JPWO2012063827A1 - Slurry for all solid state battery, green sheet for all solid state battery, all solid state battery, and method for producing slurry for all solid state battery - Google Patents

Abstract

An all-solid battery having excellent battery characteristics is provided by improving the dispersibility of the slurry for all-solid batteries and producing a green sheet for all-solid batteries with a smooth surface. In the all-solid-state battery slurry containing at least an inorganic material, an organic material, and a solvent, the organic material includes a nonionic dispersant having a molecular weight of at least 15000 or more.

Description

  The present invention relates to an all-solid battery slurry, and more particularly to an all-solid battery slurry having high dispersibility.

  Moreover, this invention relates to the green sheet for all-solid-state batteries which uses the said slurry for all-solid-state batteries.

  Moreover, this invention relates to the all-solid-state battery which uses the said green sheet for all-solid-state batteries.

  Furthermore, this invention relates to the manufacturing method of the slurry for all-solid-state batteries.

  In recent years, batteries, particularly secondary batteries, have been widely used for main power sources, backup power sources, and hybrid vehicle (HEV) power sources for portable electronic devices such as cellular phones and portable personal computers. Among secondary batteries, lithium ion secondary batteries that have high energy density and can be charged and discharged are widely used.

  In such a lithium ion secondary battery, an organic electrolyte (electrolytic solution) in which a lithium salt is dissolved in a carbonate ester or an ether organic solvent has been conventionally used as a medium for transferring ions.

  However, in a lithium ion secondary battery using an electrolytic solution, it cannot be asserted that there is no risk of leakage of the electrolytic solution in an unexpected situation. Moreover, since the organic solvent etc. which are used for electrolyte solution are combustible substances, further raising the safety | security of a battery is calculated | required.

  Therefore, in order to enhance the safety of the lithium ion secondary battery, it has been proposed to use a solid electrolyte as the electrolyte instead of the organic solvent electrolyte. In particular, since a compound having a NASICON structure is an ionic conductor capable of conducting lithium ions at high speed, development of an all-solid-state secondary battery using such a compound as a solid electrolyte is in progress. .

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-5279) proposes an all-solid lithium secondary battery in which all constituent elements are made of solid using a nonflammable solid electrolyte. This all-solid-state lithium secondary battery is an active material green sheet obtained by sheet-forming a slurry containing an active material made of a phosphoric acid compound, and a solid obtained by sheet-forming a slurry containing a solid electrolyte made of a phosphoric acid compound The electrolyte green sheets are laminated and heat-treated. The slurry used is to add polyvinyl butyral resin as a binder, n-butyl acetate as a solvent, and dibutyl phthalate as a plasticizer to an active material or solid electrolyte powder, and mix with a zirconia ball in a ball mill for 24 hours. It is produced by.

JP 2007-5279 A

  However, as in Patent Document 1, when a slurry is prepared by adding a binder, a solvent, and a plasticizer to an inorganic material such as an active material or a solid electrolyte, the dispersibility of the inorganic material is poor, and the slurry is used. When a green sheet was produced, there were a problem that the smoothness of the sheet surface was poor and a problem that the thickness of the sheet became non-uniform. In particular, in an all-solid battery in which at least one of the positive electrode layer or the negative electrode layer and the solid electrolyte layer are joined by sintering, the interface between the solid electrolyte layer and the electrode layer after sintering is affected by the smoothness of the sheet surface. As a result, there was a problem that the battery characteristics of the all-solid-state battery deteriorated.

  Then, the objective of this invention is providing the slurry for all-solid-state batteries which has high dispersibility.

  The slurry for an all-solid battery of the present invention is an all-solid battery slurry containing at least an inorganic material, an organic material, and a solvent, and the organic material contains a nonionic dispersant having a molecular weight of at least 15000 or more. It is characterized by doing.

  Since the slurry for an all-solid battery of the present invention contains a nonionic dispersant having a molecular weight of 15000 or more, the aggregation of the inorganic material can be sterically suppressed regardless of the acid basicity of the active site on the surface of the inorganic material. it can. Therefore, an all-solid battery slurry having high dispersibility can be obtained.

  The nonionic dispersant preferably has an ether bond, an ester bond or a hydroxyl group in the side chain in the molecule.

  The nonionic dispersant preferably contains at least one selected from polyvinyl acetal resin, cellulose resin, acrylic resin, urethane resin, vinyl acetate resin, and polyvinyl alcohol resin.

  The inorganic material preferably contains at least one selected from an electrode active material, a solid electrolyte precursor, a solid electrolyte, and a conductive agent.

  The inorganic material preferably contains a compound having a NASICON type structure.

  The content of the nonionic dispersant is preferably 0.1 to 35 parts by weight with respect to 100 parts by weight of the inorganic material. In this case, the effect of dispersing the inorganic material is sufficiently obtained, and further, the increase in viscosity of the organic vehicle can be suppressed.

  It is preferable that content of a solvent is 30-1000 weight part with respect to 100 weight part of inorganic materials. In this case, it is possible to achieve both the dispersibility and stability of the slurry for an all solid state battery.

  The volume ratio of the solvent in the all-solid battery slurry is preferably 65% or more and 85% or less, and the viscosity of the all-solid battery slurry is preferably 0.1 Pa · s or more and 3.4 Pa · s or less. In this case, it is possible to suppress the occurrence of cracks in the green sheet and to produce an all-solid battery having good battery characteristics.

  In this case, the solvents are methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol and other alcohols, n-hexane, o -It is preferable to contain at least 1 sort (s) selected from xylene, m-xylene, p-xylene, toluene, and ethylene acetate.

  Further, the solvent contains a solvent A having a dielectric constant of 6 or less and a solvent B that is soluble with the solvent A and has a dielectric constant of 17 or more, and the solvent A contains more than 1% by volume with respect to the total solvent. It is preferable to make it. In this case, it is possible to obtain a slurry composition for an all-solid battery that suppresses elution of lithium into the slurry and has high dispersibility, and it is possible to produce an all-solid battery with good battery characteristics. Because it becomes.

  In this case, the solvent A preferably contains at least one selected from n-hexane, o-xylene, m-xylene, p-xylene, toluene, and ethylene acetate.

  The solvent B preferably contains at least one selected from methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol.

  The volume ratio of the solvent A is preferably 10% or more with respect to the total solvent.

  The volume average particle diameter of the inorganic material is preferably 0.5 μm or more and 5 μm or less, and the 90 volume% average particle diameter is preferably 0.5 μm or more and 20 μm or less. In this case, an all-solid battery slurry having higher dispersibility can be obtained, and an all-solid battery having good battery characteristics can be produced.

  In this case, the average particle size of 99 volume% of the inorganic material is preferably 0.5 μm or more and 20 μm or less.

  In addition, the organic material contains a polymer material C that is a nonionic dispersant and a polymer material D that is not limited to a nonionic dispersant, and the polymer material C is mixed before the polymer material D, The average degree of polymerization of the molecular material D is preferably higher than the average degree of polymerization of the polymer material C, and the difference in solubility parameter SP value is preferably 5.0 or less. In this case, an all-solid battery slurry having higher dispersibility can be obtained, and an all-solid battery having good battery characteristics can be produced.

  In this case, the average degree of polymerization of the polymer material C is preferably 100 or more and 400 or less.

  The polymer material C and the polymer material D preferably include the same structural unit.

  The addition amount of the polymer material C is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the inorganic material.

  An all-solid battery green sheet can be produced using the all-solid battery slurry described above. In this case, the green sheet for an all-solid battery has excellent sheet surface smoothness and a uniform sheet thickness.

  Further, using the above-described green sheet for an all-solid battery, a positive electrode layer, a negative electrode layer, and a solid electrolyte layer are produced, and the positive electrode layer and the negative electrode layer are laminated and integrated through the solid electrolyte layer, and fired. A solid battery can be manufactured. In this case, since the smoothness of the surface of the green sheet is excellent, the interface between the solid electrolyte layer and the electrode layer after sintering is closely joined by sintering, thereby suppressing delamination and cracking. Therefore, the battery characteristics of the all solid state battery are also excellent.

  The manufacturing method of the slurry for all-solid-state batteries of this invention is a manufacturing method of the slurry for all-solid-state batteries containing an inorganic material, an organic material, and a solvent at least, Comprising: An organic material, an inorganic material, and a solvent are prepared. And a step of preparing a slurry by mixing an organic material, an inorganic material, and a solvent to obtain a slurry, and the organic material contains a nonionic dispersant having a molecular weight of at least 15000 or more. Yes.

  Furthermore, the method for producing the slurry for an all-solid battery of the present invention includes a step of preparing an organic material, an inorganic material, and a solvent, a mixing step of mixing the organic material, the inorganic material, and the solvent to obtain a mixture, The mixture obtained in the mixing step and a slurry preparation step of mixing another organic material to obtain a slurry, wherein the organic material contains a nonionic dispersant having a molecular weight of at least 15000 or more, and the other organic The material preferably contains at least a binder.

