricated and evaluated in the same manner. The results are shown in Table 5.
- a mixture of 25 parts by weight of polyethylene having a viscosity-average molecular weight of 1,000,000 and 75 parts by weight of paraffin wax (average molecular weight: 389) is extruded using a 4 Omm diameter twin screw extruder at an extrusion temperature of 170 ° C, and is extruded by inflation.
- a film was made. The obtained raw film was immersed in isopropanol at 60 ° C to extract and remove paraffin wax. The obtained film was longitudinally stretched 2.0 times at a temperature of 90 ° C using a roll stretching machine, and then stretched 6.0 times at a temperature of 100 ° C with a tenter stretching machine to obtain a film thickness of 22 ⁇ .
- a porous membrane having a porosity of 50%, an average pore size of 0.04 pm, and a Gurley air permeability of 440 seconds / 100 cc was obtained. This polymer porous membrane is referred to as a separator C.
- An 18650 type cylindrical battery (lithium secondary battery of Comparative Example 3-1) was prepared in the same procedure as in Example 3_1 except that separator C was used, and the evaluation was performed similarly. The results are shown in Table 5. Indicated.
- the separator C of Comparative Example 3-1 was used to clarify the effect of the presence or absence of the filler.
- the area stretching ratio was set to be about the same (approximately 12 times) with respect to the separators A and B of Examples 3-1 and 3-2.
- Example 3-1 The procedure of Example 3-1 was repeated except that dimethyl carbonate was used instead of dimethyl carbonate in preparing the electrolytic solution, and the 18650 type cylindrical battery (Example 3-4) was used. Lithium secondary battery) was fabricated and evaluated in the same way. The results are shown in Table 5.
- Example 3-5 In preparing the electrolytic solution, an 18650 type cylindrical battery (Example 3-5) was used in the same procedure as in Example 3-2, except that getyl carbonate was used instead of dimethyl carbonate. Lithium secondary battery) was fabricated and evaluated in the same way. The results are shown in Table 5. '
- Example 3-3 The procedure was the same as in Example 3-3, except that the separator C manufactured in Comparative Example 3-1 was used as the separator.
- the 850-inch cylindrical battery (the lithium secondary battery of Comparative Example 2-2) was prepared and evaluated in the same manner. Table 5 shows the results.
- Examples 3 to 3 provided with a non-aqueous electrolyte containing dimethyl carbonate or ethyl methyl carbonate and a separator containing an inorganic filler in a thermoplastic resin.
- the lithium secondary battery of No. 3 shows better cycle characteristics than Examples 3-4 and Examples 3_5 which do not contain dimethyl carbonate or ethyl methyl carbonate, and does not contain inorganic fillers
- the amount of gas generation is significantly smaller than Comparative Examples 3-1 and 3-2 using the separator.
- Comparative Examples 3-1 and 3-2 in which a separator containing no inorganic filler was used as the separator were caused by dimethyl carbonate or ethyl methyl carbonate. There is a gas generation problem.
- High-density polyethylene (“HI-Z EX 7000 FP”, manufactured by Mitsui Chemicals, weight average molecular weight: 200,000, density: 0.956 g / cm 3 , Menoletov mouth rate: 0.04 g / 1 Om in ] 100 parts by weight
- soft polypropylene (“PER R 110 E” manufactured by Idemitsu Petrochemical Co., weight average molecular weight: 330000) 8.8 parts by weight
- hydrogenated castor oil “HY—CASTOR 01 Otsu” manufactured by Toyokuni Oil Co., Ltd.
- a polymer porous membrane of 44 seconds / 100 cc was obtained. This polymer porous membrane is referred to as a separator A. In the process of stretching, the inorganic filler was not dropped off from the polymer porous membrane.
- L i C o 0 2 85 parts by weight of carbon black click 6 parts by weight of polyvinylidene fluoride (Kureha Chemical Co., trade name "KF 1000") 9 parts by weight was added and mixed, and dispersed with N-methyl-2-pyrrolidone to form a slurry. This is uniformly applied to one side of a 2 ⁇ thick aluminum foil, which is the positive electrode current collector, and after drying, the density of the positive electrode active material layer becomes 3.O g / cm 3 by a press machine. To obtain a positive electrode. Preparation of negative electrode>
- spheroidized natural graphite powder (similar to that in Examples 13 to 13) as a negative electrode active material
- 94 parts by weight of natural graphite powder and 6 parts by weight of polyvinylidene fluoride were mixed, and N-methyl-2- —Dispersed with pyrrolidone to make a slurry.
