JP5306777B2 - Method for producing ion conductive solid electrolyte - Google Patents

Description

  The present invention relates to a method for producing an ion conductive solid electrolyte such as a lithium battery. More specifically, the present invention relates to a method for producing a solid electrolyte green sheet.

In recent years, with higher performance and smaller size of portable electronic devices such as mobile phones, it is desired to increase the energy density and size of batteries used in these portable electronic devices. In general, since a high voltage is obtained and a high energy density is obtained in a lithium battery, it is expected as a power source for these portable electronic devices. Usually, in such a lithium battery, lithium transition metal composite oxides such as lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), and lithium nickelate (LiNiO ₂ ) are used as the positive electrode active material. Yes. Moreover, carbon materials, such as graphite and fibrous carbon, are used as a negative electrode active material. An organic electrolyte is used for such a lithium battery, but a polymer electrolyte obtained by mixing a polymer electrolyte and an organic electrolyte is also being studied. Since these lithium batteries or polymer electrolyte batteries use liquid as the electrolyte, they have low reliability such as liquid leakage or fire. In addition, freezing of the electrolytic solution at a low temperature or vaporization of the electrolytic solution at a high temperature may significantly impair the performance of the battery, so that the use temperature of such a battery is limited. Therefore, development of a lithium battery using a solid electrolyte having lithium ion conductivity instead of an organic electrolyte is desired as a highly reliable lithium battery.

Since a lithium battery using such a solid electrolyte does not use a flammable organic solvent, there is no risk of liquid leakage or ignition and excellent safety. For example, in Patent Document 1, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ solid electrolyte powder is used for a solid electrolyte green sheet serving as a solid electrolyte layer, and a polyvinyl butyral resin as a binder and a solvent are used. A certain n-butyl acetate and a plasticizer dibutyl phthalate are used (for example, Patent Document 1, paragraph [0189]). An appropriate amount of these are mixed and dispersed to form a slurry, which is applied using a doctor blade.

  Moreover, it is disclosed that the glossiness of ceramic green sheets containing ceramic powder and photosensitive resin affects the formation of via holes by photolithography (for example, Patent Document 2). Therefore, a green sheet having a glossiness of 70% or less is disclosed as preferable.

On the other hand, in order to know the dispersion state of the slurry containing the inorganic powder, the binder, and the dispersion medium, the shear rate applied to the slurry is controlled to form a film and dried, and the glossiness of the obtained sheet is measured. (For example, Patent Document 3).
JP 2007-5279 A Japanese Patent Laid-Open No. 10-279363 JP-A-2005-67920

  However, Patent Document 1 discloses a method for producing a green sheet, and Patent Document 2 discloses that a low glossiness is preferable for a photolithography method. Therefore, it is not always easy to obtain glossiness that is preferable in the subsequent process from a slurry in an appropriate dispersion state, because various conditions are intertwined. Absent. Moreover, even if there is an upper and lower inhomogeneity in the applied film, there is no means for easily detecting it during production, and it is difficult to maintain quality by feedback during production.

  In view of the above-mentioned problems, the present invention provides a method for producing a solid electrolyte green sheet having high homogeneity in the upper and lower portions in a coating film when a sufficiently dispersed solid electrolyte slurry is applied. More specifically, the green sheet manufacturing process includes a step of simply measuring the homogeneity of the upper and lower portions of the solid electrolyte green sheet.

  In particular, it has been found that the homogeneity of the upper and lower portions of the solid electrolyte green sheet appears as a measurable feature on the upper surface and the lower surface, respectively, and this is used to measure the glossiness that is this feature on the upper and lower surfaces. . This gloss measurement is a non-destructive measurement and can be easily introduced during the manufacturing process.

  On the carrier film surface (usually this side is the bottom surface), the glossiness of the green sheet cannot be measured directly, and it is also considered that the glossiness of the green sheet changes due to the change in surface properties accompanying the peeling of the carrier film. Therefore, the meaning of comparing the glossiness of the upper and lower surfaces has not been understood so far. However, it has been found that the comparison of the upper and lower surfaces of such glossiness is important due to the advancement of the performance of the carrier film and the stabilization of the carrier film peeling technology.

