WO2017082259A1 - 非水系二次電池用セパレータ及び非水系二次電池 - Google Patents
非水系二次電池用セパレータ及び非水系二次電池 Download PDFInfo
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- WO2017082259A1 WO2017082259A1 PCT/JP2016/083137 JP2016083137W WO2017082259A1 WO 2017082259 A1 WO2017082259 A1 WO 2017082259A1 JP 2016083137 W JP2016083137 W JP 2016083137W WO 2017082259 A1 WO2017082259 A1 WO 2017082259A1
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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
- H01M10/052—Li-accumulators
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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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
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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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/42—Acrylic resins
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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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/423—Polyamide resins
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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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/426—Fluorocarbon polymers
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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
- H01M50/431—Inorganic 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
- 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
- H01M50/443—Particulate 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
- 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
- H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
- H01M50/461—Separators, membranes or diaphragms characterised by their combination with electrodes with adhesive layers between electrodes and separators
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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
- H01M50/491—Porosity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a separator for a non-aqueous secondary battery and a non-aqueous secondary battery.
- Non-aqueous secondary batteries represented by lithium ion secondary batteries are widely used as power sources for portable electronic devices such as notebook computers, mobile phones, digital cameras, and camcorders.
- portable electronic devices such as notebook computers, mobile phones, digital cameras, and camcorders.
- the non-aqueous secondary battery exterior has been simplified and reduced in weight, and aluminum cans have been developed instead of stainless steel cans as exterior materials.
- packs made of aluminum laminate film have been developed.
- the pack made of aluminum laminate film is soft, in a battery using the pack as an exterior material (so-called soft pack battery), due to impact from the outside or expansion and contraction of the electrode due to charge / discharge, the electrode and the separator Gaps are easily formed between them, and the cycle life may be reduced.
- a technique for improving the adhesion between the electrode and the separator has been proposed.
- a separator having an adhesive porous layer containing a polyvinylidene fluoride resin on a polyolefin microporous film is known.
- the separator adheres favorably to the electrode via the adhesive porous layer, so that the cycle life of the soft pack battery can be improved.
- a separator in which an adhesive porous layer containing a polyvinylidene fluoride resin is formed on a polyolefin microporous film is suitable for a soft pack battery, and various technical proposals have been made with the aim of further improving performance.
- Patent Document 1 discloses an adhesive porous layer containing two types of polyvinylidene fluoride resins having different ratios of hexafluoropropylene monomer units.
- Patent Document 2 discloses a porous layer containing a polyvinylidene fluoride resin and inorganic particles.
- Patent Document 3 discloses a porous organic polymer film containing a polyvinylidene fluoride resin that is a terpolymer.
- Patent Document 4 discloses an adhesive porous layer containing a polyvinylidene fluoride resin in which the ratio of hexafluoropropylene monomer units is 0.1 mol% or more and 5% mol or less.
- Patent Document 5 discloses a porous layer containing a polyvinylidene fluoride resin having a weight average molecular weight of 1,000,000 or more.
- non-aqueous secondary batteries represented by lithium ion secondary batteries have been studied for application as batteries for electric power storage and electric vehicles because of their high energy density.
- non-aqueous secondary batteries are used for power storage and electric vehicles, it is necessary to increase the area, but with the increase in the area of soft pack batteries, adhesive porous materials containing polyvinylidene fluoride resin Even in the case of a separator having a layer, adhesion between the electrode and the separator is insufficient, and the battery capacity may be reduced, the charge / discharge characteristics may be deteriorated, and the battery may be swollen.
- As the area of the battery increases it is desired to improve the adhesion of the adhesive porous layer to the electrode.
- a battery including a separator having an adhesive porous layer containing a polyvinylidene fluoride resin generally manufactures a laminate of an electrode and a separator, and accommodates the laminate in an exterior material. After injecting the liquid, it is manufactured by performing a heat press treatment (referred to as “wet heat press” in this specification). As the area of the battery increases, a separator that is superior in adhesion by wet heat press is desired.
- Embodiments of the present disclosure provide a separator for a non-aqueous secondary battery that is provided with an adhesive porous layer containing a polyvinylidene fluoride-based resin and has excellent adhesion to an electrode by wet heat press.
- Another object of the embodiment of the present disclosure is to provide a non-aqueous secondary battery excellent in cell strength and cycle characteristics.
- the inorganic filler is at least one of magnesium hydroxide and magnesium oxide.
- a separator provided with an adhesive porous layer containing a polyvinylidene fluoride-based resin, which is excellent in adhesion with an electrode by wet heat press, is provided for a non-aqueous secondary battery.
- a non-aqueous secondary battery excellent in cell strength and cycle characteristics is provided.
- a numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
- process is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. .
- the “longitudinal direction” means the longitudinal direction of the porous substrate and the separator manufactured in a long shape
- the “width direction” means a direction orthogonal to the “longitudinal direction”. means.
- the “longitudinal direction” is also referred to as “MD direction”
- the “width direction” is also referred to as “TD direction”.
- the “monomer unit” of the polyvinylidene fluoride resin means a constituent unit of the polyvinylidene fluoride resin, which is obtained by polymerizing the monomers.
- a separator for a nonaqueous secondary battery of the present disclosure (also simply referred to as “separator”) includes a porous substrate and an adhesive porous layer provided on one or both surfaces of the porous substrate.
- the adhesive porous layer includes a vinylidene fluoride having a hexafluoropropylene monomer unit ratio of 5.1 mass% to 6.9 mass% and a weight average molecular weight of 810,000 to 3 million.
- -A hexafluoropropylene binary copolymer is contained, and the vinylidene fluoride-hexafluoropropylene binary copolymer accounts for 95% by mass or more of the total resin.
- VDF unit the vinylidene fluoride monomer unit
- HFP unit the hexafluoropropylene monomer unit
- HFP-HFP binary the vinylidene fluoride-hexafluoropropylene binary copolymer
- VDF-HFP binary copolymer having an HFP unit ratio of 5.1 mass% to 6.9 mass% and a weight average molecular weight of 810,000 to 3 million is referred to as “specific VDF-”. It is also referred to as “HFP binary copolymer”.
- the separator of the present disclosure is excellent in adhesion to an electrode by wet heat press by including an adhesive porous layer containing the specific VDF-HFP binary copolymer in a proportion of 95% by mass or more of the total resin. This mechanism is not necessarily clear, but is presumed as follows.
- the VDF-HFP binary copolymer In the VDF-HFP binary copolymer, the greater the proportion of HFP units, the higher the mobility of the polymer chain when heated. Therefore, when hot pressing is performed, the VDF-HFP binary copolymer is more easily bonded to the electrode as the proportion of HFP units is larger, and is also bonded under lower temperature hot pressing conditions. In addition, the VDF-HFP binary copolymer is more likely to swell in the electrolyte solution as the proportion of HFP units increases. Therefore, when wet heat pressing is performed, the VDF-HFP binary copolymer is appropriately swelled and easily adhered to the electrode when the proportion of the HFP unit is somewhat large. Therefore, if attention is paid to the behavior of the VDF-HFP binary copolymer, it is advantageous for adhesion to the electrode that the proportion of HFP units in the VDF-HFP binary copolymer is large to some extent.
- an adhesive porous layer is formed of a VDF-HFP binary copolymer having a high proportion of HFP units
- the porosity is likely to increase and the pore diameter tends to increase.
- the area of the VDF-HFP binary copolymer portion that becomes the adhesion site with the electrode on the surface of the adhesive porous layer decreases, and VDF- HFP binary copolymers will be present sparsely. Therefore, as the proportion of HFP units in the VDF-HFP binary copolymer constituting the adhesive porous layer increases, the adhesion between the adhesive porous layer and the electrode tends to weaken.
- the proportion of HFP units in the VDF-HFP binary copolymer is too large, the VDF-HFP binary copolymer tends to be dissolved in the electrolytic solution and the adhesion to the electrode tends to be weakened. Therefore, if attention is paid to the surface morphology of the adhesive porous layer, it is advantageous that the proportion of HFP units in the VDF-HFP binary copolymer is smaller, and the VDF-HFP copolymer is not dissolved in the electrolyte. For this, it is preferable that the proportion of HFP units in the VDF-HFP binary copolymer is not too large.
- the specific VDF-HFP binary copolymer has a HFP unit ratio of 5.1 mass% to 6.9 mass%.
- the specific VDF-HFP binary copolymer has a high mobility of the polymer chain when heated because the ratio of HFP units is 5.1% by mass or more. Strong adhesion can be obtained.
- the specific VDF-HFP binary copolymer has an HFP unit ratio of 6.9% by mass or less, so that an adhesive porous layer having a porosity and a pore size that are small enough not to inhibit ion permeability. Realized and realizes a surface morphology suitable for adhesion to electrodes.
- the specific VDF-HFP binary copolymer has an HFP unit ratio of 5.1 mass% to 6.9 mass%, so that it swells appropriately in the electrolytic solution. Since it adheres well to the electrode and does not dissolve in the electrolyte solution and does not swell excessively, adhesion to the electrode is maintained.
- the lower limit of the ratio of HFP units of the specific VDF-HFP binary copolymer is 5.1% by mass or more
- the upper limit of the ratio of HFP units of the specific VDF-HFP binary copolymer is It is 6.9 mass% or less, More preferably, it is 6.5 mass% or less, More preferably, it is 6.0 mass% or less.
- the specific VDF-HFP binary copolymer has a weight average molecular weight (Mw) of 810,000 to 3 million.
- Mw weight average molecular weight
- the adhesive porous layer can be sufficiently imparted with mechanical properties that can withstand the adhesion treatment with the electrode. For this reason, it is possible to increase the pressure of the hot press conditions to more firmly bond the separator to the electrode.
- the Mw of the specific VDF-HFP binary copolymer is 810,000 or more, more preferably 1 million or more, and further preferably 1.1 million or more.
- a VDF-HFP binary copolymer having an Mw of over 3 million has a too high viscosity of the coating liquid for coating and forming an adhesive porous layer, and forms an adhesive porous layer having a porous structure. Difficult to do.
- the Mw of the specific VDF-HFP binary copolymer is 3 million or less, more preferably 2.5 million or less, and further preferably 2 million or less.
- the adhesive porous layer 95% by mass or more of the total resin contained in the adhesive porous layer is the specific VDF-HFP binary copolymer.
