JP2019216061A - Lithium ion battery electrode and lithium ion battery - Google Patents

Abstract

To provide a lithium ion battery electrode having a low resistance value and having excellent durability and charge/discharge characteristics.SOLUTION: In a lithium ion battery electrode including an electrolytic solution, an electrode active material, and a resin current collector, the electrolytic solution includes a solvent including propylene carbonate and an electrolyte, the resin current collector includes a resin (P) and a conductive filler, and the crystallinity of the resin (P) constituting the resin current collector is 31 to 50.SELECTED DRAWING: None

Description

The present invention relates to a lithium-ion battery electrode and a lithium-ion battery.

In recent years, reduction of carbon dioxide emission has been urgently required for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion battery that can achieve a high energy density and a high output density.

In a lithium ion battery, generally, a positive electrode or a negative electrode active material or the like is applied to a positive electrode or negative electrode current collector using a binder to form an electrode. Further, in the case of a bipolar (bipolar) type battery, a positive electrode active material or the like is applied to one surface of a current collector using a binder to form a positive electrode layer, and a negative electrode active material is applied to the opposite surface using a binder. Are applied to form a bipolar electrode having a negative electrode layer.

In such a lithium ion battery, conventionally, a metal foil (metal current collector foil) has been used as a current collector. In recent years, so-called resin current collectors composed of a resin to which a conductive material is added instead of a metal foil have been proposed. Such a resin current collector is lighter than a metal current collector foil, and is expected to improve output per unit weight of the battery.

For example, Patent Literature 1 discloses a lithium ion battery using a solvent containing ethylene carbonate and diethyl carbonate as an electrolytic solution, and using an electrode provided with a resin current collector.

JP 2017-152383 A

However, it can be said that there is still room for improvement in obtaining a lithium ion battery electrode having a low resistance value and excellent durability and charge / discharge characteristics using a resin current collector.

In view of the above situation, an object of the present invention is to provide a lithium ion battery electrode having a low resistance value and excellent durability and charge / discharge characteristics. Another object of the present invention is to provide a lithium ion battery using the above electrode.

The inventors of the present invention have come up with the present invention as a result of intensive studies to solve the above problems.
That is, the present invention is an electrode for a lithium ion battery including an electrolytic solution, an electrode active material, and a resin current collector, wherein the electrolytic solution includes a solvent including propylene carbonate and an electrolyte, and the resin current collector includes a resin. An electrode for a lithium ion battery, comprising: (P) and a conductive filler, wherein the resin (P) constituting the resin current collector has a crystallinity of 31 to 50; A lithium ion battery characterized in that the electrode for a lithium ion battery is provided on a positive electrode and a negative electrode.

The electrode for a lithium ion battery of the present invention has a low resistance value and is excellent in durability and charge / discharge characteristics.

FIG. 1A is a perspective view schematically showing an example of a preferable separator in the lithium ion battery of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. FIG. 2 is a cross-sectional view schematically showing an example of the configuration of a frame-like member constituting a preferable separator in the lithium ion battery of the present invention. FIG. 3 is a cross-sectional view showing an example of a positional relationship between a separator main body constituting a preferable separator and respective layers constituting a frame member in the lithium ion battery of the present invention. 4 (a) to 4 (g) are explanatory views schematically showing an example of a method for manufacturing a lithium ion battery using a preferable separator in the lithium ion battery of the present invention. FIG. 5 is an explanatory view schematically showing one example of the lithium ion battery of the present invention.

The electrode for a lithium ion battery of the present invention includes an electrolytic solution, an electrode active material, and a resin current collector.The electrolytic solution includes a solvent containing propylene carbonate, and an electrolyte. (P) and a conductive filler, wherein the crystallinity of the resin (P) is 31 to 50.

In the electrode for a lithium ion battery of the present invention, a solvent containing propylene carbonate having a cyclic structure is used as a solvent used for the electrolytic solution, and the crystallinity of the resin (P) constituting the resin current collector is in a specific range. Is used. With such a configuration, the resin (P) constituting the resin current collector does not excessively swell with the electrolytic solution and does not become too familiar with the electrolytic solution. It is considered that the deterioration of the maintenance ratio can be suppressed.
As a result, it is considered that an electrode for a lithium ion battery having a low resistance value and having excellent durability and charge / discharge characteristics can be obtained.

In the electrode for a lithium ion battery of the present invention, the electrolytic solution contains a solvent containing propylene carbonate (hereinafter sometimes abbreviated as a solvent) and an electrolyte.
First, the solvent will be described.
The boiling point of the solvent is preferably 160 ° C. or higher, more preferably 180 ° C. or higher, from the viewpoint of suppressing the expansion of the electrode due to volatilization of the electrolytic solution, and from the viewpoint of preventing the electrolytic solution from withering when producing the battery. , 200 ° C. or more, and particularly preferably 220 ° C. or more.

The flash point of the solvent is preferably 80 ° C or higher, more preferably 100 ° C or higher, further preferably 120 ° C or higher, and 130 ° C or higher, from the viewpoint of preventing heat generation and expansion of the lithium ion battery. It is particularly preferable that the above is satisfied.
A method for setting the boiling point and the flash point of the solvent within the above ranges will be described below.

Solvents include propylene carbonate. It may be only propylene carbonate or may contain a non-aqueous solvent other than propylene carbonate. As a non-aqueous solvent other than propylene carbonate, ethylene carbonate is preferable.

As the non-aqueous solvent other than propylene carbonate and ethylene carbonate, those used in known non-aqueous electrolytes and the like can be used, for example, lactone compounds, cyclic or chain carbonates, chain carboxylate, cyclic or Chain ethers, phosphate esters, nitrile compounds, amide compounds, sulfones, and the like, and mixtures thereof can be used.

Examples of the lactone compound include 5-membered lactone compounds (such as γ-butyrolactone and γ-valerolactone) and 6-membered lactone compounds (such as δ-valerolactone).

Examples of the cyclic carbonate include butylene carbonate.
Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, and the like.

Examples of the chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.
Examples of the cyclic ether include tetrahydrofuran, tetrahydropyran, 1,3-dioxolan, 1,4-dioxane and the like.
Examples of the chain ether include dimethoxymethane and 1,2-dimethoxyethane.

Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, Tri (trifluoroethyl) phosphate, tri (tripperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphosphoran-2-one, 2-trifluoroethoxy-1,3,2- Examples include dioxaphosphoran-2-one and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one.
Examples of the nitrile compound include acetonitrile. Examples of the amide compound include N, N-dimethylformamide (hereinafter, also referred to as DMF).
Examples of the sulfone include a chain sulfone such as dimethyl sulfone and diethyl sulfone, and a cyclic sulfone such as sulfolane.

In the lithium ion battery electrode of the present invention, the content of propylene carbonate is preferably 50 parts by weight or more, and more preferably 70 parts by weight, based on 100 parts by weight of the solvent, from the viewpoint of suitably satisfying the above-mentioned boiling point and flash point. Parts or more is more preferable.

When the solvent is a mixture of propylene carbonate and ethylene carbonate, the content of ethylene carbonate is preferably 50 parts by weight or less based on 100 parts by weight of the solvent, from the viewpoint of suitably satisfying the above-mentioned boiling point and flash point. More preferably, the amount is 30 parts by weight or less.

As the electrolyte, those used in known electrolytes and the like can be used. Preferred examples thereof include lithium salt-based electrolytes of inorganic acids such as LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ and LiClO ₄ , A sulfonimide-based electrolyte having a fluorine atom such as LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) _{2, and} a fluorine atom such as LiC (CF ₃ SO ₂ ) ₃ Having a sulfonyl methide electrolyte.

