JP7120318B2 - solid state battery - Google Patents

Description

The present invention relates to solid state batteries.

Secondary batteries that can be repeatedly charged and discharged have been used for various purposes. For example, secondary batteries are used as power sources for electronic devices such as smartphones and laptop computers.

In secondary batteries, liquid electrolytes are commonly used as a medium for ion transport that contributes to charging and discharging. That is, a so-called electrolytic solution is used in the secondary battery. However, in such secondary batteries, safety is generally required in terms of preventing electrolyte leakage. In addition, since the organic solvent and the like used in the electrolytic solution are combustible substances, safety is required in this respect as well.

Therefore, research is being conducted on solid batteries using a solid electrolyte instead of the electrolytic solution.

JP-A-2001-176467 JP-A-10-247516 WO2012/063874

In a solid battery, the electrode body is formed of solid battery constituent materials (e.g., positive and negative electrode layers, an electrolyte layer, and a current collecting layer), so a structure that can ensure the adhesion between the battery constituent materials is important. . This is because, in a solid-state battery, if the battery components are not sufficiently in close contact with each other, the internal resistance may increase, making charging and discharging difficult.

The inventors of the present application have noticed that the previously proposed solid-state batteries still have problems to be overcome, and have found the necessity of taking countermeasures therefor. Specifically, the inventors of the present application have found that there are the following problems.

As a structure of a solid battery, a structure in which a collector layer made of metal is provided on one side of a positive electrode layer and a negative electrode layer has been proposed (see Patent Documents 1 and 2). Patent Literature 1 proposes a solid-state battery in which the adhesion is enhanced by crimping the battery components. In Patent Document 2, by making the contact point between the current collecting layer and the electrode terminal movable, the current collecting layer can follow the volume change of the electrode layer that occurs during charging and discharging, thereby preventing poor contact between the battery components in the stacking direction. A possible solid state battery has been proposed. However, in such a solid-state battery, the battery components are only in physical contact with each other, and it is difficult to say that they are solid-state batteries in which sufficient adhesion can be obtained. In addition, no consideration is given to the influence of stress between battery constituent materials that occurs during charging and discharging.

As a method for increasing the adhesion between battery constituent materials, there is a solid battery in which the battery constituent materials are sintered together so that the battery constituent materials are firmly adhered to each other (see Patent Document 3). In such a solid battery, between an electrode layer whose volume can change due to expansion/contraction that occurs during charging and discharging, and a current collecting layer whose volume cannot change or whose volume change can be small with respect to the electrode layer Due to the generated stress, the electrode layer may crack or peel off.

Specifically, in the solid battery 100 in which the positive electrode current collecting layer 10A, the positive electrode layer 20, the solid electrolyte layer 30, the negative electrode layer 40, and the negative electrode current collecting layer 10B are laminated in this order as shown in FIG. As ions move through the solid electrolyte layer 30 between the layer 20 and the negative electrode layer 40, the active material in the positive and negative electrode layers can expand/contract. On the other hand, the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B, which are in contact with the positive electrode layer 20 and the negative electrode layer 40 respectively, cannot expand/contract, or the amount of expansion/contraction may be small relative to the electrode layers. Therefore, when the solid battery 100 is charged and discharged, stress may occur between the integrally sintered positive electrode layer 20 and the positive electrode current collecting layer 10A and between the negative electrode layer 40 and the negative electrode current collecting layer 10B.

In the exemplary embodiment shown in FIG. 2, a solid-state battery 100 has a positive electrode layer 20 comprising an active material capable of swelling during discharge and a negative electrode layer 40 comprising an active material capable of contracting during discharge. Here, the positive electrode layer 20 and the negative electrode layer 40 are integrally sintered with the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B, respectively. When such a solid battery 100 is discharged, the positive electrode layer 20 tries to expand and the negative electrode layer 40 tries to contract, but the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B constrain the respective layers so that they cannot be deformed. Therefore, stress may occur inside the positive electrode layer 20 and the negative electrode layer 40 .

As described above, there is concern that cracks, peeling, and the like may occur in the positive and negative electrode layers that are affected by stress during charging and discharging. In other words, if such cracking or peeling occurs, there is a possibility that charging and discharging of the solid-state battery cannot be carried out favorably.

In view of this problem, the present invention provides a solid battery in which cracking and peeling of the positive and negative electrode layers during charge and discharge are reduced while having a structure in which the battery components are firmly adhered by integral sintering. for the purpose.

The inventors of the present application have tried to solve the above problems by taking a new approach rather than by extending the conventional technology. As a result, the inventors have invented a solid-state battery that achieves the above-described main object.

In order to achieve the above object, one embodiment of the present invention is
a solid state battery,
A positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer,
A solid state battery is provided wherein at least one of the positive electrode layer and the negative electrode layer is provided with a current collecting layer having at least one through opening.

The solid-state battery of the present invention can reduce cracking and peeling of the positive and negative electrode layers during charging and discharging while having a structure in which the battery components are firmly adhered by integral sintering.

Specifically, since the current collecting layer has through openings, the rigidity of the current collecting layer is reduced, and the current collecting layer can easily follow the deformation caused by the volume change of the positive and negative electrode layers during charging and discharging. That is, it is possible to reduce the stress generated between the battery constituent materials due to the volume change of the positive and negative electrode layers. Therefore, it is possible to suitably suppress cracking, peeling, and the like of the positive and negative electrode layers.

