Slurry composition for all-solid-state secondary battery, solid electrolyte-containing layer and all-solid-state secondary battery, and method for producing slurry composition for all-solid-state secondary battery

Abstract

The purpose of the present invention is to provide a slurry composition for an all-solid-state secondary cell, the slurry composition having exceptional fluidity and storage stability and being capable of forming a solid-electrolyte-containing layer that has exceptional ion conductivity. This slurry composition contains a solid electrolyte, a polymer, and a solvent, and the ratio of the fineness of grind of the solid electrolyte, measured using a grind gauge technique on the basis of JIS K5600-2-5:1999, with respect to the average primary particle diameter of the solid electrolyte is between 1 and 30 (exclusive).

Description

Technical Field

[0001] The present invention relates to a slurry composition for an all-solid-state secondary battery, a solid electrolyte-containing layer and an all-solid-state secondary battery, and a method for producing the slurry composition for an all-solid-state secondary battery.

Background Art

[0002] In recent years, secondary batteries such as lithium-ion secondary batteries have seen increasing demand in various applications, including portable terminals such as portable information terminals and portable electronic devices, as well as small household power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. Along with the expanding range of applications, there is a growing demand for further improvement in the safety of secondary batteries.

[0003] Therefore, as a highly safe secondary battery, all-solid-state secondary batteries using solid electrolytes instead of organic solvent electrolytes with high flammability and high fire risk during leakage have attracted attention.

[0004] Here, an all-solid-state secondary battery has a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode. The electrodes (positive electrode, negative electrode) of the all-solid-state secondary battery are formed, for example, by applying a slurry composition containing an electrode active material (positive electrode active material, negative electrode active material), a polymer as a binder, and a solid electrolyte onto a current collector, and drying the applied slurry composition to provide an electrode mixture layer (positive electrode mixture layer, negative electrode mixture layer) on the current collector. Also, the solid electrolyte layer of the all-solid-state secondary battery is formed, for example, by applying a slurry composition containing a polymer as a binder and a solid electrolyte onto an electrode or a release substrate, and drying the applied slurry composition.

[0005] And, for example, in Patent Document 1, it has been proposed to prepare a slurry composition for an all-solid-state secondary battery using a polymer containing a polymer unit having a nitrile group in a proportion within a predetermined range and having an iodine value within a predetermined range as a binder.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the above-mentioned conventional slurry composition for all-solid-state secondary batteries, there is room for improvement in enhancing fluidity and storage stability, and in enhancing the ionic conductivity of a layer containing a solid electrolyte such as a solid electrolyte layer or an electrode binder layer formed using the slurry composition (hereinafter referred to as the "solid electrolyte-containing layer").

[0008] Therefore, an object of the present invention is to provide a slurry composition for all-solid-state secondary batteries that is excellent in fluidity and storage stability and can form a solid electrolyte-containing layer excellent in ionic conductivity, and a method for producing the same. Another object of the present invention is to provide an all-solid-state secondary battery including a solid electrolyte-containing layer excellent in ionic conductivity and a solid electrolyte-containing layer excellent in ionic conductivity.

Means for Solving the Problems

[0009] The present inventor conducted intensive studies for the purpose of solving the above problems. As a result, the present inventor newly found that a slurry composition containing a solid electrolyte, a polymer, and a solvent, and having a ratio of the degree of dispersion of the solid electrolyte measured by a predetermined method to the average primary particle diameter of the solid electrolyte within a predetermined range is excellent in fluidity and storage stability, and that a solid electrolyte-containing layer excellent in ionic conductivity can be formed by using the slurry composition, thereby completing the present invention.

[0010] That is, the present invention aims to advantageously solve the above problems. The slurry composition for an all-solid-state secondary battery of the present invention is a slurry composition for an all-solid-state secondary battery containing a solid electrolyte, a polymer, and a solvent, wherein the ratio of the degree of dispersion of the solid electrolyte measured by the particle gauge method based on JIS K5600-2-5:1999 to the average primary particle diameter of the solid electrolyte is more than 1 time and less than 30 times. Thus, a slurry composition in which the ratio of the degree of dispersion to the average primary particle diameter of the solid electrolyte (hereinafter, may be abbreviated as "degree of dispersion / average primary particle diameter") is within the above-described range is excellent in fluidity and storage stability. Further, a solid electrolyte-containing layer formed using the slurry composition is excellent in ion conductivity.

[0011] In the present invention, the "average primary particle diameter" can be measured using the method described in the examples of this specification. Also, in the present invention, the "degree of dispersion" can be measured by the particle gauge method based on JIS K5600-2-5:1999 as described above.

[0012] Here, in the slurry composition for an all-solid-state secondary battery of the present invention, it is preferable that the degree of dispersion of the solid electrolyte is less than 20 μm. If the degree of dispersion of the solid electrolyte is less than the above-described value, it is possible to further improve the fluidity and storage stability of the slurry composition while further improving the ion conductivity of the solid electrolyte-containing layer.

[0013] Also, in the slurry composition for an all-solid-state secondary battery of the present invention, it is preferable that the polymer contains a vinyl cyanide monomer unit. If the polymer contains a vinyl cyanide monomer unit, it is possible to further improve the fluidity and storage stability of the slurry composition while further improving the ion conductivity of the solid electrolyte-containing layer. In the present invention, the polymer "containing a monomer unit" means that "the polymer obtained using the monomer contains a repeating unit derived from the monomer".

[0014] Furthermore, in the slurry composition for all-solid-state secondary batteries of the present invention, it is preferable that the polymer contains (meth)acrylate monomer units. If the polymer contains (meth)acrylate monomer units, the fluidity and storage stability of the slurry composition can be further enhanced while further improving the ionic conductivity of the solid electrolyte-containing layer. In the present invention, "(meth)acryl" means "acryl and / or methacryl".

[0015] And in the slurry composition for all-solid-state secondary batteries of the present invention, the content ratio of the (meth)acrylate monomer units in the polymer is preferably 25% by mass or more and 95% by mass or less. If the polymer contains (meth)acrylate monomer units in the above-described ratio, the fluidity and storage stability of the slurry composition can be further enhanced while further improving the ionic conductivity of the solid electrolyte-containing layer. In the present invention, the content ratio of each repeating unit such as the (meth)acrylate monomer units in the polymer is 1 measured using nuclear magnetic resonance (NMR) methods such as 13 H-NMR and

[0016] 3 C-NMR. ) 1 / 2 Here, in the slurry composition for all-solid-state secondary batteries of the present invention, the solvent preferably contains an organic solvent having a solubility parameter (SP value) of 6.0 (cal / cm 3 ) 1 / 2 or more and 12.0 (cal / cm In the present invention, the "solubility parameter (SP value)" means the Hansen solubility parameter (δ) (unit: (cal / cm 3 ) 1 / 2 ), and "δ 2 = δd 2 + δp 2 + δh 2It is assumed to be represented by the relational expression 「」. In the above relational expression, 「δd」 represents 「the contribution term due to the dispersion force between molecules」, 「δp」 represents 「the contribution term due to the polar interaction between molecules」, and 「δh」 represents 「the contribution term due to the hydrogen bond between molecules」, each being a physical property value depending on the substance type (see Charles M. Hansen, "Hansen Solubility Parameters: A User’s Handbook, Second Edition", CRC Press, Boca Raton FL, (2007) (hereinafter also referred to as the 「Handbook」)). For organic solvents not described in the Handbook or the like, estimated values calculated using the computer software Hansen Solubility Parameters in Practice (HSPiP) can be used.

[0017] Further, the present invention aims to advantageously solve the above problems, and the solid electrolyte-containing layer of the present invention is characterized in that it is formed using any of the above-described slurry compositions for all-solid-state secondary batteries. The solid electrolyte-containing layer formed using the above-described slurry composition for all-solid-state secondary batteries can exhibit excellent ionic conductivity.

[0018] Furthermore, the present invention aims to advantageously solve the above problems, and the all-solid-state secondary battery of the present invention is characterized by including the above-described solid electrolyte-containing layer. By using the above-described solid electrolyte-containing layer, an all-solid-state secondary battery capable of exhibiting excellent battery performance can be obtained.

[0019] Moreover, the present invention aims to advantageously solve the above problems. The method for manufacturing a slurry composition for an all-solid-state secondary battery of the present invention includes a step of performing a mixing process on a composition containing a solid electrolyte, a polymer, and a solvent and having a solid content concentration of 70% by mass or more to prepare a premix; a step of adding a further solvent to the premix having a solid content concentration of 70% by mass or more to obtain a dilution having a solid content concentration of more than 40% by mass and less than 70% by mass; a step of performing a kneading process on the dilution having a solid content concentration of more than 40% by mass and less than 70% by mass to prepare a kneaded product; and a step of adding a further solvent to the kneaded product to dilute it. The slurry composition obtained through the above-described steps is excellent in fluidity and storage stability. Further, a solid electrolyte-containing layer formed using the slurry composition is excellent in ion conductivity.

