JP2021150152A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery that is composed using a garnet type solid electrolyte, exhibits good lithium-ion conductivity, and can improve battery performance and productivity.SOLUTION: An all-solid battery 1 in which a pair of electrode layers 10 are arranged across a separator layer 11 having lithium-ion conductivity has, as a basic skeleton, a solid electrolyte body 2 having garnet type solid electrolyte particles 20 as basic constituent particles. The solid electrolyte body 2 has a particle aggregate 2A to serve as a separator layer 11 and a porous body 2B to serve as a skeleton for at least one of the pair of electrode layers 10. The average particle diameter Pd1 of the particle aggregate 2A and the average particle diameter Pd2 of the porous body 2B have a relation of Pd2>Pd1.SELECTED DRAWING: Figure 1

Description

The present invention relates to an all-solid-state battery using an ionic conductive solid electrolyte.

The all-solid-state battery has a laminated structure in which a positive electrode layer and a negative electrode layer are integrated with a separator layer interposed therebetween. The separator layer partitions the positive electrode layer and the negative electrode layer so that they can conduct ions, and is configured by using, for example, a solid electrolyte composed of a composite oxide or a phosphoric acid compound having lithium ion conductivity. In such an all-solid-state battery, since the positive electrode layer or the negative electrode layer and the separator layer are bonded to each other, the resistance tends to increase at the laminated interface of each layer. Therefore, in order to reduce the interfacial resistance between the layers, there is a configuration in which the positive electrode layer and the negative electrode layer contain a solid electrolyte.

Patent Document 1 discloses a solid electrolyte structure in which a plate-shaped dense body made of ceramics containing a solid electrolyte and a porous layer made of ceramics containing the same or different solid electrolytes are fired and integrated. There is. For the solid electrolyte structure, for example, a plate-shaped first molded body is fired to form a dense body, and then one or both surfaces are coated with a ceramic material to be a porous layer to form a second molded body. The above-mentioned material is additionally fired at a temperature lower than the firing temperature (for example, 1150 ° C.) of the dense body (for example, 1100 ° C.).

In Patent Document 1, dense body and the porous layer, Li perovskite titanium oxide containing (lithium) and Ti (titanium) _{(e.g., Li x La y TiO 3;} 0 <x, y <1) and, NASICON It is composed of a solid electrolyte composed of a phosphoric acid compound of the type (for example, Li _{1 + x} Al _x (Ti, Ge) _2-x (PO ₄ ) O ₃ ; 0 <x <1). The porous layer integrated with the dense body by firing is further filled with an active material precursor to be a positive electrode or a negative electrode, and then the main firing is performed (for example, 800 ° C.) to form an electrode. In this way, the firing temperature of the additional firing is raised to form a good connecting portion (necking) between the constituent particles of the porous layer, and a good necking is also formed at the connecting interface between the porous layer and the dense body. It is said that it will be possible.

International Publication No. 2008/059987

In recent years, as an oxide-based solid electrolyte, a lithium ion conductive solid electrolyte having a garnet-type crystal structure has attracted attention. The garnet-type solid electrolyte has, for example, a lithium lanthanum zirconium-based composite oxide (Li ₇ La ₃ Zr ₂ O ₁₂ ) containing La (lantern) and Zr (zirconium) as a basic composition, and exhibits good lithium ion conductivity. At the same time, it is electrochemically stable with respect to lithium metal, which is useful as a negative electrode material, and is therefore expected to be applied to all-solid-state batteries.

Therefore, even when a garnet-type solid electrolyte is used, the solid electrolyte structure as in Patent Document 1 is adopted, and at least one of the positive electrode layer and the negative electrode layer includes a solid electrolyte integrated with the separator layer. Is being considered. However, the solid electrolyte structure of Patent Document 1 is formed by firing a dense body as a separator layer and a porous body as an electrode at high temperatures in separate steps, and further performing main firing to form an electrode. As the number of processes increases, energy consumption increases and productivity decreases.

Therefore, when a garnet-type solid electrolyte is used, it is expected that productivity will be improved by, for example, low-temperature sintering at a temperature at which integral firing with the electrode active material is possible. However, when firing is performed at a low temperature, as in Patent Document 1, since the necking between the particles does not proceed due to the high temperature firing, the resistance at the interface where the particles contact each other becomes high, and the lithium ion conductivity becomes high. descend.

The present invention has been made in view of the above problems, and is an all-solid-state battery that is configured by using a garnet-type solid electrolyte, exhibits good lithium ion conductivity, and can improve battery performance and productivity. It is what we are trying to provide.

One aspect of the present invention is
An all-solid-state battery (1) in which a pair of electrode layers (10) are arranged with a separator layer (11) having lithium ion conductivity interposed therebetween.
It is equipped with a solid electrolyte body (2) whose basic constituent particles are garnet-type solid electrolyte particles (20) as a basic skeleton.
The solid electrolyte body is an integrally fired body containing a particle aggregate (2A) serving as the separator layer and a porous body (2B) serving as the skeleton of at least one of the pair of electrode layers. The average particle size Pd1 of the aggregate and the average particle size Pd2 of the porous body are in an all-solid-state battery having a relationship of Pd2> Pd1.

In the all-solid-state battery having the above configuration, the solid electrolyte body as the basic skeleton has a structure in which the particle aggregate serving as the separator layer and the porous body serving as the skeleton of the electrode layer are integrally fired. The solid electrolyte is densified by forming the particle aggregate with solid electrolyte particles having a smaller average particle size of Pd1, while the porous body is composed of solid electrolyte particles having a larger average particle size of Pd2. It suppresses the increase in resistance. That is, as the average particle size Pd2 increases, the number of particle interfaces forming the ion conduction path decreases and the interface resistance decreases, and the path length passing through the particles is shortened to reduce the internal resistance.

As described above, the ionic conductivity can be improved by using the solid electrolyte body in which the particle aggregates having different average particle sizes and the porous body are integrally fired as the basic skeleton. Therefore, the integral firing at a lower temperature becomes possible, and the energy consumption can be reduced. Further, since low-temperature firing is possible, energy consumption can be further reduced by, for example, firing one of the electrode layers containing the electrode active material integrally with the solid electrolyte. Therefore, it is possible to improve energy efficiency, reduce the number of processes, and improve productivity.

As described above, according to the above aspect, it is possible to provide an all-solid-state battery which is configured by using a garnet-type solid electrolyte, exhibits good lithium ion conductivity, and can improve battery performance and productivity. ..
The reference numerals in parentheses described in the scope of claims and the means for solving the problem indicate the correspondence with the specific means described in the embodiments described later, and limit the technical scope of the present invention. It's not a thing.

The schematic cross-sectional view which shows the basic structure of the all-solid-state battery in Embodiment 1. FIG. The cross-sectional view which shows the schematic structure of the all-solid-state battery in Embodiment 1. FIG. The figure which shows the structure of the porous body skeleton of the solid electrolyte body in Embodiment 1 in comparison with the conventional structure. FIG. 6 is a schematic diagram for explaining the relationship between the average particle size of the solid electrolyte particles constituting the porous skeleton of the solid electrolyte and the interfacial resistance in the first embodiment. FIG. 6 is a schematic diagram for explaining the relationship between the average particle size of the solid electrolyte particles constituting the porous skeleton of the solid electrolyte body and the internal resistance in the first embodiment. The schematic diagram for demonstrating the state of the grain growth of the solid electrolyte particle in the firing process of the conventional solid electrolyte body. FIG. 6 is a schematic configuration diagram showing a configuration of a main part of an all-solid-state battery in a modified example 1 of the first embodiment. FIG. 6 is a schematic configuration diagram showing a configuration of a main part of an all-solid-state battery in a modified example 2 of the first embodiment. FIG. 5 is a manufacturing process diagram for explaining a method for preparing solid electrolyte particles constituting an all-solid-state battery in the first embodiment. The manufacturing process drawing for demonstrating the manufacturing method of the all-solid-state battery in Embodiment 1. FIG. The manufacturing process diagram for demonstrating another example of the manufacturing method of the all-solid-state battery in Embodiment 1. FIG. FIG. 3 is a manufacturing process diagram for explaining a manufacturing method of an all-solid-state battery in the first modification of the first embodiment. FIG. 3 is a manufacturing process diagram for explaining a manufacturing method of an all-solid-state battery in the second modification of the first embodiment. FIG. 2 is an enlarged view of a main part for explaining the structure of the porous skeleton of the solid electrolyte body in the second embodiment. FIG. 6 is a schematic cross-sectional view showing a main configuration of an all-solid-state battery according to the third embodiment. The manufacturing process drawing for demonstrating the manufacturing method of the all-solid-state battery in Embodiments 2 and 3.