  Furthermore, the manufacturing method of the slurry for an all-solid-state battery of the present invention includes a step of preparing an organic material, an inorganic material, and a solvent, a mixing step of mixing the inorganic material and the solvent to obtain a mixture, and the organic material and the solvent. A nonionic dispersion having a molecular weight of at least 15000 or more, and a second mixing step of mixing the mixture and the organic vehicle. An agent can be included.

  ADVANTAGE OF THE INVENTION According to this invention, the slurry for all-solid-state batteries which has high dispersibility can be obtained, and it becomes possible to produce the all-solid-state battery with favorable battery characteristics.

It is typical sectional drawing of the battery laminated body which concerns on 1st Embodiment of this invention. It is a figure which shows the charging / discharging curve of the all-solid-state battery produced in Example 10 of the 4th experiment example. It is a graph which shows the relationship between the shear rate of the slurry 2-7 produced in the 5th experiment example, and a shear stress. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of the solid electrolyte powder P1 produced by the 8th experiment example. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of the solid electrolyte powder P2 produced in the 8th experiment example. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of the solid electrolyte powder P3 produced in the 8th experiment example. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of the solid electrolyte powder P4 produced by the 8th experiment example. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of the solid electrolyte powder P5 produced by the 8th experiment example. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of the solid electrolyte powder P6 produced by the 8th experiment example. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of the solid electrolyte powder P7 produced by the 8th experiment example. It is a figure which shows the particle size distribution curve (solid line) and the cumulative particle size distribution curve (broken line) of mixed powder P8 produced in the 8th experiment example.

Hereinafter, modes for carrying out the present invention will be described. The embodiment of the invention described here is an example for carrying out the present invention, and is not limited to the method and form described here.
[First Embodiment]
The slurry for an all-solid battery of the present invention contains at least an inorganic material, an organic material, and a solvent. One type of organic material has a nonionic dispersant having a molecular weight of 15000 or more. The dispersing agent is not particularly limited as long as it is a nonionic organic material having a molecular weight of 15000 or more having a dispersing effect, and preferably has an ether bond, an ester bond or a side chain in the molecule. Specifically, it is preferable to contain at least one selected from polyvinyl acetal resin, cellulose resin, acrylic resin, urethane resin, vinyl acetate resin, and polyvinyl alcohol resin.

  The slurry for an all-solid battery of the present invention is obtained by mixing a dispersant, an inorganic material, and a solvent. Further, various additives such as a binder and a plasticizer may be mixed. When the binder is added, a dispersant, an inorganic material, and a solvent are mixed to prepare a mixture, and the mixture and the binder are mixed. In this case, aggregation of the binder can be suppressed, and a highly dispersible slurry for an all-solid battery can be obtained.

  In addition, the said inorganic material, a solvent, a binder, etc. are not specifically limited. Examples of the inorganic material include an electrode active material, a solid electrolyte precursor, a solid electrolyte, a conductive agent and a sintering aid. The solvent may be an organic solvent or an aqueous solvent, and can be arbitrarily set in consideration of required characteristics and productivity of the secondary battery.

  FIG. 1 shows a schematic cross-sectional view of a battery stack according to an embodiment of the present invention.

  The battery stack 10 includes a solid electrolyte layer 12 including a solid electrolyte, a negative electrode layer 11, and a positive electrode layer 13. The negative electrode layer 11 and the positive electrode layer 13 are provided at positions facing each other with the solid electrolyte layer 12 interposed therebetween. Then, at least one of the negative electrode layer 11 or the positive electrode layer 13 and the solid electrolyte layer 12 are fired and bonded. Although not shown, a current collector layer may be disposed on the surface of the positive electrode layer 13 not in contact with the solid electrolyte layer 12, and the current collector layer on the surface of the negative electrode layer 11 not in contact with the solid electrolyte layer 12. May be arranged.

  The all-solid-state battery slurry (solid electrolyte slurry) for producing the solid electrolyte layer 12 contains a solid electrolyte as an inorganic material.

  Moreover, the slurry for an all-solid battery (positive electrode slurry) for producing the positive electrode layer 13 contains at least a positive electrode active material as an inorganic material, and may further contain a solid electrolyte or a conductive agent.

  The all-solid battery slurry (negative electrode slurry) for producing the negative electrode layer 11 contains at least a negative electrode active material as an inorganic material, and further contains a solid electrolyte, a conductive agent such as a metal material or a carbon material. May be.

For the solid electrolyte, for example, a material having ionic conductivity and small electronic conductivity can be used. Examples of the solid electrolyte include lithium halide, lithium nitride, lithium oxyacid salt, and derivatives thereof. Further, Li-PO compounds such as lithium phosphate (Li ₃ PO _4), LIPON mixed with nitrogen lithium phosphate _{(LiPO 4-x N x)} , Li-SiO , such as Li ₄ SiO ₄ Compounds, Li-P-Si-O compounds, Li-V-Si-O compounds, La _0.51 Li _0.35 TiO _2.94 having a perovskite structure, La _0.55 Li _0.35 TiO ₃ , Li _3x La _{2 / 3-x} TiO _{3 and the} like, and compounds having a garnet-type structure having Li, La, and Zr are mentioned, and it is particularly preferable that a compound having a nasicon-type structure is included. NASICON-type composition Li _x M _y (PO ₄₎ structure compounds having ₃ (x = 1~2, y = 1~2 , M = Ti, Ge, Al, Ga, comprising at least one of Zr) And a part of P may be substituted with B, Si or the like. Examples of the compound having a NASICON type structure include Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ and Li _1.2 Al _0.2 Ti _1.8 (PO ₄ ) ₃ .

The kind of negative electrode active material contained in the negative electrode layer 11 is not particularly limited. Examples of negative electrode active materials include graphite-lithium compounds, lithium alloys such as Li-Al, NASICON-type lithium-containing phosphate compounds such as Li ₃ V ₂ (PO ₄ ) ₃ and Li ₃ Fe ₂ (PO ₄ ) ₃ , Li An oxide of at least one element selected from the group consisting of ₄ Ti ₅ O ₁₂ , Ti, Nb, W, Si, Sn, Cr, Fe, and Mo may be used. Specifically, it preferably contains at least one oxide selected from the group consisting of titanium oxide, silicon oxide, niobium oxide, tin oxide, chromium oxide, iron oxide, and molybdenum oxide. Such an oxide has a large capacity per weight and a low potential with respect to Li. Therefore, an all-solid battery having a large capacity density, a high battery voltage, and a high energy density can be obtained.

The kind of positive electrode active material contained in the positive electrode layer 13 is not particularly limited. Examples of positive electrode active materials include layered compounds such as LiCoO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , spinel materials such as LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiFePO ₄ , LiMnPO _{4 4} , phosphorus-containing compounds such as LiCoPO ₄ , LiNiPO ₄ , and Li ₃ V ₂ (PO ₄ ) ₃ .

  The negative electrode layer 11 and the positive electrode layer 13 preferably contain a NASICON solid electrolyte. This is because when the solid electrolyte layer 12 includes a NASICON solid electrolyte, the negative electrode layer 11, the positive electrode layer 13, and the solid electrolyte layer 12 are easily joined by firing.

  At least one of the negative electrode layer 11 or the positive electrode layer 13 and the solid electrolyte layer 12 are preferably joined by laminating a plurality of green sheets to form a laminate, and firing the laminate. In this case, since at least one of the negative electrode layer 11 or the positive electrode layer 13 and the solid electrolyte layer 12 can be integrally fired and bonded, it is possible to manufacture an all-solid battery at a lower cost. .

  The all solid state battery according to the present invention is manufactured as follows as an example.

First, as an inorganic material, an electrode active material and a solid electrolyte material are prepared. At this time, in the case where the electrode active material contains oxides of two or more elements, a material in which oxides of the respective elements are mixed may be prepared. When the solid electrolyte includes a NASICON solid electrolyte, a material for the NASICON solid electrolyte is prepared. For example, a material obtained by mixing NASICON solid electrolytes having different compositions such as Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ and Li _1.2 Al _0.2 Ti _1.8 (PO ₄ ) ₃ may be used. Further, as the material for the NASICON solid electrolyte, a material containing a crystal phase of the NASICON solid electrolyte or a glass material on which the crystal phase of the NASICON solid electrolyte is deposited may be used.

  The volume average particle diameter of the inorganic material is preferably 0.5 μm or more and 5 μm or less, and the 90 volume% average particle diameter is preferably 0.5 μm or more and 20 μm or less. In this case, it is possible to suppress the aggregation and sedimentation of the inorganic material in the all-solid battery slurry, and to stabilize the slurry while the inorganic material maintains high dispersibility. When the volume average particle size of the inorganic material exceeds 5 μm, the dispersibility of the slurry decreases with time. Moreover, when the average particle diameter of 90 volume% of an inorganic material exceeds 20 micrometers, it will become easy to settle a coarse grain. Moreover, in order to suppress the sedimentation of coarse particles and further stabilize the dispersibility of the slurry, it is more preferable that the 99% by volume average particle size of the inorganic material is 0.5 μm or more and 20 μm or less.

