All-solid battery

Abstract

To provide an all-solid battery capable of achieving improvement of battery characteristics, improvement of reliability and yield rate improvement.SOLUTION: An all-solid battery comprises a multilayer chip configured by laminating solid electrolyte layers and internal electrode layers alternately in a first direction. The plurality of internal electrode layers are alternately drawn to two end faces opposed to each other in a second direction, which is orthogonal to the first direction, in the multilayer chip and a blank part is provided around the internal electrode layer. In a view in the first direction, an overlap part is formed where a peripheral edge part and the blank part of the internal electrode layer partially overlap in a third direction which is orthogonal to the first direction and the second direction. In a case where an angle formed by a straight line connecting a tip end point E1 of the internal electrode layer on the side of the blank part with a tip end point E2 of the blank part on the side of the internal electrode layer in the third direction and a straight line connecting both ends of the internal electrode layer in the third direction is defined as θ, while a thickness of the blank part is defined as t1 and a length between the tip end point E1 and the tip end point E2 in the third direction is defined as d, a relation of 0.1×t1 / tanθ≤d≤2.0×t1 / tanθ is established.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery. [Background technology]

[0002] Stacked all-solid-state batteries are safe and easy to handle secondary batteries, with no risk of fire or leakage, and are capable of reflow soldering (see, for example, Patent Document 1). A shift from conventional lithium-ion batteries that use electrolytes is being considered, and it is expected that they will be used in a wide range of fields. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-116136 Summary of the Invention [Problem to be solved by the invention]

[0004] From the viewpoint of ensuring battery capacity, it is preferable that the ends of the internal electrode layers are not thin. However, when charge and discharge are repeated, the internal electrode layers repeatedly expand and contract in volume. Therefore, if the ends of the internal electrode layers are thick, interfacial cracks may occur between the solid electrolyte layer and the internal electrode layers, which may deteriorate the battery characteristics. Therefore, from the viewpoint of suppressing interfacial cracks, it is preferable that the ends of the internal electrode layers are thin at the tip and gradually thicken from the tip toward the inside.

[0005] However, if an attempt is made to realize a shape in which the thickness gradually increases from the tip toward the inside at the end of the internal electrode layer, there is a risk of deterioration in battery characteristics and reliability due to misalignment between the solid electrolyte layer and the internal electrode layer, deformation or poor compression during compression bonding, deformation during sintering, etc. Furthermore, there is a risk of cracks occurring due to deformation during compression bonding, which may result in a decrease in yield rate.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an all-solid-state battery that can realize improved battery characteristics, improved reliability, and improved yield rate. [Means for solving the problem]

[0007] The all-solid-state battery according to the present invention includes a solid electrolyte layer having two main surfaces opposing each other in a first direction, two end surfaces opposing each other in a second direction perpendicular to the first direction, and two side surfaces opposing each other in a third direction perpendicular to the first direction and the second direction; a first internal electrode layer formed on one main surface of the solid electrolyte layer and drawn out to one end surface; a second internal electrode layer formed on the other main surface of the solid electrolyte layer and drawn out to the other end surface; a first marginal portion formed around the first internal electrode layer on one main surface of the solid electrolyte layer and having a composition different from that of the solid electrolyte layer and the first internal electrode layer; and a second marginal portion formed around the second internal electrode layer on the other main surface of the solid electrolyte layer and having a composition different from that of the solid electrolyte layer and the second internal electrode layer. and a first overlapping portion where, when viewed from the first direction, a peripheral portion of the first internal electrode layer overlaps with a portion of the first marginal portion, and a second overlapping portion where, in the third direction, a peripheral portion of the second internal electrode layer overlaps with a portion of the second marginal portion, wherein, in either the first overlapping portion or the second overlapping portion, an angle formed by a line connecting a tip point E1 of the internal electrode layer on the marginal portion side in the third direction and a tip point E2 of the marginal portion on the internal electrode layer side is θ, a thickness of the marginal portion in the first direction is t1, and a length between the tip point E1 and the tip point E2 in the third direction is d, where θ is an angle formed by a line connecting both ends of the internal electrode layer in the third direction, a thickness of the marginal portion in the first direction is t1, and a length between the tip point E1 and the tip point E2 in the third direction is d,

[0008] In the all-solid-state battery, the angle θ may be equal to or greater than 5° and less than 90°.

[0009] In the all-solid-state battery, the t1 may be 1 μm or more and 200 μm or less.

[0010] In a cross section of the all-solid-state battery including the first direction and the third direction, the outer shape of the internal electrode layer in either the first overlapping portion or the second overlapping portion may have a curvature.

[0011] In a cross section of the all-solid-state battery including the first direction and the third direction, the outer shape of the internal electrode layer in either the first overlapping portion or the second overlapping portion may have a curvature from the end point E1 to the end point E2.

[0012] In the above all-solid-state battery, when the end point E1 is located on one side in the first direction in the thickness of the internal electrode layer, the outer shape of the internal electrode layer may be curved so as to be convex toward the other side in the first direction.

[0013] In a cross section of the all-solid-state battery including the first direction and the third direction, a radius of curvature r1 of an outer shape of the internal electrode layer in either the first overlapping portion or the second overlapping portion may be 1 μm or more and 500 μm or less.

[0014] In the all-solid-state battery, r1 / t1 (%) may be 100% or more and 1000% or less.

