JP7284666B2 - All-solid battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an all-solid-state battery with high capacity and excellent output characteristics.

In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers, and the commercialization of electric vehicles, there is a growing need for secondary batteries that are compact, lightweight, and have high capacity and high energy density. It has become to.

At present, in lithium secondary batteries, especially lithium ion secondary batteries, which can meet this demand, lithium-containing composite oxides such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ) are used as positive electrode active materials. Graphite or the like is used as a negative electrode active material, and an organic electrolytic solution containing an organic solvent and a lithium salt is used as a non-aqueous electrolyte.

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

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

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

Various improvements have also been attempted in all-solid-state batteries. For example, Patent Document 1 proposes that a solid electrolyte composition for forming a positive electrode, a negative electrode, and a solid electrolyte layer contains a binder having a specific structure and an antioxidant. According to Patent Document 1, by adopting the above configuration, it is possible to configure an all-solid-state battery with excellent stability of battery voltage over time. We are verifying its effectiveness.

In addition, Patent Document 2 describes a solid electrolyte for lithium ion batteries that can suppress the generation of hydrogen sulfide when exposed to the atmosphere and can maintain high conductivity even when left in dry air. A sulfide-based solid electrolyte with an argurodite-type crystal structure has been proposed

JP 2018-88306 A WO2016/104702

Currently, the fields of application of all-solid-state batteries are rapidly expanding, and it is possible that they will be applied to applications that require high-current discharge, for example. is required.

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 a high capacity and excellent output characteristics.

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 contains a positive electrode active material, a solid electrolyte, and a conductive aid. A molded body of a positive electrode mixture, wherein the positive electrode mixture contains, as the positive electrode active material, a lithium-nickel-cobalt-manganese composite oxide represented by the following general composition formula (1), and as the solid electrolyte, A negative electrode mixture containing a sulfide-based solid electrolyte, the content of the positive electrode active material in the positive electrode mixture being 60 to 75% by mass, and the negative electrode containing a negative electrode active material, a solid electrolyte, and a conductive aid. The negative electrode mixture contains lithium titanium oxide as the negative electrode active material and a sulfide-based solid electrolyte as the solid electrolyte, and the negative electrode active material in the negative electrode mixture The content is 40 to 60% by mass, and the solid electrolyte layer is characterized by containing a sulfide-based solid electrolyte.

Li1 _+xM1O2 ⁽ ₁ )

In the general composition formula (1), -0.3 ≤ x ≤ 0.3, M ¹ is a group of three or more elements containing at least Ni, Co and Mn, and each element constituting M ¹ 0.3≤a≤0.5, 0.2≤b≤0.4, 0.2 where the proportions (mol%) of Ni, Co and Mn are a, b and c, respectively. ≦c≦0.4.

ADVANTAGE OF THE INVENTION According to this invention, the all-solid-state battery with high capacity|capacitance and excellent in output characteristics can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which represents typically an example of the all-solid-state battery of this invention.

The all-solid-state battery of the present invention includes a positive electrode having a positive electrode mixture molded body containing a positive electrode active material, a solid electrolyte, and a conductive aid, and a negative electrode mixture containing a negative electrode active material, a solid electrolyte, and a conductive aid. and a solid electrolyte layer interposed between the positive electrode and the negative electrode.

In the all-solid-state battery of the present invention, the lithium-nickel-cobalt-manganese composite oxide represented by the general composition formula (1) is used as the positive electrode active material, and the content of the positive electrode active material in the positive electrode mixture is a specific value, using lithium titanium oxide as a negative electrode active material, setting the content of the negative electrode active material in the negative electrode mixture to a specific value, and further setting the positive electrode mixture, the negative electrode mixture and the solid electrolyte in the solid electrolyte layer As, a sulfide-based solid electrolyte is used. In the present invention, by adopting these matters, in addition to increasing the capacity during light load discharge, the capacity during heavy load discharge is also increased, making it possible to improve the output characteristics.

(positive electrode)
The positive electrode of the all-solid-state battery has a molded body of a positive electrode mixture containing a positive electrode active material, a solid electrolyte, a conductive aid, and the like. A positive electrode having a structure formed by integrating with and the like can be mentioned.

The lithium-nickel-cobalt-manganese composite oxide represented by the general compositional formula (1) is used as the positive electrode active material.

In the lithium-nickel-cobalt-manganese composite oxide represented by the general compositional formula (1), Ni and Co are components that contribute to improving the capacity of the lithium-nickel-cobalt-manganese composite oxide.

