JP6958462B2 - Sulfide all-solid-state battery - Google Patents

Description

The present disclosure relates to a sulfide all-solid-state battery. The present disclosure relates to a sulfide all-solid-state battery in which a temperature rise is suppressed even when a positive electrode current collector and a negative electrode current collector are short-circuited in a nail piercing test or the like.

A lithium ion battery is used as a small battery having a high energy density. The applications of lithium-ion batteries are expanding further. In addition, higher performance of lithium-ion batteries is also required.

Among lithium-ion batteries, an all-solid-state battery in which an electrolytic solution is replaced with a solid electrolyte has attracted particular attention. This is because the all-solid-state battery uses a solid electrolyte instead of the conventional electrolytic solution, so that the energy density can be expected to be further increased.

Among all-solid-state batteries, sulfide all-solid-state batteries using a sulfide solid electrolyte as the solid electrolyte have particularly high performance, and various studies have been conducted.

For example, Patent Document 1 discloses a sulfide all-solid-state battery in which aluminum is used for the positive electrode current collector and copper or iron is used for the negative electrode current collector.

Japanese Unexamined Patent Publication No. 2014-137869

In the sulfide all-solid-state battery disclosed in Patent Document 1, the temperature of the battery rises at the time of a short circuit in which a nail is pierced from the outside of the battery as in a nail piercing test.

From this, the present inventor has found that in a conventional sulfide all-solid-state battery, the temperature of the battery rises at the time of a short circuit in which a nail is pierced from the outside of the battery as in a nail piercing test. rice field.

The present disclosure has been made to solve the above problems, and is a sulfide all-solid-state battery capable of suppressing an increase in the temperature of the battery even in the case of a short circuit in which a nail is pierced from the outside of the battery as in a nail piercing test. The purpose is to provide.

The present inventors have made extensive studies in order to achieve the above object, and completed the sulfide all-solid-state battery of the present disclosure. The aspect is as follows.
<1> A sulfide all-solid-state battery in which at least one of a positive electrode current collector and a negative electrode current collector contains a FeNi-based amorphous alloy or a Ni-based amorphous alloy.

According to the sulfide all-solid-state battery of the present disclosure, since the FeNi-based amorphous alloy or the Ni-based amorphous alloy is unlikely to react with sulfur in the solid electrolyte, there is almost no effect on the battery capacity in practical use. By using a FeNi-based amorphous alloy or a Ni-based amorphous alloy for at least one of the positive electrode current collector and the negative electrode current collector, the positive electrode current collector and the negative electrode current collector can be used even at the time of a short circuit such as a nail piercing test. Contact resistance does not decrease excessively. As a result, according to the sulfide all-solid-state battery of the present disclosure, it is possible to suppress an increase in the temperature of the battery even in a short-circuit mode such as a nail piercing test without affecting the battery capacity.

FIG. 1 is a diagram schematically showing the structure of an ordinary metal or alloy and an amorphous alloy. FIG. 2 is a diagram showing the CV (Cyclic Voltammetry) measurement results of the FeNi-based amorphous alloy and the Fe-based amorphous alloy. FIG. 3 is a schematic view showing a vertical cross section of a sample of a sulfide all-solid-state battery. FIG. 4 is a schematic diagram for three-dimensionally explaining the structure of the sample of the sulfide all-solid-state battery shown in FIG. FIG. 5 is an explanatory view showing an outline of the nail piercing test apparatus. FIG. 6 is a diagram showing the capacities of the sulfide all-solid-state batteries of Example 1, Comparative Example 1, and Conventional Example 1 during charging and discharging. FIG. 7 is a diagram showing the output of the sulfide all-solid-state batteries of Example 1, Comparative Example 1, and Conventional Example 1. FIG. 8 is a graph showing the relationship between stress and contact resistance for the combination of the positive electrode current collector and the negative electrode current collector of Example 2, Comparative Example 2, and Conventional Examples 1 and 2.

Hereinafter, embodiments of the sulfide all-solid-state battery of the present disclosure will be described in detail. The embodiments shown below do not limit the sulfide all-solid-state battery of the present disclosure.

In a sulfide all-solid-state battery, the positive electrode current collector is in contact with the positive electrode active material and the negative electrode current collector is in contact with the negative electrode active material during normal use. On the other hand, when a metal object such as a nail is inserted into the sulfide all-solid-state battery as in the nail piercing test, the positive electrode current collector and / or the negative electrode current collector is caught inside the sulfide all-solid-state battery. , The positive electrode current collector and the negative electrode current collector come into contact (short circuit). Then, due to this contact, Joule heat is generated, so that the temperature of the sulfide all-solid-state battery rises.

In a sulfide all-solid-state battery, aluminum is generally used for the positive electrode current collector and copper is used for the negative electrode current collector. Even with stainless steel, which has a higher resistance than aluminum and copper, the amount of Joule heat generated during the nail piercing test cannot be suppressed, and the performance of the sulfide all-solid-state battery during normal use deteriorates. Sometimes I did.

