JP7068025B2 - Polymers for matrix, non-aqueous electrolyte gels, and electrochemical devices. - Google Patents

Description

The present invention relates to macromolecules for matrices, non-aqueous electrolyte gels, and electrochemical devices.

A non-aqueous electrolyte secondary battery using a non-aqueous electrolyte gel using a polymer as a matrix is excellent in shape stability of the battery element inside the battery. For this reason, it is suitably used for an aluminum laminated exterior battery using an aluminum laminated film having no rigidity as an exterior material.

Aluminum laminated exterior batteries have advantages such as light weight and easy dimensional change, and their use in mobile phones, smartphones (smartphones), automobile batteries, and the like is expanding.

Japanese Unexamined Patent Publication No. 11-80296 Japanese Unexamined Patent Publication No. 2000-90728

PROGRESS IN POLYMER SCIENCE, 30 (2005) 1-9

On the other hand, with the recent progress in increasing the energy density of batteries, the internal strain due to expansion and contraction of electrodes during battery operation tends to increase. Therefore, in order to have a higher shape-retaining ability, it is required to increase the strength of the non-aqueous electrolyte gel.

In the future, it is expected that the use of non-aqueous electrolyte gels will be expanded to electrochemical devices other than non-aqueous electrolyte secondary batteries. High-strength non-aqueous electrolyte gels are also likely to be required for these electrochemical devices.

Therefore, although techniques for increasing the strength of the non-aqueous electrolyte gel have been proposed in Patent Documents 1 and 2, it cannot be said that the strength of the non-aqueous electrolyte gel is sufficiently enhanced even by these techniques. Further, Non-Patent Document 1 describes a technique for improving the mechanical strength of an aqueous gel (hydrogel), but does not mention a non-aqueous electrolyte gel using a non-aqueous solvent.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is a new and improved polymer for matrix, which can increase the strength of a non-aqueous electrolyte gel. To provide a water electrolyte gel, and an electrochemical device.

In order to solve the above problems, according to a certain viewpoint of the present invention, the matrix polymer constituting the matrix of the non-aqueous electrolyte gel, the matrix polymer is a polymer (A) and a polymer (B). ) Is contained at least in a mass ratio of (A) / (B) = 55/45 or more and 99/1 or less, and the polymer (A) is a first skeleton containing at least the skeleton represented by the following chemical formula (1). , The second skeleton including at least the skeleton represented by the following chemical formula (2) has a structure in which at least one of a graft copolymer and a block copolymer is copolymerized. However, the polymer (B) is provided with a polymer for a matrix, which is characterized by having a second skeleton.

In the chemical formulas 1 and 2, l, m, and q are integers of 1 or more.

According to this viewpoint, since the polymer for matrix has the above-mentioned structure, the non-aqueous electrolyte gel containing the polymer for matrix as a matrix has high strength.

Here, the polymer (A) may have a structure in which the second skeleton is graft-copolymerized with the first skeleton.

From this point of view, the non-aqueous electrolyte gel has even higher strength.

Further, the polymer (A) has a structure in which the first skeleton and the second skeleton are graft-copolymerized via a (meth) acrylic acid ester unit (meth), and the polymer (A) has a (meth) structure. The acrylic ester unit may be contained in the second skeleton in an amount of more than 0 mol% and 10 mol% or less with respect to the total number of moles of the units constituting the second skeleton.

From this point of view, the non-aqueous electrolyte gel has even higher strength.

Further, the polymer (B) may contain an acidic functional group-containing unit in an amount of 2 mol% or more and 10 mol% or less with respect to the total number of moles of the units constituting the polymer (B).

From this point of view, the non-aqueous electrolyte gel has even higher strength. In addition, non-aqueous electrolyte gels have high adhesive strength.

Further, the polymer for matrix may contain at least the polymer (A) and the polymer (B) in a mass ratio of (A) / (B) = 70/30 or more and 95/5 or less.

From this point of view, the non-aqueous electrolyte gel has even higher strength.

According to another aspect of the present invention, there is provided a non-aqueous electrolyte gel characterized by containing the above-mentioned matrix polymer.

The non-aqueous electrolyte gel according to this viewpoint has high strength.

According to another aspect of the present invention, there is provided an electrochemical device comprising the above-mentioned non-aqueous electrolyte gel.

Since the electrochemical device according to this viewpoint contains a non-aqueous electrolyte gel having high strength, improvement in characteristics can be expected.

Here, the electrochemical device may be a non-aqueous electrolyte secondary battery.

The non-aqueous electrolyte secondary battery according to this aspect has high characteristics, for example, high life characteristics.

As described above, according to the present invention, it is possible to increase the strength of the non-aqueous electrolyte gel.

It is sectional drawing which shows the structure of the non-aqueous electrolyte secondary battery which concerns on embodiment of this invention. It is a graph which shows the correlation between the mass ratio of the polymer (A) in the polymer for matrix, and the compression strength of a non-aqueous electrolyte gel.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<1. Configuration of non-aqueous electrolyte secondary battery>
First, the configuration of the non-aqueous electrolyte secondary battery 1 according to the embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 shows a plan sectional view of the non-aqueous electrolyte secondary battery 1 and an enlarged view of a region A of the winding element (flat winding element) 100. The non-aqueous electrolyte secondary battery 1 includes a winding element 100, an electrolytic solution, and an exterior material 40. The winding element 100 has two separators 10, a positive electrode 20, and a negative electrode 30. The two separators 10, the positive electrode 20, and the negative electrode 30 are laminated in the order of the separator 10, the negative electrode 30, the separator 10, and the positive electrode 20. Of course, the stacking order of each component is not limited to this. Further, the separator 10, the positive electrode 20, and the negative electrode 30 are wound in a flat and spiral shape. Therefore, the separator 10 is interposed between the positive electrode 20 and the negative electrode 30. Further, as will be described in detail later, the separator 10 includes a base material layer 10a and an adhesive layer 10b. Further, a positive electrode tab 50 is provided on the innermost peripheral portion of the positive electrode 20, and a negative electrode tab 60 is provided on the innermost peripheral portion of the negative electrode 30. As described above, the non-aqueous electrolyte secondary battery 1 is a winding type non-aqueous electrolyte secondary battery. Of course, the non-aqueous electrolyte secondary battery 1 is not limited to the winding type, and may be a secondary battery of any shape (for example, a laminated type).

