JP2017195033A - All-solid type secondary battery, method for manufacturing the same, and laminate green sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid type secondary battery with a high battery performance by simple manufacturing steps.SOLUTION: An all-solid type secondary battery comprises: a positive electrode layer laminated on one face of a positive electrode current collector; a negative electrode layer laminated on one face of a negative electrode current collector; and a solid electrolyte layer disposed between the positive and negative electrode layers. The all-solid type secondary battery has a cavity extending along an inter-layer plane at least either between the current collector and positive electrode layer thus laminated or between the negative electrode current collector and negative electrode layer thus laminated from a center to ends of the inter-layer plane, and opened to the outside at the ends.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique related to an all-solid-state secondary battery and a laminate green sheet.

As electronic devices such as notebook personal computers, mobile phones typified by smartphones, and digital cameras become more sophisticated, the power consumption of these electronic devices is increasing. In addition, miniaturization of these electronic devices is required. For this reason, the further high energy density is calculated | required with respect to the secondary battery used for an electronic device.
High energy density is also required for household storage batteries that are stationary applications. Further, in recent years, with the expansion of demand for secondary batteries for in-vehicle applications such as hybrid vehicles and electric vehicles, it is required to achieve both higher output density and higher energy density of secondary batteries.

In addition to this, since an organic solvent is used for the electrolyte in the secondary battery, there is a risk of leakage of the electrolyte or acceleration of thermal runaway, and there is a demand for improved safety of the secondary battery. .
At present, the most promising secondary battery that satisfies these requirements is an all-solid-state lithium ion secondary battery in which the entire configuration of the negative electrode layer, the electrolyte layer, and the positive electrode layer is made of a solid material. This all-solid-state lithium ion secondary battery is being developed as a battery having high energy density, high safety, and long life.

  However, the all-solid-state lithium ion secondary battery currently in practical use is an all-solid-state secondary battery in which each of the negative electrode layer, the solid electrolyte layer, and the positive electrode layer is very thin, and the energy density is not high. Furthermore, since the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are produced by vapor deposition or sputtering, it is necessary to produce an all solid lithium ion secondary battery in a reduced pressure atmosphere, and the conventional production method has a large area. Not suitable for mass production and mass production.

Therefore, as disclosed in Patent Document 1 to Patent Document 3, by firing the green sheets of the respective layers constituting the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, the entire area that enables large area and mass production is achieved. Techniques for producing solid lithium ion secondary batteries are being studied.
In Patent Document 1, a positive electrode layer green sheet and a negative electrode layer green sheet are fired to produce a positive electrode layer fired body and a negative electrode layer fired body, and then a positive electrode layer fired body and a negative electrode through an ion conductive inorganic material layer green sheet. It describes that a layered fired body is sandwiched and refired to form a laminated fired body. Patent Document 1 discloses an all-solid-state secondary battery produced by sandwiching the laminated fired body between two current collector plates.

In Patent Document 2, a positive electrode layer green sheet, an ion conductive inorganic material layer green sheet, and a negative electrode layer green sheet are sequentially laminated to form a laminated body, and the laminated body is collectively fired to form a laminated fired body. An all solid state secondary battery produced by sandwiching a laminated fired body between two current collector plates is disclosed.
Patent Document 3 discloses a laminate green in which a positive electrode layer green sheet and a negative electrode layer green sheet are printed on both surfaces of an ion conductive inorganic material layer green sheet, and each metal foil current collector paste is printed on the upper layer. An all-solid secondary battery produced by batch firing sheets is disclosed.

JP 2000-340255 A Japanese Patent No. 4845244 Japanese Patent No. 5430930

However, as described in Patent Document 1, when a laminated fired body including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is sandwiched between a positive electrode current collector and a negative electrode current collector, the positive electrode current collector, the positive electrode layer, and the negative electrode current collector are sandwiched. There is a problem that the interface resistance between the electric body and the negative electrode layer is high and the battery performance is poor. Moreover, in order to produce an all-solid-state secondary battery, it is necessary to go through a baking process twice, and there also exists a subject that manufacturing efficiency is bad.
Further, as described in Patent Document 2, when the laminated green sheet obtained by bonding the green sheets of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer is collectively fired, the firing process is one process. In comparison, the production efficiency is high. However, the invention disclosed in Patent Document 2 has a problem that the interface resistance between the positive electrode current collector plate and the positive electrode layer and the interface resistance between the negative electrode current collector plate and the negative electrode layer are high.

Furthermore, as described in Patent Document 3, a laminate green sheet formed by laminating a positive electrode current collector green sheet, a positive electrode layer green sheet, a solid electrolyte layer green sheet, a negative electrode layer green sheet, and a negative electrode current collector green sheet is provided. When batch firing is performed, it is considered that the interface resistance between the positive electrode current collector and the positive electrode layer and between the negative electrode current collector and the negative electrode layer is reduced. However, since the positive electrode layer green sheet and the negative electrode layer green sheet are printed on both surfaces of the solid electrolyte layer green sheet, and the metal foil current collector paste is printed on the upper layer, the manufacturing method is complicated. is there.
The present invention has been made in view of the above points, and provides an all-solid-state secondary battery having high battery performance, a laminate green sheet used for obtaining the same, and a method for producing the same. Objective.

In order to solve the above problems, an all-solid-state secondary battery according to one embodiment of the present invention includes an interlayer between a current collector and a positive electrode layer and an interlayer between a current collector and a negative electrode layer. It has a gap that extends from the center to the end of the surface along the surface between the layers and is open to the outside.
Further, the laminate green sheet according to one embodiment of the present invention includes an interlayer surface between at least one of the layers between the current collector and the positive electrode layer green sheet and between the current collector and the negative electrode layer green sheet. Having a void-forming layer extending from the center to the end of the surface along
The void-forming layer contains a binder and a porous conductor, and the thermal decomposition start temperature of the binder contained in the void-forming layer is the heat of the binder contained in the positive electrode layer green sheet, the solid electrolyte layer green sheet, and the negative electrode layer green sheet. It is characterized by being lower than the decomposition start temperature.
In addition, the method for manufacturing an all-solid-state secondary battery according to one embodiment of the present invention includes: laminating the laminated green sheet according to the one embodiment; and laminating and stacking the stacked current collector and the positive electrode layer. A gap extending from the center of the surface to the end along the surface of the interlayer is formed between at least one of the layers of the current collector and the negative electrode layer.

  According to the aspect of the present invention, it is possible to reduce the interface resistance of at least one of the interface resistance between the positive electrode current collector and the positive electrode layer and the interface resistance between the negative electrode current collector and the negative electrode layer with a simple means. Thus, it is possible to provide an all-solid secondary battery with high battery performance.

It is sectional drawing which shows the structure of the all-solid-state secondary battery described in 1st Embodiment based on this invention. It is a horizontal sectional view which shows the formation form of the 1st space | gap in the all-solid-state secondary battery described in 1st Embodiment based on this invention. It is a horizontal sectional view which shows the formation form of the 2nd space | gap in the all-solid-state secondary battery described in 1st Embodiment based on this invention. It is sectional drawing which shows the structure of the laminated body green sheet described in 1st Embodiment based on this invention. It is sectional drawing which shows the structure of the series all-solid-state secondary battery described in 2nd Embodiment based on this invention. It is sectional drawing which shows the structure of the continuous laminated body green sheet described in 2nd Embodiment based on this invention. It is sectional drawing which shows the structure of the laminated body green sheet described in 2nd Embodiment based on this invention.