  Here, the volume average particle diameter is an integrated 50% particle diameter of the particle size distribution, and the 90 volume% average particle diameter is an integrated 90% particle diameter of the particle size distribution. The particle size of the inorganic material can be measured with a laser diffraction / scattering particle size distribution measuring device. In addition, the kind of said inorganic material and a solvent are not specifically limited. Examples of the inorganic material include an electrode active material, a solid electrolyte precursor, a solid electrolyte, a conductive agent and a sintering aid. The solvent may be an organic solvent or an aqueous solvent, and can be arbitrarily set in consideration of required characteristics, productivity, and the like of an all-solid battery.

  Next, according to the manufacturing method of the slurry of this invention, each slurry of a solid electrolyte layer, a positive electrode layer, and a negative electrode layer is prepared. For example, first, an organic material and a solvent are mixed to produce an organic vehicle. As an example of a method for producing a solid electrolyte slurry for forming a solid electrolyte layer, a solid electrolyte and a solvent are mixed to produce a mixture. Next, the mixture and the organic vehicle are mixed. As a method for preparing a slurry for forming a positive electrode layer or a negative electrode layer, a positive electrode active material, a negative electrode active material, a conductive agent or the like is mixed in addition to a solid electrolyte to prepare a mixture, and an organic vehicle is added to the mixture and mixed. Thus, a slurry is prepared.

  Examples of the solvent include water, cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate, and γ-butyrolactone. Esters such as, ε-caprolactone; acylonitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran and ethylene glycol diethyl ether: alcohols such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; N -Amides such as methylpyrrolidone and N, N-dimethylformamide. These solvents may be used alone or in admixture of two or more and appropriately selected from the viewpoint of drying speed and environment. In addition, although the solvent used when manufacturing the said organic vehicle may differ from the solvent used when manufacturing the said mixture, it is preferable to use the same solvent.

  The volume ratio of the solvent in the all-solid battery slurry is 65% or more and 85% or less, and the viscosity of the all-solid battery slurry is 0.1 Pa · s or more and 3.4 Pa · s or less. preferable. The volume ratio of the solvent in the all-solid battery slurry is 65% or more and 85% or less, and the viscosity of the all-solid battery slurry is 0.1 Pa · s or more and 3.4 Pa · s or less. When the slurry applied on the material is dried, the convection of the slurry generated inside the slurry on the substrate can be suppressed, and the generation of cracks can be suppressed. When the all-solid battery slurry has a viscosity of 0.1 Pa · s or less, it is difficult to apply the slurry on the substrate, and when the all-solid battery slurry has a viscosity of 3.4 Pa · s or more, As a result, the dispersibility of the inorganic material decreases, and irregularities occur on the surface of the green sheet.

  The volume ratio [%] of the solvent in the slurry can be calculated by the volume ratio [%] of the solvent in the slurry = the volume of the solvent [cc] ÷ the volume of the slurry [cc]. Here, the volume of the slurry [cc] = the volume of the inorganic material [cc] + the volume of the organic material [cc] + the volume of the solvent [cc].

  In setting the volume ratio of the solvent in the all-solid battery slurry to 65% to 85% and the viscosity of the all-solid battery slurry to 0.1 Pa · s to 3.4 Pa · s. , Solvents include alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, n-hexane, o-xylene, It is preferable to include at least one selected from m-xylene, p-xylene, toluene, and ethylene acetate.

  Next, each of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer is formed into a green sheet. Although a shaping | molding method is not specifically limited, For example, the method using well-known coating machines, such as a die coater and a comma coater, a screen printing method, etc. are mentioned.

  Next, the green sheets of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer are laminated to form a laminate. The lamination method is not particularly limited, and examples thereof include a hot isostatic press (HIP) method, a cold isostatic press (CIP) method, and a hydrostatic press (WIP) method.

  Next, the laminate is fired. The positive electrode layer and the negative electrode layer are joined to the solid electrolyte layer by firing.

Finally, the fired laminate is sealed in, for example, a coin cell. The sealing method is not particularly limited. For example, you may seal the laminated body after baking with resin. Alternatively, insulating paste such as Al ₂ O ₃ may be applied or dipped around the laminated body and sealed by heat treatment.

Note that a conductive layer such as a metal layer may be formed on the positive electrode layer or the negative electrode layer as the current collector layer in order to efficiently draw current from the positive electrode layer or the negative electrode layer. Examples of the method for forming the conductive layer include a sputtering method. Alternatively, a metal paste may be applied or dipped and heat treated.
[Second Embodiment]
In the second embodiment, a part of the configuration of the first embodiment described above is changed.

  Specifically, the following two types of solvent A and solvent B were prepared and used as the solvent. The solvent A is composed of one having a dielectric constant of 6 or less. The solvent B is soluble with the solvent A and has a dielectric constant of 17 or more. And the ratio of the solvent A with respect to all the solvents was made to become more than 1% by volume ratio. Other configurations of the second embodiment are the same as those of the first embodiment described above.

  As the solvent A, for example, at least one selected from n-hexane, o-xylene, m-xylene, p-xylene, toluene, and ethylene acetate can be used.

  As the solvent B, for example, at least one selected from methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol is used. can do.

  In addition, it is preferable that the volume ratio of the solvent A is 10% or more and 90% or less with respect to all the solvents. This is because when a certain amount of the solvent B having a high dielectric constant is contained, a slurry having high dispersibility can be obtained by dissolving the organic material.

  The solvent A and the solvent B are used when each slurry of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer is prepared.

  In preparing the slurry, first, a mixed solvent of the solvent A and the solvent B is prepared.

  And when preparing the solid electrolyte slurry for forming a solid electrolyte layer, an organic material, a solid electrolyte, and the said mixed solvent are mixed, and a solid electrolyte slurry is prepared. Instead of this method, the solvent A and the solid electrolyte are first mixed to prepare a mixture, and then the mixture, the organic material, and the solvent B are mixed to prepare a solid electrolyte slurry. good.

  In addition, when preparing a slurry for forming a positive electrode layer or a negative electrode layer, a positive electrode active material, a negative electrode active material, a conductive agent, or the like is mixed in addition to a solid electrolyte to prepare a mixture. A slurry is prepared by mixing with the mixed solvent. Instead of this method, first, in addition to the solid electrolyte, a positive electrode active material or a negative electrode active material, a conductive agent and the like are mixed with a solvent A to prepare a mixture, and the mixture, the organic material and the solvent B are mixed. A slurry may be prepared.

  Also in the second embodiment, green sheets of a solid electrolyte layer, a positive electrode layer, and a negative electrode layer were produced using such slurry. And using these green sheets, the all-solid-state battery was produced.

According to this embodiment, it is possible to obtain a slurry composition for an all solid state battery that suppresses elution of lithium into the slurry and has high dispersibility, and to produce an all solid state battery having good battery characteristics. Is possible.
[Third Embodiment]
In the third embodiment, a part of the configuration of the first embodiment described above is also changed.

  Specifically, the organic material contains a polymer material C and a polymer material D which are nonionic dispersants, and the polymer material C is mixed with the inorganic material before the polymer material D, The average polymerization degree of the molecular material D was higher than the average polymerization degree of the polymer material C, and the difference in the solubility parameter SP value was 5.0 or less. Other configurations of the third embodiment are the same as those of the first embodiment described above.

  The solubility parameter SP value δ can be expressed by Equation 1, and is a value that serves as a measure of the solubility of the two-component solution.

Formula 1

  Here, ΔE is the molar evaporation energy and V is the molar volume. In the present embodiment, by setting the difference in SP value to 5.0 or less, the organic material contained in the slurry does not aggregate, and the inorganic material and the organic material can be uniformly mixed.

  Further, by making the average degree of polymerization of the polymer material D higher than that of the polymer material C, it is possible to obtain an all-solid-state battery slurry having high dispersibility while giving an appropriate viscosity to the slurry.

  The average degree of polymerization of the polymer material C is preferably 400 or less. Furthermore, the average degree of polymerization is preferably 100 or more. In this case, when the average degree of polymerization is greater than 400, the polymer material C tends to aggregate in the slurry, and when the average degree of polymerization is less than 2, the dispersion effect is reduced.

  Moreover, it is preferable that the polymeric material C and the polymeric material D contain the same structural unit. In this case, the polymer material C and the polymer material D are easily dispersed uniformly in the slurry, and a slurry with higher dispersibility can be obtained.

  The polymer material C and the polymer material D are used when each slurry of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer is prepared.

  When preparing a solid electrolyte slurry for forming a solid electrolyte layer, the polymer material C and the solid electrolyte are mixed to prepare a mixture, and then the polymer material D and the mixture are mixed to prepare a solid electrolyte slurry. To do.

