CN111052459B - Aqueous electrode paste and method for producing same, electrode for lithium ion battery and method for producing same, thickener powder for lithium ion battery, and lithium ion battery - Google Patents
Aqueous electrode paste and method for producing same, electrode for lithium ion battery and method for producing same, thickener powder for lithium ion battery, and lithium ion battery Download PDFInfo
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- 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
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Abstract
The method for producing a water-based electrode slurry for lithium ion batteries according to the present invention is a method for producing a water-based electrode slurry for lithium ion batteries 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, and comprises the steps of: a sieve passing portion (q) for sieving a thickener powder containing a cellulose-based water-soluble polymer to obtain the thickener powder; and mixing the electrode active material, the aqueous binder, the sieve passing portion (q), and an aqueous medium to prepare an aqueous electrode slurry.
Description
Technical Field
The present invention relates to a method for producing an aqueous electrode paste for lithium ion batteries, a method for producing an electrode for lithium ion batteries, a thickener powder for lithium ion batteries, an aqueous electrode paste, an electrode for lithium ion batteries, and a lithium ion battery.
Background
Electrodes used in lithium ion batteries generally consist primarily of electrode active material layers and current collectors. The electrode active material layer is obtained, for example, by 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 electrode slurry.
As a method for manufacturing an electrode for a lithium ion battery, for example, the methods described in patent document 1 and patent document 2 can be cited.
Patent document 1 (japanese patent application laid-open No. 2006-24550) describes a method for manufacturing an electrode plate for a positive electrode of a nonaqueous secondary battery, the method comprising: a step a of preparing a mixture coating material comprising a mixture and a liquid component E in which a thickener D is dissolved, wherein the mixture comprises an active material a, a conductive material B, a binder C, and a thickener D, the conductive material B is made of at least a carbon material, the thickener D is made of at least a water-soluble polymer, and the liquid component E is made of at least water; and a step b of applying a mixture coating to the current collector, wherein the step a of preparing the mixture coating comprises: a primary mixing step of mixing a liquid component E and a complex containing an active material A, a conductive material B, and a powdery thickener D together to obtain a primary mixture; and a secondary mixing step of mixing the primary mixture with the binder C and the additional liquid component to obtain a secondary mixture.
Patent document 2 (japanese patent application laid-open No. 2006-107896) describes a method for producing an electrode plate for a negative electrode of a nonaqueous secondary battery, which uses a paste comprising a carbon material containing graphite as a main agent, a thickener and a binder, wherein the content of iron in the graphite is 500ppm or less, the thickener is a water-soluble polymer containing carboxyl groups, the binder is a water-dispersible polymer having polar groups, and the mixing step of the paste for forming a negative electrode coating film comprises 3 steps: a primary mixing step of adding a thickener in a powder state at least in graphite and mixing the thickener with a dispersion medium; diluting and mixing the mixture obtained in the primary mixing step with a dispersion medium, and mixing; and a fine adjustment mixing step of adding a binder to the mixture obtained in the dilution mixing step and mixing the mixture to prepare a paste, wherein the shearing force of the mixing in the initial mixing step is 2.5 times or more the shearing force of the mixing in the dilution mixing step and the fine adjustment mixing step.
Prior art literature
Patent literature
Patent document 1: JP Japanese patent laid-open No. 2006-24550
Patent document 2: JP 2006-107896A
Disclosure of Invention
Problems to be solved by the invention
The inventors of the present invention studied and found that: the aqueous electrode slurries obtained by the production methods described in patent documents 1 and 2 have variations in viscosity for each batch or have variations in viscosity upon storage, and thus have unstable quality. It was also found that aggregates and pinholes are likely to occur in electrodes produced using such an aqueous electrode slurry having unstable quality.
Further, as a result of the studies by the inventors of the present invention, it was clarified that: in the preparation of the aqueous electrode paste, the aqueous electrode paste obtained by the method of adding the aqueous thickener solution by division also has variations in viscosity for each batch or changes in viscosity upon storage, and thus the quality is unstable. Further, in such a method for producing an aqueous electrode paste, since an aqueous thickener solution is separately prepared and added to the paste, the production process is numerous and the production time is long, and the productivity is poor.
The present invention has been made in view of the above circumstances, and can stably obtain an aqueous electrode slurry for a lithium ion battery electrode excellent in appearance, a thickener powder for a lithium ion battery, an electrode for a lithium ion battery excellent in appearance, and a lithium ion battery using the electrode with good productivity.
Means for solving the problems
The inventors of the present invention repeated intensive studies to achieve the above object. As a result, it has been found that by using a sieved thickener powder, an aqueous electrode slurry which can stably and with good productivity provide an electrode for a lithium ion battery excellent in appearance can be obtained, and the present invention has been completed.
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 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 comprising the steps of: a sieve passing portion (q) for passing a thickener powder containing a cellulose-based water-soluble polymer through a sieve to obtain the thickener powder; the electrode active material, the aqueous binder, and the sieve passing portion (q) are mixed with an aqueous medium to prepare an aqueous electrode slurry.
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 slurry by the method for producing an aqueous electrode slurry for a lithium ion battery; and applying the aqueous electrode slurry obtained 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 lithium ion batteries, which comprises a cellulose-based water-soluble polymer for thickening aqueous electrode slurry for lithium ion batteries, wherein the maximum particle diameter of the thickener powder in a volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measurement method is D 100 [μm]When the thickener powder is passed through the mesh, it is placed in D 100 (μm) or more D 100 The thickener powder is separated into a residual part on the screen and a passing part on the screen by a screen in a range of +5 (μm) or less, and in this case, the proportion of the residual part on the screen is 0.05 mass% or less, assuming that the total amount of the thickener powder is 100 mass%.