Next, embodiments of the present invention will be described with reference to the drawings.
Here, the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones.
Further, the embodiment described below exemplifies a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention is that the material, shape, structure, etc. of the component parts are as follows. It is not something specific. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims. That is, the all-solid-state secondary battery and the laminate green sheet according to the present invention, the method for producing the laminate-green sheet, and the method for producing the all-solid-state secondary battery are not limited to the embodiments described below. It is possible to make design changes based on the knowledge of those skilled in the art, and embodiments to which such changes are made are also included in the scope of the embodiments of the present invention.

<First Embodiment>
In the following first embodiment, a single-layer all-solid secondary battery and a method for manufacturing an all-solid secondary battery according to the present invention will be described. Further, in the following first embodiment, an all-solid secondary battery according to the present invention, a laminate green sheet used for the production thereof, a method for producing a laminate green sheet, and a method for producing an all-solid secondary battery An example will be described.

(1-1) Configuration of all-solid secondary battery [Configuration of all-solid secondary battery]
FIG. 1 is a cross-sectional view of an all solid state secondary battery described in the first embodiment.
As shown in FIG. 1, the all-solid-state secondary battery 1 according to the first embodiment has a positive electrode layer 12 laminated on one surface of a positive electrode current collector 11 and a negative electrode current collector 15 on one surface. A negative electrode layer 14 is laminated, and an inorganic solid electrolyte layer (hereinafter referred to as a solid electrolyte layer) 13 is disposed between the positive electrode layer 12 and the negative electrode layer 14.

Further, there is a gap between at least one of the layers between the positive electrode current collector 11 and the positive electrode layer 12 and the negative electrode current collector 15 and the negative electrode layer 14. In the first embodiment, the case where the gap 16 is formed between the negative electrode current collector 15 and the negative electrode layer 14 is illustrated.
As shown in FIGS. 2 and 3, the gap 16 extends from the center to the end of the surface along the surface between the layers and is open to the outside. 2 and 3 exemplify the case where the gap 16 is formed as a groove extending along the surface of the negative electrode layer 14. In the example of FIG. 2, the gap 16 passes through the center in the surface direction of the negative electrode layer 14. The case where it has extended so that it may each penetrate to the edge part of a vertical direction and a horizontal direction is illustrated. FIG. 3 illustrates a case where the gap 16 is formed by a groove extending vertically.
As will be described in detail later, this configuration is a laminate green sheet in which a positive electrode current collector 11, a positive electrode layer green sheet 12a, a solid electrolyte layer green sheet 13a, and a negative electrode layer green sheet 14a in which a void forming layer 17 is embedded are laminated. And, it is realized by the manufacturing method of the all-solid-state secondary battery 1 in which the simultaneous firing is performed in a state where the negative electrode current collector 15 is bonded.

(Solid electrolyte layer)
The solid electrolyte layer 13 includes at least one of a solid electrolyte and glass that becomes a solid electrolyte after firing.
The solid electrolyte contained in the solid electrolyte layer and the glass that becomes the solid electrolyte after firing are not particularly limited as long as the material has low electron conductivity and high lithium ion conductivity. For example, an oxide solid electrolyte or sulfide Amorphous bodies (glass bodies), crystal bodies, glass ceramics, and the like of physical solid electrolytes are used. In particular, an oxide-based solid electrolyte that can be fired at high temperature is preferable, and a NASICON type oxide, a perovskite type oxide, a LISICON type oxide, a garnet type oxide, an oxide glass, or the like is preferably used. Examples of the oxide-based solid electrolyte that can be fired at such a high temperature include Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ , Li _0.29 La _0.571 TiO ₃ , Li ₄ SiO ₄ —Li ₃ PO ₄ , Li ₃ BO ₃ —Li ₃ PO ₄ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li _3.4 V _{0 .6} Si _0.4 O ₄ or the like can be used.

  The thickness of the solid electrolyte layer 13 is preferably in the range of 1 μm to 500 μm. When the thickness of the solid electrolyte layer 13 is thinner than 1 μm, the positive electrode layer 12 and the negative electrode layer 14 are easily short-circuited, and not only the performance of the all-solid-state secondary battery 1 may be reduced but also the safety may be reduced. There is. Moreover, when the thickness of the solid electrolyte layer 13 is thicker than 500 μm, the movement of conductive ions such as lithium ions in the solid electrolyte layer 13 is likely to be inhibited, and the output of the all-solid secondary battery 1 may be lowered. .

(Positive electrode layer)
The positive electrode layer 12 includes a positive electrode active material and at least one of a solid electrolyte and a glass that becomes a solid electrolyte after firing.
The positive electrode active material contained in the positive electrode layer 12 may be any material that can occlude and release lithium ions, and is not particularly limited. The positive electrode layer 12 contains, as a positive electrode active material, an active material that exhibits a higher potential than the active material contained in the negative electrode layer 14.

As the positive electrode active material, for example, lithium nickel cobalt manganese oxide _{(LiNixCo1-y-xMnyO 2)} , lithium cobalt oxide (LiCoO _2), lithium nickelate (LiNiO _2), lithium manganate (LiMn ₂ O _4), phosphoric acid Lithium transition metal compounds such as lithium iron (LiFePO ₄ ), lithium cobalt phosphate (LiCoPO ₄ ), lithium manganese phosphate (LiMnPO ₄ ), and lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ) may be used. it can.

  Further, as the solid electrolyte contained in the positive electrode layer 12, the same material as the solid electrolyte contained in the solid electrolyte layer 13 can be used. Two or more solid electrolytes contained in the positive electrode layer 12 may be mixed and used. The solid electrolyte contained in the positive electrode layer 12 may be the same as or different from the solid electrolyte contained in the solid electrolyte layer 13 and the negative electrode layer 14 described later.

The positive electrode layer 12 may contain a conductive additive. The conductive auxiliary agent is not particularly limited as long as it has conductivity. For example, a conductive carbon material, particularly carbon black, activated carbon, carbon carbon fiber, or the like can be used.
The content of the conductive additive in the positive electrode layer 12 is preferably more than 0% by mass and less than 90% by mass with respect to the mass of the positive electrode active material. This is because if the content of the conductive auxiliary is 90% by mass or more, the amount of the positive electrode active material in the positive electrode layer 12 may be insufficient and the lithium storage capacity may be reduced.
The positive electrode layer 12 can be selected to have an arbitrary thickness according to a desired battery capacity.

(Negative electrode layer)
The negative electrode layer 14 includes a negative electrode active material and at least one of a solid electrolyte and glass that becomes a solid electrolyte after firing.
The negative electrode active material included in the negative electrode layer 14 may be any material that can occlude and release lithium ions, and is not particularly limited. The negative electrode layer 14 contains, as a negative electrode active material, an active material that shows a lower potential than the active material contained in the positive electrode layer 12.

