JP2023047443A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery that can prevent the occurrence of defects due to misalignment of a unit electrode body and a current collector that make up a multilayer electrode body when an all-solid battery equipped with a multilayer electrode body with a bipolar structure is assembled, and can suppress deterioration of characteristics due to moisture intruding inside, and that relates to goals 3, 7, 11 and 12 of the SDGs.SOLUTION: In an all-solid battery according to the present invention, a multilayer electrode body in which a plurality of unit electrode body each including a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode are laminated, and the adjacent unit electrode bodies are connected in series via a current collector is enclosed inside an exterior body, and a resin sheet containing a desiccant is attached to the peripheral surface of the multilayer electrode body.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an all-solid-state battery that can prevent defects during assembly of an all-solid-state battery that includes a laminated electrode body having a bipolar structure, and that can suppress deterioration in characteristics due to moisture entering the battery.

In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers, and the commercialization of electric vehicles, there is a growing need for compact, lightweight, high-capacity, high-energy-density batteries. ing.

At present, lithium batteries, particularly lithium ion batteries, which can meet this demand, use an organic electrolytic solution containing an organic solvent and a lithium salt as a non-aqueous electrolyte.

With the further development of lithium-ion battery application equipment, there is a demand for longer life, higher capacity, and higher energy density of lithium-ion batteries. Reliability of the lithium-ion battery is also highly demanded.

However, since the organic electrolyte used in lithium-ion batteries contains an organic solvent, which is a combustible substance, there is a possibility that the organic electrolyte will generate abnormal heat when an abnormal situation such as a short circuit occurs in the battery. There is In addition, with the recent trends toward higher energy densities in lithium ion batteries and an increase in the amount of organic solvents in organic electrolytes, the reliability of lithium ion batteries is required to be even higher.

Under the circumstances described above, an all-solid-state lithium battery (all-solid-state battery) that does not use an organic solvent has attracted attention (Patent Documents 1 and 2, etc.). The all-solid-state battery uses a molded body of a solid electrolyte that does not use an organic solvent instead of a conventional organic solvent-based electrolyte, and has a high degree of safety without the risk of abnormal heat generation of the solid electrolyte.

All-solid-state batteries are not only highly safe, but also highly reliable, highly resistant to environmental conditions, and have a long life. It is expected to be a maintenance-free battery that can By providing society with all-solid-state batteries, among the 17 Sustainable Development Goals (SDGs) established by the United Nations, Goal 3 (ensure healthy lives and promote well-being for all at all ages). Goal 7 (Ensure access to affordable, reliable, sustainable and modern energy for all), Goal 11 (Inclusive, Safe, Resilient and Sustainable Cities and Human Settlements). and achieve Goal 12 (Ensure sustainable production and consumption patterns).

By the way, in lithium batteries, there is a problem that various characteristics such as an increase in internal resistance and a decrease in capacity are caused by moisture intruding into the battery, and there is a demand to prevent such problems from occurring.

For example, in Patent Document 3, a synthetic resin housing (exterior body) that allows external moisture to enter the interior more easily than a metal container is used, and, for example, a supporting electrolyte, a solvent, and a polymer for gelation In a battery using a non-fluid electrolyte layer containing , a technique has been proposed for avoiding the occurrence of the above problems by arranging a moisture absorbent inside.

However, in a battery having an electrolyte containing a solvent, there is concern that part of the elements constituting the hygroscopic agent will be eluted into the solvent, resulting in deterioration of characteristics due to the hygroscopic agent placed inside. In addition, there is a possibility that the surface of the hygroscopic agent will become wet with the solvent, thereby failing to function as a hygroscopic agent.

In addition, in all-solid-state batteries, it has been proposed to have a bipolar structure that can achieve high voltage and high capacity by stacking and connecting a plurality of power generation elements (unit cells) in series (Patent document 4). In the battery with the bipolar structure, when a plurality of power generation elements are sequentially stacked to assemble the battery, positional deviation may occur, which may cause problems such as occurrence of short circuit and increase in internal resistance. Therefore, it is necessary to deal with it.

JP 2017-40531 A JP 2017-168387 A JP-A-2000-243357 JP 2021-64584 A

The present invention has been made in view of the above circumstances, and an object of the present invention is to assemble a unit electrode body and a current collector that constitute the stacked electrode body when assembling an all-solid-state battery having a stacked electrode body having a bipolar structure. An object of the present invention is to provide an all-solid-state battery capable of preventing the occurrence of defects due to misalignment and suppressing deterioration of characteristics due to moisture entering the inside.

In the all-solid-state battery of the present invention, a laminated electrode body in which a plurality of unit electrode bodies are stacked and adjacent unit electrode bodies are connected in series via a current collector is enclosed in the exterior body, A resin sheet containing a desiccant is attached to the peripheral surface of the laminated electrode body.

ADVANTAGE OF THE INVENTION According to the present invention, when assembling an all-solid-state battery having a laminated electrode body having a bipolar structure, it is possible to prevent the positional deviation of the unit electrode bodies and current collectors constituting the laminated electrode body from occurring, thereby preventing the occurrence of short circuits. It is possible to provide an all-solid-state battery that can prevent an increase in internal resistance, etc., and can suppress deterioration in characteristics due to moisture entering the inside.

1 is a longitudinal sectional view schematically showing an example of an all-solid-state battery of the present invention; FIG.

In the all-solid-state battery of the present invention, a plurality of unit electrode bodies each having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode are laminated, and adjacent unit electrode bodies serve as current collectors. A laminated electrode body serially connected via a wall is enclosed in the exterior body, and the peripheral surface of the laminated electrode body, that is, the unit electrode body and the current collector are laminated in a columnar shape. A resin sheet containing a desiccant is attached to the side surface of the stacked electrode assembly.