Further, according to the present invention, there is provided an aqueous electrode slurry comprising: the lithium ion battery thickener powder comprises an electrode active material selected from a positive electrode active material and a negative electrode active material, an aqueous binder, the lithium ion battery thickener powder, and an aqueous medium, wherein the lithium ion battery thickener powder 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 positive electrode active materials and negative electrode active materials; a water-based adhesive; and an adhesive 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 includes the electrode for a lithium ion battery.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, it is possible to provide an aqueous electrode slurry capable of stably obtaining an electrode for a lithium ion battery excellent in appearance with good productivity, a thickener powder for a lithium ion battery, an electrode for a lithium ion battery excellent in appearance, and a lithium ion battery using the electrode.
Drawings
The above objects, and other objects, features, and advantages will be further apparent from the following description of the 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 a lithium ion battery according to an 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 reference numerals are given to the same components, and the description thereof is omitted. In the drawings, each component schematically shows a shape, a size, and a layout relationship to the extent that the present invention can be understood, and is different from the actual size.
In the present embodiment, "a to B" in the numerical range represents a or more and B or less unless otherwise specified.
< method for producing aqueous electrode slurry for lithium ion batteries >
First, a method for producing the aqueous electrode slurry for a lithium ion battery according to the present embodiment will be described.
The aqueous electrode slurry for a lithium ion battery according to the present embodiment contains 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 aqueous electrode slurry for a lithium ion battery is produced by a method comprising at least the following steps (a) and (B).
Step (A): a step of sieving the thickener powder containing the cellulose-based water-soluble polymer to obtain a sieve passing portion (q)
Step (B): a step of preparing an aqueous electrode slurry by mixing an electrode active material (a), an aqueous binder (b), a sieve passing portion (q), and an aqueous medium (c)
The inventors of the present invention studied and found that: the aqueous electrode slurries obtained by the production methods described in patent documents 1 and 2 have variations in viscosity for each batch or have variations in viscosity during storage, and thus have unstable quality. It was also found that aggregates are easily generated in electrodes produced using such an aqueous electrode slurry having unstable quality.
Further, as a result of the studies by the inventors of the present invention, it was clarified that: in the preparation of the aqueous electrode paste, the aqueous electrode paste obtained by the method of adding the thickener aqueous solution in a divided manner also has a variation in viscosity for each batch or a variation in viscosity upon storage, and thus the quality is unstable. Further, in such a method for producing an aqueous electrode paste, since an aqueous thickener solution is separately prepared and added to the paste, the production process is numerous and the production time is long, and the productivity is poor.
That is, as is clear from the studies of the inventors of the present invention, the conventional aqueous electrode slurry has room for improvement from the viewpoint of obtaining an electrode for a lithium ion battery excellent in appearance stably and with good productivity.
The inventors of the present invention have made intensive studies to achieve the above object. As a result, it was found that the quality stability of the aqueous electrode slurry obtained by adding a specific amount of the water-insoluble component to the conventional thickener powder containing a cellulose-based water-soluble polymer was lowered.
In addition, it is clear that in the method of adding the aqueous thickener solution separately, the aqueous thickener solution is added also after the thickening step, and therefore the quality stability of the aqueous electrode slurry is lowered.
For this reason, the inventors of the present invention have studied further. 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 was used, an aqueous electrode slurry excellent in quality stability could be stably obtained. Further, it was found that the use of the aqueous electrode slurry thus obtained can suppress the occurrence of aggregates, and can stably provide an electrode for a lithium ion battery having excellent appearance.
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 excellent in quality stability can be stably obtained. By using such an aqueous electrode slurry, an electrode for a lithium ion battery excellent in appearance can be stably obtained.
In the method for producing the aqueous electrode slurry for lithium ion batteries according to the present embodiment, the maximum particle diameter of the sieve passing portion (q) in the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measurement method is defined as D 100 [μm]At the time, the sieve passing portion (q) is passed through the mesh at D 100 (μm) or more D 100 The ratio of the above-mentioned screen passing portion (q) is preferably 0.05 mass% or less, more preferably 0.03 mass% or less, and even more preferably 0.01 mass% or less, when the total amount of the screen passing portion (q) is 100 mass% or less. The lower limit of the ratio of the above-mentioned residual portion on the screen is not particularly limited, but is, for example, 0.00 mass% or more.
Maximum particle diameter D of the sieve passing portion (q) 100 For example, the particle size distribution can be measured by using a particle size distribution measuring apparatus ("Malvern Instruments" manufactured by the company under the model name: mastersizer 2000). The maximum particle diameter D 100 The particle diameter is defined as a particle diameter in which a volume fraction is 100% integrated (accumulated) in a volume-based particle diameter distribution.
In the present embodiment, the ratio of the above-mentioned residual portion on the screen means an index of the amount of the fiber component derived from the cellulose-based water-soluble polymer contained in the screen passing portion (q). That is, the smaller the proportion of the above-mentioned residual portion 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 the cellulose-based water-soluble polymer can be obtained by a known method, but various commercially available products can be used.