More specifically, the following can be provided.
(1) In a method for producing an ion conductive solid electrolyte containing an inorganic compound powder and an organic binder exhibiting lithium ion conductivity at least after heat treatment, a slurry production process for producing a slurry by mixing the inorganic compound powder and the organic binder; Applying the slurry to a carrier film to prepare a coating film; peeling the coating film from the carrier film to prepare a green sheet; and the green sheet on the carrier film side and the upper surface side. A measurement step of measuring a 60-degree specular gloss on each of the surfaces, and when the difference between the measured specular gloss on the side of the carrier film and the specular gloss on the upper side is 50 or less, It is possible to provide a method for manufacturing an ion conductive solid electrolyte. In order to further improve the ion conductivity and density of the produced ion conductive solid electrolyte, the difference between the measured specular gloss of the side surface of the carrier film and the specular gloss of the upper side surface is 45 or less. More preferably, it is most preferably 40 or less.

  Here, as an organic binder, what can combine an inorganic particle may be used, and the general purpose binder marketed as a shaping | molding adjuvant for press molding, rubber press, extrusion molding, and injection molding can be used. Specifically, acrylic resin, ethyl cellulose, polyvinyl butyral, methacrylic resin, urethane resin, butyl methacrylate, vinyl copolymer and the like can be used.

  Here, the green sheet is a mixture of organic binders, plasticizers, solvents, etc., mixed into the powder mainly of ceramics such as glass and inorganic oxide before firing, and formed into a thin plate shape. It can mean an unfired body. This molding can be performed by a doctor blade, calendar method, spin coating, dip coating or other coating method, ink jet, bubble jet (registered trademark), offset printing method, die coater method, spray method, etc., mixed slurry From this, a thin plate-like green sheet can be made. In general, the mixed slurry is formed on a film such as PET that has been subjected to a release treatment, and is peeled off after drying. The green sheet before firing is flexible, and can be cut into an arbitrary shape or laminated.

  In the present specification, the green sheet may include a solid electrolyte green sheet to be a solid electrolyte, and the green sheet laminate may include a solid electrolyte green sheet laminate. Moreover, becoming a solid electrolyte layer by heat treatment can include making the green sheet laminate to be capable of functioning as a solid electrolyte layer by performing a firing treatment described later. For example, it has predetermined ion conductivity.

  The coating film is peeled off from the carrier film when the coating film is sufficiently dried, and care is taken so that part or all of the coating film is not torn or stretched.

Here, the glossiness is defined in JISZ8741 or ISO2813. That is, the glossiness of 100 is defined as the mirror surface of a glass having a refractive index of 1.567 where the specular reflectance at an incident angle of 60 degrees is 10%. However, since the glass surface is easily affected by moisture or the like, here, glass having a refractive index of around 1.500 (glossiness of 90%) is measured as an actual reference plane. More specifically, according to JIS K7105 “Plastic optical property test method” stipulated by the Japan Industrial Standards Committee, it is obtained by measuring 60 ° specular gloss using a gloss checker IG-310 (manufactured by Horiba Seisakusho). be able to. That is, it can be obtained by the following equation.
G (60 °) = Φs / Φos × Gos (60 °) (Formula 1)
Here, Φs is a specular reflected light beam from the sample surface with respect to an incident angle of 60 °, Φos is a specularly reflected light beam from the standard surface with respect to an incident angle of 60 °, and Gos (60 °) is the standard surface used. Glossiness (%). Whether the quality is good or not is determined by comparing the glossiness thus obtained. Here, the non-defective product means that the performance of the obtained solid electrolyte is sufficiently secured. Specifically, the lithium ion conductivity at 25 ° C. is 1 × 10 ⁻⁴ S · cm ⁻¹ or more, and has a density of 95% or more with respect to the true density of the lithium ion conductive inorganic compound in the solid electrolyte. That is.

(2) The ion conductive solid electrolyte according to the above (1) is further provided with a laminating step of laminating at least two of the green sheets determined to be non-defective and press-bonding them in a predetermined pressure range to produce a laminate. A method can be provided.

