JP2021108255A - All-solid battery and method for manufacturing the same - Google Patents

Abstract

To provide an all-solid battery which allows the satisfactory fixing strength of an external electrode to be ensured, and a method for manufacturing the same.SOLUTION: An all-solid battery comprises: a laminate chip in which a plurality of solid electrolyte layers containing a solid electrolyte and a plurality of internal electrodes containing an electrode active substance are laminated alternately, which has an almost rectangular parallelepiped shape, and in which the plurality of internal electrodes are exposed from two side faces other than two faces in a lamination direction alternately; and a pair of external electrodes formed so as to be in contact with the two side faces. At least one of the pair of external electrodes includes, as a sub-member, at least one of the solid electrolyte and electrode active substance. The sub-member contains at least one or more common metal component elements of components included in the laminate chip. The common metal component elements are gradually inclined from inside the laminate chip to inside at least one of the pair of external electrodes, in concentration.SELECTED DRAWING: Figure 3

Description

The present invention relates to an all-solid-state battery and a method for manufacturing the same.

In recent years, secondary batteries have been used in various fields. Secondary batteries using an electrolytic solution have problems such as leakage of the electrolytic solution. Therefore, an all-solid-state battery having a solid electrolyte and having other components made of solid is being developed.

In the field of all-solid-state batteries, in order to achieve high energy density, two or more sets of battery units (also referred to as single cells) consisting of a positive electrode, a solid electrolyte, and a negative electrode are laminated and integrated. A laminated all-solid-state battery including a laminated body has been proposed (see, for example, Patent Document 1).

International Publication No. 2018/181379 Japanese Unexamined Patent Publication No. 2007-80812

In a laminated all-solid-state battery, structural destruction due to a volume change of the electrode active material during charging and discharging can be a problem. Specifically, peeling of the external electrode can be a problem. Therefore, it is one of the problems to secure sufficient adhesion strength to the external electrode.

Therefore, as a method for ensuring the adhesion strength of the external terminal electrode, copper powder is mixed as the conductive material of the external electrode material and glass frit is mixed as the sintering aid, and the external electrode material composed of copper powder and glass frit is sintered. A method of coating and forming on the end of a laminated all-solid-state battery and then baking is disclosed (see, for example, Patent Document 2). However, in this method, it is difficult to secure sufficient adhesion strength because a clear interface is formed between the external terminal electrode and the chip body.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an all-solid-state battery capable of ensuring sufficient adhesion strength of an external electrode and a method for manufacturing the same.

The all-solid battery according to the present invention has a substantially rectangular shape in which a plurality of solid electrolyte layers containing a solid electrolyte and a plurality of internal electrodes containing an electrode active material are alternately laminated, and has a shape other than the two surfaces in the stacking direction. A laminated chip in which a plurality of the internal electrodes are alternately exposed on two side surfaces and a pair of external electrodes formed so as to be in contact with the two side surfaces are provided, and at least one of the pair of external electrodes is a solid electrolyte. And at least one of the electrode active material is contained as an auxiliary member, and the auxiliary member contains at least one common metal component element of the components contained in the laminated chip, and the concentration of the common metal component element is high. It is characterized by having an inclination that gradually decreases from the inside of the laminated chip to the inside of at least one of the pair of external electrodes.

In the all-solid-state battery, the auxiliary member may be a solid electrolyte in which one or more metal component elements are common to the solid electrolyte contained in the solid electrolyte layer.

In the all-solid-state battery, the sub-member may be an electrode active material in which the electrode active material contained in the internal electrode and one or more metal component elements are common.

In the all-solid-state battery, the auxiliary member has a solid electrolyte in which the solid electrolyte contained in the solid electrolyte layer and one or more metal component elements are common, and an electrode active material contained in the internal electrode and one or more metal component elements in common. It may contain the electrode active material of.

In the all-solid-state battery, the concentration of the common component element is lower on the outer surface of at least one of the pair of external electrodes than at the interface between at least one of the pair of external electrodes and the laminated chip. A plating layer may be provided on the outer surface.

In the all-solid-state battery, the auxiliary member may have the same crystal structure as the solid electrolyte or the electrode active material in the laminated chip.

In the all-solid-state battery, the solid electrolyte contained in the solid electrolyte layer may have a NASICON type crystal structure.

In the all-solid-state battery, the pair of external electrodes may contain a carbon material, a metal material, or an alloy as a conductive material.

In the method for producing an all-solid-state battery according to the present invention, a plurality of green sheets containing a solid electrolyte powder and a plurality of electrode layer paste coatings containing an electrode active material are alternately laminated and have a substantially rectangular shape. A preparatory step for preparing a laminate in which a plurality of the electrode layer paste coatings are alternately exposed on two sides other than the two surfaces at the end in the stacking direction, and on the two sides, a conductive material, a solid electrolyte powder, and an electrode. The sub-member includes a coating step of applying a paste for an external electrode containing at least one of the sub-members of the active material powder, and a firing step of firing the laminate after the coating step. It is characterized by containing at least one common metal component element of the components contained in the laminated chip obtained by firing the laminated body.

In another method for manufacturing an all-solid-state battery according to the present invention, a plurality of solid electrolyte layers containing a solid electrolyte and a plurality of internal electrodes containing an electrode active material are alternately laminated, have a substantially rectangular shape, and have a stacking direction. A step of preparing a laminated chip in which a plurality of the internal electrodes are alternately exposed on two sides other than the two sides of the end, and at least one of a conductive material, a solid electrolyte powder, and an electrode active material powder on the two sides. The sub-member includes a step of applying and baking an external electrode paste containing the sub-member, and the sub-member is characterized by containing at least one common metal component element of the components contained in the laminated chip. And.

According to the present invention, it is possible to provide an all-solid-state battery capable of ensuring sufficient fixing strength of an external electrode and a method for manufacturing the same.