  In addition, when preparing a slurry for forming the positive electrode layer or the negative electrode layer, a positive electrode active material, a negative electrode active material, a conductive agent, or the like is mixed in addition to the solid electrolyte to prepare a mixture, and the mixture and the polymer material C Are mixed with the polymer material D to prepare a slurry.

  Note that the polymer material C may be mixed with a solvent in advance to produce the organic vehicle C, and the organic vehicle C and the inorganic material may be mixed. Alternatively, the polymer material D may be mixed with a solvent in advance to produce the organic vehicle D, and then a mixture of the organic vehicle C and the inorganic material and the organic vehicle D may be mixed to prepare a slurry.

  By mixing the polymer material C having a low average degree of polymerization and the inorganic material, the polymer material C is adsorbed on the surface of the inorganic material and improves the dispersibility of the slurry. Furthermore, by mixing the polymer material D having a high average degree of polymerization, it is considered that the polymer material D functions as a binder while maintaining dispersibility, and gives an appropriate viscosity to the slurry. Therefore, the average degree of polymerization of the polymer material D is not particularly limited as long as it is higher than the average degree of polymerization of the polymer material C. Further, if the polymer material C and the polymer material D are polymer materials having the same structural formula, they are uniformed in the slurry, so that a slurry with higher dispersibility can be obtained.

  Also in the third embodiment, green sheets of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer were produced using such slurry. And using these green sheets, the all-solid-state battery was produced.

  According to this embodiment, it is possible to obtain an all-solid battery slurry having higher dispersibility, and it is possible to produce an all-solid battery with good battery characteristics.

Experimental example

  In order to confirm the effectiveness of the present invention, the following experiment was conducted.

[First Experimental Example]
In the first experimental example, different types of organic materials to be dispersed were changed to produce a plurality of types of dispersions, and the dispersibility of each dispersion was compared. Specifically, a dispersion using a nonionic dispersant having a molecular weight of 20000 (Example 1), a dispersion using an anionic dispersant (Comparative Example 1), and a dispersion using a cationic dispersant ( Comparative Example 2) was prepared and the dispersibility was compared.

In addition, about the material of each Example and each comparative example, the manufacturing method, etc. which are not described in particular below, it was based on the content disclosed by 1st Embodiment mentioned above.
Example 1
A nonionic dispersant (polyvinyl butyral having a molecular weight of 20000) was used as a dispersant, which was dissolved in alcohol as a solvent to prepare a dispersant solution E. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent. A glass powder having a composition of NASICON solid electrolyte: Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (hereinafter referred to as inorganic powder a) was used as the inorganic powder.

100 parts by weight of inorganic powder a and 150 parts by weight of dispersant solution E were weighed, and inorganic powder a and dispersant solution E were mixed to prepare dispersion E.
(Comparative Example 1)
An anionic dispersant (Marialim, NOF Corporation) was used as a dispersant and dissolved in alcohol as a solvent to prepare a dispersant solution F. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent.

100 parts by weight of inorganic powder a and 150 parts by weight of dispersant solution F were weighed, and inorganic powder a and dispersant solution F were mixed to prepare dispersion F.
(Comparative Example 2)
A cationic dispersant (Arcard C-50, Lion Co., Ltd.) was used as a dispersant and dissolved in alcohol as a solvent to prepare a dispersant solution G. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent.

  100 parts by weight of the inorganic powder a and 150 parts by weight of the dispersant solution G were weighed, and the inorganic powder a and the dispersant solution G were mixed to prepare a dispersion G.

  In order to confirm the influence of the polarity of the dispersant on the dispersibility of the inorganic powder in the slurry, the dispersions EG were evaluated for dispersibility based on the presence or absence of thixotropy. (Table 1) Dispersibility of the dispersion is evaluated by the presence or absence of thixotropy by reciprocating the range of 0 to 200 [1 / s] by strain control using ARES RFSIII manufactured by TA Instruments Inc. did. The evaluation was based on Example 1 where the thixotropy was low (or equivalent), and the thixotropy was x.

  The dispersibility of Example 1 using a nonionic system having a molecular weight of 20000 was good, and Comparative Examples 1 and 2 using a cationic and anionic dispersant were inferior to this.

The inorganic powder a has both acidic and basic active sites on its surface. Anionic dispersants are adsorbed at acidic active sites and cationic dispersants are adsorbed at basic active sites, functioning as dispersants for NASICON solid electrolytes. Both act on both acid and basic active sites. Can not do it. On the other hand, since nonionic dispersants can act on both acid and basic active sites, the adsorption layer formed on the particle surface layer is more uniform than when anionic or cationic dispersants are used. It is presumed that the highest dispersibility was obtained when a nonionic dispersant was used because the steric barrier action for preventing contact between the two became higher.
[Second Experimental Example]
In the second experimental example, a dispersion was prepared using a nonionic dispersant as the organic material to be dispersed. However, the dispersibility of each dispersion obtained by changing the molecular weight of the nonionic dispersant was changed. Compared. Specifically, the molecular weight was changed to 15000 (Example 2), 18000 (Example 3), and 12000 (Comparative Example 3).

In addition, about the material of each Example and each comparative example, the manufacturing method, etc. which are not described in particular below, it was based on the content disclosed by 1st Embodiment mentioned above.
(Example 2)
A nonionic dispersant (polyvinyl butyral having a molecular weight of 15000) was used as a dispersant, and this was dissolved in alcohol as a solvent to prepare a dispersant solution H. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent.

100 parts by weight of inorganic powder a and 150 parts by weight of dispersant solution H were weighed, and inorganic powder a and dispersant solution H were mixed to prepare dispersion H.
(Example 3)
A nonionic dispersant (polyvinyl butyral having a molecular weight of 18000) was used as a dispersant, and this was dissolved in alcohol as a solvent to prepare a dispersant solution I. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent.

100 parts by weight of the inorganic powder a and 150 parts by weight of the dispersant solution I were weighed, and the inorganic powder a and the dispersant solution I were mixed to prepare a dispersion I.
(Comparative Example 3)
A nonionic dispersant (polyvinyl butyral having a molecular weight of 12000) was used as a dispersant, and this was dissolved in alcohol as a solvent to prepare a dispersant solution J. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent.

  100 parts by weight of the inorganic powder a and 150 parts by weight of the dispersant solution J were weighed, and the inorganic powder a and the dispersant solution J were mixed to prepare a dispersion J.

  In order to confirm the influence of the molecular weight of the dispersant on the dispersibility of the inorganic powder in the slurry, the dispersions H to J were evaluated based on the presence or absence of thixotropy. The evaluation was based on Example 1 where the thixotropy was low (or equivalent), and the thixotropy was x.

The comparative example 3 had poor dispersibility, and the examples 2 and 3 had good dispersibility. In the slurry of Comparative Example 3, it is presumed that since the dispersant has a low molecular weight, the inorganic powders contacted and aggregated to reduce dispersibility. On the other hand, in the case of Example 2 and Example 3 using a dispersant having a molecular weight of 15,000 or more, the steric barrier action to prevent the particles from contacting each other is high, and thus high dispersibility is obtained. Presumed.
[Third experimental example]
In the third experimental example, a dispersion was prepared using a nonionic dispersant having a molecular weight of 20000 for the organic material to be dispersed. However, the dispersibility of each obtained dispersion was varied by changing the content thereof. (Examples 4 to 9).

In addition, about the material of each Example, the manufacturing method, etc. which are not described in particular below, it was based on the content disclosed by 1st Embodiment mentioned above.
Example 4
A nonionic dispersant (polyvinyl butyral having a molecular weight of 20000) was used as a dispersant, and this was dissolved in alcohol as a solvent to prepare a dispersant solution K. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent.

With respect to 100 parts by weight of the inorganic powder a, 12 parts by weight of the dispersant solution K was weighed, and the inorganic powder a and the dispersant solution K were mixed to prepare a dispersion K1.
(Example 5)
A dispersion K2 was produced in the same manner as in Example 4. In the dispersion K2, 60 parts by weight of the dispersant solution K was mixed with 100 parts by weight of the inorganic powder a.
(Example 6)
A dispersion K3 was produced in the same manner as in Example 4. In dispersion K3, 120 parts by weight of dispersant solution K was mixed with 100 parts by weight of inorganic powder a.
(Example 7)
A dispersion K4 was produced in the same manner as in Example 4. In dispersion K4, 240 parts by weight of dispersant solution K was mixed with 100 parts by weight of inorganic powder a.
(Example 8)
A dispersion K5 was prepared in the same manner as in Example 4. In dispersion K5, 420 parts by weight of dispersant solution K was mixed with 100 parts by weight of inorganic powder a.
Example 9
A dispersion K6 was produced in the same manner as in Example 4. In dispersion K6, 480 parts by weight of dispersant solution K was mixed with 100 parts by weight of inorganic powder a.