- This was uniformly applied to one surface of a copper foil of the negative electrode is a collector thickness of 1 8Myupaiiota, after drying, the density of the more negative electrode active material layer in the press was pressed so that the 1. 5 gZc m 3 To form a negative electrode.
- the negative electrode plate and the positive electrode plate produced as described above were wound together with the separator A in an overlapping manner, and the outermost periphery was stopped with a tape to form a spiral electrode body.
- This electrode body was inserted into the cylindrical battery case made of stainless steel through the opening. Then, the negative electrode lead connected to the negative electrode of the electrode body is welded to the inner bottom of the battery case, and the positive electrode lead connected to the positive electrode of the electrode body is connected to the battery when the gas pressure inside the battery rises to a predetermined level or more. Welded with the bottom of the working current interrupter. At the bottom of the sealing plate, an explosion-proof valve and current interrupter were installed. After the electrolyte was injected, the battery case was sealed at the opening with a sealing plate and an insulating gasket made of polypropylene (PP) to obtain a lithium secondary battery of Example 4-1.
- PP polypropylene
- End-of-charge voltage at a constant current equivalent to 0.2 C over a 25 ° C period (the current value for discharging the rated capacity per hour with a discharge capacity of 1 hour is 1 C, and so on) 4.2 3 cycles of charge / discharge at 3 V with a discharge end voltage of 3 V to stabilize.
- High-density polyethylene ““HI-ZEX 7000 FP”, manufactured by Mitsui Chemicals, weight average molecular weight: 200,000, density: 0.956 g / cm 3 , menoleto flow rate: 0.04 g / 1 Om in] 100 Parts by weight, soft polypropylene [PERR 110 E, manufactured by Idemitsu Petrochemical Co., weight average molecular weight: 330,000] 8.8 parts by weight, hardened castor oil [HY—CASTOR OIL, molecular weight 938, manufactured by Toyokuni Oil Company] 8.
- a cylindrical battery (the lithium secondary battery of Example 4-2) was manufactured in the same procedure as in Example 4-1 except that the separator B was used, and the battery was evaluated in the same manner. The results are shown in Table 6.
- Example 4-11 In the preparation of the non-aqueous electrolyte, the cylindrical mold was prepared in the same procedure as in Example 4-1 except that CHB was mixed so that the concentration in the non-aqueous electrolyte was 3% by weight. A battery (the lithium secondary battery of Example 4-3) was produced, and its evaluation was similarly performed. The results are shown in Table 6.
- Example 4-11 In the preparation of the non-aqueous electrolyte, a cylindrical mold was prepared in the same procedure as in Example 4-1 except that CHB was mixed so that the concentration in the non-aqueous electrolyte was 1% by weight. Batteries (lithium secondary batteries of Examples 4-4) were fabricated and evaluated in the same manner. The results are shown in Table 6.
- Example 4-11 a cylindrical battery (the lithium of Example 4-5) was prepared in the same manner as in Example 4-11 except that biphenyl (BP) was used instead of CHB when preparing the non-aqueous electrolyte.
- BP biphenyl
- a secondary battery was fabricated and evaluated in the same manner. The results are shown in Table 6. Note that BP indicated 3.3 as the exothermicity in the exothermicity measurement test described above.
- Example 4-5 a cylindrical battery (the lithium secondary battery of Example 4-6) was manufactured in the same procedure as in Example 4-5, except that the separator B was used as the separator. They were fabricated and evaluated in the same manner. Table 6 shows the results. (Comparative Example 4-1)
- An original film was prepared by extrusion inflation method. The obtained raw film was immersed in isopropanol at 60 ° C to extract and remove paraffin wax. The obtained film was longitudinally stretched 2.0 times at a temperature of 90 ° C using a roll stretching machine, and then stretched 6.0 times at a temperature of 100 ° C with a tenter stretching machine.
- a cylindrical battery (lithium secondary battery of Comparative Example 4-1) was produced in the same procedure as in Example 4-1 except that the separator C was used, and the evaluation was performed in the same manner. The results are shown in Table 6. '
- Example 4-5 a cylindrical battery (the lithium secondary battery of Comparative Example 4-12) was produced in the same procedure as in Example 4-15 except that the separator C was used as the separator, and the evaluation was performed similarly. Table 6 shows the results.