  In the lamination step, a plurality of green sheets are stacked to make a temporary laminate. And this temporary laminated body is pressurized in the predetermined pressure range, and the crimping | compression-bonding between layers is aimed at. When pressurizing the temporary laminate, it may be heated simultaneously with pressurization. The pressure at the time of pressurization is preferably 1 MPa or more, more preferably 5 MPa or more, and still more preferably 10 MPa or more. The upper limit of the pressure is not particularly limited. However, if it is too high, the industrial cost is excessive and the productivity is lowered. Therefore, the pressure is preferably 500 MPa or less, more preferably 450 MPa or less, and further preferably 400 MPa or less. When heating simultaneously with pressurization, it is preferable that the ultimate temperature is heated to a temperature at which the respective layers of the green sheet laminate can be sufficiently bonded. For example, it is preferably 15 to 99 ° C, more preferably 20 to 90 ° C, and most preferably 25 to 85 ° C. If this temperature is low, the binder component may not be sufficiently softened. On the other hand, when the temperature of the pressure bonding is too high, the solvent contained in the green sheet is vaporized, and there is a risk that deformation or cracking may occur due to decomposition of the organic binder or additive.

  When the green sheets are pressed against each other, it is desirable to use a means capable of simultaneously pressing the entire surface of the green sheet laminate with a uniform pressure in order to apply a uniform pressure. For example, a uniaxial press, an isotropic pressure press, or the like can be used. In the uniaxial press, the maximum compression stress is likely to be generated on the upper surface because it is pressed by the piston, and when the tip end surface area of the piston is small, it is difficult to uniformly press the entire upper surface of the green sheet laminate. Therefore, it is preferable to use an isotropic pressure press. In the isotropic press, since the pressure medium is a fluid such as water, the heating can be performed by heating the pressure medium to a predetermined temperature. Moreover, although a green sheet laminated body is a comparatively flat sheet | seat, when it increases in thickness until it can be said that it is a block shape, a hydrostatic pressure is equally applied also to a side surface. The pressing force on the side surface is not preferable because it does not press between the layers of the sheet and does not contribute to adhesion, but rather may promote delamination. Therefore, it is preferable that the thickness is sufficiently smaller than the length and width. For example, the thickness is 25% or less, more preferably 20% or less, and most preferably 15% or less of the shortest side in the vertical and horizontal lengths. Further, since the green sheet laminate is a relatively soft and flexible sheet, the green sheet laminate is sandwiched from both sides of the green sheet laminate by a rigid plate-like member having a size larger than the sheet surface of the green sheet laminate. It is preferable.

(3) The ion conductive solid electrolyte according to (1) above, wherein a weight ratio of the inorganic compound powder and the organic binder contained in the green sheet as a non-defective product is 1.5 or more. A method of manufacturing can be provided.

  In the weight ratio of the inorganic compound and the organic binder, if the amount of the inorganic compound is too large, the dispersion cannot be performed sufficiently and it is difficult to form a uniform film. Therefore, the weight ratio of inorganic compound / organic binder is preferably 12 or less, more preferably 11.5 or less, and still more preferably 9 or less. On the other hand, when there are too many organic binders, there will be many voids as a result of firing, and the solid electrolyte may be cracked or cracked because it is not dense. Therefore, the weight ratio is preferably 1.5 or more, more preferably 2.5 or more, and still more preferably 3 or more.

(4) The method for producing an ion conductive solid electrolyte according to any one of (1) to (3) above, wherein an average particle size of the inorganic compound powder is 3 μm or less. .

  The average particle size of the inorganic compound powder is preferably 3 μm or less, more preferably 2 μm or less, and most preferably 1 μm or less in order to increase the filling rate. The lower limit of the average particle size of the inorganic powder is preferably 0.01 μm or more, more preferably 0.05 μm or more, and most preferably 0.1 μm or more in order to disperse uniformly. .

(5) The method for producing an ion conductive solid electrolyte according to (2) above, wherein the green sheet has a thickness of 1 to 100 μm and the laminate has a thickness of 10 to 1000 μm. be able to.

  The thickness of each green sheet to be laminated is preferably 100 μm or less, more preferably 90 μm or less, and most preferably 80 μm or less so that the dispersion medium can be easily volatilized. On the other hand, if the thickness is too thin, productivity and mechanical strength are lowered, and therefore the thickness of each green sheet is preferably 1 μm or more, more preferably 2 μm or more, and most preferably 3 μm or more. As for the thickness of the green sheet, for example, the thickness of a plurality of points selected at random on the upper surface or lower surface of the sheet can be measured with a film thickness meter. The selected points are pre-assigned evenly (for example, grid points by equally divided vertical and horizontal grids, etc. However, there is a possibility that the point of 5% of the vertical or horizontal length may come off from the edge of the sheet. It may be excluded.)

