WO2016031163A1 - 非水系二次電池用積層体および非水系二次電池部材の製造方法 - Google Patents
非水系二次電池用積層体および非水系二次電池部材の製造方法 Download PDFInfo
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- WO2016031163A1 WO2016031163A1 PCT/JP2015/004042 JP2015004042W WO2016031163A1 WO 2016031163 A1 WO2016031163 A1 WO 2016031163A1 JP 2015004042 W JP2015004042 W JP 2015004042W WO 2016031163 A1 WO2016031163 A1 WO 2016031163A1
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
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- 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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- 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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- 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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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/42—Acrylic resins
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
Definitions
- the present invention relates to a laminate for a non-aqueous secondary battery and a method for producing a non-aqueous secondary battery member, and more specifically, for a non-aqueous secondary battery in which a functional layer is provided on a release substrate.
- the present invention relates to a laminate and a method for producing a non-aqueous secondary battery member by transferring a functional layer from a laminate for a non-aqueous secondary battery onto a substrate for a non-aqueous secondary battery.
- Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes abbreviated as “secondary batteries”) have the characteristics of being small and lightweight, having high energy density, and capable of repeated charge and discharge. It is used for a wide range of purposes.
- the secondary battery generally includes a non-aqueous secondary battery member such as a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode.
- a non-aqueous secondary battery functional layer (hereinafter sometimes abbreviated as “functional layer composition”) containing a material component and a dispersion medium such as water, a non-aqueous secondary A secondary battery member formed on a battery substrate is used.
- a slurry-like composition for a non-aqueous secondary battery functional layer (hereinafter sometimes abbreviated as “functional layer composition”) containing a material component and a dispersion medium such as water)
- a non-aqueous secondary A secondary battery member formed on a battery substrate is used.
- there are two electrodes formed by further forming a functional layer on an electrode base material provided with an electrode mixture layer on a current collector, and a separator formed by forming a functional layer on a separator base material used as a secondary battery member (see, for example, Patent Documents 1 and 2).
- porous membrane layer formed on an electrode base material or a separator base material, Comprising: The core layer comprised by the polymer formed by superposing
- a porous membrane layer comprising a binder composed of polymer particles having a heterogeneous structure composed of a shell layer composed of a polymer obtained by polymerizing a group-containing monomer component, and a non-conductive particle, and a porous membrane layer having excellent strength
- a high level of lithium ion diffusibility is exhibited in the lithium ion secondary battery.
- Patent Document 2 a porous film layer containing non-conductive particles and a binder is formed on a separator substrate, and a particulate weight having a predetermined glass transition temperature is formed on the porous film layer. It has been reported that a separator further provided with an adhesive layer containing coalescence has good adhesion to an electrode and exhibits excellent high-temperature cycle characteristics and rate characteristics for a secondary battery. .
- a functional layer is once provided on a release base material to form a laminate for a nonaqueous secondary battery
- a technique is used in which the functional layer is transferred onto the secondary battery substrate, for example, by bonding the secondary battery laminate to the secondary battery substrate.
- the functional layer on the release substrate is transferred onto the secondary battery substrate while suitably transferring the functional layer so that a part of the functional layer does not remain on the release substrate as much as possible. It is required that the later functional layer exhibit excellent performance.
- the transferability of the functional layer and the electrolyte of the functional layer in the electrolyte solution It was difficult to secure both adhesive properties at the same time.
- the secondary battery could not exhibit sufficiently excellent electrical characteristics (for example, high temperature cycle characteristics and low temperature output characteristics).
- the binder component such as polymer particles and particulate polymer contained in the functional layer of the above prior art is inferior in adhesion in the electrolytic solution as compared with the adhesion in the dry state.
- a functional layer is temporarily provided on a release substrate to form a secondary battery laminate, and the secondary battery laminate is used to form a functional layer on the secondary battery substrate. In doing so, there is room for improvement in terms of ensuring both the transferability of the functional layer and the adhesion in the electrolyte in a well-balanced manner and improving the electrical characteristics of the secondary battery.
- an object of this invention is to provide the laminated body for non-aqueous secondary batteries provided with the functional layer which has the outstanding transcription
- Another object of the present invention is to provide a method for producing a non-aqueous secondary battery member capable of exhibiting excellent electrical characteristics in a non-aqueous secondary battery using a laminate for a non-aqueous secondary battery. To do.
- the present inventor has intensively studied for the purpose of solving the above problems. And this inventor is the functional layer containing the organic particle which has a specific core-shell structure provided with the core part and shell part which have specific electrolyte solution swelling degree, respectively, and the contact angle with respect to water is specific. If a laminate for a secondary battery provided on a release substrate that is greater than or equal to the value is used, the functional layer has high transferability, and the functional layer after transfer has excellent adhesion in an electrolyte solution, In addition, the inventors have found that the secondary battery can exhibit excellent electrical characteristics, and have completed the present invention.
- the present invention aims to advantageously solve the above problems, and the laminate for a non-aqueous secondary battery of the present invention is adjacent to a release substrate and the release substrate.
- a non-aqueous secondary battery laminate including the functional layer, wherein the functional layer includes organic particles and a binder, and the organic particles have a core portion and an outer surface of the core portion.
- a core shell structure including a partially covering shell portion, wherein the core portion is made of a polymer having an electrolyte swelling degree of 5 to 30 times, and the shell portion has an electrolyte swelling degree of 1 It is made of a polymer exceeding 4 times and not exceeding 4 times, and the contact angle of the release substrate with respect to water is 70 ° or more.
- the functional layer containing the organic particles having a specific core-shell structure including the core portion and the shell portion having a specific degree of electrolyte swelling, and the binder has a contact angle with water at a specific value or more.
- a laminate for a secondary battery provided on a certain release substrate is used, a high-performance functional layer can be suitably transferred onto the substrate for a non-aqueous secondary battery.
- the “electrolyte swelling degree” of the polymer of the core part and the shell part of the organic particles, and the “contact angle with water” of the release substrate are measured according to the examples in the present specification. It can be measured using a method.
- the glass transition temperature of the polymer in the core portion is 0 ° C. or higher and 150 ° C. or lower, and the glass transition temperature of the polymer in the shell portion is 50 ° C.
- the temperature is preferably 200 ° C. or lower. If the glass transition temperature of the polymer of the core part and the shell part is within the above-mentioned ranges, the adhesion of the functional layer in the electrolyte solution, and the high temperature cycle characteristics and low temperature output characteristics of the secondary battery are further improved. Because you can.
- the "glass transition temperature" of the core part of an organic particle and a shell part can be measured using the measuring method as described in the Example of this specification.
- the binder preferably has a glass transition temperature of ⁇ 50 ° C. or more and 25 ° C. or less. This is because if the glass transition temperature of the binder is within the above range, the transferability of the functional layer and the low-temperature output characteristics of the secondary battery can be further improved.
- the "glass transition temperature" of a binder can be measured using the measuring method as described in the Example of this specification.
- this invention aims at solving the said subject advantageously, and the manufacturing method of the non-aqueous secondary battery member of this invention is equipped with a functional layer on the base material for non-aqueous secondary batteries.
- a method for producing a non-aqueous secondary battery member comprising: a release substrate; and a laminate for a non-aqueous secondary battery including the functional layer disposed adjacent to the release substrate, The functional layer is disposed so as to be adjacent to the non-aqueous secondary battery substrate, and the functional layer is adhered to the non-aqueous secondary battery substrate, and the release substrate is peeled from the functional layer.
- the functional layer includes organic particles and a binder, and the organic particles have a core-shell structure including a core portion and a shell portion that partially covers an outer surface of the core portion.
- the core portion is made of a polymer having an electrolyte swelling degree of 5 to 30 times, Part is, the electrolyte swelling degree is from 1 fold 4 times or less of the polymer, the contact angle with water of the release substrate is equal to or 70 ° or more.
- the functional layer containing the organic particles having a specific core-shell structure including the core portion and the shell portion having a specific degree of electrolyte swelling, and the binder has a contact angle with water at a specific value or more. If the laminated body for secondary batteries provided on a certain release base material is used, the secondary battery member which can exhibit the electrical property excellent in the secondary battery can be manufactured.
- transfer property and can express a high function in a non-aqueous secondary battery can be provided.
- the laminate for a non-aqueous secondary battery of the present invention is used for the purpose of producing a non-aqueous secondary battery member having a functional layer by transferring the functional layer onto a non-aqueous battery substrate.
- the manufacturing method of the nonaqueous secondary battery member of this invention manufactures a nonaqueous secondary battery member provided with a functional layer and the base material for nonaqueous secondary batteries using the laminated body for nonaqueous secondary batteries. It is a method to do.
- the functional layer may be a porous film layer for improving the heat resistance and strength of the secondary battery member such as a separator or an electrode, or an adhesive layer for bonding the secondary battery members. Alternatively, it may be a layer that exhibits both functions of the porous membrane layer and the adhesive layer.
- the laminate for a non-aqueous secondary battery includes a release substrate and a functional layer that is disposed so as to be in contact with the release substrate and includes at least organic particles and a binder. And the contact angle with respect to the water of a mold release base material is more than a specific value, the organic particle and the binder are used together in the functional layer, and the organic particle has a specific core-shell structure. If the laminate for a non-aqueous secondary battery of the present invention is used, the functional layer can be suitably transferred onto the base material for the secondary battery, and the functional layer after the transfer has adhesiveness in the electrolytic solution. In addition to being excellent, the secondary battery can exhibit excellent electrical characteristics.
- a secondary battery member having a functional layer can be produced even when a device for applying the functional layer composition is not provided. Moreover, if the laminated body for non-aqueous secondary batteries of this invention is used, a functional layer can be easily provided also on the secondary battery base material (for example, nonwoven fabric with a large hole diameter) with which application of the composition for functional layers is difficult. It becomes possible.
- the functional layer constituting the secondary battery laminate includes organic particles and a binder as described above, and optionally non-conductive particles (except those corresponding to organic particles and a binder), and other components. Can be included. And a functional layer is transcribe
- Organic particles serve as an adhesive that firmly bonds the secondary battery members, for example, the separator and the electrode, in the electrolytic solution.
- the organic particles serve as a binder that firmly binds the non-conductive particles to each other in the electrolytic solution.
- the organic particles have a core-shell structure including a core portion and a shell portion that partially covers the outer surface of the core portion, and the core portion has a weight of 5 to 30 times the electrolyte swelling degree.
- the shell part is made of a polymer having an electrolyte solution swelling degree of more than 1 and 4 times or less.
- the organic particles having the above structure and properties exhibit excellent adhesion in the electrolytic solution, and can improve the electrical characteristics of the non-aqueous secondary battery including the functional layer.
- secondary battery members electrodes, separators formed by forming a functional layer on an electrode base material or separator base material may be stored and transported in a wound state, but the functional layer is formed. Even when the secondary battery substrate is rolled up, blocking (sticking of secondary battery members through the functional layer) hardly occurs, and the handling property is excellent.
- the polymer constituting the shell part of the organic particles swells with respect to the electrolytic solution.
- the functional group of the polymer of the swollen shell part is activated, and the surface of the secondary battery substrate (for example, a separator substrate or electrode substrate with which the functional layer is in contact) or the surface of the non-conductive particles
- the shell portion can be firmly bonded to the secondary battery member and the non-conductive particles in the electrolytic solution due to factors such as the occurrence of mechanical or electrical interaction.
- the secondary battery members (for example, the separator and the electrode) are strongly bonded in the electrolytic solution by the functional layer containing organic particles, or the non-conductive particles are strongly bonded in the electrolytic solution. It is presumed that the strength and heat resistance can be increased.
- the separator and the electrode can be strongly bonded in the electrolytic solution as described above. Therefore, in a secondary battery including the functional layer, the functional layer It is hard to produce a space
- the distance between the positive electrode and the negative electrode is difficult to increase in the secondary battery, the internal resistance of the secondary battery can be reduced, and the reaction of the electrochemical reaction at the electrode The field is difficult to be uneven. Furthermore, in the secondary battery, even when charging and discharging are repeated, it is difficult to form a gap between the separator and the electrode, and the battery capacity is unlikely to decrease. As a result, it is presumed that excellent swelling resistance and high-temperature cycle characteristics can be realized. Furthermore, the polymer constituting the core portion of the organic particles swells greatly with respect to the electrolytic solution.
- the polymer in the core part of the organic particles is not completely covered by the shell part. Therefore, ions easily pass through the core portion in the electrolytic solution, so that the organic particles can exhibit high ion diffusibility. Therefore, if the organic particles are used, it is possible to suppress an increase in resistance due to the functional layer and to suppress a decrease in electrical characteristics such as low-temperature output characteristics.
- the polymer which comprises a shell part normally does not have adhesiveness in the state which is not swollen in electrolyte solution, but it expresses adhesiveness only by swelling in electrolyte solution.
- the organic particles usually do not exhibit adhesiveness in a state where they are not swollen in the electrolytic solution.
- the functional layer containing the organic particles usually does not exhibit great adhesiveness in a state where it is not swollen in the electrolyte solution, and the base material such as the separator base material on which the functional layer is formed is overlapped. It is presumed that blocking is unlikely to occur.
- the organic particles do not exhibit any adhesive properties unless they are swollen in the electrolytic solution, and are heated to, for example, a certain temperature or higher (for example, 50 ° C. or higher) even if they are not swollen in the electrolytic solution. Therefore, adhesiveness can be expressed.
- the organic particles have a core-shell structure including a core part and a shell part that covers the outer surface of the core part.
- the shell portion partially covers the outer surface of the core portion. That is, the shell part of the organic particles covers the outer surface of the core part, but does not cover the entire outer surface of the core part. Even if it appears that the outer surface of the core part is completely covered by the shell part, the shell part is outside the core part as long as a hole that communicates the inside and outside of the shell part is formed.
- a shell part that partially covers the surface Therefore, for example, organic particles including a shell portion having pores communicating from the outer surface of the shell portion (that is, the peripheral surface of the organic particle) to the outer surface of the core portion are included in the organic particles.
- the organic particles 100 have a core-shell structure including a core part 110 and a shell part 120.
- the core part 110 is a part which is inside the shell part 120 in the organic particle 100.
- the shell part 120 is a part that covers the outer surface 110 ⁇ / b> S of the core part 110, and is usually the outermost part of the organic particles 100.
- the shell portion 120 does not cover the entire outer surface 110S of the core portion 110, but partially covers the outer surface 110S of the core portion 110.
- the average ratio (coverage) at which the outer surface of the core part is covered by the shell part is preferably 10% or more, more preferably 20% or more, and further preferably 30% or more, preferably It is 95% or less, more preferably 90% or less, and still more preferably 70% or less.
- the average ratio by which the outer surface of a core part is covered with a shell part can be measured from the observation result of the cross-sectional structure of an organic particle. Specifically, it can be measured by the method described below. First, organic particles are sufficiently dispersed in a room temperature curable epoxy resin, and then embedded to produce a block piece containing organic particles. Next, the block piece is cut into a thin piece having a thickness of 80 nm to 200 nm with a microtome equipped with a diamond blade to produce a measurement sample. Thereafter, if necessary, the measurement sample is stained using, for example, ruthenium tetroxide or osmium tetroxide.
- this measurement sample is set in a transmission electron microscope (TEM), and a cross-sectional structure of the organic particles is photographed.
- the magnification of the electron microscope is preferably such that the cross section of one organic particle enters the field of view, specifically about 10,000 times.
- a circumferential length D1 corresponding to the outer surface of the core portion and a length D2 of the portion where the outer surface of the core portion and the shell portion abut are measured.