The sieve is not particularly limitedThe 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 measurement method was defined as D 100 [μm]In the case of using a mesh at D 100 (μm) or more D 100 A sieve having a mesh size of +30 (. Mu.m) or less is more preferably used 100 (μm) or more D 100 A sieve having a mesh size of +20 (. Mu.m) or less, more preferably having a mesh size of D 100 (μm) or more D 100 A sieve having a mesh size of +10 (. Mu.m) or less is particularly preferably used 100 (μm) or more D 100 A sieve in a range of +5 (. Mu.m) or less. Thus, the fiber component derived from the cellulose-based water-soluble polymer contained in the thickener powder can be effectively removed, and the sieve passing portion (q) of the thickener powder having a ratio of the remaining portion on the sieve of the upper limit value or less can be effectively obtained.
In the step (B), the electrode active material (a), the aqueous binder (B), the sieve passing portion (q), and the aqueous medium (c) are mixed to prepare an aqueous electrode slurry. In this case, the conductive auxiliary (d) may be mixed together.
The step (B) preferably includes the following steps (B-1) to (B-3). This can more stably obtain an aqueous electrode slurry having excellent quality stability.
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): a step of adding one or two liquid components selected from an aqueous emulsion solution 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 further 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 electrode active material (a) and the sieve passing portion (q). In this case, the mixed conductive assistant (d) may be mixed together to form a powder.
In this 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 due to the thickener can be further suppressed in the subsequent step. This suppresses the generation of gel components derived from the thickener in the aqueous electrode slurry obtained.
As is clear from the study of the present inventors, aggregates are likely to occur in electrodes for lithium ion batteries 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.
The inventors of the present invention have further studied intensively for this purpose. As a result, it was found that the use of the sieve passing portion (q) of the thickener powder according to the present embodiment can suppress the occurrence of aggregates on the electrode surface, and can stably obtain an electrode for a lithium ion battery having excellent appearance.
As a 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). In addition, the planetary mixer is a mixer having rotation and revolution functions as a mixing mechanism. The planetary mixer having planetary motion means a mixer provided with blades having rotation and revolution functions as a mixing mechanism.
In the step (B-2), one or two liquid components selected from the 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, thereby preparing a slurry precursor.
The step (B-2) preferably includes 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 an aqueous medium (c) and an aqueous binder (B) with a powder mixture. By including the fusion 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 in wetting by the powder mixture, from scattering during uniform mixing of the powder mixture, and the like.
The thickening step (B-2-2) is a step of mixing the powder mixture and the liquid component uniformly to obtain a slurry precursor by setting the wet mixing speed to be higher than that in the fusion step (B-2-1).
As a mixer for performing the 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 constituting the aqueous electrode slurry while suppressing scattering of each material.
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 suppressing the powder mixture from being gradually pushed up at the edge of the mixer during wet mixing, the wetting bias of the powder mixture, the powder mixture scattering during 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 suppressing the powder mixture from being gradually pushed up at the edge of the mixer during wet mixing, the wetting bias of the powder mixture, the powder mixture scattering during 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 minutes 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.
If 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 more moderate, and therefore, the molecular chain cleavage of the thickener can be suppressed, 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 resulting aqueous electrode slurry can be further suppressed.
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, and therefore, the molecular chain cleavage of the thickener can be suppressed, the gel component derived from the thickener can be broken more easily, 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 or more and 180 minutes or more.
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 reduce the shearing force applied to the slurry precursor, thereby suppressing the cleavage of the molecular chain of the thickener and improving the dispersibility of each material.
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 the aqueous emulsion solution containing the aqueous medium (c) and the aqueous binder (B) are further added to the slurry precursor obtained in the step (B-2) and wet-mixed, thereby preparing the aqueous electrode slurry.
As a mixer for performing wet mixing, a planetary mixer is preferably used, and a planetary mixer is more preferably used. By using such a mixer, mixing can be performed sufficiently while stirring at a low speed. Therefore, the dispersibility of each material constituting the aqueous electrode paste can be improved while suppressing the cleavage of the molecular chain of the thickener by stirring and mixing and the aggregation of the aqueous binders (b) with each other. As a result, an aqueous electrode slurry having further excellent quality stability can be obtained.
Further, since the dispersibility of the aqueous electrode slurry obtained 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 revolution speed of the wet mixing in the step (B-3), preferably both of the rotation speed and 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 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 slurry according to the present embodiment may further include the step (C): and (3) performing vacuum defoaming. Thus, air bubbles involved in the slurry can be removed, and the spreadability of the slurry can be improved.
The vacuum degassing may be performed by sealing the vessel and the shaft of the mixer to remove bubbles, or may be performed after transferring to another vessel.
< thickener powder for lithium ion Battery (p) >)
The thickener powder (p) for lithium ion batteries according to the present embodiment is used for thickening an aqueous electrode slurry for lithium ion batteriesThe thickener powder contains cellulose water-soluble polymer, and the maximum particle diameter of the thickener powder (p) in the volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measurement method is defined as D 100 [μm]At the time, the thickener powder (p) is put in D by passing through the mesh 100 (μm) or more D 100 The thickener powder (p) is separated into an on-screen residue and a screen passing portion by a screen in a range of +5 (μm) or less, and in this case, the proportion of the on-screen residue is 0.05 mass% or less, preferably 0.03 mass% or less, more preferably 0.01 mass% or less, when the total amount of the thickener powder (p) is 100 mass%. The lower limit of the ratio of the residual portion on the screen is not particularly limited, but is, for example, 0.00 mass% or more.
Maximum particle diameter D of thickener powder (p) 100 For example, the particle size distribution can be measured by a particle size distribution measuring apparatus (model name: mastersizer2000, manufactured by Malvern Instruments). The maximum particle diameter D 100 The particle diameter is defined as a particle diameter in which a volume fraction is 100% integrated (accumulated) in a volume-based particle diameter distribution.
