WO2024024746A1 - Nonaqueous electrolyte secondary battery positive electrode and nonaqueous electrolyte secondary battery - Google Patents
Nonaqueous electrolyte secondary battery positive electrode and nonaqueous electrolyte secondary battery Download PDFInfo
- Publication number
- WO2024024746A1 WO2024024746A1 PCT/JP2023/027062 JP2023027062W WO2024024746A1 WO 2024024746 A1 WO2024024746 A1 WO 2024024746A1 JP 2023027062 W JP2023027062 W JP 2023027062W WO 2024024746 A1 WO2024024746 A1 WO 2024024746A1
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- WIPO (PCT)
- Prior art keywords
- positive electrode
- binder
- secondary battery
- electrolyte secondary
- range
- Prior art date
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- 239000011255 nonaqueous electrolyte Substances 0.000 title claims abstract description 47
- 239000011230 binding agent Substances 0.000 claims abstract description 83
- 239000002245 particle Substances 0.000 claims abstract description 23
- 239000007774 positive electrode material Substances 0.000 claims abstract description 10
- 239000002131 composite material Substances 0.000 claims description 54
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 claims description 22
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- BLTXWCKMNMYXEA-UHFFFAOYSA-N 1,1,2-trifluoro-2-(trifluoromethoxy)ethene Chemical compound FC(F)=C(F)OC(F)(F)F BLTXWCKMNMYXEA-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present disclosure relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.
- Patent Document 1 includes a positive electrode current collector and a positive electrode composite material layer disposed on the positive electrode current collector, and the positive electrode composite material layer has an average particle size (D50) of 0.02 to 0.02.
- a positive electrode for a non-aqueous electrolyte secondary battery is disclosed, which includes a vinylidene fluoride polymer as a binder, consisting of component A having a diameter of 5 ⁇ m and component B having an average particle diameter (D50) of 1.1 to 50 ⁇ m.
- Patent Document 2 includes a positive electrode current collector and a positive electrode composite material layer disposed on the positive electrode current collector, and the positive electrode composite material layer has a weight average molecular weight in the range of 300,000 to 400,000.
- a positive electrode for a non-aqueous electrolyte secondary battery comprising a first binder of a vinylidene fluoride copolymer having a weight average molecular weight of 800,000 to 1,000,000 and a second binder of a vinylidene fluoride polymer having a weight average molecular weight in the range of 800,000 to 1,000,000. ing.
- the binder content in the positive electrode it is preferable to reduce the binder content in the positive electrode. However, if the binder content is reduced, the positive electrode current collector and positive electrode composite layer (ie, the peel strength between the positive electrode current collector and the positive electrode composite layer decreases).
- an object of the present disclosure is to provide a positive electrode for a non-aqueous electrolyte secondary battery that has excellent peel strength between a positive electrode current collector and a positive electrode composite layer, and a secondary battery including the positive electrode.
- a positive electrode for a non-aqueous electrolyte secondary battery that is one aspect of the present disclosure includes a positive electrode current collector, and a positive electrode composite layer provided on the positive electrode current collector and containing a positive electrode active material and a binder, and wherein the positive electrode composite layer includes a positive electrode active material and a binder.
- Binder A has a weight average molecular weight in the range of 400,000 to 800,000 and an average particle diameter (D50) in the range of 50 to 500 nm
- Binder A has a weight average molecular weight in the range of 1 million to 1.5 million and has an average particle diameter (D50) of 50 to 500 nm.
- the binder B has a diameter (D50) in the range of 50 ⁇ m to 500 ⁇ m.
- a non-aqueous electrolyte secondary battery that is one aspect of the present disclosure is characterized by comprising the above-described positive electrode for a non-aqueous electrolyte secondary battery.
- a positive electrode for a non-aqueous electrolyte secondary battery that has excellent peel strength between a positive electrode current collector and a positive electrode composite layer, and a non-aqueous electrolyte secondary battery including the positive electrode.
- FIG. 1 is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery that is an example of an embodiment.
- FIG. 1 is a schematic cross-sectional view of a positive electrode that is an example of an embodiment.
- FIG. 1 is a schematic cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment.
- the non-aqueous electrolyte secondary battery 10 shown in FIG. It includes arranged insulating plates 18 and 19 and a battery case 15 that accommodates the above-mentioned members.
- the battery case 15 includes a case body 16 having a cylindrical shape with a bottom and a sealing body 17 that closes an opening of the case body 16.
- other forms of electrode bodies may be applied, such as a laminated type electrode body in which positive electrodes and negative electrodes are alternately laminated with separators interposed therebetween.
- examples of the battery case 15 include a metal case having a cylindrical shape, a square shape, a coin shape, a button shape, etc., a resin case formed by laminating resin sheets (so-called laminate type), and the like.
- the non-aqueous electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
- non-aqueous solvents include esters, ethers, nitriles, amides, and mixed solvents of two or more of these.
- the non-aqueous solvent may contain a halogen-substituted product in which at least a portion of hydrogen in these solvents is replaced with a halogen atom such as fluorine.
- a lithium salt such as LiPF 6 is used as the electrolyte salt.
- the nonaqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte such as a gel polymer.
- the case body 16 is, for example, a cylindrical metal container with a bottom.
- a gasket 28 is provided between the case body 16 and the sealing body 17 to ensure airtightness inside the battery.
- the case main body 16 has an overhanging portion 22 that supports the sealing body 17 and has, for example, a part of a side surface overhanging inward.
- the projecting portion 22 is preferably formed in an annular shape along the circumferential direction of the case body 16, and supports the sealing body 17 on its upper surface.
- the sealing body 17 has a structure in which a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side.
- Each member constituting the sealing body 17 has, for example, a disk shape or a ring shape, and each member except the insulating member 25 is electrically connected to each other.
- the lower valve body 24 and the upper valve body 26 are connected to each other at their central portions, and an insulating member 25 is interposed between their respective peripheral portions.
- the lower valve body 24 deforms and ruptures so as to push the upper valve body 26 toward the cap 27, and the lower valve body 24 and the upper valve body The current path between bodies 26 is interrupted.
- the upper valve body 26 breaks and gas is discharged from the opening of the cap 27.
- the positive electrode lead 20 attached to the positive electrode 11 extends toward the sealing body 17 side through the through hole of the insulating plate 18, and the negative electrode lead 21 attached to the negative electrode 12 is insulated. It passes through the outside of the plate 19 and extends to the bottom side of the case body 16.
- the positive electrode lead 20 is connected by welding or the like to the lower surface of the filter 23, which is the bottom plate of the sealing body 17, and the cap 27, which is the top plate of the sealing body 17 and electrically connected to the filter 23, serves as a positive terminal.
- the negative electrode lead 21 is connected to the bottom inner surface of the case body 16 by welding or the like, and the case body 16 serves as a negative electrode terminal.
- the positive electrode 11, negative electrode 12, and separator 13 will be explained in detail below.
- FIG. 2 is a schematic cross-sectional view of a positive electrode that is an example of an embodiment.
- the positive electrode 11 includes a positive electrode current collector 40 and a positive electrode composite material layer 42 provided on the positive electrode current collector 40.
- a metal foil such as aluminum that is stable in the potential range of the positive electrode 11, a film with the metal disposed on the surface, or the like can be used.
- the positive electrode composite material layer 42 contains a positive electrode active material and a binder. It is preferable that the positive electrode composite material layer 42 further contains a conductive material.
- the positive electrode composite material layer 42 may be provided on only one surface of the positive electrode current collector 40, or may be provided on both surfaces.
- the positive electrode 11 is formed by applying a positive electrode composite material slurry containing a positive electrode active material, a binder, a conductive material, etc. onto the positive electrode current collector 40 and drying it to form a positive electrode composite material layer 42, and then rolling the positive electrode with a rolling roller or the like. It is produced by rolling the composite material layer 42.
- Examples of the positive electrode active material included in the positive electrode composite layer 42 include lithium composite oxides containing transition metal elements such as Co, Mn, and Ni.
- Lithium composite oxides include, for example, Ni, Co, Mn, Al, Zr, B, Mg, Sc, Y, Ti, Fe, Cu, Zn, Cr, Pb, Sn, Na, K, Ba, Sr, Ca, It may contain W, Mo, Nb, Si, or the like.
- the lithium composite oxides may be used alone or in combination.
- the positive electrode active material has the general formula: Li a Ni x Co y M 1-x-y O 2 (where a, x, y are 0.97 ⁇ a ⁇ 1.2, 0.8 ⁇ x ⁇ 1.0, 0 ⁇ y ⁇ 0.2, M is Mn, Al, B, W, Sr, Mg, Mo, Nb, Ti , Si, and Zr).
- Examples of the conductive material included in the positive electrode composite layer 42 include amorphous carbon (eg, carbon black, acetylene black, Ketjen black, etc.), graphite, carbon-based materials such as carbon nanotubes, metal particles, and the like.
- amorphous carbon eg, carbon black, acetylene black, Ketjen black, etc.
- graphite e.g., graphite
- carbon-based materials such as carbon nanotubes, metal particles, and the like.
- the binders contained in the positive electrode composite layer 42 have a weight average molecular weight in the range of 400,000 to 800,000, binder A which has an average particle diameter (D50) in the range of 50 nm to 500 nm, and binder A with a weight average molecular weight in the range of 1 million to 800,000. 1.5 million and a binder B having an average particle size (D50) in a range of 50 ⁇ m to 500 ⁇ m.
- the average particle size (D50) is the median diameter at which the volume integrated value is 50% in the particle size distribution measured using a laser diffraction/scattering particle size distribution analyzer (MT3000II, manufactured by Microtrac Bell Co., Ltd.). be.
- the weight average molecular weight can be measured using gel permeation chromatography (GPC) and calculated using polystyrene as a standard sample.
- GPC gel permeation chromatography
- a sample for GPC measurement can be prepared by adjusting the sample (binder A or B) to 0.2 wt% with an NMP eluent, allowing it to stand overnight at room temperature, and then filtering it with a 0.45 ⁇ m surface blank filter.
- GPC can be measured using, for example, Agilent 1200 (column; TSKgelSuperAWM-H manufactured by Tosoh) at a flow rate of 0.5 mL/min and a measurement temperature of 40°C.