[0020] Here, in the method for manufacturing a slurry composition for an all-solid-state secondary battery of the present invention, it is preferable that the polymer contains a vinyl cyanide monomer unit. If the polymer contains a vinyl cyanide monomer unit, it is possible to further enhance the fluidity and storage stability of the slurry composition while further improving the ion conductivity of the solid electrolyte-containing layer.

[0021] Moreover, in the method for manufacturing a slurry composition for an all-solid-state secondary battery of the present invention, it is preferable that the polymer contains a (meth)acrylic acid ester monomer unit. If the polymer contains a (meth)acrylic acid ester monomer unit, it is possible to further enhance the fluidity and storage stability of the slurry composition while further improving the ion conductivity of the solid electrolyte-containing layer.

[0022] Furthermore, in the method for manufacturing a slurry composition for an all-solid-state secondary battery of the present invention, it is preferable that the content ratio of the (meth)acrylic acid ester monomer unit in the polymer is 25% by mass or more and 95% by mass or less. If the polymer contains a (meth)acrylic acid ester monomer unit in the above-described ratio, it is possible to further enhance the fluidity and storage stability of the slurry composition while further improving the ion conductivity of the solid electrolyte-containing layer.

[0023] And in the method for producing the slurry composition for all-solid-state secondary battery of the present invention, the solvent has a solubility parameter (SP value) of 6.0 (cal / cm 3 ) 1 / 2 or more and 12.0 (cal / cm 3 ) 1 / 2 or less, and preferably contains the following organic solvents. By using an organic solvent having a solubility parameter (SP value) within the above-described range as the solvent, the fluidity and storage stability of the slurry composition can be further enhanced. Furthermore, side reactions between the solid electrolyte and the solvent can be suppressed.

[0024] Here, in the method for producing the slurry composition for all-solid-state secondary battery of the present invention, in the step of preparing the premix, it is preferable to perform a plurality of mixing treatments with different solid content concentrations of the mixing targets by adding the solvent. By preparing the premix as described above, while further enhancing the fluidity and storage stability of the slurry composition, the ion conductivity of the solid electrolyte-containing layer can be further improved.

Advantages of the Invention

[0025] According to the present invention, it is possible to provide a slurry composition for all-solid-state secondary battery and a method for producing the same, which are excellent in fluidity and storage stability and can form a solid electrolyte-containing layer excellent in ion conductivity. Further, according to the present invention, it is possible to provide an all-solid-state secondary battery including a solid electrolyte-containing layer excellent in ion conductivity and a solid electrolyte-containing layer excellent in ion conductivity.

Modes for Carrying Out the Invention

[0026] Hereinafter, embodiments of the present invention will be described in detail. Here, the slurry composition for all-solid-state secondary batteries of the present invention is used when forming a solid electrolyte-containing layer such as an electrode mixture layer or a solid electrolyte layer in an all-solid-state secondary battery such as an all-solid-state lithium-ion secondary battery. Further, the slurry composition for all-solid-state secondary batteries of the present invention can be prepared, for example, using the method for producing the slurry composition for all-solid-state secondary batteries of the present invention. And, the all-solid-state secondary battery of the present invention comprises a solid electrolyte-containing layer of the present invention formed using the slurry composition for all-solid-state secondary batteries of the present invention in at least one layer selected from the group consisting of a positive electrode mixture layer of a positive electrode, a negative electrode mixture layer of a negative electrode, and a solid electrolyte layer.

[0027] (Slurry composition for all-solid-state secondary batteries) The slurry composition for all-solid-state secondary batteries of the present invention contains a solid electrolyte, a polymer, and a solvent, and may further contain at least one selected from the group consisting of an electrode active material, a conductive material, and other components, optionally. Further, the slurry composition for all-solid-state secondary batteries of the present invention requires that the ratio of the degree of dispersion measured by the particle gauge method based on JIS K5600-2-5:1999 to the average primary particle diameter of the solid electrolyte is more than 1 time and less than 30 times.

[0028] And, since the slurry composition for all-solid-state secondary batteries of the present invention contains a solid electrolyte and a polymer that can function as a binder, it can be used for forming a solid electrolyte-containing layer such as an electrode mixture layer or a solid electrolyte layer. Further, since the degree of dispersion / average primary particle diameter of the solid electrolyte in the slurry composition for all-solid-state secondary batteries of the present invention is more than 1 time and less than 30 times, it is excellent in fluidity and storage stability, and a solid electrolyte-containing layer excellent in ion conductivity can be formed.

[0029] (Solid electrolyte) The solid electrolyte is not particularly limited as long as it is particles made of a solid having ion conductivity, but an inorganic solid electrolyte can be preferably used. As the inorganic solid electrolyte, a crystalline inorganic ion conductor, an amorphous inorganic ion conductor, or a mixture thereof can be used without particular limitation. And, for example, when all-solid-state secondary battery is an all-solid-state lithium ion secondary battery, as the inorganic solid electrolyte, usually, a crystalline inorganic lithium ion conductor, an amorphous inorganic lithium ion conductor, or a mixture thereof can be used. Among them, from the viewpoint of forming a solid electrolyte-containing layer excellent in ion conductivity, the inorganic solid electrolyte preferably contains at least one of a sulfide-based inorganic solid electrolyte and an oxide-based inorganic solid electrolyte. Hereinafter, as an example, the case where the slurry composition for all-solid-state secondary battery is a slurry composition for all-solid-state lithium ion secondary battery will be described, but the present invention is not limited to the following example.

[0030] And, examples of the crystalline inorganic lithium ion conductor include Li3N, LISICON (Li 14 Zn(GeO4)4), perovskite type (e.g., Li 0.5 La 0.5 TiO3), garnet type (e.g., Li7La3Zr2O 12 ), LIPON (Li 3+y PO 4-x N x ), Thio-LISICON (Li 3.25 Ge 0.25 P 0.75 S4), and the like. The above-described crystalline inorganic lithium ion conductors can be used alone or in combination of two or more.

[0031] Examples of the amorphous inorganic lithium ion conductor include substances containing sulfur atoms and having ion conductivity. More specifically, those obtained by using a raw material composition containing glass Li-Si-S-O, Li-P-S, and a sulfide of an element of Group 13 to Group 15 of the periodic table and Li2S, and the like can be mentioned. Here, examples of the Group 13 to Group 15 elements include Al, Si, Ge, P, As, Sb, etc. Specific examples of the sulfides of the Group 13 to Group 15 elements include Al2S3, SiS2, GeS2, P2S3, P2S5, As2S3, Sb2S3, etc. Further, examples of the method for synthesizing an amorphous inorganic lithium ion conductor using a raw material composition include amorphization methods such as mechanical milling and melt quenching. And as the amorphous inorganic lithium ion conductor using a raw material composition containing Li2S and the sulfides of the Group 13 to Group 15 elements of the periodic table, Li2S-P2S5, Li2S-SiS2, Li2S-GeS2 or Li2S-Al2S3 is preferable, and Li2S-P2S5 is more preferable. The above-mentioned amorphous inorganic lithium ion conductor can be used alone or in combination of two or more.

[0032] Among the above, as the inorganic solid electrolyte for all-solid-state lithium ion secondary batteries, from the viewpoint of forming a solid electrolyte-containing layer excellent in ion conductivity, amorphous sulfides containing Li and P, Li7La3Zr2O 12 are preferable. The amorphous sulfides containing Li and P, and Li7La3Zr2O 12 have high lithium ion conductivity, so when used as an inorganic solid electrolyte, the internal resistance of the battery can be reduced and the output characteristics can be improved.

[0033] Incidentally, the amorphous sulfide containing Li and P is more preferably a sulfide glass composed of Li2S and P2S5 from the viewpoints of reducing the internal resistance of the battery and improving the output characteristics, and is particularly preferably a sulfide glass produced from a mixed raw material of Li2S and P2S5 with a molar ratio of Li2S:P2S5 of 65:35 to 85:15. Further, the amorphous sulfide containing Li and P is preferably a sulfide glass ceramic obtained by reacting a mixed raw material of Li2S and P2S5 with a molar ratio of Li2S:P2S5 of 65:35 to 85:15 by a mechanochemical method. Incidentally, from the viewpoint of maintaining a high lithium ion conductivity, the mixed raw material preferably has a molar ratio of Li2S:P2S5 of 68:32 to 80:20.

[0034] Incidentally, the inorganic solid electrolyte may contain at least one sulfide selected from the group consisting of Al2S3, B2S3, and SiS2 as starting materials in addition to the above Li2S and P2S5 to such an extent that the ion conductivity is not decreased. Adding such a sulfide can stabilize the glass component in the inorganic solid electrolyte. Similarly, the inorganic solid electrolyte may contain at least one lithium orthooxoacid selected from the group consisting of Li3PO4, Li4SiO4, Li4GeO4, Li3BO3, and Li3AlO3 in addition to Li2S and P2S5. Including such a lithium orthooxoacid can stabilize the glass component in the inorganic solid electrolyte.