However, the present inventor has found that when an amorphous alloy is used for at least one of the positive electrode current collector and the negative electrode current collector, Joule heat can be remarkably suppressed during the nail piercing test.

Although not bound by theory, I think that the reason for this can be explained using FIG. 1 as follows.

FIG. 1 is a diagram schematically showing the structure of an ordinary metal or alloy and an amorphous alloy. In FIG. 1, (a) shows the structure of a normal metal or alloy, and (b) shows the structure of an amorphous alloy.

Both ordinary metals or alloys and amorphous alloys have a surface coating 200 such as an oxide. The surface coating 200 has a certain degree of conductivity, unlike a high-resistance coating that is artificially applied. Due to this conductivity, electrons can move inside the surface coating 200 during normal use of the sulfide all-solid-state battery.

An ordinary metal or alloy is a collection of crystal grains. For this reason, as shown in FIG. 1A, the surface coating 200 of a normal metal or alloy has an intersection 225 with a grain boundary 220. At this intersection 225, the thickness of the surface coating 200 is locally reduced.

On the other hand, as shown in FIG. 1 (b), since the inside of the amorphous alloy is an amorphous body 230, the crystal grains 210 and the crystal grain boundaries 220 (FIG. 1 (see (a)) does not exist. From this, as shown in FIG. 1 (b), the thickness of the surface coating 200 of the amorphous alloy is relatively uniform. As described above, the state of the surface coating 200 is different between the ordinary metal or alloy and the amorphous alloy.

In normal use of the sulfide all-solid-state battery, the smaller the resistance generated by the surface coating 200, the smaller the internal resistance of the sulfide all-solid-state battery, which is preferable. On the other hand, at the time of the nail piercing test, the larger the resistance generated by the surface coating 200, the more the amount of Joule heat generated can be suppressed, which is preferable.

Stress is applied to the current collector of the sulfide all-solid-state battery. The magnitude of the stress is 0.01 to 40 MPa in normal use and 100 MPa or more in the nail piercing test.

In a normal metal or alloy, there is an intersection 225, as shown in FIG. 1 (a). Further, among ordinary metals or alloys, in aluminum and copper, the surface coating 200 is thin as a whole. Therefore, even if the stress applied to the current collector increases, the conductivity of the surface coating 200 does not increase so much. However, even if the stress applied to the current collector is 0.01 to 40 MPa (corresponding to normal use), its conductivity is already sufficiently large, and the intersection 225 is an electron path. Therefore, the resistance generated by the surface coating 200 is small regardless of the stress applied to the current collector. As a result, when aluminum and copper are used for the current collector, the performance as a sulfide all-solid-state battery is good in normal use, but the amount of Joule heat generated cannot be suppressed in the nail piercing test.

On the other hand, among ordinary metals or alloys, in stainless steel, the surface coating 200 is thick as a whole. Therefore, when the stress applied to the current collector is about 0.01 MPa, the conductivity of the surface coating 200 is not good, the intersection 225 is hardly deformed, and the intersection 225 is unlikely to become an electron path. Therefore, the resistance generated by the surface coating 200 remains high. However, as the stress applied to the current collector increases, the thickness of the surface coating 200 decreases and its conductivity increases. Further, when the intersection 225 is deformed, the intersection 225 becomes an electron path, and the resistance generated by the surface coating 200 is reduced. Further, when the stress applied to the current collector becomes 100 MPa or more as in the nail piercing test, the resistance generated by the surface coating 200 is further reduced and becomes equivalent to the case where aluminum and copper are used for the current collector. .. For this reason, if stainless steel is used for the current collector, the amount of Joule heat generated cannot be suppressed during the nail piercing test.

On the other hand, as shown in FIG. 1B, the surface coating 200 of the amorphous alloy has no intersection 225, has a relatively uniform thickness, and is dense. Therefore, when an amorphous alloy is used for the current collector, even if the stress applied to the current collector increases from the stress during normal use to the stress during the nail piercing test, the resistance generated by the surface coating 200 almost changes. do not. The resistance generated by the surface coating 200 has no problem in practical use during normal use of the sulfide all-solid-state battery, and can suppress the amount of Joule heat generated during the nail piercing test.

However, in the case of a sulfide all-solid-state battery, it is necessary to further study the battery capacity among the performances during normal use. The Fe-based amorphous alloy easily reacts with sulfur in the solid electrolyte. On the other hand, the FeNi-based amorphous alloy or the Ni-based amorphous alloy is less likely to react with sulfur in the solid electrolyte. Therefore, if a FeNi-based amorphous alloy or a Ni-based amorphous alloy is used for at least one of the positive electrode current collector and the negative electrode current collector, the battery capacity of the sulfide all-solid-state battery can be improved.

FIG. 2 is a diagram showing the CV (Cyclic Voltammetry) measurement results of the FeNi-based amorphous alloy and the Fe-based amorphous alloy. The solid line shows the measurement result for the FeNi-based amorphous alloy, and the broken line shows the measurement result for the Fe-based amorphous alloy. The working electrode was an Fe-based amorphous alloy or FeNi-based amorphous alloy, and the reference electrode was an In-Li alloy. The CV test was performed by inserting these electrodes into a sulfide solid electrolyte.

