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

Abstract

To provide a new electrode film original fabric used as a material of an electrode, and also to provide 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 0.1 MPa, and the elongation rate in indicating breaking strength is 15% or more. (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 binder includes polyisobutylene. (3)The binder includes 1.5 mass% or more and 3.0 mass% or less of the polyisobutylene with respect to the entire mixture.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to electrode film raw materials, electrodes, electrode laminates, electrochemical devices, and equipment. [Background technology]

[0002] In recent years, the importance of rechargeable batteries used as power sources has been increasing. Active research and development is underway on rechargeable batteries, ranging from small ones used in portable electronic devices to medium and large-sized ones used in electric vehicles and home energy storage systems.

[0003] A secondary battery has a pair of electrodes containing an active material and an electrolyte placed 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. As for these electrodes, a known configuration is in which an active material layer containing either the positive electrode active material or the negative electrode active material is laminated with a current collector that has excellent conductivity.

[0004] The active material layer described above is formed by dispersing powdered active material and a binder in a solvent to prepare a slurry mixture, coating the resulting mixture onto a current collector, and then press-forming it. The laminate of the active material layer and the current collector is then cut into the 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 Publication No. 2019-169444 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As mentioned above, manufacturing electrodes requires multi-stage processing, including preparation of the mixture, coating of the mixture, drying, and press working. There is room for improvement in terms of materials to simplify the secondary battery manufacturing process and reduce manufacturing costs.

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

[0008] This invention has been made in view of these circumstances, and aims to provide a novel electrode film raw material that can be used as an electrode material. It also aims to provide electrodes, electrode laminates, electrochemical devices, and equipment that use such electrode film raw material as a material. [Means for solving the problem]

[0009] The inventors believed that if they could create a material with properties that would allow it to be used as an electrode without the need for a current collector, they could eliminate the processes of preparing the mixture and coating the current collector with the mixture, as described above. Furthermore, they believed that if the material were in film form, an electrochemical device could be easily manufactured by cutting the film (electrode film raw material) and attaching it to a battery element.

[0010] The inventors have diligently considered the above points and completed the invention. In order to solve the above problems, one aspect of the present invention includes the following aspects.

[0011] [1] An electrode film base material consisting of a mixture containing an active material and a binder, satisfying the following conditions (1) to (3). (1) The breaking strength determined by the measurement method described below is 0.1 MPa or higher, and the elongation at the time of the breaking strength is 15% or higher. (Measurement Method) The electrode film raw material is cut into pieces with a width of 15 mm and a length of 50 mm to obtain a test piece. The strength obtained by measuring the strength of the test piece at 75% of the maximum stress when the chuck distance is 30 mm and the tensile speed is 100 mm / min is defined as the breaking strength. (2) The binder contains polyisobutylene. (3) The binder contains 1.5% by mass or more and 3.0% by mass or less of the polyisobutylene with respect to the whole mixture.

[0012] [2]An electrode film raw sheet having an active material layer made of a mixture containing an active material and a binder, not having a current collector, and satisfying the following (1) to (3). (1) The breaking strength determined by the following measurement method is 0.1 MPa or more, and the elongation rate when showing the breaking strength is 15% or more. (Measurement method) The strength at 75% of the maximum stress when measuring a test piece obtained by cutting the electrode film raw sheet into a size of 15 mm in width and 50 mm in length under the conditions of a chuck distance of 30 mm and a tensile speed of 100 mm / min is defined as the breaking strength. (2) The binder contains polyisobutylene. (3) The binder contains 1.5 mass% or more and 3.0 mass% or less of the polyisobutylene with respect to the whole mixture.

[0013] [3] The electrode film raw sheet according to [1] or [2] laminated with a release film.

[0014] [4] An electrode made of the electrode film raw sheet according to any one of [1] to [3].

[0015] [5] An electrode laminate in which the electrode according to [4] and a separator or a solid electrolyte membrane are laminated.

[0016] [6] An electrochemical device having the electrode laminate according to [5].