- Example 4-11 A cylindrical battery (the lithium secondary battery of Example 4-7) was prepared in the same manner as in Example 4-1 except that CHB was not added when preparing the non-aqueous electrolyte. was prepared and evaluated in the same manner, and the results are shown in Table 6. (Comparative Examples 4-1-3)
- Example 4-1 A cylindrical battery (Example 4-1) was prepared in the same manner as in Example 4-1 except that 2,4-difluoroisole (DFA) was used instead of CHB when preparing the non-aqueous electrolyte. Comparative Example 4-3 lithium secondary battery) was fabricated and evaluated in the same manner. The results are shown in Table 6.
- DFA 2,4-difluoroisole
- DFA showed 0.5 as the exothermicity in the exothermicity measurement test described above.
- the separator C by the extraction method used in Comparative Examples 4-1 and 4_2 was the same as the separators 8 and B manufactured by the interfacial peeling method in Examples 4-1 to 417. It is obtained by stretching a raw sheet of thickness at the same area stretching ratio (approximately 12 times), but the average pore diameter is significantly different.
- the average pore diameters of separator and B are 0.27 ⁇ and 0.19pm.
- the separator C is 0.04 ⁇ .
- separators 8 and 7 containing an inorganic filler it is considered that the oxidation of the separator is also suppressed as described above, thereby suppressing the polymerization reaction of the overcharge inhibitor during high-temperature storage. This is also considered to be the cause of maintaining the high-temperature storage characteristics.
- the pore size of the obtained porous membrane does not become so large, but rather becomes small even if the stretching ratio is increased, because the film becomes dense (shrinkage in the thickness direction due to stretching). Therefore, it is difficult to realize an effective separator to prevent clogging.
- a battery was manufactured according to the following procedure.
- High-density polyethylene [HI-Z EX 7000 FP, manufactured by Mitsui Chemicals, weight average molecular weight: 200,000, density: 0.0 SS e gZcm 3 melt flow rate; 0.04 g / 1 Om in] 100 parts by weight , Flexible polypropylene [PER R110E, manufactured by Idemitsu Petrochemical Co., weight average molecular weight: 330,000] 8.8 parts by weight, hardened castor oil [HY-CAS TORO IL, manufactured by Toyokuni Oil Co., molecular weight 938] 8 8 parts by weight, barium sulfate (number-based average particle size 0.1 8 ⁇ ) 176.5 parts by weight as inorganic filler
- the resin composition was melt-kneaded, and the obtained resin composition was subjected to inflation molding at a temperature of 210 ° C to obtain a raw sheet.
- the thickness of the raw sheet was 105 ⁇ on average.
- the obtained raw sheet was sequentially stretched 4 times in the machine direction (MD) at 90 ° C, and then 2,9 times in the width direction (TD) at 120 ° C to obtain a film thickness of 26 ⁇ .
- Porosity 64% average pore size (average pore size defined by ASTM F316-86) 0.27 ⁇
- Gurley air permeability Gurley air permeability determined by JISP 8117 44 seconds 1
- a polymer porous membrane of 00 cc was obtained. This polymer porous membrane is referred to as a separator A.
- the separator A was dried under the drying conditions shown in Table 7 to obtain a separator having a water content shown in Table 7.
- L i C o 0 2 85 parts by weight of carbon black click 6 parts by weight of polyvinylidene fluoride (Kureha Chemical Co., trade name "KF 1 000") 9 weight
- the mixture was mixed with N-methyl-2-pyrrolidone to form a slurry. This is uniformly applied to one side of a 2 ⁇ thick aluminum foil, which is the positive electrode current collector, dried, and then pressed by a press so that the density of the positive electrode active material layer becomes 3.O gZcm 3.
- the drying conditions of the positive electrode and the water content of the obtained positive electrode are shown below. Preparation of negative electrode>
- Sphericalized natural graphite powder (similar to that in Examples 13 to 13) was used as the negative electrode active material, and 94 parts by weight of natural graphite powder and 6 parts by weight of polyvinylidene fluoride were used. They were mixed and dispersed with N-methyl-1-pyrrolidone to form a slurry. This was uniformly applied to one surface of a copper foil having a thickness of 18 ⁇ a negative electrode current collector, dried, and pressed to a density of more active material layer to press becomes 1. 5 gZcm 3 negative And Table 7 shows the drying conditions of the negative electrode and the water content of the obtained negative electrode.
- An 18650 type cylindrical battery was produced using the separator, the non-aqueous electrolyte, the positive electrode and the negative electrode. That is, the positive electrode and the negative electrode were wound through the separator to form an electrode group, which was sealed in a battery can. Thereafter, 4.5 g of the above-mentioned electrolyte solution was injected into the battery can in which the electrode group was loaded, and was sufficiently penetrated into the electrode, followed by caulking.