- ratio Rc by which the outer surface of the core part of the organic particle is covered with a shell part is computed by the following formula (1) using measured length D1 and length D2.
- Covering ratio Rc (%) (D2 / D1) ⁇ 100 (1)
- the covering ratio Rc is measured for 20 or more organic particles, and an average value thereof is calculated to obtain an average ratio (covering ratio) at which the outer surface of the core portion is covered by the shell portion.
- the covering ratio Rc can be calculated manually from the cross-sectional structure, but can also be calculated using commercially available image analysis software.
- image analysis software for example, “AnalySIS Pro” (manufactured by Olympus Corporation) can be used.
- the volume average particle diameter D50 of the organic particles is preferably 0.1 ⁇ m or more, more preferably 0.2 ⁇ m or more, preferably 1 ⁇ m or less, more preferably 0.8 ⁇ m or less.
- the volume average particle diameter D50 of the organic particles is calculated from the small diameter side in the particle diameter distribution of the water dispersion solution adjusted to a solid content concentration of 15% by mass using a laser diffraction particle diameter distribution measuring device. It can be determined as the particle diameter at which the accumulated volume is 50%.
- the organic particles may include arbitrary constituent elements other than the above-described core part and shell part as long as the intended effect is not significantly impaired.
- the organic particles may have a portion formed of a polymer different from the core portion inside the core portion.
- the seed particles used when the organic particles are produced by the seed polymerization method may remain inside the core portion.
- the organic particles include only the core part and the shell part from the viewpoint of remarkably exhibiting the intended effect.
- the core part of the organic particle is made of a polymer having a predetermined degree of swelling with respect to the electrolytic solution.
- the electrolyte swelling degree of the polymer of the core part needs to be 5 times or more, preferably 6 times or more, more preferably 7 times or more, and 30 It is necessary that it is not more than twice, preferably not more than 25 times, more preferably not more than 20 times, and still more preferably not more than 15 times.
- the electrolyte solution swelling degree of the polymer of the core part below the upper limit of the above range, it is possible to improve the adhesion of the organic particles in the electrolyte solution and improve the high temperature cycle characteristics of the secondary battery. .
- elution of the core portion into the electrolyte can be sufficiently suppressed.
- inhibition of ionic conduction resulting from the functional layer becoming a film is suppressed, and the low-temperature output characteristics of the secondary battery can be ensured.
- EC ethylene carbonate
- DEC diethyl carbonate
- VC vinylene carbonate
- the electrolyte solution swelling degree of the polymer of a core part can be specifically measured as follows.
- the polymer of the core part of organic particle is prepared.
- the polymer obtained by performing the same process as that performed in order to form a core part in preparation of an organic particle is prepared.
- a film is produced with the prepared polymer.
- the polymer is solid, the polymer is dried at a temperature of 25 ° C. for 48 hours, and then the polymer is formed into a film to produce a film having a thickness of 0.5 mm.
- the polymer is a solution or dispersion such as latex
- the solution or dispersion is placed in a petri dish made of polytetrafluoroethylene, dried at a temperature of 25 ° C. for 48 hours, A 0.5 mm film is produced.
- the film produced as described above is cut into a 1 cm square to obtain a test piece.
- the weight of this test piece is measured and set to W0.
- this test piece is immersed in the said electrolyte solution at the temperature of 60 degreeC for 72 hours, and the test piece is taken out from electrolyte solution.
- the type and amount of the monomer for producing the polymer of the core part are determined. Appropriate selection can be mentioned. Generally, when the SP value of a polymer is close to the SP value of an electrolytic solution, the polymer tends to swell in the electrolytic solution. On the other hand, when the SP value of the polymer is far from the SP value of the electrolytic solution, the polymer tends to hardly swell in the electrolytic solution.
- the SP value means a solubility parameter.
- the SP value can be calculated using the method introduced in Hansen Solubility Parameters A User's Handbook, 2nd Ed (CRCPless). Further, the SP value of an organic compound can be estimated from the molecular structure of the organic compound. Specifically, it can be calculated by using simulation software (for example, “HSPiP” (http://www.hansen-solution.com)) that can calculate the SP value from the SMILE equation. In this simulation software, Hansen SOLUBILITY PARAMETERS A User's Handbook Second Edition, Charles M. et al. The SP value is obtained based on the theory described in Hansen.
- a monomer having an electrolyte solution swelling degree within the above range can be appropriately selected and used.
- monomers include vinyl chloride monomers such as vinyl chloride and vinylidene chloride; vinyl acetate monomers such as vinyl acetate; styrene, ⁇ -methylstyrene, styrenesulfonic acid, butoxystyrene, Aromatic vinyl monomers such as vinylnaphthalene; vinylamine monomers such as vinylamine; vinylamide monomers such as N-vinylformamide and N-vinylacetamide; monomers having a carboxylic acid group; sulfonic acid groups Monomers having acid groups, monomers having phosphoric acid groups, monomers having hydroxyl groups, etc .; (meth) acrylic acid derivatives such as 2-hydroxyethyl methacrylate; methyl acrylate, acrylic acid (Meth) acrylic acid ester monomers such as ethyl, methyl meth
- the polymer of the core part preferably contains a (meth) acrylic acid ester monomer unit or a (meth) acrylonitrile monomer unit, and more preferably contains a (meth) acrylic acid ester monomer unit. It is particularly preferred that it contains a monomer unit derived from methyl methacrylate. This makes it easy to control the degree of swelling of the polymer and further enhances the ion diffusibility of the functional layer using organic particles.
- “comprising a monomer unit” means “a monomer-derived structural unit is contained in a polymer obtained using the monomer”.
- the ratio of the (meth) acrylic acid ester monomer unit in the polymer of the core part is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 80% by mass or more, and preferably 98%. It is not more than mass%, more preferably not more than 97 mass%, still more preferably not more than 95 mass%.
- the ratio of the (meth) acrylic acid ester monomer unit below the upper limit of the above range, the adhesion of the organic particles in the electrolytic solution is improved, and the high-temperature cycle characteristics of the secondary battery are further improved. be able to.
- the polymer of the core part may include an acid group-containing monomer unit.
- the acid group-containing monomer a monomer having an acid group, for example, a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and And monomers having a hydroxyl group.
- Examples of the monomer having a carboxylic acid group include monocarboxylic acid and dicarboxylic acid.
- Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, and crotonic acid.
- Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid and the like.
- Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methyl. Examples thereof include propanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid.
- (meth) allyl means allyl and / or methallyl.
- examples of the monomer having a phosphoric acid group include phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, and ethyl phosphate- (meth) acryloyloxyethyl phosphate.
- (meth) acryloyl means acryloyl and / or methacryloyl.
- Examples of the monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.
- an acid group-containing monomer a monomer having a carboxylic acid group is preferable, among which monocarboxylic acid is preferable, and (meth) acrylic acid is more preferable.
- an acid group containing monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
- the ratio of the acid group content body unit in the polymer of the core part is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 3% by mass or more, and preferably 20% by mass. Hereinafter, it is more preferably 10% by mass or less, and further preferably 7% by mass or less.
- the polymer of the core part preferably contains a crosslinkable monomer unit in addition to the monomer unit.
- a crosslinkable monomer is a monomer that can form a crosslinked structure during or after polymerization by heating or irradiation with energy rays. By including a crosslinkable monomer unit, the degree of swelling of the polymer can be easily within the above range.
- crosslinkable monomer examples include polyfunctional monomers having two or more polymerization reactive groups in the monomer.
- polyfunctional monomers include divinyl compounds such as divinylbenzene; di (meth) acrylic acid esters such as diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, and 1,3-butylene glycol diacrylate.
- di (meth) acrylic acid esters such as diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, and 1,3-butylene glycol diacrylate.
- tri (meth) acrylic acid ester compounds such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate
- ethylenically unsaturated monomers containing epoxy groups such as allyl glycidyl ether and glycidyl methacrylate; and the like.
- ethylene glycol dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate are preferable, and ethylene glycol dimethacrylate is more preferable from the viewpoint of easily controlling the degree of electrolyte solution swelling of the polymer in the core portion.
- these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
- the ratio of the crosslinkable monomer unit is preferably determined in consideration of the type and amount of the monomer used.
- the specific ratio of the crosslinkable monomer unit in the polymer of the core part is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.5% by mass or more. Preferably it is 7 mass% or less, More preferably, it is 6 mass% or less, More preferably, it is 4.5 mass% or less.
- the ratio of the crosslinkable monomer unit By setting the ratio of the crosslinkable monomer unit to be equal to or higher than the lower limit of the above range, the adhesion of the organic particles in the electrolytic solution can be enhanced, and the high temperature cycle characteristics can be further improved. Moreover, the polymerization stability at the time of preparation of organic particles is ensured by making the ratio of the crosslinkable monomer unit not more than the upper limit of the above range, and the obtained organic particles can be made into suitable particles.
- the glass transition temperature of the polymer in the core part is preferably 0 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 60 ° C. or higher, preferably 150 ° C. or lower, more preferably 130 ° C. or lower, still more preferably. Is 110 ° C. or lower.
- the diameter of the core part is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, particularly preferably 80% or more, with respect to 100% of the volume average particle diameter of the organic particles. Preferably it is 99% or less, More preferably, it is 98.5% or less, More preferably, it is 98% or less.
- the diameter of the core part is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, particularly preferably 80% or more, with respect to 100% of the volume average particle diameter of the organic particles.
- it is 99% or less, More preferably, it is 98.5% or less, More preferably, it is 98% or less.
- the adhesiveness of the organic particles can be enhanced by setting the diameter of the core portion to be equal to or less than the upper limit value of the above range.
- the diameter of the core part can be measured as the volume average particle diameter D50 of the particulate polymer before forming the shell part, which is obtained in the process of producing the organic particles.
- the particulate polymer before forming such a shell portion corresponds to the particulate polymer constituting the core portion.
- the volume average particle diameter D50 of the particulate polymer before forming the shell part can be measured in the same manner as the volume average particle diameter D50 of the organic particles.
- the shell part of the organic particle is made of a polymer having a predetermined electrolyte solution swelling degree smaller than the electrolyte solution swelling degree of the core part.
- the electrolyte swelling degree of the polymer of the shell portion needs to be more than 1 time and 4 times or less, preferably 1.1 times or more, and 1.2 times or more. Is preferably 3.5 times or less, more preferably 3 times or less, and even more preferably 2.5 times or less.
- the adhesiveness of the organic particles in the electrolytic solution can be improved, and the high-temperature cycle characteristics of the secondary battery can be improved.
- the electrolyte solution swelling degree of the polymer of the shell part below the upper limit of the above range, it is possible to improve the adhesion of organic particles in the electrolyte solution and to improve the high-temperature cycle characteristics of the secondary battery. .
- the inhibition of ionic conduction resulting from the functional layer becoming a film is suppressed, and the low-temperature output characteristics of the secondary battery can be ensured.
- the electrolytic solution used for measuring the degree of electrolytic solution swelling of the polymer in the shell portion the same electrolytic solution used for measuring the degree of electrolytic solution swelling of the polymer in the core portion is used.
- the electrolyte solution swelling degree of the polymer of a shell part can be specifically measured as follows.
- the polymer of the shell part of organic particles is prepared.
- a polymer is produced in the same manner as the production method of the core part, using the monomer composition used for the formation of the shell part instead of the monomer composition used for the formation of the core part.
- a film is produced from the polymer in the shell portion by the same method as the method for measuring the degree of swelling of the polymer in the core portion, a test piece is obtained from the film, and the degree of swelling S is measured.
- the kind and amount of the monomer for producing the polymer of the shell part Is appropriately selected.
- a monomer used for preparing the polymer of the shell portion a monomer having an electrolyte solution swelling degree within the above range can be appropriately selected and used.
- examples of such a monomer include the same monomers as those exemplified as monomers that can be used to produce the core polymer.
- such a monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
- an aromatic vinyl monomer is preferable as the monomer used for the preparation of the shell polymer. That is, the polymer of the shell part preferably includes an aromatic vinyl monomer unit.
- aromatic vinyl monomers styrene derivatives such as styrene and styrene sulfonic acid are more preferable. If an aromatic vinyl monomer is used, it is easy to control the degree of electrolyte swelling of the polymer. Moreover, the adhesiveness of the organic particles can be further enhanced.
- the ratio of the aromatic vinyl monomer unit in the polymer of the shell part is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 85% by mass or more, and preferably 100% by mass or less. More preferably, it is 99.9 mass% or less, More preferably, it is 99.5 mass% or less.
- the polymer of the shell part may contain an acid group-containing monomer unit in addition to the aromatic vinyl monomer unit.
- the acid group-containing monomer a monomer having an acid group, for example, a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and And monomers having a hydroxyl group.
- examples of the acid group-containing monomer include monomers similar to the monomers that can constitute the acid group-containing monomer unit that can be included in the core portion.
- an acid group-containing monomer a monomer having a carboxylic acid group is preferable, among which monocarboxylic acid is preferable, and (meth) acrylic acid is more preferable.
- an acid group containing monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
- the ratio of the acid group-containing monomer unit in the polymer of the shell part is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 3% by mass or more, and preferably 20% by mass. Hereinafter, it is more preferably 10% by mass or less, and further preferably 7% by mass or less. Improve the dispersibility of the organic particles in the functional layer by keeping the ratio of the acid group-containing monomer unit in the above range, and express good adhesiveness over the entire surface of the functional layer, particularly in the electrolytic solution. Can do.
- the polymer of the shell part may contain a crosslinkable monomer unit.
- the crosslinkable monomer include monomers similar to those exemplified as the crosslinkable monomer that can be used in the core polymer.
- crosslinked monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
- the ratio of the crosslinkable monomer unit in the polymer of the shell part is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, further preferably 0.5% by mass or more, preferably Is 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less.
- the glass transition temperature of the polymer in the shell part is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, still more preferably 70 ° C. or higher, preferably 200 ° C. or lower, more preferably 180 ° C. or lower, still more preferably. Is 150 ° C. or lower.
- the shell part preferably has an average thickness that falls within a predetermined range with respect to the volume average particle diameter D50 of the organic particles.
- the average thickness (core-shell ratio) of the shell part with respect to the volume average particle diameter D50 of the organic particles is preferably 1.5% or more, more preferably 2% or more, preferably 40% or less, more preferably. Is 30% or less, more preferably 20% or less.
- the average thickness of the shell portion is obtained by observing the cross-sectional structure of the organic particles using a transmission electron microscope (TEM). Specifically, the maximum thickness of the shell portion in the cross-sectional structure of the organic particles is measured using TEM, and the average value of the maximum thickness of the shell portions of 20 or more organic particles arbitrarily selected is determined as the average thickness of the shell portion.
- the shell part is composed of polymer particles, and the particles constituting the shell part do not overlap in the radial direction of the organic particles, and the polymer part constitutes the shell part with a single layer. In such a case, the number average particle diameter of the particles constituting the shell portion is defined as the average thickness of the shell portion.
- the form of the shell part is not particularly limited, but the shell part is preferably composed of polymer particles.
- the shell part is composed of polymer particles, a plurality of particles constituting the shell part may overlap in the radial direction of the organic particles. However, in the radial direction of the organic particles, it is preferable that the particles constituting the shell portion do not overlap each other, and those polymer particles constitute the shell portion as a single layer.
- the number average particle diameter of the particles constituting the shell part is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 30 nm or more, preferably It is 200 nm or less, More preferably, it is 150 nm or less, More preferably, it is 100 nm or less.