(Embodiment 1)
Hereinafter, the first embodiment relating to the all-solid-state battery will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the all-solid-state battery 1 is configured as an all-solid-state lithium-ion secondary battery, and is a pair of a separator layer 11 having lithium ion conductivity and arranged so as to sandwich the separator layer 11. The electrode layer 10 (positive electrode layer 12 and negative electrode layer 13) is provided. The all-solid-state battery 1 includes a solid electrolyte body 2 having garnet-type solid electrolyte particles 20 as basic constituent particles as a basic skeleton. The solid electrolyte body 2 is configured as an integrally fired body including a particle aggregate 2A serving as a separator layer 2 and a porous body 2B serving as a skeleton of at least one of the pair of electrode layers 10.

As shown in FIG. 1, in the solid electrolyte body 2, the particle aggregate 2A to be the separator layer 2 is composed of the solid electrolyte particles 20 having an average particle size of Pd1, and the porous body 2B to be the skeleton of at least one electrode layer 10 is , 20 solid electrolyte particles having an average particle size of Pd2. At this time, the solid electrolyte 2 is configured so that the average particle size Pd1 and the average particle size Pd2 have a relationship of Pd2> Pd1.

Preferably, the ratio Pd2 / Pd1 of the average particle size Pd2 of the porous body 2B to the average particle size Pd1 of the particle aggregate 2A is preferably 1.5 or more.
The average particle diameter Pd, Pd1, Pd2 in this embodiment, the average particle diameter _{Pd (D 50), Pd1 (} D 50), means Pd2 _{(D 50).} That is, in the particle size distribution curve of an arbitrary number (for example, 50) of solid electrolyte particles 20 randomly selected based on the image analysis (for example, SEM image) of the cross section of the integrally fired body, the ratio of the integrated number. The particle size at which is 50% is defined as the average particle size Pd. The average particle diameter _{Pd1 (D 50), Pd2 (} D 50) , respectively, for the solid electrolyte particles 20 constituting the particle aggregate 2A, the porous body 2B, the ratio of the accumulated number in the particle size distribution curve becomes 50% particle The diameter.

Preferably, as the solid electrolyte particles 20, particles containing a lithium lanthanum zirconium-based composite oxide can be used. Further, it is desirable that the average particle size Pd1 of the particle aggregate 2A is 10 μm or less. As a result, in the separator layer 11 that separates the pair of electrode layers 10, the voids between the particles become smaller and more compact, while the effect of suppressing the increase in resistance can be obtained in the porous body 2B in which the average particle size Pd2 becomes larger. ..

As shown in the right figure of FIG. 3, in the solid electrolyte body 2, the porous body 2B, which is at least one of the pair of electrode layers 10, is averaged larger than the average particle size Pd1 of the particle aggregate 2A, which is the separator layer 11. It is composed of solid electrolyte particles 20 having a particle size of Pd2. As a result, as shown in the left figure of FIG. 3, the particle interface in the ion conduction path formed by the solid electrolyte particles 20 is reduced as compared with the case where the porous body 2B and the particle aggregate 2A have the same average particle size Pd. , The resistance of the ion conduction path can be reduced to improve the battery performance. For the particle aggregate 2A, the separator layer 11 can be densified with a smaller average particle size Pd1.

As shown in FIG. 1, one of the pair of electrode layers 10 can be configured as a complex 2C containing the solid electrolyte particles 20 and the electrode active material 30. The other of the pair of electrode layers 10 is composed of a porous body 2B which is a solid electrolyte body 2. Alternatively, as shown in FIG. 2, in the solid electrolyte body 2, the electrode layer 10 can be formed by filling the porous body 2B with the electrode active material 30. Preferably, the porous body 2B has a porosity of 40% by volume or more, and the effect of making the average particle size Pd2 of the porous body 2B larger than the average particle size Pd1 of the particle aggregate 2A is effective. It gets higher.
The effect of the structure of the solid electrolyte body 2 and a specific structural example of the electrode layer 10 will be described later.

(Structure of all-solid-state battery 1)
Next, a detailed configuration example of the all-solid-state battery 1 will be described.
The all-solid-state battery 1 shown in FIG. 2 is used, for example, as a power source for automobiles that can be charged and discharged or a power source for various devices, and includes a separator layer 11, a positive electrode layer 12, and a negative electrode layer 13. It has a laminated structure. The separator layer 11 is disposed between the positive electrode layer 12 and the negative electrode layer 13, separates the two layers, and functions as an ion conductor having lithium ion conductivity. In the present embodiment, the direction in which the layers constituting the all-solid-state battery 1 are laminated (the thickness direction of each layer) will be described below as the stacking direction X.

The positive electrode layer 12 and the negative electrode layer 13 are a pair of electrode layers 10 and include an electrode active material 30. Specifically, the positive electrode layer 12 contains the positive electrode active material 31, and the negative electrode layer 12 contains the negative electrode active material 32. Further, a positive electrode current collector 14 and a negative electrode current collector 15 are arranged outside the positive electrode layer 12 and the negative electrode layer 13, respectively, to form an all-solid-state battery 1.

The all-solid-state battery 1 includes a lithium-ion conductive solid electrolyte 2 as a basic skeleton. The solid electrolyte body 2 contains the first solid electrolyte particles 21 and the second solid electrolyte particles 22 as the solid electrolyte particles 20 which are the basic constituent particles, and is composed of the first solid electrolyte particles 21 and the particle aggregate 2A. It is composed of an integrally fired body with a porous body 2B composed of the second solid electrolyte particles 22. The particle aggregate 2A constitutes the separator layer 11, and the porous body 2B is the skeleton of at least one of the positive electrode layer 12 and the negative electrode layer 13, or both skeletons.

As shown in FIG. 1, in a typical configuration example of this embodiment, the solid electrolyte body 2 is an integrally fired body of a particle aggregate 2A serving as a separator layer 11 and a porous body 2B serving as a skeleton of a negative electrode layer 13. It is configured. The particle aggregate 2A is a dense body in which a large number of first solid electrolyte particles 21 are assembled, and the porous body 2B has a three-dimensional network structure in which a large number of second solid electrolyte particles 22 are connected to each other, and a large number of particles are inside. The holes 23 are formed.

Further, the solid electrolyte body 2 can be configured as an integrally fired body including the positive electrode layer 12. The positive electrode layer 12 is configured as a complex 2C containing the solid electrolyte particles 20 and the positive electrode active material 31 which is an electrode active material. That is, the composite 2C serving as the positive electrode layer 12, the particle aggregate 2A serving as the separator layer 11, and the porous body 2B serving as the skeleton of the negative electrode layer 13 are integrated by simultaneous firing.

When configured as an integrally fired body including the positive electrode layer 12, the integrally fired body functions as the all-solid-state battery 1 by forming the positive electrode current collector 14 and the negative electrode current collector 15. That is, in the porous body 2B (negative electrode layer 13) in contact with the negative electrode current collector 15, lithium ions move from the positive electrode layer 12 during charging, receive electrons, and the lithium metal which is the negative electrode active material 32 is precipitated (Li). ^{+ +} e ^- → Li).

As described above, the all-solid-state battery 1 includes the solid electrolyte body 2 as the basic skeleton, and the porous body 2B having a larger particle size is the skeleton of the negative electrode layer 13 with respect to the particle aggregate 2A which is the separator layer 11. Become. As shown in FIG. 1, the negative electrode layer 13 may be composed of only the porous body 2B, or as shown in FIG. 2, the negative electrode active material 32 is filled in the pores 23 of the porous body 2B. Therefore, the negative electrode layer 13 may be formed.

The solid electrolyte particles 20 constituting the positive electrode layer 12 are not particularly limited, but for example, the first solid electrolyte particles 21 similar to the separator layer 11 can be used.

By adopting a layer structure in which the solid electrolyte particles 20 having different particle sizes are combined in the solid electrolyte body 2 which is the basic skeleton, the effect of suppressing the current concentration can be obtained. For example, if the particle size is the same, it is considered that the portion where the current concentration occurs is concentrated on the separator layer 11 and the resistance becomes larger, whereas the resistance becomes smaller inside the porous body 2B having a larger particle size. , Battery performance is improved because uniform battery reaction is possible.

The solid electrolyte particles 20 constituting the solid electrolyte body 2 and the positive electrode layer 12 are particles containing an oxide solid electrolyte having a garnet-type crystal structure (hereinafter, appropriately referred to as a garnet-type solid electrolyte) as a main component. The garnet-type solid electrolyte exhibits high lithium ion conductivity and is stable with respect to lithium metal, and is therefore useful as a solid electrolyte material used in the all-solid-state battery 1.

The garnet-type solid electrolyte is not particularly limited, but for example, a lithium lanthanum zirconium-based composite oxide having a basic composition of _{Li 7} La ₃ Zr ₂ O _{12 (hereinafter, appropriately referred to as LLZ) is preferable.} Used. It may have a composition in which a part of La of LLZ is replaced with an element such as Sr or Ca, or a part of Zr is replaced with an element such as Nb or Ta.
The first solid electrolyte particles 21 and the second solid electrolyte particles 22 constituting the solid electrolyte body 2 preferably have the same composition, but do not necessarily have the same composition.