It is a schematic cross-sectional view which shows the basic structure of an all-solid-state battery. It is a schematic cross-sectional view of the all-solid-state battery which concerns on embodiment. (A) to (f) are diagrams for explaining the auxiliary members. It is a schematic sectional view of another all-solid-state battery. It is a schematic sectional view of another all-solid-state battery. It is a figure which illustrates the flow of the manufacturing method of an all-solid-state battery. (A) and (b) are diagrams illustrating the laminating process. It is a figure which illustrates the flow of the other manufacturing method of an all-solid-state battery. (A) to (f) are diagrams for explaining Example 4 and Comparative Examples 1 and 2.

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

(Embodiment)
FIG. 1 is a schematic cross-sectional view showing the basic structure of the all-solid-state battery 100. As illustrated in FIG. 1, the all-solid-state battery 100 has a structure in which the solid electrolyte layer 30 is sandwiched between the first internal electrode 10 and the second internal electrode 20. The first internal electrode 10 is formed on the first main surface of the solid electrolyte layer 30, has a structure in which the first internal electrode layer 11 and the first current collector layer 12 are laminated, and the solid electrolyte layer 30. A first internal electrode layer 11 is provided on the side. The second internal electrode 20 is formed on the second main surface of the solid electrolyte layer 30, has a structure in which the second internal electrode layer 21 and the second current collector layer 22 are laminated, and the solid electrolyte layer 30. A second internal electrode layer 21 is provided on the side.

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 the present embodiment, as an example, the first internal electrode 10 is used as the positive electrode, and the second internal electrode 20 is used as the negative electrode.

The solid electrolyte layer 30 contains a solid electrolyte having ionic conductivity as a main component. 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 having a NASICON structure. The phosphate-based solid electrolyte having a NASICON structure has a property of having high conductivity and being stable in the atmosphere. The phosphate-based solid electrolyte is, for example, a phosphate containing lithium. The phosphate is not particularly limited, and examples thereof include a lithium complex phosphate salt with Ti (for example, LiTi ₂ (PO ₄ ) ₃ ). Alternatively, Ti can be partially or wholly replaced with a tetravalent transition metal such as Ge, Sn, Hf, Zr or the like. Further, in order to increase the Li content, it may be partially replaced 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 (PO ₄ ) ₃ , Li _{1 + x} Al _x Zr _2-x (PO ₄ ) ₃ , Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ And so on. _{For example, the Li-Al-Ge-PO 4} system to which the same transition metal as the transition metal contained in the phosphate having an olivine crystal structure contained in the first internal electrode layer 11 and the second internal electrode layer 21 is added in advance. The material is preferred. For example, if the phosphate containing Co and Li are contained in the first internal electrode layer 11 and the second internal electrode layer 21, Co added in advance the Li-Al-Ge-PO ₄ based material solid electrolyte It is preferably contained in the layer 30. In this case, the effect of suppressing the elution of the transition metal contained in the electrode active material into the electrolyte can be obtained. When the first internal electrode layer 11 and the second internal electrode layer 21 contain a phosphate containing a transition element other than Co and Li, the Li-Al-Ge-PO ₄ system to which the transition metal is added in advance is used. The material is preferably contained in the solid electrolyte layer 30.

Of the first internal electrode layer 11 and the second internal electrode layer 21, at least the first internal electrode layer 11 used as a positive electrode contains a substance having an olivine type crystal structure as an electrode active material. The second internal electrode layer 21 also preferably contains the electrode active material. Examples of such an electrode active material include phosphates containing a transition metal and lithium. The olivine-type crystal structure is a crystal possessed by natural olivine and can be discriminated by X-ray diffraction.

As a typical example of the electrode active material having an olivine type crystal structure, LiCoPO ₄ containing Co or the like can be used. In this chemical formula, a phosphate or the like in which the transition metal Co is replaced can also be used. Here, the ratio of _{Li and PO 4} can fluctuate depending on the valence. It is preferable to use Co, Mn, Fe, Ni or the like as the transition metal.

The electrode active material having an olivine type crystal structure acts as a positive electrode active material in the first internal electrode layer 11 that acts as a positive electrode. For example, when the first internal electrode layer 11 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 21 also contains an electrode active material having an olivine type crystal structure, the mechanism of action of the second internal electrode layer 21 that acts as a negative electrode has not been completely clarified. The effects of increasing the discharge capacity and increasing the operating potential due to the discharge, which are presumed to be based on the formation of a partially solidified state with the negative electrode active material, are exhibited.

When both the first internal electrode layer 11 and the second internal electrode layer 21 contain an electrode active material having an olivine type crystal structure, the respective electrode active materials are preferably different from each other even if they are the same. May include transition metals. The fact that "they may be the same or different from each other" means that the electrode active materials contained in the first internal electrode layer 11 and the second internal electrode layer 21 may contain the same kind of transition metal, or may be mutually exclusive. It means that different types of transition metals may be included. The first internal electrode layer 11 and the second internal electrode layer 21 may contain only one type of transition metal, or may contain two or more types of transition metals. Preferably, the first internal electrode layer 11 and the second internal electrode layer 21 contain the same type of transition metal. More preferably, the electrode active materials contained in both internal electrode layers have the same chemical composition. When the first internal electrode layer 11 and the second internal electrode layer 21 contain the same kind of transition metal or an electrode active material having the same composition, the composition similarity between the two internal electrode layers is enhanced. Therefore, even if the terminals of the all-solid-state battery 100 are attached in the opposite direction, it has the effect of being able to withstand actual use without malfunction depending on the application.

Of the first internal electrode layer 11 and the second internal electrode layer 21, the second internal electrode layer 21 may further contain a substance known as a negative electrode active material. By containing the negative electrode active material only in one internal electrode layer, it becomes clear that the one internal electrode layer acts as a negative electrode and the other internal electrode layer acts as a positive electrode. When the negative electrode active material is contained only in one internal electrode layer, the one internal electrode layer is preferably the second internal electrode layer 21. In addition, both internal electrode layers may contain a substance known as a negative electrode active material. For the negative electrode active material of the electrode, the prior art in the secondary battery can be appropriately referred to, and for example, compounds such as titanium oxide, lithium titanium composite oxide, lithium titanium composite phosphate, carbon, and vanadium lithium phosphate. Can be mentioned.

