CN111052459A - Method for producing aqueous electrode slurry for lithium ion battery, method for producing electrode for lithium ion battery, thickener powder for lithium ion battery, aqueous electrode slurry, electrode for lithium ion battery, and lithium ion battery - Google Patents
Method for producing aqueous electrode slurry for lithium ion battery, method for producing electrode for lithium ion battery, thickener powder for lithium ion battery, aqueous electrode slurry, electrode for lithium ion battery, and lithium ion battery Download PDFInfo
- Publication number
- CN111052459A CN111052459A CN201880053550.6A CN201880053550A CN111052459A CN 111052459 A CN111052459 A CN 111052459A CN 201880053550 A CN201880053550 A CN 201880053550A CN 111052459 A CN111052459 A CN 111052459A
- Authority
- CN
- China
- Prior art keywords
- aqueous
- lithium ion
- ion battery
- electrode
- thickener
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The method for producing an aqueous electrode slurry for a lithium ion battery according to the present invention is a method for producing an aqueous electrode slurry for a lithium ion battery, which comprises an electrode active material selected from a positive electrode active material and a negative electrode active material, an aqueous binder, a thickener, and an aqueous medium, and comprises the steps of: a screen passing part (q) for obtaining a thickener powder by screening a thickener powder containing a cellulose-based water-soluble polymer; and mixing the electrode active material, the aqueous binder, the sieve passage part (q), and the aqueous medium to prepare an aqueous electrode slurry.
Description
Technical Field
The present invention relates to a method for producing an aqueous electrode slurry for a lithium ion battery, a method for producing an electrode for a lithium ion battery, a thickener powder for a lithium ion battery, an aqueous electrode slurry, an electrode for a lithium ion battery, and a lithium ion battery.
Background
The electrode used in the lithium ion battery is generally mainly composed of an electrode active material layer and a current collector. The electrode active material layer is obtained by, for example, applying an aqueous electrode slurry containing an electrode active material, a thickener (thickener), an aqueous binder, and the like to the surface of a current collector such as a metal foil, and drying the applied aqueous electrode slurry.
Examples of a method for producing an electrode for a lithium ion battery include methods described in patent documents 1 and 2.
Patent document 1 (japanese unexamined patent application publication No. 2006-245051) describes a method for producing a positive electrode plate for a nonaqueous secondary battery, the method including: a step (a) of preparing an electrode material mixture coating material containing an electrode material mixture and a liquid component (E) in which a thickener (D) is dissolved, wherein the electrode material mixture contains an active material (A), a conductive material (B), a binder (C), and the thickener (D), the conductive material (B) is composed of at least a carbon material, the thickener (D) is composed of at least a water-soluble polymer, and the liquid component (E) is composed of at least water; and a step b of applying the mixture material coating to the current collector to prepare a mixture material coating, the step a including: a primary kneading step of kneading a mixture containing an active material A, a conductive material B, and a powdery thickener D together with a liquid component E to obtain a primary kneaded product; and a secondary kneading step of kneading the primary kneaded product, the binder C and the additional liquid component together to obtain a secondary kneaded product.
Patent document 2 (japanese unexamined patent application, first publication No. 2006-107896) discloses a method for manufacturing an electrode plate for a negative electrode of a nonaqueous secondary battery, which uses a paste obtained by kneading and dispersing a carbon material containing graphite as a main component, a thickener, and a binder, wherein the method for manufacturing an electrode plate for a negative electrode of a nonaqueous secondary battery comprises 3 steps of: a primary mixing step of adding a thickener at least in the form of powder to graphite and mixing the powder with a dispersion medium; diluting and uniformly mixing, namely diluting and uniformly mixing the uniformly mixed substance in the primary uniformly mixing process by using a dispersion medium; and a fine adjustment kneading step of adding a binder to the kneaded material in the dilution kneading step and kneading the mixture to form a paste, wherein the shearing force of kneading in the initial kneading step is 2.5 times or more as high as the shearing force of kneading in the dilution kneading step and the fine adjustment kneading step.
Documents of the prior art
Patent document
Patent document 1: JP 2006-245051A
Patent document 2: JP 2006-107896A
Disclosure of Invention
Problems to be solved by the invention
The present inventors have made studies to find out the following cases: the aqueous electrode slurry obtained by the production methods described in patent documents 1 and 2 has a variation in viscosity among batches, or has a viscosity that changes during storage, and thus has unstable quality. It was also found that aggregates and pinholes were likely to occur in the electrode produced using the aqueous electrode slurry having unstable quality.
Further, the inventors of the present invention have made studies to find out the following cases: in the preparation of the aqueous electrode slurry, the aqueous electrode slurry obtained by the method of adding the aqueous thickener solution in divided portions also has variations in viscosity among the batches, or the viscosity changes during storage, and the quality is unstable. Further, in such a method for producing an aqueous electrode slurry, since the thickener aqueous solution is separately prepared and added to the slurry in a divided manner, the production process is increased and the production time is long, which results in poor productivity.
The present invention has been made in view of the above circumstances, and provides an aqueous electrode slurry and a thickener powder for a lithium ion battery, which can stably and efficiently obtain an electrode for a lithium ion battery having an excellent appearance, and a lithium ion battery using the same.
Means for solving the problems
The present inventors repeated intensive studies to achieve the above object. As a result, they have found that an aqueous electrode slurry capable of stably obtaining an electrode for a lithium ion battery excellent in appearance with good productivity can be obtained by using a thickener powder that is sieved, and have completed the present invention.
According to the present invention, there is provided a method for producing an aqueous electrode slurry for a lithium ion battery, the aqueous electrode slurry for a lithium ion battery including an electrode active material selected from a positive electrode active material and a negative electrode active material, an aqueous binder, a thickener, and an aqueous medium, the method comprising the steps of: a screen passing part (q) for passing a thickener powder containing a cellulose-based water-soluble polymer through a screen to obtain the thickener powder; an aqueous electrode slurry is prepared by mixing an electrode active material, an aqueous binder, the sieve passage part (q), and an aqueous medium.
Further, according to the present invention, there is provided a method for manufacturing an electrode for a lithium ion battery, comprising the steps of: preparing an aqueous electrode paste by the above-mentioned method for producing an aqueous electrode paste for a lithium ion battery; and applying the obtained aqueous electrode slurry on a substrate, drying the aqueous electrode slurry, and removing the aqueous medium to form an electrode active material layer on the substrate.
Further, according to the present invention, there is provided a thickener powder for a lithium ion battery, which is used for thickening an aqueous electrode slurry for a lithium ion battery, contains a cellulose-based water-soluble polymer, and has a volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measuring method, wherein the maximum particle diameter of the thickener powder is represented by D100[μm]When the thickener powder is in D state through the mesh100(mum) D100A sieve having a particle size of +5(μm) or less for dividing the thickener powder into an oversize residual fraction and an oversize pass fraction, wherein the oversize residual fraction is 0.05 mass% or less when the total amount of the thickener powder is 100 mass%.
Further, according to the present invention, there is provided an aqueous electrode paste comprising: an electrode active material selected from a positive electrode active material and a negative electrode active material, an aqueous binder, the thickener powder for lithium ion batteries, and an aqueous medium, wherein the thickener powder for lithium ion batteries is dissolved in the aqueous medium.
Further, according to the present invention, there is provided an electrode for a lithium ion battery, comprising: an electrode active material selected from a positive electrode active material and a negative electrode active material; a water-based binder; and a binder comprising the thickener powder for lithium ion batteries.