[0015] In the all-solid-state battery, the number of stacked internal electrode layers may be 2 or more and 200 or less.

[0016] In the all-solid-state battery, among the plurality of internal electrode layers, 90% or more of the total number of layers may satisfy the relationship 0.1×t1 / tan θ≦d≦2.0×t1 / tan θ.

[0017] Another all-solid-state battery according to the present invention includes a solid electrolyte layer having two main surfaces facing each other in a first direction, two end surfaces facing each other in a second direction perpendicular to the first direction, and two side surfaces facing each other in a third direction perpendicular to the first direction and the second direction; a first internal electrode layer formed on one main surface of the solid electrolyte layer and drawn out to one end surface; a second internal electrode layer formed on the other main surface of the solid electrolyte layer and drawn out to the other end surface; a first marginal portion formed around the first internal electrode layer on one main surface of the solid electrolyte layer and having a composition different from that of the solid electrolyte layer and the first internal electrode layer; and a second marginal portion formed around the second internal electrode layer on the other main surface of the solid electrolyte layer and having a composition different from that of the solid electrolyte layer and the first internal electrode layer. and a second marginal portion having a different composition from the second internal electrode layer, and a first overlapping portion in which, when viewed from the first direction, a peripheral portion of the first internal electrode layer overlaps with a portion of the first marginal portion, and a second overlapping portion in which a peripheral portion of the second internal electrode layer overlaps with a portion of the second marginal portion, in the third direction, wherein, in either the first overlapping portion or the second overlapping portion, when the end point of the marginal portion side of the internal electrode layer in the third direction is taken as end point E1 and the end point of the marginal portion side of the internal electrode layer is taken as end point E2, if the end point E1 is located on one side of the first direction in the thickness of the internal electrode layer, the outer shape of the internal electrode layer is curved and convex toward the other side of the first direction. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an all-solid-state battery that can realize improved battery characteristics, improved reliability, and improved yield rate. [Brief explanation of the drawings]

[0019] [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 partial cross-sectional perspective view of a stacked-type all-solid-state battery in which a plurality of battery units are stacked. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4]FIG. 3 is a cross-sectional view taken along line BB in FIG. 2. [Figure 5] 1(a) is an enlarged view of a cross section of a side margin, and FIG. 1(b) is an enlarged view of a cross section of a first end margin. [Figure 6] FIG. 4 is an enlarged cross-sectional view of the vicinity of the boundary between the first marginal portion and the first internal electrode layer. [Figure 7] FIG. 4 is an enlarged cross-sectional view of the vicinity of the boundary between the first marginal portion and the first internal electrode layer. [Figure 8] FIG. 4 is an enlarged cross-sectional view of the vicinity of the boundary between the first marginal portion and the first internal electrode layer. [Figure 9] FIG. 1 is a diagram illustrating a flow of a method for manufacturing an all-solid-state battery. [Figure 10] 1(a) and 1(b) are diagrams illustrating the lamination process. [Figure 11] 1A to 1C are diagrams illustrating a lamination process. [Figure 12] FIG. 1 is a diagram illustrating a printing process. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments will be described with reference to the drawings.

[0021] (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 layer 10 and a second internal electrode layer 20. The first internal electrode layer 10 is formed on a first main surface of the solid electrolyte layer 30. The second internal electrode layer 20 is formed on a second main surface of the solid electrolyte layer 30. For example, the first internal electrode layer 10, the second internal electrode layer 20, and the solid electrolyte layer 30 are sintered bodies obtained by sintering powder materials.

[0022] When the all-solid-state battery 100 is used as a secondary battery, one of the first internal electrode layer 10 and the second internal electrode layer 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 layer 10 is used as a positive electrode layer, and the second internal electrode layer 20 is used as a negative electrode layer.

[0023] 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 (LAGP) material to which the same transition metal as that contained in the phosphate having an olivine crystal structure contained in the first internal electrode layer 10 and the second internal electrode layer 20 has been added in advance is preferred. For example, when a phosphate containing Co and Li is contained in the first internal electrode layer 10 and the second internal electrode layer 20, it is preferred that a Li-Al-Ge-PO4-based material to which Co has been added in advance is contained in the solid electrolyte layer 30. In this case, an effect of suppressing the elution of the transition metal contained in the electrode active material into the electrolyte can be obtained. When a phosphate containing Li and a transition element other than Co is contained in the first internal electrode layer 10 and the second internal electrode layer 20, it is preferred that a Li-Al-Ge-PO4-based material to which the transition metal has been added in advance is contained in the solid electrolyte layer 30.

[0024] The first internal electrode layer 10 used as the positive electrode contains a substance having an olivine crystal structure as an electrode active material. It is preferable that the second internal electrode layer 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.

[0025] 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.

[0026] The electrode active material having an olivine-type crystal structure acts as a positive electrode active material in the first internal electrode layer 10 acting as a positive electrode. For example, when only the first internal electrode layer 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 layer 20 also contains an electrode active material having an olivine-type crystal structure, the second internal electrode layer 20 acting 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.