The electrolyte concentration in the electrolytic solution is not particularly limited, but is preferably from 0.1 to 5 mol / L, more preferably from 0.5 to 4 mol / L, from the viewpoint of handleability of the electrolytic solution and battery capacity. More preferably, it is 1 to 3 mol / L.

The lithium ion battery electrode of the present invention includes a resin current collector.
In the resin current collector, the resin (P) constituting the resin current collector has a crystallinity of 31 to 50.
Such a resin (P) does not excessively swell with the above-mentioned electrolytic solution or does not become too familiar with the electrolytic solution. It is considered possible.
The crystallinity of the resin (P) is preferably from 35 to 47, and more preferably from 38 to 44.
In the present specification, the degree of crystallinity of the resin (P) is determined from the area of the endothermic peak in the differential scanning calorimetry (DSC) measurement in accordance with “JIS K7122-1987 Method for Measuring Heat of Transition of Plastics”. / G) is determined, and the crystallinity is calculated by the following equation based on the measured heat of fusion.
Crystallinity = (measured heat of fusion / heat of complete crystal fusion) × 100
In the above formula, the heat of fusion of the complete crystal is the heat of fusion when extrapolated so that the crystallinity becomes 100.

The resin (P) is preferably a mixture containing two or more resins having different crystallinities. Due to such a configuration of the resin (P), the dispersion of the conductive carbon filler described later is biased in the crystalline part and the non-crystalline part of the resin (P), which is suitable for forming a conductive path. Since it can be in a state, low resistance, potential resistance and prevention of liquid bleeding can be suitably imparted.
When the resin (P) is a mixture containing two or more resins, the crystallinity of the resin (P) is calculated by calculating a weighted average value of the crystallinity from each crystallinity of the resin before mixing. This is defined as the crystallinity of the resin (P).

Examples of the resin (P) include a mixture of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polycycloolefin (PCO). These resins may be modified products (hereinafter, referred to as modified polyolefins).
Among these resins, polyethylene and polypropylene are preferable in terms of moisture-proof properties and mechanical strength.
Examples of the polypropylene include homopolypropylene, random polypropylene, block polypropylene, polypropylene having a long-chain branched structure, acid-modified polypropylene, and metallocene-based polypropylene.
Homopolypropylene is a homopolymer of propylene. Random polypropylene is a copolymer containing a small amount (preferably 4.5% by weight or less) of ethylene units introduced randomly. Block polypropylene is a composition in which ethylene propylene rubber (EPR) is dispersed in homopolypropylene, and has a “sea-island structure” in which “islands” containing EPRs float in “sea” of homopolypropylene. I have. Examples of the polypropylene having a long-chain branched structure include polypropylene described in JP-A-2001-253910 and the like. The acid-modified polypropylene is a polypropylene having a carboxyl group introduced therein, and can be obtained by reacting an unsaturated carboxylic acid such as maleic anhydride and polypropylene with a known method such as a reaction in the presence of an organic peroxide. . Metallocene-based polypropylene is a random copolymer of ethylene and propylene polymerized by a metallocene catalyst.

Examples of the modified polyolefin include those obtained by introducing a polar functional group into polyethylene, polypropylene or a copolymer thereof. Examples of the polar functional group include a carboxyl group, a 1,3-dioxo-2-oxapropylene group, a hydroxyl group, Examples include an amino group, an amide group, and an imide group.

As examples of modified polyolefins having a polar functional group introduced into polyethylene, polypropylene or a copolymer thereof, Admer series manufactured by Mitsui Chemicals, Inc. and the like are commercially available.

Among these polyolefins, polyolefins having high crystallinity are more preferable.
Examples of the resin having a high crystallinity include homopolypropylene, block polypropylene, high-density polyethylene (HDPE), and metallocene polypropylene.

As a mixture containing two or more resins having different crystallinities, for example, a mixture of at least two or more selected from the group consisting of homopolypropylene, block polypropylene, high-density polyethylene (HDPE), and metallocene-based polypropylene is preferable.

When the resin (P) is a mixture containing two or more resins having different degrees of crystallinity, the degree of crystallinity contained in the resin (P) is determined from the viewpoint that the conductive carbon filler can suitably form a conductive path. Is the resin (p1) with the smallest resin and the resin (p2) with the largest crystallinity, the difference in crystallinity between the resin (p1) and the resin (p2) is 5 to 18 Is more preferable, and it is more preferable that it is 10-18.

As the resin constituting the resin (P), for example, the following can be obtained from the market.
Homopolypropylene: “Sun Allomer PM600A: Crystallinity 44” and “Sun Allomer PM900A: Crystallinity 47” are all block polypropylene manufactured by Sun Allomer Co., Ltd .: “Qualia CM688A: Crystallinity 34”, “Sun Allomer PC684S: Crystallinity 37”. "And" Sun Allomer PM854X: Crystallinity 39 "are all manufactured by Sun Allomer Co., Ltd. High Density Polyethylene (HDPE):" Suntech B680: Crystallinity 52 ", and" Suntech A260: Crystallinity 60 "are all Asahi Kasei Chemicals Corporation ) Random polypropylene: "Sun Allomer PC630A: crystallinity 31" manufactured by Sun Allomer Co., Ltd., "Sun Allomer PB222A: crystallinity 25," metallocene polypropylene manufactured by Sun Allomer Co., Ltd .: "Wintech WFX6: crystallinity 40" Japan Polypropylene Co., Ltd.

As the resin (P), a resin having a crystallinity of 31 to 50 can be appropriately selected from the above resins, and a preferable combination thereof is a resin having a crystallinity of 30 to 40, A resin having a crystallinity of 45 to 55 is mixed at a weight ratio of 30:70 to 70:30.

The content of the resin (P) contained in the resin current collector is preferably 30 to 60% by weight based on 100 parts by weight of the resin current collector from the viewpoint of the strength of the resin current collector.

The resin current collector contains a conductive filler.
The conductive filler is selected from materials having conductivity, but from the viewpoint of suppressing ion permeation in the current collector, it is preferable to use a material having no conductivity with respect to ions used as the charge transfer medium. Here, the ion used as the charge transfer medium is, for example, lithium ion in the case of a lithium ion battery.

Examples of the material of the conductive filler include metals [nickel, aluminum, stainless steel (SUS), silver, copper and titanium, etc.], and conductive carbon [graphite and carbon black (acetylene black, Ketjen black, furnace black, channel black, thermal black). Lamp black, etc.], and mixtures thereof, and the like, but are not limited thereto.
These conductive fillers may be used alone or in a combination of two or more. Further, these alloys or metal oxides may be used. From the viewpoint of electrical stability, preferably conductive carbon, nickel, aluminum, stainless steel, silver, copper, titanium and mixtures thereof, more preferably conductive carbon, nickel, silver, aluminum and stainless steel, Preferably, conductive carbon and nickel are used. Further, these conductive fillers may be those obtained by coating a conductive material (metal of the above-described conductive fillers) around a particle-based ceramic material or a resin material by plating or the like.

The content of the conductive filler in the resin current collector is preferably 5 to 90 parts by weight, more preferably 20 to 80 parts by weight, in 100 parts by weight of the resin current collector from the viewpoint of conductivity. .

In particular, when the conductive filler is conductive carbon, the content of the conductive carbon is preferably 20% by weight or more and 30% by weight or less based on the total weight of the resin (P) and the conductive carbon. In this case, it is preferable to use it as a positive electrode resin current collector.

The shape (form) of the conductive filler is not limited to the particle form, and may be a form other than the particle form, and may be a form practically used as a so-called filler-based conductive material such as a carbon nanotube.

In the present specification, the “particle diameter” means the maximum distance L among the distances between any two points on the outline of the conductive filler. As the value of the “average particle diameter”, a value calculated as an average value of particle diameters of particles observed in several to several tens of visual fields using a scanning electron microscope (SEM) is adopted.