  In order to confirm the influence of the content of the dispersant on the dispersibility of the inorganic powder in the slurry, the dispersibility of the dispersions K1 to K6 was evaluated based on the presence or absence of thixotropy.

  The dispersibility of the dispersion was evaluated based on the presence or absence of thixotropy by reciprocating the range of 0 to 200 [1 / s] by strain control using ARES RFSIII manufactured by TA Instruments Inc.

  Table 3 shows the evaluation results.

  The dispersibility after the dispersions K1 to K6 were prepared and allowed to stand at room temperature for 24 hours was similarly evaluated.

  Table 4 shows the evaluation results after standing at room temperature for 24 hours.

  It was confirmed that the content of the nonionic dispersant was particularly preferably in the range of 5 to 35 with respect to 100 parts by weight of the inorganic powder. Further, the dispersibility of the dispersion after the prepared dispersion was allowed to stand for 24 hours was evaluated. For evaluation of dispersibility, the dispersion was allowed to stand at room temperature for 24 hours, and then the presence or absence of thixotropy was evaluated in the same manner as in Example 1. Dispersions K1 and K6 showed some thixotropy after standing for 24 hours. Therefore, it turns out that it is more effective when content of a dispersing agent is 5-35 weight part.

[Example 4]
In the fourth experimental example, various types of organic materials to be dispersed are changed to produce a plurality of types of slurries, a plurality of types of green sheets are produced using the slurries, and the green sheets are used. A plurality of types of all-solid-state batteries were prepared and their characteristics were compared. Specifically, when using a nonionic dispersant having a molecular weight of 20000 (Example 10), using an anionic dispersant (Comparative Example 4), and using a cationic dispersant (Comparative Example 5). ).

In addition, about the material of each Example and each comparative example, the manufacturing method, etc. which are not described in particular below, it was based on the content disclosed by 1st Embodiment mentioned above.
(Example 10)
A nonionic dispersant (polyvinyl butyral having a molecular weight of 20000) was used as a dispersant, and this was dissolved in alcohol as a solvent to prepare a dispersant solution L. The dispersant was 10 parts by weight with respect to 100 parts by weight of the solvent.

Li ₃ V ₂ (PO ₄ ) ₃ having a NASICON structure is used as the electrode active material, and the electrode active material and the inorganic powder a are weighed at a weight ratio of 1: 1. A mixed solution was prepared by mixing (mixing step 1).

  Next, polyvinyl alcohol was added as a binder to the mixed solution to prepare an electrode slurry (mixing step 2). The mixing ratio was LVP: binder = 80: 20 by mass ratio.

  Further, the inorganic powder a and the dispersant solution L were mixed (mixing step 1), then the binder was added and further mixed to prepare a solid electrolyte slurry (mixing step 2). The mixing ratio was LAGP: binder = 80: 20 by mass ratio.

  Next, the electrode slurry was formed into a sheet with a thickness of 30 μm on a PET film using a doctor blade, and punched out to a diameter of 10 mm to produce an electrode green sheet.

  Moreover, the solid electrolyte slurry was formed into a sheet shape with a thickness of 50 μm on a PET film using a doctor blade, and punched to φ10 mm to produce a solid electrolyte green sheet.

  Next, the four solid electrolyte green sheets which peeled PET film from the said solid electrolyte green sheet were laminated | stacked, and the solid electrolyte layer was obtained by crimping | bonding at 60 degreeC. The reason for laminating a plurality of green sheets is to give sufficient mechanical strength to the solid electrolyte layer after sintering to facilitate the handling of the solid electrolyte layer in the process described later, without laminating a plurality of sheets. There is no particular problem as a solid electrolyte layer.

One electrode green sheet from which the PET film was peeled from the electrode green sheet was laminated on one surface of the obtained solid electrolyte layer and pressed at 60 ° C. to form a positive electrode layer. In the same manner, two electrode green sheets were pressure bonded to the other surface of the solid electrolyte layer to form a negative electrode layer, thereby obtaining a laminate. The reason for the difference in the number of electrode green sheets used in the positive electrode layer and the negative electrode layer is that Li ₃ V ₂ (PO ₄ ) ₃ is used as the positive electrode active material and Li ₃ V ₂ is used as the negative electrode active material. (PO ₄ ) This is because the capacity per ₃ grams differs by about twice. The thicknesses of the positive and negative electrode layers can be appropriately changed according to the material of the active material to be used.

  Next, the obtained laminate was heat-treated at 500 ° C. in an air atmosphere to remove the binder.

  Thereafter, heat treatment was performed at 750 ° C. in a nitrogen atmosphere to sinter the laminate, and a sintered type all-solid battery was produced.

The obtained all solid state battery is sealed in a 2032 type coin-type battery, and a constant current / constant voltage charge / discharge is performed at a current density of 100 μA / cm ^{2 in} a voltage range of 3.0 to 4.5 V, and a charge / discharge test is performed. did.

The sealing method is not particularly limited, and the sintered laminate may be sealed with a resin. An insulating paste such as Al ₂ O ₃ may be applied or dipped around the laminate, and this may be heat treated and sealed. In order to efficiently draw current from the positive and negative electrode layers, a conductive layer such as a metal layer may be formed on the positive and negative electrode layers as a current collector layer by sputtering or the like. Alternatively, a conductive layer may be formed by applying or dipping a metal paste or the like on the positive and negative electrode layers and heat-treating it.

FIG. 2 shows the charge / discharge characteristics of the all-solid-state battery according to Example 10. It was confirmed that the all solid state battery according to the present invention has good charge / discharge characteristics.
(Comparative Example 4)
An all-solid battery was produced in the same manner as in Example 10. However, an anionic dispersant (Marialim, NOF Corporation) was used as a dispersant, and a dispersant solution M was used as a dispersant solution. As a result, the dispersibility of the slurry was poor, the surface of the produced green sheet was uneven, and a good green sheet could not be formed. Furthermore, when the charging / discharging characteristic of the produced all-solid-state battery was measured, it was not able to charge / discharge.
(Comparative Example 5)
An all-solid battery was produced in the same manner as in Example 10. However, a cationic dispersant (Arcard C-50, Lion Corporation) was used as a dispersant, and a dispersant solution N was used as a dispersant solution.

  As a result, the dispersibility of the slurry was poor, the surface of the produced green sheet was uneven, and a good green sheet could not be formed. Furthermore, when the charging / discharging characteristic of the produced all-solid-state battery was measured, it was not able to charge / discharge.

  Table 5 shows comparison results of characteristics of Example 10, Comparative Example 4, and Comparative Example 5.

  As can be seen from the comparison results, the surface of the green sheet is uneven when the dispersibility of the slurry is poor. Furthermore, it is considered that by making a plurality of such green sheets with poor surface smoothness to produce a battery laminate and sintering it, conduction inside the battery laminate worsens and charging / discharging becomes impossible. .

[Fifth Experimental Example]
In the fifth experimental example, a plurality of types of solid electrolyte slurries are prepared by changing the volume ratio of the solvent in the slurry and the viscosity of the slurry, and a plurality of types of solid electrolyte green sheets are prepared using these slurries. Then, using these green sheets, multiple types of all-solid-state batteries were produced and their characteristics were compared. As characteristics, the dispersibility of the slurry, the presence or absence of cracks on the surface of the green sheet, and the charge / discharge characteristics of the all solid state battery were observed.

  Note that materials, manufacturing methods, and the like that are not particularly described below are based on the contents disclosed in the first embodiment.

As an inorganic powder, a solid electrolyte powder having a crystal phase of a lithium-containing phosphate compound Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) having a NASICON structure was prepared.

  A polyvinyl butyral resin having a molecular weight of 20000 was prepared as an organic material.

  Alcohol was prepared as a solvent.

First, a solid electrolyte was produced. Specifically, Li ₂ CO ₃ , Al ₂ O ₃ , GeO ₂ , H ₃ PO ₄ are mixed in a mortar, melted in an air atmosphere at 1200 ° C. for 5 hours, and then the melt is dropped into running water, A glass powder having the composition of LAGP was prepared. The glass powder was coarsely pulverized in a mortar, fired at 600 ° C., and pulverized by a dry jet mill to produce a solid electrolyte powder having a LAGP crystal phase.

  Next, a solid electrolyte slurry was prepared. Specifically, polyvinyl butyral resin and alcohol were mixed at a ratio shown in Table 6 to prepare an organic vehicle. The produced organic vehicle, solid electrolyte powder, and cobblestone were enclosed in a polyethylene pot and rotated on a pot rack to produce slurries 1-7.

  And the solvent ratio which occupies for the solid electrolyte slurry of the slurry 1-7 was computed. The calculation was based on the following method.

  The solid electrolyte powder and the polyvinyl butyral resin were each gently submerged in a graduated cylinder containing toluene, and the true density of the solid electrolyte powder and the polyvinyl butyral resin was calculated from the volume of toluene increased at this time. The true density of the alcohol was measured using a liquid hydrometer. As a result of measurement, the true density of the solid electrolyte powder was 2.90 g / cc, the true density of the polyvinyl butyral resin was 1.10 g / cc, and the true density of the alcohol was 0.83 g / cc. The volume ratio of the solvent in the slurries 1 to 7 was calculated from the mixing ratio shown in Table 6 and the solid electrolyte powder, polyvinyl butyral resin, and the true density of the alcohol.

