All-solid-state battery and method for manufacturing the same

Abstract

To provide an all-solid battery having a cover layer which can suppress a correlation peeling in an integral sintering and has moisture prevention performance, and a manufacturing method of the same.SOLUTION: An all-solid battery contains: a lamination structure in which an oxidation system solid electrolyte layer having an ion conductive performance and an electrode layer containing an electrode active material are alternately laminated; and a cover layer that is provided to at least one of an upper surface and a lower surface of a lamination direction of the lamination structure. The cover layer contains: the oxidation system solid electrolyte layer; and a filler material having a sinter temperature higher than that of the oxidation system solid electrolyte layer, and having an insulation property.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery and a method for manufacturing the same. [Background technology]

[0002] In recent years, demand for secondary batteries has been expanding rapidly, and lithium-ion secondary batteries using organic electrolytes have been put to practical use. However, due to concerns about electrolyte leakage and other issues, expectations are growing for safer oxide-based solid electrolytes, and the development of all-solid-state batteries using oxide-based solid electrolytes is actively progressing. Furthermore, in order to improve capacity density, it is desirable to stack multiple battery units. When stacking multiple units, techniques have been disclosed for providing cover layers above and below the stacking direction of the all-solid-state battery (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-82522 [Patent Document 2] Japanese Patent Publication No. 2020-149782 [Patent Document 3] International Publication No. 2018 / 181545 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable that the cover layer be made of a material that does not interdiffuse with the solid electrolyte layer during firing, and therefore, in Patent Documents 1 and 2, a material with the same composition as the solid electrolyte layer is used for the cover layer material. However, in a stacked-type all-solid-state battery, in addition to the cover layer and solid electrolyte layer, multiple layers made primarily of different materials, such as a positive electrode layer, a negative electrode layer, and a reverse pattern layer, are stacked, and if such a stacked-type all-solid-state battery is to be co-fired, there is a concern that delamination may occur due to differences in the shrinkage behavior of each layer.

[0005] In Patent Document 3, a moisture-proof layer is provided in contact with the laminate to prevent a decrease in battery capacity due to a reaction between the active material contained in the electrode layer and moisture. However, in Patent Document 3, the moisture-proof layer is provided by a method such as spray coating or dip coating after the laminate is fired, and the moisture-proof property of the laminate before the formation of the moisture-proof layer is not guaranteed.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide an all-solid-state battery including a cover layer that can suppress delamination during co-firing and has moisture-proof properties, and a manufacturing method thereof. [Means for solving the problem]

[0007] The all-solid-state battery according to the present invention comprises a laminated structure in which oxide-based solid electrolyte layers having ion conductivity and electrode layers containing an electrode active material are alternately laminated, and a cover layer provided on at least one of the upper and lower surfaces in the lamination direction of the laminated structure, wherein the cover layer contains an oxide-based solid electrolyte and an insulating filler material having a higher sintering temperature than the oxide-based solid electrolyte.

[0008] In the cover layer of the all-solid-state battery, the volume ratio of the filler material to the oxide-based solid electrolyte may be 10 vol % or more.

[0009] In the all-solid-state battery, the electrical conductivity including the electronic conductivity and the ionic conductivity of the filler material is 10 -8 It may be S / cm or less.

[0010] In the all-solid-state battery, the filler material may be alumina or SiO2 glass.

[0011] In the all-solid-state battery, the filler may have a shape such that the average circularity of the cross section is 0.6 or more.

[0012] In the all-solid-state battery, the filler may have a D50% particle size of 0.5 μm or more and 8 μm or less.

[0013] In the all-solid-state battery, between the oxide-based solid electrolyte layer and the cover layer, the D0% particle size in the particle size distribution of the solid electrolyte of one layer may be between the D0% particle size and the D10% particle size in the particle size distribution of the solid electrolyte of the other layer, and the D100% particle size in the particle size distribution of the solid electrolyte of the one layer may be between the D90% particle size and the D100% particle size in the particle size distribution of the solid electrolyte of the other layer.

[0014] In the all-solid-state battery, the oxide-based solid electrolyte of the cover layer may be a solid electrolyte having a NASICON-type crystal structure.

[0015] In the all-solid-state battery, the main component of the solid electrolyte layer may be a solid electrolyte having a NASICON-type crystal structure.

[0016] In the all-solid-state battery, the oxide-based solid electrolyte of the cover layer may have the same composition as a main component of the solid electrolyte layer.

[0017] In the all-solid-state battery, the oxide-based solid electrolyte of the cover layer may be a glass material.

[0018] In the all-solid-state battery, the electrode layer may contain an oxide-based solid electrolyte having ion conductivity.

[0019] The method for producing an all-solid-state battery according to the present invention includes a preparation step of preparing a ceramic laminate in which a cover sheet containing an oxide-based solid electrolyte powder and an insulating filler material having a higher sintering temperature than the oxide-based solid electrolyte powder is laminated on at least one of the upper and lower surfaces in the lamination direction of a laminate in which solid electrolyte green sheets containing an oxide-based solid electrolyte powder having ion conductivity and internal electrode patterns containing an electrode active material powder are alternately stacked, and a firing step of firing the ceramic laminate.