In the present embodiment, the ratio of the above-mentioned residual portion on the screen means 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 residual portion on the screen, the smaller the proportion of the fiber component derived from the cellulose-based water-soluble polymer contained in the thickener powder (p).
The inventors of the present invention studied and found that: the aqueous electrode slurries obtained by the production methods described in patent documents 1 and 2 have variations in viscosity for each batch or have variations in viscosity upon storage, and thus have unstable quality. In addition, aggregates are easily generated in electrodes manufactured using such an aqueous electrode slurry having unstable quality.
Further, the inventors of the present invention studied the following cases: in the preparation of the aqueous electrode paste, the aqueous electrode paste obtained by the method of adding the aqueous thickener solution by division also has a variation in viscosity for each batch or a variation in viscosity upon storage, and thus the quality is unstable. Further, in such a method for producing an aqueous electrode paste, since an aqueous thickener solution is separately prepared and added to the paste, the production process is numerous and the production time is long, and the productivity is poor.
That is, as is clear from the studies 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 inventors of the present invention repeated intensive studies to achieve the above object. As a result, it was found that the quality stability of the aqueous electrode slurry obtained by adding a specific amount of the water-insoluble component to the conventional thickener powder containing a cellulose-based water-soluble polymer was lowered.
In addition, it is clear that in the method of adding the aqueous thickener solution separately, the aqueous thickener solution is added also after the thickening step, and therefore the quality stability of the aqueous electrode slurry is lowered.
For this reason, the present inventors have further studied intensively. As a result, it was found that when the thickener powder (p) having the proportion of the remaining portion on the screen of the above-mentioned upper limit value or less is used, an aqueous electrode slurry excellent in quality stability can be stably obtained. Further, it was found that the use of the aqueous electrode slurry thus obtained can suppress the occurrence of aggregates and pinholes, and can stably provide an electrode for a lithium ion battery having excellent appearance.
That is, by using the thickener powder (p) having the proportion of the remaining portion on the screen of the upper limit value or less, an aqueous electrode slurry excellent in quality stability can be stably obtained. Further, by using such an aqueous electrode slurry, an electrode for a lithium ion battery excellent in appearance can be stably obtained.
The thickener powder (p) preferably contains a cellulose-based water-soluble polymer as a main component. The term "comprising a cellulose-based water-soluble polymer as a main component" means that the thickener powder (p) comprises 50 mass% or more of the 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, methyl ethyl hydroxy cellulose, methyl cellulose, 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 salts is preferably contained, and one or more selected from carboxymethyl cellulose, ammonium salt of carboxymethyl cellulose, sodium salt of carboxymethyl cellulose, and potassium salt of carboxymethyl cellulose is more preferably contained.
In the thickener powder (p) for lithium ion batteries according to the present embodiment, the residual part on the screen is not particularly limited, and for example, the thickener powder (p) contains a fiber component derived from the cellulose-based water-soluble polymer.
In the thickener powder (p) for lithium ion batteries according to the present embodiment, the viscosity calculated under the following condition 1 is preferably 10mpa·s to 20000mpa·s, more preferably 100mpa·s to 10000mpa·s, still more preferably 1000mpa·s to 8000mpa·s, and particularly preferably 2000mpa·s to 4000mpa·s.
Condition 1: the thickener powder (p) was dissolved in water to obtain an aqueous thickener solution having a concentration of 1.3 mass%. Next, a type B viscometer was used, and the shear rate was 3.4s at 25 ℃ -1 The viscosity of the aqueous thickener solution is measured under the conditions of (1).
This can further improve the spreadability of the aqueous electrode paste obtained.
< method for producing thickener powder (p)
Next, a method for producing the thickener powder (p) for lithium ion batteries 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, the step of sieving the cellulose-containing water-soluble polymer thickener powder can be performed in accordance with the step (a) in the above-described method for producing the aqueous electrode slurry for a lithium ion battery, and therefore, the description thereof is omitted here.
< aqueous electrode slurry >
Next, the aqueous electrode slurry according to the present embodiment will be described.
The aqueous electrode slurry according to the present embodiment contains 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 lithium ion batteries according to the present embodiment, and an aqueous medium (c), in which the thickener powder (p) for lithium ion batteries is dissolved. The aqueous electrode slurry according to the present embodiment preferably further contains a conductive additive (d) from the viewpoint of improving the electron conductivity of the obtained electrode.
Here, in the aqueous electrode slurry according to the present embodiment, the thickener powder (p) for lithium ion batteries 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 according to 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 normal positive electrode active material that can be used in a positive electrode of a lithium ion battery. Examples thereof include lithium and transition metal composite oxides such as lithium-nickel composite oxides, lithium cobalt composite oxides, lithium manganese composite oxides, and lithium-manganese-nickel composite oxides; tiS (TiS) 2 、FeS、MoS 2 A transition metal sulfide; mnO, V 2 O 5 、V 6 O 13 、TiO 2 And 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. Their compounds may partially replace a part of the elements with other elements in order to enhance 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 large capacity and a large energy density in addition to a high action potential.
The positive electrode active material may be used alone or in combination of 1 or more than 2.
The negative electrode active material is not particularly limited as long as it is a normal negative electrode active material that can be used in a negative electrode of a lithium ion battery. Examples thereof include carbon materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; lithium metal such as lithium metal and lithium alloy; metals such as silicon and tin; conductive polymers such as polyacene, polyacetylene, polypyrrole, and the like. 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 or in combination of 1 or more than 2.
