JP5705614B2 - All solid battery - Google Patents

Description

  The present invention relates to an all-solid-state battery in which main components are formed from a solid.

  As a conventional all-solid battery, a battery composed of three layers of a positive electrode, a solid electrolyte, and a negative electrode is known.

  An all-solid battery employing a solid electrolyte does not move because the electrolyte is solid. Therefore, problems such as electrolyte leakage are unlikely to occur, and a simple housing without electrolyte mixing can be employed even if it is not clearly partitioned by a battery housing or the like.

  In addition, by adopting a solid electrolyte, even when metallic lithium or the like is employed as a negative electrode active material, generation of dendrites does not proceed, and high safety can be realized (Patent Document 1, etc.).

International Publication No. 09/139382

  By the way, a general positive electrode active material is often in the form of particles. The positive electrode active material exchanges lithium ions accompanying the battery reaction through the surface. In the case of a secondary battery using a conventional electrolyte solution, the electrolyte solution penetrates into the gaps between the particles of the positive electrode active material, and can efficiently transfer lithium ions on the surface of the positive electrode active material.

  The inventors of the present application, as in the case of a conventional secondary battery using an electrolytic solution, for the purpose of efficiently transferring lithium ions as in the case of a conventional secondary battery using an electrolytic solution. An attempt was made to reduce the lithium ion conduction resistance by bringing a solid electrolyte into contact with the surface of the particulate positive electrode active material. Here, the solid electrolyte used is the electrolyte disclosed in Patent Document 1 or the hydride-based solid electrolyte from which it was based.

  As a result of manufacturing and examining a battery in which the positive electrode active material and the solid electrolyte were brought into contact with each other, irreversible decomposition of the positive electrode active material in contact with the solid electrolyte was observed, and a decrease in battery capacity was observed.

  The present inventors have completed the present invention in view of the above circumstances, and an object to be solved is to provide an all solid state battery in which a decrease in battery capacity is suppressed.

  As a result of intensive studies aimed at solving the above problems, the present inventors have found that the decrease in battery capacity is due to the reduction of the positive electrode active material by the reducing action of the hydride-based solid electrolyte contained in the solid electrolyte. I found out. The positive electrode active material used for the test was an oxide-type positive electrode active material generally employed in lithium batteries. That is, the oxide contained in the oxide-type positive electrode active material is reduced by the hydride-based solid electrolyte, so that the function as the active material is lost, and the battery capacity is reduced.

  Therefore, as a result of intensive studies, the present inventors have succeeded in preventing reduction even when contacting a solid electrolyte by adopting an appropriate positive electrode active material. Specifically, the portion in contact with the solid electrolyte in the positive electrode active material is configured from a material that cannot be reduced by the solid electrolyte.

Based on the above findings, the present inventors have completed the following invention. That is, the invention according to claim 1, which solves the above problem, includes a positive electrode having a positive electrode current collector and a positive electrode layer formed on a surface of the positive electrode current collector, a negative electrode current collector, and the negative electrode current collector. A negative electrode having a negative electrode layer formed on the surface thereof, and an electrolyte formed from a first solid electrolyte interposed between the positive and negative electrodes and having lithium ion conductivity,
The positive electrode layer is composed of a base part that is a continuous phase made of a second solid electrolyte having lithium ion conductivity, and an active material part that is dispersed in the base part and contains a positive electrode active material,
The first and second solid electrolytes are lithium ion conductive materials having hydride-based solid electrolytes that are independently selected;
The negative electrode active material constituting the negative electrode layer contains metallic lithium,
It is an all solid state battery in which the mole fraction of Li in the negative electrode layer in a use state of the battery is 25 mol% or more.

  According to this configuration, the lithium material can be smoothly exchanged by dispersing the active material portion in the second solid electrolyte. Further, by adopting an appropriate positive electrode active material on the surface in contact with the second solid electrolyte, even if it comes into contact with the solid electrolyte, it is not reduced, and the battery capacity associated with the reduction of the positive electrode active material by the second solid electrolyte is reduced. Reduction can be suppressed. When it is not a positive electrode active material, a compound that does not inhibit lithium ion conduction or electron conduction is desirable.

  Here, the “continuous phase” is to prevent the lithium ion conduction from being transferred by the positive electrode active material. That is, by forming the “continuous phase”, the barrier for lithium ion conduction is reduced, so that the battery output is increased. In particular, from the viewpoint of lithium ion conductivity, it is desirable that the “continuous phase” is a single phase without an interface such as a grain boundary, as well as those that are in close contact with each other. In particular, it is desirable that there is no change in composition, or that the change is small and the conduction resistance when lithium ions are conducted is small. In addition, it is not an indispensable requirement until the whole becomes one continuously.