[0020] In the method for manufacturing an all-solid-state battery, a sintering temperature of the oxide-based solid electrolyte powder of the cover sheet may be lower than a sintering temperature in the sintering step, and a sintering temperature of the filler material may be higher than a sintering temperature in the sintering step. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide an all-solid-state battery that can suppress relative peeling during co-firing and has a moisture-proof cover layer, and a method for manufacturing the same. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery. [Figure 2] FIG. 1 is a schematic cross-sectional view of a stacked-type all-solid-state battery. [Figure 3] FIG. 1 is a schematic cross-sectional view of another stacked-type all-solid-state battery. [Figure 4] FIG. 2 is a schematic cross-sectional view of a cover layer. [Figure 5] FIG. 1 is a diagram illustrating a flow of a method for manufacturing an all-solid-state battery. [Figure 6] 1(a) and 1(b) are diagrams illustrating the lamination process. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments will be described with reference to the drawings.

[0024] (Embodiment) Fig. 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery 100. As illustrated in Fig. 1, the all-solid-state battery 100 has a structure in which a solid electrolyte layer 30 is sandwiched between a first internal electrode 10 (first electrode layer) and a second internal electrode 20 (second electrode layer). The first internal electrode 10 is formed on a first main surface of the solid electrolyte layer 30. The second internal electrode 20 is formed on a second main surface of the solid electrolyte layer 30.

[0025] When the all-solid-state battery 100 is used as a secondary battery, one of the first internal electrode 10 and the second internal electrode 20 is used as a positive electrode, and the other is used as a negative electrode. In this embodiment, as an example, the first internal electrode 10 is used as a positive electrode layer, and the second internal electrode 20 is used as a negative electrode layer.

[0026] The solid electrolyte layer 30 has a NASICON-type crystal structure and is mainly composed of an oxide-based solid electrolyte having ion conductivity. The solid electrolyte of the solid electrolyte layer 30 is, for example, an oxide-based solid electrolyte having lithium ion conductivity. The solid electrolyte is, for example, a phosphate-based solid electrolyte. A phosphate-based solid electrolyte having a NASICON-type crystal structure has high conductivity and is stable in the air. The phosphate-based solid electrolyte is, for example, a phosphate containing lithium. The phosphate is not particularly limited, but examples include composite lithium phosphate salts with Ti (e.g., LiTi2(PO4)3). Alternatively, Ti can be partially or completely substituted with a tetravalent transition metal such as Ge, Sn, Hf, or Zr. Furthermore, to increase the Li content, it may be partially substituted with a trivalent transition metal such as Al, Ga, In, Y, or La. More specifically, for example, Li 1+x Al x Ge 2-x (PO4)3 and Li 1+x Al x Zr 2-x (PO4)3, Li 1+x Al x Ti 2-x(PO4)3, etc. For example, a Li-Al-Ge-PO4-based material to which the same transition metal as that contained in the phosphate having an olivine crystal structure contained in the first internal electrode 10 and the second internal electrode 20 has been added in advance is preferred. For example, when the first internal electrode 10 and the second internal electrode 20 contain a phosphate containing Co and Li, it is preferred that the solid electrolyte layer 30 contain a Li-Al-Ge-PO4-based material to which Co has been added in advance. In this case, it is possible to obtain an effect of suppressing the elution of the transition metal contained in the electrode active material into the electrolyte. When the first internal electrode 10 and the second internal electrode 20 contain a phosphate containing Li and a transition element other than Co, it is preferred that the solid electrolyte layer 30 contain a Li-Al-Ge-PO4-based material to which the transition metal has been added in advance.

[0027] The first internal electrode 10 used as a positive electrode contains a substance having an olivine crystal structure as an electrode active material. It is preferable that the second internal electrode 20 also contains the electrode active material. An example of such an electrode active material is a phosphate containing a transition metal and lithium. The olivine crystal structure is a crystal possessed by natural olivine, and can be identified by X-ray diffraction.

[0028] A typical example of an electrode active material with an olivine crystal structure is LiCoPO4, which contains Co. Phosphates in which the transition metal Co is substituted in this chemical formula can also be used. The ratio of Li and PO4 can vary depending on the valence. It is preferable to use Co, Mn, Fe, Ni, etc. as the transition metal.

[0029] The electrode active material having an olivine-type crystal structure acts as a positive electrode active material in the first internal electrode 10 that acts as a positive electrode. For example, when only the first internal electrode 10 contains an electrode active material having an olivine-type crystal structure, the electrode active material acts as a positive electrode active material. When the second internal electrode 20 also contains an electrode active material having an olivine-type crystal structure, the second internal electrode 20 that acts as a negative electrode exhibits the effects of increasing the discharge capacity and increasing the operating potential with discharge, which are presumed to be based on the formation of a partial solid solution state with the negative electrode active material, although the mechanism of action is not fully understood.

[0030] When both the first internal electrode 10 and the second internal electrode 20 contain an electrode active material having an olivine crystal structure, the respective electrode active materials preferably contain transition metals that may be the same or different from each other. The phrase "may be the same or different from each other" means that the electrode active materials contained in the first internal electrode 10 and the second internal electrode 20 may contain the same type of transition metal or different types of transition metals. The first internal electrode 10 and the second internal electrode 20 may contain only one type of transition metal or two or more types of transition metals. Preferably, the first internal electrode 10 and the second internal electrode 20 contain the same type of transition metal. More preferably, the electrode active materials contained in both electrodes have the same chemical composition. The first internal electrode 10 and the second internal electrode 20 contain the same type of transition metal or electrode active material with the same composition, which increases the similarity of the compositions of the two internal electrode layers, has the effect of being able to withstand actual use without malfunctioning depending on the application, even if the terminals of the all-solid-state battery 100 are attached in reverse.