- Binder A which has a small weight average molecular weight and average particle size, is relatively easy to disperse uniformly within the positive electrode composite layer 42
- binder B which has a large weight average molecular weight and average particle size, exhibits strong adhesive force.
- the presence of such binders A and B in the positive electrode composite material layer 42 results in the positive electrode 11 having excellent peel strength between the positive electrode current collector 40 and the positive electrode composite material layer 42. Further, by using binders A and B, high peel strength can be obtained even with a small amount of binder, which may contribute to increasing the capacity of the battery.
- the ratio of binder A to binder B is preferably in the range of 5:95 to 50:50 in terms of mass ratio.
- the ratio of binder A and binder B satisfies the above range, it becomes possible to further increase the peel strength between the positive electrode current collector 40 and the positive electrode composite layer 42, compared to the case where the ratio between binder A and binder B does not satisfy the above range. .
- the weight average molecular weight of the binder A is preferably in the range of 450,000 to 700,000, and the average particle size (D50 ) is preferably in the range of 100 nm to 400 nm.
- the weight average molecular weight of the binder B is preferably in the range of 1.1 million to 1.4 million, and the average particle size (D50) is preferably in the range of 70 ⁇ m to 400 ⁇ m.
- binder materials can be used as long as the weight average molecular weight and average particle size satisfy the above ranges, such as fluororesins, polyimide resins, acrylic resins, polyolefin resins, etc. Resin, polyacrylonitrile (PAN), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salt, polyacrylic acid (PAA) or its salt (PAA-Na, PAA-K) etc., and may also be a partially neutralized salt), polyvinyl alcohol (PVA), and the like.
- fluororesins are preferred because of their high binding strength.
- vinylidene fluoride polymers are preferred because the molecular weight can be easily controlled.
- the vinylidene fluoride polymer may be a vinylidene fluoride homopolymer, a vinylidene fluoride polymer derivative, or a vinylidene fluoride copolymer.
- the vinylidene fluoride homopolymer is, for example, polyvinylidene fluoride (PVDF).
- the vinylidene fluoride polymer derivative is, for example, polyvinylidene fluoride into which a carbonyl group has been introduced.
- a vinylidene fluoride copolymer is a copolymer of a vinylidene fluoride monomer and a monomer other than vinylidene fluoride.
- at least one of binders A and B is preferably a vinylidene fluoride polymer derivative or a vinylidene fluoride copolymer because of its high binding strength.
- the monomers other than vinylidene fluoride constituting the vinylidene fluoride copolymer are not particularly limited, but include, for example, fluorine-based monomers that can be copolymerized with vinylidene fluoride, or hydrocarbon-based monomers such as ethylene and propylene. Examples include monomers, carboxyl group-containing monomers, and carboxylic acid anhydride group-containing monomers. Note that the other monomers may be used alone or in combination of two or more types.
- vinylidene fluoride copolymer a copolymer of vinylidene fluoride (VDF) and a fluoromonomer copolymerizable with vinylidene fluoride is preferred.
- fluorine-based monomers include vinyl fluoride, trifluoroethylene (TrFE), tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and perfluoroalkyl represented by perfluoromethyl vinyl ether. Examples include vinyl ether.
- Examples of the copolymer of vinylidene fluoride and a fluoromonomer include VDF-TFE copolymer, VDF-TFE-HFP copolymer, VDF-HFP copolymer, VDF-CTFE copolymer, Examples include VDF-TFE-CTFE copolymer and VDF-HFP-CTFE copolymer.
- vinylidene fluoride copolymer when the total of all monomers used as raw materials is 100 mol%, vinylidene fluoride is preferably used in an amount of 50 mol% or more, more preferably 80 mol% or more.
- the weight average molecular weight of the binder may be adjusted by any known method, such as adjusting the polymerization conditions (temperature, pressure, etc.) when manufacturing the binder, or adding additives such as crosslinking agents and chain transfer agents. Examples include a method of doing so.
- the volume average particle diameter of the binder may be adjusted by any known method, such as a method of destroying the latex of a polymer corresponding to the binder, or a method of selecting a polymerization recipe (emulsion polymerization, suspension polymerization, etc.). Examples include control using a combination of stirring operation and dispersion stabilizer. Examples of methods for destroying latex include methods such as salting out aggregation, acid precipitation aggregation, and freezing and thawing.
- the content of the positive electrode active material contained in the positive electrode composite material layer 42 is, for example, 90% by mass or more with respect to the total mass of the positive electrode composite material layer 42.
- the content of the conductive material contained in the positive electrode composite material layer 42 is preferably in the range of 0.5% by mass to 5% by mass with respect to the total mass of the positive electrode composite material layer 42.
- the total content of binders A and B contained in the positive electrode composite material layer 42 is determined from the viewpoint of achieving both a high capacity of the battery and an improvement in the peel strength between the positive electrode current collector 40 and the positive electrode composite material layer 42. It is preferably in the range of 0.5% by mass to 5% by mass, and more preferably in the range of 0.5% by mass to 3% by mass, based on the total mass of the material layer 42.
- the negative electrode 12 includes a negative electrode current collector and a negative electrode composite material layer provided on the negative electrode current collector.
- a negative electrode current collector for example, a foil made of a metal such as copper that is stable in the potential range of the negative electrode, a film having the metal disposed on the surface layer, or the like is used.
- the negative electrode composite material layer contains a negative electrode active material, and further contains a binder, a conductive material, and the like.
- a negative electrode composite slurry containing a negative electrode active material, a binder, etc. is prepared, and this negative electrode composite slurry is applied onto a negative electrode current collector and dried to form a negative electrode composite material layer. It can be produced by rolling a negative electrode composite material layer.
- the negative electrode active material is not particularly limited as long as it is a material capable of intercalating and deintercalating lithium ions; for example, metal lithium, lithium-aluminum alloy, lithium-lead alloy, lithium-silicon alloy, lithium- Examples include lithium alloys such as tin alloys, carbon materials such as graphite, coke, and fired organic materials, and metal oxides such as SnO 2 , SnO, and TiO 2 . These may be used alone or in combination of two or more.
- the binding material and the conductive material may be the same materials as in the case of the positive electrode 11, for example.
- separator 13 for example, a porous sheet having ion permeability and insulation properties is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator include olefin resins such as polyethylene and polypropylene, cellulose, and the like.
- the separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin.
- a multilayer separator including a polyethylene layer and a polypropylene layer may be used, or a separator whose surface is coated with a material such as aramid resin or ceramic may be used.
- binder A a vinylidene fluoride copolymer having a weight average molecular weight of 470,000 and an average particle size of 158 nm was prepared.
- binder B a vinylidene fluoride copolymer having a weight average molecular weight of 1,180,000 and an average particle size of 71 ⁇ m was prepared.
- Binder A and binder B were mixed at a mass ratio of 5:95 to obtain a mixed binder.
- a lithium composite oxide represented by LiNi 0.8 Co 0.15 Al 0.05 O 2 a mixed binder, and a conductive material were mixed at a mass ratio of 98.5:0.7:0.8.
- a suitable amount of N-methyl-2-pyrrolidone was added to the mixture and stirred to prepare a positive electrode composite slurry.
- the above positive electrode composite slurry was applied to both sides of a 15 ⁇ m thick aluminum foil and then dried to form a coating film. Thereafter, the coating film was rolled with a rolling roller to produce a positive electrode in which positive electrode mixture layers were formed on both sides of the positive electrode current collector.
- Graphite, CMC, and SBR were mixed at a mass ratio of 98:1:1, and the mixture was kneaded with water to prepare a negative electrode composite slurry.
- This negative electrode composite material slurry was applied to both sides of a copper foil with a thickness of 8 ⁇ m, and after the coating film was dried, it was rolled with a rolling roller to form a negative electrode composite material layer on both sides of the negative electrode current collector. was created.
- EC ethylene carbonate
- MEC methyl ethyl carbonate
- non-aqueous electrolyte secondary battery (1) A separator (a composite film of polyethylene and polypropylene) was interposed between the positive electrode and the negative electrode, and the electrode body was wound to produce a wound type electrode body. Leads were attached to each of the positive and negative electrodes. (2) The electrode body was inserted into the case body, the negative lead was welded to the bottom of the case body, and the positive lead was welded to the sealing body. (3) After injecting the non-aqueous electrolyte into the case body, the open end of the case body was caulked to the sealing body via the gasket. This was used as the non-aqueous electrolyte secondary battery of Example 1.
- a separator a composite film of polyethylene and polypropylene
- Example 2 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 25:75 was used in producing the positive electrode.
- Example 3 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 50:50 was used in producing the positive electrode.
- Example 4 A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 75:25 was used in producing the positive electrode.
- Example 1 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only binder B was used without using a mixed binder in producing the positive electrode.
- Example 2 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only binder A was used without using a mixed binder in producing the positive electrode.
- ⁇ Comparative example 3> In producing the positive electrode, only binder B was used without using a mixed binder, and the lithium composite oxide, binder B, and conductive material were mixed in a mass ratio of 98.3:0.9:0.8. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the components were mixed at the same ratio.
- ⁇ Comparative example 4> In producing the positive electrode, only binder A was used without using a mixed binder, and the lithium composite oxide, binder A, and conductive material were mixed in a mass ratio of 98.3:0.9:0.8. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the components were mixed at the same ratio.
- the non-aqueous electrolyte secondary batteries of each example and each comparative example were charged at a constant current of 1 C to 4.2 V, and then charged at a constant voltage of 4.2 V to 1/50 C. did. Thereafter, constant current discharge was performed at 0.5C to 2.5V. The discharge capacity at this time was measured and defined as the battery capacity.
- Table 1 summarizes the peel strength and battery capacity results of each Example and each Comparative Example. Each result is shown as a reference value (100) for Comparative Example 1, and relative values for other Examples and Comparative Examples.
- Examples 1 to 4 all showed higher peel strength than Comparative Examples 1 to 2.
- the peel strength of the positive electrode was increased by increasing the binder content in the positive electrode composite layer compared to the Example, but the peel strength of the positive electrode was increased by the increased binder content. Since the content of the active material was reduced, the battery capacity was lower than in the example.