Examples of the negative electrode active material include carbon materials such as hard carbon, soft carbon, and graphite, alloy materials such as Sn-based alloys and Si-based alloys, nitrides such as LiCoN, and lithium titanate (Li ₄ Ti ₅ O ₁₂ ). Lithium transition metal oxides such as lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ) can be used. Moreover, you may use metal lithium foil as a negative electrode active material.

  Further, as the solid electrolyte contained in the negative electrode layer 14, the same material as the solid electrolyte contained in the solid electrolyte layer 13 and the positive electrode layer 12 can be used. Two or more kinds of solid electrolytes contained in the negative electrode layer 14 may be mixed and used. Further, the solid electrolyte contained in the negative electrode layer 14 may be the same as or different from the solid electrolyte contained in the solid electrolyte layer 13 and the positive electrode layer 12.

The negative electrode layer 14 may contain a conductive additive. The conductive auxiliary agent is not particularly limited as long as it has conductivity similar to the conductive auxiliary agent contained in the positive electrode layer 12. For example, a conductive carbon material, particularly carbon black, activated carbon, carbon carbon fiber, or the like is used. be able to.
The content of the conductive additive in the negative electrode layer 14 is preferably more than 0% by mass and less than 90% by mass with respect to the mass of the negative electrode active material. This is because when the content of the conductive auxiliary is 90% by mass or more, the amount of the negative electrode active material in the negative electrode layer 14 is insufficient, and the lithium storage capacity may be reduced.
The negative electrode layer 14 can be selected to have an arbitrary thickness according to a desired battery capacity.

(Void)
The void 16 may be formed in at least one of the layer between the stacked positive electrode current collector 11 and the positive electrode layer 12 and the layer between the stacked negative electrode current collector 15 and the negative electrode layer 14. It suffices if it extends from the center in the surface direction to the end in the surface direction and opens to the outside. In FIGS. 2 and 3, the gap is formed on the negative electrode layer 14 side of the interlayer between the stacked negative electrode current collector 15 and negative electrode layer 14. However, the void may be formed on the current collector 15 side. .

By forming voids 16 that are open to the outside between the layers as described above, the decomposition gas of the binder generated in the firing process of the laminate green sheet can be discharged out of the laminate without any delay, and cracks are generated in the laminate fired body, resulting in battery performance. Can be suppressed.
Here, without being limited to the configuration shown in FIG. 1, the gap 16 may be formed between the positive electrode current collector 11 and the positive electrode layer 12. In addition, the gap 16 may be formed both between the stacked positive electrode current collector 11 and the positive electrode layer 12 and between the stacked negative electrode current collector 15 and the negative electrode layer 14.

Moreover, the space | gap 16 will not be limited to the extended form of FIG.2 and FIG.3, if it extends from the center part of the surface direction of an interlayer to an edge part, and is open | released outside. The gap may extend, for example, so as to meander along the surface, that is, in a curved shape.
In plan view, the area of the gap 16 at the surface position between the layers is preferably 0.5% or more and less than 10% of the contact area between the metal current collector and the electrode layer. The size (depth) of the gap 16 in the thickness direction is preferably 5% or more and less than 20% of the thickness of the electrode layer to be formed. When these conditions deviate greatly, there is a possibility that the battery performance will be deteriorated due to cracks in the electrode layer, or electronic conduction being inhibited between the current collector and the electrode layer.
In addition, the cross-sectional shape of the groove | channel which comprises the space | gap 16 does not need to be a rectangle, A semicircle shape etc. may be sufficient.

(Metal current collector)
In the present embodiment, the positive electrode current collector 11 stacked in close contact with the positive electrode layer 12 and the negative electrode current collector 15 stacked in close contact with the negative electrode layer 14 are metal foil current collectors each composed of a metal foil. The case where it comprises is illustrated. In the present specification, when both the positive electrode current collector 11 and the negative electrode current collector 15 are indicated, or when the positive electrode current collector 11 and the negative electrode current collector 15 are not distinguished, the positive electrode current collector 11 is used. The negative electrode current collector 15 may be referred to as a “metal current collector”.

  The material of the metal current collector is not particularly limited as long as it is a conductive material. For example, a metal material such as stainless steel, nickel, aluminum, iron, titanium, copper, palladium, gold and platinum may be used. it can. The material for the metal current collector is preferably selected in consideration of not being melted and decomposed under the firing conditions described later, or the battery operating potential and conductivity applied to the metal current collector.

  The thickness of the metal current collector is preferably 3 μm or more and 50 μm or less. When the thickness of the metal foil current collector is 3 μm or more and 50 μm or less, the metal foil current collector is not easily cracked during the production of the laminated fired body, and the thickness sufficiently supports the laminated green sheet 10 Is obtained.

(1-2) Configuration of Laminated Green Sheet Hereinafter, the laminated green sheet 10 of the present embodiment will be described.
[Configuration of laminated green sheet]
FIG. 4 is a cross-sectional view of the multilayer green sheet 10 used in the first embodiment.
As shown in FIG. 4, the laminate green sheet 10 in the first embodiment includes a positive electrode current collector 11 made of a metal foil current collector, and a positive electrode layer green sheet 12 a provided on the positive electrode current collector 11. The solid electrolyte layer green sheet 13a provided on the positive electrode layer green sheet 12a, the negative electrode layer green sheet 14a provided on the solid electrolyte layer green sheet 13a, and the negative electrode current collector provided on the negative electrode layer green sheet 14a A negative electrode current collector 15 composed of a body 15 and a void forming layer 17 disposed between the negative electrode layer green sheet 14 a and the negative electrode current collector 15 are provided.

4 illustrates the case where the all-solid-state secondary battery 1 of FIG. 1 is formed, and thus illustrates the case where the gap forming layer 17 is disposed between the negative electrode layer green sheet 14a and the negative electrode current collector 15. ing. What is necessary is just to provide the space | gap formation layer 17 according to the all-solid-state secondary battery 1 to form.
As will be described later, the binder contained in the void forming layer 17 is one that is more easily decomposed by heat than the binder contained in each of the positive electrode layer green sheet 12a, the solid electrolyte layer green sheet 13a, and the negative electrode layer green sheet 14a. Form. That is, the gap forming layer 17 is formed so that the gap 16 is formed faster than the binder of each green sheet is decomposed.
Hereinafter, each green sheet and the void forming layer 17 will be described.

(Solid electrolyte layer green sheet)
The solid electrolyte layer green sheet 13a is formed using a slurry for solid electrolyte in which a binder made of a solid electrolyte and an organic resin is dispersed in a solvent. That is, the solid electrolyte layer green sheet 13a is formed by applying or printing the solid electrolyte slurry on the positive electrode layer green sheet 12a or the negative electrode layer green sheet 14a described later and drying. The method for preparing the solid electrolyte slurry is not particularly limited.
The solid electrolyte layer 13 is obtained by firing the solid electrolyte layer green sheet 13a.