In the production of the first internal electrode layer 11 and the second internal electrode layer 21, in addition to these electrode active materials, a solid electrolyte having ionic conductivity, a conductive material (conductive auxiliary agent) such as carbon or metal, or the like is further added. It may be added. For these members, a paste for the electrode layer can be obtained by uniformly dispersing the binder and the plasticizer in water or an organic solvent. Examples of the metal of the conductive auxiliary agent include Pd, Ni, Cu, Fe, and alloys containing these.

The first current collector layer 12 and the second current collector layer 22 contain a conductive material as a main component. For example, as the conductive material of the first current collector layer 12 and the second current collector layer 22, metal, carbon, or the like can be used.

FIG. 2 is a schematic cross-sectional view of a laminated all-solid-state battery 100a in which a plurality of battery units are laminated. The all-solid-state battery 100a includes a laminated chip 60 having a substantially rectangular parallelepiped shape. In the laminated chip 60, the first external electrode 40a and the second external electrode 40b are provided so as to be in contact with two side surfaces, which are two of the four surfaces other than the upper surface and the lower surface of the end in the stacking direction. The two side surfaces may be two adjacent side surfaces or two side surfaces facing each other. In the present embodiment, it is assumed that the first external electrode 40a and the second external electrode 40b are provided so as to be in contact with two side surfaces (hereinafter, referred to as two end surfaces) facing each other.

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

In the all-solid-state battery 100a, a plurality of first current collector layers 12 and a plurality of second current collector layers 22 are alternately laminated. The edge edges of the plurality of first current collector layers 12 are exposed on the first end face of the laminated chip 60 and not on the second end face. The edge edges of the plurality of second current collector layers 22 are exposed on the second end face of the laminated chip 60 and not on the first end face. As a result, the first current collector layer 12 and the second current collector layer 22 are alternately conducted to the first external electrode 40a and the second external electrode 40b.

The first internal electrode layer 11 is laminated on the first current collector layer 12. A solid electrolyte layer 30 is laminated on the first internal electrode layer 11. The solid electrolyte layer 30 extends from the first external electrode 40a to the second external electrode 40b. The second internal electrode layer 21 is laminated on the solid electrolyte layer 30. A second current collector layer 22 is laminated on the second internal electrode layer 21. Another second internal electrode layer 21 is laminated on the second current collector layer 22. Another solid electrolyte layer 30 is laminated on the second internal electrode layer 21. The solid electrolyte layer 30 extends from the first external electrode 40a to the second external electrode 40b. The first internal electrode layer 11 is laminated on the solid electrolyte layer 30. In the all-solid-state battery 100a, these stacking units are repeated. As a result, the all-solid-state battery 100a has a structure in which a plurality of battery units are stacked.

The first current collector layer 12 and the two layers of the first internal electrode layer 11 sandwiching the first current collector layer 12 are regarded as one internal electrode, and the second current collector layer 22 and the two layers of the second internal electrode sandwiching the first current collector layer 22 are regarded as one internal electrode. Considering the layer 21 as one internal electrode, it can be said that the laminated chip 60 has a structure in which a plurality of internal electrodes and a plurality of solid electrolyte layers are alternately laminated.

In such a laminated all-solid-state battery 100a, structural destruction due to a volume change of the electrode active material during charging and discharging can be a problem. Specifically, due to the volume of the electrode active material, peeling of the first external electrode 40a and the first internal electrode 10 from the laminated chip 60 can be a problem. Therefore, it is one of the problems to secure sufficient adhesion strength to the first external electrode 40a and the second external electrode 40b.

Therefore, in order to secure the fixing strength of the external electrode, it is conceivable to mix the glass frit as a sintering aid with the external power paste and bake the external power paste to form the external electrode. However, in this method, the solid electrolyte concentration and the electrode active material concentration change abruptly between the laminated chip 60 and the first external electrode 40a and the second external electrode 40b, and the first external electrode 40a and the second external electrode 40a and the second external electrode 40a and the second external electrode 40b. Since a clear interface is formed between the electrode 40b and the laminated chip 60, it is difficult to secure sufficient adhesion strength.

Therefore, the all-solid-state battery 100a according to the present embodiment has a structure capable of ensuring sufficient adhesion strength to the first external electrode 40a and the second external electrode 40b. Specifically, the first external electrode 40a and the second external electrode 40b contain at least one of a solid electrolyte and an electrode active material as auxiliary members together with the conductive material.

First, a case where at least one of the first external electrode 40a and the second external electrode 40b contains a solid electrolyte as an auxiliary member will be described. The solid electrolyte contained in the first external electrode 40a and the second external electrode 40b contains one or more of each metal component element of the material contained in the laminated chip 60. Further, the concentration of the metal component element has an inclination that gradually decreases (gradually decreases) from the inside of the laminated chip 60 toward the first external electrode 40a and the second external electrode 40b. Here, "gradual decrease" includes continuous decrease (monotonous decrease), and when the concentration is measured at a plurality of sample points toward the first external electrode 40a and the second external electrode 40b. It includes decreasing as a whole while repeating up and down.

For example, as illustrated in FIG. 3A, the first external electrode 40a and the second external electrode 40b share one or more of each metal component element of the solid electrolyte contained in the solid electrolyte layer 30 as a common metal component element. Contains the solid electrolyte 41, which is included as. For example, when the solid electrolyte of the solid electrolyte layer 30 is a Li-Al-Ge-PO _4- based material, the solid electrolyte 41 is a Li-Al-Ge-PO _4- based material or a Li-Al-Zr-PO _{4-based material.} Materials, Li-Al-Ti-PO ₄ series materials and the like. As illustrated by the dotted line in FIG. 3B, the concentration of at least one metal component element common between the solid electrolyte and the solid electrolyte 41 contained in the solid electrolyte layer 30 is determined from the laminated chip 60 to the first external electrode 40a. And gradually decrease toward the second external electrode 40b. For example, as an example, the concentration of Li gradually starts to decrease from the inside of the laminated chip 60 toward the first external electrode 40a and the second external electrode 40b from the laminated chip 60, and the laminated chip 60 and the first external electrode 40a and It straddles the interface with the second external electrode 40b and is lowered to the inside of the first external electrode 40a and the second external electrode 40b. In FIG. 3B, the concentrations of the conductive materials contained in the first external electrode 40a and the second external electrode 40b are also shown by solid lines.

