JP6477503B2 - Slurry composition for lithium ion secondary battery electrode, electrode for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a slurry composition for lithium ion secondary battery electrodes, an electrode for lithium ion secondary batteries, and a lithium ion secondary battery.

  Lithium ion secondary batteries are characterized by small size, light weight, high energy density, and capable of repeated charge and discharge, and are used in a wide range of applications. Therefore, in recent years, for the purpose of further improving the performance of lithium ion secondary batteries, improvement of battery members such as electrodes has been studied.

  Here, an electrode for a lithium ion secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector. Then, on the current collector, a slurry composition in which an electrode active material, a binder (binder), and a conductive material and the like blended as necessary are dispersed in a dispersion medium is used as the electrode mixture layer. It is formed by applying and drying. Therefore, in recent years, in order to achieve further performance improvement of the lithium ion secondary battery, improvement of a slurry composition used for forming an electrode mixture layer has been attempted.

  Specifically, by using a predetermined binder, the binding properties of the components constituting the electrode mixture layer such as the electrode active material and the binding properties between the electrode mixture layer and the current collector are enhanced. It has been proposed to improve the powder resistance and peel strength of an electrode for lithium ion secondary batteries, and the cycle characteristics of lithium ion secondary batteries.

More specifically, for example, in Patent Document 1, a particulate polymer in which the mode particle size of the primary particles is 0.01 μm or more and less than 0.25 μm, and the mode particle size of the primary particles is 0.25 μm or more and less than 3 μm The binding property of the components constituting the electrode mixture layer and the binding between the electrode mixture layer and the current collector by using the binder formed by mixing the particulate polymer which is It has been proposed to enhance sex.
For example, in Patent Document 2, the number average particle diameter is 50 to 300 nm, and the ratio of weight average particle diameter to number average particle diameter (weight average particle diameter / number average particle diameter) is 1.05 or more By using a certain carboxy-modified copolymer as a binder, it has been proposed to improve the binding properties of the components constituting the electrode mixture layer and the binding properties of the electrode mixture layer and the current collector. .
Furthermore, for example, in Patent Document 3, the existence ratio of particles having a particle diameter of 0.01 μm or more and less than 0.25 μm is 2 to 60% by volume, and the existence ratio of particles having a particle diameter of 0.25 μm to 0.5 μm By using polymer particles in an amount of 40 to 98% by volume as a binder, it is possible to enhance the binding properties of the components constituting the electrode mixture layer and the binding properties of the electrode mixture layer and the current collector. Proposed.

Japanese Patent Application Publication No. 2003-100298 JP, 2010-192434, A Patent No. 5093544

  However, in the above-described conventional techniques, only the relationship between the particle diameter of the particulate polymer used as a binder and the binding property is noted, and the slurry composition and the slurry composition are used. No attention has been paid to other components contained in the electrode mixture layer, for example, the electrode active material.

  Therefore, the above-described conventional techniques have room for improvement in that the rate characteristics and the like of the lithium ion secondary battery are further improved by improving the electrode active material as well as the binder.

Therefore, the present invention is excellent in the binding properties of the components constituting the electrode mixture layer, the binding properties of the electrode mixture layer and the current collector, and the cycle characteristics and rate characteristics of the lithium ion secondary battery. An object of the present invention is to provide a slurry composition for a lithium ion secondary battery electrode that can be used.
Further, the present invention is excellent in the binding property between the components constituting the electrode mixture layer and the binding property between the electrode mixture layer and the current collector, and has excellent cycle characteristics and rate characteristics in the lithium ion secondary battery. An object of the present invention is to provide an electrode for a lithium ion secondary battery that can be exhibited.
Another object of the present invention is to provide a lithium ion secondary battery excellent in cycle characteristics and rate characteristics.

  The present inventors diligently studied for the purpose of solving the above-mentioned problems. The present inventors then combine the components constituting the electrode mixture layer by using an electrode active material having a predetermined pore volume and a particulate binder having a predetermined particle diameter in combination. The present invention has been accomplished by finding that the adhesion and the adhesion between the electrode mixture layer and the current collector, and the cycle characteristics and rate characteristics of the lithium ion secondary battery can be made excellent.

That is, the present invention aims to advantageously solve the above-mentioned problems, and the slurry composition for a lithium ion secondary battery electrode of the present invention has a mercury intrusion pore volume of 0.1 cm ³ / g or more. It is characterized in that it contains an electrode active material of 2.0 cm ³ / g or less, a particulate binder having a number average particle diameter of 200 nm or more and 600 nm or less, and water. Thus, if the electrode active material having a mercury intrusion pore volume of a predetermined size and the particulate binder having a number average particle diameter of a predetermined size are used in combination, a slurry composition can be used. When an electrode for a lithium ion secondary battery and a lithium ion secondary battery are produced, the components constituting the electrode mixture layer, the electrode mixture layer and the current collector can be favorably bound, and also excellent Thus, a lithium ion secondary battery having excellent cycle characteristics and rate characteristics is obtained.

  Here, in the slurry composition for a lithium ion secondary battery electrode of the present invention, the surface acid amount of the particulate binder is preferably 0.01 mmol / g or more and 0.5 mmol / g or less. If the surface acid content of the particulate binder is 0.01 mmol / g or more and 0.5 mmol / g or less, the binding property of the particulate binder can be enhanced, and a slurry containing the particulate binder It is because the stability of the composition can be enhanced.

  Furthermore, in the slurry composition for a lithium ion secondary battery electrode of the present invention, the gel content of the particulate binder is preferably 30% by mass to 99% by mass. If the gel content of the particulate binder is 30% by mass or more and 99% by mass or less, the swelling of the electrode is suppressed while securing the flexibility of the electrode for a lithium ion secondary battery produced using the slurry composition Because you can do it.

  Moreover, this invention aims at solving the said subject advantageously, The electrode for lithium ion secondary batteries of this invention is either of the slurry compositions for lithium ion secondary battery electrodes mentioned above It has an electrode mixture layer obtained by using it. Thus, when the electrode mixture layer is formed using the above-described slurry composition for lithium ion secondary battery electrodes, the binding properties of the components constituting the electrode mixture layer, the electrode mixture layer, and the current collector Thus, it is possible to obtain an electrode for a lithium ion secondary battery, which is excellent in the binding property with the above, and can exhibit excellent cycle characteristics and rate characteristics in the lithium ion secondary battery.

  Furthermore, this invention aims at solving the said subject advantageously, The lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, a separator, and electrolyte solution, At least the said positive electrode and the said negative electrode One of the electrodes is the above-described electrode for a lithium ion secondary battery. As described above, when at least one of the positive electrode and the negative electrode is constituted by the above-described electrode for a lithium ion secondary battery, a lithium ion secondary battery excellent in cycle characteristics and rate characteristics can be obtained.

According to the present invention, the binding properties of the components constituting the electrode mixture layer, the binding properties between the electrode mixture layer and the current collector, and the cycle characteristics and rate characteristics of the lithium ion secondary battery are excellent. The slurry composition for lithium ion secondary battery electrodes which can be used is obtained.
Further, according to the present invention, the cycleability is excellent for the lithium ion secondary battery, because it is excellent in the binding property between the components constituting the electrode mixture layer and the binding property between the electrode mixture layer and the current collector. And an electrode for a lithium ion secondary battery capable of exhibiting rate characteristics.
Furthermore, according to the present invention, a lithium ion secondary battery excellent in cycle characteristics and rate characteristics can be obtained.

It is a graph which shows the hydrochloric acid addition amount-electrical conductivity curve created when calculating the surface acid amount of a particulate-form binder.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the slurry composition for lithium ion secondary battery electrodes of this invention is used for formation of the electrode of a lithium ion secondary battery. Moreover, the electrode for lithium ion secondary batteries of this invention can be manufactured using the slurry composition for lithium ion secondary battery electrodes of this invention. Furthermore, the lithium ion secondary battery of the present invention is characterized in that the electrode for a lithium ion secondary battery of the present invention is used.

(Slurry composition for lithium ion secondary battery electrode)
The slurry composition for lithium ion secondary battery electrodes of the present invention has an electrode active material having a mercury intrusion pore volume of 0.1 cm ³ / g or more and 2.0 cm ³ / g or less, and a number average particle diameter of 200 nm or more and 600 nm It is the slurry composition of the water system containing the particulate-form binder which is the following, and water. In addition to the electrode active material and the particulate binder, the slurry composition for a lithium ion secondary battery electrode of the present invention may contain other components such as a conductive material and a viscosity modifier as required. Good.

<Electrode active material>
The electrode active material is a substance that transfers electrons at the electrode (positive electrode, negative electrode) of the lithium ion secondary battery. And, as an electrode active material (a positive electrode active material, a negative electrode active material) of a lithium ion secondary battery, usually, a material capable of inserting and extracting lithium is used.

[Positive electrode active material]
Specifically, as the positive electrode active material, a compound containing a transition metal, for example, a transition metal oxide, a transition metal sulfide, a composite metal oxide of lithium and a transition metal, and the like can be used. In addition, as a transition metal, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo etc. are mentioned, for example.