  Moreover, the viscosity of the slurries 1-7 was measured. The measurement was based on the following method.

  Slurries 1 to 7 were allowed to stand at room temperature for 3 hours, and then shear stress [Pa in the range of shear rate 0 to 200 [1 / s] by strain control using ARES RFSIII manufactured by TA Instruments Inc. ] Was measured. In addition, since only a slight sediment was confirmed after the slurry 1 was allowed to stand, viscosity measurement was not performed.

  From the measurement results of the slurries 2 to 7, the viscosities were calculated by approximating the slurries 2 to 7 to pseudoplastic fluids. Formula 2 was used as an approximate expression. FIG. 3 shows measurement results and approximate curves. Slurries 2-7 could be approximated accurately with the approximate expression of Expression 2. (Decision coefficient R2> 0.998)

Formula 2

  Next, a solid electrolyte green sheet was produced. Specifically, slurry 2 to 7 was applied on a PET film using a doctor blade, and dried on a hot plate heated to 40 ° C. to produce green sheets 2 to 7 to be solid electrolyte green sheets. In addition, the coating thickness of the slurry 2-7 was adjusted so that the thickness of the green sheets 2-7 might be set to 50 micrometers.

  Next, the occurrence of cracks on the surface of the solid electrolyte green sheet was observed. Specifically, although not shown, the surfaces of the green sheets 2 to 7 were observed with a scanning electron microscope to confirm the presence or absence of cracks. The results are shown in Table 7.

  As shown in Table 7, the volume ratio of the solvent in the slurry is 65.3% to 81.4%, and the green sheet without cracks can be produced in the range of 0.10 to 3.45 Pa · s. Was confirmed.

  Moreover, the slurry 8 and 9 was produced with the mixing ratio shown in Table 8 by the same method, and the viscosity was computed. Moreover, the green sheets 8 and 9 were produced using the slurry 8 and 9, and the presence or absence of the crack was confirmed.

  Furthermore, Table 9 shows the results of calculation of the volume ratio and viscosity of the slurry 8 and 9, and the presence or absence of cracks.

  Even when the volume ratio of the solvent in the slurry was in the range of 65.3% to 85.4%, it was confirmed that the green sheet would crack if the viscosity was 0.1 Pa · s or less. Moreover, even if the viscosity of the slurry was in the range of 0.1 to 3.4 Pa · s, it was confirmed that if the volume ratio of the solvent in the slurry was 80% or more, the green sheet was cracked.

  From the above results, it was confirmed that a crack-free green sheet could be produced when the volume ratio of the solvent in the slurry was 65% to 85% and the viscosity was in the range of 0.1 to 3.4 Pa · s. .

  Subsequently, an all-solid battery was produced and evaluated.

  First, a solid electrolyte slurry was produced anew. Specifically, LAGP, polyvinyl butyral resin, and alcohol were mixed at a ratio shown in Table 10 to prepare a solid electrolyte slurry.

  Table 11 shows the results of calculation of the volume ratio and viscosity of the solid electrolyte slurry, and the presence or absence of cracks.

Next, an electrode slurry was prepared. Specifically, Li ₃ V ₂ (PO ₄ ) ₃ having a NASICON structure was used as the electrode active material. The electrode active material: 45 parts by weight, LAGP: 50 parts by weight, carbon material: 5 parts by weight as a conductive agent, and the solid electrolyte slurry: 170 parts by weight were mixed to prepare an electrode slurry.

  Next, a green sheet was produced. Specifically, the electrode slurry was formed into a sheet shape with a thickness of 30 μm on a PET film using a doctor blade, and punched out to φ10 mm to prepare an electrode green sheet. Moreover, the solid electrolyte slurry was formed into a sheet shape with a thickness of 50 μm on a PET film using a doctor blade, and punched to φ10 mm to produce a solid electrolyte green sheet.

Next, a battery stack was produced. Specifically, four solid electrolyte green sheets from which the PET film was peeled off from the solid electrolyte green sheet were stacked and pressed at 60 ° C. to obtain a solid electrolyte layer. Subsequently, one electrode green sheet from which the PET film was peeled from the electrode green sheet was laminated on one surface of the obtained solid electrolyte layer, and pressed at 60 ° C. to form a positive electrode layer. In the same manner, two electrode green sheets were pressure-bonded to the other surface of the solid electrolyte layer to form a negative electrode layer, thereby obtaining a battery laminate. The reason for the difference in the number of electrode green sheets used in the positive electrode layer and the negative electrode layer is that Li ₃ V ₂ (PO ₄ ) ₃ is used as the positive electrode active material and Li ₃ V ₂ is used as the negative electrode active material. (PO ₄ ) This is because the capacity per ₃ grams differs by about twice. The thicknesses of the positive and negative electrode layers can be appropriately changed according to the material of the electrode active material to be used.

  Next, an all-solid battery was produced. Specifically, the obtained battery stack was heat-treated at 500 ° C. in an air atmosphere to remove the organic material. Then, it heat-processed at 750 degreeC in nitrogen atmosphere, the battery laminated body was sintered, and the all-solid-state battery was obtained.

The obtained all solid state battery is sealed in a 2032 type coin-type battery, and a constant current / constant voltage charge / discharge is performed at a current density of 100 μA / cm ^{2 in} a voltage range of 3.0 to 4.5 V, and a charge / discharge test is performed. did.

It was confirmed that the all solid state battery according to this experimental example has good charge / discharge characteristics without cracks.
[Sixth experimental example]
In the sixth experimental example, a solid electrolyte containing lithium was dispersed in each of a plurality of solvents having different dielectric constants, and the amount of lithium eluted from the solid electrolyte into the solvent was examined. From these results, the relationship between the dielectric constant of the solvent and the amount of lithium eluted was examined.

  First, a plurality of solvents having different dielectric constants were prepared.

Further, as the solid electrolyte was prepared NASICON type solid electrolyte _{Li 1.2 Al 0.2 Ti 1.8 (PO} 4) 3 (LATP).

  Then, 150 parts by weight of each solvent and 100 parts by weight of the solid electrolyte are enclosed in a polyethylene pot together with cobblestones, rotated on a pot rack at 150 rpm for 6 hours, and then left at room temperature to extract a supernatant. The concentration of lithium ions dissolved in each solvent was measured with an inductively coupled plasma optical emission spectrometer (ICP-AES).

  Table 12 shows the dielectric constant of the solvent (numerical values in parentheses) and the elution amount of lithium.

As shown in the table, it was found that in a solvent having a dielectric constant of 17 or more, the amount of lithium eluted was as high as 2.0 ppm or more.
[Seventh experimental example]
In the seventh experimental example, a solvent A having a dielectric constant of 6 or less and a solvent B having a dielectric constant of 17 or more are mixed at different mixing ratios to prepare mixed solvents a to j. The amount of lithium eluted from the solid electrolyte into the solvent was examined. However, the solvent j was only solvent B. From these results, the relationship between the dielectric constants of the solvent A and the solvent B, the mixing ratio of the solvent A and the solvent B, and the lithium elution amount was examined. Unless otherwise specified, the solid electrolyte, the elution amount measurement method, and the like were the same as in the sixth experimental example.

  First, a solvent A having a dielectric constant of 6 or less and a solvent B having a dielectric constant of 17 or more were mixed at a volume ratio shown in Table 13 to prepare mixed solvents a to j.

  Then, 150 parts by weight of each of the mixed solvents a to j and 100 parts by weight of the solid electrolyte are enclosed in a polyethylene pot together with cobblestones, rotated on a pot rack at 150 rpm for 6 hours, and then allowed to stand at room temperature to obtain a supernatant. The concentration of lithium ions extracted and dissolved in each solvent was measured with an inductively coupled plasma emission spectrometer (ICP-AES).

  Table 13 shows the lithium elution amounts of the mixed solvents a to j.

In the mixed solvent e in which the content of the solvent A is 1% in the volume ratio to the total solvent, the elution amount of lithium is 2.5 ppm or more, but in other mixed solvents, it is less than 2.5 ppm. And it was good. From this result, in a mixed solvent in which a nonpolar or low polarity solvent having a dielectric constant of 6 or less and a polar solvent having a dielectric constant of 17 or more are mixed, the mixing ratio of the nonpolar or low polarity solvent having a dielectric constant of 6 or less It can be confirmed that the elution of lithium from the solid electrolyte powder can be suppressed by increasing the volume ratio of 1% by volume in the total solvent.
[Example 8]
In the eighth experimental example, the volume average particle size of the inorganic powder contained in the slurry is changed to produce a plurality of types of solid electrolyte powders P1 to P8, and these solid electrolyte powders are used to produce solid electrolyte slurries P1 to P1. P8 was produced and their dispersibility was compared.