When the total amount of the 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, more preferably 85 parts by mass or more and 99.85 parts by mass or less.
(aqueous adhesive (b))
The aqueous binder (b) is not particularly limited as long as it can form an electrode and has sufficient electrochemical stability, and examples thereof include polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, polyimide, and the like. These aqueous binders (b) may be used singly or in combination of two or more. Among these, styrene butadiene rubber is preferable.
In the present embodiment, the aqueous binder (b) is a mixture that can be dispersed in an aqueous medium to form an aqueous emulsion.
When the total amount of the 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 adhesiveness of the binder, and the battery characteristics is further excellent.
The aqueous binder (b) is used as an aqueous emulsion solution by dispersing a powdery substance in an aqueous medium. This improves the dispersibility of the aqueous binder (b) without inhibiting contact between the electrode active materials (a), between the conductive assistants (d), and between the electrode active materials (a) and the conductive assistants (d).
The aqueous medium for dispersing the aqueous binder (b) is not particularly limited as long as the aqueous binder (b) can be dispersed, and 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.
(thickener powder (p))
The thickener powder (p) according to the present embodiment can be used.
The thickener powder (p) may be used alone or in combination of 1 or more than 2 kinds. When the total amount of the 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 paste, the adhesiveness of the binder, and the battery characteristics becomes more excellent.
(aqueous Medium (c))
The aqueous medium (c) according to the present embodiment is not particularly limited, and distilled water, ion-exchanged water, tap water, industrial water, or the like can be used, for example. 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 aid (d))
The aqueous electrode slurry according to the present embodiment preferably further contains a conductive additive (d) from the viewpoint of improving the electron conductivity of the obtained electrode.
The conductive additive (d) has electron conductivity, and is not particularly limited as long as the conductivity of the electrode is improved. Examples of the conductive additive (d) according to the present embodiment include acetylene black, ketjen black, carbon nanofibers, and carbon materials such as graphite having a smaller particle diameter than graphite used as an active material. These conductive assistants (d) may be used alone or in combination of 1 or more than 2.
The content of the conductive additive (d) is preferably 0.01 mass part or more and 10.0 mass parts or less, more preferably 0.05 mass part or more and 5.0 mass parts 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 amount of the 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, 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 mass part or more and 10.0 mass parts or less, and more preferably 0.05 mass part or more and 5.0 mass parts or less. The content of the thickener powder (p) is preferably 0.01 mass part or more and 10.0 mass parts or less, more preferably 0.05 mass part or more and 5.0 mass parts or less. The content of the conductive additive (d) is preferably 0.01 mass part or more and 10.0 mass parts or less, and more preferably 0.05 mass part or more and 5.0 mass parts 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 an electrode 100 for a lithium ion battery according to an embodiment of the present invention. The electrode 100 for a lithium ion battery 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 thickener powder (p) for a lithium ion battery.
< method for producing electrode for lithium ion Battery >
Next, a method for manufacturing the electrode 100 for a lithium ion battery according to the present embodiment will be described.
The method for manufacturing the electrode 100 for a lithium ion battery according to the present embodiment includes at least the following 2 steps (1) and (2). Thus, an electrode for a lithium ion battery having excellent appearance can be stably obtained.
(1) The process for preparing an aqueous electrode slurry according to the method for preparing an aqueous electrode slurry for a lithium ion battery according to the present embodiment
(2) A step of forming an electrode active material layer 103 on the substrate 101 by applying the aqueous electrode slurry obtained to the substrate 101, drying the aqueous electrode slurry, and removing the aqueous medium
The step (1) is similar to the method for producing the aqueous electrode slurry for lithium ion batteries according to the present embodiment, and therefore, the description thereof is omitted here. Step (2) is described 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 to the 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 the electrode 100 for a lithium ion battery in which the electrode active material layer 103 is formed on the substrate 101 is obtained.
The method of applying the aqueous electrode slurry to the substrate 101 may be a generally known method. Examples of the method include a reverse roll method, a direct roll coating method, a doctor blade method, a blade 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 paste may be applied to only one side of the substrate 101 or to both sides. When the coating is applied to both surfaces of the substrate 101, the coating may be applied sequentially on one surface or simultaneously on both surfaces. In addition, the 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 corresponding to the size of the battery.
The method for drying the aqueous electrode slurry to be applied can be a generally known method. For example, heat sealing, vacuum, infrared, far infrared, electron beam, 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 base material 101 used for manufacturing the electrode 100 for a lithium ion battery according to the present embodiment, for example, a general current collector usable in a lithium ion battery can be used.
Copper, stainless steel, nickel, titanium, or an alloy thereof can be used as the negative electrode current collector, and copper is particularly preferred.
Aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used as the positive electrode current collector, and among these, aluminum is particularly preferred.
The shape of the current collector is not particularly limited, and a foil-shaped current collector can be used, for example, in a thickness range of 0.001 to 0.5 mm.
The electrode 100 for a lithium ion battery 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 molding method, a calender molding method (Calendar press method), and the like. The pressing pressure is not particularly limited, and is, for example, 0.2 to 3t/cm 2 Is not limited in terms of the range of (a).
The thickness and density of the electrode 100 for a lithium ion battery according to the present embodiment are not particularly limited as they are appropriately determined according to the use of the battery, and can 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 the 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 separator 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 wound body can be used as the electrode. As the exterior body, a metal exterior body and an aluminum laminate exterior body 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, and flat type.