Here, as the transition metal oxide, for example, MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O-P ₂ O ₅ , non-crystal Quality MoO ₃ , amorphous V ₂ O ₅ , amorphous V ₆ O _{13 and the} like.
As a transition metal sulfide, TiS ₂ , TiS ₃ , amorphous MoS ₂ , FeS, etc. may be mentioned.
As a composite metal oxide of lithium and transition metal, a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel type structure, a lithium-containing composite metal oxide having an olivine type structure, etc. are mentioned Be

Examples of lithium-containing composite metal oxides having a layered structure include lithium-containing cobalt oxides (LiCoO ₂ ), lithium-containing nickel oxides (LiNiO ₂ ), lithium-containing composite oxides of Co—Ni—Mn (Li (Co) Mn Ni) O ₂ ), Ni-Mn-Al lithium-containing composite oxide, Ni-Co-Al lithium-containing composite oxide, solid solution of LiMaO ₂ and Li ₂ MbO ₃ and the like can be mentioned. As the lithium-containing complex oxide of Co-Ni-Mn, Li [ Ni 0.5 Co 0.2 Mn 0.3] O 2, Li [Ni 1/3 Co 1/3 Mn 1/3] such as O ₂ and the like. Moreover, as a solid solution of LiMaO ₂ and Li ₂ MbO ₃ , for example, xLiMaO ₂ · (1-x) Li ₂ MbO _{3 and the} like can be mentioned. Here, x represents a number satisfying 0 <x <1, Ma represents one or more transition metals having an average oxidation state of 3+, and Mb represents one or more transition metals having an average oxidation state of 4+. Represent. As such a solid solution, Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O _{2 and the} like can be mentioned.
In the present specification, the "average oxidation state" indicates the average oxidation state of the "one or more transition metals", and is calculated from the molar amount and the valence of the transition metal. For example, when “one or more transition metals” is composed of 50 mol% of Ni ²⁺ and 50 mol% of Mn ^{4 +} , the average oxidation state of “one or more transition metals” is (0. 5) x (2+) + (0.5) x (4 +) = 3 +.

As a lithium-containing composite metal oxide having a spinel type structure, for example, a compound in which part of Mn of lithium manganate (LiMn ₂ O ₄ ) or lithium manganate (LiMn ₂ O ₄ ) is substituted with another transition metal Can be mentioned. Specific examples include _{Li s [Mn 2-t Mc} t] O 4 , such as LiNi _0.5 Mn _1.5 O _4. Here, Mc represents one or more transition metals having an average oxidation state of 4+. Specific examples of Mc include Ni, Co, Fe, Cu, Cr and the like. Further, t represents a number satisfying 0 <t <1, and s represents a number satisfying 0 ≦ s ≦ 1. Note that, as a positive electrode active material, a lithium-excess spinel compound represented by Li _{1 + x} Mn _2-x O ₄ (0 <X <2) can be used.

As a lithium-containing composite metal oxide having an olivine type structure, for example, olivine type phosphorus represented by Li _y MdPO ₄ such as olivine type lithium iron phosphate (LiFePO ₄ ) or olivine type lithium manganese phosphate (LiMnPO ₄ ) And lithium acid compounds. Here, Md represents one or more types of transition metals having an average oxidation state of 3+, and examples thereof include Mn, Fe, Co, and the like. Further, y represents a number satisfying 0 ≦ y ≦ 2. Furthermore, the olivine-type lithium phosphate compound represented by Li _y MdPO ₄ may have Md partially substituted by another metal. Examples of metals that can be substituted include Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B and Mo.

[Anode active material]
Moreover, as a negative electrode active material, a carbon type negative electrode active material, a metal type negative electrode active material, and the negative electrode active material which combined these, etc. are mentioned, for example.

  Here, the carbon-based negative electrode active material is an active material having carbon as a main skeleton capable of inserting (also referred to as “doping”) lithium. Examples of the carbon-based negative electrode active material include carbonaceous materials and graphitic materials.

The carbonaceous material is a material having a low degree of graphitization (i.e., low crystallinity) obtained by heat-treating a carbon precursor at 2000 ° C. or less to carbonize it. The lower limit of the heat treatment temperature at the time of carbonization is not particularly limited, but can be, for example, 500 ° C. or more.
And, as a carbonaceous material, for example, graphitizable carbon which easily changes the structure of carbon depending on the heat treatment temperature, non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon and the like can be mentioned. .
Here, as the graphitizable carbon, for example, a carbon material using a tar pitch obtained from petroleum or coal as a raw material can be mentioned. Specific examples thereof include coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, and pyrolytic vapor grown carbon fibers.
Moreover, as non-graphitizable carbon, for example, a phenol resin fired body, polyacrylonitrile carbon fiber, quasi-isotropic carbon, a furfuryl alcohol resin fired body (PFA), hard carbon and the like can be mentioned.

The graphitic material is a material having high crystallinity close to that of graphite, which is obtained by heat-treating graphitizable carbon at 2000 ° C. or higher. The upper limit of the heat treatment temperature is not particularly limited, but can be, for example, 5000 ° C. or less.
And as a graphite material, natural graphite, artificial graphite, etc. are mentioned, for example.
Here, as the artificial graphite, for example, artificial graphite obtained by heat treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB obtained by heat treating MCMB at 2000 ° C. or higher, and mesophase pitch carbon fiber at 2000 ° C. The graphitized mesophase pitch carbon fiber etc. which were heat-treated above are mentioned.

  The metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of inserting lithium in its structure, and the theoretical electric capacity per unit mass when lithium is inserted is 500 mAh / An active material of g or more. As the metal-based active material, for example, lithium metal, a single metal capable of forming a lithium alloy (for example, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn) Sr, Zn, Ti, etc.) and alloys thereof, and oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. thereof. Among these, as the metal-based negative electrode active material, a silicon-containing active material (silicon-based negative electrode active material) is preferable. By using the silicon-based negative electrode active material, the capacity of the lithium ion secondary battery can be increased.

The silicon-based negative electrode active material includes, for example, silicon (Si), an alloy containing silicon, SiO, SiO _x , a composite of a Si-containing material obtained by coating or compounding a Si-containing material with conductive carbon and conductive carbon Etc. These silicon-based negative electrode active materials may be used alone or in combination of two or more.

  Examples of the alloy containing silicon include an alloy composition containing silicon, aluminum, and a transition metal such as iron, and further containing a rare earth element such as tin and yttrium.

SiO _x is a compound containing at least one of SiO and SiO ₂ and Si, and x is usually at least 0.01 and less than 2. Then, SiO _x can be formed, for example, by utilizing disproportionation reaction of silicon monoxide (SiO). Specifically, SiO _x can be prepared by heat treating SiO, optionally in the presence of a polymer such as polyvinyl alcohol, to produce silicon and silicon dioxide. The heat treatment can be performed at a temperature of 900 ° C. or higher, preferably 1000 ° C. or higher, in an atmosphere containing an organic gas and / or a vapor, after grinding and mixing SiO and optionally a polymer.

  As a composite of Si-containing material and conductive carbon, for example, a ground mixture of SiO, a polymer such as polyvinyl alcohol and optionally a carbon material is heat-treated under an atmosphere containing, for example, an organic gas and / or a vapor. Compounds can be mentioned. Also, a method of coating the surface of SiO particles by chemical vapor deposition using an organic gas or the like, a method of composite particle formation (granulation) of SiO particles and graphite or artificial graphite by mechanochemical method, etc. It can also be obtained by the known methods of

[Mercury intrusion pore volume]
And the electrode active material used for the slurry composition for lithium ion secondary battery electrodes of this invention has a pore. In addition, the electrode active material needs to have a mercury intrusion pore volume of 0.1 cm ³ / g or more and 2.0 cm ³ / g or less, preferably 0.4 cm ³ / g or more, 0 more preferably .9cm ³ / g or more, is preferably 1.5 cm ³ / g or less, and more preferably less 1.1 cm ³ / g. By using an electrode active material having a mercury intrusion pore volume of 0.1 cm ³ / g or more, the rate characteristic of a lithium ion secondary battery manufactured using a slurry composition using the pores of the electrode active material is obtained. It is because it can be improved. Further, by using an electrode active material having a mercury intrusion pore volume of 2.0 cm ³ / g or less, it is possible to suppress that the particulate binder described later enters into the pores of the electrode active material, and the electrode mixture While being able to make the components which comprise a layer, an electrode compound material layer, and a collector bind | bond well, the rate characteristic of the lithium ion secondary battery produced using a slurry composition is prevented from falling. Because you can do it.

  In the present invention, “mercury intrusion pore volume” can be obtained from a mercury intrusion curve measured by mercury intrusion method, and the mercury intrusion amount when pressure is increased from 4 kPa to 400 MPa (ie, when pressure is 400 MPa) The difference between the amount of injected mercury and the amount of injected mercury at a pressure of 4 kPa.

  And the mercury intrusion pore volume of the electrode active material can be adjusted, for example, using known methods such as changing the manufacturing conditions of the electrode active material, and pulverizing treatment, firing and CVD treatment of the electrode active material. .

<Particulate binder>
In the electrode (positive electrode, negative electrode) provided with an electrode mixture layer formed using the slurry composition for lithium ion secondary battery electrodes of the present invention, the particulate binder is either one or more of each component in the electrode mixture layer or each Combine the components with the current collector. As the particulate binder, a polymer dispersible in an aqueous medium such as water can be used.