- the adhesive porous layer does not substantially contain any other resin other than the specific VDF-HFP binary copolymer, and substantially contains only the specific VDF-HFP binary copolymer as a binder resin. It means to do.
- the adhesive porous layer of the present embodiment suppresses the non-uniformity of the porous structure due to uneven mixing of multiple types of resins, is excellent in the uniformity of the porous structure, and adheres to the electrode. A suitable surface morphology is achieved.
- the separator of the present disclosure is excellent in adhesion to an electrode by hot pressing, and particularly excellent in adhesion to an electrode by wet heat pressing.
- the separator of the present disclosure is not only applied to an electrode using a solvent-based binder (specifically, a polyvinylidene fluoride-based resin), but also to an electrode using an aqueous binder (specifically, a styrene-butadiene copolymer). Excellent adhesion.
- a solvent-based binder specifically, a polyvinylidene fluoride-based resin
- an aqueous binder specifically, a styrene-butadiene copolymer
- the nonaqueous secondary battery to which the separator of this indication is applied is excellent in cell strength. Moreover, since the separator of this indication is excellent in the uniformity of the porous structure of an adhesive porous layer, and is excellent in the adhesion
- the separator of the present disclosure the formation of a gap between the electrode and the separator due to the expansion and contraction of the electrode accompanying charging / discharging or the impact from the outside is suppressed. Therefore, the separator of the present disclosure is suitable for a soft pack battery having an aluminum laminate film pack as an exterior material. According to the separator of the present disclosure, a soft pack battery having high battery performance is provided.
- the adhesive porous layer contains the specific VDF-HFP binary copolymer in a proportion of 95% by mass or more of the total resin, so that a relatively low pressure and low temperature heat can be obtained. Even with pressing, it adheres well to the electrode.
- the hot press conditions are high pressure and high temperature, the porous structure of the adhesive porous layer is crushed.
- the hot press conditions can be relatively gentle, The ion permeability of the separator after bonding is maintained, and the battery characteristics are excellent.
- the temperature at the time of performing the wet heat press can be set to a relatively low temperature, so that gas generation due to decomposition of the electrolytic solution and the electrolyte is suppressed.
- the adhesive porous layer contains the specific VDF-HFP binary copolymer in a proportion of 95% by mass or more of the total resin, so that the porous substrate and the adhesive porous layer The adhesion between the layers is also improved, and the peel resistance between the layers is improved.
- the adhesive porous layer contains the specific VDF-HFP binary copolymer in a proportion of 95% by mass or more of the total resin, so that the porous substrate and the adhesive porous layer Excellent ion transfer at the interface between layers.
- a separator formed by applying an adhesive porous layer to a porous substrate is likely to clog the interface between the two, and the ion migration at the interface deteriorates, realizing good battery characteristics. There were things that were difficult.
- the adhesive porous layer according to an embodiment of the present disclosure has a fine porous structure, and therefore has an even distribution of pores and a large number of pores. Therefore, the probability that the hole of the porous substrate and the hole of the adhesive porous layer can be connected is increased, and the deterioration of the battery performance due to clogging can be suppressed.
- One embodiment of the separator of the present disclosure has good adhesion to the electrode even by a heat press process (referred to as “dry heat press” in this specification) performed without impregnating the electrolyte.
- dry heat press a heat press process
- the laminate Prior to the wet heat press, if the laminate is dry heat pressed to adhere the electrode and the separator, deformation of the laminate can be suppressed.
- the porous substrate means a substrate having pores or voids therein.
- a substrate include a microporous membrane; a porous sheet made of a fibrous material such as a nonwoven fabric and paper; a composite porous material in which one or more other porous layers are laminated on a microporous membrane or a porous sheet. Sheet; and the like.
- a microporous membrane means a membrane that has a large number of micropores inside and has a structure in which these micropores are connected, allowing gas or liquid to pass from one surface to the other. To do.
- the porous base material contains an organic material and / or an inorganic material having electrical insulation.
- the porous substrate preferably contains a thermoplastic resin from the viewpoint of imparting a shutdown function to the porous substrate.
- the shutdown function refers to a function of preventing thermal runaway of the battery by blocking the movement of ions by dissolving the material and closing the pores of the porous base material when the battery temperature increases.
- the thermoplastic resin a thermoplastic resin having a melting point of less than 200 ° C. is preferable.
- the thermoplastic resin include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; among these, polyolefins are preferable.
- a microporous membrane containing polyolefin As the porous substrate, a microporous membrane containing polyolefin (referred to as “polyolefin microporous membrane”) is preferable.
- the polyolefin microporous membrane include polyolefin microporous membranes that are applied to conventional separators for non-aqueous secondary batteries, and it is possible to select those having sufficient mechanical properties and ion permeability. preferable.
- the polyolefin microporous membrane preferably contains polyethylene from the viewpoint of exhibiting a shutdown function, and the polyethylene content is preferably 95% by mass or more of the total mass of the polyolefin microporous membrane.
- the polyolefin microporous membrane is preferably a polyolefin microporous membrane containing polyethylene and polypropylene from the viewpoint of imparting heat resistance that does not easily break when exposed to high temperatures.
- a polyolefin microporous membrane include a microporous membrane in which polyethylene and polypropylene are mixed in one layer.
- the microporous membrane preferably contains 95% by mass or more of polyethylene and 5% by mass or less of polypropylene from the viewpoint of achieving both a shutdown function and heat resistance.
- the polyolefin microporous membrane has a laminated structure of two or more layers, at least one layer contains polyethylene, and at least one layer contains polypropylene, preferable.
- the polyolefin contained in the polyolefin microporous membrane is preferably a polyolefin having a weight average molecular weight (Mw) of 100,000 to 5,000,000.
- Mw weight average molecular weight
- the Mw of the polyolefin is 100,000 or more, sufficient mechanical properties can be secured.
- the Mw of the polyolefin is 5 million or less, the shutdown characteristics are good and the film is easy to mold.
- the polyolefin microporous membrane can be produced, for example, by the following method.
- the melted polyolefin resin is extruded from a T-die to form a sheet, which is crystallized and then stretched, and further heat-treated to form a microporous film.
- a polyolefin resin melted together with a plasticizer such as liquid paraffin is extruded from a T-die, cooled and formed into a sheet, and after stretching, the plasticizer is extracted and heat treated to form a microporous membrane. is there.
- porous sheets made of fibrous materials include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; heat resistant resins such as aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyetherketone, and polyetherimide; Nonwoven fabric, paper, etc. made of the fibrous material of
- the heat resistant resin means a polymer having a melting point of 200 ° C. or higher, or a polymer having no melting point and a decomposition temperature of 200 ° C. or higher.
- the composite porous sheet examples include a microporous film or a sheet in which a functional layer is laminated on a porous sheet. Such a composite porous sheet is preferable from the viewpoint of further function addition by the functional layer.
- a porous layer containing a heat resistant resin or a porous layer containing a heat resistant resin and an inorganic filler is preferable.
- the heat resistant resin examples include aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyetherketone, and polyetherimide.
- the inorganic filler include metal oxides such as alumina and metal hydroxides such as magnesium hydroxide.
- a method of providing a functional layer on a microporous membrane or a porous sheet a method of applying a functional layer to a microporous membrane or a porous sheet, a method of bonding a microporous membrane or a porous sheet and a functional layer with an adhesive And a method of thermocompression bonding a microporous membrane or a porous sheet and a functional layer.
- the porous substrate may be subjected to various surface treatments within the range that does not impair the properties of the porous substrate for the purpose of improving the wettability with the coating liquid for forming the adhesive porous layer. Good.
- the surface treatment include corona treatment, plasma treatment, flame treatment, and ultraviolet irradiation treatment.
- the thickness of the porous substrate is preferably 3 ⁇ m to 25 ⁇ m, more preferably 5 ⁇ m to 25 ⁇ m, and even more preferably 5 ⁇ m to 20 ⁇ m from the viewpoint of obtaining good mechanical properties and internal resistance.
- the porosity of the porous substrate is preferably 20% to 60% from the viewpoint of obtaining an appropriate membrane resistance and shutdown function.
- the Gurley value (JIS P8117: 2009) of the porous substrate is preferably 50 seconds / 100 cc to 800 seconds / 100 cc from the viewpoint of preventing short circuit of the battery and obtaining sufficient ion permeability, and 50 seconds / 100 cc to 400 seconds / 100 cc is more preferable.
- the puncture strength of the porous substrate is preferably 200 g or more, and more preferably 250 g or more, from the viewpoint of improving the production yield.
- the piercing strength of the porous substrate is measured by performing a piercing test using a KES-G5 handy compression tester manufactured by Kato Tech Co., Ltd. under the conditions of a radius of curvature of the needle tip of 0.5 mm and a piercing speed of 2 mm / sec. Refers to load (g).
- the average pore diameter of the porous substrate is preferably 20 nm to 100 nm.
- the average pore diameter of the porous substrate is 20 nm or more, ions easily move and good battery performance is easily obtained.
- the average pore diameter of the porous substrate is more preferably 30 nm or more, and further preferably 40 nm or more.
- the average pore diameter of the porous substrate is 100 nm or less, the peel strength between the porous substrate and the adhesive porous layer can be improved, and a good shutdown function can be exhibited.
- the average pore diameter of the porous substrate is more preferably 90 nm or less, and further preferably 80 nm or less.
- the average pore diameter of the porous substrate is a value measured using a palm porometer, and can be measured using, for example, a palm porometer (CFP-1500-A manufactured by PMI) in accordance with ASTM E1294-89. .
- the adhesive porous layer is a porous layer that is provided on one side or both sides of a porous substrate and contains a specific VDF-HFP binary copolymer.
- the adhesive porous layer has a large number of micropores inside and has a structure in which these micropores are connected, and gas or liquid can pass from one surface to the other.
- the adhesive porous layer is a layer that is provided on one or both sides of the porous substrate as the outermost layer of the separator, and can adhere to the electrode when the separator and the electrode are stacked and hot pressed.
- the adhesive porous layer is preferably on both sides rather than only on one side of the porous substrate from the viewpoint of excellent cell strength and battery cycle characteristics (capacity retention rate). This is because when the adhesive porous layer is on both sides of the porous substrate, both sides of the separator are well adhered to both electrodes via the adhesive porous layer.
- the adhesive porous layer contains at least a specific VDF-HFP binary copolymer.