  Further, the thickness of the laminate in which each green sheet is laminated is preferably 1000 μm or less, more preferably 750 μm or less, and most preferably 500 μm or less so that the binder can be stably removed in a short time in the degreasing step. On the other hand, if it is made too thin, handling after firing becomes poor, and therefore it is preferably 10 μm or more, more preferably 15 μm or more, and most preferably 20 μm or more.

  Further, when the thickness of the green sheet is set to a predetermined value, it is desirable to form the green sheet uniformly with the thickness value. This is because it is easy to produce a green sheet laminate. Moreover, when the produced green sheet laminated body is baked, it becomes easy to perform heating uniformly, and it is considered that warpage of each layer of the laminated body and peeling between the layers hardly occur.

(6) The ion conductivity according to any one of (1) to (5) above, wherein the measurement step is performed in an environment where the amount of dust of 0.5 μm or more per cubic meter is 140000 or less. A method for producing a solid electrolyte can be provided.

  Glossiness measurement is performed using specular reflectance at a predetermined angle. Also, since it may be adsorbed on the measurement surface and light may be scattered on the surface, contamination that may scatter light is also possible. Less dust and dust are better.

(7) In the laminating step, it is possible to provide a method for producing an ion conductive solid electrolyte as described in (2) above, wherein the pressurizing time for laminating is 5 seconds or more.

  The pressurization time is preferably 5 seconds or more, more preferably 10 seconds or more, and most preferably 15 seconds or more in order to provide sufficient adhesion. If the pressurization time is too short, the green sheet laminate tends to be peeled off and the adhesion may be insufficient.

(8) In the said lamination process, the specific gravity of the said green sheet to laminate | stack is 1.1-2.4, The manufacturing method of the ion conductive solid electrolyte as described in said (2) or (7) characterized by the above-mentioned. Can be provided.

  The specific gravity of the green sheet is preferably 1.1 to 2.4, more preferably 1.2 to 2.3, and most preferably 1.3 to 2.2. If the specific gravity is too large, the binder becomes too dense and it may be difficult to remove the binder in the firing step. On the other hand, if the specific gravity is too small, a dense solid electrolyte may not be obtained after firing. The specific gravity of the green sheet can be measured with an X-ray film pressure gauge and a balance.

(9) The method for producing an ion conductive solid electrolyte according to any one of (1) to (8), wherein in the slurry production step, the inorganic compound particles include glass or glass ceramics. Can be provided.

  Here, the glass ceramic may include a material obtained by precipitating a lithium ion conductive crystal phase in a glass phase by heat-treating the glass. A material composed of an amorphous solid and a crystal may be included. The crystal precipitation can be detected by, for example, an X-ray diffraction method or the like when a crystal layer is formed by sufficient growth after generation of crystal nuclei. Furthermore, the glass ceramics can include those in which all of the glass phase is phase-transformed into a crystalline phase when there are almost no vacancies, that is, those having a crystal content of 100% by mass (crystallinity of 100%). In general, ceramics that are difficult to melt tend to have vacancies and crystal grain boundaries between crystal grains remaining after sintering. However, in the glass ceramic here, since crystals are precipitated from the mother glass, it is possible to prevent vacancies and grain boundaries from remaining. Since ionic conduction is remarkably suppressed by vacancies and grain boundaries between crystal grains, in the case of ceramics, the ionic conductivity is considered to be considerably lower than the conductivity of the crystal grains themselves. Since glass ceramics can suppress a decrease in ionic conductivity between crystals by controlling the crystallization process, the ionic conductivity of the same degree as that of crystal particles can be maintained as a whole. The inorganic particles may be glass as long as a lithium ion conductive crystal phase is precipitated in the glass phase by heat treatment. This glass becomes glass ceramics when the green sheet is sintered.

(10) The ion conductivity according to any one of (1) to (9) above, wherein in the slurry production step, the inorganic compound particles include glass that exhibits lithium ion conductivity by heat treatment. A method for producing a solid electrolyte can be provided.

