JP2020087882A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery having good cycle characteristics.SOLUTION: The problem is solved by providing an all-solid battery in this disclosure, which comprises: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer formed between the positive and negative electrode layers. In the all-solid battery, the negative electrode layer contains a Si-based active material. The Si-based active material contains secondary particles having primary particles. When the volume of the secondary particle is represented by V, and the pore volume of the secondary particle is V, the ratio (V/V) of Vto Vis 0.3 or more and 0.6 or less. The Si-based active material contains a needle-like conductive material among the primary particles.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to all-solid-state batteries.

The all-solid-state battery is a battery having a solid electrolyte layer between a positive electrode and a negative electrode, and has an advantage that a safety device can be simplified more easily than a liquid-type battery having an electrolytic solution containing a flammable organic solvent. ..

For example, Patent Document 1 discloses a lithium ion secondary battery having a negative electrode in which a Si-based active material, a conductive auxiliary agent, and a current collector are connected by a metal bond. Further, Patent Document 2 has a sulfide solid electrolyte and a negative electrode active material, and the negative electrode active material is a composite particle having a carbon material containing Si or Sn, and the particle diameter of Si or Sn is 94 nm or less. , A negative electrode for an all-solid-state battery in which the negative electrode active material has a particle size of 15 μm or less and the negative electrode has a porosity of 5% to 30%.

JP, 2010-21848, A JP, 2017-054720, A

Since the Si-based active material has a large volume change during charge/discharge, the resistance tends to increase each time the charge/discharge cycle is repeated. The present disclosure has been made in view of the above circumstances, and its main object is to provide an all-solid-state battery having good cycle characteristics.

In order to solve the above problems, in the present disclosure, a positive electrode layer, a negative electrode layer, an all-solid battery having a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, the negative electrode layer Contains a Si-based active material, the Si-based active material is a secondary particle having a plurality of primary particles, the volume of the secondary particle is V _P, and the void volume of the secondary particle is V _V when the proportion of the _{V V} with respect to the _{V P (V V / V P} ) is 0.3 or more and 0.6 or less, the Si-based active material, between said plurality of primary particles Provided is an all-solid-state battery containing a needle-shaped conductive material.

According to the present disclosure, V _V /V _P is in a specific range, and the Si-based active material contains a needle-shaped conductive material between a plurality of primary particles, whereby an all-solid-state battery having good cycle characteristics. Can be

The all-solid-state battery according to the present disclosure has the effect of having good cycle characteristics.

It is a schematic sectional drawing which shows an example of the all-solid-state battery in this indication. It is an image figure of the section of the negative electrode active material in this indication. It is a graph which showed the result of an example and a comparative example. It is the figure which showed typically the relationship of the porosity and the resistance increase rate based on the result of an Example and a comparative example.

Hereinafter, the all-solid-state battery in the present disclosure will be described in detail.

FIG. 1 is a schematic cross-sectional view showing an example of the all-solid-state battery in the present disclosure. Further, FIG. 2 is an image diagram of a cross section of the Si-based active material in the present disclosure. The all-solid-state battery 10 shown in FIG. 1 has a positive electrode layer 1, a negative electrode layer 2, and a solid electrolyte layer 3 formed between the positive electrode layer 1 and the negative electrode layer 2. Further, the all-solid-state battery 10 has a positive electrode current collector 4 that collects current from the positive electrode layer 1 and a negative electrode current collector 5 that collects current from the negative electrode layer 2. The negative electrode layer 2 contains a Si-based active material that is a secondary particle having a plurality of primary particles. Further, as shown in FIG. 2, the Si-based active material in the present disclosure contains a needle-shaped conductive material between the primary particles and has voids inside the secondary particles. When the volume of the secondary particles is V _P and the void volume of the secondary particles is V _V , V _V /V _P is in a specific range. In the present disclosure, V _V /V _P may be simply referred to as a porosity.