Further, according to the present invention, there is provided a lithium ion battery comprising at least a positive electrode, an electrolyte and a negative electrode, wherein at least one of the positive electrode and the negative electrode comprises the electrode for lithium ion battery.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, it is possible to provide an aqueous electrode slurry and a thickener powder for a lithium ion battery, which can stably obtain an electrode for a lithium ion battery having excellent appearance with good productivity, an electrode for a lithium ion battery having excellent appearance, and a lithium ion battery using the electrode.
Drawings
The above objects, other objects, features and advantages will be further apparent from the following description of preferred embodiments and the accompanying drawings.
Fig. 1 is a cross-sectional view showing an example of the structure of an electrode for a lithium ion battery according to an embodiment of the present invention.
Fig. 2 is a cross-sectional view showing an example of the structure of the lithium ion battery according to the embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described below with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description thereof is omitted as appropriate. In the drawings, the respective constituent elements are schematically illustrated in shape, size, and arrangement to the extent that the present invention can be understood, and are different from actual dimensions.
In the present embodiment, "a to B" in the numerical range means a to B unless otherwise specified.
< method for producing aqueous electrode slurry for lithium ion Battery >
First, a method for producing an aqueous electrode slurry for a lithium ion battery according to the present embodiment will be described.
In the method for producing an aqueous electrode slurry according to the present embodiment, the aqueous electrode slurry for a lithium ion battery includes an electrode active material (a) selected from a positive electrode active material and a negative electrode active material, an aqueous binder (B), a thickener, and an aqueous medium (c), and the method for producing an aqueous electrode slurry for a lithium ion battery includes at least the following steps (a) and (B).
Step (A): a step of obtaining a screen passing part (q) of a thickener powder by screening the thickener powder containing the cellulose-based water-soluble polymer
A step (B): preparing an aqueous electrode slurry by mixing an electrode active material (a), an aqueous binder (b), a sieve-passing part (q), and an aqueous medium (c)
The present inventors have made studies to find out the following cases: the aqueous electrode slurry obtained by the production methods described in patent documents 1 and 2 has a variation in viscosity among batches, or has a viscosity that changes during storage, and thus has unstable quality. It was also found that in an electrode produced using such an aqueous electrode slurry having unstable quality, aggregates are likely to be generated.
Further, the inventors of the present invention have made studies to find out the following cases: in the preparation of the aqueous electrode slurry, the aqueous electrode slurry obtained by the method of adding the thickener aqueous solution in divided portions also has variations in viscosity among the batches, or the viscosity changes during storage, and the quality is unstable. Further, in such a method for producing an aqueous electrode slurry, since the thickener aqueous solution is separately prepared and added to the slurry in a divided manner, the production process is increased and the production time is long, which results in poor productivity.
That is, as is clear from the study of the inventors of the present invention, the conventional aqueous electrode slurry has room for improvement from the viewpoint of stably obtaining an electrode for a lithium ion battery excellent in appearance with good productivity.
The present inventors have conducted extensive studies to achieve the above object. As a result, it was found that when a conventional thickener powder containing a cellulose-based water-soluble polymer contains an insoluble component and a specific amount of the insoluble component is contained, the quality stability of the obtained aqueous electrode slurry is lowered.
In addition, in the method of adding the aqueous thickener solution in divided portions, since the aqueous thickener solution is also added after the thickening step, the quality stability of the aqueous electrode slurry is lowered.
The inventors of the present invention have further studied. As a result, it was found that when the sieve-passing portion (q) obtained by sieving the thickener powder containing the cellulose-based water-soluble polymer is used, an aqueous electrode slurry having excellent quality stability can be stably obtained. It has been found that when the aqueous electrode slurry thus obtained is used, the occurrence of aggregates can be suppressed, and an electrode for a lithium ion battery excellent in appearance can be stably obtained.
That is, by using the sieve-passing portion (q) obtained by sieving the thickener powder containing the cellulose-based water-soluble polymer, an aqueous electrode slurry having excellent quality stability can be stably obtained. By using such an aqueous electrode slurry, an electrode for a lithium ion battery having excellent appearance can be stably obtained.
In the method for producing an aqueous electrode slurry for a lithium ion battery according to the present embodiment, the maximum particle diameter of the sieve passage portion (q) in the volume-based particle size distribution measured by laser diffraction scattering particle size distribution measurement is D100[μm]At the time, the sieve passing part (q) is passed through the mesh at D100(mum) D100When the sieve passage portion (q) is subdivided into the oversize residual portion and the oversize passage portion by a sieve in the range of +5(μm) or less, the proportion of the oversize residual portion is preferably 0.05% by mass or less, more preferably 0.03% by mass or less, and still more preferably 0.01% by mass or less, assuming that the total amount of the sieve passage portion (q) is 100% by mass. The lower limit of the proportion of the residue on the sieve is not particularly limited, and is, for example, 0.00 massMore than the amount percent.
Maximum particle diameter D of the Sieve-passing portion (q)100For example, it can be measured using a particle size distribution measuring apparatus ("Mastersizer 2000 model name, manufactured by Malvern instruments"). The maximum particle diameter D100The term "particle diameter" means a particle diameter at which the cumulative volume percentage in a volume-based particle diameter distribution becomes 100%.
In the present embodiment, the ratio of the above-mentioned oversize residual fraction is an index derived from the amount of the fiber component of the cellulose-based water-soluble polymer contained in the oversize passing fraction (q). That is, it means that the smaller the proportion of the above-mentioned residue on the sieve, the smaller the amount of the fiber component derived from the cellulose-based water-soluble polymer contained in the sieve-passing portion (q).
In the step (a), the thickener powder containing the cellulose-based water-soluble polymer is sieved to obtain a sieve-passing portion (q) of the thickener powder.
The thickener powder containing a cellulose-based water-soluble polymer can be used by a known method, but various commercially available products can be used.
The sieve is not particularly limited, and the maximum particle diameter of the thickener powder before sieving in the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measuring method is represented by D100[μm]When D is a mesh, it is preferable to use100(mum) D100A sieve having a mesh size of D of 30(μm) or less is preferably used100(mum) D100A sieve having a mesh size of not more than +20(μm), more preferably D100(mum) D100A sieve having a mesh size of D of not more than +10(μm) is particularly preferably used100(mum) D100A sieve having a particle size of +5(μm) or less. This enables the fiber component derived from the cellulose-based water-soluble polymer contained in the thickener powder to be effectively removed, and the sieve-passing portion (q) of the thickener powder in which the proportion of the residue on the sieve is not more than the above upper limit can be efficiently obtained.
In the step (B), the electrode active material (a), the aqueous binder (B), the sieve passage portion (q), and the aqueous medium (c) are mixed to prepare an aqueous electrode slurry. In this case, the conductive assistant (d) may be mixed together.
The step (B) preferably includes the following steps (B-1) to (B-3). This enables to obtain an aqueous electrode slurry having excellent quality stability more stably.
Step (B-1): a step of preparing a mixture containing the electrode active material (a) and the sieve-passing portion (q) by dry-mixing the electrode active material (a) and the sieve-passing portion (q) in a powder state
Step (B-2): adding one or two liquid components selected from emulsion aqueous solutions containing an aqueous medium (c) and an aqueous binder (b) to the mixture, and wet-mixing the mixture to prepare a slurry precursor
Step (B-3): a step of preparing the aqueous electrode slurry by adding one or two liquid components selected from an aqueous emulsion solution containing an aqueous medium (c) and an aqueous binder (b) to the slurry precursor and wet-mixing the mixture
In the step (B-1), the electrode active material (a) and the sieve-passing portion (q) are dry-mixed in a powder state to prepare a mixture containing the powder of the electrode active material (a) and the sieve-passing portion (q). In this case, the mixed conductive additive (d) may be mixed together with the powder.