According to a second aspect of the present invention, there is provided a positive electrode having a thin-film positive electrode current collector and a positive electrode layer formed only on one surface side of the positive electrode current collector, a thin-film negative electrode current collector, and the negative electrode current collector. A first solid electrolyte having a lithium ion conductivity interposed between the positive and negative electrodes and a negative electrode having a negative electrode layer formed only on one side of the positive electrode facing the side on which the positive electrode layer is formed A plurality of unit cells electrically connected in series without partitioning each other.
The positive electrode layer is composed of a base material part that is a continuous phase made of a second solid electrolyte having lithium ion conductivity, an active material part dispersed in the base material part and containing a positive electrode active material, and a conductive material,
The first and second solid electrolytes are lithium ion conductive materials having hydride-based solid electrolytes that are independently selected;
The negative electrode active material constituting the negative electrode layer contains metallic lithium,
It is an all solid state battery in which the mole fraction of Li in the negative electrode layer in a use state of the battery is 25 mol% or more.

  According to this configuration, in addition to the above-described effects, the battery casing can be simplified. That is, by adopting a solid electrolyte, it is possible to prevent a short circuit through the electrolyte between different single cells.

The invention according to claim 1 or 2 further includes an active material portion comprising an organic positive electrode active material, an inorganic positive electrode active material, and an oxide positive electrode active material coated with a lithium ion conductor or a carbon material. It consists of 1 type, or 2 or more types of materials selected from the group which consists of.

According to a third aspect of the present invention, the organic positive electrode active material is at least one of anthracene, tetracene, pentacene, and hexacene .

In the invention described in claim 1 or 2, the inorganic positive electrode active material is at least one of fluoride perovskite MF ₃ (M is any one of Fe, V, Ti, Co, and Mn). .

According to a fourth aspect of the present invention, the lithium ion conductor is at least one of LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , LiTiO ₃ , Li ₂ ZrO ₃ , Li ₄ SiO ₄ , LiTaO ₃ , and the oxide The type positive electrode active material is a lithium-containing compound having a layered rock salt type or cubic rock salt type crystal structure, or a lithium-containing compound having a spinel structure, and has a general formula Li _{2 + x} Mn _1-y M _y O _{2 + z} (M is other than Mn) At least one element consisting of Al, Sn, and an alkaline earth metal element, represented by −0.5 ≦ x ≦ 0.5, 0 ≦ y <1, 0 ≦ z <0.3). It is at least one of the above lithium-containing compounds.

  According to these configurations, since a material having excellent durability can be adopted as the positive electrode active material, high durability can be realized even for the obtained all-solid battery.

According to a fifth aspect of the present invention, the negative electrode layer is formed of a base portion that is a continuous phase made of a third solid electrolyte having lithium ion conductivity, and is dispersed in the base portion and formed from a negative electrode active material. Active material part,
The negative electrode active material is selected from the group consisting of metallic lithium, a lithium alloy, a metal material capable of occluding and releasing lithium, an alloy material capable of occluding and releasing lithium, and a compound capable of occluding and releasing lithium. 1 type, or 2 or more types of negative electrode materials.

  According to this configuration, the volume change that proceeds with the progress of the battery reaction in the negative electrode active material is absorbed by the voids in the base material portion and does not appear in the volume change of the negative electrode itself. When metallic lithium etc. are employ | adopted independently, the volume changes with progress of charging / discharging.

  For example, the case where there is a void in the base material part included in the negative electrode layer will be described. When the volume of the negative electrode active material increases, the volume change is absorbed by the negative electrode active material entering the voids. When the volume of the negative electrode active material is reduced, the change in volume of the negative electrode active material is absorbed by the increase in the size of the voids in the base material portion.

  Here, in the present invention, when the negative electrode active material contracts and the voids increase, the volume of the negative electrode layer does not decrease or the condition for suppressing the volume contraction is the base material portion in the negative electrode layer. The requirement that the third solid electrolyte constituting the liquid crystal form a continuous phase is added. Here, the “continuous phase” means that no volume change occurs even if the maximum shrinkage assumed for the volume of the negative electrode active material contained in the negative electrode layer has progressed (or only an acceptable volume change). This means that the third solid electrolyte is continuously present in the negative electrode layer. Furthermore, by forming a “continuous phase”, the battery output is increased because the barrier in lithium ion conduction is reduced. In particular, from the viewpoint of lithium ion conductivity, the “continuous phase” may be a single phase without an interface such as a grain boundary, or may be in contact with each other. In particular, it is desirable that there is no change in composition, or that the change is small and the conduction resistance when lithium ions are conducted is small. In addition, it is not an indispensable requirement until the whole becomes one continuously.

  Further, even if it is assumed that all the gaps between the negative electrode active materials are filled with the solid electrolyte, the formation conditions of the negative electrode layer under the condition that no further lithium ions move to the negative electrode active material are selected. Therefore, since the volume of the negative electrode active material proceeds only in the direction of decreasing due to the progress of the battery reaction, the volume change of the negative electrode active material is absorbed by the increase of voids formed around the negative electrode active material. Therefore, it does not appear as a volume change of the negative electrode layer.

In the invention described in claim 6 , the negative electrode active material is in the form of particles.

  That is, by making the negative electrode active material dispersed in the negative electrode layer into a particulate form, a base material is interposed between the particulate negative electrode active materials. Therefore, the volume change can hardly affect the volume of the negative electrode layer.