(1-1. Configuration of separator)
Next, each component of the winding element 100 will be described in detail. First, the separator 10 will be described. The separator 10 is interposed between the positive electrode 20 and the negative electrode 30. Further, the separator 10 is wound in a flat and spiral shape.

The separator 10 includes a base material layer 10a and an adhesive layer 10b. The base material layer 10a is a so-called strip-shaped porous film. The base material layer 10a is not particularly limited, and may be any material as long as it is used as a separator for, for example, a lithium ion secondary battery. As the base material layer 10a, it is preferable to use a porous film, a non-woven fabric, or the like exhibiting excellent high-rate discharge performance alone or in combination. Examples of the resin constituting the base material layer 10a include a polyolefin-based resin typified by polyethylene, polymer, etc., a polyethylene terephthalate, a polybutylene terephthalate, and the like. Polyester resin, PVDF, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoropolymer. Ethylene (tellafluoroethylene) polymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene (fluoroethylene) polymer, vinylidene fluoride-hexafluoroacetonee copolymer, fluoride. Vinylidene-ethylene polymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexa. Fluoropropylene (hexafluoropropylene) polymer, vinylidene fluoride-ethylene (ethylene) -tetrafluoroethylene (tellafluoroethylene) copolymer and the like can be mentioned.

The adhesive layer 10b adheres the separator 10, the positive electrode 20, and the negative electrode 30. The adhesive layer 10b is composed of a non-aqueous electrolyte gel. The non-aqueous electrolyte gel is a matrix polymer gelled by an electrolytic solution. In other words, the polymer for the matrix constitutes the matrix of the non-aqueous electrolyte gel. Hereinafter, the polymer for matrix will be described in detail.

The polymer for matrix contains at least the polymer (A) and the polymer (B) in a mass ratio of (A) / (B) = 55/45 or more and 99/1 or less. The polymer (A) has a first skeleton containing at least the skeleton represented by the following chemical formula (1) and a second skeleton containing at least the skeleton represented by the following chemical formula (2). It has a structure in which at least one of the block copolymers is copolymerized. The polymer (B) has a second skeleton. In chemical formulas 1 and 2, l, m, and q are integers of 1 or more.

Polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) can both form a non-aqueous electrolyte gel by themselves. However, these non-aqueous electrolyte gels did not have sufficient strength. Therefore, the present inventor tried to prepare a non-aqueous electrolyte gel by mixing polyvinylidene fluoride and polyacrylonitrile. As a result, the compatibility between polyvinylidene fluoride and polyacrylonitrile was poor, and the non-aqueous electrolyte gel was separated into two layers.

Therefore, the present inventor has diligently studied a technique for enhancing the compatibility of polyvinylidene fluoride and polyacrylonitrile. As a result, the present inventor has come up with the idea of copolymerizing polyvinylidene fluoride with acrylonitrile. The copolymer of polyvinylidene fluoride and acrylonitrile has high compatibility with polyacrylonitrile because the acrylonitrile chain in the copolymer is compatible with polyacrylonitrile. The present inventor further developed this finding and came up with the matrix polymer according to the present embodiment.

As described above, in the polymer (A), a first skeleton containing at least the skeleton represented by the chemical formula (1) and a second skeleton containing at least the skeleton represented by the chemical formula (2) are graft-copolymerized. And block copolymerization, it has a structure copolymerized in at least one or more embodiments. As a result, the second skeleton in the polymer (A) has an affinity with the polymer (B), so that the compatibility between the polymer (A) and the polymer (B) can be enhanced.

The first skeleton has a vinylidene fluoride unit and an acrylic acid unit as represented by the chemical formula (1). Here, the molar ratio (l / m) of the vinylidene fluoride unit and the acrylic acid unit is preferably 95/5 or more and 99.8 / 0.2 or less. If the molar ratio is less than 95/5, the crystallinity of the vinylidene fluoride unit may decrease and the gel strength may decrease, and if the molar ratio is larger than 99.8 / 0.2, the amount of acrylic acid unit is too small. It may not be possible to graft-copolymerize the second skeleton with the first skeleton. As described above, the main component of the first skeleton is vinylidene fluoride. Therefore, the first skeleton has properties similar to vinylidene fluoride. For example, the first skeleton has the characteristics of being highly crystalline and hard.

The second skeleton is preferably graft-copolymerized with the first skeleton. That is, it is preferable that the second skeleton is graft-copolymerized with the acrylic acid unit constituting the first skeleton. In this case, the polymer (A) has a so-called comb-shaped shape. Then, since the second skeleton forming the tooth of the comb tooth is compatible with the polymer (B), the compatibility between the polymer (A) and the polymer (B) becomes higher, and the strength of the non-aqueous electrolyte gel becomes stronger. Will be higher.