When integrally fired with the solid electrolyte body 2, the positive electrode active material 31 can be arbitrarily selected in the positive electrode layer 12, but preferably lithium (Li) and at least nickel (Ni) and cobalt (Co). A composite oxide containing one of them is used. Examples of such a composite oxide include lithium-containing transition metal oxides _{such as LiCoO 2} (LCO) and LiNi _1/3 Mn _1/3 Co _1/3 O _{2 (NMC).}

Further, in the negative electrode layer 13, for example, lithium metal is preferably used as the negative electrode active material 32. By using a lithium metal having a low electrode potential for the negative electrode layer 13, the battery electromotive force can be increased and the output can be increased. The negative electrode active material 32 may be any material that can be impregnated in a state of being flowed into the porous body 2B after the formation of the solid electrolyte body 2, and may be, for example, a lithium alloy or the like. In this way, when a substance that can flow during filling is used as the electrode active material 30, it can be configured to come into contact with the surface of the particles forming the inner wall surface of the pores 23 of the porous body 2B after filling. preferable.

Here, the first solid electrolyte particles 21 and the second solid electrolyte particles 22 have different average particle diameters Pd, and the average particle diameter Pd2 of the second solid electrolyte particles 22 is the average particles of the first solid electrolyte particles 21. It is prepared to be larger than the diameter Pd1 (that is, Pd2> Pd1). Preferably, the ratio Pd2 / Pd1 of the average particle size Pd2 of the second solid electrolyte particles 22 to the average particle size Pd1 of the first solid electrolyte particles 21 is preferably 1.5 or more. More preferably, the ratio Pd2 / Pd1 is preferably 2 or more, and the resistance at the time of ion conduction can be greatly reduced with respect to the case where the average particle size Pd is the same.

By forming the solid electrolyte body 2 to be composed of the particle aggregate 2A and the porous body 2B, the positive electrode layer 12 and the negative electrode layer 13 can be separated via the separator layer 11 which is a dense particle aggregate 2A. At the same time, the negative electrode layer 13 (that is, one of the pair of electrode layers 10) can be formed by the porous body 2B integrated with the particle aggregate 2A, and the resistance between the layers can be reduced. Further, by forming the porous body 2B with the second solid electrolyte particles 22 having a larger average particle size Pd, the interfacial resistance and the internal resistance can be reduced, and the resistance in the porous body 2B can be reduced.

As schematically shown in FIG. 4, when the solid electrolyte particles 20 are linearly aligned and arranged between the points A and the points B corresponding to the two points in the stacking direction X of the porous body 2B, the average particles thereof. The larger the diameter Pd, the smaller the number of particles between the points AB, in other words, the total number of interfaces 24 formed between the particles. For example, when the first solid electrolyte particles 21 and the second solid electrolyte particles 22 are compared, in the illustrated example in which the ratio Pd2 / Pd1 is larger than 2, the first solid electrolyte particles 21 having a smaller average particle size Pd have an interface. While the number is 6, the number of interfaces in the second solid electrolyte particle 22 is reduced to 2 and less than half.

Further, as shown in FIG. 5, since the porous body 2B has a three-dimensional network structure, the ion conduction path 25 formed by connecting the second solid electrolyte particles 22 (for example, in the figure, is two-dimensional). ), It becomes curved. In that case, the larger the average particle size Pd, the shorter the ion conduction path 25. As shown in the figure, since the ion conduction path 25 between the points A and B is formed so as to be the shortest distance, the ion conduction path 25 formed by the first solid electrolyte particles 21 having a smaller average particle size Pd , The ion conduction path 25 formed by the second solid electrolyte particles 22 becomes shorter, and the internal resistance of the ion conduction path 25 is reduced accordingly. Therefore, in combination with the above-mentioned effect of reducing the interfacial resistance between particles, the resistance of the electrode layer 10 can be significantly reduced.

Here, as shown in FIG. 6, in the conventional method, the interfacial resistance can be reduced by the grain growth by high-temperature sintering of the solid electrolyte particles 200. That is, from the initial state of firing in which the particle interfaces are in contact, through the middle stage of firing in which the particles are bonded to each other to form the necking 201, the grain growth further progresses, and the larger solid electrolyte particles 202 integrated in the latter stage of firing. Is obtained. However, when this method is used for a garnet-type solid electrolyte, La ₂ Zr ₂ O ₇ in which Li is volatilized is easily generated by high-temperature firing, and a garnet-type solid electrolyte having a desired composition cannot be stably produced. There are concerns. Further, the higher the firing temperature, the higher the energy consumption. Further, as in the configuration of FIG. 1, when the positive electrode layer 12 is the complex 2C, the garnet-type solid electrolyte reacts with the positive electrode active material 31 at a high temperature, so that it cannot be integrally fired.

Even in such a case, by adopting the configuration of this embodiment, it is possible to obtain an integrally fired body including the positive electrode layer 12. That is, in the solid electrolyte body 2, by appropriately setting the ratio Pd2 / Pd1 of the average particle size Pd of the particle aggregate 2A and the porous body 2B, the solid electrolyte can be obtained even in the sintering at a low temperature without grain growth. The resistance in the ion conduction path of the body 2 can be reduced.

Then, by enabling sintering at a low temperature, the composite 2C to be the positive electrode layer 12 is integrally fired with the solid electrolyte body 2, and the number of manufacturing steps is reduced while suppressing the reaction with the positive electrode active material 31. Energy consumption can be suppressed. Therefore, it is possible to improve the productivity and obtain a high-quality all-solid-state battery 1 having excellent battery performance.

In the solid electrolyte body 2, the particle aggregate 2A to be the separator layer 11 is preferably configured by using the first solid electrolyte particles 21 having an average particle size Pd1 of 10 μm or less. At this time, as the average particle size Pd1 of the first solid electrolyte particles 21 is smaller, the gaps between the particles become smaller and denser, and the separator layer 11 can be made thinner (for example, about 40 μm). In general, the thinner the separator layer 11, the lower the resistance, and the thinner the separator layer 11 is, the more the ratio of the electrode layer 10 containing the electrode active material 30 can be relatively increased, so that the battery performance can be improved. It is advantageous.

The solid electrolyte slurry is obtained by dispersing the solid electrolyte particles 20 in an organic solvent, and additives such as a binder component, a plasticizer, and a dispersant can be appropriately added. The organic solvent can be arbitrarily selected, as long as it can dissolve the binder component and disperse the solid electrolyte particles 20. Preferably, as the organic solvent, an alcohol solvent such as ethanol, 1-butanol and 2-butanol, an ester solvent such as isoamyl acetate and the like can be used.

The binder component is for enhancing the binding force between the particles, and for example, an organic binder component such as an acrylic resin-based binder component or a binder component having a hydroxyl group can be used. Examples of the binder component having a hydroxyl group include polyvinyl butyral (PVB) and polyvinyl alcohol (PVA). Further, a plasticizer for imparting plasticity at the time of molding may be contained. As the plasticizer, for example, dioctyl adipate (DOA) is used.

A pore-forming material is further added to the solid electrolyte slurry for forming the porous body 2B. The pore-forming material may be any material that is burnt down in the firing process, and for example, an acrylic resin such as polymethyl methacrylate (PMMA), a pore-forming material made of a resin material such as nylon resin, or the like can be used. At this time, since the space formed by burning the pore-forming material after firing becomes the pores 23, it is desired to appropriately adjust the amount of the pore-forming material added in consideration of the shrinkage during firing and the like. A porous body 2B having a porosity can be obtained.

The porosity of the porous body 2B can be arbitrarily set. For example, by setting it to 20% by volume or more, a resistance reducing effect can be obtained by increasing the average particle size Pd2. Preferably, the porosity is 40% by volume or more, so that the effect of the structure of this embodiment can be easily obtained, and a sufficient space in which the electrode active material 30 can be filled is formed. Generally, as the number of pores 23 contained in the porous body 2B increases, the resistance tends to increase. Therefore, the higher the porosity, the higher the effect of increasing the ratio Pd2 / Pd1. More preferably, it is appropriately adjusted within the range where the porosity is 80% by volume or less.

(Modification 1 of Solid Electrolyte 2)
As shown in FIG. 7 as a modification 1, the solid electrolyte body 2 may have a structure having porous bodies 2B on both sides of the particle structure 2A. In that case, the particle aggregate 2A serving as the separator layer 11 and the two porous bodies 2B serving as both skeletons of the positive electrode layer 12 and the negative electrode layer 13 are integrally fired. The positive electrode layer 12 is not formed as the composite 2C, but is formed by filling the pores 23 of the porous body 2B, which is the skeleton, with the positive electrode active material 31 after forming the integrally fired body to be the solid electrolyte body 2. ..