FIG. 1 is a cross-sectional view schematically showing an integrally sintered solid battery. FIG. 2 is a cross-sectional view schematically showing the solid-state battery shown in FIG. 1, in which stress is generated in the electrode layers during discharge. 3A to 3C are schematic diagrams of a solid-state battery according to an embodiment of the present invention (FIG. 3A: cross-sectional view of solid-state battery and perspective view of current collection layer; FIG. 3B: solid-state battery with hollow through opening FIG. 3C: Cross-sectional view of a solid-state battery in which the electrode material is embedded in the through-opening). 4A-4F are schematic plan views of a current collecting layer having through openings according to one embodiment of the present invention. 5A to 5C are schematic diagrams of a solid-state battery according to an embodiment of the present invention (FIG. 5A: cross-sectional view of solid-state battery, FIG. 5B: plan view of current collection layer with hollow through opening, FIG. 5C : A plan view of a current collecting layer in which an electrode material is embedded in a through opening). FIG. 6 is a cross-sectional view schematically showing a solid-state battery according to one embodiment of the invention.

The "solid battery" of the present invention will be described in detail below. Although the description will be made with reference to the drawings as necessary, the illustrated contents are only schematically and exemplarily shown for understanding of the present invention, and the external appearance, dimensional ratio, etc. may differ from the actual product.

The “planar view” referred to in this specification is based on the form when an object is viewed from above or below along the thickness direction based on the stacking direction of each layer constituting the solid-state battery. In addition, the term “cross-sectional view” as used herein refers to a form when viewed from a direction substantially perpendicular to the thickness direction based on the lamination direction of each layer constituting the solid-state battery (in short, parallel to the thickness direction form when cut on a smooth surface). "Up-down direction" and "left-right direction" used directly or indirectly in this specification correspond to the up-down direction and left-right direction in the drawings, respectively. Unless otherwise specified, the same reference numerals or symbols indicate the same members/parts or the same meanings. In a preferred embodiment, the downward vertical direction (that is, the direction in which gravity acts) corresponds to the "downward direction", and the opposite direction corresponds to the "upward direction".

As used herein, the term “solid battery” broadly refers to a battery whose components are made of solids, and in a narrow sense, its components (particularly preferably all components) are made of solids. refers to all-solid-state batteries that In a preferred embodiment, the solid-state battery in the present invention is a stacked-type solid-state battery configured such that each layer forming a battery structural unit is stacked with each other, and each such layer is preferably made of a sintered body. The term "solid battery" includes not only a so-called "secondary battery" that can be repeatedly charged and discharged, but also a "primary battery" that can only be discharged. In one preferred aspect of the present invention, the "solid battery" is a secondary battery. "Secondary battery" is not limited to its name, and can include, for example, "power storage device".

[Basic configuration of solid-state battery]
A solid battery has a solid battery laminate that includes at least one battery structural unit along the stacking direction, which consists of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed therebetween.

In a solid battery, each layer constituting the battery is formed by firing, and a positive electrode layer, a negative electrode layer, a solid electrolyte layer, and the like form sintered layers. Preferably, the positive electrode layer, the negative electrode layer, and the solid electrolyte are each integrally sintered with each other, so that the battery constituent units form an integrally sintered body. Here, "integral firing" refers to simultaneously firing a laminated body before firing in which each layer is laminated. It may be formed by any method such as a sheet method. Further, "integrally sintered" refers to being formed by "integrally firing", and "integrally sintered body" refers to being formed by "integral firing".

The positive electrode layer is an electrode layer containing at least a positive electrode active material. The positive electrode layer may further comprise a solid electrolyte and/or a positive current collecting layer. In a preferred aspect, the positive electrode layer is composed of a sintered body including at least positive electrode active material particles, solid electrolyte particles, and a positive electrode current collecting layer. On the other hand, the negative electrode layer is an electrode layer containing at least a negative electrode active material. The negative electrode layer may further comprise a solid electrolyte and/or a negative electrode collector layer. In a preferred embodiment, the negative electrode layer is composed of a sintered body including at least negative electrode active material particles, solid electrolyte particles, and a negative electrode current collecting layer.

A positive electrode active material and a negative electrode active material are substances involved in electron transfer in a solid-state battery. Ions are transferred (conducted) between the positive electrode layer and the negative electrode layer via the solid electrolyte, and electrons are transferred, whereby charging and discharging are performed. The positive electrode layer and the negative electrode layer are preferably layers capable of intercalating and deintercalating lithium ions. In other words, it is preferable that the battery is an all-solid secondary battery in which lithium ions move between the positive electrode layer and the negative electrode layer via the solid electrolyte to charge and discharge the battery.

(Positive electrode active material)
Examples of the positive electrode active material contained in the positive electrode layer include a lithium-containing phosphate compound having a Nasicon type structure, a lithium-containing phosphate compound having an olivine type structure, a lithium-containing layered oxide, and a lithium-containing compound having a spinel type structure. At least one selected from the group consisting of oxides and the like can be mentioned. _{Li3V2 (} PO4) ₃ etc. _are mentioned as an example of the lithium containing phosphate compound which has a Nasicon type structure. _{Li3Fe2 (} PO4) _{3 , LiMnPO4} etc. are mentioned as an example of the lithium containing phosphate compound which has an olivine structure. Examples of lithium-containing layered oxides include LiCoO ₂ and LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ . Examples of lithium-containing oxides having a spinel structure include LiMn ₂ O ₄ and LiNi _0.5 Mn _1.5 O ₄ .

(Negative electrode active material)
Examples of the negative electrode active material contained in the negative electrode layer include oxides containing at least one element selected from the group consisting of Ti, Si, Sn, Cr, Fe, Nb, and Mo, graphite-lithium compounds, lithium alloys, At least one selected from the group consisting of a lithium-containing phosphate compound having a Nasicon-type structure, a lithium-containing phosphate compound having an olivine-type structure, and a lithium-containing oxide having a spinel-type structure. Examples of lithium alloys include Li—Al and the like. _{Li3V2 (} PO4) ₃ etc. _are mentioned as an example of the lithium containing phosphate compound which has a Nasicon type structure. _{Li3Fe2 (} PO4) ₃ etc. _are mentioned as an example of the lithium containing phosphate compound which has an olivine structure. An example of a lithium-containing oxide having a spinel structure includes Li ₄ Ti ₅ O ₁₂ and the like.