The glass constituting the inorganic compound particles may be one in which lithium ion conductive crystals are precipitated by heat-treating the glass. When these glasses in the green sheet are sintered, the individual powders are united, and lithium ion conductive crystals are deposited to express lithium ion conductivity. Thus, a solid electrolyte having high density and high lithium ion conductivity is obtained. Can be obtained. As such a glass _{Li 1 + x + z M x} (Ge 1-y Ti y) 2-x Si z P 3-z O 12 ( where, 0 ≦ x ≦ 0.8,0 ≦ y ≦ 1.0,0 ≦ a glass having a Li ₂ O—Al ₂ O ₃ —TiO ₂ —SiO ₂ —P ₂ O ₅ -based composition for precipitating crystals of z ≦ 0.6, one or more selected from M = Al and Ga, There are sulfide-based glasses that precipitate crystals such as Li ₇ PS ₆ , Li ₄ P ₂ S ₆ , and Li ₃ PS ₄ .

(11) The glass is expressed in mol% based on oxide,
Li ₂ O 10-25%, and Al ₂ O ₃ and / or Ga ₂ O ₃ 0-15%, and TiO ₂ and / or GeO ₂ 25-50%, and SiO ₂ 0-15%, and P ₂ O ₅ 26-40%
It is possible to provide a method for producing an ion conductive solid electrolyte as described in (10) above, wherein

The glass having the above composition is subjected to heat treatment to produce Li _{1 + x + z} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1). 0.0, 0 ≦ z ≦ 0.6, M = one or more selected from Al and Ga).

(12) In the slurry manufacturing step, the inorganic compound particles are lithium ion conductive glass ceramics, and the ion conductive solid electrolyte according to any one of (1) to (11) is manufactured. A method can be provided.

Examples of the lithium ion conductive glass ceramics include glass ceramics having sulfide crystals such as Li ₇ PS ₆ , Li ₄ P ₂ S ₆ , Li ₃ PS _4, and Li _{1 + x + z} M _x (Ge _1-y Ti _{y 2-x} Si _z P _3-z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, 0 ≦ z ≦ 0.6, M = Al, Ga, one or more selected from Glass ceramics having a crystal of In particular _{Li 1 + x + z M x} (Ge 1-y Ti y) 2-x Si z P 3-z O 12 ( where, 0 ≦ x ≦ 0.8,0 ≦ y ≦ 1.0,0 ≦ z ≦ 0.6 , M = Al or one selected from Al and Ga) is preferable because of its high chemical stability.

  In addition, it is advantageous in terms of ion conduction that the crystal does not include a crystal grain boundary that impedes ion conduction, but glass ceramics in particular have almost no vacancies or crystal grain boundaries that impede ion conduction. In view of high ion conductivity and excellent chemical stability, it is preferable compared to ceramics and the like. In addition to glass ceramics, examples of a material that has almost no vacancies or crystal grain boundaries that hinder ion conduction include single crystals of the above crystals, which are difficult to manufacture and expensive. Lithium ion conductive glass ceramics are also advantageous from the viewpoint of ease of production and cost.

Here, lithium ion conductivity means that the lithium ion conductivity shows a value of 1 × 10 ⁻⁸ S · cm ⁻¹ or more at 25 ° C. Further, vacancies and grain boundaries that hinder ion conduction mean that the conductivity of the entire inorganic substance including lithium ion conductive crystals is 1/10 of the conductivity of the lithium ion conductive crystals themselves in the inorganic substance. Ion conductivity inhibitors such as vacancies and grain boundaries that decrease below.

(13) The method for producing an ion conductive solid electrolyte according to any one of (1) to (11), wherein in the slurry production step, the inorganic compound particles are lithium ion conductive ceramics. Can be provided.

(14) The inorganic compound particles include Li _{1 + x + z} M _x (Ge _1-y Ti _y ) _2−x Si _z P _3−z O ₁₂ (where 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0). , 0 ≦ z ≦ 0.6, one or more selected from M = Al and Ga). The ion conductive solid electrolyte according to (12) or (13) is produced. A method can be provided.

Examples of the lithium ion conductive ceramic include crystals having a perovskite structure having lithium ion conductivity such as LiN, LISICON, La _0.55 Li _0.35 TiO _3, and crystals such as LiTi ₂ P ₃ O ₁₂ having a NASICON type structure. Ceramics are raised. From the viewpoint of lithium ion conductivity, chemical stability, cost, etc., Li _{1 + x + z} M _x (Ge _1-y Ti _y ) _2−x Si _z P _3−z O ₁₂ (however, 0 ≦ x ≦ 0.8, Ceramics having a crystal of 0 ≦ y ≦ 1.0, 0 ≦ z ≦ 0.6, and one or more selected from M = Al and Ga are preferable.

