JP2022083502A - All-solid- state battery positive electrode and all-solid battery - Google Patents

Abstract

To provide an all-solid-state battery having excellent load characteristics and a positive electrode capable of forming the all-solid-state battery, and relate to goals 12, 3, 7, and 11 of sustainable development goals (SDGs).SOLUTION: A positive electrode for an all-solid battery according to the present invention includes a positive electrode active material composed of primary particles and a molded body of a positive electrode mixture containing a solid electrolyte, and the positive electrode active material includes a reaction suppression layer for suppressing the reaction on the positive electrode active material and the solid electrolyte layer, and the ratio ra/rs of the average particle size ra of the positive electrode active material to the average particle size rs of the solid electrolyte is 2 or more and 20 or less. Further, an all-solid-state battery according to the present invention includes a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and includes the positive electrode for the all-solid-state battery according to the present invention.SELECTED DRAWING: Figure 1

Description

The present invention relates to an all-solid-state battery having excellent load characteristics and a positive electrode capable of forming the all-solid-state battery.

In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers and the practical application of electric vehicles, small and lightweight batteries with high capacity and high energy density have been required. ing.

At present, in lithium batteries that can meet this demand, particularly lithium ion batteries, an organic electrolyte solution containing an organic solvent and a lithium salt is used as a non-aqueous electrolyte.

With the further development of equipment to which lithium-ion batteries are applied, there is a demand for longer life, higher capacity, and higher energy density of lithium-ion batteries, as well as longer life, higher capacity, and higher energy density. The reliability of energy-dense lithium-ion batteries is also highly demanded.

However, since the organic electrolytic solution used in the lithium-ion battery contains an organic solvent which is a flammable substance, the organic electrolytic solution may generate abnormal heat when an abnormal situation such as a short circuit occurs in the battery. There is. Further, with the recent increase in energy density of lithium ion batteries and the increasing tendency of the amount of organic solvent in organic electrolytic solutions, the reliability of lithium ion batteries is further required.

Under the above circumstances, 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 the conventional organic solvent-based electrolyte, and has high safety without the risk of abnormal heat generation of the solid electrolyte.

In addition, all-solid-state batteries have not only high safety, but also high reliability and high environmental resistance, and have a long life, so they can contribute to the development of society and at the same time continue to contribute to safety and security. It is expected as a maintenance-free battery that can be used. Of the 17 goals of the Sustainable Development Goals (SDGs) established by the United Nations by providing all-solid-state batteries to society, Goal 12 (to ensure sustainable production and consumption) and Goal 3 (for all ages) Ensuring a healthy life for all and promoting welfare), Goal 7 (ensuring access to cheap, reliable and sustainable modern energy for all), and Goal 11 [Inclusive Achieve safe, resilient and sustainable cities and human settlements].

Further, various improvements have been attempted in the all-solid-state battery. For example, in Patent Document 1, an electrode in which an active material having a specific particle size and a solid electrolyte having a specific particle size are mixed at a specific weight ratio and used is applied in an all-solid-state battery. Techniques for increasing the utilization rate of active materials have been proposed.

Further, Patent Document 2 describes the particle size of the positive electrode active material in the positive electrode active material layer of the positive electrode layer or the particle size of the negative electrode active material in the negative electrode active material layer of the negative electrode layer, and the solid in the solid electrolyte layer adjacent to these layers. A technique for reducing the interfacial resistance between the positive electrode active material layer or the negative electrode active material layer and the solid electrolyte layer by setting the ratio to the particle size of the electrolyte within a specific range has been proposed.

Japanese Unexamined Patent Publication No. 8-195219 Japanese Unexamined Patent Publication No. 2016-1596

By the way, at present, the fields of application of all-solid-state batteries are expanding rapidly, and for example, they can be applied to applications that require discharge at a large current value. It is required to increase.

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 having excellent load characteristics and a positive electrode capable of forming the all-solid-state battery.

The positive electrode for an all-solid battery of the present invention has a positive electrode active material composed of primary particles and a molded body of a positive electrode mixture containing a solid electrolyte, and the positive electrode active material is a positive electrode active material and the solid electrolyte. It is characterized by having a reaction suppressing layer for suppressing the reaction on the surface, and the ratio ra / rs of the average particle size ra of the positive electrode active material to the average particle size rs of the solid electrolyte is 2 or more and 20 or less. It is something to do.

Further, the all-solid-state battery of the present invention is characterized by having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and the positive electrode of the present invention has a positive electrode for an all-solid-state battery of the present invention. Is to be.

The all-solid-state battery of the present invention includes a primary battery (all-solid-state primary battery) and a secondary battery (all-solid-state secondary battery).

According to the present invention, it is possible to provide an all-solid-state battery having excellent load characteristics and a positive electrode capable of forming the all-solid-state battery.

It is sectional drawing which shows typically the example of the all-solid-state battery of this invention. It is a top view schematically showing another example of the all-solid-state battery of this invention. FIG. 2 is a cross-sectional view taken along the line II of FIG.

<Positive electrode for all-solid-state battery>
The positive electrode for an all-solid battery of the present invention has a positive electrode active material composed of primary particles and a molded body of a positive electrode mixture containing a solid electrolyte, and the positive electrode active material comprises the positive electrode active material and the solid electrolyte. It has a reaction suppressing layer for suppressing the reaction on the surface, and the ratio ra / rs of the average particle size ra of the positive electrode active material to the average particle size rs of the solid electrolyte is 2 or more and 20 or less.

In order to enhance the load characteristics of the all-solid-state battery, it is desirable to allow lithium ions to move more smoothly between the positive electrode active material and the solid electrolyte in the positive electrode.