[0017] [7] An apparatus having the electrochemical device according to [6]. [Advantages of the Invention]

[0018] According to the present invention, a novel electrode film raw sheet used as a material for an electrode can be provided. Further, an electrode, an electrode laminate, an electrochemical device, and an apparatus using such an electrode film raw sheet as a material can be provided. [Brief Description of the Drawings]

[0019] [Figure 1]FIG. 1 is a schematic diagram showing the electrode film stock 1 of the present embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the electrode film stock 2 of the present embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [Electrode Film Stock, Electrode] FIG. 1 is a schematic diagram showing the electrode film stock 1 of the present embodiment.

[0021] The term "electrode film stock" refers to a film-shaped molded body before being processed into an electrode. Typically, the electrode film stock is a long molded body formed in a strip shape, or a sheet-shaped molded body obtained by processing such a strip-shaped molded body into individual sheets.

[0022] The electrode film stock 1 shown in FIG. 1 is sandwiched between release films 10 from both sides. As the release film 10, known materials such as a PET film having a release treatment can be adopted.

[0023] The electrode film stock 1 is composed of a mixture containing an active material and a binder. The electrode film stock 1 does not have a current collector.

[0024] The electrode film stock 1 has characteristic functions of (a) being self-supporting and (b) being usable as an electrode.

[0025] (a) Being self-supporting The electrode film stock 1 can be processed into a negative electrode by cutting it into a desired shape. The electrode film stock 1 may be used as the negative electrode as it is. The obtained negative electrode can maintain the shape cut without attachments such as a base material. Having such properties is sometimes referred to as "self-supporting" or "self-supporting type" in this specification.

[0026] Furthermore, the negative electrode of an electrochemical device generally undergoes significant volume changes during charging and discharging. Therefore, when using electrode film raw material 1 as the negative electrode of an electrochemical device, it is required to counteract the volume changes during charging and discharging and maintain the shape and performance of the negative electrode.

[0027] The electrode film raw material 1 can exist without support and has rigidity that can withstand the volume changes described above.

[0028] (b) Can be used as an electrode The electrode film raw material 1 can be used as a negative electrode in electrochemical devices such as secondary batteries and capacitors by cutting it into a desired shape. In other words, the electrode film raw material 1 has low electronic resistance and high ionic conductivity, to the extent that it can be used as a negative electrode.

[0029] The electrodes obtained by cutting electrode film raw material 1 having the functions of (a) and (b) are self-supporting (self-supporting electrodes) and can be used as electrodes for electrochemical devices such as secondary batteries and capacitors simply by attaching them to the components of these electrochemical devices.

[0030] The following describes the components of electrode film raw material 1 in order.

[0031] (active material) As the active material, powdered substances known as negative electrode active materials for secondary batteries and negative electrode active materials for capacitors can be used.

[0032] When a lithium-ion secondary battery is used as the secondary battery, the negative electrode active material of the lithium-ion secondary battery can be selected from at least one of the following: carbon-based materials such as graphite, metallic lithium, lithium compounds such as lithium titanate, metals such as aluminum, tin, and silicon that can form alloys with lithium, alloys of lithium with other metals, and metal oxides such as silicon oxide. The negative electrode active material of the lithium-ion secondary battery can be any material that can reversibly dope and dedope lithium ions.

[0033] For lithium-ion secondary batteries, active materials with a volume-average particle size of 0.1 to 100 μm are used.

[0034] When a lithium-ion capacitor is used as the capacitor, examples of negative electrode active materials for the lithium-ion capacitor include carbon-based materials such as graphite, and the negative electrode active materials for lithium-ion secondary batteries mentioned above.

[0035] For lithium-ion capacitors, active materials with a volume-average particle size of 0.1 to 100 μm are used.

[0036] (binder) A binder is a material used to bind particles such as active materials, and for example, a resin can be used. As the binder, a known thermoplastic resin used as an electrode material for the above purpose can be used. The binder is required not to undergo reductive decomposition at 0-3V (vs. Li / Li+).