- the adhesive porous layer may further contain a resin other than the specific VDF-HFP binary copolymer, a filler, and the like.
- the specific VDF-HFP binary copolymer is a binary copolymer having only VDF units and HFP units. From the viewpoint that VDF-HFP binary copolymer can be firmly bonded to an electrode at an appropriate bonding temperature as compared with a multi-component copolymer having VDF units, HFP units and other monomer units. preferable.
- the specific VDF-HFP binary copolymer has a HFP unit ratio of 5.1 mass% to 6.9 mass%.
- the proportion of HFP units significantly affects the bonding temperature, and if it is less than 5.1% by mass, hot pressing at a high temperature is required, and the hot pressing process may adversely affect the performance of the battery. If the ratio of HFP units exceeds 6.9% by mass, the VDF-HFP binary copolymer may not be able to maintain sufficient adhesion with the electrode within the normally assumed battery operating temperature range.
- the ratio of HFP units in the specific VDF-HFP binary copolymer is more preferably 6.5% by mass or less, and still more preferably 6.0% by mass or less.
- the specific VDF-HFP binary copolymer has a weight average molecular weight (Mw) of 810,000-3 million.
- Mw weight average molecular weight
- the Mw of the specific VDF-HFP binary copolymer is more preferably 1 million or more, further preferably 1.1 million or more, more preferably 2.5 million or less, and further preferably 2 million or less.
- Examples of the method for producing the specific VDF-HFP binary copolymer include emulsion polymerization and suspension polymerization. It is also possible to select a commercially available VDF-HFP binary copolymer that satisfies the ratio of HFP units and the weight average molecular weight.
- the content of the specific VDF-HFP binary copolymer contained in the adhesive porous layer is 95% by mass or more of the total amount of all resins contained in the adhesive porous layer, more preferably 97% by mass or more, More preferably, it is 98 mass% or more, More preferably, it is 99 mass% or more, Most preferably, it is 100 mass%.
- the adhesive porous layer may contain a polyvinylidene fluoride resin other than the specific VDF-HFP binary copolymer, or may contain a resin other than the polyvinylidene fluoride resin. Good. However, the resin other than the specific VDF-HFP binary copolymer contained in the adhesive porous layer is 5% by mass or less of the total amount of all resins contained in the adhesive porous layer.
- polyvinylidene fluoride resin other than the specific VDF-HFP binary copolymer examples include, for example, a VDF-HFP binary copolymer in which the proportion of HFP units is different from that of the specific VDF-HFP binary copolymer; Homopolymer (ie, polyvinylidene fluoride); a copolymer of vinylidene fluoride and at least one selected from fluorine-containing monomers such as tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, and vinyl fluoride A copolymer of vinylidene fluoride, hexafluoropropylene, and at least one selected from fluorine-containing monomers such as tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, and vinyl fluoride.
- Homopolymer ie, polyvinylidene fluoride
- Resins other than polyvinylidene fluoride resins include fluorine rubber, acrylic resins, styrene-butadiene copolymers, vinyl nitrile compounds (acrylonitrile, methacrylonitrile, etc.) homopolymers or copolymers, carboxymethyl cellulose , Hydroxyalkyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyether (polyethylene oxide, polypropylene oxide, etc.) and the like.
- the adhesive porous layer may contain a filler made of an inorganic material or an organic material for the purpose of improving the slipperiness and heat resistance of the separator. In that case, it is preferable to make it content and particle size which do not interfere with the effect of this indication.
- the average primary particle diameter of the filler is preferably 0.01 ⁇ m to 5 ⁇ m, the lower limit is more preferably 0.1 ⁇ m or more, the upper limit is more preferably 1.5 ⁇ m or less, and even more preferably 1 ⁇ m or less.
- the particle size distribution of the filler is preferably 0.1 ⁇ m ⁇ d90 ⁇ d10 ⁇ 3 ⁇ m.
- d10 represents a 10% cumulative particle diameter ( ⁇ m) in the volume-based particle size distribution calculated from the small particle side
- d90 represents a 90% cumulative particle in the volume-based particle size distribution calculated from the small particle side. Represents the diameter ( ⁇ m).
- the particle size distribution is measured using, for example, a laser diffraction particle size distribution measuring apparatus (for example, Mastersizer 2000 manufactured by Sysmex Corporation), using water as a dispersion medium, and a small amount of a nonionic surfactant Triton X-100 as a dispersant. Done with.
- the adhesive porous layer preferably contains an inorganic filler from the viewpoint of further improving the heat resistance of the separator, the cell strength, and ensuring the safety of the battery.
- the inorganic filler in the present disclosure is preferably an inorganic filler that is stable with respect to the electrolytic solution and electrochemically stable.
- metal hydroxide such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, cerium hydroxide, nickel hydroxide, boron hydroxide; magnesium oxide, alumina, titania Metal oxides such as silica, zirconia and barium titanate; carbonates such as magnesium carbonate and calcium carbonate; sulfates such as magnesium sulfate, calcium sulfate and barium sulfate; metal fluorides such as magnesium fluoride and calcium fluoride; And clay minerals such as calcium silicate and talc.
- These inorganic fillers may be used alone or in combination of two or more.
- the inorganic filler may be surface-modified with a silane coupling agent or the like.
- the inorganic filler in the present disclosure is preferably at least one of a metal hydroxide and a metal oxide from the viewpoint of ensuring stability in the battery and battery safety.
- the inorganic filler in the present disclosure is preferably an inorganic compound containing magnesium (for example, magnesium hydroxide, magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium fluoride, etc.) from the viewpoint of suppressing gas generation in the battery.
- magnesium hydroxide or magnesium oxide is more preferred.
- the gas generated by the decomposition of the electrolyte or electrolyte contains hydrogen fluoride as the main component. Inorganic compounds containing magnesium easily form a film on the particle surface by reaction with hydrogen fluoride. It is presumed that the reaction with hydrogen fluoride is limited, and the generation reaction of gas that easily occurs in a chain is suppressed.
- the particle shape of the inorganic filler is not limited, and may be a shape close to a sphere or a plate shape, but from the viewpoint of suppressing short circuit of the battery, it should be a plate-like particle or a non-aggregated primary particle. Is preferred.
- the content of the inorganic filler contained in the adhesive porous layer is preferably 40% by volume to 85% by volume based on the total solid content of the adhesive porous layer.
- the content of the inorganic filler is more preferably 45% by volume or more of the total solid content of the adhesive porous layer, more preferably 50% by volume or more, and more preferably 80% by volume or less, More preferably, it is 75 volume% or less.
- organic filler examples include cross-linked acrylic resins such as cross-linked polymethyl methacrylate, cross-linked polystyrene, and the like, and cross-linked polymethyl methacrylate is preferable.
- the adhesive porous layer in the present disclosure may contain additives such as a dispersant such as a surfactant, a wetting agent, an antifoaming agent, and a pH adjusting agent.
- a dispersant such as a surfactant, a wetting agent, an antifoaming agent, and a pH adjusting agent.
- the dispersant is added to the coating solution for forming the adhesive porous layer for the purpose of improving dispersibility, coating property, and storage stability.
- Wetting agents, antifoaming agents, and pH adjusters are used in coating liquids for forming an adhesive porous layer, for example, for the purpose of improving familiarity with porous substrates, and for entraining air in the coating liquid. It is added for the purpose of suppressing or adjusting the pH.
- the thickness of the adhesive porous layer is preferably 0.5 ⁇ m to 5 ⁇ m on one side of the porous substrate.
- the thickness is more preferably 1 ⁇ m or more.
- the thickness is more preferably 4.5 ⁇ m or less, and further preferably 4 ⁇ m or less.
- the difference between the coating amount on one side and the coating amount on the other side is 20% by mass or less of the total coating amount on both sides. Is preferred.
- the content is 20% by mass or less, the separator is difficult to curl, the handling property is good, and the cycle characteristics of the battery are good.
- the porosity of the adhesive porous layer is preferably 30% to 80%.
- the porosity is 80% or less, it is possible to secure mechanical properties that can withstand the pressing process for bonding to the electrode, and the surface opening ratio does not become too high, which is suitable for securing the adhesive force.
- a porosity of 30% or more is preferable from the viewpoint of improving ion permeability.
- the average pore size of the adhesive porous layer is preferably 10 nm to 300 nm, more preferably 20 nm to 200 nm.
- the average pore size is 10 nm or more (preferably 20 nm or more)
- the adhesive porous layer is impregnated with the electrolyte, the pores are not easily blocked even if the resin contained in the adhesive porous layer swells.
- the average pore diameter is 300 nm or less (preferably 200 nm or less)
- non-uniformity of the opening is suppressed on the surface of the adhesive porous layer, and the adhesion points are evenly distributed, and the adhesion to the electrode is excellent.
- the average pore diameter is 300 nm or less (preferably 200 nm or less)
- the uniformity of ion migration is high, and the cycle characteristics and load characteristics of the battery are excellent.
- d is an average pore diameter (diameter) of the adhesive porous layer
- V is a pore volume per 1 m 2 of the adhesive porous layer
- S is a pore surface area per 1 m 2 of the adhesive porous layer.
- the pore volume V per 1 m 2 of the adhesive porous layer is calculated from the porosity of the adhesive porous layer.
- the pore surface area S per 1 m 2 of the adhesive porous layer is determined by the following method.
- a specific surface area of the porous substrate (m 2 / g) and specific surface area of the separator (m 2 / g), by applying the BET equation to the nitrogen gas adsorption method, is calculated from the nitrogen gas adsorption.
- the specific surface area (m 2 / g) is multiplied by the basis weight (g / m 2 ) to calculate the pore surface area per 1 m 2 .
- the pore surface area per 1 m 2 of the porous substrate is subtracted from the pore surface area per 1 m 2 of the separator to calculate the pore surface area S per 1 m 2 of the adhesive porous layer.
- the thickness of the separator of the present disclosure is preferably 5 ⁇ m to 35 ⁇ m, more preferably 5 ⁇ m to 30 ⁇ m, still more preferably 10 ⁇ m to 25 ⁇ m, and even more preferably 10 ⁇ m to 20 ⁇ m, from the viewpoints of mechanical strength, battery energy density, and output characteristics. .
- the porosity of the separator of the present disclosure is preferably 30% to 60% from the viewpoints of mechanical strength, adhesion to electrodes, and ion permeability.
