JP2023038432A - All-solid-state battery - Google Patents

Abstract

To provide an all-solid-state battery capable of suppressing the deterioration of characteristics due to moisture entering inside the all-solid-state battery, the all-solid-state battery of the present invention relating to the goals 12, 3, 7 and 11 of the SDGs.SOLUTION: An all-solid-state battery of the present invention is characterized in that an electrode laminate including a positive electrode, a negative electrode and a solid electrolyte layer disposed between the positive electrode and the negative electrode is enclosed inside an exterior body, and particles (A) of a sulfide-based solid electrolyte are disposed in a void part inside the exterior body. In the all-solid-state battery of the present invention, it is preferable that at least one of the positive electrode, the negative electrode and the solid electrolyte layer constituting the electrode laminate contains a sulfide-based solid electrolyte.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an all-solid-state battery capable of suppressing deterioration of characteristics due to moisture intruding into 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. 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 all-solid-state batteries to society, among the 17 Sustainable Development Goals (SDGs) established by the United Nations, Goal 12 (Ensure sustainable production and consumption patterns), Goal 3 (All ages Goal 7 (Ensure access to affordable, reliable, sustainable and modern energy for all) and Goal 11 (Ensure healthy lives and promote well-being for all); to realize safe, resilient and sustainable cities and human settlements].

Various improvements have been attempted in all-solid-state batteries as well. Techniques have been proposed for preventing short circuits caused by contamination of an electrolyte layer interposed between a positive electrode and a negative electrode by active material particles detached from the positive electrode and the negative electrode.

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 2, a housing (exterior body) made of synthetic resin, into which external moisture is more likely to enter than a metal container, is used. 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.

JP 2009-64644 A JP-A-2000-243357

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an all-solid-state battery capable of suppressing deterioration of characteristics caused by moisture intruding into the battery.

In the all-solid-state battery of the present invention, an electrode laminate having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode is enclosed in an exterior body, and the inside of the exterior body It is characterized in that particles (A) of a sulfide-based solid electrolyte are arranged in the void portions.

Advantageous Effects of Invention According to the present invention, it is possible to provide an all-solid-state battery capable of suppressing deterioration in characteristics due to moisture intruding 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, an electrode laminate having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode is enclosed in an exterior body. Particles (A) of the sulfide-based solid electrolyte are arranged in the void part inside the body, that is, in the gap where the constituent elements such as the electrode laminate housed in the exterior body of the all-solid-state battery are not arranged. There is.

Since sulfide-based solid electrolytes tend to absorb moisture and react easily, for example, when they are contained in the solid electrolyte layer or electrodes of an all-solid-state battery, the reaction impairs the function of the sulfide-based solid electrolyte. There is a possibility that the characteristics may deteriorate. However, when the particles (A) of the sulfide-based solid electrolyte are placed in the voids inside the exterior body other than the solid electrolyte layer and the electrodes, the particles (A) absorb moisture in the exterior body. , it is possible to reduce the amount of water contained in the solid electrolyte layer and electrodes, which causes deterioration of the solid electrolyte and the active material. In addition, since the particles (A) of the sulfide-based solid electrolyte themselves do not affect the functions of the solid electrolyte layer and the electrode, even if the particles (A) are degraded by moisture, the battery characteristics do not deteriorate. As a result, in the all-solid-state battery of the present invention, it is possible to suppress deterioration in characteristics due to moisture that penetrates inside.

Sulfide solid electrolyte particles (A) include 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 system In addition to particles such as glass, thio-LISICON type particles [Li ₁₀ GeP ₂ S ₁₂ , Li _9.54 Si _1.74 P _1.44 S], 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 _11.7 Cl _0.3 , 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 ;} (provided that 0.05≦f≦0.9, −3.0f+1.8≦g≦−3.0f+5.7), Li _7-h PS _6-h Cl _i Br _j (provided that h=i+j, 0<h≦1.8, 0.1≦i/j≦10.0)] can also be used.

Since the particles (A) of the sulfide-based solid electrolyte are in the form of particles, they can efficiently absorb moisture inside the exterior body of the all-solid-state battery. Particles (A) are not particularly limited in ^shape , and may be either ^primary particles or secondary particles. g or more is more preferable. Particles (A) having such a specific surface area can more efficiently absorb moisture inside the exterior body of the all-solid-state battery.