[0037] In addition to the aforementioned "binding of particles such as active materials," the functions of a binder include (i) imparting high strength to the electrode film base material, (ii) adjusting electrical resistance (reducing resistance), and (iii) adjusting other physical properties. Binders that have a particularly strong function of (i) will be described as "high-strength binders," binders that have a particularly strong function of (ii) will be described as "resistance-adjusting binders," and (iii) will be described as "other binders."

[0038] (i) High-strength binder Elastomers can be used as high-strength binders. Binders with elastomer properties can impart flexibility and strength to electrodes, and can suppress damage caused by volume changes of the active material during electrode use.

[0039] For high-strength binders, it is desirable to have a tensile strength of 5 MPa or higher. Furthermore, high-strength binders are required to be stable with respect to the electrolyte and electrochemically stable within electrochemical elements (batteries, capacitors).

[0040] For example, when a lithium-ion battery is used as the electrochemical element and electrodes obtained by cutting electrode film raw material 1 are used, it is required that the high-strength binder does not leach from the electrodes into the electrolyte filled inside the battery.

[0041] The tensile strength of the high-strength binder shall be the value obtained by measuring the fracture strength, as described later.

[0042] In this embodiment, polyisobutylene (PIB) is used as the high-strength binder.

[0043] Furthermore, in this embodiment, the binder used to supplement mechanical strength may include styrene-butadiene rubber (SBR), acrylate-based binders, polyimide-based binders, olefin-based binders, etc. By adding these binders, rigidity can be imparted to the electrode film base 1. The binder used to supplement mechanical strength is required not to undergo reductive decomposition at 0-3V (vs. Li / Li+).

[0044] Furthermore, the binder may include, in addition to the binders mentioned above, the following copolymers containing styrene and a conjugated diene, as a high-strength binder. • Styrene-isoprene copolymer • Styrene-butadiene-methyl methacrylate copolymer (MBS) • Acrylonitrile-styrene-butadiene copolymer (ABS) • Acrylonitrile-styrene-butadiene-methyl methacrylate copolymer (MABS) Carboxylated styrene-butadiene rubber • Styrene-butadiene-styrene block copolymer (SBS) • Styrene-isoprene-styrene block copolymer (SIS) • Styrene-isoprene-butadiene-styrene block copolymer (SIBS)

[0045] The above copolymer may also be copolymerized with other copolymerizable vinyl monomers.

[0046] As for vinyl monomers, • Acrylate monomers such as alkyl acrylates • Methacrylate monomers such as alkyl methacrylates • Acrylamide monomers such as alkoxyacrylamide Methacrylamide monomers such as alkoxymethacrylamides • Carboxylic acid monomers such as acrylic acid • Nitrile monomers such as acrylonitrile • Vinyl ester monomers such as vinyl acetate • Halogenated vinyl monomers such as polyvinyl chloride • Polyfunctional monomers such as allyl acrylate These are some examples.

[0047] These vinyl monomers may be copolymerized in the above copolymer in the form of one type, or two or more types.

[0048] (ii) Binder for adjusting resistance) For resistance adjustment, polyvinylidene fluoride (PVdF), acrylate-based binders, and polyimide-based binders can be used.

[0049] (i) High-strength binders are considered to be electrochemically inert, and if the active material is completely covered with (i) high-strength binder, it is thought that the electrochemical reaction of the active material will not occur and the resistance of the electrodes will increase. In contrast, by using (ii) resistance-adjusting binders as described above in combination, the increase in resistance caused by covering the active material with (i) high-strength binder can be suppressed.

[0050] (iii) Other binders (adhesive binders) As an adhesive binder, resin materials having reactive functional groups or anchoring effects can be used. Examples of reactive functional groups include hydroxyl groups (-OH) and carboxyl groups (-COOH). When the electrode film base material contains such a binder, it is expected that the reactive functional groups will react at the bonding surface when the electrode obtained from the electrode film base material is bonded to other components, thereby increasing the adhesive strength.

[0051] Furthermore, the inclusion of an adhesive binder in the electrode film raw material makes it easier to bond the self-supporting electrodes manufactured from the electrode film raw material to other components.

[0052] The adhesive binder should preferably be electrochemically stable and maintain its adhesive properties even when exposed to other components, particularly electrolytes.