[0031] The second internal electrode 20 contains a negative electrode active material. By including a negative electrode active material in only one electrode, it becomes clear that the one electrode functions as a negative electrode and the other electrode functions as a positive electrode. It is also possible to include a material known as a negative electrode active material in both electrodes. Regarding the negative electrode active material of the electrode, reference can be made to conventional secondary battery technology, and examples include compounds such as titanium oxide, lithium titanium composite oxide, lithium titanium composite phosphate, carbon, and lithium vanadium phosphate.

[0032] In the production of the first internal electrode 10 and the second internal electrode 20, in addition to these electrode active materials, a solid electrolyte having ion conductivity, a conductive material (conductive additive), etc. are added. For these components, an internal electrode paste can be obtained by uniformly dispersing a binder and a plasticizer in water or an organic solvent. A carbon material or the like may be included as the conductive additive. A metal may be included as the conductive additive. Examples of the metal for the conductive additive include Pd, Ni, Cu, Fe, and alloys containing these. The solid electrolyte included in the first internal electrode 10 and the second internal electrode 20 can be, for example, the same as the main solid electrolyte of the solid electrolyte layer 30.

[0033] The thickness of the solid electrolyte layer 30 is, for example, 5 μm to 30 μm, 7 μm to 25 μm, or 10 μm to 20 μm. The thickness of the first internal electrode 10 and the second internal electrode 20 is, for example, 5 μm to 50 μm, 7 μm to 45 μm, or 10 μm to 40 μm. The thickness of each layer can be measured, for example, as the average value of thicknesses at 10 different points on one layer.

[0034] 2 is a schematic cross-sectional view of a stacked-type all-solid-state battery 100a in which a plurality of battery units are stacked. The all-solid-state battery 100a includes a stacked chip 60 having a substantially rectangular parallelepiped shape. In the stacked chip 60, a first external electrode 40a and a second external electrode 40b are provided so as to contact two side surfaces, which are two of the four surfaces other than the top and bottom surfaces at the ends in the stacking direction. The two side surfaces may be two adjacent side surfaces or two side surfaces facing each other. In this embodiment, the first external electrode 40a and the second external electrode 40b are provided so as to contact two side surfaces facing each other (hereinafter referred to as two end surfaces).

[0035] In the following description, components having the same composition range, thickness range, and particle size distribution range as those of the all-solid-state battery 100 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0036] In the all-solid-state battery 100a, a plurality of first internal electrodes 10 and a plurality of second internal electrodes 20 are alternately stacked with solid electrolyte layers 30 interposed therebetween. The edges of the plurality of first internal electrodes 10 are exposed at the first end face of the laminated chip 60 but are not exposed at the second end face. The edges of the plurality of second internal electrodes 20 are exposed at the second end face of the laminated chip 60 but are not exposed at the first end face. As a result, the first internal electrodes 10 and the second internal electrodes 20 are alternately electrically connected to the first external electrode 40a and the second external electrode 40b. The solid electrolyte layer 30 extends from the first external electrode 40a to the second external electrode 40b. In this way, the all-solid-state battery 100a has a structure in which a plurality of battery units are stacked.

[0037] A cover layer 50 is laminated on the upper surface of the laminated structure of the first internal electrode 10, the solid electrolyte layer 30, and the second internal electrode 20. The cover layer 50 is in contact with the internal electrode of the uppermost layer (either the first internal electrode 10 or the second internal electrode 20) and is in contact with part of the solid electrolyte layer 30. A cover layer 50 is also laminated on the lower surface of the laminated structure. The cover layer 50 is in contact with the internal electrode of the lowermost layer (either the first internal electrode 10 or the second internal electrode 20) and is in contact with part of the solid electrolyte layer 30.

[0038] The first internal electrode 10 and the second internal electrode 20 may each include a current collector layer. For example, as illustrated in FIG. 3, a first current collector layer 11 may be provided within the first internal electrode 10. Furthermore, a second current collector layer 21 may be provided within the second internal electrode 20. The first current collector layer 11 and the second current collector layer 21 are mainly composed of a conductive material. For example, metal, carbon, or the like can be used as the conductive material for the first current collector layer 11 and the second current collector layer 21. Connecting the first current collector layer 11 to the first external electrode 40a and connecting the second current collector layer 21 to the second external electrode 40b improves current collection efficiency.

[0039] 2 and 3 , a stacked all-solid-state battery such as the all-solid-state battery 100a shown in FIG. 2 or 3 is composed of multiple stacked layers composed primarily of different materials. Therefore, when attempting to simultaneously fire these layers, delamination may occur due to differences in the shrinkage behavior of each layer. Furthermore, in order to prevent a decrease in battery capacity due to a reaction between the electrode active material contained in the electrode layer and moisture, it is necessary to provide the stacked all-solid-state battery with moisture-proofing properties. Therefore, the cover layer 50 according to this embodiment has a moisture-proofing configuration that can prevent delamination during simultaneous firing.

[0040] Fig. 4 is a schematic diagram showing a cross section of the cover layer 50. As shown in Fig. 4, the cover layer 50 includes an oxide-based solid electrolyte 50a and an insulating filler material 50b that has a higher sintering temperature than the solid electrolyte 50a. For example, particles of the solid electrolyte 50a and particles of the filler material 50b are randomly dispersed and arranged.