As can be seen from FIG. 2, the FeNi-based amorphous alloy has lower reactivity with sulfur than the Fe-based amorphous alloy. Since the Ni-based amorphous alloy contains almost no Fe, it is considered that the reactivity of the Ni-based amorphous alloy with sulfur is even lower than that of the FeNi-based amorphous alloy.

As described above, in the case of a sulfide all-solid-state battery, when FeNi-based amorphous alloy or Ni-based amorphous alloy is used for at least one of the positive electrode current collector and the negative electrode current collector, the decrease in battery capacity is suppressed. , When a short circuit such as a nail piercing test is performed, the temperature rise of the battery can be suppressed. The Fe-based amorphous alloy means an amorphous alloy containing Fe as a main component. The FeNi-based amorphous alloy means an amorphous alloy containing Fe and Ni as main components. The Ni-based amorphous alloy means an amorphous alloy containing Ni as a main component. Here, the "main component" means a component (element) having the highest content (atomic%) in the alloy. For example, an amorphous alloy containing Fe as a main component has the highest Fe content among the alloys. Among the amorphous alloys containing Fe and Ni as main components, the total content of Fe and Ni is the highest among the alloys. Amorphous alloys containing Ni as a main component have the highest Ni content among the alloys.

The constituent requirements of the sulfide all-solid-state battery of the present disclosure, which have been completed based on the findings and the like described so far, will be described below.

《Sulfide all-solid-state battery》
In the sulfide all-solid-state battery of the present disclosure, at least one of the positive electrode current collector and the negative electrode current collector contains a FeNi-based amorphous alloy or a Ni-based amorphous alloy. Hereinafter, the positive electrode current collector and the negative electrode current collector of the sulfide all-solid-state battery of the present disclosure will be described.

<Positive current collector and negative electrode current collector>
All of the positive electrode current collectors do not have to be FeNi-based amorphous alloys or Ni-based amorphous alloys. For example, only the portion in contact with the positive electrode active material layer may be a FeNi-based amorphous alloy or a Ni-based amorphous alloy, and the tab portion may be a metal or an alloy (excluding the amorphous alloy). The same applies to the negative electrode current collector.

The FeNi-based amorphous alloy or the Ni-based amorphous alloy may be wholly amorphous or at least partially amorphous. The amorphous content in the FeNi-based amorphous alloy or the Ni-based amorphous alloy is preferably 50% by volume or more. This is because when the amorphous content is 50% by volume or more, the surface coating is less likely to be locally thinned due to the grain boundaries. From this point of view, the amorphous content is more preferably 65% by volume or more, and even more preferably 80% by volume or more. On the other hand, the fact that all of the FeNi-based amorphous alloy or the Ni-based amorphous alloy is amorphous causes a significant increase in manufacturing cost. Even if the content of the amorphous material in the FeNi-based amorphous alloy or the Ni-based amorphous alloy is 97% by volume or less, 95% by volume or less, or 90% by volume or less, there is no problem in practical use.

The FeNi-based amorphous alloy used in the current collector of the sulfide all-solid-state battery of the present disclosure contains Fe and Ni as main components, and if at least a part of the alloy is amorphous, Fe and Ni. It may contain a component (element) other than the above. Regarding the composition of the FeNi-based amorphous alloy, the total content of Fe and Ni is preferably 60 atomic% or more, more preferably 70 atomic% or more.

Examples of the FeNi-based amorphous alloy include alloys containing 25 to 45 atomic% Fe, 30 to 50 atomic% Ni, and 10 to 20 atomic% B, and the balance being an unavoidable impurity. ..

The FeNi-based amorphous alloy contains, for example, 25 to 45 atomic% Fe, 30 to 50 atomic% Ni, 10 to 20 atomic% B, and further 0 to 5 atomic% Mo, 0 to 3 atoms. % Co, 0 to 3 atomic% Cr, 0 to 3 atomic% Mn, 0 to 3 atomic% Nb, 0 to 2 atomic% Si, and 0 to 2 atomic% C at least. Examples thereof include an alloy containing at least one kind and having a composition in which the balance is an unavoidable impurity. When Mo is selected in this FeNi-based amorphous alloy, this alloy may be referred to as a Ni-Fe-Mo-B-based amorphous alloy.

Examples of the unavoidable impurities of the FeNi-based amorphous alloy described so far include Al, Mn, Zn, Ti, and Cu. Inevitable impurities refer to impurities that are unavoidably contained in raw materials and / or in the manufacturing process. The content of unavoidable impurities is preferably 2 atomic% or less, more preferably 1 atomic% or less.

The Ni-based amorphous alloy used in the current collector of the sulfide all-solid-state battery of the present disclosure has a component other than Ni as long as Ni is the main component and at least a part of the alloy is amorphous. Element) may be contained. The content of Ni in the Ni-based amorphous alloy is preferably 40 atomic% or more, more preferably 50 atomic% or more, and even more preferably 60 atomic% or more.