[0027] When both the first internal electrode layer 10 and the second internal electrode layer 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. "May be the same or different from each other" means that the electrode active materials contained in the first internal electrode layer 10 and the second internal electrode layer 20 may contain the same type of transition metal, or may contain different types of transition metals. The first internal electrode layer 10 and the second internal electrode layer 20 may contain only one type of transition metal, or may contain two or more types of transition metals. Preferably, the first internal electrode layer 10 and the second internal electrode layer 20 contain the same type of transition metal. More preferably, the electrode active materials contained in both electrodes have the same chemical composition. Since the first internal electrode layer 10 and the second internal electrode layer 20 contain the same type of transition metal or contain electrode active materials of the same composition, the similarity of the compositions of both internal electrode layers is increased, and even if the terminals of the all-solid-state battery 100 are attached with the positive and negative terminals reversed, there is an effect that the battery can withstand actual use without malfunctioning depending on the application.

[0028] The second internal electrode layer 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.

[0029] In the production of the first internal electrode layer 10 and the second internal electrode layer 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 layer 10 and the second internal electrode layer 20 can be, for example, the same as the main component solid electrolyte of the solid electrolyte layer 30.

[0030] FIG. 2 is a partial cross-sectional perspective view of a stacked-type all-solid-state battery 100a in which a plurality of battery units are stacked. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. FIG. 4 is a cross-sectional view taken along line BB in FIG. 2. 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).

[0031] 2 to 4, the Z-axis direction (first direction) is the stacking direction, and is the direction in which the upper and lower surfaces of the laminated chip 60 face each other. The X-axis direction (second direction) is the direction in which the two end faces of the laminated chip 60 face each other, and is the facing direction in which the first external electrode 40a and the second external electrode 40b face each other. The Y-axis direction (third direction) is the width direction of the first internal electrode layer 10 and the second internal electrode layer 20, and is the facing direction in which two of the four side faces of the laminated chip 60 other than the two end faces face each other. The X-axis direction, Y-axis direction, and Z-axis direction are perpendicular to each other.

[0032] In the following description, components having the same composition ranges and thickness ranges as those of the all-solid-state battery 100 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0033] In the all-solid-state battery 100a, a plurality of first internal electrode layers 10 and a plurality of second internal electrode layers 20 are alternately stacked with solid electrolyte layers 30 interposed therebetween. The edges of the plurality of first internal electrode layers 10 in the X-axis direction are drawn to the first end face of the laminated chip 60 but not to the second end face. The edges of the plurality of second internal electrode layers 20 in the X-axis direction are drawn to the second end face of the laminated chip 60 but not to the first end face. As a result, the first internal electrode layers 10 and the second internal electrode layers 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 manner, the all-solid-state battery 100a has a structure in which a plurality of battery units are stacked.

[0034] A cover layer 50 is laminated on the upper end surface of the laminated portion of the first internal electrode layer 10, the solid electrolyte layer 30, and the second internal electrode layer 20. The cover layer 50 is in contact with the uppermost internal electrode layer (either the first internal electrode layer 10 or the second internal electrode layer 20) and is in contact with a part of the solid electrolyte layer 30. A cover layer 50 is also laminated on the lower end surface of the laminate. The cover layer 50 is in contact with the lowermost internal electrode layer (either the first internal electrode layer 10 or the second internal electrode layer 20) and is in contact with a part of the solid electrolyte layer 30. For example, the cover layer 50 is a sintered body obtained by sintering a powder material.

[0035] 3, the region where the first internal electrode layer 10 connected to the first external electrode 40a and the second internal electrode layer 20 connected to the second external electrode 40b face each other is a region where battery capacity is generated. Therefore, this region is referred to as a battery capacity region 70. In other words, the battery capacity region 70 is a region where two adjacent internal electrode layers connected to different external electrodes face each other.

[0036] The region where the first internal electrode layers 10 connected to the first external electrode 40a face each other without the second internal electrode layer 20 connected to the second external electrode 40b interposed therebetween is referred to as the first end margin 80a. The region where the first internal electrode layers 10 connected to the second external electrode 40b face each other without the first internal electrode layer 10 connected to the first external electrode 40a interposed therebetween is referred to as the second end margin 80b. In other words, the end margin is the region where internal electrode layers connected to the same external electrode face each other without the internal electrode layer connected to a different external electrode interposed therebetween. The first end margin 80a and the second end margin 80b are regions that do not contribute to battery capacity.

[0037] 4, in the laminated chip 60, the regions extending from the two side surfaces of the laminated chip 60 to the first internal electrode layers 10 and the second internal electrode layers 20 are referred to as side margins 90. In other words, the side margins 90 are regions provided so as to cover the ends of the plurality of first internal electrode layers 10 and second internal electrode layers 20 stacked in the laminate, which extend toward the two side surfaces.

[0038] 5(a) is an enlarged view of a cross section of the side margin 90. The side margin 90 has a structure in which solid electrolyte layers 30 and margins are alternately stacked in the stacking direction of the first internal electrode layers 10 and the second internal electrode layers 20 in the battery capacity region 70. A first margin 95a is provided in the same layer as the first internal electrode layer 10. A second margin 95b is provided in the same layer as the second internal electrode layer 20. With this configuration, a step between the battery capacity region 70 and the side margin 90 is suppressed.