- Example 5-1 The same as in Example 5-1 except that the drying conditions of the separator were changed as shown in Table 7 (however, the separator was not dried in Example 5-5), and the separator had the water content shown in Table 7. Then, each battery was manufactured.
- a battery was produced in the same manner as in Example 5-1 except that the separator B produced by the following method was used as the separator.
- a mixture of 25 parts by weight of polyethylene having a viscosity average molecular weight of 1,000,000 and 75 parts by weight of paraffin wax (average molecular weight of 389) is extruded using a 4 Omm diameter twin screw extruder at an extrusion temperature of 170 ° C and an original film by inflation. It was created. The obtained raw film was immersed in isopropanol at 60 ° C to extract and remove paraffin wax *.
- the obtained film was longitudinally stretched 2.0 times at a temperature of 90 ° C using a roll stretching machine, and then stretched 6.0 times at a temperature of 100 ° C with a tenter stretching machine to obtain a film thickness of 22 ⁇ ,
- a porous membrane having a porosity of 50%, an average pore size of 0.04 ⁇ , and a Gurley air permeability of 440 seconds / 100 cc was obtained.
- This polymer porous membrane is referred to as a separator B.
- This separator B was dried under the drying conditions shown in Table 7 to obtain a separator having a water content shown in Table 7.
- the following evaluations were performed on the batteries obtained in Examples 5-1 to 5-6, and the results are shown in Table 8.
- the trickle charge test was performed only on the batteries of Examples 5-2 and 5-6, and the results are shown in Table 9.
- End-of-charge voltage at a constant current equivalent to 0.2 C over 25 ° (the current value for discharging the rated capacity per hour with a discharge capacity of 1 hour is 1 C, and so on) 4.2 V, 3 cycles of charge / discharge at the discharge end voltage of 3 V to stabilize.
- the fourth cycle is charged to a charge end voltage of 4.2 V with a current equivalent to 0.5 C, and the charge current value is 0.05 C Charge until the current value becomes equivalent to 4.2 V-constant current constant voltage charge (CCCV charge) (0.05 C cut), then discharge 3 V at the constant current value equivalent to 0.2 C Was.
- the battery that has been initially charged and discharged is charged to a final charge voltage of 4.2 V at 25 ° C with a current equivalent to 0.5 C, and the charge current value is equivalent to 0.05 C. Charge until the current value is reached.
- 4.2 V constant current, constant voltage charge (CCCV charge) (0.05 C cut) was performed.
- the electrode interface resistance was determined by the AC impedance method, and the results are shown in Table 8.
- the measurement temperature is 25 ° C
- the measurement frequency is 20 kHz to 0.01 Hz
- the applied voltage is 1 OmV.
- the measurement of the interface resistance by the AC impedance method is described in, for example, Japanese Patent Application Laid-Open No. Hei 9-111701.
- the use of the lithium secondary battery of the present invention is not particularly limited, and the lithium secondary battery can be used for various known uses. Specific examples include notebook computers, pen input computers, Pile personal computer, e-book player, mobile phone, mobile fax, mobile copy, mobile printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, mini disk, transceiver, electronic notebook, calculator, memory Cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, clocks, strobes, cameras, and other small devices, and large devices such as electric vehicles and hybrid vehicles.
- the lithium secondary battery of the present invention achieves high capacity and has excellent cycle characteristics, it can be used in applications requiring high capacity such as various types of information communication terminals and mobile devices and used repeatedly. Especially excellent effects can be obtained.
- the lithium secondary battery of the present invention has excellent cycle characteristics and high low-temperature rate characteristics, so that particularly excellent effects can be obtained in applications repeatedly used in an environment with a large difference in temperature.
- the lithium secondary battery of the present invention is excellent in overcharge safety and has high high-temperature storage characteristics, so that it is particularly effective when used under relatively high-Pen conditions.
- the lithium secondary battery of the present invention is effective for preventing deterioration due to so-called trickle charge used to compensate for a capacity decrease due to self-discharge of a battery of a personal computer or the like, and thus is useful as a secondary battery for a personal computer. is there.