As the electrolyte in the electrolyte solution of the battery, a known lithium salt may be used, and may be selected according to the type of the active material. Examples thereof include LiClO 4 、LiBF 6 、LiPF 6 、LiCF 3 SO 3 、LiCF 3 CO 2 、LiAsF 6 、LiSbF 6 、LiB 10 Cl 10 、LiAlCl 4 、LiCl、LiBr、LiB(C 2 H 5 ) 4 、CF 3 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 is not particularly limited as long as it is a solvent 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 gamma-butyrolactone and gamma-valerolactone; ethers such as trimethoxy methane, 1, 2-trimethoxy ethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxapentanes such as 1, 3-dioxolane and 4-methyl-1, 3-dioxolane; nitrogen-containing compounds such as acetonitrile, nitromethane, formamide, dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate; triesters of phosphoric acid, diethylene glycol dimethyl ether; triethylene glycol dimethyl ether; sulfolanes such as sulfolane and methyl sulfolane; 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 or in combination of 1 or more than 2.
Examples of the spacer include porous spacers. Examples of the form of the spacer include a film, and a nonwoven fabric.
Examples of the porous spacer include polyolefin porous spacers such as polypropylene-based and polyethylene-based; porous spacers formed from polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene copolymers, and the like.
While 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 may be employed.
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 thereto.
Example 1
< preparation of Screen passing portion (q)
First, carboxymethyl cellulose powder (MAC series, maximum particle diameter D, manufactured by "company", japan, inc.) (registered trademark) was mixed with the cellulose powder 100 :50 μm) was passed through a sieve having a mesh of 53 μm ("a-layer, material, manufactured by the company: stainless steel, trade name: the "stant-run ふ is cut off and the obtained screen passes through Part (q 1).
< preparation of aqueous electrode paste >
(1) Working procedure (B-1)
960g of graphite as a negative electrode active material, 10g of the sieve passing portion (q 1) of the carboxymethyl cellulose powder obtained as described above, and 10g of carbon black as a conductive additive were charged into a planetary mixer of a planetary motion type.
Next, dry mixing was performed at 20℃for 60 minutes to obtain a powder mixture.
(2) Fusion process (B-2-1)
Then, water was added to the planetary-motion planetary mixer in which the above step (B-1) was completed. Then at the rotation speed: 0.15m/sec, revolution speed: 0.04m/sec, temperature: wet mixing was performed at 20 ℃ for 2 minutes to fuse water with the powder mixture.
(3) Thickening process (B-2-2)
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) Working procedure (B-3)
Next, an aqueous SBR solution in which Styrene Butadiene Rubber (SBR) was dispersed in water and the solid content concentration was 40% by mass was prepared. 50g of the resulting SBR aqueous solution was added to a planetary-motion planetary mixer having completed the thickening step (B-2-2).
Then at the rotation speed: 0.25m/sec, revolution speed: 0.08m/sec, temperature: wet mixing was performed at 20 ℃ for 10 minutes.
(5) Working procedure (C)
Then, vacuum defoaming was performed to obtain an aqueous electrode slurry.
The solid content concentration of the aqueous electrode slurry was adjusted to 50 mass% by adjusting the amount of water added in the fusion step (B-2-1).
< preparation of negative electrode >
The aqueous electrode slurry thus obtained was applied to one surface of a copper foil as a current collector using a die coater, and dried. Next, the obtained electrode was pressed to obtain a negative electrode.
< evaluation >
(determination of the proportion of the residual fraction on the Screen)
The sieve obtained above was passed through the section (q 1) (maximum particle diameter D 100 :50 μm) was passed through a sieve having a mesh of 53 μm ("a-layer, material, manufactured by the company: stainless steel, trade name: the screen passing portion (q 1) is subdivided into a screen residue portion and a screen passing portion. Next, the mass x (g) of the on-screen residual part remaining on the screen without passing through the screen was measured, and the proportion of the on-screen residual part in the screen passing part (q 1) was calculated by the following formula.
Ratio of residual fraction on screen (% by mass) =100×x/y
Here, y in the formula is the mass (g) of the sieve passing portion (q 1) of the sieved carboxymethyl cellulose powder.
(evaluation of storage stability of thickener aqueous solution)
The carboxymethyl cellulose powder was passed through a sieve of part (q 1) and dissolved in water at 25℃for 10 minutes at 200rpm to obtain an aqueous thickener solution having a concentration of 1.3 mass%. Shear rate 3.4s at 25℃using a type B viscometer -1 The viscosity of the aqueous thickener solution was 3000 mPas as a result of measurement under the conditions of (2).
Next, 100g of the obtained thickener aqueous solution was placed in a plastic container with a lid, and the container was kept at a temperature of 25℃for 3 days in a state of being covered with the lid.
Next, the aqueous thickener solution after 3 days was subjected to measurement at 25℃and a shear rate of 3.4s using a type B viscometer -1 Viscosity below. Thereafter, the viscosity change rate was calculated by the following formula, and the storage stability of the aqueous thickener solution was evaluated based on the following criteria.
Viscosity change rate [% ] =100× (viscosity after 3 days holding)/(viscosity before 3 days holding)
And (3) the following materials: the viscosity change rate is more than 80% and less than 120%
O: the viscosity change rate is 120% or more and less than 150%, or 50% or more and less than 80%
X: the viscosity change rate is 150% or more, or 10% or more and less than 50%
(evaluation of storage stability of aqueous electrode paste)
100g of the aqueous electrode slurry thus obtained was placed in a plastic container with a lid, and the container was kept at a temperature of 25℃for 3 days with the lid closed.