[0035] Here, in the slurry composition of the present invention, the solid electrolyte exists as a plurality of particles (solid electrolyte particles). And in the slurry composition of the present invention, at least a part of the plurality of solid electrolyte particles aggregates and exists as an aggregate. This aggregate is an aggregate containing at least a solid electrolyte and may optionally contain a polymer as a binder or the like. And the size of the aggregate correlates with the degree of dispersion measured by the particle gauge method based on JIS K5600-2-5:1999 described above. According to the study by the present inventors, when the above-mentioned degree of dispersion and the average primary particle diameter of the solid electrolyte (i.e., the average particle diameter when the solid electrolyte particles exist independently) have a predetermined relationship, the intended effect of the present invention can be achieved.

[0036] Specifically, for the slurry composition of the present invention, it is necessary that the degree of dispersion / average primary particle diameter of the solid electrolyte is more than 1 time and less than 30 times, preferably more than 2 times, more preferably more than 3 times, still more preferably 4 times or more, preferably less than 25 times, more preferably less than 20 times, and still more preferably 16 times or less. When the degree of dispersion / average primary particle diameter of the solid electrolyte is more than 1 time and less than 30 times, the fluidity and storage stability of the slurry composition can be enhanced, and the ionic conductivity of the solid electrolyte-containing layer can be improved. When the degree of dispersion / average primary particle diameter of the solid electrolyte is 1 time or less (usually 1 time), it is presumed that the polymer as a binder does not cover the surface of the solid electrolyte, and thus the solid electrolyte deteriorates due to moisture or the like, resulting in a decrease in the ionic conductivity of the solid electrolyte-containing layer. On the other hand, when the degree of dispersion / average primary particle diameter of the solid electrolyte is 30 times or more, the solid electrolyte is excessively aggregated, so that the fluidity and storage properties of the slurry composition are impaired. It is also presumed that due to the excessive aggregation of the solid electrolyte, the surface coating of the solid electrolyte by the polymer becomes insufficient, and thus the solid electrolyte deteriorates due to moisture or the like, resulting in a decrease in the ionic conductivity of the solid electrolyte-containing layer.

[0037] Here, the average primary particle diameter of the solid electrolyte is preferably 0.1 μm or more, more preferably 0.2 μm or more, still more preferably 0.5 μm or more, particularly preferably 1 μm or more, preferably 10 μm or less, more preferably 7 μm or less, still more preferably 5 μm or less, and particularly preferably 3 μm or less. If the average primary particle diameter of the solid electrolyte is 0.1 μm or more, the fluidity and storage stability of the slurry composition can be further enhanced, and the ionic conductivity of the solid electrolyte-containing layer can be further improved. On the other hand, if the average primary particle diameter of the solid electrolyte is 10 μm or less, the ionic conductivity of the solid electrolyte-containing layer can be further improved.

[0038] And the degree of dispersion of the solid electrolyte measured by the particle gauge method based on JIS K5600-2-5:1999 is preferably more than 1 μm, more preferably more than 2 μm, still more preferably more than 3 μm, preferably less than 20 μm, more preferably less than 15 μm, still more preferably less than 10 μm, and particularly preferably less than 7 μm. If the degree of dispersion of the solid electrolyte is more than 1 μm, the ionic conductivity of the solid electrolyte-containing layer can be further improved. On the other hand, if the degree of dispersion of the solid electrolyte is less than 20 μm, the fluidity and storage stability of the slurry composition can be further enhanced, and the ionic conductivity of the solid electrolyte-containing layer can be further improved. Note that the degree of dispersion of the solid electrolyte can be adjusted, for example, by changing the average primary particle diameter of the solid electrolyte, the composition of the polymer, the type of solvent, and the manufacturing conditions of the slurry composition.

[0039] <Polymer> The polymer can be used without particular limitation as long as it is a high molecular compound that can function as a binder. As for the polymer, from the viewpoint of better dispersing the solid electrolyte by well coating the surface of the solid electrolyte (that is, reducing the degree of dispersion of the solid electrolyte), and further improving the fluidity and storage stability of the slurry composition and the ionic conductivity of the solid electrolyte-containing layer, it is preferable to use a polymer containing at least one of a vinyl cyanide monomer unit and a (meth)acrylate monomer unit. Note that one kind of polymer may be used alone, or two or more kinds may be used in combination.

[0040] [Vinyl cyanide monomer unit] Examples of the vinyl cyanide monomer capable of forming a vinyl cyanide monomer unit include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, etc. Among them, acrylonitrile is preferable. Note that the polymer may contain only one kind of vinyl cyanide monomer unit, or may contain two or more kinds.

[0041] And the content ratio of the vinyl cyanide monomer unit in the polymer is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, particularly preferably 10% by mass or more, preferably 35% by mass or less, more preferably 28% by mass or less, and still more preferably 26% by mass or less, with the total repeating units (the total of monomer units and structural units; the same applies hereinafter) constituting the polymer being 100% by mass. If the ratio of the vinyl cyanide monomer unit in the polymer is 2% by mass or more, the solid electrolyte can be well dispersed. Therefore, both the fluidity and storage stability of the slurry composition can be further enhanced, and the ionic conductivity of the solid electrolyte-containing layer can be further improved. On the other hand, if the ratio of the vinyl cyanide monomer unit in the polymer is 35% by mass or less, the solubility of the polymer in the solvent does not excessively decrease, and the dispersibility of the solid electrolyte possessed by the polymer is ensured. Therefore, the fluidity and storage stability of the slurry composition and the ionic conductivity of the solid electrolyte-containing layer can be sufficiently improved.

[0042] [(Meth)acrylate monomer unit] (Meth)acrylate monomers capable of forming (meth)acrylate monomer units include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate; alkoxy acrylates such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate; 2-(perfluoroalkyl)ethyl acrylates such as 2-(perfluorobutyl)ethyl acrylate, 2-(perfluoropentyl)ethyl acrylate; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, tridecyl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate; alkoxy methacrylates such as 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate; 2-(perfluoroalkyl)ethyl methacrylates such as 2-(perfluorobutyl)ethyl methacrylate, 2-(perfluoropentyl)ethyl methacrylate; benzyl acrylate; benzyl methacrylate; and the like. Further, (meth)acrylate monomers also include diesters of α,β-ethylenically unsaturated dicarboxylic acids, and examples thereof include lower alkyl diesters of itaconic acid such as diethyl itaconate and dibutyl itaconate. Among them, methyl acrylate, ethyl acrylate, methyl methacrylate, n-butyl acrylate, t-butyl acrylate, and dibutyl itaconate are preferable, and ethyl acrylate and n-butyl acrylate are more preferable. The polymer may contain only one kind of (meth)acrylic acid ester monomer unit or may contain two or more kinds.

[0043] And the content ratio of the (meth)acrylic acid ester monomer unit in the polymer is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, and particularly preferably 75% by mass or less, with respect to 100% by mass of all the repeating units constituting the polymer. If the ratio of the (meth)acrylic acid ester monomer unit in the polymer is 25% by mass or more, the solid electrolyte can be well dispersed. Therefore, the fluidity and storage stability of the slurry composition can be further enhanced, and the ionic conductivity of the solid electrolyte-containing layer can be further improved. On the other hand, if the ratio of the (meth)acrylic acid ester monomer unit in the polymer is 95% by mass or less, the solubility of the polymer in the solvent does not excessively decrease, and the dispersibility of the solid electrolyte possessed by the polymer is ensured. Therefore, the fluidity and storage stability of the slurry composition and the ionic conductivity of the solid electrolyte-containing layer can be sufficiently improved.

[0044] [Other repeating units] The polymer may also contain repeating units other than the above-described vinyl cyanide monomer unit and (meth)acrylic acid ester monomer unit. Examples of such other repeating units preferably include repeating units derived from hydrophobic monomers (hydrophobic monomers) such as aromatic vinyl monomer units, aliphatic conjugated diene monomer units, and alkylene structural units. In the present invention, the monomer being "hydrophobic" means that "the solubility of the monomer itself in water (at 25°C) is 1 g / 1 L or less". Further, in the present invention, a monomer corresponding to a vinyl cyanide monomer or a (meth)acrylate monomer is not included in the hydrophobic monomers even if the solubility in water (at 25°C) is 1 g / 1 L or less, and is considered to correspond to a vinyl cyanide monomer or a (meth)acrylate monomer. Note that the polymer may contain only one kind of other repeating unit or may contain two or more kinds.

[0045] - Aromatic vinyl monomer unit - Examples of the aromatic vinyl monomer that can form an aromatic vinyl monomer unit include styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, α-methylstyrene, divinylbenzene, and the like.

[0046] - Aliphatic conjugated diene monomer unit - Examples of the aliphatic conjugated diene monomer that can form an aliphatic conjugated diene monomer unit include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and the like.