In the present invention, in the molded body of the positive electrode mixture constituting the positive electrode, a positive electrode active material having a reaction suppressing layer for suppressing the reaction with the solid electrolyte on the surface is contained in the state of primary particles, and the average of the solid electrolytes is contained. By setting the ratio of the average particle size of the positive electrode active material to the particle size within a specific range, the contact between the positive electrode active material and the solid electrolyte is improved, and the lithium ions can move smoothly between the two. The load characteristics of solid-state batteries can be improved.

The positive electrode for an all-solid-state battery of the present invention has a molded body of a positive electrode mixture, and may be composed of only a molded body of a positive electrode mixture or a layer made of a molded body of a positive electrode mixture (positive electrode mixture layer). Examples thereof include those having a structure formed on a current collector.

In the case of a positive electrode for an all-solid battery used in an all-solid primary battery, the base material of the positive electrode active material (positive electrode active material having a reaction suppressing layer on the surface) contained in the positive electrode mixture is a conventionally known non-water-based material. The same positive electrode active material used in the electrolyte primary battery can be used. Specifically, for example, manganese dioxide, lithium-containing manganese oxide [for example, LiMn _{3 O6} or the same crystal structure as manganese dioxide (β-type, γ-type, or a structure in which β-type and γ-type are mixed, etc.) 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, particularly preferably 1% by mass or less], Li _a Ti. Lithium-containing composite oxides such as _{5/3 O4} ( _4/3 ≤ a <7/3); vanadium oxides; niobium oxides; titanium oxides; sulfides such as iron disulfide; graphite fluoride; Ag ₂ Silver sulfides such as S; nickel oxides such as NiO ₂ : and the like.

Further, in the case of a positive electrode for an all-solid battery used for an all-solid secondary battery, a base material for a positive electrode active material (a positive electrode active material having a reaction suppressing layer on the surface) contained in the positive electrode mixture has been conventionally known. A positive electrode active material used in a non-aqueous electrolyte secondary battery, that is, the same active material capable of storing and releasing Li (lithium) ions can be used. 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, at least one element selected from the group consisting of 0≤x≤1,0. Spinel-type lithium manganese composite oxide represented by ≦ r ≦ 1), Li _r Mn _{(1-s-t) Nis} 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, which are at least one element selected from the group consisting of 0≤r≤1.2,0. A layered compound represented by <s <0.5, 0 ≦ t ≦ 0.5, u + v <1, −0.1 ≦ u ≦ 0.2, 0 ≦ v ≦ 0.1), Li _1-x Co. _{1-r Mr} O ₂ (However, M is Al, Mg, Ti, V, Cr, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, Ba, Mn, Bi. , Ca, F, P, Sr, W, Si, Ta, K, S, Er and Na at least one element selected from the group consisting of 0≤x≤1, 0≤r≤0.5. ), Li _1-x Ni _{1-r Mr} O ₂ (where M is Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb). , Mo, Sn, Sb and Ba, at least one element selected from the group consisting of, 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5), a lithium nickel composite oxide, Li _{1 + s−. x} M _1-r N _r PO ₄ F _s (where M is at least one element selected from the group consisting of Fe, Mn and Co, and N is Al, Mg, Ti, Zr, Ni and Cu. , Zn, Ga, Ge, Nb, Mo, Sn, Sb, V and Ba, which is at least one element selected from the group consisting of 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5, 0 ≦ s. Olivin-type composite oxide represented by ≦ 1), Li _2-x M _1-r N _r P ₂ O ₇ (where M is at least one element selected from the group consisting of Fe, Mn and Co. N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V and Ba, and is 0. ≤x≤2, 0≤r≤0.5) The represented pyrophosphoric acid compound and the like can be exemplified, and only one of these may be used, or two or more thereof may be used in combination.

In the case of a positive electrode for an all-solid-state battery used in an all-solid-state secondary battery, the lithium cobalt composite oxide (A) represented by the following general formula (1) is preferably used among the above-exemplified positive electrode active materials.

LiCo _1-ab-c Al _a M ¹ _b M ² _c O ₂ (1)

In the general formula (1), M ¹ is at least one element selected from the group consisting of Mg, Ni and Na, and M ² is Mn, Fe, Cu, Zr, Ti, Bi, Ca, F, It is at least one element selected from the group consisting of P, Sr, W, Ba, Nb, Si, Zn, Mo, V, Sn, Sb, Ta, Ge, Cr, K, S and Er, and is 0 <. a <0.1, 0 <b <0.1, a + b <0.1, 0 ≦ c.

When the lithium cobalt composite oxide (A) is used as a positive electrode active material for a non-aqueous electrolyte secondary battery using ^an organic electrolytic solution, the inside of the battery is affected by the action of additive elements such as Al and M1 element contained therein. It is a material that increases resistance. However, in the case of a non-aqueous electrolyte secondary battery having an organic electrolyte, since the electrolyte that transfers ions between the positive electrode and the negative electrode is a liquid (electrolyte), the original internal resistance is small, so lithium. The above-mentioned increase in internal resistance due to the cobalt composite oxide (A) has almost no effect on the battery characteristics. On the other hand, in an all-solid secondary battery in which ions are transferred between the positive electrode and the negative electrode with a solid electrolyte, the increase in internal resistance due to the action of the positive electrode active material may cause deterioration of battery characteristics such as load characteristics. is expected.

However, when the lithium cobalt composite oxide (A) is used as the positive electrode active material of the all-solid-state secondary battery, contrary to such an expectation, the internal resistance is lowered as compared with the case where LiCoO ₂ is used as the positive electrode active material, for example. This is possible, and the load characteristics of the all-solid-state secondary battery can be further enhanced.