In the present embodiment, by performing the step (B-1), the dispersibility of the electrode active material (a) and the thickener can be improved, and the formation of a gel component derived from the thickener can be further suppressed in the subsequent step. This can suppress the generation of a gel component derived from the thickener in the obtained aqueous electrode slurry.
As is clear from the study of the present inventors, in an electrode for a lithium ion battery produced using an aqueous electrode slurry obtained by a production method including a step of dry-mixing an electrode active material and a thickener in a powder state, aggregates are likely to be generated.
The present inventors have conducted further intensive studies. As a result, it was found that the generation of aggregates on the electrode surface can be suppressed by using the sieve passage part (q) of the thickener powder according to the present embodiment, and an electrode for a lithium ion battery excellent in appearance can be stably obtained.
As the mixer for performing dry mixing, a planetary mixer is preferably used, and a planetary mixer is more preferably used. By using such a mixer, the electrode active material (a) and the sieve-passing portion (q) can be sufficiently mixed while suppressing scattering of the electrode active material (a) and the sieve-passing portion (q). The planetary agitator is an agitator having a rotation and revolution function as an agitation mechanism. The planetary motion type planetary mixer is a mixer having a paddle having rotation and revolution functions as a mixing mechanism.
In the step (B-2), one or two liquid components selected from an aqueous emulsion solution containing the aqueous medium (c) and the aqueous binder (B) are added to the mixture obtained in the step (B-1) and wet-mixed to prepare a slurry precursor.
The step (B-2) preferably comprises a fusion step (B-2-1) and a thickening step (B-2-2). The fusion step (B-2-1) is a step of fusing one or more liquid components selected from an aqueous emulsion solution containing the aqueous medium (c) and the aqueous binder (B) with the powder mixture. By including the fusing step (B-2-1), the powder mixture can be suppressed from being gradually pushed up at the edge of the mixer during wet mixing, from being biased to wet, from being scattered during mixing, and the like.
The thickening step (B-2-2) is a step of setting the wet mixing speed higher than that in the fusing step (B-2-1) and mixing the powder mixture and the liquid component to obtain a slurry precursor.
As the mixer for wet mixing in the step (B-2), a planetary mixer is preferably used, and a planetary mixer is more preferably used. By using such a mixer, it is possible to improve the dispersibility of each material while suppressing the scattering of each material constituting the aqueous electrode slurry.
The rotation speed of the wet mixing in the fusion step (B-2-1) is not particularly limited, but is preferably in the range of 0.10m/sec to 0.50 m/sec.
When the rotation speed of the wet mixing in the fusion step (B-2-1) is within the above range, the liquid component and the powder mixture can be sufficiently fused while the powder mixture is more effectively suppressed from being gradually pushed up at the edge of the mixer during the wet mixing, from being biased to be wet, from being scattered during the mixing, and the like.
The revolution speed of the wet mixing in the fusion step (B-2-1) is not particularly limited, but is preferably in the range of 0.01m/sec to 0.10 m/sec.
When the revolution speed of the wet mixing in the fusion step (B-2-1) is within the above range, the liquid component and the powder mixture can be sufficiently fused while the powder mixture is more effectively suppressed from being gradually pushed up at the edge of the mixer during the wet mixing, from being biased to be wet, from being scattered during the mixing, and the like.
The mixing time of the wet mixing in the fusion step (B-2-1) is not particularly limited, and is preferably, for example, 0.1 to 30 minutes.
The rotation speed of the wet mixing in the thickening step (B-2-2) is preferably in the range of 0.60m/sec to 10.00 m/sec.
When the rotation speed of the wet mixing in the thickening step (B-2-2) is within the above range, the shearing force applied to the slurry precursor can be further moderate, and therefore, the molecular chain of the thickener can be suppressed from being cut, the gel component derived from the thickener can be more easily broken, and the generation of the gel component derived from the thickener in the obtained aqueous electrode slurry can be further suppressed.
In addition, the revolution speed of the wet mixing in the thickening step (B-2-2) is preferably in the range of 0.20m/sec to 3.00 m/sec.
When the revolution speed of the wet mixing in the thickening step (B-2-2) is within the above range, the shearing force applied to the slurry precursor can be made more moderate, so that the molecular chain of the thickener can be suppressed from being cut, the gel component derived from the thickener can be more easily broken, and the generation of the gel component derived from the thickener in the obtained aqueous electrode slurry can be further suppressed.
The mixing time of the wet mixing in the thickening step (B-2-2) is not particularly limited, and is, for example, 10 minutes to 180 minutes.
In the step (B-2), the solid content concentration of the slurry precursor is preferably adjusted to 30.0 mass% or more and 70.0 mass% or less. This makes it possible to suppress the cleavage of the molecular chain of the thickener and improve the dispersibility of each material, since the shearing force applied to the slurry precursor can be made more moderate.
The solid content concentration of the slurry precursor can be adjusted by adjusting the concentration and the addition amount of the liquid component.
In the step (B-3), one or two liquid components selected from an aqueous emulsion solution containing an aqueous medium (c) and an aqueous binder (B) are further added to the slurry precursor obtained in the step (B-2) and wet-mixed to prepare the aqueous electrode slurry.
As the mixer for performing wet mixing, a planetary mixer is preferably used, and a planetary mixer is more preferably used. By using such a mixer, sufficient mixing can be performed while stirring at a low speed. Therefore, the dispersibility of each material constituting the aqueous electrode slurry can be improved while suppressing the blocking of the molecular chain of the thickener by the stirring and mixing and the aggregation of the aqueous binders (b). As a result, an aqueous electrode slurry having further excellent quality stability can be obtained.
In addition, since the dispersibility of the obtained aqueous electrode slurry is further excellent, a further uniform electrode active material layer can be obtained by using such an aqueous electrode slurry. As a result, a lithium ion battery having further excellent battery characteristics can be obtained.
In the present embodiment, at least one of the rotation speed and the revolution speed of the wet mixing in the step (B-3), preferably both the rotation speed and the revolution speed, is preferably set to be lower than the rotation speed of the wet mixing in the thickening step (B-2-2). This can further suppress aggregation of the aqueous binders (b) due to stirring and mixing, and can improve the dispersibility of each material constituting the aqueous electrode slurry.
The mixing time of the wet mixing in the step (B-3) is not particularly limited, and is, for example, 5 minutes to 60 minutes.
The solid content concentration of the aqueous electrode slurry can be adjusted by adjusting the concentration and the addition amount of the liquid component.
The method for producing an aqueous electrode paste according to the present embodiment may further include the step (C): and (5) performing vacuum defoaming. Therefore, air bubbles involved in the slurry can be removed, and the smearing property of the slurry can be improved.
The vacuum defoaming may be performed by sealing the container or the shaft portion of the mixer to remove bubbles, or may be performed after transferring to another container.
< thickener powder (p) for lithium ion batteries >
The thickener powder (p) for a lithium ion battery according to the present embodiment is a thickener powder used for thickening an aqueous electrode slurry for a lithium ion battery, and comprises a cellulose-based water-soluble polymer, and the maximum particle diameter of the thickener powder (p) in a volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measurement method is represented by D100[μm]At the time, the thickener powder (p) is placed in D by passing through the mesh100(mum) D100The screen of +5(μm) or less separates the thickener powder (p) into an oversize residual fraction and an oversize pass fraction, and the proportion of the oversize residual fraction is 0.05 mass% or less, preferably 0.03 mass% or less, and more preferably 0.01 mass% or less, when the total amount of the thickener powder (p) is 100 mass%. The lower limit of the proportion of the residue on the sieve is not particularly limited, and is, for example, 0.00 mass% or more.