In the lithium-nickel-cobalt-manganese composite oxide represented by the general compositional formula (1), Mn is a component that enhances the thermal stability of the lithium-nickel-cobalt-manganese composite oxide. Furthermore, since the lithium-nickel-cobalt-manganese composite oxide contains Co together with Mn, Co acts to suppress variation in the Mn valence associated with Li doping and dedoping during charging and discharging of the battery. Therefore, the average valence of Mn can be stabilized at a value near tetravalence, and the reversibility of charging and discharging can be further enhanced. Therefore, by using such a lithium-nickel-cobalt-manganese composite oxide, it is possible to construct a battery with better charge-discharge cycle characteristics.

In the lithium-nickel-cobalt-manganese composite oxide represented by the general composition formula (1), the proportions (mol%) of Ni, Co and Mn among the elements constituting ^M1 are a, b and c, respectively. 0.3≦a≦0.5, 0.2≦b≦0.4, and 0.2≦c≦0.4. When the proportions of Ni, Co, and Mn in the element group ^M1 are within the ranges described above, the effects of Ni, Co, and Mn are effectively exhibited, and the output characteristics of the all-solid-state battery are improved. .

In the lithium-nickel-cobalt-manganese composite oxide represented by the general composition formula (1), the element group ^M1 may be composed only of Ni, Co and Mn. , Zr, Nb, Mo, W, Al, Si, Ga, Ge and Sn. However, the total proportion d of Mg, Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge and Sn is 5 mol% or less when the total number of elements in the element group ^M1 is 100 mol%. preferably 1 mol % or less. Elements other than Ni, Co, and Mn in the element group ^M1 may be uniformly distributed in the lithium-nickel-cobalt-manganese composite oxide, or may be segregated on the particle surface or the like.

The lithium-nickel-cobalt-manganese composite oxide having the above composition has a high true density of 4.55 to 4.95 g/cm ³ and is a material having a high volumetric energy density. The true density of the lithium-nickel-cobalt-manganese composite oxide containing Mn within a certain range varies greatly depending on its composition. , for example, is considered to be a large value close to the true density of LiCoO ₂ . In addition, the capacity per mass of the lithium-nickel-cobalt-manganese composite oxide can be increased, and the material can be made excellent in reversibility.

The lithium-nickel-cobalt-manganese composite oxide has a high true density particularly when the composition is close to the stoichiometric ratio. ≦0.3 is preferable, and by adjusting the value of x in this manner, the true density and reversibility can be enhanced. x is more preferably −0.05 or more and 0.05 or less, and in this case, the true density of the lithium-nickel-cobalt-manganese composite oxide is set to a higher value of 4.6 g/cm ³ or more. can be done.

The lithium-nickel-cobalt-manganese composite oxide represented by the general composition formula (1) includes Li-containing compounds (lithium hydroxide, etc.), Ni-containing compounds (nickel sulfate, etc.), Co-containing compounds (cobalt sulfate, etc.), and Mn-containing compounds. It can be produced by mixing a compound (manganese sulfate, etc.) and a compound (oxide, hydroxide, sulfate, etc.) containing other elements included in the element group ^M1 , followed by firing. Further, in order to synthesize a lithium-nickel-cobalt-manganese composite oxide with higher purity, a composite compound (hydroxide, oxide, etc.) containing a plurality of elements included in the element group ^M1 is mixed with a Li-containing compound. , preferably calcined.

The firing conditions may be, for example, 800 to 1050° C. for 1 to 24 hours, but preheating is performed by heating to a temperature lower than the firing temperature (eg, 250 to 850° C.) and maintaining at that temperature. and then the temperature is raised to the firing temperature to allow the reaction to proceed. The preheating time is not particularly limited, but it is usually about 0.5 to 30 hours. The atmosphere during firing may be an atmosphere containing oxygen (that is, the air), a mixed atmosphere of an inert gas (argon, helium, nitrogen, etc.) and oxygen gas, an oxygen gas atmosphere, or the like. The initial oxygen concentration (by volume) is preferably 15% or more, more preferably 18% or more.