Next, the aqueous electrode slurry before and after the holding was measured for a shear rate of 3.4s at 25℃using a B-type viscometer -1 Viscosity below. 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 [% ] =100× (viscosity after 3 days holding)/(viscosity before 3 days holding)
And (3) the following materials: the viscosity change rate is more than 80% and less than 120%
O: the viscosity change rate is 120% or more and less than 150%, or 50% or more and less than 80%
Delta: the viscosity change rate is 150% or more or 10% or less than 50% or more
X: the aqueous electrode slurry was separated (visually judged) by the above-mentioned holding test
The results obtained are shown in table 1.
(evaluation of viscosity deviation of aqueous electrode paste)
The viscosity deviation of the aqueous electrode paste was evaluated as follows. First, 5 aqueous electrode slurries under the same conditions were prepared as samples. Next, the aqueous electrode slurry thus obtained was measured at 25℃with a type B viscometer at a shear rate of 3.4s -1 The maximum deviation amount was calculated from the following equation, and the deviation of each batch of the aqueous electrode slurry was evaluated based on the following criteria.
Maximum deviation (mPa-s) = (maximum viscosity in 5 samples) - (minimum viscosity in 5 samples)
And (3) the following materials: the maximum deviation is less than 500 mPa.s
O: a maximum deviation of 500 mPas or more and less than 1000 mPas
X: maximum deviation of 1000 mPas or more
(evaluation of quality of negative electrode)
1500 negative electrodes (1 cm. Times.1 cm) were produced in total, and the proportion of acceptable products (qualified product ratio) was calculated.
The obtained negative electrode surface was observed with an optical microscope at a magnification of 100 times, and the presence or absence of aggregates and pinholes on the negative electrode surface was examined. Next, no aggregates or pinholes were observed, and at least 1 was found to be defective. Next, the ratio of the qualified products was calculated as the qualified product ratio, and evaluated based on the following criteria.
And (3) the following materials: the qualified rate is more than 98 percent
O: the qualified rate is more than 95% and less than 98%
X: the qualified 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 the aqueous electrode paste was obtained were the same, the productivity of the negative electrode was evaluated based on the time taken until the aqueous electrode paste was obtained (hereinafter referred to as the production time of the aqueous electrode paste). Here, in the evaluation criteria below, the production time of the aqueous electrode paste in comparative example 2 was set to 100.
And (3) the following materials: the production time of the aqueous electrode slurry is less than 70
O: the production time of the aqueous electrode slurry is more than 70 and less than 100
X: the preparation time of the aqueous electrode slurry is more than 100
Example 2
In the production of the mesh passing portion (q), a mesh of 63 μm was used instead of a mesh of 53 μm (stainless steel, material, trade name: stainless steel, brand: "super ふ v,") in order to produce an aqueous electrode slurry and a negative electrode under the same conditions as in example 1, except that stainless steel, material, trade name: super ふ v, ", were used, and each evaluation was performed in the same manner as in example 1. The results obtained are shown in table 1.
Example 3
In the production of the mesh passing portion (q), a mesh of 73 μm was used instead of a mesh of 53 μm (stainless steel, material, trade name: stainless steel, brand: "super ふ v,") and an aqueous electrode paste and a negative electrode were produced under the same conditions as in example 1, except that stainless steel, trade name: "super ふ v,", were used, and each evaluation was performed in the same manner as in example 1. The results obtained are shown in table 1.
Comparative example 1
An aqueous electrode paste and a negative electrode were prepared under the same conditions as in example 1, except that carboxymethyl cellulose powder ("MAC series manufactured by" company "manufactured by japan) was used as it is without sieving instead of using the sieve passing portion (q 1), and each evaluation was performed in the same manner as in example 1. The results obtained are shown in table 1.
Here, the ratio of the residual portion on the screen of comparative example 1 in table 1 was determined by the following method.
First, carboxymethyl cellulose powder ("MAC series manufactured by" company, japan "or" registered trademark ") was passed through a sieve having a mesh size of 53 μm (" mesh made by "company, material: stainless steel, trade name:" stant-line ふ j-line "). Next, the mass x' (g) of the on-screen residue remaining on the screen without passing through the screen was measured, and the ratio of the on-screen residue in the carboxymethyl cellulose powder was calculated by the following formula.
The ratio of the residual fraction on the screen (% by mass) =100×x '/y'
Here, y' in the formula is the mass (g) of the sieved carboxymethyl cellulose powder.
Comparative example 2
< preparation of thickener aqueous solution B >
First, carboxymethyl cellulose powder ("MAC series manufactured by" corporation ", japan) was dissolved in ion-exchanged water at 20 ℃ to obtain a thickener aqueous solution a having a concentration of 1.3 mass%. Next, the resulting aqueous thickener solution was filtered through a filter having an average pore size of 1. Mu.m, to obtain an aqueous thickener solution B.
< preparation of aqueous electrode paste >
(1) Step 1
960g of graphite as a negative electrode active material and 10g of carbon black as a conductive additive were charged into a planetary mixer of a planetary motion type.
Next, dry mixing was performed at 20℃for 60 minutes to obtain a powder mixture.
(2) Step 2
Next, water and the aqueous thickener solution B were added to the planetary-motion planetary mixer in which the above step 1 was completed. Then at the rotation speed: 0.15m/sec, revolution speed: 0.04m/sec, temperature: wet mixing was performed at 20 ℃ for 2 minutes to fuse water with the powder mixture.
