WO2013069083A1

WO2013069083A1 - All-solid-state battery

Info

Publication number: WO2013069083A1
Application number: PCT/JP2011/075614
Authority: WO
Inventors: 達哉古賀; 元長谷川; 杉浦　功一; 敬介大森
Original assignee: トヨタ自動車株式会社
Priority date: 2011-11-07
Filing date: 2011-11-07
Publication date: 2013-05-16

Abstract

The present invention addresses the problem of providing an all-solid-state battery which has low battery resistance and high capacity. The present invention solves the above-described problem by providing an all-solid-state battery, which comprises a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer that is formed between the positive electrode active material layer and the negative electrode active material layer, and which is characterized in that: the positive electrode active material layer contains a positive electrode active material and a solid electrolyte material; the ratio of the positive electrode active material relative to the total of the positive electrode active material and the solid electrolyte material is larger than 50% by volume; and the ratio of the average particle diameter of the positive electrode active material relative to that of the solid electrolyte material is not less than 0.9.

Description

All solid battery

The present invention relates to an all solid state battery having low battery resistance and high capacity.

For example, since lithium secondary batteries have high electromotive force and high energy density, they are widely used in the fields of information-related equipment and communication equipment. On the other hand, in the field of automobiles, development of electric vehicles and hybrid vehicles has been urgently caused by environmental problems and resource problems, and lithium secondary batteries are also being studied as power sources for these.

Since lithium secondary batteries currently on the market use an electrolyte containing a flammable organic solvent, they are equipped with a safety device that prevents the temperature rise during short-circuiting and in terms of structure and materials for short-circuit prevention. Improvement is needed. In contrast, an all-solid lithium secondary battery in which the electrolyte solution is changed to a solid electrolyte layer to make the battery all solid does not use a flammable organic solvent in the battery, so the safety device can be simplified and manufactured. It is considered to be excellent in cost and productivity.

Such an all-solid battery generally has a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. For example, Patent Document 1 includes a positive electrode active material that is at least one of LiCoO ₂ and LiNiO ₂ and a sulfide solid electrolyte material, and the average particle size of the positive electrode active material is in the range of 1 to 5 μm. A positive electrode layer forming material in which the volume fraction of the active material is in the range of 37 to 42 vol% is disclosed. This technique aims to improve lithium ion conductivity while maintaining good electron conductivity.

JP 2009-238636 A

From the viewpoint of improving the energy density of the battery, the proportion of the positive electrode active material contained in the positive electrode active material layer is preferably higher. On the other hand, for example, in Example 1 of Patent Document 1, a positive electrode active material layer in which the volume ratio of the positive electrode active material is 40 vol%, the average particle size of the positive electrode active material is 4 μm, and the average particle size of the sulfide solid electrolyte material is 7 μm. However, in this case, if only the volume ratio of the positive electrode active material is simply increased, there is a problem that the battery resistance increases and the capacity decreases. The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide an all solid state battery having low battery resistance and high capacity.

In order to achieve the above object, in the present invention, a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer are all included. In the solid battery, the positive electrode active material layer contains a positive electrode active material and a solid electrolyte material, and the ratio of the positive electrode active material to the total of the positive electrode active material and the solid electrolyte material is greater than 50% by volume, Provided is an all-solid battery characterized in that an average particle diameter ratio of the positive electrode active material to a solid electrolyte material is 0.9 or more.

According to the present invention, in the positive electrode active material layer, since the volume ratio of the positive electrode active material and the average particle diameter ratio of the positive electrode active material to the solid electrolyte material are in a specific range, the battery resistance is low and the capacity is reduced. A high all-solid-state battery can be obtained.

In the above invention, the positive electrode active material preferably has an average particle size of 20 μm or less, and the solid electrolyte material preferably has an average particle size of 18 μm or less. This is because lower resistance and higher capacity can be achieved.

In the above invention, it is preferable that an average particle diameter of the positive electrode active material is 5 μm or less and an average particle diameter of the solid electrolyte material is 3 μm or less. This is because the contact area (reaction area) between the positive electrode active material and the solid electrolyte material can be increased, and further reduction in resistance and increase in capacity can be achieved.

In the above invention, the solid electrolyte material preferably has an average particle size of 0.8 μm or more. This is because a decrease in ionic conductivity due to an increase in grain boundary resistance can be suppressed.

In the above invention, the average particle size ratio of the positive electrode active material to the solid electrolyte material is preferably 1.6 or more.

In the present invention, it is possible to provide an all-solid battery having a low battery resistance and a high capacity.