For the positive electrode active material, only the lithium-nickel-cobalt-manganese composite oxide represented by the general compositional formula (1) may be used, and the lithium-nickel-cobalt-manganese composite oxide represented by the general compositional formula (1) and other positive electrode active materials may be used in combination. Other positive electrode active materials that can be used in combination with the lithium-nickel-cobalt-manganese composite oxide represented by the general compositional formula (1) include various positive electrode active materials used as positive electrode active materials for lithium ion secondary batteries [ lithium-containing composite oxides other than the lithium-nickel-cobalt-manganese composite oxide represented by the general composition formula (1)]. However, the proportion of the positive electrode active material other than the lithium-nickel-cobalt-manganese composite oxide represented by the general compositional formula (1) in the total amount of the positive electrode active material is preferably 30% by mass or less.

The content of the positive electrode active material in the positive electrode mixture is 60% by mass or more, preferably 65% by mass or more, from the viewpoint of enhancing the output characteristics of the all-solid-state battery and further increasing the capacity. It is 75% by mass or less, preferably 70% by mass.

A sulfide-based solid electrolyte is used for the solid electrolyte of the positive electrode. Sulfide-based solid electrolytes have particularly excellent ion conductivity among solid electrolytes that can be used in all-solid-state batteries. improves.

Examples of sulfide-based solid electrolytes include Li ₂ SP ₂ S ₅ , Li ₂ S-SiS ₂ , Li ₂ SP ₂ S ₅ -GeS ₂ , Li ₂ S-B ₂ S ₃ -based glasses, and the like. In addition to these, Li ₁₀ GeP ₂ S ₁₂ (LGPS type), which has recently attracted attention as having high lithium ion conductivity, and a sulfide-based solid electrolyte having an aldirodite type crystal structure can also be used.

Examples of sulfide-based solid electrolytes having an aldirodite-type crystal structure include materials represented by the following general compositional formula (2).

Li _7-p+q PS _6-p Cl _p+q (2)

In the general composition formula (2), 0.05≦q≦0.9 and −3.0p+1.8≦q≦−3.0p+5.7.

The sulfide-based solid electrolyte referred to in this specification may consist of a single phase of a crystal phase of an aldirodite-type crystal structure (cubic aldirodite-type crystal structure). and a crystalline phase represented by LiCl. The mixed phase contains only the crystal phase of the aldirodite type crystal structure and the crystal phase represented by LiCl, or the crystal phase of the aldirodite type crystal structure and the crystal phase represented by LiCl, and other crystal phases. including if and when

In the case of a sulfide-based solid electrolyte composed of a mixed phase containing a crystal phase of an aldirodite-type crystal structure and a crystal phase represented by LiCl, in the general composition formula (2), 0.05 ≤ p ≤ 0.4 , and −3.0p+3.9≦q≦−3.0p+5.7.

Details of the sulfide-based solid electrolyte having an aldirodite-type crystal structure represented by the general composition formula (2) are disclosed in Patent Document 2, and can be produced by the method described in Patent Document 2.

For the sulfide-based solid electrolyte, one or more of the above-exemplified ones can be used. Since the output characteristics of the battery are further improved, It is more preferable to use a sulfide-based solid electrolyte having an aldirodite-type crystal structure.

Although only the sulfide-based solid electrolyte may be used for the positive electrode, other solid electrolytes can also be used together with the sulfide-based solid electrolyte. Solid electrolytes that can be used in combination with sulfide-based solid electrolytes include hydride-based solid electrolytes and oxide-based solid electrolytes.

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

Examples of oxide-based solid electrolytes include Li ₇ La ₃ Zr ₂ O ₁₂ , LiTi(PO ₄ ) ₃ , LiGe(PO ₄ ) ₃ and LiLaTiO ₃ .

However, the proportion of solid electrolytes other than sulfide-based solid electrolytes in the total amount of solid electrolytes used in the positive electrode mixture is preferably 30% by mass or less.

The content of the solid electrolyte in the positive electrode mixture is 25 parts by mass or more when the content of the positive electrode active material is 100 parts by mass, from the viewpoint of further enhancing the output characteristics of the all-solid-state battery and further increasing the capacity. is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and preferably 65 parts by mass or less, more preferably 60 parts by mass or less , 50 parts by mass or less.

A carbon material such as carbon black can be used as the conductive aid for the positive electrode.