In the resin current collector of the present invention, in addition to the resin (P) and the conductive filler, other components (a dispersant, a cross-linking accelerator, a cross-linking agent, a coloring agent, and an ultraviolet ray) as long as the effects of the present invention are not impaired. An absorbent, a plasticizer) and the like can be appropriately added.

The thickness of the resin current collector of the present invention is not particularly limited, but is preferably 5 to 400 μm.

The resin current collector of the present invention can be manufactured by a known method, and for example, can be manufactured by the following method.
First, a resin current collector material is obtained by mixing the resin (P), the conductive filler, and other components as necessary. As a mixing method, a method in which a master batch of a conductive filler is obtained and then further mixed with a resin (P), a method using a resin (P), a conductive filler, and a master batch of other components as necessary , And a method of batch-mixing all the raw materials, and the like. The mixing is performed by using a well-known mixer such as a kneader, an internal mixer, a Banbury mixer, and a roll. Can be used.

The order of addition of each component at the time of mixing is not particularly limited. The obtained mixture may be further pelletized or powdered with a pelletizer or the like.

By molding the obtained resin current collector material into, for example, a film shape, the resin current collector of the present invention can be obtained. Examples of the method for forming a film include known film forming methods such as a T-die method, an inflation method, and a calendar method. The resin current collector of the present invention can also be obtained by a molding method other than film molding.

In the electrode for a lithium ion battery of the present invention, the swelling ratio of the resin current collector to the electrolyte solvent is preferably 0.1% or less, more preferably 0.0%.
When the swelling ratio is 0.1% or less, sufficient durability can be imparted to the electrode for a lithium ion battery of the present invention.
The swelling ratio of the resin current collector can be measured by the following method.
A resin current collector material containing a resin (P) and a conductive filler is applied on a horizontal glass plate and air-dried for half a day at room temperature. Next, it is left still for 3 hours in a vacuum drier heated to 80 ° C. Thereafter, the material is cooled to room temperature, and a resin current collector material cut out to a size of 10 × 40 × 0.2 mm is used as a test piece. This test piece is immersed in an electrolytic solution used for manufacturing an electrode for a lithium ion battery at 50 ° C. for 3 days to prepare a resin current collector material in a saturated liquid absorbing state.
The swelling ratio can be determined by the following equation from the change in weight of the test piece before and after liquid absorption.
Swelling ratio [%] = [(weight of test piece after liquid absorption−weight of test piece before liquid absorption) / weight of test piece before liquid absorption] × 100

The electrode for a lithium ion battery of the present invention includes an electrode active material.
As the electrode active material, a positive electrode active material or a negative electrode active material can be used.
As the positive electrode active material, a known positive electrode active material for a lithium ion battery can be used, and a composite oxide of lithium and a transition metal 複合 a composite oxide containing one kind of transition metal (LiCoO ₂ , LiNiO ₂ , LiAlMnO ₄ , LiMnO ₂ ) ₂ and LiMn ₂ O _4, etc.), composite oxide transition metal element is two (e.g. _{LiFeMnO 4, LiNi 1-x Co} x O 2, LiMn 1-y Co y O 2, LiNi 1/3 Co 1 / ₃ Al _1/3 O ₂ and _{LiNi 0.8 Co 0.15 Al 0.05 O 2} ) and a composite oxide metal element is three or more [e.g. _{LiM a M 'b M''} c O 2 (M , M ′ and M ″ are different transition metal elements and satisfy a + b + c = 1. For example, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ), etc. Transfer metal phosphates (eg, LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ and LiNiPO ₄ ), transition metal oxides (eg, MnO ₂ and V ₂ O ₅ ), transition metal sulfides (eg, MoS ₂ and TiS ₂ ) and conductivity Polymers (for example, polyaniline, polyvinylidene fluoride, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polyvinylcarbazole) and the like may be used, and two or more kinds may be used in combination.
Note that the lithium-containing transition metal phosphate may be one in which part of the transition metal site is substituted with another transition metal.

The volume average particle diameter of the positive electrode active material is preferably 0.01 to 100 μm, more preferably 0.1 to 35 μm, and still more preferably 2 to 30 μm, from the viewpoint of electric characteristics of the battery. .

As the negative electrode active material, a known negative electrode active material for a lithium ion battery can be used, and a carbon-based material [graphite, non-graphitizable carbon, amorphous carbon, a resin fired body (for example, carbonized by firing a phenol resin, a furan resin, or the like) ), Coke (eg, pitch coke, needle coke, petroleum coke, etc.) and carbon fiber, etc.), silicon-based materials [silicon, silicon oxide (SiOx), silicon-carbon composite (carbon particles whose surface is made of silicon and silicon). And / or silicon carbide, silicon particles or silicon oxide particles whose surfaces are coated with carbon and / or silicon carbide, and silicon carbide, etc.) and silicon alloys (silicon-aluminum alloy, silicon-lithium alloy, silicon-nickel) Alloys, silicon-iron alloys, silicon-titanium alloys, silicon-manganese alloys, silicon-copper alloys, silicon-tin alloys, etc.), conductive polymers ( For example, polyacetylene and polypyrrole), metals (such as tin, aluminum, zirconium and titanium), metal oxides (such as titanium oxide and lithium-titanium oxide) and metal alloys (such as lithium-tin alloy, lithium-aluminum alloy and lithium) -Aluminum-manganese alloys, etc.) and mixtures of these with carbon-based materials.
Among the above-mentioned negative electrode active materials, those which do not contain lithium or lithium ions therein may be subjected to a pre-doping treatment in which part or all of the negative electrode active material contains lithium or lithium ions in advance.

Among these, from the viewpoint of battery capacity and the like, carbon-based materials, silicon-based materials and mixtures thereof are preferable, and as the carbon-based materials, graphite, non-graphitizable carbon and amorphous carbon are more preferable, and as the silicon-based materials, , Silicon oxide and a silicon-carbon composite are more preferred.

The volume average particle diameter of the negative electrode active material is preferably from 0.01 to 100 μm, more preferably from 0.1 to 20 μm, and even more preferably from 2 to 10 μm, from the viewpoint of the electrical characteristics of the battery.

In this specification, the volume average particle diameter of the electrode active material means a particle diameter (Dv50) at an integrated value of 50% in a particle size distribution obtained by a microtrack method (laser diffraction / scattering method). The microtrack method is a method of obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light. For measurement of the volume average particle size, a micro track manufactured by Nikkiso Co., Ltd. can be used.

It is preferable that the electrode for a lithium ion battery of the present invention contains a conductive auxiliary in the resin current collector.
The conductive assistant is selected from materials having conductivity.
Specifically, metal [nickel, aluminum, stainless steel (SUS), silver, copper and titanium, etc.], carbon [graphite and carbon black (acetylene black, Ketjen black, furnace black, channel black, thermal lamp black, etc.), etc. ], And mixtures thereof, but are not limited thereto.
These conductive assistants may be used alone or in combination of two or more. Further, these alloys or metal oxides may be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium, and mixtures thereof are preferable, silver, aluminum, stainless steel, and carbon are more preferable, and carbon is more preferable. In addition, as these conductive aids, those obtained by coating a conductive material (a metal among the above-described conductive aid materials) around a particle-based ceramic material or a resin material by plating or the like may be used.

The average particle diameter of the conductive additive is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm, and more preferably 0. More preferably, it is 0.03 to 1 μm. In the present specification, the “particle diameter” means the maximum distance L among the distances between any two points on the contour of the conductive additive. As the value of the “average particle diameter”, the average value of the particle diameter of particles observed in several to several tens of visual fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is used. It is assumed that the calculated value is used.

The shape (form) of the conductive assistant is not limited to the particle form, but may be a form other than the particle form, and may be a form practically used as a so-called filler-based conductive aid such as a carbon nanotube.