- the peel strength between the positive electrode composite material layer and the positive electrode current collector can be increased with a small amount of binder, so that the decrease in battery capacity can also be suppressed.
- [Additional notes] (1) comprising a positive electrode current collector and a positive electrode composite layer provided on the positive electrode current collector and containing a positive electrode active material and a binder,
- the binder has a weight average molecular weight in the range of 400,000 to 800,000
- binder A has an average particle diameter (D50) in the range of 50 to 500 nm, and a weight average molecular weight in the range of 1 million to 1.5 million
- the binder A is any one of (1) to (3) above, which is a polyvinylidene fluoride, a derivative of polyvinylidene fluoride, or a vinylidene fluoride copolymer, which is a copolymer containing vinylidene fluoride.
- a non-aqueous electrolyte secondary battery comprising the positive electrode for a non-aqueous electrolyte secondary battery according to any one of (1) to (4) above.
Abstract
A nonaqueous electrolyte secondary battery positive electrode (11) is characterized by comprising a positive electrode current collector (40) and a positive electrode mixture layer (42) that is provided on the positive electrode current collector (40) and that includes a positive electrode active material and binders, and is characterized in that the binders include: a binder A having a weight average molecular weight in a range of 400,000-800,000 and having an average particle diameter (D50) in a range of 50-500 nm; and a binder B having a weight average molecular weight in a range of 1,000,000-1,500,000 and having an average particle diameter (D50) in a range of 50-500 μm.
Description
本開示は、非水電解質二次電池用正極及び非水電解質二次電池に関する。
The present disclosure relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.
例えば、特許文献１には、正極集電体と、正極集電体上に配置される正極合材層とを備え、正極合材層は、平均粒径（Ｄ５０）が０．０２～０．５μｍである成分Ａ及び平均粒径（Ｄ５０）が１．１～５０μｍである成分Ｂからなるフッ化ビニリデン系重合体をバインダーとして含む非水電解質二次電池用正極が開示されている。
For example, Patent Document 1 includes a positive electrode current collector and a positive electrode composite material layer disposed on the positive electrode current collector, and the positive electrode composite material layer has an average particle size (D50) of 0.02 to 0.02. A positive electrode for a non-aqueous electrolyte secondary battery is disclosed, which includes a vinylidene fluoride polymer as a binder, consisting of component A having a diameter of 5 μm and component B having an average particle diameter (D50) of 1.1 to 50 μm.
また、例えば、特許文献２には、正極集電体と、正極集電体上に配置される正極合材層とを備え、正極合材層は、重量平均分子量が３０万～４０万の範囲であるフッ化ビニリデン共重合体の第１バインダーと、重量平均分子量が８０万～１００万の範囲であるフッ化ビニリデン系重合体の第２バインダーを含む非水電解質二次電池用正極が開示されている。
Further, for example, Patent Document 2 includes a positive electrode current collector and a positive electrode composite material layer disposed on the positive electrode current collector, and the positive electrode composite material layer has a weight average molecular weight in the range of 300,000 to 400,000. Disclosed is a positive electrode for a non-aqueous electrolyte secondary battery comprising a first binder of a vinylidene fluoride copolymer having a weight average molecular weight of 800,000 to 1,000,000 and a second binder of a vinylidene fluoride polymer having a weight average molecular weight in the range of 800,000 to 1,000,000. ing.
ところで、非水電解質二次電池の高容量化のためには、正極内のバインダーの含有率を低減することが好ましいが、バインダーの含有率を低減させると、正極集電体と正極合材層との密着力が低下する（すなわち、正極集電体と正極合材層との剥離強度が低下する）。
By the way, in order to increase the capacity of a non-aqueous electrolyte secondary battery, it is preferable to reduce the binder content in the positive electrode. However, if the binder content is reduced, the positive electrode current collector and positive electrode composite layer (ie, the peel strength between the positive electrode current collector and the positive electrode composite layer decreases).
そこで、本開示の目的は、正極集電体と正極合材層との剥離強度に優れた非水電解質二次電池用正極及び当該正極を備える二次電池を提供することである。
Therefore, an object of the present disclosure is to provide a positive electrode for a non-aqueous electrolyte secondary battery that has excellent peel strength between a positive electrode current collector and a positive electrode composite layer, and a secondary battery including the positive electrode.
本開示の一態様である非水電解質二次電池用正極は、正極集電体と、前記正極集電体上に設けられ、正極活物質及びバインダーを含む正極合材層とを備え、前記バインダーは、重量平均分子量が４０万～８０万の範囲であり、平均粒径（Ｄ５０）が５０ｎｍ～５００ｎｍの範囲であるバインダーＡと、重量平均分子量が１００万～１５０万の範囲であり、平均粒径（Ｄ５０）が５０μｍ～５００μｍの範囲であるバインダーＢとを含むことを特徴とする。
A positive electrode for a non-aqueous electrolyte secondary battery that is one aspect of the present disclosure includes a positive electrode current collector, and a positive electrode composite layer provided on the positive electrode current collector and containing a positive electrode active material and a binder, and wherein the positive electrode composite layer includes a positive electrode active material and a binder. Binder A has a weight average molecular weight in the range of 400,000 to 800,000 and an average particle diameter (D50) in the range of 50 to 500 nm, and Binder A has a weight average molecular weight in the range of 1 million to 1.5 million and has an average particle diameter (D50) of 50 to 500 nm. The binder B has a diameter (D50) in the range of 50 μm to 500 μm.
また、本開示の一態様である非水電解質二次電池は、上記非水電解質二次電池用正極を備えることを特徴とする。
Further, a non-aqueous electrolyte secondary battery that is one aspect of the present disclosure is characterized by comprising the above-described positive electrode for a non-aqueous electrolyte secondary battery.
本開示の一態様によれば、正極集電体と正極合材層との剥離強度に優れた非水電電解質二次電池用正極及び当該正極を備える非水電解質二次電池を提供することができる。
According to one aspect of the present disclosure, it is possible to provide a positive electrode for a non-aqueous electrolyte secondary battery that has excellent peel strength between a positive electrode current collector and a positive electrode composite layer, and a non-aqueous electrolyte secondary battery including the positive electrode. .
以下に、本開示の一態様である非水電解質二次電池の一例について説明する。
An example of a non-aqueous electrolyte secondary battery that is one embodiment of the present disclosure will be described below.
図１は、実施形態の一例である非水電解質二次電池の模式断面図である。図１に示す非水電解質二次電池１０は、正極１１及び負極１２がセパレータ１３を介して巻回されてなる巻回型の電極体１４と、非水電解質と、電極体１４の上下にそれぞれ配置された絶縁板１８，１９と、上記部材を収容する電池ケース１５と、を備える。電池ケース１５は、有底円筒形状のケース本体１６と、ケース本体１６の開口部を塞ぐ封口体１７とにより構成される。なお、巻回型の電極体１４の代わりに、正極及び負極がセパレータを介して交互に積層されてなる積層型の電極体など、他の形態の電極体が適用されてもよい。また、電池ケース１５としては、円筒形、角形、コイン形、ボタン形等の金属製ケース、樹脂シートをラミネートして形成された樹脂製ケース（所謂ラミネート型）などが例示できる。
FIG. 1 is a schematic cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment. The non-aqueous electrolyte secondary battery 10 shown in FIG. It includes arranged insulating plates 18 and 19 and a battery case 15 that accommodates the above-mentioned members. The battery case 15 includes a case body 16 having a cylindrical shape with a bottom and a sealing body 17 that closes an opening of the case body 16. Note that, instead of the wound type electrode body 14, other forms of electrode bodies may be applied, such as a laminated type electrode body in which positive electrodes and negative electrodes are alternately laminated with separators interposed therebetween. Further, examples of the battery case 15 include a metal case having a cylindrical shape, a square shape, a coin shape, a button shape, etc., a resin case formed by laminating resin sheets (so-called laminate type), and the like.
非水電解質は、例えば、非水溶媒と、非水溶媒に溶解した電解質塩とを含む。非水溶媒には、例えばエステル類、エーテル類、ニトリル類、アミド類、及びこれらの２種以上の混合溶媒等が用いられる。非水溶媒は、これら溶媒の水素の少なくとも一部をフッ素等のハロゲン原子で置換したハロゲン置換体を含有していてもよい。電解質塩には、例えばＬｉＰＦ６等のリチウム塩が使用される。なお、非水電解質は液体電解質に限定されず、ゲル状ポリマー等の固体電解質であってもよい。
The non-aqueous electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents used include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain a halogen-substituted product in which at least a portion of hydrogen in these solvents is replaced with a halogen atom such as fluorine. For example, a lithium salt such as LiPF 6 is used as the electrolyte salt. Note that the nonaqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte such as a gel polymer.
ケース本体１６は、例えば有底円筒形状の金属製容器である。ケース本体１６と封口体１７との間にはガスケット２８が設けられ、電池内部の密閉性が確保される。ケース本体１６は、例えば側面部の一部が内側に張出した、封口体１７を支持する張り出し部２２を有する。張り出し部２２は、ケース本体１６の周方向に沿って環状に形成されることが好ましく、その上面で封口体１７を支持する。
The case body 16 is, for example, a cylindrical metal container with a bottom. A gasket 28 is provided between the case body 16 and the sealing body 17 to ensure airtightness inside the battery. The case main body 16 has an overhanging portion 22 that supports the sealing body 17 and has, for example, a part of a side surface overhanging inward. The projecting portion 22 is preferably formed in an annular shape along the circumferential direction of the case body 16, and supports the sealing body 17 on its upper surface.