- the number average particle diameter of the particles constituting the shell part can be obtained by observing the cross-sectional structure of the organic particles using a transmission electron microscope (TEM). Specifically, the longest diameter of the particles constituting the shell portion in the cross-sectional structure of the organic particles is measured, and the average value of the longest diameters of the particles constituting the shell portions of 20 or more organic particles arbitrarily selected is determined as the shell.
- the number average particle diameter of the particles constituting the part can be used.
- the organic particles having the core-shell structure described above use, for example, a polymer monomer in the core part and a polymer monomer in the shell part, and change the ratio of these monomers over time.
- the organic particles can be prepared by a continuous multi-stage emulsion polymerization method and a multi-stage suspension polymerization method in which the polymer of the previous stage is sequentially coated with the polymer of the subsequent stage.
- an emulsifier for example, an anionic surfactant such as sodium dodecylbenzenesulfonate and sodium dodecylsulfate, a nonionic surfactant such as polyoxyethylene nonylphenyl ether and sorbitan monolaurate, or Cationic surfactants such as octadecylamine acetate can be used.
- anionic surfactant such as sodium dodecylbenzenesulfonate and sodium dodecylsulfate
- a nonionic surfactant such as polyoxyethylene nonylphenyl ether and sorbitan monolaurate
- Cationic surfactants such as octadecylamine acetate
- polymerization initiator examples include peroxides such as t-butylperoxy-2-ethylhexanoate, potassium persulfate, cumene peroxide, 2,2′-azobis (2-methyl-N- (2 An azo compound such as -hydroxyethyl) -propionamide) or 2,2'-azobis (2-amidinopropane) hydrochloride can be used.
- a monomer and an emulsifier that form a core part are mixed, and emulsion polymerization is performed at once to obtain a particulate polymer constituting the core part.
- the organic particle which has the core shell structure mentioned above can be obtained by superposing
- the monomer that forms the polymer of the shell portion is divided into a plurality of times or continuously supplied to the polymerization system.
- the monomer that forms the polymer of the shell part is divided into a polymerization system or continuously supplied, whereby the polymer constituting the shell part is formed into particles, and these particles are bonded to the core part. Thereby, the shell part which covers a core part partially can be formed.
- the particle diameter of the particles constituting the shell part and the It is possible to control the average thickness.
- the particle diameter of the particles constituting the shell part and the shell part It is possible to control the average thickness.
- the monomer that forms the polymer of the shell part preferably includes a hydrophobic monomer, and particularly preferably includes an aromatic vinyl monomer.
- a shell part that partially covers the core part can also be formed by appropriately adjusting the amount of the emulsifier.
- the volume average particle diameter D50 of the particulate polymer constituting the core part, the volume average particle diameter D50 of the organic particles after forming the shell part, and the number average particle diameter of the particles constituting the shell part are:
- the desired range can be achieved by adjusting the amount of emulsifier, the amount of monomer, and the like.
- the average ratio of the outer surface of the core portion covered by the shell portion corresponds to the volume average particle diameter D50 of the particulate polymer constituting the core portion, for example, the amount of emulsifier and the weight of the shell portion.
- the desired range can be obtained by adjusting the amount of the monomer forming the coalescence.
- Binder As described above, the organic particles usually do not exhibit adhesiveness in a state where they are not swollen in the electrolytic solution. Therefore, the component contained in the functional layer is prevented from dropping off from the functional layer before being immersed in the electrolytic solution, and the functional layer is formed on the release substrate and the functional layer on the secondary battery substrate. It is necessary to use a binding material from the viewpoint of suitably transferring to the substrate.
- the “binder” does not include the organic particles described above. And as a binder, it is preferable to make the functional layer contain the particulate polymer for functional layers which can exhibit adhesiveness higher than an organic particle in the environment of the temperature 25 degreeC which is not swollen in electrolyte solution.
- the components constituting the functional layer are prevented from dropping from the functional layer in both the swollen state and the unswelled state in the electrolyte. can do.
- the adhesion in the dry state of the functional layer to both the release substrate and the secondary battery substrate can be ensured, the laminate for the secondary battery can be reliably manufactured, And the secondary battery member provided with a functional layer can be easily manufactured using the said laminated body for secondary batteries.
- the functional layer particulate polymer used in combination with the organic particles include known particulate polymers that are water-insoluble and dispersible in water, such as thermoplastic elastomers. And as a thermoplastic elastomer, a conjugated diene polymer and an acrylic polymer are preferable, and an acrylic polymer is more preferable.
- the conjugated diene polymer refers to a polymer containing a conjugated diene monomer unit, and specific examples of the conjugated diene polymer include aromatic vinyl monomers such as styrene-butadiene copolymer (SBR). Examples thereof include a polymer containing a monomer unit and an aliphatic conjugated diene monomer unit.
- an acrylic polymer refers to the polymer containing a (meth) acrylic acid ester monomer unit.
- these particulate polymers for functional layers may be used individually by 1 type, and may be used in combination of 2 or more types. However, when using a particulate polymer for a functional layer in which two or more types are combined, such a polymer is different from the organic particles having a core-shell structure made of a polymer having a predetermined degree of electrolyte swelling described above. .
- the acrylic polymer as the particulate polymer for the functional layer contains a (meth) acrylonitrile monomer unit. Thereby, the intensity
- the (meth) acrylonitrile monomer unit relative to the total amount of the (meth) acrylonitrile monomer unit and the (meth) acrylic acid ester monomer unit.
- the proportion of the amount is preferably 1% by mass or more, more preferably 2% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less.
- the acrylic polymer as the particulate polymer for the functional layer swells moderately with respect to the electrolytic solution by making the ratio not more than the upper limit value of the above range, the ion conductivity of the functional layer is reduced and A decrease in the low-temperature output characteristics of the secondary battery can be suppressed.
- the glass transition temperature of the functional layer particulate polymer as the binder is preferably ⁇ 50 ° C. or higher, more preferably ⁇ 40 ° C. or higher, preferably 25 ° C. or lower, more preferably 0 ° C. or lower. More preferably, it is ⁇ 5 ° C. or lower.
- the volume average particle diameter D50 of the functional layer particulate polymer is preferably 0.1 ⁇ m or more and 0.5 ⁇ m or less.
- the volume average particle diameter D50 of the functional layer particulate polymer is preferably 0.1 ⁇ m or more and 0.5 ⁇ m or less.
- the compounding quantity of the particulate polymer for functional layers as a binder in a functional layer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more per 100 parts by mass of the organic particles. Moreover, it is preferable that it is 40 mass parts or less, and it is more preferable that it is 30 mass parts or less.
- the functional layer can be easily peeled from the release substrate, and the transferability of the functional layer is further improved. Can be increased. In addition, it is possible to suppress the ion diffusibility of the functional layer from being lowered and to secure the low-temperature output characteristics of the secondary battery.
- Examples of the method for producing the functional layer particulate polymer include a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method.
- the emulsion polymerization method and the suspension polymerization method are preferable because polymerization can be performed in water, and an aqueous dispersion containing a particulate polymer can be suitably used as a material for the functional layer composition as it is.
- the reaction system contains a dispersing agent.
- the functional layer particulate polymer is usually formed of a polymer substantially constituting the functional layer, but may be accompanied by optional components such as additives used in the polymerization.
- Non-conductive particles blended in the functional layer that can function as the porous membrane layer are not particularly limited, and may include known nonconductive particles used in nonaqueous secondary batteries.
- non-conductive particles both inorganic fine particles and organic fine particles other than the organic particles and the functional layer particulate polymer (binder) described above can be used. Fine particles are used.
- a material of nonelectroconductive particle the material which exists stably in the use environment of a non-aqueous secondary battery and is electrochemically stable is preferable.
- non-conductive particle material examples include aluminum oxide (alumina), hydrated aluminum oxide (boehmite), silicon oxide, magnesium oxide (magnesia), calcium oxide, titanium oxide (titania).
- Oxide particles such as BaTiO 3 , ZrO, alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalently bonded crystal particles such as silicon and diamond; barium sulfate, calcium fluoride, barium fluoride Insoluble ion crystal particles such as; clay fine particles such as talc and montmorillonite;
- these particles may be subjected to element substitution, surface treatment, solid solution, and the like as necessary.
- the nonelectroconductive particle mentioned above may be used individually by 1 type, and may be used in combination of 2 or more types.
- the compounding quantity in the functional layer of a nonelectroconductive particle can be adjusted suitably.
- the functional layer may contain any other component in addition to the components described above.
- these other components include known additives such as a wetting agent, a viscosity modifier, and an electrolytic solution additive. These other components may be used alone or in combination of two or more.
- the functional layer is usually formed by applying and drying the functional layer composition on a release substrate. Therefore, it is preferable to use a wetting agent from the viewpoint of improving coating unevenness on the release substrate of the functional layer composition.
- the blending amount of the wetting agent in the functional layer (and the functional layer composition) is preferably 0.1 parts by mass or more and more preferably 0.5 parts by mass or more per 100 parts by mass of the organic particles. Preferably, it is 10 parts by mass or less, and more preferably 5 parts by mass or less.
- the content of the wetting agent below the upper limit of the above range, the transferability of the functional layer when the functional layer is formed on the secondary battery substrate using the secondary battery laminate is further increased. In addition, the adhesion of the functional layer in the electrolytic solution can be ensured.
- the release substrate constituting the secondary battery laminate is one in which the above-described functional layer is disposed adjacent to the release substrate, and when the functional layer is transferred onto the secondary battery substrate. Is a substrate that can be easily peeled off from the functional layer.
- the shape (film etc.) and material of a mold release base material are not specifically limited, A well-known thing is employable.
- the contact angle of the release substrate with respect to water needs to be 70 ° or more, preferably 80 ° or more, more preferably 90 ° or more, and 98 ° or more. More preferably, it is preferably 130 ° or less, more preferably 120 ° or less, and even more preferably 105 ° or less.
- the contact angle of the release substrate with respect to water is less than 70 °, the functional layer formed from the aqueous functional layer composition will excessively adhere to the release substrate, ensuring the transferability of the functional layer. Can not do it.
- the contact angle with respect to water is 130 ° or less, application unevenness when applying the functional layer composition onto the release substrate can be suppressed.
- the method for producing a laminate for a secondary battery by forming a functional layer on the release substrate is not particularly limited, but usually a method of drying the functional layer composition on the release substrate is adopted. To do.
- each component contained in the composition for functional layers can be selected according to what is contained in the functional layer mentioned above, and the suitable abundance ratio in the composition for functional layers of these each component is a functional layer. It is the same as the preferred abundance ratio of each component therein.
- composition for functional layer of non-aqueous secondary battery is not particularly limited, but usually, organic particles, a binder, water as a dispersion medium, non-conductive particles and wettability used as necessary.
- a functional layer composition is prepared by mixing with other components such as an agent.
- the mixing method is not particularly limited, in order to disperse each component efficiently, mixing is usually performed using a disperser as a mixing device.
- the disperser is preferably an apparatus capable of uniformly dispersing and mixing the above components. Examples include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer.
- a high dispersion apparatus such as a bead mill, a roll mill, or a fill mix is also included.
- the viscosity of the functional layer composition to be obtained is not particularly limited, but is preferably 1 mPa ⁇ s or more, more preferably 5 mPa ⁇ s or more, still more preferably 10 mPa ⁇ s or more, and 15 mPa ⁇ s. s or more is particularly preferable, 100 mPa ⁇ s or less is preferable, and 90 mPa ⁇ s or less is more preferable. If the viscosity of the functional layer composition is within the above range, the coating property of the functional layer composition on the mold release substrate while satisfactorily dispersing each component such as organic particles in the functional layer composition. Can be secured.
- “viscosity” refers to a value measured using a B-type viscometer at a temperature of 25 ° C. and a rotational speed of 60 rpm.
- the surface tension of the functional layer composition is preferably 20 mN / m or more, more preferably 25 mN / m or more, preferably 50 mN / m or less, and 40 mN / m or less. Is more preferable. If the surface tension of the composition for functional layers is more than the lower limit of the said range, the adhesiveness in the electrolyte solution of the functional layer obtained can further be improved. On the other hand, if the surface tension of the functional layer composition is equal to or less than the upper limit of the above range, coating unevenness when the functional layer composition is applied onto the release substrate can be suppressed. Improves the transferability.
- the surface tension of the functional layer composition can be appropriately adjusted, for example, by changing the amount of a wetting agent or a binder. In the present invention, the “surface tension” of the functional layer composition can be measured using the measuring method described in the examples of the present specification.
- Method for forming functional layer on release substrate As a method of forming a functional layer on a release substrate using the functional layer composition described above, the following methods 1) and 2): 1) A method in which the functional layer composition is applied to the surface of the release substrate and then dried. 2) A method in which the release substrate is dipped in the functional layer composition and then dried. Among these, the method 1) is particularly preferable because the thickness of the functional layer can be easily controlled. Specifically, the method 1) includes a step of applying the functional layer composition onto the release substrate (application step), and drying the functional layer composition applied onto the release substrate to function. A step of forming a layer (functional layer forming step).
- the method for coating the functional layer composition on the release substrate is not particularly limited.
- the gravure method and the spray coating method are preferable from the viewpoint of forming a thin functional layer.
- the method for drying the composition for the functional layer on the release substrate is not particularly limited, and a known method can be used, for example, drying with hot air, hot air, low-humidity air, vacuum Examples include drying and drying methods by irradiation with infrared rays or electron beams.
- the drying conditions are not particularly limited, but the drying temperature is preferably 30 to 80 ° C., and the drying time is preferably 30 seconds to 10 minutes.
- the thickness of the functional layer formed on the release substrate is preferably 0.01 ⁇ m or more, more preferably 0.1 ⁇ m or more, still more preferably 0.5 ⁇ m or more, preferably 20 ⁇ m or less, more preferably Is 10 ⁇ m or less, more preferably 5 ⁇ m or less.
- the thickness of the functional layer is not less than the lower limit of the above range, the strength of the functional layer can be sufficiently ensured, and when the thickness of the functional layer is not more than the upper limit of the above range, the ion diffusibility of the functional layer can be secured.
- the low temperature output characteristics of the secondary battery can be further improved.
- the adhesive strength between a functional layer and a mold release base material becomes like this.
- it is 5 N / m or more, More preferably, it is 10 N / m or more, Preferably it is 50 N / m or less, More preferably, it is 40 N / m or less. If the adhesive strength between the functional layer and the release substrate is equal to or higher than the lower limit of the above range, it is difficult for the components in the functional layer to fall off from the release substrate, and the functional layer is securely held on the release substrate. Is possible.
- the adhesive strength between the functional layer and the release substrate is not more than the upper limit of the above range, the functional layer can be easily peeled from the release substrate, and the transferability of the functional layer can be further enhanced.
- the “adhesive strength” between the functional layer and the release substrate can be measured using the measuring method described in the examples of the present specification.
- the adhesive strength between the functional layer and the release substrate is between the functional layer and the secondary battery substrate. It is preferably smaller than the adhesive strength.
- the adhesive strength between the functional layer and the secondary battery base material electrode base material, separator base material
- the adhesive strength between the battery substrates is generally correlated with and approximate to the adhesive strength between the functional layer and the aluminum foil. Therefore, the adhesive strength between the functional layer and the release substrate is preferably smaller than the adhesive strength between the functional layer and the aluminum foil. And the adhesive strength between a functional layer and aluminum foil becomes like this.
