JP7130037B2 - Lithium ion battery electrode, lithium ion battery electrode slurry, method for producing lithium ion battery electrode, and lithium ion battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lithium ion battery electrode, a lithium ion battery electrode slurry, a method for producing a lithium ion battery electrode, and a lithium ion battery.

Electrodes used in lithium ion batteries are generally mainly composed of an electrode active material layer and a current collector layer. The electrode active material layer can be obtained, for example, by applying an electrode slurry containing an electrode active material, a binder resin, a thickening agent and the like to the surface of a current collector layer such as a metal foil and drying it.

Techniques related to such electrodes for lithium ion batteries include those described in Patent Documents 1 and 2, for example.

Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-114747) discloses that a negative electrode plate formed by forming a negative electrode active material layer by coating a negative electrode mixture paste on at least one surface of a metal foil and drying the lithium In the method for producing an ion secondary battery, as the negative electrode mixture paste, a first kneading of kneading a powdery negative electrode active material and a first thickening agent with a solvent, and a first kneading after the first kneading Manufactured by second kneading in which a second thickener and a solvent are added to the kneaded material and kneaded, and third kneading in which a binder is added to the kneaded material after the second kneading and kneaded. wherein the first thickening agent is carboxymethyl cellulose having a molecular weight of 330,000 or less, and the second thickening agent is carboxymethyl cellulose having a molecular weight of 330,000 or more. A method for manufacturing a secondary battery is described.

In Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-203561), an electrode active material mixture paste obtained by kneading electrode active material particles together with a kneading solvent is applied to an electrode core material and dried to form a paste on the electrode core material. In the method for manufacturing an electrode plate of a non-aqueous electrolyte secondary battery for forming an electrode active material layer, the electrode active material mixture paste is composed of electrode active material particles and carboxymethyl cellulose, and has a weight average amount Mw of 3.5 million. In the following, those having a polydispersity (weight average content Mw/number average content Mn) of 6 or more and a water solvent are kneaded to obtain (viscosity A at a shear rate of 2 sec ^-1 / viscosity A at a shear rate of 40 sec ^-1 The viscosity B) is 3.8 or more and the viscosity B is in the range of 500 to 1500 mPa·sec, and the electrode active material mixture paste is used so that the opening is 4 to the D50 value of the electrode active material particles. A method for producing an electrode plate of a non-aqueous electrolyte secondary battery is described, wherein the electrode core material is coated through a filter having a D50 value of the electrode active material particles or more within the range of 5 times. ing.

JP 2013-114747 A JP 2014-203561 A

According to studies by the present inventors, lithium-ion battery electrodes obtained by conventional manufacturing methods may have low peel strength, and there is room for improvement in the adhesiveness between the current collector layer and the electrode active material layer. It became clear.
If the peel strength of the lithium-ion battery electrode is low, the productivity of the electrode and the battery will decrease, and the electrode active material layer will fall off during the battery assembly process, resulting in deterioration of battery quality and battery cycle characteristics. There is concern that problems such as

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an electrode for a lithium ion battery having excellent adhesiveness between a current collector layer and an electrode active material layer.

The inventors of the present invention have made intensive studies in order to achieve the above problems. As a result, the mixture containing the thickener is kneaded under conditions such that decomposition of the thickener is suppressed, that is, under conditions such that the weight average molecular weight of the thickener contained in the electrode slurry is within a specific range, and the electrode slurry is obtained. By preparing the obtained electrode slurry and the weight average molecular weight of the thickener in the electrode can be maintained at a high value, as a result, excellent adhesion between the current collector layer and the electrode active material layer The inventors have completed the present invention by discovering that an electrode for a lithium ion battery can be obtained.

According to the invention,
a current collector layer;
an electrode active material layer provided on at least one surface of the current collector layer and containing an electrode active material, a binder resin and a thickening agent;
An electrode for a lithium ion battery comprising
The weight average molecular weight (Mw) of the thickening agent extracted from the electrode active material layer, which is calculated in terms of pullulan using a gel permeation chromatography (GPC) method, is 2000000 or more ,
The ratio (Mw/Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the thickening agent extracted from the electrode active material layer, calculated in terms of pullulan using the GPC method, is 6. is less than .0,
Provided is a lithium ion battery electrode, wherein the thickener contains a cellulose-based water-soluble polymer, and the cellulose-based water-soluble polymer has a degree of etherification of 0.50 or more and 1.0 or less .

Furthermore, according to the present invention,
An electrode slurry for a lithium ion battery containing an electrode active material, a binder resin, a thickener and an aqueous medium,
The weight average molecular weight (Mw) of the thickener extracted from the lithium ion battery electrode slurry, which is calculated in terms of pullulan using a gel permeation chromatography (GPC) method, is 2000000 or more,
Ratio (Mw/Mn) of the weight average molecular weight (Mw) of the thickener extracted from the lithium ion battery electrode slurry and the number average molecular weight (Mn), which is calculated in terms of pullulan using the GPC method. is less than 6.0,
There is provided an electrode slurry for a lithium ion battery, wherein the thickener contains a cellulose-based water-soluble polymer, and the cellulose-based water-soluble polymer has a degree of etherification of 0.50 or more and 1.0 or less.

Furthermore, according to the present invention,
a current collector layer;
and an electrode active material layer provided on at least one surface of the current collector layer and composed of the solid content of the lithium ion battery electrode slurry.

Furthermore, according to the present invention,
A manufacturing method for manufacturing the lithium ion battery electrode,
Including the step of preparing the electrode slurry for the lithium ion battery,
The step of preparing the lithium ion battery electrode slurry includes:
The weight average molecular weight (Mw) of the thickener is 2,000,000 or more, calculated in terms of pullulan using the GPC method, and the weight average of the thickening agent, calculated in terms of pullulan using the GPC method. A step of kneading a mixture containing an electrode active material, a binder resin and a thickening agent under conditions such that the ratio (Mw/Mn) of the molecular weight (Mw) to the number average molecular weight (Mn) is less than 6.0. A method is provided for making an electrode for a lithium ion battery comprising:

Moreover, according to the present invention,
Provided is a lithium ion battery comprising the lithium ion battery electrode described above.

ADVANTAGE OF THE INVENTION According to this invention, the electrode for lithium ion batteries which was excellent in the adhesiveness of a collector layer and an electrode active material layer can be provided.

The above objectives, as well as other objectives, features and advantages, will become further apparent from the preferred embodiments described below and the accompanying drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows an example of the structure of the electrode for lithium ion batteries of embodiment which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows an example of the structure of the lithium ion battery of embodiment which concerns on this invention.

An embodiment of the present invention will be described below with reference to the drawings. In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. In addition, each component in the drawings schematically shows the shape, size, and arrangement relationship to the extent that the present invention can be understood, and is different from the actual size.
In this embodiment, unless otherwise specified, a layer containing an electrode active material is called an electrode active material layer, and a current collector layer on which the electrode active material layer is formed is called an electrode. Further, in the present embodiment, the numerical range "A to B" represents from A to B, unless otherwise specified.

<Lithium ion battery electrode and lithium ion battery electrode slurry>
First, a lithium ion battery electrode and a lithium ion battery electrode slurry according to the present embodiment will be described. FIG. 1 is a cross-sectional view showing an example of the structure of a lithium-ion battery electrode 100 according to an embodiment of the invention.
The lithium ion battery electrode 100 according to the present embodiment includes a current collector layer 101 and an electrode active material provided on at least one surface of the current collector layer 101 and containing an electrode active material, a binder resin, and a thickener. and a material layer 103, wherein the weight average molecular weight (Mw) of the thickener extracted from the electrode active material layer 103 is 2000000 or more, calculated in terms of pullulan using a gel permeation chromatography (GPC) method. is.
Further, the lithium ion battery electrode slurry according to the present embodiment contains an electrode active material, a binder resin, a thickener and an aqueous medium, and is calculated in terms of pullulan using a gel permeation chromatography (GPC) method. The thickener extracted from the lithium ion battery electrode slurry has a weight average molecular weight (Mw) of 2,000,000 or more.
In addition, the lithium ion battery electrode 100 according to the present embodiment is provided on at least one surface of the current collector layer 101 and the current collector layer 101, and the lithium ion battery electrode slurry according to the present embodiment and the weight of the thickener extracted from the electrode active material layer 103, which is calculated in terms of pullulan using a gel permeation chromatography (GPC) method. The average molecular weight (Mw) may be 2,000,000 or more.
Here, in the electrode slurry according to the present embodiment, the thickener is dissolved in the electrode slurry and is not in a powder state.
Also, the lithium ion battery according to the present embodiment is a lithium ion primary battery or a lithium ion secondary battery, preferably a lithium ion secondary battery.