It is a schematic sectional drawing which shows an example of the all-solid-state battery of this invention. 3 is a result of battery capacity evaluation for the batteries obtained in Examples 1 to 4 and Comparative Examples 1 to 5. FIG. 3 is a result of battery resistance evaluation (1C discharge) for the batteries obtained in Examples 1 to 4 and Comparative Examples 1 to 5. FIG. 3 shows the results of battery capacity evaluation for the batteries obtained in Examples 5 to 9 and Comparative Example 6. FIG. 6 is a result of battery resistance evaluation (1C discharge) for the batteries obtained in Examples 5 to 9 and Comparative Example 6. FIG. FIG. 6 is a result of battery resistance evaluation (10C discharge) for the batteries obtained in Examples 5 to 9 and Comparative Example 6. FIG.

Hereinafter, the all solid state battery of the present invention will be described in detail.

An all solid state battery of the present invention is an all solid state battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. The positive electrode active material layer contains a positive electrode active material and a solid electrolyte material, and the ratio of the positive electrode active material to the total of the positive electrode active material and the solid electrolyte material is greater than 50% by volume. The average particle size ratio of the positive electrode active material is 0.9 or more.

FIG. 1 is a schematic sectional view showing an example of the all solid state battery of the present invention. An all-solid battery 10 in FIG. 1 includes a positive electrode active material layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3 formed between the positive electrode active material layer 1 and the negative electrode active material layer 2, and a solid electrolyte layer 3. A positive electrode current collector 4 formed on the surface of the negative electrode active material layer 1 opposite to the solid electrolyte layer 3, a negative electrode current collector 5 formed on the surface of the negative electrode active material layer 2 opposite to the solid electrolyte layer 3, Have The positive electrode active material layer 1 contains a positive electrode active material (for example, an oxide active material) and a solid electrolyte material (for example, a sulfide solid electrolyte material), and the volume ratio of the positive electrode active material and the positive electrode active material with respect to the solid electrolyte material. The average particle size ratio is in a specific range.

According to the present invention, in the positive electrode active material layer, since the volume ratio of the positive electrode active material and the average particle diameter ratio of the positive electrode active material to the solid electrolyte material are in a specific range, the battery resistance is low and the capacity is reduced. A high all-solid-state battery can be obtained. That is, in the positive electrode active material layer, when the volume ratio of the positive electrode active material is higher than the volume ratio of the solid electrolyte material, the average particle size ratio is adjusted to a specific value or more to increase the capacity of the all solid state battery. Can be planned.

As described above, for example, in Example 1 of Patent Document 1, the positive electrode active material has a volume ratio of 40 vol%, the positive electrode active material has an average particle diameter of 4 μm, and the sulfide solid electrolyte material has an average particle diameter of 7 μm. Although an active material layer is described, in this case, if only the volume ratio of the positive electrode active material is simply increased, there is a problem that battery resistance increases and capacity decreases. The reason is considered as follows. That is, when the average particle size ratio (positive electrode active material / solid electrolyte material) is low and the volume ratio of the positive electrode active material is simply increased, (i) the ion conduction path in the positive electrode active material layer becomes thin (or (Ii) a problem that the contact area between the positive electrode active material and the solid electrolyte material becomes small. Regarding (i), it is considered that when the ion conduction path is shortened, the supply of metal ions to and from the reaction site where metal ions are inserted into and desorbed from the positive electrode active material becomes rate-determined, battery resistance increases, and capacity decreases. Furthermore, since the active material isolated by interruption of the ion conduction path is not involved in the reaction, it is considered that the capacity is also reduced by this factor. Regarding (ii), it is considered that when the contact area is small, the number of reaction points at which metal ions are inserted into and desorbed from the positive electrode active material is decreased, battery resistance is increased, and capacity is decreased. If both the positive electrode active material and the solid electrolyte material have a predetermined hardness and the positive electrode active material layer is not pressed into the fine gaps between the particles even if the positive electrode active material layer is pressed, (ii) It is thought that the effect appears prominently.

On the other hand, in this invention, the ion conduction path in a positive electrode active material layer is ensured by making the said average particle diameter ratio more than a specific value. As a result, it is considered that the battery resistance decreases and the capacity increases. Moreover, the contact area of a positive electrode active material and a solid electrolyte material becomes large by making the said average particle diameter ratio more than a specific value. As a result, it is considered that the reaction points at which metal ions are inserted into and desorbed from the positive electrode active material increase, the battery resistance decreases, and the capacity increases. In addition, it was confirmed by observing the cross section of a positive electrode active material layer that the ion conduction path was ensured and the contact area increased.
Hereinafter, the all solid state battery of the present invention will be described for each configuration.

1. Positive electrode active material layer The positive electrode active material layer in the present invention is a layer containing at least a positive electrode active material and a solid electrolyte material. In the positive electrode active material layer in the present invention, the ratio of the positive electrode active material to the total of the positive electrode active material and the solid electrolyte material is usually larger than 50% by volume, preferably 55% by volume or more, and preferably 60% by volume or more. It is more preferable. This is because if the volume ratio is too small, the energy density may not be sufficiently improved. On the other hand, the ratio is not particularly limited, but is preferably 95% by volume or less, more preferably 90% by volume or less, and still more preferably 85% by volume or less. This is because if the volume ratio is too large, the ion conduction path may not be sufficiently secured.

