WO2018117519A1 - Binder for secondary battery, binder resin composition for secondary battery, electrode for secondary battery, and secondary battery - Google Patents

Abstract

According to the present invention, provided is a binder for a secondary battery, the binder comprising: a first copolymer unit comprising a carboxyl group-containing acrylic monomer and at least one of an acrylic acid derivative monomer and substituted or unsubstituted styrene; and a second copolymer unit comprising a residue of a polymer azo initiator, wherein the ratio of mass of the second copolymer unit relative to the total mass of the first copolymer unit and the second copolymer unit is 10-40 mass%.

Description

Secondary Battery Binder, Secondary Battery Binder Resin Composition, Secondary Battery Electrode, and Secondary Battery

The present invention relates to a secondary battery binder, a secondary battery binder resin composition, a secondary battery electrode, and a secondary battery.

Non-aqueous electrolyte secondary batteries are widely used as a power source for portable devices such as notebook computers (Note PCs) or mobile phones, and have high expectations for their development in terms of high voltage and high capacity. As a negative electrode material (negative electrode active material) of such a nonaqueous electrolyte secondary battery, a graphite carbon material such as natural graphite or artificial graphite capable of detaching and inserting Li ions in addition to lithium metal or lithium alloy is used.

In recent years, miniaturized and multifunctional portable battery cells have been required to have higher capacities, and in view of this demand, a novel negative electrode active material is substituted for a carbon-based active material (for example, a graphite carbon material) which is widely used as a negative electrode active material. This is under review. Tin (Sn) alloys, silicon (Si) alloys, silicon (Si) oxides, lithium (Li) nitrides, etc. are attracting attention as a novel negative electrode active material, but at this point, any of the new negative electrode materials has graphite charge / discharge cycle characteristics. Lagging behind in carbon materials.

The carbon-based active material has a layered structure, and Li is inserted / deleted between the layers during charge and discharge, so that the expansion / contraction during Li insertion / deletion is small. On the other hand, the novel negative electrode material, especially the silicon-based active material, has a more complicated structure than the carbon-based active material, and at the same time, the amount of Li inserted / deleted per unit mass during charge / discharge is large. For this reason, the silicon-based active material has a large expansion / contraction due to charge / discharge, and as a result, the electrode swells greatly in a charge / discharge cycle in which expansion / contraction is repeated, resulting in short circuit of the active material due to destruction of the electrode structure. The electroconductivity falls. For this reason, charge / discharge cycle life is known to fall extremely compared with graphite carbon material.

For this reason, in general, in order to achieve both high capacity and charge / discharge cycle life, not only a new anode material is used alone, but also often used in a mixed system with a carbon-based active material. However, even in this case, since the expansion and contraction of the new anode material is large, it is difficult to increase the capacity because the electrode swells.

In recent years, in order to solve the trouble of the high capacity furnace, the method of suppressing swelling of an electrode has been developed by using a high strength resin as a binder. According to this method, since swelling of an electrode is suppressed by a binder, it can be expected that an electrode structure is maintained and the fall of charge-discharge cycle life is suppressed.

As such a binder resin, for example, a polyimide-based binder is known, but since the polyimide-based binder is an organic solvent-based binder, there is a side that is difficult to use as a negative electrode binder in which an aqueous binder is mainly used. Therefore, the above problem cannot be solved fundamentally.

On the other hand, sodium polyacrylate is known as an aqueous high strength binder. This binder is easy to use as a binder for the negative electrode because it is water-based, but the flexibility of the electrode is remarkably lowered, and cracks are easily generated, or the electrode is easily curled during drying. There is this. Moreover, the swelling inhibitory effect was also inadequate. Therefore, even this binder could not fundamentally solve the above problem.

Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is water-based, and a new and improved secondary battery binder and secondary battery, which are easy to handle while being able to suppress electrode swelling of a lithium ion secondary battery, are secondary. It is to provide a battery binder resin composition, a secondary battery electrode, and a secondary battery.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, According to one aspect of this invention, the residue of a 1st copolymer unit containing any 1 or more types of a carboxyl group-containing acrylic monomer, an acrylic acid derivative monomer, and substituted or unsubstituted styrene, and the residue of a polymeric azo initiator A secondary copolymer comprising a second copolymer unit, wherein the mass ratio of the second copolymer unit to the total mass of the first copolymer unit and the second copolymer unit is 10 to 40% by mass. A battery binder is provided.

The carboxyl group-containing acrylic monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, mono methyl maleic acid, 2-carboxyethyl acrylate, and 2-carboxyethyl methacrylate.

The acrylic acid derivative monomer may be at least one member selected from the group consisting of nitrile group-containing acrylic monomers, acrylic acid esters, and acrylamides.

The nitrile group-containing acrylic monomer may be at least one selected from the group consisting of acrylonitrile, methacrylonitrile, 2-cyanoethyl acrylate, and 2-cyanoethyl methacrylate.

At least some of the carboxyl group-containing acrylic monomers may be alkali metal salts or ammonium salts.

The first copolymer unit may include an alkali metal salt or an ammonium salt as the carboxyl group-containing acrylic monomer, and may include a nitrile group-containing acrylic monomer as the acrylic acid derivative monomer.

The second copolymer unit may include at least one of polyether and polysiloxane as a residue of the polymer azo initiator.

According to another aspect of the present invention, there is provided a secondary battery binder resin composition comprising the secondary battery binder.

According to another aspect of the present invention, there is provided a secondary battery electrode comprising the secondary battery binder.

The secondary battery electrode may further include carboxymethyl cellulose (CMC) as the secondary battery binder.

