Electrode film raw material, electrodes, electrode laminates, electrochemical devices and equipment

Abstract

To provide a new electrode film original fabric used as a material of an electrode, an electrode using the electrode film original fabric as a material, an electrode laminate, an electrochemical device and an instrument.SOLUTION: There is provided an electrode film original fabric which includes a mixture containing an active material and a binder and satisfies the following conditions (1)-(3). (1) The breaking strength obtained by the following measurement method is equal to or greater than 0.2 MPa. (The measurement method) The strength of 75% of the maximum stress is set to the breaking strength when a testing piece obtained by cutting an electrode film original fabric into the size of 15 mm of the width and 50 mm of the length is measured under such a condition that an inter-chuck distance is 30 mm and a tensile speed is 100 mm / min. (2) The active material includes lithium iron phosphate and the binder includes styrene-butadiene rubber and polyvinylidene fluoride. (3) The binder includes 0.75 mass% or more and 2.95 mass% or less of the styrene-butadiene rubber and 0.25 mass% or more and 5.25 mass% or less of the polyvinylidene fluoride with respect to the entire mixture.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrode film substrate, an electrode, an electrode laminate, an electrochemical device, and an apparatus. [Background technology]

[0002] In recent years, secondary batteries have become increasingly important as power sources. Research and development of secondary batteries is being actively conducted, from small ones used as power sources for portable electronic devices to medium and large ones used in electric vehicles and home storage batteries.

[0003] A secondary battery has a pair of electrodes containing active materials and an electrolyte disposed between the electrodes. The pair of electrodes includes a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material. A known configuration of these electrodes is one in which an active material layer containing a positive electrode active material or a negative electrode active material is stacked on a current collector with excellent conductivity.

[0004] The active material layer is formed by dispersing a powdered active material and a binder in a solvent to prepare a slurry mixture, applying the mixture to a current collector, and pressing the mixture. The laminate of the active material layer and the current collector is cut into a desired battery shape and used as an electrode (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-169444 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, the production of an electrode requires multiple steps, such as preparation of a mixture, coating of the mixture, drying, pressing, etc. There is room for improvement in terms of materials in order to simplify the manufacturing process of a secondary battery and reduce the manufacturing cost.

[0007] Similar problems may arise not only in secondary batteries but also in other electrochemical elements such as capacitors.

[0008] In recent years, with the increasing size and general use of secondary batteries, inexpensive electrode materials are in demand. Among known positive electrode active materials, lithium iron phosphate (LFP) is known as a relatively inexpensive material. Unlike other known positive electrode active materials such as lithium cobalt oxide, LFP does not contain rare earth elements and is based on iron. Therefore, it has the advantage of being inexpensive and unlikely to run out.

[0009] However, LFP is known to have poor electrical conductivity. Therefore, when using LFP as a positive electrode active material, it is often necessary to coat the surface of the LFP particles with carbon or use a conductive filler in combination, which negates the advantage of low cost and makes it a difficult material to use.

[0010] The present invention has been made in view of the above circumstances, and has an object to provide a novel electrode film raw material to be used as a material for electrodes, and a further object to provide electrodes, electrode laminates, electrochemical devices, and equipment that use such an electrode film raw material as a material. [Means for solving the problem]

[0011] The inventors believed that if they could realize a material with properties that allow it to be used as an electrode without a current collector, it would be possible to eliminate the above-mentioned processes of preparing the mixture and applying the mixture to the current collector. Furthermore, by forming the material into a film, it would be possible to easily manufacture electrochemical devices by cutting the film (raw electrode film) and attaching it to a battery element. Furthermore, they believed that by using inexpensive LFP as the active material, they could provide a material that would enable inexpensive manufacture of electrochemical devices.

[0012] The present inventors have conducted extensive research in light of the above-mentioned points and have completed the present invention. In order to solve the above-mentioned problems, one aspect of the present invention includes the following aspects.