[0047] - Alkylene structural unit - The alkylene structural unit is a repeating unit composed only of an alkylene structure represented by the general formula: -C n H 2n - [where n is an integer of 2 or more]. The alkylene structural unit may be linear or branched, but the alkylene structural unit is preferably linear, that is, a linear alkylene structural unit. And the method for introducing the alkylene structural unit into the polymer is not particularly limited, but for example, the following method (1) or (2): (1) A method of polymerizing a monomer composition containing an aliphatic conjugated diene monomer and hydrogenating the obtained polymer to convert the aliphatic conjugated diene monomer unit into an alkylene structural unit (2)A method for polymerizing a monomer composition containing a 1-olefin monomer to prepare a polymer may be mentioned.

[0048] In addition, examples of the aliphatic conjugated diene monomer used in the method of (1) above include the aliphatic conjugated diene monomers as listed above that can form aliphatic conjugated diene monomer units. Among them, 1,3-butadiene is preferable. That is, the alkylene structural unit obtained by the method of (1) above is preferably a structural unit obtained by hydrogenating an aliphatic conjugated diene monomer unit (aliphatic conjugated diene hydride unit), and more preferably a structural unit obtained by hydrogenating a 1,3-butadiene unit (1,3-butadiene hydride unit). The selective hydrogenation of the aliphatic conjugated diene monomer unit can be carried out using known methods such as the oil layer hydrogenation method and the aqueous layer hydrogenation method. Examples of the 1-olefin monomer include ethylene, propylene, 1-butene, 1-hexene, etc. Among them, ethylene is preferable. These aliphatic conjugated diene monomers and 1-olefin monomers can be used alone or in combination of two or more.

[0049] As other repeating units, from the viewpoint of well dispersing the electrode active material and the conductive material in the slurry composition, repeating units derived from hydrophobic monomers are preferable, and styrene units, 1,3-butadiene units, 1,3-butadiene hydride units, and ethylene units are more preferable.

[0050] In addition, from the viewpoint of well dispersing the electrode active material and the conductive material in the slurry composition, the repeating units derived from hydrophobic monomers in the polymer are preferably 10% by mass or more, more preferably 12% by mass or more, still more preferably 14% by mass or more, preferably 60% by mass or less, more preferably 55% by mass or less, still more preferably 50% by mass or less, and particularly preferably 45% by mass or less, with the total repeating units constituting the polymer being 100% by mass.

[0051] [Preparation method] The preparation method of the polymer described above is not particularly limited, and it can be prepared by polymerizing a monomer composition containing the above-described monomers and then arbitrarily hydrogenating (hydrogenating) the obtained polymer. Here, the polymerization mode is not particularly limited, and any method such as solution polymerization method, suspension polymerization method, bulk polymerization method, emulsion polymerization method, etc. can be used. Also, as the polymerization reaction, any reaction such as ionic polymerization, radical polymerization, living radical polymerization, etc. can be used. And the hydrogenation method is not particularly limited, and a general method using a catalyst (for example, refer to International Publication No. 2012 / 165120, International Publication No. 2013 / 080989, and JP-A No. 2013-8485) can be used.

[0052] [Content] The amount of the polymer contained in the slurry composition of the present invention is not particularly limited, but it is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 1 part by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and still more preferably 4 parts by mass or less per 100 parts by mass of the solid electrolyte. If the content of the polymer in the slurry composition is 0.1 part by mass or more per 100 parts by mass of the solid electrolyte, the function as a binder can be sufficiently exhibited while the solid electrolyte can be well dispersed. Therefore, the fluidity and storage stability of the slurry composition can be further enhanced, and the ionic conductivity of the solid electrolyte-containing layer can be further improved. On the other hand, if the content of the polymer in the slurry composition is 10 parts by mass or less per 100 parts by mass of the solid electrolyte, the ionic conductivity of the solid electrolyte-containing layer can be sufficiently ensured.

[0053] [Solvent] As the solvent, it is preferable to use an organic solvent. Here, the organic solvent has a solubility parameter (SP value) of preferably 6.0 (cal / cm 3 ) 1 / 2 or more, and preferably 6.5 (cal / cm 3) 1 / 2 It is more preferable that it is as follows, 7.5 (cal / cm 3 ) 1 / 2 It is even more preferable that it is as follows, 8.0 (cal / cm 3 ) 1 / 2 It is particularly preferable that it is as follows, 12.0 (cal / cm 3 ) 1 / 2 It is preferable that it is below, 10.0 (cal / cm 3 ) 1 / 2 It is more preferable that it is below, 9.5 (cal / cm 3 ) 1 / 2 It is even more preferable that it is below, 9.0 (cal / cm 3 ) 1 / 2 It is particularly preferable that it is below. If an organic solvent whose solubility parameter (SP value) is within the above-described range is used, the solid electrolyte can be dispersed well, and the fluidity and storage stability of the slurry composition can be further enhanced. Furthermore, side reactions between the solid electrolyte and the solvent can be suppressed.

[0054] And specifically, as the solvent, from the viewpoint of further improving the fluidity and storage stability of the slurry composition and suppressing side reactions between the solid electrolyte and the solvent, diisobutyl ketone (8.9), toluene (8.9), xylene (8.5), cyclopentyl methyl ether (8.4), butyl butyrate (8.1), dibutyl ether (7.4), hexane (7.3), decane (6.5) are preferable, and diisobutyl ketone, cyclopentyl methyl ether, toluene, butyl butyrate, xylene are more preferable. The numerical values in parentheses described immediately after each solvent name are the solubility parameter (SP value) (unit: (cal / cm 3 ) 1 / 2 )). Note that the solvent can be used alone or as a mixture of two or more.

[0055] <Electrode active material> The electrode active material is a substance that transfers electrons in the electrodes of all-solid-state secondary batteries. And, for example, when the all-solid-state secondary battery is an all-solid-state lithium-ion secondary battery, usually, a substance that can occlude and release lithium is used as the electrode active material. Note that hereinafter, as an example, the case where the slurry composition for all-solid-state secondary batteries is the slurry composition for all-solid-state lithium-ion secondary batteries will be described, but the present invention is not limited to the following example.

[0056] And, as the positive electrode active material for all-solid-state lithium-ion secondary batteries, there are, without particular limitation, a positive electrode active material composed of an inorganic compound and a positive electrode active material composed of an organic compound. Note that the positive electrode active material may be a mixture of an inorganic compound and an organic compound.

[0057] Examples of the positive electrode active material composed of an inorganic compound include transition metal oxides, composite oxides of lithium and transition metals (lithium-containing composite metal oxides), transition metal sulfides, etc. As the above transition metals, Fe, Co, Ni, Mn, etc. are used. Specific examples of the inorganic compounds used as the positive electrode active material include lithium-containing composite metal oxides such as LiCoO2 (lithium cobaltate), LiNiO2, LiMnO2, LiMn2O4, LiFePO4, LiFeVO4; transition metal sulfides such as TiS2, TiS3, amorphous MoS2; Cu2V2O3, amorphous V2O-P2O5, MoO3, V2O5, V6O 13 and other transition metal oxides; and the like. These compounds may be partially element-substituted. The above-described positive electrode active material composed of an inorganic compound can be used alone or in combination of two or more.

[0058] Examples of the positive electrode active material composed of an organic compound include polyaniline, polypyrrole, polyacene, disulfide-based compounds, polysulfide-based compounds, N-fluoropyridinium salts, etc. The above-described positive electrode active material composed of an organic compound can be used alone or in combination of two or more.

[0059] In addition, examples of the negative electrode active material for all-solid-state lithium-ion secondary batteries include allotropes of carbon such as graphite and coke. Note that the negative electrode active material made of an allotrope of carbon can also be used in the form of a mixture or coating with a metal, metal salt, oxide, or the like. Further, examples of the negative electrode active material include oxides or sulfates such as silicon, tin, zinc, manganese, iron, and nickel; metallic lithium; lithium alloys such as Li-Al, Li-Bi-Cd, and Li-Sn-Cd; lithium transition metal nitrides; silicone; and the like. The above-described negative electrode active materials can be used alone or in combination of two or more.

[0060] <Conductive material> The conductive material is for ensuring electrical contact between the electrode active materials in the electrode composite layer formed using a slurry composition for all-solid-state secondary batteries (slurry composition for all-solid-state secondary battery electrodes). Examples of the conductive material include conductive carbon materials such as carbon black (e.g., acetylene black, Ketjenblack (registered trademark), furnace black, etc.), single-layer or multi-layer carbon nanotubes (multi-layer carbon nanotubes include cup-stacked types), carbon nanohorns, vapor-grown carbon fibers, mild carbon fibers obtained by crushing polymer fibers after firing, single-layer or multi-layer graphene, and carbon nonwoven sheets obtained by firing nonwoven fabrics made of polymer fibers; and fibers or foils of various metals can be used. These can be used alone or in combination of two or more.