[0039] The first marginal portion 95a and the second marginal portion 95b have a different composition from the solid electrolyte layer 30. For example, the first marginal portion 95a and the second marginal portion 95b may have the same main component as the solid electrolyte layer 30, and the additive element in the first marginal portion 95a and the second marginal portion 95b may be different from the additive element in the solid electrolyte layer 30. Alternatively, the first marginal portion 95a and the second marginal portion 95b may have the same main component as the solid electrolyte layer 30, the additive element in the first marginal portion 95a and the second marginal portion 95b may be the same as the additive element in the solid electrolyte layer 30, and the concentration of the additive element in the first marginal portion 95a and the second marginal portion 95b may be different from the concentration of the additive element in the solid electrolyte layer 30. Alternatively, the main component of the first marginal portion 95a and the second marginal portion 95b may be different from the main component of the solid electrolyte layer 30. The lithium ion conductivity of the first marginal portion 95a and the second marginal portion 95b is lower than the lithium ion conductivity of the solid electrolyte layer 30. When the XZ cross section or the YZ cross section is observed with a scanning electron microscope (SEM), interfaces are observed between the first marginal portion 95a and the second marginal portion 95b and the solid electrolyte layer 30.

[0040] Moreover, the first marginal portions 95a either do not contain an electrode active material or have a lower electrode active material concentration than the first internal electrode layers 10. Moreover, the second marginal portions 95b either do not contain an electrode active material or have a lower electrode active material concentration than the second internal electrode layers 20. As a result, when observed with an SEM, an interface is observed between the first marginal portions 95a and the first internal electrode layers 10, and an interface is observed between the second marginal portions 95b and the second internal electrode layers 20.

[0041] For example, the material of the first marginal portion 95a and the second marginal portion 95b is glass, alumina, or the like.

[0042] FIG. 5(b) is an enlarged cross-sectional view of the first end margin 80a. In the first end margin 80a, every other one of the multiple stacked internal electrode layers extends to the end face of the first end margin 80a. That is, in the first end margin 80a, the first internal electrode layer 10 extends to the end face, but the second internal electrode layer 20 does not extend to the end face. A second margin 95b is provided in the same layer as the second internal electrode layer 20. Furthermore, in the layer where the first internal electrode layer 10 extends to the end face of the first end margin 80a, the first margin 95a is not stacked. This configuration suppresses a step between the battery capacity region 70 and the first end margin 80a. In the second end margin 80b, the second internal electrode layer 20 extends to the end face, but the first internal electrode layer 10 does not extend to the end face. In the second end margin 80b, in the same layer as the first internal electrode layer 10, a first marginal portion 95a is provided.

[0043] From the viewpoint of ensuring battery capacity, it is preferable that the ends of the internal electrode layers are not thin. However, when charge and discharge are repeated, the internal electrode layers repeatedly expand and contract in volume. Therefore, if the ends of the internal electrode layers are thick, interfacial cracks may occur between the solid electrolyte layer and the internal electrode layers, which may deteriorate the battery characteristics. Therefore, from the viewpoint of suppressing interfacial cracks, it is preferable that the ends of the internal electrode layers are thin at the tip and gradually thicken from the tip toward the inside.

[0044] However, if an attempt is made to realize a shape in which the thickness gradually increases from the tip toward the inside at the end of the internal electrode layer, there is a risk of deterioration in battery characteristics and reliability due to misalignment between the solid electrolyte layer and the internal electrode layer, deformation or poor compression during compression bonding, deformation during sintering, etc. Furthermore, there is a risk of cracks occurring due to deformation during compression bonding, which may result in a decrease in yield rate.

[0045] In contrast, the all-solid-state battery 100a according to this embodiment has a configuration that can achieve improved battery characteristics, improved reliability, and improved yield rate. Details will be described below.

[0046] 6 is an enlarged cross-sectional view of the vicinity of the boundary between the first marginal portion 95a and the first internal electrode layer 10. Note that, although the relationship between the first marginal portion 95a and the first internal electrode layer 10 will be described below, the first marginal portion 95a may be read as the second marginal portion 95b, and the first internal electrode layer 10 may be read as the second internal electrode layer 20.

[0047] 6, in the YZ cross section, when viewed from the Z-axis direction, the first internal electrode layer 10 and the first marginal portion 95a overlap in the Y-axis direction from the tip of the first internal electrode layer 10 on the first marginal portion 95a side to the tip of the first marginal portion 95a on the first internal electrode layer 10 side. This overlapping portion is referred to as an overlapping portion 200. In the overlapping portion 200, the first internal electrode layer 10 and the first marginal portion 95a are not mixed with each other and exist independently.

[0048] In the overlapping portion 200, the thickness of the first internal electrode layer 10 gradually increases from the tip on the first marginal portion 95a side toward the Y-axis direction. On the other hand, in the overlapping portion 200, the thickness of the first marginal portion 95a gradually increases from the tip on the first internal electrode layer 10 side toward the opposite side in the Y-axis direction. With this configuration, the thickness of the overlapping portion 200 in the YZ cross section is approximately constant at different points in the Y-axis direction.

[0049] The length of the overlapping portion 200 in the Y-axis direction is referred to as length d. Length d corresponds to the distance in the Y-axis direction from the tip point E1 of the first internal electrode layer 10 on the first marginal portion 95a side to the tip point E2 of the first marginal portion 95a on the first internal electrode layer 10 side. In the overlapping portion 200, the angle formed by the line L1 connecting the tip point E1 of the first internal electrode layer 10 on the first marginal portion 95a side and the tip point E2 of the first marginal portion 95a on the first internal electrode layer 10 side, and the line L2 connecting both ends of the first internal electrode layer 10 in the Y-axis direction is referred to as the electrode end angle θ.