(Positive layer green sheet)
The positive electrode layer green sheet 12a is formed using a positive electrode slurry in which a binder composed of a positive electrode active material, a solid electrolyte, and an organic substance is dispersed in a solvent. That is, the positive electrode slurry is applied or printed on the positive electrode current collector 11 or the solid electrolyte layer green sheet 13a made of a metal foil current collector, and dried to form the positive electrode layer green sheet 12a. When the gap 16 is formed between the positive electrode current collector 11 and the positive electrode layer 12, a gap forming layer 17 described later is formed on the positive electrode current collector 11 in advance, and the positive electrode layer green sheet 12a is fired. Thus, the positive electrode layer 12 is obtained.

(Negative electrode layer green sheet)
The negative electrode layer green sheet 14a is formed using a negative electrode slurry in which a binder made of a negative electrode active material, a solid electrolyte, and an organic substance is dispersed in a solvent. That is, the negative electrode slurry is applied or printed on the negative electrode current collector 15 or the solid electrolyte layer green sheet 13a made of a metal foil current collector, and dried to form the negative electrode layer green sheet 14a. When the gap 16 is formed between the negative electrode current collector 15 and the negative electrode layer 14, a gap forming layer 17 described later is formed on the negative electrode current collector 15 in advance, and the negative electrode layer green sheet 14a is fired. Thus, the negative electrode layer 14 is obtained.

(Void forming layer)
The void forming layer 17 only needs to contain a binder for low-temperature firing and a porous conductor. The binder for low-temperature firing contained in the void forming layer 17 has a thermal decomposition start temperature lower than the thermal decomposition start temperature of the binder contained in the positive electrode layer green sheet 12a, the solid electrolyte layer green sheet 13a, and the negative electrode layer green sheet 14a. It is not specifically limited, More preferably, what decomposes | disassembles 90% or more at 500 degrees C or less is preferable. As a binder for low temperature baking, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, an acrylic resin etc. can be used, for example.

In addition, the void forming layer may contain a substance that decreases or disappears at a temperature lower than the thermal decomposition start temperature of the binder, such as a foaming agent, microcapsules, and organic fibers.
The void forming layer 17 is formed by applying or printing on a metal foil current collector and drying a void forming layer slurry in which a binder for low-temperature firing and a porous conductor are dispersed in a solvent. The method for preparing the void forming layer slurry is not particularly limited.
The void 16 is obtained by thermally decomposing the void forming layer 17.

(Metal current collector)
When the laminated green sheet 10 is manufactured, the metal current collector is bonded to the positive electrode green sheet 12a or the positive electrode current collector 11 stacked in close contact with the negative electrode green sheet 14a or the negative electrode current collector 15 stacked in close contact with the negative electrode green sheet 14a. It is. The positive electrode current collector 11 and the negative electrode current collector 15 are the positive electrode current collector 11 and the negative electrode current collector 15 used in the all solid state secondary battery 1.

  In addition to the configuration shown in FIG. 4, the laminate green sheet 10 includes a positive electrode current collector 11 made of a metal foil current collector, a positive electrode layer green sheet 12 a provided on the positive electrode current collector 11, and a positive electrode A gap forming layer 17 disposed between the current collector 11 and the positive electrode layer green sheet 12a, a solid electrolyte layer green sheet 13a provided on the positive electrode layer green sheet 12a, and a solid electrolyte layer green sheet 13a The structure provided with the negative electrode layer green sheet 14a and the negative electrode collector 15 which consists of a metal foil collector provided on the negative electrode layer green sheet 14a may be sufficient.

(1-3) Manufacturing method of laminated body green sheet 10 Hereinafter, the manufacturing method of the laminated body green sheet 10 and the all-solid-state secondary battery 1 is demonstrated.
The manufacturing method of the laminated body green sheet 10 is a method of forming a positive electrode layer green sheet 12a by applying or printing a positive electrode slurry containing a positive electrode active material on a positive electrode current collector 11 made of a metal current collector and drying it. Green sheet forming step, solid electrolyte layer green sheet forming step of forming solid electrolyte layer green sheet 13a by applying or printing slurry for solid electrolyte containing solid electrolyte on positive electrode layer green sheet 12a and drying, and solid electrolyte layer A negative electrode layer green sheet forming step of forming a negative electrode layer green sheet 14a by applying or printing a negative electrode slurry containing a negative electrode active material on the green sheet 13a and drying it, and a negative electrode current collector 15 comprising a metal foil current collector A void forming layer forming step of forming a void forming layer 17 by applying or printing a slurry for void forming layer thereon and then drying, and a negative electrode current collector 5 and void forming layer 17 comprises a negative electrode layer green sheets 14a and bonded crimped to collector step. By the above-described pressure bonding, the gap forming layer 17 is embedded in the negative electrode layer green sheet 14a.

(Method for producing solid electrolyte layer green sheet)
The solid electrolyte layer green sheet 13a is formed by applying or printing a solid electrolyte slurry formed by mixing a solid electrolyte and an organic substance binder together with a solvent and then drying. The solid electrolyte slurry is applied on, for example, a positive electrode layer green sheet 12a or a negative electrode layer green sheet 14a described later. The method for preparing the solid electrolyte slurry is not particularly limited.

(Method for producing positive electrode layer green sheet)
The positive electrode layer green sheet 12 a is formed by mixing a positive electrode active material, a solid electrolyte, and an organic substance binder together with a solvent and applying or printing a positive electrode slurry, followed by drying. The positive electrode slurry is applied on the positive electrode current collector 11 or a solid electrolyte layer green sheet 13a described later. The method for preparing the positive electrode slurry is not particularly limited.

(Method for producing negative electrode layer green sheet)
The negative electrode layer green sheet 14a is formed by mixing a negative electrode active material, a solid electrolyte, and an organic substance binder together with a solvent and applying or printing a negative electrode slurry, followed by drying. The negative electrode slurry is applied on the negative electrode current collector 15 or a solid electrolyte layer green sheet 13a described later. The method for preparing the negative electrode slurry is not particularly limited.
As the binder contained in each green sheet, for example, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinylidene fluoride, polytetrafluoroethylene, ethyl cellulose, acrylic resin, and the like can be used.

(Method for producing void forming layer)
The void forming layer 17 is formed by applying or printing on a metal foil current collector and drying a void forming layer slurry in which a binder for low-temperature firing and a porous conductor are dispersed in a solvent. The method for preparing the void forming layer slurry is not particularly limited.
Further, by performing flat plate press, roll press, hot press, cold isostatic press, hot isostatic press, etc. on the metal current collector on which the void forming layer 17 has been formed, the void forming layer 17 has an appropriate thickness. Can be molded.

Such voids 16 are obtained by firing the void forming layer 17.
In the positive electrode layer green sheet 12a, the negative electrode layer green sheet 14a, and the solid electrolyte layer green sheet 13a, the binder is preferably contained in an amount of 3% by mass to 40% by mass, and more preferably 3% by mass to 25% by mass. preferable. That is, the content of the binder with respect to the entire solid content excluding the solvent from each slurry is preferably 3% by mass or more and 40% by mass or less, and more preferably 3% by mass or more and 25% by mass or less.