[0053] For example, when a lithium-ion battery is used as an electrochemical element and electrodes obtained by cutting electrode film raw material 1 are used, the adhesive binder must not leach from the electrodes into the electrolyte filled in the battery, and the reactive functional groups must not be easily deactivated even when exposed to the electrolyte.

[0054] Furthermore, the adhesive binder is required not to undergo reductive decomposition at 0-3V (vs. Li / Li+).

[0055] Examples of such binders include at least one selected from carboxymethylcellulose (CMC) binders, polyacrylic acid (PAA) binders, vinyl alcohol binders, and epoxy binders.

[0056] The mixture constituting the electrode film base material may contain additives such as conductive materials, in addition to the active material and binder mentioned above, as necessary for adjusting physical properties. Examples of conductive materials include at least one selected from carbon black such as acetylene black, carbon fibers, activated carbon, metal powder, conductive polymers, etc. The conductive material does not need to have the same activity as the active material; it is sufficient if it is a material that improves conductivity inside the electrode.

[0057] Furthermore, the mixture constituting the electrode film base material may also contain carbon nanotubes (CNTs). Electrode film base materials with added CNTs are expected to exhibit improved tensile strength and improved conductivity.

[0058] Furthermore, the thickness of the electrode film raw material is preferably between 1 μm and 1000 μm.

[0059] The electrode film base material, consisting of the mixture of the above materials, satisfies the following requirements (1) to (3) in order to exhibit the functions of (a) and (b) above.

[0060] (Requirement (1)) Electrode film raw material 1 has a breaking strength of 0.1 MPa or higher, determined by the measurement method described below, and an elongation of 15% or higher at the point of breaking strength.

[0061] (Methods for measuring breaking strength and elongation) The fracture strength is defined as 75% of the maximum stress obtained when a test specimen, obtained by cutting an electrode film roll to a size of 15 mm in width and 50 mm in length, is measured under conditions of a chuck distance of 30 mm and a tensile speed of 100 mm / min.

[0062] Furthermore, the elongation rate is determined from the distance between the chucks of the test specimen when it exhibits its breaking strength, using the following formula (1). Growth rate (%) = (L1 - L0) / L0 × 100 …(1) L0: Initial value of the distance between chucks (30mm) L1: Chuck distance when indicating breaking strength

[0063] The maximum stress is defined as the magnitude of the tensile force (N) at which the test specimen fractures, and the stress at 75% of the maximum stress is determined. The 75% stress (N) is then calculated by measuring the cross-sectional area (mm²) of the test specimen in a virtual plane perpendicular to the tensile direction. 2 The value obtained by dividing by (N / mm 2 The breaking strength is calculated as (= MPa).

[0064] The measurement is performed twice, and the arithmetic mean of the two measurements is adopted as the breaking strength.

[0065] The electrode film raw material possesses such tensile strength that the electrodes cut from the raw material can stand on their own. This self-supporting capability facilitates handling of the electrodes during subsequent assembly processes.

[0066] A breaking strength of 0.2 MPa or higher is preferable. While a higher breaking strength is preferable because it makes the material less prone to breakage, a strength of 10 MPa or less is acceptable, and even 5 MPa or less is acceptable.

[0067] Furthermore, electrode film raw material 1 has the characteristic of resisting volume changes during charging and discharging and maintaining its shape and performance as a negative electrode. Because the elongation rate of electrode film raw material 1 when it exhibits its breaking strength is 15% or more, degradation due to volume changes in the negative electrode active material during charging and discharging is less likely to occur, and the performance of the negative electrode cut from the electrode film raw material is easily maintained.

[0068] The measurement is taken twice, and the arithmetic mean of the two measurements is used as the growth rate.

[0069] The growth rate is preferably 20% or more, and more preferably 25% or more. Furthermore, the growth rate may be 500% or less, and may also be 300% or less.

[0070] (Requirements (2)(3)) Because it possesses the properties described in requirements (1) and (2) above, electrode film raw material 1 satisfies the following requirements (2) and (3). Requirement (2): The binder contains polyisobutylene. Requirement (3): The binder shall contain 1.5% by mass or more and 3.0% by mass or less of polyisobutylene relative to the whole mixture.