[0050] The thickness of the first internal electrode layer 10 is referred to as thickness t1. Thickness t1 can be measured by measuring the thickness at 10 different locations in the Y-axis direction and calculating the average value. The thickness of the first marginal portion 95a is referred to as thickness t2. Thickness t2 can be measured by measuring the thickness at 10 different locations in the Y-axis direction and calculating the average value.

[0051] If the length d of the overlapping portion 200 is short, the thickness of the first internal electrode layer 10 suddenly increases along the Y-axis direction at the overlapping portion 200. This may result in a decrease in battery characteristics and reliability due to misalignment between the solid electrolyte layer 30 and the first internal electrode layer 10, deformation or poor compression during compression bonding, deformation during sintering, and the like. Furthermore, cracks may occur due to deformation during compression bonding, resulting in a decrease in yield. Therefore, in this embodiment, a lower limit is set for the length d. However, through extensive research by the inventors, it has been found that the lower limit of the length d needs to be adjusted depending on the thickness t1 and angle θ of the first internal electrode layer 10. Specifically, in this embodiment, it has been found that 0°<θ<90° and the relationship 0.1×t1 / tanθ≦d is required. The units of d and t1 are “μm,” and the unit of θ is “degree.”

[0052] On the other hand, if the length d of the overlapping portion 200 is long, there will be many regions where the thickness of the first internal electrode layer 10 is insufficient, which may result in insufficient battery capacity. Therefore, in this embodiment, an upper limit is set for the length d. However, through intensive research by the inventors, it has been found that it is necessary to adjust the upper limit of the length d depending on the thickness t1 and angle θ of the first internal electrode layer 10. Specifically, in this embodiment, it has been found that the relationship d≦2.0×t1 / tan θ is required.

[0053] As described above, by satisfying the relationship 0°<θ<90° and 0.1×t1 / tanθ≦d≦2.0×t1 / tanθ, it is possible to achieve improved battery characteristics, improved reliability, and improved yield rate.

[0054] From the viewpoint of making the length d of the overlapping portion 200 sufficiently long, it is preferable that the relationship 0.2×t1 / tan θ≦d holds, and it is more preferable that the relationship 0.3×t1 / tan θ≦d holds.

[0055] From the viewpoint of sufficiently shortening the length d of the overlapping portion 200, it is preferable that the relationship d≦1.9×t1 / tan θ holds, and it is more preferable that the relationship d≦1.8×t1 / tan θ holds.

[0056] From the viewpoint of making the length d of the overlapping portion 200 sufficiently long, the angle θ is preferably 95° or less, and more preferably 80° or less.

[0057] From the viewpoint of sufficiently shortening the length d of the overlapping portion 200, the angle θ is preferably 5° or more, and more preferably 10° or more.

[0058] The thickness t1 of the first internal electrode layer 10 is 1 μm or more and 200 μm or less, 1 μm or more and 1000 μm or less, or 1 μm or more and 2000 μm or less.

[0059] 7, it is preferable that the outer shape of the portion where the first internal electrode layer 10 contacts the first marginal portion 95a in the overlapping portion 200 has a curvature. In this case, the contact area between the first internal electrode layer 10 and the first marginal portion 95a in the overlapping portion 200 becomes large, and interfacial peeling between the first internal electrode layer 10 and the first marginal portion 95a can be suppressed.

[0060] For example, it is preferable that the outer shape of the first internal electrode layer 10 has a curvature from the end point E1 on the first marginal portion 95a side of the first internal electrode layer 10 to the end point E2 on the first marginal portion 95a side of the first internal electrode layer 10. For example, it is preferable that the outer shape of the first internal electrode layer 10 is curved so as to be convex toward one side in the Z-axis direction from the end point E1 to the end point E2. For example, when the end point E1 is located on one side in the Z-axis direction in the thickness of the first internal electrode layer 10, it is preferable that the outer shape of the first internal electrode layer 10 is curved so as to be convex toward the other side in the Z-axis direction. In this case, the first internal electrode layer 10 can be made thicker, thereby increasing the battery capacity.

[0061] Here, a method for measuring the curvature of the outer shape of the first internal electrode layer 10 at the overlapping portion 200 in the YZ cross section will be described. As illustrated in FIG. 8, a circle passing through two points, the tip point E1 and the tip point E2, is assumed. Furthermore, an approximate circle is created by fitting it to the outer shape of the first internal electrode layer 10. The radius of this approximate circle is defined as the radius of curvature r1. The VHX Series + measurement system VH-M100 manufactured by KEYENCE can be used to create the approximate circle.

[0062] If the curvature radius r1 is large, the contact area between the first internal electrode layer 10 and the first marginal portion 95a may not be large enough. Therefore, it is preferable to set an upper limit to the curvature radius r1. In this embodiment, the curvature radius r1 is preferably 500 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less.

[0063] On the other hand, if the radius of curvature r1 is small, the film thickness increases rapidly, which may cause interface separation and lead to short circuits. Therefore, it is preferable to set a lower limit for the radius of curvature r1. In this embodiment, the radius of curvature r1 is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more.

[0064] If r1 / t1 (%) is large, there is a risk of a decrease in capacity density. Therefore, it is preferable to set an upper limit to r1 / t1 (%). In this embodiment, r1 / t1 (%) is preferably 1000% or less, more preferably 900% or less, and even more preferably 800% or less. Note that if r1 and t1 are equal, r1 / t1 (%) = 100%.