封口体１７は、電極体１４側から順に、フィルタ２３、下弁体２４、絶縁部材２５、上弁体２６、及びキャップ２７が積層された構造を有する。封口体１７を構成する各部材は、例えば円板形状又はリング形状を有し、絶縁部材２５を除く各部材は互いに電気的に接続されている。下弁体２４と上弁体２６は各々の中央部で互いに接続され、各々の周縁部の間には絶縁部材２５が介在している。内部短絡等による発熱で非水電解質二次電池１０の内圧が上昇すると、例えば下弁体２４が上弁体２６をキャップ２７側に押し上げるように変形して破断し、下弁体２４と上弁体２６の間の電流経路が遮断される。さらに内圧が上昇すると、上弁体２６が破断し、キャップ２７の開口部からガスが排出される。
The sealing body 17 has a structure in which a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side. Each member constituting the sealing body 17 has, for example, a disk shape or a ring shape, and each member except the insulating member 25 is electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected to each other at their central portions, and an insulating member 25 is interposed between their respective peripheral portions. When the internal pressure of the nonaqueous electrolyte secondary battery 10 increases due to heat generation due to an internal short circuit, for example, the lower valve body 24 deforms and ruptures so as to push the upper valve body 26 toward the cap 27, and the lower valve body 24 and the upper valve body The current path between bodies 26 is interrupted. When the internal pressure further increases, the upper valve body 26 breaks and gas is discharged from the opening of the cap 27.
図１に示す非水電解質二次電池１０では、正極１１に取り付けられた正極リード２０が絶縁板１８の貫通孔を通って封口体１７側に延び、負極１２に取り付けられた負極リード２１が絶縁板１９の外側を通ってケース本体１６の底部側に延びている。正極リード２０は封口体１７の底板であるフィルタ２３の下面に溶接等で接続され、フィルタ２３と電気的に接続された封口体１７の天板であるキャップ２７が正極端子となる。負極リード２１はケース本体１６の底部内面に溶接等で接続され、ケース本体１６が負極端子となる。
In the nonaqueous electrolyte secondary battery 10 shown in FIG. 1, the positive electrode lead 20 attached to the positive electrode 11 extends toward the sealing body 17 side through the through hole of the insulating plate 18, and the negative electrode lead 21 attached to the negative electrode 12 is insulated. It passes through the outside of the plate 19 and extends to the bottom side of the case body 16. The positive electrode lead 20 is connected by welding or the like to the lower surface of the filter 23, which is the bottom plate of the sealing body 17, and the cap 27, which is the top plate of the sealing body 17 and electrically connected to the filter 23, serves as a positive terminal. The negative electrode lead 21 is connected to the bottom inner surface of the case body 16 by welding or the like, and the case body 16 serves as a negative electrode terminal.
以下に、正極１１、負極１２、セパレータ１３について詳述する。
The positive electrode 11, negative electrode 12, and separator 13 will be explained in detail below.
［正極］
図２は、実施形態の一例である正極の模式断面図である。正極１１は、正極集電体４０と、正極集電体４０上に設けられた正極合材層４２と、を備える。正極集電体４０には、アルミニウム等の正極１１の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。正極合材層４２は、正極活物質、バインダーを含む。正極合材層４２は、更に、導電材を含むことが好ましい。正極合材層４２は、正極集電体４０の一方の面のみに設けられてもよいし、両面に設けられてもよい [Positive electrode]
FIG. 2 is a schematic cross-sectional view of a positive electrode that is an example of an embodiment. Thepositive electrode 11 includes a positive electrode current collector 40 and a positive electrode composite material layer 42 provided on the positive electrode current collector 40. For the positive electrode current collector 40, a metal foil such as aluminum that is stable in the potential range of the positive electrode 11, a film with the metal disposed on the surface, or the like can be used. The positive electrode composite material layer 42 contains a positive electrode active material and a binder. It is preferable that the positive electrode composite material layer 42 further contains a conductive material. The positive electrode composite material layer 42 may be provided on only one surface of the positive electrode current collector 40, or may be provided on both surfaces.
図２は、実施形態の一例である正極の模式断面図である。正極１１は、正極集電体４０と、正極集電体４０上に設けられた正極合材層４２と、を備える。正極集電体４０には、アルミニウム等の正極１１の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。正極合材層４２は、正極活物質、バインダーを含む。正極合材層４２は、更に、導電材を含むことが好ましい。正極合材層４２は、正極集電体４０の一方の面のみに設けられてもよいし、両面に設けられてもよい [Positive electrode]
FIG. 2 is a schematic cross-sectional view of a positive electrode that is an example of an embodiment. The
正極１１は、例えば、正極活物質、バインダー、導電材等を含む正極合材スラリーを正極集電体４０上に塗布、乾燥して正極合材層４２を形成した後、圧延ローラ等により、正極合材層４２を圧延することにより作製される。
For example, the positive electrode 11 is formed by applying a positive electrode composite material slurry containing a positive electrode active material, a binder, a conductive material, etc. onto the positive electrode current collector 40 and drying it to form a positive electrode composite material layer 42, and then rolling the positive electrode with a rolling roller or the like. It is produced by rolling the composite material layer 42.
正極合材層４２に含まれる正極活物質としては、Ｃｏ、Ｍｎ、Ｎｉ等の遷移金属元素を含有するリチウム複合酸化物が例示できる。リチウム複合酸化物は、例えば、Ｎｉ、Ｃｏ、Ｍｎ、Ａｌ、Ｚｒ、Ｂ、Ｍｇ、Ｓｃ、Ｙ、Ｔｉ、Ｆｅ、Ｃｕ、Ｚｎ、Ｃｒ、Ｐｂ、Ｓｎ、Ｎａ、Ｋ、Ｂａ、Ｓｒ、Ｃａ、Ｗ、Ｍｏ、Ｎｂ、又はＳｉ等を含んでいてよい。リチウム複合酸化物は、１種単独で用いてもよいし、複数種を混合して用いてもよい。
Examples of the positive electrode active material included in the positive electrode composite layer 42 include lithium composite oxides containing transition metal elements such as Co, Mn, and Ni. Lithium composite oxides include, for example, Ni, Co, Mn, Al, Zr, B, Mg, Sc, Y, Ti, Fe, Cu, Zn, Cr, Pb, Sn, Na, K, Ba, Sr, Ca, It may contain W, Mo, Nb, Si, or the like. The lithium composite oxides may be used alone or in combination.
また、正極活物質は、例えば、電池の高容量化を図ることができる点で、一般式：ＬｉａＮｉｘＣｏｙＭ１－ｘ－ｙＯ２（式中、ａ，ｘ，ｙは、０．９７≦ａ≦１．２、０．８≦ｘ≦１．０、０≦ｙ≦０．２を満たし、Ｍは、Ｍｎ、Ａｌ、Ｂ、Ｗ、Ｓｒ、Ｍｇ、Ｍｏ、Ｎｂ、Ｔｉ、Ｓｉ及びＺｒからなる群より選択される少なくとも１種を含む）で表されるリチウム複合酸化物を含むことが好ましい。
In addition, the positive electrode active material has the general formula: Li a Ni x Co y M 1-x-y O 2 (where a, x, y are 0.97≦a≦1.2, 0.8≦x≦1.0, 0≦y≦0.2, M is Mn, Al, B, W, Sr, Mg, Mo, Nb, Ti , Si, and Zr).
正極合材層４２に含まれる導電材は、例えば、非晶質炭素（例えば、カーボンブラック、アセチレンブラック、ケッチェンブラック等）、黒鉛、カーボンナノチューブ等の炭素系材料、金属粒子等が挙げられる。
Examples of the conductive material included in the positive electrode composite layer 42 include amorphous carbon (eg, carbon black, acetylene black, Ketjen black, etc.), graphite, carbon-based materials such as carbon nanotubes, metal particles, and the like.
正極合材層４２に含まれるバインダーは、重量平均分子量が４０万～８０万の範囲であり、平均粒径（Ｄ５０）が５０ｎｍ～５００ｎｍの範囲であるバインダーＡと、重量平均分子量が１００万～１５０万の範囲であり、平均粒径（Ｄ５０）が５０μｍ～５００μｍの範囲であるバインダーＢとを含む。平均粒径（Ｄ５０）は、レーザ回折・散乱式粒度分布測定装置（マイクロトラック・ベル株式会社製、ＭＴ３０００ＩＩ）を用いて測定される粒子径分布において、体積積算値が５０％となるメジアン径である。重量平均分子量は、ゲル浸透クロマトグラフィー（ＧＰＣ）を利用して測定を行い、ポリスチレンを標準サンプルとして算出することができる。ＧＰＣの測定用サンプルは、試料（バインダーＡ又はＢ）をＮＭＰ溶離液で０．２ｗｔ％に調整し、室温にて一晩静置後に０．４５μｍ面ブランフィルタ―にてろ過することで準備できる。ＧＰＣは、例えばＡｇｉｌｅｎｔ１２００（カラム；東ソー製ＴＳＫｇｅｌＳｕｐｅｒＡＷＭ－Ｈ）を用いて、流速０．５ｍＬ／ｍｉｎ、測定温度４０℃で測定することができる。
The binders contained in the positive electrode composite layer 42 have a weight average molecular weight in the range of 400,000 to 800,000, binder A which has an average particle diameter (D50) in the range of 50 nm to 500 nm, and binder A with a weight average molecular weight in the range of 1 million to 800,000. 1.5 million and a binder B having an average particle size (D50) in a range of 50 μm to 500 μm. The average particle size (D50) is the median diameter at which the volume integrated value is 50% in the particle size distribution measured using a laser diffraction/scattering particle size distribution analyzer (MT3000II, manufactured by Microtrac Bell Co., Ltd.). be. The weight average molecular weight can be measured using gel permeation chromatography (GPC) and calculated using polystyrene as a standard sample. A sample for GPC measurement can be prepared by adjusting the sample (binder A or B) to 0.2 wt% with an NMP eluent, allowing it to stand overnight at room temperature, and then filtering it with a 0.45 μm surface blank filter. . GPC can be measured using, for example, Agilent 1200 (column; TSKgelSuperAWM-H manufactured by Tosoh) at a flow rate of 0.5 mL/min and a measurement temperature of 40°C.
重量平均分子量及び平均粒径の小さいバインダーＡは正極合材層４２内に比較的に均一に分散し易く、重量平均分子量及び平均粒径の大きいバインダーＢは強い接着力を発揮する。このようなバインダーＡ及びＢが正極合材層４２内に存在することで、正極集電体４０と正極合材層４２の剥離強度に優れた正極１１となる。また、バインダーＡ及びＢを使用することで、少ないバインダー量でも、高い剥離強度が得られるため、電池の高容量化に寄与する場合がある。
Binder A, which has a small weight average molecular weight and average particle size, is relatively easy to disperse uniformly within the positive electrode composite layer 42, and binder B, which has a large weight average molecular weight and average particle size, exhibits strong adhesive force. The presence of such binders A and B in the positive electrode composite material layer 42 results in the positive electrode 11 having excellent peel strength between the positive electrode current collector 40 and the positive electrode composite material layer 42. Further, by using binders A and B, high peel strength can be obtained even with a small amount of binder, which may contribute to increasing the capacity of the battery.