[0013] [1] An electrode film raw sheet made of a mixture containing an active material and a binder, which satisfies the following (1) to (3): (1) The breaking strength measured by the following method is 0.2 MPa or more. (Measurement method) The electrode film raw material was cut into a size of 15 mm in width and 50 mm in length to obtain a test piece, and the strength at 75% of the maximum stress when measured under conditions of a chuck distance of 30 mm and a pulling speed of 100 mm / min was taken as the breaking strength. (2) The active material includes lithium iron phosphate, and the binder includes styrene butadiene rubber and polyvinylidene fluoride. (3) The binder contains the styrene-butadiene rubber in an amount of 0.75% by mass or more and 2.95% by mass or less and the polyvinylidene fluoride in an amount of 0.25% by mass or more and 5.25% by mass or less, based on the total mass of the mixture.

[0014] [2] An electrode film raw material having an active material layer made of a mixture containing an active material and a binder, no current collector, and satisfying the following (1) to (3): (1) The breaking strength measured by the following method is 0.2 MPa or more. (Measurement method) The electrode film raw material was cut into a size of 15 mm in width and 50 mm in length to obtain a test piece, and the strength at 75% of the maximum stress when measured under conditions of a chuck distance of 30 mm and a pulling speed of 100 mm / min was taken as the breaking strength. (2) The active material includes lithium iron phosphate, and the binder includes styrene butadiene rubber and polyvinylidene fluoride. (3) The binder contains the styrene-butadiene rubber in an amount of 0.75% by mass or more and 2.95% by mass or less and the polyvinylidene fluoride in an amount of 0.25% by mass or more and 5.25% by mass or less, based on the total mass of the mixture.

[0015] [3] The electrode film substrate according to [1] or [2], wherein the active material is lithium iron phosphate and the binder is made of styrene-butadiene rubber and polyvinylidene fluoride.

[0016] [4] The electrode film substrate according to any one of [1] to [3], on which a release film is laminated.

[0017] [5] An electrode made from the electrode film substrate described in any one of [1] to [4].

[0018] [6] An electrode laminate comprising the electrode according to [5] and a separator or a solid electrolyte membrane laminated together.

[0019] [7] An electrochemical device having the electrode laminate according to [6].

[0020] [8] An apparatus having the electrochemical device according to [7]. [Effects of the Invention]

[0021] The present invention can provide a novel electrode film raw sheet used as a material for electrodes, and can also provide electrodes, electrode laminates, electrochemical devices, and equipment that use such an electrode film raw sheet as a material. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram showing an electrode film raw sheet 1 of this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the electrode film raw material 2 of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] [Electrode film roll, electrodes] FIG. 1 is a schematic diagram showing an electrode film raw sheet 1 of this embodiment.

[0024] The term "raw electrode film" refers to a film-like molded product before being processed into an electrode. Typically, the raw electrode film is a long, strip-shaped molded product, or a sheet-shaped molded product obtained by processing such a strip-shaped molded product into sheets.

[0025] 1 is sandwiched on both sides by release films 10. As the release film 10, a known material such as a PET film that has been subjected to a release treatment can be used.

[0026] The electrode film raw sheet 1 is made of a mixture containing an active material and a binder, and does not have a current collector.

[0027] The electrode film raw sheet 1 has the characteristic functions of (a) being self-standing and (b) being usable as an electrode.

[0028] (a) Become independent The electrode film raw roll 1 can be processed into an electrode by cutting it into a desired shape. The electrode film raw roll 1 can also be used as an electrode as is. The resulting electrode can maintain the cut shape without any accessories such as a substrate. In this specification, having such properties is sometimes referred to as "self-supporting" or "self-standing." In other words, the electrode film raw roll 1 has enough rigidity to exist without support.

[0029] (b) Can be used as an electrode By cutting the electrode film raw sheet 1 into a desired shape, it can be used as an electrode for electrochemical devices such as secondary batteries and capacitors. That is, the electrode film raw sheet 1 has low electronic resistance and high ionic conductivity that enable it to be used as an electrode.

[0030] The electrode obtained by cutting the electrode film raw material 1 having the functions (a) and (b) is self-supporting (a free-standing electrode) and can be used as an electrode for an electrochemical device such as a secondary battery or a capacitor simply by attaching it to a component of the electrochemical device.

[0031] Each component of the electrode film raw sheet 1 will be described below in order.