According to another aspect of the present invention, there is provided a secondary battery comprising the above secondary battery electrode.

The secondary battery electrode may be a negative electrode.

As described above, the secondary battery binder according to the present invention can be suppressed by using the secondary battery binder according to the present invention as an aqueous binder for the secondary battery electrode. In addition, the binder for secondary batteries according to the present invention also has good handling properties.

1 is a side cross-sectional view schematically showing the configuration of a lithium ion secondary battery.

EMBODIMENT OF THE INVENTION Preferred embodiment of this invention is described in detail, referring an accompanying drawing below. In addition, in this specification and drawing, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol about the component which has substantially the same functional structure.

<1. Composition of Lithium-ion Secondary Battery>

First, the structure of the lithium ion secondary battery 10 which concerns on this embodiment with reference to FIG. 1 is demonstrated. The lithium ion secondary battery 10 includes a positive electrode 20, a negative electrode 30, a separator 40, and a nonaqueous electrolyte. The charge arrival voltage (redox potential) of the lithium ion secondary battery 10 is, for example, 4.0 V (vs. Li / Li ⁺ ) or more, 5.0 V or less, particularly 4.2 V or more and 5.0 V or less. The form of the lithium ion secondary battery 10 is not specifically limited. In other words, the lithium ion secondary battery 10 may be any of cylindrical, rectangular, laminate, button, and the like.

(1-1.anode 20)

The positive electrode 20 includes a current collector 21 and a positive electrode active material layer 22. The current collector 21 may be any conductor, and is composed of, for example, aluminum, stainless steel, nickel coated steel, or the like. The positive electrode active material layer 22 contains at least a positive electrode active material, and may further contain a conductive agent and a binder for a positive electrode.

The positive electrode active material is, for example, a solid solution oxide containing lithium, but is not particularly limited as long as it is a material capable of electrochemically storing and releasing lithium ions. Solid solution oxides include, for example, Li _a Mn _x Co _y Ni _z O ₂ (1.150 ≦ a ≦ 1.430, 0.45 ≦ _x ≦ 0.6, 0.10 ≦ _y ≦ 0.15, 0.20 ≦ _z ≦ 0.28), LiMn _x Co _y Ni _z O ₂ (0.3 ≦ x ≦ 0.85, 0.10 ≦ y ≦ 0.3, 0.10 ≦ z ≦ 0.3) and LiMn _1.5 Ni _0.5 O ₄ .

The conductive agent is, for example, carbon black such as Ketjenblack, acetylene black, natural graphite, artificial graphite, or the like, but is not particularly limited as long as it is for enhancing the conductivity of the positive electrode.

The binder for the positive electrode is, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, cellulose nitrate, and the like. 21) If it can be bound up, it is not particularly limited.

The positive electrode active material layer 22 is manufactured by the following manufacturing method, for example. In other words, first, the positive electrode active material, the conductive agent, and the binder for the positive electrode are dry mixed to prepare a positive electrode mixture.

Next, the positive electrode mixture is dispersed in a suitable organic solvent to prepare a positive electrode mixture slurry, and the positive electrode mixture slurry is applied onto the current collector 21, dried, and rolled to prepare a positive electrode active material layer.

(1-2.cathode 30)

The negative electrode 30 includes a current collector 31 and a negative electrode active material layer 32. The current collector 31 may be any conductor, and is composed of, for example, aluminum, stainless steel, nickel plated steel, or the like. The negative electrode active material layer 32 includes at least a negative electrode active material and a negative electrode binder. The negative electrode active material may be, for example, a graphite active material (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.), a mixture of fine particles of silicon or tin or oxides thereof, and a graphite active material, Fine particles of silicon or tin, alloys based on silicon or tin, titanium oxide compounds such as Li ₄ Ti ₅ O ₁₂ , lithium nitride and the like are conceivable. Oxides of silicon are represented by SiO _x (0 ≦ _x ≦ 2). In addition to these, metal lithium etc. are mentioned as a negative electrode active material. On the other hand, in this embodiment, since the negative electrode binder possesses the following constitution, the swelling of the electrode can be suppressed even when a negative electrode active material, for example, a silicon-based active material that expands and contracts greatly during charging and discharging is used.

The negative electrode binder includes a copolymer binder.

The negative electrode binder may further include a negative electrode binder used in the conventional lithium ion secondary battery 10, and may further include, for example, carboxymethyl cellulose (CMC). The copolymer binder is a block copolymer comprising a first copolymer repeating unit and a second copolymer repeating unit.

The first copolymer repeating unit contains at least one of a carboxyl group-containing acrylic monomer, an acrylic acid derivative monomer and a substituted or unsubstituted styrene. The first copolymer repeating unit is a repeating unit for expressing the strength and the electrolyte resistance of the negative electrode binder. Since the copolymer binder includes the first copolymer repeating unit, swelling of the negative electrode 30 can be suppressed. In the first copolymer repeating unit, at least one or more of carboxyl group-containing acrylic monomers, acrylic acid derivative monomers and substituted or unsubstituted styrenes are randomly copolymerized.

Herein, the carboxyl group-containing acrylic monomer is preferably any one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethyl maleic acid, 2-carboxyethyl acrylate, and 2-carboxyethyl methacrylate.

Moreover, it is more preferable that at least a part of the carboxyl group-containing acrylic monomer is an alkali metal salt or an ammonium salt. In this case, the characteristics of the lithium ion secondary battery 10 are further improved. Here, the alkali metal salt or ammonium salt may be any one or more alkali metal salts or ammonium salts selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, and mono methyl maleic acid.