[0071] The binder may include the various binders described above, provided that requirements (2) and (3) are met.

[0072] In the electrode film raw material described above, the mixture constituting the electrode film raw material preferably contains 85% to 98.5% by mass of active material and 1.5% to 15% by mass of binder, relative to the total mixture.

[0073] If the mixture contains additives such as conductive materials, the mixture should contain the additives in proportions determined by preliminary experiments according to the function of the additives, relative to the total mixture. For example, if the mixture contains a conductive material as an additive, the mixture should contain 85% to 98% by mass of the active material, 1% to 10% by mass of the binder, and 0.5% to 5% by mass of the conductive material, relative to the total mixture.

[0074] [Manufacturing method for electrode film raw material] The electrode film base material can be manufactured by applying a slurry (paint) obtained by dissolving or dispersing the above-mentioned mixture in a solvent onto a support, and then removing the solvent.

[0075] The solvent used should be one that can dissolve at least the binder. Examples of solvents include hydrocarbon solvents, alcohol solvents, ether solvents, ketone solvents, ester solvents, amide solvents, halogen solvents, sulfur solvents, and inorganic solvents.

[0076] Examples of hydrocarbon solvents include heptane, cyclohexane, toluene, and xylene.

[0077] Examples of alcohol-based solvents include methanol and ethanol.

[0078] Examples of ether-based solvents include tetrahydrofuran and dioxane.

[0079] Examples of ketone solvents include acetone and methyl ethyl ketone.

[0080] Examples of ester solvents include ethyl acetate and ethyl lactate.

[0081] Examples of amide solvents include dimethylformamide and N-methyl-2-pyrrolidone.

[0082] Examples of halogenated solvents include chloroform and dichloromethane.

[0083] Examples of sulfur-based solvents include dimethyl sulfoxide and sulfolane.

[0084] Water is an example of an inorganic solvent.

[0085] The above solvents may be used individually, or a mixed solvent consisting of two or more solvents may be used.

[0086] The method for preparing the paint is not particularly limited, but it may be done by mixing the active material, binder, and any optional additives one by one or two or more simultaneously with a solvent and dissolving or dispersing them in the solvent.

[0087] There are no restrictions on the order in which solid components (active material, binder, and optional additives) are added to the solvent. Insoluble components may be added to a solution in which soluble components are dissolved in the solvent to disperse the insoluble components in the solution. Alternatively, soluble components may be added to a dispersion in which insoluble components are dispersed in the solvent to dissolve the soluble components in the dispersion.

[0088] After preparing the slurry or solution, a solvent may be added to adjust the viscosity of the paint.

[0089] The paint's condition may be adjusted through processes such as defoaming and filtration. Additives such as defoamers, viscosity modifiers, thickeners, diluents, surfactants, and stabilizers may also be added to the paint.

[0090] The method of applying the paint is not particularly limited, but examples include blade coating, dip coating, spray coating, bar coating, and die coating.

[0091] The object to which the paint is applied (support) is preferably a resin film that has been treated with a release agent. The support may be a long strip, or it may be a small sheet obtained by processing a long support into individual sheets.

[0092] Furthermore, the object to which the paint is applied may be battery components such as current collectors, separators, and solid electrolytes. The paint film and the battery components may be integrated by directly applying the paint to these battery components.

[0093] An electrode sheet base can be formed by removing the solvent from the coating film formed by applying the paint. The solvent can be removed by heating, reduced pressure, blowing air, or a combination thereof.

[0094] The dried coating can also be press-formed. For example, compressing the dried coating with a press can improve the contact state of particles such as active material and conductive material contained in the electrodes.

[0095] When a long, strip-shaped material is used as the support, the electrode film raw material may be stored and transported in a roll, or it may be further processed into multiple sheet-like electrode film raw materials.

[0096] In this way, electrode film raw material is obtained.