[0032] (active material) The electrode film raw material 1 contains lithium iron phosphate (LiFePO4, hereinafter sometimes abbreviated as "LFP") with an olivine crystal structure as its active material. Because LFP contains iron as its main raw material, it has the advantage of being able to be produced more cheaply than other positive electrode active materials that contain rare metals. Furthermore, LFP is known to be highly safe because the strong bond between phosphorus and oxygen atoms in the crystals makes it resistant to breakdown of its crystalline structure during use or in high-temperature environments.

[0033] The active material of the electrode film raw sheet 1 may contain lithium manganese iron phosphate (LMFP), in which part of the iron in LFP is replaced with Mn. LMFP has an olivine crystal structure, similar to LFP.

[0034] The active material contained in the electrode film raw sheet 1 contains LFP in an amount of more than 50 mass % of the total active material, preferably 80 mass % or more, and more preferably 100 mass %.

[0035] The active material of the electrode film raw sheet 1 may include a known positive electrode active material other than LFP. Examples of such positive electrode active materials include at least one selected from composite oxides of lithium and transition metals such as cobalt, manganese, and nickel, and polymers with Li storage capacity. The positive electrode active material of a lithium-ion secondary battery may be any compound capable of reversibly doping and dedoping lithium ions.

[0036] For example, positive electrode active materials that can be used in combination with LFP include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO4), and Ni-Mn-Co ternary (NMC) active materials (LiNi x Mn y Co z O2), Ni-Co-Al ternary system (NCA system) active material (LiNi x Co y Al z O2) and the like.

[0037] The active material has a volume average particle size of 0.1 to 100 μm.

[0038] (binder) The binder is a material used to bind particles of the active material, etc., and is, for example, a resin. As the binder, known thermoplastic resins used for the above-mentioned purposes as electrode materials can be used.

[0039] In addition to the above-mentioned "binding of particles of active material and the like," the functions of the binder include (i) imparting high strength to the electrode film raw material, (ii) adjusting electrical resistance (reducing resistance), and (iii) adjusting other physical properties. Binders that particularly strongly possess function (i) will be described as "high-strength binders," binders that particularly strongly possess function (ii) as "resistance-adjusting binders," and binders that particularly strongly possess function (iii) as "other binders."

[0040] (i) High-strength binder An elastomer can be used as the high-strength binder. A binder with elastomeric properties can impart flexibility and strength to the electrode, and can suppress breakage due to volumetric changes of the active material during use of the electrode.

[0041] A high-strength binder desirably has a tensile strength of 5 MPa or more. Furthermore, the high-strength binder is required to be stable to the electrolyte inside the electrochemical element (battery, capacitor) and is also required to be electrochemically stable.

[0042] For example, when a lithium-ion battery is used as the electrochemical element and an electrode obtained by cutting the electrode film roll 1 is used, the high-strength binder is required not to leach out from the electrode into the electrolyte filled in the battery. In addition, the high-strength binder is required not to undergo oxidative decomposition at 3 to 5 V (vs. Li / Li+).

[0043] The tensile strength of the high-strength binder is a value measured by the breaking strength measuring method described below.

[0044] In this embodiment, a styrene-butadiene copolymer (SBR) is used as the high-strength binder.

[0045] Furthermore, the binder may contain, as a high-strength binder, the following copolymer containing styrene and a conjugated diene, in addition to SBR. Styrene-isoprene copolymer Styrene-butadiene-methyl methacrylate copolymer (MBS) Acrylonitrile-styrene-butadiene copolymer (ABS) Acrylonitrile-styrene-butadiene-methyl methacrylate copolymer (MABS) Carboxy-modified styrene butadiene rubber Styrene-butadiene-styrene block copolymer (SBS) Styrene-isoprene-styrene block copolymer (SIS) Styrene-isoprene-butadiene-styrene block copolymer (SIBS)

[0046] The above copolymers, excluding SBR, may be copolymerized with other copolymerizable vinyl monomers.

[0047] Vinyl monomers include: Acrylate monomers such as alkyl acrylate Methacrylate monomers such as alkyl methacrylate Acrylamide monomers such as alkoxyacrylamides Methacrylamide monomers such as alkoxymethacrylamides Carboxylic acid monomers such as acrylic acid Nitrile monomers such as acrylonitrile Vinyl ester monomers such as vinyl acetate Vinyl chloride and other vinyl halide monomers Polyfunctional monomers such as allyl acrylate Examples include:

[0048] One or more of these vinyl monomers may be copolymerized in the copolymer.