When the first internal electrode layer 11 contains a solid electrolyte, the first external electrode 40a contains one or more of the metal component elements of the solid electrolyte contained in the first internal electrode layer 11 as a common metal component element. The solid electrolyte 41 may be contained. In this case, the concentration of at least one of the common metal component elements gradually decreases from the laminated chip 60 toward the first external electrode 40a.

When the second internal electrode layer 21 contains a solid electrolyte, the second external electrode 40b contains one or more of the metal component elements of the solid electrolyte contained in the second internal electrode layer 21 as a common metal component element. The solid electrolyte 41 may be contained. In this case, the concentration of at least one of the common metal component elements gradually decreases from the laminated chip 60 toward the second external electrode 40b.

For example, the solid electrolyte contained in the first external electrode 40a and the second external electrode 40b is an oxide-based solid electrolyte. However, from the viewpoint of improving the adhesion between compounds having similar structures, the solid electrolyte contained in the first external electrode 40a and the second external electrode 40b has the same crystal structure as the solid electrolyte contained in the laminated chip 60. It is preferable to have. For example, if the solid electrolyte contained in the laminated chip 60 has a NASICON structure, it is preferable that the solid electrolyte contained in the first external electrode 40a and the second external electrode 40b also has a NASICON structure.

Next, a case where the first external electrode 40a contains an electrode active material as an auxiliary member will be described. The electrode active material contained in the first external electrode 40a includes one or more of each metal component element of the material contained in the laminated chip 60. Further, the concentration of the metal component element has an inclination that gradually decreases from the laminated chip 60 toward the first external electrode 40a.

For example, as illustrated in FIG. 3C, the first external electrode 40a is an electrode containing at least one of each metal component element of the electrode active material contained in the first internal electrode layer 11 as a common metal component element. Contains the active material 42. For example, when the electrode active material of the first internal electrode layer 11 is a Li-Co-PO _4- based material, the electrode active material 42 is also a Li-Co-PO _4- based material or the like. As illustrated by the broken line in FIG. 3D, the concentration of at least one metal component element common between the electrode active material and the electrode active material 42 contained in the first internal electrode layer 11 is the concentration from the laminated chip 60 to the th. 1 It gradually decreases toward the external electrode 40a. For example, the concentration of Co starts to gradually decrease from the inside of the laminated chip 60 toward the first external electrode 40a from the laminated chip 60, straddles the interface between the laminated chip 60 and the first external electrode 40a, and is the first external electrode. It decreases to within 40a. In FIG. 3D, the concentrations of the conductive materials contained in the first external electrode 40a and the second external electrode 40b are also shown by solid lines.

Next, a case where the second external electrode 40b contains an electrode active material will be described. The electrode active material contained in the second external electrode 40b contains one or more of each metal component element of the material contained in the laminated chip 60. Further, the concentration of the metal component element has an inclination that gradually decreases from the laminated chip 60 toward the second external electrode 40b.

For example, as illustrated in FIG. 3C, the second external electrode 40b is an electrode containing at least one of each metal component element of the electrode active material contained in the second internal electrode layer 21 as a common metal component element. Contains the active material 42. For example, when the electrode active material of the second internal electrode layer 21 is a Li-Al-Ti-PO _4- based material, the electrode active material 42 is also a Li-Al-Ti-PO _4- based material or the like. As illustrated by the broken line in FIG. 3D, the concentration of at least one metal component element common between the electrode active material and the electrode active material 42 contained in the second internal electrode layer 21 is the concentration from the laminated chip 60 to the th. 2 It gradually decreases toward the external electrode 40b. For example, the concentration of Ti gradually starts to decrease from the inside of the laminated chip 60 toward the second external electrode 40b from the laminated chip 60, straddles the interface between the laminated chip 60 and the second external electrode 40b, and is the second external electrode. It decreases to within 40b.

Next, as illustrated in FIG. 3E, a case where the first external electrode 40a contains the solid electrolyte 41 and the electrode active material 42 will be described. In this case, as illustrated by the dotted line in FIG. 3 (f), the concentration of at least one metal component element common between the solid electrolyte and the solid electrolyte 41 contained in the solid electrolyte layer 30 is the concentration from the laminated chip 60 to the first. It gradually decreases toward the external electrode 40a. Further, as illustrated by the broken line in FIG. 3 (f), the concentration of at least one metal component element common between the electrode active material and the electrode active material 42 included in the first internal electrode layer 11 is the laminated chip 60. It gradually decreases toward the first external electrode 40a.

Next, a case where the second external electrode 40b contains the solid electrolyte 41 and the electrode active material 42 will be described. As illustrated by the dotted line in FIG. 3 (f), the concentration of at least one of the metal component elements common between the solid electrolyte and the solid electrolyte 41 contained in the solid electrolyte layer 30 is determined from the laminated chip 60 to the second external electrode 40b. It is gradually decreasing toward. Further, as illustrated by the broken line in FIG. 3 (f), the concentration of at least one metal component element common between the electrode active material and the electrode active material 42 included in the second internal electrode layer 21 is the laminated chip 60. It gradually decreases toward the second external electrode 40b. In FIG. 3 (f), the concentrations of the conductive materials contained in the first external electrode 40a and the second external electrode 40b are also shown by solid lines.

As described above, the solid electrolyte and the electrode active material contained in the first external electrode 40a and the second external electrode 40b contain a metal component element common to at least one or more of the metal component elements contained in the laminated chip 60, and the common metal component element. Since the concentration of the metal component element of the above has an inclination that gradually decreases from the inside of the laminated chip 60 to the inside of the first external electrode 40a and the second external electrode 40b, the laminated chip 60 and the first external electrode 40a And it becomes difficult to form a clear interface with the second external electrode 40b. As a result, the adhesive strength of the first external electrode 40a and the second external electrode 40b to the laminated chip 60 is improved, and sufficient adhesive strength can be obtained. As a result, the film peeling of the first external electrode 40a and the second external electrode 40b can be suppressed, and the internal resistance of the all-solid-state battery 100a can be suppressed.