Here, the weight average molecular weight (Mw) of the thickener extracted from the lithium ion battery electrode slurry according to the present embodiment can be measured, for example, by the following procedure.
(1) About 12.5 g of the electrode slurry is weighed into a volumetric flask, and distilled water is added to make 50 mL.
(2) After lightly shaking to make a uniform solution (for example, visually confirmed), an ultracentrifuge (manufactured by Hitachi Koki Co., Ltd., product name: Hitachi separation ultracentrifuge, model: CP80WX, rotor: angle rotor P70AT) is used to perform ultracentrifugation (30000 rpm (66000 G) x 30 minutes).
(3) The supernatant after the separation obtained in (2) is collected and ultracentrifuged again (30000 rpm (66000 G)×30 minutes). Furthermore, the supernatant is recovered and ultracentrifuged again (30000 rpm (66000 G)×30 minutes). These ultracentrifugation operations remove electrode active materials, binder resins, conductive aids, and the like in the slurry.
(4) The supernatant obtained in (3) is filtered through a 0.45 μm filter, and the obtained filtrate is further filtered through a 0.20 μm filter. This removes the electrode active material, the binder resin, the conductive aid, etc. remaining in the supernatant liquid obtained in (3). The resulting filtrate was diluted 5-fold with a measurement solvent (0.1 M sodium chloride aqueous solution), and the molecular weight distribution of the thickener was measured under the following measurement conditions. calculate. Here, the pullulan-equivalent weight average molecular weight is a value calculated using a calibration curve prepared using monodisperse pullulan as a standard substance.
(Measurement condition)
Apparatus: Gel permeation chromatograph GPC (manufactured by Tosoh Corporation, pump model: DP-8020)
Detector: Differential refractive index detector RI (manufactured by Tosoh Corporation, RI-8020 type, sensitivity 16)
Column: TSKgel guard column PW _XL (1 piece), TSKgel PW _XL (2 pieces) (φ6 mm × 4 cm, φ7.8 mm × 30 cm, manufactured by Tosoh Corporation)
Solvent: 0.1 M aqueous sodium chloride solution Flow rate: 0.5 mL/min
Column temperature: 45°C
Injection volume: 0.2 mL
Reference material: Monodisperse pullulan (manufactured by Showa Denko)

Also, the weight average molecular weight (Mw) of the thickener extracted from the electrode active material layer 103 can be measured, for example, by the following procedure.
(1) About 1.0 g of an electrode active material layer is scraped off from a lithium ion battery electrode into a container, and distilled water is added and stirred to form a slurry.
(2) About 12.5 g of the obtained electrode slurry is weighed into a volumetric flask, and distilled water is added to make 50 mL.
(3) After lightly shaking to make a uniform solution (for example, visually confirmed), an ultracentrifuge (manufactured by Hitachi Koki Co., Ltd., product name: Hitachi separation ultracentrifuge, model: CP80WX, rotor: angle rotor P70AT) is used to perform ultracentrifugation (30000 rpm (66000 G) x 30 minutes).
(4) The supernatant after the separation obtained in (3) is collected and ultracentrifuged again (30000 rpm (66000 G)×30 minutes). Furthermore, the supernatant is recovered and ultracentrifuged again (30000 rpm (66000 G)×30 minutes). These ultracentrifugation operations remove electrode active materials, binder resins, conductive aids, and the like in the slurry.
(5) The supernatant obtained in (4) is filtered through a 0.45 μm filter, and the obtained filtrate is further filtered through a 0.20 μm filter. This removes the electrode active material, the binder resin, the conductive aid, etc. remaining in the supernatant liquid obtained in (4). The resulting filtrate was diluted 5-fold with a measurement solvent (0.1 M sodium chloride aqueous solution), and the molecular weight distribution of the thickener was measured under the following measurement conditions. calculate. Here, the pullulan-equivalent weight average molecular weight is a value calculated using a calibration curve prepared using monodisperse pullulan as a standard substance.

As described above, according to the study of the present inventors, the peel strength of the lithium ion battery electrode obtained by the conventional manufacturing method may be low, and the adhesion between the current collector layer and the electrode active material layer may be affected. It became clear that there was room for improvement.
If the peel strength of the lithium-ion battery electrode is low, the productivity of the electrode and the battery will decrease, and the electrode active material layer will fall off during the battery assembly process, resulting in deterioration of battery quality and battery cycle characteristics. There is concern that problems such as
The inventors of the present invention have made intensive studies in order to achieve the above problems. As a result, in lithium-ion battery electrodes with low peel strength, the weight average molecular weight of the thickener contained in the electrode is larger than the weight average molecular weight of the raw material thickener used as a raw material before being added to the slurry. found that it was declining. That is, in the step of producing a lithium ion battery electrode, more specifically in the step of preparing a lithium ion battery electrode slurry, when the molecular chains of the thickener are decomposed and the weight average molecular weight is greatly reduced, It has been found that the adhesion between the conductor layer and the electrode active material layer is lowered, and a lithium ion battery electrode having a low peel strength can be obtained.
The inventors of the present invention further conducted extensive studies based on the above findings. As a result, the mixture containing the thickening agent is kneaded under conditions such that the decomposition of the thickening agent is suppressed, that is, under conditions such that the weight average molecular weight of the thickening agent contained in the lithium ion battery electrode slurry is equal to or higher than the above lower limit. By preparing the electrode slurry, the weight average molecular weight of the thickener in the resulting electrode slurry and lithium ion battery electrode can be maintained at a high value. It was found that a lithium ion battery electrode having excellent adhesion to the layer can be obtained.
That is, according to the present embodiment, the weight-average molecular weight of the thickener extracted from the electrode active material layer or the electrode slurry for a lithium ion battery is equal to or higher than the above lower limit, so that the current collector layer and the electrode active material layer It is possible to obtain an electrode for a lithium ion battery that has excellent adhesiveness to.

Here, by setting the weight-average molecular weight of the thickener extracted from the electrode active material layer or the lithium ion battery electrode slurry to the above lower limit or more, the adhesion between the current collector layer and the electrode active material layer is excellent. Although the reason why such a lithium ion battery electrode can be obtained is not necessarily clear, the following reasons are conceivable.
First, the higher the weight-average molecular weight of the thickener in the lithium ion battery electrode slurry, the higher the elasticity than the viscosity. considered to be developed. When the three-dimensional network in the lithium ion battery electrode slurry develops, the movement of the binder resin to the electrode active material layer surface is suppressed when drying the lithium ion battery electrode slurry applied to the current collector layer. As a result, it is thought that uneven distribution of the binder resin on the surface of the electrode active material layer can be suppressed.
As a result of suppressing uneven distribution of the binder resin on the surface of the electrode active material layer, the amount of the binder resin at the interface between the current collector layer and the electrode active material layer can be increased. It is believed that the adhesion to the layer can be improved.
That is, according to the present embodiment, the weight-average molecular weight of the thickener extracted from the electrode active material layer or the electrode slurry for a lithium ion battery is equal to or higher than the above lower limit, so that the current collector layer and the electrode active material layer It is possible to obtain an electrode for a lithium ion battery having excellent adhesion to.
That is, according to the present embodiment, the weight-average molecular weight of the thickener extracted from the electrode active material layer or the lithium-ion battery electrode slurry is set to the lower limit value or more, so that the binder resin adheres to the surface of the electrode active material layer. can be suppressed, and the adhesion between the current collector layer and the electrode active material layer can be improved.
As described above, according to the present embodiment, it is possible to provide a lithium ion battery electrode having excellent adhesiveness between the current collector layer and the electrode active material layer.

In addition, the lower limit of the weight average molecular weight (Mw) of the thickener extracted from the electrode active material layer or electrode slurry, which is calculated in terms of pullulan using the GPC method, is 2,000,000 or more. It is preferably 2,100,000 or more, more preferably 2,200,000 or more, from the viewpoint of further improving the adhesiveness to the active material layer.
The upper limit of the weight-average molecular weight (Mw) of the thickener extracted from the electrode active material layer or electrode slurry, which is calculated in terms of pullulan using the GPC method, is not particularly limited, but is preferably 5,000,000 or less. , 4,000,000 or less, more preferably 3,000,000 or less, and particularly preferably 2,800,000 or less. When the weight average molecular weight is equal to or less than the above upper limit, the solubility of the thickener in the aqueous medium is improved, and the solid content concentration of the electrode slurry can be increased. Elastic modulus can be effectively increased. As a result, the uneven distribution of the binder resin on the surface of the electrode active material layer can be further suppressed, so that the adhesiveness between the current collector layer and the electrode active material layer can be further improved.

In the lithium ion battery electrode according to the present embodiment, the weight average molecular weight (Mw) and the number average molecular weight of the thickener extracted from the electrode active material layer or electrode slurry, which are calculated in terms of pullulan using the GPC method, The ratio (Mw/Mn) to (Mn) is preferably less than 6.0 and 5.9 or less from the viewpoint of further improving the adhesion between the current collector layer and the electrode active material layer. is more preferably 5.8 or less, and from the viewpoint of improving the stability of the electrode slurry, it is preferably 2.0 or more, more preferably 3.0 or more, and even more preferably 4.0 or more.

The weight-average molecular weight (Mw) and Mw/Mn of the thickener extracted from the electrode active material layer and the electrode slurry according to the present embodiment are determined by the weight-average molecular weight of the raw material thickener and the manufacturing conditions such as the preparation method of the electrode slurry. can be realized by highly controlling the More specifically, as a raw material thickener, a weight average molecular weight (Mw) of 2,500,000 or more, preferably 3,000,000 or more ultra-high molecular weight thickener is used, and the decomposition of the thickener is suppressed. It is particularly important to knead the mixture containing the electrode active material, the binder resin and the thickener under such conditions, that is, under mild conditions such that the weight average molecular weight (Mw) of the thickener can be maintained at the above lower limit or more. be.

In the electrode slurry according to the present embodiment, from the viewpoint of improving the coatability of the electrode slurry and the dispersion stability of each material constituting the electrode slurry, using a Brookfield viscometer, 25 ° C., shear rate 3 Viscosity measured under the condition of .4s ^-1 is preferably 1000 mPa s or more and 20000 mPa s or less, more preferably 2000 mPa s or more and 15000 mPa s or less, still more preferably 4000 mPa s or more and 14000 mPa s or less, Particularly preferably, it is 5000 mPa·s or more and 13000 mPa·s or less.
The viscosity of the electrode slurry according to the present embodiment includes, for example, the solid content concentration of the electrode slurry, the mixing ratio of each material constituting the electrode slurry, the type of each material constituting the electrode slurry, and the hard kneading during preparation of the electrode slurry. It can be adjusted by controlling manufacturing conditions such as solid content concentration, mixing speed and mixing time in the process.