According to the present disclosure, the V _V /V _P is in a specific range, and the Si-based active material contains the needle-shaped conductive material between the primary particles, thereby providing an all-solid-state battery having good cycle characteristics. be able to. Specifically, a volume change of the Si-based active material is achieved by using a Si-based active material that is a secondary particle having voids at a specific ratio and by containing a needle-shaped conductive material between the primary particles. Can be suppressed, and for example, the generation of cracks between the Si-based active material and the solid electrolyte can be suppressed. As a result, an increase in resistance can be suppressed (a decrease in ionic conductivity can be suppressed), and an all-solid-state battery having good cycle characteristics can be obtained. It is presumed that the reason why the volume change of the Si-based active material can be suppressed is that the conductive material acts as a filler and contributes to the skeleton maintenance of the Si-based active material due to the needle-shaped conductive material between the plurality of primary particles. To be done.

1. Negative Electrode Layer The negative electrode layer is a layer containing at least a negative electrode active material.

The negative electrode layer contains a Si-based active material as a negative electrode active material. The Si-based active material is preferably an active material that can be alloyed with Li. Examples of the Si-based active material include simple substance of Si, Si alloy, and Si oxide. The Si alloy preferably contains the Si element as a main component. The proportion of the Si element in the Si alloy may be, for example, 50 mol% or more, 70 mol% or more, and 90 mol% or more. Examples of the Si oxide include SiO.

The Si-based active material is a secondary particle having a plurality of primary particles. Also, the volume of the secondary particles and _{V P,} the void volume of the secondary particles and _{V V,} the ratio of _{V V} for _{V P} and _{V V} / _{V P.} The value of V _V /V _P is 0.3 or more, and may be, for example, 0.35 or more, or may be 0.4 or more. On the other hand, the value of V _V /V _P is 0.6 or less, and may be, for example, 0.55 or less, or may be 0.5 or less. When the value of V V _/ V _P is too small, no longer completely absorb the expansion in the secondary particles, the resistivity is likely to increase. On the other hand, if the value of V _V /V _P is too large, the space not used in the secondary particles increases, and the primary particles may be isolated or the contact between the Si-based active material and the solid electrolyte may be easily broken.

V _V and V _P can be determined by measuring a cross-sectional image of the Si-based active material with a scanning electron microscope (SEM). In other words, V _P can be approximated as the outer surface area of the cross section of the Si-based active material, and V _V can be approximated as the void area of the cross section of the Si-based active material. One secondary particle is specified from the cross-sectional image, the outer shape area S _P is obtained from the outer shape, and the void area S _V is obtained from the void. From these values, S _V /S _P is calculated. This operation is performed for other secondary particles, and the average value of S _V /S _P is calculated. The number of samples is preferably large, for example, 20 or more, 50 or more, or 100 or more. The average value of _{S V} / S _P, is employed as the _V V / V _P.

Further, in the present disclosure, when the long side length of the primary particles is a, the short side length is b, and the ratio of b to a is b/a, the value of b/a is, for example, 0.5. It is above, and may be 0.6 or more, and may be 0.8 or more. On the other hand, the value of b/a may be 1 or less than 1. By using such primary particles, an all-solid-state battery having better cycle characteristics can be obtained.

The long side length a and the short side length b can be obtained by measuring the cross-sectional image of the primary particles. Specifically, one primary particle is specified from the cross-sectional image, a straight line is drawn in the specified region, and the longest part is defined as the long side a. On the other hand, the shortest side is the smallest length portion that is orthogonal to the long side a. B/a is calculated from these values. This operation is also performed on other primary particles, and the average value of b/a is obtained. The number of samples is preferably large, for example, 20 or more, 50 or more, or 100 or more.

The average particle diameter (D ₅₀ ) of the primary particles is not particularly limited, but is, for example, 50 nm or more, and may be 100 nm or more. On the other hand, the average particle diameter (D ₅₀ ) of the primary particles is, for example, 1 μm or less, and may be 500 nm or less.