When a battery using LiCoO ₂ as a positive electrode active material is charged, Co expands due to a change in valence. In a battery using an organic electrolyte, even if the volume of the positive electrode active material changes due to this, the contact with the positive electrode active material is not impaired because the electrolyte that transfers ions is liquid. On the other hand, in an all-solid secondary battery, the electrolyte that transfers ions in the positive electrode is a solid (solid electrolyte), so the volume of the positive electrode active material changes due to the charging and discharging of the battery, resulting in a gap between the positive electrode and the solid electrolyte. This will occur, and the internal resistance of the positive electrode, and eventually the internal resistance of the battery, will increase.

However, in the case of the lithium cobalt composite oxide (A) represented by the general formula ( ¹ ), the expansion of Co is suppressed by the action of Al and the element M1 even in the charged state, so that the positive electrode active material. The total amount of expansion (volume change) becomes smaller. Therefore, by using a positive electrode for an all-solid-state battery using lithium cobalt composite oxide (A) as a positive electrode active material, contact between the lithium cobalt composite oxide (A) and the solid electrolyte in the positive electrode even when charged and discharged. Can be maintained well and the internal resistance can be kept low, so that an all-solid-state secondary battery having better load characteristics can be obtained.

In the lithium cobalt composite oxide (A), Al is an element substituted with Co sites and M ¹ is an element substituted with Li sites, both of which are the expansion amounts of Co during charging [lithium cobalt composite oxide (A). It has the effect of reducing the amount of expansion.

The lithium cobalt composite oxide (A) may contain at least one element of Mg, Ni and Na as the element M ¹ , but has the same ionic radius as Li to be substituted and is further filled. Mg is preferable because it does not change the valence during discharge.

In the lithium cobalt composite oxide (A), the amount a of Al is greater than 0 and less than 0.1, and the amount b of the element M1 is greater than ⁰ and less than 0.1 from the viewpoint of suppressing the amount of expansion during charging. And a + b is less than 0.1. The amount ^a of Al is preferably 0.005 or more, and the amount b of the element M1 is preferably 0.005 or more. Further, the amount a of Al is preferably 0.08 or ^less , and the amount b of the element M1 is preferably 0.08 or less.

The lithium cobalt composite oxide (A) may or may not contain the element M ² (the amount c may be 0), but if the amount of the element M ² is too large, for example. As the amount of Co decreases, the capacity of the lithium cobalt composite oxide (A) may decrease. Therefore, the amount c of the element M ² is preferably 0.05 or less.

The molded product of the positive electrode mixture contains the positive electrode active material in the state of primary particles. As a result, the contact between the positive electrode active material and the solid electrolyte in the molded body of the positive electrode mixture is improved, so that the load characteristics of the all-solid-state battery are improved.

The molded body of the positive electrode mixture may contain a positive electrode active material composed of primary particles and a positive electrode active material existing as secondary particles. Examples of the positive electrode active material existing as secondary particles include secondary particles of various positive electrode active materials exemplified above as those that can be contained in the positive electrode mixture. However, the ratio of the positive electrode active material existing as secondary particles in the positive electrode mixture to the total amount of the positive electrode active material is better, preferably 20% by mass or less, and more preferably 10% by mass or less. .. Further, the positive electrode active material in the positive electrode mixture may be a positive electrode active material composed entirely of primary particles. Therefore, the lower limit of the ratio of the positive electrode active material existing as the secondary particles to the total amount of the positive electrode active material is 0% by mass.

As the positive electrode active material composed of primary particles, a commercially available positive electrode active material can be used. Although some secondary particles are mixed in the positive electrode active material, those composed mostly of primary particles can also be used.

The positive electrode active material (positive electrode active material composed of primary particles) contained in the molded body of the positive electrode mixture has a reaction suppressing layer on the surface thereof for suppressing the reaction with the solid electrolyte contained in the positive electrode.

When the positive electrode active material and the solid electrolyte come into direct contact with each other in the molded body of the positive electrode mixture, the solid electrolyte may oxidize to form a resistance layer, and the ionic conductivity in the molded body may decrease. By providing a reaction suppression layer that suppresses the reaction with the solid electrolyte on the surface of the positive electrode active material and preventing direct contact between the positive electrode active material and the solid electrolyte, the ionic conductivity in the molded body due to the oxidation of the solid electrolyte The decrease can be suppressed.

The reaction suppressing layer may be made of a material having ionic conductivity and capable of suppressing the reaction between the positive electrode active material and the solid electrolyte. As the material that can form the reaction suppression layer, for example, an oxide containing Li and at least one element selected from the group consisting of Nb, P, B, Si, Ge, Ti and Zr, more specifically. Examples include Nb-containing oxides such as LiNbO ₃ , Li ₃ PO ₄ , Li ₃ BO ₃ , Li ₄ SiO ₄ , Li ₄ GeO ₄ , LiTIO ₃ , LiZrO ₃ , Li ₂ WO ₄ . The reaction suppression layer may contain only one of these oxides, or may contain two or more of these oxides, and a plurality of these oxides may be a composite compound. May be formed. Among these oxides, it is preferable to use an Nb _- containing oxide, and it is more preferable to use LiNbO3.

The reaction suppressing layer is preferably present on the surface in an amount of 0.1 to 1.0 part 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.

Examples of the method for forming the reaction suppressing layer on the surface of the positive electrode active material include a sol-gel method, a mechanofusion method, a CVD method, a PVD method, and an ALD method.