According to a seventh aspect of the present invention, the negative electrode layer is obtained by impregnating the third solid electrolyte into the voids of the active material portion composed of an aggregate of particles of the negative electrode active material.

  In particular, by filling the gap between the particulate negative electrode active materials with the third solid electrolyte, the volume change derived from the negative electrode active material can be reliably suppressed. Furthermore, the strength of the base material portion made of the third solid electrolyte can be increased, and the lithium ion conductivity can be improved.

According to an eighth aspect of the present invention, at least one of the first to third solid electrolytes is the hydride-based solid electrolyte and MX _a (M is an alkali metal or alkaline earth metal; X is a halogen atom, NR ₂ A mixture with an alkali metal compound represented by a group selected from the group consisting of a group (R is hydrogen or an alkyl group) and an N ₂ R group (R is hydrogen or an alkyl group), a is 1 or 2) or Those reactants.

  A lithium ion conductive material obtained by mixing or reacting at least one of an alkali metal compound or an alkaline earth metal compound with a hydride-based solid electrolyte has improved lithium ion conductivity and sufficient mechanical strength.

In the invention according to claim 9 , the alkali metal compound is LiF, LiCl, LiBr, LiI, RbI, and CsI.

  These alkali metal compounds achieve both high lithium ion conductivity and sufficient mechanical strength in the presence of a hydride-based solid electrolyte.

The invention according to claim 10 is characterized in that the alkaline earth metal compound is BeF ₂ , BeCl ₂ , BeBr ₂ , BeI ₂ , MgF ₂ , MgCl ₂ , MgBr ₂ , MgI ₂ , CaF ₂ , CaCl ₂ , CaBr ₂ , _{CaI 2, SrF 2, SrCl 2} , SrBr 2, SrI 2, BaF 2, BaCl 2, BaBr 2, and is BaI _2. These alkaline earth metal compounds achieve both high lithium ion conductivity and sufficient mechanical strength in the presence of a hydride-based solid electrolyte.

The invention according to claim 11 is characterized in that the hydride-based solid electrolyte is LiBH ₄ , LiAlH ₄ , Li ₃ AlH ₆ , LiBH (Et) ₃ , LiBH (s-Bu) ₃ , LiNH ₂ , Li ₂ NH, Li [OC (CH ₃ ) ₃ ] ₃ AlH, Li (OCH ₃ ) ₃ AlH, and Li (OC ₂ H ₅ ) ₃ H.

  These hydride-based solid electrolytes have both high lithium ion conductivity and sufficient mechanical strength in the presence of an alkali metal compound.

According to a twelfth aspect of the present invention, the first to third solid electrolytes are the same lithium ion conductive material.

  By forming the first to third solid electrolytes from the same solid electrolyte, the lithium ion conductivity between the positive electrode layer and the electrolyte and between the negative electrode layer and the electrolyte can be improved. In particular, the lithium ion conductivity can be further improved by forming between the two like the above-mentioned “continuous phase”.

According to a thirteenth aspect of the present invention, the hydride-based solid electrolyte is LiBH ₄ .

Is an SEM photograph of a mixture of metal Li and LiBH ₄ in the embodiment. Is a diagram showing an XRD spectrum of a mixture of XRD spectra and metal Li and LiBH ₄ of LiBH ₄ in the embodiment. It is a figure which shows the measurement result of the electrical conductivity in an Example. It is a figure which shows the measurement result of the discharge capacity in an Example.

  The all-solid-state battery of this invention is demonstrated in detail based on embodiment.

(All-solid battery)
The all solid state battery of the present invention has a positive electrode, a negative electrode, and an electrolyte. The form of the all-solid-state battery of this embodiment is not particularly limited, and a positive electrode, a negative electrode, and an electrolyte are formed into a sheet shape, and they are stacked and wound, and a wound battery, a stacked battery to be stacked, etc. A normal form can be adopted. Although the form of a positive electrode, a negative electrode, and electrolyte is not specifically limited, A sheet form and a plate form can be illustrated, respectively.

  In addition, since the whole solid state battery of the present embodiment is composed entirely of solid, there is a low possibility that the electrolyte moves, and when a battery pack is formed by connecting a plurality of unit cells composed of a positive electrode, a negative electrode, and an electrolyte. There is no need to strictly divide each single cell.

The electrolyte is formed from a first solid electrolyte having lithium ion conductivity. The electrolyte is interposed between the positive electrode and the negative electrode. The thickness of the electrolyte is not particularly limited. The first solid electrolyte is a lithium ion conductive material having a hydride-based solid electrolyte. The first solid electrolyte may be formed from a single compound or a mixture of a plurality of compounds. When the mixture is employed, it can be mixed in the form of particles, mixed at the molecular level, or laminated in layers. Here, the hydride-based solid electrolyte is LiBH ₄ , LiAlH ₄ , Li ₃ AlH ₆ , LiBH (Et) ₃ , LiBH (s-Bu) ₃ , LiNH ₂ , Li ₂ NH, Li [OC (CH ₃ ) ₃ ]. ₃ AlH, Li (OCH ₃ ) ₃ AlH, and Li (OC ₂ H ₅ ) ₃ H are desirable. In particular, it is desirable to employ LiBH _4.