In the positive electrode active material layer of the present invention, the average particle size ratio of the positive electrode active material to the solid electrolyte material is usually 0.9 or more, preferably 1 or more, and preferably 1.6 or more. More preferred. This is because if the average particle size ratio is too small, the ion conduction path and the contact area between the two may not be sufficiently secured. On the other hand, the average particle diameter ratio is not particularly limited, but is preferably 20 or less, more preferably 15 or less, and still more preferably 10 or less, for example. If the average particle size ratio is too large, the contact area between the two may decrease due to the large particle size of the positive electrode active material, or the grain boundary due to the small particle size of the solid electrolyte material. This is because the resistance may increase. Here, the average particle size ratio can be calculated by dividing the average particle size of the positive electrode active material by the average particle size of the solid electrolyte material. The average and particle size is usually refers to the average particle diameter D ₅₀ was measured with a particle size distribution measurement, a value calculated by a scanning electron microscope (SEM) may be an average particle diameter. In the calculation by SEM, the longest diameter and the shortest diameter of particles (n ≧ 100) of the solid electrolyte material are measured, and the average value is obtained.

The average particle diameter of the positive electrode active material is not particularly limited, but is preferably, for example, 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less. This is because if the average particle diameter of the positive electrode active material is too large, there is a possibility that a sufficient contact area between the positive electrode active material and the solid electrolyte material cannot be secured. In particular, when the average particle diameter of the positive electrode active material is 5 μm or less, as will be described in Examples described later, an all-solid battery capable of increasing discharge capacity and capable of high-rate discharge can be obtained. On the other hand, the average particle size of the positive electrode active material is, for example, preferably 0.1 μm or more, and more preferably 2 μm or more. This is because if the average particle diameter of the positive electrode active material is too small, the grain boundaries increase and the grain boundary resistance increases.

The average particle size of the solid electrolyte material is not particularly limited, but is preferably, for example, 18 μm or less, more preferably 8 μm or less, and further preferably 3 μm or less. This is because if the average particle size of the solid electrolyte material is too large, there is a possibility that a sufficient contact area between the solid electrolyte material and the positive electrode active material cannot be secured. In particular, when the average particle size of the solid electrolyte material is 3 μm or less, as will be described later in Examples, the discharge capacity is increased, and an all-solid battery capable of high rate discharge can be obtained. On the other hand, the average particle size of the solid electrolyte material is preferably 0.01 μm or more, for example, preferably 0.1 μm or more, and more preferably 0.8 μm or more. This is because the grain boundary resistance may increase if the average particle size of the solid electrolyte material is too small.

Although the positive electrode active material in this invention is not specifically limited, For example, an oxide active material and a sulfide active material can be mentioned. For example, as an oxide active material used as a positive electrode active material of an all-solid-state lithium battery, a rock salt layer type such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ Active material, spinel type active material such as LiMn ₂ O ₄ and Li (Ni _0.5 Mn _1.5 ) O ₄ , reverse spinel type active material such as LiNiVO ₄ and LiCoVO ₄ , LiFePO ₄ , LiMnPO ₄ , LiCoPO ₄ , olivine active material LiNiPO ₄ _etc., can be cited _{_{Li 2 FeSiO 4, Li 2 MnSiO}} Si -containing active material such as _4. Further, as an oxide active material, a rock salt layer shape in which a part of transition metal is substituted with a different metal, such as LiNi _0.8 Co _(0.2-x) Al _x O ₂ (0 <x <0.2). Type active material, Li _{1 + x} Mn _2-xy M _y O ₄ (M is at least one of Al, Mg, Co, Fe, Ni, Zn, and 0 <x + y <2). A spinel active material whose part is replaced with a different metal, or lithium titanate such as Li ₄ Ti ₅ O ₁₂ may be used. On the other hand, examples of the sulfide active material include copper chevrel, iron sulfide, cobalt sulfide, nickel sulfide and the like.

A coat layer is preferably formed on the surface of the positive electrode active material. This is because, for example, the generation of the high resistance layer due to the reaction between the oxide active material and the sulfide solid electrolyte material can be suppressed. Examples of the material for the coating layer include an oxide material having ion conductivity. Specifically, lithium niobate (LiNbO ₃ ), lithium titanate (for example, Li ₄ Ti ₅ O ₁₂ ), lithium phosphate (Li ₃ PO ₄ ), LATP (for example Li _1.5 Al _0.5 Ti _1.5 (PO ₄ ) ₃ ), LAGP (for example Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ ) , Li ₂ WO ₄ , Li ₂ ZrO ₃ , Li ₄ SiO ₄ , Li ₂ CO ₃ , Li ₂ BO _{2 and the} like. In addition, metal oxides (metal oxides not containing Li) such as ZrO ₂ , Al ₂ O ₃ , HgO, WO ₃ , BaTiO ₃ , and Pb (Zr, Ti) O ₃ are present on the surface of the positive electrode active material. You may do it. This is because the resistance can be further reduced.