The acrylic acid derivative monomer is preferably any one or more selected from the group consisting of nitrile group-containing acrylic monomers, acrylic esters and acrylamides. The nitrile group-containing acrylic monomer is preferably any one or more selected from the group consisting of acrylonitrile, methacrylonitrile, 2-cyanoethyl acrylate, and 2-cyanoethyl methacrylate.

It is particularly preferable that the first copolymer repeating unit contains an alkali metal salt or an ammonium salt as the carboxyl group-containing acrylic monomer and a nitrile group-containing acrylic monomer as the acrylic acid derivative monomer. In this case, the characteristics of the lithium ion secondary battery 10 are further improved.

The weight ratio of the carboxyl group-containing acrylic monomer to at least one of the acrylic acid derivative monomer and the substituted or unsubstituted styrene is not particularly limited, but may be, for example, about 2.5: 1.0 to 2.0: 1.0.

It is preferable that the glass transition point of a 1st copolymer repeating unit is 150 degreeC or more and 250 degrees C or less. In this case, the characteristics of the lithium ion secondary battery 10 are further improved.

The second copolymer repeat unit comprises a moiety of the polymeric azo initiator. The second copolymer repeating unit is a repeating unit for expressing flexibility and swelling by the electrolyte solution. In other words, the binder for the negative electrode deteriorates battery characteristics by merely high strength. For this reason, in this embodiment, a certain degree of flexibility and swelling property are given to the binder for negative electrodes by a 2nd copolymer repeating unit.

Here, it is preferable that a 2nd copolymer repeating unit contains at least 1 sort (s) of a polyether and polysiloxane as a residue of a polymeric azo initiator. Here, as polyether, polyethylene glycol is preferable, for example.

The weight ratio of the second copolymer repeating unit to the total weight of the first copolymer repeating unit and the second copolymer repeating unit is preferably 10 to 40% by weight.

It is preferable that the glass transition point of a 2nd copolymer repeating unit is -150 degreeC or more and 50 degrees C or less.

In this case, the characteristics of the lithium ion secondary battery 10 are further improved.

(1-3. Specific Example of First Copolymer Repeating Unit)

The first copolymer repeating unit is represented by, for example, the following formulas (1) to (24). Of course, a 1st copolymer repeating unit is not limited to the following example.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

[Formula 10]

[Formula 11]

[Formula 12]

[Formula 13]

[Formula 14]

[Formula 15]

[Formula 16]

[Formula 17]

[Formula 18]

[Formula 19]

[Formula 20]

[Formula 21]

[Formula 22]

[Formula 23]

[Formula 24]

(1-4. Specific Example of Second Copolymer Repeating Unit)

The second copolymer repeating unit is represented by the following general formulas (25) to (26), for example. Of course, a 2nd copolymer repeating unit is not limited to the following example.

[Formula 25]

[Formula 26]

In the formulas (25) and (26), the functional groups that R ₁ to R ₃ can take are represented by the following formulas (27) to (29).

R ₁ = -Me, -Et, -Pr (27)

R ₂ = -Me, -Et, -Pr, -CN, -CO ₂ Me, -CO ₂ Et, -CO ₂ Pr, -CONHMe, -CONHEt, -CONHPr (28)

R ₃ = -CH _2- , -C ₂ H _4- , -C ₃ H _6- (29)

Therefore, the binder for negative electrodes is represented by following General formula (30), for example. Of course, the negative electrode binder may have a structure in which the formulas (1) to (24) and the formulas (25) to (26) are arbitrarily combined.

[Formula 30]

(1-5.Separator)

The separator 40 is not particularly limited, and any separator may be used as long as the separator 40 is used as a separator of a lithium ion secondary battery. As a separator, it is preferable to use together porous film, a nonwoven fabric, etc. which show the outstanding high rate discharge performance alone or in combination. The resin constituting the separator is, for example, a polyolefin resin represented by polyethylene, polypropylene, or the like, polyethylene terephthalate, polybutylene terephthalate, or the like. Typical polyester resin, PVDF, vinylidene fluoride (VDF) -hexafluoro propylene (HFP) copolymer, vinylidene fluoride-perfluoro vinyl ether copolymer, vinylidene Fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoro Acetone (hexafluoroacetone) copolymer, vinylidene fluoride-ethylene Polymers, vinylidene fluoride-propylene copolymers, vinylidene fluoride-trifluoro propylene copolymers, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene Copolymers, vinylidene fluoride-ethylene (ethylene) -tetrafluoroethylene copolymers, and the like.

(1-6.Non-aqueous electrolyte)

The nonaqueous electrolyte can be used without particular limitation, such as a nonaqueous electrolyte which can conventionally be used for a lithium secondary battery. The nonaqueous electrolyte has a composition in which an electrolyte salt is contained in the nonaqueous solvent. As the non-aqueous solvent, for example, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate (ester); cyclic esters such as γ-butyrolactone and γ-valerolactone; Chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; Chain esters such as methyl formate, methyl acetate and butyric acid methyl; Tetrahydrofuran or derivatives thereof; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, methyl diglyme, etc. Ethers; Nitriles such as acetonitrile and benzonitrile; Dioxolane or derivatives thereof; Ethylene sulfide, sulfolane, sultone, or derivatives thereof, or the like, or a mixture of two or more thereof, and the like.