  It is desirable that the first solid electrolyte further has at least one of an alkali metal compound or an alkaline earth metal compound. The hydride-based solid electrolyte and the alkali metal compound or alkaline earth metal compound are either simply mixed or produce a reactant. The hydride solid electrolyte and the alkali metal compound or alkaline earth metal compound can be mixed by a mechanical mixing operation (mixing by a mixer, a pulverizer, etc.), but it is desirable to melt and mix them. . When the alkali metal compound or alkaline earth metal compound is used as the lithium ion conductive material, the addition amount of the alkali metal compound or alkaline earth metal compound is 5% to 100 based on the number of moles of the hydride-based solid electrolyte. % Is desirable, and it is further desirable to be 10% to 100%. As the alkali metal compound, lithium halide (particularly LiF, LiCl, LiBr, LiI) is desirably employed.

  The positive electrode has a positive electrode current collector and a positive electrode layer formed on the surface of the positive electrode current collector. As the positive electrode current collector, for example, a metal such as aluminum or stainless steel in a net, punched metal, foam metal, plate shape, foil shape, or the like can be used. A battery housing can also be used as the positive electrode current collector.

The positive electrode layer includes a base material portion that is a continuous phase made of a second solid electrolyte having lithium ion conductivity, and an active material portion that is dispersed in the base material portion and formed from the negative electrode active material. In addition to these, necessary components can be mixed in the positive electrode layer. Examples of necessary components include conductive materials and binders. Since the 2nd solid electrolyte which comprises a base material part is a solid electrolyte which can be selected from the same choice as the 1st solid electrolyte mentioned above, detailed explanation is omitted. The second solid electrolyte may be the same as or different from the first solid electrolyte. In particular, by adopting the same material, the lithium ion conductivity with the electrolyte can be made favorable. The method of dispersing the active material part in the base material part is not particularly limited, but the active material part is made into particles and solidified. Then, the method of liquefying and pressurizing and filling the second solid electrolyte may be mentioned. Moreover, the method of making the active material part pulverized and the liquefied 2nd solid electrolyte mixed (or liquefying after mixing) and solidifying is mentioned. Furthermore, there is a method in which both the active material part and the second solid electrolyte are liquefied and mixed (or liquefied after mixing) and solidified. Further, the second solid electrolyte and the active material part can be mixed in a solid state (particulate, massive, etc.) (by a general mixing operation, pulverization operation, etc.). Can be mixed as they are), or can be integrated (compressed, etc., and part of the interface between the two can be dissolved and fused by adjusting the heating temperature and time). Whether or not the base material portion becomes a continuous phase can be adjusted by changing the mixing ratio and mixing conditions of the second solid electrolyte constituting the base material portion and the positive electrode active material constituting the active material portion. is there.

  The active material part is also preferably a continuous phase from the viewpoint of improving electrical conductivity. A preferable range of the particle diameter when the active material part is dispersed in a particulate form in the base material part is preferably about 6 μm to 20 μm, although it depends on the use conditions of the battery. Further, when the positive electrode layer is formed, when the second solid electrolyte is mixed in the form of particles, it is desirable that the volume average particle size is about 2 μm to 30 μm.

  The positive electrode layer includes a base portion that is a continuous phase made of a second solid electrolyte having lithium ion conductivity, and an active material portion that is dispersed in the base portion and includes a positive electrode active material. As the active material part, one or more selected from the group consisting of an organic positive electrode active material, an inorganic positive electrode active material, and an oxide-type positive electrode active material coated with a lithium ion conductor or a carbon material It can be comprised from the material of.

Organic-based positive electrode active material polycyclic aromatic hydrocarbons and has a polyacene skeleton structure (anthracene, tetracene, pentacene, Hekisase emissions) is at least one of. The inorganic positive electrode active material is at least one of fluoride perovskite MF ₃ (M is any one of Fe, V, Ti, Co, and Mn) . The lithium ion conductor is at least one of LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , LiTiO ₃ , Li ₂ ZrO ₃ , Li ₄ SiO ₄ , and LiTaO ₃ . The oxide type positive electrode active material is a lithium-containing compound having a layered rock salt type or cubic rock salt type crystal structure, or a lithium-containing compound having a spinel type structure, and is represented by the general formula Li _{2 + x} Mn _1-y M _y O _{2 + z} (M is At least one element composed of transition metal elements other than Mn, Al, Sn, and alkaline earth metal elements, -0.5 ≦ x ≦ 0.5, 0 ≦ y <1, 0 ≦ z <0.3) It is at least one of the above lithium-containing compounds represented. Examples of the carbon material include carbon materials such as carbon black, acetylene black, and graphite, or a mixture of two or more carbon materials.