In addition, the positive electrode layer and/or the negative electrode layer may contain an electron conductive material. Electron-conductive materials contained in the positive electrode layer and/or the negative electrode layer include at least one metal material such as silver, palladium, gold, platinum, aluminum, copper and nickel, and carbon. Although not particularly limited, copper is less likely to react with the positive electrode active material, the negative electrode active material, the solid electrolyte material, and the like, and is effective in reducing the internal resistance of the solid battery.

Furthermore, the positive electrode layer and/or the negative electrode layer may contain a sintering aid. Sintering aids include at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide and phosphorus oxide.

The thicknesses of the positive electrode layer and the negative electrode layer are not particularly limited, and for example, each may independently be 2 μm or more and 50 μm or less, particularly 5 μm or more and 30 μm or less.

(solid electrolyte)
A solid electrolyte is a material that can conduct lithium ions. In particular, a solid electrolyte, which constitutes a battery structural unit in a solid battery, forms a layer capable of conducting lithium ions between the positive electrode layer and the negative electrode layer. Note that the solid electrolyte may be provided at least between the positive electrode layer and the negative electrode layer. That is, the solid electrolyte may also exist around the positive electrode layer and/or the negative electrode layer so as to protrude from between the positive electrode layer and the negative electrode layer. Specific solid electrolytes include, for example, a lithium-containing phosphate compound having a nasicon structure, an oxide having a perovskite structure, and an oxide having a garnet-type or garnet-like structure. Lithium-containing phosphate compounds having a Nasicon structure include Li _x My (PO ₄ ) ₃ ( _1≤x≤2 , 1≤y≤2, M is selected from the group consisting of Ti, Ge, Al, Ga and Zr). selected at least one). An example of the lithium-containing phosphate compound having a Nasicon structure includes Li _1.2 Al _0.2 Ti _1.8 (PO ₄ ) ₃ and the like. An example of an oxide having a perovskite structure is La _0.55 Li _0.35 TiO ₃ or the like. An example of the oxide having a garnet _- type or _{garnet -} like structure is _Li7La3Zr2O12 .

The solid electrolyte layer may contain a sintering aid. The sintering aid contained in the solid electrolyte layer may be selected, for example, from materials similar to those of the sintering aid that can be contained in the positive electrode layer and/or the negative electrode layer.

The thickness of the solid electrolyte layer is not particularly limited, and may be, for example, 1 μm or more and 15 μm or less, particularly 1 μm or more and 5 μm or less.

(Positive collector layer/negative collector layer)
As the positive electrode current collecting layer that constitutes the positive electrode current collecting layer and the negative electrode current collecting layer that constitutes the negative electrode current collecting layer, it is preferable to use materials having high electrical conductivity, such as silver, palladium, gold, platinum, aluminum, and copper. , nickel and the like are preferably used. In particular, copper is preferable because it hardly reacts with the positive electrode active material, the negative electrode active material, and the solid electrolyte material, and is effective in reducing the internal resistance of the solid battery. Each of the positive electrode current collecting layer and the negative electrode current collecting layer has an electrical connection portion for electrical connection with the outside, and may be configured to be electrically connectable to a terminal. The positive current collecting layer and the negative current collecting layer may each have the form of a foil. From the viewpoint of improving electronic conductivity and reducing manufacturing costs by integral sintering, it is preferable that each of the positive electrode current collecting layer and the negative electrode current collecting layer has a form of integral sintering. In addition, when the positive electrode current collecting layer and the negative electrode current collecting layer have the form of a sintered body, they may be composed of, for example, a sintered body containing an electron conductive material and a sintering aid. The electronically conductive material contained in the positive electrode current collecting layer and the negative electrode current collecting layer may be selected, for example, from the same electronically conductive materials that can be contained in the positive electrode layer and/or the negative electrode layer. The sintering aid contained in the positive electrode current collecting layer and the negative electrode current collecting layer may be selected, for example, from materials similar to those of the sintering aid that can be contained in the positive electrode layer and/or the negative electrode layer.

The thicknesses of the positive electrode current collecting layer and the negative electrode current collecting layer are not particularly limited.

(insulating layer)
The insulating layer is formed, for example, between one battery structural unit and the other battery structural unit that are adjacent to each other along the stacking direction. Thereby, it is possible to avoid migration of ions between such adjacent battery structural units and prevent excessive occlusion and release of ions. The insulating layer may be formed adjacent to the positive electrode layer and/or the negative electrode layer in plan view of the solid battery. An insulating layer broadly refers to a layer composed of a material that does not conduct electricity, that is, a layer composed of a non-conductive material, and in a narrow sense refers to a layer composed of an insulating material. Although not particularly limited, the insulating layer may be made of, for example, a glass material, a ceramic material, or the like. A glass material, for example, may be selected as the insulating layer. Although not particularly limited, glass materials include soda lime glass, potash glass, borate glass, borosilicate glass, borosilicate barium glass, borate glass, barium borate glass, At least one selected from the group consisting of bismuth borosilicate glass, bismuth zinc borate glass, bismuth silicate glass, phosphate glass, aluminophosphate glass, and phosphate glass. can be mentioned.

(protective layer)
A protective layer can generally be formed on the outermost side of a solid-state battery for electrical, physical and/or chemical protection. It is preferable that the material constituting the protective layer is excellent in insulation, durability and/or moisture resistance, and environmentally safe. For example, it is preferable to use glass, ceramics, thermosetting resin and/or photosetting resin.