Further, the polymer (A) preferably has a structure in which the first skeleton and the second skeleton are graft-copolymerized via a (meth) acrylic acid ester unit. The present inventor examined the first skeleton and the second skeleton. As a result, the present inventor has found that the second skeleton can be easily graft-copolymerized with the first skeleton by binding the acrylic acid unit to the end of the second skeleton. When the terminal is an acrylonitrile unit, the electron-withdrawing property of the nitrile group affects and the halogen group at the terminal is difficult to be desorbed. As a result, it is presumed that the grafting reaction is inhibited. Here, it is preferable that the acrylic acid ester unit is contained in the second skeleton in an amount of more than 0 mol% and 10 mol% or less with respect to the total number of moles of the units constituting the second skeleton. In this case, the second skeleton can be easily graft-copolymerized by the first skeleton. The preferred upper limit is 5 mol% or less, and the preferred lower limit is 1 mol% or more.

From the viewpoint of not inhibiting the grafting reaction, the acrylic acid ester unit has a solvent affinity when used as a matrix (when the alkyl chain of the ester becomes long, the affinity with the electrolyte solvent decreases and the performance as a matrix deteriorates). It is preferable to select from the viewpoint. As the acrylic acid ester unit, for example, a primary (meth) acrylic acid ester such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl acrylate, etc. is used. be able to.

Here, the mass average molecular weight of the polymer (A) is preferably 100,000 or more and 3,000,000 or less. The mass average molecular weight can be measured, for example, by gel permeation chromatography (GPC).

The structure of the polymer (A) is specified by, for example, the following method. That is, 1H-NMR of the polymer (A) observes a chemical shift of protons corresponding to the skeletons of the chemical formulas (1) and (2). Next, differential thermal analysis (DSC) is measured to determine the melting point (Tm) derived from the structure of chemical formula (1) and the glass transition temperature (Tg) derived from the structure of chemical formula (2) in the polymer (A). Both are observed. As a result, it can be seen that the polymer (A) has both the skeletons of the chemical formula (1) and the chemical formula (2). Furthermore, when the gel permeation chromatography (GPC) of the polymer (A) is measured, a monomodal result indicating that the polymer (A) is a single substance is obtained. Therefore, it has the skeletons of the chemical formulas (1) and (2). It can be seen that there is not a mixture of macromolecules, but a chemically bound macromolecule (A). Further, when the polymer (A) is dissolved in a solvent (for example, 1-methyl-2-pyrrolidone) that dissolves the polymer (A), the layers do not separate, so that the chemical formulas (1) and (2) It can be seen that it is not a mixture (the polymer having the skeleton of the chemical formula (1) and the polymer having the skeleton of the chemical formula (2) are incompatible, so that they are separated into two layers even under a soluble solvent).

The polymer (B) has a second skeleton as described above. The polymer (B) is generally a polyacrylonitrile (PAN) or a polymer obtained by copolymerizing polyacrylonitrile with another unit.

The polymer (B) preferably contains an acidic functional group-containing unit in an amount of 2 mol% or more and 10 mol% or less with respect to the total number of moles of the units constituting the polymer (B). In this case, the adhesiveness between the non-aqueous electrolyte gel and each electrode is improved.

Here, examples of the acidic functional group-containing unit include acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-acrylamide-2-methylpropanesulfonic acid, 2-methacryloxyethyl acid phosphate and the like. The polymer (B) may contain one or more acidic functional group-containing units. The polymer (B) preferably contains acrylic acid as an acidic functional group-containing unit.

Here, the mass average molecular weight of the polymer (B) is preferably 100,000 or more and 3,000,000 or less. The mass average molecular weight can be measured, for example, by gel permeation chromatography (GPC).

The structure of the polymer (B) can be specified by, for example, 1H-NMR.

In the chemical formulas (1) and (2), any of the hydrogen atoms bonded to the carbon atom may be substituted with a hydrocarbon group.

The polymer for matrix contains at least the polymer (A) and the polymer (B) in a mass ratio of (A) / (B) = 55/45 or more and 99/1 or less. When the present inventor diligently studied the mass ratios of the polymers (A) and (B), the mass ratios of the polymers (A) and the polymer (B) were (A) / (B) = 55/45 or more 99. It was found that the strength of the non-aqueous electrolyte gel is specifically increased when the value is 1/1 or less. The present inventor considers the reason as follows. That is, the first skeleton constituting the polymer (A) has the characteristics of being harder and more brittle than the second skeleton and the polymer (B). On the other hand, the second skeleton and the polymer (B) have the characteristics of being softer and more supple than the first skeleton. Then, in the non-aqueous electrolyte gel, the second skeleton of the polymer (A) is intricately intertwined with the polymer (B). The first skeleton is dispersed and arranged in the non-aqueous electrolyte gel. When some external force (for example, strain due to expansion and contraction of the electrode during battery operation) acts on such a non-aqueous electrolyte gel, the first skeleton is destroyed in preference to the second skeleton or the polymer (B). .. That is, the first skeleton dispersed in the non-aqueous electrolyte gel is destroyed, so that the stress concentration of the non-aqueous electrolyte gel on a specific portion is suppressed. As a result, it is considered that the strength of the non-aqueous electrolyte gel is improved.

The preferable mass ratio of the polymer (A) and the polymer (B) is (A) / (B) = 60/40 or more and 98/2 or less, and more preferably (A) / (B) = 70 /. It is 30 or more and 95/5 or less, more preferably (A) / (B) = 75/25 or more and 93/7 or less, and further preferably (A) / (B) = 80/20 or more and 85 /. It is 15 or less. In this case, the strength of the non-aqueous electrolyte gel is further improved.

The non-aqueous electrolyte gel according to the present embodiment has high strength because the matrix polymer having the above-mentioned structure is a matrix. Therefore, even if the internal strain due to the expansion and contraction of the electrodes during battery operation becomes large, the electrolyte gel can firmly bond each electrode to the separator 10. Therefore, high shape retention is realized.

The thickness of the adhesive layer 10b is not particularly limited, but may be, for example, 0.5 to 5 μm.