As the electrolyte salt, for example, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiPF _{6 -x} (C _n F _{2n + 1} ) _x [where 1 <x <6, n = 1 or 2] ₁ of lithium (Li), sodium (Na) or potassium (K) such as LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO ₄ , KSCN Inorganic Ion Salts Containing Species, 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, (nC ₄ H ₉ ) ₄ NClO ₄ , (nC ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, (C ₂ H ₅ ) ₄ N- _{benzoate, (C 2 H 5) 4} N- phthalate, dodecyl benzene sulfonic acid lithium keel (dodecyl benzene sulphonic acid) and the like organic ion salts such as, those ionic compounds alone, or two kinds of It is possible to mix and use the above. On the other hand, the concentration of the electrolyte salt may be the same as the nonaqueous electrolyte used in the conventional lithium secondary battery, and there is no particular limitation. In the present embodiment, a nonaqueous electrolyte containing an appropriate lithium compound (electrolyte salt) at a concentration of about 0.8 to 1.5 mol / L can be used.

On the other hand, various additives may be added to the nonaqueous electrolyte. Such additives include cathodic additives, cathodic additives, ester additives, carbonic acid ester additives, sulfate ester additives, phosphate ester additives, boric acid ester additives, acid anhydride additives, and electrolyte systems. Additives and the like. Any one of these may be added to the nonaqueous electrolyte, and a plurality of kinds of additives may be added to the nonaqueous electrolyte.

<2. Manufacturing Method of Lithium Ion Secondary Battery>

Next, the manufacturing method of the lithium ion secondary battery 10 is demonstrated. The anode 20 is manufactured as follows. First, a slurry is formed by dispersing the positive electrode active material, the conductive agent, and the positive electrode binder in the above ratio in a solvent (for example, N-methyl-2-pyrrolidone). Next, the slurry is formed on the current collector 21 (for example, applied) and dried to form the positive electrode active material layer 22.

In addition, the method of application | coating is not specifically limited. As a coating method, the knife coater method, the gravure coater method, etc. are mentioned, for example.

Each following application process can also be performed by the same method. Next, the positive electrode active material layer 22 is pressed to have a density within the above range by a press. Thus, the anode 20 is manufactured.

The negative electrode 30 is also manufactured in the same manner as the positive electrode 20. First, a negative electrode active material and a negative electrode binder (specifically, a binder resin composition containing a negative electrode binder) are mixed, and the mixture is dispersed in a solvent (for example, N-methyl-2-pyrrolidone) to prepare a slurry. Form. Subsequently, the slurry is formed (for example, coated) on the current collector 31 and dried to form the negative electrode active material layer 32. As for the temperature at the time of drying, 150 degreeC or more is preferable. Subsequently, the negative electrode active material layer 32 is pressed by a press to have a density within the above range. Thus, the cathode 30 is manufactured.

Here, a binder resin composition is manufactured by heating, stirring a mixed liquid (reaction liquid) of the monomer which comprises a 1st copolymer repeating unit, and a polymeric azo initiator. The weight ratio of the polymer azo initiator is 10 to 40% by weight based on the total weight of the monomer and the polymer azo initiator constituting the first copolymer repeating unit. Detailed conditions will be described in the Examples.

Subsequently, the separator 40 is placed between the positive electrode 20 and the negative electrode 30 to produce an electrode structure. Subsequently, the electrode structure is processed into a desired shape (e.g., cylindrical, square, laminated, button, etc.) and inserted into a container of the above type. Subsequently, the nonaqueous electrolyte is injected into the container, and the pores in the separator 40 are impregnated with the electrolyte solution. Thereby, a lithium ion secondary battery is manufactured.

As mentioned above, according to this embodiment, the binder which has the structure mentioned above as a binder for negative electrodes is used. This negative electrode binder is an aqueous binder. In addition, although the detail is demonstrated in an Example, swelling of the negative electrode 30 is suppressed. As a result, dropping of the active material and deterioration of electron conductivity due to destruction of the electrode structure are suppressed, and the life of the secondary battery is improved. Moreover, this binder for negative electrodes is also favorable in handling property.

Hereinafter, examples and comparative examples of the present invention are described. Such following examples are only examples of the present invention, and the present invention is not limited to the following examples.

EXAMPLE

<1. Binder Resin Composition Synthesis>

Next, the Example of this embodiment is described. First, the synthesis example of a binder resin composition is demonstrated. In addition, the compounding ratio of the monomer and polymeric azo initiator described below shall show a weight ratio unless it rejects in particular.

(Example 1: Sodium polyacrylate (PAALi) / polyacrylonitrile (PAN) / polyethylene glycol (PEG) = Synthesis example of 60/30/10)

In a 200 ml four-necked detachable flask equipped with a stirrer, a thermometer, and a cooling tube, 119 g of distilled water and acrylic acid (25 g, 0.833 mol) were added, and the internal pressure was reduced to 10 mmHg by a diaphragm pump, and the internal pressure was atmospheric pressure with nitrogen. The operation to return to was repeated three times. Acrylonitrile (30 g, 0.565 mol), high molecular weight azo initiator (VPE-0201 manufactured by Wako Pure Chemical Industries, Ltd. (PEG chain number average molecular weight 2000), 10.0 g, 0.005 mol (molar number as initiator)) were added, and the result was 400 rpm. Stirred. When the temperature of the reaction liquid controlled heating stably between 65 degreeC-70 degreeC, when the temperature was heated to 80 degreeC for 4 hours and made to react for 4 hours, the binder resin composition which is a massive solid was obtained.

After cooling to room temperature, lithium hydroxide monohydrate (34.2 g, 0.98 equivalents to acrylic acid) was added and stirred until the binder resin composition was completely dissolved.