As described above, the positive electrode layer 12 does not need to be configured as the composite 2C, and both the positive electrode layer 12 and the negative electrode layer 13 have the porous body 2B as a skeleton, and the electrode active material is contained in the pores 23 thereof. (Positive electrode active material 31 or negative electrode active material 32) may be filled.

Also in this configuration, the effect of reducing the ionic conduction resistance of the porous body 2B which is the skeleton of the positive electrode layer 12 and the negative electrode layer 13 can be obtained while sintering the solid electrolyte body 2 at a low temperature. Also in this case, after the solid electrolyte body 2 is formed as an integrally fired body, the porous body 2B to be the positive electrode layer 12 is filled with the positive electrode active material 31, and the porous body 2B to be the negative electrode layer 13 is filled with the negative electrode active material 32. By doing so, the all-solid-state battery 1 can be obtained.

In the positive electrode layer 12, the positive electrode active material 31 may be any material that can be made fluid by being heated or dissolved in a solvent. Preferably, for example, sulfur (S) or the like is used, and the porous body 2B is impregnated with fluidity so that the pores 23 can be filled to form the positive electrode layer 12. Further, as the negative electrode active material 32 in the negative electrode layer 13, for example, a lithium metal or a lithium alloy is preferably used, and similarly, the negative electrode layer 13 is impregnated with the porous body 2B in a state of having fluidity. Can be formed. When such a flowable substance is used as the positive electrode active material 31 or the negative electrode active material 32, it can be configured to come into surface contact with the particle surface forming the inner wall surface of the pores 23 of the porous body 2B after filling. ,preferable.

(Modification 2 of Solid Electrolyte 2)
Alternatively, as shown in FIG. 8 as a modification 2, the solid electrolyte body 2 may have a porous body 2B serving as a positive electrode layer 31 on one side of the particle structure 2A. In that case, the solid electrolyte body 2 is configured as an integrally fired body of the particle aggregate 2A serving as the separator layer 11 and the porous body 2B serving as the skeleton of the positive electrode layer 12. Similar to the first modification, the positive electrode layer 12 is formed by filling the pores 23 of the porous body 2B, which is the skeleton, with the positive electrode active material 31 after forming the integrally fired body to be the solid electrolyte body 2. .. The negative electrode layer 13 is configured as a layer containing a negative electrode active material 32 (hereinafter, appropriately referred to as a negative electrode active material layer) made of a sheet-shaped metal material such as lithium metal or a lithium alloy, and this metal sheet is referred to as a solid electrolyte. It can be formed by sticking it on 2.

In this way, the negative electrode layer 13 can be made of a sheet-like metal material to form a layer that does not contain the solid electrolyte particles 20. In that case, by forming the skeleton of the positive electrode layer 12 with the solid electrolyte body 2, the ionic conduction resistance of the porous body 2B serving as the skeleton of the positive electrode layer 12 is reduced while the solid electrolyte body 2 is low-temperature sintered. The effect is obtained.

Therefore, even with the configuration of the solid electrolyte body 2 of these modified examples, energy consumption can be suppressed, productivity can be improved, and a high-quality all-solid-state battery 1 having excellent battery performance can be obtained.

Next, referring to the steps shown in FIGS. 9 to 11, a procedure for preparing the solid electrolyte particles 20 made of a garnet-type solid electrolyte material and a solid electrolyte body 2 are produced using the obtained solid electrolyte particles 20. Further, an example of the procedure for manufacturing the all-solid-state battery 1 will be described. Here, the solid electrolyte body 2 corresponds to the configuration shown in FIG. 1 and includes the particle aggregate 2A serving as the separator layer 11 and the porous body 2B serving as the skeleton of the negative electrode layer 13 and becomes the positive electrode layer 12. It is configured as an integrally fired body with the composite body 2C.

(Preparation step of solid electrolyte particles 20)
In the step of preparing the solid electrolyte particles 20 shown in FIG. 9, as the garnet-type solid electrolyte constituting the solid electrolyte particles 20, LLZ or a part thereof is elementally substituted. For example, a case where Li _6.75 La ₃ Zr _1.75 Nb _0.25 O ₁₂ (hereinafter, appropriately referred to as LLZN) in which a part of Zr is replaced with Nb will be described below.

First, as raw materials for the synthesis of LLZN, powders of LiOH · H ₂ O, La (OH) ₃ , ZrO ₂ and Nb ₂ O ₅ are prepared and weighed so as to have a theoretical composition. The powders of these synthetic raw materials are mixed in the first mixing step (101) using a planetary ball mill or the like, and then the mixed raw materials are fired in the atmospheric atmosphere in the first firing step (102). LLZN powder is synthesized by (for example, 700 ° C.).

_{Further, LiOH · H 2} O is added to the obtained LLZN powder, and the mixture is mixed using a planetary ball mill or the like in the second mixing step (103). Then, in the second firing step (104), this mixed raw material is fired in an air atmosphere (for example, 700 ° C.) to obtain LLZN powder which becomes solid electrolyte particles 20. _{The amount of LiOH / H 2} O added in the second mixing step (103) supplements the Li component that volatilizes during firing, and is, for example, based on the amount of LLZN powder recovered after the first firing step (102). It can be decided as appropriate.

The particle size of the obtained LLZN powder can be appropriately adjusted in the first mixing step (101) and the second mixing step (103) by, for example, changing the crushing time at the time of mixing and crushing. Alternatively, the particle size can be adjusted by changing the diameter of the balls for mixing and crushing used at the time of mixing and crushing. As a result, for the first solid electrolyte particles 21 serving as the separator layer 11 and the second solid electrolyte particles 22 serving as the electrode layer 10, the average particle diameters Pd1 and Pd2 and the ratio Pd2 / Pd1 of the average particle diameters are set to desired values. It becomes possible to adjust to.

(Manufacturing process of all-solid-state battery 1)
Next, in the production step shown in FIG. 10, the integrally fired body containing the solid electrolyte body 2 is produced using the LLZN powder obtained as described above. Here, the solid electrolyte body 2 has the configuration shown in FIG. 1, and includes the particle aggregate 2A serving as the separator layer 11 and the porous body 2B serving as the skeleton of the negative electrode layer 13, and also serves as the positive electrode layer 12. It is configured as an integrally fired body with the composite body 2C. The separator layer 11 and each electrode layer 10 are formed into a sheet using a solid electrolyte slurry containing LLZN powder or the like, and the sheets for each of these layers are laminated and integrated by firing.

In the solid electrolyte slurry to be the separator layer 11, first, in the first mixing step (11), the LLZN powder to be the first solid electrolyte particles 21 was added to an organic solvent and dispersed and mixed using a rotation / revolution mixer or the like. Further, in the second mixing step (12), a binder solution and a plasticizing agent are added and uniformly mixed. As the organic solvent, for example, an alcohol solvent such as ethanol is used. The binder solution is prepared by dissolving an organic binder component such as an acrylic binder in an organic solvent in advance, and the amount of the binder component added is such that the sheet strength after molding and the shrinkage amount after firing are within an allowable range. (For example, about 9% by mass to 20% by mass with respect to the solid content). As the plasticizer, for example, dioctyl adipate (DOA) is used.

By performing sheet molding on this solid electrolyte slurry using a known applicator in the sheet molding step (13) (for example, Gap: 300 μm), a predetermined thickness becomes a particle aggregate 2A constituting the separator layer 11. Solid electrolyte sheet can be obtained.

In the solid electrolyte slurry serving as the skeleton of the negative electrode layer 13, first, in the first mixing step (21), the LLZN powder to be the second solid electrolyte particles 22 and the pore-forming material are used as an organic solvent (for example, ethanol or the like). It is obtained by adding a binder solution and a plasticizer in the second mixing step (22) to the mixture which has been added and dispersed and mixed using a rotation / revolution mixer or the like, and uniformly mixed. As the pore-forming material, for example, particles such as acrylic resin are used, and as the binder solution and the plasticizer, the same ones as those of the separator layer 11 are used.

By performing sheet molding on this solid electrolyte slurry using a known applicator in the sheet molding step (23) (for example, Gap: 300 μm), a predetermined thickness becomes a porous body 2B constituting the skeleton of the negative electrode layer 13. A solid electrolyte sheet can be obtained.

In the solid electrolyte slurry to be the positive electrode layer 12, first, in the first mixing step (31), the LLZN powder to be the first solid electrolyte particles 21 and the positive electrode active material 31 are added to an organic solvent (for example, ethanol or the like). Then, in the second mixing step (32), a binder solution and a plasticizing agent are added to the mixture dispersed and mixed using a rotation / revolution mixer or the like, and the mixture is uniformly mixed. As the positive electrode active material 31, for example, LiCoO ₂ (hereinafter, appropriately abbreviated as LCO) is used, and the binder solution and the plasticizer are the same as those of the separator layer 11.