In the all-solid-state battery of the present invention, the resin sheet attached to the peripheral surface of the laminated electrode body can prevent the unit electrode body and current collector constituting the laminated electrode body from being misaligned. In addition, part or all of the moisture that has entered the interior of the exterior body is absorbed by the resin sheet due to the action of the desiccant contained in the resin sheet, so that the solid electrolyte and the active material deteriorate due to such moisture. can be suppressed. As a result, in the all-solid-state battery of the present invention, it is possible to prevent occurrence of a short circuit and an increase in internal resistance due to displacement of the unit electrode body and current collector, as well as suppress deterioration of characteristics due to moisture intruding inside.

Further, for example, in the case of a battery having an electrolytic solution containing a solvent (including a gel-like polymer), when a desiccant is placed in the outer package, part of the elements constituting the desiccant is dissolved in the electrolyte. There is a risk that the battery characteristics will be impaired by elution into the solvent of the desiccant, or that the surface of the desiccant will become wet with the solvent, and the moisture absorption function will not occur. , the occurrence of such problems can also be prevented.

As the desiccant in the resin sheet containing the desiccant, it is sufficient that it can adsorb moisture entering the inside of the battery, and the mechanism may be either chemical adsorption or physical adsorption. Specifically, drying agents that chemically adsorb moisture such as calcium oxide, calcium chloride, magnesium perchlorate, barium oxide, barium perchlorate, phosphorus pentoxide, strontium oxide, and magnesium sulfate; moisture such as synthetic zeolite and silica gel a desiccant that physically adsorbs ; and the like, and calcium oxide is preferably used. One desiccant may be used, or two or more desiccants may be used.

From the viewpoint of moisture adsorption, the desiccant is preferably a powder having a BET specific surface area of 10 m ² /g or more, more preferably 30 m ² /g or more, more preferably 40 m ² /g. It is particularly preferable that it is above. The BET specific surface area of the desiccant referred to in this specification is a value determined by the BET method in accordance with Japanese Industrial Standards (JIS) K 6217. For example, a specific surface area measuring device ("Macsorb HM model-1201").

A resin sheet containing a desiccant is formed by molding a composition containing a desiccant and a resin into a sheet, and the resin in the resin sheet plays a role of retaining the desiccant contained in the sheet. . As the resin, the same resins as those used in batteries such as lithium batteries, such as separators and electrode binders, can be used. Specifically, polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers; polyesters such as polyethylene terephthalate and copolyester; fluorine resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE); butadiene rubber; and the like, and polyolefin and fluororesin are preferably used. One type of resin may be used, or two or more types may be used.

In the resin sheet containing the desiccant, the content of the desiccant is preferably 30% by mass or more, more preferably 50% by mass or more, from the viewpoint of further enhancing the moisture adsorption performance inside the battery. However, if the amount of desiccant in the resin sheet is too large, for example, the composition may not be formed into a sheet shape, so the content of the desiccant in the resin sheet is 95% by mass or less. and more preferably 85% by mass or less.

In the resin sheet containing a desiccant, the component other than the desiccant may be only the resin, and other components (surfactant, antistatic agent, pigment, indicator, fragrance, lubricant filler, antioxidant, etc.) may contain. The content of the resin in the resin sheet is, for example, preferably 5% by mass or more, more preferably 15% by mass or more, preferably 70% by mass or less, and 50% by mass or less. is more preferred. When the resin sheet contains a desiccant and a component other than the resin, the contents of the desiccant and the resin may be set within a range that satisfies the preferred values described above.

The thickness of the resin sheet containing the desiccant is not particularly limited, but in general, it is preferably 50 μm or more in order to obtain a certain level of moisture absorption. In order to prevent a decrease in capacity, the thickness is preferably 500 μm or less.

When a composition containing a desiccant and a resin is molded into a sheet to form a resin sheet, it is preferable that the desiccant and the like are sufficiently dried before being blended to form the composition. Moreover, in the mixing of the desiccant and the resin, if necessary, the resin may be melted and mixed by heating.

In addition, from the viewpoint of moisture adsorption, it is preferable that the resin is fibrillated. can be fibrillated.

A commercially available resin sheet containing a desiccant may be used. (trade name)" can also be used.

FIG. 1 shows a longitudinal sectional view schematically showing an example of the all-solid-state battery of the present invention. The all-solid-state battery 1 shown in FIG. 1 has a coin-shaped (also called a button-shaped) exterior body composed of an exterior can 3, a sealing can 4, and a gasket 5, and contains two unit electrode bodies 20, It has a shape in which a laminated electrode body 2 configured by laminating 20 is enclosed.

In the all-solid-state battery 1, the sealing can 4 is fitted into the opening of the outer can 3 via a gasket 5, and the opening end of the outer can 3 is tightened inward, whereby the gasket 5 is attached to the sealing can. 4, the opening of the outer can 3 is sealed, and the inside of the battery has a sealed structure.

Each of the unit electrode bodies 20 , 20 is configured by stacking a positive electrode 21 and a negative electrode 22 with a solid electrolyte layer 23 interposed therebetween. A current collector 6 is arranged between the positive electrode 21 of the unit electrode body 20 on the upper side in the figure and the negative electrode 22 of the unit electrode body 20 on the lower side in the figure. The upper unit electrode body 20 and the lower unit electrode body 20 are connected in series. Therefore, the positive electrode 21 in the upper unit electrode body 20, the current collector 6, and the negative electrode 22 in the lower unit electrode body 20 form a bipolar structure.