The solid content concentration of the electrode slurry according to the present embodiment is preferably 35% by mass or more and 65% by mass or less from the viewpoint of improving the coatability of the electrode slurry and the dispersion stability of each material constituting the electrode slurry. , more preferably 40% by mass or more and 60% by mass or less, still more preferably 40% by mass or more and 58% by mass or less, and particularly preferably 45% by mass or more and 55% by mass or less.

From the viewpoint of improving the dispersion stability of the electrode slurry, the pH of the electrode slurry according to the present embodiment is, for example, 6.0 or more and 8.0 or less, preferably 6.5 or more and 7.5 or less.
Although the method for adjusting the pH of the electrode slurry according to the present embodiment is not particularly limited, for example, it is adjusted by adjusting the compounding ratio of each material constituting the electrode slurry, the type of each material constituting the electrode slurry, and the like. be able to.

<Constituent Materials for Electrode Active Material Layer and Electrode Slurry for Lithium Ion Battery>
Next, each material constituting the electrode active material layer and the lithium ion battery electrode slurry according to the present embodiment will be described.
The electrode active material layer according to this embodiment contains an electrode active material selected from a positive electrode active material and a negative electrode active material, a binder resin, a thickener, and, if necessary, a conductive aid.
The electrode slurry according to the present embodiment contains an electrode active material selected from a positive electrode active material and a negative electrode active material, a binder resin, a thickener, an aqueous medium, and, if necessary, a conductive aid. include.

(electrode active material)
The electrode active material according to this embodiment is appropriately selected according to the application. A positive electrode active material is used when manufacturing a positive electrode, and a negative electrode active material is used when manufacturing a negative electrode.
In the present embodiment, when a negative electrode active material is used as the electrode active material, the effect of improving the peel strength of the present embodiment can be obtained particularly effectively.

The positive electrode active material is not particularly limited as long as it is a normal positive electrode active material that can be used for the positive electrode of a lithium ion battery. For example, composite oxides of lithium and transition metals such as lithium-nickel composite oxides, lithium-cobalt composite oxides, lithium-manganese composite oxides, lithium-manganese-nickel composite oxides; transitions such as TiS ₂ , FeS, MoS ₂ Metal sulfides; _MnO , _V2O5 , _V6O13 , transition metal oxides such as _TiO2 , olivine _- type lithium phosphate oxides, and the like.
The olivine-type lithium phosphate is, for example, at least one selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe. It contains the elements Lithium, Phosphorus and Oxygen. These compounds may have some elements partially substituted with other elements in order to improve their properties.

Among these, olivine-type lithium iron phosphate oxide, lithium cobalt composite oxide, lithium nickel composite oxide, lithium manganese composite oxide, and lithium-manganese-nickel composite oxide are preferred. These positive electrode active materials have high action potentials, large capacities, and high energy densities.
A positive electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.

The negative electrode active material is not particularly limited as long as it is a normal negative electrode active material that can be used for the negative electrode of a lithium ion battery. For example, carbon materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; lithium-based metals such as lithium metal and lithium alloy; metals such as silicon and tin; polyacene, polyacetylene, polypyrrole, etc. and the like. Among these, carbon materials are preferable, and graphite materials such as natural graphite and artificial graphite are particularly preferable.
A negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the electrode active material is preferably 70 parts by mass or more and 99.97 parts by mass or less, and is preferably 85 parts by mass or more when the total amount of the solid content of the entire electrode active material layer or the electrode slurry is 100 parts by mass. It is more preferably 99.85 parts by mass or less.

The graphite material is not particularly limited as long as it is a normal graphite material that can be used for the negative electrode of a lithium ion battery. Examples include natural graphite, artificial graphite produced by heat-treating petroleum-based and coal-based coke, and the like.
Here, natural graphite means graphite that is naturally produced as an ore. The natural graphite used as the core material of the present embodiment is not particularly limited in its place of origin, properties, and type.
Artificial graphite refers to graphite produced by an artificial method and graphite that is close to a perfect crystal of graphite. Such artificial graphite can be obtained, for example, by using tar or coke obtained from residues of dry distillation of coal, distillation of crude oil, or the like as raw materials and subjecting them to a firing process and a graphitization process.

The graphite material has graphite powder as a core material, and at least a part of the surface of the graphite powder is coated with a carbon material having a lower crystallinity than the graphite powder (hereinafter also referred to as surface-coated graphite. ) is preferred. In particular, it is preferable that the edges of the graphite powder are coated with the carbon material. By coating the edges of the graphite powder, it is possible to suppress the irreversible reaction between the edges and the electrolytic solution, and as a result, it is possible to suppress the decrease in the initial charge-discharge efficiency due to the increase in the irreversible capacity. can.
Further, when surface-coated graphite is used, the binding property with the binder resin can be improved more than when graphite is used alone, so the amount of the binder resin can be reduced. As a result, the battery characteristics of the resulting lithium ion battery can be improved.
Here, the carbon material having lower crystallinity than the graphite powder is, for example, amorphous carbon such as soft carbon and hard carbon.

Graphite powder used as the core material includes, for example, natural graphite, artificial graphite produced by heat-treating petroleum-based or coal-based coke, and the like. In this embodiment, one of these graphite powders may be used alone, or two or more of them may be used in combination. Among these, natural graphite is preferable from the viewpoint of cost.

The surface-coated graphite according to the present embodiment is obtained by mixing an organic compound that is carbonized in a baking process to become a carbon material with lower crystallinity than the graphite powder and the graphite powder, and then baking and carbonizing the organic compound. It can be made by

The organic compound to be mixed with the graphite powder is not particularly limited as long as it can be carbonized by firing to obtain a carbon material with lower crystallinity than the graphite powder. Examples include petroleum-based tar and coal-based tar. tar such as petroleum-based pitch, coal-based pitch, etc.; thermoplastic resins such as polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl alcohol, polyvinylidene chloride, polyacrylonitrile; curable resins; natural resins such as cellulose; aromatic hydrocarbons such as naphthalene, alkylnaphthalene and anthracene;
In this embodiment, these organic compounds may be used singly or in combination of two or more. In addition, these organic compounds may be used by dissolving or dispersing them in a solvent, if necessary.
Among the above organic compounds, tar and pitch are preferred from the viewpoint of cost.

The ratio of the organic compound-derived carbon material in the surface-coated graphite according to the present embodiment (hereinafter referred to as "coating amount") is preferably 0.7% by mass or more when the negative electrode active material is 100% by mass. It is 0% by mass or less.
By making the coating amount of the carbon material equal to or less than the above upper limit, the area for intercalating and deintercalating lithium ions is increased, and the rate characteristics of the resulting lithium ion battery can be improved.
By making the coating amount of the carbon material equal to or more than the above lower limit, it is possible to suppress the decrease in the initial charging/discharging efficiency due to the increase in the irreversible capacity. Moreover, the stability of the obtained electrode slurry can be improved by making the coating amount of the carbon material equal to or higher than the above lower limit.
Here, the coating amount can be calculated by thermogravimetric analysis. More specifically, using a thermogravimetric analyzer (for example, TGA7 analyzer manufactured by PerkinElmer), when the negative electrode active material is heated to 900 ° C. at a temperature increase rate of 5 ° C./min in an oxygen atmosphere, the mass The mass reduction from the temperature at which the decrease starts to the temperature at which the rate of mass decrease slows down and then accelerates can be used as the amount of coating.

The specific surface area of the electrode active material by the nitrogen adsorption BET method is preferably 1.0 m ² /g or more and 6.0 m ² /g or less, more preferably 2.0 m ² /g or more and 5.0 m ² /g or less. be.
By making the specific surface area equal to or less than the above upper limit, it is possible to suppress the decrease in the initial charge-discharge efficiency due to the increase in the irreversible capacity. Further, by setting the specific surface area to the above upper limit value or less, the stability of the obtained electrode slurry can be improved.
By making the specific surface area equal to or higher than the above lower limit, the area for intercalating and deintercalating lithium ions is increased, and the rate characteristics of the resulting lithium ion battery can be improved.
Further, by setting the specific surface area within the above range, the binding property of the binder resin can be improved.

The average particle size of the electrode active material is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and particularly preferably 8 μm or more, from the viewpoint of suppressing side reactions during charging and discharging and suppressing deterioration of charging and discharging efficiency. , from the viewpoint of input/output characteristics and electrode fabrication (smoothness of the electrode surface, etc.), the thickness is preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less. Here, the average particle diameter means the particle diameter (median diameter: d ₅₀ ) at 50% of the integrated value in the particle size distribution (volume basis) according to the laser diffraction scattering method.

(binder resin)
The binder resin is not particularly limited as long as it can be formed into an electrode and has sufficient electrochemical stability. For example, a rubber binder resin, an acrylic binder resin, or the like can be used.
The binder resin according to the present embodiment is formed of latex particles, and is preferably dispersed in water to be used as an aqueous emulsion solution. That is, the binder resin according to the present embodiment is preferably a so-called water-based binder resin that is formed from latex particles of the binder resin and that can be dispersed in water to form an aqueous emulsion solution. Thereby, the binder resin can be contained in the electrode active material layer without impeding contact between the electrode active materials, between the conductive aids, and between the electrode active material and the conductive aids.
The water in which the binder resin is dispersed may be a mixture of water such as alcohol and a highly hydrophilic solvent.