The reaction solution was reduced to about 2 ml and the weight of the nonvolatile matter (NV) was measured to be 13.2 wt% (theoretical value 13.5 wt%).

In addition, the binder resin composition after measuring the non-volatile content (NV) is reduced to about 7 to 10 mg, and at 5 ° C / min to -100 ° C to 270 ° C under nitrogen atmosphere in X-DSC7000 manufactured by SII (Seiko Instruments Inc.). When Tg measurement was performed by heating at a temperature increase rate, Tg derived from PEG was observed around -55 ° C, and Tg derived from a copolymer of PAALi and PAN was observed near 235 ° C.

(Example 2: Sodium polyacrylate (PAALi) / polyacrylonitrile (PAN) / polyethylene glycol (PEG) = Synthesis example of 55/30/15)

Distilled water 118g, acrylic acid (55g, 0.763mol), acrylonitrile (30g, 0.565mol), polymer azo initiator (VPE-0201 (PEG chain number average molecular weight 2000) manufactured by Wako Pure Chemical Industries, Ltd.), 15.0g, 0.0075mol (Molar number as initiator)) and lithium hydroxide monohydrate (31.4 g, 0.98 equivalents to acrylic acid) were used and synthesized in the same manner as in Example 1 above. It was 13.2 weight% (theoretical value 13.5 weight%) when the weight of the non-volatile matter (NV) of the reaction liquid was measured. In addition, Tg was observed in two places around -55 degreeC and around 235 degreeC.

(Example 3: Sodium polyacrylate (PAALi) / polyacrylonitrile (PAN) / polyethylene glycol (PEG) = Synthesis example of 50/30/20)

116 g of distilled water, acrylic acid (50 g, 0.694 mol), acrylonitrile (30 g, 0.565 mol), polymer azo initiator (VPE-0201 (PEG chain number average molecular weight 2000) manufactured by Wako Pure Chemical Industries, Ltd.), 20.0 g, 0.01 mol (Moles as initiator)) and lithium hydroxide monohydrate (28.5 g, 0.98 equivalents to acrylic acid) were used and synthesized in the same manner as in Example 1. It was 13.0 weight% (theoretical value 13.5 weight%) when the non volatile matter (NV) of the reaction liquid was measured. In addition, Tg was observed in two places around -55 degreeC and around 235 degreeC.

Example 4 Synthesis Example of Sodium Polyacrylate (PAALi) / Polyacrylonitrile (PAN) / Polyethylene Glycol (PEG) = 50/20/30

116 g of distilled water, acrylic acid (50 g, 0.694 mol), acrylonitrile (20 g, 0.377 mol), polymer azo initiator (VPE-0201 (PEG chain number average molecular weight 2000) manufactured by Wako Pure Chemical Industries, Ltd.), 30.0 g, 0.015 mol (Moles as initiator)) and lithium hydroxide monohydrate (28.5 g, 0.98 equivalents to acrylic acid) were used and synthesized in the same manner as in Example 1. It was 13.0 weight% (theoretical value 13.5 weight%) when the weight of the non volatile matter (NV) of the reaction liquid was measured. Moreover, Tg was observed in two places about -55 degreeC and 235 degreeC vicinity.

Example 5 Synthesis Example of Sodium Polyacrylate (PAALi) / Polyacrylonitrile (PAN) / Polysiloxan = 60/30/10

119 g of distilled water, acrylic acid (60 g, 0.833 mol), acrylonitrile (30 g, 0.565 mol), polymer azo initiator (VPE-1001 (Polysiloxan chain number average molecular weight 10000) manufactured by Wako Pure Chemical Industries, Ltd., 10.0 g, 0.001 mol) (Molar number as initiator)) and lithium hydroxide monohydrate (34.2 g, 0.98 equivalents to acrylic acid) were used and synthesized in the same manner as in Example 1. It was 13.2 weight% (theoretical value 13.5 weight%) when the mass of the non-volatile matter (NV) of the reaction liquid was measured. In addition, Tg was observed only in one place near 235 degreeC. Since Tg derived from polysiloxane exists in -100 degrees C or less and it fell out of the measurement range, it is thought that it was not observed.

Example 6 Synthesis Example of Sodium Polyacrylate (PAALi) / Polyacrylonitrile (PAN) / Polysiloxan = 55/30/15

Distilled water 118g, acrylic acid (55g, 0.763mol), acrylonitrile (30g, 0.565mol), polymer azo initiator (VPE-1001 (Polysiloxan chain number average molecular weight 10000) made by Wako Pure Chemical Industries, Ltd., 15.0g, 0.0015mol) (Molar number as initiator)) and lithium hydroxide monohydrate (31.4 g, 0.98 equivalents to acrylic acid) were used and synthesized in the same manner as in Example 1 above. It was 13.1 weight% (theoretical value 13.5 weight%) when the weight of the non-volatile matter (NV) of the reaction liquid was measured. In addition, Tg was observed in one place near 235 degreeC. Since Tg derived from polysiloxane exists in -100 degrees C or less and it fell out of the measurement range, it is thought that it was not observed.

Example 7 Synthesis Example of Sodium Polyacrylate (PAALi) / Polyacrylonitrile (PAN) / Polysiloxan = 50/30/15

116 g of distilled water, acrylic acid (50 g, 0.694 mol), acrylonitrile (30 g, 0.565 mol), polymer azo initiator (VPE-1001 (Polysiloxan chain number average molecular weight 10000) manufactured by Wako Pure Chemical Industries, Ltd., 20.0 g, 0.002 mol) (Moles as initiator)) and lithium hydroxide monohydrate (28.5 g, 0.98 equivalents to acrylic acid) were used and synthesized in the same manner as in Example 1. It was 13.1 weight% (theoretical value 13.5 weight%) when the weight of the non-volatile matter (NV) of the reaction liquid was measured. In addition, Tg was observed in one place near 235 degreeC. Since Tg derived from polysiloxane exists in -100 degrees C or less and it fell out of the measurement range, it is thought that it was not observed.