(Terminal)
Solid-state batteries are generally provided with terminals (for example, external terminals). In particular, terminals are provided on the sides of the solid-state battery. More specifically, a positive electrode side terminal connected to the positive electrode layer and a negative electrode side terminal connected to the negative electrode layer are provided. Such terminals are preferably made of a material with high electrical conductivity. The material of the terminal is not particularly limited, but at least one selected from the group consisting of silver, gold, platinum, aluminum, copper, tin and nickel can be used.

[Features of the solid-state battery of the present invention]
The solid-state battery of the present invention is a battery having a structure in which at least one electrode layer having a current-collecting layer is integrally sintered and the battery components are firmly adhered to each other. It has characteristics.

At least one electrode layer in the present invention is integrally sintered. In integral sintering, a dense structure can be formed between battery constituent materials by firing a plurality of battery constituent materials. That is, the integrally sintered electrode layer has a structure in which the battery components are firmly adhered to each other. Therefore, in the solid-state battery, the movement of electrons and/or ions is facilitated between the strongly adhered battery components, and high electronic conductivity and ionic conductivity can be obtained.

The current collection layer in the present invention has at least one through opening. A plurality of through openings may be provided, and the plurality of through openings may have substantially the same shape. Also, the plurality of through openings may be distributed substantially uniformly. In the exemplary embodiment shown in FIG. 4, the plurality of through openings may have substantially the same shape as each other (see FIGS. 4A-4F), or the plurality of through openings may be substantially uniformly distributed (FIG. 4C). (see FIG. 4F). With the structure described above, the rigidity of the current collecting layer can be uniformly lowered, and the current collecting layer can have good flexibility. By using such a current collecting layer, the current collecting layer can follow the deformation caused by the volume change of the positive and negative electrode layers during charging and discharging, thereby reducing the stress generated between the battery constituent materials. Therefore, it is possible to suitably suppress cracking, peeling, and the like of the positive and negative electrode layers.

As used herein, the term "through opening" refers to a hollow portion in which the material forming the current collecting layer does not exist on the front and back of the current collecting layer in plan view. Also, "through apertures" do not include holes that may be caused by firing or micropores that may be accidentally or undesirably created. For that matter, micropores in porous materials such as porous sintered metals are not included.

The current collecting layer having at least one through opening in the present invention may be provided on one side or both sides of the electrode layer. Alternatively, it may be provided within the electrode layer. The structure described above is preferable from the viewpoint of reducing stress and improving electronic conductivity. That is, by integrally sintering the electrode layer and the low-rigidity collector layer, in a solid battery having high electronic conductivity, cracking and peeling occurring in the positive and negative electrode layers during charging and discharging can be suppressed appropriately.

The terms "substantially identical" and "substantially uniform" as used herein refer not only to cases in which the target shape and/or dimensions are completely the same, but also cases in which the shape and/or dimensions differ to the extent of manufacturing error. It is a concept that also includes

The solid-state battery of the present invention may have any shape in plan view. From the viewpoint of preventing mix-up when mounting on a substrate, the solid-state battery may be rectangular in plan view.

In the exemplary embodiment shown in FIG. 3A, in the battery structural unit 100′, the positive electrode layer 20, the solid electrolyte layer 30, and the negative electrode layer 40 are provided in this order. A positive electrode current collecting layer 10A and a negative electrode current collecting layer 10B are provided. These layers are integrally sintered to form a dense structure between them. That is, the positive electrode layer 20 and the positive electrode current collecting layer 10A and/or the negative electrode layer 40 and the negative electrode current collecting layer 10B that are sintered together have a structure in which the layers are firmly adhered to each other.

In the case of a solid battery comprising a plurality of battery structural units, it is sufficient that a collector layer having a through opening is provided on at least one side of the positive electrode layer or the negative electrode layer in such a solid battery. Other positive electrode layers and negative electrode layers may be provided with current collecting layers having through openings, may be provided with current collecting layers without through openings, or may be provided with no current collecting layers. , or a combination thereof. From the viewpoint of reducing stress and improving electron conductivity, it is preferable that all of the positive electrode layers and the negative electrode layers are provided with current collecting layers having through openings.

In this way, since the current collecting layer has through openings, the rigidity of the current collecting layer is reduced, and the stress generated between the positive and negative electrode layers and the current collecting layer due to the volume change accompanying the expansion/contraction of the positive and negative electrode layers during charging and discharging. can be reduced. In other words, in a solid battery having high electronic conductivity and ionic conductivity due to integral sintering, cracking and peeling occurring in the positive and negative electrode layers during charging and discharging are preferably suppressed. In other words, a solid-state battery with improved long-term reliability can be provided by suppressing a decrease in charge-discharge capacity of the solid-state battery.

In a preferred embodiment, the through openings are arranged such that the current collecting layer forms a geometric shape in plan view of the current collecting layer. Here, the term “geometric shape” refers to a regular shape, for example, a shape in which the through openings are arranged in a lattice shape, a honeycomb shape, or the like in plan view of the current collecting layer. Such a geometrical shape of the current collecting layer allows all points of the electrode layer to be closer to the current collecting layer and have a lower resistance. In addition, by forming a structure in which stress is generated substantially uniformly with respect to force from any direction, strength can be imparted isotropically.

As used herein, the term "lattice" refers to a shape in which a plurality of vertical lines and horizontal lines intersect. Hollow regions partitioned by these lines are rectangular or square. In a broad sense, the term "honeycomb" refers to a structure in which hollow regions of any shape are closely arranged, and in a narrow sense, it refers to a structure in which hexagonal hollow regions are tightly arranged. . The term “hollow region” refers to a hollow region where no material forming the current collecting layer exists over the front and back of the current collecting layer, and as described later, such a region may be filled with an electrode material.