When the content of the binder is less than 3% by mass, for example, active materials or solid electrolytes may not be sufficiently bound. On the other hand, when the content of the binder is larger than 40% by mass, the battery capacity per volume decreases.
The positive electrode layer green sheet 12a, the negative electrode layer green sheet 14a, and the solid electrolyte layer green sheet 13a may contain a firing aid that promotes formation of a matrix structure in each green sheet during firing and lowers the firing temperature. . The firing aid is not particularly limited as long as it does not react with the positive electrode active material, the negative electrode active material, and the solid electrolyte, and the softening point temperature is lower than the fusion temperature of the positive electrode active material, the negative electrode active material, and the solid electrolyte. Can be used. By adjusting the content and firing temperature of the firing aids of the positive electrode layer green sheet 12a, the negative electrode layer green sheet 14a and the solid electrolyte layer green sheet 13a, While preventing cracks due to internal stress, formation of a matrix structure can be promoted.

  The solvent used for the positive electrode slurry, the negative electrode slurry, the solid electrolyte slurry, and the void forming layer slurry is not particularly limited as long as it can dissolve the above-mentioned binder. For example, alcohols such as ethanol, isopropanol, and n-butanol , Toluene, terpineol, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethylene glycol ethyl ether, isophorone, butyl lactate, dioctyl phthalate, dioctyl adipate, benzyl alcohol, N, N-dimethylformamide (DMF), N- An organic solvent such as methyl-2-pyrrolidone (NMP) and water can be used. In addition, these solvents may be used independently and may use 2 or more types together. Since the slurry can be easily dried, the boiling point of the solvent is preferably 200 ° C. or lower.

  The positive electrode slurry and the negative electrode slurry can be prepared by mixing the above-described positive electrode active material or negative electrode active material, solid electrolyte, binder, conductive assistant, firing assistant, and the like with a solvent. Moreover, the slurry for solid electrolyte can be produced by mixing the solid electrolyte, the binder, the conductive aid, the firing aid and the like described above with a solvent. The method for mixing the slurry is not particularly limited, and additives such as thickeners, plasticizers, antifoaming agents, leveling agents, and adhesion imparting agents may be added as necessary.

  Specific examples of coating and printing methods for positive electrode slurry, negative electrode slurry, solid electrolyte slurry and void forming layer slurry include a doctor blade method, a calendar method, a spin coating method, a dip coating method, an ink jet method, and an offset method. Method, die coating method, spraying method, screen printing method and the like can be used.

The drying method of the positive electrode slurry, the negative electrode slurry, the solid electrolyte slurry, and the void forming layer slurry is not particularly limited, and for example, heat drying, vacuum drying, heat vacuum drying, and the like can be used. The drying atmosphere is not particularly limited, and can be performed, for example, in an air atmosphere or an inert atmosphere (a nitrogen atmosphere or an argon atmosphere).
The positive electrode layer green sheet, the solid electrolyte layer green sheet, and the negative electrode layer green sheet constitute a laminate green sheet that is sequentially laminated.

(Current collector pasting process)
The method for attaching each current collector made of a metal foil current collector or the like is not particularly limited. For example, a flat plate press, a roll press, a hot press, a cold isostatic press, a hot isostatic press, or the like can be used.

(1-4) Manufacturing method of all-solid-state secondary battery The all-solid-state secondary battery 1 of this embodiment is formed by baking the laminated body green sheet 10 collectively.
That is, the manufacturing method of the all-solid-state secondary battery 1 of this embodiment includes a positive electrode layer green sheet forming step of forming the positive electrode layer green sheet 12a on the positive electrode current collector 11, and a solid electrolyte layer on the positive electrode layer green sheet 12a. The laminate green sheet 10 is generated including a solid electrolyte layer green sheet forming step for forming the green sheet 13a and a negative electrode layer green sheet forming step for forming the negative electrode green sheet 14a on the solid electrolyte layer green sheet 13a. A laminate green sheet forming step is provided. Moreover, the manufacturing method of the all-solid-state secondary battery 1 of this embodiment sticks the negative electrode collector 15 on the negative electrode layer green sheet 14a exposed on the surface of the laminated body green sheet 10, as shown in FIG. A negative electrode current collector bonding step, and a firing step of firing the laminate 1a including the laminate green sheet 10 and the negative electrode current collector 15.

  The heating temperature in the firing step is a temperature equal to or higher than the thermal decomposition temperature of the binder contained in the laminate green sheet 10 and lower than the oxidation temperature of the positive electrode active material and the negative electrode active material or lower than the combustion temperature of the metal foil current collector. Is preferred. Specifically, the heating temperature is preferably 300 ° C. or higher and 1100 ° C. or lower, and more preferably 300 ° C. or higher and 900 ° C. or lower. When the heating temperature is lower than 300 ° C., the binder does not completely burn out in the baking step and becomes a residue, which may hinder electronic conduction or ionic conduction. On the other hand, when the heating temperature is higher than 1100 ° C., the positive electrode active material, the negative electrode active material, and the solid electrolyte may be melted / altered to deteriorate the battery performance.

The atmosphere in the firing step is not particularly limited, and can be performed, for example, in an air atmosphere or an inert atmosphere (a nitrogen atmosphere or an argon atmosphere). When there is a concern about the reaction between the positive electrode active material and the negative electrode active material and the metal foil current collector or the decrease in conductivity of the metal foil current collector, it is desirable to perform the firing step in an inert atmosphere.
The firing time in the firing step is not particularly limited as long as the binder used is sufficiently decomposed.

  In the present embodiment, at least one of the interfacial resistance between the positive electrode current collector and the positive electrode layer and the interfacial resistance between the negative electrode current collector and the negative electrode layer is achieved by a simple means of forming the gap 16 as described above. It becomes possible to reduce the interface resistance. As a result, it is possible to provide an all-solid secondary battery with high battery performance.

<Second Embodiment>
In the second embodiment, a laminated all solid state secondary battery (series all solid state secondary battery) and an all solid state secondary battery manufacturing method according to the present invention will be described. Moreover, in the following 2nd Embodiment, the manufacturing method of the continuous laminated body green sheet used for manufacture of the all-solid-state secondary battery which concerns on this invention, and a continuous laminated body green sheet is demonstrated.
In the present embodiment, members having the same configurations as those in the first embodiment will be described using common reference numerals.

(2-1) Configuration of series all solid state secondary battery [Configuration of series all solid state secondary battery]
As shown in FIG. 5, the series all-solid-state secondary battery (hereinafter referred to as all-solid-state secondary battery) 21 in the second embodiment is configured by successively laminating a plurality of electrode laminates 20. Yes.
The electrode laminate 20 includes a positive electrode current collector 11 made of a metal foil, a positive electrode layer 12, a gap 16 provided between the positive electrode current collector 11 and the positive electrode layer 12, and a solid electrolyte layer provided on the positive electrode layer 12. 13 and a negative electrode layer 14 provided on the solid electrolyte layer 13. That is, the electrode laminate 20 includes a laminate in which the solid electrolyte layer 13 is disposed between the positive electrode layer 12 and the negative electrode layer 14, and the positive electrode current collector 11.