[0061] Note that the content of the conductive material in the slurry composition for all-solid-state secondary batteries is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less per 100 parts by mass of the electrode active material. If the amount of the conductive material is within the above range, sufficient electrical contact between the electrode active materials can be ensured, and excellent battery characteristics (such as output characteristics) can be exhibited in the all-solid-state secondary battery.

[0062] <Other components> In addition, examples of other components that the slurry composition for all-solid-state secondary batteries may optionally contain include dispersants, leveling agents, defoaming agents, and reinforcing materials. Further, for example, when the all-solid-state secondary battery is an all-solid-state lithium-ion secondary battery, lithium salts may also be included as other components. These other components are not particularly limited as long as they do not affect the battery reaction.

[0063] And as for other components such as lithium salts, dispersants, leveling agents, defoaming agents, and reinforcing materials, they are not particularly limited, and for example, those described in JP-A-2012-243476 can be used. Also, their blending amounts are not particularly limited, and for example, they can be set to the amounts described in JP-A-2012-243476.

[0064] <Properties> Note that the solid content concentration of the slurry composition for all-solid-state secondary batteries is not particularly limited, but for example, it can be 30% by mass or more and less than 70% by mass.

[0065] (Method for manufacturing a slurry composition for all-solid-state secondary batteries) And the above-described slurry composition of the present invention can be prepared, for example, using the method for manufacturing a slurry composition for all-solid-state secondary batteries of the present invention. Here, the manufacturing method of the present invention includes a step of performing a mixing process on a composition containing a solid electrolyte, a polymer, and a solvent and having a solid content concentration of 70% by mass or more to prepare a premix (premixing step), a step of adding a solvent to the premix having a solid content concentration of 70% by mass or more to obtain a diluted product having a solid content concentration of more than 40% by mass and less than 70% by mass (first dilution step), a step of performing a kneading process on the diluted product having a solid content concentration of more than 40% by mass and less than 70% to prepare a kneaded product (kneading step), and a step of adding a solvent to the kneaded product to dilute it (second dilution step). And the slurry composition obtained through the above-described steps is excellent in fluidity and storage stability, and a solid electrolyte-containing layer excellent in ion conductivity can be formed by using the slurry composition.

[0066] In addition, the method for manufacturing the slurry composition of the present invention described above may include steps other than the premixing step, the first dilution step, the kneading step, and the second dilution step. Further, in the method for manufacturing the slurry composition of the present invention described above, in addition to the solid electrolyte, the polymer, and the solvent, an electrode active material, a conductive material, and other components can be optionally used. The electrode active material, the conductive material, and other components are not particularly limited. For example, in the premixing step, they can be subjected to a mixing treatment together with the solid electrolyte, the polymer, and the solvent and included in the premix. And, as the solid electrolyte, the polymer, the solvent, the electrode active material, the conductive material, and other components in the "method for manufacturing a slurry composition for an all-solid-state secondary battery", those similar to those described in the "slurry composition for an all-solid-state secondary battery" can be used, and their preferred examples and preferred contents are also the same as those described in the "slurry composition for an all-solid-state secondary battery".

[0067] <Premixing step> In the premixing step, a composition (starting composition) containing at least a solid electrolyte, a polymer, and a solvent is subjected to a mixing treatment in a state where the solid content concentration is 70% by mass or more to prepare a premix having a solid content concentration of 70% by mass or more. By performing the mixing treatment on the composition having a solid content concentration of 70% by mass or more, the solid electrolyte can be favorably dispersed in the resulting slurry composition. The upper limit of the solid content concentration of the starting composition and the premix is not particularly limited, but can be, for example, 90% by mass or less, respectively.

[0068] The mixing device used for the mixing treatment in the premixing step is not particularly limited, and known devices such as a planetary mixer can be used. Also, when obtaining the premix in the premixing step, the solvent may be charged into the mixing device all at once, continuously, or intermittently, but intermittent charging is more preferable. And in the premixing step, it is preferable to perform a plurality of mixing treatments with different solid content concentrations of the mixing target due to the addition of the solvent. By changing the solid content concentration of the composition to be mixed step by step from a high state to a low state and performing the mixing treatment at each solid content concentration, the solid electrolyte can be dispersed well, and the fluidity and storage stability of the slurry composition, as well as the ion conductivity of the solid electrolyte-containing layer, can be further improved.

[0069] The number of times of the above mixing treatment is not particularly limited, but it is preferably 2 or more times, and more preferably 3 or more times. If the number of times of the mixing treatment is 2 or more times, the solid electrolyte can be dispersed better, and the fluidity and storage stability of the slurry composition, as well as the ion conductivity of the solid electrolyte-containing layer, can be further improved. On the other hand, the upper limit of the number of times of the mixing treatment is not particularly limited, but from the viewpoint of the production efficiency of the slurry composition, it is preferably 8 or less times, and more preferably 7 or less times. Also, the conditions of the mixing treatment are not particularly limited. For example, the time of each mixing treatment can be in the range of 10 seconds or more and 10 minutes or less.

[0070] <First Dilution Step> In the first dilution step, a solvent is added to the premix obtained in the premixing step to obtain a diluent (first diluent) with a solid content concentration of more than 40% by mass and less than 70% by mass. The solvent added in the first dilution step may be the same as or different from the solvent used in the mixture preparation step, but the same one is preferable.

[0071] <Kneading Step> In the kneading step, a first diluent having a solid content concentration of more than 40% by mass and less than 70% by mass obtained in the first dilution step is kneaded to obtain a kneaded product. By performing a kneading process on the first diluent having a solid content concentration within the above-described range, sufficient shear can be applied to the first diluent to be kneaded. Therefore, the solid electrolyte can be dispersed well, and the fluidity and storage stability of the slurry composition, as well as the ionic conductivity of the solid electrolyte-containing layer, can be further improved.

[0072] The kneading device used for the kneading process in the kneading step is not particularly limited as long as it can apply shear to the first diluent having a solid content concentration within the above-described range, and a known device can be used. And as the kneading device, for example, the mixing device used in the premixing step can be used as it is.

[0073] Also, in the kneading step, it is preferable to perform a plurality of kneading processes with different solid content concentrations of the kneading target by adding a solvent. In this way, by changing the solid content concentration of the first diluent to be kneaded step by step from a high state to a low state and performing the kneading process at each solid content concentration, the solid electrolyte can be dispersed well, and the fluidity and storage stability of the slurry composition, as well as the ionic conductivity of the solid electrolyte-containing layer, can be further improved. The number of times of the above kneading process is not particularly limited, but is preferably 2 or more times, and more preferably 3 or more times. If the number of times of the kneading process is 2 or more times, the solid electrolyte can be dispersed better, and the fluidity and storage stability of the slurry composition, as well as the ionic conductivity of the solid electrolyte-containing layer, can be further improved. On the other hand, the upper limit of the number of times of the kneading process is not particularly limited, but from the viewpoint of the production efficiency of the slurry composition, it is preferably 5 or less times, and more preferably 4 or less times. Also, the conditions of the kneading process are not particularly limited. For example, the time of each kneading process can be in the range of 10 seconds or more and 10 minutes or less.

[0074] <Second Dilution Step> In the second dilution step, a solvent is added to the kneaded product obtained in the kneading step. The solvent added in the second dilution step may be the same as or different from the solvents used in the premixing step and the first dilution step, but the same solvent is preferred.

[0075] Note that the kneaded product (second diluted product) to which the solvent is added in the second dilution step may be used as a slurry composition as it is, or may be used as a slurry composition after passing through other steps such as further mixing treatment. In the method for producing the slurry composition of the present invention, the solid electrolyte may be crushed, for example, during the premixing step, the first dilution step, the kneading step, and / or the second dilution step. That is, the adjustment of the average primary particle diameter of the solid electrolyte may be performed when implementing the method for producing the slurry composition of the present invention.

[0076] (Solid electrolyte-containing layer) The solid electrolyte-containing layer of the present invention is a layer containing a solid electrolyte. Examples of the solid electrolyte-containing layer include an electrode binder layer (positive electrode binder layer, negative electrode binder layer) that exchanges electrons through an electrochemical reaction, and a solid electrolyte layer provided between a positive electrode binder layer and a negative electrode binder layer facing each other. The solid electrolyte-containing layer of the present invention is formed using the above-described slurry composition for all-solid-state secondary batteries. For example, after applying the above-described slurry composition to the surface of a suitable substrate to form a coating film, the formed coating film is dried to form the solid electrolyte-containing layer. That is, the solid electrolyte-containing layer of the present invention is composed of a dried product of the above-described slurry composition, and usually contains a solid electrolyte and a polymer, and may further contain at least one selected from the group consisting of an electrode active material, a conductive material, and other components. Note that each component contained in the solid electrolyte-containing layer was contained in the above slurry composition, and the content ratio of these components is usually equal to the content ratio in the above slurry composition.