[0097] Figure 2 is a schematic diagram showing the electrode film raw material 2 of this embodiment. The electrode film base 2 shown in Figure 2 has an active material layer 21 and a functional layer 22. The electrode film base 2 is also sandwiched between release films 10 on both sides. The active material layer 21 is made of a mixture containing an active material and a binder.

[0098] The electrode film raw material 2 does not have a current collector.

[0099] The mixture constituting the active material layer 21 can be the same as the mixture constituting the electrode film base roll 1 described above.

[0100] 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.

[0101] Electrode film raw material 2 also satisfies the above requirements (1) to (3).

[0102] Electrode film raw material 2 can be manufactured by first creating an active material layer 21 corresponding to electrode film raw material 1 in the same manner as described above, and then creating a functional layer 22 on the surface of the active material layer 21. The functional layer 22 can be manufactured as appropriate using known materials and known methods.

[0103] According to the electrode film raw material with the above configuration, it is possible to provide a novel electrode film raw material that can be used as an electrode material.

[0104] Furthermore, electrodes with the above configuration are self-supporting and easy to handle.

[0105] [Electrode Laminate] The electrode laminate is a laminate in which the aforementioned electrodes and a separator or solid electrolyte membrane are stacked. In the electrode laminate, the electrodes may be in direct contact with the separator or solid electrolyte membrane, or other members may be sandwiched between them.

[0106] Electrode stacks consisting of electrodes and separators are primarily used in electrochemical devices that utilize electrolytes. Electrode stacks consisting of electrodes and solid electrolytes are used in all-solid-state secondary batteries, a type of electrochemical device.

[0107] A separator is a material that insulates the positive and negative electrodes and has the ion permeability necessary for the function of the electrodes. The separator is not particularly limited and can be any known resin film, porous membrane, etc.

[0108] Examples of resin films include polypropylene, polyethylene, polyolefin, aramid, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyamide, and polyethersulfone. To impart ion permeability, the resin film may be made porous.

[0109] Examples of porous membranes include woven fabrics, nonwoven fabrics, cellulose, and ceramics.

[0110] A solid electrolyte membrane is a component made by processing a commonly known solid electrolyte into a plate or film shape. Both commonly known inorganic solid electrolytes and polymer solid electrolytes can be used as materials for the solid electrolyte membrane.

[0111] Any of the following can be used as the inorganic solid electrolyte: sulfide-based inorganic solid electrolytes, oxide-based inorganic solid electrolytes, or other lithium-based inorganic solid electrolytes.

[0112] 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.

[0113] Examples of oxide-based inorganic solid electrolytes include NASICON types such as LiTi2(PO4)3, LiZr2(PO4)3, and LiGe2(PO4)3, (La 0.5+x Li 0.5-3x Examples include perovskite-type materials such as TiO3.

[0114] 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.

[0115] Examples of polymer-based solid electrolytes include polymer materials that exhibit ion conductivity, such as polyethylene oxide, polypropylene oxide, and copolymers thereof.

[0116] 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脱落 of particles such as active substances on the surface of the electrode and the excessive reaction between the electrolyte and the electrode.

[0117] [Electrochemical device] The electrochemical device has the above electrode laminate. Examples of the electrochemical device include secondary batteries and capacitors.

[0118] Examples of secondary batteries include battery cells, modules fabricated by connecting a plurality of cells, packs fabricated by connecting a plurality of modules, etc. The products of the electrochemical device may be equipped with sensors, control circuits, etc. for preventing abnormalities such as overcharging and over-discharging. In order to electrically connect the battery to the outside, leads (terminals) may be attached to the electrodes.

[0119] Electrode stacks with separators are used in secondary batteries containing an electrolyte. Examples of electrolytes for lithium-ion secondary batteries include solutions obtained by dissolving lithium salts in a non-aqueous solvent. Examples of lithium salts include LiPF6, LiBF4, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)2NLi. Examples of non-aqueous solvents include carbonates (carbonate esters) such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0120] The electrochemical device can be fabricated by combining the above electrode stack with other necessary components, such as a separator or another electrode (counter electrode). The counter electrode may be different from the electrode in this embodiment.