  The method for coating the surface of the oxide positive electrode active material with a lithium ion conductor and / or a carbon material is not particularly limited. Oxide-type positive electrode active material and lithium ion conductor or carbon material are mixed in the form of particles (preferably the particle size of oxide-type positive electrode active material is larger), or oxide-type positive electrode active material particles And the lithium ion conductor solution are mixed, and then the solvent is evaporated to deposit the lithium ion conductor on the surface, or the carbon material precursor (polymer compound, etc.) is made into a solution and the oxide positive electrode active material After mixing, the surface can be coated by carbonizing the precursor. If the surface of the oxide-type positive electrode active material is coated to some extent, a decrease in battery capacity due to a reducing action can be suppressed. Desirably, a sufficient effect can be obtained if the surface with which the second solid electrolyte is in direct contact is coated. It is particularly desirable to coat the entire particle.

  The binder has an action of holding the active material particles. As the binder, an organic binder or an inorganic binder can be used. For example, polyvinylidene fluoride (PVDF), polyvinylidene chloride, polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC) And the like.

  The conductive material has an action of ensuring the electrical conductivity of the positive electrode. Examples of the conductive material include one or a mixture of two or more carbon materials such as carbon black, acetylene black, and graphite. Also, the surface of the active material can be carbon coated. The carbon coating method is not particularly limited, but by mixing an active material with a carbon source such as a polymer compound (polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, etc.), and then firing and carbonizing. The surface can also be carbon coated. After firing, a pulverization operation or the like can be appropriately performed. The conductive material can also serve as a carbon material that covers the surface of the oxide-type positive electrode active material.

  The negative electrode has a negative electrode current collector and a negative electrode layer formed on the surface of the negative electrode current collector. The negative electrode current collector can be made of, for example, copper, nickel or the like in the form of a net, punched metal, foam metal, plate, foil, or the like. A battery casing can also be used as the negative electrode current collector.

  A negative electrode layer is employ | adopted with the component added only as a negative electrode active material or as needed.

  Negative electrode active materials include metallic lithium, lithium alloys, metal materials that can store and release lithium, and alloy materials that can store and release lithium (not only alloys consisting of metals but also alloys of metals and metalloids). The structure includes solid solution, eutectic (eutectic mixture), intermetallic compounds or compounds in which two or more of them coexist), and compounds capable of occluding and releasing lithium (carbon 1 type or 2 types or more of negative electrode materials selected from the group which consists of material etc.).

Metal elements and metalloid elements that can constitute metal materials and alloy materials include tin (Sn), lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn), and antimony (Sb). ), Bismuth (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y ) And hafnium (Hf). Examples of these alloy materials or compounds include those represented by the chemical formula Ma _f Mb _g Li _h or the chemical formula Ma _s Mc _t Md _u . In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, Mb represents at least one of a metal element and a metalloid element other than lithium and Ma, Mc represents at least one of non-metallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. The values of f, g, h, s, t, and u are f> 0, g ≧ 0, h ≧ 0, s> 0, t> 0, and u ≧ 0, respectively.

  Among these, a simple substance, alloy or compound of Group 4B metal element or semimetal element in the short-period type periodic table is preferable, and silicon (Si) or tin (Sn), or an alloy or compound thereof is particularly preferable. These may be crystalline or amorphous.

Examples of the anode material capable of inserting and extracting lithium further include other metal compounds such as oxide, sulfide, or lithium nitride such as LiN ₃ . Examples of the oxide include MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , NiS, and MoS. In addition, examples of the oxide that has a relatively low potential and can occlude and release lithium include iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, and tin oxide. Examples of the sulfide include NiS and MoS.

  As a negative electrode layer, it is desirable to have a base material part as another necessary component. The base material portion is made of a third solid electrolyte having lithium ion conductivity, and forms a continuous phase in the negative electrode layer. An active material part is dispersed in the base material part. The active material portion is formed from a negative electrode active material. In this case, the negative electrode layer preferably has a molar fraction of Li of 25 mol% or more, and more preferably 30 mol% or more.

  The method of dispersing the active material part in the base material part in the case of comprising the base material part and the active material is not particularly limited, but after the active material part is made into particles and solidified, the third solid electrolyte is liquefied and added. The method of pressure filling is mentioned. Moreover, the method of mixing the particle-ized active material part and the liquefied 3rd solid electrolyte (or liquefying after mixing) and making it solidify is mentioned. Furthermore, there is a method in which both the negative electrode active material and the third solid electrolyte are liquefied and mixed (or liquefied after mixing) and solidified. Further, the third solid electrolyte and the negative electrode active material can be mixed in a solid state (particulate, massive, etc.) (by a general mixing operation, pulverizing operation, etc.). Can be mixed as they are), or can be integrated (compressed, etc., and part of the interface between the two can be dissolved and fused by adjusting the heating temperature and time). Whether or not the base material part becomes a continuous phase can be adjusted by changing the mixing ratio and mixing conditions of the third solid electrolyte constituting the base material part and the negative electrode active material constituting the active material part. is there.