The Si-based active material in the present disclosure contains a needle-shaped conductive material between a plurality of primary particles. The needle shape in the present disclosure refers to an elongated shape in which the length of the long side is twice or more the length of the short side. Further, the needle shape may be a linear shape or a curved shape, and can be referred to as a rod shape or a fiber shape. Further, a plurality of needle-shaped conductive materials may be entwined with each other. When such a conductive material exists between a plurality of primary particles, it plays a role of a filler, and it is possible to favorably affect the skeleton maintenance of the Si-based active material during expansion and contraction of the Si-based active material. Presumed.

The conductive material in the present disclosure is not particularly limited as long as it is needle-shaped, and examples thereof include VGCF (vapor grown carbon fiber) and CNT (carbon nanotube).

In the needle-shaped conductive material according to the present disclosure, the length of the long side is twice or more the length of the short side, and may be, for example, 10 times or more, or 50 times or more. On the other hand, the length of the long side may be 500 times or less, or 100 times or less the length of the short side.

The long side of the needle-shaped conductive material in the present disclosure is, for example, 5 μm or more and 15 μm or less. In addition, the short side of the needle-shaped conductive material in the present disclosure is, for example, 50 nm or more and 200 nm or less.

The Si-based active material in the present disclosure preferably does not contain a conductive material other than needle-like particles such as particles, but may contain a small amount of conductive material. Examples of the granular conductive material include acetylene black (AB) and Ketjen black (KB).

The proportion of the needle-shaped conductive material in the Si-based active material is not particularly limited, but is, for example, 0.5% by weight or more, and may be 1% by weight or more. Further, the ratio of the conductive material is, for example, 10% by weight or less, and may be 5% by weight or less. If the proportion of the conductive material is too small, the effects of the present disclosure may not be fully enjoyed. On the other hand, if the proportion of the conductive material is too large, the productivity may deteriorate.

In the Si-based active material, a binder may be present between adjacent primary particles. Examples of the binder include polyimide. Moreover, you may use the general binder used for a negative electrode layer. The proportion of the binder contained in the Si-based active material is, for example, 0.5% by weight or more, and may be 1% by weight or more. On the other hand, the proportion of the binder contained in the Si-based active material is, for example, 5% by weight or less.

As a method for producing the Si-based active material, for example, a preparatory step of preparing a slurry containing primary particles of the Si-based active material, a conductive material (also referred to as a first conductive material), a binder, and a dispersion medium. And a granulation step of subjecting the slurry to a granulation treatment. Examples of the dispersion medium used in the slurry include water. Examples of the binder include a polyimide precursor (polyamic acid). Further, as a method for forming a slurry, a mixture containing primary particles of a Si-based active material, a first conductive material, a binder, and a dispersion medium is kneaded using a kneading device such as a planetary mixer. There is a method of doing. The solid content concentration of the slurry is, for example, 5% by weight or more and 30% by weight or less.

On the other hand, examples of the granulation treatment include a treatment using a nozzle type spray dryer. The liquid transfer rate is, for example, 20 mL/h or more and 200 mL/h or less. The atomizing gas pressure is, for example, 0.1 MPa or more and 0.4 MPa or less. The drying temperature is, for example, 140°C or higher and 200°C or lower. Further, for example, when the slurry contains a polyimide precursor as a binder, it is preferable to perform heat treatment after the granulation step to form the polyimide. The heat treatment temperature is, for example, 250° C. or higher and 350° C. or lower. The heat treatment time is, for example, 1 hour or more and 10 hours or less. The heat treatment atmosphere is preferably an inert atmosphere or vacuum. This is because oxidation of the Si-based active material can be prevented.

The voids of the Si-based active material can be adjusted by appropriately setting the manufacturing conditions. For example, when the solid content of the slurry is reduced, the voids tend to be large. On the other hand, for example, when the amount of binder is increased, the voids tend to become smaller.

The negative electrode layer may contain only the Si-based active material as the negative electrode active material, or may contain other active material. In the latter case, the proportion of the Si-based active material in all the negative electrode active materials may be 50% by weight or more, 70% by weight or more, and 90% by weight or more.

The ratio of the negative electrode active material in the negative electrode layer is, for example, 20% by weight or more, 30% by weight or more, or 40% by weight or more. On the other hand, the ratio of the negative electrode active material in the negative electrode layer is 95% by weight or less, may be 90% by weight or less, and may be 80% by weight or less.

