WO2013100001A1

WO2013100001A1 - All-solid cell and method for manufacturing same

Info

Publication number: WO2013100001A1
Application number: PCT/JP2012/083768
Authority: WO
Inventors: 倍太尾内; 充吉岡; 剛司林; 彰佑伊藤; 武郎石倉
Original assignee: 株式会社村田製作所
Priority date: 2011-12-28
Filing date: 2012-12-27
Publication date: 2013-07-04

Abstract

Provided are: an all-solid cell wherein water in an atmosphere can be prevented from entering a cell body, and mechanical strength of the cell body can be reinforced; and a method for manufacturing the all-solid cell. This all-solid cell includes: a cell body (11), which includes a positive electrode layer and/or a negative electrode layer, and a solid electrolyte layer; an insulating layer (32), which covers the cell body (11), and which contains a resin; and an interlayer, which is provided between the cell body (11) and the insulating layer (32), and which is in contact with both the cell body (11) and the insulating layer (32). The interlayer contains a component that constitutes the cell body (11), and the resin component that constitutes the insulating layer (32).

Description

All-solid battery and method for manufacturing the same

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

In recent years, the demand for batteries as a power source for portable electronic devices such as mobile phones and portable personal computers has greatly increased. In a battery used for such an application, an electrolyte (electrolytic solution) such as an organic solvent has been conventionally used as a medium for moving ions.

However, the battery having the above configuration has a risk of leakage of the electrolyte. Moreover, the organic solvent etc. which are used for electrolyte solution are combustible substances. For this reason, it is required to further increase the safety of the battery.

Therefore, it has been proposed to use a solid electrolyte instead of the electrolytic solution as one countermeasure for improving the safety of the battery. Furthermore, development of an all-solid battery in which a solid electrolyte is used as an electrolyte and the other constituent elements are also made of solid is being promoted. The exterior body and sealing material which consist of an insulating material which covers the whole component of such all-solid-state battery are arrange | positioned around the component of all-solid-state battery.

For example, Japanese Patent Application Laid-Open No. 2011-124084 (hereinafter referred to as Patent Document 1) discloses a configuration of an all-solid battery, and the all-solid battery includes a power generation element including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. And a current collector, and an exterior body that covers the periphery of the single battery. Patent Document 1 describes that an insulating material such as an epoxy resin or a polybutadiene resin can be used as a material of the exterior body.

Further, for example, Japanese Patent No. 4043296 (hereinafter referred to as Patent Document 2) discloses the configuration of an all-solid battery, and this all-solid battery is formed on a substrate and the substrate by sputtering or the like. A single battery (battery body) composed of a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a negative electrode current collector layer and a protective layer, and a plurality of single cells are stacked, It is provided with a sealing material made of an insulating material such as glass or ceramics.

Japanese Unexamined Patent Publication No. 2011-124084 Japanese Patent No. 4043296

However, as a result of various studies by the inventors on the structure of an all-solid-state battery as described in Patent Document 1 and Patent Document 2, it has been found that there are the following problems.

As disclosed in Patent Document 1 or Patent Document 2, even if the battery body of an all-solid-state battery is sealed with an exterior body or a sealing material made of an insulating material, moisture in the atmosphere can be blocked. Inability to do so causes problems such as deterioration of battery characteristics of all solid state batteries. In particular, when the battery body is composed of a sulfide or a fired body, the sulfide or the fired body reacts with moisture in the atmosphere, and the battery characteristics of the all-solid battery are deteriorated.

The mechanism by which the battery characteristics of all-solid-state batteries deteriorate due to moisture is unknown, but it is assumed that the cause is that the material of the battery body is corroded due to water being electrolyzed by the positive or negative electrode potential. Is done.

Further, when the battery body is composed of a fired body, the fired body has high hardness, but has low toughness and is brittle. Therefore, if the fired body is cracked by vibration or impact, the battery of an all-solid battery is used. There are problems such as significant loss of properties.

Accordingly, an object of the present invention is to provide an all-solid battery capable of preventing moisture in the atmosphere from entering the battery body and reinforcing the mechanical strength of the battery body, and a method for manufacturing the same. It is to be.

As a result of various studies conducted by the inventors to solve the above-described problems, an intervening layer is provided between the battery element body and the insulating layer, thereby preventing moisture in the atmosphere from entering the battery element body. It has been found that the mechanical strength of the battery body can be reinforced. Based on such knowledge of the inventors, the present invention has the following features.

An all-solid battery according to the present invention includes a battery element including at least one of a positive electrode layer or a negative electrode layer and a solid electrolyte layer, an insulating layer covering the battery element and including a resin, a battery An intervening layer interposed between the element body and the insulating layer and in contact with both the battery element body and the insulating layer is provided. The intervening layer includes a component constituting the battery element body and a resin component constituting the insulating layer.

In the all solid state battery of the present invention, the battery body preferably includes a current collector layer.

Further, in the all solid state battery of the present invention, it is preferable that the battery body is composed of a fired body.

In the above case, it is preferable that the intervening layer includes a fired body and a resin component present in the voids of the fired body.