  The active material part is also preferably a continuous phase from the viewpoint of improving electrical conductivity. A preferable range of the particle diameter when the active material part is dispersed in a particulate form in the base material part is preferably about 1 μm to 6 μm, although it depends on the use conditions of the battery. In forming the negative electrode layer, when the third solid electrolyte is mixed in the form of particles, it is desirable that the volume average particle size is about 2 μm to 30 μm.

  It is not hindered to add a conductive material, a binder or the like to the negative electrode layer as necessary. The conductive material can be added for the purpose of supplementing conductivity when the electrical conductivity between the negative electrode active materials and between the negative electrode active material and the negative electrode current collector is not sufficient. Examples of the conductive material include carbon materials, metal materials and alloy materials that cannot occlude and release lithium ions. The binder has an action of connecting between the constituent elements included in the negative electrode layer and between the constituent elements and the negative electrode current collector. As the binder, an organic binder or an inorganic binder can be used, and examples thereof include compounds such as PVDF, polyvinylidene chloride, PTFE, and CMC.

  Since the 3rd solid electrolyte which comprises a base material part is a solid electrolyte which can be selected from the same choice as the 1st and 2nd solid electrolyte mentioned above, detailed explanation is omitted. The third solid electrolyte may be the same as or different from the first and second solid electrolytes. In particular, by adopting the same, lithium ion conductivity with the electrolyte can be made favorable.

The all solid state battery of the present invention will be described in more detail based on the following examples.
(Measurement of electrical conductivity)
- and LiBH ₄ as producing the hydride-based solid electrolyte of the test sample, and the material capable of constituting a negative electrode layer using a metal Li as a negative electrode active material was prepared. A plurality of samples were prepared so that the mixing ratio between them was the lithium mole fraction (mol% Li) shown in FIG. The calculation of the lithium mole fraction is as described above, and is calculated based on the number of moles of metal Li contained in the mixture of metal Li and LiBH ₄ .

As a specific manufacturing method, metal Li and LiBH ₄ were mixed at a predetermined mixing ratio. Mixing was done physically. Then, it compressed and pelletized. The size of the pellet was 10 mm in diameter and 1 mm in thickness. The mixture before compression was observed by SEM. In SEM, a secondary electron image and a reflected electron image were measured. In the backscattered electron image, the region where the abundance ratio of the atoms having a large atomic number is higher is observed brighter, so that the distribution of LiBH ₄ was expected to be clarified.

The results are shown in FIG. As is clear from FIG. 1, it was suggested that LiBH ₄ existed uniformly around the metal Li without much difference between the secondary electron image and the reflected electron image.

Moreover, XRD measurement was performed for each of LiBH ₄ and the mixture. The results are shown in FIG. As is clear from FIG. 2, neither the generated peak nor the disappeared peak can be found even if the XRD spectra of both are compared, and the metal Li and LiBH ₄ are simply mixed in the mixture. In the meantime, it was clarified that the interaction did not progress enough to change the crystal structure.
Measurement and results The pellet was sandwiched between platinum electrodes, and the electrical conductivity was measured. The electrical conductivity was measured by an alternating current impedance method using an SI-1260 impedance analyzer (manufactured by Solartron).

The results are shown in FIG. As is clear from FIG. 3, it has been clarified that when the Li mole fraction increases in the vicinity of 20 mol% (25 mol% or more), the transition from ionic conduction to electron conduction occurs. That is, it became clear that when the molar fraction of Li exceeds 20 mol%, the electron conduction becomes dominant.
(Measurement of charge / discharge characteristics)
- and LiBH ₄ as prepared hydride-based solid electrolyte test cells, and the material capable of constituting a negative electrode layer using a metal Li as a negative electrode active material was prepared. The mixing ratio of the two was adjusted so that the lithium mole fraction (mol% Li) was 25 mol%.

As a specific manufacturing method, metal Li and LiBH ₄ were mixed at a predetermined mixing ratio. Mixing was done physically. Then, it compressed and pelletized and it was set as the negative electrode layer (negative electrode pellet). The size of the pellet was 10 mm in diameter and 0.093 mm in thickness.

Furthermore, a pellet (diameter: 10 mm, thickness: 0.76 mm) made of LiBH ₄ as the first solid electrolyte was prepared as an electrolyte.

LiBH ₄ as a hydride-based solid electrolyte, a positive electrode active material, and a conductive material were mixed at a mass ratio of 2: 7: 1 and compressed to produce a positive electrode layer pellet (diameter 10 mm, thickness 0.13 mm). . As the positive electrode active material, FeF ₃ (inorganic positive electrode active material: Test Example A), LiNiO ₂ (oxide type positive electrode active material, surface coated with Li ₄ Ti ₅ O ₁₂ : Test Example B), LiNiO ₂ (oxide type positive electrode active material, surface not coated: Test Example C) was employed.