Maximum particle diameter D of thickener powder (p)100For example, the particle size distribution can be measured by using a particle size distribution measuring apparatus (model name: Mastersizer2000, manufactured by Malvern instruments Co., Ltd.). The maximum particle diameter D100Is meant to be in volumeThe cumulative (cumulative) volume percentage in the standard particle size distribution is 100% of the particle size.
In the present embodiment, the proportion of the above-mentioned oversize residue is an index of the amount of the fiber component derived from the cellulose-based water-soluble polymer contained in the thickener powder (p). That is, the smaller the proportion of the above-mentioned oversize residue, the smaller the proportion of the fibrous component derived from the cellulose-based water-soluble polymer contained in the thickener powder (p).
The present inventors have made studies to find out the following cases: the aqueous electrode slurry obtained by the production methods described in patent documents 1 and 2 has a variation in viscosity among batches, or has a viscosity that changes during storage, and thus has unstable quality. In addition, aggregates are likely to be generated in an electrode manufactured using such an aqueous electrode slurry having unstable quality.
Further, the inventors of the present invention have studied the following cases: in the preparation of the aqueous electrode slurry, the aqueous electrode slurry obtained by the method of adding the thickener aqueous solution in divided portions also has variations in viscosity among the respective batches, or the viscosity changes during storage, and the quality is unstable. Further, in such a method for producing an aqueous electrode slurry, since the thickener aqueous solution is separately prepared and added to the slurry in a divided manner, the production process is increased and the production time is long, which results in poor productivity.
That is, as is clear from the study of the inventors of the present invention, the conventional aqueous electrode slurry has room for improvement from the viewpoint of stably and efficiently obtaining an electrode for a lithium ion battery excellent in appearance.
The present inventors repeated intensive studies to achieve the above object. As a result, it was found that when a thickener powder containing a conventional cellulose-based water-soluble polymer contains a water-insoluble component and a specific amount of the water-insoluble component is contained, the quality stability of the obtained aqueous electrode slurry is lowered.
In addition, in the method of adding the aqueous thickener solution in divided portions, since the aqueous thickener solution is also added after the thickening step, the quality stability of the aqueous electrode slurry is lowered.
Therefore, the present inventors have conducted further intensive studies. As a result, it has been found that when the thickener powder (p) having a proportion of the on-screen residue of not more than the upper limit is used, an aqueous electrode slurry having excellent quality stability can be stably obtained. It has been found that when the aqueous electrode slurry thus obtained is used, the occurrence of aggregates and pinholes can be suppressed, and an electrode for a lithium ion battery excellent in appearance can be stably obtained.
That is, by using the thickener powder (p) having the ratio of the on-screen residue portion of not more than the upper limit value, an aqueous electrode slurry having excellent quality stability can be stably obtained. By using such an aqueous electrode slurry, an electrode for a lithium ion battery having excellent appearance can be stably obtained.
The thickener powder (p) preferably contains a cellulose-based water-soluble polymer as a main component. Here, the term "containing a cellulose-based water-soluble polymer as a main component" means that the thickener powder (p) contains 50 mass% or more of a cellulose-based water-soluble polymer. The thickener powder (p) preferably contains 70 mass% or more of a cellulose-based water-soluble polymer, more preferably 90 mass% or more of a cellulose-based water-soluble polymer, and particularly preferably 99 mass% or more of a cellulose-based water-soluble polymer.
The cellulose-based water-soluble polymer is not particularly limited as long as the spreadability of the aqueous electrode paste is improved. As the cellulose-based water-soluble polymer, for example, one or more selected from cellulose-based polymers such as carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, methylethyl hydroxy cellulose, methyl cellulose, and hydroxypropyl cellulose, and cellulose-based polymer salts such as ammonium salts and alkali metal salts of these cellulose-based polymers can be used.
Among them, at least one selected from carboxymethyl cellulose and carboxymethyl cellulose salt is preferably contained, and more preferably, one or more selected from carboxymethyl cellulose, ammonium salt of carboxymethyl cellulose, sodium salt of carboxymethyl cellulose, and potassium salt of carboxymethyl cellulose is contained.
In the thickener powder (p) for a lithium ion battery according to the present embodiment, the oversize residue is not particularly limited, and includes, for example, a fiber component derived from the cellulose-based water-soluble polymer.
In the thickener powder (p) for a lithium ion battery according to the present embodiment, the viscosity calculated under the following condition 1 is preferably 10mPa · s or more and 20000mPa · s or less, more preferably 100mPa · s or more and 10000mPa · s or less, further preferably 1000mPa · s or more and 8000mPa · s or less, and particularly preferably 2000mPa · s or more and 4000mPa · s or less.
Condition 1: the thickener powder (p) was dissolved in water to obtain a thickener aqueous solution having a concentration of 1.3 mass%. Then, using a type B viscometer, the shear rate was 3.4s at 25 ℃-1The viscosity of the aqueous thickener solution was measured under the conditions of (1).
This can further improve the spreadability of the resulting aqueous electrode paste.
< method for producing thickener powder (p) >
Next, a method for producing the thickener powder (p) for a lithium ion battery according to the present embodiment will be described.
The thickener powder (p) according to the present embodiment can be obtained by, for example, sieving a thickener powder containing a cellulose-based water-soluble polymer. However, the method for producing the thickener powder (p) for lithium ion batteries according to the present embodiment is not limited to the method of sieving.
Here, since the step of sieving the thickener powder containing the cellulose-based water-soluble polymer can be performed following the step (a) in the above-described method for producing an aqueous electrode slurry for a lithium ion battery, the description thereof is omitted here.
< aqueous electrode slurry >
Next, the aqueous electrode paste according to the present embodiment will be described.
The aqueous electrode slurry according to the present embodiment includes an electrode active material (a) selected from a positive electrode active material and a negative electrode active material, an aqueous binder (b), the thickener powder (p) for a lithium ion battery according to the present embodiment, and an aqueous medium (c), and the thickener powder (p) for a lithium ion battery is dissolved in the aqueous medium (c). The aqueous electrode paste according to the present embodiment preferably further contains a conductive assistant (d) in order to improve the electron conductivity of the resulting electrode.
Here, in the aqueous electrode slurry according to the present embodiment, the thickener powder (p) for a lithium ion battery is dissolved in the aqueous electrode slurry, and is not in a powder state.
(electrode active Material (a))
The electrode active material (a) according to the present embodiment is appropriately selected depending on the application. The positive electrode active material is used for producing the positive electrode, and the negative electrode active material is used for producing the negative electrode.
The positive electrode active material is not particularly limited as long as it is a general positive electrode active material that can be used for a positive electrode of a lithium ion battery. Examples thereof include composite oxides of lithium and transition metals such as lithium nickel composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, and lithium-manganese-nickel composite oxide; TiS2、FeS、MoS2Isotransition metal sulfides; MnO and V2O5、V6O13、TiO2And transition metal oxides, olivine-type lithium phosphorus oxides, and the like.
The olivine-type lithium phosphorus oxide contains, for example, at least one element selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe, lithium, phosphorus, and oxygen. Some elements may be partially substituted with other elements in order to improve their properties.
Among them, olivine-type lithium iron phosphorus oxide, lithium cobalt composite oxide, lithium nickel composite oxide, lithium manganese composite oxide, and lithium-manganese-nickel composite oxide are preferable. These positive electrode active materials have a high action potential, a large capacity, and a large energy density.