In the all solid state battery of the present invention, it is preferable that the resin includes at least one selected from the group consisting of a thermosetting resin, a thermoplastic resin, and a photocurable resin.

It is preferable that the all solid state battery of the present invention further includes an exterior member that covers the insulating layer.

The manufacturing method of an all-solid battery according to one aspect of the present invention includes the following steps.

(A) An unsintered layer production step of fabricating an unsintered electrode layer that is an unsintered body of at least one of the positive electrode layer and the negative electrode layer, and an unsintered solid electrolyte layer that is an unsintered body of the solid electrolyte layer.

(B) Laminate forming step of forming a laminate by laminating an unsintered electrode layer and an unsintered solid electrolyte layer

(C) Firing step of firing the laminated body to produce a battery body composed of the fired body

(D) Step of coating the battery body with resin

(E) An insulating layer containing a solidified resin component by solidifying a resin, a solidified resin component and a fired body component, and interposed between the battery body and the insulating layer, the battery body and the insulating layer Forming an intervening layer in contact with both

The manufacturing method of an all-solid battery according to another aspect of the present invention includes the following steps.

(D) Step of coating the battery body with resin

(F) A step of impregnating the resin in the voids of the fired body constituting the battery body

(G) an insulating layer containing a solidified resin component by solidifying the resin and a resin component solidified in the gap between the fired body and the fired body, and interposed between the battery element body and the insulating layer; Forming an intervening layer in contact with both the element body and the insulating layer

According to the present invention, it is possible to prevent moisture in the atmosphere from entering the battery element body and to reinforce the mechanical strength of the battery element body, thereby improving cycle characteristics.

It is sectional drawing which shows typically the cross-section of the laminated body which comprises the battery body of the all-solid-state battery as one embodiment of this invention. 1 is a perspective view schematically showing a battery body of an all solid state battery as one embodiment of the present invention. It is a top view which shows typically an all-solid-state battery as one embodiment of this invention. It is a photograph which shows the torn surface of the resin coating body in the all-solid-state battery produced in the Example of this invention. It is a scanning electron microscope (SEM) photograph which shows the area | region enclosed by the broken-line part of FIG. It is a scanning electron microscope (SEM) photograph which expands and shows an intervening layer in FIG. 6 is a scanning electron microscope (SEM) photograph showing the positive electrode layer in an enlarged manner in FIG. 5.

As shown in FIG. 1, in the all-solid-state battery stack 1 according to one embodiment of the present invention, a plurality of unit cell structures 5 each including a positive electrode layer 2, a solid electrolyte layer 3, and a negative electrode layer 4 are provided. For example, two are connected in series via the current collector layer 6. The current collector layer 6 disposed inside the laminate 1 of the all-solid battery is provided between the positive electrode layer 2 and the negative electrode layer 4. The structure of the laminated body may be a single battery structure including a pair of positive electrode layer and negative electrode layer, or may be a structure in which a plurality of single battery structures are connected in series as described above. A structure in which battery structures are connected in parallel and stacked may be used, or a structure in which a plurality of unit cell structures are connected in combination of series and parallel may be used. The battery body to be described later includes at least one electrode layer of the positive electrode layer 2 or the negative electrode layer 4 and the solid electrolyte layer 3, and may include the current collector layer 6.

Each of the positive electrode layer 2 and the negative electrode layer 4 includes a solid electrolyte and an electrode active material, and the solid electrolyte layer 3 includes a solid electrolyte. Each of the positive electrode layer 2 and the negative electrode layer 4 may contain carbon, a metal, etc. as an electron conductive material. The laminate 1 (the positive electrode layer 2, the solid electrolyte layer 3, the negative electrode layer 4, and the current collector layer 6) is configured in the form of a compression molded body (sulfide or the like), a fired body (oxide or the like), or a thin film. The When the laminate 1 is configured in the form of a fired body, the positive electrode layer 2, the solid electrolyte layer 3, the negative electrode layer 4, and the current collector layer 6 may be integrally fired, or the positive electrode layer 2, The solid electrolyte layer 3, the negative electrode layer 4, and the current collector layer 6 may be separately fired and the fired layers may be laminated.

As shown in FIG. 2, terminal layers 22 are formed on both sides of the battery body 11 as necessary. The battery body 11 is composed of, for example, the laminate 1 shown in FIG. The terminal layer 22 is provided with positive and negative terminals 23. In this way, the battery element 21 is configured. An insulating layer 32 containing a resin is formed outside the battery element 21. Thereby, the insulating layer 32 containing resin is formed so as to cover the battery body 11. An intervening layer (not shown) is formed between the battery body 11 and the insulating layer 32. The intervening layer includes a component constituting the battery body 11 and a resin component constituting the insulating layer 32. In this way, the resin coating 31 of the battery body 11 is formed.

By forming an intervening layer between the battery element 11 and the insulating layer 32, it is possible to prevent moisture in the atmosphere from entering the battery element 11, and the mechanical strength of the battery element 11. It becomes possible to reinforce.