[0049] ((ii) Resistance adjusting binder) In this embodiment, polyvinylidene fluoride (PVdF) is used as the resistance adjusting binder.

[0050] Furthermore, the binder may contain, as a resistance adjusting binder, an acrylate binder or a polyimide binder in addition to PVdF. The resistance adjusting binder is required not to undergo oxidative decomposition at 3 to 5 V (vs. Li / Li+).

[0051] (i) High-strength binders are considered to be electrochemically inactive, and if the active material is completely covered with (i) high-strength binders, the electrochemical reaction of the active material will not occur and the resistance of the electrode will increase. In contrast, by using the above-mentioned (ii) resistance-adjusting binders in combination, the increase in resistance caused by covering the active material with (i) high-strength binders can be suppressed.

[0052] ((iii) Other binders (adhesive binders) Resin materials with reactive functional groups or anchoring effects can be used as adhesive binders. Examples of reactive functional groups include hydroxyl groups (-OH) and carboxyl groups (-COOH). If the electrode film raw roll contains such a binder, the reactive functional groups will react at the bonding surface when the electrode obtained from the electrode film raw roll is bonded to another component, which is expected to increase the adhesive strength.

[0053] Furthermore, by including an adhesive binder in the electrode film raw sheet, a free-standing electrode manufactured from the electrode film raw sheet can be easily adhered to other members.

[0054] It is desirable that the adhesive binder be electrochemically stable and maintain adhesiveness even when exposed to other members, particularly the electrolyte.

[0055] For example, when a lithium ion battery is employed as the electrochemical element and an electrode obtained by cutting the electrode film roll 1 is used, the adhesive binder is required to not dissolve from the electrode into the electrolyte solution filled in the battery, and to have reactive functional groups that are not easily deactivated even when exposed to the electrolyte solution.

[0056] In addition, the adhesive binder is required not to undergo oxidative decomposition at 3 to 5 V (vs. Li / Li+).

[0057] Such binders include at least one selected from the group consisting of carboxymethyl cellulose (CMC) binders, polyacrylic acid (PAA) binders, vinyl alcohol binders, and epoxy binders.

[0058] Polyisobutylene (PIB) can also be used as the adhesive binder.

[0059] The mixture constituting the electrode film raw sheet may contain, in addition to the above-mentioned active material and binder, additives such as conductive materials as necessary to adjust physical properties. Examples of conductive materials include at least one selected from carbon black such as acetylene black, carbon fiber, activated carbon, metal powder, conductive polymers, etc. The conductive material does not need to be as active as the active material, and may be any material that improves conductivity inside the electrode.

[0060] The mixture constituting the electrode film raw sheet may also contain carbon nanotubes (CNTs). Improved breaking strength and improved electrical conductivity can be expected from the electrode film raw sheet to which CNTs are added.

[0061] The thickness of the electrode film raw sheet is preferably 1 μm or more and 1000 μm or less.

[0062] The electrode film raw sheet made of the mixture of the above materials satisfies the following requirements (1) to (3) in order to exhibit the above functions (a) and (b).

[0063] (Requirement (1)) As described above, the electrode film raw sheet 1 has the characteristic of “(a) being self-standing.” The electrode film raw sheet 1 having such rigidity has a breaking strength of 0.2 MPa or more as determined by the following measurement method.

[0064] (Method for measuring breaking strength) The electrode film raw material is cut into a test piece having a width of 15 mm and a length of 50 mm, and the strength at 75% of the maximum stress when measured under conditions of a chuck distance of 30 mm and a pulling speed of 100 mm / min is defined as the breaking strength.

[0065] The magnitude of the tensile force (N) when the test piece breaks is taken as the maximum stress, and the stress at 75% of the maximum stress is calculated. The 75% stress (N) is multiplied by the cross-sectional area (mm 2 ) divided by (N / mm 2 = MPa) is calculated as the breaking strength.

[0066] The measurement is carried out five times, and the arithmetic mean value of the five measurements is used as the breaking strength.