The adhesive layer 10b may further contain heat-resistant particles in order to improve the heat resistance of the adhesive layer 10b. Here, the heat-resistant particles applicable to this embodiment are not particularly limited. For example, the heat-resistant particles may be organic particles, inorganic particles, or a mixture thereof. However, inorganic particles are more preferable because they often have better heat resistance than organic particles.

Examples of the organic particles include cross-linked polystyrene (cross-linked PS), cross-linked polymethyl methacrylate (cross-linked PMMA), silicone resin, epoxy cured product, polyether sulfone, and polyamide-imide. Examples thereof include fine particles of polyimide (polyimide), melamine resin, polyphenylene sulfide resin, and the like. The organic particles may be composed of one of these, or may be composed of two or more. The inorganic particles are, for example, ceramic particles, and more specifically, metal oxide particles. Examples of the metal oxide particles include fine particles of alumina, boehmite, titania, zirconia, magnesia, zinc oxide, aluminum hydroxide, magnesium hydroxide and the like.

As the positive electrode 20, the negative electrode 30, the electrolytic solution, and the exterior material, those that can be used in a general non-aqueous electrolyte secondary battery can be arbitrarily used. These are summarized below.

(1-2. Configuration of positive electrode)
The positive electrode 20 has a positive electrode current collector 20a, a positive electrode active material layer 20b formed on both sides of the positive electrode current collector 20a, and a positive electrode tab 50.

The positive electrode current collector 20a is made of, for example, aluminum, stainless steel, nickel-plated steel, or the like. A positive electrode tab 50 is connected to the positive electrode current collector 20a. The positive electrode current collector 20a is a so-called band-shaped current collector.

The positive electrode active material layer 20b contains at least the positive electrode active material, and may further contain a conductive agent and a binder. The positive electrode active material is not particularly limited as long as it is a substance capable of reversibly storing and releasing lithium ions, and is, for example, lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, and nickel cobalt aluminum acid. Lithium (hereinafter, may be referred to as "NCA"), lithium cobalt manganate (hereinafter, may be referred to as "NCM"), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, sulfur. , Iron oxide, vanadium oxide and the like. These positive electrode active materials may be used alone or in combination of two or more.

Among the examples of the positive electrode active material mentioned above, the positive electrode active material is particularly preferably a lithium salt of a transition metal oxide having a layered rock salt type structure. Examples of the lithium salt of the transition metal oxide having such a layered rock salt type structure include Li _{1-x-y-z Ni x} Coy Al _z O ₂ (NCA) or Li _1-x-y-z Ni. The lithium salt of the ternary transition metal oxide represented by _{x Coy Mn z O 2} (NCM) (0 <x <1, 0 <y <1, 0 <z <1, and x + y + z <1) Can be mentioned.

Examples of the conductive agent include carbon black such as Ketjenblack and acetylene black, carbon fiber, fibrous carbon such as carbon nanotubes, natural graphite, artificial graphite and the like, which enhance the conductivity of the positive electrode. There are no particular restrictions as long as it is for the purpose.

The binder binds the positive electrode active materials to each other and also binds the positive electrode active material and the positive electrode current collector 20a. The type of the binder is not particularly limited, and any binder used for the positive electrode active material layer of the conventional lithium ion secondary battery can be used. For example, polyvinylidene fluoride (polyvinylidene fluoride), vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene ( tetrafluoroetherylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, ethylenepropylenediene (ethylene-polyethylene-diene) ternary copolymer, styrene butadiene rubber (Stylene-butadiene rubber) rubber. polymer-butadiene rubber, fluororubber, polyvinylidene acetate, polymethylmethacrylate, polyethylene (polyethylene), polyethylene (polyethylene), nitrocellulose (cellulose), etc. The present invention is not particularly limited as long as it can be bound onto the positive electrode current collector 20a. Further, a known additive or the like may be further added to the positive electrode active material layer 20b.

(1-3. Configuration of negative electrode)
The negative electrode 30 includes a negative electrode current collector 30a, a negative electrode active material layer 30b formed on both sides of the negative electrode current collector 30a, and a negative electrode tab 60. The negative electrode 30 may be a so-called water-based negative electrode.

The negative electrode current collector 30a is made of, for example, copper (Cu), nickel (Ni), or the like. A negative electrode tab 60 is connected to the negative electrode current collector 30a. The negative electrode current collector 30a is a so-called band-shaped current collector.

The negative electrode active material layer 30b contains at least the negative electrode active material, and may further contain a thickener and a binder. The negative electrode active material constituting the negative electrode active material layer 30b is not particularly limited as long as it is a substance capable of alloying with lithium or reversible occlusion and release of lithium (Li). Examples of the negative electrode active material include metals such as lithium, indium (In), tin (Sn), aluminum (Al), and silicon (Si), alloys and oxides thereof, and Li _4/3 Ti _5/3 O ₄ . , SnO and other transition metal oxides, artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, non-graphitizable carbon, graphite carbon fiber, resin calcined carbon, thermally decomposed gas Examples thereof include carbon materials such as phase-growth carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin calcined carbon, graphite, and graphite-based carbon fibers. These negative electrode active materials may be used alone or in combination of two or more. Above all, it is preferable to use a graphite-based material as the main material.

The thickener adjusts the viscosity of the negative electrode mixture slurry to a viscosity suitable for coating, and functions as a binder in the negative electrode active material layer 30b. As the thickener, a water-soluble polymer is preferably used, and examples thereof include a cellulose-based polymer, a polyacrylic acid-based polymer, polyvinyl alcohol, polyethylene oxide, and the like. Examples of the cellulosic polymer include a metal salt or an ammonium salt of carboxymethyl cellulose (CMC), a cellulose derivative such as methyl cellulose, ethyl cellulose, and hydroxyalkyl cellulose. .. Other examples include polyvinylpyrrolidone (PVP), starch, phosphate starch, casein, various modified starches, chitin, chitosan derivatives and the like. These thickeners can be used alone or in combination of two or more. Of these, cellulosic polymers are preferred, and alkali metal salts of carboxymethyl cellulose are particularly preferred.