When the battery body 11 is configured in the form of a compression molded body (sulfide or the like), a component such as sulfide and a resin component react to form an intervening layer. Thus, by forming the intervening layer from the reactant, the mechanical strength of the battery body 11 can be effectively reinforced, and as a result, the strength of the all-solid battery can be improved.

When the battery body 11 is configured in the form of a fired body (oxide or the like), the above-described effects can be obtained even when the intervening layer is formed from a mixture of a component such as an oxide and a resin component. Can do.

In this case, it is possible to prevent moisture in the atmosphere from entering the battery body 11, improve the mechanical strength of the all solid state battery, and improve cycle characteristics. This is because the low toughness of the fired body is reinforced by a resin having higher toughness than the fired body, and furthermore, firing with low toughness that constitutes the battery body 11, which is originally a substance that is difficult to bond. By closely bonding the body and the high toughness resin constituting the insulating layer 32 via the intervening layer in which both are mixed, the strength of the resin can be effectively reinforced to the fired body. Because.

Although details of the cause of improving the cycle characteristics of the all-solid-state battery by improving the mechanical strength of the all-solid-state battery are unknown, the following may be considered. First, a stable capacity can be charged or discharged by suppressing cracking of the fired body due to vibration or impact. In addition, the electrode active material contained in the fired body expands or contracts with charge or discharge, and the expansion and contraction are repeated, whereby the fired body is cracked or fine cracks are generated inside the fired body. As a result, the electron conduction path or ion conduction path essential for charging or discharging is destroyed, and the capacity is reduced. It is estimated that such a decrease in capacity can be suppressed by improving the mechanical strength of the all-solid-state battery.

Further, when the battery body 11 is configured in the form of a fired body (oxide or the like), the intervening layer is preferably formed from the fired body and a resin component present in the voids of the fired body. . Thus, by configuring the intervening layer so that the resin component exists in the voids of the porous fired body, the mechanical strength of the battery body 11 can be effectively reinforced, and as a result, The strength of the solid battery can be improved. In this case, since the resin is dispersed inside the three-dimensional network formed by the fired body, the strength of the resin can be effectively reinforced with respect to the fired body.

The thickness of the insulating layer 32 is not particularly limited, but is preferably 5 μm or more, and more preferably 20 μm or more in order to ensure the mechanical strength of the insulating layer 32. If the insulating layer 32 becomes too thick, the volume energy density of the all-solid-state battery decreases, so 20 to 100 μm is most preferable.

The thickness of the intervening layer is not particularly limited, but if the intervening layer is too thin, it is difficult to obtain an effect of closely bonding the fired body and the insulating layer 32. Therefore, the thickness of the intervening layer is preferably 1 μm or more. More preferably. Further, when the fired body is thin, the resin exists in a wide range from the surface of the fired body to the center, or the fired body itself may be an intervening layer, but even in this case, the above-described effects can be obtained. .

The porosity of the surface of the fired body is not particularly limited, but is preferably 5% or more in order for the intervening layer to be formed from the fired body and the resin component present in the voids of the fired body, % Or more is more preferable. In addition, in order to effectively reinforce the strength of the resin by increasing the porosity in the vicinity of the surface of the fired body compared to the inside of the fired body and increasing the proportion of the resin in the intervening layer, You may provide a porous layer in the surface part of.

As the above-mentioned resin, one kind selected from a thermosetting resin, a thermoplastic resin, and a photocurable resin, or a mixture containing two or more kinds can be used. The type of the resin is not particularly limited, and can be appropriately selected from the viewpoints of insulation, adhesion to the fired body, and potential window width (or difficulty in oxidation / reduction).

The type of thermosetting resin is not particularly limited, but epoxy resin, phenol resin, urea resin (urea resin), melamine resin, unsaturated polyester resin, polyimide resin, diallyl phthalate resin, silicon resin, polyaminobismaleimide resin, casein resin , A furan resin, a polyurethane resin, and a mixture containing at least one selected from alkyd resins or two or more thereof can be used.

The type of thermoplastic resin is not particularly limited, but polyethylene resin, polystyrene resin, polypropylene resin, polyphenylene sulfide resin, polyparaxylylene resin, liquid crystal polymer, vinyl chloride resin, polyvinyl alcohol resin, polymethyl methacrylate (methacrylic resin), Polyphenylene oxide resin, polyurethane resin, ionomer resin, polyacetal resin (polyoxymethylene), polyamide resin, vinylidene chloride resin, polyethylene terephthalate, polyether ether ketone resin, polyether imide resin, polyether sulfone resin, and fluorine resin ( It is possible to use at least one selected from polytetrafluoroethylene) or a mixture containing two or more.

The type of the photo-curable resin is not particularly limited, but at least one selected from silicone resins, acrylic resins, and vinyl ester resins, or a mixture containing two or more types can be used.

As shown in FIG. 3, the all-solid-state battery 41 includes an exterior member 42 that covers the insulating layer 32 of the resin coating 31 shown in FIG.