[Number average particle size]
The particulate binder used for the slurry composition for a lithium ion secondary battery electrode of the present invention needs to have a number average particle diameter of 200 nm or more and 600 nm or less, and preferably 250 nm or more, The thickness is more preferably 270 nm or more, preferably 400 nm or less, and more preferably 380 nm or less. By using a particulate binder having a number average particle diameter of 200 nm or more, the particulate binder can be prevented from entering the pores of the electrode active material described above, and the components constituting the electrode mixture layer and each other and While being able to bind | bond the electrode compound material layer and a collector favorably, it is because it can prevent that the rate characteristic of the lithium ion secondary battery produced using a slurry composition falls. In addition, by using a particulate binder having a number average particle diameter of 600 nm or less, the contact area between the particulate binder and the component or current collector that is bound via the particulate binder. It is possible to suppress the decrease of H.sub.2 and to bond the components of the electrode mixture layer and the electrode mixture layer to the current collector.

  Here, in the present invention, “number average particle diameter” refers to a particle diameter at which the value of integrated distribution is 50% in the particle diameter-number integrated distribution measured using a laser diffraction / scattering type particle size distribution measuring device. Point to.

  The number average particle diameter of the particulate binder can be adjusted by changing the production conditions of the polymer used as the particulate binder. Specifically, for example, when a polymer used as a particulate binder is prepared by seed polymerization, the number average of the particulate binder is adjusted by adjusting the number and particle diameter of seed particles used for polymerization. The particle size can be controlled.

[[Number average particle diameter / mercury intrusion pore volume]]
From the viewpoint of sufficiently suppressing entry of the particulate binder into the pores of the electrode active material, the ratio of the number average particle diameter of the particulate binder to the mercury intrusion pore volume of the electrode active material (number of particles) The average particle size / mercury pore size (mercury pore size) is preferably 1.5 × 10 ⁻⁵ g / cm ² or more, more preferably 2.3 × 10 ⁻⁵ g / cm ² or more, and 2 More preferably, it is not less than 0.5 × 10 ⁻⁵ g / cm ² . Further, from the viewpoint of more favorably binding the components constituting the electrode mixture layer and the electrode mixture layer and the current collector, the number average of the particulate binders relative to the mercury intrusion pore volume of the electrode active material The particle size ratio (number average particle size / mercury pore size) is preferably 6.4 × 10 ⁻⁵ g / cm ² or less, and 5.5 × 10 ⁻⁵ g / cm ² or less Is more preferably 4.0 × 10 ⁻⁵ g / cm ² or less.

[Surface acid content]
Here, in the particulate binder, the surface acid content is preferably 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, and preferably 0.03 mmol / g or more. It is more preferably 0.5 mmol / g or less, more preferably 0.4 mmol / g or less, and still more preferably 0.2 mmol / g or less. When the surface acid amount of the particulate binder is 0.01 mmol / g or more, the wettability to the water of the particulate binder is improved, and thereby the particulate binder is suitably dispersed in water, This is because the storage stability of the slurry composition is improved. In addition, when the surface acid content of the particulate binder is 0.5 mmol / g or less, even when a particulate binder having a relatively large particle diameter is used as in the present invention, the particulate binder is used. This is because the binding strength of the bonding material is sufficiently high, and the components constituting the electrode mixture layer, and the electrode mixture layer and the current collector can be well bonded.

In the present invention, the "surface acid amount" refers to the surface acid amount per 1 g of the solid content of the particulate binder, and can be calculated by the following method.
First, an aqueous dispersion containing a particulate binder is prepared. The aqueous dispersion containing the particulate binder is placed in a glass container washed with distilled water, and the solution conductivity meter is set and stirred. Stirring is continued until the addition of hydrochloric acid described later is completed.
A 0.1 N aqueous solution of sodium hydroxide was added to the aqueous dispersion containing the particulate binder so that the electrical conductivity of the aqueous dispersion containing the particulate binder would be 2.5 to 3.0 mS. Do. After 6 minutes, the electrical conductivity is measured. This value is taken as the electrical conductivity at the start of measurement.
Furthermore, 0.5 mL of 0.1 N hydrochloric acid is added to the aqueous dispersion containing the particulate binder, and the electrical conductivity is measured after 30 seconds. Thereafter, 0.5 mL of 0.1 N hydrochloric acid is again added, and after 30 seconds, the conductivity is measured. This operation is repeated at intervals of 30 seconds until the electric conductivity of the aqueous dispersion containing the particulate binder becomes equal to or higher than the electric conductivity at the start of the measurement.
The graph of the obtained conductivity data is used with the conductivity (unit "mS") as the vertical axis (Y coordinate axis) and the accumulated amount of hydrochloric acid added (unit "mmol") as the horizontal axis (X coordinate axis). Plot to Thereby, as shown in FIG. 1, a hydrochloric acid addition amount-conductivity curve having three inflection points is obtained. Let the X coordinates of the three inflection points and the X coordinates at the end of the addition of hydrochloric acid be P1, P2, P3 and P4, respectively, in ascending order of values. The approximate straight line L1 is obtained by the least squares method for data in the four sections of X coordinate from zero to coordinate P1, from coordinate P1 to coordinate P2, from coordinate P2 to coordinate P3, and from coordinate P3 to coordinate P4. , L2, L3 and L4. The X coordinate of the intersection of the approximate straight line L1 and the approximate straight line L2 is A1 (mmol), the X coordinate of the intersection of the approximate straight line L2 and the approximate straight line L3 is A2 (mmol), and the X coordinate of the intersection of the approximate straight line L3 and the approximate straight line L4 Coordinates are A3 (mmol).
The amount of surface acid per 1 g of the particulate binder is given as a value (mmol / g) converted to hydrochloric acid from the following formula (a). The amount of acid in the aqueous phase per 1 g of the particulate binder (the amount of acid present in the aqueous phase of the aqueous dispersion containing the particulate binder per 1 g of solid content of the particulate binder) The acid amount of (also referred to as “the amount of acid in the aqueous phase of the particulate binder”) is given as a value (mmol / g) converted to hydrochloric acid from the following formula (b). Further, the total amount of acid per 1 g of the particulate binder dispersed in water is the sum of the formula (a) and the formula (b) as represented by the following formula (c).
(A) Surface acid content per gram of particulate binder = (A2-A1) / solid content of particulate binder in water dispersion (b) acid in aqueous phase per gram of particulate binder Amount = (A3-A2) / solid content of particulate binder in aqueous dispersion (c) Total acid amount per 1 g of particulate binder dispersed in water = (A3-A1) / in aqueous dispersion Solids content of particulate binder in Japan

  The surface acid content of the particulate binder can be adjusted by changing the type and amount of the monomer used for producing the polymer used as the particulate binder. Specifically, for example, the amount of surface acid can be increased by increasing the amount of use of an acidic group-containing monomer such as a monomer containing a carboxylic acid group.

[Gel content]
The particulate binder preferably has a gel content of 30% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more, and 99% by mass. % Or less is preferable, 95% by mass or less is more preferable, and 92% by mass or less is even more preferable. If the gel content of the particulate binder is 30% by mass or more, the strength of the particulate binder can be increased, and the swelling of the electrode can be suppressed. In addition, when the gel content of the particulate binder is 99% by mass or less, the particulate binder is prevented from losing toughness and becoming brittle, and the components constituting the electrode mixture layer and the electrode mixture are prevented. This is because the layer and the current collector can be bound well.

  In the present invention, the "gel content" can be measured using the measurement method described in the examples of the present specification.

  The gel content of the particulate binder can be adjusted by changing the polymerization conditions of the polymer used as the particulate binder. For example, a chain transfer agent (for example, t- The gel content can be increased by decreasing the amount of dodecyl mercaptan etc.), and the gel content can be reduced by increasing the amount of chain transfer agent used during polymerization.

[Type of polymer]
Here, as a polymer used as a particulate-form binder, a well-known polymer, for example, a diene polymer, an acrylic polymer, a fluoropolymer, a silicon polymer, etc. are mentioned. One of these polymers may be used alone, or two or more of them may be used in combination at an arbitrary ratio.

Specifically, for example, when the slurry composition for a lithium ion secondary battery electrode is a slurry composition for a negative electrode, the polymer may be a diene polymer, particularly an aliphatic conjugated diene monomer unit and an aromatic It is preferable to use a copolymer having a vinyl monomer unit or a hydrogenated product thereof. Aliphatic conjugated diene monomer unit which is a flexible repeating unit having low rigidity and capable of enhancing binding property, and the solubility of the polymer in the electrolytic solution is reduced to thereby form particles in the electrolytic solution This is because a copolymer having an aromatic vinyl monomer unit capable of enhancing the stability of the binder can well exhibit the function as a particulate binder.
In the present invention, “containing a monomer unit” means that “a structural unit derived from a monomer is contained in a polymer obtained using the monomer”.

[[Monomer used for preparation of copolymer having aliphatic conjugated diene monomer unit and aromatic vinyl monomer unit]]
Here, when a copolymer having an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit is used as a particulate binder, an aliphatic conjugated diene capable of forming an aliphatic conjugated diene monomer unit The monomer is not particularly limited, and 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene And substituted linear conjugated pentadienes, substituted and branched conjugated hexadienes, and the like can be used. In addition, an aliphatic conjugated diene monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  And in the copolymer, the content ratio of the aliphatic conjugated diene monomer unit is preferably 20% by mass or more, more preferably 30% by mass or more, preferably 70% by mass or less, more preferably 60% by mass % Or less. It is because the softness | flexibility of the electrode formed using a slurry composition can be improved because the content rate of an aliphatic conjugated diene monomer unit is 20 mass% or more. In addition, when the content ratio of the aliphatic conjugated diene monomer unit is 70% by mass or less, the binding ability of the particulate binder formed of the copolymer becomes sufficiently high, and the component constituting the electrode mixture layer It is because it is possible to bond the electrode mixture layer and the current collector well.