バインダーＡとバインダーＢとの割合は、質量比で、５：９５～５０：５０の範囲が好ましい。バインダーＡとバインダーＢとの割合が上記範囲を満たすことで、上記範囲を満たさない場合と比較して、正極集電体４０と正極合材層４２との剥離強度をより高めることが可能となる。
The ratio of binder A to binder B is preferably in the range of 5:95 to 50:50 in terms of mass ratio. When the ratio of binder A and binder B satisfies the above range, it becomes possible to further increase the peel strength between the positive electrode current collector 40 and the positive electrode composite layer 42, compared to the case where the ratio between binder A and binder B does not satisfy the above range. .
バインダーＡは、正極集電体４０と正極合材層４２との剥離強度をより高めることが可能となる点で、重量平均分子量は、４５万～７０万の範囲が好ましく、平均粒径（Ｄ５０）は、１００ｎｍ～４００ｎｍの範囲が好ましい。また、バインダーＢは、正極集電体４０と正極合材層４２との剥離強度をより高めることが可能となる点で、重量平均分子量は、１１０万～１４０万の範囲が好ましく、平均粒径（Ｄ５０）は、７０μｍ～４００μｍの範囲が好ましい。
The weight average molecular weight of the binder A is preferably in the range of 450,000 to 700,000, and the average particle size (D50 ) is preferably in the range of 100 nm to 400 nm. In addition, the weight average molecular weight of the binder B is preferably in the range of 1.1 million to 1.4 million, and the average particle size (D50) is preferably in the range of 70 μm to 400 μm.
バインダーＡ及びＢは、重量平均分子量及び平均粒径が上記範囲を満たしていれば、従来公知のバインダー材料を使用することができ、例えば、フッ素系樹脂、ポリイミド系樹脂、アクリル系樹脂、ポリオレフィン系樹脂、ポリアクリロニトリル（ＰＡＮ）、スチレン－ブタジエンゴム（ＳＢＲ）、ニトリル－ブタジエンゴム（ＮＢＲ）、カルボキシメチルセルロース（ＣＭＣ）又はその塩、ポリアクリル酸（ＰＡＡ）又はその塩（ＰＡＡ－Ｎａ、ＰＡＡ－Ｋ等、また部分中和型の塩であってもよい）、ポリビニルアルコール（ＰＶＡ）等が挙げられる。これらの中では、結着力が高い点等から、フッ素系樹脂が好ましい。さらに、フッ素系樹脂の中では、分子量の制御が容易である点等から、フッ化ビニリデン系重合体が好ましい。
For binders A and B, conventionally known binder materials can be used as long as the weight average molecular weight and average particle size satisfy the above ranges, such as fluororesins, polyimide resins, acrylic resins, polyolefin resins, etc. Resin, polyacrylonitrile (PAN), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salt, polyacrylic acid (PAA) or its salt (PAA-Na, PAA-K) etc., and may also be a partially neutralized salt), polyvinyl alcohol (PVA), and the like. Among these, fluororesins are preferred because of their high binding strength. Further, among the fluororesins, vinylidene fluoride polymers are preferred because the molecular weight can be easily controlled.
フッ化ビニリデン系重合体は、フッ化ビニリデン単独重合体、フッ化ビニリデン重合体の誘導体、フッ化ビニリデン共重合体のいずれでもよい。フッ化ビニリデン単独重合体は、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）等である。フッ化ビニリデン重合体の誘導体は、例えば、カルボニル基を導入したポリフッ化ビニリデンである。フッ化ビニリデン共重合体は、フッ化ビニリデン単量体と、フッ化ビニリデン以外の単量体との共重合体である。これらのうち、結着力が高い点等から、バインダーＡ及びＢのうちの少なくともいずれか一方は、フッ化ビニリデン重合体の誘導体またはフッ化ビニリデン共重合体であることが好ましい。
The vinylidene fluoride polymer may be a vinylidene fluoride homopolymer, a vinylidene fluoride polymer derivative, or a vinylidene fluoride copolymer. The vinylidene fluoride homopolymer is, for example, polyvinylidene fluoride (PVDF). The vinylidene fluoride polymer derivative is, for example, polyvinylidene fluoride into which a carbonyl group has been introduced. A vinylidene fluoride copolymer is a copolymer of a vinylidene fluoride monomer and a monomer other than vinylidene fluoride. Among these, at least one of binders A and B is preferably a vinylidene fluoride polymer derivative or a vinylidene fluoride copolymer because of its high binding strength.
フッ化ビニリデン共重合体を構成するフッ化ビニリデン以外の単量体としては、特に限定はないが、例えばフッ化ビニリデンと共重合可能なフッ素系単量体、あるいはエチレン、プロピレン等の炭化水素系単量体、カルボキシル基含有モノマー、カルボン酸無水物基含有モノマーが挙げられる。なお、他のモノマーは、一種単独でも、二種以上でもよい。
The monomers other than vinylidene fluoride constituting the vinylidene fluoride copolymer are not particularly limited, but include, for example, fluorine-based monomers that can be copolymerized with vinylidene fluoride, or hydrocarbon-based monomers such as ethylene and propylene. Examples include monomers, carboxyl group-containing monomers, and carboxylic acid anhydride group-containing monomers. Note that the other monomers may be used alone or in combination of two or more types.
フッ化ビニリデン共重合体としては、フッ化ビニリデン（ＶＤＦ）と、フッ化ビニリデンと共重合可能なフッ素系単量体との共重合体が好ましい。フッ素系単量体としては、フッ化ビニル、トリフルオロエチレン（ＴｒＦＥ）、テトラフルオロエチレン（ＴＦＥ）、クロロトリフルオロエチレン（ＣＴＦＥ）、ヘキサフルオロプロピレン（ＨＦＰ）、ペルフルオロメチルビニルエーテルに代表されるペルフルオロアルキルビニルエーテル等を挙げることができる。フッ化ビニリデンと、フッ素系単量体との共重合体としては、例えば、ＶＤＦ－ＴＦＥ共重合体、ＶＤＦ－ＴＦＥ－ＨＦＰ共重合体、ＶＤＦ－ＨＦＰ共重合体、ＶＤＦ－ＣＴＦＥ共重合体、ＶＤＦ－ＴＦＥ－ＣＴＦＥ共重合体、ＶＤＦ－ＨＦＰ－ＣＴＦＥ共重合体等が挙げられる。
As the vinylidene fluoride copolymer, a copolymer of vinylidene fluoride (VDF) and a fluoromonomer copolymerizable with vinylidene fluoride is preferred. Examples of fluorine-based monomers include vinyl fluoride, trifluoroethylene (TrFE), tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and perfluoroalkyl represented by perfluoromethyl vinyl ether. Examples include vinyl ether. Examples of the copolymer of vinylidene fluoride and a fluoromonomer include VDF-TFE copolymer, VDF-TFE-HFP copolymer, VDF-HFP copolymer, VDF-CTFE copolymer, Examples include VDF-TFE-CTFE copolymer and VDF-HFP-CTFE copolymer.
フッ化ビニリデン共重合体は、原料として使用する全モノマーの合計を１００モル％とすると、フッ化ビニリデンを、５０モル％以上用いることが好ましく、８０モル％以上用いることがより好ましい。
In the vinylidene fluoride copolymer, when the total of all monomers used as raw materials is 100 mol%, vinylidene fluoride is preferably used in an amount of 50 mol% or more, more preferably 80 mol% or more.
バインダーの重量平均分子量の調整方法としては、公知の方法でよく、例えば、バインダーを製造する際の重合条件（温度や圧力等）を調整したり、架橋剤や連鎖移動剤等の添加剤を添加したりする方法等が挙げられる。また、バインダーの体積平均粒径の調整方法としては、公知の方法でよく、例えば、バインダーに相当する重合体のラテックスを破壊する方法や、重合処方の選択（乳化重合や懸濁重合等）と攪拌操作および分散安定剤の組み合わせによる制御等が挙げられる。ラテックスを破壊する方法としては、例えば、塩析凝集、酸析凝集、凍結融解等の方法等が挙げられる。
The weight average molecular weight of the binder may be adjusted by any known method, such as adjusting the polymerization conditions (temperature, pressure, etc.) when manufacturing the binder, or adding additives such as crosslinking agents and chain transfer agents. Examples include a method of doing so. In addition, the volume average particle diameter of the binder may be adjusted by any known method, such as a method of destroying the latex of a polymer corresponding to the binder, or a method of selecting a polymerization recipe (emulsion polymerization, suspension polymerization, etc.). Examples include control using a combination of stirring operation and dispersion stabilizer. Examples of methods for destroying latex include methods such as salting out aggregation, acid precipitation aggregation, and freezing and thawing.
正極合材層４２に含まれる正極活物質の含有量は、正極合材層４２の総質量に対して、例えば、９０質量％以上であることが好ましい。正極合材層４２に含まれる導電材の含有量は、正極合材層４２の総質量に対して、０．５質量％～５質量％の範囲であることが好ましい。
It is preferable that the content of the positive electrode active material contained in the positive electrode composite material layer 42 is, for example, 90% by mass or more with respect to the total mass of the positive electrode composite material layer 42. The content of the conductive material contained in the positive electrode composite material layer 42 is preferably in the range of 0.5% by mass to 5% by mass with respect to the total mass of the positive electrode composite material layer 42.
正極合材層４２に含まれるバインダーＡ及びＢの総含有量は、電池の高容量化と正極集電体４０と正極合材層４２との剥離強度の向上の両立を図る点で、正極合材層４２の総質量に対して、０．５質量％～５質量％の範囲であることが好ましく、０．５質量％～３質量％の範囲であることがより好ましい。
The total content of binders A and B contained in the positive electrode composite material layer 42 is determined from the viewpoint of achieving both a high capacity of the battery and an improvement in the peel strength between the positive electrode current collector 40 and the positive electrode composite material layer 42. It is preferably in the range of 0.5% by mass to 5% by mass, and more preferably in the range of 0.5% by mass to 3% by mass, based on the total mass of the material layer 42.