In addition, the all-solid-state secondary battery 21 is in close contact with the positive electrode layer 12 or the negative electrode layer 14 between the stacked electrode stacks 20 and on the outer side in the stacking direction of the stacked electrode stacks 20. A plurality of metal current collectors (positive electrode current collector 11 or negative electrode current collector 15).
As will be described in detail later, this structure is obtained by stacking green sheets 20a to 20e in which a gap forming layer 17, a positive electrode layer green sheet 12a, a solid electrolyte layer green sheet 13a, and a negative electrode layer green sheet 14a are stacked. 11 is realized by the manufacturing method of the all-solid-state secondary battery 21 in which a plurality of layers are stacked via the electrode 11 and the outer surface is sandwiched between the positive electrode current collector 11 and the negative electrode current collector 15.

The positive electrode layer 12, the solid electrolyte layer 13, the negative electrode layer 14, and the gap 16, and the positive electrode current collector 11 or the negative electrode current collector 15, are the positive electrode layer 12, the solid electrolyte layer 13, the negative electrode layer 14, and the gap of the first embodiment. 16 and the positive electrode current collector 11 or the negative electrode current collector 15, and thus the description thereof is omitted.
In addition to the configuration shown in FIG. 5, the all-solid secondary battery 21 has a negative electrode current collector 15, a negative electrode layer 14 provided on the negative electrode current collector 15, a negative electrode current collector 15, and a negative electrode layer 14. , A solid electrolyte layer 13 provided on the negative electrode layer 14, a positive electrode layer 12 provided on the solid electrolyte layer 13, and a positive electrode current collector provided on the positive electrode layer 12 The structure provided with the body 11 may be sufficient.

(2-2) Configuration of Continuous Laminated Green Sheet Hereinafter, the continuous laminated green sheet will be described.
[Configuration of laminated green sheet]
As shown in FIG. 6, the continuous laminate green sheet 30 in the second embodiment includes a positive electrode current collector 11, a positive electrode layer green sheet 12 a provided on the positive electrode current collector 11, and a positive electrode current collector 11. Gap forming layer 17 provided between the positive electrode layer green sheet 12a, the solid electrolyte layer green sheet 13a provided on the positive electrode layer green sheet 12a, and the negative electrode layer green provided on the solid electrolyte layer green sheet 13a Laminated green sheets 20a to 20e each having a sheet 14a are continuously laminated.

  That is, the multilayer green sheets 20a to 20e have the same configuration as that in which the negative electrode current collector 15 is not bonded to the multilayer green sheet 10 of the first embodiment. Since the solid electrolyte layer green sheet 13a and the negative electrode layer green sheet 14a are the same as the solid electrolyte layer green sheet 13a and the negative electrode layer green sheet 14a of the multilayer green sheet 10 of the first embodiment, description thereof is omitted. The void forming layer 17 is formed on the positive electrode current collector 11, and the positive electrode layer green sheet 12a is formed on the positive electrode current collector 11 on which the void forming layer 17 is formed. This is the same as the positive electrode layer green sheet 12 a and the gap forming layer 17 of the multilayer green sheet 10. The configuration of 20a is shown in FIG.

(2-3) Manufacturing method of continuous laminated body green sheet Hereinafter, the manufacturing method of the continuous laminated body green sheet 30 and the all-solid-state secondary battery 21 is demonstrated.
The manufacturing method of the continuous laminated body green sheet 30 is provided with the green sheet lamination | stacking process of laminating | stacking multiple laminated body green sheets 20a-20e continuously.

  The continuous laminate green sheet 30 is, for example, one laminate green sheet (eg, laminate green sheet 20b) of the plurality of laminate green sheets 20a to 20e and the other laminate green. It is formed by adhering a negative electrode layer green sheet 14a of a sheet (for example, laminated green sheet 20a) so as to be adjacent to each other. The laminating method of the laminated green sheets 20a to 20e is not particularly limited, and for example, a flat plate press, a roll press, a hot press, a cold isostatic press, a hot isostatic press, or the like can be used.

In addition to the configuration shown in FIG.
A negative electrode current collector 15 made of a metal foil current collector, a negative electrode layer green sheet 14a provided on the negative electrode current collector 15, and a gap disposed between the negative electrode current collector 15 and the negative electrode layer green sheet 14a. The formation layer 17, the solid electrolyte layer green sheet 13a provided on the negative electrode layer green sheet 14a, the positive electrode layer green sheet 12a provided on the solid electrolyte layer green sheet 13a, and the positive electrode layer green sheet 12a And a positive electrode current collector 11 made of a metal foil current collector.

(2-4) Manufacturing method of serial all-solid-state secondary battery The all-solid-state secondary battery 21 of 2nd Embodiment is formed by degreasing | defatting a binder from the continuous laminated body green sheet 30, and baking.
That is, in the manufacturing method of the all-solid-state secondary battery 21 of the present embodiment, the void forming layer 17 is formed by applying or printing the void forming layer slurry on the positive electrode current collector 11 made of the metal foil current collector and then drying. A positive electrode layer green for forming a positive electrode layer green sheet 12a by applying or printing a positive electrode slurry containing a positive electrode active material on the positive electrode current collector 11 on which the void forming layer 17 has been formed. A solid electrolyte layer green sheet forming step for forming a solid electrolyte layer green sheet 13a by applying or printing a solid electrolyte slurry containing a solid electrolyte on the positive electrode layer green sheet 12a, followed by drying, and a solid electrolyte layer green A negative electrode layer green sheet that forms a negative electrode layer green sheet 14a by applying or printing a negative electrode slurry containing a negative electrode active material on the sheet 13a and drying it. Include forming step comprises a laminate green sheet forming step of forming a laminate green sheet 20 (20a to 20e).

  Moreover, the manufacturing method of the all-solid-state secondary battery 21 of this embodiment is on the negative electrode layer green sheet 14a exposed on the surface of the continuous laminated body green sheet 30 after laminating | stacking multiple laminated body green sheets 20 (20a-20e). In addition, a continuous laminate green sheet forming step for bonding a negative electrode current collector 15 for bonding a negative electrode current collector 15 made of a metal foil current collector, and a firing step for firing them are provided.

The heating temperature, the method for attaching the metal foil current collector, and the like in the firing step of the second embodiment are the same as those in the first embodiment, and thus the description thereof is omitted.
As described above, the all-solid-state secondary battery 21 of the second embodiment can be formed by firing the continuous laminate green sheet 30 at once. As a result, it is possible to manufacture the all-solid-state secondary battery 21 in one firing step while suppressing the interface resistance between the positive electrode current collector 11 and the positive electrode layer 12, the negative electrode current collector 15 and the negative electrode layer 14. became.

Hereinafter, the all-solid-state secondary battery described in the present embodiment will be described with specific examples and comparative examples. In addition, the structure of the all-solid-state secondary battery based on this invention is not restrict | limited by a following example.
Example 1
[Slurry preparation process]
<Preparation of slurry for positive electrode>
50 parts by mass of lithium cobaltate (LiCoO ₂ ) powder as a positive electrode active material, 50 parts by mass of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (hereinafter LAGP) powder as a solid electrolyte, and acetylene as a conductive additive 20 parts by mass of black and 16 parts by mass of polyvinyl butyral (PVB) resin as a binder were mixed with terpineol as a solvent to form a slurry, and the slurry was defoamed to prepare a positive electrode slurry.