[0065] On the other hand, if r1 / t1 (%) is small, the contact area decreases, which may cause interface separation and lead to a short circuit. Therefore, it is preferable to set a lower limit for r1 / t1 (%). In this embodiment, 1 / t1 (%) is preferably 100% or more, more preferably 105% or more, and even more preferably 110% or more.

[0066] The total number of stacked first internal electrode layers 10 and second internal electrode layers 20 is 2 to 200 layers, 2 to 500 layers, or 2 to 1000 layers.

[0067] Of all the first internal electrode layers 10 and second internal electrode layers 20 in the laminated chip 60, it is preferable that the relationship 0.1×t1 / tanθ≦d≦2.0×t1 / tanθ holds for 50% or more of the internal electrode layers, it is more preferable that the relationship 0.1×t1 / tanθ≦d≦2.0×t1 / tanθ holds for 70% or more of the internal electrode layers, and it is even more preferable that the relationship 0.1×t1 / tanθ≦d≦2.0×t1 / tanθ holds for 90% or more of the internal electrode layers.

[0068] Next, a method for manufacturing the all-solid-state battery 100a will be described. Fig. 9 is a diagram illustrating a flow of the method for manufacturing the all-solid-state battery 100a.

[0069] (Electrolyte raw material powder production process) 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.

[0070] (Cover raw powder production process) The 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. The obtained raw material powder can be dry-milled to adjust the average particle size to the desired size. For example, the desired average particle size can be adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls.

[0071] (raw powder production process for blank areas) The raw material powder for the first and second marginal portions 95a and 95b is prepared. For example, raw materials, additives, and the like are mixed and solid-phase synthesis is used to prepare the raw material powder for the marginal portions. The obtained raw material powder can be dry-milled to adjust the average particle size to the desired size. For example, the desired average particle size is adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls.

[0072] (Electrode layer paste preparation process) Next, internal electrode pastes for producing the first internal electrode layer 10 and the second internal electrode layer 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 be used as the conductive additive. Examples of the metal 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.

[0073] 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.

[0074] (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.

[0075] (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.

[0076] (Lamination process) As illustrated in FIG. 10( a), an internal electrode paste 52 is printed on one side of a solid electrolyte green sheet 51. A margin paste 53 is printed on the peripheral area of ​​the solid electrolyte green sheet 51 where the internal electrode paste 52 is not printed. The margin paste 53 can be formed by applying a raw material powder for the margin using the same method as in the solid electrolyte green sheet preparation process. As illustrated in FIG. 10( b), multiple printed solid electrolyte green sheets 51 are stacked with an alternating offset. As illustrated in FIG. 11, a laminate is obtained by pressing cover sheets 54 from above and below in the stacking direction. In this case, a green chip having a substantially rectangular parallelepiped shape is obtained in the laminate so that the internal electrode paste 52 for the first internal electrode layer 10 is exposed on one end face and the internal electrode paste 52 for the second internal electrode layer 20 is exposed on the other end face. The cover sheet 54 can be formed by applying a raw material powder for the cover layer using the same method as in the solid electrolyte green sheet preparation process. The cover sheet 54 is formed to be thicker than the solid electrolyte green sheet 51. The thickness may be increased during coating, or by stacking a plurality of coated sheets.

[0077] As illustrated in FIG. 12, when printing the marginal portion paste 53 around the internal electrode paste 52, part of the marginal portion paste 53 is printed overlapping the peripheral edge of the internal electrode paste 52, thereby forming the overlapping portion 200 described in FIG. 6 after firing. The shape of the overlapping portion 200 can be adjusted by adjusting the viscosity of the internal electrode paste 52. For example, by increasing the viscosity of the internal electrode paste 52, the peripheral edge of the printed internal electrode paste 52 rises. As a result, as described in FIG. 7, when the tip point E1 is located on one side in the Z-axis direction in the thickness of the first internal electrode layer 10 in the YZ cross section, the outer shape of the first internal electrode layer 10 becomes curved and convex toward the other side in the Z-axis direction.

[0078] (Firing process) Next, the resulting green chip is fired to obtain the laminated chip 60. 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. A re-oxidation treatment may be performed after firing. Then, external electrode paste is applied to two end surfaces of the laminated chip 60 and cured to form the first external electrode 40a and the second external electrode 40b.

[0079] According to the manufacturing method of this embodiment, the overlapping portion 200 described in Figures 6 to 8 can be formed by adjusting the conditions for printing a portion of the margin paste 53 overlapping the peripheral edge of the internal electrode paste 52. [Example]

[0080] Examples 1 to 5 A stacked all-solid-state battery was fabricated according to the above embodiment. An internal electrode paste for the internal electrode layers was applied onto a solid electrolyte green sheet by screen printing. A margin paste for the margin was printed around the internal electrode paste on the solid electrolyte green sheet. In this case, a portion of the margin paste was overlapped on the peripheral edge of the internal electrode paste. Multiple solid electrolyte green sheets were stacked so that the internal electrode paste was pulled out alternately to the left and right. The sheets were cut to a predetermined size to obtain a green chip for a stacked all-solid-state battery. The green chip was sintered by degreasing and firing, and an external electrode paste was applied and hardened to form an external electrode, thereby obtaining a stacked all-solid-state battery.