Examples of the rubber binder resin include styrene/butadiene copolymer rubber.
Examples of acrylic binder resins include polymers (homopolymers or copolymer) and the like. Examples of the copolymer include copolymers containing acrylic units and styrene units, copolymers containing acrylic units and silicon units, and the like.
These binder resins may be used individually by 1 type, and may be used in combination of 2 or more types. Among these, styrene/butadiene copolymer rubber is particularly preferred from the viewpoints of excellent binding properties, affinity with the electrolytic solution, price, electrochemical stability, and the like.

The content of the binder resin is preferably 0.01 parts by mass or more and 10.0 parts by mass or less when the total solid content of the electrode active material layer or the electrode slurry is 100 parts by mass. More preferably, the amount is not less than 5.0 parts by mass and not more than 5.0 parts by mass. When the content of the binder resin is within the above range, the balance between the coatability of the electrode slurry, the binding property of the binder resin and the battery characteristics is further improved.

The binder resin is, for example, dispersed in an aqueous medium and used as an aqueous emulsion solution. Thereby, the dispersibility of the binder resin can be improved without impeding the contact between the electrode active materials, between the conductive aids, and between the electrode active material and the conductive aids.
The aqueous medium in which the binder resin is dispersed is not particularly limited as long as it can disperse the binder resin. Distilled water, ion-exchanged water, city water, industrial water and the like can be used. Among these, distilled water and ion-exchanged water are preferred. In addition, water may be mixed with a highly hydrophilic solvent such as alcohol.

Styrene-butadiene copolymer rubber is a copolymer composed mainly of styrene and 1,3-butadiene. Here, the main component means that the total content of the styrene-derived structural units and the 1,3-butadiene-derived structural units in the styrene/butadiene copolymer rubber is the total polymerized units of the styrene/butadiene copolymer rubber. It means the case of 50% by mass or more.
The mass ratio (St/BD) between the structural unit derived from styrene (hereinafter also referred to as St) and the structural unit derived from 1,3-butadiene (hereinafter also referred to as BD) is, for example, 10/90 to 90/ 10.

The styrene/butadiene copolymer rubber may be obtained by copolymerizing monomer components other than styrene and 1,3-butadiene. Examples thereof include conjugated diene-based monomers, unsaturated carboxylic acid monomers, and other known copolymerizable monomers.
Conjugated diene-based monomers include, for example, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and piperylene.
Examples of unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid.

Although the method for producing the styrene-butadiene copolymer rubber is not particularly limited, it is preferably produced by an emulsion polymerization method. Using an emulsion polymerization method, latex particles containing styrene-butadiene copolymer rubber can be obtained.
A conventionally known method can be used as the emulsion polymerization. For example, styrene, 1,3-butadiene, and various copolymerizable monomer components described above are preferably produced by adding a polymerization initiator in the presence of an emulsifier and subjecting them to emulsion polymerization in water. can be done.

(thickener)
Examples of thickeners include water-soluble polymers such as cellulose-based water-soluble polymers; polycarboxylic acids; polyethylene oxide; polyvinylpyrrolidone; polyacrylates such as sodium polyacrylate; These thickeners may be used singly or in combination of two or more.
Among these, cellulose-based water-soluble polymers are preferred.

Cellulose-based water-soluble polymers include, for example, cellulosic polymers such as carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, methylethylhydroxycellulose, methylcellulose, and hydroxypropylcellulose, and ammonium salts and alkali metal salts of these cellulosic polymers. 1 or 2 or more selected from cellulose-based polymer salts and the like can be used.
Among these, it is preferable to include at least one selected from carboxymethylcellulose and carboxymethylcellulose salts, and one or more selected from carboxymethylcellulose, ammonium salts of carboxymethylcellulose, sodium salts of carboxymethylcellulose and potassium salts of carboxymethylcellulose. It is more preferable to include

The etherification degree of the cellulose-based water-soluble polymer is 0.50 or more and 1.0 because it can improve the solubility of the cellulose-based water-soluble polymer in an aqueous medium and increase the solid content concentration of the electrode slurry. is preferably 0.75 or more and 0.90 or less.
Here, the degree of etherification refers to the degree of substitution of a hydroxyl group to a carboxymethyl group or the like per anhydroglucose unit in the cellulose-based water-soluble polymer.

The content of the thickener is preferably 0.01 parts by mass or more and 10.0 parts by mass or less when the total solid content of the electrode active material layer or the electrode slurry is 100 parts by mass. 05 parts by mass or more and 5.0 parts by mass or less is more preferable. When the content of the thickener is within the above range, the balance between the coatability of the electrode slurry, the binding property of the binder resin, and the battery characteristics is further improved.

(Conductivity aid)
It is preferable that the electrode active material layer and the electrode slurry according to the present embodiment further contain a conductive aid from the viewpoint of improving the electron conductivity of the resulting electrode.
The conductive aid has electronic conductivity and is not particularly limited as long as it improves the conductivity of the electrode. Examples of the conductive aid according to the present embodiment include carbon materials such as acetylene black, ketjen black, carbon black, carbon nanofibers, and graphite having a particle size smaller than that of the graphite used as the active material. These conductive aids may be used singly or in combination of two or more.

The content of the conductive aid is preferably 0.01 parts by mass or more and 10.0 parts by mass or less when the total amount of the solid content of the entire electrode active material layer or the electrode slurry is 100 parts by mass. 05 parts by mass or more and 5.0 parts by mass or less is more preferable.
When the content of the conductive aid is within the above range, the balance between the coatability of the electrode slurry and the binding property of the binder resin is even more excellent.

The specific surface area of the conductive aid as determined by the nitrogen adsorption BET method is preferably 50 m ² /g or more and 1000 m ² /g or less from the viewpoint of the balance between the coatability of the electrode slurry and the conductivity of the electrode.

(Aqueous medium)
The aqueous medium according to this embodiment is not particularly limited, and for example, distilled water, ion-exchanged water, city water, industrial water, etc. can be used. Among these, distilled water and ion-exchanged water are preferred. In addition, water may be mixed with a highly hydrophilic solvent such as alcohol.

In the electrode active material layer according to the present embodiment, when the entire electrode active material layer is 100 parts by mass, the content of the electrode active material is preferably 70 parts by mass or more and 99.97 parts by mass or less, and more preferably It is 85 parts by mass or more and 99.85 parts by mass or less. Also, the content of the binder resin is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass. The content of the thickener is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, more preferably 0.05 parts by mass or more and 5.0 parts by mass or less. Moreover, the content of the conductive aid is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass.
When the content of each component constituting the electrode active material layer is within the above range, the balance between the handling properties of the lithium ion battery electrode and the battery characteristics of the obtained lithium ion battery is particularly excellent.

In the electrode slurry according to the present embodiment, when the total solid content of the electrode slurry is 100 parts by mass, the content of the electrode active material is preferably 70 parts by mass or more and 99.97 parts by mass or less, more preferably 85 parts by mass. It is more than 99.85 parts by mass and less than 99.85 parts by mass. Also, the content of the binder resin is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass. The content of the thickener is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, more preferably 0.05 parts by mass or more and 5.0 parts by mass or less. Moreover, the content of the conductive aid is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass.
When the content of each component constituting the electrode slurry is within the above range, the balance between the quality stability of the electrode slurry and the battery characteristics of the resulting lithium ion battery is particularly excellent.

<Method for producing lithium ion battery electrode slurry and lithium ion battery electrode>
Next, a method for producing the lithium ion battery electrode slurry and the lithium ion battery electrode according to the present embodiment will be described.
In order to obtain a lithium ion battery electrode slurry or a lithium ion battery electrode in which the weight average molecular weight (Mw) of the thickener extracted from the electrode slurry or the electrode active material layer is within the above range, (1) increase in raw materials It is important to highly control manufacturing conditions such as the weight average molecular weight of the viscous agent and (2) the method of preparing the electrode slurry. That is, the lithium ion battery electrode slurry and the lithium ion battery electrode according to the present embodiment can be obtained for the first time by a manufacturing method that highly controls various factors related to the following two conditions (1) and (2). .
(1) Weight-average molecular weight of raw material thickener (2) Preparation method of electrode slurry (in particular, manufacturing conditions such as solid content concentration, mixing speed, kneading time, etc. in the hard kneading process when preparing electrode slurry)

However, the lithium ion battery electrode slurry and the lithium ion battery electrode according to the present embodiment are based on the premise that various factors related to the above two conditions are highly controlled, and other specific manufacturing conditions, for example, are various. can be adopted. In other words, the electrode slurry for a lithium ion battery and the electrode for a lithium ion battery according to the present embodiment are produced by adopting a known method except for highly controlling various factors related to the above two conditions. It is possible to
An example of a lithium ion battery electrode slurry and a method for producing a lithium ion battery electrode according to the present embodiment will be described below on the premise that various factors related to the above two conditions are highly controlled.

The method for manufacturing the lithium ion battery electrode 100 according to the present embodiment preferably includes the following two steps (1) and (2).
(1) A step of preparing an electrode slurry by mixing an electrode active material, a binder resin, a thickener, an aqueous medium, and, if necessary, a conductive aid (2) The obtained electrode slurry is Step of forming electrode active material layer 103 on current collector layer 101 by coating and drying on current collector layer 101 and removing the aqueous medium. Each step will be described below.

First, (1) an electrode slurry is prepared by mixing an electrode active material, a binder resin, a thickener, an aqueous medium, and, if necessary, a conductive aid. Since the types and blending ratios of the electrode active material, binder resin, thickener, and conductive aid have been described above, description thereof will be omitted here.