［負極］
負極１２は、負極集電体と、負極集電体上に設けられた負極合材層と、を有する。負極集電体は、例えば、銅などの負極の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等が用いられる。 [Negative electrode]
Thenegative electrode 12 includes a negative electrode current collector and a negative electrode composite material layer provided on the negative electrode current collector. As the negative electrode current collector, for example, a foil made of a metal such as copper that is stable in the potential range of the negative electrode, a film having the metal disposed on the surface layer, or the like is used.
負極１２は、負極集電体と、負極集電体上に設けられた負極合材層と、を有する。負極集電体は、例えば、銅などの負極の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等が用いられる。 [Negative electrode]
The
負極合材層は、負極活物質を含み、さらに、結着材や導電材等を含むことが好ましい。負極１２は、例えば、負極活物質、結着材等を含む負極合材スラリーを調製し、この負極合材スラリーを負極集電体上に塗布、乾燥して負極合材層を形成し、この負極合材層を圧延することにより作製できる。
It is preferable that the negative electrode composite material layer contains a negative electrode active material, and further contains a binder, a conductive material, and the like. For the negative electrode 12, for example, a negative electrode composite slurry containing a negative electrode active material, a binder, etc. is prepared, and this negative electrode composite slurry is applied onto a negative electrode current collector and dried to form a negative electrode composite material layer. It can be produced by rolling a negative electrode composite material layer.
負極活物質は、リチウムイオンを吸蔵・放出することが可能な材料であれば特に制限されるものではなく、例えば、金属リチウム、リチウム－アルミニウム合金、リチウム－鉛合金、リチウム－シリコン合金、リチウム－スズ合金等のリチウム合金、黒鉛、コークス、有機物焼成体等の炭素材料、ＳｎＯ２、ＳｎＯ、ＴｉＯ２等の金属酸化物等が挙げられる。これらは、１種単独でもよいし、２種以上を組み合わせて使用してもよい。
The negative electrode active material is not particularly limited as long as it is a material capable of intercalating and deintercalating lithium ions; for example, metal lithium, lithium-aluminum alloy, lithium-lead alloy, lithium-silicon alloy, lithium- Examples include lithium alloys such as tin alloys, carbon materials such as graphite, coke, and fired organic materials, and metal oxides such as SnO 2 , SnO, and TiO 2 . These may be used alone or in combination of two or more.
結着材や導電材は、例えば、正極１１の場合と同様の材料でよい。
The binding material and the conductive material may be the same materials as in the case of the positive electrode 11, for example.
［セパレータ］
セパレータ１３には、例えば、イオン透過性及び絶縁性を有する多孔性シート等が用いられる。多孔性シートの具体例としては、微多孔薄膜、織布、不織布等が挙げられる。セパレータの材質としては、ポリエチレン、ポリプロピレン等のオレフィン系樹脂、セルロースなどが好適である。セパレータ１３は、セルロース繊維層及びオレフィン系樹脂等の熱可塑性樹脂繊維層を有する積層体であってもよい。また、ポリエチレン層及びポリプロピレン層を含む多層セパレータであってもよく、セパレータの表面にアラミド系樹脂、セラミック等の材料が塗布されたものを用いてもよい。 [Separator]
For theseparator 13, for example, a porous sheet having ion permeability and insulation properties is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator include olefin resins such as polyethylene and polypropylene, cellulose, and the like. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. Alternatively, a multilayer separator including a polyethylene layer and a polypropylene layer may be used, or a separator whose surface is coated with a material such as aramid resin or ceramic may be used.
セパレータ１３には、例えば、イオン透過性及び絶縁性を有する多孔性シート等が用いられる。多孔性シートの具体例としては、微多孔薄膜、織布、不織布等が挙げられる。セパレータの材質としては、ポリエチレン、ポリプロピレン等のオレフィン系樹脂、セルロースなどが好適である。セパレータ１３は、セルロース繊維層及びオレフィン系樹脂等の熱可塑性樹脂繊維層を有する積層体であってもよい。また、ポリエチレン層及びポリプロピレン層を含む多層セパレータであってもよく、セパレータの表面にアラミド系樹脂、セラミック等の材料が塗布されたものを用いてもよい。 [Separator]
For the
以下、実施例により本開示をさらに説明するが、本開示はこれらの実施例に限定されるものではない。
Hereinafter, the present disclosure will be further explained with reference to Examples, but the present disclosure is not limited to these Examples.
＜実施例１＞
［正極の作製］
バインダーＡとして、重量平均分子量４７万、平均粒径１５８ｎｍのフッ化ビニリデン系共重合体を準備した。また、バインダーＢとして、重量平均分子量１１８万、平均粒径７１μｍのフッ化ビニリデン系共重合体を準備した。バインダーＡとバインダーＢとを、５：９５の質量比で混合し、混合バインダーを得た。そして、ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２で表されるリチウム複合酸化物と、混合バインダーと、導電材とを、９８．５：０．７：０．８質量比で混合した混合物に、Ｎ－メチル－２－ピロリドンを適量加えて撹拌することにより、正極合材スラリーを調製した。 <Example 1>
[Preparation of positive electrode]
As binder A, a vinylidene fluoride copolymer having a weight average molecular weight of 470,000 and an average particle size of 158 nm was prepared. Further, as binder B, a vinylidene fluoride copolymer having a weight average molecular weight of 1,180,000 and an average particle size of 71 μm was prepared. Binder A and binder B were mixed at a mass ratio of 5:95 to obtain a mixed binder. Then, a lithium composite oxide represented by LiNi 0.8 Co 0.15 Al 0.05 O 2 , a mixed binder, and a conductive material were mixed at a mass ratio of 98.5:0.7:0.8. A suitable amount of N-methyl-2-pyrrolidone was added to the mixture and stirred to prepare a positive electrode composite slurry.
［正極の作製］
バインダーＡとして、重量平均分子量４７万、平均粒径１５８ｎｍのフッ化ビニリデン系共重合体を準備した。また、バインダーＢとして、重量平均分子量１１８万、平均粒径７１μｍのフッ化ビニリデン系共重合体を準備した。バインダーＡとバインダーＢとを、５：９５の質量比で混合し、混合バインダーを得た。そして、ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２で表されるリチウム複合酸化物と、混合バインダーと、導電材とを、９８．５：０．７：０．８質量比で混合した混合物に、Ｎ－メチル－２－ピロリドンを適量加えて撹拌することにより、正極合材スラリーを調製した。 <Example 1>
[Preparation of positive electrode]
As binder A, a vinylidene fluoride copolymer having a weight average molecular weight of 470,000 and an average particle size of 158 nm was prepared. Further, as binder B, a vinylidene fluoride copolymer having a weight average molecular weight of 1,180,000 and an average particle size of 71 μm was prepared. Binder A and binder B were mixed at a mass ratio of 5:95 to obtain a mixed binder. Then, a lithium composite oxide represented by LiNi 0.8 Co 0.15 Al 0.05 O 2 , a mixed binder, and a conductive material were mixed at a mass ratio of 98.5:0.7:0.8. A suitable amount of N-methyl-2-pyrrolidone was added to the mixture and stirred to prepare a positive electrode composite slurry.
上記正極合材スラリーを厚さ１５μｍのアルミニウム箔の両面に塗布した後、乾燥して、塗膜を形成した。その後、圧延ローラにより塗膜を圧延することにより、正極集電体の両面に正極合材層が形成された正極を作製した。
The above positive electrode composite slurry was applied to both sides of a 15 μm thick aluminum foil and then dried to form a coating film. Thereafter, the coating film was rolled with a rolling roller to produce a positive electrode in which positive electrode mixture layers were formed on both sides of the positive electrode current collector.
［負極の作製］
黒鉛、ＣＭＣ、ＳＢＲの質量比が９８：１：１となるように混合し、当該混合物を水と共に混練して、負極合材スラリーを調製した。この負極合材スラリーを、厚さ８μｍの銅箔の両面に塗布し、塗膜を乾燥した後、圧延ローラにより圧延することにより、負極集電体の両面に負極合材層が形成された負極を作製した。 [Preparation of negative electrode]
Graphite, CMC, and SBR were mixed at a mass ratio of 98:1:1, and the mixture was kneaded with water to prepare a negative electrode composite slurry. This negative electrode composite material slurry was applied to both sides of a copper foil with a thickness of 8 μm, and after the coating film was dried, it was rolled with a rolling roller to form a negative electrode composite material layer on both sides of the negative electrode current collector. was created.
黒鉛、ＣＭＣ、ＳＢＲの質量比が９８：１：１となるように混合し、当該混合物を水と共に混練して、負極合材スラリーを調製した。この負極合材スラリーを、厚さ８μｍの銅箔の両面に塗布し、塗膜を乾燥した後、圧延ローラにより圧延することにより、負極集電体の両面に負極合材層が形成された負極を作製した。 [Preparation of negative electrode]
Graphite, CMC, and SBR were mixed at a mass ratio of 98:1:1, and the mixture was kneaded with water to prepare a negative electrode composite slurry. This negative electrode composite material slurry was applied to both sides of a copper foil with a thickness of 8 μm, and after the coating film was dried, it was rolled with a rolling roller to form a negative electrode composite material layer on both sides of the negative electrode current collector. was created.
［非水電解質の作製］
エチレンカーボネート（ＥＣ）と、メチルエチルカーボネート（ＭＥＣ）とからなる混合溶媒（体積比で、ＥＣ：ＭＥＣ＝１：３）に、ＬｉＰＦ６を１ｍｏｌ／Ｌの濃度で溶解した。これを非水電解質とした。 [Preparation of non-aqueous electrolyte]
LiPF 6 was dissolved at a concentration of 1 mol/L in a mixed solvent consisting of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (EC:MEC=1:3 by volume). This was used as a non-aqueous electrolyte.