By performing sheet molding on this solid electrolyte slurry using a known applicator in the sheet molding step (33) (for example, Gap: 300 μm), a solid electrolyte sheet having a predetermined thickness to be the positive electrode layer 12 is obtained. Can be done.

Next, in the laminating step (14), the solid electrolyte sheets obtained in the sheet forming steps 13 to 33 are laminated. In this case, the solid electrolyte sheet for the separator layer 11 obtained in the sheet molding step 13 is sandwiched between the solid electrolyte sheet for the positive electrode layer 12 and the solid for the negative electrode layer 13 obtained in the sheet molding steps 23 and 33. Place the electrolyte sheet.

In the subsequent pressure molding step (15), this laminate is pressurized in a heated state using a warm hydrostatic press (WIP) or the like (for example, 85 ° C. × 50 MPa). Further, in the firing step (16), firing is performed in an atmospheric atmosphere (for example, 750 ° C.) to obtain an integrally fired body including the positive electrode layer 12. The firing temperature is equal to or higher than the temperature at which the pore-forming material contained in the solid electrolyte sheet for the negative electrode layer 13 can be burnt (for example, 600 ° C. or higher) and lower than the temperature at which volatilization of the Li component can be suppressed (for example, 950). It is set to be ℃ or less). Preferably, the temperature is below a temperature (for example, 850 ° C. or lower) at which the reaction between the positive electrode active material 31 contained in the solid electrolyte sheet for the positive electrode layer 12 and the LLZN powder to be the first solid electrolyte particles 21 can be suppressed. desirable.

As a result, an integrally fired body of the positive electrode layer 12 and the solid electrolyte body 2 containing the particle aggregate 2A and the porous body 2B can be obtained. Further, in the positive electrode current collector forming step (17), a gold (Au) paste is applied to the positive electrode layer 12 side of the integrally fired body and baked (for example, 450 ° C.) to form the positive electrode current collector 14. Further, in the negative electrode current collector forming step (18), a copper (Cu) paste is applied to the negative electrode layer 13 side of the integrally fired body and baked (for example, 150 ° C.) to form the negative electrode current collector 15.

As shown in FIG. 2, the porous body 2B of the obtained integrally fired body may be filled with the negative electrode active material 32. In that case, as shown in FIG. 11, a negative electrode forming step (100) is added to the current collector forming step after the firing step (16) of FIG. Specifically, first, in the positive electrode current collector forming step (17) similar to FIG. 10, the positive electrode current collector 14 is formed on the positive electrode layer 12 side of the integrally fired body, and then the negative electrode forming step (100). In, the negative electrode active material 32 is filled. As the negative electrode active material 32, for example, powdered lithium metal is used, which is liquefied by heating to a temperature equal to or higher than the melting point (for example, about 180 ° C.) and impregnated into the pores 23 of the porous body 2B. Then, the negative electrode layer 13 is formed.

At this time, in the configuration in which the porous body 2B is filled with lithium metal as the negative electrode active material 32, the lithium metal also functions as the negative electrode current collector 15, so that the negative electrode current collector 15 may not be formed. The negative electrode current collector 15 can also be formed in the negative electrode current collector forming step (18) after the negative electrode forming step (100). In that case, it is desirable to appropriately select the current collector material and the forming conditions to suppress the influence on the negative electrode layer 13. For example, an iron-based metal leaf such as stainless steel (SUS) is used as the negative electrode current collector. It can be used as 15.

In this way, the solid electrolyte body 2 which has the porous body 2B on one side and is integrally fired with the positive electrode is used as the basic skeleton, and the porous body which becomes the negative electrode layer 13 with respect to the average particle size Pd1 of the particle aggregate 2A which becomes the separator layer 11. An all-solid-state battery 1 having a large average particle size Pd2 of 2B can be obtained.

(Manufacturing process of all-solid-state battery 1 according to Modification 1)
As shown in FIG. 12, the solid electrolyte body 2 corresponds to the configuration shown in FIG. 7, and has the skeletons of the positive electrode layer 12 and the negative electrode layer 13 on both sides of the particle aggregate 2A to be the separator layer 11. It is configured as an integrally fired body containing the porous body 2B. The separator layer 11 and each electrode layer 10 are formed into a sheet using a solid electrolyte slurry containing LLZN powder or the like, and the sheets for each of these layers are laminated and integrated by firing.

In the solid electrolyte slurry to be the separator layer 11, the LLZN powder to be the first solid electrolyte particles 21 is dispersed in an organic solvent in the same manner as in the first mixing step (11) and the second mixing step (12) in FIG. A binder solution and a plasticizer are further added to the mixed product, and the mixture is uniformly mixed. In the sheet molding step (13), this solid electrolyte slurry is sheet-molded using a known applicator (for example, Gap: 300 μm) to obtain a solid electrolyte sheet having a predetermined thickness to be a particle aggregate 2A.

The solid electrolyte slurry serving as the skeleton of the positive electrode layer 12 and the negative electrode layer 13 is the LLZN powder which becomes the second solid electrolyte particles 22 in the same manner as in the first mixing step (21) and the second mixing step (22) in FIG. And the pore-forming material are dispersed and mixed in an organic solvent, and a binder solution and a plasticizing agent are further added and uniformly mixed. In the sheet molding step (23), this solid electrolyte slurry is sheet-molded using a known applicator (for example, Gap: 300 μm) to obtain a solid electrolyte sheet having a predetermined thickness as a porous body 2B.

Next, in the laminating step (24), the solid electrolyte sheets obtained in the sheet forming steps 13 and 23 are laminated. In this case, the solid electrolyte sheet for the separator layer 11 obtained in the sheet molding step 13 is sandwiched between the solid electrolyte sheet for the positive electrode layer 12 and the solid electrolyte sheet for the negative electrode layer 13 obtained in the sheet molding step 23. To place.

After that, in the pressure forming step (25) and the firing step (26), pressure is applied using WIP or the like in the same manner as in the pressure forming step (15) and the firing step (16) in FIG. 10 (for example, 85). By firing in an air atmosphere (for example, 750 ° C.), an integrally fired body is obtained.

Then, in the negative electrode forming step (201), one of the obtained porous body 2B of the integrally fired body is filled with the negative electrode active material 32. As the negative electrode active material 32, for example, powdered lithium metal is used, which is liquefied by heating to a temperature equal to or higher than the melting point (for example, about 180 ° C.) and impregnated into the pores 23 of the porous body 2B. Then, the negative electrode layer 13 is formed. Further, in the positive electrode forming step (202), the other side of the porous body 2B of the integrally fired body is filled with the positive electrode active material 31. As the positive electrode active material 31, for example, powdery sulfur is used, and by heating to a temperature equal to or higher than the melting point (for example, about 120 ° C.), it is liquefied and impregnated into the pores 23 of the porous body 2B. , The positive electrode layer 12 is formed.

Further, in the positive electrode current collector forming step (27), gold (Au) is deposited on the positive electrode layer 12 side of the integrally fired body by a vapor deposition method to form the positive electrode current collector 14. Further, in the negative electrode current collector forming step (28), copper (Cu) is deposited on the negative electrode layer 13 side of the integrally fired body by a vapor deposition method to form the negative electrode current collector 15. As described above, the formation of the positive electrode current collector 14 and the negative electrode current collector 15 is not limited to the baking of the metal paste described above, and can be formed by any method such as vacuum deposition.

As a result, an integrally fired body of the particle aggregate 2A and the solid electrolyte body 2 containing the porous body 2B serving as the skeleton of the positive electrode layer 12 and the negative electrode layer 13 can be obtained. In this way, the solid electrolyte body 2 having the porous body 2B on both sides is used as the basic skeleton, and the average grain size of the porous body 2B serving as the negative electrode layer 13 is compared with the average particle size Pd1 of the particle aggregate 2A serving as the separator layer 11. An all-solid-state battery 1 having a large diameter Pd2 can be obtained.

(Manufacturing process of all-solid-state battery 1 according to Modification 2)
As shown in FIG. 13, the solid electrolyte body 2 corresponds to the configuration shown in FIG. 8 and includes a particle aggregate 2A as the separator layer 11 and a porous body 2B as the skeleton of the positive electrode layer 12. It is configured as a fired body. The separator layer 11 and the positive electrode layer 12 are each formed into a sheet using a solid electrolyte slurry containing LLZN powder or the like, and the sheets for each of these layers are laminated and integrated by firing. The negative electrode layer 13 is composed of a negative electrode active material layer and does not contain the solid electrolyte particles 20.

In the solid electrolyte slurry to be the separator layer 11, the LLZN powder to be the first solid electrolyte particles 21 is dispersed in an organic solvent in the same manner as in the first mixing step (11) and the second mixing step (12) in FIG. A binder solution and a plasticizer are further added to the mixed product, and the mixture is uniformly mixed. In the sheet molding step (13), this solid electrolyte slurry is sheet-molded using a known applicator (for example, Gap: 300 μm) to obtain a solid electrolyte sheet having a predetermined thickness to be a particle aggregate 2A.