When the molded body of the positive electrode mixture also contains the positive electrode active material existing as the secondary particles, the positive electrode active material existing as the secondary particles (the primary of the positive electrode active material constituting the secondary particles). The particles) also preferably have the above-mentioned reaction suppressing layer.

The content of the positive electrode active material in the positive electrode mixture is preferably 60 to 95% by mass.

The solid electrolyte contained in the molded body of the positive electrode mixture is not particularly limited as long as it has lithium ion conductivity, and for example, a sulfide-based solid electrolyte, a hydride-based solid electrolyte, a halide-based solid electrolyte, and oxidation. Physical solid electrolytes can be used.

Examples of the sulfide-based solid electrolyte include particles such as Li ₂ SP ₂ S ₅ , Li ₂ S-SiS ₂ , Li ₂ SP ₂ S ₅ -GeS ₂ , and Li ₂ SB ₂ S ₃ glass. In addition to these, the thio-LISION type, which has been attracting attention as having high Li ion conductivity in recent years [Li ₁₀ GeP ₂ S ₁₂ , Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _{0 .3} , etc., Li _{12-12ab + c + 6d-e} M ¹ _{3 + ab-c-d} M ² _b M ³ _c M ⁴ _d M ⁵ _12-e X _e (where M ¹ is Si, Ge or Sn, M ² is P or V, M ³ is Al, Ga, Y or Sb, M ⁴ is Zn, Ca or Ba, M ⁵ is S or S and O, and X is F, Cl, Br or Li _{7-f + g} PS _{6 - x} Cl _{x + y} (however, 0. 05 ≤ f ≤ 0.9, -3.0 f + 1.8 ≤ g ≤ -3.0 f + 5.7), Li _7-h PS _6-h Cl _i Br _j (however, h = i + j, 0) <The one represented by h≤1.8, 0.1≤i / j≤10.0, etc.] can also be used.

Examples of the hydride-based solid electrolyte include a solid solution of LiBH ₄ , LiBH ₄ and the following alkali metal compound (for example, one having a molar ratio of LiBH ₄ to the alkali metal compound of 1: 1 to 20: 1). Can be mentioned. Examples of the alkali metal compound in the solid solution include lithium halide (LiI, LiBr, LiF, LiCl, etc.), rubidium halide (RbI, RbBr, RbF, RbCl, etc.), and cesium halide (CsI, CsBr, CsF, CsCl, etc.). , At least one selected from the group consisting of lithium amide, rubidium amide and cesium amide.

Examples of the halide-based solid electrolyte include monoclinic type LiAlCl ₄ , defective spinel type or layered structure LiInBr ₄ , and monoclinic type Li _{6-3m Ym} X ₆ (however, 0 < _m <2 and 0 <m <2). X = Cl or Br) and the like, and other known substances as described in, for example, International Publication No. 2020/070958 and International Publication No. 2020/070955 can be used.

Examples of the oxide-based solid electrolyte 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 , Perobskite type Li _3q La _{2 / 3-q} TiO ₃ and the like can be mentioned.

Among these solid electrolytes, sulfide-based solid electrolytes are preferable because they have high lithium ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferable, and lithium ion conductivity is particularly high and chemically stable. A argylodite-type sulfide-based solid electrolyte having high properties is more preferable.

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

When the average particle size of the solid electrolyte contained in the molded body of the positive electrode mixture is rs (μm), and the average particle size of the positive electrode active material composed of the primary particles contained in the molded body of the positive electrode mixture is ra (μm). , The ratio of ra to rs, ra / rs, is 2 or more and 20 or less. When the value of ra / rs is within the above range, the contact between the positive electrode active material and the solid electrolyte in the molded body of the positive electrode mixture becomes good, and the ions can move smoothly between them. Therefore, the resistance value of the positive electrode for an all-solid-state battery can be reduced, and the load characteristics of the all-solid-state battery (all-solid-state battery of the present invention) in which this positive electrode is used can be enhanced. The value of ra / rs is more preferably 5 or more, and more preferably 15 or less.

The average particle size of the solid electrolyte is preferably 0.4 μm or more, and preferably 2.5 μm or less.

Further, the average particle size of the positive electrode active material composed of primary particles is preferably 2 μm or more, more preferably 5 μm or more, preferably 30 μm or less, and more preferably 10 μm or less. ..

When the molded body of the positive electrode mixture contains a positive electrode active material existing in the state of secondary particles, the average particle size of the secondary particles is about the same as the average particle size of the positive electrode active material composed of primary particles. It is preferable to have.

The average particle size of various particles (positive electrode active material, solid electrolyte, etc.) referred to in the present specification is determined by using a particle size distribution measuring device (such as the Microtrack particle size distribution measuring device "HRA9320" manufactured by Nikkiso Co., Ltd.). It means the value (D ₅₀ ) of the 50% diameter in the integrated fraction of the volume standard when the integrated volume is obtained from.

For the average particle size of the positive electrode active material and the solid electrolyte, observe the surface of the molded body of the positive electrode mixture with a scanning electron microscope (SEM), and observe a specific number (for example, 30) of the positive electrode active material and the solid electrolyte, respectively. Can also be obtained as the average value (number average value) of all the values of the particle size measured using the SEM scale. Then, the average particle size of the positive electrode active material and the average particle size of the solid electrolyte obtained by this method are the average particle size of the positive electrode active material and the average particle size of the solid electrolyte obtained by using the particle size distribution measuring device. The present inventors have confirmed that they are almost equivalent.