Examples of the Ni-based amorphous alloy include alloys containing 60 to 80 atomic% of Ni, 2 to 15 atomic% of Si, and 5 to 15 atomic% of B, and the balance of which is an unavoidable impurity. Be done.

The Ni-based amorphous alloy contains, for example, 60 to 80 atomic% Ni, 2 to 15 atomic% Si, and 5 to 15 atomic% B, and further contains 2 to 20 atomic% Cr, 2 to 5 Examples thereof include an alloy containing one or more selected from atomic% Fe, 2 to 5 atomic% W, and 15 to 20 atomic% Co, and having a composition in which the balance is an unavoidable impurity.

Examples of the Ni-based amorphous alloy include alloys containing 40 to 70 atomic% of Ni, 15 to 20 atomic% of B, and 10 to 15 atomic% of Cr, and the balance of which is an unavoidable impurity. Be done.

The Ni-based amorphous alloy contains, for example, 40 to 70 atomic% Ni, 15 to 20 atomic% B, and 10 to 15 atomic% Cr, and further contains 15 to 20 atomic% Co, 2 to 5. Examples thereof include alloys containing one or more selected from atomic% Fe and 2 to 5 atomic% Mo and having a composition in which the balance is an unavoidable impurity.

Examples of the Ni-based amorphous alloy include alloys containing 60 to 85 atomic% of Ni and 15 to 20 atomic% of P and having a composition in which the balance is an unavoidable impurity.

The Ni-based amorphous alloy contains 60 to 85 atomic% of Ni and 15 to 20 atomic% of P, and further contains 15 to 20 atomic% of Cr, and has a composition in which the balance is an unavoidable impurity. Alloys can be mentioned.

Examples of the unavoidable impurities of the Ni-based amorphous alloy described so far include C, Al, Mn, Zn, Ti, and Cu. Inevitable impurities refer to impurities that are unavoidably contained in raw materials and / or in the manufacturing process. The content of unavoidable impurities is preferably 2 atomic% or less, more preferably 1 atomic% or less.

The FeNi-based amorphous alloy or Ni-based amorphous alloy described above includes FeNi-based amorphous alloys or Ni-based amorphous alloys used as soft magnetic materials. The positive electrode current collector and / or the negative electrode current collector of the sulfide all-solid-state battery of the present disclosure need not be a soft magnetic material. However, FeNi-based amorphous alloys or Ni-based amorphous alloys used as soft magnetic materials often have an amorphous content of 50% by volume or more, and therefore the surface coating thereof is relatively uniform and dense. From this, the FeNi-based amorphous alloy or the Ni-based amorphous alloy used as the soft magnetic material is suitable for use in the sulfide all-solid-state battery of the present disclosure. Further, a current collector of the sulfide all-solid-state battery of the present disclosure is obtained by adding an element for improving the magnetic properties to a FeNi-based amorphous alloy or a Ni-based amorphous alloy used as such a soft magnetic material. Can be used as. Examples of the element for improving the magnetic property include a rare earth element and the like.

In the sulfide all-solid-state battery of the present disclosure, at least one of the positive electrode current collector and the negative electrode current collector contains a FeNi-based amorphous alloy or a Ni-based amorphous alloy. A metal or alloy well known as a sulfide all-solid-state battery can be applied to the current collector that does not contain a FeNi-based amorphous alloy or a Ni-based amorphous alloy.

In the sulfide all-solid-state battery of the present disclosure, it is preferable to use a FeNi-based amorphous alloy or a Ni-based amorphous alloy for the positive electrode current collector. By doing so, the output during normal use increases. When a FeNi-based amorphous alloy or a Ni-based amorphous alloy is used for the negative electrode current collector, various metals such as silver, copper, gold, aluminum, nickel, iron, stainless steel, titanium, etc. are used for the positive electrode current collector. Alternatively, these alloys can be used. Among various metals, it is preferable to use aluminum from the viewpoint of chemical stability. A FeNi-based amorphous alloy or a Ni-based amorphous alloy may be used for both the positive electrode current collector and the negative electrode current collector. Alternatively, a FeNi-based amorphous alloy or a Ni-based amorphous alloy may be used for the positive electrode current collector, and an amorphous alloy other than the FeNi-based amorphous alloy or the Ni-based amorphous alloy may be used for the negative electrode current collector.

When a FeNi-based amorphous alloy or a Ni-based amorphous alloy is used for the positive electrode current collector, various metals such as silver, copper, gold, aluminum, nickel, iron, stainless steel, titanium, etc. are used for the negative electrode current collector. Alternatively, these alloys can be used. Among various metals, it is preferable to use copper from the viewpoint of chemical stability.

As long as both the positive electrode current collector and the negative electrode current collector function as the current collector of the sulfide all-solid-state battery, the form thereof is not particularly limited and may be a well-known form. For example, thin plates, thin pieces (ribbons), foils and the like can be mentioned. The FeNi-based amorphous alloy or Ni-based amorphous alloy used for at least one of the positive electrode current collector and the negative electrode current collector is typically produced by a liquid quenching method. From this, as the form of the positive electrode current collector and / or the negative electrode current collector, a thin piece (ribbon), a foil, or the like is convenient. The method for producing the FeNi-based amorphous alloy or the Ni-based amorphous alloy will be described later.