Thus, by providing the exterior member 42 that suppresses water vapor intrusion outside the insulating layer 32, the mechanical strength of the fired body is reinforced by the insulating layer 32 and the intervening layer. Exposure to moisture can be suppressed. In addition, you may use insulating layer 32 itself as an exterior member which suppresses water vapor permeation.

When the laminate 1 shown in FIG. 1 is configured in the form of a compression molded body, the following materials are used.

The positive electrode layer 2 includes, for example, Li ₂ FeS ₂ , Li _2.33 Fe _0.67 S ₂ or the like as a positive electrode active material, and Li ₇ P ₃ S ₁₁ that is an ion conductive compound as a solid electrolyte. The negative electrode layer 4 includes, for example, a carbon material as a negative electrode active material and Li ₇ P ₃ S ₁₁ which is an ion conductive compound as a solid electrolyte. The solid electrolyte layer 3 sandwiched between the positive electrode layer 2 and the negative electrode layer 4 includes, for example, Li ₇ P ₃ S ₁₁ that is an ion conductive compound as the solid electrolyte. The positive electrode layer 2, the negative electrode layer 4, and the solid electrolyte layer 3 are each produced by compression molding raw material powder. The solid electrolyte only needs to contain at least lithium and sulfur as constituent elements, and examples of such a compound include compounds such as Li ₂ S—B ₂ S ₃ . In addition to lithium and sulfur as constituent elements, the solid electrolyte preferably further contains phosphorus. Examples of such compounds include Li ₇ P ₃ S ₁₁ , Li ₃ PS ₄ and their anions. Examples thereof include those partially oxygen-substituted. The composition ratio of the elements constituting the solid electrolyte is not limited to the above-described ratio. The positive electrode active material only needs to contain lithium, iron, and sulfur as constituent elements, and examples of such compounds include compounds such as Li ₂ FeS ₂ and Li _2.33 Fe _0.67 S ₂ . Further, other positive electrode active materials include compounds such as lithium titanium sulfide and lithium vanadium sulfide. The composition ratio of the elements constituting the positive electrode active material is not limited to the above-described ratio.

1 is configured in the form of a fired body, the following materials are used.

As the solid electrolyte contained in the solid electrolyte layer 3 or the solid electrolyte contained in the positive electrode layer 2 or the negative electrode layer 4, a lithium-containing phosphate compound having a NASICON structure can be used. Lithium-containing phosphoric acid compound having a NASICON-type structure, the chemical formula _{_{_{Li x M y (PO 4)}}} 3 ( Formula, x 1 ≦ x ≦ 2, y is a number in the range of 1 ≦ y ≦ 2, M Includes one or more elements selected from the group consisting of Ti, Ge, Al, Ga and Zr), for example, Li _1.5 Al _0.5 Ti _1.5 (PO ₄ ) ₃ . In this case, part of P in the above chemical formula may be substituted with B, Si, or the like. For example, two or more compounds having different compositions of lithium-containing phosphate compounds having a NASICON type structure such as Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ and Li _1.2 Al _0.2 Ti _1.8 (PO ₄ ) ₃ are mixed. You may use the mixture.

In addition, the lithium-containing phosphate compound having a NASICON structure used in the above solid electrolyte includes a crystal phase of a lithium-containing phosphate compound having a NASICON structure, or a lithium-containing phosphate having a NASICON structure by heat treatment You may use the glass which precipitates the crystal phase of a phosphoric acid compound.

In addition, as a material used for said solid electrolyte, it is possible to use the material which has ion conductivity and is so small that electronic conductivity can be disregarded other than the lithium-containing phosphate compound which has a NASICON structure. Examples of such a material include lithium halide, lithium nitride, lithium oxyacid salt, and derivatives thereof. In addition, Li-PO system compounds such as lithium phosphate (Li ₃ PO ₄ ), LIPON (LiPO _4−x N _x ) in which nitrogen is mixed with lithium phosphate, and Li—Si—O such as Li ₄ SiO ₄ _Such as La-based compounds, Li-P-Si-O based compounds, Li-V-Si-O based compounds, La _0.51 Li _0.35 TiO _2.94 , La _0.55 Li _0.35 TiO ₃ , Li _3x La _{2 / 3-x} TiO ₃ Examples thereof include compounds having a lobskite structure, compounds having a garnet structure having Li, La, and Zr.

Examples of the positive electrode active material include a lithium-containing phosphate compound having a NASICON structure such as Li ₃ V ₂ (PO ₄ ) ₃ , a lithium-containing phosphate compound having an olivine structure such as LiFePO ₄ and LiMnPO ₄ , LiCoO ₂ , and LiCo. It is possible to use a layered compound such as _1/3 Ni _1/3 Mn _1/3 O ₂ or a lithium-containing compound having a spinel type structure such as LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , Li ₄ Ti ₅ O _12. it can.

As the negative electrode active material, MOx (M includes at least one element selected from the group consisting of Ti, Si, Sn, Cr, Fe, Nb and Mo, x is 0.9 ≦ x ≦ 2.0. A compound having a composition represented by the following formula can be used. For example, a mixture in which two or more active materials having a composition represented by MOx containing different elements M such as TiO ₂ and SiO ₂ may be used. As the negative electrode active material, graphite-lithium compounds, lithium alloys such as Li-Al, oxidation of Li ₃ V ₂ (PO ₄ ) ₃ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Li ₄ Ti ₅ O _12, etc. Thing, etc. can be used. The negative electrode layer 4 may be formed from metallic lithium.