[0067] When the electrode film raw sheet has such breaking strength, the electrodes cut from the electrode film raw sheet can be made to stand on their own. Making the electrodes stand on their own makes it easier to handle the electrodes in the subsequent assembly process.

[0068] The breaking strength is preferably 0.1 MPa or more, more preferably 0.2 MPa or more. Although a higher breaking strength is preferable because it is less likely to break, it is sufficient that the breaking strength is 10 MPa or less, and may be 5 MPa or less.

[0069] (Requirements (2)(3)) As described above, the electrode film raw sheet 1 has the characteristic of being “(b) usable as an electrode.” The electrode film raw sheet 1 having such properties satisfies the following requirements (2) and (3). Requirement (2): The active material contains lithium iron phosphate, and the binder contains styrene-butadiene rubber and polyvinylidene fluoride. Requirement (3): The binder contains 0.75% by mass or more and 2.95% by mass or less of styrene-butadiene rubber and 0.25% by mass or more and 5.25% by mass or less of polyvinylidene fluoride relative to the entire mixture.

[0070] The binder may include any of the various binders described above, provided that the binder satisfies requirement (3).

[0071] In the electrode film raw sheet described above, the mixture constituting the electrode film raw sheet preferably contains 85% by mass to 97% by mass of active material and 3% by mass to 15% by mass of binder relative to the entire mixture.

[0072] When the mixture contains an additive such as a conductive material, the mixture may contain the additive in a proportion determined by preliminary experiments based on the function of the additive. For example, when the mixture contains a conductive material as an additive, the mixture may contain 85% by mass to 97% by mass of active material, 1% by mass to 10% by mass of binder, and 2% by mass to 5% by mass of conductive material, based on the total mixture.

[0073] [Manufacturing method of electrode film raw material] The electrode film raw sheet can be produced by applying a slurry (paint) prepared by dissolving or dispersing the above-mentioned mixture in a solvent onto a support, and then removing the solvent.

[0074] The solvent to be used is one that can dissolve at least the binder, and examples of the solvent include hydrocarbon solvents, alcohol solvents, ether solvents, ketone solvents, ester solvents, amide solvents, halogen solvents, sulfur solvents, and inorganic solvents.

[0075] Examples of hydrocarbon solvents include heptane, cyclohexane, toluene, and xylene.

[0076] Examples of the alcohol solvent include methanol and ethanol.

[0077] Examples of the ether solvent include tetrahydrofuran and dioxane.

[0078] Examples of the ketone solvent include acetone and methyl ethyl ketone.

[0079] Examples of the ester solvent include ethyl acetate and ethyl lactate.

[0080] Examples of the amide solvent include dimethylformamide and N-methyl-2-pyrrolidone.

[0081] Examples of halogen-based solvents include chloroform and dichloromethane.

[0082] Examples of sulfur-based solvents include dimethyl sulfoxide and sulfolane.

[0083] An example of the inorganic solvent is water.

[0084] The above solvents may be used alone or in the form of a mixed solvent of two or more kinds.

[0085] The method for preparing the coating material is not particularly limited, but may be such that the active material, binder, optional additives, etc. are mixed with a solvent one by one or two or more at the same time, and dissolved or dispersed in the solvent.

[0086] There is no restriction on the order in which the solid components (active material, binder, and optional additives) are added to the solvent. The insoluble components may be added to a solution in which the soluble components are dissolved in a solvent, and the insoluble components may be dispersed in the solution. Alternatively, the soluble components may be added to a dispersion in which the insoluble components are dispersed in a solvent, and the soluble components may be dissolved in the dispersion.

[0087] After preparing the slurry or solution, a solvent may be further added to adjust the viscosity of the coating material.

[0088] The condition of the paint may be adjusted by treatment such as defoaming, filtration, etc. Additives such as defoamers, viscosity modifiers, thickeners, diluents, surfactants, stabilizers, etc. may also be added to the paint.

[0089] The method for applying the coating material is not particularly limited, but examples thereof include blade coating, dip coating, spray coating, bar coating, and die coating.

[0090] The object to be coated with the paint (substrate) is preferably a release-treated resin film. The substrate may be a long strip, or may be a small sheet obtained by processing a long substrate into sheets.