[0041] During the co-firing, the solid electrolyte 50a contained in the cover layer 50 is sintered together with the solid electrolyte layer 30 and the electrode layer that are in contact with the cover layer 50, thereby achieving high adhesion between the cover layer 50 and the solid electrolyte layer 30 and the electrode layer that are in contact with the cover layer 50. This makes it possible to suppress delamination between the layers.

[0042] Furthermore, because the sintering temperature of the filler material 50b contained in the cover layer 50 is higher than that of the solid electrolyte 50a, the filler material 50b does not sinter or grow during co-firing, maintaining the particle shape of the filler material 50b. This suppresses in-plane shrinkage of the cover layer 50 and suppresses or absorbs stress or strain due to differences in the shrinkage behavior of each layer, thereby preventing delamination.

[0043] Furthermore, since the filler material 50b in the cover layer 50 has insulating properties, the cover layer 50 provides moisture resistance.

[0044] From the above, the cover layer 50 according to this embodiment can suppress delamination during co-firing and can also achieve moisture resistance.

[0045] For example, the filler material 50b may be alumina (Al2O3), SiO2 glass, ZrO2, or the like.

[0046] If the particle size of the filler material 50b is too small, the filler particles may form aggregates, which may cause voids during co-firing with the solid electrolyte 50a. Therefore, it is preferable to set a lower limit for the D50% particle size of the filler material 50b. For example, the D50% particle size of the filler material 50b is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 2.0 μm or more. The particle size of the filler material 50b can be measured in the powder stage using a particle size distribution analyzer that utilizes a laser diffraction / scattering method, and can be measured after firing by image analysis of SEM images.

[0047] If the particle size of the filler material 50b is too large, the filler particles will be larger than the thickness of one cover sheet layer, which may result in an unsmooth sheet. Therefore, it is preferable to set an upper limit on the D50% particle size of the filler material 50b. For example, the D50% particle size of the filler material 50b is preferably 8 μm or less, more preferably 6 μm or less, and even more preferably 4 μm or less.

[0048] From the viewpoint of obtaining high adhesion between the cover layer 50 and the solid electrolyte layer 30 and electrode layer that are in contact with the cover layer 50, it is preferable that the filler material 50b have an irregular shape. If the particles of the filler material 50b present on the surface that is in contact with the solid electrolyte layer 30 and the electrode layer are spherical, they will be in point contact with the solid electrolyte layer 30 and the electrode layer, whereas if the particles of the filler material 50b are irregular, they will be in surface contact with the solid electrolyte layer 30 and the electrode layer more frequently, thereby further improving adhesion. Here, "irregular shape" means that the shape of the filler material 50b has an average cross-sectional circularity of 0.6 or more.

[0049] If the amount of filler material 50b in the cover layer 50 is small, sufficient moisture resistance may not be achieved. Therefore, it is preferable to set a lower limit for the amount of filler material 50b in the cover layer 50. For example, if the total volume of the solid electrolyte 50a and filler material 50b in the cover layer 50 is 100 vol%, the ratio of the filler material 50b is preferably 10 vol% or more, more preferably 20 vol% or more, and even more preferably 30 vol% or more. Regarding the volume ratio, a cross section of the all-solid-state battery 100 is subjected to FIB processing and then SEM observation. The FIB processing and SEM observation are repeated to obtain a cross-sectional image of the entire cover layer 50 of the all-solid-state battery 100, and these are then image-processed to construct a three-dimensional structure. Because the contrast ratio between the filler material 50b and the glass material is clearly generated in the SEM image, the volume ratio of the filler material 50b can be calculated based on the light and dark contrast.

[0050] On the other hand, if the amount of filler material 50b in the cover layer 50 is large, the amount of solid electrolyte 50a will be small, and sufficient adhesion may not be obtained. Therefore, it is preferable to set an upper limit on the amount of filler material 50b in the cover layer 50. For example, when the total volume of the solid electrolyte 50a and filler material 50b in the cover layer 50 is 100 vol%, the ratio of filler material 50b is preferably 80 vol% or less, more preferably 70 vol% or less, and even more preferably 65 vol% or less.

[0051] In order to obtain sufficient moisture resistance, the filler material 50b preferably has sufficient insulating properties. For example, the electrical conductivity of the filler material 50b, including electronic conductivity and ionic conductivity, is 10 -8 S / cm or less is preferable, and 10 -12 S / cm or less is more preferable, and 10 -14 It is more preferable that the viscosity is S / cm or less.

[0052] From the viewpoint of improving the adhesion of the cover layer 50, it is preferable that the solid electrolyte 50a has a structure common to the oxide-based solid electrolyte that is the main component of the solid electrolyte layer 30, the oxide-based solid electrolyte contained in the first internal electrode 10, and the oxide-based solid electrolyte contained in the second internal electrode 20. For example, it is preferable that the solid electrolyte 50a has a NASICON-type crystal structure. It is also preferable that the solid electrolyte 50a has the same composition as the oxide-based solid electrolyte that is the main component of the solid electrolyte layer 30. It is also preferable that the solid electrolyte 50a is a glass material.

[0053] Furthermore, when the particle size distribution of the solid electrolyte 50a in the cover layer 50 and the particle size distribution of the oxide-based solid electrolyte in the solid electrolyte layer 30 are similar, the timing of softening of the solid electrolyte particles in each layer is synchronized during co-firing, facilitating sintering between the layers. Therefore, it is preferable that the solid electrolyte 50a in the cover layer 50 has a particle size distribution similar to that of the oxide-based solid electrolyte that is the main component in the solid electrolyte layer 30. For example, similar particle size distributions are defined as a state in which the D0% particle size in the particle size distribution of the solid electrolyte in one layer is between the D0% particle size and the D10% particle size in the particle size distribution of the solid electrolyte in the other layer, and the D100% particle size in the particle size distribution of the solid electrolyte in the other layer is between the D90% particle size and the D100% particle size in the particle size distribution of the solid electrolyte in the other layer.