In the all-solid-state battery laminate 1 of the present invention, the solid electrolyte layer 3 includes a solid electrolyte composed of a lithium-containing phosphate compound having a NASICON structure, and at least one of the positive electrode layer 2 or the negative electrode layer 4 has a NASICON structure. It is preferable that the solid electrolyte which consists of said lithium containing phosphoric acid compound is included.

In the case where the solid electrolyte and the electrode active material are configured in the form of a fired body, in order to manufacture the all-solid battery laminate 1 configured as described above, in the present invention, first, the positive electrode layer 2 or the negative electrode layer 4 is used. An unsintered electrode layer that is at least one of the unsintered bodies and an unsintered solid electrolyte layer that is an unsintered body of the solid electrolyte layer 3 are prepared (unsintered layer manufacturing step). Thereafter, the produced unfired electrode layer and the unfired solid electrolyte layer are laminated to form a laminate (laminated body forming step). Then, the obtained laminate is fired to produce a battery body 11 composed of the fired body (firing step). The positive electrode layer 2 and / or the negative electrode layer 4 and the solid electrolyte layer 3 are joined by firing.

Next, the battery body 11 is covered with resin. Then, the resin is impregnated in the voids of the fired body constituting the battery body 11. Further, by solidifying the resin, the insulating layer 32 including the solidified resin component and the resin component solidified in the gap between the fired body and the fired body are interposed between the battery element body 11 and the insulating layer 32. Then, an intervening layer in contact with both the battery body 11 and the insulating layer 32 is formed.

In this way, the all-solid-state battery 41 including the intervening layer disposed between the battery element body 11 (fired body) and the insulating layer 32 and in contact with both the battery element body 11 (fired body) and the insulating layer 32 is provided. Can be produced.

The intervening layer is not necessarily formed on the entire outer surface of the battery element body 11 (fired body), but is formed on at least a part of the surface of the battery element body 11 (fired body). An effect of suppressing deterioration of battery characteristics on the surface can be expected. Therefore, in the step of covering the battery body 11 with the resin, the surface of the battery body 11 may be partially covered.

There are no particular limitations on the method of coating the surface of the battery body 11 (fired body) with resin, the method of impregnating the resin in the voids of the fired body, and the method of solidifying the resin to form the insulating layer 32 and the intervening layer. When a thermoplastic resin or a thermoplastic resin is used as the resin, in addition to extrusion molding and injection molding, for example, a method of applying a liquid or semi-solid resin at a high temperature to the surface of the fired body, high temperature A method of immersing the fired body in a liquid or semi-solid resin, a method of covering the surface of the fired body at a high temperature by melting or solidifying the solid resin powder or debris, etc. it can.

The method for coating the surface of the fired body with a photocurable resin is not particularly limited. For example, a solution obtained by dissolving a resin monomer or oligomer together with a photopolymerization initiator is applied to the surface of the fired body or sprayed, and a solvent is used. After vaporizing, a method of solidifying the resin by irradiating ultraviolet rays or the like can be used.

In order to impregnate the resin in the voids of the fired body, the surface of the fired body is coated with resin, and then the fired body is allowed to stand still. The fired body is heat-treated to increase the fluidity of the resin. A method such as arranging in a reduced-pressure atmosphere may also be used. In a state where the surface of the sintered body is covered with a paste-like resin, a method of impregnating the resin in the voids on the surface of the sintered body by heat treatment while reducing the pressure is particularly preferable.

In addition, as shown in FIG. 2, in order to draw an electric current efficiently from the positive electrode layer 2 and the negative electrode layer 4 (FIG. 1), a metal layer is formed on both side surfaces (the positive electrode layer 2 and the negative electrode layer 4) of the battery body 11. A terminal layer 22 (conductive layer) may be formed. Examples of the method for forming the conductive layer include a sputtering method. Alternatively, the metal paste may be applied or dipped and heat-treated.

In the laminated body forming step, it is preferable to laminate the unfired bodies of the positive electrode layer 2, the solid electrolyte layer 3, and the negative electrode layer 4 to form the unfired laminated body of the unit cell structure 5. Further, in the laminated body forming step, the laminated body 1 may be formed by laminating a plurality of laminated bodies of the unit cell structure 5 with an unfired body of the current collector layer 6 interposed therebetween. In this case, a plurality of laminated bodies of the unit cell structures 5 may be laminated electrically in series or in parallel.

The method for forming the green sheet or the printed layer as the unfired electrode layer and the unfired solid electrolyte layer is not particularly limited, but a doctor blade method, a die coater, a comma coater, or the like, or printing to form the green sheet. Screen printing or the like can be used to form the layer. The method for laminating the unfired electrode layer and the unfired solid electrolyte layer is not particularly limited, but hot isostatic pressing (HIP), cold isostatic pressing (CIP), isostatic pressing (WIP), etc. The green electrode layer and the green solid electrolyte layer can be laminated by using.