The conductive assistant may be a conductive fiber having a fibrous shape.
Examples of the conductive fiber include carbon fibers such as PAN-based carbon fiber and pitch-based carbon fiber, conductive fibers obtained by uniformly dispersing a highly conductive metal or graphite in synthetic fibers, and metals such as stainless steel. Examples include fibrous metal fibers, conductive fibers in which the surface of an organic fiber is coated with a metal, and conductive fibers in which the surface of an organic fiber is coated with a resin containing a conductive substance. Among these conductive fibers, carbon fibers are preferred. Further, a polypropylene resin into which graphene is kneaded is also preferable.
When the conductive assistant is a conductive fiber, the average fiber diameter is preferably 0.1 to 20 μm.

The electrode active material may be a coated active material in which at least a part of its surface is coated with a coating layer containing a polymer compound.
When the periphery of the electrode active material is covered with the coating layer, a change in volume of the electrode is reduced, and expansion of the electrode can be suppressed. Furthermore, the wettability of the coating active material to the electrolyte can be improved, and the time required for the step of absorbing the electrolyte into the coating active material of the electrode can be reduced.
Note that a coated active material when a positive electrode active material is used as an electrode active material is called a coated positive electrode active material, and a coated active material when a negative electrode active material is used as an electrode active material is called a coated negative electrode active material.

As the polymer compound constituting the coating layer, those described in JP-A-2017-054703 as a resin for coating a non-aqueous secondary battery active material can be suitably used.

The coating layer may include a material having the same conductivity as that of the above-described conductive auxiliary agent preferably included in the resin current collector, and a preferable example is carbon.

When a coated active material is used as the electrode active material, for example, the electrode active material is put into a universal mixer and stirred at 30 to 500 rpm. By dropping and mixing over a period of time, further mixing a conductive auxiliary agent as needed, raising the temperature to 50 to 200 ° C. with stirring, reducing the pressure to 0.007 to 0.04 MPa, and then holding for 10 to 150 minutes. A coated active material can be obtained.

Hereinafter, a method for producing the electrode for a lithium ion battery of the present invention will be described.
The electrode for a lithium ion battery of the present invention can be manufactured, for example, by forming an electrode active material layer containing an electrode active material on a resin current collector, and performing pressure or the like as necessary.
Note that an electrode active material layer using a positive electrode active material as an electrode active material is also referred to as a positive electrode active material layer, an electrode active material layer using a negative electrode active material as an electrode active material is also referred to as a negative electrode active material layer, and an electrode active material layer. An electrode active material layer using a coated positive electrode active material as a layer is also referred to as a coated positive electrode active material layer, and an electrode active material layer using a coated negative electrode active material as an electrode active material layer is also referred to as a coated negative electrode active material layer.
In the electrode active material layer, apart from the conductive material that may be included in the coating layer of the coating active material, a material having the same conductivity as the conductive auxiliary agent preferably included in the above-described resin current collector is used. They may be included, and preferred ones are also the same.

As a method of forming the electrode active material layer on the resin current collector, for example, a dispersion in which the coating active material is dispersed at a concentration of 30 to 60% by weight based on the weight of the solvent is formed on the resin current collector. After coating with a coating device such as a bar coater, a method of removing the solvent by allowing the nonwoven fabric to stand on the active material and absorbing the liquid, and pressing with a press machine if necessary is mentioned.
The electrode active material layer obtained by drying the dispersion of the coating active material does not need to be directly formed on the resin current collector.For example, the dispersion is applied to the surface of an aramid separator or the like, and dried. It can also be obtained by laminating the obtained layered product (electrode active material layer) on a resin current collector. When the electrode active material layer is an electrode active material layer obtained by drying the dispersion of the coated active material, the electrode for a lithium ion battery of the present invention is obtained by adding an electrolytic solution to the obtained electrode active material layer. Can be manufactured.
When forming the electrode active material layer, a dispersion in which the coating active material is dispersed in the electrolyte at a concentration of 30 to 60% by weight based on the weight of the electrolyte is coated on a resin current collector with a bar coater or the like. The electrode for a lithium ion battery of the present invention can also be manufactured by absorbing and pressing an unnecessary electrolytic solution as necessary after coating with the coating device of (1).

The mixing ratio of the electrode active material and the polymer compound constituting the coating layer is not particularly limited, but the electrode active material: polymer compound = 1: 0.001 to 0.1 by weight. preferable.

As a solvent for dispersing the coating active material, 1-methyl-2-pyrrolidone, methyl ethyl ketone, DMF, dimethylacetamide, N, N-dimethylaminopropylamine, tetrahydrofuran, the above-described electrolyte solution, and the like can be used.

A lithium ion battery using the electrode for a lithium ion battery of the present invention is obtained by combining a counter electrode and storing it in a cell container together with a separator, injecting an electrolytic solution, and sealing the cell container.
In addition, a positive electrode is formed on one surface of the resin current collector, and a negative electrode is formed on the other surface to produce a bipolar (bipolar) electrode. The bipolar (bipolar) electrode is laminated with a separator to form a cell container. , The electrolyte solution is injected, and the cell container is sealed.
Further, the electrode for a lithium ion battery of the present invention may be provided on one of the positive electrode and the negative electrode, but the electrode for a lithium ion battery of the present invention is preferably provided on the positive electrode and the negative electrode.
A lithium ion battery having such a separator and including the electrode for a lithium ion battery of the present invention on the positive electrode and the negative electrode is also one embodiment of the present invention.

In the lithium ion battery of the present invention, the separator comprises a sheet-shaped separator main body made of a polyolefin porous membrane and a frame-shaped member arranged annularly along the outer periphery of the separator main body from the viewpoint of production efficiency. The frame-shaped member preferably includes a heat-resistant annular support member and a seal layer disposed on the surface of the heat-resistant annular support member and capable of thermocompression bonding with the positive electrode current collector or the negative electrode current collector.

A preferred configuration of the separator in the lithium ion battery of the present invention will be described with reference to FIGS. 1 (a) and 1 (b).
FIG. 1A is a perspective view schematically showing an example of a separator, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A.
As shown in FIG. 1A, the lithium ion battery separator 1 includes a flat plate-shaped separator body 10 and a frame-shaped member 20 that is annularly arranged along the outer periphery of the separator body 10.
Further, as shown in FIGS. 1A and 1B, since the outer dimensions of the frame member 20 are larger than the outer dimensions of the separator body 10, the side surfaces of the separator body 10 are covered by the frame member 20. ing.

Next, the configuration of a frame-like member that forms a preferable separator in the lithium ion battery of the present invention will be described with reference to FIG.
FIG. 2 is a cross-sectional view schematically illustrating an example of the configuration of a frame-shaped member that forms the separator.
As shown in FIG. 2, the frame-shaped member (20) constituting the separator includes a heat-resistant annular support member 21 and a sealing layer capable of being thermocompression-bonded to a positive electrode current collector or a negative electrode current collector disposed on the surface thereof. 22.
As shown in FIG. 2, the seal layer 22 forming the frame member 20 includes a first seal layer 22a capable of thermocompression bonding with the positive electrode current collector, and a second seal layer 22 capable of thermocompression bonding with the negative electrode current collector. The frame-shaped member 20 may be a laminate in which the heat-resistant annular support member 21 is disposed between the first seal layer 22a and the second seal layer 22b. In the frame-shaped member shown in FIG. 2, the description of the separator main body is omitted, but the position where the separator main body is arranged is not particularly limited.