  Moreover, as an aromatic vinyl monomer which can form an aromatic vinyl monomer unit, it does not specifically limit, Styrene, alpha-methylstyrene, vinyl toluene, divinylbenzene etc. can be used. In addition, an aromatic vinyl monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  And in the copolymer, the content rate of the aromatic vinyl monomer unit is preferably 30% by mass or more, more preferably 40% by mass or more, preferably 80% by mass or less, more preferably 70% by mass It is below. It is because the electrolytic solution resistance of the electrode formed using a slurry composition can be improved because the content rate of an aromatic vinyl monomer unit is 30 mass% or more. In addition, when the content of the aromatic vinyl monomer unit is 80% by mass or less, the binding ability of the particulate binder made of the copolymer becomes sufficiently high, and the components constituting the electrode mixture layer And the electrode mixture layer and the current collector can be well bonded.

  A copolymer having an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit contains a 1,3-butadiene unit as an aliphatic conjugated diene monomer unit, and is an aromatic vinyl monomer unit It is preferred that the copolymer contains a styrene unit (i.e., a styrene-butadiene copolymer or a hydrogenated styrene-butadiene copolymer).

  Further, a copolymer having the above-mentioned aliphatic conjugated diene monomer unit and aromatic vinyl monomer unit is an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated monomer unit having a hydroxyl group, a sulfonic acid It is preferable to include at least one selected from the group consisting of unsaturated monomer units having a group. Among them, the copolymer preferably contains an ethylenically unsaturated carboxylic acid monomer unit.

Here, as an ethylenically unsaturated carboxylic acid monomer capable of forming an ethylenically unsaturated carboxylic acid monomer unit, an ethylenically unsaturated monocarboxylic acid and a derivative thereof, an ethylenically unsaturated dicarboxylic acid and an acid anhydride thereof And derivatives thereof.
Examples of ethylenically unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid and the like. And as an example of the derivative of the ethylenically unsaturated monocarboxylic acid, 2-ethyl acrylic acid, isocrotonic acid, α-acetoxy acrylic acid, β-trans-aryloxy acrylic acid, α-chloro-β-E-methoxy acrylic Acids, β-diaminoacrylic acid and the like can be mentioned.
Examples of ethylenically unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid and the like. And as an example of the acid anhydride of ethylenically unsaturated dicarboxylic acid, maleic anhydride, a diacrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride etc. are mentioned. Furthermore, examples of derivatives of ethylenically unsaturated dicarboxylic acids include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate And dodecyl maleate, octadecyl maleate, fluoroalkyl maleate and the like.
One of these may be used alone, or two or more of them may be used in combination at an arbitrary ratio.

  And in the copolymer, the content ratio of the ethylenically unsaturated carboxylic acid monomer unit is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 5% by mass or less And more preferably 1% by mass or less. It is because the storage stability of the slurry composition containing a particulate-form binder is ensured because the content rate of an ethylenically unsaturated carboxylic acid monomer unit is 0.1 mass% or more. On the other hand, when the content ratio of the ethylenically unsaturated carboxylic acid monomer unit is 5% by mass or less, the binding strength of the particulate binder made of the copolymer becomes sufficiently high, and the electrode mixture layer is formed. Components and the electrode mixture layer and the current collector can be well bonded.

Moreover, as an unsaturated monomer having a hydroxyl group capable of forming an unsaturated monomer unit having a hydroxyl group, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl Acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2- Hydroxyethyl methyl fumarate and the like.
One of these may be used alone, or two or more of them may be used in combination at an arbitrary ratio.

  And in the copolymer, the content ratio of the unsaturated monomer unit having a hydroxyl group is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 5% by mass or less. More preferably, it is 1% by mass or less. It is because the storage stability of the slurry composition containing a particulate-form binder is ensured because the content rate of the unsaturated monomer unit which has a hydroxyl group is 0.1 mass% or more. On the other hand, when the content of the unsaturated monomer unit having a hydroxyl group is 5% by mass or less, the binding capacity of the particulate binder made of the copolymer becomes sufficiently high, and the electrode mixture layer is formed. This is because the components and the electrode mixture layer and the current collector can be favorably bound.

  Furthermore, as an unsaturated monomer having a sulfonic acid group capable of forming an unsaturated monomer unit having a sulfonic acid group, for example, vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) acrylic sulfonic acid, styrene sulfone An acid, ethyl (meth) acrylic acid-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid and the like can be mentioned. One of these may be used alone, or two or more of them may be used in combination at an arbitrary ratio. In the present specification, “(meth) acrylic” means acrylic and / or methacrylic.

  And in the copolymer, the content ratio of the unsaturated monomer unit having a sulfonic acid group is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 5% by mass The following content is more preferably 1% by mass or less. It is because the storage stability of the slurry composition containing a particulate-form binder is ensured because the content rate of the unsaturated monomer unit which has a sulfonic acid group is 0.1 mass% or more. On the other hand, when the content ratio of the unsaturated monomer unit having a sulfonic acid group is 5% by mass or less, the binding strength of the particulate binder made of a copolymer becomes sufficiently high, and the electrode mixture layer is formed. It is because the components to comprise, an electrode compound material layer, and a collector can be couple | bonded favorable.

  Furthermore, the copolymer having the above-mentioned aliphatic conjugated diene monomer unit and aromatic vinyl monomer unit may contain (meth) acrylic acid ester monomer unit in addition to the above-mentioned monomer unit. preferable.

  Here, as a (meth) acrylic acid ester monomer capable of forming a (meth) acrylic acid ester monomer unit, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t- Acrylic acid alkyl esters such as butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl Methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate Methacrylic acid alkyl esters and the like. One of these may be used alone, or two or more of these may be used in combination.

  And, in the copolymer, the content ratio of the (meth) acrylic acid ester monomer unit is preferably 1% by mass or more, more preferably 3% by mass or more, preferably 10% by mass or less, more preferably It is 7% by mass or less.

Moreover, the copolymer having the aliphatic conjugated diene monomer unit and the aromatic vinyl monomer unit described above contains any repeating unit other than the above unless the effect of the present invention is significantly impaired. It is also good.
The content of the optional repeating unit is not particularly limited, but the upper limit is preferably 6% by mass or less, more preferably 4% by mass or less, and particularly preferably 2% by mass or less.

[Method of preparing polymer]
The method for producing the polymer used as the particulate binder is not particularly limited, and any method such as solution polymerization, suspension polymerization, bulk polymerization and emulsion polymerization may be used. As the polymerization reaction, any method such as ionic polymerization, radical polymerization, living radical polymerization can be used. Among these, it is easy to obtain a high molecular weight, and since the polymer is obtained as it is dispersed in water as it is, the treatment for redispersion is unnecessary, and it can be used as it is for the production of the slurry composition of the present invention. From the viewpoint of production efficiency, such as possible, the emulsion polymerization method is particularly preferred.
In the polymerization, seed polymerization may be performed using seed particles. And when seed polymerization is performed, arbitrary particles can be used as seed particles. That is, for example, when preparing a copolymer having the above-described aliphatic conjugated diene monomer unit and aromatic vinyl monomer unit by seed polymerization, a polymer forming the surface portion of the particulate copolymer As long as it is a copolymer mentioned above, the polymer particle of arbitrary composition can be used as a seed particle.

  And as an emulsifying agent, a dispersing agent, a polymerization initiator, a polymerization auxiliary and the like used for polymerization, those generally used can be used. The polymerization conditions can also be arbitrarily selected depending on the polymerization method, the type of polymerization initiator and the like.

[Blended amount of particulate binder]
The amount of the particulate binder in the slurry composition for a lithium ion secondary battery electrode according to the present invention is preferably 0.5 parts by mass or more per 100 parts by mass of the electrode active material described above. It is preferable that it is 5.0 mass parts or less. By setting the compounding amount of the particulate binder to 0.5 parts by mass or more per 100 parts by mass of the electrode active material, the components constituting the electrode mixture layer, the electrode mixture layer and the current collector are favorably bound. It is because it can be worn. Further, by setting the compounding amount of the particulate binder to 5.0 parts by mass or less per 100 parts by mass of the electrode active material, it is possible to form particles in a lithium ion secondary battery electrode manufactured using the slurry composition of the present invention This is because inhibition of lithium ion migration by the binder can be suppressed, and the internal resistance of the lithium ion secondary battery can be reduced.

  In addition, the slurry composition for lithium ion secondary battery electrodes of this invention may be called particulate-form binders other than the particulate-form binder mentioned above (Hereinafter, "other particulate-form binders"). That is, it may further contain a particulate binder having a number average particle diameter of less than 200 nm, or a particulate binder having a number average particle diameter of more than 600 nm. However, from the viewpoint of suppressing the entry of the electrode active material into the pores and suppressing the decrease in the binding property, the proportion of other particulate binders in the whole particulate binder is 50% by mass or less. It is more preferable that the content be 40% by mass or less, and it is further preferable that no other particulate binder be contained (that is, only one kind of particulate binder be contained).

<Other ingredients>
The slurry composition for a lithium ion secondary battery electrode of the present invention may contain components such as a conductive material, a viscosity modifier, a reinforcing material, a leveling agent, and an electrolyte solution additive, in addition to the above components. When the slurry composition for a lithium ion secondary battery electrode of the present invention is a slurry composition for a lithium ion secondary battery positive electrode, the slurry composition preferably contains a conductive material such as acetylene black.
These other components are not particularly limited as long as they do not affect the battery reaction, and known components such as those described in WO 2012/115096 and JP 2012-204303 A may be used. it can. The viscosity modifier is not particularly limited, and carboxymethyl cellulose or a salt thereof can be suitably used. And the quantity of carboxymethylcellulose or its salt mix | blended as a viscosity modifier can be 1.0 mass part or less with respect to 100 mass parts of electrode active materials, for example.