The slurry for forming the green sheet or the printing layer includes an organic vehicle in which an organic material is dissolved in a solvent, a main material (a positive electrode active material and a solid electrolyte, a negative electrode active material and a solid electrolyte, a solid electrolyte, or a current collector material. ) And wet mixed. Media can be used in wet mixing, and specifically, a ball mill method, a viscomill method, or the like can be used. On the other hand, a wet mixing method that does not use media may be used, and a sand mill method, a high-pressure homogenizer method, a kneader dispersion method, or the like can be used. The organic material contained in the slurry for forming the green sheet or the printing layer is not particularly limited, and polyvinyl acetal resin, cellulose resin, acrylic resin, urethane resin, and the like can be used.

The slurry may contain a plasticizer. Although the kind of plasticizer is not particularly limited, phthalic acid esters such as dioctyl phthalate and diisononyl phthalate may be used.

In the firing step, the atmosphere is not particularly limited, but it is preferably performed under conditions that do not change the valence of the transition metal contained in the electrode active material. The firing temperature is preferably 400 ° C. or higher and 1000 ° C. or lower.

Next, specific examples of the present invention will be described. In addition, the Example shown below is an example and this invention is not limited to the following Example.

Hereinafter, examples 1 to 3 of the all solid state battery including the intervening layer and comparative examples of the all solid state battery not including the intervening layer will be described.

(Preparation of materials)
First, in order to produce an all-solid battery, the following materials were prepared as starting materials for the solid electrolyte layer, the positive electrode layer, the negative electrode layer, and the current collector layer.

A glass powder having a composition of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ as a solid electrolyte material, a powder containing a crystal phase of NASICON structure having a composition of Li ₃ V ₂ (PO ₄ ) ₃ as a positive electrode active material, A titanium dioxide powder having an anatase type crystal structure as a negative electrode active material, a carbon powder as an electron conductive material, and a glass ceramic powder having a composition of Li _1.0 Ge _2.0 (PO ₄ ) ₃ as a fireable material were prepared.

Each slurry was prepared by the following method using the above materials.

(Preparation of slurry)
As raw materials for the solid electrolyte, positive electrode, negative electrode, and current collector, the main material, butyral resin, and alcohol were weighed at a mass ratio of 100: 15: 140. And after dissolving butyral resin in alcohol, after enclosing in a container together with the main material and media and rotating the container, the medium is taken out from the container, so that the solid electrolyte slurry, the positive electrode slurry, the negative electrode slurry, the current collector slurry Was made.

Main materials are solid electrolyte material for solid electrolyte slurry, positive electrode active material for positive electrode slurry, powder mixed with electron conductive material and solid electrolyte material in mass ratio of 45:15:40, negative electrode active material for negative electrode slurry The powder in which the electron conductive material and the solid electrolyte material were mixed at a mass ratio of 45:15:40, and the current collector slurry used was a powder in which the electron conductive material and the calcinable material were mixed at a mass ratio of 10:90. .

Each green sheet was produced by the following method using each obtained slurry.

(Unbaked layer (green sheet) production process)
Each slurry was coated on a polyethylene terephthalate (PET) film using a doctor blade method, dried on a hot plate heated to a temperature of 40 ° C., and formed into a sheet shape to a predetermined thickness, A sheet was prepared by cutting into a size of 25 mm × 25 mm. The thickness of the green sheet was 35 μm for the solid electrolyte sheet, 25 μm for the positive electrode sheet, 15 μm for the negative electrode sheet, and 15 μm for the current collector sheet.

Using each obtained green sheet, a laminate was formed by the following method.

(Laminate formation process)
As each green sheet peeled off from the PET film was stacked one by one, it was thermocompression bonded sequentially by sandwiching it between two stainless steel flat plates. The thermocompression bonding was performed by heating a flat plate made of stainless steel to a temperature of 60 ° C. and applying a pressure of 1000 kg / cm ² . Then, the laminated body of the green sheet | seat pressure-bonded was sealed in the polyethylene film container in the vacuum state, the polyethylene film container was immersed in water, and the pressure was applied to water. A pressure of 180 MPa was applied to the water by an isotropic pressure press. Thus, the laminated body 1 (FIG. 1) was formed. As shown in FIG. 1, the laminated body 1 has a structure in which two unit cell structures 5 are laminated so as to be electrically connected in series. Two unit cell structures 5 are connected in series via a current collector layer 6 made of two current collector green sheets. The unit cell structure 5 includes a positive electrode layer 2 composed of two positive electrode green sheets, a solid electrolyte layer 3 composed of two solid electrolyte green sheets, and a negative electrode layer 4 composed of two negative electrode sheets.

(Baking process)
The laminate 1 having a plane size of 25 mm × 25 mm was cut into a size of 10 mm × 10 mm, sandwiched between two porous setters, and fired in a state where a pressure of ² kg / cm ² was applied to the setter. The laminated body 1 is baked at a temperature of 500 ° C. in a nitrogen gas atmosphere containing 1% by volume of oxygen to remove the butyral resin and then baked at a temperature of 700 ° C. in a nitrogen gas atmosphere. went.