エチレンカーボネート（ＥＣ）と、メチルエチルカーボネート（ＭＥＣ）とからなる混合溶媒（体積比で、ＥＣ：ＭＥＣ＝１：３）に、ＬｉＰＦ６を１ｍｏｌ／Ｌの濃度で溶解した。これを非水電解質とした。 [Preparation of non-aqueous electrolyte]
LiPF 6 was dissolved at a concentration of 1 mol/L in a mixed solvent consisting of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (EC:MEC=1:3 by volume). This was used as a non-aqueous electrolyte.
［非水電解質二次電池の作製］
（１）正極と負極との間に、セパレータ（ポリエチレンとポリプロピレンの複合フィルム）を介して巻回し、巻回型の電極体を作製した。正極と負極それぞれにリードを取り付けた。
（２）電極体をケース本体に挿入し、負極側のリードをケース本体の底に溶接し、正極側のリードを封口体に溶接した。
（３）ケース本体内に非水電解質を注入した後、ケース本体の開口端部を、ガスケットを介して封口体にかしめた。これを実施例１の非水電解質二次電池とした。 [Preparation of non-aqueous electrolyte secondary battery]
(1) A separator (a composite film of polyethylene and polypropylene) was interposed between the positive electrode and the negative electrode, and the electrode body was wound to produce a wound type electrode body. Leads were attached to each of the positive and negative electrodes.
(2) The electrode body was inserted into the case body, the negative lead was welded to the bottom of the case body, and the positive lead was welded to the sealing body.
(3) After injecting the non-aqueous electrolyte into the case body, the open end of the case body was caulked to the sealing body via the gasket. This was used as the non-aqueous electrolyte secondary battery of Example 1.
（１）正極と負極との間に、セパレータ（ポリエチレンとポリプロピレンの複合フィルム）を介して巻回し、巻回型の電極体を作製した。正極と負極それぞれにリードを取り付けた。
（２）電極体をケース本体に挿入し、負極側のリードをケース本体の底に溶接し、正極側のリードを封口体に溶接した。
（３）ケース本体内に非水電解質を注入した後、ケース本体の開口端部を、ガスケットを介して封口体にかしめた。これを実施例１の非水電解質二次電池とした。 [Preparation of non-aqueous electrolyte secondary battery]
(1) A separator (a composite film of polyethylene and polypropylene) was interposed between the positive electrode and the negative electrode, and the electrode body was wound to produce a wound type electrode body. Leads were attached to each of the positive and negative electrodes.
(2) The electrode body was inserted into the case body, the negative lead was welded to the bottom of the case body, and the positive lead was welded to the sealing body.
(3) After injecting the non-aqueous electrolyte into the case body, the open end of the case body was caulked to the sealing body via the gasket. This was used as the non-aqueous electrolyte secondary battery of Example 1.
＜実施例２＞
正極の作製において、バインダーＡとバインダーＢとを、２５：７５の質量比で混合した混合バインダーを用いたこと以外、実施例１と同様にして非水電解質二次電池を作製した。 <Example 2>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 25:75 was used in producing the positive electrode.
正極の作製において、バインダーＡとバインダーＢとを、２５：７５の質量比で混合した混合バインダーを用いたこと以外、実施例１と同様にして非水電解質二次電池を作製した。 <Example 2>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 25:75 was used in producing the positive electrode.
＜実施例３＞
正極の作製において、バインダーＡとバインダーＢとを、５０：５０の質量比で混合した混合バインダーを用いたこと以外、実施例１と同様にして非水電解質二次電池を作製した。 <Example 3>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 50:50 was used in producing the positive electrode.
正極の作製において、バインダーＡとバインダーＢとを、５０：５０の質量比で混合した混合バインダーを用いたこと以外、実施例１と同様にして非水電解質二次電池を作製した。 <Example 3>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 50:50 was used in producing the positive electrode.
＜実施例４＞
正極の作製において、バインダーＡとバインダーＢとを、７５：２５の質量比で混合した混合バインダーを用いたこと以外、実施例１と同様にして非水電解質二次電池を作製した。 <Example 4>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 75:25 was used in producing the positive electrode.
正極の作製において、バインダーＡとバインダーＢとを、７５：２５の質量比で混合した混合バインダーを用いたこと以外、実施例１と同様にして非水電解質二次電池を作製した。 <Example 4>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed binder in which binder A and binder B were mixed at a mass ratio of 75:25 was used in producing the positive electrode.
＜比較例１＞
正極の作製において、混合バインダーを使用せず、バインダーＢのみを使用したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 1>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only binder B was used without using a mixed binder in producing the positive electrode.
正極の作製において、混合バインダーを使用せず、バインダーＢのみを使用したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 1>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only binder B was used without using a mixed binder in producing the positive electrode.
＜比較例２＞
正極の作製において、混合バインダーを使用せず、バインダーＡのみを使用したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 2>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only binder A was used without using a mixed binder in producing the positive electrode.
正極の作製において、混合バインダーを使用せず、バインダーＡのみを使用したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 2>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only binder A was used without using a mixed binder in producing the positive electrode.
＜比較例３＞
正極の作製において、混合バインダーを使用せず、バインダーＢのみを使用したこと、また、リチウム複合酸化物と、バインダーＢと、導電材とを、９８．３：０．９：０．８の質量比で混合したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 3>
In producing the positive electrode, only binder B was used without using a mixed binder, and the lithium composite oxide, binder B, and conductive material were mixed in a mass ratio of 98.3:0.9:0.8. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the components were mixed at the same ratio.
正極の作製において、混合バインダーを使用せず、バインダーＢのみを使用したこと、また、リチウム複合酸化物と、バインダーＢと、導電材とを、９８．３：０．９：０．８の質量比で混合したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 3>
In producing the positive electrode, only binder B was used without using a mixed binder, and the lithium composite oxide, binder B, and conductive material were mixed in a mass ratio of 98.3:0.9:0.8. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the components were mixed at the same ratio.
＜比較例４＞
正極の作製において、混合バインダーを使用せず、バインダーＡのみを使用したこと、また、リチウム複合酸化物と、バインダーＡと、導電材とを、９８．３：０．９：０．８の質量比で混合したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 4>
In producing the positive electrode, only binder A was used without using a mixed binder, and the lithium composite oxide, binder A, and conductive material were mixed in a mass ratio of 98.3:0.9:0.8. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the components were mixed at the same ratio.
正極の作製において、混合バインダーを使用せず、バインダーＡのみを使用したこと、また、リチウム複合酸化物と、バインダーＡと、導電材とを、９８．３：０．９：０．８の質量比で混合したこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Comparative example 4>
In producing the positive electrode, only binder A was used without using a mixed binder, and the lithium composite oxide, binder A, and conductive material were mixed in a mass ratio of 98.3:0.9:0.8. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the components were mixed at the same ratio.
［剥離強度］
テンシロン（オリエンテック社製、ＳＴＡ－１１５０）を用いて、各実施例及び各比較例の正極面に対し、９０°方向に正極集電体（アルミニウム箔）を引きはがすことで、正極合材層と正極集電体の剥離強度を測定した。剥離強度は、各実施例及び各比較例において５回測定を行い、その平均を剥離強度とした。 [Peel strength]
Using Tensilon (manufactured by Orientec, STA-1150), the positive electrode current collector (aluminum foil) was peeled off in a 90° direction from the positive electrode surface of each example and each comparative example, and the positive electrode composite material layer was removed. The peel strength of the positive electrode current collector was measured. The peel strength was measured five times in each Example and each Comparative Example, and the average thereof was taken as the peel strength.
テンシロン（オリエンテック社製、ＳＴＡ－１１５０）を用いて、各実施例及び各比較例の正極面に対し、９０°方向に正極集電体（アルミニウム箔）を引きはがすことで、正極合材層と正極集電体の剥離強度を測定した。剥離強度は、各実施例及び各比較例において５回測定を行い、その平均を剥離強度とした。 [Peel strength]
Using Tensilon (manufactured by Orientec, STA-1150), the positive electrode current collector (aluminum foil) was peeled off in a 90° direction from the positive electrode surface of each example and each comparative example, and the positive electrode composite material layer was removed. The peel strength of the positive electrode current collector was measured. The peel strength was measured five times in each Example and each Comparative Example, and the average thereof was taken as the peel strength.
［電池容量］
環境温度２５℃の下、各実施例及び各比較例の非水電解質二次電池を、１Ｃで、４．２Ｖまで定電流充電した後、４．２Ｖで、１／５０Ｃになるまで定電圧充電した。その後、０．５Ｃで、２．５Ｖまで定電流放電した。この時の放電容量を測定し、電池容量とした。 [Battery capacity]
At an environmental temperature of 25° C., the non-aqueous electrolyte secondary batteries of each example and each comparative example were charged at a constant current of 1 C to 4.2 V, and then charged at a constant voltage of 4.2 V to 1/50 C. did. Thereafter, constant current discharge was performed at 0.5C to 2.5V. The discharge capacity at this time was measured and defined as the battery capacity.
環境温度２５℃の下、各実施例及び各比較例の非水電解質二次電池を、１Ｃで、４．２Ｖまで定電流充電した後、４．２Ｖで、１／５０Ｃになるまで定電圧充電した。その後、０．５Ｃで、２．５Ｖまで定電流放電した。この時の放電容量を測定し、電池容量とした。 [Battery capacity]
At an environmental temperature of 25° C., the non-aqueous electrolyte secondary batteries of each example and each comparative example were charged at a constant current of 1 C to 4.2 V, and then charged at a constant voltage of 4.2 V to 1/50 C. did. Thereafter, constant current discharge was performed at 0.5C to 2.5V. The discharge capacity at this time was measured and defined as the battery capacity.
表１に、各実施例及び各比較例の剥離強度及び電池容量の結果をまとめた。各結果は、比較例１の結果を基準値（１００）として、他の実施例及び比較例を相対値として示した。
Table 1 summarizes the peel strength and battery capacity results of each Example and each Comparative Example. Each result is shown as a reference value (100) for Comparative Example 1, and relative values for other Examples and Comparative Examples.