The binder binds the negative electrode active materials to each other. The binder is not particularly limited as long as it can be used as a binder for the negative electrode. Examples of the binder that can be used in this embodiment include fine particles of an elastomer-based polymer. Examples of the elastomer polymer include SBR (styrene butadiene rubber), BR (butadiene rubber), NBR (nitrile butadiene rubber), NR (natural rubber), IR (isoprene rubber), and EPDM (ethylene-propylene-diene ternary copolymer). Combined), CR (chloroprene rubber), CSM (chlorosulfonated polyethylene), acrylic acid ester, methacrylic acid ester copolymer, and partially hydrides, complete hydrides, acrylic acid ester-based copolymers, etc. Can be mentioned. These may be modified with a monomer having a polar functional group such as a carboxylic acid, a sulfonic acid, a phosphoric acid, or a hydroxyl group in order to improve the binding property.

The content ratio of the thickener and the binder in the negative electrode active material layer 30b is not particularly limited, and may be any content ratio applicable to the conventional negative electrode active material layer. Further, a known additive or the like may be further added to the negative electrode active material layer 30b.

(1-4. Electrolyte)

The electrolytic solution is a solution in which an electrolyte is dissolved in an organic solvent. Examples of the electrolyte satisfying the above characteristics include LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ). (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NClO ₄ , (n-C ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ) ₄ N-malate, (C ₂ H ₅ ) ₄ N-benzoate, (C ₂ H ₅ ) ₄ N-phtalate, stearyl sulphonic acid lithium, octyl sulphonic acid Examples thereof include organic ion salts such as lithium benzenesulfonate (dodecyl benzene sulphonic acid). Examples of the organic solvent include ethylene carbonate (EC) / ethyl propionate (ethyl propionate), propylene carbonate (polylene carbonate), ethylene carbonate (ethylene carbononate), butylene carbonate (ethylene carbononate), and chloroethylene carbonate (chloroethylene carbonate). ), Cyclic carbonate esters such as vinylene carbonate; cyclic esters such as γ-butyrolactone, γ-valerolactone; dimethyl carbonate, diethyl carbonate. ), Chain carbonates such as ethyl methyl carbonate; methyl format, methyl acetate, butyl acid methyl, ethyl acetate, propyl acetate. Chain esters such as acetyl, ethyl propionate, propyl propionate, etc .; tetrahydrofuran (Tetrahydrofuran) or derivatives thereof; 1,3-dioxane, 1,4-dioxane. ), 1,2-Dimethoxyethane, 1,4-dibutoxyethane, ethers such as methyldilyme; acetonitrile, benzonitrile, etc. Examples thereof include nitriles; dioxolane or a derivative thereof; ethylene sulfide (estylene sulfide), sulfolane, sultone or a derivative thereof, or a mixture thereof alone or a mixture thereof.

(1-5. Exterior material)
The exterior material 40 may be any material as long as it is used for the exterior material of the non-aqueous electrolyte secondary battery, but it is preferably a flexible exterior material. Such an exterior material is, for example, an aluminum laminated film, but may be a metal exterior material.

<3. Manufacturing method of non-aqueous electrolyte secondary battery ＞
Next, a method for manufacturing the non-aqueous electrolyte secondary battery 1 will be described. First, a gel matrix coating separator, a positive electrode 20, and a negative electrode 30 are manufactured.

(3-1. Manufacturing method of gel matrix coated separator)
An adhesive layer slurry is prepared by dissolving the polymers (A) and (B) in a solvent (for example, N-methylpyrrolidone (NMP)) at the above-mentioned mass ratio. Then, the adhesive layer slurry is applied to at least one surface of both surfaces of the base material layer 10a to form a coating layer. Then, before the coating layer dries, the coating layer and the base material layer 10a are immersed in a water bath. As a result, the matrix polymer is deposited on the surface of the base material layer 10a. That is, a matrix layer is formed on the surface of the base material layer 10a. Then, the base material layer 10a on which the matrix layer is formed is washed with water and dried. By the above steps, a gel matrix coating separator is produced.

(3-2. Manufacturing method of positive electrode)
The material of the positive electrode active material layer 20b is dispersed in a solvent to form a positive electrode mixture slurry, and the positive electrode mixture slurry is applied onto the positive electrode current collector 20a. As a result, a coating layer is formed. Then, the coating layer is dried. Then, the dried coating layer is rolled together with the positive electrode current collector 20a. Then, the positive electrode tab 50 is fixed to the end of the positive electrode current collector 20a by welding or the like. As a result, the positive electrode 20 is manufactured.

(3-3. Manufacturing method of negative electrode)
A negative electrode mixture slurry is formed by dispersing the material of the negative electrode active material layer 30b in a solvent, and this negative electrode mixture slurry is applied onto the negative electrode current collector 30a. This forms a coating layer. Then, the coating layer is dried. Then, the dried coating layer is rolled together with the negative electrode current collector 30a. Then, the negative electrode tab 60 is fixed to the end of the negative electrode current collector 30a by welding or the like. As a result, the negative electrode 30 is manufactured.

(3-4. Manufacturing method of winding element)
Then, the gel matrix coating separator, the negative electrode 30, the gel matrix coating separator, and the positive electrode 20 are laminated in this order to produce an electrode laminate. Then, the electrode laminate is wound flat. As a result, the back surface of the portion of the electrode laminate (that is, the positive electrode 20) is brought into contact with the back surface of the other portion of the electrode laminate 100a (that is, the separator 10). As a result, a compression prewinding element is manufactured. Then, the flat winding element is manufactured by crushing the compression prewinding element. Here, the pressurizing direction when crushing the compression prewinding element is, for example, the arrow B direction shown in FIG.