Further, since the solid electrolyte and the electrode active material contained in the first external electrode 40a and the second external electrode 40b contain a metal component element common to at least one of the metal component elements contained in the laminated chip 60, the laminated chip 60 The deviation of the material composition inside is suppressed. Specifically, the deviation of the material composition of the solid electrolyte layer 30, the first internal electrode layer 11, and the second internal electrode layer 21 is suppressed. As a result, deterioration of battery characteristics is suppressed. As a result, the decrease in battery capacity is suppressed.

The solid electrolyte and the electrode active material contained in the first external electrode 40a and the second external electrode 40b preferably contain the same metal component elements as the solid electrolyte and the electrode active material contained in the laminated chip 60, and their compositions are the same. Is preferable.

For example, as a specific combination of electrode active materials, LiCoPO ₄ is used as the electrode active material of the first internal electrode layer 11 and the first external electrode 40a, and Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ). ₃ can be used as the electrode active material of the second internal electrode layer 21 and the second external electrode 40b.

The concentration of each component of the solid electrolyte and the electrode active material contained in the first external electrode 40a and the second external electrode 40b can be measured by a laser ablation ICP (Inductively Coupled Plasma) mass spectrometry method or the like.

The innermost layer formed on the first end surface of the laminated chip 60 is the first external electrode 40a, and a plating layer may be further provided on the surface of the first external electrode 40a. Similarly, the innermost layer formed on the second end surface of the laminated chip 60 may be the second external electrode 40b, and a plating layer may be further provided on the surface of the second external electrode 40b. For example, as illustrated in FIG. 4, a plating layer 41a may be provided on the surface of the first external electrode 40a. Further, the plating layer 41b may be provided on the surface of the second external electrode 40b. The plating layer 41a and the plating layer 41b have, for example, a double structure in which the first layer is Ni-plated and the second layer is Sn-plated from the inside.

When the plating layer 41a and the plating layer 41b are provided, it is preferable that the amount of the component that inhibits plating is small on the surfaces of the first external electrode 40a and the second external electrode 40b. Therefore, the concentrations of the auxiliary members (at least one of the solid electrolyte and the electrode active material) on the outer surfaces of the first external electrode 40a and the second external electrode 40b are determined by the laminated chip 60, the first external electrode 40a, and the second external electrode. It is preferably lower than the concentration at the interface with 40b. For example, in the first external electrode 40a and the second external electrode 40b, the concentration of the auxiliary member gradually decreases from the laminated chip 60 toward the first external electrode 40a and the second external electrode 40b, and the first external electrode 40a and the second external electrode 40b It is preferable that the second external electrode 40b does not increase toward the surface. In this case, since the amount of auxiliary members is reduced on the surfaces of the first external electrode 40a and the second external electrode 40b, the inhibition of plating is suppressed.

The all-solid-state battery 100a does not have to include a current collector layer. For example, as illustrated in FIG. 5, the first current collector layer 12 and the second current collector layer 22 may not be provided. In this case, the first internal electrode 10 is formed only by the first internal electrode layer 11, and the second internal electrode 20 is formed only by the second internal electrode layer 21.

Subsequently, a method for manufacturing the all-solid-state battery 100a illustrated in FIG. 2 will be described. FIG. 6 is a diagram illustrating a flow of a method for manufacturing the all-solid-state battery 100a.

(Ceramic raw material powder manufacturing process)
First, a powder of the solid electrolyte constituting the above-mentioned solid electrolyte layer 30 is prepared. For example, a powder of a solid electrolyte constituting the solid electrolyte layer 30 can be produced by mixing raw materials, additives and the like and using a solid phase synthesis method or the like. The obtained powder can be adjusted to a desired average particle size by dry pulverization. For example, it is adjusted to a desired average particle size with a planetary ball mill using a _{ZrO 2 ball having a diameter of 5 mm.}

Additives include sintering aids. As a sintering aid, for example, glass such as Li-B-O-based compound, Li-Si-O-based compound, Li-CO-based compound, Li-SO-based compound, Li-PO-based compound and the like. It contains glass components such as one or more of the components.

(Solid electrolyte green sheet manufacturing process)
Next, the obtained powder is uniformly dispersed in an aqueous solvent or an organic solvent together with a binder, a dispersant, a plasticizer, etc., and wet-pulverized to carry out wet pulverization to obtain a solid electrolyte slurry having a desired average particle size. To get. At this time, a bead mill, a wet jet mill, various kneaders, a high-pressure homogenizer, or the like can be used, and it is preferable to use the bead mill from the viewpoint that the particle size distribution can be adjusted and dispersed at the same time. A binder is added to the obtained solid electrolyte slurry to obtain a solid electrolyte paste. By applying the obtained solid electrolyte paste, a solid electrolyte green sheet can be produced. The coating method is not particularly limited, and a slot die method, a reverse coating method, a gravure coating method, a bar coating method, a doctor blade method and the like can be used. The particle size distribution after wet pulverization can be measured, for example, by using a laser diffraction measuring device using a laser diffraction scattering method.

(Paste preparation process for internal power)
Next, an internal electric paste for producing the first internal electrode layer 11 and the second internal electrode layer 21 described above is produced. For example, a paste for internal electric power can be obtained by uniformly dispersing a conductive auxiliary agent, an electrode active material, a solid electrolyte material, a binder, a plasticizer, or the like in water or an organic solvent. As the solid electrolyte material, the above-mentioned solid electrolyte paste may be used. As the conductive auxiliary agent, Pd, Ni, Cu, Fe, alloys containing these, various carbon materials, and the like may be further used. When the composition of the first internal electrode layer 11 and the composition of the second internal electrode layer 21 are different, each internal electric paste may be prepared individually.