A conductive auxiliary agent can be contained in the molded product of the positive electrode mixture. Specific examples thereof include carbon materials such as graphite (natural graphite, artificial graphite), graphene, carbon black, carbon nanofibers, and carbon nanotubes. For example, when Ag _2S is used as the positive electrode active material, a conductive Ag is generated during the discharge reaction, so that the conductive auxiliary agent may not be contained. When the conductive auxiliary agent is contained in the molded product of the positive electrode mixture, the content in the positive electrode mixture is preferably 1 to 10% by mass.

The resin binder may or may not be contained in the molded product of the positive electrode mixture. Examples of the resin binder include fluororesins such as polyvinylidene fluoride (PVDF). However, since the resin binder acts as a resistance component in the molded body of the positive electrode mixture, it is desirable that the amount thereof is as small as possible. Therefore, it is preferable that the molded body of the positive electrode mixture does not contain a resin binder, or if it does, the content of the positive electrode mixture is 0.5% by mass or less. The content of the resin binder in the positive electrode mixture is more preferably 0.3% by mass or less, and further preferably 0% by mass (that is, the resin binder is not contained).

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

The molded body of the positive electrode mixture is, for example, compressed by pressure molding or the like, which is prepared by mixing a positive electrode active material with a conductive auxiliary agent, a binder, a solid electrolyte, etc. added as needed. Can be formed with.

In the case of a positive electrode having a current collector, it can be manufactured by bonding the molded body of the positive electrode mixture formed by the above method by crimping it to the current collector.

Further, the above-mentioned positive electrode mixture and the solvent are mixed to prepare a positive electrode mixture-containing composition, which is placed on a substrate such as a current collector or a solid electrolyte layer (in the case of forming a solid electrolyte battery) facing the positive electrode. A molded body of the positive electrode mixture may be formed by applying the mixture to the above-mentioned material, drying the mixture, and then performing a pressing process.

As the solvent of the positive electrode mixture-containing composition, water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) can be used. When the solid electrolyte is also contained in the positive electrode mixture-containing composition, 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 cause a chemical reaction with a very small amount of water, and are therefore represented by hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene. It is preferable to use a non-polar aproton solvent. In particular, it is more preferable to use a super dehydrating solvent having a water content of 0.001% by mass (10 ppm) or less. In addition, fluorine-based solvents such as "Bertrel (registered trademark)" manufactured by Mitsui Dupont Fluorochemical, "Zeorolla (registered trademark)" manufactured by Zeon Corporation, and "Novec (registered trademark)" manufactured by Sumitomo 3M, as well as , Dichloromethane, diethyl ether and other non-aqueous organic solvents can also be used.

The thickness of the molded body of the positive electrode mixture (in the case of an electrode having a current collector, the thickness of the molded body of the positive electrode mixture per one side of the current collector; the same applies hereinafter) is usually 50 μm or more. From the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. The thickness of the molded product of the positive electrode mixture is usually 3000 μm or less.

In the case of a positive electrode manufactured by forming a positive electrode mixture layer made of a molded body of the positive electrode mixture on a current collector using a positive electrode mixture-containing composition containing a solvent, the positive electrode mixture layer is used. The thickness of the above is preferably 50 to 1000 μm.

<All-solid-state battery>
The all-solid-state battery of the present invention has a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and the positive electrode is the positive electrode for the all-solid-state battery of the present invention.

(Negative electrode)
The negative electrode of the all-solid-state battery has, for example, a molded body of a negative electrode mixture containing a negative electrode active material and a solid electrolyte, and is composed of only a molded body of the negative electrode mixture or a layer made of a molded body of the negative electrode mixture. A structure having a (negative electrode mixture layer) formed on the current collector can be used.

Examples of the negative electrode active material when the all-solid-state battery is a primary battery include metallic lithium and lithium alloys (lithium-aluminum alloys).

When the all-solid-state battery is a secondary battery, the negative electrode active material includes metallic lithium, lithium alloy (lithium-aluminum alloy), graphite, thermally decomposed carbons, cokes, glassy carbon, and organic polymers. Examples thereof include a calcined body of a compound, carbon materials such as mesocarbon microbeads, carbon fibers, and activated carbon; alloys containing elements that can be alloyed with lithium such as Si and Sn; and oxides of Si and Sn.

The content of the negative electrode active material in the negative electrode mixture is preferably 40 to 95% by mass.

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

A conductive auxiliary agent can be contained in the molded product of the negative electrode mixture. Specific examples thereof include the same conductive auxiliaries as those exemplified above as those that can be contained in the molded body of the positive electrode mixture. The content of the conductive auxiliary agent in the negative electrode mixture is preferably 1 to 10% by mass.

Further, the resin binder may or may not be contained in the molded body of the negative electrode mixture. Examples of the resin binder include fluororesins such as polyvinylidene fluoride (PVDF). However, since the resin binder acts as a resistance component even in the molded body of the negative electrode mixture, it is desirable that the amount thereof is as small as possible. Therefore, it is preferable that the molded body of the negative electrode mixture does not contain a resin binder, or if it does, the content of the negative electrode mixture is 0.5% by mass or less. The content of the resin binder in the negative electrode mixture is more preferably 0.3% by mass or less, and further preferably 0% by mass (that is, the resin binder is not contained).

When a current collector is used for the negative electrode having the molded body of the negative electrode mixture, copper or nickel foil, punching metal, net, expanded metal, foamed metal; carbon sheet; etc. may be used as the current collector. can.