[0054] The thickness of the cover layer 50 is, for example, 5 μm to 100 μm, 10 μm to 85 μm, or 15 μm to 70 μm. The thickness of the cover layer 50 can be measured, for example, as the average value of thicknesses at 10 different points on one layer.

[0055] Next, a description will be given of a method for manufacturing the all-solid-state battery 100a illustrated in Fig. 2. Fig. 5 is a diagram illustrating a flow of the method for manufacturing the all-solid-state battery 100a.

[0056] (Process for producing raw material powder for solid electrolyte layer) First, raw material powder for the solid electrolyte layer that constitutes the above-described solid electrolyte layer 30 is prepared. For example, raw materials, additives, etc. are mixed and a solid-phase synthesis method or the like is used to prepare raw material powder for an oxide-based solid electrolyte. The obtained raw material powder can be dry-pulverized to adjust the average particle size to a desired value. For example, the desired average particle size is adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls.

[0057] (Cover layer raw material powder production process) First, a ceramic raw material powder for the cover layer 50 is prepared. For example, raw materials, additives, etc. are mixed and the raw material powder for the cover layer can be prepared using a solid-phase synthesis method or the like. The raw material powder includes raw material powder for the solid electrolyte 50a and raw material powder for the filler material 50b. The obtained raw material powder can be adjusted to the desired average particle size by dry milling. For example, the desired average particle size can be adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls.

[0058] (Electrode layer paste preparation process) Next, internal electrode pastes for producing the first internal electrode 10 and the second internal electrode 20 are separately prepared. For example, the internal electrode pastes can be obtained by uniformly dispersing a conductive additive, an electrode active material, a solid electrolyte material, a sintering additive, a binder, a plasticizer, etc. in water or an organic solvent. The solid electrolyte paste described above may be used as the solid electrolyte material. A carbon material or the like may be used as the conductive additive. A metal may also be used as the conductive additive. Examples of metals for the conductive additive include Pd, Ni, Cu, Fe, and alloys containing these. Pd, Ni, Cu, Fe, alloys containing these, and various carbon materials may also be used.

[0059] The sintering aid of the internal electrode paste contains one or more glass components such as Li-BO based compounds, Li-Si-O based compounds, Li-CO based compounds, Li-SO based compounds, and Li-PO based compounds.

[0060] (External electrode paste manufacturing process) Next, an external electrode paste for producing the first external electrode 40a and the second external electrode 40b is prepared. For example, the external electrode paste can be obtained by uniformly dispersing a conductive material, glass frit, a binder, a plasticizer, etc. in water or an organic solvent.

[0061] (Solid electrolyte green sheet manufacturing process) The raw material powder for the solid electrolyte layer is uniformly dispersed in an aqueous or organic solvent along with a binder, dispersant, plasticizer, etc., and then wet-pulverized to obtain a solid electrolyte slurry with a desired average particle size. This process can be performed using a bead mill, wet jet mill, various kneaders, high-pressure homogenizers, etc., with the bead mill being preferred because it allows for simultaneous adjustment of particle size distribution and dispersion. A binder is added to the resulting solid electrolyte slurry to obtain a solid electrolyte paste. The resulting solid electrolyte paste can be coated to produce a solid electrolyte green sheet 51. The coating method is not particularly limited, and can include slot die coating, reverse coating, gravure coating, bar coating, doctor blade coating, etc. The particle size distribution after wet-pulverization can be measured, for example, using a laser diffraction measurement device using laser diffraction scattering.

[0062] (Lamination process) As shown in FIG. 6( a), an internal electrode paste 52 is printed on one side of a solid electrolyte green sheet 51. A reverse pattern 53 is printed on the area of ​​the solid electrolyte green sheet 51 where the internal electrode paste 52 is not printed. The reverse pattern 53 may be the same as the solid electrolyte green sheet 51. After printing, multiple solid electrolyte green sheets 51 are stacked with alternating offsets. As shown in FIG. 6( b), a laminate is obtained by pressing cover sheets 54 from above and below in the stacking direction. In this case, a laminate having a substantially rectangular parallelepiped shape is obtained, with the internal electrode paste 52 for the first internal electrode 10 exposed on one end surface and the internal electrode paste 52 for the second internal electrode 20 exposed on the other end surface. The cover sheet 54 can be formed by applying raw material powder for the cover layer using a method similar to that used in the solid electrolyte green sheet preparation process. The cover sheet 54 is formed thicker than the solid electrolyte green sheet 51. The thickness may be increased during coating, or by stacking multiple coated sheets.

[0063] Next, external electrode paste 55 is applied to each of the two end faces by dipping or the like and then dried, thereby obtaining a molded body for forming the all-solid-state battery 100a.

[0064] (Firing process) Next, the obtained ceramic laminate is fired. Firing conditions include, but are not limited to, an oxidizing or non-oxidizing atmosphere, with a maximum temperature of preferably 400°C to 1000°C, more preferably 500°C to 900°C. A step of maintaining the temperature in an oxidizing atmosphere at a temperature lower than the maximum temperature may be added to thoroughly remove the binder before the maximum temperature is reached. Firing at as low a temperature as possible is desirable to reduce process costs. After firing, a reoxidation treatment may be performed. Through the above steps, an all-solid-state battery 100a is produced.