Regarding the composition of the Fe-based amorphous alloy used for reference in CV measurement and the like, the Fe content is preferably 50 atomic% or more, more preferably 60 atomic% or more, and even more preferably 70 atomic% or more. ..

Examples of the Fe-based amorphous alloy include alloys containing 2 to 25 atomic% of Si and 2 to 25 atomic% of B, with the balance being Fe and unavoidable impurities. Regarding the lower limit of the Si content, 4 atomic% is more preferable, and 8 atomic% is even more preferable. On the other hand, regarding the upper limit of the Si content, 20 atomic% is preferable, and 10 atomic% is even more preferable. Further, regarding the lower limit of the content of B, 5 atomic% is more preferable, and 10 atomic% is even more preferable. On the other hand, regarding the upper limit of the B content, 20 atomic% is more preferable, and 15 atomic% or less is even more preferable. This Fe-based amorphous alloy may be called a Fe—Si—B-based amorphous alloy.

In the above-mentioned Fe-based amorphous alloy, C, Al, Cr, W, P, Mn, Zn, Ti, Nb, Ta, Mo, Cu, and rare earth elements are used instead of 0.1 to 8.0 atomic% of Fe. It may contain one or more selected from. Even if these elements are contained in the Fe-based amorphous alloy in an amount of 0.1 to 8.0 atomic%, the effects of the secondary battery of the present disclosure are not impaired, and specific properties such as heat resistance and corrosion resistance are improved. do. The lower limit of the content of these elements may be 0.5 atomic%, 1.0 atomic%, or 3.0 atomic%. On the other hand, the upper limit of the content of these elements may be 6.0 atomic%, 5.0 atomic%, or 4.0 atoms.

Inevitable impurities refer to impurities that are unavoidably contained in raw materials and / or in the manufacturing process. The content of unavoidable impurities is preferably 2 atomic% or less, more preferably 1 atomic% or less.

The sulfide all-solid-state battery of the present disclosure includes a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector in this order. The positive electrode current collector and the negative electrode current collector are as described above, but the well-known embodiment of the sulfide all-solid-state battery can be applied to the positive electrode active material layer, the solid electrolyte layer, and the negative electrode electrolyte layer. Hereinafter, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer will be described.

<Positive electrode active material layer>
The raw material of the positive electrode active material layer contains the positive electrode active material and optionally a conductive additive, a binder, and a solid electrolyte. For these, the following materials can be selected. As the solid electrolyte, the materials mentioned for the solid electrolyte layer can be used.

The positive electrode active material includes at least one transition metal selected from manganese, cobalt, nickel and titanium and a metal oxide containing lithium, for example, lithium cobaltate, lithium nickelate, lithium manganate, or lithium nickel cobalt manganate. Etc., can be selected from dissimilar element-substituted Li-Mn spinel, lithium titanate, lithium metallic phosphate, or a combination thereof.

The positive electrode active material may be coated with a substance having lithium ion conductive performance and capable of maintaining the morphology of the active material or the coating layer that does not flow even when in contact with the separate layer. Specifically, the positive electrode active material may be coated with _{, for example, LiNbO 3} , Li ₄ Ti ₅ O ₁₂ , Li ₃ PO _{4, or the like.}

As the conductive auxiliary agent, select from carbon materials such as VGCF (gas phase growth method carbon fiber, Vapor Green Carbon Fiber), acetylene black, Ketjen black (registered trademark), carbon nanotubes, or a combination thereof. Can be done.

The binder can be selected from a polymer resin, for example, polyvinylidene fluoride (PVdF), butadiene rubber (BR), styrene butadiene rubber (SBR), or a combination thereof.

<Solid electrolyte layer>
The solid electrolyte layer of the sulfide all-solid-state battery of the present disclosure contains a sulfide solid electrolyte as a main component. "The main component is a sulfide solid electrolyte" means that the most abundant component in the solid electrolyte layer is the sulfide solid electrolyte. The content of the sulfide solid electrolyte with respect to the entire solid electrolyte layer is preferably 50% by mass or more, more preferably 65% by mass or more, and even more preferably 85% by mass or more. On the other hand, even if the entire solid electrolyte layer is not a sulfide solid electrolyte, there is no practical problem, and the content of the sulfide solid electrolyte is 97% by mass or less, 95% by mass or less, or 90% by mass or less. good.

Examples of the sulfide-based solid electrolyte include a sulfide-based crystalline solid electrolyte and a sulfide-based amorphous solid electrolyte. Examples of the sulfide-based crystalline solid electrolyte include glass ceramics such as _{Li 7} P ₃ S ₁₁ and Li _3.25 P _0.75 S _4. Examples of the sulfide-based amorphous solid electrolyte include Li ₂ S-P ₂ S ₅ , Li ₂ O, Li ₂ S, P ₂ S ₅ , Li ₂ S, P ₂ S ₅ , Li ₂ S-SiS _2. , LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ S-P ₂ S ₅ , LiI-Li ₂ S-P ₂ O ₅ , LiI-Li ₃ PO _4- P ₂ S ₅ , and Li ₂ SP ₂ S _{5 and the} like can be mentioned.