Example 8 Synthesis Example of Sodium Polyacrylate (PAALi) / Polyacrylonitrile (PAN) / Polysiloxan = 50/20/30

116 g of distilled water, acrylic acid (50 g, 0.694 mol), acrylonitrile (20 g, 0.377 mol), polymer azo initiator (VPE-1001 (Polysiloxan chain number average molecular weight 10000) manufactured by Wako Pure Chemical Industries, Ltd., 30.0 g, 0.003 mol) (Moles as initiator)) and lithium hydroxide monohydrate (28.5 g, 0.98 equivalents to acrylic acid) were used and synthesized in the same manner as in Example 1. It was 13.1 weight% (theoretical value 13.5 weight%) when the weight of the non-volatile matter (NV) of the reaction liquid was measured. In addition, Tg was observed in one place near 235 degreeC. Since Tg derived from polysiloxane exists in -100 degrees C or less and it fell out of the measurement range, it is thought that it was not observed.

<2. Cathode Production>

(Comparative Example 1)

Graphite silicon composite anode (silicon content 60% by weight) 14.5% by weight, artificial graphite 79.0% by weight, acetylene black 2.0% by weight, styrene butadiene copolymer (SBR) 3.0% by weight, carboxymethyl cellulose (CMC) 1.5% by weight An aqueous negative electrode mixture slurry was prepared. On the other hand, the nonvolatile components in the negative electrode mixture slurry was 55% by weight based on the total weight of the slurry.

(Production of the cathode)

Subsequently, the gap of the bar coater was adjusted so that the amount of the coated mixture (surface density) after drying was 9.55 mg / cm ² , and the negative electrode mixture slurry was uniformed to copper foil (current collector, thickness 10 μm) by the bar coater. Was applied. Subsequently, the negative electrode mixture slurry was dried for 15 minutes with a blower type dryer set at 80 ° C. Subsequently, the negative electrode mixture after drying was pressed in a roll press so that the mixture density became 1.65 g / cm ³ . Subsequently, the negative electrode mixture was vacuum dried at 150 ° C. for 6 hours to prepare a negative electrode.

(Example 9)

A negative electrode was prepared in the same manner as in Comparative Example 1, except that 4.5 wt% of the binder resin composition synthesized in Example 1 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR) and 1.5 wt% of the carboxymethylcellulose (CMC). . On the other hand, no crack was generated in the cathode during the production of the cathode. In addition, during drying of the negative electrode, the negative electrode was hardly dried.

(Example 10)

A negative electrode was prepared in the same manner as in Comparative Example 1, except that 4.5 wt% of the binder resin composition synthesized in Example 2 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR) and 1.5 wt% of the carboxymethylcellulose (CMC). .

(Example 11)

A negative electrode was prepared in the same manner as in Comparative Example 1, except that 4.5 wt% of the binder resin composition synthesized in Example 3 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR) and 1.5 wt% of the carboxymethylcellulose (CMC). .

(Example 12)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 4.5 wt% of the binder resin composition synthesized in Example 4 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR) and 1.5 wt% of the carboxymethylcellulose (CMC). .

(Example 13)

A negative electrode was prepared in the same manner as in Comparative Example 1, except that 4.5 wt% of the binder resin composition synthesized in Example 5 was used instead of 3.0 wt% of styrene butadiene copolymer (SBR) and 1.5 wt% of carboxymethylcellulose (CMC). .

(Example 14)

A negative electrode was prepared in the same manner as in Comparative Example 1, except that 4.5 wt% of the binder resin composition synthesized in Example 6 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR) and 1.5 wt% of the carboxymethylcellulose (CMC). .

(Example 15)

A negative electrode was prepared in the same manner as in Comparative Example 1, except that 4.5 wt% of the binder resin composition synthesized in Example 7 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR) and 1.5 wt% of the carboxymethylcellulose (CMC). .

(Example 16)

A negative electrode was prepared in the same manner as in Comparative Example 1, except that 4.5 wt% of the binder resin composition synthesized in Example 8 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR) and 1.5 wt% of the carboxymethylcellulose (CMC). .

(Example 17)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 1 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 18)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 2 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 19)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 3 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 20)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 4 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 21)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 5 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 22)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 6 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 23)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 7 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 24)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 3.0 wt% of the binder resin composition synthesized in Example 8 was used instead of 3.0 wt% of the styrene butadiene copolymer (SBR).

(Example 25)

A negative electrode was prepared in the same manner as in Comparative Example 1 except that 1.5 wt% of the binder resin composition synthesized in Example 2 and 3.0 wt% of the carboxymethylcellulose (CMC) were used instead of 3.0 wt% of the styrene butadiene copolymer (SBR). .

<3. Anode Manufacturing>

(Production of Anode Mixture Slurry)

Solid solution oxide Li _{1 . 2} 0Mn _{0 . 55} Co _{0 . 10} Ni _{0 .} 96 weight percent ₁₅ O ₂ , 2 weight percent Ketjen Black and 2 weight percent polyvinylidene fluoride were dispersed in N-methyl-2-pyrrolidone to form a positive electrode mixture slurry. On the other hand, the nonvolatile components in the positive electrode mixture slurry was 50% by weight based on the total weight of the slurry.