[0077] Since the solid electrolyte-containing layer of the present invention is formed from the slurry composition for all-solid-state secondary batteries of the present invention, it can exhibit excellent ionic conductivity.

[0078] <Base material> Here, there is no limitation on the base material to which the slurry composition is applied. For example, a coating film of the slurry composition may be formed on the surface of a release base material, the coating film may be dried to form a solid electrolyte-containing layer, and the release base material may be peeled off from the solid electrolyte-containing layer. In this way, the solid electrolyte-containing layer peeled off from the release base material can also be used as a self-supporting film for forming battery members (for example, electrodes and solid electrolyte layers, etc.) of an all-solid-state secondary battery. However, from the viewpoint of increasing the manufacturing efficiency of battery members by omitting the step of peeling the solid electrolyte-containing layer, it is preferable to use a current collector or an electrode as the base material. Specifically, when preparing the electrode mixture layer, it is preferable to apply the slurry composition onto a current collector as the base material. Further, when preparing the solid electrolyte layer, it is preferable to apply the slurry composition onto an electrode (positive electrode or negative electrode).

[0079] [Current collector] As the current collector, a material having electrical conductivity and being electrochemically durable is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. can be used. Among them, a copper foil is particularly preferable as the current collector used for the negative electrode. Also, an aluminum foil is particularly preferable as the current collector used for the positive electrode. Note that the above materials may be used alone or in combination of two or more in any ratio.

[0080] [Electrode] The electrodes (positive electrode and negative electrode) are not particularly limited, but examples include electrodes in which an electrode mixture layer containing an electrode active material, a solid electrolyte, and an electrode binder is formed on the above-described current collector. The electrode active material, solid electrolyte, and electrode binder contained in the electrode mixture layer in the electrode are not particularly limited, and known ones can be used. Note that the electrode mixture layer in the electrode may correspond to the solid electrolyte-containing layer of the present invention.

[0081] <Method for forming solid electrolyte-containing layer> As methods for forming a solid electrolyte-containing layer on a substrate such as the above-described current collector and electrode, the following methods can be mentioned. 1) A method of applying the slurry composition of the present invention to the surface of the substrate (in the case of an electrode, the surface on the side of the electrode binder layer, the same applies hereinafter) and then drying it; 2) A method of immersing the substrate in the slurry composition of the present invention and then drying it; and 3) A method of applying the slurry composition of the present invention on a release substrate, drying it to produce a solid electrolyte-containing layer, and transferring the obtained solid electrolyte-containing layer to the surface of an electrode or the like. Among these, the method of 1) is particularly preferable because it is easy to control the layer thickness of the solid electrolyte-containing layer. The method of 1) specifically includes a step of applying the slurry composition on the substrate (coating step) and a step of drying the slurry composition applied on the substrate to form a solid electrolyte-containing layer (solid electrolyte-containing layer forming step).

[0082] [Coating step] And in the coating step, there is no particular limitation on the method of applying the slurry composition on the substrate, and examples thereof include methods such as the doctor blade method, reverse roll method, direct roll method, gravure method, extrusion method, and brush coating method.

[0083] [Solid electrolyte-containing layer forming step] Also, in the solid electrolyte-containing layer forming step, there is no particular limitation on the method of drying the slurry composition on the substrate, and known methods can be used. Examples of the drying method include drying methods using warm air, hot air, low-humidity air, vacuum drying method, and drying methods by irradiation with infrared rays, electron beams, etc. In addition, when the solid electrolyte-containing layer is an electrode binder layer, it is preferable to perform a pressing treatment using a roll press or the like after drying. By performing the pressing treatment, the obtained electrode binder layer can be made denser.

[0084] (Electrode) And, an electrode formed by forming an electrode mixture layer on a current collector using the slurry composition for all-solid-state secondary batteries of the present invention includes a solid electrolyte, a polymer as a binder, and an electrode active material, and optionally further includes at least one selected from the group consisting of a conductive material and other components, and can exhibit excellent ionic conductivity.

[0085] (Solid electrolyte layer) Further, a solid electrolyte layer formed using the slurry composition for all-solid-state secondary batteries of the present invention includes a solid electrolyte and a polymer as a binder, and optionally further contains other components, and can exhibit excellent ionic conductivity. Note that the solid electrolyte layer usually does not contain an electrode active material.

[0086] (All-solid-state secondary battery) The all-solid-state secondary battery of the present invention usually has a positive electrode, a solid electrolyte layer, and a negative electrode, and is characterized in that at least one of the positive electrode mixture layer of the positive electrode, the negative electrode mixture layer of the negative electrode, and the solid electrolyte layer is the solid electrolyte-containing layer of the present invention. That is, the all-solid-state secondary battery of the present invention includes a positive electrode provided with a positive electrode mixture layer formed using the slurry composition for all-solid-state secondary battery positive electrodes as the slurry composition for all-solid-state secondary batteries of the present invention, a negative electrode provided with a negative electrode mixture layer formed using the slurry composition for all-solid-state secondary battery negative electrodes as the slurry composition for all-solid-state secondary batteries of the present invention, and at least one of a solid electrolyte layer formed using the slurry composition for all-solid-state secondary battery electrolyte layers as the slurry composition for all-solid-state secondary batteries of the present invention. And, since the all-solid-state secondary battery of the present invention includes the solid electrolyte-containing layer of the present invention, it is excellent in battery performance such as output characteristics.

[0087] Here, as an all-solid-state secondary battery electrode having an electrode mixture layer that does not correspond to the solid electrolyte-containing layer of the present invention and can be used in the all-solid-state secondary battery of the present invention, any all-solid-state secondary battery electrode can be used without particular limitation as long as it has an electrode mixture layer that does not correspond to the solid electrolyte-containing layer of the present invention.

[0088] In addition, as the solid electrolyte layer that can be used in the all-solid-state secondary battery of the present invention and does not correspond to the solid electrolyte-containing layer of the present invention, there is no particular limitation, and for example, any solid electrolyte layer such as the solid electrolyte layer described in JP-A-2012-243476, JP-A-2013-143299, and JP-A-2016-143614 can be used.

[0089] Then, in the all-solid-state secondary battery of the present invention, the positive electrode and the negative electrode are laminated so that the positive electrode mixture layer of the positive electrode and the negative electrode mixture layer of the negative electrode face each other with the solid electrolyte layer interposed therebetween, and after arbitrarily pressing to obtain a laminate, depending on the battery shape, it can be obtained by putting it into a battery case as it is, or by winding, folding, etc., and sealing. Incidentally, if necessary, an expanded metal, an overcurrent prevention element such as a fuse and a PTC element, a lead plate, etc. can be put into the battery case to prevent an increase in pressure inside the battery and overcharge / discharge. The shape of the battery may be any of a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, etc.

Examples

[0090] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, “%” and “parts” representing amounts are based on mass unless otherwise specified. In the examples and comparative examples, the average primary particle diameter and dispersity of the solid electrolyte, the content ratio of each repeating unit of the polymer, the fluidity and storage stability of the slurry composition, and the ionic conductivity of the solid electrolyte-containing layer were evaluated by the following methods.