The solid electrolyte layer may optionally contain a crystalline compound or a crystalline oxide, an oxide-based amorphous solid electrolyte, a thio-LiSiO-based crystal, or the like. Examples of the crystalline compound or crystalline oxide include Li I, Li ₃ N, Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ Li ₃ Zr ₂ O ₁₂ , Li ₆ BaLa ₂ Ta ₂ O ₁₂ , and Li ₃ PO. _{(4-3 / 2w)} N _w (w <1) and the like can be mentioned. Examples of the oxide-based amorphous solid electrolyte include Li ₂ O-B ₂ O _3- P ₂ O ₅ and Li ₂ O-SiO ₂ . The crystals of thio-LiSiO system, for _example, Li _3.24 P _{0.24 Ge 0.76} S _4, and the like.

<Negative electrode active material layer>
The raw material of the negative electrode active material layer contains a negative electrode active material and optionally a conductive auxiliary agent, a binder, and a solid electrolyte. For these, the following materials can be selected.

The negative electrode active material is selected from substances capable of occluding and releasing metal ions such as lithium ions, from carbon materials such as graphite and hard carbon, silicon materials such as Si and Si alloys, or a combination thereof. You can choose. You can also choose from metallic materials such as indium, aluminum, or tin, or a combination thereof.

When a graphite material, which is a crystalline carbon material, is used as the negative electrode active material, the surface of graphite may be amorphously coated.

As the conductive auxiliary agent and the binder of the negative electrode active material layer, the materials mentioned for the positive electrode active material layer can be used. Further, as the solid electrolyte, the materials mentioned for the solid electrolyte layer can be used.

<< Manufacturing method of sulfide all-solid-state battery >>
If a FeNi-based amorphous alloy or a Ni-based amorphous alloy is used for at least one of the positive electrode current collector and the negative electrode current collector, a well-known method can be applied to the method for producing a sulfide all-solid-state battery.

For example, the positive electrode current collector, the raw material of the positive electrode active material layer, the raw material of the solid electrolyte layer, the raw material of the negative electrode active material layer, and the negative electrode current collector are charged into the mold in this order and compressed.

The FeNi-based amorphous alloy or Ni-based amorphous alloy used for the positive electrode current collector and / or the negative electrode current collector can be produced by a well-known method. Examples of the method for producing the FeNi-based amorphous alloy or the Ni-based amorphous alloy include a single roll method and a double roll method. When casting flakes (ribbons) by the single roll method or the twin roll method, the flakes (ribbons) discharged from the single rolls or the twin rolls may be continuously rolled for casting control. When an amorphous alloy other than the FeNi-based amorphous alloy or the Ni-based amorphous alloy is used for the positive electrode current collector and / or the negative electrode current collector, the manufacturing method thereof is the same as the manufacturing method of the FeNi-based amorphous alloy or the Ni-based amorphous alloy. Can be compliant.

Hereinafter, the sulfide all-solid-state battery of the present disclosure will be described in more detail with reference to Examples and Comparative Examples. The sulfide all-solid-state battery of the present disclosure is not limited to these.

(Preparation of sample)
As a sample, a medium-sized (0.24 Ah) sulfide all-solid-state battery was prepared. FIG. 3 is a schematic view showing a vertical cross section of a sample of a sulfide all-solid-state battery. The sample of the sulfide all-solid-state battery 100 includes a positive electrode current collector 10, a positive electrode active material layer 20, a solid electrolyte layer 30, a negative electrode active material layer 40, and a negative electrode current collector 50 in this order. The positive electrode current collector 10, the raw material of the positive electrode active material layer 20, the raw material of the solid electrolyte layer 30, the raw material of the negative electrode active material layer 40, and the negative electrode current collector 50 are charged into a mold in this order and compressed. Then, a sample of the sulfide all-solid-state battery 100 was prepared. Regarding the raw materials of the positive electrode active material layer 20, the raw material of the solid electrolyte layer 30, and the raw materials of the negative electrode active material layer 40, the positive electrode active material layer 20, the solid electrolyte layer 30, and the negative electrode active material layer 40 are 50.3 μm and 39, respectively. The required amount of each raw material was charged into the mold so as to have a thickness of 0.8 μm and 30.0 μm.

FIG. 4 is a schematic diagram for three-dimensionally explaining the structure of the sample of the sulfide all-solid-state battery 100 shown in FIG. In FIG. 4, each of the positive electrode current collector 10, the positive electrode active material layer 20, the solid electrolyte layer 30, the negative electrode active material layer 40, and the negative electrode current collector 50 is arranged so that the structure of the sulfide all-solid-state battery 100 can be easily understood. It is shown separately for convenience. Further, each of the positive electrode current collector 10, the positive electrode active material layer 20, the solid electrolyte layer 30, the negative electrode active material layer 40, and the negative electrode current collector 50 is shown by moving them in the left-right direction for convenience. As shown in FIG. 3, the positive electrode current collector 10 and the negative electrode current collector 50 have tab portions 12 and 52, respectively.