The content of the conductive agent in the positive electrode mixture is 2.5 when the content of the positive electrode active material is 100 parts by mass, from the viewpoint of further enhancing the output characteristics of the all-solid-state battery and further increasing the capacity. It is preferably at least 3.0 parts by mass, more preferably at least 3.0 parts by mass, even more preferably at least 4.0 parts by mass, and preferably at most 6.5 parts by mass. It is more preferably 0.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

The positive electrode mixture may or may not contain a resin binder. Examples of the resin binder include fluorine resin such as polyvinylidene fluoride (PVDF). However, since the resin binder acts as a resistance component in the positive electrode mixture, the amount thereof should be as small as possible. Therefore, it is preferable that the positive electrode mixture does not contain a resin binder, or if it contains a resin binder, the content thereof 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 more preferably 0% by mass (that is, does not contain the resin binder).

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

The molded positive electrode mixture is prepared by, for example, mixing a positive electrode active material, a solid electrolyte, a conductive aid, and a binder added depending on the non-vaginal use, and press-molding the positive electrode mixture. It can be formed by compression.

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

The thickness of the positive electrode mixture molded body (in the case of a positive electrode having a current collector, the thickness of the positive electrode mixture molded body per one side of the current collector; hereinafter the same) is determined from the viewpoint of increasing the capacity of the battery. , 200 μm or more. Generally, the output characteristics of a battery tend to be improved by making the positive electrode and the negative electrode thinner, but according to the present invention, the output characteristics can be improved even when the molded body of the positive electrode mixture is as thick as 200 μm or more. It is possible. Therefore, in the present invention, the effect becomes more remarkable when the thickness of the molded body of the positive electrode mixture is, for example, 200 μm or more. In addition, the thickness of the positive electrode mixture molded body is usually 2000 μm or less.

(negative electrode)
The negative electrode of the all-solid-state battery has a molded body of a negative electrode mixture containing lithium titanium oxide as a negative electrode active material, a solid electrolyte, a conductive aid, and the like. Examples include a negative electrode having a structure in which a molded body and a current collector are integrated.

Examples of lithium titanium oxides include those represented by the following general compositional formula (3).

Li[Li _1/3-a M ² _a Ti _5/3-b M ³ _b ]O ₄ (3)

In the general composition formula (3), ^M2 is at least one element selected from the group consisting of Na, Mg, K, Ca, Sr and Ba, and ^M3 is Al, V, Cr, Fe, At least one element selected from the group consisting of Co, Ni, Zn, Ym, Zr, Nb, Mo, Ta and W, where 0≤a<1/3 and 0≤b<5/3.

That is, in the lithium titanium oxide represented by the general composition formula (3), part of the Li sites may be substituted with the element ^M2 . However, in the general compositional formula (3), a representing the ratio of the element ^M2 is preferably less than 1/3. In the lithium titanium oxide represented by the general composition formula (3), Li may not be substituted with the element ^M2 , so a representing the ratio of the element ^M2 may be 0.

Further, in the lithium titanium oxide represented by the general composition formula (3), the element ^M3 is a component for increasing the electronic conductivity of the lithium titanium oxide, and b representing the ratio of the element ^M3 is 0 When ≦b<5/3, the effect of improving the electron conductivity can be satisfactorily ensured.

For the negative electrode active material, a negative electrode active material other than the lithium titanium oxide used in lithium ion secondary batteries and the like can be used together with the lithium titanium oxide. However, the proportion of the negative electrode active material other than the lithium titanium oxide in the total amount of the negative electrode active material is preferably 30% by mass or less.

The content of the negative electrode active material in the negative electrode mixture is 40% by mass or more, preferably 45% by mass or more, from the viewpoint of improving the output characteristics of the all-solid-state battery and further increasing the capacity. It is 60% by mass or less, preferably 55% by mass.

A sulfide-based solid electrolyte is used for the solid electrolyte of the negative electrode. Sulfide-based solid electrolytes are particularly excellent in ion conductivity among solid electrolytes that can be used in all-solid-state batteries. Battery output characteristics are improved.

For the sulfide-based solid electrolyte, one or two or more of the same solid electrolytes as exemplified above as the solid electrolyte that can be used for the positive electrode can be used. Among the sulfide-based solid electrolytes exemplified above, it is more preferable to use a sulfide-based solid electrolyte having an aldirodite-type crystal structure represented by the general composition formula (2) because the output characteristics of the battery are further improved. preferable.

Although only a sulfide-based solid electrolyte may be used for the negative electrode, other solid electrolytes can also be used together with the sulfide-based solid electrolyte. Solid electrolytes that can be used in combination with sulfide-based solid electrolytes include the same hydride-based solid electrolytes and oxide-based solid electrolytes as those previously exemplified as those that can be used for the positive electrode.