(Paste preparation process for current collector)
Next, a current collector paste for producing the first current collector layer 12 and the second current collector layer 22 described above is produced. For example, a paste for a current collector can be obtained by uniformly dispersing Pd powder, carbon black, plate-shaped graphite carbon, binder, dispersant, plasticizer, etc. in water or an organic solvent.

(Paste preparation process for external power)
Next, an external electric paste for producing the first external electrode 40a and the second external electrode 40b described above is produced. For example, a paste for external electricity can be obtained by uniformly dispersing a conductive material, an electrode active material, a solid electrolyte, a binder, a plasticizer, or the like in water or an organic solvent. When the solid electrolyte is contained in the paste for external power, the solid electrolyte may be a solid electrolyte in which one or more of the metal component elements of the solid electrolyte contained in the solid electrolyte green sheet are common, or the paste for internal power is used. One or more of each metal component element of the solid electrolyte contained in the above is a common solid electrolyte. When the electrode active material is contained in the external power paste, one or more of the metal component elements of the electrode active material contained in the internal power paste is a common electrode active material. When different auxiliary members are included in the first external electrode 40a and the second external electrode 40b, each external power paste may be prepared individually.

(Laminating process)
As illustrated in FIG. 7A, the internal power paste 52 is printed on one surface of the solid electrolyte green sheet 51, the current collector paste 53 is further printed, and the internal power paste 52 is further printed. The reverse pattern 54 is printed on the solid electrolyte green sheet 51 in the area where the internal current paste 52 and the current collector paste 53 are not printed. As the reverse pattern 54, the same one as that of the solid electrolyte green sheet 51 can be used. A plurality of printed solid electrolyte green sheets 51 are laminated by alternately shifting them, and a cover sheet 55 to which the plurality of solid electrolyte green sheets are bonded is pressure-bonded from above and below in the stacking direction to obtain a laminated body. In this case, in the laminated body, a substantially rectangular parallelepiped-shaped laminated body is obtained so that the pair of the internal current paste 52 and the current collector paste 53 are alternately exposed on the two end faces. Next, as illustrated in FIG. 7B, the external electric paste 56 is applied to each of the two end faces by a dip method or the like and dried. As a result, a molded body for forming the all-solid-state battery 100a is obtained.

(Baking process)
Next, the obtained laminate is fired. The firing conditions are under an oxidizing atmosphere or a non-oxidizing atmosphere, and the maximum temperature is preferably 400 ° C. to 1000 ° C., more preferably 500 ° C. to 900 ° C., and the like is not particularly limited. In order to sufficiently remove the binder before reaching the maximum temperature, a step of holding the binder at a temperature lower than the maximum temperature in an oxidizing atmosphere may be provided. In order to reduce the process cost, it is desirable to bake at the lowest possible temperature. After firing, a reoxidation treatment may be performed. By the above steps, the all-solid-state battery 100a is produced.

According to the present embodiment, at least one of the solid electrolyte and the electrode active material is contained as an auxiliary member in the paste for external power. When the paste for external power contains a solid electrolyte, the solid electrolyte diffuses toward the solid electrolyte contained in the solid electrolyte green sheet at the time of firing. On the other hand, the solid electrolyte contained in the solid electrolyte green sheet also diffuses toward the solid electrolyte contained in the paste for external electricity. As a result, in the first external electrode 40a and the second external electrode 40b after firing, the metal component element concentration common between the solid electrolyte of the external electrical paste and the solid electrolyte contained in the solid electrolyte green sheet is the laminated chip 60. Therefore, the inclination gradually decreases toward the first external electrode 40a and the second external electrode 40b. As a result, it becomes difficult to form a clear interface between the laminated chip 60 and the first external electrode 40a and the second external electrode 40b. As a result, the adhesion strength of the first external electrode 40a and the second external electrode 40b is improved.

When the electrode active material is contained in the external power paste, it diffuses toward the electrode active material contained in the internal power paste at the time of firing. On the other hand, the electrode active material contained in the internal power paste also diffuses toward the electrode active material contained in the external power paste. As a result, in the first external electrode 40a and the second external electrode 40b after firing, the metal component element concentration common between the electrode active material of the internal power paste and the electrode active material contained in the external power paste is laminated. The tip 60 has an inclination that gradually decreases toward the first external electrode 40a and the second external electrode 40b. As a result, it becomes difficult to form a clear interface between the laminated chip 60 and the first external electrode 40a and the second external electrode 40b. As a result, the adhesion strength of the first external electrode 40a and the second external electrode 40b is improved.

The all-solid-state battery 100a illustrated in FIG. 4 is plated by using the first external electrode 40a and the second external electrode 40b obtained by firing the paste for external power as the base layer and plating the base layer. Layers 41a and 41b can be formed.

For the all-solid-state battery 100a illustrated in FIG. 5, the step of applying the current collector paste 53 may be omitted in the step of FIG. 7A.

The first external electrode 40a and the second external electrode 40b may be baked after the firing step. FIG. 8 is a flow chart illustrating the manufacturing method in this case. For example, the external power paste 56 is not applied in the laminating step, but the external power paste 56 is applied to the two end faces of the laminated chip 60 obtained in the firing step and baked. Thereby, the first external electrode 40a and the second external electrode 40b can be formed.

Hereinafter, an all-solid-state battery was produced according to the embodiment, and its characteristics were investigated.

(Example 1)
Co ₃ O ₄ , Li ₂ CO ₃ , ammonium dihydrogen phosphate, Al ₂ O ₃ , and GeO ₂ are mixed, and a predetermined amount of Co is contained as a solid electrolyte material powder. Li _1.3 Al _0.3 Ge _1.7 ( PO ₄ ) ₃ was prepared by the solid phase synthesis method. The obtained powder was dry-pulverized with _{ZrO 2 balls.} Further, a solid electrolyte slurry was prepared by wet pulverization (dispersion medium: ion-exchanged water or ethanol). A binder was added to the obtained slurry to obtain a solid electrolyte paste, and a solid electrolyte green sheet was prepared.