[0081] For each of Examples 1 to 5, conditions were set so that the thickness t1 of the internal electrode layer after firing, the length d of the overlapping portion, and the angle θ would be the target values. For Examples 3 to 5, the viscosity of the internal electrode paste was adjusted so that the curvature of the outer shape of the portion where the internal electrode layer contacts the blank portion in the overlapping portion would be the target value.

[0082] (Comparative Example 1) In Comparative Example 1, when printing the internal electrode paste, the margin paste was not overlapped on the peripheral edge of the internal electrode paste. Conditions were set so that the thickness t1 of the internal electrode layer after firing, the length d of the overlapping portion, and the angle θ would be the target values. Other conditions were the same as in Examples 1 to 5.

[0083] The angle θ described in Fig. 6 was 15° in Example 1, 50° in Example 2, 15° in Example 3, 30° in Example 4, 50° in Example 5, and 15° in Comparative Example 1. The thickness t1 described in Fig. 6 was 15 µm in Example 1, 50 µm in Example 2, 15 µm in Example 3, 30 µm in Example 4, 50 µm in Example 5, and 15 µm in Comparative Example 1. The length d of the overlapping portion described in Fig. 6 was 150 µm in Example 1, 40 µm in Example 2, 150 µm in Example 3, 80 µm in Example 4, and 40 µm in Example 5.

[0084] 0.1×t1×tanθ was 5.6 in Example 1, 4.2 in Example 2, 5.6 in Example 3, 5.3 in Example 4, 4.2 in Example 5, and 5.6 in Comparative Example 1. 2.0×t1 / tanθ was 112.0 in Example 1, 83.9 in Example 2, 112.0 in Example 3, 105.0 in Example 4, 83.9 in Example 5, and 112.0 in Comparative Example 1.

[0085] The r1 described in FIG. 8 was 100 μm in Example 3, 50 μm in Example 4, and 20 μm in Example 5. The r1 / t1 (%) was 700% in Example 3, 170% in Example 4, and 150% in Example 5. No curvature was observed in Examples 1 and 2. The measurement results are shown in Table 1. [Table 1]

[0086] (Good product rate) For each of Examples 1 to 5 and Comparative Example 1, 300 samples each having 120 internal electrode layers were produced. For each of Examples 1 to 5 and Comparative Example 1, 300 samples were visually inspected, and those in which delamination and cracking were not observed were deemed to be non-defective. If the non-defective rate was 95% or higher, the non-defective rate was judged as passing "◯", if the non-defective rate was 50% or higher, the non-defective rate was judged as somewhat good "△", and if the non-defective rate was less than 50%, the non-defective rate was judged as failing "X".

[0087] (Short rate) For each of Examples 1 to 5 and Comparative Example 1, 100 samples each having 20 internal electrode layers were produced. For each of Examples 1 to 5 and Comparative Example 1, 100 samples were inspected for the presence or absence of short circuits. If the short circuit rate was 5% or less, the short circuit rate was judged as passing "◯", if the short circuit rate was 20% or less, the short circuit rate was judged as somewhat good "△", and if the short circuit rate was 30% or less, the short circuit rate was judged as failing "X".

[0088] (Cycle characteristics) For the samples of Examples 1 to 5 and Comparative Example 1, charging and discharging were repeated at 10 C in a voltage range of 2.5 V to 0 V at 25° C., and the cycle characteristics were determined as (200th discharge capacity / initial discharge capacity) relative to the initial discharge capacity. If the cycle characteristic was 80% or more and 100% or less, the cycle characteristics were judged as passing (◯); if the cycle characteristic was 60% or more and 70% or less, the cycle characteristics were judged as somewhat good (Δ); and if the cycle characteristic was less than 60%, the cycle characteristics were judged as failing (×).

[0089] (Capacitance value) The capacitance values ​​were measured for the samples of Examples 1 to 5 and Comparative Example 1. The capacitance value of Example 3 was set to 100%, and for samples other than Example 3, the ratio to the capacitance value of Example 3 was measured. The measured value of Example 1 was 100%, the measured value of Example 2 was 300%, the measured value of Example 4 was 200%, the measured value of Example 5 was 300%, and the measured value of Comparative Example 1 was 70%. If the measured value was greater than 100%, the capacitance value was judged as very good "◎", if the measured value was 80% or more and 100% or less, the capacitance value was judged as good "◯", if the measured value was 50% or more and less than 80%, the capacitance value was judged as somewhat good "△", and if the measured value was less than 50%, the capacitance value was judged as unacceptable "X".

[0090] (water resistance) If the water resistance is good, the cycle characteristics are also good, and if the water resistance is not good, the cycle characteristics are not good. Therefore, if the cycle characteristics were judged as pass "◯", the water resistance was judged as pass "◯", if the cycle characteristics were judged as somewhat good "△", the water resistance was judged as somewhat good "△", and if the cycle characteristics were judged as fail "×", the water resistance was judged as fail "×".

[0091] (Overall judgment) If there was no failure "x" in any of the pass rate, cycle characteristics, water resistance, and short-circuit rate, the overall judgment was rated as pass "o". If there was a failure "x" in at least one of the pass rate, cycle characteristics, water resistance, and short-circuit rate, the overall judgment was rated as fail "x". The results are shown in Table 2. [Table 2]

[0092] In all of Examples 1 to 5, the overall evaluation was a pass mark "◯". This is thought to be because 0°<θ<90° and the relationship 0.1×t1 / tanθ≦d≦2.0×t1 / tanθ was established. In Comparative Example 1, the overall evaluation was a fail mark "×". This is thought to be because the relationship 0°<θ<90° and 0.1×t1 / tanθ≦d≦2.0×t1 / tanθ was not established.