- the Gurley value (JIS P8117: 2009) of the separator of the present disclosure is preferably 50 seconds / 100 cc to 800 seconds / 100 cc, and preferably 50 seconds / 100 cc to 400 seconds / 100 cc, from the viewpoint of a good balance between mechanical strength and membrane resistance. More preferred.
- a value obtained by subtracting the Gurley value of the porous substrate from the Gurley value of the separator (the state in which the adhesive porous layer is formed on the porous substrate) (hereinafter referred to as “Gurley”).
- the value difference is preferably 300 seconds / 100 cc or less, more preferably 150 seconds / 100 cc or less, and still more preferably 100 seconds / 100 cc or less.
- the Gurley value difference is 300 seconds / 100 cc or less, the adhesive porous layer does not become too dense, the ion permeability is kept good, and excellent battery characteristics are obtained.
- the Gurley value difference is preferably 0 second / 100 cc or more, and preferably 10 seconds / 100 cc or more from the viewpoint of increasing the adhesive force between the adhesive porous layer and the porous substrate.
- the film resistance of the separator of the present disclosure in view of the load characteristics of the battery, preferably 1ohm ⁇ cm 2 ⁇ 10ohm ⁇ cm 2.
- the membrane resistance is a resistance value when the separator is impregnated with an electrolytic solution, and is measured by an alternating current method.
- the value of the membrane resistance varies depending on the type and temperature of the electrolytic solution, and the above values are obtained by using a mixed solvent of 1 mol / L LiBF 4 -propylene carbonate: ethylene carbonate (mass ratio 1: 1) as the electrolytic solution at a temperature of 20 ° C. It is the value measured by.
- the puncture strength of the separator of the present disclosure is preferably 200 g to 1000 g, and more preferably 250 g to 600 g.
- the method for measuring the puncture strength of the separator is the same as the method for measuring the puncture strength of the porous substrate.
- the thermal shrinkage rate at 120 ° C. of the separator of the present disclosure is preferably 10% or less in both the MD direction and the TD direction from the viewpoint of the balance between shape stability and shutdown characteristics.
- the curvature of the separator of the present disclosure is preferably 1.5 to 2.5 from the viewpoint of ion permeability.
- the water content (mass basis) contained in the separator of the present disclosure is preferably 1000 ppm or less.
- the smaller the moisture content of the separator the more the reaction between the electrolytic solution and water can be suppressed when the battery is configured, the gas generation in the battery can be suppressed, and the cycle characteristics of the battery are improved.
- the amount of water contained in the separator of the present disclosure is more preferably 800 ppm or less, and further preferably 500 ppm or less.
- the separator of the present disclosure is formed by, for example, coating a coating liquid containing a polyvinylidene fluoride resin on a porous substrate to form a coating layer, and then solidifying the polyvinylidene fluoride resin contained in the coating layer By making it, it manufactures with the method of forming an adhesive porous layer on a porous base material.
- the adhesive porous layer can be formed, for example, by the following wet coating method.
- the wet coating method includes (i) a coating liquid preparation step in which a polyvinylidene fluoride resin is dissolved or dispersed in a solvent to prepare a coating liquid, and (ii) the coating liquid is applied onto a porous substrate.
- a coating step for forming a coating layer (iii) bringing the coating layer into contact with a coagulation liquid, solidifying the polyvinylidene fluoride resin while inducing phase separation, and then adhering the porous layer on the porous substrate (Iv) a water washing step for washing the composite membrane with water, and (v) a drying step for removing water from the composite membrane.
- NMP N-methyl-2-pyrrolidone
- DMAc dimethylacetamide
- Polar amide solvents such as dimethylformamide and dimethylformamide are preferably used.
- phase separation agent that induces phase separation in a good solvent.
- the phase separation agent include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol (TPG).
- TPG tripropylene glycol
- the solvent used for preparing the coating liquid is a mixture containing 60% by mass or more of a good solvent and 5% to 40% by mass of a phase separation agent from the viewpoint of forming an adhesive porous layer having a good porous structure.
- a solvent is preferred.
- a coating liquid for forming an adhesive porous layer a coating liquid in which a polyvinylidene fluoride resin is dissolved in a mixed solvent of a good solvent such as DMAc and NMP and a poor solvent such as water and TPG is used. It is done.
- the coating solution containing a poor solvent is easily gelled depending on the environmental conditions after the preparation, and when gelled, an adhesive porous layer having a fine porous structure cannot be formed, There is a possibility that streaks occur on the surface of the adhesive porous layer. Since the porous structure and the surface morphology of the adhesive porous layer affect the adhesion to the electrode and the battery characteristics, the coating solution is required to have storage stability.
- the binder resin contained in the coating liquid for forming the adhesive porous layer is substantially only the specific VDF-HFP binary copolymer.
- the detailed mechanism is unknown, but the storage stability of the coating liquid is high and gelation is difficult. Therefore, even when a coating solution that is not immediately after preparation is used, a fine porous structure develops, an adhesive porous layer having a good surface morphology is formed, and the cycle characteristics and load characteristics of the battery are excellent.
- the concentration of the polyvinylidene fluoride resin in the coating liquid is preferably 3% by mass to 10% by mass with respect to the total mass of the coating liquid from the viewpoint of forming an adhesive porous layer having a good porous structure.
- the filler and other components When the filler and other components are included in the adhesive porous layer, the filler and other components may be dissolved or dispersed in the coating solution.
- the coating liquid may contain a dispersant such as a surfactant, a wetting agent, an antifoaming agent, a pH adjusting agent, and the like. These additives may remain in the adhesive porous layer as long as they are electrochemically stable in the use range of the non-aqueous secondary battery and do not inhibit the reaction in the battery.
- a dispersant such as a surfactant, a wetting agent, an antifoaming agent, a pH adjusting agent, and the like.
- the coagulating liquid is generally composed of a good solvent and a phase separation agent used for preparing the coating liquid and water. It is preferable in production that the mixing ratio of the good solvent and the phase separation agent is matched to the mixing ratio of the mixed solvent used for preparing the coating liquid.
- the water content of the coagulation liquid is preferably 40% by mass to 90% by mass from the viewpoint of formation of a porous structure and productivity.
- the conventional coating method using a Mayer bar, a die coater, a reverse roll coater, a gravure coater or the like may be applied to the coating liquid on the porous substrate.
- the adhesive porous layer is formed on both surfaces of the porous substrate, it is preferable from the viewpoint of productivity to apply the coating liquid to both surfaces simultaneously on both surfaces.
- the adhesive porous layer can be manufactured by a dry coating method in addition to the wet coating method described above.
- the dry coating method is a method in which a coating liquid containing a polyvinylidene fluoride resin and a solvent is applied to a porous substrate, and this coating layer is dried to volatilize and remove the solvent. How to get.
- the wet coating method is preferred in that a good porous structure can be obtained.
- the separator of the present disclosure can also be produced by a method in which an adhesive porous layer is produced as an independent sheet, and this adhesive porous layer is stacked on a porous substrate and combined by thermocompression bonding or an adhesive.
- Examples of the method for producing the adhesive porous layer as an independent sheet include a method of forming the adhesive porous layer on the release sheet by applying the wet coating method or the dry coating method described above.
- the non-aqueous secondary battery of the present disclosure is a non-aqueous secondary battery that obtains an electromotive force by doping or dedoping lithium, and includes a positive electrode, a negative electrode, and a separator of the present disclosure.
- Doping means occlusion, loading, adsorption, or insertion, and means a phenomenon in which lithium ions enter an active material of an electrode such as a positive electrode.
- the non-aqueous secondary battery of the present disclosure has, for example, a structure in which a battery element in which a negative electrode and a positive electrode are opposed to each other with a separator enclosed in an exterior material together with an electrolytic solution.
- the non-aqueous secondary battery of the present disclosure is particularly suitable for a lithium ion secondary battery.
- the non-aqueous secondary battery of the present disclosure can be efficiently manufactured by using the separator of the present disclosure that is excellent in adhesion to electrodes.
- the non-aqueous secondary battery of the present disclosure is excellent in cell strength by including the separator of the present disclosure that is excellent in adhesion to an electrode. Moreover, the non-aqueous secondary battery of this indication is excellent in cycling characteristics by providing the separator of this indication which is excellent in the uniformity of the porous structure of an adhesive porous layer, and excellent in adhesion
- the positive electrode may have a structure in which an active material layer containing a positive electrode active material and a binder resin is formed on a current collector.
- the active material layer may further contain a conductive additive.
- the positive electrode active material include lithium-containing transition metal oxides. Specifically, LiCoO 2 , LiNiO 2 , LiMn 1/2 Ni 1/2 O 2 , LiCo 1/3 Mn 1/3 Ni 1 / 3 O 2, LiMn 2 O 4 , LiFePO 4, LiCo 1/2 Ni 1/2 O 2, LiAl 1/4 Ni 3/4 O 2 and the like.
- the binder resin include polyvinylidene fluoride resin.
- the conductive aid include carbon materials such as acetylene black, ketjen black, and graphite powder.
- the current collector include aluminum foil, titanium foil, and stainless steel foil having a thickness of 5 ⁇ m to 20 ⁇ m.
- the adhesive porous layer is excellent in oxidation resistance, by disposing the adhesive porous layer on the positive electrode side of the non-aqueous secondary battery, as the positive electrode active material, It is easy to apply LiMn 1/2 Ni 1/2 O 2 , LiCo 1/3 Mn 1/3 Ni 1/3 O 2 or the like that can operate at a high voltage of 4.2 V or higher.
- the negative electrode may have a structure in which an active material layer containing a negative electrode active material and a binder resin is formed on a current collector.
- the active material layer may further contain a conductive additive.
- the negative electrode active material include materials that can occlude lithium electrochemically, and specific examples include carbon materials; alloys of silicon, tin, aluminum, and the like with lithium.
- the binder resin include polyvinylidene fluoride resin and styrene-butadiene copolymer.
- the conductive aid include carbon materials such as acetylene black, ketjen black, and graphite powder.
- Examples of the current collector include copper foil, nickel foil, and stainless steel foil having a thickness of 5 ⁇ m to 20 ⁇ m. Moreover, it may replace with said negative electrode and may use metal lithium foil as a negative electrode.