However, the proportion of solid electrolytes other than sulfide-based solid electrolytes in the total amount of solid electrolytes used in the negative electrode mixture is preferably 30% by mass or less.

The content of the solid electrolyte in the negative electrode mixture is 50 parts by mass or more when the content of the negative electrode active material is 100 parts by mass, from the viewpoint of further enhancing the output characteristics of the all-solid-state battery and further increasing the capacity. is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and preferably 130 parts by mass or less, more preferably 120 parts by mass or less , 110 parts by mass or less.

A carbon material such as carbon black can be used as the conductive aid for the negative electrode.

The content of the conductive aid in the negative electrode mixture is 10 parts by mass when the content of the negative electrode active material is 100 parts by mass, from the viewpoint of further enhancing the output characteristics of the all-solid-state battery and further increasing the capacity. It is preferably 12 parts by mass or more, more preferably 15 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less. It is preferably 22 parts by mass or less, and more preferably 22 parts by mass or less.

The negative electrode mixture may or may not contain a resin binder. Examples of the resin binder include fluorine resin such as polyvinylidene fluoride (PVDF). However, since the resin binder acts as a resistance component even in the negative electrode mixture, its amount should be as small as possible. Therefore, similarly to the positive electrode mixture, the negative electrode mixture preferably does not contain a resin binder, or if it does contain the binder, the content is preferably 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 more preferably 0% by mass (that is, does not contain the resin binder).

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

The molded body of the negative electrode mixture is prepared by, for example, mixing the negative electrode active material, the solid electrolyte, the conductive aid, and the binder added according to the non-vaginal use, and press molding the negative electrode mixture. It can be formed by compression.

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

The thickness of the negative electrode mixture molded body (in the case of a negative electrode having a current collector, the thickness of the positive electrode mixture molded body per one side of the current collector; hereinafter the same) is determined from the viewpoint of increasing the capacity of the battery. , 200 μm or more. Generally, the output characteristics of a battery tend to be improved by making the positive and negative electrodes thinner, but according to the present invention, the output characteristics can be improved even when the molded body of the negative electrode mixture is as thick as 200 μm or more. It is possible. Therefore, in the present invention, the effect becomes more remarkable when the thickness of the molded body of the negative electrode mixture is, for example, 200 μm or more. In the present invention, the effect is particularly remarkable when the thickness of the molded positive electrode mixture is 200 μm or more and the thickness of the molded negative electrode mixture is 200 μm or more. In addition, the thickness of the molded body of the negative electrode mixture is usually 3000 μm or less.

(Solid electrolyte layer)
A sulfide-based solid electrolyte is also used as the solid electrolyte in the solid electrolyte layer of the all-solid-state battery. Sulfide-based solid electrolytes are particularly excellent in ion conductivity among solid electrolytes that can be used in all-solid-state batteries. Battery output characteristics are improved.

For the sulfide-based solid electrolyte, one or two or more of the same solid electrolytes as exemplified above as the solid electrolyte that can be used for the positive electrode can be used. Among the sulfide-based solid electrolytes exemplified above, it is more preferable to use a sulfide-based solid electrolyte having an aldirodite-type crystal structure represented by the general composition formula (2) because the output characteristics of the battery are further improved. preferable.

Although only a sulfide-based solid electrolyte may be used for the solid electrolyte layer, other solid electrolytes can also be used together with the sulfide-based solid electrolyte. Solid electrolytes that can be used in combination with sulfide-based solid electrolytes include the same hydride-based solid electrolytes and oxide-based solid electrolytes as those previously exemplified as those that can be used for the positive electrode.

However, the proportion of solid electrolytes other than sulfide-based solid electrolytes in the total amount of solid electrolytes used in the solid electrolyte layer is preferably 30% by mass or less.

The solid electrolyte layer is formed by applying a composition for forming a solid electrolyte layer prepared by dispersing the solid electrolyte in a solvent onto the base material, the positive electrode, and the negative electrode, drying it, and performing pressure molding such as press treatment as necessary. It can be formed by doing.

As for the solvent used in the solid electrolyte layer-forming 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 are represented by hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene, since chemical reactions occur with minute amounts of moisture. Preference is given to using non-polar aprotic solvents. In particular, it is more preferable to use a super-dehydrated solvent with a water content of 0.001% by mass (10 ppm) or less. In addition, fluorine-based solvents such as "Vertrel (registered trademark)" manufactured by Mitsui-DuPont Fluorochemicals, "Zeorolla (registered trademark)" manufactured by Nippon Zeon, "Novec (registered trademark)" manufactured by Sumitomo 3M, and , dichloromethane, and diethyl ether can also be used.