[0065] In addition, by sequentially stacking the internal electrode paste, the current collector paste containing a conductive material, and the internal electrode paste, a current collector layer can be formed within the first internal electrode 10 and the second internal electrode 20.

[0066] According to the manufacturing method of this embodiment, in the firing step, the solid electrolyte 50a contained in the cover layer 50 is sintered together with the solid electrolyte layer 30 and the electrode layer that are in contact with the cover layer 50, thereby achieving high adhesion between the cover layer 50 and the solid electrolyte layer 30 and the electrode layer that are in contact with the cover layer 50. This makes it possible to suppress delamination between the cover layer 50 and the electrode layer.

[0067] Furthermore, because the sintering temperature of the filler material 50b contained in the cover layer 50 is higher than that of the solid electrolyte 50a, the filler material 50b does not sinter or grow during co-firing, thereby maintaining the particle shape of the filler material 50b. This prevents in-plane shrinkage of the cover layer 50, suppresses deformation of the cover layer 50, and prevents delamination.

[0068] Furthermore, since the filler material 50b in the cover layer 50, which is suppressed from changing its shape, has insulating properties, the cover layer 50 provides moisture resistance.

[0069] The sintering temperature of the raw material powder of the solid electrolyte 50a is preferably lower than the sintering temperature in the sintering process, and the sintering temperature of the filler material 50b is preferably higher than the sintering temperature in the sintering process. In this case, sintering of the solid electrolyte 50a improves the adhesion of the cover layer 50 and maintains the particle shape of the filler material 50b. [Example]

[0070] Example 1 Irregularly shaped alumina with a D50% particle size of 3 μm was used as the filler material. Li-Al-Ge-PO glass (hereinafter referred to as LAGP-g), a solid electrolyte obtained by melt quenching, was ground to a D50% particle size of 1.5 μm using a wet ball mill. The filler material and solid electrolyte were mixed in a volume ratio of 70:30 and uniformly dispersed in water or an organic solvent along with binders, dispersants, plasticizers, etc. to obtain a slurry. The resulting slurry was coated to fabricate cover sheets of the desired thickness. Cover sheets were placed on the top and bottom layers of a stack of solid electrolyte green sheets with printed electrodes and pressed together to obtain a ceramic laminate. This ceramic laminate was degreased and fired by heat treatment.

[0071] No delamination due to heat treatment was observed in any of the layers. Observation of cross-sectional SEM images after heat treatment revealed that LAGP-g had sintered on the surface of the irregularly shaped alumina filler particles, functioning as an adhesive between the alumina fillers. In addition, the LAGP-g in the cover layer had sintered with the LAGP-g in each electrode layer and solid electrolyte layer, improving the adhesion between the cover layer and electrode layer, and between the cover layer and solid electrolyte layer.

[0072] Example 2 Irregularly shaped SiO2 glass with a D50% particle size of 3 μm was used as the filler material. LAGP-g, a solid electrolyte obtained by melt quenching, was ground to a D50% particle size of 1.5 μm using a wet ball mill. The filler material and solid electrolyte were mixed in a volume ratio of 70:30 and uniformly dispersed in water or an organic solvent along with binders, dispersants, plasticizers, etc. to obtain a slurry. The resulting slurry was applied to fabricate cover sheets of the desired thickness. Cover sheets were placed on the top and bottom layers of a stack of solid electrolyte green sheets with printed electrodes and pressed together to obtain a ceramic laminate. This ceramic laminate was degreased and fired by heat treatment.

[0073] No delamination due to heat treatment was observed in any of the layers. Observation of cross-sectional SEM images after heat treatment revealed that LAGP-g had sintered on the surface of the irregularly shaped SiO2 glass filler particles, functioning as an adhesive between the SiO2 glass fillers. In addition, the LAGP-g in the cover layer had sintered with the LAGP-g in each electrode layer and solid electrolyte layer, improving the adhesion between the cover layer and electrode layer, and between the cover layer and solid electrolyte layer.

[0074] Example 3 Irregularly shaped alumina with a D50% particle size of 3 μm was used as the filler material. LAGP-g, a solid electrolyte obtained by melt quenching, was ground to a D50% particle size of 1.5 μm using a wet ball mill. The filler material and solid electrolyte were mixed in a volume ratio of 20:80 and uniformly dispersed in water or an organic solvent along with binders, dispersants, plasticizers, etc. to obtain a slurry. The resulting slurry was applied to fabricate cover sheets of the desired thickness. Cover sheets were placed on the top and bottom layers of a stack of solid electrolyte green sheets with printed electrodes and pressed together to obtain a ceramic laminate. This ceramic laminate was degreased and fired by heat treatment.

[0075] No delamination due to heat treatment was observed in any of the layers. Observation of cross-sectional SEM images after heat treatment revealed that LAGP-g had sintered on the surface of the irregularly shaped alumina filler particles, functioning as an adhesive between the alumina fillers. In addition, the LAGP-g in the cover layer had sintered with the LAGP-g in each electrode layer and solid electrolyte layer, improving the adhesion between the cover layer and electrode layer, and between the cover layer and solid electrolyte layer.