[0091] <Average primary particle diameter> The average primary particle diameter of the solid electrolyte was determined by observing 100 solid electrolyte particles with an electron microscope, measuring the particle diameter according to JIS Z8827-1:2008, and calculating the arithmetic mean value of those values. <Dispersity> The degree of dispersion of the solid electrolyte was measured by the particle gauge method based on JIS K5600-2-5:1999. For the measurement, a PI-901 particle size analyzer (grinder meter) (manufactured by Tester Sangyo Co., Ltd., measurement range: 0 to 100 μm) was used. <Content ratio of each repeating unit> After coagulating 100 g of the binder composition with 1 L of methanol, it was vacuum dried at 60 °C for 12 hours. The obtained dried polymer was 1 analyzed by 1H-NMR. Based on the obtained analysis values, the content ratio (mass %) of each repeating unit contained in the polymer was calculated. <Fluidity> The viscosity of the slurry composition was measured with a Brookfield B-type viscometer (60 rpm, 25 °C). The smaller the viscosity value, the better the fluidity of the slurry composition. A: Viscosity is less than 3000 mPa·s B: Viscosity is 3000 mPa·s or more and less than 5000 mPa·s C: Viscosity is 5000 mPa·s or more and less than 8000 mPa·s D: Viscosity is 8000 mPa·s or more or does not disperse (no fluidity due to excessive aggregation, viscosity measurement impossible.) <Storage stability> 1 g of the slurry composition immediately after preparation was dried on a hot plate at 130 °C for 1 hour to vaporize the solvent, and the initial solid content concentration (%) was measured. Separately, the slurry composition immediately after preparation was stored in a sealed state at 25 °C. After storing for 1 week, 1 g of the supernatant of the slurry composition was sampled, and the solid content concentration after storage (%) was measured in the same manner as the initial solid content concentration. Then, the solid content concentration retention rate = solid content concentration after storage / initial solid content concentration × 100 (%) was calculated. The larger the solid content concentration retention rate, the smaller the degree of sedimentation of the solid content, indicating that the slurry composition has excellent storage stability. A: Solid content concentration retention rate is 90% or more B: Solid content concentration retention rate is 80% or more and less than 90% C: Solid content concentration retention rate is 50% or more and less than 80% D: Solid content concentration retention rate is less than 50% <Ionic conductivity> First, in a glove box (with a water content of 1 ppm or less), the slurry composition was dried on a hot plate at 130 °C, and the obtained powder was formed into a cylindrical shape with a diameter of 10 mm and a thickness of 1 mm to obtain a measurement sample. For this measurement sample, the Li-ion conductivity (at 25 °C) was measured by the alternating current impedance method. For the measurement, a frequency response analyzer (manufactured by Solartron Analytical, product name "Solartron (registered trademark) 1260") was used, and the measurement conditions were an applied voltage of 10 mV and a measurement frequency range of 0.01 MHz to 1 MHz. The obtained Li-ion conductivity was designated as S0. Separately, in a dry room (with a water content of 127 ppm or less and a dew point equivalent to -40 °C), the slurry composition was dried on a hot plate at 130 °C, and the obtained powder was formed into a cylindrical shape with a diameter of 11.28 mm and a thickness of 0.5 mm to obtain a measurement sample. For this measurement sample, the Li-ion conductivity (at 25 °C) was measured in the same manner as S0 above. The obtained Li-ion conductivity was designated as S1. Then, the conductivity retention rate = S1 / S0 × 100 (%) was determined and evaluated according to the following criteria. The larger the conductivity retention rate, the more the deterioration of the solid electrolyte due to moisture is suppressed, indicating that the solid electrolyte-containing layer prepared using the slurry composition can exhibit excellent ion conductivity. A: Conductivity retention rate is 90% or more B: Conductivity retention rate is 80% or more and less than 90% C: Conductivity retention rate is 50% or more and less than 80% D: Conductivity retention rate is less than 50%

[0092] (Example 1) (Preparation of Binder Composition) To a 1 L flask with a septum equipped with a stirrer, 100 parts of ion-exchanged water and 0.2 part of sodium dodecylbenzenesulfonate as an emulsifier were added. The gas phase was replaced with nitrogen gas, and after heating to 60 °C, 0.25 part of potassium persulfate (KPS) as a polymerization initiator was dissolved in 20.0 parts of ion-exchanged water and added. On one hand, 40 parts of ion-exchanged water, 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier, 15 parts of styrene as an aromatic vinyl monomer, 75 parts of n-butyl acrylate as a (meth)acrylate monomer, and 10 parts of acrylonitrile as a vinyl cyanide monomer were mixed in another container to obtain a monomer composition. This monomer composition was continuously added to the 1-L flask with a septum over 3 hours for polymerization. During the addition, the reaction was carried out at 60°C. After the addition was completed, the reaction was terminated by further stirring at 80°C for 3 hours. Subsequently, an appropriate amount of butyl butyrate was added to the obtained aqueous dispersion of the polymer to obtain a mixture. Then, vacuum distillation was carried out at 80°C to remove water and excess butyl butyrate from the mixture, and a binder composition (a butyl butyrate solution of the polymer, solid content concentration 8%) was obtained. And the content ratio of each repeating unit in the obtained polymer was measured. The results are shown in Table 1. <Preparation of Slurry Composition for All-Solid-State Secondary Battery> As follows, a slurry composition for an all-solid-state secondary battery was prepared by multi-stage mixing and kneading. [Premixing Step] 100 parts of a sulfide glass (Li2S / P2S5 = 70 mol% / 30 mol%, average primary particle diameter: 1.0 μm) composed of Li2S and P2S5 as a solid electrolyte and 2 parts (equivalent amount of solid content) of the above binder composition were mixed (Mixing Process 1). Butyl butyrate was added to the mixed solution obtained in Mixing Process 1 to prepare a composition with a solid content concentration of 80%. This composition was mixed at 2000 rpm for 2 minutes using a planetary mixer (product name "Bubble Removing and Kneading Tarou (Registered Trademark) ARE310". The same applies hereinafter.) (Mixing Process 2). Butyl butyrate was added to the mixed solution obtained in Mixing Process 2 to prepare a composition with a solid content concentration of 70%. This composition was mixed at 2000 rpm for 2 minutes using a planetary mixer (Mixing Process 3). [First Dilution Step] Next, butyl butyrate was added to the mixed solution (premix) with a solid content concentration of 70% obtained in Mixing Process 3 to prepare a composition (first diluent) with a solid content concentration of 65%. [Kneading Step] Then, the first diluent with a solid content concentration of 65% obtained in the first dilution step was kneaded at 2000 rpm for 2 minutes using a rotary mixer (kneading treatment 1). Butyl butyrate was added to the mixture obtained in the kneading treatment 1 to prepare a composition with a solid content concentration of 60%. This composition was mixed at 2000 rpm for 2 minutes using a rotary mixer (kneading treatment 2). Butyl butyrate was added to the mixture obtained in the kneading treatment 2 (solid content concentration 60%) to prepare a composition with a solid content concentration of 55%. This composition was kneaded at 2000 rpm for 2 minutes using a rotary mixer (kneading treatment 3). [Second Dilution Step] Furthermore, butyl butyrate was added to the mixture (kneaded product) obtained in the kneading treatment 3 to prepare a composition (second diluent) with a solid content concentration of 50%. This composition was mixed at 2000 rpm for 2 minutes using a rotary mixer to prepare a slurry composition for all-solid-state secondary batteries (solid content concentration 50%). Then, evaluations of dispersibility, fluidity, storage stability, and ionic conductivity were performed. The results are shown in Table 1.

[0093] (Examples 2 - 7) When preparing the binder composition and the slurry composition, except that xylene (Example 2), toluene (Example 3), hexane (Example 4), decane (Example 5), cyclopentyl methyl ether (Example 6), and diisobutyl ketone (Example 7) were used instead of butyl butyrate respectively, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0094] (Example 8) When preparing the binder composition, except that the amount of acrylonitrile was changed to 28 parts, the amount of n-butyl acrylate was changed to 62 parts, and the amount of styrene was changed to 10 parts, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0095] (Example 9) When preparing the binder composition, except that the amount of acrylonitrile was changed to 3 parts, the amount of n-butyl acrylate was changed to 80 parts, and the amount of styrene was changed to 17 parts, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0096] (Example 10) When preparing the binder composition, except that the amount of acrylonitrile was changed to 5 parts, the amount of n-butyl acrylate was changed to 90 parts, and the amount of styrene was changed to 5 parts, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0097] (Example 11) When preparing the binder composition, except that as the (meth)acrylic acid ester monomer, 50 parts of n-butyl acrylate and 25 parts of ethyl acrylate were used instead of 75 parts of n-butyl acrylate, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0098] (Example 12) Except that a binder composition prepared as follows was used, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1. (Preparation of Binder Composition) Into a reactor, 2 parts of potassium oleate as an emulsifier, 0.1 part of potassium phosphate as a stabilizer, and 150 parts of water were charged. Further, 14 parts of acrylonitrile as a vinyl cyanide monomer, 43 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 43 parts of n-butyl acrylate as a (meth)acrylate monomer, and 0.31 part of t-dodecyl mercaptan as a molecular weight regulator were added. In the presence of 0.015 part of ferrous sulfate as an activator and 0.05 part of paramethane hydroperoxide as a polymerization initiator, emulsion polymerization was initiated at 10°C. When the polymerization conversion rate reached 85%, 0.2 part of hydroxylamine sulfate per 100 parts of the monomer was added to terminate the polymerization. Subsequent to the termination of polymerization, the mixture was heated, and at 70°C under reduced pressure, unreacted monomers were recovered by steam distillation. Then, 2 parts of alkylated phenol as an antioxidant was added to obtain a polymer latex. 400 mL of the obtained polymer latex (total solid content: 48 g) was charged into a 1-liter autoclave equipped with a stirrer, and nitrogen gas was passed through for 10 minutes to remove dissolved oxygen in the polymer latex. Thereafter, 50 mg of palladium acetate as a hydrogenation reaction catalyst was dissolved in 180 mL of water to which nitric acid four times the molar amount of Pd was added, and then added. After replacing the inside of the system with hydrogen gas twice, the contents of the autoclave were heated to 50°C under a pressure of hydrogen gas up to 3 MPa, and hydrogenation reaction was carried out for 6 hours. The contents were returned to room temperature, and after making the inside of the system a nitrogen atmosphere, it was concentrated using an evaporator until the solid content concentration reached 40% to obtain an aqueous dispersion of a polymer (hydrogenated nitrile rubber). Subsequently, an appropriate amount of butyl butyrate was added to the obtained aqueous dispersion of the polymer to obtain a mixture. Thereafter, vacuum distillation was carried out at 80°C to remove water and excess butyl butyrate from the mixture, and a binder composition (butyl butyrate solution of the polymer, solid content concentration 8%) was obtained. And the content ratio of each repeating unit in the obtained polymer was measured. The results are shown in Table 1.