<Preparation of slurry for solid electrolyte>
100 parts by mass of LAGP powder as a solid electrolyte and 16 parts by mass of PVB resin as a binder were mixed with terpineol as a solvent to form a slurry, and this slurry was defoamed to prepare a slurry for solid electrolyte.
<Preparation of slurry for negative electrode>
50 parts by mass of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) powder as a negative electrode active material, 50 parts by mass of LAGP powder as a solid electrolyte, 20 parts by mass of graphite as a conductive additive, and 16 parts by mass of PVB resin as a binder are terpineol as a solvent The slurry was defoamed to prepare a slurry for negative electrode.

<Slurry for void forming layer>
100 parts by mass of carbon nanotube powder and 20 parts by mass of an acrylic resin as a binder for low-temperature firing were mixed with cyclohexanone as a solvent to form a slurry, and this slurry was defoamed to prepare a void forming layer slurry.
<Negative electrode collector manufacturing process with void forming layer>
A stainless steel metal current collector foil with a thickness of 20 μm was used as the negative electrode current collector. On one surface of the current collector foil, the void forming layer slurry is screen-printed so that a gap forming layer having a width of 1 mm is formed every 10 mm so as to intersect vertically and horizontally, and dried to form a void as shown in FIG. A negative electrode current collector having a layer formed thereon was produced.

<Laminated green sheet production process>
A stainless steel metal current collector foil with a thickness of 20 μm was used as the positive electrode current collector. A positive electrode slurry was applied to one surface of the current collector foil and dried to prepare a positive electrode layer green sheet.
Subsequently, on the surface of the positive electrode layer green sheet opposite to the surface facing the current collector foil, a slurry for solid electrolyte is applied and dried to produce a solid electrolyte layer green sheet. Further, the positive electrode of the solid electrolyte layer green sheet The negative electrode slurry was applied on the surface opposite to the surface facing the layer green sheet and dried to prepare a negative electrode layer green sheet.
Subsequently, a negative electrode current collector with a void forming layer was bonded onto the negative electrode layer green sheet, and pressed at 80 ° C. and 1000 kgf / cm ² (98 MPa). Thereafter, the positive electrode current collector and the negative electrode current collector were cut into individual elements so as to be exposed on different surfaces of the laminate.
As a result, a laminate green sheet as shown in FIG. 4 was produced.

<Baking process>
The laminate cut into individual elements was heated from room temperature to 700 ° C. at a temperature rising rate of 100 ° C./min in a nitrogen stream, and held at that temperature for 30 minutes for firing. Thereafter, the laminate was allowed to cool to room temperature in a furnace, and an all-solid secondary battery of Example 1 as shown in FIG. 1 was produced.
<Measurement of thermal decomposition start temperature>
About the PVB resin contained in the positive electrode, the solid electrolyte layer, and the negative electrode of the laminate green sheet described above, and the acrylic resin contained in the void forming layer, using a thermal mass measuring device, the temperature rising rate is 100 in a nitrogen stream. The temperature was raised from room temperature to 700 ° C. at a rate of ° C./min, and the thermal decomposition start temperature was measured. The thermal decomposition start temperature was a temperature at which the cumulative mass reduction rate was 10% or more.
As a result of the measurement, the thermal decomposition start temperature of the PVB resin was 370 ° C. The thermal decomposition starting temperature of the acrylic resin was 345 ° C.

(Example 2)
On one surface of the negative electrode current collector, the void forming layer slurry is screen-printed so that a gap forming layer having a width of 1 mm is formed in a stripe shape every 10 mm, and dried to form a void forming layer as shown in FIG. An all-solid-state secondary battery of Example 2 was produced in the same manner as in Example 1 except that a negative electrode current collector formed with a negative electrode was produced.

(Example 3)
<Positive electrode current collector manufacturing process with void forming layer>
A stainless steel metal current collector foil with a thickness of 20 μm was used as the positive electrode current collector. On one surface of the current collector foil, the void forming layer slurry is screen-printed so that a gap forming layer having a width of 1 mm is formed every 10 mm so as to intersect vertically and horizontally, and dried to form a void as shown in FIG. A positive electrode current collector having a layer formed thereon was produced.

<Continuous laminated green sheet manufacturing process>
A positive electrode slurry was applied to the surface of the positive electrode current collector on which the void forming layer was formed, on the gap forming layer side, and dried to prepare a positive electrode layer green sheet.
Subsequently, on the surface of the positive electrode layer green sheet opposite to the surface facing the current collector foil, a slurry for solid electrolyte is applied and dried to produce a solid electrolyte layer green sheet. Further, the positive electrode of the solid electrolyte layer green sheet The negative electrode slurry was applied on the surface opposite to the surface facing the layer green sheet and dried to prepare a negative electrode layer green sheet.

Thereby, a laminate green sheet as shown in FIG. 7 was produced, and this was further cut into a predetermined size to produce a laminate. Five laminates were produced. Subsequently, five laminated bodies were laminated in order to form a continuous laminated green sheet. Finally, on the negative electrode layer green sheet that is not in contact with the current collector foil, a negative electrode current collector made of a stainless steel metal current collector foil having a thickness of 20 μm, which is the same as the positive electrode current collector foil, is mounted, as shown in FIG. A continuous laminate (continuous laminate green sheet) was obtained. Subsequently, the whole of the continuous laminate was pressurized at 80 ° C. and 1000 kgf / cm ² (98 MPa).

<Baking process>
The continuous laminate was heated from room temperature to 700 ° C. in a nitrogen stream at a heating rate of 100 ° C./min, held at that temperature for 30 minutes, then cooled to room temperature by cooling in the furnace, as shown in FIG. A serial all solid state secondary battery of Example 3 which is a continuous laminated fired body was produced.
(Comparative Example 1)
An all-solid-state secondary battery of Comparative Example 1 was produced in the same manner as in Example 1 except that the void forming layer was not formed on the negative electrode current collector foil.

(Comparative Example 2)
Comparative Example 2 in the same manner as in Example 1 except that the binder contained in the positive electrode, the solid electrolyte layer, and the negative electrode of the laminate green sheet was an acrylic resin, and the binder contained in the void forming layer was a PVB resin. An all solid state secondary battery was prepared.
(Comparative Example 3)
A series all-solid-state secondary battery of Comparative Example 3 was produced in the same manner as in Example 3 except that no void forming layer was formed on the negative electrode current collector foil.

[Electrochemical evaluation]
The electrochemical evaluation was performed about the produced all-solid-state secondary battery and series all-solid-state secondary battery as follows.
(Evaluation method of all-solid-state secondary batteries of Example 1, Example 2, Comparative Example 1 and Comparative Example 2)
Ten all solid state secondary batteries of each Example and Comparative Example were prepared and evaluated.
The all solid state secondary batteries of Examples and Comparative Examples were charged with a constant current of 0.2 C until the voltage reached 2.7 V, and then discharged with a constant current of 0.2 C to a voltage of 1.5 V. The discharge capacity (0.2 C discharge capacity) at this time was defined as the reference capacity A. The reference capacity A was an average value of discharge capacities of ten all solid state secondary batteries.