(15) The ion-conductive solid electrolyte according to any one of (2), (7), and (8) above, further comprising a step of heat-treating the laminate at 500 ° C. to 1200 ° C. A method can be provided.

  A baking process is performed in said temperature range, and includes a degreasing process and a sintering process. A degreasing process is a process which processes a green sheet laminated body at high temperature, gasifies components, such as organic binders other than the inorganic substance to comprise, and discharges | emits from a green sheet laminated body. The sintering step is a step of sintering and bonding inorganic particles constituting the green sheet laminate by treating the green sheet laminate at a higher temperature than the degreasing step. In any of the degreasing step and the sintering step, it is preferable to perform exhaust in order to keep the atmosphere in the furnace constant. Although a known firing furnace such as a gas furnace or a microwave furnace can be used for the firing step, it is preferable to use an electric furnace for reasons such as environment, temperature distribution in the furnace, and cost.

(16) A battery comprising a solid electrolyte produced by the method for producing an ion conductive solid electrolyte according to any one of (1) to (15) above can be provided.

  As described above, the solid electrolyte green sheet having high homogeneity in the upper and lower portions in the coating film of the solid electrolyte slurry can be produced. In particular, since the homogeneity can be confirmed by a simple nondestructive inspection method of comparing the glossiness of the upper and lower surfaces of the solid electrolyte green sheet, the degree of freedom in the manufacturing process is increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following description is made for explaining the embodiments of the present invention, and the present invention is limited to these embodiments. It is not a thing. The same or the same type of elements are denoted by the same or related symbols, and redundant description is omitted.

  FIG. 1 relates to an embodiment of the present invention, and in a method for producing an ion conductive solid electrolyte containing an inorganic compound powder and an organic binder, a step of applying a slurry to a carrier film to produce a coating film; It is a schematic diagram of the line 10 which performs the process of drying and producing a green sheet. A coating film 19 is applied onto the carrier film 16 that is fed from the carrier film roll 14 by the doctor blade 12 and is conveyed by the conveying roller 18. A schematic diagram of this doctor blade is shown in FIG. The slurry stored in the slurry dam 13 by the doctor blade is applied onto the carrier film 16 through the opening 15. Next, the coating film 19 is transported to a drying furnace 20 and dried therein. Thereafter, the film is wound around the drum 22 together with the carrier film 16. As shown in FIG. 3, the coating film 19 with the carrier film 16 on the drum 22 is partially developed outside the line, and the sample portion 24 is sampled and cut out. The sample portion 24 cut out in this way was measured for the glossiness of the surface (the side without the carrier film) with the carrier film 16 attached, and then the carrier film 16 was peeled off and its surface (on the carrier film side) Surface) is measured.

[Example]
(Preparation of solid electrolyte green sheet)
H ₃ PO ₄ , Al (PO ₃ ) ₃ , Li ₂ CO ₃ , SiO ₂ , and TiO ₂ are used as raw materials. These are mol% in terms of oxide, 33.8% of P ₂ O ₅ and Al ₂ O. ₃ was 7.6%, Li ₂ O was 14.5%, TiO ₂ was 41.3%, and SiO ₂ was 2.8%. The glass melt was heated and melted for 3 hours at 1450 ° C. in an electric furnace while stirring. Thereafter, the glass melt was dropped into running water to obtain flaky glass.

  The obtained glass flakes were pulverized and classified by a ball mill to obtain glass fine particles having an average particle diameter of 1.1 μm. Further, the mixture was finely pulverized using a wet bead mill using ethanol, and the slurry was further dried by spray drying to obtain glass microparticles having an average particle size of 0.5 μm.

  A dispersant was added to the acrylic resin as a binder dispersed in the glass fine particles and water, and the mixture was stirred for 48 hours with a ball mill to prepare a slurry. The glass fine particles contained in the slurry at this time were 60.5 mass%, and the acrylic resin was 11.0 mass%.

  A 40 μm-thick coating film is formed on a PET film that has been subjected to a release treatment with a doctor blade, and the resulting slurry is first dried at 40 ° C., secondarily dried at 60 ° C., and thirdly dried at 90 ° C. A green sheet was obtained.