The positive electrode active material may be used alone in 1 kind, or may be used in combination with 2 or more kinds.
The negative electrode active material is not particularly limited as long as it is a general negative electrode active material that can be used in a negative electrode of a lithium ion battery. Examples of the carbon material include natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; lithium metals such as lithium metal and lithium alloys; metals such as silicon and tin; and conductive polymers such as polyacene, polyacetylene, and polypyrrole. Among them, carbon materials are preferable, and graphite materials such as natural graphite and artificial graphite are particularly preferable.
The negative electrode active material may be used alone in 1 kind, or may be used in combination with 2 or more kinds.
When the total solid content of the aqueous electrode slurry is 100 parts by mass, the content of the electrode active material (a) is preferably 70 parts by mass or more and 99.97 parts by mass or less, and more preferably 85 parts by mass or more and 99.85 parts by mass or less.
(Water-based adhesive (b))
The aqueous binder (b) is not particularly limited as long as it can be used for electrode molding and has sufficient electrochemical stability, and examples thereof include polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, and polyimide. These water-based binders (b) may be used alone or in combination of two or more. Of these, styrene butadiene rubber is preferred.
In the present embodiment, the aqueous binder (b) is a mixture which can be dispersed in an aqueous medium to form an emulsion aqueous solution.
When the total solid content of the aqueous electrode slurry is 100 parts by mass, the content of the aqueous binder (b) is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass. When the content of the aqueous binder (b) is within the above range, the balance of the spreadability of the aqueous electrode paste, the adhesive property of the binder, and the battery characteristics is further improved.
The aqueous binder (b) is used as an emulsion aqueous solution by dispersing a powdery substance in an aqueous medium. This can improve the dispersibility of the aqueous binder (b) without inhibiting the contact between the electrode active materials (a), between the conductive additives (d), or between the electrode active materials (a) and the conductive additives (d).
The aqueous medium in which the aqueous binder (b) is dispersed is not particularly limited as long as the aqueous binder (b) can be dispersed, and distilled water, ion-exchanged water, tap water, industrial water, and the like can be used. Among these, distilled water and ion-exchanged water are preferable. In addition, a solvent having high hydrophilicity with water, such as alcohol, may be mixed with water.
(thickener powder (p))
As the thickener powder (p), the thickener powder (p) according to the present embodiment can be used.
The thickener powder (p) may be used alone in 1 kind, or may be used in combination of 2 or more kinds. When the total solid content of the aqueous electrode slurry is 100 parts by mass, the content of the thickener powder (p) is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass. When the content of the thickener powder (p) is within the above range, the balance of the spreadability of the aqueous electrode slurry, the adhesive property of the binder, and the battery characteristics is more excellent.
(aqueous medium (c))
The aqueous medium (c) according to the present embodiment is not particularly limited, and for example, distilled water, ion-exchanged water, tap water, industrial water, or the like can be used. Among these, distilled water and ion-exchanged water are preferable. In addition, a solvent having high hydrophilicity with water, such as alcohol, may be mixed with water.
(conductive auxiliary (d))
The aqueous electrode paste according to the present embodiment preferably further contains a conductive assistant (d) from the viewpoint of improving the electron conductivity of the resulting electrode.
The conductive aid (d) has electron conductivity, and is not particularly limited as long as the conductivity of the electrode is improved. Examples of the conductive aid (d) according to the present embodiment include carbon materials such as acetylene black, ketjen black, carbon nanofibers, and graphite having a particle diameter smaller than that of graphite used as an active material. These conductive aids (d) may be used alone in 1 kind, or may be used in combination of 2 or more kinds.
The content of the conductive additive (d) is preferably 0.01 mass part or more and 10.0 mass part or less, and more preferably 0.05 mass part or more and 5.0 mass part or less, with the total amount of the solid content of the aqueous electrode slurry being 100 mass parts.
When the content of the conductive additive (d) is within the above range, the balance between the spreadability of the aqueous electrode paste and the adhesiveness of the binder is further improved.
When the total solid content of the aqueous electrode slurry is 100 parts by mass, the content of the electrode active material (a) in the aqueous electrode slurry of the present embodiment is preferably 70 parts by mass or more and 99.97 parts by mass or less, and more preferably 85 parts by mass or more and 99.85 parts by mass or less. The content of the aqueous binder (b) 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 powder (p) is preferably 0.01 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass. The content of the conductive auxiliary (d) is preferably 0.01 mass part or more and 10.0 mass part or less, and more preferably 0.05 mass part or more and 5.0 mass part or less.
When the content of each component constituting the aqueous electrode slurry is within the above range, the balance between the quality stability of the aqueous electrode slurry and the battery characteristics of the obtained lithium ion battery is particularly excellent.
< electrode for lithium ion Battery >
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 present invention. The lithium ion battery electrode 100 according to the present embodiment includes an electrode active material (a) selected from a positive electrode active material and a negative electrode active material, an aqueous binder (b), and a binder composed of a lithium ion battery thickener powder (p).
< method for producing electrode for lithium ion Battery >
Next, a method for manufacturing the lithium ion battery electrode 100 according to the present embodiment will be described.
The method for manufacturing the lithium ion battery electrode 100 according to the present embodiment includes at least the following 2 steps (1) and (2). This enables to stably obtain an electrode for a lithium ion battery excellent in appearance.
(1) A step of preparing an aqueous electrode slurry by the method for producing an aqueous electrode slurry for a lithium ion battery according to the present embodiment
(2) A step of applying the obtained aqueous electrode slurry to the substrate 101, drying the resultant, and removing the aqueous medium to form the electrode active material layer 103 on the substrate 101
The step (1) is the same as the method for producing the aqueous electrode slurry for a lithium ion battery according to the present embodiment, and therefore, the description thereof is omitted here. The step (2) is explained below.
(2) In the step of forming the electrode active material layer, for example, the aqueous electrode slurry obtained in the step (1) is applied onto a substrate 101 such as a current collector and dried to remove the aqueous medium, thereby forming the electrode active material layer 103 on the substrate 101, and obtaining the electrode 100 for a lithium ion battery in which the electrode active material layer 103 is formed on the substrate 101.
A generally known method can be used for applying the aqueous electrode paste to the substrate 101. Examples thereof include a reverse roll method, a direct roll coating method, a doctor blade method, a knife edge method, an extrusion method, a curtain coating method, a gravure method, a bar coating method, a dipping method, and an extrusion method.
The aqueous electrode slurry may be applied to only one surface of the substrate 101, or may be applied to both surfaces. When the coating is applied to both surfaces of the substrate 101, the coating may be sequentially applied to one surface and one surface, or may be applied to both surfaces simultaneously. In addition, coating may be performed continuously or intermittently on the surface of the substrate 101. The thickness, length, and width of the coating layer can be appropriately determined according to the size of the battery.
A generally known method can be used for drying the applied aqueous electrode slurry. For example, heat sealing, vacuum, infrared rays, far infrared rays, electron rays, and low temperature wind can be used alone or in combination. The drying temperature is, for example, in the range of 30 ℃ to 350 ℃.
As the substrate 101 used for manufacturing the electrode 100 for a lithium ion battery according to the present embodiment, for example, a general current collector that can be used in a lithium ion battery can be used.
As the negative electrode current collector, copper, stainless steel, nickel, titanium, or an alloy thereof can be used, and among these, copper is particularly preferable.
As the positive electrode current collector, aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used, and among these, aluminum is particularly preferable.
The shape of the current collector is not particularly limited, and for example, a foil-like current collector can be used within a thickness range of 0.001 to 0.5 mm.