The solid electrolyte slurry serving as the skeleton of the positive electrode layer 12 contains the LLZN powder to be the second solid electrolyte particles 22 and pore-forming in the same manner as in the first mixing step (21) and the second mixing step (22) in FIG. The material is obtained by dispersing and mixing the material in an organic solvent, further adding a binder solution and a plasticizer, and uniformly mixing the materials. In the sheet molding step (23), this solid electrolyte slurry is sheet-molded using a known applicator (for example, Gap: 300 μm) to obtain a solid electrolyte sheet having a predetermined thickness as a porous body 2B.

Next, in the laminating step (34), the solid electrolyte sheets obtained in the sheet forming steps 13 and 23 are laminated. In this case, the solid electrolyte sheet for the positive electrode layer 12 obtained in the sheet molding step 23 is arranged so as to sandwich the solid electrolyte sheet for the separator layer 11 obtained in the sheet molding step 13.

Then, in the pressure forming step (35) and the firing step (36), pressure is applied using WIP or the like in the same manner as in the pressure forming step (15) and the firing step (16) in FIG. 10 (for example, 85). By firing in an air atmosphere (for example, 750 ° C.), an integrally fired body is obtained.

Further, in the positive electrode forming step (300), the positive electrode layer 12 is formed by filling the obtained porous body 2B of the integrally fired body with the positive electrode active material 31 (for example, sulfur). Further, in the positive electrode current collector forming step (37), gold (Au) is vapor-deposited on the positive electrode layer 12 side of the integrally fired body to form the positive electrode current collector 14. Then, in the negative electrode active material layer forming step (38), as the negative electrode active material layer, for example, a negative electrode active material 32 (for example, lithium metal) formed into a sheet is placed on the opposite side of the porous body 2B of the integrally fired body. By sticking, the negative electrode layer 13 is formed.

As a result, an integrally fired body of the particle aggregate 2A and the solid electrolyte body 2 containing the porous body 2B serving as the skeleton of the positive electrode layer 12 can be obtained. In this way, the solid electrolyte body 2 having the porous body 2B on one side as the basic skeleton, and the porous body 2B serving as the positive electrode layer 12 with respect to the average particle size Pd1 of the particle aggregate 2A serving as the separator layer 11. An all-solid-state battery 1 having a large average particle size Pd2 can be obtained.

(Test Examples 1 to 4, Comparative Examples 1 to 2)
By the procedure shown in FIG. 9 above, the solid electrolyte particles 20 to be the first solid electrolyte particles 21 or the second solid electrolyte particles 22 were produced. Using these, an integrally fired body containing the solid electrolyte body 2 and the positive electrode layer 12 was further prepared and evaluated by the procedure shown in FIG. LLZN was used as the garnet-type solid electrolyte. Further, the positive electrode layer 12 was configured as a complex 2C containing the first solid electrolyte particles 21 and the positive electrode active material 31. LCO was used as the positive electrode active material 31.

As shown in Table 1, in the solid electrolyte body 2, the average particle size Pd1 of the particle aggregate 2A to be the separator layer 11 is set to 2 μm, and the average particle size Pd2 of the porous body 2B to be the skeleton of the negative electrode layer 13 is changed. , The effect when the ratio Pd2 / Pd1 was changed in the range of 0.2 to 6 was investigated. In Test Examples 1 to 4, the ratios Pd2 / Pd1 were 2, 1.5, 4, and 6.2, respectively, and the ratios Pd2 / Pd1 were set to 1 and 0.2, which were designated as Comparative Examples 1 and 2. .. In Comparative Example 1, when the average particle diameters Pd1 and Pd2 of the particle aggregate 2A and the porous body 2B are the same (that is, the ratio Pd2 / Pd1 = 1), Comparative Example 2 is larger than the average particle diameter Pd1 of the particle aggregate 2A. This is the case when the average particle size Pd2 of the porous body 2B is small (that is, the ratio Pd2 / Pd1 <1).

In Test Examples 1 to 4 and Comparative Examples 1 and 2, the porosity of the porous body 2B serving as the skeleton of the negative electrode layer 13 was set to 50%. The total resistance between the positive and negative electrodes of the integrally fired body was measured in a state where the solid electrolyte body 2 was not filled with the negative electrode active material 32. The total resistance was calculated based on the impedance measurement result, and the ratio of the total resistance when the total resistance in Comparative Example 1 was set to 100% was calculated and shown in Table 1.

In the solid electrolyte body 2, the average particle size Pd1 of the particle aggregate 2A and the average particle size Pd2 of the porous body 2B are the particle sizes of 50 randomly selected parts obtained by performing image analysis of the cross section of the integrally fired body. Was measured, and the particle size at which the integrated% in the particle size distribution curve was 50% was calculated. Further, the porosity of the porous body 2B of the integrally fired body was quantified into a portion corresponding to the second solid electrolyte particle 22 and a portion corresponding to the pore 23 by image analysis of the cross section, and the porosity of the pore 23 portion was determined. The ratio was calculated.

As is clear from the comparison of Test Examples 1 to 4 and Comparative Examples 1 and 2, in Comparative Example 2 (ratio Pd2 / Pd1 = 0.2), the total is as opposed to Comparative Example 1 in which the ratio Pd2 / Pd1 = 1. The resistance has increased to 250%. Compared to this, as in Test Examples 1 and 2, by increasing the ratio Pd2 / Pd1 to 2, 1.5, which is larger than 1, the total resistance becomes 30% and 60%, and the ratio Pd2 / Pd1 is small. The total resistance tends to decrease as the total resistance increases. However, even if the ratio Pd2 / Pd1 is further increased to 4, 6.2 as in Test Examples 3 and 4, the total resistance does not change significantly to 32% and 24%, and almost converges. Therefore, the ratio Pd2 / Pd1 is preferably adjusted to be 1.5 or more, more preferably 2 or more.

(Test Examples 5 to 7, Comparative Examples 3 to 5)
As shown in Table 2, for the integrally fired body having the same configuration as that of Test Example 1, the ratio of Pd2 / Pd1 = 2 and the total resistance when the porosity of the porous body 2B to be the negative electrode layer 13 was changed. I investigated the changes. The cases where the porosities were set to 20%, 40%, and 70% were set as Test Examples 5 to 7, respectively, and the results are also shown in Table 2. At this time, when the ratio of the average particle diameters of the particle aggregate 2A and the porous body 2B is Pd2 / Pd1 = 1, the porosity of the porous body 2B is similarly changed to 20%, 40%, and 70%. The change in the total resistance of the above was examined, and the ratio of the total resistance to the comparative examples 3 to 5 (total resistance = 100%) was calculated.

As is clear from the comparison between Test Example 1 shown in Table 1 above and Test Examples 5 to 7 and Comparative Examples 3 to 5, the total resistances of Test Examples 5 to 7 with the ratio Pd2 / Pd1 = 2 are different, respectively. It is reduced as compared with Comparative Examples 3 to 5 having the same porosity. At this time, in Test Example 5 having a porosity of 20%, the total resistance was 81%, whereas as in Test Examples 1 and 6 to 7, the porosity was 40%, 50%, and 70%. The higher the value, the lower the total resistance to 38%, 30%, and 22%, and the higher the effect. Therefore, the porosity is preferably adjusted to be 40% or more.

(Test Examples 8 to 11, Comparative Examples 6 to 9)
As shown in Table 3, for the integrally fired body having the same configuration as that of Test Example 1, the ratio was Pd2 / Pd1 = 2, and the average particle size Pd1 of the particle aggregate 2A to be the separator layer 11 was changed. The change in resistance was investigated. The cases where the average particle size Pd1 of the particle aggregate 2A was 1 μm, 5 μm, 7 μm, and 10 μm were set as Test Examples 8 to 11, respectively, and the results are also shown in Table 3. At this time, when the ratio of the average particle size of the particle aggregate 2A and the porous body 2B was Pd2 / Pd1 = 1, the average particle size Pd1 of the particle aggregate 2A was similarly changed to 1 μm, 5 μm, 7 μm, and 10 μm. The change in total resistance at that time was investigated, and the ratio of total resistance to Comparative Examples 6 to 9 (total resistance = 100%) was calculated.

As is clear from the comparison of Test Examples 8 to 11 and Comparative Examples 6 to 9, in Test Examples 8 to 11 in which the ratio Pd2 / Pd1 = 2, the total resistances of Comparative Examples 6 have the same average particle size Pd1. It is reduced to ~ 9. At this time, in Test Example 11 having an average particle size Pd1 of 10 μm, the total resistance was reduced to 60%, and further, as in Test Examples 8 to 10, the smaller the average particle size Pd1 was, the smaller the total particle size Pd1 was 7 μm, 5 μm, and 1 μm. The resistance is reduced to 54%, 36%, and 25%, and the effect is high. Therefore, the average particle size Pd1 of the particle aggregate 2A is preferably adjusted to be 10 μm or less.