Moreover, the negative electrode layer may contain at least one of a solid electrolyte and a binder, if necessary. Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. Examples of the sulfide solid electrolyte include a Li element, an X element (X is at least one of P, Si, Ge, Sn, B, Al, Ga, and In), and a solid electrolyte containing an S element. Can be mentioned. The sulfide solid electrolyte may further contain at least one of O element and halogen element. Examples of the oxide solid electrolyte include a Li element, a Y element (Y is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and an O element. And a solid electrolyte containing. The nitride solid electrolyte may be, for example, Li ₃ N, and the halide solid electrolyte may be, for example, LiCl, LiI, or LiBr. Examples of the binder include rubber-based binders such as butylene rubber (BR) and styrene-butadiene rubber (SBR), and fluoride-based binders such as polyvinylidene fluoride (PVDF).

Further, the negative electrode layer may contain a second conductive material in addition to the conductive material (first conductive material) contained in the Si-based active material. Examples of the second conductive material include a carbon material. Examples of the carbon material include particulate carbon materials such as acetylene black and Ketjen black, and fibrous carbon materials such as carbon fibers, carbon nanotubes and carbon nanofibers. The second conductive material may be different from or the same as the first conductive material, but the same is preferable.

When the negative electrode layer contains the first conductive material and the second conductive material, the proportion of the first conductive material in all the conductive materials in the negative electrode layer may be 50% by weight or more, and 70% by weight. It may be more than 90% by weight.

The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less. As a method of forming the negative electrode layer, for example, a method of applying a slurry containing at least the SiO-based active material after the above-mentioned granulation treatment and a dispersion medium and drying it can be mentioned. The second conductive material may be added when preparing the slurry.

2. Positive Electrode Layer The positive electrode layer is a layer containing at least a positive electrode active material. Further, the positive electrode layer may contain at least one of a solid electrolyte, a conductive material and a binder, if necessary.

Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include rock salt layered active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , Li _{4 and the like.} Examples thereof include spinel-type active materials such as Ti ₅ O ₁₂ and Li(Ni _0.5 Mn _1.5 )O ₄ , and olivine-type active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ and LiCoPO ₄ . Further, a coating layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material. This is because the reaction between the positive electrode active material and the solid electrolyte can be suppressed.

Examples of the shape of the positive electrode active material include particles. The average secondary particle (D ₅₀ ) of the positive electrode active material is not particularly limited, but is, for example, 10 nm or more, and may be 100 nm or more. On the other hand, the average secondary particle diameter (D ₅₀ ) of the positive electrode active material is, for example, 50 μm or less, and may be 20 μm or less.

The proportion of the positive electrode active material in the positive electrode layer is, for example, 20% by weight or more, 30% by weight or more, or 40% by weight or more. On the other hand, the proportion of the positive electrode active material is, for example, 80% by weight or less, 70% by weight or less, or 60% by weight or less.

The solid electrolyte and the binder used in the positive electrode layer are the same as those described in the above “1. Negative electrode layer”, and thus the description thereof is omitted here.

Examples of the conductive material include carbon materials. Examples of the carbon material include particulate carbon materials such as acetylene black and Ketjen black, and fibrous carbon materials such as carbon fibers, carbon nanotubes and carbon nanofibers.

The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less. As a method of forming the positive electrode layer, for example, a method of applying a slurry containing at least a positive electrode active material and a dispersion medium and drying it can be mentioned.

3. Solid Electrolyte Layer The solid electrolyte layer is a layer arranged between the positive electrode layer and the negative electrode layer. The solid electrolyte layer contains at least a solid electrolyte and may contain a binder if necessary. The solid electrolyte and the binder are the same as those described in the above “1. Negative electrode layer”, and thus the description thereof is omitted here. Above all, the solid electrolyte layer preferably contains a sulfide solid electrolyte as the solid electrolyte.

The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less. Examples of the method of forming the solid electrolyte layer include a method of compression-molding the solid electrolyte.