The lithium ion battery electrode 100 according to the present embodiment may be pressed as needed. As a method of pressing, a generally known method can be used. Examples thereof include a metal mold pressing method and a calender pressing method (calandar pressing method). The pressing pressure is not particularly limited, and is, for example, 0.2 to 3t/cm2The range of (1).
The thickness and density of the lithium ion battery electrode 100 according to the present embodiment are not particularly limited, and may be appropriately determined according to the use application of the battery, and may be set in accordance with generally known information.
< lithium ion Battery >
Next, the lithium ion battery 150 according to the present embodiment will be described. Fig. 2 is a cross-sectional view showing an example of the structure of a lithium ion battery 150 according to an embodiment of the present invention.
The lithium ion battery 150 according to the present embodiment includes at least the positive electrode 120, the electrolyte 110, and the negative electrode 130, and at least one of the positive electrode 120 and the negative electrode 130 includes the electrode 100 for a lithium ion battery according to the present embodiment. The lithium ion battery 150 according to the present embodiment may include a spacer as necessary.
The lithium ion battery 150 according to the present embodiment can be manufactured by a known method.
For example, a laminate or a roll can be used as the electrode. As the outer package, a metal outer package or an aluminum laminate outer package can be suitably used. The shape of the battery may be any shape such as coin type, button type, sheet type, cylinder type, square type, flat type, etc.
As an electrolyte in the electrolytic solution of the battery, any known lithium salt can be used, and it may be selected depending on the kind of the active material. For example, LiClO can be mentioned4、LiBF6、LiPF6、LiCF3SO3、LiCF3CO2、LiAsF6、LiSbF6、LiB10Cl10、LiAlCl4、LiCl、LiBr、LiB(C2H5)4、CF3SO3Li、CH3SO3Li、LiCF3SO3、LiC4F9SO3、Li(CF3SO2)2N, lithium lower fatty acid carboxylate, and the like.
The solvent that dissolves the electrolyte is not particularly limited as long as it is a solvent that is generally used as a liquid component for dissolving the electrolyte, and examples thereof include carbonates such as Ethylene Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), and Vinylene Carbonate (VC); lactones such as γ -butyrolactone and γ -valerolactone; ethers such as trimethoxymethane, 1, 2-trimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxolanyls such as 1, 3-dioxolane and 4-methyl-1, 3-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; phosphoric acid triesters, diethylene glycol dimethyl ethers; triethylene glycol dimethyl ethers; sulfolanes such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1, 3-propane sultone, 1, 4-butane sultone, and naphthalene sultone. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds.
Examples of the spacer include a porous spacer. Examples of the form of the spacer include a film, and a nonwoven fabric.
Examples of the porous separator include polyolefin porous separators such as polypropylene-based and polyethylene-based separators; a porous spacer formed of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene copolymer, or the like.
While the embodiments of the present invention have been described above, these are merely illustrative of the present invention, and various configurations other than the above-described configurations can be adopted.
The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within a range that can achieve the object of the present invention are included in the present invention.
Examples
The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.
(example 1)
< preparation of Sieve passing portion (q) >
First, an input device for making MAC series and maximum particle diameter D of carboxymethyl cellulose powder ("japanese system" サンロ - ズ "(registered trademark)100: 50 μm) was passed through a sieve having a mesh opening of 53 μm (manufactured by アズワン, material: stainless steel, trade name: "ステンレスふゐい"), resulting in a sieve pass fraction (q 1).
< preparation of aqueous electrode slurry >
(1) Step (B-1)
960g of graphite as a negative electrode active material, 10g of the above-obtained carboxymethyl cellulose powder sieve-passing portion (q1), and 10g of carbon black as a conductive aid were charged into a planetary motion type planetary mixer.
Then, the mixture was dry-mixed at 20 ℃ for 60 minutes to obtain a powder mixture.
(2) Fusing procedure (B-2-1)
Next, water was added to the planetary mixer having completed the step (B-1). Then, at the rotation speed: 0.15m/sec, revolution speed: 0.04m/sec, temperature: wet mixing was carried out at 20 ℃ for 2 minutes to fuse water with the powder mixture.
(3) Thick mixing process (B-2-2)
Then, at the rotation speed: 4.50m/sec, revolution speed: 1.50m/sec, temperature: wet mixing was performed at 20 ℃ for 40 minutes to obtain a slurry precursor.
(4) Step (B-3)
Next, an aqueous solution of Styrene Butadiene Rubber (SBR) having a solid content concentration of 40 mass% in which SBR was dispersed in water was prepared. 50g of the obtained SBR aqueous solution was added to the planetary mixer after completion of the thickening step (B-2-2).
Then, at the rotation speed: 0.25m/sec, revolution speed: 0.08m/sec, temperature: wet mixing was carried out at 20 ℃ for 10 minutes.
(5) Process (C)
Then, vacuum defoaming was performed to obtain an aqueous electrode paste.
The solid content concentration of the aqueous electrode slurry was adjusted to 50% by mass by adjusting the amount of water added in the blending step (B-2-1).
< preparation of negative electrode >
The obtained aqueous electrode slurry was applied to one surface of a copper foil as a current collector using a die coater, and dried. The resulting electrode was then pressed to obtain a negative electrode.
< evaluation >
(measurement of the proportion of the residue on the Screen)
The sieve-passing portion (q1) (largest particle diameter D) obtained above was subjected to100: 50 μm) was passed through a sieve having a mesh opening of 53 μm (manufactured by アズワン, material: stainless steel, trade name: "ステンレスふゐい"), the sieve-passing fraction (q1) is again divided into an oversize residue fraction and a sieve-passing fraction. Next, the mass x (g) of the oversize remaining on the screen without passing through the screen was measured, and the proportion of the oversize remaining in the screen passing portion (q1) was calculated by the following equation.
The ratio (% by mass) of the residue on the sieve was 100 Xx/y
Here, y in the formula is the mass (g) of the sieved passing portion (q1) of the sieved carboxymethylcellulose powder.
(evaluation of storage stability of thickener aqueous solution)
The sieve-passing portion (q1) of the carboxymethyl cellulose powder was dissolved in water at 25 ℃ for 10 minutes at 200rpm to obtain a 1.3 mass% aqueous solution of the thickener. Using a type B viscometer at 25 ℃ and a shear rate of 3.4s-1The viscosity of the aqueous thickener solution was measured under the conditions (1), and the viscosity was 3000 mPas.
Then, 100g of the obtained thickener aqueous solution was put into a plastic container with a lid, and the container was kept at 25 ℃ for 3 days in a state where the lid was closed.
Next, the viscosity of the thickener aqueous solution after 3 days holding was measured at 25 ℃ and a shear rate of 3.4s using a B-type viscometer-1Viscosity of (b). Then, the viscosity change rate was calculated by the following formula, and the storage stability of the thickener aqueous solution was evaluated based on the following criteria.
Viscosity change rate [% ] × (viscosity after 3 days hold)/(viscosity before 3 days hold)
◎ the viscosity change rate is more than 80% and less than 120%
○ the viscosity change rate is more than 120% and less than 150%, or more than 50% and less than 80%
X: the viscosity change rate is more than 150 percent, or more than 10 percent and less than 50 percent
(evaluation of storage stability of aqueous electrode paste)
100g of the obtained aqueous electrode paste was put into a plastic container with a lid, and the container was kept at 25 ℃ for 3 days with the lid closed.
Next, the aqueous electrode slurry before and after the retention was measured at 25 ℃ and a shear rate of 3.4s using a B-type viscometer-1Viscosity of (b). Then, the viscosity change rate was calculated by the following formula, and the storage stability of the aqueous electrode slurry was evaluated based on the following criteria.