- the non-aqueous secondary battery of the present disclosure can be applied not only to a negative electrode using a solvent-based binder (specifically, polyvinylidene fluoride resin) but also to an aqueous binder (specifically In addition, it is excellent in adhesion to a negative electrode using a styrene-butadiene copolymer.
- a solvent-based binder specifically, polyvinylidene fluoride resin
- an aqueous binder specifically In addition, it is excellent in adhesion to a negative electrode using a styrene-butadiene copolymer.
- the electrode preferably contains a large amount of binder resin in the active material layer from the viewpoint of adhesion to the separator.
- the active material layer contains a large amount of active material, and the amount of the binder resin is relatively small. Since the separator of this indication is excellent in adhesion with an electrode, it becomes possible to increase the amount of active materials by reducing the amount of binder resin of an active material layer, and can raise the energy density of a battery.
- the electrolytic solution is a solution in which a lithium salt is dissolved in a non-aqueous solvent.
- the lithium salt include LiPF 6 , LiBF 4 , LiClO 4, and the like.
- the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorine-substituted products thereof; ⁇ -Cyclic esters such as butyrolactone and ⁇ -valerolactone; these may be used alone or in admixture.
- cyclic carbonate and chain carbonate were mixed at a mass ratio (cyclic carbonate: chain carbonate) of 20:80 to 40:60, and lithium salt was dissolved in 0.5 mol / L to 1.5 mol / L. Those are preferred.
- Examples of exterior materials include metal cans and aluminum laminate film packs.
- the battery has a square shape, a cylindrical shape, a coin shape, and the like, but the separator of the present disclosure is suitable for any shape.
- the non-aqueous secondary battery of the present disclosure is manufactured by manufacturing a laminated body in which the separator of the present disclosure is disposed between a positive electrode and a negative electrode, and using the laminated body, for example, according to any of 1) and 2) below Can be manufactured.
- the laminate is housed in an exterior material (for example, an aluminum laminate film pack; the same applies hereinafter), an electrolyte is injected therein, and the laminate is hot-pressed (wet heat press) from above the exterior material. And sealing of the exterior material.
- an exterior material for example, an aluminum laminate film pack; the same applies hereinafter
- the laminate After heat-pressing (dry heat-pressing) the laminate and bonding the electrode and the separator, the laminate is accommodated in an exterior material, an electrolyte solution is injected therein, and the laminate is further hot-pressed (wet) from above the exterior material. Heat press) to bond the electrode and the separator and seal the exterior material.
- the laminate is hot pressed in a state where the specific VDF-HFP binary copolymer contained in the adhesive porous layer of the separator is swollen in the electrolyte, and the electrode and the separator are well bonded.
- a non-aqueous secondary battery excellent in cell strength and battery characteristics can be obtained.
- the manufacturing method of 2) since the electrode and the separator are bonded prior to housing the laminate in the exterior material, deformation of the laminate that occurs during transportation for housing in the exterior material is suppressed. .
- the laminate is further hot-pressed in a state where the specific VDF-HFP binary copolymer contained in the adhesive porous layer of the separator is swollen in the electrolyte solution. And the separator becomes stronger.
- the wet heat press in the production method 2) may be performed under such a mild condition that the adhesion between the electrode and the separator, which has been somewhat attenuated by impregnation with the electrolyte solution, is recovered, that is, the temperature of the wet heat press is relatively low. Since it can set, the gas generation resulting from decomposition
- the press pressure is preferably 0.5 MPa to 2 MPa, and the temperature is preferably 70 ° C. to 110 ° C.
- the press pressure is preferably 0.5 MPa to 5 MPa, and the temperature is preferably 20 ° C. to 100 ° C.
- the separator of the present disclosure can be bonded by overlapping with the electrode. Therefore, although pressing is not an essential step in battery production, it is preferable to perform pressing from the viewpoint of strengthening the adhesion between the electrode and the separator. Further, from the viewpoint of strengthening the adhesion between the electrode and the separator, the press is preferably a press while heating (hot press).
- the method of arranging the separator between the positive electrode and the negative electrode may be a method of stacking at least one layer of the positive electrode, the separator, and the negative electrode in this order (so-called stack method).
- the separators may be stacked in this order and rolled in the length direction.
- separator and the non-aqueous secondary battery of the present disclosure will be described more specifically with reference to examples.
- separator and the non-aqueous secondary battery of the present disclosure are not limited to the following examples.
- the proportion of HFP units in the polyvinylidene fluoride resin was determined from the NMR spectrum. Specifically, 20 mg of polyvinylidene fluoride resin was dissolved in 0.6 mL of heavy dimethyl sulfoxide at 100 ° C., and a 19 F-NMR spectrum was measured at 100 ° C.
- the weight average molecular weight (Mw) of the polyvinylidene fluoride resin was measured by gel permeation chromatography (GPC).
- GPC gel permeation chromatography
- a GPC apparatus “GPC-900” manufactured by JASCO Corporation is used, TSKgel SUPER AWM-H manufactured by Tosoh Corporation is used for the column, dimethylformamide is used for the solvent, the temperature is 40 ° C., and the flow rate is 10 mL.
- the molecular weight in terms of polystyrene was obtained under the conditions of / min.
- the separator was cut into 10 cm ⁇ 10 cm, the mass was measured, and this mass was divided by the area to determine the basis weight of the separator. Moreover, the porous base material used for preparation of a separator was cut out to 10 cm x 10 cm, the mass was measured, and this mass was divided
- the film thickness of the porous substrate and the separator was measured using a contact-type thickness meter (LITEMATIC manufactured by Mitutoyo Corporation).
- the measurement terminal is a cylinder with a diameter of 5 mm, and is adjusted so that a load of 7 g is applied during the measurement. Any 20 points within 10 cm ⁇ 10 cm are measured, and the average value is calculated. did.
- the layer thickness of the adhesive porous layer was determined by subtracting the thickness of the porous substrate from the thickness of the separator.
- the porosity of the porous substrate and the separator was determined according to the following calculation method.
- the constituent materials are a, b, c,..., N
- the mass of each constituent material is Wa, Wb, Wc,..., Wn (g / cm 2 )
- the true density of each constituent material is da, db, dc,..., dn (g / cm 3 )
- the porosity ⁇ (%) is obtained from the following equation.
- ⁇ ⁇ 1 ⁇ (Wa / da + Wb / db + Wc / dc +... + Wn / dn) / t ⁇ ⁇ 100
- Gurley value The Gurley values of the porous substrate and the separator were measured with a Gurley type densometer (G-B2C manufactured by Toyo Seiki Co., Ltd.) according to JIS P8117: 2009.
- the electrode and the aluminum foil (thickness 20 ⁇ m) obtained above were cut into a width of 1.5 cm and a length of 7 cm, respectively, and each separator obtained in the following examples and comparative examples was 1.8 cm in width and 7.5 cm in length. Cut into.
- An electrode-separator-aluminum foil is laminated in this order to produce a laminate, and an electrolytic solution (1 mol / L LiBF 4 -ethylene carbonate: propylene carbonate [mass ratio 1: 1]) is immersed in the laminate to obtain aluminum. It accommodated in the pack made from a laminate film, and sealed under reduced pressure using the vacuum sealer. Next, the laminated body was hot-pressed together with the pack using a hot press machine, and the electrode and the separator were bonded.
- the conditions for hot pressing were a pressure of 1 MPa, a temperature of 90 ° C., and a pressing time of 2 minutes. Thereafter, the pack was opened, the laminate was taken out, and the one obtained by removing the aluminum foil from the laminate was used as a measurement sample.
- the uncoated surface of the electrode of the measurement sample was fixed to a metal plate with double-sided tape, and the metal plate was fixed to the lower chuck of Tensilon (STB-1225S manufactured by A & D). At this time, the metal plate was fixed to Tensilon so that the length direction of the measurement sample was the gravity direction.
- the separator was peeled from the electrode by about 2 cm from the lower end, and the end was fixed to the upper chuck so that the tensile angle (angle of the separator with respect to the measurement sample) was 180 °.
- the separator was pulled at a pulling speed of 20 mm / min, and the load when the separator was peeled off from the electrode was measured.
- Loads from 10 mm to 40 mm at the start of measurement were sampled at intervals of 0.4 mm. This measurement was performed three times, the average was calculated, and the wet adhesion force with the electrode (N / 15 mm, adhesion force between the electrode and the separator by wet heat press) was used.
- the separator was cut out to a size of 600 cm 2 and placed in an aluminum laminate film pack, the electrolyte was poured into the pack, the separator was impregnated with the electrolyte, and the pack was sealed to obtain a test cell.
- As the electrolytic solution 1 mol / L LiPF 6 -ethylene carbonate: ethyl methyl carbonate (mass ratio 3: 7) was used.
- the test cell was placed in an environment at a temperature of 85 ° C. for 3 days, and the volume of the test cell before and after the heat treatment was measured.
- the positive electrode and the negative electrode were wound through the separators obtained in the following examples and comparative examples, and lead tabs were welded to obtain battery elements.
- the battery element was housed in an aluminum laminate film pack and impregnated with an electrolytic solution, followed by heat press (wet heat press) at a pressure of 1 MPa, a temperature of 90 ° C., and a time of 2 minutes to seal the exterior.
- a test secondary battery (length 65 mm, width 35 mm, thickness 2.5 mm, capacity 700 mAh) was obtained.
- As the electrolytic solution 1 mol / L LiPF 6 -ethylene carbonate: diethyl carbonate (mass ratio 3: 7) was used.
- test secondary battery obtained above was subjected to a three-point bending test in accordance with ISO178 to determine the cell strength (N).
- a test secondary battery was prepared by the same manufacturing method as described above. Under an environment of 25 ° C., 4.2 V constant current / constant voltage charging at 1C was performed for 2 hours, and 300 cycles of charge / discharge cycles were performed under the condition of 3V cutoff constant current discharging at 1C. Based on the discharge capacity obtained in the first cycle, the ratio of the discharge capacity obtained after 300 cycles was obtained as a percentage, and this was used as an index of cycle characteristics.
- Example 2 to 5 An adhesive porous layer was formed on both sides of the polyethylene microporous membrane in the same manner as in Example 1 except that the VDF-HFP binary copolymer was changed to another VDF-HFP binary copolymer shown in Table 1. The formed separator was produced.
