JP7211262B2 - Method for manufacturing sulfide all-solid-state battery - Google Patents

Description

The present application is a method for manufacturing a sulfide all-solid-state battery.

2. Description of the Related Art Conventionally, there are cases in which an aging process is provided in a manufacturing method of a liquid-based battery. For example, Patent Document 1 discloses that the irreversible capacity can be reduced by performing an aging process before initial charging of an alkaline secondary battery. This is to degrade the material and generate overvoltage.

On the other hand, the method for manufacturing an all-solid-state battery may also include an aging step. For example, Patent Literature 2 discloses that aging is performed on assembled batteries after initial charging in order to make the electric characteristics of all assembled batteries approximately the same. Patent Document 3 discloses performing an aging process in order to polymerize a monomer having a vinyl group or a derivative thereof to obtain a polymer, and to obtain a gel electrolyte or a complete solid electrolyte by solidifying the monomer solution. . In addition, Patent Document 3 discloses that an aging process is performed after the initial charge when manufacturing a lithium ion battery. Furthermore, Patent Document 3 discloses that the initial charged state is maintained for 48 hours or longer.

JP-A-09-274932 JP 2015-118867 A JP-A-2002-280074

Generally, when a liquid-based battery is manufactured, an aging process is performed before initial charging. There are two reasons for this. The first is to form a film on the surface of the negative electrode. This reduces the resistance and suppresses the decomposition of the electrolyte. The second reason is that aging is performed before the initial charge to dissolve the metal foreign matter mixed in the positive electrode side and deposit it on the negative electrode side, thereby promoting a short circuit. As a result, it is possible to prevent outflow of defective products by short-circuiting in advance before shipment.

The second reason among the above is also an important concept for all-solid-state batteries. Generally, metals dissolve at high potentials and deposit at low potentials. Therefore, in a liquid-based battery, by performing an aging process before the first charge, it is possible to dissolve metal foreign substances in the positive electrode, transport the dissolved metal ions in the electrolyte by liquid diffusion, and deposit them on the negative electrode side. can. This allows the battery to be short-circuited. On the other hand, in an all-solid-state battery, even if metal foreign matter is dissolved on the positive electrode side, the metal ions cannot be diffused into the electrolyte and cannot reach the negative electrode. That is, under normal conditions, the battery will not short-circuit.
Therefore, it has been difficult to prevent outflow of defective products by short-circuiting all-solid-state batteries in advance before shipment.

Accordingly, an object of the present application is to provide a method for producing a sulfide solid electrolyte that can prevent outflow of defective products.

As a result of intensive studies, the inventors of the present invention have found that by using a sulfide solid electrolyte as the solid electrolyte used in the all-solid electrolyte, it is possible to short-circuit in advance before shipment. Specifically, by using a sulfide solid electrolyte, a chemical reaction (sulfurization) is caused between the metal foreign matter mixed on both sides of the positive and negative electrodes and the sulfide solid electrolyte, and if the sulfided metal foreign matter becomes conductive, the battery It has been found that a short circuit can be generated.

Here, it is known that the above-mentioned sulfurization reaction is also basically promoted at a higher potential. Therefore, it is relatively easy to sulfurize foreign metals mixed in on the positive electrode side with a high potential, but it is difficult to sulfurize foreign metals mixed in on the negative electrode side with a low potential. Therefore, it was thought that a short circuit might not be detected during the endurance test because sulfurization of metal foreign matter mixed in the negative electrode side progresses slowly. Therefore, the present inventors have found that the detection rate of short circuit occurrence can be increased by performing an aging process before initial charge in order to accelerate the progress of sulfuration of metal foreign matter mixed in the negative electrode side.

As described in Patent Literatures 2 and 3, when the aging process is performed after the initial charge, the potential of the negative electrode is lowered, so the sulfuration rate of metal foreign matter is slow, and there is a risk that a short circuit cannot be detected.

Based on the above findings, the present application provides a sulfide solid electrolyte layer having a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer as one means for solving the above problems. Disclosed is a method for manufacturing a sulfide all-solid-state battery, in which the all-solid-state sulfide battery is aged before initial charging.

According to the manufacturing method of the sulfide all-solid-state battery disclosed in the present application, it is possible to prevent outflow of defective products.