Viscosity change rate [% ] × (viscosity after 3 days hold)/(viscosity before 3 days hold)
◎ the viscosity change rate is more than 80% and less than 120%
○ the viscosity change rate is more than 120% and less than 150%, or more than 50% and less than 80%
△ the viscosity change rate is more than 150% or less than 10% and more than 50%
X: the aqueous electrode slurry was separated by the above retention test (judged by visual observation)
The results obtained are shown in table 1.
(evaluation of viscosity deviation of aqueous electrode slurry)
The viscosity variation of the aqueous electrode slurry was evaluated as follows. First, 5 aqueous electrode slurries under the same conditions were prepared as samples. Next, the obtained aqueous electrode slurry was measured at 25 ℃ and a shear rate of 3.4s using a B-type viscometer-1The maximum deviation amount was calculated from the following formula, and the deviation of the aqueous electrode slurry per batch was evaluated based on the following criteria.
Maximum deviation (mPa · s) — (maximum viscosity in 5 samples) - (minimum viscosity in 5 samples)
◎ maximum deviation less than 500 mPas
○ maximum deviation of 500 mPas or more and less than 1000 mPas
X: maximum deviation amount of 1000 mPas or more
(evaluation of percent of pass of negative electrode)
A total of 1500 negative electrodes (1 cm. times.1 cm) were produced, and the percentage of acceptable products (acceptable rate) was calculated.
The obtained surface of the negative electrode was observed with an optical microscope at a magnification of 100 times, and the presence or absence of aggregates and pinholes on the surface of the negative electrode was examined. Next, the product was judged as a good product in which no aggregate or pin hole was observed, and the product was judged as a defective product in which at least 1 site of aggregate or pin hole was observed. Next, the percentage of non-defective products was calculated as a non-defective product rate, and evaluated on the following criteria.
◎ high qualified rate (above 98%)
○ percent, the qualified product rate is more than 95 percent and less than 98 percent
X: the qualified product rate is less than 95 percent
(evaluation of productivity of negative electrode)
The productivity of the negative electrode was evaluated according to the following criteria. In each of examples and comparative examples, since the steps after obtaining the aqueous electrode slurry were the same, the productivity of the negative electrode was evaluated based on the time taken until obtaining the aqueous electrode slurry (hereinafter, referred to as the production time of the aqueous electrode slurry). In the evaluation criteria below, the production time of the aqueous electrode slurry in comparative example 2 was set to 100.
◎ aqueous electrode paste production time less than 70
○ aqueous electrode slurry production time is more than 70 and less than 100
X: the time for preparing the aqueous electrode slurry is more than 100
(example 2)
In the production of the sieve passage part (q), an aqueous electrode slurry and a negative electrode were produced under the same conditions as in example 1 except that a sieve having a mesh size of 63 μm (manufactured by アズワン ", stainless steel, trade name:" ステンレスふゐい ") was used instead of the sieve having a mesh size of 53 μm (manufactured by アズワン", manufactured by stainless steel, trade name: "ステンレスふゐい"), and the respective evaluations were carried out in the same manner as in example 1. The results obtained are shown in table 1.
(example 3)
In the preparation of the sieve passage part (q), an aqueous electrode slurry and a negative electrode were prepared under the same conditions as in example 1 except that a sieve having a mesh size of 73 μm (manufactured by アズワン corporation, manufactured by アズワン), a stainless steel, and a trade name: "ステンレスふゐい", were used instead of the sieve having a mesh size of 53 μm (manufactured by アズワン ", stainless steel, and trade name:" ステンレスふゐい "), and the respective evaluations were performed in the same manner as in example 1. The results obtained are shown in table 1.
Comparative example 1
Instead of using the sieve-passing portion (q1) of carboxymethyl cellulose powder, carboxymethyl cellulose powder ("MAC series manufactured by" サンロ — ズ "(registered trademark)) was used as it is without sieving, and an aqueous electrode slurry and a negative electrode were prepared under the same conditions as in example 1, and evaluations were performed in the same manner as in example 1. The results obtained are shown in table 1.
Here, the ratio of the on-sieve residue of comparative example 1 in table 1 was determined by the following method.
First, carboxymethyl cellulose powder ("MAC series manufactured by japan" company "サンロ - ズ" (registered trademark)) was passed through a 53 μm mesh sieve ("アズワン" company "manufactured by material: stainless steel, trade name:" ステンレスふゐい "). Next, the mass x' (g) of the oversize remaining on the sieve without passing through the sieve was measured, and the proportion of the oversize remaining in the carboxymethylcellulose powder was calculated by the following formula.
The proportion (mass%) of the residue on the sieve was 100 × x '/y'
Here, y' in the formula is the mass (g) of the sieved carboxymethylcellulose powder.
Comparative example 2
< preparation of thickener aqueous solution B >
First, carboxymethyl cellulose powder ("MAC series manufactured by japanese corporation" サンロ - ズ "(registered trademark)) is dissolved in ion-exchanged water at 20 ℃. The resulting thickener aqueous solution was filtered through a filter having an average pore diameter of 1 μm to obtain a thickener aqueous solution B.
< preparation of aqueous electrode slurry >
(1) Step 1
960g of graphite as a negative electrode active material and 10g of carbon black as a conductive auxiliary agent were charged into a planetary motion type planetary mixer.
Then, the mixture was dry-mixed at 20 ℃ for 60 minutes to obtain a powder mixture.
(2) Step 2
Next, water and the thickener aqueous solution B were added to the planetary mixer having completed the step 1. Then, at the rotation speed: 0.15m/sec, revolution speed: 0.04m/sec, temperature: wet mixing was carried out at 20 ℃ for 2 minutes to fuse water with the powder mixture.
(3) Step 3
Next, water and the thickener aqueous solution B were added to the planetary mixer having completed the step 2. Next, at the rotation speed: 4.50m/sec, revolution speed: 1.50m/sec, temperature: wet mixing was performed at 20 ℃ for 40 minutes to obtain a slurry precursor.
(4) Step 4
Next, an aqueous solution of Styrene Butadiene Rubber (SBR) having a solid content concentration of 40 mass% in which SBR was dispersed in water was prepared. The obtained SBR aqueous solution 50g and thickener aqueous solution B were added to the planetary mixer having finished step 3. The total amount of the thickener powder contained in the thickener aqueous solution B used in the steps 2 to 4 was 10 g.
Then, at the rotation speed: 0.25m/sec, revolution speed: 0.08m/sec, temperature: wet mixing was carried out at 20 ℃ for 10 minutes.
(5) Step 5
Then, vacuum defoaming was performed to obtain an aqueous electrode paste.
The solid content concentration of the aqueous electrode slurry was adjusted to 50% by mass by adjusting the amount of water added in each step.
< preparation of negative electrode >
The obtained aqueous electrode slurry was applied to one surface of a copper foil as a current collector using a die coater, and dried. The obtained negative electrode is then pressed to obtain a negative electrode.
The obtained thickener aqueous solution, aqueous electrode slurry and negative electrode were evaluated in the same manner as in example 1. The results obtained are shown in table 1.
Comparative example 3
An aqueous electrode slurry and a negative electrode were prepared in the same manner as in comparative example 2 except that the thickener aqueous solution a was used instead of the thickener aqueous solution B, and each evaluation was performed in the same manner as in example 1. The results obtained are shown in table 1.
[ Table 1]
TABLE 1
The present application claims priority based on japanese application laid-open at 2017, 9/1, the disclosure of which is incorporated herein in its entirety.