  Note that materials, manufacturing methods, and the like that are not particularly described below are based on the contents disclosed in the first embodiment.

First, a solid electrolyte was produced. Specifically, Li ₂ CO ₃ , Al ₂ O ₃ , GeO ₂ , H ₃ PO ₄ are mixed in a mortar and melted at 1200 ° C. for 5 hours in an air atmosphere, and then the melt is dropped into running water, A glass powder having a composition of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ was produced. The obtained glass powder was coarsely pulverized in a mortar and then fired at 600 ° C. to obtain a lithium-containing phosphate compound having a crystal phase of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) having a NASICON structure. . The lithium-containing phosphoric acid compound was pulverized by a dry jet mill to prepare solid electrolyte powders P1 to P7 having different volume average particle diameter, 90 volume% average particle diameter, and 99 volume% average particle diameter.

Separately, Li ₂ CO ₃ , V ₂ O ₅ , H ₃ PO ₄ are mixed in a mortar, baked at 400 ° C. for 10 hours in an air atmosphere, and then mixed with carbon powder as a conductive agent, A glass powder having a composition of Li ₃ V ₂ (PO ₄ ) ₃ (LVP) was produced. The obtained glass powder was pulverized in a mortar, then calcined at 900 ° C. for 10 hours in an argon atmosphere, and pulverized in a dry jet mill to obtain a carbon-active material composite powder having an LVP crystal phase having a NASICON structure. Obtained. The amount of carbon powder added was 10 parts by weight of carbon powder with respect to 90 parts by weight of LAGP powder. The obtained carbon-active material composite powder and the solid electrolyte powder D were mixed at a weight ratio of 1: 1 to obtain a composite powder P8.

  Table 14 shows the volume average particle diameter, the 90 volume% average particle diameter, and the 99 volume% average particle diameter of the solid electrolyte powders P1 to P7 and the composite powder P8. The particle size distribution, volume average particle diameter, 90 volume% average particle diameter, and 99 volume% average particle diameter of the solid electrolyte powder were measured by a laser diffraction scattering type particle size distribution measuring apparatus. (Microtrack HRA: Nikkiso Co., Ltd.)

  4 is a solid electrolyte powder P1, FIG. 5 is a solid electrolyte powder P2, FIG. 6 is a solid electrolyte powder P3, FIG. 7 is a solid electrolyte powder P4, FIG. 8 is a solid electrolyte powder P5, FIG. 9 is a solid electrolyte powder P6, and FIG. Shows the particle size distribution curve (solid line) and cumulative particle size distribution curve (broken line) of the solid electrolyte powder P7, and FIG.

  And the slurry was produced as follows using the obtained solid electrolyte powder P1-P7 and composite powder P8.

  First, 20 parts by weight of polyvinyl butyral resin was dissolved in 100 parts by weight of an alcohol solvent to prepare an organic vehicle. A polyvinyl butyral resin having a molecular weight of 20000 was used.

  Next, 100 parts by weight of solid electrolyte powders P1 to P7 or composite powder P8 and 150 parts by weight of an organic vehicle were mixed and stirred to prepare slurries P1 to P8.

  Then, the dispersibility of the slurries P1 to P8 was reciprocated in the range of 0 to 200 [1 / s] by strain control using ARES RFSIII manufactured by TA Instruments Inc., and the presence or absence of thixotropy was examined. And evaluated. The measurement was performed twice immediately after the slurry was produced and after the slurry was allowed to stand at room temperature for 24 hours.

  Table 15 shows the evaluation results of the dispersibility of the slurries P1 to P8. In the evaluation, based on the slurry G shown below, ◯ was given when the thixotropy was low (or not confirmed), and x was given when the thixotropy was high. In addition, a case where the thixotropy is slightly high to the extent that there is no problem in slurry production was indicated as Δ.

From these results, it was confirmed that in the slurry in which the volume average particle size of the solid electrolyte powder is 5 μm or less and the 90% by volume particle size is 20 μm or less, the dispersibility immediately after the preparation of the slurry is high. Furthermore, it was confirmed that the dispersibility after standing for 24 hours was high in a slurry having a particle size of 99% by volume of the solid electrolyte powder of 20 μm or less. Even in a slurry containing electrode active material powder and solid electrolyte powder, like slurry P8, a slurry with high dispersibility can be obtained by setting the volume average particle size of the mixed powder to 5 μm or less and the 99% by volume particle size to 20 μm or less. It was confirmed that can be produced.
[Example 9]
In the ninth experimental example, the polymer material C and the polymer material D are used as the organic material contained in the slurry, the polymer material C is mixed before the polymer material D, and the average of the polymer materials D is determined. Slurries Q1 to Q13 were prepared such that the degree of polymerization was higher than the average degree of polymerization of the polymer material C and the difference in solubility parameter SP value was 5.0 or less, and their dispersibility was compared.

  Note that materials, production methods, and the like that are not particularly described below are based on the contents disclosed in the above-described third embodiment.

As the polymer material C and the polymer material D, a polyvinyl acetal resin having a basic structure represented by the chemical formula 1 was used. In addition, R in Chemical Formula 1 is a propyl group (C ₃ H ₇ —). Table 16 shows values of repeating units X, Y, and Z of the structural units of the polymer materials C and D. Table 17 shows the degree of polymerization and the molecular weight of the polyvinyl acetal resin used as the polymer material C or the polymer material D.

First, an organic vehicle C was prepared by mixing 5 parts by weight of a polymer material C having an average polymerization degree n ₁ with 100 parts by weight of an alcohol solvent. An organic vehicle D was prepared by mixing 20 parts by weight of a polymer material D having an average degree of polymerization n ₂ with 100 parts by weight of an alcohol solvent.

As inorganic powder, lithium-containing phosphate compound Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (hereinafter referred to as LAGP): 100 parts by weight of organic vehicle C: 15 parts by weight of organic vehicle C was mixed as the inorganic powder. Produced. Next, 100 parts by weight of the organic vehicle D was weighed with respect to 100 parts by weight of the inorganic powder (LAGP). After the mixed solution and the organic vehicle C were mixed for 12 hours, the organic vehicle D was added and mixed for 12 hours to prepare a solid electrolyte slurry. The average degree of polymerization was determined by dissolving the polymer material in a solvent such as tetrahydrofuran and measuring the number average molecular weight and the weight average molecular weight using GPC (Gel Permeation Chromatography). The polymerization degree can be calculated from the obtained number average molecular weight and weight average molecular weight and the degree of butyralization determined by H ¹ -NMR measurement.

Using the polymer material C having an average degree of polymerization n ₁ of 100 and the polymer material D having an average degree of polymerization of 200, a solid electrolyte slurry Q1 was produced by the method described above.

Using the polymer material C having an average degree of polymerization n ₁ of 200 and the polymer material D having an average degree of polymerization of 400, a solid electrolyte slurry Q2 was produced by the method described above.

Using the polymer material C having an average degree of polymerization n ₁ of 400 and the polymer material D having an average degree of polymerization of 600, a solid electrolyte slurry Q3 was produced by the method described above.

Using the polymer material C having an average degree of polymerization n ₁ of 600 and the polymer material D having an average degree of polymerization of 800, a solid electrolyte slurry Q4 was produced by the method described above.

Using the polymer material C having an average degree of polymerization n ₁ of 400 and the polymer material D having an average degree of polymerization of 1000, a solid electrolyte slurry Q5 was produced by the method described above.

Using the polymer material C having an average degree of polymerization n ₁ of 400 and the polymer material D having an average degree of polymerization of 1700, a solid electrolyte slurry Q6 was produced by the method described above.

Using the polymer material C having an average degree of polymerization n ₁ of 1700 and the polymer material D having an average degree of polymerization of 400, a solid electrolyte slurry Q7 was produced by the method described above.

  The polymer materials C and D used in the slurries Q1 to Q7 were each mixed with a solvent having a known SP value, and the SP value was determined from the solubility of the polymer material when stirred. Solvents having different SP values were prepared, and a polymer material was mixed in each solvent. The maximum SP value of the solvent in which the polymer was dissolved was assumed to be SP of the polymer material. The difference between the SP values of the polymer materials C and D thus obtained was calculated, and it was confirmed whether the difference between the SP values of the polymer materials C and D was 5.0 or less. The results are shown in Table 18.

  Next, the solid electrolyte slurry dispersibility of the slurries Q1 to Q7 was reciprocated in the range of 0 to 200 [1 / s] by strain control using ARES RFSIII manufactured by TA Instruments Inc., and thixotropy The presence or absence of was examined and evaluated. The results are shown in Table 19.

  The dispersibility of the slurries Q1 to Q6 was good, but the slurry Q7 showed thixotropy and poor dispersibility. The slurry Q7 agglomerated during the mixing process of the organic vehicle C and the inorganic powder, and then remained agglomerated even when the organic vehicle D was mixed. The polymer material C has a higher degree of polymerization than the polymer material D and is considered to have aggregated.