The thickness of the solid electrolyte layer is preferably 100-300 μm.

(electrode body)
The positive electrode and the negative electrode can be used in a battery in the form of a laminated electrode body in which a solid electrolyte layer is interposed, or a wound electrode body in which the laminated electrode body is further wound.

When forming the electrode body, it is preferable from the viewpoint of increasing the mechanical strength of the electrode body that the positive electrode, the negative electrode, and the solid electrolyte layer are laminated and pressure-molded.

(Battery form)
FIG. 1 shows a cross-sectional view schematically showing an example of the all-solid-state battery of the present invention. In the battery 1 shown in FIG. 1, a positive electrode 10, a negative electrode 20, and a positive electrode 10 and a negative electrode 20 are placed in an outer case formed of an outer can 40, a sealing can 50, and a resin gasket 60 interposed therebetween. A solid electrolyte layer 30 intervening between is encapsulated.

The sealing can 50 is fitted to the opening of the outer can 40 via a gasket 60, and the open end of the outer can 40 is tightened inward, whereby the gasket 60 abuts the sealing can 50. , the opening of the exterior can 40 is sealed to form a sealed structure inside the device.

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

The form of the all-solid-state battery is one having an outer body composed of an outer can, a sealing can, and a gasket, as shown in FIG. Not limited, for example, those having an outer body made of a resin film or a metal-resin laminated film, or a metallic bottomed tubular (cylindrical or rectangular) outer can and its opening sealed It may have an exterior body having a sealing structure for stopping.

The all-solid-state battery of the present invention can be applied to the same uses as conventionally known secondary batteries, but since it has a solid electrolyte instead of an organic electrolyte, it has excellent heat resistance and can It can be preferably used for applications that are exposed to

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

Example 1
<Preparation of positive electrode>
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (positive electrode active material) having an average particle size of 4 μm, a sulfide solid electrolyte (Li ₆ PS ₅ Cl), and a carbon nanotube (Showa Denko Co., Ltd.) as a conductive agent "VGCF" (trade name)] manufactured by the company were mixed at a mass ratio of 65:32:3 and well kneaded to prepare a positive electrode mixture. Next, 80 mg of the positive electrode mixture was placed in a powder molding die having a diameter of 6 mm, and pressure molding was performed using a pressing machine to prepare a positive electrode composed of a positive electrode mixture compact.

<Formation of Solid Electrolyte Layer>
Next, 15 mg of the sulfide solid electrolyte is placed on the positive electrode mixture compact in the powder molding mold, and pressure-molding is performed using a press to form the positive electrode mixture compact. A solid electrolyte layer was formed on the substrate.

<Production of negative electrode>
Lithium titanate (Li ₄ Ti ₅ O ₁₂ , negative electrode active material) having an average particle size of 7 μm, the sulfide solid electrolyte, and carbon nanotubes (“VGCF” (trade name) manufactured by Showa Denko Co., Ltd.), which is a conductive agent, were weighed. They were mixed at a ratio of 50:41:9 and well kneaded to prepare a negative electrode mixture. Next, 150 mg of the negative electrode mixture is placed on the solid electrolyte layer in the powder molding mold, pressure-molded using a press, and a molded negative electrode mixture is placed on the solid electrolyte layer. By forming a negative electrode made of this, a laminate in which the positive electrode, the solid electrolyte layer and the negative electrode are laminated was produced. At this time, the thickness of the laminate was 3300 μm, the thickness of the positive electrode mixture molded body was 850 μm, the thickness of the negative electrode mixture molded body was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

A copper foam substrate [Celmet (trade name) made by Sumitomo Electric Industries, Ltd., thickness: 1 mm, porosity: 97%] was punched into a size of 6 mmφ and placed on the inner bottom surface of a stainless steel sealing can. Then, the laminate of the positive electrode/solid electrolyte layer/negative electrode is stacked thereon so that the negative electrode faces the substrate side, and furthermore, an aluminum foaming base manufactured by Sumitomo Electric Industries, Ltd. is punched to the same size as the above. A material [Celmet (trade name) made of aluminum, thickness: 1 mm, porosity: 97%] is placed on the positive electrode of the laminate, and then a stainless steel outer can is placed and sealed. , a flat all-solid-state battery was fabricated.