- the adhesive strength between the functional layer and the aluminum foil is not less than the lower limit of the above range, the adhesive strength between the functional layer and the secondary battery substrate is sufficient. On the other hand, if the adhesive strength between the functional layer and the aluminum foil is less than or equal to the upper limit of the above range, the functional layer has an ion diffusibility because the functional layer is prevented from being densified at the time of pressure bonding with securing the adhesive strength. As a result, the low temperature output characteristics of the secondary battery are improved.
- the “adhesive strength” between the functional layer and the aluminum foil can be measured using the measuring method described in the examples of the present specification.
- a functional layer is formed on a non-aqueous secondary battery substrate, and the non-aqueous secondary battery member (electrode) having the functional layer is provided.
- Separator can be manufactured.
- the non-aqueous secondary battery laminate is disposed so that the functional layer is adjacent to the non-aqueous secondary battery substrate, and the functional layer Including a step of adhering a non-aqueous secondary battery substrate (bonding step) and a step of peeling the release substrate from the functional layer (peeling step).
- the non-aqueous secondary battery member manufactured using the method for manufacturing a non-aqueous secondary battery member of the present invention can exhibit excellent electrical characteristics (low temperature output characteristics, high temperature cycle characteristics) in the secondary battery. .
- the base material for a secondary battery to which the functional layer is bonded in the bonding step is not particularly limited.
- a separator base material can be used as the secondary battery substrate, and when manufacturing an electrode as a secondary battery member, a secondary battery substrate is used.
- an electrode substrate formed by forming an electrode mixture layer on a current collector can be used.
- the functional layer may be formed on a separator substrate or an electrode substrate having a porous film layer on the surface.
- the separator substrate is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, the film thickness of the entire separator can be reduced, thereby increasing the ratio of the electrode active material in the secondary battery and increasing the capacity per volume.
- a microporous film made of a resin such as polyethylene, polypropylene, polybutene, or polyvinyl chloride is preferable.
- Electrode substrate Although it does not specifically limit as an electrode base material (a positive electrode base material and a negative electrode base material), The electrode base material with which the electrode compound-material layer was formed on the electrical power collector is mentioned.
- the current collector, the components in the electrode mixture layer (for example, the electrode active material (positive electrode active material, negative electrode active material) and the electrode mixture layer binder (positive electrode mixture layer binder, negative electrode composite) As the material layer binder) and the like, and the method for forming the electrode mixture layer on the current collector known ones can be used, for example, those described in JP2013-145663A be able to.
- the method of adhering the functional layer constituting the secondary battery laminate and the base material for the secondary battery is not particularly limited, but pressure adhesion using a mold press or a roll press is preferable.
- the pressure bonding conditions pressure, temperature, time, etc.
- the temperature of the roll can be appropriately set in the range of 50 to 200 ° C.
- the method of peeling the release substrate from the functional layer to obtain a secondary battery member having the functional layer on the secondary battery substrate is not particularly limited, and a known method can be adopted. .
- Non-aqueous secondary battery By using a non-aqueous secondary battery member manufactured by the method for manufacturing a non-aqueous secondary battery member of the present invention, a non-aqueous secondary battery having excellent electrical characteristics such as high-temperature cycle characteristics and low-temperature output characteristics is manufactured. Can do.
- At least one secondary battery member may be a secondary battery member manufactured by the method for manufacturing a non-aqueous secondary battery member of the present invention. That is, at least one of the positive electrode, the negative electrode, and the separator used for the secondary battery has a functional layer.
- a positive electrode and a negative electrode having a functional layer an electrode in which a functional layer is provided on an electrode substrate formed by forming an electrode mixture layer on a current collector can be used.
- a separator which has a functional layer the separator which provides a functional layer on a separator base material, and the separator which consists of a functional layer can be used.
- an electrode base material and a separator base material the thing similar to the thing quoted by the term of the manufacturing method of a non-aqueous secondary battery member can be used.
- a positive electrode, a negative electrode, and a separator which do not have a functional layer it does not specifically limit, The electrode which consists of an electrode base material mentioned above, and the separator which consists of a separator base material mentioned above can be used.
- an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used.
- a lithium salt is used in a lithium ion secondary battery.
- the lithium salt include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi, and the like.
- LiPF 6 , LiClO 4 , and CF 3 SO 3 Li are preferable because they are easily dissolved in a solvent and exhibit a high degree of dissociation.
- electrolyte may be used individually by 1 type and may be used in combination of 2 or more types.
- the lithium ion conductivity tends to increase as the supporting electrolyte having a higher degree of dissociation is used, so that the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
- the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
- dimethyl carbonate (DMC) dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC).
- Carbonates such as propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC); esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfolane, Sulfur-containing compounds such as dimethyl sulfoxide; are preferably used.
- carbonates are preferable because they have a high dielectric constant and a wide stable potential region.
- the lower the viscosity of the solvent used the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted depending on the type of solvent.
- the concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate.
- a non-aqueous secondary battery for example, stacks a positive electrode and a negative electrode through a separator, and rolls or folds this as necessary into a battery container, and injects an electrolyte into the battery container to seal it.
- at least 1 secondary battery member be a secondary battery member manufactured with the manufacturing method of the non-aqueous secondary battery member of this invention among a positive electrode, a negative electrode, and a separator.
- an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like may be placed in the battery container as necessary to prevent an increase in pressure inside the battery or overcharge / discharge.
- the shape of the battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.
- the degree of swelling of the electrolyte of the polymer constituting the organic particles the average ratio (coverage) of the outer surface of the core portion of the organic particles covered by the shell portion, the average thickness of the shell portion of the organic particles ( Core-shell ratio), volume average particle diameter D50 of each particle (organic particles and functional layer particulate polymer), and each polymer (core portion polymer, shell portion polymer and functional layer particulate polymer).
- ⁇ Swelling degree of electrolyte of polymer constituting organic particles Using the monomer composition used for the preparation of the core part and the shell part of the organic particles, a polymer to be a measurement sample under the same polymerization conditions as the polymerization conditions of the core part and the shell part (polymer and shell of the core part) Part of the polymer) was prepared. Next, the obtained aqueous dispersion was put into a petri dish made of polytetrafluoroethylene and dried at a temperature of 25 ° C. for 48 hours to produce a film having a thickness of 0.5 mm. And the obtained film was cut
- the stained measurement sample was set in a transmission electron microscope (“JEM-3100F” manufactured by JEOL Ltd.), and a cross-sectional structure of organic particles was photographed at an acceleration voltage of 80 kV.
- the magnification of the electron microscope was set so that the cross section of one organic particle was in the visual field.
- the circumference length D1 of the core portion and the length D2 of the portion where the outer surface of the core portion and the shell portion come into contact are measured, and the following equation (1)
- the ratio Rc of the outer surface of the core part of the organic particle covered by the shell part was calculated.
- Covering ratio Rc (%) (D2 / D1) ⁇ 100 (1)
- covering ratio Rc was measured about 20 organic particles selected arbitrarily, the average value was calculated, and it was set as the average ratio (covering ratio) where the outer surface of a core part is covered with a shell part.
- the longest diameter of the polymer particles constituting the shell portion was measured for 20 organic particles arbitrarily selected, and the average value of the longest diameters was taken as the average thickness of the shell portion. Further, when the shell portion had a shape other than the particles, the cross-sectional structure of the organic particles was observed with a transmission electron microscope in the same manner as the above-described method for measuring the coverage. And the maximum thickness of the shell part was measured from the cross-sectional structure of the observed organic particle. The maximum thickness of the shell part was measured for 20 arbitrarily selected organic particles, and the average value of the maximum thickness was taken as the average thickness of the shell part.
- the volume average particle diameter D50 of each particle is a laser diffraction particle size distribution measuring apparatus (manufactured by Shimadzu Corporation) of an aqueous dispersion adjusted to a solid content concentration of 15% by mass.
- the particle size is such that the cumulative volume calculated from the small diameter side is 50%.
- Tg Glass transition temperature
- a measurement sample obtained by drying the aqueous dispersion containing the obtained functional layer particulate polymer was used.
- a differential thermal analysis measuring device product name “EXSTAR DSC6220” manufactured by SII Nano Technology, Inc.
- 10 mg of the above-mentioned measurement sample is weighed on an aluminum pan, and an empty aluminum pan is used as a reference.
- the DSC curve was measured in the range of ⁇ 100 ° C. to 500 ° C. at a rate of temperature increase of 10 ° C./min and at normal temperature and humidity.
- a laminate for a secondary battery including a release substrate and a functional layer was cut into a rectangle having a length of 100 mm and a width of 10 mm to obtain a test piece.
- the test piece was peeled off by attaching cellophane tape (as defined in JIS Z1522) to the surface of the functional layer with the functional layer down, and pulling one end of the release substrate vertically upward at a pulling speed of 50 mm / min. (The cellophane tape was fixed on a horizontal test stand). This measurement was performed 3 times, the average value of stress was calculated
- the obtained laminate of the functional layer and the aluminum foil was cut into a rectangle having a length of 100 mm and a width of 10 mm to obtain a test piece.
- the cellophane tape (as defined in JIS Z1522) is attached to the surface of the functional layer with the functional layer down, and one end of the aluminum foil is pulled vertically upward at a pulling speed of 50 mm / min. Stress was measured (cellophane tape was fixed on a horizontal test bench). This measurement was performed 3 times, the average value of stress was calculated
- ⁇ Adhesiveness of functional layer in electrolytic solution (adhesive strength after electrolytic solution immersion between functional layer and electrode substrate)>
- An electrode comprising a functional layer on an electrode substrate was cut into a rectangle having a length of 100 mm and a width of 10 mm to obtain a test piece.
- the test piece was taken out from the electrolytic solution, and the electrolytic solution adhering to the surface of the functional layer was wiped off.
- a laminate for a secondary battery including a release substrate and a functional layer was cut into a rectangle having a length of 100 mm and a width of 10 mm to obtain a test piece. (Note that the mass M0 of the rectangular release substrate alone having a length of 100 mm and a width of 10 mm was separately measured.)
- the test specimen and the electrode base material were the electrode mixture layer in which the functional layer side of the test piece was the electrode base material.
- M0 / M1 ratio is 90 mass% or more
- B: M0 / M1 ratio is 80 mass% or more and less than 90 mass%
- C: M0 / M1 ratio is 60 mass% or more and less than 80 mass%
- D: M0 / M1 ratio is 60 mass% ⁇ % ⁇ Contact angle of release substrate to water> Using a contact angle meter (“DM-701” manufactured by Kyowa Interface Chemical Co., Ltd.), 3 microliters of distilled water was dropped onto the surface of the release substrate, and the contact angle (°) 10 seconds after the dropping was measured.
- DM-701 manufactured by Kyowa Interface Chemical Co., Ltd.
- the manufactured wound lithium ion secondary battery with a discharge capacity of 1000 mAh was allowed to stand for 24 hours in an environment at 25 ° C., and then, a constant voltage / constant current of 4.35 V and 0.1 C in an environment at 25 ° C. Charging and discharging operations were performed by charging at a constant current of 2.75 V and 0.1 C, and the initial capacity C0 was measured.
- Capacity maintenance ratio ⁇ C (C1 / C0) ⁇ 100 before and after the cycle was calculated and evaluated according to the following criteria. It shows that it is excellent in high temperature cycling characteristics, so that the value of capacity
- Example 1 ⁇ Preparation of organic particles> In a 5 MPa pressure vessel with a stirrer, 75 parts of methyl methacrylate as a (meth) acrylic acid ester monomer, 4 parts of methacrylic acid as an acid group-containing monomer, and a crosslinkable monomer for forming a core part of organic particles After adding 1 part of ethylene glycol dimethacrylate as a body, 1 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.5 part of potassium persulfate as a polymerization initiator, and after sufficiently stirring The polymerization was started by heating to 60 ° C.
- the functional layer particulate polymer thus obtained had a volume average particle diameter D50 of 0.36 ⁇ m and a glass transition temperature of ⁇ 35 ° C.
- ⁇ Preparation of Nonaqueous Secondary Battery Functional Layer Composition 100 parts of aqueous dispersion containing organic particles is mixed with solid content, 21 parts of water dispersion containing particulate polymer for functional layer is mixed with solid content, and 1 part of wetting agent (manufactured by San Nopco, “SN366”) is mixed. Further, ion exchange water was added so that the solid content concentration was 39% to obtain a composition for a functional layer. The surface tension of the obtained functional layer composition was measured. The results are shown in Table 1.
- the functional layer composition was applied onto a release substrate a (“PET38AL-5” manufactured by Lintec Corporation) and dried at 50 ° C. for 3 minutes. Thereby, the laminated body for secondary batteries provided with the functional layer whose thickness is 1 micrometer on the mold release base material a was obtained. Using the obtained secondary battery laminate, the adhesive strength between the functional layer and the release substrate, the adhesive strength between the functional layer and the aluminum foil, and the transferability of the functional layer were evaluated. The results are shown in Table 1.
- a 5% aqueous sodium hydroxide solution was added to the mixture containing the particulate binder and the pH was adjusted to 8, and then the unreacted monomer was removed by heating under reduced pressure. Then, it cooled to 30 degrees C or less, and obtained the water dispersion liquid containing a desired particulate-form binder.
- aqueous dispersion containing the above-mentioned particulate binder is added to the obtained mixed liquid, and ion-exchanged water corresponding to the solid content, and the final solid content concentration is adjusted to 52%. And mixed for another 10 minutes. This was defoamed under reduced pressure to obtain a negative electrode slurry composition having good fluidity. Then, the negative electrode slurry composition obtained as described above was applied on a copper foil having a thickness of 20 ⁇ m, which is a current collector, with a comma coater so that the film thickness after drying was about 150 ⁇ m. , Dried. This drying was performed by conveying the copper foil in an oven at 60 ° C.
- the negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode substrate after pressing with a negative electrode mixture layer thickness of 80 ⁇ m.
- the obtained positive electrode slurry composition was applied onto a 20 ⁇ m-thick aluminum foil as a current collector by a comma coater so that the film thickness after drying was about 150 ⁇ m and dried. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material.
- the positive electrode raw material before pressing was rolled with a roll press to obtain a positive electrode after pressing with a positive electrode mixture layer thickness of 80 ⁇ m.
- the pressed positive electrode obtained above was cut out to 49 cm ⁇ 5 cm and placed so that the surface of the positive electrode mixture layer side was on the upper side, and a separator cut out to 55 cm ⁇ 5.5 cm (made by Celgard, “2500 ”, A thickness of 25 ⁇ m). Furthermore, the negative electrode provided with the functional layer obtained above was cut out to 50 cm ⁇ 5.2 cm, and this was disposed on the separator so that the surface on the functional layer side faces the separator. This was wound with a winding machine to obtain a wound body. The wound body is pressed at 60 ° C.
- Examples 2 and 3 In the same manner as in Example 1, except that the ratio of the monomer added for forming the core part of the organic particles was changed as shown in Table 1 described later when the aqueous dispersion containing the organic particles was prepared. Particles, functional layer particulate polymer, functional layer composition, secondary battery laminate, negative electrode including the functional layer, positive electrode, and lithium ion secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Examples 4 and 5 Except having changed as shown in Table 1 mentioned later at the time of preparation of the aqueous dispersion containing organic particles, and having changed as shown in Table 1 mentioned below for the shell part formation of organic particles, it carried out similarly to Example 1. , Organic particles, particulate polymer for functional layer, functional layer composition, laminate for secondary battery, negative electrode including functional layer, positive electrode and lithium ion secondary battery. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Example 6 In the same manner as in Example 1 except that the amount of the functional layer particulate polymer was changed as shown in Table 1 described later when the functional layer composition was prepared, the organic particles and the functional layer particulate weight were changed. A coalescence, a composition for a functional layer, a laminate for a secondary battery, a negative electrode including a functional layer, a positive electrode, and a lithium ion secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Example 8 Except that the acrylic polymer 2 prepared as described below was used instead of the acrylic polymer 1 as the functional layer particulate polymer in the preparation of the functional layer composition, the same as in Example 1. , Organic particles, functional layer composition, laminate for secondary battery, negative electrode provided with functional layer, positive electrode and lithium ion secondary battery. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- the functional layer particulate polymer thus obtained had a volume average particle diameter D50 of 0.3 ⁇ m and a glass transition temperature of ⁇ 2 ° C.