[0099] (Example 13) A slurry composition for an all-solid-state secondary battery was prepared in the same manner as in Example 12, except that xylene was used instead of butyl butyrate during the preparation of the binder composition and the slurry composition. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0100] (Example 14) A slurry composition for an all-solid-state secondary battery was prepared in the same manner as in Example 12, except that the amount of acrylonitrile was changed to 24 parts, the amount of 1,3-butadiene was changed to 33 parts, and the amount of n-butyl acrylate was changed to 43 parts during the preparation of the binder composition. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0101] (Example 15) (Preparation of Binder Composition) A binder composition was prepared in the same manner as in Example 1. (Preparation of Slurry Composition for All-Solid-State Secondary Battery) A slurry composition for an all-solid-state secondary battery was prepared by multi-stage mixing and kneading as follows. [Premixing Step] 100 parts of a sulfide glass (Li2S / P2S5 = 70 mol% / 30 mol%, average primary particle diameter: 1.0 μm) composed of Li2S and P2S5 as a solid electrolyte and 2 parts (equivalent amount of solid content) of the above binder composition were mixed (Mixing Treatment 1). Butyl butyrate was added to the mixed solution obtained in Mixing Treatment 1 to prepare a composition with a solid content concentration of 70%. This composition was mixed at 2000 rpm for 2 minutes using a planetary mixer (product name "Bubble Removing Knetaro (registered trademark) ARE310". The same applies hereinafter) (Mixing Treatment 2). [First Dilution Step] Next, butyl butyrate was added to the mixed solution (premix) with a solid content concentration of 70% obtained in Mixing Treatment 2 to prepare a composition (first diluent) with a solid content concentration of 65%. [Kneading Step] Then, the first diluent with a solid content concentration of 65% obtained in the first dilution step was kneaded at 2000 rpm for 2 minutes using a planetary mixer (Kneading Treatment 1). [Second Dilution Process] Furthermore, butyl butyrate was added to the mixed solution (kneaded product) obtained in the kneading process 1 to prepare a composition (second diluent) with a solid content concentration of 50%. This composition was mixed at 2000 rpm for 2 minutes using a rotary-revolution mixer to prepare a slurry composition for all-solid-state secondary batteries (solid content concentration: 50%). Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0102] (Example 16) When preparing the slurry composition, an oxide-based inorganic solid electrolyte (Li7La3Zr2O 12 , average primary particle diameter: 1.2 μm) was used instead of the sulfide glass composed of Li2S and P2S5. In the same manner as in Example 2, a slurry composition for all-solid-state secondary batteries was prepared. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0103] (Example 17) When preparing the slurry composition, an oxide-based inorganic solid electrolyte (Li7La3Zr2O 12 , average primary particle diameter: 1.2 μm) was used instead of the sulfide glass composed of Li2S and P2S5. In the same manner as in Example 13, a slurry composition for all-solid-state secondary batteries was prepared. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0104] (Comparative Example 1) [Preparation of Binder Composition] A binder composition was prepared in the same manner as in Example 1. [Preparation of Slurry Composition for All-Solid-State Secondary Batteries] 100 parts of a sulfide glass composed of Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, average primary particle diameter: 1.0 μm) as a solid electrolyte, 2 parts (equivalent amount of solid content) of the above binder composition, and butyl butyrate were mixed together using a rotary-revolution mixer to prepare a slurry composition for all-solid-state secondary batteries with a solid content concentration of 50%. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0105] (Comparative Example 2) <Preparation of Binder Composition> A binder composition was prepared in the same manner as in Example 2. <Preparation of Slurry Composition for All-Solid-State Secondary Battery> 100 parts of a sulfide glass (Li2S / P2S5 = 70 mol% / 30 mol%, average primary particle diameter: 1.0 μm) composed of Li2S and P2S5 as a solid electrolyte, 2 parts (equivalent amount of solid content) of the above binder composition, and xylene were mixed together using a rotation-revolution mixer to prepare a slurry composition for all-solid-state secondary battery with a solid content concentration of 50%. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0106] (Comparative Example 3) <Preparation of Binder Composition> A binder composition was prepared in the same manner as in Example 1. <Preparation of Slurry Composition for All-Solid-State Secondary Battery> 100 parts of an oxide-based inorganic solid electrolyte (Li7La3Zr2O 12 , average primary particle diameter: 1.2 μm) as a solid electrolyte, 2 parts (equivalent amount of solid content) of the above binder composition, and butyl butyrate were mixed together using a rotation-revolution mixer to prepare a slurry composition for all-solid-state secondary battery with a solid content concentration of 50%. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0107] (Comparative Example 4) A slurry composition for all-solid-state secondary battery was prepared in the same manner as in Example 1, except that the amount of acrylonitrile was changed to 40 parts, the amount of n-butyl acrylate was changed to 50 parts, and the amount of styrene was changed to 10 parts during the preparation of the binder composition. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0108] (Comparative Example 5) When preparing the binder composition, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1, except that the amount of acrylonitrile was changed to 0 part, the amount of n-butyl acrylate was changed to 90 parts, and the amount of styrene was changed to 10 parts. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0109] (Comparative Example 6) When preparing the binder composition and the slurry composition, a slurry composition for all-solid-state secondary batteries was prepared in the same manner as in Example 1, except that N-methyl-2-pyrrolidone was used instead of butyl butyrate. Then, various evaluations were conducted in the same manner as in Example 1. The results are shown in Table 2.

[0110] In Tables 1 and 2 shown below, "Sulfide" indicates sulfide glass, "Oxide" indicates Li7La3Zr2O 12 and, "AN" indicates acrylonitrile unit, "BA" indicates n-butyl acrylate unit, "EA" indicates ethyl acrylate unit, "ST" indicates styrene unit, "H-BD" indicates 1,3-butadiene hydride unit, "CPME" indicates cyclopentyl methyl ether, "DIK" indicates diisobutyl ketone, "NMP" indicates N-methyl-2-pyrrolidone, "Batch" indicates batch mixing.

[0111]

Table 1

[0112]

Table 2

[0113] From Tables 1 to 2, it can be seen that the slurry compositions for all-solid-state secondary batteries of Examples 1 to 17 are excellent in fluidity and storage stability, and can form a solid electrolyte-containing layer excellent in ionic conductivity. On the other hand, from Table 2, it can be seen that the slurry compositions for all-solid-state secondary batteries of Comparative Examples 1 to 6, in which the dispersity / average primary particle diameter is outside the predetermined range, are inferior in fluidity and storage stability, and cannot form a solid electrolyte-containing layer excellent in ionic conductivity.

Industrial Applicability

[0114] According to the present invention, it is possible to provide a slurry composition for an all-solid-state secondary battery that is excellent in fluidity and storage stability and can form a solid electrolyte-containing layer excellent in ionic conductivity, and a method for producing the same. Further, according to the present invention, it is possible to provide an all-solid-state secondary battery including a solid electrolyte-containing layer excellent in ionic conductivity and a solid electrolyte-containing layer excellent in ionic conductivity.

Claims

1. A step of performing a mixing process on a composition containing a solid electrolyte, a polymer, and a solvent and having a solid content concentration of 70% by mass or more to prepare a premix; A step of further adding a solvent to the premix having a solid content concentration of 70% by mass or more to obtain a dilution having a solid content concentration of more than 40% by mass and less than 70% by mass; A step of performing a kneading process on the dilution having a solid content concentration of more than 40% by mass and less than 70% to prepare a kneaded product; A step of further adding a solvent to the kneaded product and diluting it; A method for producing a slurry composition for an all-solid-state secondary battery, comprising:

2. The method for producing a slurry composition for an all-solid-state secondary battery according to claim 1, wherein the polymer contains a vinyl cyanide monomer unit.

3. The method for producing a slurry composition for an all-solid-state secondary battery according to claim 1 or 2, wherein the polymer contains a (meth)acrylate monomer unit.

4. The method for producing a slurry composition for an all-solid-state secondary battery according to claim 3, wherein the content ratio of the (meth)acrylate monomer unit in the polymer is 25% by mass or more and 95% by mass or less.

5. The solvent has a solubility parameter (SP value) of 6.0 (cal / cm ３ ), １／２ or more and 12.0 (cal / cm ３ ), １／２ and the method for producing a slurry composition for an all-solid-state secondary battery according to any one of claims 1 to 4, which contains the following organic solvents.

6. The method for producing a slurry composition for an all-solid-state secondary battery according to any one of claims 1 to 5, wherein in the step of preparing the premix, a plurality of mixing processes with different solid content concentrations of the mixing target are performed by adding a solvent.

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