The solid electrolyte material in the present invention is not particularly limited, and examples thereof include a sulfide solid electrolyte material and an oxide solid electrolyte material. The sulfide solid electrolyte material is preferable in that it has a higher ion conductivity than the oxide solid electrolyte material, and the oxide solid electrolyte material has higher chemical stability than the sulfide solid electrolyte material. This is preferable. In addition, the solid electrolyte material in the present invention may be an amorphous material or a crystalline material. The amorphous material can be obtained, for example, by applying a mechanical milling method or a melt quenching method to the raw material composition. The crystalline material can be obtained, for example, by applying a solid phase method to the raw material composition. In the present invention, a material (glass ceramic) obtained by heat-treating an amorphous material at a temperature equal to or higher than the crystallization temperature may be used as the solid electrolyte material.

Examples of the sulfide solid electrolyte material having Li ion conductivity include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₅ —LiI, Li ₂ S—P ₂ S ₅ —LiCl, and Li ₂ S. _{_{_{_{-P 2 S 5 -LiBr, Li 2}}}} S-P 2 S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2, Li 2 S-SiS 2 - LiI, Li ₂ S—SiS ₂ —LiBr, Li ₂ S—SiS ₂ —LiCl, Li ₂ S—SiS ₂ —B ₂ S ₃ —LiI, Li ₂ S—SiS ₂ —P ₂ S ₅ —LiI, Li ₂ _{_{_{_{S-B 2 S 3, Li}}}} 2 S-P 2 S 5 -Z m S n ( however, m, n is the number of positive .Z is, Ge, Zn, one of _{Ga.), Li 2 S-} GeS _{_{_{_{2, Li 2 S-SiS 2}}}} -Li 3 PO 4, Li 2 S- iS ₂ -Li _x MO _y (provided that, x, y is a positive number .M is, P, Si, Ge, B , Al, Ga, either an _In.), be mentioned Li ₁₀ GeP _{2 S 12} or the like Can do. On the other hand, examples of the oxide solid electrolyte material having Li ion conductivity include Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—SiO ₂ , LiLaTaO (eg, Li ₅ La ₃ Ta ₂ O _12). ), LiLaZrO (eg, Li ₇ La ₃ Zr ₂ O ₁₂ ), LiBaLaTaO (eg, Li ₆ BaLa ₂ Ta ₂ O ₁₂ ), Li _{1 + x} Si _x P _1-x O ₄ (0 ≦ x <1, eg, Li _3.6 Si _0.6 P _0.4 O ₄ ), Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), Li ₃ PO _{(4-3 / 2x)} N _x (0 ≦ x <1), and the like. In the present invention, LiI and Li ₃ N can be used as other solid electrolyte materials.

In particular, in the present invention, the sulfide solid electrolyte material is a raw material composition containing Li ₂ S and a sulfide of A (A is at least one of P, Si, Ge, Al, and B). It is preferable to use it. The raw material composition may further contain a halogen compound. Examples of the sulfide of A include P ₂ S ₃ , P ₂ S ₅ , SiS ₂ , GeS ₂ , Al ₂ S ₃ , B ₂ S _{3 and the} like. Examples of the halogen compound include LiF, LiPF ₆ , LiCl, LiBr, LiI, and the like, and LiI is preferable.

The sulfide solid electrolyte material has an ortho-composition anion structure (PS ₄ ^3- structure, SiS ₄ ^4- structure, GeS ₄ ^4- structure, AlS ₃ ^3- structure, BS ₃ ^3- structure) as a main component. It is preferable to have. This is because a sulfide solid electrolyte material having high chemical stability can be obtained. The ratio of the anion structure of the ortho composition is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, based on the total anion structure in the ion conductor, 90 mol % Or more is particularly preferable. The ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, NMR, XPS, or the like.

Here, ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present invention, the crystal composition in which Li ₂ S is added most in the sulfide is called the ortho composition. For example, in the Li ₂ S—P ₂ S ₅ system, Li ₃ PS ₄ corresponds to the ortho composition, in the Li ₂ S—Al ₂ S ₃ system, Li ₃ AlS ₃ corresponds to the ortho composition, and Li ₂ S—B ₂ In the S ₃ system, Li ₃ BS ₃ corresponds to the ortho composition, in the Li ₂ S—SiS ₂ system, Li ₄ SiS ₄ corresponds to the ortho composition, and in the Li ₂ S—GeS ₂ system, Li ₄ GeS _{4 corresponds} to the ortho composition. Applicable.