[0093] 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]

[0094] 10 First internal electrode layer 20 Second internal electrode layer 30 Solid electrolyte layer 40a First external electrode 40b 2nd external electrode 50 cover layers 51 Solid electrolyte green sheet 52 Internal electrode paste 53 Margin paste 54 Cover Sheet 60 stacked chips 70 battery capacity area 80a First End Margin 80b Second end margin 90 Side Margin 95a First margin 95b Second margin 100,100a solid state battery 200 overlapping part

Claims

1. a solid electrolyte layer having two main surfaces opposing each other in a first direction, two end surfaces opposing each other in a second direction perpendicular to the first direction, and two side surfaces opposing each other in a third direction perpendicular to the first direction and the second direction; a first internal electrode layer formed on one main surface of the solid electrolyte layer and extending to one end surface; a second internal electrode layer formed on the other main surface of the solid electrolyte layer and drawn out to the other end surface; a first marginal portion formed around the first internal electrode layer on one main surface of the solid electrolyte layer, the first marginal portion having a composition different from that of the solid electrolyte layer and the first internal electrode layer; a second marginal portion formed around the second internal electrode layer on the other main surface of the solid electrolyte layer, the second marginal portion having a composition different from that of the solid electrolyte layer and the second internal electrode layer; when viewed from the first direction, the wiring includes a first overlapping portion in which a peripheral edge portion of the first internal electrode layer overlaps with a part of the first marginal portion in the third direction, and a second overlapping portion in which a peripheral edge portion of the second internal electrode layer overlaps with a part of the second marginal portion, an angle formed by a line connecting an end point E1 of the internal electrode layer on the marginal portion side in the third direction and an end point E2 of the marginal portion on the internal electrode layer side in the third direction and a line connecting both ends of the internal electrode layer in the third direction is θ, a thickness of the marginal portion in the first direction is t1, and a length between the end point E1 and the end point E2 in the third direction is d, in either the first overlapping portion or the second overlapping portion, wherein θ is an angle formed by a line connecting both ends of the internal electrode layer in the third direction and an end point E2 of the marginal portion in the third direction, ...

2. The all-solid-state battery according to claim 1 , wherein the angle θ is equal to or greater than 5° and less than 90°.

3. The all-solid-state battery according to claim 1 , wherein t1 is 5 μm or more and 200 μm or less.

4. 2. The all-solid-state battery according to claim 1, wherein in a cross section including the first direction and the third direction, an outer shape of the internal electrode layer in either the first overlapping portion or the second overlapping portion has a curvature.

5. 5. The all-solid-state battery according to claim 4, wherein in a cross section including the first direction and the third direction, an outer shape of the internal electrode layer in either the first overlapping portion or the second overlapping portion has a curvature from the end point E1 to the end point E2.

6. 5. The all-solid-state battery according to claim 4, wherein when the tip point E1 is located on one side in the first direction in a thickness direction of the internal electrode layer, an outer shape of the internal electrode layer is curved so as to be convex toward the other side in the first direction.

7. 5. The all-solid-state battery according to claim 4, wherein in a cross section including the first direction and the third direction, a radius of curvature r1 of an outer shape of the internal electrode layer in either the first overlapping portion or the second overlapping portion is 1 μm or more and 500 μm or less.

8. The all-solid-state battery according to claim 7 , wherein r1 / t1 (%) is 100% or more and 1000% or less.

9. 2. The all-solid-state battery according to claim 1, wherein the number of stacked internal electrode layers is 2 or more and 200 or less.

10. 2. The all-solid-state battery according to claim 1, wherein, of the plurality of internal electrode layers, 90% or more of the total number of layers of the internal electrode layers satisfy the relationship 0.1×t1 / tanθ≦d≦2.0×t1 / tanθ.

11. a solid electrolyte layer having two main surfaces opposing each other in a first direction, two end surfaces opposing each other in a second direction perpendicular to the first direction, and two side surfaces opposing each other in a third direction perpendicular to the first direction and the second direction; a first internal electrode layer formed on one main surface of the solid electrolyte layer and extending to one end surface; a second internal electrode layer formed on the other main surface of the solid electrolyte layer and drawn out to the other end surface; a first marginal portion formed around the first internal electrode layer on one main surface of the solid electrolyte layer, the first marginal portion having a composition different from that of the solid electrolyte layer and the first internal electrode layer; a second marginal portion formed around the second internal electrode layer on the other main surface of the solid electrolyte layer, the second marginal portion having a composition different from that of the solid electrolyte layer and the second internal electrode layer; when viewed from the first direction, the wiring includes a first overlapping portion in which a peripheral edge portion of the first internal electrode layer overlaps with a part of the first marginal portion in the third direction, and a second overlapping portion in which a peripheral edge portion of the second internal electrode layer overlaps with a part of the second marginal portion, an end point E1 of the internal electrode layer on the marginal portion side in the third direction in either the first overlapping portion or the second overlapping portion, and an end point E2 of the internal electrode layer on the marginal portion side in the third direction in which the end point E1 is located on one side in the first direction in a thickness of the internal electrode layer; and an outer shape of the internal electrode layer is curved so as to be convex on the other side in the first direction.

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