(Production of battery elements)
A battery element 21 shown in FIG. 2 was produced.

Specifically, first, a metal paste containing silver particles was applied to both surfaces of the battery body (fired body) 11 to form a metal paste layer as the terminal layer 22. Next, the terminal layer 22 is dried on the terminal layer 22 with the stainless steel leads as the positive and negative terminals 23 placed thereon, and the positive and negative terminals 23 are placed on both surfaces of the battery body 11. Stuck.

Using the battery element 21 thus produced, all-solid batteries of Examples 1 to 3 and a comparative example were produced as described below.

Example 1
As shown in FIG. 2, a resin coating 31 was produced by coating the battery element 21 with an epoxy resin.

Specifically, first, the battery element 21 is placed in a polytetrafluoroethylene mold, and an epoxy resin liquid sealant (manufactured by Panasonic Electric Works Co., Ltd., model number CV5788) is injected into the mold. Heated at a temperature for 1 hour, impregnated with a liquid sealant in the voids on the surface of the sintered body, and then heated at a temperature of 150 ° C. for 1 hour to cure the epoxy resin to insulate outside the battery element 21 Layer 32 was formed. Next, the polytetrafluoroethylene mold was removed, and the resin coating 31 was taken out.

In the above process, in order to improve the sealing property by the insulating layer 32, the terminal 23 is partially covered with a polypropylene film 33 in advance as shown in FIG. 3, and the terminal 23 and the insulating layer 32 are made of polypropylene. The film 33 is in close contact with the film 33.

Thereafter, the resin coating 31 shown in FIG. 2 was covered with the exterior member 42 as shown in FIG. 3 to produce the all-solid-state battery 41 of Example 1. As the exterior member 42, an aluminum laminate film (manufactured by Dai Nippon Printing Co., Ltd., model number D-EL40H) in which a resin layer, a water vapor blocking layer, and an adhesive layer are integrally laminated was used. The resin-coated body 31 is disposed between two aluminum laminate films cut to a predetermined size, and the aluminum laminate films are bonded together by pressing a flat plate heated to a temperature of 150 ° C. Produced.

In the above process, in order to improve the sealing performance by the exterior member 42, the terminal 23 is partially covered with a polypropylene film 33 in advance as shown in FIG. 3, and the terminal 23 and the exterior member 42 are made of polypropylene. The film 33 is in close contact with the film 33.

(Example 2)
The resin-coated body 31 shown in FIG. 2 was not covered with the exterior member 42 as shown in FIG.

(Example 3)
As shown in FIG. 2, the resin coating 31 was produced by coating the battery element 21 with a high-density polyethylene resin.

Specifically, first, a battery element 21 is disposed between two high-density polyethylene resin films cut to a predetermined size, and a flat plate heated to a temperature of 250 ° C. is pressed against the high-density polyethylene resin. The high-density polyethylene resin film was bonded to each other while the resin film was softened and the resin was impregnated in the voids on the surface of the sintered body to form the insulating layer 32 on the outside of the battery element 21.

Thereafter, in the same manner as in Example 1, the resin coating 31 was covered with an aluminum laminate film as the exterior member 42 to produce the all-solid-state battery 41 of Example 3.

(Comparative example)
The battery element 21 was not covered with a resin, but was covered with an exterior member 42 to produce an all-solid battery of a comparative example. The process of covering with the exterior member 42 is the same as in the first embodiment.

(Observation of resin coating)
In the all-solid-state battery 41 of Example 1, the resin coating 31 was observed.

Fig. 4 shows a photograph of the fracture surface of the resin coating. The white layer of the battery body 11 is a solid electrolyte layer, and the black layer corresponds to a layer containing carbon, that is, a positive electrode layer, a negative electrode layer, and a current collector layer. As will be described later, the intervening layer is also included in the black layer. A structure in which the insulating layer 32 covers the outside of the battery body 11 was confirmed.

FIG. 5 shows a scanning electron microscope (SEM) photograph of the area surrounded by the broken line in FIG. When considered together with the photograph of FIG. 4, it was confirmed that 32 in FIG. 5 is an insulating layer and 63 is a solid electrolyte layer. A layer 62 corresponding to a positive electrode layer having a thickness of about 20 μm and a layer 61 corresponding to an intervening layer having a thickness of about 20 μm were confirmed between the insulating layer 32 and the positive electrode layer 62.

FIG. 6 shows a scanning electron microscope (SEM) photograph in which the layer 61 of FIG. 5 is enlarged. FIG. 7 shows a scanning electron microscope (SEM) photograph in which the layer 62 of FIG. 5 is enlarged. As shown in FIG. 7, the layer 62 has an uneven cross-sectional structure, and it was confirmed that the positive electrode active material, the conductive agent, and the main material of the solid electrolyte material were fired in a state of including voids. . On the other hand, as shown in FIG. 6, the layer 61 was confirmed to have a relatively smooth cross-sectional structure because the epoxy resin entered the voids of the positive electrode layer and was cured.