For example, in the case of the Li ₂ S—P ₂ S ₅ system, the ratio of Li ₂ S and P ₂ S ₅ to obtain the ortho composition is Li ₂ S: P ₂ S ₅ = 75: 25 on a molar basis. The same applies to the Li ₂ S—Al ₂ S ₃ system and the Li ₂ S—B ₂ S ₃ system. On the other hand, in the case of the Li ₂ S—SiS ₂ system, the ratio of Li ₂ S and SiS ₂ for obtaining the ortho composition is Li ₂ S: SiS ₂ = 66.7: 33.3 on a molar basis. The same applies to the case of the Li ₂ S—GeS ₂ system.

The raw material composition is, when containing Li ₂ S and _P 2 _{S 5,} the proportion of Li ₂ S to the total of Li ₂ S and _P 2 _{S 5} is preferably in the range of 70 mol% ~ 80 mol% 72 mol% to 78 mol% is more preferable, and 74 mol% to 76 mol% is more preferable. Incidentally, the raw material composition is, when containing Li ₂ S and _Al 2 _{S 3,} which is the same when containing Li ₂ S and _B 2 _{S 3.} On the other hand, the raw material composition is, when containing Li ₂ S and SiS _2, the ratio of Li ₂ S to the total of Li ₂ S and SiS ₂ is in the range of 62.5mol% ~ 70.9mol% Is more preferable, within the range of 63 mol% to 70 mol%, more preferably within the range of 64 mol% to 68 mol%. The same applies when the raw material composition contains Li ₂ S and GeS ₂ .

When the raw material composition contains a halogen compound, the proportion of the halogen compound in the raw material composition is preferably in the range of 1 mol% to 60 mol%, and preferably in the range of 5 mol% to 40 mol%. More preferably, it is more preferably in the range of 10 mol% to 40 mol%.

The positive electrode active material layer in the present invention is a layer containing at least the positive electrode active material and the solid electrolyte material, and may contain only the positive electrode active material layer and the solid electrolyte material, and at least of the conductive material and the binder. One may be further contained. The total ratio of the positive electrode active material and the solid electrolyte material in the positive electrode active material layer is, for example, 80% by weight or more, preferably 85% by weight or more, and more preferably 90% by weight or more. The total may be 100% by weight.

The positive electrode active material layer may further contain a conductive material. By adding a conductive material, the electronic conductivity of the positive electrode active material layer can be improved. Examples of the conductive material include carbon materials such as acetylene black (AB), ketjen black (KB), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), and carbon nanofiber (CNF). it can. The positive electrode active material layer may further contain a binder. By adding a binder, flexibility can be imparted to the positive electrode active material layer. Examples of the binder include butylene rubber, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and the like. In addition, the thickness of the positive electrode active material layer varies depending on the type of the target battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.

2. Negative electrode active material layer The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and further contains at least one of a solid electrolyte material, a conductive material and a binder as necessary. Also good.

Although the negative electrode active material in this invention is not specifically limited, For example, a carbon active material, a metal active material, an oxide active material etc. can be mentioned. Examples of the carbon active material include graphite such as mesocarbon microbeads (MCMB) and highly oriented graphite (HOPG), and amorphous carbon such as hard carbon and soft carbon. Examples of the metal active material include In, Al, Si, Sn, and alloys containing at least one of these elements. As oxide active material may include, for example _{_{_{_{Nb 2 O 5, Li 4 Ti}}}} 5 O 12, SiO and the like.

Examples of the shape of the negative electrode active material include a particle shape and a film shape. The average particle size of the particulate negative electrode active material is preferably in the range of 0.1 μm to 50 μm, for example. The method for obtaining the average particle diameter is as described above. In addition, the content of the negative electrode active material in the negative electrode active material layer is preferably in the range of, for example, 10% by weight to 99% by weight, and more preferably in the range of 20% by weight to 90% by weight.

The negative electrode active material layer preferably contains a solid electrolyte material, and more preferably contains a sulfide solid electrolyte material. This is because the ion conductivity in the negative electrode active material layer can be improved. In addition, since it is the same as that of the content described in said "1. positive electrode active material layer" about solid electrolyte material, description here is abbreviate | omitted. The content of the solid electrolyte material in the negative electrode active material layer is, for example, preferably in the range of 1% by weight to 90% by weight, and more preferably in the range of 10% by weight to 80% by weight.

The negative electrode active material layer may further contain a conductive material. The negative electrode active material layer may further contain a binder. The conductive material and the binder are the same as those described in “1. Cathode active material layer”, and are not described here. In addition, the thickness of the negative electrode active material layer varies depending on the type of the target battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.