(3) Step 3
Next, water and the aqueous thickener solution B were added to the planetary-motion planetary mixer in which the above step 2 was completed. 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) Procedure 4
Next, an aqueous SBR solution in which Styrene Butadiene Rubber (SBR) was dispersed in water and the solid content concentration was 40% by mass was prepared. 50g of the resulting SBR aqueous solution and the thickener aqueous solution B were added to a planetary-motion planetary mixer having completed the step 3. The total amount of thickener powder contained in the thickener aqueous solution B used in steps 2 to 4 was 10g.
Thereafter, at the rotation speed: 0.25m/sec, revolution speed: 0.08m/sec, temperature: wet mixing was carried out at 20 ℃ for 10 minutes.
(5) Procedure 5
Then, vacuum defoaming was performed to obtain an aqueous electrode slurry.
The solid content concentration of the aqueous electrode slurry was adjusted to 50 mass% by adjusting the amount of water added in each step.
< preparation of negative electrode >
The aqueous electrode slurry thus obtained was applied to one surface of a copper foil as a current collector using a die coater, and dried. Next, the obtained negative electrode was 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 paste and a negative electrode were produced 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 publication No. 2017-168773, filed on 1 at 9 of 2017, the disclosure of which is incorporated herein in its entirety.
Claims (11)
1. A method for producing an aqueous electrode slurry for lithium ion batteries, 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,
The method for producing the aqueous electrode slurry for lithium ion batteries is characterized by comprising the following steps:
a sieve passing portion q for obtaining a thickener powder containing a cellulose-based water-soluble polymer by sieving the thickener powder; and
an electrode active material, an aqueous binder, the sieve passing portion q, and an aqueous medium are mixed to prepare an aqueous electrode slurry,
the maximum particle diameter of the sieve passing portion q in the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measuring method is set to D 100 When the particle size of the particles is smaller than the particle size,
passing the screen through part q through a mesh at D 100 μm or more and D 100 The above-mentioned sieve passing portion q is subdivided into an above-sieve residue portion and a sieve passing portion by a sieve in a range of +5 μm or less, and in this case, the ratio of the above-sieve residue portion is 0.05 mass% or less when the total amount of the above-mentioned sieve passing portion q is set to 100 mass%.
2. The method for producing an aqueous electrode slurry for lithium ion batteries according to claim 1, wherein,
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.
3. The method for producing an aqueous electrode slurry for lithium ion batteries according to claim 2, wherein,
the step of preparing the aqueous electrode slurry further comprises the steps of:
adding one or two liquid components selected from an aqueous emulsion solution containing the aqueous medium and the aqueous binder to the mixture containing the electrode active material and the sieve passing portion q, and wet-mixing the mixture to prepare a slurry precursor;
the aqueous electrode paste is prepared by further 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.
4. 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 3;
the aqueous electrode slurry thus obtained is applied to a substrate and dried, and the aqueous medium is removed, whereby an electrode active material layer is formed on the substrate.
5. A thickener powder for lithium ion batteries used in the thickening of aqueous electrode slurry for lithium ion batteries, characterized in that,
The thickener powder for lithium ion batteries comprises a cellulose-based water-soluble polymer,
the maximum particle diameter of the thickener powder in the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measurement method is set as D 100 When the particle size of the particles is smaller than the particle size,
passing the thickener powder through a mesh at D 100 μm or more and D 100 The thickener powder is separated into an on-screen residue and a screen passing portion by a screen in a range of +5 μm or less, and in this case, the proportion of the on-screen residue is 0.05 mass% or less when the total amount of the thickener powder is set to 100 mass%.
6. The thickener powder for lithium ion batteries according to claim 5, wherein,
the cellulose-based water-soluble polymer contains at least one selected from carboxymethyl cellulose and carboxymethyl cellulose salts.
7. The thickener powder for lithium ion batteries according to claim 5 or 6, wherein,
the viscosity calculated under the following condition 1 is 10 mPas to 20000 mPas,
condition 1: the thickener powder was dissolved in water to give an aqueous thickener solution having a concentration of 1.3% by mass, followed by shearing at 25℃for 3.4s using a B-type viscometer -1 The viscosity of the aqueous thickener solution is measured under the conditions of (1).
8. The thickener powder for lithium ion batteries according to claim 5 or 6, wherein,
the on-screen residue contains a fibrous component derived from the cellulose-based water-soluble polymer.
9. An aqueous electrode slurry comprising:
an electrode active material selected from positive electrode active materials and negative electrode active materials;
a water-based adhesive;
the thickener powder for lithium ion batteries according to any one of claims 5 to 8; and
the aqueous medium is a water-based medium,
the thickener powder for lithium ion batteries is dissolved in the aqueous medium.
10. An electrode for a lithium ion battery, comprising:
an electrode active material selected from positive electrode active materials and negative electrode active materials;
a water-based adhesive; and
an adhesive comprising the thickener powder for lithium ion batteries according to any one of claims 5 to 8.
11. A lithium ion battery comprising at least a positive electrode, an electrolyte and a negative electrode, characterized in that,
at least one of the positive electrode and the negative electrode comprises the electrode for a lithium ion battery according to claim 10.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017168273 | 2017-09-01 | ||
| JP2017-168273 | 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 |
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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 |
| KR101541789B1 (en) | 2008-11-26 | 2015-08-04 | 닛뽄세이시가부시끼가이샤 | 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 |
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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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| JP7161478B2 (en) | 2022-10-26 |
| CN111052459A (en) | 2020-04-21 |
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