In the battery 1 shown in FIG. 1, although not shown, the inner surface of the sealing can 4 is electrically connected to the negative electrode 22 of the upper unit electrode body 20 via a current collector, thereby also serving as a negative electrode terminal. Although not shown, the inner surface of the outer can 3 is electrically connected to the positive electrode 21 of the lower unit electrode body 20 via a current collector, thereby also serving as a positive electrode terminal. Depending on the application of the battery, the outer can can also serve as the negative terminal, and the sealing can can also serve as the positive terminal.

In the all-solid-state battery 1 , a resin sheet 7 containing a desiccant is attached to the peripheral surface of the laminated electrode assembly 2 .

For example, in the case of a coin-shaped battery having an exterior body (battery container) having an exterior can and a sealing can as shown in FIG. ) or near the peripheral edge of the sealing can (between the sealing can 4 and the gasket 5 in the case of the battery 1 in FIG. 1). Therefore, in the all-solid-state battery, by attaching a resin sheet containing a desiccant to the peripheral surface of the laminated electrode body, as described above, it is possible to prevent the displacement of the unit electrode bodies and current collectors constituting the laminated electrode body. In addition, since the desiccant of the resin sheet on the surface of the laminated electrode body absorbs the moisture before it reaches the laminated electrode body, the reaction between the solid electrolyte and the active material of the laminated electrode body and the moisture causes the battery It is possible to suppress the deterioration of the characteristics.

The position on the peripheral surface of the laminated electrode body to which the resin sheet containing the desiccant is attached is not particularly limited as long as it is possible to prevent the displacement of the unit electrode body and the current collector. However, from the viewpoint of more effectively absorbing intruding moisture, it is preferable that the area is as wide as possible, and it is more preferable that the resin sheet is attached to the entire peripheral surface of the laminated electrode body.

As will be described later, in the all-solid-state battery, in addition to the solid electrolyte layer containing a solid electrolyte, the positive electrode usually contains a solid electrolyte, and the negative electrode also contains a solid electrolyte. At least one of the positive electrode, the negative electrode and the solid electrolyte layer contains a solid electrolyte that is highly reactive with moisture, such as a sulfide solid electrolyte, a hydride solid electrolyte, and a part of an oxide solid electrolyte. In this case, the effect of the present invention for suppressing deterioration of properties due to moisture that has entered inside becomes more pronounced.

The all-solid-state battery of the present invention includes primary batteries and secondary batteries.

(positive electrode)
The positive electrode related to the all-solid-state battery contains a positive electrode mixture containing a positive electrode active material and a solid electrolyte. and a structure in which a mixture layer) is formed on a current collector.

When the all-solid-state battery is a primary battery, the same positive electrode active material as used in conventionally known non-aqueous electrolyte primary batteries can be used. Specifically, for example, manganese dioxide, lithium-containing manganese oxide [for example, LiMn ₃ O ₆ , or the same crystal structure as manganese dioxide (β-type, γ-type, or a structure in which β-type and γ-type are mixed) is used. a composite oxide having a Li content of 3.5% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, and particularly preferably 1% by mass or less], Li _a Ti Lithium-containing composite oxides such as _5/3 O ₄ (4/3≦a<7/3); vanadium oxides; niobium oxides; titanium oxides; sulfides such as iron disulfide _; silver sulfides such as S; nickel oxides such as _NiO2 ;

In addition, when the all-solid-state battery is a secondary battery, the positive electrode active material used in conventionally known non-aqueous electrolyte secondary batteries, that is, an active material capable of intercalating and deintercalating Li (lithium) ions can be used the same as Specifically, Li _1-x M _r Mn _2-r O ₄ (where M is Li, Na, K, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Zr, Fe, Co , Ni, Cu, Zn, Al, Sn, Sb, In, Nb, Ta, Mo, W, Y, Ru and Rh, wherein 0≦x≦1,0 ≤ r ≤ 1), Li _r Mn _(1-st) Ni _s M _t O _(2-u) F _v (where M is Co, Mg, Al , B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr and W, and 0≤r≤1.2,0 <s < 0.5, 0 ≤ t ≤ 0.5, u + v < 1, −0.1 ≤ u ≤ 0.2, 0 ≤ v ≤ 0.1), Li _1-x Co _{1-rM r} O ₂ , where M is from the group consisting of Al, Mg, Ti, V, Cr, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba Lithium-cobalt composite oxide, Li _1-x Ni _1-r M _r O ₂ (at least one selected element, represented by 0≦x≦1, 0≦r≦0.5), provided that M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba; ≤ 1, 0 ≤ r ≤ 0.5), Li _1+s−x M _1−r N _r PO ₄ F _s (where M is selected from the group consisting of Fe, Mn and Co At least one selected element, wherein N is at least selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V and Ba An olivine-type composite oxide Li _2-x M _1- r _{N r} P ₂ O, which is one element and is represented by 0 ≤ x ≤ 1, 0 ≤ r ≤ 0.5, 0 ≤ s ≤ 1) ₇ (where M is at least one element selected from the group consisting of Fe, Mn and Co; N is Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo , Sn, Sb, V and Ba, and can be exemplified by pyrophosphate compounds represented by 0 ≤ x ≤ 2, 0 ≤ r ≤ 0.5). Only one of these may be used, or two or more thereof may be used in combination.

When the all-solid-state battery is a secondary battery, the average particle size of the positive electrode active material is preferably 1 μm or more, more preferably 2 μm or more, and preferably 10 μm or less, and 8 μm or less. is more preferable. The positive electrode active material may be primary particles or secondary particles obtained by agglomeration of primary particles. When a positive electrode active material having an average particle size within the above range is used, a large amount of interface with the solid electrolyte contained in the positive electrode can be obtained, so that the load characteristics of the battery are further improved.