The specific surface area of the particles (A) of the sulfide-based solid electrolyte can be adjusted, for example, by adjusting the average particle size of the particles (A). However, if the specific surface area is made too large ^, the particle diameter becomes too small and the handleability is deteriorated. is preferred.

The specific surface area of the particles (A) of the sulfide-based solid electrolyte referred to in this specification is a value determined by the BET method according to Japanese Industrial Standards (JIS) K 6217. For example, the specific surface area is measured by the nitrogen adsorption method. It can be measured using an apparatus ("Macsorb HM model-1201" manufactured by Mountech).

The average particle size of the particles (A) of the sulfide-based solid electrolyte is preferably 0.1 to 5.0 μm.

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 has a positive electrode 21, a negative electrode 22, and a positive electrode 21 inside it. and a negative electrode 22 in which a pellet-shaped electrode laminate 2 having a solid electrolyte layer 23 interposed is enclosed. That is, in the all-solid-state battery 1, the sealing can 4 is fitted to the opening of the outer can 3 via the gasket 5, and the opening end of the outer can 3 is tightened inward, whereby the gasket 5 is tightened. By contacting the sealing can 4, the opening of the outer can 3 is sealed, and the inside of the battery has a closed structure. The outer can 3 also serves as a positive electrode terminal, and the sealing can 4 also serves as a negative electrode terminal. In the all-solid-state battery 1 shown in FIG. 1, the positive electrode 21 of the electrode stack 2 is in contact with the outer can 3, and the negative electrode 22 is in contact with the sealing can 4. However, in the all-solid-state battery of the present invention, Alternatively, the electrode laminate may be accommodated so that the positive electrode is in contact with the sealed can and the negative electrode is in contact with the outer can.

In the all-solid-state battery 1, the circumference of the electrode laminate 2 in the radial direction, that is, the electrode laminate in a plan view from the flat surface side of the electrode laminate 2 (for example, a plan view from the upper side of FIG. 1) Particles (A) 6 of a sulfide-based solid electrolyte are accommodated in a portion corresponding to the outside of the outer end of 2 . Note that FIG. 1 shows the particles (A) 6 of the sulfide-based solid electrolyte integrally where the particles (A) 6 are arranged, since if each particle is illustrated, the drawing becomes complicated. ing.

In the all-solid-state battery, there is no particular limitation on the arrangement of the particles (A) of the sulfide-based solid electrolyte, and they may be arranged in any of the gaps of the outer package. In the case of a coin-shaped battery having an exterior body (battery container) having a can, the vicinity of the peripheral edge of the exterior can (between the exterior can 3 and the gasket 5 in the case of the battery 1 in FIG. 1) or the periphery of the sealing can Since water tends to enter from the vicinity of the end portion (between the sealing can 4 and the gasket 5 in the case of the battery 1 in FIG. 1), it is desirable to arrange the particles (A) near the end portion. As shown in FIG. 1, it is preferable to arrange them radially around the electrode laminate.

From the viewpoint of better ensuring the above-mentioned effect by disposing the sulfide-based solid electrolyte particles (A), the mass of the sulfide-based solid electrolyte particles (A) disposed in the battery is It is preferable that the proportion is at least a certain amount with respect to the mass (the total mass of the electrode laminate including the positive electrode, the negative electrode, and the solid electrolyte layer).

More specifically, although it depends on the size of the battery, the mass of the sulfide-based solid electrolyte particles (A) arranged in the battery is, for example, 0.2% or more of the total mass of the electrode laminate. It is preferably at least 1%, more preferably at least 1%, and particularly preferably at least 1.5%. The mass of the particles (A) of the sulfide-based solid electrolyte placed in the battery is not particularly limited as long as it can be accommodated inside the battery. is preferably 4% or less, and particularly preferably 3% or less.

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). using only one of may be used, or two or more 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.

As the sulfide-based solid electrolyte, the same sulfide-based solid electrolyte as the sulfide-based solid electrolyte particles (A) can be used. The sulfide-based solid electrolyte contained in the positive electrode mixture may be of the same type as the sulfide-based solid electrolyte related to the sulfide-based solid electrolyte particles (A), or may be of a different type.