Preparation of Slurry Composition for Lithium Ion Secondary Battery Electrode
The slurry composition for a lithium ion secondary battery electrode of the present invention can be prepared by dispersing the above-described components in an aqueous medium as a dispersion medium. Specifically, mixing the above respective components with the aqueous medium using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, lees crusher, ultrasonic disperser, homogenizer, planetary mixer, film mix, etc. The slurry composition can be prepared by
Here, although water is usually used as the aqueous medium, an aqueous solution of any compound, a mixed solution of a small amount of organic medium and water, or the like may be used. Moreover, solid content concentration of a slurry composition can be made into the density | concentration which can disperse | distribute each component uniformly, for example, 30 mass% or more and 90 mass% or less. Furthermore, the mixing of the above respective components with the aqueous medium can be carried out usually in a temperature range of from room temperature to 80 ° C., for from 10 minutes to several hours or less.

(Electrode for lithium ion secondary battery)
The lithium ion secondary battery electrode of the present invention can be manufactured using the slurry composition for lithium ion secondary battery electrodes of the present invention.
Here, the electrode for a lithium ion secondary battery of the present invention comprises a current collector and an electrode mixture layer formed on the current collector, and the electrode mixture layer is a lithium ion secondary battery of the present invention. It is obtained from the slurry composition for electrodes. In addition, each component contained in the electrode mixture layer is contained in the slurry composition for lithium ion secondary battery electrodes of this invention, The suitable abundance ratio of these each component is an electrode. It is the same as the preferred abundance ratio of each component in the slurry composition.
And the electrode for lithium ion secondary batteries of this invention is excellent in the binding property of the components which comprise an electrode mixture layer, and the binding property of an electrode mixture layer and a collector, and a lithium ion secondary The battery can exhibit excellent cycle characteristics and rate characteristics.

<Method of manufacturing electrode for lithium ion secondary battery>
The electrode for a lithium ion secondary battery of the present invention includes, for example, a step (coating step) of applying the above-described slurry composition for a lithium ion secondary battery electrode on a current collector, lithium coated on the current collector The slurry composition for an ion secondary battery electrode is dried to form an electrode mixture layer on a current collector (drying step).
In addition, the electrode for lithium ion secondary batteries of this invention dry-granulates the slurry composition for lithium ion secondary battery electrodes mentioned above, prepares composite particle, and it is an electrode on a collector using the said composite particle. It can also be manufactured by a method of forming a mixture layer.

[Coating process]
Here, the method for applying the above-described slurry composition for lithium ion secondary battery electrodes on a current collector is not particularly limited, and any known method can be used. Specifically, as a coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brushing method, or the like can be used. At this time, the slurry composition may be applied to only one side of the current collector, or may be applied to both sides. The thickness of the slurry film on the current collector before coating and before drying can be appropriately set according to the desired thickness, density, coating weight and the like of the electrode mixture layer obtained by drying.

  Here, as a current collector to which the slurry composition is applied, a material having electrical conductivity and electrochemical durability is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum or the like can be used. Among them, aluminum foil (aluminum) is particularly preferable as the current collector used for the positive electrode. Moreover, as a collector used for a negative electrode, copper foil is especially preferable. In addition, the said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[Drying process]
The method for drying the slurry composition on the current collector is not particularly limited, and any known method can be used, such as hot air, hot air, drying with low humidity, vacuum drying, infrared rays, electron beam, etc. The drying method by irradiation is mentioned. By thus drying the slurry composition on the current collector, an electrode mixture layer is formed on the current collector, and an electrode for a lithium ion secondary battery comprising the current collector and the electrode mixture layer is obtained. be able to.

  The electrode mixture layer may be subjected to pressure treatment using a die press or a roll press after the drying step. The pressure treatment can improve the adhesion between the electrode mixture layer and the current collector.

<Properties of lithium-ion secondary battery electrode>
Here, it is preferable that the electrode for a lithium ion secondary battery formed by forming the electrode mixture layer on the current collector as described above has the following properties.

[Amount of electrode mixture layer]
That is, the lithium ion secondary battery electrode preferably has a weight per unit area (mass of the electrode mixture layer per unit area) of 7.0 mg / cm ² or more, and 8.0 mg / cm 2 more preferably ² or more, further preferably 10.0 mg / cm ² or more, preferably 18.0 mg / cm ² or less, more preferably 17.0 mg / cm ² or less. Usually, when the weight per unit area is increased and the thickness of the electrode mixture layer is increased, the binding property of the electrode mixture layer to the current collector is reduced, but in the electrode for lithium ion secondary batteries of the present invention Since a large particulate binder is used, reduction in peel strength can be suppressed even with the above-mentioned coated weight.

[Density of electrode mixture layer]
The density of the electrode mixture layer of the lithium ion secondary battery electrode is preferably 1.4 g / cm ³ or more, more preferably 1.5 g / cm ³ or more, and 1.9 g / cm ^3. preferably cm ³ or less, more preferably 1.8 g / cm ³ or less. When the density of the electrode mixture layer is in the above range, the binding property between the current collector and the electrode mixture layer becomes good, and an electrode excellent in the powder removal resistance and the electrical characteristics can be obtained.

(Lithium ion secondary battery)
The lithium ion secondary battery of the present invention comprises a positive electrode, a negative electrode, an electrolytic solution, and a separator, and the lithium ion secondary battery electrode of the present invention is used as at least one of the positive electrode and the negative electrode. And since the lithium ion secondary battery of this invention is equipped with the electrode for lithium ion secondary batteries of this invention, it is excellent in the electrical characteristics, such as a rate characteristic and cycling characteristics.

<Electrode>
As described above, the lithium ion secondary battery electrode of the present invention is used as at least one of the positive electrode and the negative electrode. That is, the positive electrode of the lithium ion secondary battery of the present invention may be the electrode of the present invention and the negative electrode may be another known negative electrode, and the negative electrode of the secondary battery of the present invention is the electrode of the present invention and the positive electrode is the other And the positive electrode and the negative electrode of the lithium ion secondary battery of the present invention may be the electrodes of the present invention.

<Electrolyte solution>
As the electrolytic solution, an electrolytic solution in which an electrolyte is dissolved in a solvent can be used.
Here, an organic solvent capable of dissolving an electrolyte can be used as the solvent. Specifically, as a solvent, alkyl carbonate solvents such as ethylene carbonate, propylene carbonate, γ-butyrolactone, etc., 2,5-dimethyltetrahydrofuran, tetrahydrofuran, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl acetate, dimethoxyethane It is possible to use one to which a viscosity adjusting solvent such as dioxolane, methyl propionate or methyl formate is added.
A lithium salt can be used as the electrolyte. As a lithium salt, the thing of Unexamined-Japanese-Patent No. 2012-204303 can be used, for example. Among these lithium salts, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable as the electrolyte from the viewpoint of being easily dissolved in an organic solvent and exhibiting a high degree of dissociation.

<Separator>
As a separator, the thing of Unexamined-Japanese-Patent No. 2012-204303 can be used, for example. Among these, it is possible to reduce the film thickness of the whole separator, thereby increasing the ratio of the electrode active material in the lithium ion secondary battery to increase the capacity per volume, and it is possible to use polyolefin. A microporous membrane made of a resin of the type (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred.

<Method of manufacturing lithium ion secondary battery>
In the lithium ion secondary battery of the present invention, for example, a positive electrode and a negative electrode are stacked via a separator, and this is wound or folded according to the battery shape as needed, and placed in a battery container, It can manufacture by inject | pouring and sealing electrolyte solution. A fuse, an over current protection element such as a PTC element, an expanded metal, a lead plate, etc. may be provided if necessary to prevent the pressure rise inside the lithium ion secondary battery and the occurrence of overcharge and discharge and the like. . The shape of the lithium ion secondary battery may be, for example, a coin, a button, a sheet, a cylinder, a square, or a flat.

EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, “%” and “parts” representing amounts are based on mass unless otherwise specified.
In Examples and Comparative Examples, the mercury intrusion pore volume of the electrode active material, the number average particle diameter of the particulate binder, the surface acid content and the gel content, the stability of the slurry composition, the peel strength of the electrode and the swelling resistance The properties and the high temperature cycle characteristics and rate characteristics of the lithium ion secondary battery were evaluated using the following methods, respectively.