- Example 9 (Examples 9 and 10)
- the release substrate b (Nissha Printing Co., Ltd., “Nisssha Techsol RX101”)
- the release substrate c (Daicel Value Coating Co., Ltd.) Except for using “T788”)
- organic particles, functional layer particulate polymer, functional layer composition, secondary battery laminate, negative electrode provided with functional layer, positive electrode And a lithium ion secondary battery was manufactured.
- Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Example 11 and 12 The organic particles, the functional layer particulate polymer, and the functional layer composition were the same as in Example 1 except that the amount of the wetting agent was changed as shown in Table 1 to be described later when the functional layer composition was prepared.
- Products, a laminate for a secondary battery, a negative electrode including a functional layer, a positive electrode, and a lithium ion secondary battery were manufactured.
- Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Example 1 The same as Example 1 except that the ratio of the monomer added for forming the core part and the shell part of the organic particles was changed as shown in Table 1 to be described later when preparing the aqueous dispersion containing the organic particles.
- organic particles, a functional layer particulate polymer, a functional layer composition, a secondary battery laminate, a negative electrode including a functional layer, a positive electrode, and a lithium ion secondary battery were produced.
- Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Comparative Example 2 In the same manner as in Example 1, except that the ratio of the monomer added for forming the core part of the organic particles was changed as shown in Table 1 described later when the aqueous dispersion containing the organic particles was prepared. Particles, functional layer particulate polymer, functional layer composition, secondary battery laminate, negative electrode including the functional layer, positive electrode, and lithium ion secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Example 3 In the same manner as in Example 1, except that the ratio of the monomer added for forming the shell part of the organic particles was changed as shown in Table 1 to be described later when the aqueous dispersion containing the organic particles was prepared. Particles, functional layer particulate polymer, functional layer composition, secondary battery laminate, negative electrode including the functional layer, positive electrode, and lithium ion secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- Example 4 In the same manner as in Example 1 except that a polyethylene release substrate d was used instead of the release substrate a during the production of the secondary battery laminate, the organic particles and the functional layer particulate weights were used. A coalescence, a composition for a functional layer, a laminate for a secondary battery, a negative electrode including a functional layer, a positive electrode, and a lithium ion secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1 described later.
- MMA indicates methyl methacrylate
- MAA indicates methacrylic acid
- EDMA refers to ethylene glycol dimethacrylate
- ST indicates styrene
- NaSS indicates sodium styrene sulfonate
- AN indicates acrylonitrile
- ACL1 indicates acrylic polymer 1
- ACL2 indicates the acrylic polymer 2.
- a functional layer containing organic particles having a predetermined core-shell structure and a binder is separated from water having a contact angle with water of a predetermined value or more.
- the transferability of the functional layer is excellent, and in addition, the functional layer exhibits good adhesion in the electrolytic solution, It can be seen that the secondary battery can exhibit excellent high-temperature cycle characteristics and low-temperature output characteristics.
- Examples 1 to 3 in Table 1 above by adjusting the monomer composition of the core portion of the organic particles and the degree of electrolyte swelling, the adhesion of the functional layer in the electrolyte, and the secondary battery It can be seen that the high-temperature cycle characteristics and the low-temperature output characteristics can be further improved.
- Examples 1, 4 and 5 in Table 1 above by adjusting the monomer composition of the shell portion of the organic particles and the degree of swelling of the electrolytic solution, the adhesiveness of the functional layer in the electrolytic solution, and the secondary It can be seen that the high-temperature cycle characteristics of the battery can be further improved.
- Examples 1, 6, and 7 in Table 1 above by changing the amount of the functional layer particulate polymer as a binder, the transferability of the functional layer and the adhesion in the electrolyte solution, and It can be seen that the high-temperature cycle characteristics and low-temperature output characteristics of the secondary battery can be further improved.
- Examples 1 and 8 in Table 1 above by adjusting the monomer composition and Tg of the particulate polymer for the functional layer as the binder, the transferability of the functional layer and in the electrolyte solution are adjusted. It can be seen that the adhesion and the high temperature cycle characteristics and low temperature output characteristics of the secondary battery can be further improved.
- transfer property and can express a high function in a non-aqueous secondary battery can be provided.
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Abstract
Description
具体的には、集電体上に電極合材層を設けてなる電極基材の上に更に機能層を形成してなる電極や、セパレータ基材上に機能層を形成してなるセパレータが二次電池部材として使用されている(例えば特許文献1、2参照)。
また特許文献2では、セパレータ基材の上に、非導電性粒子および結着材を含有する多孔膜の層を形成するとともに、この多孔膜層上に、所定のガラス転移温度を有する粒子状重合体を含有する接着剤層を更に設けてなるセパレータが、電極との良好な接着性を有し、そして、二次電池に優れた高温サイクル特性およびレート特性を発揮させるとの報告がされている。
特に、上記従来技術の機能層に含まれるポリマー粒子や粒子状重合体等の結着材成分は、乾燥状態での接着性に比して電解液中での接着性に劣る。そのため、当該従来技術の機能層の電解液中での接着性を確保するため、結着材成分の量を増加させると、離型基材への接着性が過度に増大することにより機能層の転写性が損なわれ、結果として機能層に優れた性能を発揮させることができないという問題があった。
したがって、上記従来の技術には、機能層を一旦離型基材上に設け二次電池用積層体とし、当該二次電池用積層体を用いて二次電池用基材上に機能層を形成する際に、機能層の転写性および電解液中での接着性の双方をバランスよく確保し、そして、二次電池の電気的特性を向上させるという点において改善の余地があった。
また、本発明は、非水系二次電池に優れた電気的特性を発揮させ得る非水系二次電池部材を、非水系二次電池用積層体を用いて製造する方法を提供することを目的とする。
ここで、本発明において、有機粒子のコア部およびシェル部の重合体の「電解液膨潤度」、並びに離型基材の「水に対する接触角」は、本明細書の実施例に記載の測定方法を用いて測定することができる。
ここで、本発明において、有機粒子のコア部およびシェル部の「ガラス転移温度」は、本明細書の実施例に記載の測定方法を用いて測定することができる。
ここで、本発明において、結着材の「ガラス転移温度」は、本明細書の実施例に記載の測定方法を用いて測定することができる。
また、本発明によれば、非水系二次電池に優れた電気的特性を発揮させ得る非水系二次電池部材を、非水系二次電池用積層体を用いて製造する方法を提供することができる。
ここで、本発明の非水系二次電池用積層体は、機能層を非水系電池用基材上に転写させ、機能層を備える非水系二次電池部材を製造する用途に用いられるものである。また、本発明の非水系二次電池部材の製造方法は、非水系二次電池用積層体を用いて、機能層と非水系二次電池用基材とを備える非水系二次電池部材を製造する方法である。
なお、機能層は、セパレータや電極等の二次電池部材の耐熱性および強度を向上させるための多孔膜層であってもよいし、二次電池部材同士を接着させるための接着層であってもよいし、多孔膜層と接着層との双方の機能を発揮する層であってもよい。
非水系二次電池用積層体は、離型基材、および当該離型基材に接するように配置され、少なくとも有機粒子および結着材を含む機能層を備える。そして離型基材の水に対する接触角が特定の値以上であり、機能層中で有機粒子と結着材が併用されており、そして有機粒子が特定のコアシェル構造を有する。
本発明の非水系二次電池用積層体を用いれば、機能層を好適に二次電池用基材上に転写することができ、当該転写後の機能層は、電解液中での接着性に優れる上、二次電池に優れた電気的特性を発揮させることができる。加えて、本発明の非水系二次電池用積層体を用いれば、機能層用組成物を塗布するための装置を有さない場合でも、機能層を備える二次電池部材の製造が可能である。また、本発明の非水系二次電池用積層体を用いれば、機能層用組成物の塗布が困難な二次電池基材(例えば孔径が大きい不織布)上にも容易に機能層を設けることが可能となる。
二次電池用積層体を構成する機能層は、上述のように有機粒子および結着材を含み、任意に非導電性粒子(有機粒子および結着材に該当するものを除く)、その他の成分を含み得る。そして機能層は、二次電池用基材上へと転写され、セパレータや電極などの二次電池部材を構成する。
有機粒子は、接着層として機能する機能層においては、電解液中で二次電池部材同士、例えばセパレータと電極とを強固に接着させる接着剤としての機能を担う。また、有機粒子は、多孔膜層として機能する機能層においては、電解液中で非導電性粒子同士を強固に結着させる結着材としての機能を担う。そして、有機粒子は、コア部と、コア部の外表面を部分的に覆うシェル部とを備えるコアシェル構造を有しており、コア部は、電解液膨潤度が5倍以上30倍以下の重合体からなり、且つ、シェル部は、電解液膨潤度が1倍超4倍以下の重合体からなることを特徴とする。