The electrode slurry is obtained by dispersing or dissolving an electrode active material, a binder resin, a thickener, and optionally a conductive aid in an aqueous medium.
In the step of preparing the electrode slurry, the condition that the weight-average molecular weight (Mw) of the thickener calculated in terms of pullulan using the GPC method is equal to or higher than the above lower limit, that is, the weight-average molecular weight (Mw ) is maintained at the above lower limit or more, it is important to knead the mixture containing the electrode active material, the binder resin and the thickener.

In this embodiment, the step of preparing the electrode slurry includes, for example, the following slurry precursor preparation step (B) and electrode slurry preparation step (C), and optionally includes a dry mixing step (A). Here, in the slurry precursor preparation step (B), the decomposition of the thickener is particularly likely to occur. It is important to adjust production conditions such as solid content concentration, mixing speed and kneading time in step (B).
For example, the higher the solid content concentration, the greater the shear applied to the slurry precursor, and the more easily the molecular chains of the thickener are cut. Therefore, as the solid content concentration of the slurry precursor becomes relatively higher, the decomposition of the thickener can be suppressed by slowing down the mixing speed or shortening the kneading time when kneading the slurry precursor. As a result, the weight average molecular weight (Mw) can be maintained at a high value.

Dry mixing step (A): step of preparing a powder mixture containing the electrode active material and the thickener powder by dry mixing the electrode active material and the thickener powder in a powder state Slurry precursor preparation step (B): A slurry precursor is prepared by adding one or more liquid components selected from an aqueous medium, an aqueous emulsion solution containing a binder resin, and a thickener solution to a mixture or an electrode active material and wet-mixing them. Step Electrode slurry preparation step (C): One or more liquid components selected from an aqueous medium, an aqueous emulsion solution containing a binder resin, and a thickening agent solution are further added to the slurry precursor and wet-mixed. A step of preparing an electrode slurry by using a thickener solution instead of a thickener powder as a raw material thickener. In this case, the thickening agent solution can be added at the stage of the slurry precursor preparation step (B) or the electrode slurry preparation step (C) without performing the step (A).

In the dry mixing step (A), a powder mixture containing the electrode active material and the thickener powder is prepared by dry-mixing the electrode active material and the thickener powder in powder form. At this time, the powder may be mixed together with a conductive aid. Moreover, in the step (B), when the thickening agent is added as a thickening agent solution, the dry mixing step (A) may be performed only with the electrode active material and the conductive aid.
In the present embodiment, by performing the dry mixing step (A), the dispersibility of the electrode active material and the thickener can be improved, and in the subsequent steps, the formation of the gel component derived from the thickener is further suppressed. can. As a result, generation of a gel component derived from the thickener in the obtained electrode slurry can be suppressed, and the storage elastic modulus of the electrode slurry can be improved.

As a mixer for dry mixing, a planetary motion type mixer is preferably used, and a planetary motion type planetary mixer is more preferably used. By using such a mixer, it is possible to sufficiently mix the electrode active material and the thickener powder while suppressing scattering of the electrode active material and the thickener powder. Note that the planetary motion mixer is a mixer having rotation and revolution functions as a stirring mechanism. A planetary motion type planetary mixer refers to a mixer having blades having rotation and revolution functions as a stirring mechanism.

The rotation speed of the dry mixing in the dry mixing step (A) is preferably in the range of 0.05 m / sec or more and 0.55 m / sec or less, and is in the range of 0.07 m / sec or more and 0.52 m / sec or less. More preferably within
When the autorotation speed of the dry mixing in the dry mixing step (A) is within the above range, the electrode active material and the thickener powder are sufficiently mixed while suppressing scattering of the electrode active material and the thickener powder. be able to.

In addition, the revolution speed of the dry mixing in the dry mixing step (A) is preferably in the range of 0.01 m / sec or more and 0.20 m / sec or less, and 0.02 m / sec or more and 0.15 m / sec or less. is more preferably within the range of
When the revolution speed of the dry mixing in the dry mixing step (A) is within the above range, the electrode active material and the thickener powder are sufficiently mixed while suppressing scattering of the electrode active material and the thickener powder. be able to.

The mixing time of the dry mixing in the dry mixing step (A) is not particularly limited, but is, for example, 5 minutes or more and 120 minutes or less, preferably 10 minutes or more and 60 minutes or less.

In the slurry precursor preparation step (B), an aqueous emulsion solution containing an aqueous medium and a binder resin is added to the powder mixture obtained in the step (A), or the powder containing the electrode active material when the step (A) is not performed. and a thickening agent solution are added and wet-mixed to prepare a slurry precursor.

As a mixer for performing wet mixing in the slurry precursor preparation step (B), a planetary motion mixer is preferably used, and a planetary motion planetary mixer is more preferably used. By using such a mixer, it is possible to improve the dispersibility of each material while suppressing scattering of each material constituting the electrode slurry.

Here, the slurry precursor preparation step (B) is not particularly limited, but it may be a two or more step process including at least the first hard kneading step (B2) and the second hard kneading step (B3). Furthermore, if necessary, a familiarization step (B1) performed before the first hard kneading step (B2) may be performed.

In the blending step (B1), the powder mixture obtained in the step (A), or the powder containing the electrode active material when the step (A) is not performed, is mixed with an aqueous medium, an aqueous emulsion solution containing a binder resin, and a thickened It is a step of blending one or two or more liquid components selected from the agent solution. By including this familiarization step (B1), it is possible to prevent the powder from rising to the edge of the mixer during wet mixing, the uneven wetting of the powder, and the scattering of the powder during kneading. can be suppressed within the range of

The rotation speed of the wet mixing in the blending step (B1) is preferably in the range of 0.10 m / sec or more and 2.5 m / sec or less, and is in the range of 0.15 m / sec or more and 2.0 m / sec or less. More preferably within
If the rotation speed of the wet mixing in the blending step (B1) is within the above range, the powder will rise to the edge of the mixer during wet mixing, the wetting of the powder will be uneven, and the powder will The liquid component can be sufficiently blended with the powder material while effectively suppressing scattering of the material during kneading.

In addition, the revolution speed of the wet mixing in the familiarization step (B1) is preferably in the range of 0.03 m / sec to 1.00 m / sec, and 0.04 m / sec to 0.80 m / sec. is more preferably within the range of
If the revolution speed of the wet mixing in the blending step (B1) is within the above range, the powder will rise to the edge of the mixer during wet mixing, the wetting of the powder will be uneven, and the powder will The liquid component can be sufficiently blended with the powder material while effectively suppressing scattering of the material during kneading.

The mixing time of the wet mixing in the blending step (B1) is not particularly limited, but is, for example, preferably 0.5 minutes or more and 120 minutes or less, more preferably 2 minutes or more and 60 minutes or less.

Further, the first hard kneading step (B2) and the second hard kneading step (B3) are steps of kneading the powder material and the liquid component to obtain a slurry precursor.

The mixing time of the wet mixing in the first hard kneading step (B2) is not particularly limited, but is, for example, 5 minutes or more and 120 minutes or less.

The mixing time of the wet mixing in the second hard kneading step (B3) is not particularly limited, but is, for example, 5 minutes or more and 120 minutes or less.

In the first hard kneading step (B2) and the second hard kneading step (B3), it is preferable to adjust the solid content concentration of the slurry precursor to 55% by mass or more and 77% by mass or less, and 58% by mass or more and 74% by mass. % or less, and more preferably 60% by mass or more and 73% by mass or less.

The rotation speed of the wet mixing in the first hard kneading step (B2) and the second hard kneading step (B3) (linear velocity of the blades of the planetary motion mixer) is 0.10 m / sec or more and 3.0 m / sec. It is preferably within the following range, and more preferably within the range of 0.20 m/sec or more and 2.5 m/sec or less.

In addition, the revolution speed of the wet mixing in the first hard kneading step (B2) and the second hard kneading step (B3) (linear velocity of the blades of the planetary motion mixer) is 0.01 m / sec or more and 2.0 m /sec or less, and more preferably 0.05 m/sec or more and 1.0 m/sec or less.

In the electrode slurry preparation step (C), one or two selected from an aqueous medium, an aqueous emulsion solution containing a binder resin, and a thickener solution are added to the slurry precursor obtained in the slurry precursor preparation step (B). The electrode slurry is prepared by further adding the above liquid components and wet-mixing them.

As a mixer for performing wet mixing in the electrode slurry preparation step (C), a planetary motion mixer is preferably used, and a planetary motion planetary mixer is more preferably used. By using such a mixer, it is possible to sufficiently mix while stirring at a low speed. Therefore, it is possible to improve the dispersibility of each material constituting the electrode slurry while suppressing breakage of the molecular chain of the thickener due to stirring and mixing and suppressing aggregation of the binder resin. As a result, an electrode slurry with even better quality stability can be obtained.
In addition, the resulting electrode slurry has even better dispersibility, so that the use of such an electrode slurry makes it possible to obtain a more uniform electrode active material layer. As a result, a battery with even better battery characteristics can be obtained.

In the present embodiment, the rotation speed of the wet mixing in the electrode slurry preparation step (C) (the linear speed of the blades of the planetary motion mixer) is not particularly limited. Within range.
Further, in the present embodiment, the revolution speed of wet mixing (linear speed of the blades of the planetary motion mixer) in the electrode slurry preparation step (C) is not particularly limited. Within the following range.

The mixing time of the wet mixing in the electrode slurry preparation step (C) is not particularly limited, but is, for example, 5 minutes or more and 60 minutes or less.

The solid content concentration of the electrode slurry in the electrode slurry preparing step (C) can be adjusted by adjusting the concentration and amount of the liquid component added.

The method for producing an electrode slurry according to the present embodiment may further include a defoaming step (D): a vacuum defoaming step. As a result, air bubbles entrained in the slurry can be removed, and the coatability of the slurry can be improved.
Vacuum defoaming may be performed by sealing the container or shaft of the mixer to remove air bubbles, or by transferring the mixture to another container.