(Comparative Examples 10 to 11)
As shown in Table 4, in the integrally fired body having the same configuration as that of Test Example 1, the solid electrolyte body 2 was replaced with the garnet type solid electrolyte, and Li _{1 + x} Al _x (Ti, Ge) which is a pearcon type solid electrolyte. _{The change in total resistance when 2-x} (PO ₄ ) O ₃ ; 0 <x <1) was investigated. At this time, the case where the average particle size Pd1 of the particle aggregate 2A, the ratio Pd2 / Pd1 of the average particle size of the particle aggregate 2A and the porous body 2B, and the porosity of the negative electrode layer 13 are the same as in Test Example 1 above. A case similar to Comparative Example 10 and Comparative Example 1 was designated as Comparative Example 11. The ratio of the total resistance of Comparative Example 10 to Comparative Example 11 (total resistance = 100%) was calculated, and the results are shown in Table 4 together with Test Example 1 and Comparative Example 1.

As is clear from the comparison of Comparative Examples 10 to 11, even in the solid electrolyte 2 using the Nashicon-type phosphoric acid compound, the ratio Pd2 / Pd1 = 2 was set with respect to Comparative Example 11 having the ratio Pd2 / Pd1 = 1. Although the total resistance was reduced to 80% in Comparative Example 10, a large reduction effect was not observed as in Test Example 1 (total resistance = 30%) with respect to Comparative Example 1. Therefore, it is desirable that the solid electrolyte body 2 is composed of a garnet-type solid electrolyte, and the effect of adjusting the ratio Pd2 / Pd1 is higher than that of the Nashicon-type solid electrolyte.

(Embodiment 2)
Hereinafter, the second embodiment relating to the all-solid-state battery will be described with reference to the drawings.
As shown in FIG. 14, the solid electrolyte body 2 constituting the all-solid-state battery 1 can have the lithium-containing compound 4 in the particle gaps of the solid electrolyte particles 20. The other basic configurations of the solid electrolyte body 2 and the configurations of the all-solid-state battery 1 including the solid electrolyte body 2 are the same as those in the first embodiment, and the differences will be mainly described below.
In addition, among the codes used in the second and subsequent embodiments, the same codes as those used in the above-described embodiments represent the same components and the like as those in the above-mentioned embodiments, unless otherwise specified.

The lithium-containing compound 4 exists as an alternative compound in the gap formed between the particles of the solid electrolyte particles 20, which are the basic constituent particles of the solid electrolyte body 2, and connects the particles so that lithium ions can be conducted. Specifically, the lithium-containing compound 4 is a compound having lithium ion conductivity and forming a liquid phase at the firing temperature of the solid electrolyte 2, preferably lithium (Li) and boron (B). A compound containing the compound (hereinafter, appropriately referred to as an LB compound) is used. Examples of the LB compound include _{lithium boron-containing oxides such as Li 3} BO ₃ and Li _{2 + x} B _x C _1-x O ₃ (0 <x <1).

Such a lithium-containing compound 4 is added to the solid electrolyte slurry containing the solid electrolyte particles 20 to form a liquid phase in the firing step, so that the lithium-containing compound 4 infiltrates between the particles of the solid electrolyte particles 20 (left view of FIG. 14). reference). At this time, due to the surface tension of the liquid, the adjacent solid electrolyte particles 20 are attracted to each other and easily come into contact with each other, and the gap between the particles is reduced. After that, the lithium-containing compound 4 (other form compound) crystallizes so as to fill the particle gaps of the solid electrolyte particles 20 (automorphic compound) that maintain the particle shape at the time of firing. As a result, the contact area at the interface of the solid electrolyte particles 20 is increased, and the lithium-containing compound 4 contained in the particle gaps contributes to ionic conduction, so that the resistance of the solid electrolyte 2 can be reduced.

In addition, when a compound is "automorphic", it means that the crystal morphology is clear. On the other hand, "polymorphism" means that the crystal morphology is not clear, and in the solid electrolyte body 2B, the polymorphic compound 4 is formed between the self-shaped garnet-type solid electrolyte particles 20. It has a structure in which the lithium-containing compound 4 is contained.

The lithium-containing compound 4 is preferably contained in the gaps between the second solid electrolyte particles 22, which are the solid electrolyte particles 20, in the porous body 2B of the solid electrolyte body 2, and improves the ionic conductivity in the porous body 2B. More preferably, in the particle aggregate 2A of the solid electrolyte body 2, it is desirable that the particles are contained in the particle gaps of the first solid electrolyte particles 21 which are the solid electrolyte particles 20, and the gaps between the particles of the particle aggregate 2A are reduced. And contributes to densification.

(Embodiment 3)
Hereinafter, the third embodiment relating to the all-solid-state battery will be described with reference to the drawings.
As shown in FIG. 15, the solid electrolyte body 2 constituting the all-solid-state battery 1 can have the electron conductive substance 5 on the surface exposed to the pores 23 of the porous body 2B. The other basic configurations of the solid electrolyte body 2 and the configurations of the all-solid-state battery 1 including the solid electrolyte body 2 are the same as those in the first embodiment, and the differences will be mainly described below.

Specifically, the electron conductive substance 5 may cover at least a part of the surface of the second solid electrolyte particles 22 exposed in the pores 23 of the porous body 2B to form an electron conductive surface coating film. can. As the electron conductive substance 5, preferably, a metal such as copper (Cu), gold (Au), magnesium (Mg), indium (In), or a substance having electron conductivity such as carbon (C) is used. Used. The film of the electron conductive substance 5 can be formed by integrally firing the solid electrolyte body 2 and then using a vapor deposition method or the like. Alternatively, a film of the electron conductive substance 5 may be formed on the surface of the pores 23 of the porous body 2B by using a slurry or the like containing nanoparticles of the electron conductive substance 5.

When such a film of the electron conductive substance 5 is provided on the surface of the pores 23 of the porous body 2B, the electron conductive path is formed in contact with the surface of the porous body 2B which is the path of ion conduction. Will be. Thus, increasing the area of the portion where electrons and ions are associated, cell reaction ^{(Li + + e - → Li} ) is promoted. In the illustrated configuration, when the film of the electron conductive substance 5 is not provided, the portion where the electrons and the ions meet is only the contact point between the porous body 2B and the negative electrode current collector 15, so that the battery reaction occurs. Progression is suppressed. On the other hand, in the portion where the film of the electron conductive substance 5 is formed, the battery reaction can proceed, and the resistance can be further reduced.

The electron conductive substance 5 may cover the inner surface of the pores 23 of the porous body 2B in a thin film shape. Since the electron conduction by the electron conductive substance 5 is generally faster than the ionic conduction, it has an effect in a small amount and does not have to cover the entire surface of the pores 23. The blending amount of the electron conductive substance 5 can be appropriately set so as to obtain a desired effect.

(Manufacturing process of all-solid-state battery 1 according to Embodiments 2 and 3)
As shown in FIG. 16, the solid electrolyte body 2 has a configuration in which the lithium-containing compound 4 shown in FIG. 14 or the electron conductive substance 5 shown in FIG. 15 is added to the configuration shown in FIG. Corresponds to. The solid electrolyte body 2 includes a particle aggregate 2A serving as a separator layer 11 and a porous body 2B serving as a skeleton of the negative electrode layer 13, and is configured as an integrally fired body with a composite body 2C serving as a positive electrode layer 12. The separator layer 11 and each electrode layer 10 are formed into a sheet using a solid electrolyte slurry containing LLZN powder or the like, and the sheets for each of these layers are laminated and integrated by firing.

In the solid electrolyte slurry to be the separator layer 11, the LLZN powder to be the first solid electrolyte particles 21 is dispersed in an organic solvent in the same manner as in the first mixing step (11) and the second mixing step (12) in FIG. A binder solution and a plasticizer are further added to the mixed product, and the mixture is uniformly mixed. As shown in parentheses in the figure, when the lithium-containing compound 4 is contained, it is added to the solid electrolyte slurry together with the LLZN powder in the first mixing step (11). The solid electrolyte slurry containing the lithium-containing compound 4 is similarly sheet-molded in the sheet molding step (13) (for example, Gap: 300 μm) to obtain a solid electrolyte sheet to be a particle aggregate 2A.

The solid electrolyte slurry serving as the skeleton of the negative electrode layer 13 contains the LLZN powder to be the second solid electrolyte particles 22 and pore-forming in the same manner as in the first mixing step (21) and the second mixing step (22) in FIG. It is obtained by uniformly mixing the material with a binder solution and a plasticizing agent added to the material dispersed and mixed in an organic solvent. As shown in parentheses in the figure, when the lithium-containing compound 4 is contained, it is added to the solid electrolyte slurry together with the LLZN powder in the first mixing step (11). The solid electrolyte slurry containing the lithium-containing compound 4 is similarly sheet-molded in the sheet molding step (23) (for example, Gap: 300 μm) to obtain a solid electrolyte sheet to be a porous body 2B.