[0121] The container for housing the electrode stack can be made from laminate film, metal, or the like. The electrode stack may be arranged flat within the container, or it may be housed in a curved, bent, wound, or otherwise modified state.

[0122] [device] Modules can be created by connecting multiple cells. Packs can be created by connecting multiple modules. Devices made using batteries such as cells, modules, and packs are not particularly limited, but examples include electronic devices such as smartphones, mobile phones, computers, and displays, as well as transportation equipment such as electric vehicles and hybrid vehicles.

[0123] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention. [Examples]

[0124] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0125] (Examples 1-4, Comparative Examples 1-3) The materials used in the examples and comparative examples are as follows:

[0126] (binder) SBR: Styrene-butadiene rubber, manufactured by Sigma-Aldrich, part number 430072 PAA: Polyacrylic acid, manufactured by Fujimori Kogyo Co., Ltd., model number TR-853 PIB: Polyisobutylene, manufactured by BASF, model number N150

[0127] (Negative electrode active material) Graphite: Manufactured by Showa Denko Materials Co., Ltd., mosaic coke-based artificial graphite, model number MAGE3

[0128] (Conductive material) AB: Acetylene Black, manufactured by Alfa Aesar, model number 45527

[0129] Each binder was dissolved in a solvent to obtain solutions of the following concentrations. Then, the binders were mixed in the ratios shown in Table 1 to obtain binder solutions. SBR: 24% by mass toluene solution PAA: 40% by mass ethyl acetate solution PIB: 6% by mass toluene solution

[0130] Using a vibrating mixer, the active material and conductive material (acetylene black) were mixed in the ratios shown in Table 1 to obtain a mixed powder.

[0131] The mixed powder and binder solution were mixed in the ratios shown in Table 1 to form a slurry. Toluene was then added to adjust the viscosity.

[0132] The slurry was degassed and passed through a sieve with a mesh size of 100 μm to obtain the paints of the examples and comparative examples.

[0133] The obtained paint was applied to the PET film subjected to release treatment at a rate of 3 mAh / cm 2 . Specifically, from the target capacity of the electrode and the specific capacity of the active material used (unit: mAh / g), the mass per unit area of the active material (coating mass, unit: g / cm 2 ) was calculated and applied. The coating film was dried by heating at 90 °C for 5 minutes. After drying, it was compressed with a roll press to a density of 1.4 g / cm 3 to obtain the electrode film raw materials for the examples and comparative examples.

[0134] The specific capacity of the active material used was the manufacturer's nominal value of the active material used.

[0135] [Measurement of breaking strength and elongation] The breaking strength and elongation of the electrode film raw material were measured by the method described in the above (Measurement method of breaking strength and elongation).

[0136] [Fabrication of battery: Electrode film raw material with negative electrode active material] A negative electrode for coin-type battery R2032 was cut out from the electrode film raw material. After drying each member at 105 °C in vacuo, assembly was carried out in a glove box under an argon atmosphere.

[0137] The test electrode prepared was placed on the lower lid for coin-type battery R2032. After placing a separator (Celgard 2300 manufactured by Celgard) on the test electrode, an electrolyte solution (1 mol / L solution of LiPF6) was injected. As the solvent of the electrolyte solution, a mixed solvent obtained by mixing ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate at a volume ratio of 1:1:1 was used.

[0138] After placing a counter electrode (lithium metal) on the separator and covering it, it was left standing for 12 hours to immerse the electrolyte solution throughout, thereby fabricating a lithium secondary battery.

[0139] [Measurement method of SOC-OCV value] The amount of active material contained in the test electrode fabricated from the electrode film raw material was calculated, and the theoretical capacity (mAh / g) of the test electrode was determined from the theoretical capacity of the active material and the amount of active material. Next, the prepared lithium secondary battery is charged at 0.1C for 30 minutes, followed by a 5-minute rest period, and this process is repeated a total of 22 times. The number of charge cycles until the voltage reached 0.05V was defined as the SOC-OCV value.

[0140] When the SOC-OCV value measured using the above method was 16 or more, it was determined that the electrode was sufficiently usable.