Li CoPO _{4 and Li 1.3} Al _0.3 Ti _1.7 (PO ₄ ) ₃ containing a predetermined amount of Co were synthesized by the solid phase synthesis method in the same manner as described above. The LiCoPO ₄ and Li-Al-Ti-PO ₄ materials were highly dispersed by a wet bead mill or the like to prepare a ceramic paste consisting of only ceramic particles. Next, the ceramic paste and the conductive material were mixed well to prepare a paste for internal electricity.

As a paste for external power, a paste that is a composite of conductive carbon and auxiliary members was produced. As auxiliary member, using a Li-Al-Ge-PO ₄ based material serving as a solid electrolyte.

A paste for internal power was printed on the solid electrolyte green sheet using a screen having a predetermined pattern, carbon was further printed as a paste for the current collector layer, and a paste for internal power was further printed. The printed solid electrolyte green sheet is stacked 10 sheets by shifting the electrodes to the left and right so that the electrodes are pulled out, and the solid electrolyte green sheet is laminated up and down as a cover layer, and crimped by a hot pressure press to make a dicer. The laminate was cut to a predetermined size. As a result, a laminated body having a substantially rectangular parallelepiped shape was obtained. In the laminated body, the external power paste was applied to one end face where the internal power paste was exposed by a dip method and dried. The external power paste was applied to the other end face where the internal power paste was exposed by a dip method and dried. Then, it was heat-treated at 300 ° C. or higher and 500 ° C. or lower to degreas, and then heat-treated at 900 ° C. or lower and sintered to prepare a sintered body.

(Example 2)
As a by-member telex paste, using Li-Al-Ti-Po ₄ based material serving as an electrode active material. Other conditions were the same as in Example 1.

(Example 3)
As an auxiliary member of the paste for external power, a Li-Al-Ge-PO _4- based material that functions as a solid electrolyte and a Li-Al-Ti-PO _4- based material that functions as a negative electrode active material were used. Other conditions were the same as in Example 1.

(Example 4)
As an auxiliary member of the paste for external power, a Li-Al-Ge-PO _4- based material that functions as a solid electrolyte and a Li-Al-Ti-PO _4- based material that functions as a negative electrode active material were used. By applying the pastes having different auxiliary member concentrations a plurality of times, the concentration distribution was different from that of Example 3. Other conditions were the same as in Example 1.

(Comparative Example 1)
As a paste for external power, a paste that is a composite of conductive carbon and glass frit was prepared. Other conditions were the same as in Example 1.

(Comparative Example 2)
A conductive carbon paste was prepared as a paste for external electricity. That is, in Comparative Example 2, neither the solid electrolyte nor the electrode active material was contained in the paste for external electricity. Other conditions were the same as in Example 1.

In the vicinity of the interface between the laminated chip 60 and the first external electrode 40a and the second external electrode 40b, the concentration of a common metal component element between the laminated chip 60 and the first external electrode 40a and the second external electrode 40b is measured. It was measured. Laser ablation ICP mass spectrometry was used for the measurement. The results are shown in Table 1. In Example 1, a laminated chip 60 over the first external electrode 40a and the second external electrode 40b, and decreasing the concentration of Li-Al-Ge-PO ₄ material, becomes substantially constant value. In Example 2, a laminated chip 60 over the first external electrode 40a and the second external electrode 40b, and decreasing the concentration of Li-Al-Ti-Po ₄ based material, becomes substantially constant value. _{In Example 3, the concentrations of the Li-Al-Ge-PO 4-} based material and the Li-Al-Ti-PO _4- based material gradually decrease from the laminated chip 60 to the first external electrode 40a and the second external electrode 40b, and are omitted. It became a constant value. In Example 4, as shown in FIG. 9 (e) and FIG. 9 (f), the the laminated chip 60 over the first external electrode 40a and the second external electrode 40b, Li-Al-Ge- PO 4 material and Li gradually increases after the concentration of the -Al-Ti-PO ₄ based material is gradually reduced, it was higher on the surface of the first external electrode 40a and the second external electrode 40b. In FIG. 9 (f), the dotted line _{indicates the concentration of the Li-Al-Ge-PO 4-} based material, the broken line represents the concentration of the Li-Al-Ti-PO _4- based material, and the solid line indicates the concentration of the conductive material. Is shown. In Comparative Example 1, as shown in FIGS. 9A and 9B, the concentration of the glass frit 43 gradually increased from the laminated chip 60 to the first external electrode 40a and the second external electrode 40b, and became a substantially constant value. It became. In FIG. 9B, the alternate long and short dash line indicates the concentration of the glass frit 43, the dotted line indicates the concentration of the Li-Al-Ge-PO _4- based material, and the broken line indicates the concentration of the Li-Al-Ti-PO _4- based material. The concentration is shown, and the solid line shows the concentration of the conductive material. In Comparative Example 2, as shown in FIGS. 9 (c) and 9 (d), no auxiliary member was added. In FIG. 9D, the dotted line _{indicates the concentration of the Li-Al-Ge-PO 4-} based material, the broken line represents the concentration of the Li-Al-Ti-PO _4- based material, and the solid line indicates the concentration of the conductive material. Is shown.

The internal resistance and capacity of each of the all-solid-state batteries of Examples 1 to 4 and Comparative Examples 1 and 2 (number of samples = 10) were measured before and after the lapse of 2000 cycles of charge and discharge. If the average internal resistance increased by 5% or more from the initial value, it was judged as rejected "x", and if not, it was judged as passed "〇". If the average capacity is 10% or more lower than the initial value, it is judged as rejected "x", and if not, it is judged as passed "〇".