Next, a polymethacrylic ester acrylic resin having an average degree of polymerization n ₁ of 500 is used as the polymer material C, and a polymethacrylic ester acrylic resin having an average degree of polymerization n ₂ of 1000 is used as the polymer material D. The experiment was conducted using this. In this case, the molecular weight of the polymer material C is 22000, and the molecular weight of the polymer material D is 44000.

  When the SP values of the polymer materials C and D were measured by the method described above, both were 9.3. Therefore, the difference in SP value is zero.

  By the method described above, a solid electrolyte slurry Q8 was produced using LAGP as the inorganic powder. When the dispersibility of the slurry Q8 was evaluated by the above method, it was confirmed that a slurry having no thixotropy and high dispersibility was obtained. That is, even when a resin different from the polyvinyl acetal resin is used, a slurry having no thixotropy and high dispersibility can be obtained by using a material having an SP value of 5.0 or less for the polymer materials C and D. It was confirmed.

As the polymer materials C and D, the above-mentioned polyvinyl acetal resin was used, and LAGP was used as the inorganic powder. However, the average degree of polymerization n ₁ of the polymer material C is 400, and the average degree of polymerization n ₂ of the polymer material D is 800.

  By the method described above, solid electrolyte slurry Q8 was prepared so that the content of polymer material C was 0.05 parts by weight with respect to LAGP: 100 parts by weight. In addition, 100 parts by weight of the organic vehicle D was added to 100 parts by weight of the inorganic powder.

  Solid electrolyte slurry Q9 was produced by the same method as slurry Q8. However, the content of the polymer material C was 0.1 parts by weight with respect to 100 parts by weight of LAGP.

  Solid electrolyte slurry Q10 was produced in the same manner as slurry Q8. However, the content of the polymer material C was 1 part by weight with respect to LAGP: 100 parts by weight.

  A solid electrolyte slurry Q11 was produced by the same method as that for the slurry Q8. However, the content of the polymer material C was 10 parts by weight with respect to LAGP: 100 parts by weight.

  A solid electrolyte slurry Q12 was produced by the same method as that for the slurry Q8. However, the content of the polymer material C was 20 parts by weight with respect to LAGP: 100 parts by weight.

  A solid electrolyte slurry Q13 was produced by the same method as that for the slurry Q8. However, the content of the polymer material C was 30 parts by weight with respect to LAGP: 100 parts by weight.

  In order to confirm the influence of the content of the polymer material C on the dispersibility of the inorganic powder in the slurry, both the mixed solution before mixing the organic vehicle D and the slurry after mixing the organic vehicle D are described above. The dispersibility was evaluated by investigating the presence or absence of thixotropy. As apparent from Table 20, the amount of the organic material C added is preferably in the range of 0.1 to 20 with respect to 100 parts by weight of the inorganic powder.

  The slurry for all solid state battery of the present invention can improve the dispersibility of the slurry for all solid state battery and produce a green sheet for all solid state battery having a smooth surface. Therefore, it is useful for the production of an all-solid battery having excellent battery characteristics.

10: Laminate 11: Negative electrode layer 12: Solid electrolyte layer 13: Positive electrode layer

Claims (25)

An all-solid-state battery slurry containing at least an inorganic material, an organic material, and a solvent,
The said organic material is a slurry for all-solid-state batteries containing the nonionic dispersing agent which has a molecular weight of 15000 or more.   The all-solid-state battery slurry according to claim 1, wherein the nonionic dispersant has an ether bond, an ester bond, or a side chain in the molecule.   The all-solid-state battery according to claim 1 or 2, wherein the nonionic dispersant contains at least one selected from polyvinyl acetal resin, cellulose resin, acrylic resin, urethane resin, vinyl acetate resin, and polyvinyl alcohol resin. slurry.   The all-solid-state battery slurry according to any one of claims 1 to 3, wherein the inorganic material contains at least one selected from an electrode active material, a solid electrolyte precursor, a solid electrolyte, and a conductive agent.   The all-solid-state battery slurry according to any one of claims 1 to 4, wherein the inorganic material contains a compound having a NASICON structure.   The all-solid-state battery slurry according to any one of claims 1 to 5, wherein a content of the nonionic dispersant is 0.1 to 35 parts by weight with respect to 100 parts by weight of the inorganic material.   The slurry for an all-solid-state battery according to any one of claims 1 to 6, wherein a content of the solvent is 30 to 1000 parts by weight with respect to 100 parts by weight of the inorganic material.   2. The volume ratio of the solvent in the all-solid battery slurry is 65% or more and 85% or less, and the viscosity of the all-solid battery slurry is 0.1 Pa · s or more and 3.4 Pa · s or less. The slurry for all-solid-state batteries described in any one of -7.   The solvent is methanol, ethanol, 1-propanol, or isopropanol. Selected from alcohols such as 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, n-hexane, o-xylene, m-xylene, p-xylene, toluene, ethylene acetate The slurry for an all-solid-state battery according to claim 8, comprising at least one selected from the group consisting of: The solvent contains a solvent A having a dielectric constant of 6 or less and a solvent B soluble in the solvent A and having a dielectric constant of 17 or more;
The slurry for all-solid-state batteries described in any one of Claims 1-7 which contains more than 1% of the said solvent A with a volume ratio with respect to all the solvents.   The all-solid-state battery slurry according to claim 10, wherein the solvent A contains at least one selected from n-hexane, o-xylene, m-xylene, p-xylene, toluene, and ethylene acetate.   The solvent B is methanol, ethanol, 1-propanol, isopropanol. The slurry for an all-solid-state battery according to claim 10 or 11, comprising at least one selected from 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol.   The slurry for an all-solid-state battery according to any one of claims 10 to 12, wherein the volume ratio of the solvent A is 10% or more with respect to the total solvent.   The volume average particle diameter of the inorganic material is 0.5 μm or more and 5 μm or less, and the 90% by volume average particle diameter is 0.5 μm or more and 20 μm or less. Slurry for all solid state batteries.   The all-solid-state battery slurry according to claim 14, wherein an average particle size of 99% by volume of the inorganic material is 0.5 μm or more and 20 μm or less. The organic material contains a polymer material C that is the nonionic dispersant, and a polymer material D,
The polymer material C is mixed before the polymer material D,
The average polymerization degree of the polymer material D is higher than the average polymerization degree of the polymer material C, and the difference in solubility parameter SP value is 5.0 or less. Slurry for all solid state batteries.   The slurry for an all-solid-state battery according to claim 16, wherein the polymer material C has an average degree of polymerization of 100 or more and 400 or less.   The all-solid-state battery slurry according to claim 16 or 17, wherein the polymer material C and the polymer material D include the same structural unit.   The slurry for an all-solid-state battery according to any one of claims 16 to 18, wherein the content of the polymer material C is 0.1 to 20 parts by weight with respect to 100 parts by weight of the inorganic material.   An all-solid-state battery green sheet using the all-solid-state battery slurry according to claim 1.   A positive electrode layer, a negative electrode layer, and a solid electrolyte layer are prepared using the all-solid-state battery green sheet according to claim 20, and the positive electrode layer and the negative electrode layer are laminated and integrated through the solid electrolyte layer, and then fired. All-solid battery. A step of preparing an organic material, an inorganic material, and a solvent;
A method for producing a slurry for an all-solid-state battery comprising a slurry preparation step of mixing an organic material, an inorganic material, and a solvent to obtain a slurry,
The said organic material is a manufacturing method of the slurry for all-solid-state batteries containing the nonionic dispersing agent which has a molecular weight of 15000 or more. A step of preparing an organic material, an inorganic material, and a solvent;
A mixing step of mixing an organic material, an inorganic material, and a solvent to obtain a mixture;
A method for producing a slurry for an all-solid-state battery, comprising a slurry preparation step of mixing the mixture obtained in the mixing step with another organic material to obtain a slurry,
The method for producing a slurry for an all-solid-state battery, wherein the organic material includes a nonionic dispersant having a molecular weight of at least 15000 and the other organic material includes at least a binder. The organic material contains the polymer material C that is the nonionic dispersant and the polymer material D,
The organic material mixed in the mixing step is the polymer material C,
The other organic material mixed in the slurry preparation step is the polymer material D,
The average polymerization degree of the polymer material D is higher than the average polymerization degree of the polymer material C, and the difference in solubility parameter SP value is 5.0 or less. Production method. A step of preparing an organic material, an inorganic material, and a solvent;
A mixing step of mixing an inorganic material and a solvent to obtain a mixture;
An organic vehicle production process for producing an organic vehicle by mixing an organic material and a solvent;
A second mixing step of mixing the mixture and the organic vehicle, and a method for producing an all-solid battery slurry,
The said organic material is a manufacturing method of the slurry for all-solid-state batteries containing the nonionic dispersing agent which has a molecular weight of 15000 or more.

Images