Next, (2) the electrode active material layer 103 is formed on the collector layer 101 by applying the obtained electrode slurry onto the collector layer 101 and drying it to remove the aqueous medium. Thereby, the electrode 100 for a lithium ion battery having excellent adhesiveness between the current collector layer 101 and the electrode active material layer 103 can be obtained.

That is, the lithium ion battery electrode 100 according to the present embodiment is obtained by coating the electrode slurry according to the present embodiment on a current collector layer 101 such as a positive electrode current collector and a negative electrode current collector, drying it, and removing an aqueous medium. It can be obtained by forming the electrode active material layer 103 on the collector layer 101 by removing it.

A generally known method can be used as a method for applying the electrode slurry according to the present embodiment onto the current collector layer 101 . For example, a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method and a squeeze method can be used. Among these methods, the doctor blade method, the knife method, and the extrusion method are preferable in that a good surface condition of the coating layer can be obtained according to the physical properties such as the viscosity and the drying property of the electrode slurry.

The electrode slurry according to this embodiment may be applied to only one side of the current collector layer 101 or to both sides. When coating both surfaces of the current collector layer 101, the coating may be performed one by one successively or simultaneously on both surfaces. Moreover, the surface of the collector layer 101 may be coated continuously or intermittently. The thickness, length, and width of the coating layer can be appropriately determined according to the size of the battery.

As the current collector layer 101 used for manufacturing the lithium ion battery electrode 100 according to the present embodiment, for example, a normal current collector that can be used for lithium ion batteries can be used.
Copper, stainless steel, nickel, titanium, or alloys thereof can be used as the negative electrode current collector, and among these, copper is particularly preferred.
Aluminum, stainless steel, nickel, titanium, alloys thereof, or the like can be used as the positive electrode current collector, and among these, aluminum is particularly preferable.
Although the shape of the current collector is not particularly limited, for example, a foil-like one having a thickness in the range of 0.001 to 0.5 mm can be used.

The thickness and density of the electrode active material layer 103 according to the present embodiment are not particularly limited because they are appropriately determined according to the intended use of the battery, and can be set according to generally known information.

A commonly known method can be used for drying the applied electrode slurry. For example, hot air, vacuum, infrared rays, far infrared rays, electron beams and cold air can be used alone or in combination. The drying temperature is, for example, in the range of 30°C or higher and 350°C or lower.

The lithium-ion battery electrode according to this embodiment may be pressed if necessary. A generally known method can be used as the pressing method. For example, a die press method, a calender press method, and the like can be mentioned. Although the pressing pressure is not particularly limited, it is in the range of 0.2 to 3 t/cm ² , for example.

The thickness and density of the lithium-ion battery electrode according to the present embodiment are not particularly limited because they are appropriately determined according to the intended use of the battery, and can be set according to generally known information.

<Lithium-ion battery>
Next, the lithium ion battery 150 according to this embodiment will be described. FIG. 2 is a cross-sectional view showing an example of the structure of the lithium ion battery 150 according to the embodiment of the invention.
The lithium ion battery 150 according to this embodiment includes the lithium ion battery electrode according to this embodiment. More specifically, the lithium ion battery 150 according to the present embodiment includes, for example, at least a positive electrode 120, an electrolyte layer 110, and a negative electrode 130, and at least one of the positive electrode 120 and the negative electrode 130 is lithium according to the present embodiment. Includes electrodes for ion batteries. In addition, the lithium ion battery 150 according to this embodiment may contain a separator as needed.
In the lithium ion battery 150 according to the present embodiment, at least one of the positive electrode 120 and the negative electrode 130 includes the lithium ion battery electrode according to the present embodiment. Therefore, the quality of the battery and the cycle characteristics of the battery are good.
The lithium ion battery 150 according to this embodiment can be produced according to a known method.
Examples of the form of the electrode include a laminate and a wound body. Examples of the exterior body include a metal exterior body and an aluminum laminate exterior body. Examples of the shape of the battery include coin-shaped, button-shaped, sheet-shaped, cylindrical, square-shaped, and flat-shaped.

As the electrolyte used for the electrolyte layer 110, any known lithium salt can be used, and the electrolyte may be selected according to the type of active material. For example, LiClO4, _LiBF6 , _LiPF6 , _{LiCF3SO3 , LiCF3CO2 , LiAsF6} , _LiSbF6 , _LiB10Cl10 , _LiAlCl4 , LiCl, LiBr, _{LiB ( C2H5} ) _{4 , CF3} SO ₃ Li, CH ₃ SO ₃ Li, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, lithium lower fatty acid carboxylate, and the like.

The solvent for dissolving the electrolyte used in the electrolyte layer 110 is not particularly limited as long as it is commonly used as a liquid component for dissolving the electrolyte. Examples include ethylene carbonate (EC) and propylene carbonate (PC). , butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; Ethers such as methoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran; sulfoxides such as dimethylsulfoxide; 1,3-dioxolane, 4-methyl-1,3- Oxolanes such as dioxolane; Nitrogen-containing compounds such as acetonitrile, nitromethane, formamide and dimethylformamide; Organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate and ethyl propionate; and diglymes; triglymes; sulfolane, methylsulfolane and other sulfolane; 3-methyl-2-oxazolidinone and other oxazolidinones; . These may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of separators include porous separators. Examples of the form of the separator include membranes, films, non-woven fabrics, and the like.
Examples of the porous separator include polyolefin porous separators such as polypropylene and polyethylene; porous separators made of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride hexafluoropropylene copolymer, etc. is mentioned.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can also be adopted.
Moreover, the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.
Examples of embodiments are added below.
1. a current collector layer;
an electrode active material layer provided on at least one surface of the current collector layer and containing an electrode active material, a binder resin and a thickening agent;
An electrode for a lithium ion battery comprising
An electrode for a lithium ion battery, wherein the thickener extracted from the electrode active material layer has a weight-average molecular weight (Mw) of 2,000,000 or more, calculated in terms of pullulan using a gel permeation chromatography (GPC) method.
2. 1. In the lithium ion battery electrode according to
The ratio (Mw/Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the thickening agent extracted from the electrode active material layer, calculated in terms of pullulan using the GPC method, is 6. An electrode for a lithium ion battery that is less than .0.
3. 1. or 2. In the lithium ion battery electrode according to
An electrode for a lithium ion battery, wherein the electrode active material comprises a carbon material.
4. 1. to 3. In the lithium ion battery electrode according to any one of
An electrode for a lithium ion battery, wherein the thickener comprises a cellulose-based water-soluble polymer.
5. 4. In the lithium ion battery electrode according to
An electrode for a lithium ion battery, wherein the cellulose-based water-soluble polymer has a degree of etherification of 0.50 or more and 1.0 or less.
6. 1. to 5. In the lithium ion battery electrode according to any one of
An electrode for a lithium ion battery, wherein the binder resin comprises at least one resin selected from rubber binder resins and acrylic binder resins.
7. 6. In the lithium ion battery electrode according to
An electrode for a lithium ion battery, wherein the binder resin contains a styrene-butadiene copolymer rubber.
8. 1. to 7. In the lithium ion battery electrode according to any one of
When the entire electrode active material layer is 100 parts by mass,
The content of the electrode active material is 70 parts by mass or more and 99.97 parts by mass or less,
The content of the thickener is 0.01 parts by mass or more and 10.0 parts by mass or less,
A lithium ion battery electrode, wherein the content of the binder resin is 0.01 parts by mass or more and 10.0 parts by mass or less.
9. 1. to 8. In the lithium ion battery electrode according to any one of
The electrode for a lithium ion battery, wherein the electrode active material layer further contains a conductive aid.
10. An electrode slurry for a lithium ion battery containing an electrode active material, a binder resin, a thickener and an aqueous medium,
For a lithium ion battery, wherein the thickener extracted from the lithium ion battery electrode slurry has a weight average molecular weight (Mw) of 2,000,000 or more, calculated in terms of pullulan using a gel permeation chromatography (GPC) method. electrode slurry.
11. 10. In the lithium ion battery electrode slurry according to
Ratio (Mw/Mn) of the weight average molecular weight (Mw) of the thickener extracted from the lithium ion battery electrode slurry and the number average molecular weight (Mn), which is calculated in terms of pullulan using the GPC method. is less than 6.0 for a lithium ion battery electrode slurry.
12. 10. or 11. In the lithium ion battery electrode slurry according to
An electrode slurry for a lithium ion battery, wherein the electrode active material contains a carbon material.
12. 10. 12. In the lithium ion battery electrode slurry according to any one of
An electrode slurry for a lithium ion battery, wherein the thickener contains a cellulose-based water-soluble polymer.
14. 13. In the lithium ion battery electrode slurry according to
An electrode slurry for a lithium ion battery, wherein the cellulose-based water-soluble polymer has a degree of etherification of 0.50 or more and 1.0 or less.
15. 10. to 14. In the lithium ion battery electrode slurry according to any one of
An electrode slurry for a lithium ion battery, wherein the binder resin contains at least one resin selected from a rubber binder resin and an acrylic binder resin.
16. 15. In the lithium ion battery electrode slurry according to
An electrode slurry for a lithium ion battery, wherein the binder resin contains a styrene-butadiene copolymer rubber.
17. 10. to 16. In the lithium ion battery electrode slurry according to any one of
When the total solid content of the lithium ion battery electrode slurry is 100 parts by mass,
The content of the electrode active material is 70 parts by mass or more and 99.97 parts by mass or less,
The content of the thickener is 0.01 parts by mass or more and 10.0 parts by mass or less,
An electrode slurry for a lithium ion battery, wherein the content of the binder resin is 0.01 parts by mass or more and 10.0 parts by mass or less.
18. 10. to 17. In the lithium ion battery electrode slurry according to any one of
An electrode slurry for a lithium ion battery, further comprising a conductive aid.
19. a current collector layer;
10. provided on at least one surface of the current collector layer; to 18. and an electrode active material layer composed of the solid content of the electrode slurry for a lithium ion battery according to any one of the above.
20. 19. A manufacturing method for manufacturing a lithium ion battery electrode according to
10. to 18. A step of preparing a lithium ion battery electrode slurry according to any one of
The step of preparing the lithium ion battery electrode slurry includes:
A step of kneading a mixture containing an electrode active material, a binder resin and a thickening agent under conditions such that the weight average molecular weight (Mw) of the thickening agent, calculated in terms of pullulan using the GPC method, is 2,000,000 or more. A method for producing a lithium ion battery electrode comprising:
21. 1. to 9. and 19. A lithium ion battery comprising the electrode for a lithium ion battery according to any one of .