4. Other members The all-solid battery in the present disclosure has at least the above-mentioned negative electrode layer, positive electrode layer, and solid electrolyte layer. Further, it usually has a positive electrode current collector for collecting current in the positive electrode layer and a negative electrode current collector for collecting current in the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium and carbon. On the other hand, examples of the material of the negative electrode current collector include SUS, copper, nickel and carbon. The thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably selected appropriately according to the application of the battery. In addition, the all-solid-state battery in the present disclosure may have a battery case that houses the above-described negative electrode layer, positive electrode layer, and solid electrolyte layer.

5. All-solid-state battery The all-solid-state battery in the present disclosure is preferably an all-solid-state lithium battery. Further, the all-solid-state battery in the present disclosure may be a primary battery or a secondary battery, but is preferably a secondary battery among them. This is because it can be repeatedly charged and discharged and is useful as, for example, a vehicle battery. Further, the all-solid-state battery in the present disclosure may be a single battery or a laminated battery. The laminated battery may be a monopolar type laminated battery (parallel connection type laminated battery) or a bipolar type laminated battery (series connection type laminated battery). Examples of the shape of the all-solid-state battery include a coin type, a laminated type, a cylindrical type, and a square type.

The present disclosure is not limited to the above embodiment. The above-described embodiment is merely an example, has a configuration that is substantially the same as the technical idea described in the scope of the claims of the present disclosure, and any technique that achieves the same effect can be used It is included in the technical scope of the disclosure.

[Example 1]
(Preparation of positive electrode structure)
The positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) and the sulfide solid electrolyte (LiI-Li ₂ O-Li ₂ S-P ₂ S ₅ ) were used as the positive electrode active material: sulfide solid electrolyte. =75:25 weight ratio. After that, the PVDF binder was weighed to 1.5 parts by weight and the conductive material (VGCF, manufactured by Showa Denko KK) to 3.0 parts by weight with respect to 100 parts by weight of the positive electrode active material. These materials were mixed, butyl butyrate was added, and the solid content was adjusted to 63% by weight. Then, the mixture was kneaded for 1 minute using an ultrasonic homogenizer to obtain a positive electrode slurry. The obtained positive electrode slurry was applied to the surface of a positive electrode current collector (Al foil, manufactured by Showa Denko KK) using an applicator (350 μm) and dried by heating. Then, it roll-pressed at 25° C. and a linear pressure of 1 ton/cm to obtain a positive electrode structure having a positive electrode current collector and a positive electrode layer.

(Preparation of negative electrode active material)
Si particles (primary particles), a conductive material (VGCF, manufactured by Showa Denko KK) having a length of 6 μm and a diameter of 150 nm, a polyimide precursor (polyamic acid), and water are mixed and kneaded with a planetary mixer. Then, a slurry was obtained. The obtained slurry was dried using a nozzle type spray dryer and granulated. Then, heat treatment was performed in an inert atmosphere to obtain a negative electrode active material.

(Preparation of negative electrode structure)
Negative electrode active material and the sulfide solid electrolyte was produced _{(LiI-Li 2 O-Li} 2 S-P 2 S 5), the negative electrode active material: and weighed 42 weight ratio of: sulfide solid electrolyte = 58. Then, it was weighed so that the PVDF binder was 1.5 parts by weight and the conductive material (VGCF) was 5.0 parts by weight with respect to 100 parts by weight of the negative electrode active material. These materials were mixed, butyl butyrate was added, and the solid content was adjusted to 63% by weight. Then, the mixture was kneaded for 1 minute using an ultrasonic homogenizer to obtain a negative electrode slurry. The obtained negative electrode slurry was applied to the surface of the negative electrode current collector (Cu foil) using an applicator, and heated and dried. After that, roll pressing was performed at 25° C. and a linear pressure of 1 ton/cm to obtain a negative electrode structure having a negative electrode current collector and a negative electrode layer. The thickness of the negative electrode layer was adjusted so that the negative electrode capacity was 2.5 with respect to the positive electrode capacity.