3. Solid electrolyte layer The solid electrolyte layer in the present invention is a layer containing at least a solid electrolyte material. The solid electrolyte material is the same as the contents described in “1. Positive electrode active material layer”, and therefore the description thereof is omitted here.

The content of the solid electrolyte material in the solid electrolyte layer is, for example, preferably 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more. The solid electrolyte layer may contain a binder or may be composed only of a solid electrolyte material. The thickness of the solid electrolyte layer varies greatly depending on the configuration of the battery. For example, the thickness is preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm.

4). Other Configurations The all solid state battery of the present invention has at least the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material layer. Examples of the material for the positive electrode current collector include SUS, nickel, chromium, gold, platinum, aluminum, iron, titanium, zinc, and carbon. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, iron, titanium, cobalt, zinc, and carbon. In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the battery. Moreover, a general battery case can be used for the battery case used for this invention, For example, the battery case made from SUS, the battery case made from aluminum, an aluminum laminated foil etc. can be mentioned.

5. All-solid battery Examples of the all-solid battery of the present invention include an all-solid lithium battery, an all-solid sodium battery, an all-solid magnesium battery, an all-solid calcium battery, and the like. Among these, an all-solid lithium battery is preferable. The all solid state battery of the present invention may be a primary battery or a secondary battery, but is preferably a secondary battery. This is because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery. In addition, examples of the shape of the all solid state battery of the present invention include a coin type, a laminate type, a cylindrical type, and a square type. Moreover, the manufacturing method of the all-solid-state battery of this invention will not be specifically limited if it is a method which can obtain the all-solid-state battery mentioned above.

Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

The present invention will be described more specifically with reference to the following examples.

[Example 1]
(Synthesis of sulfide solid electrolyte materials)
As starting materials, lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and lithium iodide (LiI) were used. Next, Li ₂ S and P ₂ S ₅ were weighed so as to have a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Next, LiI was weighed so that the LiI ratio was 30 mol%. The weighed starting materials were mixed in an agate mortar for 5 minutes, 2 g of the mixture was charged into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (water content of 30 ppm or less, 4 g) was charged, and ZrO _{2 was} further added. A ball (φ = 5 mm, 53 g) was charged, and the container was completely sealed. This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed for 40 hours at a base plate rotation speed of 500 rpm. Then, heptane was removed by drying at 100 ° C. to obtain a sulfide glass. 0.5 g of the obtained sulfide glass was put in a glass tube in an Ar atmosphere, and the glass tube was put in a SUS sealed container. The sealed container was heat treated at 190 ° C. for 10 hours to obtain a sulfide solid electrolyte material (sulfide glass ceramic). The resulting sulfide solid electrolyte material, stainless steel mesh sieve was classified with an average particle diameter _{D 50} was obtained 6.7 .mu.m, 16.3, a sulfide solid electrolyte material 34.8Myuemu.

(Production of battery)
A composition prepared by dissolving equimolar LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₅ in an ethanol solvent was prepared as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (manufactured by Nichia Corporation). ) Was spray coated using a tumbling fluidized coating apparatus (SFP-01, manufactured by POWREC Co., Ltd.). Thereafter, the coated LiNi _1/3 Co _1/3 Mn _1/3 O ₂ was heat-treated at 350 ° C. under atmospheric pressure for 1 hour, and LiNbO ₃ coated LiNi _1/3 Co _1/3. Mn _1/3 O ₂ was obtained. The obtained positive electrode active material, stainless steel mesh sieve classified was used to adjust the average particle diameter D ₅₀ at a predetermined value.

Next, 224.9 mg of the positive electrode active material (average particle size D ₅₀ = 16 μm), 3.0 mg of a conductive material (VGCF, manufactured by Showa Denko), and the sulfide solid electrolyte material (average particle size D ₅₀ = 6) (7 μm) and 75.1 mg were added to 10 g of dehydrated heptane (manufactured by Kanto Chemical Co., Ltd.) and mixed well. Thereafter, dehydrated heptane was removed by drying to obtain a positive electrode mixture. The volume ratio of the positive electrode active material and the sulfide solid electrolyte material in the positive electrode mixture was positive electrode active material: sulfide solid electrolyte material = 60: 40.

Next, negative electrode active material (natural graphite-based carbon, manufactured by Mitsubishi Chemical Corporation, average particle diameter D ₅₀ = 10 μm) 9.06 mg, and the sulfide solid electrolyte material (average particle diameter D ₅₀ = 16.3 μm) 8.24 mg, Were mixed to obtain a negative electrode mixture.

Then, 1 cm ² of the mold in the sulfide solid electrolyte material (average particle diameter _D 50 = _34.8μm) was added 65 mg, was pressed at a pressure of 1 ton / cm ^2, to form a solid electrolyte layer. 20.5 mg of the positive electrode mixture was added to one surface of the obtained solid electrolyte layer and pressed at a pressure of 1 ton / cm ² to form a positive electrode active material layer. Next, 17.0 mg of the negative electrode mixture was added to the other surface of the solid electrolyte layer and pressed at a pressure of 4 ton / cm ² to form a negative electrode active material layer. A battery was produced using the obtained power generation element.