<Mercury pressure pore size>
The mercury intrusion pore volume of the electrode active material was measured using a mercury porosimeter (manufactured by Micromeritics, Autopore IV 9510). Specifically, 0.2 g of an electrode active material is injected into a powder cell, deaerated for 10 minutes at room temperature under vacuum, pretreated, introduced mercury under reduced pressure, and then changed the pressure. The amount of mercury intrusion was measured. From the obtained mercury intrusion curve, the amount of mercury intrusion when the pressure was increased from 4 kPa to 400 MPa was calculated and used as the mercury intrusion pore volume.
<Number average particle diameter>
The number average particle diameter of the particulate binder was measured using a laser diffraction / scattering type particle size distribution measuring apparatus (manufactured by Beckman Coulter, LS 230). Specifically, for an aqueous dispersion containing a particulate binder, the particle diameter-number cumulative distribution of the particulate binder is measured using a laser diffraction / scattering particle size distribution measuring apparatus, and the value of the cumulative distribution is The particle diameter of 50% was defined as the number average particle diameter of the particulate binder.
<Surface acid content>
First, an aqueous dispersion (solid content concentration: 2% by mass) containing a particulate binder was prepared. In a 150 mL glass container washed with distilled water, 50 g of the aqueous dispersion containing the particulate binder was placed, and the solution conductivity meter was set and stirred. Stirring was continued until the addition of hydrochloric acid described later was completed.
A 0.1 N aqueous solution of sodium hydroxide was added to the aqueous dispersion containing the particulate binder so that the electrical conductivity of the aqueous dispersion containing the particulate binder would be 2.5 to 3.0 mS. did. After 6 minutes, the electrical conductivity was measured. This value was taken as the electrical conductivity at the start of the measurement.
Furthermore, 0.5 mL of 0.1 N hydrochloric acid was added to the aqueous dispersion containing the particulate binder, and the electrical conductivity was measured after 30 seconds. Thereafter, 0.5 mL of 0.1 N hydrochloric acid was again added, and after 30 seconds, the conductivity was measured. This operation was repeated at intervals of 30 seconds until the electric conductivity of the aqueous dispersion containing the particulate binder became equal to or higher than the electric conductivity at the start of the measurement.
The obtained conductivity data is plotted on a graph in which the conductivity (unit "mS") is on the vertical axis (Y coordinate axis) and the accumulated amount of hydrochloric acid added (unit "mmol") is on the horizontal axis (X coordinate axis). I plotted it. As a result, as shown in FIG. 1, a hydrochloric acid addition amount-conductivity curve having three inflection points was obtained. The X-coordinates of the three inflection points are P1, P2, and P3 in order from the smaller value. The approximate straight lines L1, L2 and L3 were determined by the least squares method for data in three sections, where the X coordinate is from zero to coordinate P1, from coordinate P1 to coordinate P2, and from coordinate P2 to coordinate P3. . The X coordinate of the intersection of the approximate straight line L1 and the approximate straight line L2 is A1 (mmol), and the X coordinate of the intersection of the approximate straight line L2 and the approximate straight line L3 is A2 (mmol).
The amount of surface acid per 1 g of the particulate binder was determined as a value (mmol / g) converted to hydrochloric acid from the following formula.
Amount of surface acid per gram of particulate binder = A2-A1
<Gel content>
An aqueous dispersion containing a particulate binder was prepared, and the aqueous dispersion was dried under an environment of a humidity of 50% and a temperature of 23 to 25 ° C. to form a film having a thickness of 1 ± 0.3 mm. The film was dried in a vacuum dryer at a temperature of 60 ° C. for 10 hours. Thereafter, the dried film was cut into 3 to 5 mm squares, and approximately 1 g was precisely weighed. The mass of the film piece obtained by cutting is set to w0.
The film pieces were immersed in 50 g of tetrahydrofuran (THF) for 24 hours. Then, the film piece pulled up from THF was vacuum-dried at a temperature of 105 ° C. for 3 hours, and the mass w1 of the insoluble matter was measured.
And gel content (mass%) was computed according to the following formula.
Gel content (mass%) = (w1 / w0) × 100
<Stability of Slurry Composition>
The viscosities of the slurry composition before and after standing were compared, and the stability of the slurry composition was evaluated from the viscosity change rate. Specifically, first, the prepared slurry composition was placed in a container, and the initial viscosity η 0 was measured at a temperature of 25 ° C. and a rotation number of 60 rpm. The viscosity was measured with a B-type viscometer (TVB-10, manufactured by Toki Sangyo Co., Ltd.). Thereafter, the slurry composition in the container was allowed to stand at a temperature of 5 ° C. for 72 hours, and then the temperature was returned to 25 ° C. Then, the viscosity was measured again in the same manner as described above, and after standing, the viscosity η1 was determined. From the measured initial viscosity η 0 and the after-rest viscosity 粘度 1, the viscosity change rate shown by Δη = {(η 1−η 0) / η 0} × 100 (%) was determined and evaluated according to the following criteria. The smaller the value of the viscosity change rate Δη, the better the storage stability of the slurry composition.
A: Δη less than 10% B: Δη 10% or more and less than 30% C: Δη 30% or more <Peel strength>
The produced electrode was cut into a rectangle of width 1.0 cm × length 10 cm as a test piece. Then, the surface of the test piece on the electrode mixture layer side was fixed upward, and a cellophane tape was attached to the surface of the test piece on the electrode mixture layer side. Under the present circumstances, the cellophane tape used what was prescribed | regulated to JISZ1522. Thereafter, the stress when peeling off the cellophane tape from the one end of the test piece at a speed of 50 mm / min in the direction of 180 ° (the other end side of the test piece) was measured. The measurement was performed 10 times, the average value of stress was determined, and this was taken as the peel strength (N / m). The larger the peel strength, the better the binding property of the electrode mixture layer to the current collector.
<Swelling resistance>
Before the assembly of the lithium ion secondary battery, the thickness of 10 points of the negative electrode was measured with a thickness meter, and the average value d0 (μm) was calculated. In addition, the assembled lithium ion secondary battery is allowed to stand for 24 hours in a 25 ° C. environment, then charged to 4.2 V at a constant current of 1 C in a 25 ° C. environment to 3.0 V An operation of charging and discharging was performed. Thereafter, for the lithium ion secondary battery, a charge and discharge operation of charging to 4.2 V and discharging to 3.0 V at a constant current of 1 C in a temperature 60 ° C. environment was repeated 1000 cycles. Thereafter, the lithium ion secondary battery was disassembled, the negative electrode was taken out, and the thickness of 10 points of the taken negative electrode was measured with a thickness meter, and the average value d1 (μm) was calculated. Then, the swelling ratio Δd of the negative electrode = {(d1−d0) / d0} × 100 (%) was calculated. Here, as the swelling ratio Δd is smaller, the negative electrode is more excellent in the swelling resistance, indicating that the life characteristics of the lithium ion secondary battery are better.
<High temperature cycle characteristics>
After allowing the prepared lithium ion secondary battery to stand for 24 hours, a charge / discharge operation of charging to 4.2 V and discharging to 3.0 V at a charge / discharge rate of 0.1 C is performed to obtain an initial capacity C0 It was measured. Furthermore, charge and discharge were repeated in an environment at a temperature of 60 ° C., and a capacity C2 after 100 cycles was measured. Then, a capacity change rate ΔC represented by ΔC = (C 2 / C 0) × 100 (%) was obtained. The higher the value of the rate of change in capacitance ΔC, the better the high-temperature cycle characteristics.
<Rate characteristics>
The prepared lithium ion secondary battery was charged to 4.2 V at 0.1 C, then discharged to 3.0 V at 0.1 C, and the 0.1 C discharge capacity was determined. Thereafter, the battery was charged to 4.2 V at 0.1 C and discharged to 3.0 V at 1 C to determine 1 C discharge capacity. This measurement was performed on 10 cells of the lithium ion secondary battery, and the average value of each measured value was taken as a 0.1 C discharge capacity a and a 1 C discharge capacity b. And the capacity | capacitance retention (= (b / a) x 100 (%)) represented by the ratio of 1 C discharge capacity b with respect to 0.1 C discharge capacity a was calculated | required, and the following references | standards evaluated. The higher the capacity retention, the better the rate characteristics.
SA: Capacity retention is 93% or more A: Capacity retention is 90% or more and less than 93% B: Capacity retention is 80% or more and less than 90% C: Capacity retention is 50% or more and less than 80% D: Capacity retention Less than 50%