Next, the all solid state secondary batteries of the examples and comparative examples were charged to a voltage of 2.7 V at a constant current of 0.2 C, and then discharged to a voltage of 1.5 V at a constant current of 5 C. The discharge capacity at this time was set to 5C discharge capacity B. Similarly to the reference capacity A, the 5C discharge capacity B was also an average value of the discharge capacity of 10 all solid state secondary batteries.
Finally, for each of the all-solid-state secondary batteries of each of the examples and comparative examples, a discharge capacity maintenance ratio represented by a ratio of the discharge capacity of the 5C discharge capacity B to the reference capacity A (B / A (%)) is obtained. This was used as an evaluation standard for electrochemical evaluation.

(Evaluation method of series all-solid-state secondary battery of Example 3 and Comparative Example 3)
Ten serial all-solid-state secondary batteries of Example 3 and Comparative Example 3 were prepared and evaluated.
The series all solid state secondary battery was charged with a constant current of 0.2 C until the voltage reached 13.5 V, and then discharged with a constant current of 0.2 C to a voltage of 7.5 V. The discharge capacity (0.2 C discharge capacity) at this time was defined as the reference capacity A. The reference capacity A was the average value of the discharge capacity of 10 serial all solid state secondary batteries.

Next, the series all-solid secondary battery was charged to a voltage of 13.5 V at a constant current of 0.2 C, and then discharged to a voltage of 7.5 V at a constant current of 5 C. The discharge capacity at this time was set to 5C discharge capacity B. Similarly to the reference capacity A, the 5C discharge capacity B was also set to the average value of the discharge capacity of 10 series all solid state secondary batteries.
Finally, for each of the series all-solid-state secondary batteries, a discharge capacity maintenance ratio represented by a ratio of the discharge capacity of the 5C discharge capacity B to the reference capacity A (B / A (%)) is obtained. Evaluation criteria for chemical evaluation were used.
Table 1 below shows the evaluation results of the electrochemical evaluation.

  As shown in Table 1, each of the all-solid-state secondary batteries of Examples 1 to 3 had an electrochemical evaluation result showing a sufficient discharge capacity retention rate. The all-solid-state secondary battery of Example 3 has a continuous laminated structure, so that the binder is not easily decomposed, and the discharge capacity retention rate is lower than that of Examples 1 and 2, but the electrochemical evaluation has no problem. It was speculated that it showed.

  On the other hand, in the all solid state secondary battery of Comparative Example 1, the decomposition gas of the binder was delayed in the firing process, and the binder of each green sheet remained up to the sintering temperature of the inorganic particles, so that the sintering was hindered and the interface resistance was low. Since the discharge capacity was high, the discharge capacity A, the discharge capacity B, and the discharge capacity maintenance ratio were significantly reduced. Further, in Comparative Example 2, since the decomposition gas of the binder was generated from each green sheet prior to the formation of the voids, the binder remained and the sintering of the inorganic particles was inhibited although it was less than Comparative Example 1. Since the interfacial resistance increased, the discharge capacity A, the discharge capacity B, and the discharge capacity maintenance ratio decreased. Furthermore, the all-solid-state secondary battery of Comparative Example 3 has a continuous laminated structure, so that the binder is difficult to be decomposed, and delamination occurs between the current collector foil and the positive electrode and between the current collector foil and the negative electrode, resulting in an interface resistance. Due to the increase, the discharge capacity A, the discharge capacity B, and the discharge capacity maintenance rate decreased.

As described above, the all-solid-state secondary battery has at least one of the positive electrode current collector-between the positive electrode and the negative electrode current collector-the negative electrode at the end in the surface direction from the center in the surface direction of the electrode Thus, the discharge capacity A, the discharge capacity B, and the discharge capacity retention rate were not significantly reduced, and an all-solid secondary battery with good battery performance could be obtained.
Moreover, since the all-solid-state secondary battery manufactured by the manufacturing method of this embodiment can be produced by firing the laminated green sheet at once, the production process of the all-solid-state secondary battery is simplified.

  The scope of the present invention is not limited to the illustrated and described exemplary embodiments, but also includes all embodiments that provide equivalent effects to those intended by the present invention. Further, the scope of the invention is not limited to the combinations of features of the invention defined by the claims, but can be defined by any desired combination of specific features among all the disclosed features.

DESCRIPTION OF SYMBOLS 1 All-solid-state secondary battery 10,20,20a-20e Laminated body green sheet 11 Positive electrode collector 12 Positive electrode layer 12a Positive electrode layer green sheet 13 Solid electrolyte layer 13a Solid electrolyte layer green sheet 14 Negative electrode layer 14a Negative electrode layer green sheet 15 Negative electrode Current collector 16 Gap 17 Gap formation layer 20 Electrode laminate 21 Series all solid secondary battery 30 Continuous laminate green sheet

Claims (6)

A positive electrode layer is laminated on one surface of the positive electrode current collector, a negative electrode layer is laminated on one surface of the negative electrode current collector, and a solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer,
Extending from the center of the surface to the end along the surface between the positive electrode current collector and the positive electrode layer and at least one of the negative electrode current collector and the negative electrode layer And an all-solid-state secondary battery having a void open to the outside. A laminate in which a solid electrolyte layer is disposed between a positive electrode layer and a negative electrode layer is continuously laminated with a current collector made of a positive electrode current collector or a negative electrode current collector interposed therebetween,
Extending from the center of the surface to the end along the surface between the current collector and the positive electrode layer and at least one of the current collector and the negative electrode layer. An all-solid-state secondary battery having a void open to the outside.   3. The all-solid-state secondary battery according to claim 1, wherein the positive electrode current collector and the negative electrode current collector are metal foil current collectors made of metal foil.   The area of the gap between the layers is 0.5% or more and less than 10% of the contact area between the electrode layer formed of one of the positive electrode layer or the negative electrode layer and the current collector. The all solid state secondary battery according to any one of claims 1 to 3. A solid electrolyte layer green sheet is disposed between the positive electrode layer green sheet and the negative electrode layer green sheet, and each of the positive electrode layer green sheet and the negative electrode layer green sheet has a positive electrode on a surface opposite to the solid electrolyte layer green sheet. A current collector consisting of a current collector or a negative electrode current collector is laminated,
The center part of the surface along the surface between the layers between the stacked current collector and the positive electrode layer green sheet and between the stacked current collector and the negative electrode layer green sheet. Having a void-forming layer extending from the end to the end,
The void-forming layer contains a binder and a porous conductor, and the thermal decomposition start temperature of the binder contained in the void-forming layer is the heat of the binder contained in the positive electrode layer green sheet, the solid electrolyte layer green sheet, and the negative electrode layer green sheet. A laminate green sheet characterized by being lower than the decomposition start temperature.   The laminated green sheet according to claim 5 is collectively fired, and between at least one of the layers between the laminated current collector and the positive electrode layer and between the laminated current collector and the negative electrode layer, A method for producing an all-solid-state secondary battery, wherein a gap extending from a central portion to an end portion of a surface is formed along a surface between layers.

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