Table 1 shows the combinations of the materials constituting the positive electrode current collector 10 and the negative electrode current collector 50. Table 1 also shows the thickness of each current collector. As the Fe-based amorphous alloy foil in Table 1, Metaglas (registered trademark) 2605S3A manufactured by Hitachi Metals, Ltd. was used. This alloy is a Fe-Si-B-based amorphous alloy produced by the single roll method. Further, as the Ni-based amorphous alloy foil shown in Table 1, 2826 MB of Metaglas (registered trademark) manufactured by Hitachi Metals, Ltd. was used. This alloy is a Ni-Fe-Mo-B-based amorphous alloy produced by the single roll method.

The positive electrode active material layer contains 84.7% by mass of lithium nickel cobalt manganate, 13.4% by mass of a sulfide-based amorphous solid electrolyte, 0.6% by mass of a binder, and 1.3% by mass of VGCF. Made. In the positive electrode active material layer, the active material was 75% by volume and the solid electrolyte was 25% by volume.

The solid electrolyte layer was prepared by blending 99.6% by mass of a sulfide-based amorphous solid electrolyte and 0.4% by mass of a binder.

The negative electrode active material layer was prepared by blending 54.5% by mass of Si, 42.3% by mass of a sulfide-based amorphous solid electrolyte, 1.1% by mass of a binder, and 2.1% by mass of VGCF. In the negative electrode active material layer, the active material was 55% by volume and the solid electrolyte was 45% by volume.

<evaluation>
Nail piercing tests were performed on the samples of Example 1, Comparative Example 1, and Conventional Example 1. ^{In addition, the capacities (mAh / g) and output (mW / cm 2} ) during charging and discharging were measured for the samples of Example 1, Comparative Example 1, and Conventional Example 1. Then, among the combinations of the positive electrode current collector and the negative electrode current collector shown in Table 1, the surface resistance was measured for the combinations of Example 2, Comparative Example 2, and Conventional Examples 1 and 2.

The nail piercing test was carried out by taking into account the current flowing from the secondary battery other than the test specimen secondary battery at the short-circuited portion. FIG. 5 is an explanatory view showing an outline of the nail piercing test apparatus. The specimen secondary battery 60 is stored in the first container 70, and the electronic supply secondary battery 85 is stored in the second container 80. The specimen secondary battery 60 was obtained by stacking two cell batteries. In the electronic supply secondary battery 85, 36 single batteries were stacked. The test object secondary battery 60 and the electronic supply secondary battery 85 are connected in parallel, and an ammeter 90 is connected between them. The test was carried out in a state where the temperature inside the first container 70 and the second container 80 was 25 ° C., and the SOC (State of Charge) of the specimen secondary battery 60 was 100%. A nail 95 having a diameter of 8 mm and a tip angle of 60 degrees was inserted into a nail piercing position 72 near the center of the test specimen secondary battery 60 at a speed of 0.5 mm / sec and tested.

<Evaluation results>
Regarding the nail piercing test, the temperature of the battery of the conventional example 1 rapidly increased after the nail piercing, whereas the temperature increase of the battery of the first embodiment was sufficiently suppressed. The temperature rise of the battery of Example 1 was about 10% of the temperature rise of the battery of Conventional Example 1. From this, even when the temperature rise of the battery of Comparative Example 1 was about 17% of the temperature rise of the battery of Conventional Example 1, the temperature rise of the battery of Example 1 was further about 7%. It was confirmed that it was suppressed.

FIG. 6 is a diagram showing the capacities of the batteries of Example 1, Comparative Example 1, and Conventional Example 1 during charging and discharging. For each battery, the left side shows the capacity when charging and the left side shows the capacity when discharging. In FIG. 6, the capacity of the battery of Conventional Example 1 is standardized as 100.

FIG. 7 is a diagram showing the output of the batteries of Example 1, Comparative Example 1, and Conventional Example 1. In FIG. 7, for each battery, the output of the battery of Conventional Example 1 is standardized as 100.

As can be seen from FIG. 6, it was confirmed that the battery of Example 1 had the smallest effect on the capacity as compared with Conventional Example 1. Further, as can be seen from FIG. 7, it was confirmed that the output of the battery of Example 1 was increased as compared with that of Conventional Example 1.

FIG. 8 is a graph showing the relationship between stress and contact resistance for the combination of the positive electrode current collector and the negative electrode current collector of Example 2, Comparative Example 2, and Conventional Examples 1 and 2.

In a sulfide all-solid-state battery, the combination of the positive electrode current collector and the negative electrode current collector that satisfies both the performance during normal use and the suppression of temperature rise during the nail piercing test is the stress applied to the current collector and the positive electrode. It can be evaluated by the relationship between the contact resistance between the current collector and the negative electrode current collector.