[0091] Furthermore, the object to be coated with the coating material may be a battery component such as a current collector, a separator, a solid electrolyte, etc. The coating material may be directly applied to these battery components to integrate the coating film with the battery component.

[0092] The electrode sheet raw material can be obtained by removing the solvent from the coating film formed by applying the paint. The solvent can be removed by heating, reducing pressure, blowing air, or a combination of these.

[0093] The dried coating film may be subjected to press processing. For example, by compressing the dried coating film with a press or the like, the contact state between particles of the active material, conductive material, etc. contained in the electrode can be improved.

[0094] When a long, strip-shaped support is used, the electrode film raw material may be wound into a roll for storage and transportation, or may be further processed into a plurality of sheet-shaped electrode film raw material sheets.

[0095] In this way, an electrode film raw material is obtained.

[0096] FIG. 3 is a schematic diagram showing the electrode film raw sheet 2 of this embodiment. The electrode film raw sheet 2 shown in Fig. 3 has an active material layer 21 and a functional layer 22. The electrode film raw sheet 2 is also sandwiched on both sides by release films 10. The active material layer 21 is made of a mixture containing an active material and a binder.

[0097] The electrode film raw sheet 2 does not have a current collector.

[0098] The mixture constituting the active material layer 21 can be the same as the mixture constituting the electrode film substrate 1 described above.

[0099] The functional layer 22 is not particularly limited as long as it is a layer attached for the purpose of improving the function of the electrode. Examples of the functional layer 22 include a heat dissipation layer, a planarization layer, a stress relaxation layer, and an adhesion layer.

[0100] The electrode film raw sheet 2 also satisfies the above requirements (1) to (3).

[0101] The electrode film raw sheet 2 can be produced by producing an active material layer 21 corresponding to the electrode film raw sheet 1 in the same manner as the above-described electrode film raw sheet 1, and then producing a functional layer 22 on the surface of the active material layer 21. The functional layer 22 can be produced appropriately using a known material and a known method.

[0102] According to the electrode film raw sheet having the above-described configuration, a novel electrode film raw sheet to be used as a material for electrodes can be provided.

[0103] Furthermore, the electrode having the above-described structure can stand on its own and is easy to handle.

[0104] [Electrode laminate] The electrode stack is a stack in which the above-mentioned electrode and a separator or a solid electrolyte membrane are stacked. In the electrode stack, the electrode may be in direct contact with the separator or the solid electrolyte membrane, or another member may be sandwiched between them.

[0105] Electrode laminates made of electrodes and separators are primarily used in electrochemical devices that use electrolytic solutions, while electrode laminates made of electrodes and solid electrolytes are used in all-solid-state secondary batteries, which are a type of electrochemical device.

[0106] The separator is a material that insulates the positive electrode from the negative electrode and has the ion permeability necessary for the function of the electrodes. The separator is not particularly limited, and known resin films, porous membranes, etc. can be used.

[0107] Examples of resin films include polypropylene, polyethylene, polyolefin, aramid, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyamide, polyethersulfone, etc. The resin film may be made porous to impart ion permeability.

[0108] Examples of porous membranes include woven fabric, nonwoven fabric, cellulose, and ceramic.

[0109] The solid electrolyte membrane is a member obtained by processing a commonly known solid electrolyte into a plate or film shape. As the material for the solid electrolyte membrane, either a commonly known inorganic solid electrolyte or a commonly known polymer solid electrolyte can be used.

[0110] As the inorganic solid electrolyte, any of sulfide-based inorganic solid electrolytes, oxide-based inorganic solid electrolytes, and other lithium-based inorganic solid electrolytes can be used.

[0111] Examples of sulfide-based inorganic solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, Li2S-Al2S3, Li2S-SiS2-Li3PO4, Li2S-P2S5-GeS2, Li2S-Li2O-P2S5-SiS2, Li2S-GeS2-P2S5-SiS2, and Li2S-SnS2-P2S5-SiS2.

[0112] Examples of oxide-based inorganic solid electrolytes include NASICON-type electrolytes such as LiTi2(PO4)3, LiZr2(PO4)3, and LiGe2(PO4)3, and (La0.5+x Li 0.5-3x Examples include perovskite types such as (Li)TiO3.