The molded body of the negative electrode mixture is, for example, a negative electrode mixture prepared by mixing a negative electrode active material and a solid electrolyte, and a conductive additive or a binder added as needed, and compressed by pressure molding or the like. It can be formed by. In the case of a negative electrode composed of only a molded body of a negative electrode mixture, it can be manufactured by the above 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 above method by crimping it to the current collector.

Further, 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 solid electrolyte, and a conductive auxiliary agent or a binder added as needed are dispersed in a solvent. ) Is applied to the current collector, dried, and then subjected to pressure molding such as calendering if necessary 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 of the composition containing the negative electrode mixture, but the solvent when the solid electrolyte is also contained in the composition containing the negative electrode mixture does not easily deteriorate the solid electrolyte. It is desirable to select the above, and it is preferable to use the same solvent as the various solvents exemplified above as the solvent for the positive mixture-containing composition containing the solid electrolyte.

The thickness of the molded body of the negative electrode mixture (in the case of a negative electrode having a current collector, the thickness of the molded body of the negative electrode mixture per one side of the current collector; the same applies hereinafter) is usually 50 μm or more. From the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. The thickness of the molded product of the negative electrode mixture is usually 3000 μm or less.

In the case of a negative electrode manufactured by forming a negative electrode mixture layer composed of a molded body of the 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 the above is preferably 50 to 1000 μm.

Further, as the negative electrode, a metal foil or the like as a negative electrode active material may be used as it is, or a structure in which a metal foil as a negative electrode active material and a current collector are laminated may be used.

In the case of a negative electrode having a structure in which a negative electrode active material and a current collector are laminated, it can be obtained by bonding the metal foil and the current collector together, for example. As the current collector in this case, the same current collector as that exemplified above can be used as the current collector that can be used for the negative electrode having the molded body of the negative electrode mixture.

In the case of a negative electrode having a metal foil as a negative electrode active material, examples of the negative electrode active material include metallic lithium and lithium alloys. Examples of the alloying element related to the lithium alloy include aluminum, lead, bismuth, indium, gallium and the like, but aluminum and indium are preferable. The ratio of alloying elements in the lithium alloy (when a plurality of alloying elements are contained, the total ratio thereof) 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 foil, a laminated body laminated by crimping a layer containing an alloy element for forming a lithium alloy on the surface of a lithium layer (a layer containing lithium) composed of a metallic 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 contacting the laminate with a 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 pressure-bonding a metallic lithium foil and a foil composed of an alloying element.

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

For the layer containing the alloying elements related to the laminated body for forming a negative electrode, for example, a foil composed 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 even more preferably 12 μm or less.

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

(Solid electrolyte layer)
The solid electrolytes constituting the solid electrolyte layer of the all-solid battery include various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solids exemplified above as those that can be used for the positive electrode. One or more of the electrolytes can be used. However, in order to improve the battery characteristics, it is desirable to contain a sulfide-based solid electrolyte, and it is more desirable to contain an algyrodite-type sulfide-based solid electrolyte. Further, it is more desirable that both the positive electrode and the solid electrolyte layer, and when the negative electrode is a molded body of a negative electrode mixture containing a solid electrolyte, the negative electrode also contains a sulfide-based solid electrolyte, and argylodite-type sulfide. It is particularly desirable to contain a physical solid electrolyte.

The solid electrolyte layer may have a porous body such as a non-woven fabric made of resin as a support.

The solid electrolyte layer is a method of 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 onto a base material, a positive electrode, and a negative electrode, and dried. If necessary, it can be formed by a method of performing pressure molding such as press processing: or the like.

It is desirable to select a solvent that does not easily deteriorate the solid electrolyte as the solvent used for the composition for forming the solid electrolyte layer, and the various solvents exemplified above as the solvent for the composition containing the positive electrode mixture containing the solid electrolyte. It is preferable to use the same one.

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

(Electrode body)
The positive electrode and the negative electrode can be used in a battery in the form of a laminated electrode body laminated via a solid electrolyte layer or a wound electrode body wound around the laminated electrode body.

When forming the electrode body, it is preferable to perform pressure molding in a state where the positive electrode body, the negative electrode body and the solid electrolyte layer are laminated from the viewpoint of increasing the mechanical strength of the electrode body.

(Battery form)
FIG. 1 shows a cross-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 positive electrode 10 for an all-solid-state battery and a negative electrode of the present invention in an outer body formed of an outer can 40, a sealing can 50, and a resin gasket 60 interposed between them. 20 and the solid electrolyte layer 30 interposed between the positive electrode 10 and the negative electrode 20 are enclosed.

The sealing can 50 is fitted to the opening of the outer can 40 via the gasket 60, and the opening end of the outer can 40 is tightened inward, whereby the gasket 60 comes into contact with the sealing can 50. The opening of the outer can 40 is sealed and the inside of the element has a closed structure.

Stainless steel cans can be used for the outer can and the sealing can. In addition, polypropylene, nylon, etc. can be used as the material of the gasket, and if heat resistance is required in relation to the use of the battery, tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), etc. can be used. Heat resistance of fluororesin, polyphenylene ether (PEE), polysulphon (PSF), polyarylate (PAR), polyethersulphon (PES), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), etc. with a melting point of more than 240 ° C. Resin can also be used. Further, if the battery is applied to applications requiring heat resistance, a glass hermetic seal can be used for the sealing.

In addition, FIGS. 2 and 3 show drawings schematically showing other examples of the all-solid-state battery of the present invention. FIG. 2 is a plan view of the all-solid-state battery, and FIG. 3 is a sectional view taken along line I-I of FIG.