[0141] [Capacity maintenance rate] The fabricated lithium secondary battery was charged to 2.0V at 0.05C (SOC 0%) and then left to rest for 5 minutes. After this, constant current discharge was performed at 0.05C, and the discharge capacity under constant current discharge was measured. Three consecutive measurements were taken, and the arithmetic mean of the discharge capacities of the first, second, and third measurements was defined as the "discharge capacity at 0.05C" (initial discharge capacity) (1C = 3mA / cm²). 2 ).

[0142] Subsequently, a load test was performed under the same conditions as above, except that constant current discharge was performed at 0.1C, 0.2C, 0.4C, and 0.6C. After that, the "discharge capacity at 0.05C" (discharge capacity after the load test) was measured again using the method described above, and the capacity retention rate was determined. Electrode film raw materials with a capacity retention rate of 90% or more can be judged to be good quality.

[0143] (Calculation method) The capacity retention rate was calculated using the following formula. Capacity retention rate = [Initial discharge capacity] / [Discharge capacity after load test] × 100%

[0144] The evaluation results are shown in Table 1. In the table, "Unmeasurable" for the breaking strength means that the test specimen was too brittle to measure. An electrode film roll with an unmeasurable breaking strength can be judged as not being able to stand on its own.

[0145] [Table 1]

[0146] The evaluation results showed that each electrode film base material from Examples 1 to 4 exhibited good electrochemical properties (SOC-OCV, capacity retention rate).

[0147] On the other hand, the electrode film raw material of Comparative Example 1 had a PIB content in the binder below the specified level, and its breaking strength and elongation did not meet the requirements. It was found that such electrode film raw materials have poor electrochemical properties.

[0148] The electrode film raw material of Comparative Example 2 contained a large amount of SBR as a binder to compensate for mechanical strength instead of PIB, but it was suggested that the capacity retention rate was poor and it could not adequately withstand the volume change associated with charging and discharging.

[0149] Furthermore, while the electrode film raw material of Comparative Example 3 contained a large amount of PAA, an adhesive binder, instead of PIB, and exhibited excellent electrochemical properties, it was found that its tensile strength and elongation could not be measured, and it could not stand on its own.

[0150] Based on the above results, it has been found that the present invention is useful. [Explanation of Symbols]

[0151] 1,2... Electrode film base roll, 10... Release film, 21... Active material layer, 22... Functional layer

Claims

1. An electrode film base material comprising a mixture containing an active material and a binder, satisfying the following conditions (1) to (3). (1) The breaking strength determined by the measurement method described below is 0.1 MPa or higher, and the elongation at the time of the breaking strength is 15% or higher. (Measurement Method) The electrode film raw material is cut to a size of 15 mm in width and 50 mm in length, and the strength obtained from the test piece is measured under conditions of a chuck distance of 30 mm and a tensile speed of 100 mm / min. The strength at 75% of the maximum stress is defined as the breaking strength. (2) The binder contains polyisobutylene. (3) The binder contains 1.5% by mass or more and 3.0% by mass or less of the polyisobutylene with respect to the whole mixture.

2. It has an active material layer made of a mixture containing an active material and a binder, Without a current collector, An electrode film raw material that satisfies the following conditions (1) to (3). (1) The breaking strength determined by the measurement method described below is 0.1 MPa or higher, and the elongation at the time of the breaking strength is 15% or higher. (Measurement Method) The electrode film raw material is cut to a size of 15 mm in width and 50 mm in length, and the strength obtained from the test piece is measured under conditions of a chuck distance of 30 mm and a tensile speed of 100 mm / min. The strength at 75% of the maximum stress is defined as the breaking strength. (2) The binder contains polyisobutylene. (3) The binder contains 1.5% by mass or more and 3.0% by mass or less of the polyisobutylene with respect to the whole mixture.

3. An electrode film raw material according to claim 1, wherein a release film is laminated.

4. An electrode made from the electrode film raw material described in claim 1.

5. The electrode according to claim 4, An electrode laminate in which a separator or solid electrolyte membrane is stacked.

6. An electrochemical device having the electrode stack described in claim 5.

7. An apparatus having the electrochemical device described in claim 6.

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