- Example 6 The VDF-HFP binary copolymer is mixed with a first VDF-HFP binary copolymer (HFP unit ratio 5.4 mass%, weight average molecular weight 1.13 million) and a second VDF-HFP binary copolymer. Adhesiveness to both sides of the polyethylene microporous membrane in the same manner as in Example 1 except that the mixture (mass ratio 99: 1) with a blend (HFP unit ratio 2.5 mass%, weight average molecular weight 1,500,000) was changed. A separator in which a porous layer was formed was produced.
- VDF-HFP binary copolymer was changed to another VDF-HFP binary copolymer (HFP unit ratio 5.4 mass%, weight average molecular weight 3.1 million), and polyethylene microporous as in Example 1. An attempt was made to form an adhesive porous layer on both sides of the membrane, but the viscosity of the coating solution was too high to form the adhesive porous layer.
- VDF-HFP binary copolymer was converted to vinylidene fluoride-hexafluoropropylene-chlorotrifluoroethylene terpolymer (HFP unit ratio 5.2 mass%, CTFE unit ratio 3.8 mass%, weight average).
- a separator having an adhesive porous layer formed on both sides of a polyethylene microporous membrane was prepared in the same manner as in Example 1 except that the molecular weight was changed to 600,000.
- Example 7 to 13 In the coating solution in which the resin is dissolved, magnesium hydroxide (Kisuma 5P manufactured by Kyowa Chemical Industry Co., Ltd., average primary particle size 0.8 ⁇ m, BET specific surface area 6.8 m 2 / g) as an inorganic filler is shown in Table 1. Volume ratio relative to the total solid content) and stirred until uniform to produce a coating solution, and the coating amount of the coating solution was changed as shown in Table 1 and was the same as in Example 5. Thus, a separator having an adhesive porous layer formed on both sides of a polyethylene microporous membrane was produced.
- Example 14 A separator having an adhesive porous layer formed on both sides of a polyethylene microporous membrane was produced in the same manner as in Example 5 except that the coating amount of the coating solution was changed as shown in Table 1.
- a separator having an adhesive porous layer formed on both sides of a polyethylene microporous membrane was prepared in the same manner as in Example 11 except that the volume ratio]) was changed.
- Example 16 Adhesive porous layers were formed on both sides of the polyethylene microporous membrane in the same manner as in Example 11 except that the inorganic filler was changed to magnesium oxide (PUREMAG FNM-G manufactured by Tateho Chemical Industry Co., Ltd., average primary particle size 0.5 ⁇ m). The formed separator was produced.
- Example 17 An adhesive porous layer is formed on both sides of a polyethylene microporous membrane in the same manner as in Example 11 except that the inorganic filler is changed to alumina (AL-160SG-3, Showa Denko Co., Ltd., average primary particle size 0.5 ⁇ m). A separator was prepared.
- Example 18 An adhesive porous layer was formed on both sides of the polyethylene microporous membrane in the same manner as in Example 11 except that the VDF-HFP binary copolymer was changed to another VDF-HFP binary copolymer shown in Table 1. The formed separator was produced.
- Table 1 shows the physical properties and evaluation results of the separators of Examples 1 to 18 and Comparative Examples 1 to 6.
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Abstract
Description
本開示の実施形態は、ポリフッ化ビニリデン系樹脂を含有する接着性多孔質層を備えたセパレータであって、ウェットヒートプレスによる電極との接着に優れる非水系二次電池用セパレータを提供することを目的とする。
また、本開示の実施形態は、セル強度及びサイクル特性に優れる非水系二次電池を提供することを目的とする。
[2] 前記接着性多孔質層の片面の厚さが0.5μm以上5μm以下である、上記[1]に記載の非水系二次電池用セパレータ。
[3] 前記接着性多孔質層がさらに無機フィラーを含有する、上記[1]又は[2]に記載の非水系二次電池用セパレータ。
[4] 前記無機フィラーが、金属水酸化物及び金属酸化物から選択される少なくとも1種である、上記[3]に記載の非水系二次電池用セパレータ。
[5] 前記無機フィラーが、水酸化マグネシウム及び酸化マグネシウムの少なくともいずれかである、上記[3]に記載の非水系二次電池用セパレータ。
[6] 前記接着性多孔質層における前記無機フィラーの含有量が、前記接着性多孔質層の全固形分量の40体積%以上85体積%以下である、上記[3]~[5]のいずれかに記載の非水系二次電池用セパレータ。
[7] 正極と、負極と、前記正極及び前記負極の間に配置された上記[1]~[6]のいずれかに記載の非水系二次電池用セパレータとを備え、リチウムのドープ・脱ドープにより起電力を得る非水系二次電池。
また、本開示の実施形態によれば、セル強度及びサイクル特性に優れる非水系二次電池が提供される。
本開示の非水系二次電池用セパレータ(単に「セパレータ」ともいう。)は、多孔質基材と、多孔質基材の片面又は両面に設けられた接着性多孔質層とを備える。本開示のセパレータにおいて、接着性多孔質層は、ヘキサフルオロプロピレン単量体単位の割合が5.1質量%~6.9質量%で且つ重量平均分子量が81万~300万であるフッ化ビニリデン-ヘキサフルオロプロピレン二元共重合体を含有し、該フッ化ビニリデン-ヘキサフルオロプロピレン二元共重合体が全樹脂の95質量%以上を占める。
また、VDF-HFP二元共重合体は、HFP単位の割合が多いほど、電解液に膨潤しやすい。そのため、ウェットヒートプレスを行った際、VDF-HFP二元共重合体は、HFP単位の割合がある程度多い方が適度に膨潤し電極に接着しやすい。
したがって、VDF-HFP二元共重合体の挙動に着目すれば、VDF-HFP二元共重合体のHFP単位の割合はある程度多い方が電極への接着に有利である。
また、VDF-HFP二元共重合体のHFP単位の割合が多過ぎると、電解液に溶解しやすく、電極との接着が弱まる傾向がある。
したがって、接着性多孔質層の表面モルホロジーに着目すれば、VDF-HFP二元共重合体のHFP単位の割合は少ない方が有利であるし、VDF-HFP共重合体が電解液に溶解しないためには、VDF-HFP二元共重合体のHFP単位の割合は多過ぎない方が好ましい。
特定VDF-HFP二元共重合体は、HFP単位の割合が5.1質量%以上であることにより、加熱した際のポリマー鎖の運動性が高く、熱プレスを行った際に電極に対して強い接着を得ることができる。一方、特定VDF-HFP二元共重合体は、HFP単位の割合が6.9質量%以下であることにより、イオン透過性を阻害しない程度に空孔率や孔径が小さな接着性多孔質層を実現し、電極との接着に好適な表面モルホロジーを実現する。
また、特定VDF-HFP二元共重合体は、HFP単位の割合が5.1質量%~6.9質量%であることにより、電解液に適度に膨潤するのでウェットヒートプレスを行った際に電極に対してよく接着し、電解液に溶解しにくく過度に膨潤することもないので電極との接着が保たれる。
上記の観点から、特定VDF-HFP二元共重合体のHFP単位の割合の下限は、5.1質量%以上であり、特定VDF-HFP二元共重合体のHFP単位の割合の上限は、6.9質量%以下であり、より好ましくは6.5質量%以下であり、更に好ましくは6.0質量%以下である。
特定VDF-HFP二元共重合体は、Mwが81万以上であることにより、電極との接着処理に耐え得る力学特性を接着性多孔質層に十分に付与することができる。そのため、熱プレス条件の圧力を高めて、セパレータをより強固に電極に接着させることも可能である。
上記の観点から、特定VDF-HFP二元共重合体のMwは、81万以上であり、より好ましくは100万以上であり、更に好ましくは110万以上である。
一方、Mwが300万を超えるVDF-HFP二元共重合体は、接着性多孔質層を塗工成形するための塗工液の粘度が高くなり過ぎ、多孔構造の接着性多孔質層を成形することが困難である。
上記の観点から、特定VDF-HFP二元共重合体のMwは、300万以下であり、より好ましくは250万以下であり、更に好ましくは200万以下である。
また、本開示のセパレータが接着性多孔質層の多孔質構造の均一性に優れ電極に対する接着に優れるので、本開示のセパレータを適用した非水系二次電池は、サイクル特性に優れる。
従来、多孔質基材に接着性多孔質層を塗工して形成したセパレータは両者の界面が目詰まりしやすく、当該界面でのイオン移動が悪化してしまい、良好な電池特性を実現するのが難しいことがあった。