Example 2
Positive electrode/solid electrolyte layer/negative electrode was prepared in the same manner as in Example 1, except that the ratio of the positive electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the positive electrode mixture was changed to 75:23:2 by mass. A flat all-solid-state battery was produced in the same manner as in Example 1, except that a laminate was produced and this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Example 3
Positive electrode/solid electrolyte layer/negative electrode was prepared in the same manner as in Example 1, except that the ratio of the negative electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the negative electrode mixture was changed to 60:33:72 by mass. A flat all-solid-state battery was produced in the same manner as in Example 1, except that a laminate was produced and this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Example 4
Positive electrode/solid electrolyte layer/negative electrode was prepared in the same manner as in Example 1, except that the ratio of the negative electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the negative electrode mixture was changed to 40:49:11 by mass. A flat all-solid-state battery was produced in the same manner as in Example 1, except that a laminate was produced and this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Example 5
Positive electrode/solid electrolyte was prepared in the same manner as in Example 1, except that the ratio of the positive electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the positive electrode mixture was changed to 60:36.5:3.5 by mass. A layer/negative laminate was produced, and a flat all-solid-state battery was produced in the same manner as in Example 1, except that this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Comparative example 1
Positive electrode/solid electrolyte was prepared in the same manner as in Example 1, except that the ratio of the positive electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the positive electrode mixture was changed to 80:18.5:1.5 by mass. A layer/negative laminate was produced, and a flat all-solid-state battery was produced in the same manner as in Example 1, except that this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Comparative example 2
A positive electrode/solid electrolyte layer/negative electrode was prepared in the same manner as in Example 1, except that the ratio of the negative electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the negative electrode mixture was changed to 65:30:5 by mass. A flat all-solid-state battery was produced in the same manner as in Example 1, except that a laminate was produced and this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Comparative example 3
Positive electrode/solid electrolyte layer/negative electrode was prepared in the same manner as in Example 1, except that the ratio of the positive electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the positive electrode mixture was changed to 55:41:4 by mass. A flat all-solid-state battery was produced in the same manner as in Example 1, except that a laminate was produced and this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Comparative example 4
A positive electrode/solid electrolyte layer/negative electrode was prepared in the same manner as in Example 1, except that the ratio of the negative electrode active material, the sulfide-based solid electrolyte, and the conductive aid in the negative electrode mixture was changed to 35:53:12 by mass. A flat all-solid-state battery was produced in the same manner as in Example 1, except that a laminate was produced and this laminate was used. In the laminate, the thickness of the laminate was 3300 μm, the thickness of the molded positive electrode mixture was 850 μm, the thickness of the molded negative electrode mixture was 2250 μm, and the thickness of the solid electrolyte layer was 200 μm.

Initial capacity measurement and output characteristic evaluation were performed by the following methods for each of the flat all-solid-state batteries of Examples and Comparative Examples.

<Initial capacity measurement>
The flat all-solid-state batteries of Examples and Comparative Examples were charged at a constant current value of 0.02 C until the voltage reached 2.8 V, and then charged at a constant voltage until the current value reached 0.002 C. After that, the battery was discharged at a current value of 0.02 C until the voltage reached 1 V, and the discharge capacity (initial capacity) at that time was measured.

<Evaluation of output characteristics>
Each of the flat all-solid-state batteries of Examples and Comparative Examples was subjected to constant-current charging and constant-voltage charging under the same conditions as in the initial capacity measurement, and then discharged at a current value of 0.2 C until the voltage reached 1 V. , the discharge capacity (0.2C discharge capacity) at this time was measured.

Then, for each battery, the value obtained by dividing the 0.2C discharge capacity by the initial capacity was expressed as a percentage to obtain the capacity retention rate, and the output characteristics were evaluated.

Table 1 shows the compositions of the positive electrode mixture and the negative electrode mixture in each of the flat all-solid-state batteries of Examples and Comparative Examples, and Table 2 shows the above evaluation results. Among the compositions of the positive electrode mixture in Table 1, the content of the “positive electrode active material” is the content (% by mass) in 100% by mass of the positive electrode mixture, and the content of the “solid electrolyte” and the “conduction aid” is It is the amount (parts by mass) relative to 100 parts by mass of the positive electrode active material, and the content of the “negative electrode active material” in the composition of the negative electrode mixture is the content (% by mass) in 100% by mass of the negative electrode mixture, and the “solid The contents of "electrolyte" and "conductive aid" are the amounts (parts by mass) per 100 parts by mass of the negative electrode active material.