During normal use of a sulfide all-solid-state battery, the positive electrode current collector is in contact with the positive electrode active material and the negative electrode current collector is in contact with the negative electrode active material. Therefore, the positive electrode current collector and the negative electrode current collector are in contact with each other. Is not in contact with. Nevertheless, a combination of a positive electrode current collector and a negative electrode current collector that satisfies the performance during normal use is a combination of the stress applied to the current collector and the surface resistance of the positive electrode current collector and the negative electrode current collector. The reasons that can be evaluated in relation to each other are considered to be as follows.

The resistance generated by the surface coating 200 has a great influence on the performance during normal use, and the resistance generated by the surface coating 200 changes depending on the stress applied to the surface coating 200. This is because the stress applied to the surface coating 200 changes in the same manner regardless of the presence or absence of the positive electrode active material and the negative electrode pressure material.

In FIG. 8, the broken line indicates the stress range during normal use of the secondary battery and the allowable range of contact resistance at that time, and the alternate long and short dash line indicates the stress range at the time of short circuit such as a nail piercing test and the stress range at that time. Indicates the allowable range of contact resistance. The "allowable range of contact resistance" means a range in which the performance as a battery can be maintained during normal use, and a range in which an increase in battery temperature can be suppressed during a short circuit such as a nail piercing test. Means.

From FIG. 8, it is understood that when an amorphous alloy is used for at least one of the positive electrode current collector and the negative electrode current collector, the surface resistance does not decrease excessively even at the time of a short circuit such as a nail piercing test, and the temperature rise of the battery can be suppressed. can. The fact that the surface resistance does not decrease excessively even during a short circuit such as a nail piercing test is considered to be due to the properties of the surface coating of the amorphous alloy, as described above. Therefore, the suppression of the temperature rise at the time of a short circuit such as a nail piercing test does not depend on the type of the battery and the type of the amorphous alloy of the positive electrode current collector or the negative electrode current collector. Therefore, in a sulfide all-solid-state battery, even if at least one of the positive electrode current collector and the negative electrode current collector is a FeNi-based amorphous alloy or a Ni-based amorphous alloy, it is possible to suppress an increase in temperature at the time of a short circuit such as a nail piercing test. Understandable. Since the amorphous alloy is a FeNi-based amorphous alloy or a Ni-based amorphous alloy, the reactivity with sulfur in the sulfide-based solid electrolyte is low, so that a decrease in battery capacity can be suppressed.

From the above results, the effect of the sulfide all-solid-state battery of the present disclosure could be confirmed.

10 Positive electrode current collector 12 Tab part 20 Positive electrode active material layer 30 Solid electrolyte layer 40 Negative electrode active material layer 50 Negative electrode current collector 52 Tab part 60 Specimen secondary battery 70 First container 72 Nail piercing position 80 Second container 85 Electronics Secondary battery for supply 90 Current meter 95 Nail 100 Sulfurized all-solid-state battery 200 Surface coating 210 Crystal grain 220 Crystal grain boundary 225 Intersection 230 Amorphous body

Claims (1)

At least one of the positive electrode current collector and the negative electrode current collector, seen containing a FeNi-based amorphous alloy or Ni-based amorphous alloy,
The FeNi-based amorphous alloy
An alloy containing 25 to 45 atomic% Fe, 30 to 50 atomic% Ni, and 10 to 20 atomic% B, and the balance being an unavoidable impurity, or an alloy.
It contains 25 to 45 atomic% Fe, 30 to 50 atomic% Ni, 10 to 20 atomic% B, and further contains 0 to 5 atomic% Mo, 0 to 3 atomic% Co, and 0 to 3 atomic%. Cr, Mn of 0 to 3 atomic%, Nb selected from 0 to 3 atomic%, Si of 0 to 2 atomic%, and at least one selected from C of 0 to 2 atomic%, and the balance is An alloy having a composition that is an unavoidable impurity,
The Ni-based amorphous alloy
An alloy containing 60-80 atomic% Ni, 2-15 atomic% Si, and 5-15 atomic% B, with the balance being an unavoidable impurity.
It contains 60-80 atomic% Ni, 2-15 atomic% Si, and 5-15 atomic% B, and further contains 2-20 atomic% Cr, 2-5 atomic% Fe, 2-5 atoms. An alloy containing one or more selected from% W and 15 to 20 atomic% Co, and having a composition in which the balance is an unavoidable impurity.
An alloy containing 40 to 70 atomic% Ni, 15 to 20 atomic% B, and 10 to 15 atomic% Cr, and having a composition in which the balance is an unavoidable impurity.
It contains 40-70 atomic% Ni, 15-20 atomic% B, and 10-15 atomic% Cr, and further contains 15-20 atomic% Co, 2-5 atomic% Fe, and 2-5. An alloy containing one or more selected from atomic% Mo and having a composition in which the balance is an unavoidable impurity.
An alloy containing 60 to 85 atomic% Ni and 15 to 20 atomic% P and having a composition in which the balance is an unavoidable impurity, or
An alloy containing 60 to 85 atomic% of Ni and 15 to 20 atomic% of P, further containing 15 to 20 atomic% of Cr, and having a composition in which the balance is an unavoidable impurity.
A sulfide all-solid-state battery.

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