Example 1
Preparation of Seed Particle A
In a reactor equipped with a stirrer, 60.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 38.0 parts of styrene as an aromatic vinyl monomer, and a single amount of ethylenically unsaturated carboxylic acid 2.0 parts of methacrylic acid as a body, 4.0 parts of sodium dodecylbenzene sulfonate as an emulsifier, 260 parts of ion exchanged water, and 0.3 parts of potassium persulfate as a polymerization initiator are added at a temperature of 60 ° C. It was polymerized for time.
Thus, an aqueous dispersion of seed particles A made of a polymer having a number average particle diameter of 58 nm was obtained.
<Preparation of Seed Particles B>
In a reactor equipped with a stirrer, 2.5 parts of the aqueous dispersion of seed particles A based on solid content (that is, mass of seed particles A) and 0.2 parts of sodium dodecylbenzene sulfonate as an emulsifier, 0.5 parts of potassium persulfate as a polymerization initiator and 100 parts of ion exchanged water were mixed to obtain a mixture A. Then, the mixture A was heated to a temperature of 80.degree. On the other hand, in another container, 31.9 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 44.8 parts of styrene as an aromatic vinyl monomer, (meth) acrylic acid ester monomer 19.7 parts of methyl methacrylate as, 2.8 parts of itaconic acid as an ethylenically unsaturated carboxylic acid monomer, 0.8 parts of acrylamide as a monomer forming any repeating unit, dodecyl as an emulsifier A dispersion of monomer mixture A was prepared by mixing 0.5 parts of sodium benzenesulfonate and 100 parts of ion-exchanged water. A dispersion of this monomer mixture A was continuously added to the above mixture A for 4 hours to polymerize. The temperature of the reaction system during the continuous addition of the dispersion of monomer mixture A was maintained at 80 ° C. to carry out the reaction. After completion of the continuous addition, the reaction was further continued at a temperature of 90 ° C. for 3 hours.
Thus, an aqueous dispersion of seed particles B composed of a polymer having a number average particle diameter of 175 nm was obtained.
<Preparation of Particulate Binding Material A>
In a reactor equipped with a stirrer, 25.0 parts of the aqueous dispersion of seed particles B based on solid content (that is, mass of seed particles B), 0.2 parts of sodium dodecylbenzene sulfonate as an emulsifier, A mixture B was obtained by adding 0.5 parts of potassium persulfate as a polymerization initiator and 100 parts of ion-exchanged water. Then, the mixture B was heated to a temperature of 80.degree. On the other hand, in another container, 33.2 parts of 1,3-butadiene as an aliphatic conjugated diene-based monomer, 60.6 parts of styrene as an aromatic vinyl monomer, (meth) acrylic acid ester amount 5.0 parts of methyl methacrylate (methyl methacrylate) as a body, 0.2 parts of acrylic acid as an ethylenically unsaturated carboxylic acid monomer, 0.5 parts of sodium dodecylbenzene sulfonate as an emulsifier, as a chain transfer agent A dispersion of monomer mixture B was prepared by mixing 0.15 parts of t-dodecyl mercaptan of the above and 100 parts of ion-exchanged water. The dispersion of this monomer mixture B was continuously added into the above mixture B for 4 hours to polymerize. The temperature of the reaction system during the continuous addition of the dispersion of monomer mixture B was maintained at 70 ° C. to carry out the reaction. After completion of the continuous addition, 1 part of 2-hydroxyethyl acrylate as a hydroxyl group-containing unsaturated monomer was further added. The reaction was stopped by cooling when the polymerization conversion reached 96%.
Thus, an aqueous dispersion of a particulate binder A made of a polymer having a number average particle diameter of 300 nm was obtained.
Preparation of Slurry Composition for Lithium Ion Secondary Battery Anode
As a negative electrode active material, artificial graphite (number average particle diameter: 24.5 μm, graphite interlayer distance (d-spacing (d value) of (002) plane by X-ray diffraction method): 0.354 nm) was prepared.
Further, carboxymethyl cellulose (abbreviated as "CMC", "Daicel 2200" manufactured by Daicel Chemical Industries, Ltd.) was prepared as a viscosity modifier. The degree of polymerization of CMC was 1700, and the degree of etherification was 0.65.
Then, for a planetary mixer with a disper, 100 parts of artificial graphite, 1 part of a 1% aqueous solution of carboxymethylcellulose in terms of solid content, and 1 part of an aqueous dispersion of particulate binder A in terms of solid content The solid content concentration was adjusted to 55% with ion-exchanged water, and the mixture was stirred for 60 minutes at a temperature of 25.degree. Next, the solid content concentration was adjusted to 52% with ion-exchanged water, and the mixture was further stirred at a temperature of 25 ° C. for 15 minutes to obtain a slurry composition for a lithium ion secondary battery negative electrode. And the stability of the slurry composition was evaluated. The results are shown in Table 1.
<Production of Negative Electrode for Lithium Ion Secondary Battery>
The slurry composition for a lithium ion secondary battery negative electrode was applied by a comma coater to the surface of a copper foil having a thickness of 20 μm, which is a current collector, so that the film thickness after drying was about 150 μm. The copper foil coated with the slurry composition for lithium ion secondary battery negative electrode is applied at a speed of 0.5 m / min for 2 minutes in an oven at a temperature of 60 ° C. and for 2 minutes in an oven at a temperature of 120 ° C. By conveying, the slurry composition on the copper foil was dried to obtain a negative electrode original fabric.
And the obtained negative electrode original fabric was pressed with the roll press machine, and the thickness of the negative electrode compound material layer obtained the negative electrode for lithium ion secondary batteries whose thickness is 75 micrometers. The density of the negative electrode mixture layer of the obtained negative electrode was 1.6 g / cm ³ , and the basis weight was 12.0 mg / cm ² . And the peel strength and swelling resistance of the negative electrode were evaluated. The results are shown in Table 1.
<Manufacture of positive electrode for lithium ion secondary battery>
In a planetary mixer, 95 parts of LiCoO ₂ as a positive electrode active material, 2 parts of acetylene black as a conductive material, 3 parts of PVDF (polyvinylidene fluoride) as a binder, and 20 parts of 2-methylpyrilodon as a solvent In addition, they were mixed to prepare a slurry composition for a lithium ion secondary battery positive electrode.
The obtained slurry composition for a lithium ion secondary battery positive electrode was applied by a comma coater on a 20 μm thick aluminum foil as a current collector such that the film thickness after drying was about 200 μm. Thereafter, the aluminum foil to which the slurry composition for lithium ion secondary battery positive electrode was applied was dried by transporting it in an oven at a temperature of 60 ° C. for 2 minutes at a speed of 0.5 m / min. Then, it heat-processed at the temperature of 120 degreeC for 2 minutes, and obtained the positive electrode original fabric.
The obtained positive electrode material sheet was pressed by a roll press to obtain a positive electrode for a lithium ion secondary battery.
<Manufacturing of lithium ion secondary battery>
A single layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm; manufactured by a dry method; porosity 55%) was prepared and cut into a square of 5 cm × 5 cm. In addition, an aluminum packaging material was prepared as an exterior of the battery.
And the produced positive electrode was cut out to a square of 4 cm x 4 cm, and it arrange | positioned so that the surface by the side of a current collector might contact aluminum packaging material exterior. Next, the above-mentioned square separator was disposed on the surface of the positive electrode mixture layer of the positive electrode. Furthermore, the prepared negative electrode was cut into a square of 4.2 cm × 4.2 cm, and this was placed on the separator so that the surface on the negative electrode mixture layer side faced the separator. After that, a LiPF ₆ solution with a concentration of 1.0 M as an electrolytic solution (the solvent is a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3/7 (volume ratio), and 2 mass% of vinylene carbonate is contained as an additive) Was filled. Furthermore, heat sealing was performed at 150 ° C., and the opening of the aluminum packaging material was sealed and closed to manufacture a lithium ion secondary battery. Then, rate characteristics and cycle characteristics of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Example 2)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder B was used instead of the particulate binder A. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material B>
The amount of the aqueous dispersion of the seed particles B was 12.0 parts on a solids basis, the amount of styrene as the aromatic vinyl monomer was 60.7 parts, and the acrylic as the ethylenically unsaturated carboxylic acid monomer A particulate binder B was prepared in the same manner as the particulate binder A except that the amount of acid was 0.1 parts and the amount of t-dodecyl mercaptan as a chain transfer agent was 0.16 parts.

(Example 3)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder A was changed to the particulate binder C prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material C>
The amount of the aqueous dispersion of seed particles B is 12.0 parts on a solids basis, the amount of styrene as an aromatic vinyl monomer is 60.8 parts, and an ethylenically unsaturated carboxylic acid monomer is used Then, a particulate binder C was prepared in the same manner as the particulate binder A except that the amount of t-dodecyl mercaptan as a chain transfer agent was changed to 0.16 parts.

(Example 4)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder A was changed to the particulate binder D prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material D>
The amount of the aqueous dispersion of seed particles B is 50.0 parts on a solids basis, the amount of styrene as an aromatic vinyl monomer is 62.0 parts, and acrylic acid as an ethylenically unsaturated carboxylic acid monomer In place of 3.8 parts of itaconic acid, no (meth) acrylic acid ester monomer, and 0.14 parts of t-dodecyl mercaptan as a chain transfer agent. A particulate binder D was prepared in the same manner as the adhesive A.

(Example 5)
In place of the particulate binder A, the particulate binder E prepared by the following method is used, and the artificial graphite used in Example 1 is crushed as a negative electrode active material (pulverizer: Crypt made by Earth Technica Corp. Slurry composition for lithium ion secondary battery negative electrode in the same manner as in Example 1 except that the negative electrode active material obtained by using a Ron KTM type 0, rotational speed: 2000 rpm, grinding speed: 20 kg / hr), lithium ion A negative electrode for secondary battery, a positive electrode for lithium ion secondary battery and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material E>
A particulate binder E was prepared in the same manner as the particulate binder A except that the amount of the aqueous dispersion of the seed particles B was 30.0 parts on a solids basis.

(Example 6)
Slurry composition for lithium ion secondary battery negative electrode in the same manner as in Example 5 except that the negative electrode active material obtained by firing and CVD the artificial graphite used in Example 1 was used as the negative electrode active material, lithium A negative electrode for an ion secondary battery, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. In addition, baking was performed at a temperature of 900 ° C. for 1 hour while maintaining a fluidized state while supplying a nitrogen gas at a rate of 1 L / minute into the fluidized reactor under a nitrogen atmosphere using a fluidized reactor. In the CVD process after firing, nitrogen gas containing benzene (benzene concentration: 1 g / L) is introduced at a rate of 1 L / min into a fluidizing reactor, and the fired particles are allowed to flow at a temperature of 900 ° C. I did it for a minute. The results are shown in Table 1.

(Example 7)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder A was changed to the particulate binder F prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material F>
The amount of the aqueous dispersion of the seed particles B is 30.0 parts on a solids basis, the amount of styrene as the aromatic vinyl monomer is 60.4 parts, and the acrylic as the ethylenically unsaturated carboxylic acid monomer A particulate binder F was prepared in the same manner as the particulate binder A except that the amount of acid was 0.4 parts and the amount of t-dodecyl mercaptan as a chain transfer agent was 0.14 parts.