In the preferred separator of the lithium ion battery of the present invention, the frame-like member arranged annularly along the outer periphery of the separator main body supports the separator main body, so that the handleability is excellent as compared with the case where the separator main body is used alone. Furthermore, even when the separator main body is exposed to conditions that cause thermal deformation, the heat-resistant annular support member retains its shape, thereby suppressing thermal deformation of the separator main body. Further, since the frame-shaped member is disposed only on the outer peripheral portion of the separator main body, the thickness of the separator main body sandwiched between the positive electrode active material layer and the negative electrode active material layer is maintained thin, and It does not increase the ionic resistance of the material. Therefore, in the preferable separator of the lithium ion battery of the present invention, both excellent handleability and suppression of thermal deformation can be achieved without changing the thickness of the separator. And since the seal layer formed on the surface of the heat-resistant annular support member enables the adhesion between the separator and the current collector, it is necessary to separately prepare an adhesive when adhering the separator and the current collector. Therefore, the manufacturing process can be simplified.

The surface of the heat-resistant annular support member refers to the surface of the heat-resistant annular support member facing the current collector, but the other surface (for example, the outer surface or the inner surface of the heat-resistant annular support member) is provided with a seal layer. It may be arranged. That is, the seal layer may be provided only on the surface of the heat-resistant annular support member facing the current collector, or may be provided on other surfaces.

The heat-resistant annular support member desirably contains a heat-resistant resin composition having a melting temperature of 200 ° C. or higher.
When the heat-resistant sensible support member contains the heat-resistant resin composition having a melting temperature of 200 ° C. or higher, the frame-shaped member is less likely to be deformed by heat.
The melting temperature (also simply referred to as a melting point) of the heat-resistant resin composition is measured by differential scanning calorimetry in accordance with JIS K7121-1987.

Examples of the resin constituting the heat-resistant resin composition include thermosetting resin (epoxy resin and polyimide), engineering resin [polyamide (nylon 6 melting temperature: about 230 ° C., nylon 66 melting temperature: about 270 ° C.), polycarbonate (Melting temperature also called PC: about 150 ° C) and polyetheretherketone (melting temperature also called PEEK: about 330 ° C), etc.) and high melting point thermoplastic resin polyethylene terephthalate (melting temperature also called PET: about 250 ° C), Polyethylene naphthalate (also referred to as PEN, melting temperature: about 260 ° C.), high melting point polypropylene (melting temperature: about 160 to 170 ° C.), and the like.
In addition, a high melting point thermoplastic resin refers to a thermoplastic resin whose melting temperature measured by differential scanning calorimetry in accordance with JIS K7121-1987 is 150 ° C or higher.

The heat-resistant resin composition desirably contains at least one resin selected from the group consisting of polyamide, polyethylene terephthalate, polyethylene naphthalate, high melting point polypropylene, polycarbonate, and polyether ether ketone.

The heat resistant resin composition may include a filler.
When the heat-resistant resin composition contains a filler, the melting temperature can be improved.
Examples of the filler include an inorganic filler such as glass fiber and carbon fiber.
Examples of the heat-resistant resin composition containing a filler include a resin obtained by impregnating glass fiber with an epoxy resin before curing (also referred to as glass epoxy) and a carbon fiber reinforced resin.

In a preferred separator of the lithium ion battery of the present invention, even when the frame member to be configured is a laminate in which a heat-resistant annular support member is disposed between the first seal layer and the second seal layer, the laminate is It is merely arranged along the outer peripheral portion of the separator main body constituting the separator. That is, the central portion of the separator does not have a laminated structure. Therefore, the internal resistance of the battery can be reduced.

In the preferred separator of the lithium ion battery of the present invention, the seal layer constituting the frame member may have a single-layer structure or a multi-layer structure.
That is, the seal layer may be composed of a first seal layer capable of thermocompression bonding with the positive electrode current collector, and a second seal layer capable of thermocompression bonding with the negative electrode current collector.

The material forming the seal layer only needs to be capable of being thermocompression-bonded to the resin current collector, and preferably contains, for example, polyolefin.
Examples of the polyolefin constituting the seal layer include commercially available polyolefin-based hot melt adhesive resins [Admer manufactured by Mitsui Chemicals, Inc. and Mersen manufactured by Tosoh Corporation] and low-melting-point polyethylene.
When the seal layer has a multilayer structure, the materials forming the first seal layer and the second seal layer may be the same or different.
In addition, low melting point polyethylene refers to polyethylene whose melting temperature measured by differential scanning calorimetry is less than 150 ° C. in accordance with JIS K7121-1987, and from the viewpoint of suppressing the temperature rise of the separator body during thermocompression bonding, The melting temperature of the low melting point polyethylene used for the seal layer is preferably 100 ° C. or lower. The low-melting-point polyethylene that can be used as a preferable separator in the lithium-ion battery of the present invention includes commercially available low-density polyethylene resins and high-density polyethylene resins.

In the preferred separator of the lithium ion battery of the present invention, the thickness of the frame-shaped member is not particularly limited, but is preferably from 60 to 600 μm.

In the separator which is preferable in the lithium ion battery of the present invention, the thickness of the sealing layer is not particularly limited, but is desirably 10 to 100 μm in total.
When the thickness of the sealing layer is 10 to 100 μm, the adhesiveness to the current collector becomes good, which is preferable.

In the preferred separator of the lithium ion battery of the present invention, the thickness of the heat-resistant annular support member is not particularly limited, but is preferably 50 to 500 μm.
When the thickness of the heat-resistant annular support member is 50 to 500 μm, it is difficult to be thermally deformed, which is preferable.
The heat-resistant annular support member may be composed of two or more layers. When the heat-resistant annular support member is composed of two or more layers, the separator body is disposed between the heat-resistant annular support members. May be.

In the preferred separator of the lithium ion battery of the present invention, the method of joining the separator main body and the frame-shaped member is not particularly limited, but may be joined by an adhesive, or may be connected to the positive electrode current collector or the negative electrode current collector by heat. The bonding may be performed using a part of the seal layer that can be pressed.
Examples of the adhesive include the above-mentioned commercially available polyolefin-based hot melt adhesive resin and low melting point polyethylene.
Alternatively, by forming the frame-shaped member directly on the separator main body by a method such as cooling after applying the raw material of the frame-shaped member to the separator main body in a molten state, the separator main body and the frame-shaped member may be separated from each other. Can be joined.

In the preferred separator of the lithium ion battery of the present invention, the thickness of the sheet-shaped separator body made of the polyolefin porous membrane is not particularly limited, but is preferably from 10 to 1000 μm.

In a preferred separator of the lithium ion battery of the present invention, a known separator for a lithium ion battery made of a porous polyolefin [Hypore manufactured by Asahi Kasei Corporation, Celgard manufactured by Asahi Kasei Corporation, and Yupore manufactured by Ube Industries, Ltd.] Etc.] can be used.

The preferred separator of the lithium ion battery of the present invention is not particularly limited in a plan view shape, but may be a polygon such as a triangle, a quadrangle, or a pentagon, a circle, an ellipse, or the like.
In the lithium ion battery of the present invention, the shapes of the separator main body and the frame-like member that constitute a preferable separator conform to the shapes of the above-described resin current collector (the positive electrode current collector and the negative electrode current collector) and the shape of the battery outer package. And adjust it.

The outer dimensions of the separator body in top view are preferably larger than the inner dimensions of the frame member and less than or equal to the outer dimensions of the frame member, from the connection between the separator body and the frame member.
The outer dimensions of the separator body satisfying the above conditions include, for example, a dimension larger than the inner dimension of the frame member and smaller than the outer dimension, and the same dimension as the outer dimension of the frame member. It is more desirable that the dimension be larger than the inner dimension of the frame-shaped member and smaller than the outer dimension.
If the outer dimensions of the separator main body are larger than the inner dimensions of the frame-shaped member and smaller than the outer dimensions, the separator main body and the frame-shaped member are joined with a sufficient area. The frame member does not peel off.
On the other hand, if the external dimensions of the separator main body are larger than the external dimensions of the frame-shaped member, the separator main body protrudes outward from the frame-shaped member, and thus becomes an unnecessary space when manufacturing a lithium-ion battery, resulting in energy consumption. The density may be reduced. Further, if the outer dimensions of the separator main body are the same as the outer dimensions of the frame-shaped member, the separator main body will be exposed on the side surface of the lithium ion battery separator, so that leakage of the electrolyte from the separator main body is prevented. In some cases, additional measures may be required.