The average particle diameter of various particles (positive electrode active material, solid electrolyte, etc.) referred to in this specification is measured using a particle size distribution measuring device (Microtrac particle size distribution measuring device “HRA9320” manufactured by Nikkiso Co., Ltd.). means the 50% diameter value (D ₅₀ ) in the volume-based integrated fraction when the integrated volume is obtained from .

When the all-solid-state battery is a secondary battery, the positive electrode active material preferably has, on its surface, a reaction suppression layer for suppressing reaction with the solid electrolyte contained in the positive electrode.

If the positive electrode active material and the solid electrolyte are in direct contact with each other in the molded body of the positive electrode mixture, the solid electrolyte may be oxidized to form a resistance layer, which may reduce the ionic conductivity in the molded body. A reaction suppression layer that suppresses the reaction with the solid electrolyte is provided on the surface of the positive electrode active material to prevent direct contact between the positive electrode active material and the solid electrolyte. Decrease can be suppressed.

The reaction suppression layer may be composed of a material that has ion conductivity and that can suppress the reaction between the positive electrode active material and the solid electrolyte. Materials that can constitute the reaction suppression layer include, for example, oxides containing Li and at least one element selected from the group consisting of Nb, P, B, Si, Ge, Ti and Zr, more specifically include Nb-containing oxides _{such as LiNbO3, Li3PO4} , _{Li3BO3 , Li4SiO4 , Li4GeO4} , _LiTiO3 , _LiZrO3 , _Li2WO4 and the _like . The reaction-suppressing layer may contain only one of these oxides, or may contain two or more of these oxides. may form Among these oxides, Nb-containing oxides are preferably used, and LiNbO ₃ is more preferably used.

The reaction suppressing layer is preferably present on the surface in an amount of 0.1 to 1.0 parts by mass with respect to 100 parts by mass of the positive electrode active material. Within this range, the reaction between the positive electrode active material and the solid electrolyte can be satisfactorily suppressed.

Sol-gel method, mechanofusion method, CVD method, PVD method, ALD method and the like can be used as methods for forming the reaction suppressing layer on the surface of the positive electrode active material.

The content of the positive electrode active material in the positive electrode mixture is preferably 60 to 98% by mass.

The positive electrode mixture can contain a conductive aid. Specific examples thereof include carbon materials such as graphite (natural graphite, artificial graphite), graphene, carbon black, carbon nanofiber, and carbon nanotube. For example, when Ag ₂ S is used as the active material, conductive Ag is generated during the discharge reaction, so the conductive additive does not have to be contained. When the positive electrode mixture contains a conductive aid, the content is preferably 1 to 10% by mass.

Also, the positive electrode mixture can contain a binder. Specific examples thereof include fluororesins such as PVDF. For example, when the positive electrode mixture contains a sulfide-based solid electrolyte (details will be described later), even if a binder is not used, good moldability is obtained in forming a positive electrode mixture molded body. If it can be ensured, the positive electrode mixture may not contain a binder.

When a binder is required in the positive electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when the positive electrode mixture contains a sulfide-based solid electrolyte and therefore can obtain moldability without requiring a binder, the content is preferably 0.5% by mass or less. , 0.3% by mass or less, and more preferably 0% by mass (that is, no binder is contained).

The solid electrolyte to be contained in the positive electrode mixture is not particularly limited as long as it has lithium ion conductivity. Examples include sulfide solid electrolytes, hydride solid electrolytes, halide solid electrolytes, and oxide solid electrolytes. etc. can be used.

Sulfide-based solid electrolytes include particles of Li ₂ SP ₂ S ₅ , Li ₂ S--SiS ₂ , Li ₂ SP ₂ S ₅ -GeS ₂ , Li ₂ S--B ₂ S ₃ -based glasses, and the like. In addition to these, thio-LISICON type materials [Li ₁₀ GeP ₂ S ₁₂ , Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _{0 ,} which have recently attracted attention as having high lithium ion conductivity Li _{12-12a-b+c+6d-e} M ¹ _3+a-b-c-d M ² _b M ³ _c M ⁴ _d M ⁵ _12-e X _e , such as _.3 , where M ¹ is Si, Ge or Sn; ^M2 is P or V, ^M3 is Al, Ga, Y or Sb, ^M4 is Zn, Ca, or Ba, ^M5 is either S or S and O, X is F, Cl, Br or I, 0≦a<3, 0≦b+c+d≦3, 0≦e≦3] and aldirodite type [Li _7-f+g PS _6-x Cl _x+y such as Li ₆ PS ₅ Cl (where 0. 05≦f≦0.9, −3.0f+1.8≦g≦−3.0f+5.7), Li _7-h PS _6-h Cl _i Br _j (where h=i+j, 0 <h≦1.8, 0.1≦i/j≦10.0)] can also be used.

Examples of hydride-based solid electrolytes include LiBH ₄ , solid solutions of LiBH ₄ and the following alkali metal compounds (for example, those having a molar ratio of LiBH ₄ and alkali metal compounds of 1:1 to 20:1), and the like. mentioned. Examples of alkali metal compounds in the solid solution include lithium halides (LiI, LiBr, LiF, LiCl, etc.), rubidium halides (RbI, RbBr, RbF, RbCl, etc.), cesium halides (CsI, CsBr, CsF, CsCl, etc.). , lithium amide, rubidium amide and cesium amide.