[Examples 2 and 3, Comparative Examples 1 to 3]
A battery was fabricated in the same manner as in Example 1 except that the conditions such as the average particle diameter of the positive electrode active material and the sulfide solid electrolyte material were changed as shown in Table 1.

[Example 4]
281.3 mg of the positive electrode active material (average particle size D ₅₀ = 16 μm) used in Example 1, 3.3 mg of a conductive material (VGCF, manufactured by Showa Denko), and the sulfide solid electrolyte material (average particle size D ₅₀₎ = 6.7 μm) and 46.9 mg were added to 10 g of dehydrated heptane (manufactured by Kanto Chemical) and mixed well. Thereafter, dehydrated heptane was removed by drying to obtain a positive electrode mixture. In addition, the volume ratio of the positive electrode active material and the sulfide solid electrolyte material in the positive electrode mixture was positive electrode active material: sulfide solid electrolyte material = 75: 25.

Then, 1 cm ² of the mold in the sulfide solid electrolyte material (average particle diameter _D 50 = _34.8μm) was added 65 mg, was pressed at a pressure of 1 ton / cm ^2, to form a solid electrolyte layer. 17.7 mg of the positive electrode mixture was added to one surface of the obtained solid electrolyte layer and pressed at a pressure of 1 ton / cm ² to form a positive electrode active material layer. Next, 17.0 mg of the negative electrode mixture used in Example 1 was added to the other surface of the solid electrolyte layer, and pressed at a pressure of 4 ton / cm ² to form a negative electrode active material layer. A battery was produced using the obtained power generation element.

[Comparative Examples 4 and 5]
A battery was fabricated in the same manner as in Example 4 except that the conditions such as the average particle diameter of the positive electrode active material and the sulfide solid electrolyte material were changed as shown in Table 2.

[Evaluation 1]
(1) Battery capacity evaluation The batteries obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were charged with a constant current to 4.55 V at a 10-hour rate (0.1 C, 0.304 mA). Thereafter, the operation was stopped for 15 minutes, and a constant current was discharged to 3.0 V at a 10-hour rate (0.1 C, 0.304 mA), and the discharge capacity was determined.

(2) Battery resistance evaluation The batteries obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were charged with a constant current-constant voltage (end current 0.015 mA) up to 3.6V. Thereafter, the operation was stopped for 15 minutes, and constant current discharge was performed for 5 seconds at a rate of 1 hour (1C, 3.04 mA). The battery resistance was obtained from the voltage drop and current value at this time (R = ΔV / I).

Also, the relationship between the average particle size ratio (A / B) and the discharge capacity is shown in FIG. As shown in FIG. 2, when the average particle size ratio (A / B) was 0.9 or more, the discharge capacity increased. Moreover, the relationship between average particle diameter ratio (A / B) and battery resistance is shown in FIG. As shown in FIG. 3, when the average particle size ratio (A / B) was 0.9 or more, the battery resistance decreased.

[Example 5]
The resulting sulfide solid electrolyte material in Example 1 (sulfide glass ceramics), stainless steel mesh sieve was classified with an average particle diameter D ₅₀ was obtained 6.7 .mu.m, a sulfide solid electrolyte material of 16 [mu] m. Also, the sulfide solid electrolyte material obtained in Example 1 (sulfide glass ceramics), and pulverized in a ball mill, 0.8 [mu] m average particle diameter _{D 50,} 1.5 [mu] m, 2.5 [mu] m sulfide solid electrolyte material Got.

Next, in a polypropylene (PP) container, the positive electrode active material (average particle size D ₅₀ = 4 μm), the sulfide solid electrolyte material (average particle size D ₅₀ = 0.8 μm), a conductive material (VGCF, Showa) Denko), a binder (5% by weight heptane solution of butylene rubber binder) and dehydrated heptane were added. Next, the PP container is stirred for 30 seconds with an ultrasonic dispersion apparatus (SMH, UH-50), and then the PP solution is stirred for 3 minutes with a shaker (Shiba Chemical Co., Ltd., TTM-1). Shake it. The obtained composition was coated on a carbon coated Al foil (Showa Denko, SDX) by a blade method using an applicator. Then, it dried for 30 minutes on a 100 degreeC hotplate, and obtained the positive electrode. The volume ratio of the positive electrode active material and the sulfide solid electrolyte material in the positive electrode mixture was positive electrode active material: sulfide solid electrolyte material = 60: 40.