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

(Example 1)
<Preparation of electrode slurry>
(A) Dry mixing step In a planetary motion planetary mixer (pot size: 1600 L), carbon material 1 (average particle diameter d ₅₀ : 16 μm, specific surface area by nitrogen adsorption BET method: 3.4 m ² as an electrode active material) / g) 620 kg, and carboxymethyl cellulose powder as a raw material thickener (manufactured by Nippon Paper Industries Co., Ltd., MAC350HC (registered trademark), degree of etherification: 0.8, weight average molecular weight Mw: 3230000, Mw / Mn = 7.56) 7 kg and 3 kg of carbon black (specific surface area determined by nitrogen adsorption BET method: 60 m ² /g) in which primary particles of about 30 nm are agglomerated in chain form as a conductive agent were added. Then, dry mixing was performed for 20 minutes under the conditions of rotation speed: 0.26 m/sec, revolution speed: 0.08 m/sec, and temperature: 20°C to obtain a powder mixture. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.
Hereinafter, the average particle diameter d50 was measured with a _MT3000 device manufactured by Microtrac, and the specific surface area was obtained by the nitrogen adsorption BET method using Quanta Sorb manufactured by Quantachrome Corporation.
Also, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the raw material thickener before being used to prepare the electrode slurry were measured by the following procedure.
A thickener aqueous solution with a concentration of 1.2% by mass was diluted 5 times with a measurement solvent (0.1M sodium chloride aqueous solution), and the molecular weight distribution of the thickener was measured under the following measurement conditions. The pullulan-equivalent weight average molecular weight (Mw) and number average molecular weight (Mn) were calculated from the above. Here, the pullulan-equivalent weight average molecular weight is a value calculated using a calibration curve prepared using monodisperse pullulan as a standard substance.
(Measurement condition)
Apparatus: Gel permeation chromatograph GPC (manufactured by Tosoh Corporation, pump model: DP-8020)
Detector: Differential refractive index detector RI (manufactured by Tosoh Corporation, RI-8020 type, sensitivity 16)
Column: TSKgel guard column PW _XL (1 piece), TSKgel PW _XL (2 pieces) (φ6 mm × 4 cm, φ7.8 mm × 30 cm, manufactured by Tosoh Corporation)
Solvent: 0.1 M aqueous sodium chloride solution Flow rate: 0.5 mL/min
Column temperature: 45°C
Injection volume: 0.2 mL
Reference material: Monodisperse pullulan (manufactured by Showa Denko)

Here, carbon material 1 (graphite whose surface is coated with amorphous carbon) was produced as follows.
Natural graphite with an average particle size d ₅₀ of 16 μm and a specific surface area of 3.4 m ² /g was used as the core material.
99.0 parts by mass of this natural graphite powder and 1.0 parts by mass of coal-based pitch powder were mixed in a solid phase by simple mixing using a V blender. The obtained mixed powder was placed in a graphite crucible and heat-treated at 1300° C. for 1 hour in a nitrogen stream to obtain graphite whose surface was coated with amorphous carbon.

(B2) First solid kneading step Next, water was added to the planetary motion type planetary mixer after the dry mixing step (A) was completed so that the solid content concentration of the resulting slurry precursor was 71% by mass. . After that, wet mixing was performed for 15 minutes under conditions of rotation speed: 0.45 m/sec, revolution speed: 0.14 m/sec, temperature: 20°C, and atmospheric pressure. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.

(B3) Second hard kneading step Next, water is added to the planetary motion type planetary mixer after the first hard kneading step (B2) is completed so that the solid content concentration of the resulting slurry precursor is 63% by mass. was added, and while the rotation speed, revolution speed, and temperature were the same as in the first hard kneading step (B2), wet mixing was performed for 30 minutes under atmospheric pressure conditions to obtain an electrode slurry precursor.

(C) Electrode Slurry Preparation Step Next, an SBR emulsion aqueous solution having a solid content concentration of 40% by mass was prepared by dispersing styrene-butadiene copolymer rubber (SBR) as a binder resin in water. 24 kg of the obtained SBR emulsion aqueous solution was added to a planetary motion type planetary mixer after the hard kneading process was completed.
After that, wet mixing was performed for 40 minutes under conditions of rotation speed: 0.52 m/sec, revolution speed: 0.15 m/sec, and temperature: 20°C. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.

(D) Degassing Step Subsequently, vacuum degassing was performed to obtain an electrode slurry.
The final solid content concentration of the electrode slurry was adjusted to 51% by mass by adding water in the step (C) of preparing the electrode slurry.

<Production of electrodes>
The resulting electrode slurry was applied to both sides of a copper foil as a current collector layer using a die coater and dried. Then, the obtained electrode was pressed to obtain an electrode (negative electrode).

<Evaluation>
(1) Measurement of Viscosity of Electrode Slurry Using a Brookfield viscometer (Rotational viscometer manufactured by Brookfield), the viscosity of the electrode slurry was measured at 25° C. and a shear rate of 3.4 s ⁻¹ .

(2) Peel strength test The peel strength of the obtained electrode was measured by the following procedure. A 20 mm wide and 10 cm long electrode was cut out, and one side of the electrode was attached to a plate with double-sided tape. Then, the plate was fixed and the electrode was peeled off in the direction of 90° at a speed of 100 mm/min. The peel strength (mN/mm) at that time was measured three times, and the average value was taken as the peel strength.

(3) Measurement of Molecular Weight of Thickener The weight average molecular weight (Mw) and number average molecular weight (Mn) of the thickener extracted from the electrode slurry were measured by the following procedures.
(3-1) About 12.5 g of the electrode slurry was weighed into a volumetric flask, and distilled water was added to make 50 mL.
(3-2) After lightly shaking to make a uniform solution (for example, visually confirmed), an ultracentrifuge (manufactured by Hitachi Koki Co., Ltd., product name: Hitachi separation ultracentrifuge, model: CP80WX, rotor: Ultracentrifugation (30000 rpm (66000 G) x 30 minutes) was performed using an angle rotor P70AT).
(3-3) The supernatant after the separation obtained in (3-2) was collected and subjected to ultracentrifugation (30000 rpm (66000 G)×30 minutes) again. Furthermore, the supernatant was collected and ultracentrifuged again (30000 rpm (66000 G)×30 minutes). These ultracentrifugation operations removed the electrode active material, the binder resin and the conductive aid in the slurry.
(3-4) The supernatant obtained in (3-3) was filtered through a 0.45 μm filter, and the obtained filtrate was further filtered through a 0.20 μm filter. As a result, the electrode active material, binder resin and conductive aid remaining in the supernatant obtained in (3-3) were removed. The resulting filtrate was diluted 5-fold with a measurement solvent (0.1 M aqueous sodium chloride solution), and the molecular weight distribution of the thickener was measured under the following measurement conditions. Mw) and number average molecular weight (Mn) were calculated respectively. Here, the pullulan-equivalent weight average molecular weight is a value calculated using a calibration curve prepared using monodisperse pullulan as a standard substance.
(Measurement condition)
Apparatus: Gel permeation chromatograph GPC (manufactured by Tosoh Corporation, pump model: DP-8020)
Detector: Differential refractive index detector RI (manufactured by Tosoh Corporation, RI-8020 type, sensitivity 16)
Column: TSKgel guard column PW _XL (1 piece), TSKgel PW _XL (2 pieces) (φ6 mm × 4 cm, φ7.8 mm × 30 cm, manufactured by Tosoh Corporation)
Solvent: 0.1 M aqueous sodium chloride solution Flow rate: 0.5 mL/min
Column temperature: 45°C
Injection volume: 0.2 mL
Reference material: Monodisperse pullulan (manufactured by Showa Denko)

Table 1 shows the obtained evaluation results.

(Example 2)
The solid content concentration and mixing time in the first solid kneading step (B2) were changed to the values shown in Table 1, and carbon material 2 (natural graphite, average particle diameter d ₅₀ ) was used instead of carbon material 1 as the electrode active material. : 13 μm, specific surface area by nitrogen adsorption BET method: 3.6 m ² /g), and an electrode slurry and an electrode were prepared in the same manner as in Example 1 except that the second hard kneading step (B3) was not performed. , each evaluation was performed. Table 1 shows the results obtained.