これに対し、本開示の一実施形態における接着性多孔質層は、微細な多孔質構造が発達しているため、空孔の分布が均一で且つ孔の数が多い。そのため、多孔質基材の孔と接着性多孔質層の孔とを接続できる確率が高くなり、目詰まりによる電池性能の低下を抑制し得る。
本開示において多孔質基材とは、内部に空孔ないし空隙を有する基材を意味する。このような基材としては、微多孔膜;繊維状物からなる、不織布、紙等の多孔性シート;微多孔膜又は多孔性シートに他の多孔性の層を1層以上積層した複合多孔質シート;などが挙げられる。微多孔膜とは、内部に多数の微細孔を有し、これら微細孔が連結された構造となっており、一方の面から他方の面へと気体あるいは液体が通過可能となった膜を意味する。
多孔質基材の厚さは、良好な力学特性と内部抵抗を得る観点から、3μm~25μmが好ましく、5μm~25μmがより好ましく、5μm~20μmが更に好ましい。
本開示において接着性多孔質層は、多孔質基材の片面又は両面に設けられ、特定VDF-HFP二元共重合体を含有する多孔質層である。
本開示において特定VDF-HFP二元共重合体は、VDF単位とHFP単位のみを有する二元共重合体である。VDF-HFP二元共重合体は、VDF単位とHFP単位とそれ以外の他の単量体単位とを有する多元共重合体に比べて、適当な接着温度にて強固に電極と接着できる観点から好ましい。
本開示において接着性多孔質層は、特定VDF-HFP二元共重合体以外のポリフッ化ビニリデン系樹脂を含有していてもよく、ポリフッ化ビニリデン系樹脂以外の他の樹脂を含有していてもよい。ただし、接着性多孔質層に含まれる特定VDF-HFP二元共重合体以外の樹脂は、接着性多孔質層に含まれる全樹脂の総量の5質量%以下である。
本開示において接着性多孔質層は、セパレータの滑り性や耐熱性を向上させる目的で、無機物又は有機物からなるフィラーを含有していてもよい。その場合、本開示の効果を妨げない程度の含有量や粒子サイズとすることが好ましい。
接着性多孔質層は、セパレータの耐熱性、セル強度のさらなる向上及び電池の安全性確保の観点から、無機フィラーを含有することが好ましい。
本開示における有機フィラーとしては、例えば、架橋ポリメタクリル酸メチル等の架橋アクリル樹脂、架橋ポリスチレンなどが挙げられ、架橋ポリメタクリル酸メチルが好ましい。
本開示における接着性多孔質層は、界面活性剤等の分散剤、湿潤剤、消泡剤、pH調整剤などの添加剤を含有していてもよい。分散剤は、接着性多孔質層を形成するための塗工液に、分散性、塗工性及び保存安定性を向上させる目的で添加される。湿潤剤、消泡剤、pH調整剤は、接着性多孔質層を形成するための塗工液に、例えば、多孔質基材との馴染みをよくする目的、塗工液へのエア噛み込みを抑制する目的、又はpH調整の目的で添加される。
接着性多孔質層の厚さは、多孔質基材の片面において、0.5μm~5μmが好ましい。前記厚さが0.5μm以上であると、電極との接着により優れ、結果、電池のセル強度がより優れる。この観点からは、前記厚さは、1μm以上がより好ましい。一方、前記厚さが5μm以下であると、電池のサイクル特性及び負荷特性がより優れる。この観点からは、前記厚さは、4.5μm以下がより好ましく、4μm以下が更に好ましい。
d=4V/S
式中、dは接着性多孔質層の平均孔径(直径)、Vは接着性多孔質層1m2当たりの空孔体積、Sは接着性多孔質層1m2当たりの空孔表面積を表す。
接着性多孔質層1m2当たりの空孔体積Vは、接着性多孔質層の空孔率から算出する。
接着性多孔質層1m2当たりの空孔表面積Sは、以下の方法で求める。
まず、多孔質基材の比表面積(m2/g)とセパレータの比表面積(m2/g)とを、窒素ガス吸着法にBET式を適用することにより、窒素ガス吸着量から算出する。これらの比表面積(m2/g)にそれぞれの目付(g/m2)を乗算して、それぞれの1m2当たりの空孔表面積を算出する。そして、多孔質基材1m2当たりの空孔表面積をセパレータ1m2当たりの空孔表面積から減算して、接着性多孔質層1m2当たりの空孔表面積Sを算出する。
本開示のセパレータの厚さは、機械的強度、電池のエネルギー密度及び出力特性の観点から、5μm~35μmが好ましく、5μm~30μmがより好ましく、10μm~25μmが更に好ましく、10μm~20μmが更に好ましい。
本開示のセパレータは、例えば、ポリフッ化ビニリデン系樹脂を含有する塗工液を多孔質基材上に塗工し塗工層を形成し、次いで塗工層に含まれるポリフッ化ビニリデン系樹脂を固化させることで、接着性多孔質層を多孔質基材上に形成する方法で製造される。具体的には、接着性多孔質層は、例えば、以下の湿式塗工法によって形成することができる。
しかし、貧溶媒を含有する塗工液は、調製後の環境条件にもよるがゲル化しやすく、ゲル化した場合は、微細な多孔質構造が発達した接着性多孔質層を形成できなかったり、接着性多孔質層の表面にスジが発生したりする虞がある。接着性多孔質層の多孔質構造と表面モルホロジーは、電極との接着性と電池特性に影響を与えるため、塗工液には保存安定性が求められる。
本実施形態では、接着性多孔質層形成用の塗工液に含まれるバインダ樹脂が実質的に特定VDF-HFP二元共重合体のみである。このことにより、詳細なメカニズムは不明であるが、塗工液の保存安定性が高くゲル化しにくい。そのため、調製直後でない塗工液を用いても、微細な多孔質構造が発達し、表面モルホロジーの良好な接着性多孔質層が形成され、電池のサイクル特性や負荷特性に優れる。
本開示の非水系二次電池は、リチウムのドープ・脱ドープにより起電力を得る非水系二次電池であり、正極と、負極と、本開示のセパレータとを備える。ドープとは、吸蔵、担持、吸着、又は挿入を意味し、正極等の電極の活物質にリチウムイオンが入る現象を意味する。
また、本開示の非水系二次電池は、接着性多孔質層の多孔質構造の均一性に優れ電極との接着に優れる本開示のセパレータを備えることにより、サイクル特性に優れる。
また、上記2)の製造方法によれば、セパレータの接着性多孔質層に含まれる特定VDF-HFP二元共重合体が電解液に膨潤した状態でさらに積層体が熱プレスされるので、電極とセパレータの接着がより強固になる。
また、上記2)の製造方法におけるウェットヒートプレスは、電解液の含浸によっていくらか減弱した電極-セパレータ間の接着を回復させる程度の穏やかな条件でよく、つまりウェットヒートプレスの温度を比較的低温に設定できるので、電池製造時における電池内での電解液及び電解質の分解に起因するガス発生が抑制される。
実施例及び比較例に適用した測定方法及び評価方法は、以下のとおりである。
ポリフッ化ビニリデン系樹脂のHFP単位の割合はNMRスペクトルから求めた。具体的には、ポリフッ化ビニリデン系樹脂20mgを重ジメチルスルホキシド0.6mLに100℃にて溶解し、100℃で19F-NMRスペクトルを測定した。
ポリフッ化ビニリデン系樹脂の重量平均分子量(Mw)は、ゲルパーミエーションクロマトグラフィー(GPC)により測定した。GPCによる分子量測定は、日本分光社製のGPC装置「GPC-900」を用い、カラムに東ソー社製TSKgel SUPER AWM-Hを2本用い、溶媒にジメチルホルムアミドを使用し、温度40℃、流量10mL/分の条件で測定し、ポリスチレン換算の分子量を得た。
セパレータを10cm×10cmに切り出し質量を測定し、この質量を面積で除することで、セパレータの目付を求めた。また、セパレータの作製に用いた多孔質基材を10cm×10cmに切り出し質量を測定し、この質量を面積で除することで、多孔質基材の目付を求めた。そして、セパレータの目付から多孔質基材の目付を減算することで、接着性多孔質層の両面の合計の塗工量を求めた。
多孔質基材及びセパレータの膜厚は、接触式の厚み計(ミツトヨ社製LITEMATIC)を用いて測定した。測定端子は直径5mmの円柱状のものを用い、測定中には7gの荷重が印加されるように調整して行い、10cm×10cm内の任意の20点を測定して、その平均値を算出した。
多孔質基材及びセパレータの空孔率は、下記の算出方法に従って求めた。
構成材料がa、b、c、…、nであり、各構成材料の質量がWa、Wb、Wc、…、Wn(g/cm2)であり、各構成材料の真密度がda、db、dc、…、dn(g/cm3)であり、膜厚をt(cm)としたとき、空孔率ε(%)は以下の式より求められる。
ε={1-(Wa/da+Wb/db+Wc/dc+…+Wn/dn)/t}×100
多孔質基材及びセパレータのガーレ値は、JIS P8117:2009に従い、ガーレ式デンソメータ(東洋精機社製G-B2C)にて測定した。
セパレータを水平な台に置き、先端直径2mmのハンダゴテを加熱して先端温度を260℃にした状態で該ハンダゴテの先端をセパレータ表面に60秒間接触させ、接触によってセパレータに生じた穴の面積(mm2)を測定した。セパレータの耐熱性が高いほど、セパレータに生じる穴の面積は小さい。
正極活物質であるコバルト酸リチウム粉末91g、導電助剤であるアセチレンブラック3g、及びバインダであるポリフッ化ビニリデン3gを、ポリフッ化ビニリデンの濃度が5質量%となるようにN-メチル-ピロリドンに溶解し、双腕式混合機にて攪拌し、正極用スラリーを調製した。この正極用スラリーを厚さ20μmのアルミ箔の片面に塗布し、乾燥後プレスして、正極活物質層を有する正極(片面塗工)をセパレータと電極とのウェット接着力評価用電極として得た。
セパレータを600cm2の大きさに切り出してアルミラミネートフィルム製パック中に入れ、パック中に電解液を注入してセパレータに電解液を含浸させ、パックを封止して試験セルを得た。電解液としては、1mol/L LiPF6-エチレンカーボネート:エチルメチルカーボネート(質量比3:7)を用いた。試験セルを温度85℃の環境下に3日間置き、熱処理前後の試験セルの体積を測定した。熱処理後の試験セルの体積V2から熱処理前の試験セルの体積V1を減ずることでガス発生量V(=V2-V1、単位:ml)を求めた。
正極活物質であるコバルト酸リチウム粉末91g、導電助剤であるアセチレンブラック3g、及びバインダであるポリフッ化ビニリデン3gを、ポリフッ化ビニリデンの濃度が5質量%となるようにN-メチル-ピロリドンに溶解し、双腕式混合機にて攪拌し、正極用スラリーを調製した。この正極用スラリーを厚さ20μmのアルミ箔に塗布し、乾燥後プレスして、正極活物質層を有する正極を得た。
前述と同じ製造方法により試験用二次電池を作製した。25℃の環境下、1Cにて4.2V定電流定電圧充電を2時間、1Cにて3Vカットオフの定電流放電との条件で充放電サイクルを300サイクル行った。初回サイクルで得られた放電容量を基準に300サイクル後に得られた放電容量の比を百分率で求め、これをサイクル特性の指標とした。
[実施例1]
VDF-HFP二元共重合体(HFP単位の割合5.1質量%、重量平均分子量113万)を、樹脂濃度が5質量%となるように、ジメチルアセトアミドとトリプロピレングリコールの混合溶媒(ジメチルアセトアミド:トリプロピレングリコール=80:20[質量比])に溶解し、接着性多孔質形成用の塗工液を作製した。この塗工液をポリエチレン微多孔膜(膜厚9μm、空孔率38%、ガーレ値160秒/100cc)の両面に等量塗工し、凝固液(水:ジメチルアセトアミド:トリプロピレングリコール=62:30:8[質量比]、温度40℃)に浸漬して固化させた。次いで、これを水洗し乾燥して、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを得た。
VDF-HFP二元共重合体を、表1に示す他のVDF-HFP二元共重合体に変更した以外は実施例1と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
VDF-HFP二元共重合体を、第一のVDF-HFP二元共重合体(HFP単位の割合5.4質量%、重量平均分子量113万)と、第二のVDF-HFP二元共重合体(HFP単位の割合2.5質量%、重量平均分子量150万)との混合物(質量比99:1)に変更した以外は実施例1と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
第一のVDF-HFP二元共重合体と第二のVDF-HFP二元共重合体の混合比を90:10に変更した以外は実施例6と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
VDF-HFP二元共重合体を、表1に示す他のVDF-HFP二元共重合体に変更した以外は実施例1と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
VDF-HFP二元共重合体を他のVDF-HFP二元共重合体(HFP単位の割合5.4質量%、重量平均分子量310万)に変更し、実施例1と同様にしてポリエチレン微多孔膜の両面に接着性多孔質層を形成することを試みたが、塗工液の粘度が高過ぎ、接着性多孔質層を形成できなかった。
VDF-HFP二元共重合体を、フッ化ビニリデン-ヘキサフルオロプロピレン-クロロトリフルオロエチレン三元共重合体(HFP単位の割合5.2質量%、CTFE単位の割合3.8質量%、重量平均分子量60万)に変更した以外は実施例1と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