即ち、有機粒子のシェル部を構成する重合体は、電解液に対して膨潤する。このとき、例えば膨潤したシェル部の重合体が有する官能基が活性化して二次電池用基材(例えば、機能層が接するセパレータ基材、電極基材等)や非導電性粒子の表面と化学的または電気的な相互作用を生じるなどの要因により、シェル部は電解液中で二次電池部材や非導電性粒子と強固に接着できる。そのため、有機粒子を含む機能層により二次電池部材同士(例えば、セパレータと電極)を電解液中において強力に接着したり、非導電性粒子同士を電解液中において強力に接着して機能層の強度および耐熱性を高めたりすることが可能となっているものと推察される。
また、有機粒子を含む機能層を接着層として使用した場合、上述したように電解液中においてセパレータと電極とを強力に接着することができるので、当該機能層を備える二次電池では、機能層を介して接着された二次電池部材間(例えば、セパレータと電極との間)に空隙を生じ難い。そのため、有機粒子を含む機能層を使用した二次電池では、二次電池内において正極と負極との距離が大きくなり難く、二次電池の内部抵抗を小さくできると共に、電極における電気化学反応の反応場が不均一になり難い。更に、当該二次電池では、充放電を繰り返してもセパレータと電極との間に空隙ができ難く、電池容量が低下しにくい。これにより、優れた耐膨らみ性や高温サイクル特性などを実現できるものと推察される。
更に、有機粒子のコア部を構成する重合体は、電解液に対して大きく膨潤する。そして、重合体は、電解液に大きく膨潤した状態では、重合体の分子間の隙間が大きくなり、その分子間をイオンが通り易くなる。また、有機粒子のコア部の重合体は、シェル部によって完全に覆われてはいない。そのため、電解液中においてイオンがコア部を通りやすくなるので、有機粒子は高いイオン拡散性を発現できる。従って、上記有機粒子を使用すれば、機能層による抵抗の上昇を抑制し、低温出力特性などの電気的特性の低下を抑制することも可能である。
また、シェル部を構成する重合体は、電解液に膨潤していない状態においては、通常、接着性を有さず、電解液に膨潤することにより始めて接着性を発現する。そのため、有機粒子は、電解液に膨潤していない状態において、通常、接着性を発現しない。このため、その有機粒子を含む機能層は、電解液に膨潤していない状態では、通常、大きな接着性を発現せず、その機能層が形成されたセパレータ基材等の基材は、重ねてもブロッキングを生じ難いものと推察される。なお、有機粒子は、電解液に膨潤しない限りは接着性を全く発揮しないというものではなく、電解液に膨潤していない状態であっても、例えば一定温度以上(例えば50℃以上)に加熱されることにより、接着性を発現し得る。
ここで、有機粒子は、コア部と、コア部の外表面を覆うシェル部とを備えるコアシェル構造を有している。また、シェル部は、コア部の外表面を部分的に覆っている。即ち、有機粒子のシェル部は、コア部の外表面を覆っているが、コア部の外表面の全体を覆ってはいない。外観上、コア部の外表面がシェル部によって完全に覆われているように見える場合であっても、シェル部の内外を連通する孔が形成されていれば、そのシェル部はコア部の外表面を部分的に覆うシェル部である。したがって、例えば、シェル部の外表面(即ち、有機粒子の周面)からコア部の外表面まで連通する細孔を有するシェル部を備える有機粒子は、上記有機粒子に含まれる。
まず、有機粒子を常温硬化性のエポキシ樹脂中に十分に分散させた後、包埋し、有機粒子を含有するブロック片を作製する。次に、ブロック片を、ダイヤモンド刃を備えたミクロトームで厚さ80nm~200nmの薄片状に切り出して、測定用試料を作製する。その後、必要に応じて、例えば四酸化ルテニウムまたは四酸化オスミウムを用いて測定用試料に染色処理を施す。
次に、この測定用試料を、透過型電子顕微鏡(TEM)にセットして、有機粒子の断面構造を写真撮影する。電子顕微鏡の倍率は、有機粒子1個の断面が視野に入る倍率が好ましく、具体的には10,000倍程度が好ましい。
撮影された有機粒子の断面構造において、コア部の外表面に相当する周の長さD1、および、コア部の外表面とシェル部とが当接する部分の長さD2を測定する。そして、測定された長さD1および長さD2を用いて、下記の式(1)により、その有機粒子のコア部の外表面がシェル部によって覆われる割合Rcを算出する。
被覆割合Rc(%)=(D2/D1)×100 ・・・(1)
前記の被覆割合Rcを、20個以上の有機粒子について測定し、その平均値を計算して、コア部の外表面がシェル部によって覆われる平均割合(被覆率)とする。
ここで、前記の被覆割合Rcは、断面構造からマニュアルで計算することもできるが、市販の画像解析ソフトを用いて計算することもできる。市販の画像解析ソフトとして、例えば「AnalySIS Pro」(オリンパス株式会社製)を用いることができる。
なお、有機粒子の体積平均粒子径D50は、固形分濃度15質量%に調整した水分散溶液の、レーザー回折式粒子径分布測定装置を用いて湿式測定された粒子径分布において、小径側から計算した累積体積が50%となる粒子径として求めうる。
有機粒子のコア部は、電解液に対して所定の膨潤度を有する重合体からなる。具体的には、コア部の重合体の電解液膨潤度は、5倍以上であることが必要であり、6倍以上であることが好ましく、7倍以上であることがより好ましく、また、30倍以下であることが必要であり、25倍以下であることが好ましく、20倍以下であることがより好ましく、15倍以下であることが更に好ましい。コア部の重合体の電解液膨潤度を前記範囲の下限値以上にすることにより、機能層のイオン拡散性を高め、二次電池の低温出力特性などの電気的特性を向上させることができる。また、コア部の重合体の電解液膨潤度を前記範囲の上限値以下にすることにより、電解液中での有機粒子の接着性を高め、二次電池の高温サイクル特性を向上させることができる。加えてコア部の電解液中への溶出を十分に抑制することができる。更に、機能層が膜化することに起因するイオン伝導の阻害が抑制され、二次電池の低温出力特性を確保することができる。
まず、有機粒子のコア部の重合体を用意する。例えば、有機粒子の調製においてコア部を形成するために行うのと同様の工程を行うことにより得られた重合体を用意する。その後、用意した重合体によりフィルムを作製する。例えば重合体が固体であれば、温度25℃、48時間の条件で重合体を乾燥した後、その重合体をフィルム状に成形して、厚み0.5mmのフィルムを作製する。また、例えば、重合体がラテックス等の溶液または分散液である場合は、その溶液または分散液を、ポリテトラフルオロエチレン製のシャーレに入れ、温度25℃、48時間の条件で乾燥して、厚み0.5mmのフィルムを作製する。
次に、上記のようにして作製したフィルムを1cm角に裁断して、試験片を得る。この試験片の重量を測定し、W0とする。また、この試験片を上記電解液に温度60℃で72時間浸漬し、その試験片を電解液から取り出す。取り出した試験片の表面の電解液を拭き取り、浸漬後の試験片の重量W1を測定する。
そして、これらの重量W0およびW1を用いて、膨潤度S(倍)を、S=W1/W0にて計算する。
そして、SP値は、Hansen Solubility Parameters A User’s Handbook,2ndEd(CRCPress)で紹介される方法を用いて算出することができる。
また、有機化合物のSP値は、その有機化合物の分子構造から推算することも可能である。具体的には、SMILEの式からSP値を計算できるシミュレーションソフトウェア(例えば「HSPiP」(http=//www.hansen-solubility.com))を用いて計算しうる。このシミュレーションソフトウェアでは、Hansen SOLUBILITY PARAMETERS A User’s Handbook SecondEdition、Charles M.Hansenに記載の理論に基づき、SP値が求められている。
なお、本明細書において「(メタ)アクリル」とは、アクリルおよび/またはメタクリルを意味し、「(メタ)アクリロ」は、アクリロおよび/またはメタクリロを意味する。
なお、本発明において「単量体単位を含む」とは、「その単量体を用いて得た重合体中に単量体由来の構造単位が含まれている」ことを意味する。
また、スルホン酸基を有する単量体としては、例えば、ビニルスルホン酸、メチルビニルスルホン酸、(メタ)アリルスルホン酸、(メタ)アクリル酸-2-スルホン酸エチル、2-アクリルアミド-2-メチルプロパンスルホン酸、3-アリロキシ-2-ヒドロキシプロパンスルホン酸などが挙げられる。なお、本明細書において、「(メタ)アリル」とは、アリルおよび/またはメタリルを意味する。
更に、リン酸基を有する単量体としては、例えば、リン酸-2-(メタ)アクリロイルオキシエチル、リン酸メチル-2-(メタ)アクリロイルオキシエチル、リン酸エチル-(メタ)アクリロイルオキシエチルなどが挙げられる。なお、本明細書において、「(メタ)アクリロイル」とは、アクリロイルおよび/またはメタクリロイルを意味する。
また、水酸基を有する単量体としては、例えば、アクリル酸-2-ヒドロキシエチル、アクリル酸-2-ヒドロキシプロピル、メタクリル酸-2-ヒドロキシエチル、メタクリル酸-2-ヒドロキシプロピルなどが挙げられる。
また、酸基含有単量体は、1種類を単独で用いてもよく、2種類以上を任意の比率で組み合わせて用いてもよい。
有機粒子のシェル部は、コア部の電解液膨潤度よりも小さい所定の電解液膨潤度を有する重合体からなる。具体的には、シェル部の重合体の電解液膨潤度は、1倍超4倍以下であることが必要であり、1.1倍以上であることが好ましく、1.2倍以上であることがより好ましく、また、3.5倍以下であることが好ましく、3倍以下であることがより好ましく、2.5倍以下であることが更に好ましい。シェル部の重合体の電解液膨潤度を前記範囲の下限値以上にすることにより、機能層のイオン拡散性を高め、二次電池の低温出力特性を向上させることができる。さらに、電解液中での有機粒子の接着性を高め、二次電池の高温サイクル特性を向上させることができる。また、シェル部の重合体の電解液膨潤度を前記範囲の上限値以下にすることにより、電解液中での有機粒子の接着性を高め、二次電池の高温サイクル特性を向上させることができる。加えて、機能層が膜化することに起因するイオン伝導の阻害が抑制され、二次電池の低温出力特性を確保することができる。
まず、有機粒子のシェル部の重合体を用意する。例えば、有機粒子の調製において、コア部の形成に用いる単量体組成物の代わりにシェル部の形成に用いる単量体組成物を用いて、コア部の製造方法と同様にして重合体を製造する。
その後、コア部の重合体の膨潤度の測定方法と同様の方法で、シェル部の重合体によりフィルムを作製し、そのフィルムから試験片を得て、膨潤度Sを測定する。
また、酸基含有単量体は、1種類を単独で用いてもよく、2種類以上を任意の比率で組み合わせて用いてもよい。
そして、上述したコアシェル構造を有する有機粒子は、例えば、コア部の重合体の単量体と、シェル部の重合体の単量体とを用い、経時的にそれらの単量体の比率を変えて段階的に重合することにより、調製することができる。具体的には、有機粒子は、先の段階の重合体を後の段階の重合体が順次に被覆するような連続した多段階乳化重合法および多段階懸濁重合法によって調製することができる。
上述した通り、有機粒子は、電解液に膨潤していない状態では、通常、接着性を発現しない。そのため、電解液への浸漬前に機能層に含まれる成分が機能層から脱落するのを抑制し、かつ離型基材上への機能層の形成および当該機能層の二次電池用基材上への転写を好適に行う観点から、結着材を使用することが必要である。なお、「結着材」には上述した有機粒子は含まれない。そして結着材として、電解液に膨潤していない温度25℃の環境下において有機粒子よりも高い接着性を発揮し得る、機能層用粒子状重合体を機能層に含有させることが好ましい。機能層用粒子状重合体などの結着材を用いることにより、電解液に膨潤している状態および膨潤していない状態の両方において、機能層を構成する成分が機能層から脱落するのを抑制することができる。加えて、離型基材および二次電池用基材双方への機能層の乾燥状態での接着性を確保することができるため、二次電池用積層体の製造を確実に行うことができ、しかも当該二次電池用積層体を用いて、機能層を備える二次電池部材を容易に製造することができる。
ここで、共役ジエン系重合体とは、共役ジエン単量体単位を含む重合体を指し、共役ジエン系重合体の具体例としては、スチレン-ブタジエン共重合体(SBR)などの芳香族ビニル単量体単位および脂肪族共役ジエン単量体単位を含む重合体が挙げられる。また、アクリル系重合体とは、(メタ)アクリル酸エステル単量体単位を含む重合体を指す。
なお、これらの機能層用粒子状重合体は、1種類を単独で使用してもよいし、2種類以上を組み合わせて用いてもよい。ただし、2種類以上を組み合わせた機能層用粒子状重合体を用いる場合、かかる重合体は、上述した所定の電解液膨潤度を有する重合体からなるコアシェル構造を有する有機粒子とは異なるものである。
多孔膜層として機能し得る機能層に配合される非導電性粒子としては、特に限定されることなく、非水系二次電池に用いられる既知の非導電性粒子を挙げることができる。
具体的には、非導電性粒子としては、無機微粒子と、上述した有機粒子および機能層用粒子状重合体(結着材)以外の有機微粒子との双方を用いることができるが、通常は無機微粒子が用いられる。なかでも、非導電性粒子の材料としては、非水系二次電池の使用環境下で安定に存在し、電気化学的に安定である材料が好ましい。このような観点から非導電性粒子の材料の好ましい例を挙げると、酸化アルミニウム(アルミナ)、水和アルミニウム酸化物(ベーマイト)、酸化ケイ素、酸化マグネシウム(マグネシア)、酸化カルシウム、酸化チタン(チタニア)、BaTiO3、ZrO、アルミナ-シリカ複合酸化物等の酸化物粒子;窒化アルミニウム、窒化ホウ素等の窒化物粒子;シリコン、ダイヤモンド等の共有結合性結晶粒子;硫酸バリウム、フッ化カルシウム、フッ化バリウム等の難溶性イオン結晶粒子;タルク、モンモリロナイト等の粘土微粒子;などが挙げられる。また、これらの粒子は必要に応じて元素置換、表面処理、固溶体化等が施されていてもよい。
なお、上述した非導電性粒子は、1種類を単独で使用してもよいし、2種類以上を組み合わせて用いてもよい。また非導電性粒子の機能層中の配合量は適宜調整し得る。
機能層は、上述した成分以外にも、任意のその他の成分を含んでいてもよい。これらのその他の成分としては、例えば、濡れ剤、粘度調整剤、電解液添加剤などの既知の添加剤が挙げられる。これらのその他の成分は、1種類を単独で使用してもよいし、2種類以上を組み合わせて用いてもよい
機能層中(および機能層用組成物)中の濡れ剤の配合量は、有機粒子100質量部当たり、0.1質量部以上であることが好ましく、0.5質量部以上であることがより好ましく、10質量部以下であることが好ましく、5質量部以下であることがより好ましい。濡れ剤の含有量を前記範囲の下限値以上にすることにより、機能層用組成物の塗布ムラを抑制することができ、得られる機能層の離型基材への接着性を確保することができる。一方、濡れ剤の含有量を前記範囲の上限値以下にすることにより、二次電池用積層体を用いて二次電池用基材上に機能層を形成する際の機能層の転写性を更に高め、また、電解液中での機能層の接着性を確保することができる。
二次電池用積層体を構成する離型基材は、その上に隣接して上述の機能層が配置されるものであり、また当該機能層を二次電池用基材上に転写する際には、機能層から容易に剥離し得る基材である。なお、離型基材の形状(フィルムなど)、材質は特に限定されず、公知のものを採用することができる。
ここで、離型基材の水に対する接触角は70°以上であることが必要であり、80°以上であることが好ましく、90°以上であることがより好ましく、98°以上であることが更に好ましく、一方、130°以下であることが好ましく、120°以下であることがより好ましく、105°以下であることが更に好ましい。離型基材の水に対する接触角が70°未満であると、水系の機能層用組成物から形成される機能層が離型基材に過度に接着することとなり、機能層の転写性を確保することができない。一方、水に対する接触角が130°以下であることで、機能層用組成物を離型基材上へ塗布する際の塗布ムラを抑制することができる。
離型基材上に機能層を形成して、二次電池用積層体を製造する方法は、特に限定されないが、通常は、機能層用組成物を離型基材上で乾燥する方法を採用する。
なお、機能層用組成物中に含まれる各成分は、上述した機能層に含まれるものに対応して選択しうり、それら各成分の機能層用組成物中の好適な存在比は、機能層中の各成分の好適な存在比と同じとする。
ここで、機能層用組成物の調製方法は、特に限定はされないが、通常は、有機粒子と、結着材と、分散媒としての水と、必要に応じて用いられる非導電性粒子および濡れ剤などのその他の成分とを混合して機能層用組成物を調製する。混合方法は特に制限されないが、各成分を効率よく分散させるため、通常は混合装置として分散機を用いて混合を行う。
分散機は、上記成分を均一に分散および混合できる装置が好ましい。例を挙げると、ボールミル、サンドミル、顔料分散機、擂潰機、超音波分散機、ホモジナイザー、プラネタリーミキサーなどが挙げられる。また、高い分散シェアを加えることができる観点から、ビーズミル、ロールミル、フィルミックス等の高分散装置も挙げられる。
上述の機能層用組成物を用いて、離型基材上に機能層を形成する方法としては、以下1)、2)の方法:
1)機能層用組成物を離型基材の表面に塗布し、次いで乾燥する方法
2)機能層用組成物に離型基材を浸漬後、これを乾燥する方法
が挙げられる。
これらの中でも、前記1)の方法が、機能層の膜厚制御をしやすいことから特に好ましい。該1)の方法は、詳細には、機能層用組成物を離型基材上に塗布する工程(塗布工程)、離型基材上に塗布された機能層用組成物を乾燥させて機能層を形成する工程(機能層形成工程)を備える。