In a further preferred aspect, the through opening has a symmetrical shape in plan view of the current collecting layer. That is, in plan view of the current collecting layer, the through opening has a line-symmetrical shape and/or a point-symmetrical shape. Here, "line symmetry" refers to a shape that overlaps with each other when the figure is inverted around the axis of symmetry in plan view, and "point symmetry" means a shape that is substantially the same even if it is rotated 180 degrees in plan view. refers to what is For example, the symmetrical shape of the through opening may be triangular, rectangular, square, diamond, hexagonal, octagonal, circular, elliptical, and the like. Such a shape of the through opening can prevent stress from concentrating on a specific portion.

In an even more preferred aspect, the current collecting layer has a symmetrical shape in plan view. That is, the planar view shape of the current collecting layer has a line-symmetrical shape and/or a point-symmetrical shape. More specifically, the planar view of the entire current collecting layer provided by the through openings is a line-symmetrical shape and/or a point-symmetrical shape. More preferably, the planar view shape of the current collecting layer as a whole is line-symmetrical and point-symmetrical. In the illustrated exemplary embodiment, the plan view shape of the current collecting layer is preferably a shape as shown in FIGS. 4C to 4F. Such a plan view shape of the current collecting layer can prevent stress from concentrating on a specific portion, and can make the charging/discharging reaction between the positive and negative electrodes more uniform.

In a preferred embodiment, when viewed from the top of the current collecting layer, the dimension of the through opening along the longitudinal direction of the current collecting layer is larger than the dimension of the through opening along the width direction of the current collecting layer. By forming the through opening in such a shape, it is possible to reduce the rigidity of the current collecting layer in the longitudinal direction, which is likely to be distorted due to the change in volume of the positive and negative electrode layers that occurs during charging and discharging, and to reduce the stress more appropriately.

As used herein, the “longitudinal direction” of the solid-state battery refers to the direction along the longitudinal dimension of the current collecting layer in plan view, and the “lateral direction” refers to the lateral dimension of the current collecting layer in plan view. pointing in the direction along In the exemplary embodiment shown in FIG. 3A, in the perspective view of the current collecting layer, the longitudinal direction indicates the horizontal direction of the drawing, and the lateral direction indicates the depth direction of the drawing. Moreover, in the embodiment in FIG. 3A, the longitudinal direction and the lateral direction are substantially perpendicular to each other. The dimension of the through opening along the longitudinal direction of the current collecting layer refers to "L" in FIG. 3A, and the dimension of the through opening along the lateral direction of the current collecting layer refers to "W" in FIG. 3A. .

In a preferred aspect, the width dimension of the solid portion forming the through opening in a plan view of the current collecting layer is substantially the same across the facing direction of the pair of external terminals. By having such a width dimension, the charging/discharging reaction between the positive and negative electrodes can be made more uniform. Also, it is possible to prevent stress from concentrating on a specific portion.

As used herein, the term "opposing direction of a pair of external terminals" refers to a direction in which the battery component is in contact with the external terminal when the battery component is provided with the pair of external terminals. In the exemplary embodiment shown in FIG. 5A, it refers to the direction in which each of the battery building blocks 100′ is in contact with its opposing pair of external terminals (ie, positive terminal 50A and negative terminal 50B). That is, in FIG. 5A, the "facing direction of the pair of external terminals" refers to the horizontal direction of the drawing, and in this embodiment, this direction coincides with the "longitudinal direction" of the solid-state battery. Further, "the width dimension of the solid portion forming the through opening" refers to the dimension of the solid portion between the through openings in the direction substantially perpendicular to the "opposing direction of the pair of external terminals". In the exemplary embodiment shown, the width dimension of the solid portion forming the through opening refers to " _W10 " in FIG. 5B.

In one preferred aspect, the current collecting layer has a mesh structure. Here, in a broad sense, the term "mesh structure" refers to having a plurality of mesh-like structures, and the hollow areas partitioned by the plurality of mesh-like structures are rectangles, triangles, other polygons, and curves such as circles and ellipses. In a narrow sense, the shape of the hollow regions partitioned by the multiple network structures are all approximately the same shape, and the regions are distributed approximately uniformly. refers to a structure in which By forming the current collecting layer into a mesh structure, the rigidity of the current collecting layer can be further reduced. Therefore, it is possible to more effectively reduce the stress generated between the positive and negative electrode layers and the current collecting layer due to the volume change associated with the expansion/contraction of the positive and negative electrode layers during charging and discharging. In addition, it is possible to prevent stress from concentrating on a specific portion, and to make the charging/discharging reaction between the positive and negative electrodes more uniform.

Hollow regions partitioned by a mesh structure in such a mesh structure may be rectangular, circular, hexagonal, or the like. Such hollow regions may be substantially identical in shape and substantially uniformly distributed. Moreover, in order to more effectively prevent stress concentration and to make the charging/discharging reaction between the positive and negative electrodes more uniform, the hollow region is preferably partitioned by a finer network structure. In the illustrated exemplary embodiment, the mesh structure in the current collection layer is a grid-like mesh structure shown in FIG. 4F.

The current collecting layer having through openings as described above may be formed, for example, by pattern printing a current collecting layer precursor of an unfired laminate using screen printing or the like, or may be formed by a green sheet method. It may have been

In a preferred embodiment, the through opening of the current collecting layer is filled with the electrode material of the positive electrode layer or the negative electrode layer. At least part of the through opening may be filled with the electrode material of the positive electrode layer or the negative electrode layer. For example, there may be at least a hollow portion in the through opening of the current collecting layer. In other words, there may be gaps in the through openings of the current collecting layer. In a more preferred embodiment, the entire through opening is filled with the electrode material. In a more preferred embodiment, all through openings in the positive current collecting layer are filled with the positive electrode material, and all through openings in the negative current collecting layer are filled with the negative electrode material. In the exemplary embodiment shown in FIG. 3C, the electrode materials of the positive electrode layer 20 and the negative electrode layer 40 are buried in all of the through openings of the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B, respectively. Here, "the whole through opening" may refer to 90% or more of the hollow area of the through opening, for example, 95% or more.