The manufactured pellets of the negative electrode layer, the electrolyte, and the positive electrode active material were laminated in this order, and sandwiched by electrodes (corresponding to the negative electrode current collector and the positive electrode current collector) from both sides to obtain a test battery.
Measurement and Results The voltage range is ² V to 4.5 V in Test Example A, 3 V to 4.1 V in Test Examples B and C, and CC− so that the current density is 0.12 mA / cm ² for this test battery. One cycle of CV charge and CC discharge was performed, and their charge / discharge curves were compared. The measurement atmosphere was 120 ° C.

As a result, the battery of Test Example C showed a reducing action of the positive electrode active material at 3.85 V before reaching the upper limit potential of charging of 4.1 V, but the battery of Test Example A was charged with the upper limit potential of 4.5 V. It was found that the battery of Test Example B did not reduce the positive electrode active material until the upper limit potential of charging of 4.1 V was reached. Therefore, it has been found that by using an inorganic positive electrode active material or an oxide type positive electrode active material whose surface is coated with Li ₄ Ti ₅ O ₁₂ as the positive electrode active material, high charge / discharge characteristics are exhibited. That is, it has been clarified that the reduction of the positive electrode active material by the hydride-based solid electrolyte does not proceed.
(Measurement of charge / discharge characteristics)
- and LiBH ₄ as prepared hydride-based solid electrolyte test cells, and the material capable of constituting a negative electrode layer using a metal Li as a negative electrode active material was prepared. The mixing ratio of the two was adjusted so that the lithium mole fraction (mol% Li) was 11 mol%, 25 mol%, and 75 mol%.

As a specific manufacturing method, metal Li and LiBH ₄ were mixed at a predetermined mixing ratio. Mixing was done physically. Then, it compressed and pelletized and it was set as the negative electrode layer (negative electrode pellet). The size of the pellet was 10 mm in diameter and 0.093 mm in thickness.

Furthermore, a pellet (diameter: 10 mm, thickness: 0.76 mm) made of LiBH ₄ as the first solid electrolyte was prepared as an electrolyte. SnCoFe pellets (diameter 10 mm, thickness 0.052 mm) as a positive electrode active material were also produced.

The manufactured pellets of the negative electrode layer, the electrolyte, and the positive electrode active material were laminated in this order, and sandwiched by electrodes (corresponding to the negative electrode current collector and the positive electrode current collector) from both sides to obtain a test battery.
-Measurement and result About this test battery, CC-CV charge and CC discharge were performed in the voltage range 0.01V-1.5V so that it might become a current density of 0.65 mA / cm < ² >, and charge / discharge capacity was measured. The measurement atmosphere was 120 ° C.

The measured discharge capacity is shown in FIG. As apparent from FIG. 4, it was found that when the molar fraction of Li exceeds about 25 mol%, the discharge capacity increases dramatically. In particular, after the molar fraction of Li exceeded 30 mol%, the improvement in discharge capacity was saturated.
(Examination of volume change during charge / discharge)
Among the test batteries prepared in the previous section, a test battery (battery of Test Example 1) having a negative electrode Li molar fraction of 50 mol% and a metal Li disk (diameter 10 mm, thickness 0.093 mm) as the negative electrode active material. The adopted test battery (battery of Test Example 2) was produced in the same manner as in the previous section, and a charge / discharge test was performed. Of the negative electrode layer at that time, the thickness of the portion corresponding to the positive electrode capacity was measured. The measurement results are shown in Table 1.

As is clear from Table 1, in the battery of Test Example 1 in which a composite of metallic lithium and LiBH ₄ was used as the negative electrode layer pellet, changes in diameter, thickness, volume, etc. associated with charging / discharging were not observed. Thus, it was revealed that the diameter, thickness, volume, and the like of the battery of Test Example 2 in which metal Li was used as the negative electrode layer pellet changed greatly with charge and discharge. In particular, in the battery of Test Example 2, the volume changed to about 1/20, and the durability of the electrode was uneasy when the number of charge / discharge repetitions was increased.

  In other words, the battery of Test Example 1, which is an example of the embodiment of the all-solid battery of the present invention, has a stable size even after repeated charging and discharging, and is complicated such as continuing to apply pressure even when the battery is used. It turns out that the operation can be omitted.

Claims (13)