In the preferred separator of the lithium ion battery of the present invention, the positional relationship between the separator body and the frame-shaped member is not particularly limited. For example, the separator body may be provided on the surface of the first seal layer (the side opposite to the heat-resistant annular support member). May be disposed, and the separator body may be disposed between the first seal layer and the heat-resistant annular support member, and may be disposed between the first heat-resistant annular support member (the first heat-resistant annular support member and the second heat-resistant annular support member). The separator body may be arranged between the heat-resistant annular support member) and the separator body may be arranged between the heat-resistant annular support member and the second seal layer. (The side opposite to the heat-resistant annular support member). The case where the separator body is arranged on the surface of the first seal layer (the side opposite to the heat-resistant annular support member) and the case where the separator body is arranged on the surface of the second seal layer (the side opposite to the heat-resistant annular support member) In this case, the entire frame-shaped member is arranged only on one side of the separator body.
In consideration of the handleability of the separator for a lithium ion battery, it is desirable that the separator body is in direct contact with the heat-resistant annular support member, and is intermediate between the heat-resistant annular support members (the first heat-resistant annular support member and the second heat-resistant annular support member). It is more desirable that the separator body is arranged between the annular support member).

Regarding the preferred separator in the lithium ion battery of the present invention, the positional relationship between the separator main body and each of the layers (the first seal layer, the second seal layer, and the heat-resistant annular support member) constituting the frame member will be described with reference to FIG. I do.
In FIG. 3, the separator main body 10 is disposed between a first heat-resistant annular support member 21 a and a second heat-resistant annular support member 21 b constituting the heat-resistant annular support member 21.
The position of the separator main body 10 is not particularly limited. For example, the separator main body 10 may be disposed so as to be in contact with only the first seal layer 22a, or disposed between the first seal layer 22a and the heat-resistant annular support member 21. May be disposed between the heat-resistant annular support member 21 and the second seal layer 22b, or may be disposed so as to be in contact with only the second seal layer 22b.
The outer dimensions of the separator body are not particularly limited, and may be larger than the inner dimensions of the frame-shaped member, or may be smaller than the outer dimensions.

[Method of manufacturing lithium ion battery separator]
The method for producing a preferred separator in the lithium ion battery of the present invention is not particularly limited, for example, a method of separately producing and combining a plate-shaped separator body and a frame-shaped member, and a method of producing a frame-shaped separator on the surface of the plate-shaped separator body. A method of sequentially laminating each layer constituting the member, and the like can be given.

As a method of arranging the frame-shaped member on the outer periphery of the separator main body, the material used for each layer constituting the frame-shaped member is formed into a film shape, and further cut into a predetermined shape. A method of bonding each to the outer periphery of the separator body by, for example, a method of cutting the film constituting each layer of the frame-shaped member into a predetermined shape, and then heating and melting and bonding each to the outer periphery of the separator body, forming the frame-shaped member After forming a laminate of the respective layers into a multilayer film, a method of bonding the laminate to the separator main body, and the like can be given. Examples of the adhesive include the above-mentioned commercially available polyolefin-based hot melt adhesive resin and low melting point polyethylene.
The method of forming the material constituting each layer into a film is not particularly limited, and examples thereof include an inflation method, a T-die method, a solution casting method, and a calendar method. The films obtained by these methods may be subjected to stretching or the like as necessary. The stretching may be uniaxial stretching or biaxial stretching. Further, a commercially available film may be cut into a predetermined shape and used.

When the film constituting each layer of the frame-shaped member is heated and melted and adhered to the outer periphery of the separator body, a known thermocompression bonding device [a heating roll and a heat sealer (such as an impulse sealer)] can be used. Further, from the viewpoint of suppressing thermal deformation of the separator body, it is preferable to heat and press-bond only the portion where the frame-shaped member is arranged, and heat-press and press only the portion to be the frame-shaped member with a heat sealer (such as an impulse sealer). Is more preferred.

As a method of sequentially laminating each layer constituting the frame-shaped member directly on the separator body, for example, a raw material solution to be a heat-resistant annular support member is applied to one surface of the separator body and dried to form a heat-resistant annular support. A member is formed, and a raw material solution to be a first seal layer is applied on the surface of the heat-resistant annular support member and dried. Subsequently, the separator body is rotated to laminate the heat-resistant annular support member and the second seal layer on the surface on which the first seal layer is not formed in the same procedure as the first seal layer. Is mentioned.
The size and arrangement of the heat-resistant annular support member, the first seal layer, and the second seal layer can be appropriately adjusted according to the positions of the frame member and the separator body in the desired lithium ion battery separator.

In the lithium ion battery of the present invention, as the separator, a porous film made of polyethylene or polypropylene, a laminated film of a porous polyethylene film and porous polypropylene, a nonwoven fabric made of synthetic fibers (such as polyester fibers and aramid fibers) or glass fibers And known separators for lithium ion batteries, such as those having ceramic fine particles such as silica, alumina and titania adhered to their surfaces.

[Production method of lithium ion battery]
Subsequently, a method of manufacturing a lithium ion battery using a preferable separator in the lithium ion battery of the present invention will be described. For example, the process is performed according to the steps shown in FIGS.
4A to 4G are explanatory views schematically showing an example of the method for manufacturing the lithium ion battery of the present invention.
As shown in FIG. 4A, a positive electrode active material slurry 30a in which the above-described electrolytic solution and the positive electrode active material are mixed is applied to one surface of the positive electrode current collector 40. By this step, as shown in FIG. 4B, a positive electrode 50 in which the positive electrode active material layer 30 is formed on one surface of the positive electrode current collector 40 can be obtained.
On the other hand, as shown in FIG. 4C, one surface of the negative electrode current collector 41 is coated with the above-described electrolytic solution and the negative electrode active material slurry 31a. By this step, as shown in FIG. 4D, a negative electrode 51 in which the negative electrode active material layer 31 is formed on one surface of the negative electrode current collector 41 can be obtained.
Thereafter, as shown in FIG. 4E, the surface of the positive electrode 50 on which the positive electrode active material layer 30 is formed faces upward, and the lithium ion battery separator 1 formed by the separator main body 10 and the frame member 20 is stacked.
Next, as shown in FIG. 4F, the separator 1 for a lithium ion battery is inverted, and is overlaid on the surface of the negative electrode 51 on which the negative electrode active material layer 31 is formed.
The lithium ion battery 100 shown in FIG. 4 (g) is obtained through the steps shown in FIGS. 4 (a) to 4 (f).
When combining the positive electrode 50 or the negative electrode 51 with the lithium ion battery separator 1, the sealing layer 22 (the part where the frame member 20 contacts the positive electrode current collector 40 or the negative electrode current collector 41) After heat-sealing the sides, it is preferable that the remaining one side be vacuum-sealed and bonded.
Although the lithium ion battery 100 shown in FIG. 4G is not housed in the battery case, it may be housed in the battery case as needed. Further, when housed in the battery exterior body, a plurality of lithium ion batteries 100 may be stacked in series or in parallel.
In the lithium ion battery of the present invention, at least one of the positive electrode current collector 40 and the negative electrode current collector 41 is a resin current collector using the above-described resin (P). If one of the positive electrode current collector 40 and the negative electrode current collector 41 is a resin current collector using the above-described resin (P), the other current collector may be a known current collector.