Since the current collecting layer is a layer that does not undergo charging/discharging reactions, the provision of the current collecting layer reduces the energy density of the solid battery. The volume ratio of layers can be increased. Thereby, a decrease in energy density can be suppressed while providing the current collecting layer. In addition, the force generated by the expansion/contraction of the electrode material present in the current collecting layer acts as a reaction force against the stress generated between the positive and negative electrode layers and the current collecting layer during charging and discharging, and the stress is more effectively reduced. can be reduced to

In a preferred embodiment, the current collecting layer has an aperture ratio of 10% or more and 45% or less due to the through openings in a plan view of the current collecting layer. When the aperture ratio is 10% or more, the stress generated between the positive and negative electrode layers and the current collecting layer can be more effectively reduced, and the desired energy density can be obtained more effectively. . When the open area ratio is 45% or less, disconnection during molding or charging/discharging can be particularly prevented, and desired electronic conductivity can be obtained more effectively. Preferably, the aperture ratio is 10% or more and 35% or less, more preferably 10% or more and 25% or less.

The term “aperture ratio” as used herein refers to the area (S _10A ′) of only the through openings of the positive electrode current collecting layer in plan view divided by the total area (S _10A ) of the positive electrode current collecting layer including the through openings. The value obtained (S _10A '/S _10A ), or the area of only the through openings of the negative electrode current collecting layer in plan view (S _10B ') is divided by the total area of the negative electrode current collecting layer including the through openings (S _10B ). The value (S _10B '/S
_10B ).

In a preferred embodiment, the thickness ratio of the collector layer to the positive electrode layer or the negative electrode layer is 0.02 or more and 2.5 or less. When the thickness ratio is 0.02 or more, disconnection during molding or charging/discharging can be particularly prevented, and desired electronic conductivity can be obtained more effectively. When it is 2.5 or less, the stress generated between the positive and negative electrode layers and the current collecting layer can be more effectively reduced, and the desired energy density can be obtained more effectively. Preferably, the thickness ratio is 0.03 or more and 1.0 or less, more preferably 0.03 or more and 0.6 or less.

The “thickness ratio” as used herein refers to the value (T _10A /T ₂₀ ) obtained by dividing the thickness (T _10A ) of the positive electrode current collecting layer by the thickness (T ₂₀ ) of the positive electrode layer, or the thickness of the negative electrode current collecting layer. It means a value (T _10B /T ₄₀ ) obtained by dividing (T _10B ) by the thickness (T ₄₀ ) of the negative electrode layer. Here, the thickness of each layer refers to the thickness of the portion where only each layer exists in the positive electrode layer and the negative electrode layer when the battery structural unit is viewed in cross section. It refers to the thickness of the part where the current collecting layer exists, regardless of whether the electrode material of the layer is buried or not.

In a preferred embodiment, the width dimension of the solid portion forming the through opening is 50 μm or more and 200 μm or less in plan view of the current collecting layer. When the width of the solid portion forming the through opening is 50 μm or more, disconnection during molding or charging/discharging can be particularly prevented. can be more effectively reduced. Preferably, the width dimension of the solid portion forming the through opening is 50 μm or more and 150 μm or less, more preferably 50 μm or more and 100 μm or less.

The parameters related to the shape of the current collecting layer and the electrode layer described above are obtained by cutting out cross-sections in the cross-sectional view direction and plane view direction by an ion milling device (model number IM4000PLUS manufactured by Hitachi High-Tech Co., Ltd.), scanning electron microscope (SEM) (Hitachi High-Tech Co., Ltd.) It refers to the dimension measured from the image observed using the model number SU-8040 manufactured by Co., Ltd., or the value calculated from the dimension.

In a preferred embodiment, the current collecting layer has a Young's modulus of 70 GPa or more and 100 GPa or less. When the Young's modulus is 70 GPa or more, disconnection during molding or charging/discharging can be particularly prevented. be able to. Preferably, Young's modulus is 70 GPa or more and 90 GPa or less, more preferably 70 GPa or more and 80 GPa or less.

The Young's modulus of the current collecting layer mentioned above refers to a value measured by a method according to the JIS standard (JIS R 1602). A desktop precision universal testing machine (manufactured by Shimadzu Corporation, Model No. AGS-5kNX) was used to measure the Young's modulus.

The solid-state battery according to the present invention is a stacked-type solid-state battery in which each layer constituting the battery structural unit is laminated, and is manufactured by a printing method such as a screen printing method, a green sheet method using a green sheet, or a combination thereof. can do. Therefore, each layer constituting the battery structural unit is composed of a sintered layer, and the positive electrode layer, the negative electrode layer, the solid electrolyte, and the current collecting layer provided on the positive electrode layer and/or the negative electrode layer are integrally sintered with each other. It is In other words, it can be said that the battery structural unit constitutes an integrally sintered body. In such an integrally sintered body, the current collecting layer has through openings.