表１に示すように、実施例１～４はいずれも、比較例１～２より、高い剥離強度を示した。比較例３及び４では、正極合材層中のバインダーの含有量を実施例より上げることで、実施例と同等レベルの剥離強度が得られたが、バインダーの含有量が増えた分だけ、正極活物質の含有量が減ったため、実施例より電池容量が低下した。このように、実施例によれば、少ないバインダー量で、正極合材層と正極集電体の剥離強度を高めることができるため、電池容量の低下も抑制できる。
As shown in Table 1, Examples 1 to 4 all showed higher peel strength than Comparative Examples 1 to 2. In Comparative Examples 3 and 4, the peel strength of the positive electrode was increased by increasing the binder content in the positive electrode composite layer compared to the Example, but the peel strength of the positive electrode was increased by the increased binder content. Since the content of the active material was reduced, the battery capacity was lower than in the example. As described above, according to the example, the peel strength between the positive electrode composite material layer and the positive electrode current collector can be increased with a small amount of binder, so that the decrease in battery capacity can also be suppressed.
［付記］
（１）
正極集電体と、前記正極集電体上に設けられ、正極活物質及びバインダーを含む正極合材層とを備え、
前記バインダーは、重量平均分子量が４０万～８０万の範囲であり、平均粒径（Ｄ５０）が５０ｎｍ～５００ｎｍの範囲であるバインダーＡと、重量平均分子量が１００万～１５０万の範囲であり、平均粒径（Ｄ５０）が５０μｍ～５００μｍの範囲であるバインダーＢとを含む、非水電解質二次電池用正極。
（２）
前記バインダーＡと前記バインダーＢとの割合は、質量比で、５：９５～５０：５０の範囲である、上記（１）に記載の非水電解質二次電池用正極。
（３）
前記バインダーＢは、ポリフッ化ビニリデン、ポリフッ化ビニリデンの誘導体、又は、フッ化ビニリデンを含む共重合体である、上記（１）又は（２）に記載の非水電解質二次電池用正極。
（４）
前記バインダーＡは、ポリフッ化ビニリデン、ポリフッ化ビニリデンの誘導体、又は、フッ化ビニリデンを含む共重合体である、フッ化ビニリデン共重合体である、上記（１）～（３）のいずれか１つに記載の非水電解質二次電池用正極。
（５）
上記（１）～（４）のいずれか１つに記載の非水電解質二次電池用正極を備える非水電解質二次電池。 [Additional notes]
(1)
comprising a positive electrode current collector and a positive electrode composite layer provided on the positive electrode current collector and containing a positive electrode active material and a binder,
The binder has a weight average molecular weight in the range of 400,000 to 800,000, binder A has an average particle diameter (D50) in the range of 50 to 500 nm, and a weight average molecular weight in the range of 1 million to 1.5 million, A positive electrode for a non-aqueous electrolyte secondary battery, comprising a binder B having an average particle size (D50) in the range of 50 μm to 500 μm.
(2)
The positive electrode for a non-aqueous electrolyte secondary battery according to (1) above, wherein the ratio of the binder A to the binder B is in the range of 5:95 to 50:50 in terms of mass ratio.
(3)
The positive electrode for a nonaqueous electrolyte secondary battery according to (1) or (2) above, wherein the binder B is polyvinylidene fluoride, a derivative of polyvinylidene fluoride, or a copolymer containing vinylidene fluoride.
(4)
The binder A is any one of (1) to (3) above, which is a polyvinylidene fluoride, a derivative of polyvinylidene fluoride, or a vinylidene fluoride copolymer, which is a copolymer containing vinylidene fluoride. A positive electrode for a non-aqueous electrolyte secondary battery as described in .
(5)
A non-aqueous electrolyte secondary battery comprising the positive electrode for a non-aqueous electrolyte secondary battery according to any one of (1) to (4) above.
（１）
正極集電体と、前記正極集電体上に設けられ、正極活物質及びバインダーを含む正極合材層とを備え、
前記バインダーは、重量平均分子量が４０万～８０万の範囲であり、平均粒径（Ｄ５０）が５０ｎｍ～５００ｎｍの範囲であるバインダーＡと、重量平均分子量が１００万～１５０万の範囲であり、平均粒径（Ｄ５０）が５０μｍ～５００μｍの範囲であるバインダーＢとを含む、非水電解質二次電池用正極。
（２）
前記バインダーＡと前記バインダーＢとの割合は、質量比で、５：９５～５０：５０の範囲である、上記（１）に記載の非水電解質二次電池用正極。
（３）
前記バインダーＢは、ポリフッ化ビニリデン、ポリフッ化ビニリデンの誘導体、又は、フッ化ビニリデンを含む共重合体である、上記（１）又は（２）に記載の非水電解質二次電池用正極。
（４）
前記バインダーＡは、ポリフッ化ビニリデン、ポリフッ化ビニリデンの誘導体、又は、フッ化ビニリデンを含む共重合体である、フッ化ビニリデン共重合体である、上記（１）～（３）のいずれか１つに記載の非水電解質二次電池用正極。
（５）
上記（１）～（４）のいずれか１つに記載の非水電解質二次電池用正極を備える非水電解質二次電池。 [Additional notes]
(1)
comprising a positive electrode current collector and a positive electrode composite layer provided on the positive electrode current collector and containing a positive electrode active material and a binder,
The binder has a weight average molecular weight in the range of 400,000 to 800,000, binder A has an average particle diameter (D50) in the range of 50 to 500 nm, and a weight average molecular weight in the range of 1 million to 1.5 million, A positive electrode for a non-aqueous electrolyte secondary battery, comprising a binder B having an average particle size (D50) in the range of 50 μm to 500 μm.
(2)
The positive electrode for a non-aqueous electrolyte secondary battery according to (1) above, wherein the ratio of the binder A to the binder B is in the range of 5:95 to 50:50 in terms of mass ratio.
(3)
The positive electrode for a nonaqueous electrolyte secondary battery according to (1) or (2) above, wherein the binder B is polyvinylidene fluoride, a derivative of polyvinylidene fluoride, or a copolymer containing vinylidene fluoride.
(4)
The binder A is any one of (1) to (3) above, which is a polyvinylidene fluoride, a derivative of polyvinylidene fluoride, or a vinylidene fluoride copolymer, which is a copolymer containing vinylidene fluoride. A positive electrode for a non-aqueous electrolyte secondary battery as described in .
(5)
A non-aqueous electrolyte secondary battery comprising the positive electrode for a non-aqueous electrolyte secondary battery according to any one of (1) to (4) above.
１０ 二次電池、１１ 正極、１２ 負極、１３ セパレータ、１４ 電極体、１５ 電池ケース、１６ ケース本体、１７ 封口体、１８，１９ 絶縁板、２０ 正極リード、２１ 負極リード、２２ 張り出し部、２３ フィルタ、２４ 下弁体、２５ 絶縁部材、２６ 上弁体、２７ キャップ、２８ ガスケット、４０ 正極集電体、４２ 正極合材層。
10 Secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Battery case, 16 Case body, 17 Sealing body, 18, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Overhang, 23 Filter , 24 lower valve body, 25 insulating member, 26 upper valve body, 27 cap, 28 gasket, 40 positive electrode current collector, 42 positive electrode composite material layer.
Claims (5)
- 正極集電体と、前記正極集電体上に設けられ、正極活物質及びバインダーを含む正極合材層とを備え、
前記バインダーは、重量平均分子量が４０万～８０万の範囲であり、平均粒径（Ｄ５０）が５０ｎｍ～５００ｎｍの範囲であるバインダーＡと、重量平均分子量が１００万～１５０万の範囲であり、平均粒径（Ｄ５０）が５０μｍ～５００μｍの範囲であるバインダーＢとを含む、非水電解質二次電池用正極。 comprising a positive electrode current collector and a positive electrode composite layer provided on the positive electrode current collector and containing a positive electrode active material and a binder,
The binder has a weight average molecular weight in the range of 400,000 to 800,000, binder A has an average particle diameter (D50) in the range of 50 to 500 nm, and a weight average molecular weight in the range of 1 million to 1.5 million, A positive electrode for a non-aqueous electrolyte secondary battery, comprising a binder B having an average particle size (D50) in the range of 50 μm to 500 μm. - 前記バインダーＡと前記バインダーＢとの割合は、質量比で、５：９５～５０：５０の範囲である、請求項１に記載の非水電解質二次電池用正極。 The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the ratio of the binder A to the binder B is in the range of 5:95 to 50:50 in terms of mass ratio.
- 前記バインダーＢは、ポリフッ化ビニリデン、ポリフッ化ビニリデンの誘導体、又は、フッ化ビニリデンを含む共重合体である、請求項１又は２に記載の非水電解質二次電池用正極。 The positive electrode for a nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the binder B is polyvinylidene fluoride, a derivative of polyvinylidene fluoride, or a copolymer containing vinylidene fluoride.
- 前記バインダーＡは、ポリフッ化ビニリデン、ポリフッ化ビニリデンの誘導体、又は、フッ化ビニリデンを含む共重合体である、請求項１又は２に記載の非水電解質二次電池用正極。 The positive electrode for a nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the binder A is polyvinylidene fluoride, a derivative of polyvinylidene fluoride, or a copolymer containing vinylidene fluoride.
- 請求項１又は２に記載の非水電解質二次電池用正極を備える非水電解質二次電池。 A non-aqueous electrolyte secondary battery comprising the positive electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012033381A (en) * | 2010-07-30 | 2012-02-16 | Panasonic Corp | Nonaqueous electrolyte secondary battery and manufacturing method thereof |
| JP2015103464A (en) * | 2013-11-27 | 2015-06-04 | 株式会社クレハ | Vinylidene fluoride-based polymer aqueous composition and its use |
| JP2020035746A (en) * | 2018-08-28 | 2020-03-05 | 三星電子株式会社Samsung Electronics Co., Ltd. | Positive electrode and lithium battery including positive electrode |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012033381A (en) * | 2010-07-30 | 2012-02-16 | Panasonic Corp | Nonaqueous electrolyte secondary battery and manufacturing method thereof |
| JP2015103464A (en) * | 2013-11-27 | 2015-06-04 | 株式会社クレハ | Vinylidene fluoride-based polymer aqueous composition and its use |
| JP2020035746A (en) * | 2018-08-28 | 2020-03-05 | 三星電子株式会社Samsung Electronics Co., Ltd. | Positive electrode and lithium battery including positive electrode |
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