Examples of halide-based solid electrolytes include monoclinic LiAlCl ₄ , defect spinel LiInBr ₄ and monoclinic Li _6-3m Y _m X ₆ (where 0<m<2 and X=Cl or Br), etc. In addition, known compounds described in, for example, International Publication No. 2020/070958 and International Publication No. 2020/070955 can be used.

Examples of oxide-based solid electrolytes include garnet-type Li ₇ La ₃ Zr ₂ O ₁₂ , NASICON-type Li _1+O Al _1+O Ti _2-O (PO ₄ ) ₃ , Li _1+p Al _1+p Ge _2-p (PO ₄ ) ₃ and perovskite-type Li _3q La _2/3-q TiO ₃ .

Among these solid electrolytes, sulfide-based solid electrolytes are preferred because of their high lithium-ion conductivity, and sulfide-based solid electrolytes containing Li and P are more preferred, particularly those having high lithium-ion conductivity and chemical stability. Aldirodite-type sulfide-based solid electrolytes with high properties are more preferable.

From the viewpoint of reducing grain boundary resistance, the average particle size of the solid electrolyte is preferably 0.1 μm or more, more preferably 0.2 μm or more. From the viewpoint of forming a sufficient contact interface, the thickness is preferably 10 μm or less, more preferably 5 μm or less.

The content of the solid electrolyte in the positive electrode mixture is preferably 4 to 40% by mass.

When a current collector is used for the positive electrode, the current collector may be foil of metal such as aluminum or stainless steel, punching metal, net, expanded metal, foamed metal, carbon sheet, or the like.

The molded body of the positive electrode mixture is produced, for example, by compressing the positive electrode mixture prepared by mixing the positive electrode active material with a conductive agent, a binder, a solid electrolyte, etc., which are added as necessary, by pressure molding or the like. can be formed with

In the case of a positive electrode having a current collector, it can be produced by bonding the positive electrode mixture molded body formed by the above-described method to the current collector by pressure bonding or the like.

Alternatively, the positive electrode mixture and a solvent are mixed to prepare a positive electrode mixture-containing composition, which is applied onto a substrate such as a current collector or a solid electrolyte layer facing the positive electrode, dried, and then pressed. may be performed to form a molded body of the positive electrode mixture.

Organic solvents such as water and N-methyl-2-pyrrolidone (NMP) can be used as the solvent for the positive electrode mixture-containing composition. When the positive electrode mixture-containing composition also contains a solid electrolyte, it is preferable to select a solvent that does not easily deteriorate the solid electrolyte. In particular, sulfide-based solid electrolytes and hydride-based solid electrolytes are represented by hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene, because chemical reactions occur with minute amounts of moisture. It is preferred to use a non-polar aprotic solvent. In particular, it is more preferable to use a super-dehydrated solvent with a water content of 0.001% by mass (10 ppm) or less. In addition, fluorine-based solvents such as "Vertrel (registered trademark)" manufactured by Mitsui-DuPont Fluorochemicals, "Zeorolla (registered trademark)" manufactured by Nippon Zeon, "Novec (registered trademark)" manufactured by Sumitomo 3M, and , dichloromethane, and diethyl ether can also be used.

From the viewpoint of increasing the density and reducing the porosity of the positive electrode mixture and further reducing the internal resistance of the positive electrode, it is preferable that the positive electrode mixture is formed by compressing the positive electrode mixture by pressure molding or the like. , more preferred.

The thickness of the molded body of the positive electrode mixture is usually 50 μm or more, and preferably 200 μm or more from the viewpoint of increasing the capacity of the battery. In addition, the thickness of the molded body of the positive electrode mixture is usually 3000 μm or less, and preferably 500 μm or less from the viewpoint of increasing the output of the battery.

In the case of a positive electrode manufactured by forming a positive electrode mixture layer made of a molded positive electrode mixture on a current collector using a positive electrode mixture-containing composition containing a solvent, the positive electrode mixture layer The thickness of is preferably 50 to 1000 μm, and more preferably 500 μm or less from the viewpoint of increasing the output of the battery.

(negative electrode)
The negative electrode of the all-solid-state battery has, for example, a molded negative electrode mixture containing a negative electrode active material, a lithium sheet, or a lithium alloy sheet.

In the case where the negative electrode is a molded body of a negative electrode mixture containing a negative electrode active material, a molded body (such as a pellet) formed by molding the negative electrode mixture or a layer (negative electrode mixture layer) made of a molded body of the negative electrode mixture is used. Examples include those having a structure formed on a current collector.

When the negative electrode has a molded negative electrode mixture, examples of the negative electrode active material include carbon materials such as graphite, simple substances containing elements such as Si and Sn, compounds (such as oxides), and alloys thereof. be done. Lithium metal and lithium alloys (lithium-aluminum alloy, lithium-indium alloy, etc.) can also be used as the negative electrode active material.

The content of the negative electrode active material in the negative electrode mixture is preferably 10 to 99% by mass.

The negative electrode mixture may contain a conductive aid. Specific examples thereof include the same conductive aids exemplified above as those that can be contained in the positive electrode mixture. The content of the conductive aid in the negative electrode mixture is preferably 1 to 10% by mass.

Further, the negative electrode mixture can contain a binder. Specific examples thereof include the same binders as previously exemplified as those that can be contained in the positive electrode mixture. For example, when the negative electrode mixture contains a sulfide-based solid electrolyte (details will be described later), even if a binder is not used, good moldability is obtained in forming the molded body of the negative electrode mixture. If it can be ensured, the negative electrode mixture may not contain a binder.