  The green sheet was cut into 200 mm squares, peeled off from the PET film, and the glossiness at an incident angle of 60 ° on both sides of the green sheet was measured at 10 locations using a handy gloss meter IG-320 manufactured by Horiba. Here, when the free surface of the green sheet was the front and the surface that was in contact with the release film was the back, the average glossiness of the front was 38 and the average glossiness of the back was 61. Here, the difference between the obtained average values was 23.

(Preparation of green sheet laminate for solid electrolyte)
A green sheet of the same lot was cut into the same size, and 8 sheets were stacked and sandwiched between PET films that had been subjected to a release treatment, and pressed and laminated with a hydrostatic pressure press. At this time, the difference of the average value of the glossiness of the front and back of the eight green sheets used for lamination was 22-24.

  Here, the specific gravity of the laminated green sheets (hereinafter referred to as green sheet laminate) was 1.91. Next, the green sheet laminate is placed on a quartz glass plate, heated at 50 ° C./h in an electric furnace, held at 500 ° C. for 3 h to remove the binder, and cooled to room temperature at 50 ° C./h to degrease. Got.

(Heat treatment of green sheet laminate for solid electrolyte and production of all solid lithium battery)
Then, sandwiched between the quartz glass plates, heated to 50 ° C./h up to 500 ° C. in an electric furnace, held for 1 h, then heated at 650 ° C./h, heat treated at 1015 ° C. for 30 min, sintered, The temperature was lowered to room temperature at 50 ° C./h to obtain a solid electrolyte. As confirmed by X-ray diffraction, the main crystal phase is Li _{1 + x + y} Al _x Ti _2−x Si _y P _3−y O ₁₂ (0 ≦ x ≦ 0.4, 0 <y ≦ 0.6). When it was confirmed and impedance measurement was performed to determine ionic conductivity, it was 3.0 × 10 ⁻⁴ Scm ⁻¹ , and density measurement was performed to determine porosity, which was 1.2%, indicating high ionic conductivity. It was confirmed that an accurate and dense solid electrolyte was obtained.

The solid electrolyte after polishing obtained above is sandwiched between permanent masks having a measurement area of 5 cm ² using a water vapor transmission rate measuring device PERMATRAN-W 3/33 MA manufactured by MOCON, and the temperature is 37.8 ° C., humidity When the water vapor transmission rate was measured at 100% RH, it was 0.1 g / m ² · 24H or less.

[Comparative Example 1]
The same glass flakes as in Examples were pulverized and classified with a ball mill to obtain glass fine particles having an average particle diameter of 5 μm. A dispersant was added to the acrylic resin as a binder dispersed in the glass fine particles and water, and the mixture was stirred for 48 hours with a ball mill to prepare a slurry. The glass fine particles contained in the slurry at this time were 60.5 mass%, and the acrylic resin was 14.0 mass%.

  A 40 μm-thick coating film is formed on a PET film that has been subjected to a release treatment with a doctor blade, and the resulting slurry is first dried at 40 ° C., secondarily dried at 60 ° C., and thirdly dried at 90 ° C. A green sheet was obtained. The green sheet was cut into 200 mm squares, peeled off from the PET film, and the glossiness at an incident angle of 60 ° on both sides of the green sheet was measured at 10 locations using a handy gloss meter IG-320 manufactured by Horiba. Here, when the free surface of the green sheet was the front and the surface that was in contact with the release film was the back, the average glossiness of the front was 15.5 and the average glossiness of the back was 68. . Here, the difference between the average values obtained was 53.5.

  The green sheets thus obtained were cut into the same size, and 8 sheets were stacked and sandwiched between PET films that had been subjected to a release treatment, and pressed and laminated with a hydrostatic pressure press. At this time, the difference of the average value of the glossiness of the front and back of the eight green sheets used for lamination was 52 to 55.

Here, the specific gravity of the laminated green sheets (hereinafter referred to as green sheet laminates) was 1.7. Next, a solid electrolyte was obtained under the heat treatment conditions of the example. As confirmed by X-ray diffraction, the main crystal phase is Li _{1 + x + y} Al _x Ti _2−x Si _y P _3−y O ₁₂ (0 ≦ x ≦ 0.4, 0 <y ≦ 0.6). When it was confirmed and impedance measurement was performed to determine ion conductivity, it was 5 × 10 ⁻⁵ S · cm ⁻¹ , and density measurement was performed to determine relative density with respect to the true density, which was 87%. The degree was as low as 6 × 10 ⁻⁵ S · cm ⁻¹ .