For example, taking the embodiment shown in FIG. 3A as an example, in the battery structural unit 100′, the positive electrode layer 20, the solid electrolyte layer 30, and the negative electrode layer 40 are provided in this order, and the through openings are provided on one side of the positive electrode layer 20 and the negative electrode layer 40. A positive electrode current collecting layer 10A and a negative electrode current collecting layer 10B are provided, respectively, and these layers are firmly adhered by integral sintering. In this embodiment, from the viewpoint of improving electron conductivity, a positive electrode current collecting layer 10A and a negative electrode current collecting layer 10B having through openings are provided on one side of both the positive electrode layer 20 and the negative electrode layer 40 . In addition, from the viewpoint of preventing stress from concentrating on a specific portion and uniformizing the charging and discharging reaction between the positive and negative electrodes, the current collecting layer has a grid-like mesh structure. As shown in FIG. 3B, the through openings of the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B may each be hollow. Electrode materials of the positive electrode layer 20 and the negative electrode layer 40 may be embedded in the through openings of the current layer 10A and the negative electrode current collecting layer 10B, respectively.

A more realistic aspect of the solid-state battery will now be described. Although it is just one example, taking the aspect shown in FIG. 5A as an example, the parallel stacked all-solid-state battery 100 has a plurality of battery configurations in which the positive electrode layer 20, the solid electrolyte layer 30, and the negative electrode layer 40 are provided in this order. The unit 100' may be provided, and one battery structural unit 100' and the other battery structural unit 100' adjacent to each other along the stacking direction are continuously and integrally sintered via the solid electrolyte layer 30. may be configured. In this embodiment, from the viewpoint of improving electron conductivity, the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B having through openings are provided on one side of all the positive electrode layers 20 and the negative electrode layers 40 . Alternatively, as shown in FIG. 6, one battery structural unit 100′ and the other battery structural unit 100′ adjacent to each other along the stacking direction are separated by an insulating layer 70 and integrally sintered. good. From the viewpoint of preventing excessive occlusion and release of ions between adjacent battery structural units and reducing the volume change of the positive and negative electrode layers during charging and discharging, one battery structural unit 100' adjacent to each other along the stacking direction is used. and the other battery structural unit 100' may be separated by the insulating layer 70 and integrally sintered.

The solid-state battery may further include terminals (external terminals). That is, the parallel-stacked all-solid-state battery 100 has a positive electrode terminal 50A electrically connected to the positive electrode current collecting layer 10A at one end of the battery structural unit 100′ and a negative electrode collector at the other end of the battery structural unit. A negative electrode terminal 50B electrically connected to the electrode layer 10B may be provided. More specifically, the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B each have an electrical connection at one end thereof for electrical connection with the outside. They are electrically connected to the positive terminal 50A and the negative terminal 50B, respectively.

As shown in FIG. 5B, the through openings of the positive electrode current collecting layer 10A and the negative electrode current collecting layer 10B may each be hollow. From the viewpoint of improving energy density and reducing stress, as shown in FIG. good.

The solid state battery may further comprise a protective layer. That is, a protective layer 60 or the like may be provided outside the solid battery laminate, the positive electrode terminal 50A, and the negative electrode terminal 50B so as to be integrally laminated with the solid battery laminate.

[Manufacturing method of solid-state battery]
As described above, the solid-state battery of the present invention can be manufactured by a printing method such as a screen printing method, a green sheet method using a green sheet, or a combination thereof. In the following, for the sake of understanding of the present invention, a case where a printing method is employed will be described in detail, but the present invention is not limited to this method.

The method for producing a solid-state battery of the present invention includes at least a step of forming an unfired laminate by a printing method and a step of firing the unfired laminate.

(Step of forming unfired laminate)
In this step, several kinds of pastes such as a positive electrode layer paste, a negative electrode layer paste, a solid electrolyte paste, a collector layer paste, and a protective layer paste are used as inks. In other words, a non-fired laminate having a predetermined structure is formed on the supporting substrate by applying the paste by a printing method.

The paste is a predetermined constituent material of each layer selected appropriately from the group consisting of a positive electrode active material, a negative electrode active material, an electron conductive material, a solid electrolyte material, a current collecting layer material, an insulating material, and a sintering aid. , can be prepared by wet-mixing an organic material dissolved in a solvent with an organic vehicle. The positive electrode layer paste contains, for example, a positive electrode active material, an electron conductive material, a solid electrolyte material, an organic material and a solvent. The negative electrode layer paste contains, for example, a negative electrode active material, an electron conductive material, a solid electrolyte material, an organic material and a solvent. The solid electrolyte layer paste contains, for example, a solid electrolyte material, a sintering aid, an organic material and a solvent. The positive electrode current collecting layer paste and the negative electrode current collecting layer paste contain an electronic conductive material, a sintering aid, an organic material and a solvent. The protective layer paste contains, for example, an insulating material, an organic material and a solvent. The insulating layer paste contains, for example, an insulating material, an organic material and a solvent.

Although the organic material contained in the paste is not particularly limited, at least one polymer material selected from the group consisting of polyvinyl acetal resin, cellulose resin, polyacrylic resin, polyurethane resin, polyvinyl acetate resin, polyvinyl alcohol resin, etc. can be used. The solvent is not particularly limited as long as it can dissolve the organic material, and for example, toluene and/or ethanol can be used.

Media can be used for wet mixing, and specifically, a ball mill method, a Visco mill method, or the like can be used. On the other hand, a wet mixing method that does not use media may be used, such as a sand mill method, a high-pressure homogenizer method, or a kneader dispersion method.

The support substrate is not particularly limited as long as it can support the green laminate, and for example, a substrate made of a polymer material such as polyethylene terephthalate can be used. When the unfired laminate is held on the substrate and subjected to the firing step, the substrate may be one that exhibits heat resistance to the firing temperature.

In printing, by sequentially laminating printed layers with a predetermined thickness and pattern shape, an unfired laminate corresponding to a predetermined solid battery structure can be formed on the substrate. A drying process is performed when forming each print layer. The drying process causes the solvent to evaporate from the green laminate. After forming the unfired laminate, the unfired laminate may be peeled off from the substrate and subjected to the firing step, or the unfired laminate may be subjected to the firing step while being held on the support substrate. good too.