<6. Manufacturing method of winding type secondary battery ＞
Next, a flat winding element and an electrolytic solution are enclosed in an exterior material to produce a secondary battery before crimping. Here, the positive electrode tab 50 and the negative electrode tab 60 are pulled out to the outside of the exterior material. Then, by pressurizing the secondary battery before crimping while heating, the flat winding element is integrated. The pressurizing direction is, for example, the arrow B direction shown in FIG. By the above steps, the non-aqueous electrolyte secondary battery 1 is manufactured.

As described above, in the present embodiment, the flat winding element is integrated by pressurizing the flat winding element while heating it. By this step, the matrix polymer in the matrix layer absorbs the electrolytic solution and swells. The matrix polymer is then completely dissolved (ie, solified) in the electrolyte. The heating temperature may be adjusted so that the matrix polymer is completely dissolved in the electrolytic solution. As an example, the heating temperature may be about 80 to 120 ° C. After that, the solized polymer for matrix is microcrystallized by cooling to form a non-aqueous electrolyte gel. The cooling temperature may be adjusted to such an extent that a non-aqueous electrolyte gel is formed, but may be, for example, room temperature (about 25 ° C.). As a result, the adhesive layer 10b is formed. The adhesive layer 10b firmly adheres to each electrode.

<1. Example 1>
Next, examples of the present invention will be described. In Example 1, the following tests were performed.

(1-1. Synthesis of polymer A)
1 kg of pure water and 0.35 g of carboxymethyl cellulose (carboxymethyl cellulose) were placed in a 2 L reaction vessel, and nitrogen substitution was performed. Next, 0.5 g of acrylic acid and 500 g of vinylidene fluoride (VDF) monomer were added to the reaction vessel, and then 1.7 g of a 75% by mass isododecane solution of t-amyl hyperpivalate was added to the reaction vessel. Introduced. Then, the temperature inside the system was raised to 50 ° C. Then, while continuously supplying a 2% by mass aqueous solution of acrylic acid into the reaction vessel, stirring was continued for 12 hours while keeping the internal pressure constant. The heating was stopped and the pressure was released until the pressure in the reaction vessel reached atmospheric pressure. Then, the reaction product was washed with water and dried. Through the above steps, an acrylic acid-modified PVDF polymer (polymer (a1)) (polymer having a first skeleton) was obtained. The characteristics of the acrylic acid-modified PVDF polymer (polymer (a1)) are as follows. The mass average molecular weight was measured by GPC (gel permeation chromatography).
Composition: VDF: Acrylic acid = 98.8: 1.2 (molar ratio)
Mass average molecular weight: 1,000,000
Melting point: 165 ° C

Further, 142.5 g of acrylonitrile was maintained at 110 ° C. for 24 hours in a nitrogen atmosphere in the presence of 5.4 g of tetrabutylammonium iodide and 2.8 g of 2-iodo-2-methylpropanenitrile. As a result, acrylonitrile was bulk polymerized. Then, 7.5 g of n-butyl acrylate was added, and the temperature was further increased to 110 ° C. for 12 hours. As a result, a polymer (b) represented by the chemical formula (2) and having n-butyl acrylate adjacent to the iodine terminal was synthesized. The mass average molecular weight by GPC (gel permeation chromatography) was 10,000. The molar ratio of acrylonitrile: n-butyl acrylate = 98: 2.

Then, 89 g of the polymer (a1) and 11 g of the polymer (b) were dissolved in 1400 g of N-methyl-2-pyrrolidone. Then, the solution was heated to 60 ° C. under a nitrogen atmosphere, and then 3.3 g of 1,8-diazabicyclo [5.4.0] -7-undecene was added and kept for 12 hours. As a result, the carboxylic acid of the polymer (a1) was reacted with the terminal iodine of the polymer (b). That is, it was grafted. Then, the product was precipitated with a large amount of methanol, filtered off, and dried to obtain a polymer (A1).

(1-2. Synthesis of polymer B)
28 g of acrylonitrile, 2 g of acrylic acid, and (acrylonitrile: molar ratio of acrylic acid = 95: 5) were added to 270 g of ion-exchanged water, and the temperature was raised to 60 ° C. under a nitrogen atmosphere. Then, 3.17 g of ammonium persulfate was added to the mixed solution and subjected to precipitation polymerization to synthesize a random copolymer represented by the chemical formula (2). The precipitate was filtered off, washed with methanol and dried to obtain a polymer (B1). The mass average molecular weight by GPC was 450,000 (polyethylene oxide equivalent).

(1-3. Preparation of non-aqueous electrolyte gel)
A non-aqueous electrolyte solution was prepared by dissolving 1 M of LiPF6 in a solvent in which ethylene carbonate / ethylmethyl carbonate was mixed at a ratio of 3: 7 (volume ratio). 19 g of this non-aqueous electrolytic solution was put into a 30 ml PFA container, and 0.98 g of the polymer (A1) and 0.02 g of (B1) ((A1) / (B1) = 98/2 mass ratio) were added thereto. The polymer was dissolved by stirring this mixture while heating it to 100 ° C. in a dry atmosphere. Then, the solution was allowed to cool to room temperature to prepare a non-aqueous electrolyte gel.

(1-4. Measurement of non-aqueous electrolyte gel strength)
The stress-displacement curve of the obtained non-aqueous electrolyte gel when the gel was compressed at 1 mm / min using a columnar indenter having a diameter of 4 mm was measured. The compressive strength (compressive elastic modulus) was calculated by linearly approximating the stress curve between the displacements of 0.5 and more and 2.0 mm or less. The results are shown in FIG.