  FIG. 5 relates to another embodiment of the present invention, in a method for producing an ion conductive solid electrolyte containing an inorganic compound powder and an organic binder, a step of applying a slurry to a carrier film to produce a coating film, It is the schematic of the process of drying a film | membrane and producing a green sheet, and the line 10 which measures a glossiness. Basically, since the configuration is the same as the line in FIG. 1, only the differences will be described. The green sheet with the carrier film exiting the drying furnace is peeled off by the carrier film 16 at the last conveying roller 18 and wound around the drum 21. On the other hand, the green sheet is conveyed as it is and wound around the drum 34. The front and back surfaces of the green sheet are measured by gloss meters 30 and 32, respectively. However, since measurement on a stationary surface is required, the belt driven by the roller 36 in synchronization with the conveyance speed of the green sheet. These gloss meters 30 and 32 are fixed to each other and are conveyed at the same speed in contact with the green sheet during measurement. In this way, the glossiness can be measured on the line, and the subsequent response can be performed quickly. If the green sheet is not strong enough, it can be backed up by a conveyor belt. At this time, the conveyor belt is provided with an opening for measuring the glossiness, and is arranged so that the glossiness meter can enter the bottom.

It is a schematic diagram of the line which performs the process of apply | coating a slurry with a doctor blade and drying the coating film. It is a perspective view which shows the detail of a doctor blade. It is a figure which shows typically how it samples from the green sheet with a carrier film. It is a figure which shows typically the preparatory process for measuring the glossiness of front and back from the sampled sample. It is a schematic diagram of the line which performs the process of apply | coating a slurry with a doctor blade and drying the coating film, and can measure glossiness as it is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Application line 12 Doctor blade 13 Slurry dam 16 Carrier film 18 Conveyance roller 19 Coating film 20 Drying furnace 30, 32 Gloss meter

Claims (8)

In a method for producing an ion conductive solid electrolyte containing an inorganic compound powder exhibiting lithium ion conductivity and an organic binder at least after heat treatment,
The inorganic compound powder is expressed in mol% based on oxide,
Li ₂ O 10-25%, and Al ₂ O ₃ and / or Ga ₂ O ₃ 0-15%, and TiO ₂ and / or GeO ₂ 25-50%, and SiO ₂ 0-15%, and P ₂ O ₅ 26-40%
Glass containing each component of
The weight ratio of the inorganic compound to the organic binder is 1.5 or more and 12 or less,
A slurry production step of preparing a slurry by mixing the inorganic compound powder and the organic binder;
Applying the slurry to a carrier film to produce a coating film;
Peeling the coating film from the carrier film to produce a green sheet;
Measuring the 60 degree specular gloss on each of the carrier film side and the upper surface side of the green sheet,
A method for producing an ion-conducting solid electrolyte, characterized in that if the difference between the measured specular gloss on the side surface of the carrier film and the specular gloss on the side surface on the upper surface is 24 or less, the product is determined to be a non-defective product.   The method for producing an ion-conducting solid electrolyte according to claim 1, further comprising a laminating step of laminating at least two green sheets that have been made non-defective and press-bonding them in a predetermined pressure range to produce a laminate. The method for producing an ion conductive solid electrolyte according to claim 1 or 2, wherein the inorganic compound powder has an average particle size of 3 µm or less.   The method for producing an ion conductive solid electrolyte according to claim 2, wherein the green sheet has a thickness of 1 to 100 μm, and the laminate has a thickness of 10 to 1000 μm. The measuring step, how the amount of dust or 0.5μm in per cubic meter to produce an ion conductive solid electrolyte according to any one of claims 1 to 4, characterized in that it is carried out at 140,000 or less environmental . In the lamination step,
The method for producing an ion conductive solid electrolyte according to claim 2, wherein the pressurizing time for laminating is 5 seconds or more. In the lamination step,
The method for producing an ion conductive solid electrolyte according to claim 2 or 6 , wherein the green sheet to be laminated has a specific gravity of 1.1 to 2.4. Furthermore, the process of heat-processing the said laminated body at 500 to 1200 degreeC is included, The method of manufacturing the ion conductive solid electrolyte in any one of Claim 2, 6 , 7 characterized by the above-mentioned.

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