[0113] Other lithium-based inorganic solid electrolyte materials include, for example, LiPON, LiNbO3, LiTaO3, Li3PO4, LiPO 4-x N x (where 0 < x ≤ 1), LiN, LiI, LISICON, etc.

[0114] Examples of polymer-based solid electrolytes include polymer materials that exhibit ion conductivity, such as polyethylene oxide, polypropylene oxide, and copolymers thereof.

[0115] Examples of other members include, for example, a protective film that protects the electrode surface. The protective film is not particularly limited as long as it is a material that can protect the electrode from, for example, the detachment of particles such as active substances on the surface of the electrode and excessive reactions between the electrolyte and the electrode.

[0116] [Electrochemical device] The electrochemical device has the above electrode laminate. Examples of the electrochemical device include a secondary battery and a capacitor.

[0117] Examples of the secondary battery include a battery cell, a module manufactured by connecting a plurality of cells, a pack manufactured by connecting a plurality of modules, etc. The product of the electrochemical device may be provided with a sensor, a control circuit, etc., for preventing abnormalities such as overcharging and over-discharging. In order to electrically connect the battery to the outside, a lead (terminal) may be attached to the electrode.

[0118] The electrode laminate having a separator is used in a secondary battery having an electrolytic solution. The electrolyte of a lithium ion secondary battery can be a solution in which a lithium salt is dissolved in a non-aqueous solvent. Examples of the lithium salt include LiPF6, LiBF4, LiAlCl4, LiClO4, CF3SO3Li, CF4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)2NLi. Examples of the non-aqueous solvent include carbonates (carbonate esters) such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0119] An electrochemical device can be produced by combining the above-described electrode laminate with other necessary components, such as a separator, another electrode (counter electrode), etc. The counter electrode may be different from the electrode of this embodiment.

[0120] The container that houses the electrode stack can be made of a laminate film, metal, etc. The electrode stack may be placed flat in the container, or may be housed in a curved, bent, wound, or other state.

[0121] [device] A module can be produced by connecting multiple cells. A pack can be produced by connecting multiple modules. Devices produced using batteries such as cells, modules, and packs include, but are not limited to, electronic devices such as smartphones, mobile phones, computers, and displays, and transportation devices such as electric vehicles and hybrid vehicles.

[0122] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention. [Example]

[0123] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0124] (Examples 1 to 11, Comparative Examples 1 to 5) The materials used in the examples and comparative examples are as follows.

[0125] (binder) SBR: Styrene-butadiene rubber, Sigma-Aldrich, model number 182877 PVdF: Polyvinylidene fluoride, Solvay, model number 5130

[0126] (Cathode active material) LFP: Formosa Lithium Iron Corp., model number SFCM30050

[0127] (Conductive material) AB: Acetylene black, manufactured by Alfa Aesar, model number 45527

[0128] Each binder was dissolved in a solvent to prepare a solution with the following concentration, and then the binders were mixed in the ratios shown in Table 1 to obtain a binder solution. SBR: 24% by mass toluene solution PVdF: 6% by mass solution in NMP (N-methyl-2-pyrrolidone)

[0129] The active material and conductive material (acetylene black) were mixed in the ratio shown in Table 1 using a vibration mixer to obtain a mixed powder.

[0130] The mixed powder and the binder solution were mixed in the ratio shown in Table 1 to form a slurry, and toluene was further added to adjust the viscosity.

[0131] The slurry was degassed and passed through a sieve with 100 μm openings to obtain coating materials for the examples and comparative examples.

[0132] The resulting paint was applied to a release-treated PET film at 5 mAh / cm2 Specifically, the mass of the active material per unit area (applied mass, unit: g / cm) was calculated based on the target electrode capacity and the specific capacity (unit: mAh / g) of the active material used. 2 The coating was dried by heating at 120°C for 12 minutes. After drying, it was compressed with a roll press to a density of 2.4 g / cm. 3 Thus, raw electrode film sheets of the examples and comparative examples were obtained.

[0133] The specific capacity of the active material was the nominal value provided by the manufacturer of the active material used.

[0134] [Measurement of breaking strength] The breaking strength of the raw electrode film was measured by the method described above in (Method for measuring breaking strength).