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 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 sulfide-based solid electrolyte contained in the negative electrode mixture may be of the same type as the sulfide-based solid electrolyte related to the sulfide-based solid electrolyte particles (A), or may be of a different type.

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 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 that constitutes 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 previously exemplified as those that can be 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 sulfide-based solid electrolyte contained in the solid electrolyte layer may be of the same type as the sulfide-based solid electrolyte related to the sulfide-based solid electrolyte particles (A), or may be of a different type.

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.

(Electrode laminate)
A positive electrode and a negative electrode are used in a battery in the form of an electrode laminate in which a solid electrolyte layer is interposed.

When forming the electrode laminate, pressure molding in a state in which the positive electrode, the negative electrode, and the solid electrolyte layer are laminated increases the mechanical strength of the electrode laminate and reduces the internal resistance. preferred from

(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)
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. An electrode laminate having a thickness of 1.57 mm in which the negative electrode, the solid electrolyte layer, and the positive electrode were integrated was obtained by pressure molding under a surface pressure of (13 tf/cm ² ).

Next, a stainless steel sealing can and a stainless steel outer can are caulked and sealed via a polyphenylene sulfide gasket, and the electrode laminate is sealed inside to obtain a coin-shaped structure having the structure shown in FIG. All-solid-state battery was fabricated.

When enclosing _the electrode laminate, _a sulfide-based solid electrolyte ( _{Li5.4PS4.4Cl0.8Br0 . 8} ) The powder [particles (A) of sulfide-based solid electrolyte]: 3.5 mg was filled and then sealed. The mass of the solid electrolyte powder was 1.9% of the mass of the electrode laminate.

Although not shown, a carbon sheet having a thickness of about 0.1 mm was inserted between the positive electrode and the outer can, and between the negative electrode and the sealing can.

(Comparative example 1)
A coin-shaped all-solid-state battery was produced in the same manner as in Example 1, except that the gap around the electrode laminate was not filled with the solid electrolyte powder and sealed.

Ten batteries each of Example 1 and Comparative Example 1 were charged and discharged, and then an alternating current of 1 kHz was applied to measure the internal resistance of the batteries, and the average value of the ten batteries was obtained. .

Next, after holding the battery in a constant temperature bath at 60° C. and a relative humidity of 90% for 36 days, the battery was taken out and allowed to cool to room temperature. The average value of 10 batteries was obtained.

For the batteries of Example 1 and Comparative Example 1, 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 determined and compared.

Table 1 shows the amount of increase in internal resistance during high-temperature storage for each battery, with the value for the battery of Comparative Example 1 being 100.

When the battery is held in a hot and humid environment, moisture gradually enters the battery from the sealing part of the battery, and reacts with the solid electrolyte, etc., thereby increasing the internal resistance of the battery. As shown in Table 1, in the battery of Example 1, the particles (A) of the sulfide-based solid electrolyte were placed in the voids inside the battery, so that the solid electrolyte contained in the electrode laminate and the like reacted with water. The amount was able to be reduced, and an increase in internal resistance was suppressed.

REFERENCE SIGNS LIST 1 all-solid battery 2 electrode laminate 21 positive electrode 22 negative electrode 23 solid electrolyte layer 3 outer can 4 sealing can 5 gasket 6 sulfide-based solid electrolyte particles (A)

Claims (5)

An all-solid-state battery in which an electrode laminate having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode is enclosed in an exterior body,
An all-solid-state battery, wherein particles (A) of a sulfide-based solid electrolyte are arranged in a void portion inside the exterior 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 electrode laminate contains a sulfide-based solid electrolyte. 3. The all-solid-state battery according to claim 1, wherein the mass of the particles (A) of the sulfide-based solid electrolyte is 0.2% or more of the mass of the electrode laminate. The all-solid-state battery according to any one of claims 1 to 3, wherein the particles (A) of the sulfide-based solid electrolyte have a specific surface area of 0.7 m ² /g or more. The electrode laminate is in the form of a pellet and enclosed inside a coin-shaped exterior body,
The all-solid-state battery according to any one of claims 1 to 4, wherein the particles (A) of the sulfide-based solid electrolyte are arranged radially around the electrode laminate.

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