(Manufacture of Anode)

Subsequently, the gap of the bar coater was adjusted so that the amount of coating material (surface density) after drying might be 22.7 mg / cm <^2> , and the positive electrode mixture slurry was apply | coated on the aluminum collector foil which is an electrical power collector by this bar coater. Subsequently, the positive electrode mixture slurry was dried for 15 minutes with a blowing type dryer set at 80 ° C. Subsequently, the positive electrode mixture after drying was pressed in a roll press so that the mixture density became 3.9 g / cm ³ . Subsequently, the positive electrode mixture was vacuum dried at 80 ° C. for 6 hours to prepare a sheet-shaped positive electrode composed of a positive electrode current collector and a positive electrode active material layer.

<4. Manufacturing of Secondary Battery>

(Comparative Example 2)

The negative electrode of Comparative Example 1 was cut into a circle with a diameter of 1.55 cm, and the positive electrode of the positive electrode manufacturing example was cut into a circle with a diameter of 1.3 cm. Next, the separator (a polyethylene microporous membrane having a thickness of 25 µ) was cut into a circle having a diameter of 1.8 cm. In a stainless steel coin outer container having a diameter of 2.0 cm, a positive electrode cut in a circle of 1.3 cm in diameter, a separator cut in a circle of 1.8 cm in diameter, a negative electrode of Comparative Example 1 cut in a circle of 1.55 cm in diameter, and a spacer as a diameter The copper foil of 200 micrometers in thickness which cut | disconnected in 1.5 cm round was overlapped in this order. Next, 150 µL of an electrolyte solution (1.4 M LiPF ₆ ethylene carbonate / diethyl carbonate / fluoroethylene carbonate = 10/70/20 mixed solution (volume ratio)) was added to the vessel. Next, the container was sealed with the cap made of stainless steel via the packing made of polypropylene, and the coin cell operation | work was sealed. Thus, a lithium ion secondary battery (coin cell) according to Comparative Example 2 was prepared.

(Example 26)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 9 was used.

(Example 27)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 10 was used.

(Example 28)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 11 was used.

(Example 29)

A related secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 12 was used.

(Example 30)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 13 was used.

(Example 31)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 14 was used.

(Example 32)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 15 was used.

(Example 33)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 16 was used.

(Example 34)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 17 was used.

(Example 35)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 18 was used.

(Example 36)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 19 was used.

(Example 37)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 20 was used.

(Example 38)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 21 was used.

(Example 39)

A secondary battery was manufactured in the same manner as in Comparative Example 2, except that the negative electrode prepared in Example 22 was used.

Example 40

All of the secondary batteries were manufactured in the same manner as in Comparative Example 2 except that the negative electrode produced in Example 23 was used.

Example 41

In the same manner as in Comparative Example 2, except that the negative electrode produced in Example 24 was used, a related secondary battery was produced.

Example 42

In the same manner as in Comparative Example 2 except that the negative electrode produced in Example 25 was used, the related secondary battery was produced.

<5. Evaluation of Electrode Inflation>

The lithium ion secondary batteries according to the examples and the comparative examples were charged and discharged once at 25 degrees at 0.2C. Then, after charging a lithium ion secondary battery at 1.0 C, the battery was disassembled and the negative electrode was taken out. The swelling of the negative electrode in a charged state was calculated | required by washing with dimethyl carbonate, air drying, measuring the thickness of a negative electrode with a micrometer, and comparing with the thickness of the negative electrode before the initial charge / discharge previously measured. Here, the value of swelling was calculated as ((thickness of negative electrode after charge)-(thickness of negative electrode before initial charge and discharge)) / (thickness of negative electrode before initial charge and discharge) × 100. The evaluation results are collectively shown in Table 1.

battery	electrode	bookbinder		Inflation (%)
		Used binder	Usage (mass%)
Comparative Example 2	Comparative Example 1	SBR / CMC	3 / 1.5	31.0
Example 26	Example 9	Example 1 / CMC	4.5 / 0	28.5
Example 27	Example 10	Example 2 / CMC	4.5 / 0	29.1
Example 28	Example 11	Example 3 / CMC	4.5 / 0	29.2
Example 29	Example 12	Example 4 / CMC	4.5 / 0	30.0
Example 30	Example 13	Example 5 / CMC	4.5 / 0	28.0
Example 31	Example 14	Example 6 / CMC	4.5 / 0	28.5
Example 32	Example 15	Example 7 / CMC	4.5 / 0	29.2
Example 33	Example 16	Example 8 / CMC	4.5 / 0	29.5
Example 34	Example 17	Example 1 / CMC	3 / 1.5	24.0
Example 35	Example 18	Example 2 / CMC	3 / 1.5	24.6
Example 36	Example 19	Example 3 / CMC	3 / 1.5	25.2
Example 37	Example 20	Example 4 / CMC	3 / 1.5	26.0
Example 38	Example 21	Example 5 / CMC	3 / 1.5	23.8
Example 39	Example 22	Example 6 / CMC	3 / 1.5	24.6
Example 40	Example 23	Example 7 / CMC	3 / 1.5	25.5
Example 41	Example 24	Example 8 / CMC	3 / 1.5	26.9
Example 42	Example 25	Example 2 / CMC	1.5 / 3	27.3

According to Table 1, it turns out that swelling of the negative electrode of the secondary battery which concerns on a present Example is suppressed.