(Example 8)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder A was changed to the particulate binder G prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material G>
The amount of the aqueous dispersion of the seed particles B is 30.0 parts on a solids basis, the amount of styrene as the aromatic vinyl monomer is 59.8 parts, and the acrylic as the ethylenically unsaturated carboxylic acid monomer A particulate binder G was prepared in the same manner as the particulate binder A except that the amount of acid was 1.0 part and the amount of t-dodecyl mercaptan as a chain transfer agent was 0.14 part.

(Example 9)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder A was changed to the particulate binder H prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material H>
The amount of styrene as an aromatic vinyl monomer is 60.4 parts, the amount of acrylic acid as an ethylenically unsaturated carboxylic acid monomer is 0.4 parts, and t-dodecyl mercaptan as a chain transfer agent A particulate binder H was prepared in the same manner as the particulate binder A except that the amount was changed to 1.5 parts.

(Example 10)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1 except that the particulate binder A was replaced with a particulate binder I prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material I>
The amount of styrene as an aromatic vinyl monomer is 60.4 parts, the amount of acrylic acid as an ethylenically unsaturated carboxylic acid monomer is 0.4 parts, and t-dodecyl mercaptan as a chain transfer agent A particulate binder I was prepared in the same manner as the particulate binder A except that the amount was changed to 0.10 parts.

(Example 11)
The amount of the slurry composition for lithium ion secondary battery negative electrode applied to the surface of copper foil when manufacturing the negative electrode for lithium ion secondary battery is changed, the thickness of the negative electrode mixture layer is 94 μm, and the density is 1.7 g / cm ^3, except that the basis weight and 16.0 mg / cm ² in the same manner as in example 1, a lithium ion secondary battery negative electrode slurry composition, a negative electrode for a lithium ion secondary battery, a positive electrode for a lithium ion secondary battery And lithium ion secondary batteries were prepared and evaluated. The results are shown in Table 1.

(Comparative example 1)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder A was replaced with a particulate binder J prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material J>
The amount of the aqueous dispersion of the seed particles B is 8.0 parts on a solids basis, the amount of styrene as the aromatic vinyl monomer is 60.0 parts, and the acrylic as the ethylenically unsaturated carboxylic acid monomer A particulate binder J was prepared in the same manner as the particulate binder A except that the amount of acid was 0.8 parts and the amount of t-dodecyl mercaptan as a chain transfer agent was 0.45 parts.

(Comparative example 2)
A slurry composition for a lithium ion secondary battery negative electrode, a lithium ion secondary battery, in the same manner as in Example 1, except that the particulate binder A was changed to the particulate binder K prepared by the following method. A negative electrode, a positive electrode for lithium ion secondary battery, and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material K>
Instead of using seed particles B, the amount of styrene as an aromatic vinyl monomer is 62.0 parts, and 3.8 parts of itaconic acid is used in place of acrylic acid as an ethylenically unsaturated carboxylic acid monomer. And a particulate binder in the same manner as the particulate binder A except that the (meth) acrylate monomer is not used and the amount of t-dodecyl mercaptan as a chain transfer agent is 0.40 parts. K was prepared.

(Comparative example 3)
In place of the particulate binder A, the particulate binder L prepared by the following method is used, and the artificial graphite used in Example 1 is crushed as a negative electrode active material (pulverizer: Crypt made by Earth Technica Corp. Slurry composition for lithium ion secondary battery negative electrode in the same manner as in Example 1 except that the negative electrode active material obtained by using a Ron KTM type 0, rotational speed: 6000 rpm, crushing speed: 20 kg / hr), lithium ion A negative electrode for secondary battery, a positive electrode for lithium ion secondary battery and a lithium ion secondary battery were produced and evaluated. The results are shown in Table 1.
<Preparation of Particulate Binding Material L>
The amount of the aqueous dispersion of the seed particles B is 30.0 parts on a solids basis, the amount of styrene as the aromatic vinyl monomer is 60.0 parts, and the acrylic as the ethylenically unsaturated carboxylic acid monomer A particulate binder L was prepared in the same manner as the particulate binder A except that the amount of acid was 0.8 parts and the amount of t-dodecyl mercaptan as a chain transfer agent was 0.90 parts.

(Comparative example 4)
A negative electrode obtained by firing and CVD treating the artificial graphite used in Example 1 as a negative electrode active material, using a particulate binder M prepared by the following method instead of the particulate binder A A slurry composition for lithium ion secondary battery negative electrode, a negative electrode for lithium ion secondary battery, a positive electrode for lithium ion secondary battery and a lithium ion secondary battery were prepared in the same manner as in Example 1 except that the active material was used. , Made an evaluation. In addition, baking was performed at a temperature of 900 ° C. for 1 hour while maintaining a fluidized state while supplying a nitrogen gas at a rate of 1 L / minute into the fluidized reactor under a nitrogen atmosphere using a fluidized reactor. In the CVD process after firing, nitrogen gas containing benzene (benzene concentration: 1 g / L) is introduced at a rate of 1 L / minute into a fluidized reactor, and the fired particles are flowed at a temperature of 900 ° C. 2 It took time. The results are shown in Table 1.
<Preparation of Particulate Binding Material M>
The amount of the aqueous dispersion of the seed particles B is 30.0 parts on a solids basis, the amount of styrene as the aromatic vinyl monomer is 55.8 parts, and the acrylic as the ethylenically unsaturated carboxylic acid monomer A particulate binder A except that the amount of acid is 10.0 parts, the (meth) acrylic acid ester monomer is not used, and the amount of t-dodecyl mercaptan as a chain transfer agent is 0.30 parts. A particulate binder M was prepared in the same manner as in the above.

(Comparative example 5)
The amount of the slurry composition for lithium ion secondary battery negative electrode applied to the surface of copper foil when manufacturing the negative electrode for lithium ion secondary battery is changed, the thickness of the negative electrode mixture layer is 94 μm, and the density is 1.7 g / Slurry composition for lithium ion secondary battery negative electrode, negative electrode for lithium ion secondary battery, positive electrode for lithium ion secondary battery in the same manner as in Comparative Example 2 except that the cm ³ and the basis weight were 16.0 mg / cm ^2. And lithium ion secondary batteries were prepared and evaluated. The results are shown in Table 1.

From Table 1, in Examples 1 to 11, it can be seen that a lithium ion secondary battery excellent in the peel strength of the negative electrode and the cycle characteristics and rate characteristics of the lithium ion secondary battery can be obtained. On the other hand, it is understood from Table 1 that in Comparative Examples 1 to 3 and 5, the peel strength is lowered. Further, it is understood that in the comparative examples 2 to 5, the rate characteristic is degraded.
From Examples 1 to 4 and 7 to 8, when the surface acid amount of the particulate binder is too small, the stability of the slurry composition decreases, and conversely, the peel strength decreases when the surface acid amount is too large. I understand that. Also, from Examples 1 and 5 to 6, it can be seen that the pore volume size affects the peel strength and rate characteristics. In Examples 5 and 6, since the number average particle diameter of the particulate binder was small and the amount of surface acid per unit surface area of the particulate binder was decreased, it is presumed that the stability of the slurry composition was lowered. Be done. Furthermore, it is seen from Examples 1 and 9 to 10 that the gel content of the particulate binder affects the peel strength, the swelling resistance and the cycle characteristics. Further, from Examples 1 and 11, it can be seen that the density and weight per unit area of the negative electrode mixture layer affect the peel strength.

According to the present invention, the binding properties of the components constituting the electrode mixture layer, the binding properties between the electrode mixture layer and the current collector, and the cycle characteristics and rate characteristics of the lithium ion secondary battery are excellent. The slurry composition for lithium ion secondary battery electrodes which can be used is obtained.
Further, according to the present invention, the cycleability is excellent for the lithium ion secondary battery, because it is excellent in the binding property between the components constituting the electrode mixture layer and the binding property between the electrode mixture layer and the current collector. And an electrode for a lithium ion secondary battery capable of exhibiting rate characteristics.
Furthermore, according to the present invention, a lithium ion secondary battery excellent in cycle characteristics and rate characteristics can be obtained.

Claims (5)

An electrode active material having a mercury intrusion pore volume of 0.1 cm ³ / g or more and 2.0 cm ³ / g or less,
A particulate binder having a number average particle diameter of 200 nm or more and 600 nm or less;
water and,
Only including,
The ratio of the number average particle diameter of the particulate binder to the mercury intrusion pore volume of the electrode active material (number average particle diameter / mercury intrusion pore volume) is 1.5 × 10 ⁻⁵ g / cm ² or more The slurry composition for lithium ion secondary battery electrodes which is 6.4 * 10 < ^-5 > g / cm < ² > or less .   The slurry composition for lithium ion secondary battery electrodes according to claim 1, wherein the surface acid amount of the particulate binder is 0.01 mmol / g or more and 0.5 mmol / g or less.   The slurry composition for lithium ion secondary battery electrodes of Claim 1 or 2 whose gel content of the said particulate-form binder is 30 to 99 mass%.   The electrode for lithium ion secondary batteries which has an electrode mixture layer obtained using the slurry composition for lithium ion secondary battery electrodes in any one of Claims 1-3. A positive electrode, a negative electrode, a separator and an electrolyte,
The lithium ion secondary battery whose at least 1 side of the said positive electrode and the said negative electrode is an electrode for lithium ion secondary batteries of Claim 4.

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