(1-5. Preparation of non-aqueous electrolyte secondary battery (gel polymer battery))
(Preparation of positive electrode)
A positive electrode mixture slurry was prepared by dissolving and dispersing lithium cobalt oxide, carbon black, and polyvinylidene fluoride (PVDF) in N-methylpyrrolidone at a solid content mass ratio of 96: 2: 2. Then, the positive electrode mixture slurry was applied to both sides of the aluminum foil current collector having a thickness of 12 μm, and then dried. A positive electrode active material layer was prepared by rolling the coated layer after drying. The total thickness of the current collector and the positive electrode active material layer was 120 μm. Then, an aluminum lead wire (positive electrode tab) was welded to the end of the current collector to obtain a positive electrode.

(Manufacturing of negative electrode)
A negative electrode mixture slurry was prepared by dissolving and dispersing graphite, an aqueous dispersion of modified SBR fine particles, and a sodium salt of carboxymethyl cellulose in an aqueous solvent at a solid content mass ratio of 97.5: 1.5: 1. Then, this negative electrode mixture slurry was applied to both sides of a copper foil current collector having a thickness of 10 μm, and then dried. A negative electrode active material layer was obtained by rolling the coated layer after drying. The total thickness of the current collector and the negative electrode active material layer was 120 μm. Then, a nickel lead wire (negative electrode tab) was welded to the end of the current collector to obtain a band-shaped negative electrode.

(Preparation of gel matrix coating separator)
The total mass of the polymer (A1) is 4.9 g and the polymer (B1) is 0.1 g (that is, the total mass of the polymers (A1) and (B1) is 5 g, and the mass ratio is (A1) / (B1) = 98/2. Was dissolved in 95 g of NMP. This solution was applied to both sides of a 9 μm-thick porous polyethylene separator film. The gel matrix polymer was deposited on the separator film by immersing it in a water bath before the coated surface was dried. Then, the film in which the polymer was precipitated was washed with water and dried to prepare a separator coated with the porous gel matrix polymer. The coating amount of the gel matrix polymer was 2 g / m ² on both sides.

(Manufacturing of non-aqueous electrolyte secondary battery)
An electrode laminate was produced by laminating the separator, the negative electrode, the separator, and the positive electrode in this order. Then, the electrode laminate was wound around a flat core. That is, the electrode laminate was wound. Here, the end portions on the positive electrode tab and the negative electrode tab side were set to start winding. As a result, a compression prewinding element was manufactured. After fixing the end of the outermost peripheral portion of the compression prewinding element with tape, the winding core was removed. Then, the compression pre-winding element was crushed by sandwiching the compression pre-winding element between the two metal plates. As a result, a flat winding element was obtained.

The flat winding element and the electrolytic solution were enclosed in a laminating film (exterior material) composed of three layers of polypropylene / aluminum / nylon. Here, the two lead wires were pulled out to the outside of the laminated film. Further, as the electrolytic solution, one in which 1 M of LiPF6 was dissolved in a solvent obtained by mixing ethylene carbonate / ethylmethyl carbonate at a ratio of 3: 7 (volume ratio) was used.

Then, the pre-crimp secondary battery was sandwiched between two 3 cm thick metal plates heated to 100 ° C. and held at a pressure of 0.5 MPa for 2 minutes. By this step, the gel matrix applied on the separator film is dissolved in the enclosed electrolytic solution. Then, the secondary battery was re-sandwiched between the two metal plates at 25 ° C., and allowed to cool for 1 hour while being held at a pressure of 0.5 MPa. By this step, the dissolved gel matrix polymer undergoes microcrystallization to form a non-aqueous electrolyte gel. By this gel formation, the flat winding element was integrated. Through the above steps, a secondary battery before initial charging was produced.

Then, the secondary battery before the initial charge was charged with a constant current up to 4.35 V at 1/10 CA (1 CA is a 1-hour discharge rate) of the design capacity, and then continuously charged with a constant voltage at 4.35 V until it became 1/20 CA. .. After that, constant current discharge was performed up to 3.0 V at 1 / 2CA. By this step, a non-aqueous electrolyte secondary battery was produced. The discharge capacity at this time was taken as the initial discharge capacity.

(1-6. Life test)
A life test was carried out in which this non-aqueous electrolyte secondary battery was charged at 0.5 CA at a temperature of 25 ° C. and discharged at 1 CA for 200 cycles. Then, the capacity retention rate was measured by dividing the discharge capacity after 200 cycles by the initial discharge capacity. The capacity retention rate of Example 1 was 84%, and the appearance of the battery after the life test did not change from the state before the start of the life test.

(1-7. Cycle swelling test)
The thickness of the prepared non-aqueous electrolyte secondary battery after the initial discharge capacity was measured was measured with a thickness gauge and used as the initial thickness. Then, at 25 ° C., 1 / 2CA constant current charge, 1 / 20CA constant voltage charge, and 1 / 2CA constant current discharge were repeated at 4.35 V for 200 cycles in this order. After that, the thickness of the battery was measured with a thickness gauge, and the rate of change (swelling rate) from the initial thickness was calculated. The swelling rate was 8%. The smaller the swelling rate, the better the dimensional stability of the battery, which is preferable. Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<2. Example 2>
The same test as in Example 1 was performed except that the mixing ratio of the polymer (A1) and the polymer (B1) was 93/7 (mass ratio). Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<3. Example 3>
The same test as in Example 1 was performed except that the mixing ratio of the polymer (A1) and the polymer (B1) was set to 83/17 (mass ratio). Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<4. Example 4>
The same test as in Example 1 was performed except that the mixing ratio of the polymer (A1) and the polymer (B1) was 75/25 (mass ratio). Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<5. Example 5>
The same test as in Example 1 was performed except that the mixing ratio of the polymer (A1) and the polymer (B1) was 60/40 (mass ratio). Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<6. Comparative Example 1>
The same test as in Example 1 was performed except that the mixing ratio of the polymer (A1) and the polymer (B1) was 50/50 (mass ratio). Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate. Distortion was observed in the appearance of the cell after the life test.