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Abstract
Description
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Priority Applications (8)
Application Number | Priority Date | Filing Date | Title |
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KR1020067014229A KR101094115B1 (ko) | 2003-12-15 | 2004-12-14 | 비수계 전해질 이차 전지 |
EP04807342.3A EP1705736B1 (en) | 2003-12-15 | 2004-12-14 | Nonaqueous electrolyte secondary battery |
CNB2004800410890A CN100541863C (zh) | 2003-12-15 | 2004-12-14 | 非水电解液二次电池 |
US11/453,006 US8137846B2 (en) | 2003-12-15 | 2006-06-15 | Nonaqueous-electrolyte secondary battery |
US13/368,983 US20120141887A1 (en) | 2003-12-15 | 2012-02-08 | Nonaqueous-electrolyte secondary battery |
US13/368,881 US20120135317A1 (en) | 2003-12-15 | 2012-02-08 | Nonaqueous-electrolyte secondary battery |
US13/368,950 US20120141886A1 (en) | 2003-12-15 | 2012-02-08 | Nonaqueous-electrolyte secondary battery |
US13/368,847 US20120141885A1 (en) | 2003-12-15 | 2012-02-08 | Nonaqueous-electrolyte secondary battery |
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JP2003-416762 | 2003-12-15 | ||
JP2003416761A JP4586359B2 (ja) | 2003-12-15 | 2003-12-15 | 非水系電解液二次電池 |
JP2003-416761 | 2003-12-15 | ||
JP2003416762A JP4635432B2 (ja) | 2003-12-15 | 2003-12-15 | 非水系電解液二次電池 |
JP2004-033618 | 2004-02-10 | ||
JP2004033618A JP4586374B2 (ja) | 2004-02-10 | 2004-02-10 | 非水系電解液二次電池 |
JP2004033617 | 2004-02-10 | ||
JP2004033619A JP4931331B2 (ja) | 2004-02-10 | 2004-02-10 | 非水系電解液二次電池 |
JP2004-033619 | 2004-02-10 | ||
JP2004-033617 | 2004-02-10 |
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US11/453,006 Continuation US8137846B2 (en) | 2003-12-15 | 2006-06-15 | Nonaqueous-electrolyte secondary battery |
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US (5) | US8137846B2 (ja) |
EP (5) | EP2472639A1 (ja) |
KR (1) | KR101094115B1 (ja) |
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- 2004-12-14 EP EP04807342.3A patent/EP1705736B1/en not_active Expired - Fee Related
- 2004-12-14 EP EP12162649.3A patent/EP2472637A3/en not_active Withdrawn
- 2004-12-14 KR KR1020067014229A patent/KR101094115B1/ko active IP Right Grant
- 2004-12-14 CN CNB2004800410890A patent/CN100541863C/zh not_active Expired - Fee Related
- 2004-12-14 EP EP12162645A patent/EP2472636A3/en not_active Withdrawn
- 2004-12-14 WO PCT/JP2004/018985 patent/WO2005057690A1/ja active Application Filing
- 2004-12-14 EP EP12162653.5A patent/EP2472638A3/en not_active Withdrawn
-
2006
- 2006-06-15 US US11/453,006 patent/US8137846B2/en not_active Expired - Fee Related
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2012
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- 2012-02-08 US US13/368,983 patent/US20120141887A1/en not_active Abandoned
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CN106340671A (zh) * | 2015-07-08 | 2017-01-18 | 宁德时代新能源科技股份有限公司 | 锂离子电池及其电解液 |
CN106054086A (zh) * | 2016-07-11 | 2016-10-26 | 深圳天珑无线科技有限公司 | 一种电池自放电检测方法及装置 |
Also Published As
Publication number | Publication date |
---|---|
EP1705736A1 (en) | 2006-09-27 |
US8137846B2 (en) | 2012-03-20 |
EP2472637A3 (en) | 2013-09-11 |
EP1705736A4 (en) | 2009-12-09 |
EP2472638A3 (en) | 2013-09-11 |
KR101094115B1 (ko) | 2011-12-15 |
KR20070019965A (ko) | 2007-02-16 |
EP2472636A3 (en) | 2012-09-05 |
US20120141885A1 (en) | 2012-06-07 |
US20120135317A1 (en) | 2012-05-31 |
EP2472637A2 (en) | 2012-07-04 |
EP2472636A2 (en) | 2012-07-04 |
CN1934728A (zh) | 2007-03-21 |
US20120141886A1 (en) | 2012-06-07 |
US20120141887A1 (en) | 2012-06-07 |
EP1705736B1 (en) | 2015-08-26 |
EP2472639A1 (en) | 2012-07-04 |
US20070048607A1 (en) | 2007-03-01 |
EP2472638A2 (en) | 2012-07-04 |
CN100541863C (zh) | 2009-09-16 |
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