If the negative electrode mixture requires a binder, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when the negative electrode mixture contains a sulfide-based solid electrolyte and therefore can obtain moldability without requiring a binder, the content is preferably 0.5% by mass or less. , 0.3% by mass or less, and more preferably 0% by mass (that is, no binder is contained).

In the negative electrode having the molded negative electrode mixture, the negative electrode mixture is made to contain a solid electrolyte. Specific examples thereof include the same solid electrolytes as previously exemplified as those that can be contained in the positive electrode mixture. Among the solid electrolytes exemplified above, it is more preferable to use a sulfide-based solid electrolyte because it has high lithium ion conductivity and has a function of improving the moldability of the negative electrode mixture.

The content of the solid electrolyte in the negative electrode mixture is preferably 4 to 49% by mass.

When a current collector is used for the negative electrode having the molded negative electrode mixture, the current collector may be copper or nickel foil, punching metal, mesh, expanded metal, foam metal, carbon sheet, or the like. can.

The molded body of the negative electrode mixture is prepared by, for example, compressing the negative electrode mixture prepared by mixing the negative electrode active material, optionally added conductive aid, solid electrolyte, binder, etc. by pressure molding or the like. can be formed by In the case of the negative electrode composed only of the molded negative electrode mixture, it can be produced by the above-described method.

In the case of a negative electrode having a current collector, it can be manufactured by bonding the molded body of the negative electrode mixture formed by the method described above to the current collector by pressure bonding or the like.

In the case of a negative electrode having a current collector, a negative electrode mixture-containing composition (paste, slurry, etc.) in which a negative electrode active material, a conductive aid added as necessary, a solid electrolyte, a binder, etc. are dispersed in a solvent ) is applied to the current collector, dried, and optionally subjected to pressure molding such as calendering to form a negative electrode mixture molded body (negative electrode mixture layer) on the surface of the current collector. It can also be manufactured by a method.

An organic solvent such as water or NMP can be used as the solvent for the negative electrode mixture-containing composition. However, when the negative electrode mixture-containing composition also contains a solid electrolyte, the solvent should not easily degrade the solid electrolyte. is preferably selected, and it is preferable to use the same solvents as the various solvents exemplified above as the solvent for the positive electrode mixture-containing composition containing the solid electrolyte.

From the viewpoint of increasing the density and reducing the porosity of the negative electrode mixture and further reducing the internal resistance of the negative electrode, the molded negative electrode mixture is preferably formed by compressing the negative electrode mixture by pressure molding or the like. , more preferred.

The thickness of the molded negative electrode mixture is usually 50 μm or more, and preferably 200 μm or more from the viewpoint of increasing the capacity of the battery. In addition, the thickness of the molded negative electrode mixture is usually 3000 μm or less, and preferably 500 μm or less from the viewpoint of increasing the output of the battery.

In the case of a negative electrode manufactured by forming a negative electrode mixture layer composed of a molded negative electrode mixture on a current collector using a negative electrode mixture-containing composition containing a solvent, the negative electrode mixture layer The thickness of is preferably 50 to 1000 μm, and more preferably 500 μm or less from the viewpoint of increasing the output of the battery.

In the case of a negative electrode having a lithium sheet or a lithium alloy sheet, a negative electrode made of these sheets alone or a laminate of these sheets and a current collector is used.

Examples of alloy elements related to lithium alloys include aluminum, lead, bismuth, indium, and gallium, with aluminum and indium being preferred. The ratio of the alloying elements in the lithium alloy (the total ratio of the alloying elements when multiple alloying elements are included) is preferably 50 atomic % or less (in this case, the balance is lithium and unavoidable impurities).

In the case of a negative electrode having a lithium alloy sheet, a layer containing alloying elements for forming a lithium alloy is laminated by pressure bonding on the surface of a lithium layer (a layer containing lithium) made of metal lithium foil or the like. It is also possible to form a lithium alloy on the surface of the lithium layer to form a negative electrode by using the laminated body and bringing this laminated body into contact with the solid electrolyte in the battery. In the case of such a negative electrode, a laminate having a layer containing an alloy element on only one side of the lithium layer may be used, or a laminate having a layer containing an alloy element on both sides of the lithium layer may be used. The laminate can be formed, for example, by press-bonding a metallic lithium foil and a foil made of an alloy element.

The current collector can also be used when a lithium alloy is formed to form a negative electrode in a battery. A laminate having a layer containing an alloy element on the opposite side may be used, having a lithium layer on both sides of the negative electrode current collector, and the side opposite to the negative electrode current collector of each lithium layer A laminate having a layer containing an alloy element may also be used. The negative electrode current collector and the lithium layer (metallic lithium foil) may be laminated by pressure bonding or the like.

For the layer containing the alloying element of the laminate for the negative electrode, for example, a foil made of these alloying elements can be used. The thickness of the layer containing the alloying element is preferably 1 μm or more, more preferably 3 μm or more, preferably 20 μm or less, and more preferably 12 μm or less.

For example, a metallic lithium foil or the like can be used for the lithium layer of the laminate used as the negative electrode. The thickness of the lithium layer is preferably 0.1 to 1.5 mm. Further, the thickness of the sheet of the negative electrode having a lithium or lithium alloy sheet is also preferably 0.1 to 1.5 mm.

In addition, when the negative electrode having a lithium sheet or a lithium alloy sheet has a current collector, the current collector may be any of the current collectors exemplified above that can be used for the negative electrode having the negative electrode mixture molded body. can be used the same as

(Solid electrolyte layer)
The solid electrolyte constituting the solid electrolyte layer interposed between the positive electrode and the negative electrode includes various sulfide-based solid electrolytes, hydride-based solid electrolytes, and halide-based solid electrolytes exemplified above as those used for the positive electrode. and one or more of oxide-based solid electrolytes can be used. However, in order to improve battery characteristics, it is desirable to contain a sulfide-based solid electrolyte, and it is more desirable to include an aldirodite-type sulfide-based solid electrolyte. It is more desirable that both the positive electrode and the solid electrolyte layer contain a sulfide-based solid electrolyte, and more preferably an aldirodite-type sulfide-based solid electrolyte.