Claims (12)
1. A method for producing an aqueous electrode slurry for a lithium ion battery, the aqueous electrode slurry for a lithium ion battery comprising an electrode active material selected from a positive electrode active material and a negative electrode active material, an aqueous binder, a thickener, and an aqueous medium,
the method for producing an aqueous electrode slurry for a lithium ion battery is characterized by comprising the following steps:
a sieving part (q) for obtaining a thickener powder by sieving the thickener powder containing a cellulose-based water-soluble polymer; and
an aqueous electrode slurry is prepared by mixing an electrode active material, an aqueous binder, the sieve passage part (q), and an aqueous medium.
2. The method for producing an aqueous electrode slurry for a lithium ion battery according to claim 1,
the maximum particle diameter of the sieve-passing part (q) in the volume-based particle size distribution measured by laser diffraction scattering particle size distribution measurement is D100[μm]When the temperature of the water is higher than the set temperature,
passing the sieve-passing portion (q) through a mesh at D100(mum) or more and D100And a sieve in the range of +5(μm) or less, wherein the sieve-passing portion (q) is further divided into an oversize residual portion and an oversize passing portion, and the proportion of the oversize residual portion is 0.05 mass% or less when the total amount of the sieve-passing portion (q) is 100 mass%.
3. The method for producing an aqueous electrode slurry for a lithium ion battery according to claim 1 or 2,
the step of preparing the aqueous electrode slurry includes the steps of:
the electrode active material and the sieve-passing portion (q) are dry-mixed in a powder state to prepare a mixture containing the electrode active material and the sieve-passing portion (q).
4. The method for producing an aqueous electrode slurry for a lithium ion battery according to claim 3,
the step of preparing the aqueous electrode slurry further comprises the steps of:
adding one or two liquid components selected from an emulsion aqueous solution containing the aqueous medium and the aqueous binder to the mixture containing the electrode active material and the sieve passage portion (q) and wet-mixing the mixture to prepare a slurry precursor;
the aqueous electrode paste is prepared by adding one or two liquid components selected from an aqueous emulsion solution containing the aqueous medium and the aqueous binder to the paste precursor and wet-mixing the mixture.
5. A method for manufacturing an electrode for a lithium ion battery, comprising the steps of:
preparing an aqueous electrode slurry by the method for producing an aqueous electrode slurry for a lithium ion battery according to any one of claims 1 to 4;
the aqueous electrode slurry thus obtained is applied to a substrate and dried, and the aqueous medium is removed, thereby forming an electrode active material layer on the substrate.
6. A thickener powder for a lithium ion battery, which is used for thickening an aqueous electrode slurry for a lithium ion battery,
the thickener powder for lithium ion batteries comprises a cellulose-based water-soluble polymer,
the maximum particle diameter of the thickener powder in a volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measuring method is defined as D100[μm]When the temperature of the water is higher than the set temperature,
passing said thickener powder throughMesh at D100(mum) or more and D100A sieve in a range of +5(μm) or less divides the thickener powder into an oversize residual fraction and an oversize pass fraction, and in this case, the proportion of the oversize residual fraction is 0.05 mass% or less when the total amount of the thickener powder is 100 mass%.
7. The thickener powder for lithium ion batteries according to claim 6,
the cellulose-based water-soluble polymer contains at least one selected from carboxymethyl cellulose and carboxymethyl cellulose salt.
8. The thickener powder for lithium ion batteries according to claim 6 or 7,
the viscosity calculated under the following condition 1 is 10 mPas to 20000 mPas,
condition 1: the thickener powder was dissolved in water to obtain a 1.3 mass% thickener aqueous solution, which was then sheared at 25 ℃ for 3.4 seconds using a B-type viscometer-1The viscosity of the aqueous thickener solution was measured under the conditions of (1).
9. The thickener powder for lithium ion batteries according to any one of claims 6 to 8, wherein,
the oversize residue contains a fiber component derived from the cellulose-based water-soluble polymer.
10. An aqueous electrode slurry, comprising:
an electrode active material selected from a positive electrode active material and a negative electrode active material;
a water-based binder;
the thickener powder for a lithium ion battery according to any one of claims 6 to 9; and
an aqueous medium containing a water-soluble polymer,
the thickener powder for lithium ion batteries is dissolved in the aqueous medium.
11. An electrode for a lithium ion battery, comprising:
an electrode active material selected from a positive electrode active material and a negative electrode active material;
a water-based binder; and
an adhesive comprising the thickener powder for lithium ion batteries according to any one of claims 6 to 9.
12. A lithium ion battery comprising at least a positive electrode, an electrolyte and a negative electrode, wherein the lithium ion battery is characterized in that,
at least one of the positive electrode and the negative electrode includes the lithium ion battery electrode according to claim 11.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017-168273 | 2017-09-01 | ||
| JP2017168273 | 2017-09-01 | ||
| PCT/JP2018/029210 WO2019044382A1 (en) | 2017-09-01 | 2018-08-03 | Method for producing aqueous electrode slurry for lithium ion batteries, method for producing electrode for lithium ion batteries, thickening agent powder for lithium ion batteries, aqueous electrode slurry, electrode for lithium ion batteries, and lithium ion battery |
Publications (2)
| Publication Number | Publication Date |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2011034962A (en) * | 2009-07-07 | 2011-02-17 | Nippon Zeon Co Ltd | Method for manufacturing electrode of lithium ion secondary battery,and lithium ion secondary battery |
| JP2011063673A (en) * | 2009-09-16 | 2011-03-31 | Daicel Chemical Industries Ltd | Aqueous paste and method for producing the same |
| CN103828104A (en) * | 2011-09-20 | 2014-05-28 | 日产化学工业株式会社 | Slurry composition for use in forming lithium-ion secondary battery electrode, containing cellulose fiber as binder, and lithium-ion secondary battery electrode |
| CN104025342A (en) * | 2011-11-25 | 2014-09-03 | 松下电器产业株式会社 | Negative electrode for lithium ion secondary batteries, method for producing same, and lithium ion secondary battery |
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| JP3490961B2 (en) | 2000-08-01 | 2004-01-26 | 第一工業製薬株式会社 | Powdery sodium carboxymethylcellulose with reduced fibrous products and method for producing the same |
| CN102232254A (en) | 2008-11-26 | 2011-11-02 | 日本制纸化学株式会社 | Carboxymethylcellulose for electrode in rechargeable battery with nonaqueous electrolyte, salt thereof, and aqueous solution thereof |
| JP2015008070A (en) | 2013-06-25 | 2015-01-15 | 株式会社豊田自動織機 | Method and device for manufacturing slurry for electrode |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011034962A (en) * | 2009-07-07 | 2011-02-17 | Nippon Zeon Co Ltd | Method for manufacturing electrode of lithium ion secondary battery,and lithium ion secondary battery |
| JP2011063673A (en) * | 2009-09-16 | 2011-03-31 | Daicel Chemical Industries Ltd | Aqueous paste and method for producing the same |
| CN103828104A (en) * | 2011-09-20 | 2014-05-28 | 日产化学工业株式会社 | Slurry composition for use in forming lithium-ion secondary battery electrode, containing cellulose fiber as binder, and lithium-ion secondary battery electrode |
| CN104025342A (en) * | 2011-11-25 | 2014-09-03 | 松下电器产业株式会社 | Negative electrode for lithium ion secondary batteries, method for producing same, and lithium ion secondary battery |
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| JPWO2019044382A1 (en) | 2020-10-01 |
| JP7161478B2 (en) | 2022-10-26 |
| WO2019044382A1 (en) | 2019-03-07 |
| CN111052459B (en) | 2023-06-06 |
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