A positive electrode having a positive electrode current collector and a positive electrode layer formed on a surface of the positive electrode current collector;
A negative electrode having a negative electrode current collector and a negative electrode layer formed on a surface of the negative electrode current collector;
An electrolyte formed from a first solid electrolyte interposed between the positive and negative electrodes and having lithium ion conductivity,
The positive electrode layer is composed of a base part that is a continuous phase made of a second solid electrolyte having lithium ion conductivity, and an active material part that is dispersed in the base part and contains a positive electrode active material,
The first and second solid electrolytes are lithium ion conductive materials having hydride-based solid electrolytes that are independently selected;
The negative electrode active material constituting the negative electrode layer contains metallic lithium,
The mole fraction of Li in the negative electrode layer in the usage state of the battery is 25 mol% or more,
The active material part is one or more selected from the group consisting of an organic positive electrode active material, an inorganic positive electrode active material, and an oxide positive electrode active material coated with a lithium ion conductor or a carbon material. And the inorganic positive electrode active material is at least one of perovskite fluoride MF ₃ (M is any one of Fe, V, Ti, Co, and Mn). . A positive electrode having a thin-film positive electrode current collector and a positive electrode layer formed only on one side of the positive electrode current collector;
A negative electrode having a thin-film negative electrode current collector and a negative electrode layer formed only on one side of the negative electrode current collector facing the side on which the positive electrode layer is formed;
An electrolyte interposed between the positive and negative electrodes and formed from a first solid electrolyte having lithium ion conductivity;
Are connected in series in series without partitioning each other,
The positive electrode layer is composed of a base material part that is a continuous phase made of a second solid electrolyte having lithium ion conductivity, an active material part dispersed in the base material part and containing a positive electrode active material, and a conductive material,
The first and second solid electrolytes are lithium ion conductive materials having hydride-based solid electrolytes that are independently selected;
The negative electrode active material constituting the negative electrode layer contains metallic lithium,
The mole fraction of Li in the negative electrode layer in the usage state of the battery is 25 mol% or more,
The active material part is one or more selected from the group consisting of an organic positive electrode active material, an inorganic positive electrode active material, and an oxide positive electrode active material coated with a lithium ion conductor or a carbon material. And the inorganic positive electrode active material is at least one of perovskite fluoride MF ₃ (M is any one of Fe, V, Ti, Co, and Mn). . The all-solid-state battery according to claim 1 , wherein the organic positive electrode active material is at least one of anthracene, tetracene, pentacene, and hexacene . The lithium ion conductor is at least one of LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , LiTiO ₃ , Li ₂ ZrO ₃ , Li ₄ SiO ₄ , LiTaO ₃ ;
The oxide-type positive electrode active material is a lithium-containing compound having a layered rock salt-type or cubic rock-salt-type crystal structure, or a lithium-containing compound having a spinel structure, and has a general formula of Li _{2 + x} Mn _1-y M _y O _{2 + z} (M Is at least one element composed of transition metal elements other than Mn, Al, Sn, and alkaline earth metal elements, -0.5 ≦ x ≦ 0.5, 0 ≦ y <1, 0 ≦ z <0.3) The all-solid-state battery according to any one of claims 1 to 3, which is at least one of the lithium-containing compounds represented by: The negative electrode layer is composed of a base part that is a continuous phase composed of a third solid electrolyte having lithium ion conductivity, and an active material part that is dispersed in the base part and formed from a negative electrode active material,
The negative electrode active material is selected from the group consisting of metallic lithium, a lithium alloy, a metal material capable of occluding and releasing lithium, an alloy material capable of occluding and releasing lithium, and a compound capable of occluding and releasing lithium. The all-solid-state battery according to any one of claims 1 to 4, wherein the all-solid-state battery is one or more negative electrode materials.   The all-solid-state battery according to claim 5, wherein the negative electrode active material is in the form of particles. The all-solid-state battery according to claim 6, wherein the negative electrode layer is obtained by impregnating the third solid electrolyte in a gap of the active material portion made of an aggregate of particles of the negative electrode active material. At least one of the first to third solid electrolytes is the hydride-based solid electrolyte and MX _a (M is an alkali metal or alkaline earth metal; X is a halogen atom, NR ₂ group (R is a hydrogen or alkyl group) ) And an N ₂ R group (R is hydrogen or an alkyl group), a is selected from the group consisting of an alkali metal compound or an alkaline earth metal compound represented by The all-solid-state battery according to any one of claims 1 to 7, which is a reactant.
However, “at least one of the first to third solid electrolytes” means “at least one of the first or second solid electrolytes” when citing claims 1 to 4. When citing claims 5 to 7, it means "at least one of the first to third solid electrolytes".   The all-solid-state battery according to claim 8, wherein the alkali metal compound is LiF, LiCl, LiBr, LiI, RbI, or CsI. The alkaline earth metal _{compound, BeF 2, BeCl 2, BeBr} 2, BeI 2, MgF 2, MgCl 2, MgBr 2, MgI 2, CaF 2, CaCl 2, CaBr 2, CaI 2, SrF 2, SrCl 2, The all-solid-state battery according to claim 8, which is SrBr ₂ , SrI ₂ , BaF ₂ , BaCl ₂ , BaBr ₂ , or BaI ₂ . The hydride-based solid electrolyte is LiBH ₄ , LiAlH ₄ , Li ₃ AlH ₆ , LiBH (Et) ₃ , LiBH (s-Bu) ₃ , LiNH ₂ , Li ₂ NH, Li [OC (CH ₃ ) ₃ ] _{3 AlH, Li (OCH 3) 3} AlH, and all-solid-state cell according to any one of claims 1 to 10 which is _{Li (OC 2 H 5) 3} H. All the said 1st-3rd solid electrolytes are the same lithium ion conductive materials, The all-solid-state battery of any one of Claims 8-11 which cites Claims 5-7 . The all-solid-state battery according to claim 1, wherein the hydride-based solid electrolyte includes LiBH ₄ .