In Examples 1 to 4, the internal resistance increase rate was determined to be acceptable. This is because the concentration of the auxiliary member gradually decreases from the laminated chip 60 to the first external electrode 40a and the second external electrode 40b, so that the adhesion strength of the first external electrode 40a and the second external electrode 40b is improved, and after the charge / discharge cycle. It is considered that this is because the volume change of the above was absorbed. On the other hand, in Comparative Example 1, the internal resistance increase rate was determined to be unacceptable. This is because the concentrations of the solid electrolyte and the electrode active material change rapidly between the laminated chip 60 and the first external electrode 40a and the second external electrode 40b, so that the laminated chip 60 and the first external electrode 40a and the first external electrode 40a and the first are changed. It is considered that this is because a clear interface is formed between the two external electrodes 40b. Also in Comparative Example 2, the internal resistance increase rate was determined to be unacceptable. This is because a clear interface is formed between the laminated chip 60 and the first external electrode 40a and the second external electrode 40b by not adding the auxiliary member, and the first external electrode 40a and the second external electrode 40b have a clear interface. It is considered that this is because sufficient adhesion strength was not obtained.

Next, in Examples 1 to 4, the capacity reduction rate was determined to be acceptable. This is because the diffusion of the same element between the laminated chip 60 and the sub-members of the first external electrode 40a and the second external electrode 40b suppresses an unintended deviation in material composition and deterioration of battery characteristics. It is believed that there is. On the other hand, in Comparative Examples 1 and 2, the capacity reduction rate was determined to be unacceptable. It is considered that this is because the diffusion causes an unintended deviation in the material composition and deterioration of the battery characteristics.

Next, with respect to Examples 1 to 4 and Comparative Examples 1 and 2, the coating property of the plating on the first external electrode 40a and the second external electrode 40b was confirmed. The number N of each sample was set to 100, and the appearance of the plating was visually inspected, and when the plating was not sufficiently coated, it was determined to be NG. The NG judgment rate is shown in Table 1. In Example 4, the plating NG rate was 3%. It is considered that this is because the outer surfaces of the first external electrode 40a and the second external electrode 40b contain a large amount of components that inhibit plating, such as a solid electrolyte and an electrode active material. On the other hand, in Examples 1 to 3, the plating NG rate was 0%. It is considered that this is because the amount of components that inhibit plating, such as the solid electrolyte and the electrode active material, was small on the outer surfaces of the first external electrode 40a and the second external electrode 40b. From this result, it was found that it is preferable that the concentration of the auxiliary member component does not increase from the laminated chip 60 to the surfaces of the first external electrode 40a and the second external electrode 40b.

Although the examples of the present invention have been described in detail above, the present invention is not limited to the specific examples, and various modifications and modifications are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 1st internal electrode 11 1st internal electrode layer 12 1st current collector layer 20 2nd internal electrode 21 2nd internal electrode layer 22 2nd current collector layer 30 Solid electrolyte layer 40a 1st external electrode 40b 2nd external electrode 41a, 41b Plating layer 51 Solid electrolyte green sheet 52 Internal electrode paste 53 Current collector paste 54 Reverse pattern 55 Cover sheet 56 External electrode paste 100,100a All-solid-state battery

Claims (10)

A plurality of solid electrolyte layers containing a solid electrolyte and a plurality of internal electrodes containing an electrode active material are alternately laminated to have a substantially rectangular parallelepiped shape, and the plurality of internal electrodes are formed on two surfaces other than the two surfaces in the stacking direction. Laminated chips that are exposed alternately,
A pair of external electrodes formed so as to be in contact with the two side surfaces are provided.
At least one of the pair of external electrodes contains at least one of a solid electrolyte and an electrode active material as an auxiliary member.
The sub-member contains at least one common metal component element of the components contained in the laminated chip.
An all-solid-state battery characterized in that the concentration of the common metal component element has an inclination that gradually decreases from the inside of the laminated chip to the inside of at least one of the pair of external electrodes. The all-solid-state battery according to claim 1, wherein the auxiliary member is a solid electrolyte in which the solid electrolyte contained in the solid electrolyte layer and one or more metal component elements are common. The all-solid-state battery according to claim 1, wherein the auxiliary member is an electrode active material in which the electrode active material contained in the internal electrode and one or more metal component elements are common. The auxiliary member includes a solid electrolyte in which the solid electrolyte contained in the solid electrolyte layer and one or more metal component elements are common, and an electrode active material in which the electrode active material contained in the internal electrode and one or more metal component elements are common. The all-solid-state battery according to claim 1, wherein the all-solid-state battery comprises. The concentration of the common component element is lower on the outer surface of at least one of the pair of external electrodes than at the interface between at least one of the pair of external electrodes and the laminated chip.
The all-solid-state battery according to any one of claims 1 to 4, wherein a plating layer is provided on the outer surface. The all-solid-state battery according to any one of claims 1 to 5, wherein the auxiliary member has the same crystal structure as the solid electrolyte or the electrode active material in the laminated chip. The all-solid-state battery according to any one of claims 1 to 6, wherein the solid electrolyte contained in the solid electrolyte layer has a NASICON type crystal structure. The all-solid-state battery according to any one of claims 1 to 7, wherein the pair of external electrodes contains a carbon material, a metal material, or an alloy as a conductive material. A plurality of green sheets containing a solid electrolyte powder and a plurality of electrode layer paste coatings containing an electrode active material are alternately laminated to have a substantially rectangular shape, and are formed on two side surfaces other than the two surfaces at the end in the stacking direction. A preparatory step for preparing a laminate in which the plurality of electrode layer paste coatings are alternately exposed, and
A coating step of applying a paste for an external electrode containing a conductive material and an auxiliary member which is at least one of a solid electrolyte powder and an electrode active material powder on the two side surfaces.
A firing step of firing the laminate after the coating step is included.
A method for producing an all-solid-state battery, wherein the auxiliary member contains at least one common metal component element of the components contained in the laminated chip obtained by firing the laminated body. A plurality of solid electrolyte layers containing a solid electrolyte and a plurality of internal electrodes containing an electrode active material are alternately laminated to have a substantially rectangular parallelepiped shape, and the plurality of internal electrodes are formed on two surfaces other than the two surfaces at the end in the stacking direction. And the process of preparing laminated chips that are exposed alternately
The two side surfaces include a step of applying and baking an external electrode paste containing a conductive material and an auxiliary member which is at least one of a solid electrolyte powder and an electrode active material powder.
A method for manufacturing an all-solid-state battery, wherein the auxiliary member contains at least one common metal component element of the components contained in the laminated chip.

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