[0076] Example 4 Spherical alumina with a D50% particle size of 3 μm was used as the filler material. LAGP-g, a solid electrolyte obtained by melt quenching, was ground to a D50% particle size of 1.5 μm using a wet ball mill. The filler material and solid electrolyte were mixed in a volume ratio of 70:30 and uniformly dispersed in water or an organic solvent along with binders, dispersants, plasticizers, etc. to obtain a slurry. The resulting slurry was applied to fabricate cover sheets of the desired thickness. Cover sheets were placed on the top and bottom layers of a stack of solid electrolyte green sheets with printed electrodes and pressed together to obtain a ceramic laminate. This ceramic laminate was degreased and fired by heat treatment.

[0077] No delamination due to heat treatment was observed in any of the layers. Observation of cross-sectional SEM images after heat treatment revealed that LAGP-g had sintered on the surface of the irregularly shaped alumina filler particles, functioning as an adhesive between the alumina fillers. In addition, the LAGP-g in the cover layer had sintered with the LAGP-g in each electrode layer and solid electrolyte layer, improving the adhesion between the cover layer and electrode layer, and between the cover layer and solid electrolyte layer.

[0078] Example 5 Irregularly shaped alumina with a D50% particle size of 3 μm was used as the filler material. LAGP-g, a solid electrolyte obtained by melt quenching, was ground to a D50% particle size of 1.5 μm using a wet ball mill. The filler material and solid electrolyte were mixed in a volume ratio of 30:70 and uniformly dispersed in water or an organic solvent along with binders, dispersants, plasticizers, etc. to obtain a slurry. The resulting slurry was applied to fabricate cover sheets of the desired thickness. Cover sheets were placed on the top and bottom layers of a stack of solid electrolyte green sheets with printed electrodes and pressed together to obtain a ceramic laminate. This ceramic laminate was degreased and fired by heat treatment.

[0079] No delamination due to heat treatment was observed in any of the layers. Observation of cross-sectional SEM images after heat treatment revealed that LAGP-g had sintered on the surface of the irregularly shaped alumina filler particles, functioning as an adhesive between the alumina fillers. In addition, the LAGP-g in the cover layer had sintered with the LAGP-g in each electrode layer and solid electrolyte layer, improving the adhesion between the cover layer and electrode layer, and between the cover layer and solid electrolyte layer.

[0080] Example 6 Irregularly shaped alumina with a D50% particle size of 3 μm was used as the filler material. LAGP-g, a solid electrolyte obtained by melt quenching, was ground to a D50% particle size of 1.5 μm using a wet ball mill. The filler material and solid electrolyte were mixed in a volume ratio of 10:90 and uniformly dispersed in water or an organic solvent along with binders, dispersants, plasticizers, etc. to obtain a slurry. The resulting slurry was applied to fabricate cover sheets of the desired thickness. Cover sheets were placed on the top and bottom layers of a stack of solid electrolyte green sheets with printed electrodes and pressed together to obtain a ceramic laminate. This ceramic laminate was degreased and fired by heat treatment.

[0081] No delamination due to heat treatment was observed in any of the layers. Observation of cross-sectional SEM images after heat treatment revealed that LAGP-g had sintered on the surface of the irregularly shaped alumina filler particles, functioning as an adhesive between the alumina fillers. In addition, the LAGP-g in the cover layer had sintered with the LAGP-g in each electrode layer and solid electrolyte layer, improving the adhesion between the cover layer and electrode layer, and between the cover layer and solid electrolyte layer.

[0082] (Comparative Example 1) LAGP-g, a solid electrolyte obtained by melt quenching, was pulverized in a wet ball mill to a D50% particle size of 1.5 μm and uniformly dispersed in water or an organic solvent along with binders, dispersants, plasticizers, etc. to obtain a slurry. The resulting slurry was then coated to produce a cover sheet of the desired thickness. In other words, no filler material was used. A ceramic laminate was obtained by placing cover sheets on the top and bottom layers of a stack of solid electrolyte green sheets on which each electrode had been printed and pressing them together. This ceramic laminate was then degreased and fired by heat treatment.

[0083] The LAGP-g in the cover layer sintered with the LAGP-g in each electrode layer and solid electrolyte layer, ensuring adhesion between the cover layer and electrode layer, and between the cover layer and solid electrolyte layer. However, because the cover layer did not contain a filler material, it shrunk significantly in the in-plane direction during heat treatment, making it difficult to maintain its shape.

[0084] (Comparative Example 2) A slurry was obtained by uniformly dispersing irregularly shaped alumina with a D50% particle size of 3 μm in water or an organic solvent along with a binder, dispersant, plasticizer, etc. The resulting slurry was then coated to produce a cover sheet of the desired thickness. In other words, no solid electrolyte was used. A ceramic laminate was obtained by placing cover sheets on the top and bottom layers of a stack of solid electrolyte green sheets on which each electrode had been printed and pressing them together. This ceramic laminate was then degreased and fired by heat treatment.

[0085] Since the cover layer did not contain a glass material, it did not shrink even when heat treated, and adhesion between the cover layer and the electrode layers and the solid electrolyte layer was not ensured.