The all-solid-state battery 100 shown in FIGS. 2 and 3 has an electrode body 200 composed of a positive electrode for an all-solid-state battery, a solid electrolyte layer, and a negative electrode of the present invention in a laminate film exterior body 500 composed of two metal laminate films. The laminated film exterior body 500 is housed, and is sealed by heat-sealing the upper and lower metal laminated films at the outer peripheral portion thereof. In addition, in FIG. 3, in order to avoid complicating the drawings, each layer constituting the laminated film exterior body 500, and the positive electrode, the negative electrode, and the separator constituting the electrode body are not shown separately.

The positive electrode of the electrode body 200 is connected to the positive electrode external terminal 300 in the battery 100, and although not shown, the negative electrode of the electrode body 200 is also connected to the negative electrode external terminal 400 in the battery 100. There is. The positive electrode external terminal 300 and the negative electrode external terminal 400 are drawn out on one end side to the outside of the laminated film exterior body 500 so that they can be connected to an external device or the like.

The form of the all-solid-state battery is as shown in FIG. 1, which has an outer body composed of an outer can, a sealing can, and a gasket, that is, a form generally called a coin-shaped battery or a button-shaped battery. , As shown in FIGS. 2 and 3, in addition to those having an exterior body made of a resin film or a metal-resin laminated film, a metal bottomed tubular (cylindrical or square tubular) exterior can. And may have an exterior body having a sealing structure for sealing the opening.

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

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

Example 1
<Manufacturing of positive electrode>
Primary particles (positive electrode active material) of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 5 μm and a layer composed of LiNbO ₃ on the surface, and algyrodite having an average particle diameter rs of 0.6 μm. A sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) having a mold structure and acetylene black (conductive auxiliary agent) were mixed at a mass ratio of 65:32: 3 and kneaded well to prepare a positive electrode mixture. .. Next, the positive electrode mixture: 75 mg was placed in a powder molding die having a diameter of 7.5 mm, and pressure molding was performed using a press machine to prepare a positive electrode made of a cylindrical positive electrode mixture molded body. The amount of the layer consisting of LiNbO ₃ on the surface of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ is 1 with respect to 100 parts by mass of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : It was a mass part.

<Formation of solid electrolyte layer>
Next, the same sulfide-based solid electrolyte as that used for producing the positive electrode: 9.6 mg was put onto the positive electrode mixture molded body in the powder molding mold, and pressure molding was performed using a press machine. A solid electrolyte layer was formed on the positive electrode mixture molded body to obtain a laminated body of the positive electrode and the solid electrolyte layer.

<Manufacturing of negative electrode>
As the negative electrode, a metal Li foil and a metal In foil formed into a cylindrical shape and stacked were used.

<Battery assembly>
A negative electrode was placed on the inner bottom surface of a stainless steel sealing can fitted with a polypropylene annular gasket with the metal In foil side facing the inner surface side of the sealing can. Next, the laminated body of the positive electrode and the solid electrolyte layer is laminated so that the solid electrolyte layer is on the negative electrode side, and then the outer can made of stainless steel is covered, and then the open end of the outer can is caulked inward. By sealing, an all-solid-state battery having a diameter of about 9 mm was produced while forming a laminated electrode body composed of a positive electrode, a solid electrolyte layer, and a negative electrode.

Example 2
The positive electrode active material is composed of primary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 2 μm and having a layer composed of LiNbO ₃ on the surface (the amount of the layer composed of LiNbO ₃ on the surface). LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass with respect to 100 parts by mass), and the solid electrolyte was changed to Li ₆ PS ₅ Cl with an average particle diameter rs of 0.9 μm. Except for the above, a positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1, and an all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Example 3
A positive electrode made of a positive electrode mixture molded body was prepared in the same manner as in Example 2 except that the solid electrolyte was changed to Li ₆ PS ₅ Cl having an average particle diameter rs of 0.4 μm, except that this positive electrode was used. An all-solid-state battery was produced in the same manner as in Example 1.

Example 4
The positive electrode active material is composed of primary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 27 μm and having a layer composed of LiNbO ₃ on the surface (the amount of the layer composed of LiNbO ₃ on the surface). LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass for 100 parts by mass), and the solid electrolyte was changed to Li ₆ PS ₅ Cl with an average particle diameter rs of 2 μm. A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1, and an all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Example 5
The positive electrode active material is composed of primary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 8 μm and a layer composed of LiNbO ₃ on the surface (the amount of the layer composed of LiNbO ₃ on the surface is A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 3 except that it was changed to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass with respect to 100 parts by mass). An all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 1
The positive electrode active material is composed of primary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 1 μm and having a layer composed of LiNbO ₃ on the surface (the amount of the layer composed of LiNbO ₃ on the surface). A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1 except that it was changed to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass with respect to 100 parts by mass). An all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 2
The positive electrode active material is composed of primary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 50 μm and having a layer composed of LiNbO ₃ on the surface (the amount of the layer composed of LiNbO ₃ on the surface). A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1 except that it was changed to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass with respect to 100 parts by mass). An all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 3
A positive electrode made of a positive electrode mixture molded body was prepared in the same manner as in Example 1 except that the solid electrolyte was changed to Li ₆ PS ₅ Cl having an average particle diameter rs of 0.2 μm, except that this positive electrode was used. An all-solid-state battery was produced in the same manner as in Example 1.

Comparative Example 4
A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1 except that the solid electrolyte was changed to Li ₆ PS ₅ Cl having an average particle diameter rs of 3 μm. An all-solid-state battery was produced in the same manner as in 1.