Further, the solid electrolyte slurry to be the positive electrode layer 12 contains the LLZN powder to be the first solid electrolyte particles 21 and the positive electrode activity in the same manner as in the first mixing step (31) and the second mixing step (32) in FIG. It is obtained by uniformly mixing the substance 31 with the substance 31 in an organic solvent by adding a binder solution and a plasticizing agent. As shown in parentheses in the figure, when the lithium-containing compound 4 is contained, it is added to the solid electrolyte slurry together with the LLZN powder in the first mixing step (31). The solid electrolyte slurry containing the lithium-containing compound 4 is sheet-molded using a known applicator in the sheet molding step (33) (for example, Gap: 300 μm) to form a positive electrode layer 12 having a predetermined thickness. A solid electrolyte sheet can be obtained. This solid electrolyte slurry is similarly sheet-molded in the sheet molding step (33) (for example, Gap: 300 μm) to obtain a solid electrolyte sheet to be a porous body 2B.

The proportion of the lithium-containing compound 4 blended in the solid electrolyte slurry is appropriately set so as not to affect the structure of each layer after firing within the range in which the effect of attracting particles by the liquid phase can be obtained. Preferably, the lithium-containing compound 4 is added so that the blending ratio with respect to the solid content in the solid electrolyte slurry is in the range of 10% by volume to 40% by volume.

Next, in the laminating step (44), the solid electrolyte sheets obtained in the sheet forming steps 13, 23, and 33 are laminated in the same manner as in the laminating step (14) in FIG. Then, in the same manner, in the pressure molding step (45) and the firing step (46), pressure is applied using WIP or the like (for example, 85 ° C. × 50 MPa) and firing is performed in an atmospheric atmosphere (for example, 750 ° C.). , An integral fired body.

When the electron conductive substance 5 is introduced into the integrally fired body, an electron conductive substance introduction step (400) is further added as shown in parentheses in the figure. As a method for introducing the electron conductive substance 5, for example, when the electron conductive substance 5 is a metal such as copper (Cu) or gold (Au), a raw material such as an atomic layer deposition (ALD) is used. The vapor deposition method using the vapor phase reaction of No. 1 is adopted, and a layer of a metal atom to be an electron conductive substance 5 is formed on the surface of the pores 23 of the porous body 2B to be the negative electrode layer 13. Alternatively, a method is used in which a slurry in which the metal nanopowder is dispersed in a solvent is prepared, and the obtained slurry is poured into the pores 23 of the porous body 2B to introduce the metal nanopowder onto the surface. When the electron conductive substance 5 is carbon (C) or the like, carbon nanotubes are dispersed in a solvent, and the obtained slurry is poured into the pores 23 of the porous body 2B, and the metal nano is placed on the surface. A method of introducing powder can be used.

Further, in the positive electrode current collector forming step (47), a gold (Au) paste is applied to the positive electrode layer 12 side of the integrally fired body and baked (for example, 450 ° C.) to form the positive electrode current collector 14. Further, in the negative electrode current collector forming step (48), a copper (Cu) paste is applied to the negative electrode layer 13 side of the integrally fired body and baked (for example, 150 ° C.) to form the negative electrode current collector 15.

In this way, the solid electrolyte body 2 integrated with the positive electrode having the porous body 2B on one side is included as the basic skeleton, the lithium-containing compound 4 is contained in the particle gap, or the electron conductive substance 5 is a pore in the porous body 2B. The all-solid-state battery 1 included in the surface of 23 is obtained. Of course, the configuration in which the lithium-containing compound 4 is contained in the particle gaps or the electron conductive substance 5 is contained in the surface of the pores 23 of the porous body 2B can be applied to the configurations shown in FIGS. 7 and 8 above.

(Test Example 12)
As shown in Table 5, the effect of adding the lithium-containing compound 4 to the solid electrolyte slurry constituting the solid electrolyte body 2 and the positive electrode layer 12 was investigated for the integrally fired body having the same configuration as that of Test Example 1. .. As the lithium-containing compound 4, an LB compound (for example, Li ₃ BO ₃ ; average particle size Pd: 0.5 μm) was used and added in the range of 10% by volume to 40% by volume. For this Comparative Example 12, the ratio of the total resistance to the Comparative Example 1 was calculated and shown in Table 5 together with the results of the Test Example 1 and the Comparative Example 1.

As is clear from the comparison between Test Examples 1 and 12 and Comparative Example 1, in Test Example 12 in which the lithium-containing compound 4 was added to the solid electrolyte slurry, the total resistance was reduced to 23%, and Test Example 1 (total resistance). A higher effect on resistance reduction was obtained than (= 30%).

(Test Example 13)
As shown in Table 5, in the integrally fired body having the same configuration as that of Test Example 1, electron conduction was carried out on the surface of the solid electrolyte body 2 exposed to the pores 23 of the porous body 2B by the procedure shown in FIG. The effect of forming a film of the sex substance 5 was investigated. A metal material (for example, Au) was used as the electron conductive substance 5, and a thin film of the electron conductive substance 5 was formed in the pores 23 of the porous body 2B by the ALD method. For this Comparative Example 13, the ratio of the total resistance to the Comparative Example 1 was calculated and shown in Table 5.

As is clear from the comparison between Test Examples 1 and 13 and Comparative Example 1, in Test Example 13 in which the electron conductive substance 5 is introduced into the inner surface of the porous body 2B which is the skeleton of the negative electrode layer 13 in the solid electrolyte body 2. The total resistance was reduced to 13%, and the effect of further reducing the resistance was obtained as compared with Test Example 12.

The present invention is not limited to each of the above embodiments, and can be applied to various embodiments without departing from the gist thereof.
For example, the all-solid-state battery provided with the solid electrolyte body having the configuration of each of the above embodiments is not limited to mobile bodies such as vehicles, but is an all-solid-state battery used for any purpose such as various household appliances, and any other use. Can be applied to.

1 All-solid-state battery 10 Electrode layer 11 Separator layer 2 Solid electrolyte 2A Particle aggregate 2B Porous 2C composite 20 Solid electrolyte particles 21 First solid electrolyte particles 22 Second solid electrolyte particles

Claims (10)

An all-solid-state battery (1) in which a pair of electrode layers (10) are arranged with a separator layer (11) having lithium ion conductivity interposed therebetween.
It is equipped with a solid electrolyte body (2) whose basic constituent particles are garnet-type solid electrolyte particles (20) as a basic skeleton.
The solid-state electrolyte is an integrally fired body containing a particle aggregate (2A) serving as the separator layer and a porous body (2B) serving as the skeleton of at least one of the pair of electrode layers. An all-solid-state battery in which the average particle size Pd1 of the aggregate and the average particle size Pd2 of the porous body have a relationship of Pd2> Pd1. The all-solid-state battery according to claim 1, wherein the ratio Pd2 / Pd1 of the average particle size Pd2 to the average particle size Pd1 is 1.5 or more. The all-solid-state battery according to claim 1 or 2, wherein the solid electrolyte particles are particles containing a lithium lanthanum zirconium-based composite oxide, and the average particle size Pd1 is 10 μm or less. The all-solid-state battery according to any one of claims 1 to 3, wherein the porous body has a porosity of 40% by volume or more. The pair of the electrode layers is a positive electrode layer (12) and a negative electrode layer (13).
The solid electrolyte body is composed of the particle aggregate and the porous body serving as the negative electrode layer.
The positive electrode layer is a composite (2C) containing the solid electrolyte particles and the positive electrode active material (31), and the composite is an integrally fired body with the solid electrolyte, claims 1 to 4. The all-solid-state battery according to any one of the above items. The all-solid-state battery according to claim 5, wherein the negative electrode layer is formed by filling the porous body with the negative electrode active material (32). The pair of the electrode layers is a positive electrode layer (12) and a negative electrode layer (13).
The solid electrolyte body is composed of the particle aggregate, the porous body serving as the positive electrode layer, and the porous body serving as the negative electrode layer.
The positive electrode layer is formed by filling the porous body with the positive electrode active material (31).
The negative electrode layer is configured by filling the porous body with the negative electrode active material (32), or by laminating a layer containing the negative electrode active material on the solid electrolyte body. The all-solid-state battery according to any one of 1 to 4. The all-solid-state battery according to any one of claims 1 to 7, wherein the solid electrolyte body has a lithium-containing compound (4) in the particle gaps of the solid electrolyte particles. The all-solid-state battery according to claim 8, wherein the lithium-containing compound is a lithium boron-containing oxide. The all-solid-state battery according to any one of claims 1 to 9, wherein the solid electrolyte body has an electron conductive substance (5) on a surface exposed to the pores (23) of the porous body.

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