Next, in a polypropylene (PP) container, a negative electrode active material (natural graphite-based carbon, manufactured by Mitsubishi Chemical, average particle size D ₅₀ = 10 μm), the sulfide solid electrolyte material (average particle size D ₅₀ = 2.5 μm) Then, a binder (5% by weight heptane solution of butylene rubber-based binder) and dehydrated heptane were added. Next, the PP container is stirred for 30 seconds with an ultrasonic dispersing device (SMH, UH-50), and then the PP solution is stirred for 30 minutes with a shaker (Shiba Chemical Co., Ltd., TTM-1). Shake it. The obtained composition was coated on Cu foil by a blade method using an applicator. Then, it dried for 30 minutes on a 100 degreeC hotplate, and obtained the negative electrode.

Next, the above-mentioned sulfide solid electrolyte material (average particle diameter D ₅₀ = 2.5 μm), binder (a 5 wt% heptane solution of butylene rubber binder) and dehydrated heptane are placed in a polypropylene (PP) container. Added. Next, the PP container is stirred for 30 seconds with an ultrasonic dispersing device (SMH, UH-50), and then the PP solution is stirred for 30 minutes with a shaker (Shiba Chemical Co., Ltd., TTM-1). Shake it. The obtained composition was coated on an Al foil by a blade method using an applicator. Then, it dried for 30 minutes on a 100 degreeC hotplate, and obtained the solid electrolyte layer on Al foil.

Next, the solid electrolyte layer is disposed in a mold of 1 cm ^2, it was pressed under a pressure of 1 ton / cm ^2. The positive electrode was placed on one surface of the obtained solid electrolyte layer and pressed at a pressure of 1 ton / cm ² . Next, the negative electrode was placed on the other surface of the solid electrolyte layer and pressed at a pressure of 4 ton / cm ² to form a negative electrode active material layer. A battery was produced using the obtained power generation element.

[Examples 6 to 9, Comparative Example 6]
A battery was fabricated in the same manner as in Example 5 except that the conditions such as the average particle diameter of the positive electrode active material and the sulfide solid electrolyte material were changed as shown in Table 3.

[Evaluation 2]
(1) Battery capacity evaluation The batteries obtained in Examples 5 to 9 and Comparative Example 6 were charged at a constant current-constant voltage to 4.55 V at a 10-hour rate (0.1 C). Thereafter, it was paused for 15 minutes, and a constant current was discharged to 3.0 V at a 10-hour rate (0.1 C) to determine the discharge capacity.

(2) Battery resistance evaluation The batteries obtained in Examples 5 to 9 and Comparative Example 6 were charged with a constant current-constant voltage up to 3.6 V (end current 0.015 mA). Thereafter, the operation was stopped for 15 minutes, and a constant current discharge was performed at a rate of 1 hour (1C) for 5 seconds. Similarly, constant current discharge was performed for 5 seconds at a rate of 0.1 hour (10 C). The battery resistance was obtained from the voltage drop and current value at this time (R = ΔV / I).

Also, the relationship between the average particle size ratio (A / B) and the discharge capacity is shown in FIG. As shown in FIG. 4, when the average particle size ratio (A / B) is 0.9 or more, the discharge capacity is increased. In Examples 5 to 7, the discharge capacity was higher than that in Examples 8 and 9. FIG. 5 shows the relationship between the average particle size ratio (A / B) and the battery resistance in 1C discharge. As shown in FIG. 5, when the average particle size ratio (A / B) was 0.9 or more, the battery resistance was low. In Examples 5 to 7, the battery resistance was further reduced as compared with Examples 8 and 9. FIG. 6 shows the relationship between the average particle size ratio (A / B) and the battery resistance in 10C discharge. As shown in FIG. 6 and Table 3, in Examples 8 and 9 and Comparative Example 6, the resistance was too high to be measured, whereas in Examples 5 to 7, the resistance was as low as measurable. there were.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 10 ... All-solid-state battery

Claims

An all solid state battery comprising a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer,
The positive electrode active material layer contains a positive electrode active material and a solid electrolyte material,
The ratio of the positive electrode active material to the total of the positive electrode active material and the solid electrolyte material is greater than 50% by volume,
An all-solid-state battery, wherein an average particle diameter ratio of the positive electrode active material to the solid electrolyte material is 0.9 or more.
2. The all-solid-state battery according to claim 1, wherein an average particle diameter of the positive electrode active material is 20 μm or less, and an average particle diameter of the solid electrolyte material is 18 μm or less.
3. The all-solid-state battery according to claim 1, wherein the positive electrode active material has an average particle size of 5 μm or less, and the solid electrolyte material has an average particle size of 3 μm or less.
The all-solid-state battery according to any one of claims 1 to 3, wherein an average particle size of the solid electrolyte material is 0.8 µm or more.
The all-solid-state battery according to any one of claims 1 to 4, wherein an average particle diameter ratio of the positive electrode active material to the solid electrolyte material is 1.6 or more.