[0135] [Battery fabrication: electrode film roll with positive electrode active material] A positive electrode for the coin-type battery R2032 was cut out from the electrode film roll. After each component was dried in a vacuum at 105°C, they were assembled in a glove box with an argon atmosphere.

[0136] The fabricated test electrode was placed on the bottom cover of a coin-type battery R2032. After placing a separator (Celgard 2300, manufactured by Celgard) on top of the test electrode, an electrolyte (1 mol / L solution of LiPF6) was poured in. The solvent used for the electrolyte was a mixed solvent of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate in a 1:1:1 (volume ratio).

[0137] A counter electrode (metallic lithium) was placed on the separator and the lid was put on, and then the battery was left to stand for 12 hours to allow the entire battery to be immersed in the electrolyte, thereby producing a lithium secondary battery.

[0138] [Capacity maintenance rate] The fabricated lithium secondary battery was charged to 3.80 V at 0.05 C (SOC 100%) and then rested for 5 minutes. After this, it was discharged at a constant current of 0.05 C, and the discharge capacity during constant current discharge was measured. Three consecutive measurements were taken, and the arithmetic mean value of the first, second, and third discharge capacities was taken as the "discharge capacity at 0.05 C" (reference capacity) (1 C = 5 mA / cm). 2 ).

[0139] In addition, the "0.6C discharge capacity" was determined using the same lithium secondary battery as that used to measure the "0.05C discharge capacity" under the same conditions as above, except that constant current discharge was performed at 0.6C.

[0140] (Calculation method) The capacity retention rate was calculated using the following formula. Capacity retention rate = 0.6C discharge capacity / 0.05C discharge capacity x 100%

[0141] The evaluation results are shown in Table 1. In the table, "Not measurable" for breaking strength means that the test piece was too brittle to measure.

[0142] [Table 1]

[0143] From the above results, it was found that the present invention is useful. [Explanation of symbols]

[0144] 1, 2... electrode film raw material, 10... release film, 21... active material layer, 22... functional layer

Claims

1. An electrode film raw sheet made of a mixture containing an active material and a binder, and satisfying the following (1) to (3): (1) The breaking strength measured by the following measurement method is 0.2 MPa or more. (Measurement method) The electrode film raw material was cut into a size of 15 mm in width and 50 mm in length to obtain a test piece, and the strength at 75% of the maximum stress when measured under conditions of a chuck distance of 30 mm and a tensile speed of 100 mm / min was taken as the breaking strength. (2) The active material includes lithium iron phosphate, and the binder includes styrene butadiene rubber and polyvinylidene fluoride. (3) The binder contains 0.75% by mass or more and 2.95% by mass or less of the styrene-butadiene rubber and 0.25% by mass or more and 5.25% by mass or less of the polyvinylidene fluoride relative to the entire mixture.

2. an active material layer made of a mixture containing an active material and a binder; No current collector is provided. An electrode film substrate that satisfies the following (1) to (3): (1) The breaking strength measured by the following measurement method is 0.2 MPa or more. (Measurement method) The electrode film raw sheet was cut into a size of 15 mm in width and 50 mm in length to obtain a test piece, and the strength at 75% of the maximum stress when measured under conditions of a chuck distance of 30 mm and a tensile speed of 100 mm / min was defined as the breaking strength. (2) The active material includes lithium iron phosphate, and the binder includes styrene butadiene rubber and polyvinylidene fluoride. (3) The binder contains 0.75% by mass or more and 2.95% by mass or less of the styrene-butadiene rubber and 0.25% by mass or more and 5.25% by mass or less of the polyvinylidene fluoride relative to the entire mixture.

3. the active material is lithium iron phosphate; 3. The electrode film substrate according to claim 1, wherein the binder comprises styrene-butadiene rubber and polyvinylidene fluoride.

4. The electrode film raw material according to claim 1 , further comprising a release film laminated thereon.

5. An electrode made from the electrode film substrate according to claim 1 .

6. The electrode according to claim 5; An electrode laminate in which a separator or a solid electrolyte membrane is laminated.

7. An electrochemical device comprising the electrode stack according to claim 6.

8. An apparatus comprising the electrochemical device according to claim 7.

Images