(Baking process)
In the firing step, the unfired laminate is subjected to firing. Although it is only an example, firing is performed in a nitrogen gas atmosphere containing oxygen gas or in the air, for example, at 500 ° C., after removing the organic material, in a nitrogen gas atmosphere or in the air, for example, 550 ° C. or higher and 1000 ° C. or lower. It is carried out by heating at The firing may be performed while pressing the unfired laminate in the stacking direction (in some cases, the stacking direction and the direction perpendicular to the stacking direction).

Through such firing, a battery structural unit is formed from the unfired laminate, and finally a desired solid battery is obtained.

(Regarding the preparation of characteristic portions in the present invention)
For the current collecting layer having through openings, for example, a current collecting layer precursor of an unfired laminate may be pattern-printed using screen printing or the like so that at least one through opening is provided. By firing such a current-collecting layer precursor, it is possible to obtain a solid-state battery having desired battery structural units comprising a current-collecting layer having through openings. The current collecting layer having through openings can be obtained by screen printing, but can also be obtained by using a resin raw material paste that disappears after baking so as to form at least one through opening. For example, a paste comprising an organic vehicle may be used to form the through openings. In such a case, the portion coated with such a paste can disappear during firing, so that a desired battery structural unit having through openings in the current collecting layer can be obtained. Similarly, a current collecting layer having through openings can be obtained by using a raw material paste containing a resin filler that can disappear during firing so as to form at least one through opening. According to the above method, a current collecting layer having a plurality of through openings, a current collecting layer having a plurality of through openings having substantially the same shape as each other, or a current collecting layer having a geometric shape in plan view are arranged. It is possible to obtain a current collecting layer, etc.

Although the embodiments of the present invention have been described above, they are merely examples of typical examples. Accordingly, those skilled in the art will easily understand that the present invention is not limited to this, and that various embodiments are conceivable without changing the gist of the present invention.

For example, in the above description, the battery structural unit illustrated in FIG. 3A, for example, has been mainly described, but the present invention is not necessarily limited to this. In the present invention, a battery structural unit having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and provided with a current collecting layer having at least one through opening for at least one of the positive electrode layer and the negative electrode layer. , can be similarly applied. Moreover, when the current collecting layer has a plurality of through openings, the shapes of the plurality of through openings do not necessarily have to be substantially the same as each other in plan view of the current collecting layer, and may include different shapes.

INDUSTRIAL APPLICABILITY The solid-state battery of the present invention can be used in various fields where power storage is assumed. Although it is only an example, the solid battery of the present invention is used in the electric, information, and communication fields where mobile devices and the like are used (for example, mobile phones, smartphones, laptop computers and digital cameras, activity meters, arm computers, electronic paper mobile devices such as mobile devices), home and small industrial applications (e.g. electric tools, golf carts, household, nursing care and industrial robots), large industrial applications (e.g. forklifts, elevators, harbor cranes) , transportation systems (for example, hybrid vehicles, electric vehicles, buses, trains, electrically assisted bicycles, electric motorcycles, etc.), power system applications (for example, various power generation, road conditioners, smart grids, general household installation type storage systems, etc.) field), medical use (medical device field such as earphone hearing aid), medical use (field of medication management system, etc.), IoT field, space / deep sea use (e.g., space probe, underwater research ship, etc.) ), etc., can be used.

10 collector layer 10A positive collector layer 10B negative collector layer 20 positive electrode layer 30 solid electrolyte layer 40 negative electrode layer 50 terminal 50A positive electrode terminal 50B negative electrode terminal 60 protective layer 70 insulating layer 100' battery structural unit 100 solid battery

Claims (11)

a solid state battery,
A positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer,
At least one of the positive electrode layer and the negative electrode layer is provided with a current collecting layer having at least one through opening ,
A solid-state battery , wherein the current collecting layer comprises a sintered layer . a solid state battery,
A positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer,
At least one of the positive electrode layer and the negative electrode layer is provided with a current collecting layer having at least one through opening ,
A solid battery , wherein the positive electrode layer, the negative electrode layer and the solid electrolyte layer are integrally sintered . 3. The solid-state battery according to claim 1, wherein the current collecting layer is provided with a plurality of through-openings, and the plurality of through-openings have substantially the same shape. 4. The solid-state battery according to any one of claims 1 to 3 , wherein said through openings are arranged such that said current collecting layer forms a geometric shape in plan view of said current collecting layer. Claims 1 to 1, wherein, in a plan view of the current collecting layer, the dimension of the through opening along the longitudinal direction of the current collecting layer is larger than the dimension of the through opening along the lateral direction of the current collecting layer. 5. The solid battery according to any one of 4 . 6. The device according to any one of claims 1 to 5 , wherein, in a plan view of the current collecting layer, the width dimension of the solid portion forming the through opening is substantially the same along the facing direction of the pair of external terminals. solid state battery. The solid-state battery according to any one of claims 1 to 6 , wherein the current collecting layer has an aperture ratio of 10% or more and 45% or less due to the through openings in a plan view of the current collecting layer. The solid-state battery according to any one of claims 1 to 7 , wherein a thickness ratio of said collector layer to said positive electrode layer or said negative electrode layer is 0.02 or more and 2.5 or less. 9. The solid-state battery according to claim 1 , wherein at least part of said through-hole is filled with the electrode material of said positive electrode layer or said negative electrode layer. The solid-state battery according to any one of claims 1 to 9 , wherein said current collecting layer has a mesh structure. 11. The solid state battery according to claim 1 , wherein said positive electrode layer and said negative electrode layer are layers capable of intercalating and deintercalating lithium ions.

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