樹脂を溶解した塗工液に、無機フィラーとして水酸化マグネシウム(協和化学工業社製キスマ5P、平均一次粒子径0.8μm、BET比表面積6.8m2/g)を表1に示す含有量(全固形分に対する体積割合)になるように添加し、均一になるまで攪拌し塗工液を作製し、塗工液の塗工量を表1に示すとおりに変更した以外は実施例5と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
塗工液の塗工量を表1に示すとおりに変更した以外は実施例5と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
無機フィラーを水酸化マグネシウム(協和化学工業社製キスマ5P)とアルミナ(昭和電工社製AL-160SG-3、平均一次粒子径0.5μm)の2種(水酸化マグネシウム:アルミナ=95:5[体積比])に変更した以外は実施例11と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
無機フィラーを酸化マグネシウム(タテホ化学工業社製PUREMAG FNM-G、平均一次粒子径0.5μm)に変更した以外は実施例11と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
無機フィラーをアルミナ(昭和電工社製AL-160SG-3、平均一次粒子径0.5μm)に変更した以外は実施例11と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
VDF-HFP二元共重合体を、表1に示す他のVDF-HFP二元共重合体に変更した以外は実施例11と同様にして、ポリエチレン微多孔膜の両面に接着性多孔質層が形成されたセパレータを作製した。
Claims (7)
- 多孔質基材と、
前記多孔質基材の片面又は両面に設けられた接着性多孔質層であって、ヘキサフルオロプロピレン単量体単位の割合が5.1質量%以上6.9質量%以下で且つ重量平均分子量が81万以上300万以下であるフッ化ビニリデン-ヘキサフルオロプロピレン二元共重合体を含有し、該フッ化ビニリデン-ヘキサフルオロプロピレン二元共重合体が全樹脂の95質量%以上を占める接着性多孔質層と、
を備えた非水系二次電池用セパレータ。 - 前記接着性多孔質層の片面の厚さが0.5μm以上5μm以下である、請求項1に記載の非水系二次電池用セパレータ。
- 前記接着性多孔質層がさらに無機フィラーを含有する、請求項1又は請求項2に記載の非水系二次電池用セパレータ。
- 前記無機フィラーが、金属水酸化物及び金属酸化物から選択される少なくとも1種である、請求項3に記載の非水系二次電池用セパレータ。
- 前記無機フィラーが、水酸化マグネシウム及び酸化マグネシウムの少なくともいずれかである、請求項3に記載の非水系二次電池用セパレータ。
- 前記接着性多孔質層における前記無機フィラーの含有量が、前記接着性多孔質層の全固形分量の40体積%以上85体積%以下である、請求項3~請求項5のいずれか一項に記載の非水系二次電池用セパレータ。
- 正極と、負極と、前記正極及び前記負極の間に配置された請求項1~請求項6のいずれか一項に記載の非水系二次電池用セパレータとを備え、リチウムのドープ・脱ドープにより起電力を得る非水系二次電池。
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN109390533A (zh) * | 2017-08-03 | 2019-02-26 | 帝人株式会社 | 非水系二次电池用隔膜及非水系二次电池 |
CN111373571A (zh) * | 2018-07-26 | 2020-07-03 | 株式会社Lg化学 | 隔板和包括该隔板的电化学装置 |
JP2020145129A (ja) * | 2019-03-08 | 2020-09-10 | 株式会社エンビジョンAescエナジーデバイス | 電池 |
CN114303281A (zh) * | 2020-03-11 | 2022-04-08 | 东丽株式会社 | 电池用隔膜 |
WO2024045506A1 (zh) * | 2022-08-30 | 2024-03-07 | 宁德时代新能源科技股份有限公司 | 粘结剂、制备方法、正极极片、二次电池及用电装置 |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR102259219B1 (ko) | 2018-07-03 | 2021-05-31 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
KR102259218B1 (ko) | 2018-07-03 | 2021-05-31 | 삼성에스디아이 주식회사 | 리튬 이차 전지용 전극, 및 이를 포함하는 리튬 이차 전지 |
CN111566843B (zh) * | 2018-09-28 | 2023-01-24 | 株式会社Lg新能源 | 具有改善的对电极的粘附性和电阻特性的用于锂二次电池的隔板和包括该隔板的锂二次电池 |
US11637350B2 (en) | 2018-10-15 | 2023-04-25 | Lg Energy Solution, Ltd. | Separator having porous coating layer including PVDF-HFP block copolymer and method for manufacturing same |
KR102323950B1 (ko) | 2018-12-12 | 2021-11-08 | 삼성에스디아이 주식회사 | 리튬 이차 전지용 전극 및 이를 포함하는 리튬 이차 전지 |
KR102492832B1 (ko) | 2019-05-03 | 2023-01-26 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
KR102425513B1 (ko) | 2019-05-03 | 2022-07-25 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
KR102492831B1 (ko) | 2019-05-03 | 2023-01-26 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
KR102425514B1 (ko) | 2019-05-03 | 2022-07-25 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
KR102487628B1 (ko) | 2019-05-03 | 2023-01-12 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
KR102425515B1 (ko) | 2019-05-03 | 2022-07-25 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
JP2021103676A (ja) * | 2020-04-17 | 2021-07-15 | 三井化学株式会社 | 二次電池セパレータ用コート材 |
CN113363486A (zh) * | 2021-05-28 | 2021-09-07 | 东莞维科电池有限公司 | 一种软包锂离子电池 |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012074367A (ja) * | 2010-08-30 | 2012-04-12 | Sony Corp | 非水電解質電池および非水電解質電池の製造方法、並びに絶縁材および絶縁材の製造方法、並びに電池パック、電子機器、電動車両、蓄電装置および電力システム |
JP2012221741A (ja) * | 2011-04-08 | 2012-11-12 | Teijin Ltd | 非水系二次電池用セパレータおよび非水系二次電池 |
WO2014021293A1 (ja) * | 2012-07-30 | 2014-02-06 | 帝人株式会社 | 非水電解質電池用セパレータ及び非水電解質電池 |
WO2014083988A1 (ja) * | 2012-11-30 | 2014-06-05 | 帝人株式会社 | 非水系二次電池用セパレータ及び非水系二次電池 |
JP2015118841A (ja) * | 2013-12-19 | 2015-06-25 | ソニー株式会社 | 二次電池用電極、二次電池、電池パック、電動車両、電力貯蔵システム、電動工具および電子機器 |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
PL3016175T3 (pl) * | 2013-06-27 | 2019-05-31 | Asahi Chemical Ind | Separator dla baterii z niewodnym elektrolitem oraz bateria z niewodnym elektrolitem |
-
2016
- 2016-11-08 JP JP2017506939A patent/JP6171117B1/ja active Active
- 2016-11-08 KR KR1020187013873A patent/KR20180077190A/ko not_active Application Discontinuation
- 2016-11-08 WO PCT/JP2016/083137 patent/WO2017082259A1/ja active Application Filing
- 2016-11-08 CN CN201680065908.8A patent/CN108352486A/zh active Pending
- 2016-11-10 TW TW105136709A patent/TW201733186A/zh unknown
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012074367A (ja) * | 2010-08-30 | 2012-04-12 | Sony Corp | 非水電解質電池および非水電解質電池の製造方法、並びに絶縁材および絶縁材の製造方法、並びに電池パック、電子機器、電動車両、蓄電装置および電力システム |
JP2012221741A (ja) * | 2011-04-08 | 2012-11-12 | Teijin Ltd | 非水系二次電池用セパレータおよび非水系二次電池 |
WO2014021293A1 (ja) * | 2012-07-30 | 2014-02-06 | 帝人株式会社 | 非水電解質電池用セパレータ及び非水電解質電池 |
WO2014083988A1 (ja) * | 2012-11-30 | 2014-06-05 | 帝人株式会社 | 非水系二次電池用セパレータ及び非水系二次電池 |
JP2015118841A (ja) * | 2013-12-19 | 2015-06-25 | ソニー株式会社 | 二次電池用電極、二次電池、電池パック、電動車両、電力貯蔵システム、電動工具および電子機器 |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN109390533A (zh) * | 2017-08-03 | 2019-02-26 | 帝人株式会社 | 非水系二次电池用隔膜及非水系二次电池 |
CN111373571A (zh) * | 2018-07-26 | 2020-07-03 | 株式会社Lg化学 | 隔板和包括该隔板的电化学装置 |
US11495866B2 (en) | 2018-07-26 | 2022-11-08 | Lg Energy Solution, Ltd. | Separator and electrochemical device comprising same |
JP2020145129A (ja) * | 2019-03-08 | 2020-09-10 | 株式会社エンビジョンAescエナジーデバイス | 電池 |
WO2020184360A1 (ja) * | 2019-03-08 | 2020-09-17 | 株式会社エンビジョンAescエナジーデバイス | 電池 |
JP7252014B2 (ja) | 2019-03-08 | 2023-04-04 | 株式会社エンビジョンAescジャパン | 電池 |
CN114303281A (zh) * | 2020-03-11 | 2022-04-08 | 东丽株式会社 | 电池用隔膜 |
WO2024045506A1 (zh) * | 2022-08-30 | 2024-03-07 | 宁德时代新能源科技股份有限公司 | 粘结剂、制备方法、正极极片、二次电池及用电装置 |
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