(Preparation of battery)
The positive electrode layer of the positive electrode structure and the negative electrode layer of the negative electrode structure were arranged so as to face each other with the solid electrolyte layer in between, and pressed at 5 ton to obtain a battery.

[Examples 2 to 3]
As shown in Table 1, a battery was obtained in the same manner as in Example 1 except that the porosity of the negative electrode active material was changed.

[Examples 4 to 7]
As shown in Table 2, a battery was obtained in the same manner as in Example 2 (porosity 0.5), except that the conductive material content was changed.

[Comparative Examples 1 to 5]
As shown in Table 1, a battery was obtained in the same manner as in Example 1 except that the negative electrode active material did not contain a conductive material and the porosity of the negative electrode active material was changed.

[Comparative Examples 6 to 10]
As shown in Table 1, as in Example 1, except that the porosity was changed and that the negative electrode active material did not include the needle-shaped conductive material (VGCF) but only the granular conductive material (AB). I got a battery.

[Comparative Examples 11 to 12]
As shown in Table 1, a battery was obtained in the same manner as in Example 1 except that the porosity of the negative electrode active material was changed.

Cross-sectional images of the negative electrode active materials obtained in Examples 1 to 7 and Comparative Examples 1 to 12 were acquired by SEM, and V _V /V _P was determined. The results are shown in Tables 1 and 2.

[Evaluation]
The batteries obtained in Examples 1 to 7 and Comparative Examples 1 to 12 were charged and discharged for 500 cycles under the conditions of 60° C., lower limit SOC 10% and upper limit SOC 90%. SOC means state of charge. The internal resistance was measured by the DCIR method for the batteries at the first cycle and the 500th cycle. The measurement conditions of the DCIR method are as follows.
OCV potential: 3.5V
Current density: 15 mA/cm ²
Discharge time: 10 seconds The ratio of the resistance at the 500th cycle to the resistance at the 1st cycle was determined as the resistance increase rate ΔR. The results are shown in Tables 1 and 2 and FIG.

As shown in Table 1 and FIG. 3, in Examples 1 to 3, ΔR was smaller than in Comparative Examples 1 to 12. As described above, it was confirmed that V _V /V _P was in a specific range and that the Si-based active material contained the needle-shaped conductive material, whereby an all-solid-state battery having good cycle characteristics could be obtained.

From the results of Examples and Comparative Examples, the relationship between the porosity (V _V /V _P ) and the resistance increase rate (ΔR) is schematically shown in FIG. From FIGS. 3 and 4, when the ratio of the void volume was too small, ΔR increased. This is presumably because the volume change of the Si-based active material due to charge/discharge could not be sufficiently relaxed. Further, if the value of V _V /V _P was too large, that is, if the ratio of the void volume was too large, ΔR increased. It is speculated that this is because the Si-based active material and the solid electrolyte in the negative electrode layer were easily separated from each other. Further, it was suggested that the porosity of about 0.5 is the most preferable.
Further, no difference was observed in the rate of increase in resistance between the case where the Si-based active material did not contain a conductive material and the case where it contained only a granular conductive material. On the other hand, when the Si-based active material contains a needle-shaped conductive material, the rate of increase in resistance was significantly suppressed. It is presumed that this is because the needle-shaped conductive material played a role of a filler and had a favorable effect on maintaining the skeleton of the extender during expansion and contraction.

Further, as shown in Table 2, it was confirmed that the larger the amount of the conductive material, the smaller the ΔR, but from the viewpoint of production technology, 0.5% by weight or more and 10% by weight or less are appropriate. Conceivable.

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

Claims (1)

A solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer,
The negative electrode layer contains a Si-based active material,
The Si-based active material is a secondary particle having a plurality of primary particles,
Wherein the volume of the secondary particles and _{V P,} the void volume of the secondary particles in the case of a _{V V,} the ratio of the _{V V} with respect to the _{V P (V V / V P} ) is 0.3 or more, 0 .6 or less,
An all-solid-state battery in which the Si-based active material contains a needle-shaped conductive material between the plurality of primary particles.