[0086] (Adhesion test) The adhesion of the cover layer was evaluated for Examples 1 to 4 and Comparative Examples 1 and 2. Specifically, a peel resistance test was conducted to evaluate the adhesion of the cover layer. The peel resistance test was conducted by attaching adhesive tape to the cover layer and then rapidly and strongly peeling it off. As a result, if there was no adhesion on the tape, the adhesion was evaluated as good (◯). If there was a small amount of adhesion on the tape, the adhesion was evaluated as somewhat good (△). If most of the adhesion was on the tape, the adhesion was evaluated as poor (×). The results are shown in Table 1. [Table 1]

[0087] The adhesion of Comparative Examples 1 and 2 was judged to be poor "×". In Comparative Example 1, it is believed that this is because the cover layer did not contain a filler material, and therefore the shape of the cover layer could not be maintained. In Comparative Example 2, it is believed that good adhesion was not obtained because the cover layer did not contain a solid electrolyte. In contrast, the adhesion of Examples 1 to 4 was judged to be good "◯" or somewhat good "Δ". This is believed to be because good adhesion was obtained by including both a solid electrolyte and a filler material in the cover layer. The reason that the adhesion of Examples 1 to 3 was better than that of Example 4 is believed to be because an irregularly shaped filler material was used.

[0088] (Moisture-proof test) The moisture resistance of the cover layer was evaluated for Examples 1 to 4 and Comparative Examples 1 and 2. Specifically, to evaluate the moisture resistance of the cover layer, a thermostatic chamber at 85°C was set to a humidity of 85%, and the all-solid-state battery was left standing in the thermostatic chamber for one week to perform a moisture resistance test. As a result, if there was no change in shape, the moisture resistance was evaluated as good "◯". If the shape was maintained but the cover surface was altered, the moisture resistance was evaluated as somewhat good "△". If it became difficult to maintain the shape, the moisture resistance was evaluated as poor "X".

[0089] The moisture resistance of Comparative Examples 1 and 2 was judged to be poor (×). This is thought to be because the cover layer of Comparative Example 1 did not contain an insulating filler material. This is thought to be because the cover layer of Comparative Example 2 did not contain a solid electrolyte, and therefore good adhesion was not obtained. In contrast, the moisture resistance of Examples 1 to 4 was judged to be good (◯) or somewhat good (Δ). This is thought to be because the cover layer that achieved adhesion contained an insulating filler material. The adhesion of Examples 1, 2, and 4 was better than that of Example 3 because the volume ratio of the filler material to the solid electrolyte in the cover layer was 30 vol% or more.

[0090] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0091] 10 1st internal electrode 20 Second internal electrode 30 Solid electrolyte layer 40a First outer electrode 40b 2nd external electrode 50 cover layers 50a solid electrolyte 50b filler material 51 Solid electrolyte green sheet 52 Internal electrode paste 53 Reverse pattern 54 Cover Sheet 55 External electrode paste 60 stacked chips 100,100a solid state battery

Claims

1. a laminated structure in which ion-conductive oxide-based solid electrolyte layers and electrode layers containing an electrode active material are alternately laminated; a cover layer provided on at least one of an upper surface and a lower surface in a stacking direction of the laminated structure, The cover layer is an all-solid-state battery including an oxide-based solid electrolyte and an insulating filler material having a higher sintering temperature than the oxide-based solid electrolyte.

2. 2. The all-solid-state battery according to claim 1, wherein a volume ratio of the filler material to the oxide-based solid electrolyte in the cover layer is 10 vol % or more.

3. The electrical conductivity, including electronic conductivity and ionic conductivity, of the filler material is 10 －８ The all-solid-state battery according to claim 1 or 2, wherein the electrical conductivity is 0.5 S / cm or less.

4. The filler material is alumina or SiO ２ The all-solid-state battery according to claim 1 , wherein the all-solid-state battery is made of glass.

5. 5. The all-solid-state battery according to claim 1, wherein the shape of the filler has an average circularity of 0.6 or more in cross section.

6. The all-solid-state battery according to claim 1 , wherein the filler has a D50% particle size of 0.5 μm or more and 8 μm or less.

7. 7. The all-solid-state battery according to claim 1, wherein, between the oxide-based solid electrolyte layer and the cover layer, the D0% particle size in the particle size distribution of the solid electrolyte of one layer is between the D0% particle size and the D10% particle size in the particle size distribution of the solid electrolyte of the other layer, and the D100% particle size in the particle size distribution of the solid electrolyte of the one layer is between the D90% particle size and the D100% particle size in the particle size distribution of the solid electrolyte of the other layer.

8. 8. The all-solid-state battery according to claim 1, wherein the oxide-based solid electrolyte of the cover layer is a solid electrolyte having a NASICON-type crystal structure.

9. 9. The all-solid-state battery according to claim 1, wherein a main component of the solid electrolyte layer is a solid electrolyte having a NASICON-type crystal structure.

10. 10. The all-solid-state battery according to claim 1, wherein the oxide-based solid electrolyte of the cover layer has the same composition as a main component of the solid electrolyte layer.

11. The all-solid-state battery according to claim 1 , wherein the oxide-based solid electrolyte of the cover layer is a glass material.

12. The all-solid-state battery according to claim 1 , wherein the electrode layer contains an oxide-based solid electrolyte having ion conductivity.

13. a preparation step of preparing a ceramic laminate in which a cover sheet containing an oxide-based solid electrolyte powder and an insulating filler material having a higher sintering temperature than the oxide-based solid electrolyte powder is laminated on at least one of an upper surface and a lower surface in the lamination direction of a laminate in which solid electrolyte green sheets containing an oxide-based solid electrolyte powder having ion conductivity and internal electrode patterns containing an electrode active material powder are alternately laminated; and a firing step of firing the ceramic laminate.

14. the sintering temperature of the oxide-based solid electrolyte powder of the cover sheet is lower than the firing temperature in the firing step; The method for manufacturing an all-solid-state battery according to claim 13 , wherein a sintering temperature of the filler material is higher than a firing temperature in the firing step.

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