The solid electrolyte layer may have a porous body such as resin nonwoven fabric as a support.

The solid electrolyte layer is formed by compressing the solid electrolyte by pressure molding or the like; a composition for forming a solid electrolyte layer prepared by dispersing the solid electrolyte in a solvent is applied on the substrate, the positive electrode, and the negative electrode, and dried; If necessary, it can be formed by a method of performing pressure molding such as press processing, etc., but it is more preferable to adopt the method of compressing the solid electrolyte.

The solvent used in the solid electrolyte layer-forming composition is desirably selected from those that do not easily deteriorate the solid electrolyte. It is preferable to use the same.

The thickness of the solid electrolyte layer is preferably 100-400 μm.

(Laminate electrode body)
The positive electrode and the negative electrode are unit electrode bodies laminated with a solid electrolyte layer interposed therebetween, and a plurality of such unit electrode bodies are stacked in order with a current collector interposed therebetween. .

The current collector to be interposed between the unit electrode bodies may be foil, punching metal, mesh, or expanded metal made of a metal such as copper, nickel, or iron that does not react with Li, or an alloy containing these (including stainless steel). , foamed metal; carbon sheet; and the like can be used. The thickness of the current collector interposed between the unit electrode bodies is preferably 10 to 200 μm.

The current collector and the unit electrode body adjacent thereto may be simply stacked, and the current collector and the positive electrode or negative electrode adjacent to the current collector are integrated by lamination or the like. may

The number of unit electrode bodies that the all-solid-state battery has is not particularly limited as long as it is plural. In the case of a flat-shaped battery, if the number of unit electrode bodies is too large, the thickness of the battery becomes too large, and the advantage of having a flat shape may be lost. do.

(Exterior body)
As an exterior body of an all-solid-state battery, for example, a battery container having an exterior can and a sealing can as shown in FIG. 1 is used. That is, an all-solid-state battery having such a battery container as an outer package is a coin-type (button-type) battery.

In the case of a battery container in which the exterior body of an all-solid-state battery has an exterior can and a sealing can, as shown in FIG. A case in which a sealed can is adhered with a resin can also be exemplified.

A stainless steel can or the like can be used for the outer can and the sealing can. In addition, polypropylene, nylon, etc. can be used for gasket materials, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), etc., can be used when heat resistance is required in relation to battery applications. Heat resistance with a melting point exceeding 240°C such as fluorine resin, polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), etc. Resin can also be used. Moreover, when the battery is applied to applications requiring heat resistance, a glass hermetic seal can be used for the sealing.

The shape of the outer package, which is a battery container having an outer can and a sealing can, in a plan view may be circular or polygonal such as quadrangular (square or rectangular). Moreover, in the case of a polygon, the corners thereof may be curved.

Furthermore, a laminate film exterior made of a metal laminate film such as an aluminum laminate film can also be used as the exterior of the all-solid-state battery.

The all-solid-state battery of the present invention can be applied to the same applications as conventionally known primary batteries and secondary batteries, but it has excellent heat resistance because it has a solid electrolyte instead of an organic electrolyte. It can be preferably used in applications exposed to high temperatures.

The present invention will be described in detail below based on examples. However, the following examples do not limit the present invention.

(Example 1)
<Fabrication of unit electrode body>
Lithium titanate (Li ₄ Ti ₅ O ₁₂ , negative electrode active material) with an average particle size of 2 μm and a sulfide-based solid electrolyte (Li _5.4 PS _4.4 Cl _0.8 Br with an average particle size of 0.7 μm) _0.8 ) and graphene (a conductive additive) were mixed at a mass ratio of 50:41:9 to prepare a negative electrode mixture.

In addition, LiCoO ₂ (positive electrode active material) having an average particle diameter of 5 μm and a LiNbO ₃ coating layer formed on the surface, and a sulfide-based solid electrolyte (Li _7.0 PS _5.4 Cl ₁ ) having an average particle diameter of 3 μm _.2 ), carbon black and vapor grown carbon fiber (VGCF) were mixed at a mass ratio of 70:26.8:1.1:2.1 to prepare a positive electrode mixture.

Next, a powder of a sulfide-based solid electrolyte (Li _5.4 PS _4.4 Cl _0.8 Br _0.8 ) having an average particle size of 0.7 μm is placed in a powder molding die, and pressed under low pressure using a press. to form a temporary molded layer of the solid electrolyte layer. Further, the negative electrode mixture was placed on the upper surface of the temporary molding layer of the solid electrolyte layer, and pressure molding was performed at a low pressure to further form a temporary molding layer of the negative electrode on the temporary molding layer of the solid electrolyte layer.

Furthermore, after the mold is turned upside down, the positive electrode mixture is placed on the top surface of the temporary molding layer of the solid electrolyte layer in the mold (the side opposite to the surface having the temporary molding layer of the negative electrode), and the whole is heated to 1300 MPa. Two unit electrode bodies each having a thickness of 0.75 mm, in which the negative electrode, the solid electrolyte layer, and the positive electrode are integrated, were produced by pressure molding under a surface pressure of (13 tf/cm ² ).