また機能層形成工程において、離型基材上の機能層用組成物を乾燥する方法としては、特に限定されず公知の方法を用いることができ、例えば温風、熱風、低湿風による乾燥、真空乾燥、赤外線や電子線などの照射による乾燥法が挙げられる。乾燥条件は特に限定されないが、乾燥温度は好ましくは30~80℃で、乾燥時間は好ましくは30秒~10分である。
なお、本発明において機能層と離型基材の「接着強度」は、本明細書の実施例に記載の測定方法を用いて測定することができる。
ここで、機能層と二次電池用基材(電極基材、セパレータ基材)の間の接着強度は、二次電池用基材の種類や材質により異なるものであるが、機能層と二次電池用基材の間の接着強度は、機能層とアルミ箔の間の接着強度に概ね相関し、そして近似するものである。したがって、機能層と離型基材の間の接着強度は、機能層とアルミ箔の間の接着強度よりも小さいことが好ましい。
そして、機能層とアルミ箔との間の接着強度は、好ましくは100N/m以上、より好ましくは150N/m以上であり、好ましくは500N/m以下、より好ましくは300N/m以下である。機能層とアルミ箔の接着強度が前記範囲の下限値以上であれば、機能層と二次電池用基材の接着強度が十分となる。一方、機能層とアルミ箔の接着強度が前記範囲の上限値以下であれば、接着強度確保に伴う機能層の加圧接着時の高密度化が抑制されるため、機能層のイオン拡散性が確保され二次電池の低温出力特性が向上する。
なお、本発明において機能層とアルミ箔の「接着強度」は、本明細書の実施例に記載の測定方法を用いて測定することができる。
上述のようにして得られる本発明の非水系二次電池用積層体を用いて、非水系二次電池用基材上に機能層を形成し、機能層を備える非水系二次電池部材(電極、セパレータ)を製造することができる。具体的には、本発明の非水系二次電池部材の製造方法は、非水系二次電池用積層体を、機能層が非水系二次電池用基材と隣接するように配置し、機能層を非水系二次電池用基材に接着させる工程(接着工程)と、離型基材を機能層から剥離する工程(剥離工程)とを含む。
本発明の非水系二次電池部材の製造方法を用いて製造される非水系二次電池部材は、二次電池に優れた電気的特性(低温出力特性、高温サイクル特性)を発揮させることができる。
接着工程において機能層を接着する二次電池用基材は、特に限定されない。二次電池部材としてのセパレータを製造する場合は、二次電池用基材としてはセパレータ基材を用いることができ、また、二次電池部材としての電極を製造する場合は、二次電池用基材としては集電体上に電極合材層を形成してなる電極基材を用いることができる。
なお、機能層が主として接着剤層として機能するものである場合には、表面に多孔膜層を設けたセパレータ基材または電極基材の上に機能層を形成してもよい。
セパレータ基材としては、特に限定されることなく、例えば特開2012-204303号公報に記載のものを用いることができる。これらの中でも、セパレータ全体の膜厚を薄くすることができ、これにより、二次電池内の電極活物質の比率を高くして体積あたりの容量を高くすることができるという点より、ポリオレフィン系(ポリエチレン、ポリプロピレン、ポリブテン、ポリ塩化ビニル)の樹脂からなる微多孔膜が好ましい。
電極基材(正極基材および負極基材)としては、特に限定されないが、集電体上に電極合材層が形成された電極基材が挙げられる。
ここで、集電体、電極合材層中の成分(例えば、電極活物質(正極活物質、負極活物質)および電極合材層用結着材(正極合材層用結着材、負極合材層用結着材)など)、並びに、集電体上への電極合材層の形成方法は、既知のものを用いることができ、例えば特開2013-145763号公報に記載のものを用いることができる。
接着工程において、二次電池用積層体を構成する機能層と二次電池用基材を接着させる方法は特に限定されないが、金型プレスやロールプレスなどを用いた加圧接着が好ましい。なお、加圧接着の条件(圧力、温度、時間など)は、用いる結着材のガラス転移温度等に応じて適宜変更し得るが、ロールプレスを用いた加圧接着を例に挙げると、例えばロールの温度を50~200℃の範囲で適宜設定し得る。
剥離工程において、離型基材を機能層から剥離して、二次電池用基材上に機能層を備える二次電池部材を得る方法は特に限定されず、既知の方法を採用することができる。
本発明の非水系二次電池部材の製造方法で製造された非水系二次電池部材を用いることで、高温サイクル特性や低温出力特性などの電気的特性に優れる非水系二次電池を製造することができる。
ここで、二次電池においては、少なくとも1つの二次電池部材が、本発明の非水系二次電池部材の製造方法で製造された二次電池部材であればよい。すなわち、二次電池に用いる正極、負極およびセパレータは、少なくとも一つが機能層を有している。具体的には、機能層を有する正極および負極としては、集電体上に電極合材層を形成してなる電極基材の上に機能層を設けてなる電極を用いることができる。また、機能層を有するセパレータとしては、セパレータ基材の上に機能層を設けてなるセパレータや、機能層よりなるセパレータを用いることができる。なお、電極基材およびセパレータ基材としては、「非水系二次電池部材の製造方法」の項で挙げたものと同様のものを用いることができる。
また、機能層を有さない正極、負極およびセパレータとしては、特に限定されることなく、上述した電極基材よりなる電極および上述したセパレータ基材よりなるセパレータを用いることができる。
電解液としては、通常、有機溶媒に支持電解質を溶解した有機電解液が用いられる。支持電解質としては、例えば、リチウムイオン二次電池においてはリチウム塩が用いられる。リチウム塩としては、例えば、LiPF6、LiAsF6、LiBF4、LiSbF6、LiAlCl4、LiClO4、CF3SO3Li、C4F9SO3Li、CF3COOLi、(CF3CO)2NLi、(CF3SO2)2NLi、(C2F5SO2)NLiなどが挙げられる。なかでも、溶媒に溶けやすく高い解離度を示すので、LiPF6、LiClO4、CF3SO3Liが好ましい。なお、電解質は1種類を単独で用いてもよく、2種類以上を組み合わせて用いてもよい。通常は、解離度の高い支持電解質を用いるほどリチウムイオン伝導度が高くなる傾向があるので、支持電解質の種類によりリチウムイオン伝導度を調節することができる。
なお、電解液中の電解質の濃度は適宜調整することができる。また、電解液には、既知の添加剤を添加してもよい。
非水系二次電池は、例えば、正極と負極とをセパレータを介して重ね合わせ、これを必要に応じて、巻く、折るなどして電池容器に入れ、電池容器に電解液を注入して封口することで製造し得る。なお、正極、負極、セパレータのうち、少なくとも一つの二次電池部材を、本発明の非水系二次電池部材の製造方法で製造された二次電池部材とする。ここで、電池容器には、必要に応じてエキスパンドメタルや、ヒューズ、PTC素子などの過電流防止素子、リード板などを入れ、電池内部の圧力上昇、過充放電の防止をしてもよい。電池の形状は、例えば、コイン型、ボタン型、シート型、円筒型、角形、扁平型など、何れであってもよい。
また、複数種類の単量体を共重合して製造される重合体において、ある単量体を重合して形成される構造単位の前記重合体における割合は、別に断らない限り、通常は、その重合体の重合に用いる全単量体に占める当該ある単量体の比率(仕込み比)と一致する。
実施例および比較例において、有機粒子を構成する重合体の電解液膨潤度、有機粒子のコア部の外表面がシェル部によって覆われる平均割合(被覆率)、有機粒子のシェル部の平均厚み(コアシェル比率)、各粒子(有機粒子および機能層用粒子状重合体)の体積平均粒子径D50、各重合体(コア部の重合体、シェル部の重合体および機能層用粒子状重合体)のガラス転移温度、非水系二次電池機能層用組成物の表面張力、機能層と離型基材の間の接着強度、機能層とアルミ箔の間の接着強度、機能層の電解液中での接着性(機能層と電極基材の間の電解液浸漬後の接着強度)、機能層の転写性、離型基材の水に対する接触角、並びに、二次電池の低温出力特性および高温サイクル特性は、下記の方法で測定および評価した。
有機粒子のコア部およびシェル部の調製に使用した単量体組成物を使用し、コア部およびシェル部の重合条件と同様の重合条件で測定試料となる重合体(コア部の重合体およびシェル部の重合体)の水分散液をそれぞれ作製した。
次に、得られた水分散液を、ポリテトラフルオロエチレン製のシャーレに入れ、温度25℃で48時間乾燥して、厚み0.5mmのフィルムを製造した。そして、得られたフィルムを1cm角に裁断し、試験片を得た。この試験片の重量を測定し、W0とした。また、前記試験片を電解液に温度60℃で72時間浸漬した。その後、試験片を電解液から取り出し、試験片の表面の電解液を拭き取り、浸漬後の試験片の重量W1を測定した。そして、これらの重量W0およびW1を用いて、膨潤度S(倍)を、S=W1/W0にて計算した。
なお、電解液としては、エチレンカーボネート(EC)と、ジエチルカーボネート(DEC)と、ビニレンカーボネート(VC)との混合溶媒(体積混合比:EC/DEC/VC=68.5/30/1.5、SP値12.7(cal/cm3)1/2)に、支持電解質としてLiPF6を1mol/Lの濃度で溶かした溶液を用いた。
<有機粒子のコア部の外表面がシェル部によって覆われる平均割合(被覆率)>
有機粒子を、可視光硬化性樹脂(日本電子株式会社製「D-800」)に十分に分散させた後、包埋し、有機粒子を含有するブロック片を作製した。次に、ブロック片を、ダイヤモンド刃を備えたミクロトームで厚さ100nmの薄片状に切り出して測定用試料を作製した。その後、四酸化ルテニウムを用いて測定用試料に染色処理を施した。
次に、染色した測定用試料を、透過型電子顕微鏡(日本電子社製「JEM-3100F」)にセットして、加速電圧80kVにて、有機粒子の断面構造を写真撮影した。電子顕微鏡の倍率は、視野に有機粒子1個の断面が入るように倍率を設定した。そして、撮影された有機粒子の断面構造において、コア部の周の長さD1、および、コア部の外表面とシェル部とが当接する部分の長さD2を計測し、下記式(1)により、その有機粒子のコア部の外表面がシェル部によって覆われる割合Rcを算出した。
被覆割合Rc(%)=(D2/D1)×100 ・・・(1)
そして、被覆割合Rcを、任意に選択した20個の有機粒子について測定し、その平均値を計算して、コア部の外表面がシェル部によって覆われる平均割合(被覆率)とした。
<有機粒子のシェル部の平均厚み(コアシェル比率)>
有機粒子のシェル部の平均厚みを、以下の手順で測定した。
シェル部が重合体の粒子により構成されている場合、上記被覆率の測定方法と同様にして、透過型電子顕微鏡によって、有機粒子の断面構造を観察した。そして、観察された有機粒子の断面構造から、シェル部を構成する重合体の粒子の最長径を測定した。任意に選択した20個の有機粒子についてシェル部を構成する重合体の粒子の最長径を測定し、その最長径の平均値をシェル部の平均厚みとした。
また、シェル部が粒子以外の形状を有している場合、上記被覆率の測定方法と同様にして、透過型電子顕微鏡によって、有機粒子の断面構造を観察した。そして、観察された有機粒子の断面構造から、シェル部の最大厚みを測定した。任意に選択した20個の有機粒子についてシェル部の最大厚みを測定し、その最大厚みの平均値をシェル部の平均厚みとした。
そして、測定されたシェル部の平均厚みを有機粒子の体積平均粒子径D50で割ることにより、有機粒子の体積平均粒子径D50に対するシェル部の平均厚みの比率であるコアシェル比率(単位:%)を計算し、シェル部の平均厚みを評価した。
<各粒子の体積平均粒子径D50>
各粒子(有機粒子および機能層用粒子状重合体)の体積平均粒子径D50は、それぞれ固形分濃度15質量%に調整した水分散溶液の、レーザー回折式粒子径分布測定装置(島津製作所社製、「SALD-3100」)により測定された粒子径分布において、小径側から計算した累積体積が50%となる粒子径とした。
<各重合体のガラス転移温度(Tg)>
コア部の重合体、シェル部の重合体のガラス転移温度の測定には、各重合体の調製に使用した単量体組成物を使用し、当該重合体の重合条件と同様の重合条件で、測定試料となる重合体を含む水分散液をそれぞれ作製し、当該水分散液を乾固させて得られる測定試料を使用した。
機能層用粒子状重合体のガラス転移温度の測定には、得られた機能層用粒子状重合体を含む水分散液を乾固させて得られる測定試料を使用した。
次に、示差熱分析測定装置(エスアイアイ・ナノテクノロジー社製、製品名「EXSTAR DSC6220」)を用い、上述の測定試料10mgをアルミパンに計量し、リファレンスとして空のアルミパンを用い、測定温度範囲-100℃~500℃の間で、昇温速度10℃/分、常温常湿下で、DSC曲線を測定した。この昇温過程で、微分信号(DDSC)が0.05mW/分/mg以上となるDSC曲線の吸熱ピークが出る直前のベースラインと、吸熱ピーク後に最初に現れる変曲点でのDSC曲線の接線との交点から、ガラス転移温度を求めた。
<非水系二次電池機能層用組成物の表面張力>
機能層用組成物の表面張力は、自動表面張力計(協和界面科学社製、「DY-300」)を用い、白金プレート法により測定した。
<機能層と離型基材の間の接着強度>
離型基材と機能層とを備える二次電池用積層体を、長さ100mm、幅10mmの長方形に切り出して試験片とした。当該試験片を、機能層を下にして機能層表面にセロハンテープ(JIS Z1522に規定されるもの)を貼り付け、離型基材の一端を鉛直上方に引っ張り速度50mm/分で引っ張って剥がしたときの応力を測定した(なお、セロハンテープは水平な試験台に固定した)。この測定を3回行い、応力の平均値を求めて、当該平均値をピール強度P1とした。測定されたピール強度P1が大きいほど、機能層と離型基材の間の接着強度が大きいことを示す。
<機能層とアルミ箔の間の接着強度>
離型基材と機能層とを備える二次電池用積層体を、機能層がアルミ箔(日本製箔社製、「1N99」)と接するようにアルミ箔上に配置した。そして温度100℃、200Kgf/cmの線圧、20m/分の速度でロールプレスを通し二次電池用積層体とアルミ箔とを張り合わせた後、機能層から離型基材をロールにて分離し、機能層をアルミ箔に転写した。得られた機能層とアルミ箔の積層体を長さ100mm、幅10mmの長方形に切り出して試験片とした。当該試験片を、機能層を下にして機能層表面にセロハンテープ(JIS Z1522に規定されるもの)を貼り付け、アルミ箔の一端を鉛直上方に引っ張り速度50mm/分で引っ張って剥がしたときの応力を測定した(なお、セロハンテープは水平な試験台に固定した)。この測定を3回行い、応力の平均値を求めて、当該平均値をピール強度P2とした。測定されたピール強度P2が大きいほど、機能層とアルミ箔の間の接着強度が大きく、即ち、機能層と二次電池用基材の間の接着強度が大きいことを示す。
<機能層の電解液中での接着性(機能層と電極基材の間の電解液浸漬後の接着強度)>
機能層を電極基材上に備えてなる電極を、長さ100mm、幅10mmの長方形に切り出して、試験片を得た。この試験片を、電解液(溶媒:EC/DEC/VC=68.5/30/1.5(体積混合比)、電解質:濃度1mol/LのLiPF6)に60℃で3日間浸漬した。電解液から試験片を取り出し、機能層の表面に付着した電解液を拭き取った。その後、電解液を拭き取った機能層の表面を下にして、機能層の表面にセロハンテープ(JIS Z1522に規定されるもの)を貼り付け、電極基材の集電体の一端を鉛直上方に引っ張り速度50mm/分で引っ張って剥がしたときの応力を測定した(なお、セロハンテープは水平な試験台に固定した)。この測定を3回行い、応力の平均値を求めて、当該平均値をピール強度P3とし、以下の基準で評価した。測定されたピール強度P3が大きいほど、機能層の電解液中での接着性が優れることを示す。
A:ピール強度P3が10N/m以上
B:ピール強度P3が5N/m以上10N/m未満
C:ピール強度P3が5N/m未満
<機能層の転写性>
離型基材と機能層とを備える二次電池用積層体を長さ100mm、幅10mmの長方形に切り出して試験片とした。(なお、長さ100mm、幅10mmの長方形状の離型基材単独の質量M0を別途測定した。)当該試験片と電極基材を、試験片の機能層側が電極基材の電極合材層側と対向するように配置し、100℃、200Kgf/cmの線圧にて、1分間プレスした。得られた離型基材と、機能層と、電極基材とをこの順に備えてなる複合体の離型基材の一端を、垂直方向に引っ貼り速度50mm/分で引っ張って離型基材を剥がすことで転写を完了した。そして転写後の離型基材の質量M1を測定した。離型基材単独の質量M0を、転写後の離型基材の質量M1で除した値に100を乗じた数値(M0/M1比率、単位:質量%)を用いて、以下の基準で評価した。M0/M1比率の値が大きいほど、転写後の離型基材に残存した機能層の質量が小さく、機能層が転写性に優れることを示す。
A:M0/M1比率が90質量%以上
B:M0/M1比率が80質量%以上90質量%未満
C:M0/M1比率が60質量%以上80質量%未満
D:M0/M1比率が60質量%未満
<離型基材の水に対する接触角>
接触角計(協和界面化学社製、「DM-701」)を用いて、離型基材表面に蒸留水を3マイクロリットル滴下し、滴下から10秒後の接触角(°)を測定した。
<二次電池の低温出力特性>
製造した1000mAh捲回型のリチウムイオン二次電池を作製し、25℃の環境下で24時間静置した。その後、25℃の環境下で、4.2V、0.1C、5時間の充電の操作を行い、その時の電圧V0を測定した。その後、-10℃環境下で、1Cの放電レートにて放電の操作を行い、放電開始15秒後の電圧V1を測定した。そして、ΔV=V0-V1で示す電圧変化を求め、下記の基準で評価した。この電圧変化が小さいほど、低温出力特性に優れていることを示す。
A:電圧変化ΔVが500mV以下
B:電圧変化ΔVが500mV超700mV以下
C:電圧変化ΔVが700mV超900mV以下