Examples of the known current collector include metal foils such as copper, aluminum, titanium, stainless steel, and nickel; the above-described resin current collector not containing the resin (P); a conductive carbon sheet; and a conductive glass sheet. .

An example in which the lithium ion battery 100 shown in FIG. 4G is housed in a battery outer case will be described with reference to FIG.
FIG. 5 is an explanatory view schematically showing one example of the lithium ion battery of the present invention.
In the lithium-ion battery 100 'shown in FIG. 5, the lithium-ion battery 100 shown in FIG. 4G is covered with a battery case, that is, a positive electrode case 150 and a negative electrode case 151.
The positive electrode casing 150 and the negative electrode casing 151 are electrically connected to corresponding current collectors (the positive electrode current collector 40 and the negative electrode current collector 41), respectively. On the other hand, an insulative resin layer (not shown) is formed in a portion that comes into contact with each battery outer package, and the positive electrode package 150 and the negative electrode package 151 are insulated.

From the viewpoint of durability and charge / discharge characteristics, the lithium ion battery of the present invention preferably has an electric resistance value increase rate of 100% or less, more preferably 90% or less.
The rate of increase in electric resistance can be determined by the following method.
At room temperature, using a charge / discharge measuring device “Battery Analyzer 1470” (manufactured by Toyo Technica Co., Ltd.), the battery was charged to 4.2 V at a current of 0.2 C, and after a pause of 10 minutes, at a current of 0.2 C. The battery is discharged to 2.5 V, and this charging and discharging is repeated for 100 cycles.
The electric resistance value of the lithium ion battery is calculated from the value 10 seconds after the start of discharging.
Electric resistance = [{voltage (V) 10 seconds after start of discharge—voltage (V) at start of discharge} / {current (A) 10 seconds after start of discharge—current (A) at start of discharge}
Electric resistance increase rate (%) = [electric resistance after 100 cycles (Ω) −initial electric resistance (Ω)] ÷ initial electric resistance (Ω) × 100]

The lithium ion battery of the present invention preferably has a capacity retention ratio of 50% or more, more preferably 60% or more, from the viewpoint of charge and discharge characteristics.
The capacity retention ratio can be determined by the following method.
At room temperature, using a charge / discharge measuring device “Battery Analyzer 1470” (manufactured by Toyo Technica Co., Ltd.), the battery was charged to 4.2 V at a current of 0.2 C, and after a pause of 10 minutes, at a current of 0.2 C. The battery is discharged to 2.5 V, and this charging and discharging is repeated for 100 cycles.
At this time, the battery capacity at the first charge (initial discharge capacity) and the battery capacity at the 100th cycle charge (discharge capacity after 100 cycles) are measured, and the discharge capacity retention rate can be calculated from the following equation. The larger the value, the less the battery deteriorates.
Discharge capacity retention rate (%) = (discharge capacity after 100 cycles / initial discharge capacity) × 100

Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to the examples unless departing from the gist of the present invention. Unless otherwise specified, parts mean parts by weight and% means% by weight.

<Preparation of electrolyte>
LiN (FSO ₂ ) ₂ was dissolved in a propylene carbonate (PC) solvent at a rate of 1 mol / L to prepare an electrolyte solution (X-1).

LiN (FSO ₂ ) ₂ was dissolved at a ratio of 1 mol / L in a mixed solvent (volume ratio 1: 1) of ethylene carbonate (EC) and propylene carbonate (PC) to prepare an electrolyte solution (X-2).

LiN (FSO ₂ ) ₂ was dissolved at a rate of 1 mol / L in a dimethyl carbonate (DMC) solvent to prepare an electrolyte solution (X-3).

The materials of the resin current collector used in the following examples are as follows.
Resin (P)
p-1: [random polypropylene, crystallinity 25, trade name "Sun Allomer PB222A", manufactured by Sun Allomer Co., Ltd.]
p-2: [random polypropylene, crystallinity 31, trade name "Sun Allomer PC630A", manufactured by Sun Allomer Co., Ltd.]
p-3: [Block polypropylene, crystallinity 34, trade name "Qualia CM688A", manufactured by Sun Allomer Co., Ltd.]
p-4: [Block polypropylene, crystallinity 37, trade name "Sun Allomer PC684S", manufactured by Sun Allomer Co., Ltd.]
p-5: [Homopolypropylene, crystallinity 47, trade name "Sun Allomer PM900A", manufactured by Sun Allomer Co., Ltd.]
p-6: [High-density polyethylene, crystallinity 52, trade name "Suntech B680", manufactured by Asahi Kasei Chemicals Corporation]
p-7: [High-density polyethylene, crystallinity 60, trade name "Suntech A260", manufactured by Asahi Kasei Chemicals Corporation]
Conductive carbon filler graphite particles: [trade name "SNH-A1F1", manufactured by JFE Chemical Corporation]
Acetylene black: [trade name "DENKA BLACK", manufactured by Denka Corporation]
Nickel powder: [trade name "Nickel Powder Type 255", manufactured by Vale]
Dispersant [trade name "UMEX 1001 (acid-modified polypropylene)", manufactured by Sanyo Chemical Industries, Ltd.]

<Example 1>
(Preparation of negative electrode resin current collector)
In a twin-screw extruder, 14 parts of p-4, 14 parts of p-5, 70 parts of nickel powder and 2 parts of dispersant are melt-kneaded under the conditions of 180 ° C., 100 rpm, and a residence time of 5 minutes to collect resin. An electrical conductor material was obtained.
The obtained resin current collector material was extruded from a T-die and rolled with a cooling roll adjusted to a temperature of 50 ° C. to obtain a negative electrode resin current collector having a film thickness of 100 μm.

(Preparation of positive electrode resin current collector)
55 parts of p-2, 30 parts of graphite particles, 10 parts of acetylene black and 5 parts of dispersant are melt-kneaded with a twin-screw extruder under the conditions of 180 ° C., 100 rpm, and a residence time of 5 minutes to collect resin. A body material was obtained.
The obtained resin current collector material was extruded from a T-die and rolled with a cooling roll adjusted to a temperature of 50 ° C. to obtain a 100 μm-thick positive electrode resin current collector.

[Swelling rate]
The resin current collector material was applied on a horizontal glass plate and air-dried at room temperature for half a day. Next, it was left still for 3 hours in a vacuum drier heated to 80 ° C. Thereafter, a resin current collector material cut into dimensions of 10 × 40 × 0.2 mm cooled to room temperature was used as a test piece. The test piece was immersed in an electrolytic solution used for producing a lithium ion battery described later at 50 ° C. for 3 days to prepare a resin current collector material in a saturated liquid absorbing state.
The swelling ratio was determined from the change in weight of the test piece before and after liquid absorption by the following equation. The results are shown in Table 2.
Swelling ratio [%] = [(weight of test piece after liquid absorption−weight of test piece before liquid absorption) / weight of test piece before liquid absorption] × 100
The case where the swelling ratio was 0.1% or less was indicated by "O", and the case where the swelling ratio exceeded 0.1% was indicated by "X".

[Preparation of negative electrode active material slurry]
63 parts of non-graphitizable carbon particles [Carbotron (registered trademark) manufactured by Kureha Battery Materials Japan Co., Ltd., volume average particle diameter 25 μm] in 36 parts of electrolyte solution (X-1) and carbon fiber as a conductive material After adding 1 part of [Donacarb Milled S-243, manufactured by Osaka Gas Chemical Co., Ltd.], the mixture was mixed at 2,000 rpm for 1.5 minutes using a planetary stirring type mixing and kneading apparatus {Awatori Neritaro [Shinky Co., Ltd.]}. The mixture was mixed to prepare a negative electrode active material slurry.

(Preparation of positive electrode active material slurry)
One part of a conductive carbon filler (trade name: Denka Black, manufactured by Denka Corporation) and 57 parts of LiNi _0.8 Co _0.15 Al _0.05 O ₂ powder as positive electrode active material particles were combined with an electrolyte (X-1). The mixture was mixed with 42 parts to prepare a positive electrode active material slurry.