(Example 3)
<Preparation of electrode slurry>
(A) Dry mixing step In a planetary motion planetary mixer (pot size: 1600 L), carbon material 1 (average particle diameter d ₅₀ : 16 μm, specific surface area by nitrogen adsorption BET method: 3.4 m ² as an electrode active material) /g) and 3 kg of carbon black (specific surface area by nitrogen adsorption BET method: 60 m ² /g) in which primary particles of about 30 nm are agglomerated in a chain as a conductive aid. Then, dry mixing was performed for 20 minutes under the conditions of rotation speed: 0.26 m/sec, revolution speed: 0.08 m/sec, and temperature: 20°C to obtain a powder mixture. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.
Hereinafter, the average particle diameter d50 was measured with a _MT3000 device manufactured by Microtrac, and the specific surface area was obtained by the nitrogen adsorption BET method using Quanta Sorb manufactured by Quantachrome Corporation.

(B1) Blending step Next, the concentration is 1.2 mass so that the solid content concentration of the resulting paste precursor is 86 mass% in the planetary motion type planetary mixer after the dry mixing step (A) is completed. % thickening agent aqueous solution (carboxymethyl cellulose (MAC350HC (registered trademark) manufactured by Nippon Paper Industries Co., Ltd., etherification degree: 0.8, weight average molecular weight Mw: 3230000, Mw / Mn = 7.56) was dissolved in water. thing) 101 kg was added. After that, wet mixing was performed for 35 minutes under the conditions of rotation speed: 1.36 m/sec, revolution speed: 0.43 m/sec, temperature: 20°C, and atmospheric pressure. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.

(B2) First kneading step Next, a thickening agent aqueous solution (carboxymethylcellulose (MAC350HC manufactured by Nippon Paper Industries Co., Ltd.) having a concentration of 1.2% by mass so that the solid content concentration of the resulting slurry precursor is 63% by mass (registered trademark), degree of etherification: 0.8, weight average molecular weight Mw: 3230000, Mw/Mn = 7.56) dissolved in water) was added. After that, wet mixing was performed for 50 minutes under conditions of rotation speed: 2.04 m/sec, revolution speed: 0.65 m/sec, temperature: 20° C., and atmospheric pressure. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.

(B3) Second hard kneading step Next, in the planetary motion type planetary mixer after the first hard kneading step (B2) has been completed, the slurry precursor obtained has a solid content concentration of 61% by mass. is 1.2% by mass of a thickening agent aqueous solution (carboxymethyl cellulose (MAC350HC (registered trademark) manufactured by Nippon Paper Industries Co., Ltd., degree of etherification: 0.8, weight average molecular weight Mw: 3230000, Mw / Mn = 7.56) dissolved in water) was added. After that, wet mixing was performed for 11 minutes under conditions of rotation speed: 2.04 m/sec, revolution speed: 0.65 m/sec, temperature: 20° C., and atmospheric pressure to obtain an electrode slurry precursor. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.

(C) Electrode Slurry Preparation Step Next, an SBR emulsion aqueous solution having a solid content concentration of 40% by mass was prepared by dispersing styrene-butadiene copolymer rubber (SBR) as a binder resin in water. 24 kg of the resulting aqueous SBR emulsion solution and an aqueous thickener solution having a concentration of 1.2% by mass (carboxymethyl cellulose (MAC350HC (registered trademark) manufactured by Nippon Paper Industries Co., Ltd., etherification degree: 0.8, weight average molecular weight Mw: 3230000 , Mw/Mn=7.56) dissolved in water) were added to the planetary motion type planetary mixer after the kneading process was completed.
After that, wet mixing was performed for 40 minutes under conditions of rotation speed: 0.52 m/sec, revolution speed: 0.15 m/sec, and temperature: 20°C. Here, the rotation speed and revolution speed are the linear velocities of the blades of the planetary motion type planetary mixer.

(D) Degassing Step Subsequently, vacuum degassing was performed to obtain an electrode slurry.
The final solid content concentration of the electrode slurry was adjusted to 51% by mass by adding water in the step (C) of preparing the electrode slurry.

<Production of electrodes>
The resulting electrode slurry was applied to both sides of a copper foil as a current collector layer using a die coater and dried. Then, the obtained electrode was pressed to obtain an electrode (negative electrode).

<Evaluation>
The same evaluation as in Example 1 was performed. Table 1 shows the results obtained.

(Example 4)
Carbon material 2 (natural graphite, average particle diameter d ₅₀ : 13 μm, specific surface area by nitrogen adsorption BET method: 3.6 m ² /g) was used as the electrode active material instead of carbon material 1. Electrode slurries and electrodes were prepared in the same manner, and each evaluation was performed. Table 1 shows the results obtained.

(Example 5 and Comparative Example 1)
Electrode slurry in the same manner as in Example 1 except that the solid content concentration and mixing time in the first hard kneading step (B2) are set to the values shown in Table 1, and the second hard kneading step (B3) is not performed. and electrodes were produced, and each evaluation was performed. Table 1 shows the results obtained.

(Comparative example 2)
An electrode slurry and an electrode were prepared in the same manner as in Example 2 except that the rotation speed and revolution speed in the first hard kneading step (B2) were changed to the values shown in Table 1, and each evaluation was performed. Table 1 shows the results obtained.

This application claims priority based on Japanese Patent Application No. 2018-108732 filed on June 6, 2018, and the entire disclosure thereof is incorporated herein.

Claims (15)

a current collector layer;
an electrode active material layer provided on at least one surface of the current collector layer and containing an electrode active material, a binder resin and a thickening agent;
An electrode for a lithium ion battery comprising
The weight average molecular weight (Mw) of the thickening agent extracted from the electrode active material layer, which is calculated in terms of pullulan using a gel permeation chromatography (GPC) method, is 2000000 or more,
The ratio (Mw/Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the thickening agent extracted from the electrode active material layer, calculated in terms of pullulan using the GPC method, is 6. is less than .0,
An electrode for a lithium ion battery, wherein the thickener contains a cellulose-based water-soluble polymer, and the cellulose-based water-soluble polymer has a degree of etherification of 0.50 or more and 1.0 or less. In the lithium ion battery electrode according to claim 1,
An electrode for a lithium ion battery, wherein the electrode active material comprises a carbon material. In the lithium ion battery electrode according to claim 1 or 2,
An electrode for a lithium ion battery, wherein the binder resin comprises at least one resin selected from rubber binder resins and acrylic binder resins. In the lithium ion battery electrode according to claim 3,
An electrode for a lithium ion battery, wherein the binder resin contains a styrene-butadiene copolymer rubber. In the lithium ion battery electrode according to any one of claims 1 to 4,
When the entire electrode active material layer is 100 parts by mass,
The content of the electrode active material is 70 parts by mass or more and 99.97 parts by mass or less,
The content of the thickener is 0.01 parts by mass or more and 10.0 parts by mass or less,
A lithium ion battery electrode, wherein the content of the binder resin is 0.01 parts by mass or more and 10.0 parts by mass or less. In the lithium ion battery electrode according to any one of claims 1 to 5,
The electrode for a lithium ion battery, wherein the electrode active material layer further contains a conductive aid. An electrode slurry for a lithium ion battery containing an electrode active material, a binder resin, a thickener and an aqueous medium,
The weight average molecular weight (Mw) of the thickener extracted from the lithium ion battery electrode slurry, which is calculated in terms of pullulan using a gel permeation chromatography (GPC) method, is 2000000 or more,
Ratio (Mw/Mn) of the weight average molecular weight (Mw) of the thickener extracted from the lithium ion battery electrode slurry and the number average molecular weight (Mn), which is calculated in terms of pullulan using the GPC method. is less than 6.0,
An electrode slurry for a lithium ion battery, wherein the thickener contains a cellulose-based water-soluble polymer, and the cellulose-based water-soluble polymer has a degree of etherification of 0.50 or more and 1.0 or less. In the lithium ion battery electrode slurry according to claim 7,
An electrode slurry for a lithium ion battery, wherein the electrode active material contains a carbon material. In the lithium ion battery electrode slurry according to claim 7 or 8,
An electrode slurry for a lithium ion battery, wherein the binder resin contains at least one resin selected from a rubber binder resin and an acrylic binder resin. In the lithium ion battery electrode slurry according to claim 9,
An electrode slurry for a lithium ion battery, wherein the binder resin contains a styrene-butadiene copolymer rubber. In the lithium ion battery electrode slurry according to any one of claims 7 to 10,
When the total solid content of the lithium ion battery electrode slurry is 100 parts by mass,
The content of the electrode active material is 70 parts by mass or more and 99.97 parts by mass or less,
The content of the thickener is 0.01 parts by mass or more and 10.0 parts by mass or less,
An electrode slurry for a lithium ion battery, wherein the content of the binder resin is 0.01 parts by mass or more and 10.0 parts by mass or less. In the lithium ion battery electrode slurry according to any one of claims 7 to 11,
An electrode slurry for a lithium ion battery, further comprising a conductive aid. a current collector layer;
and an electrode active material layer provided on at least one surface of the current collector layer and composed of the solid content of the lithium ion battery electrode slurry according to any one of claims 7 to 12. Electrodes for lithium-ion batteries. A manufacturing method for manufacturing a lithium ion battery electrode according to claim 13,
A step of preparing the lithium ion battery electrode slurry according to any one of claims 7 to 12,
The step of preparing the lithium ion battery electrode slurry includes:
The weight average molecular weight (Mw) of the thickener is 2,000,000 or more, calculated in terms of pullulan using the GPC method, and the weight average of the thickening agent, calculated in terms of pullulan using the GPC method. A step of kneading a mixture containing an electrode active material, a binder resin and a thickening agent under conditions such that the ratio (Mw/Mn) of the molecular weight (Mw) to the number average molecular weight (Mn) is less than 6.0. A method for manufacturing an electrode for a lithium ion battery comprising: A lithium ion battery comprising the lithium ion battery electrode according to any one of claims 1 to 6 and 13.

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