D:電圧変化ΔVが900mV超
<二次電池の高温サイクル特性>
製造した放電容量1000mAhの捲回型リチウムイオン二次電池を、25℃の環境下で24時間静置させた後に、25℃の環境下で、4.35V、0.1Cの定電圧・定電流充電、2.75V、0.1Cの定電流放電にて充放電の操作を行い、初期容量C0を測定した。その後、更に、60℃の環境下で、充放電を繰り返し、1000サイクル後の容量C1を測定した。そして、サイクル前後での容量維持率ΔC(%)=(C1/C0)×100を算出し、下記の基準で評価した。容量維持率ΔCの値が大きいほど、高温サイクル特性に優れていることを示す。
A:容量維持率ΔCが85%以上
B:容量維持率ΔCが75%以上85%未満
C:容量維持率ΔCが75%未満
<有機粒子の調製>
攪拌機付き5MPa耐圧容器に、有機粒子のコア部形成用として、(メタ)アクリル酸エステル単量体としてのメタクリル酸メチル75部、酸基含有単量体としてのメタクリル酸4部、架橋性単量体としてのエチレングリコールジメタクリレート1部、乳化剤としてのドデシルベンゼンスルホン酸ナトリウム1部、イオン交換水150部、および、重合開始剤としての過硫酸カリウム0.5部を添加し、十分に攪拌した後、60℃に加温して重合を開始した。重合転化率が96%になった時点で、続いて、有機粒子のシェル部形成用として、芳香族ビニル単量体としてのスチレン19部と、酸基含有単量体としてのメタクリル酸1部との混合物を連続添加し、70℃に加温して重合を継続した。添加した全単量体の重合転化率が96%になった時点で、冷却し反応を停止して、有機粒子を含む水分散液を得た。
そして、得られた有機粒子の被覆率およびコアシェル比率、体積平均粒子径D50を測定した。また、有機粒子を構成する重合体の電解液膨潤度およびガラス転移温度も測定した。結果を後述する表1に示す。
<機能層用粒子状重合体(アクリル系重合体1)の調製>
撹拌機を備えた反応器に、イオン交換水70部、乳化剤としてのラウリル硫酸ナトリウム(花王ケミカル社製、製品名「エマール2F」)0.15部、並びに過硫酸アンモニウム0.5部を、それぞれ供給し、気相部を窒素ガスで置換し、60℃に昇温した。
一方、別の容器で、イオン交換水50部、分散剤としてのドデシルベンゼンスルホン酸ナトリウム0.5部、並びに、ブチルアクリレート94部、アクリロニトリル2部、メタクリル酸2部、N-メチロールアクリルアミド1部およびアリルグリシジルエーテル1部を混合して単量体混合物を得た。この単量体混合物を4時間かけて前記反応器に連続的に添加して重合を行った。添加中は、60℃で反応を行った。添加終了後、更に70℃で3時間撹拌して反応を終了し、機能層用粒子状重合体(アクリル系重合体1)を含む水分散液を調製した。
得られた機能層用粒子状重合体の体積平均粒子径D50は0.36μm、ガラス転移温度は-35℃であった
<非水系二次電池機能層用組成物の調製>
有機粒子を含む水分散液を固形分相当で100部、機能層用粒子状重合体を含む水分散液を固形分相当で21部、濡れ剤(サンノプコ社製、「SN366」)1部を混合し、さらにイオン交換水を固形分濃度が39%になるように添加して、機能層用組成物を得た。得られた機能層用組成物の表面張力を測定した。結果を表1に示す。
<非水系二次電池用積層体の製造>
機能層用組成物を、離型基材a(リンテック社製、「PET38AL-5」)上に塗布し、50℃で3分間乾燥させた。これにより、厚みが1μmの機能層を離型基材a上に備える二次電池用積層体を得た。得られた二次電池用積層体を用いて、機能層と離型基材の間の接着強度、機能層とアルミ箔の間の接着強度、機能層の転写性を評価した。結果を表1に示す。
攪拌機付き5MPa耐圧容器に、1,3-ブタジエン33部、イタコン酸3.5部、スチレン63.5部、乳化剤としてのドデシルベンゼンスルホン酸ナトリウム0.4部、イオン交換水150部および重合開始剤としての過硫酸カリウム0.5部を入れ、十分に攪拌した後、50℃に加温して重合を開始した。重合転化率が96%になった時点で冷却して反応を停止して、負極合材層用の粒子状結着材(SBR)を含む混合物を得た。上記粒子状結着材を含む混合物に、5%水酸化ナトリウム水溶液を添加して、pH8に調整後、加熱減圧蒸留によって未反応単量体の除去を行った。その後、30℃以下まで冷却し、所望の粒子状結着材を含む水分散液を得た。
次に、負極活物質としての人造黒鉛(体積平均粒子径D50:15.6μm)100部、増粘剤としてのカルボキシメチルセルロースナトリウム塩(日本製紙社製、「MAC350HC」)の2%水溶液を固形分相当で1部、および、イオン交換水を混合して固形分濃度が68%となるように調整した後、25℃で60分間混合した。次いで、固形分濃度が62%となるようにイオン交換水で調整し、更に25℃で15分間混合した。その後、得られた混合液に、前述の粒子状結着材を含む水分散液を固形分相当で1.5部、およびイオン交換水を入れ、最終固形分濃度が52%となるように調整し、更に10分間混合した。これを減圧下で脱泡処理し、流動性の良い負極用スラリー組成物を得た。
そして、前述のようにして得られた負極用スラリー組成物を、コンマコーターで、集電体である厚さ20μmの銅箔の上に、乾燥後の膜厚が150μm程度になるように塗布し、乾燥させた。この乾燥は、銅箔を0.5m/分の速度で60℃のオーブン内を2分間かけて搬送することにより行った。その後、120℃にて2分間加熱処理してプレス前の負極原反を得た。このプレス前の負極原反をロールプレスで圧延して、負極合材層の厚さが80μmのプレス後の負極基材を得た。
<機能層を備える負極の製造(負極基材への機能層の転写)>
離型基材と機能層とを備える二次電池用積層体を、機能層が負極合材層に接するように負極基材上に配置して、温度100℃のロールプレスを通し張り合わせた後、さらに機能層から離型基材をロールにて剥離し、機能層を負極基材上へ転写することで、機能層を備える負極を得た。この負極を用いて、機能層の電解液中での接着性を評価した。結果を表1に示す。
正極活物質としてのLiCoO2(体積平均粒子径D50:12μm)を100部、導電材としてのアセチレンブラック(電気化学工業社製、「HS-100」)を2部、正極合材層用の粒子状結着材としてのポリフッ化ビニリデン(クレハ社製、「#7208」)を固形分相当で2部と、N-メチルピロリドンとを混合し、全固形分濃度を70%とした。これらをプラネタリーミキサーにより混合し、正極用スラリー組成物を調製した。
得られた正極用スラリー組成物を、コンマコーターで、集電体である厚さ20μmのアルミ箔の上に、乾燥後の膜厚が150μm程度になるように塗布し、乾燥させた。この乾燥は、アルミ箔を0.5m/分の速度で60℃のオーブン内を2分間かけて搬送することにより行った。その後、120℃にて2分間加熱処理して、正極原反を得た。このプレス前の正極原反をロールプレスで圧延して、正極合材層の厚さが80μmのプレス後の正極を得た。
上記で得られたプレス後の正極を49cm×5cmに切り出して正極合材層側の表面が上側になるように置き、その上に55cm×5.5cmに切り出したセパレータ(セルガード社製、「2500」、厚み25μm)を配置した。更に、上記で得られた機能層を備える負極を、50cm×5.2cmに切り出し、これをセパレータ上に、機能層側の表面がセパレータに向かい合うよう配置した。これを捲回機により、捲回し、捲回体を得た。この捲回体を60℃、0.5MPaでプレスし、扁平体とし、電池の外装としてのアルミ包材外装で包み、電解液(溶媒:EC/DEC/VC(体積混合比)=68.5/30/1.5、電解質:濃度1MのLiPF6)を空気が残らないように注入した。更に、アルミ包材外装の開口を密封するために、150℃のヒートシールをしてアルミ包材外装を閉口し、非水系二次電池として放電容量1000mAhの捲回型リチウムイオン二次電池を製造した。
得られたリチウムイオン二次電池を用いて、低温出力特性、高温サイクル特性を評価した。結果を後述する表1に示す。
有機粒子を含む水分散液の調製時に、有機粒子のコア部形成用として添加した単量体の割合を後述する表1に示すように変更したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
有機粒子を含む水分散液の調製時に、有機粒子のシェル部形成用として添加した単量体の種類および割合を後述する表1に示すように変更したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
機能層用組成物の調製時に、機能層用粒子状重合体の量を後述する表1に示すように変更したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
機能層用組成物の調製時に、機能層用粒子状重合体としてアクリル系重合体1に替えて後述のように調製したアクリル系重合体2を使用したこと以外は、実施例1と同様にして、有機粒子、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
<機能層用粒子状重合体(アクリル系重合体2)の調製>
撹拌機を備えた反応器に、イオン交換水70部、乳化剤としてのラウリル硫酸ナトリウム(花王ケミカル社製、製品名「エマール2F」)0.15部、並びに過硫酸アンモニウム0.5部を、それぞれ供給し、気相部を窒素ガスで置換し、60℃に昇温した。
一方、別の容器で、イオン交換水50部、分散剤としてのドデシルベンゼンスルホン酸ナトリウム0.5部、並びに、ブチルアクリレート56部、スチレン40部、メタクリル酸2部、N-メチロールアクリルアミド1部およびアリルグリシジルエーテル1部を混合して単量体混合物を得た。この単量体混合物を4時間かけて前記反応器に連続的に添加して重合を行った。添加中は、60℃で反応を行った。添加終了後、更に70℃で3時間撹拌して反応を終了し、機能層用粒子状重合体(アクリル系重合体2)を含む水分散液を調製した。
得られた機能層用粒子状重合体の体積平均粒子径D50は0.3μm、ガラス転移温度は-2℃であった
二次電池用積層体の製造時に、離型基材aに替えてそれぞれ離型基材b(日本写真印刷社製、「Nissha Techsol RX101」)、離型基材c(ダイセルバリューコーティング社製、「T788」)を使用したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
機能層用組成物の調製時に、濡れ剤の量を後述する表1のように変更したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
有機粒子を含む水分散液の調製時に、有機粒子のコア部およびシェル部形成用として添加した単量体の割合をそれぞれ後述する表1に示すように変更したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
有機粒子を含む水分散液の調製時に、有機粒子のコア部形成用として添加した単量体の割合を後述する表1に示すように変更したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
有機粒子を含む水分散液の調製時に、有機粒子のシェル部形成用として添加した単量体の割合を後述する表1に示すように変更したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
二次電池用積層体の製造時に、離型基材aに替えてポリエチレン製の離型基材dを使用したこと以外は、実施例1と同様にして、有機粒子、機能層用粒子状重合体、機能層用組成物、二次電池用積層体、機能層を備える負極、正極およびリチウムイオン二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を後述する表1に示す。
「MMA」は、メタクリル酸メチルを示し、
「MAA」は、メタクリル酸を示し、
「EDMA」は、エチレングリコールジメタクリレートを示し、
「ST」は、スチレンを示し、
「NaSS」は、スチレンスルホン酸ナトリウムを示し、
「AN」は、アクリロニトリルを示し、
「ACL1」は、アクリル系重合体1を示し、
「ACL2」は、アクリル系重合体2を示す。
また、上述の表1の実施例1~3より、有機粒子のコア部の単量体組成、電解液膨潤度を調整することで、機能層の電解液中における接着性、並びに二次電池の高温サイクル特性および低温出力特性を更に向上させ得ることがわかる。
そして、上述の表1の実施例1、4、5より、有機粒子のシェル部の単量体組成、電解液膨潤度を調整することで、機能層の電解液中における接着性、および二次電池の高温サイクル特性を更に向上させ得ることがわかる。
更に、上述の表1の実施例1、6、7より、結着材としての機能層用粒子状重合体の量を変更することで、機能層の転写性および電解液中における接着性、並びに二次電池の高温サイクル特性および低温出力特性を更に向上させ得ることがわかる。
加えて、上述の表1の実施例1、8より、結着材としての機能層用粒子状重合体の単量体組成、Tgを調整することで、機能層の転写性および電解液中における接着性、並びに二次電池の高温サイクル特性および低温出力特性を更に向上させ得ることがわかる。
また、上述の表1の実施例1、9、10より、離型基材の水に対する接触角を変更することで、機能層の転写性および電解液中における接着性、並びに二次電池の高温サイクル特性および低温出力特性を更に向上させ得ることがわかる。
そして、上述の表1の実施例1、11、12より、濡れ剤の量を変更して機能層用組成物の表面張力を変更することで、機能層の転写性および電解液中における接着性、並びに二次電池の高温サイクル特性および低温出力特性を更に向上させ得ることがわかる。
また、本発明によれば、非水系二次電池に優れた電気的特性を発揮させ得る非水系二次電池部材を、非水系二次電池用積層体を用いて製造する方法を提供することができる。
110 コア部
110S コア部の外表面
120 シェル部
Claims (4)
- 離型基材と、前記離型基材上に隣接して配置された機能層とを含む非水系二次電池用積層体であって、
前記機能層が有機粒子および結着材を含み、
前記有機粒子が、コア部と、前記コア部の外表面を部分的に覆うシェル部とを備えるコアシェル構造を有しており、
前記コア部が、電解液膨潤度が5倍以上30倍以下の重合体からなり、
前記シェル部が、電解液膨潤度が1倍超4倍以下の重合体からなり、
前記離型基材の水に対する接触角が70°以上であることを特徴とする、非水系二次電池用積層体。 - 前記コア部の重合体のガラス転移温度が、0℃以上150℃以下であり、
前記シェル部の重合体のガラス転移温度が、50℃以上200℃以下である、請求項1に記載の非水系二次電池用積層体。 - 前記結着材のガラス転移温度が-50℃以上25℃以下である、請求項1または2に記載の非水系二次電池用積層体。
- 非水系二次電池用基材上に機能層を備える非水系二次電池部材の製造方法であって、
離型基材と、前記離型基材上に隣接して配置された前記機能層とを含む非水系二次電池用積層体を、前記機能層が前記非水系二次電池用基材と隣接するように配置し、前記機能層を前記非水系二次電池用基材に接着させる工程と、
前記離型基材を前記機能層から剥離する工程と、を含み、
前記機能層が有機粒子および結着材を含み、
前記有機粒子が、コア部と、前記コア部の外表面を部分的に覆うシェル部とを備えるコアシェル構造を有しており、
前記コア部が、電解液膨潤度が5倍以上30倍以下の重合体からなり、
前記シェル部が、電解液膨潤度が1倍超4倍以下の重合体からなり、
前記離型基材の水に対する接触角が70°以上であることを特徴とする、方法。
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JPWO2020066479A1 (ja) * | 2018-09-28 | 2021-08-30 | 日本ゼオン株式会社 | 非水系二次電池用バインダー組成物、非水系二次電池機能層用スラリー組成物、非水系二次電池用機能層、非水系二次電池用電池部材および非水系二次電池 |
JPWO2020066954A1 (ja) * | 2018-09-28 | 2021-08-30 | 日本ゼオン株式会社 | 非水系二次電池用バインダー組成物、非水系二次電池機能層用スラリー組成物、非水系二次電池用機能層、非水系二次電池用電池部材および非水系二次電池 |
WO2020066954A1 (ja) * | 2018-09-28 | 2020-04-02 | 日本ゼオン株式会社 | 非水系二次電池用バインダー組成物、非水系二次電池機能層用スラリー組成物、非水系二次電池用機能層、非水系二次電池用電池部材および非水系二次電池 |
JP7548010B2 (ja) | 2018-09-28 | 2024-09-10 | 日本ゼオン株式会社 | 非水系二次電池用バインダー組成物、非水系二次電池機能層用スラリー組成物、非水系二次電池用機能層、非水系二次電池用電池部材および非水系二次電池 |
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US20170214022A1 (en) | 2017-07-27 |
JPWO2016031163A1 (ja) | 2017-06-08 |
CN106575735B (zh) | 2019-04-23 |
US10186699B2 (en) | 2019-01-22 |
KR20170044640A (ko) | 2017-04-25 |
KR102494518B1 (ko) | 2023-01-31 |
JP6504173B2 (ja) | 2019-04-24 |
CN106575735A (zh) | 2017-04-19 |
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