As shown in Tables 1 and 2, a lithium-nickel-cobalt-manganese composite oxide (positive electrode active material) having an appropriate composition and a sulfide-based solid electrolyte were used, and the content of the positive electrode active material in the positive electrode mixture was adjusted to an appropriate value. of Examples 1 to 5 using a positive electrode and a negative electrode using a lithium titanium oxide (negative electrode active material) and a sulfide-based solid electrolyte and setting the content of the negative electrode active material in the negative electrode mixture to an appropriate value. The flat-shaped all-solid-state battery had a large initial capacity and a high capacity, and also had a large capacity retention rate when the output characteristics were evaluated, and had excellent output characteristics.

On the other hand, the battery of Comparative Example 1 using the positive electrode in which the content of the positive electrode active material in the positive electrode mixture is too large, and the battery of Comparative Example 2 using the negative electrode in which the content of the negative electrode active material in the negative electrode mixture is too large. had a small capacity retention rate when evaluating output characteristics, and was inferior in output characteristics. In addition, the battery of Comparative Example 3 using the positive electrode in which the content of the positive electrode active material in the positive electrode mixture was too small and the battery of Comparative Example 4 using the negative electrode in which the content of the negative electrode active material in the negative electrode mixture was too small were The initial capacity was small.

1 All Solid Battery 10 Positive Electrode 20 Negative Electrode 30 Solid Electrolyte Layer 40 Outer Can 50 Sealing Can 60 Gasket

Claims (4)

An all-solid battery having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode,
The positive electrode has a molded body of a positive electrode mixture containing a positive electrode active material, a solid electrolyte and a conductive aid,
The positive electrode mixture has the following general composition formula (1) as the positive electrode active material
Li1 _+xM1O2 ⁽ ₁ )
[In the general composition formula (1), -0.3 ≤ x ≤ 0.3, M ¹ is a group of three or more elements including at least Ni, Co and Mn, and each of M ¹ is 0.3≦a≦0.5, 0.2≦b≦0.4, 0.3≦a≦0.5, 0.2≦b≦0.4, where the ratio (mol %) of Ni, Co, and Mn in the elements is a, b, and c, respectively. 2 ≤ c ≤ 0.4] and a sulfide-based solid electrolyte as the solid electrolyte,
The content of the positive electrode active material in the positive electrode mixture is 60 to 75% by mass,
The negative electrode has a molded body of a negative electrode mixture containing a negative electrode active material, a solid electrolyte and a conductive aid,
The negative electrode mixture contains lithium titanium oxide as the negative electrode active material and a sulfide-based solid electrolyte as the solid electrolyte,
The content of the negative electrode active material in the negative electrode mixture is 40 to 60% by mass,
When the content of the negative electrode active material in the negative electrode mixture is 100 parts by mass, the content of the solid electrolyte is 50 to 130 parts by mass, and the content of the conductive aid is 10 to 30 parts by mass. can be,
An all-solid battery, wherein the solid electrolyte layer contains a sulfide-based solid electrolyte. When the content of the positive electrode active material in the positive electrode mixture is 100 parts by mass, the content of the solid electrolyte is 25 to 65 parts by mass, and the content of the conductive aid is 2.5 to 6.0 parts by mass. The all-solid-state battery according to claim 1, which is 5 parts by mass. The positive electrode mixture, the negative electrode mixture and the solid electrolyte layer have the following general composition formula (2)
Li _7-p+q PS _6-p Cl _p+q (2)
[0.05≤q≤0.9 and -3.0p+1.8≤q≤-3.0p+5.7 in the general composition formula (2)]
3. The all-solid-state battery according to claim 1, containing a sulfide-based solid electrolyte having an aldirodite-type crystal structure represented by: As the lithium titanium oxide, the following general composition formula (3)
Li[Li _1/3-a M ² _a Ti _5/3-b M ³ _b ]O ₄ (3)
[In the general composition formula (3), ^M2 is at least one element selected from the group consisting of Na, Mg, K, Ca, Sr and Ba, and ^M3 is Al, V, Cr, Fe , Co, Ni, Zn, Ym, Zr, Nb, Mo, Ta and W, and 0≤a<1/3 and 0≤b<5/3 ]
The all-solid-state battery according to any one of claims 1 to 3 , containing the compound represented by

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