<6. Cycle Life Assessment>

The lithium ion secondary battery according to each of Examples and Comparative Examples was charged and discharged once at 25 ° C at 0.2C. Thereafter, the charge and discharge cycle of charging and discharging the lithium ion secondary battery at 1.0 C was repeated 100 times. The discharge capacity retention rate (percentage) is calculated by dividing the discharge capacity at 100 cycles (100th cycle of the 1.0C charge and discharge cycle) by the discharge capacity (initial discharge capacity) at 1 cycle (the first cycle of the 1.0C charge and discharge cycle). did. The larger the capacity maintenance rate, the better the cycle life. The evaluation results are collectively shown in Table 2. According to Table 2, it can be seen that in the present embodiment, the initial discharge capacity and the capacity retention rate are excellent.

[Revision according to Rule 26 04.01.2018]

battery	electrode	bookbinder		Initial discharge capacity (mAh)	Capacity maintenance rate (%)
		Used binder	Usage (mass%)
Comparative Example 2	Comparative Example 1	SBR / CMC	3 / 1.5	4.57	96.3
Example 26	Example 9	Example 1 / CMC	4.5 / 0	4.58	97.1
Example 27	Example 10	Example 2 / CMC	4.5 / 0	4.58	97.3
Example 28	Example 11	Example 3 / CMC	4.5 / 0	4.59	96.8
Example 29	Example 12	Example 4 / CMC	4.5 / 0	4.65	96.5
Example 30	Example 13	Example 5 / CMC	4.5 / 0	4.59	97.3
Example 31	Example 14	Example 6 / CMC	4.5 / 0	4.68	95.7
Example 32	Example 15	Example 7 / CMC	4.5 / 0	4.68	95.9
Example 33	Example 16	Example 8 / CMC	4.5 / 0	4.58	97.8
Example 34	Example 17	Example 1 / CMC	3 / 1.5	4.64	97.7
Example 35	Example 18	Example 2 / CMC	3 / 1.5	4.56	89.8
Example 36	Example 19	Example 3 / CMC	3 / 1.5	4.56	83.3
Example 37	Example 20	Example 4 / CMC	3 / 1.5	4.65	96.0
Example 38	Example 21	Example 5 / CMC	3 / 1.5	4.65	95.5
Example 39	Example 22	Example 6 / CMC	3 / 1.5	4.57	96.3
Example 40	Example 23	Example 7 / CMC	3 / 1.5	4.581	97.1
Example 41	Example 24	Example 8 / CMC	3 / 1.5	4.56	100.3
Example 42	Example 25	Example 2 / CMC	1.5 / 3	4.59	96.8

[Revision according to Rule 26 04.01.2018]
As mentioned above, although preferred embodiment was described in detail, referring an accompanying drawing, this invention is not limited to this example. Those skilled in the art to which the present invention pertains can clearly see various changes or modifications within the scope of the technical idea described in the claims. It is understood that it belongs to the technical scope of the invention.

Claims (12)

1. [Revision according to Rule 26 04.01.2018]
   

   A first copolymer unit comprising any one or more of carboxyl group-containing acrylic monomers, acrylic acid derivative monomers and substituted or unsubstituted styrenes,

   A second copolymer unit comprising residues of a polymeric azo initiator,

   The mass ratio of the said 2nd copolymer unit with respect to the total mass of the said 1st copolymer unit and the said 2nd copolymer unit is 10-40 mass%, The binder for secondary batteries characterized by the above-mentioned.
2. [Revision according to Rule 26 04.01.2018]
   

   According to claim 1,

   The carboxyl group-containing acrylic monomer is at least one member selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethyl maleic acid, 2-carboxyethyl acrylate, and 2-carboxyethyl methacrylate.
3. [Revision according to Rule 26 04.01.2018]
   

   The method according to claim 1 or 2,

   A secondary battery binder, wherein the acrylic acid derivative monomer is at least one member selected from the group consisting of nitrile group-containing acrylic monomers, acrylic esters, and acrylamides.
4. [Revision according to Rule 26 04.01.2018]
   

   The method of claim 3, wherein

   The nitrile group-containing acrylic monomer is at least one member selected from the group consisting of acrylonitrile, methacrylonitrile, 2-cyanoethyl acrylate, and 2-cyanoethyl methacrylate.
5. [Revision according to Rule 26 04.01.2018]
   

   The method according to claim 1 or 2,

   At least a part of the carboxyl group-containing acrylic monomer is an alkali metal salt or an ammonium salt.
6. [Revision according to Rule 26 04.01.2018]
   

   The method according to claim 1 or 2,

   And the first copolymer unit comprises an alkali metal salt or an ammonium salt as the carboxyl group-containing acrylic monomer, and a nitrile group-containing acrylic monomer as the acrylic acid derivative monomer.
7. [Revision according to Rule 26 04.01.2018]
   

   The method according to claim 1 or 2,

   And the second copolymer unit comprises at least one of polyether and polysiloxane as residues of the polymer azo initiator.
8. [Correction under Rule 91 04.01.2018]
   The secondary battery binder resin composition of Claim 1 or 2 containing the binder for secondary batteries.
9. [Revision according to Rule 26 04.01.2018]
   A secondary battery electrode, comprising the secondary battery binder according to claim 1.
10. [Revision according to Rule 26 04.01.2018]
    

    The method of claim 9,

    Secondary battery electrode, characterized in that it further comprises carboxymethyl cellulose (CMC) as the secondary battery binder.
11. [Revision according to Rule 26 04.01.2018]
    A secondary battery comprising the secondary battery electrode according to claim 9.
12. [Revision according to Rule 26 04.01.2018]
    

    The method of claim 11, wherein

    The secondary battery electrode is a secondary battery, characterized in that the negative electrode.

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