[Manufacture of separator body]
A flat cell guard 2500 (made of PP, thickness 25 μm) was cut into a square of 14 mm × 14 mm to obtain a separator body.

[Production of frame-shaped member]
Adhesive polyolefin-based resin film serving as a seal layer on both sides of a polyethylene naphthalate film (PEN film, Teonex Q51, thickness 250 μm, manufactured by Teijin Limited) serving as a heat-resistant annular support member [Admer VE300 manufactured by Mitsui Chemicals, Inc. , A thickness of 50 μm], and the heat-resistant annular support member and the sealing layer were adhered by a heating roll to prepare a laminate. Thereafter, the laminate is cut into a square of 15 mm × 15 mm, and furthermore, by punching out a central area of 11 mm × 11 mm, a heat-resistant annular support member (PEN layer) made of PEN and a seal layer are laminated to form a square. An annular laminate (frame-like member) having a width of 4 mm on four sides was obtained.

[Bonding of the separator body and frame member]
The center of gravity based on the outer dimensions of the frame-shaped member and the center of gravity based on the outer dimensions of the separator main body are overlapped, and one seal layer (hereinafter referred to as a second seal layer) of each frame-shaped member is brought into contact with the separator main body. The frame-shaped member is overlapped on one surface of the separator body, melted and bonded to the separator body by heating the frame-shaped member with an impulse sealer, and the frame-shaped member is annularly arranged on one surface along the outer periphery of the separator body. Thus, a separator for a lithium ion battery was obtained.

[Production of lithium ion battery]
A positive electrode active material slurry was applied to one surface of the positive electrode resin current collector to prepare a positive electrode having an electrode thickness of 300 μm. Similarly, a negative electrode active material slurry was applied to one surface of the negative electrode resin current collector to prepare a negative electrode having an electrode thickness of 300 μm. The frame-shaped separator was stacked with the surface of the positive electrode on which the positive electrode active material layer was formed facing upward. Then, the frame-shaped separator was inverted and overlaid on the surface of the negative electrode on which the negative electrode active material layer was formed. Heat sealing three sides of the sealing layer of the member on the frame (the portion where the member on the frame and the positive electrode resin current collector or the negative electrode resin current collector are in contact), and vacuum-sealing and bonding the remaining one side, lithium ion I got a battery.

[Electrode strength]
The electrode strength of the positive electrode and the negative electrode was evaluated by the following winding test.
The winding test was performed by winding the positive electrode and the negative electrode in the production of the lithium ion battery around a cylinder having a diameter of 6 mm, and visually observing whether or not the active material was separated from the resin current collector. Those in which the electrode active material layer did not peel off from the resin current collector were indicated by ○, and those in which the electrode active material layer peeled off from the resin current collector were indicated by x. The results are shown in Table 2.

[Electric resistance increase rate]
At room temperature, using a charge / discharge measuring device “Battery Analyzer 1470” (manufactured by Toyo Technica Co., Ltd.), the battery was charged to 4.2 V at a current of 0.2 C, and after a pause of 10 minutes, at a current of 0.2 C. The battery was discharged to 2.5 V, and this charge / discharge was repeated 100 cycles.
The electric resistance value of the lithium ion battery was calculated from the value of 10 seconds from the start of discharging.
Electric resistance = [{voltage (V) 10 seconds after start of discharge—voltage (V) at start of discharge} / {current (A) 10 seconds after start of discharge—current (A) at start of discharge}
The rate of increase in electric resistance was calculated from the following equation. The results are shown in Table 2.
Electric resistance increase rate (%) = [electric resistance after 100 cycles (Ω) −initial electric resistance (Ω)] ÷ initial electric resistance (Ω) × 100
The case where the rate of increase in electric resistance was 100% or less was indicated by Δ, and the case where the rate of increase exceeded 100% was indicated by ×.

[Capacity maintenance rate]
At room temperature, using a charge / discharge measuring device “Battery Analyzer 1470” (manufactured by Toyo Technica Co., Ltd.), the battery was charged to 4.2 V at a current of 0.2 C, and after a pause of 10 minutes, at a current of 0.2 C. The battery was discharged to 2.5 V, and this charge / discharge was repeated 100 cycles.
At this time, the battery capacity at the first charge (initial discharge capacity) and the battery capacity at the 100th cycle charge (discharge capacity after 100 cycles) were measured. The discharge capacity maintenance ratio was calculated from the following equation. The results are shown in Table 2. Note that the larger the numerical value, the smaller the deterioration of the battery.
Discharge capacity retention rate (%) = (discharge capacity after 100 cycles / initial discharge capacity) × 100
The case where the discharge capacity retention ratio was 50% or more was indicated by Δ, and the case where it was less than 50% was indicated by X.

<Examples 2, 4, and 7, Comparative Examples 1 to 4>
Lithium according to Examples 2, 4 and 7, and Comparative Examples 1 to 4 by the same method as in Example 1 except that the mixing ratio of resin (P) in the resin current collector and the type of electrolyte solution were changed. An ion battery was obtained. In addition, about the measurement of the swelling ratio, it measured using the electrolyte solution used when producing each lithium ion battery.

<Example 3>
A lithium ion battery according to Example 3 was obtained in the same manner as in Example 1, except that the positive electrode resin current collector was changed to a metal current collector (aluminum foil). In addition, the swelling ratio and the electrode strength were measured using the electrolytic solution used in producing the lithium ion battery.

<Examples 5 and 6>
Example 5 was repeated in the same manner as in Example 1 except that the negative electrode resin current collector was changed to a metal current collector (copper foil) and the mixing ratio of the resin (P) in the positive electrode resin current collector was changed. 6 was obtained. In addition, about the measurement of the swelling ratio, it measured using the electrolyte solution used when producing each lithium ion battery.

The electrode for a lithium ion battery of the present invention is particularly useful as an electrode for a lithium ion battery used for mobile phones, personal computers, hybrid vehicles and electric vehicles.

1 Lithium-ion battery separator 10 Separator main body 20 Frame members 21, 21a, 21b Heat-resistant annular support member 22 Seal layer 22a First seal layer 22b Second seal layer 30a Positive active material slurry 30 Positive active material layer 31a Negative active material Slurry 31 Negative electrode active material layer 40 Positive electrode current collector 41 Negative electrode current collector 50 Positive electrode 51 Negative electrode 100, 100 ′ Lithium ion battery 150 Positive case (battery case)
151 Negative Case (Battery Case)

Claims (5)

An electrode for a lithium-ion battery including an electrolyte, an electrode active material, and a resin current collector,
The electrolytic solution contains a solvent and an electrolyte containing propylene carbonate,
The resin current collector includes a resin (P) and a conductive filler,
An electrode for a lithium ion battery, wherein the resin (P) constituting the resin current collector has a crystallinity of 31 to 50. The electrode for a lithium ion battery according to claim 1, wherein the solvent is only propylene carbonate or a mixture of propylene carbonate and ethylene carbonate. The electrode for a lithium ion battery according to claim 1, wherein the resin (P) is a mixture containing two or more resins having different crystallinities. A lithium ion battery comprising a separator and comprising the electrode for a lithium ion battery according to claim 1 on a positive electrode and a negative electrode. The separator comprises a sheet-shaped separator main body made of a polyolefin porous membrane, and a frame-shaped member arranged annularly along the outer periphery of the separator main body,
5. The frame-shaped member according to claim 4, comprising a heat-resistant annular support member, and a seal layer disposed on a surface of the heat-resistant annular support member and capable of thermocompression bonding with a positive electrode current collector or a negative electrode current collector. 6. The lithium ion battery according to the above.

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