Comparative Example 5
The positive electrode active material is a primary particle of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 0.3 μm and having a layer composed of LiNbO ₃ on the surface (amount of the layer composed of LiNbO ₃ on the surface). However, the solid electrolyte was changed to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass with respect to 100 parts by mass), and the solid electrolyte was changed to Li ₆ PS ₅ Cl with an average particle diameter rs of 0.3 μm. A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1 except for the modification, and an all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 6
The positive electrode active material is composed of primary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 30 μm and a layer composed of LiNbO ₃ on the surface (the amount of the layer composed of LiNbO ₃ on the surface is LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass with respect to 100 parts by mass), and the solid electrolyte was changed to Li ₆ PS ₅ Cl with an average particle diameter rs of 20 μm. A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1, and an all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 7
Examples except that the positive electrode active material was changed to primary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter ra of 5 μm (one having no layer composed of LiNbO ₃ on the surface). A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in No. 1, and an all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 8
The positive electrode active material is composed of secondary particles of LiCo _0.98 Al _0.01 Mg _0.01 O ₂ having an average particle diameter of 5 μm and having a layer composed of LiNbO ₃ on the surface (the amount of the layer composed of LiNbO ₃ on the surface). A positive electrode made of a positive electrode mixture molded body was produced in the same manner as in Example 1 except that it was changed to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ : 1 part by mass with respect to 100 parts by mass). An all-solid-state battery was produced in the same manner as in Example 1 except that this positive electrode was used.

The load characteristics of the all-solid-state batteries of Examples and Comparative Examples were evaluated by the following methods.

After constant current charging of each of the all-solid-state batteries of Examples and Comparative Examples at a current value of 0.5 C until the voltage reaches 4.0 V, and then constant voltage charging until the current value reaches 0.02 C. The initial capacitance was measured by discharging at a current value of 0.05 C until the voltage reached 2.6 V.

After the initial characteristic evaluation, each battery was charged and discharged under the same conditions as those at the time of initial capacity measurement except that the current value at the time of discharge was changed to 0.5C, and the discharge capacity of 0.5C was measured. Then, the value obtained by dividing the 0.5C discharge capacity of each battery by the initial capacity was expressed as a percentage to obtain the capacity retention rate, and the load characteristics of each battery were evaluated.

These results are shown in Table 1 together with the composition of the positive electrode active material and the solid electrolyte in the positive electrode. The average particle size of the positive electrode active material in Comparative Example 8 is the value of the secondary particles. In Table 1, the value is described in the column of “ra”, and this value is described in the column of “ra”, and this secondary is relative to the average particle size of the solid electrolyte. The ratio of the average particle size of the particles is described in the column of "ra / rs".

As shown in Table 1, a positive electrode active material composed of primary particles having a reaction suppression layer on the surface is used, and the ratio ra / rs of the average particle size ra of the positive electrode active material and the average particle size rs of the solid electrolyte is appropriate. The all-solid-state batteries of Examples 1 to 5 having a positive electrode made of a positive electrode mixture molded body as a value had a high capacity retention rate at the time of load characteristic evaluation and had excellent load characteristics.

On the other hand, the batteries of Comparative Examples 1 to 6 having a positive electrode made of a positive electrode mixture molded body in which a positive electrode active material and a solid electrolyte are combined so that the value of ra / rs is unsuitable, and a reaction suppressing layer are provided on the surface. A battery of Comparative Example 7 having a positive electrode made of a positive electrode mixture molded body using no positive electrode active material, and Comparative Example 8 having a positive electrode made of a positive electrode mixture molded body using a positive electrode active material existing in secondary particles. The battery had a lower capacity retention rate at the time of load characteristic evaluation and was inferior in load characteristic as compared with the battery of the example.

1,100 All-solid secondary battery 10 Positive electrode 20 Negative electrode 30 Solid electrolyte layer 40 Exterior can 50 Sealed can 60 Gasket 200 Electrode body 300 Positive electrode external terminal 400 Negative electrode external terminal 500 Laminate film exterior

Claims (6)

It has a positive electrode active material composed of primary particles and a molded body of a positive electrode mixture containing a solid electrolyte.
The positive electrode active material has a reaction suppressing layer on the surface for suppressing the reaction between the positive electrode active material and the solid electrolyte.
A positive electrode for an all-solid-state battery, wherein the ratio ra / rs of the average particle diameter ra of the positive electrode active material to the average particle diameter rs of the solid electrolyte is 2 or more and 20 or less. The positive electrode for an all-solid-state battery according to claim 1, wherein the average particle diameter rs of the solid electrolyte is 0.4 to 2.5 μm. The positive electrode for an all-solid-state battery according to claim 1 or 2, wherein the average particle size ra of the positive electrode active material is 2 to 30 μm. The positive electrode for an all-solid-state battery according to any one of claims 1 to 3, wherein the reaction suppressing layer contains an Nb oxide. As the positive electrode active material, the following general formula (1)
LiCo _1-ab-c Al _a M ¹ _b M ² _c O ₂ (1)
[In the general formula (1), M ¹ is at least one element selected from the group consisting of Mg, Ni and Na, and M ² is Mn, Fe, Cu, Zr, Ti, Bi, Ca and F. , P, Sr, W, Ba, Nb, Si, Zn, Mo, V, Sn, Sb, Ta, Ge, Cr, K, S and Er, at least one element selected from the group consisting of 0. Any of claims 1 to 4 containing the lithium cobalt composite oxide (A) represented by <a <0.1, 0 <b <0.1, a + b <0.1, 0 ≦ c]. The positive electrode for all-solid-state batteries described in. An all-solid-state battery having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.
An all-solid-state battery comprising the positive electrode for an all-solid-state battery according to any one of claims 1 to 5 as the positive electrode.

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