<7. Comparative Example 2>
The same test as in Example 1 was performed except that only the polymer (A1) was used. Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<8. Comparative Example 3>
The same test as in Example 1 was performed except that only the polymer (B1) was used. Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate. The prepared non-aqueous electrolyte gel showed no stress against compressive displacement because it had almost no solid properties, although it had properties showing continuity of cross-linking. Distortion was observed in the appearance of the cell after the life test.

<9. Comparative Example 4>
The same test as in Example 1 was carried out except that an acrylic acid-modified PVDF polymer (polymer (a1)) was used. Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<10. Comparative Example 5>
The same test as in Example 1 was performed except that the mixing ratio of the polymer (a1) and the polymer (B1) was 50/50. Table 1 shows the compressive elastic modulus, the capacitance retention rate, and the swelling rate.

<11. Consideration>
Regarding the compressive strengths of Examples 1 to 5 and Comparative Examples 1, 2 and 3, a graph showing the polymer (A1) content (mass%) on the horizontal axis and the compressive strength on the vertical axis is shown in FIG. The straight line in FIG. 2 is a straight line connecting the plots of the polymer (A1) alone and the polymer (B1) alone, and if additivity is simply established, an arbitrary ratio of (A1) / (B1) is established. Is expected to be plotted near this straight line. In the actual results, when the content (mass%) of the polymer (A1) is 55% or more and 99% or less ((A) / (B) = 55/45 or more and 99/1 or less), more specifically ( When A) / (B) = 60/40 or more and 98/2 or less (Examples 1 to 5), each plot deviated from the straight line and a peculiar strength improving effect was observed. Further, when the content of the polymer (A1) is 70% or more and 95% or less ((A) / (B) = 70/30 or more and 95/5 or less), the strength improving action is obtained (Examples 2 to 4). It became more prominent.

On the other hand, the compressive strength with a 50% content (Comparative Example 1) is almost the same as the elastic modulus with a 0% content (Comparative Example 3), and is specifically with respect to the elastic modulus assumed from the additivity of the mixture. It was low. Further, when (a1) / (B1) was 50/50 (mass ratio) (Comparative Example 5), the elastic modulus did not specifically decrease as in Comparative Example 1. It is considered that this is because the polymer (a1) does not have the structure represented by the formula (2) and therefore does not interact with the polymer (B1).

Furthermore, a correlation was found between the life test results of the non-aqueous electrolyte secondary battery containing the non-aqueous electrolyte gel using the polymer for matrix, and the compressive elastic modulus and cell deformation. That is, in Examples 1 to 5, a high compressive elastic modulus was realized, the capacitance retention rate was excellent, and no strain was observed. On the other hand, in Comparative Examples 1 to 5, the compressive elastic modulus was low, and as a result, the capacitance retention rate was low. Distortion was also seen in some comparative examples.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that any person having ordinary knowledge in the field of the art to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

For example, in the above embodiment, the non-aqueous electrolyte gel is applied to a non-aqueous electrolyte secondary battery which is one of the electrochemical devices, but the present invention is not limited to such an example. The non-aqueous electrolyte gel according to the present embodiment may be applied to any electrochemical device including the non-aqueous electrolyte gel.

10 Separator 10a Base material layer 10b Adhesive layer 20 Positive electrode 20a Positive electrode current collector 20b Positive electrode active material layer 30 Negative electrode 30a Negative electrode current collector 30b Negative electrode active material layer 50 Positive electrode tab 60 Negative electrode tab

Claims (8)

A polymer for the matrix that constitutes the matrix of the non-aqueous electrolyte gel.
The polymer for matrix contains the polymer (A) and the polymer (B) at least in a mass ratio of (A) / (B) = 55/45 or more and 99/1 or less.
In the polymer (A), the first skeleton containing at least the following chemical formula (1) and the second skeleton containing at least the following chemical formula (2) are at least one of graft copolymerization and block copolymerization. It has a structure copolymerized in one or more embodiments and has a structure.
The polymer (B) is a polymer for a matrix, characterized by having the second skeleton.

In the chemical formulas 1 and 2, l, m, and q are integers of 1 or more. The polymer for a matrix according to claim 1, wherein the polymer (A) has a structure in which the second skeleton is graft-copolymerized with the first skeleton. The polymer (A) has a structure in which the first skeleton and the second skeleton are graft-copolymerized via a (meth) acrylic acid ester unit.
The (meth) acrylic acid ester unit is contained in the second skeleton in an amount of more than 0 mol% and 10 mol% or less with respect to the total number of moles of the units constituting the second skeleton. Item 2. The polymer for a matrix according to Item 2. The polymer (B) is characterized by containing an acidic functional group-containing unit in an amount of 2 mol% or more and 10 mol% or less with respect to the total number of moles of the units constituting the polymer (B). The polymer for a matrix according to any one of 1 to 3. The polymer for a matrix is characterized by containing at least the polymer (A) and the polymer (B) in a mass ratio of (A) / (B) = 70/30 or more and 95/5 or less. 1. The polymer for a matrix according to 1. A non-aqueous electrolyte gel comprising the polymer for a matrix according to any one of claims 1 to 5. An electrochemical device comprising the non-aqueous electrolyte gel according to claim 6. The electrochemical device according to claim 7, wherein the electrochemical device is a non-aqueous electrolyte secondary battery.

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