<Production of laminated electrode body>
A flexible graphite sheet “PERMA-FOIL (product name)” manufactured by Toyo Tanso Co., Ltd. (thickness: 0.1 mm, apparent density: 1.1 g/cm ³ ) was punched into the same size as the unit electrode body. Three sheets are prepared, one of which is placed on the positive electrode of one of the two unit electrode bodies, and the remaining unit electrode bodies are placed on the graphite sheet so that the negative electrode side faces the graphite sheet side. By stacking, a laminated electrode body having two unit electrode bodies connected in series via a graphite sheet (current collector) was obtained. Furthermore, a flexible seal-like desiccant “Dry Keep TFREE-Z (trade name)” manufactured by Sasaki Chemical Co., Ltd. was attached to the entire peripheral surface of the laminated electrode body to fix the unit electrode body and the current collector.

<Battery assembly>
One of the graphite sheets punched out as described above was placed on the inner bottom surface of a stainless steel sealing can fitted with an annular gasket made of polyphenylene sulfide, and a laminated electrode body was placed thereon, with the negative electrode exposed. It was arranged so that the surface on which it was placed faced the graphite sheet side. Furthermore, after placing the remaining graphite sheet on the surface where the positive electrode of the laminated electrode body is exposed and covering it with a stainless steel outer can, the open end of the outer can is caulked inward and sealed. By stopping, an all-solid secondary battery (coin-shaped all-solid secondary battery) having the structure shown in FIG. 1 was produced. Note that FIG. 1 does not show the graphite sheets arranged between the sealing can, the outer can, and the laminated electrode body.

(Comparative example 1)
In the same manner as in Example 1, two unit electrode bodies and three graphite sheets serving as current collectors were prepared. One of the graphite sheets is placed on the inner bottom surface of a stainless steel sealing can fitted with an annular gasket made of polyphenylene sulfide. It was stacked so that it would be on the sheet side. Next, one of the graphite sheets was superimposed thereon, and the other of the unit electrode bodies was further superimposed so that the positive electrode side was on the graphite sheet side, thereby forming a laminated electrode body.

A flexible seal-like desiccant is not attached to the peripheral surface of the laminated electrode body, and the remaining graphite sheet is placed on the surface where the positive electrode of the laminated electrode body is exposed. A coin-type all-solid secondary battery was produced in the same manner as in Example 1.

(Comparative example 2)
A coin-shaped all-solid secondary battery was produced in the same manner as in Comparative Example 1, except that a sealing can in which a flexible seal-like desiccant was previously cut to a width of 1 mm and pasted on the entire inner surface was used.

The all-solid secondary batteries of Example 1 and Comparative Examples 1 and 2 were evaluated as follows.

<Evaluation of internal resistance during battery assembly>
After charging and discharging 10 batteries each of Example 1 and Comparative Examples 1 and 2, an alternating current of 1 kHz was applied to measure the internal resistance of the batteries, and the average value of the 10 batteries was obtained. was used to evaluate the effect of misalignment in the laminated electrode assembly.

<Evaluation of internal resistance during high-temperature storage>
Next, after holding the battery in a constant temperature bath at 60 ° C. and a relative humidity of 90% for 80 days, the battery was taken out and allowed to cool to room temperature, and then an alternating current of 1 kHz was applied to the inside of the battery after high temperature storage. The resistance was measured and the average value of 10 cells was obtained.

For the batteries of Example 1 and Comparative Examples 1 and 2, the difference between the internal resistance of the battery after high-temperature storage and the internal resistance of the battery before storage (increase in internal resistance) was obtained and compared.

Table 1 shows the above evaluation results. In Table 1, the internal resistance during assembly of the battery and the increased amount of internal resistance during high-temperature storage are shown as relative values when the value of the battery of Comparative Example 1 is set to 100.

In the battery of Example 1, the unit electrode bodies and the graphite sheets of the laminated electrode body were fixed by the flexible seal-like desiccant in a stacked state without displacement. It was possible to lower the internal resistance of

On the other hand, in the batteries of Comparative Examples 1 and 2, positional displacement occurred in the unit electrode bodies or the graphite sheets during lamination or sealing of the unit electrode bodies and the graphite sheets. Since the pressure applied to the unit electrode body during sealing was uneven and cracks occurred, the internal resistance after assembly increased compared to the battery of Example 1.

In addition, when the battery is stored in a hot and humid environment, moisture gradually enters the battery through the sealed portion of the battery and reacts with the solid electrolyte, etc., increasing the internal resistance of the battery. However, as shown in Table 1, in the batteries of Example 1 and Comparative Example 2 in which a resin sheet containing a desiccant (flexible seal-like desiccant) was arranged on the peripheral surface of the laminated electrode body or the inner surface of the sealing can, the solid It was possible to reduce the amount of water that reacts with the electrolyte, etc., and suppress the increase in internal resistance.

1 All Solid Battery 2 Unit Electrode Body 21 Positive Electrode 22 Negative Electrode 23 Solid Electrolyte Layer 3 Outer Can 4 Sealing Can 5 Gasket 6 Current Collector 7 Resin Sheet Containing Desiccant

Claims (3)

A stack in which a plurality of unit electrode bodies each having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode are stacked, and the adjacent unit electrode bodies are connected in series via a current collector. The electrode body is an all-solid-state battery enclosed inside the exterior body,
An all-solid-state battery, wherein a resin sheet containing a desiccant is attached to the peripheral surface of the laminated electrode body. 2. The all-solid battery according to claim 1, wherein at least one of said positive electrode, said negative electrode and said solid electrolyte layer constituting said laminated electrode body contains a sulfide-based solid electrolyte. 3. The all-solid-state battery according to claim 1, wherein the resin sheet has a thickness of 500 [mu]m or less.

Images