Therefore, in the all-solid-state battery 41 of Example 1, the resin coating 31 includes the battery body 11 and the insulating layer between the battery body 11 and the insulating layer 32 containing an epoxy resin that is a thermosetting resin. It was confirmed that the intervening layer 61 in contact with both of them was formed. The intervening layer 61 is a layer in which the components of the battery body 11 and the insulating layer 32 are mixed, and the epoxy resin that forms the insulating layer 32 in the voids of the fired body that forms the battery body 11. It was confirmed to have a structure in which.

In addition, although not shown in the all-solid-state battery 41 of Example 3, the resin coating 31 using the high-density polyethylene resin that is a thermoplastic resin was also observed by the above method. It was confirmed that the structure was provided with an intervening layer as in 1.

(Charge / discharge test)
The all solid state batteries of Examples 1 to 3 and Comparative Example were subjected to a charge / discharge test according to the following conditions.

The battery was charged to a voltage of 6.4 V with a current of 50 μA in an environment of a temperature of 24 to 26 ° C. and a relative humidity of 60%, and then held at a voltage of 6.4 V for 20 hours. Thereafter, the battery was discharged to a voltage of 0 V with a current of 50 μA. The above charging / discharging was repeated 50 times.

As a result of the above charge / discharge test, Table 1 below shows the discharge capacities in the first and 50th charge / discharge in all solid state batteries of Examples 1 to 3 and the comparative example, and the retention rate of the discharge capacity calculated by the following equation. Indicates.

Discharge capacity maintenance rate [%] = (50th discharge capacity [μAh] / 1st discharge capacity [μAh]) × 100

From Table 1, it was confirmed that the all-solid batteries of Examples 1 to 3 had a higher discharge capacity retention rate and excellent cycle characteristics than the all-solid battery of Comparative Example having no intervening layer. Furthermore, it was confirmed that the all-solid-state batteries of Examples 1 and 3 having an aluminum laminate film exterior member have particularly excellent cycle characteristics.

It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the claims.

Since it is possible to prevent moisture in the atmosphere from entering the battery body, reinforce the mechanical strength of the battery body, and improve cycle characteristics, the present invention can It is particularly useful for manufacturing.

1: laminate, 2: positive electrode layer, 3: solid electrolyte layer, 4: negative electrode layer, 5: single cell structure, 6: current collector layer, 11: battery element body, 21: battery element, 22: terminal layer, 23: Terminal, 31: Resin coating, 32: Insulating layer, 33: Polypropylene film, 41: All solid state battery, 42: Exterior member, 61: Layer corresponding to intervening layer, 62: Layer corresponding to positive electrode layer, 63: A layer corresponding to the solid electrolyte layer.

Claims

A battery element body including at least one of a positive electrode layer or a negative electrode layer and a solid electrolyte layer;
An insulating layer that covers the battery body and includes a resin;
An intervening layer interposed between the battery element body and the insulating layer and in contact with both the battery element body and the insulating layer;
The all-solid-state battery in which the said intervening layer contains the component which comprises the said battery element | base_body, and the resin component which comprises the said insulating layer.
The all-solid-state battery according to claim 1, wherein the battery body includes a current collector layer.
The all-solid-state battery according to claim 1 or 2, wherein the battery body is composed of a fired body.
The all-solid-state battery according to claim 3, wherein the intervening layer includes the fired body and the resin component present in a void of the fired body.
The all solid according to any one of claims 1 to 4, wherein the resin includes at least one selected from the group consisting of a thermosetting resin, a thermoplastic resin, and a photocurable resin. battery.
The all-solid-state battery according to any one of claims 1 to 5, further comprising an exterior member that covers the insulating layer.
An unsintered electrode layer that is an unsintered body of at least one of the positive electrode layer and the negative electrode layer and an unsintered solid electrolyte layer that is an unsintered body of the solid electrolyte layer;
A laminate forming step of forming a laminate by laminating the unfired electrode layer and the unfired solid electrolyte layer;
A firing step of firing the laminate to produce a battery body composed of the fired body,
Coating the battery body with a resin;
By solidifying the resin, an insulating layer containing a solidified resin component, a solidified resin component and the fired body component are interposed between the battery body and the insulating layer, and the battery body and the And a step of forming an intervening layer in contact with both of the insulating layers.
An unsintered electrode layer that is an unsintered body of at least one of the positive electrode layer and the negative electrode layer and an unsintered solid electrolyte layer that is an unsintered body of the solid electrolyte layer;
A laminate forming step of forming a laminate by laminating the unfired electrode layer and the unfired solid electrolyte layer;
A firing step of firing the laminate to produce a battery body composed of the fired body,
Coating the battery body with a resin;
Impregnating the resin in the voids of the fired body constituting the battery body; and
By solidifying the resin, an insulating layer containing a solidified resin component, and a resin component solidified in a gap between the fired body and the fired body, are interposed between the battery body and the insulating layer. And a step of forming an intervening layer in contact with both of the battery element body and the insulating layer.