1 is a flow chart of a method 100 for manufacturing a sulfide all-solid-state battery. FIG. 4 is a diagram showing the relationship between the number of short-circuit days and temperature in a sulfurization rate study experiment; FIG. 4 is a diagram showing the relationship between the sulfurization rate and temperature in a sulfurization rate study experiment;

[Method for manufacturing sulfide all-solid-state battery]
Hereinafter, a method for manufacturing a sulfide all-solid-state battery of the present disclosure will be described using a method 100 for manufacturing a sulfide all-solid-state battery (hereinafter sometimes referred to as “manufacturing method 100”), which is one embodiment.

A method 100 for manufacturing a sulfide all-solid-state battery includes aging a sulfide all-solid-state battery having a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer before initial charging. It is characterized by Specifically, the method 100 for manufacturing a sulfide all-solid-state battery comprises a step S1 for obtaining a sulfide all-solid-state battery (hereinafter sometimes referred to as a “sulfide all-solid-state battery preparation step S1”); A step S2 of aging the sulfide all-solid-state battery after the battery manufacturing step S1 (hereinafter sometimes referred to as “aging step S2”), and a step S3 of initial charging the sulfide all-solid-state battery after the aging step S2 (hereinafter , sometimes referred to as "initial charging step S3"). Further, after the initial charging step S3, a step S4 of discharging the sulfide all-solid-state battery (hereinafter sometimes referred to as "discharging step S4") may be included.
A flowchart of the manufacturing method 100 is shown in FIG.

(Sulfide all-solid-state battery manufacturing step S1)
The sulfide all-solid battery manufacturing step S1 is a step of manufacturing a sulfide all-solid battery having a sulfide all-solid electrolyte. A sulfide all-solid-state battery includes a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. In addition, a positive electrode current collector is arranged at least on the positive electrode side surface among the end surfaces of the sulfide all-solid-state battery in the stacking direction. Further, a negative electrode current collector is arranged at least on the negative electrode side surface among the end surfaces of the sulfide all-solid-state battery in the stacking direction. However, the positive electrode current collector and the negative electrode current collector may also be provided inside the sulfide all-solid-state battery.

The positive electrode layer contains at least a positive electrode active material. In addition to the positive electrode active material, the positive electrode layer can optionally contain a solid electrolyte, a binder, a conductive agent, and the like. A known positive electrode active material may be used as the positive electrode active material. For example, when constructing a lithium ion battery, various kinds of lithium cobalt oxide, lithium nickel oxide, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , lithium manganate, spinel-based lithium compounds, etc. are used as the positive electrode active material. A lithium-containing composite oxide can be used. The surface of the positive electrode active material may be coated with an oxide layer such as a lithium niobate layer, a lithium titanate layer, or a lithium phosphate layer. The solid electrolyte that can be contained in the positive electrode layer is preferably a sulfide solid electrolyte. The sulfide solid electrolyte is not particularly limited, and known sulfide solid electrolytes can be used. For example, Li ₃ PS ₄ , Li ₂ SP ₂ S ₅ , Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Si ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiI-LiBr, LiI-Li ₂ SP ₂ S ₅ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ SP ₂ S ₅ -GeS ₂ etc. can be mentioned. Examples of binders that can be contained in the positive electrode layer include butadiene rubber (BR), butylene rubber (IIR), acrylate butadiene rubber (ABR), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF- HFP) and the like. Conductive agents that can be contained in the negative electrode layer include carbon materials such as acetylene black, ketjen black, and vapor grown carbon fiber (VGCF), and metal materials such as nickel, aluminum, and stainless steel. The content of each component in the positive electrode layer may be the same as the conventional one. The shape of the positive electrode layer may also be the same as the conventional one. In particular, a sheet-shaped positive electrode layer is preferable from the viewpoint of easily constructing a sulfide all-solid-state battery. In this case, the thickness of the positive electrode layer is, for example, preferably 0.1 μm or more and 1 mm or less, more preferably 1 μm or more and 150 μm or less.

The negative electrode layer contains at least a negative electrode active material. In addition to the negative electrode active material, the negative electrode layer can optionally contain a solid electrolyte, a binder, a conductive agent, and the like. A known negative electrode active material may be used as the negative electrode active material. For example, when constructing a lithium ion battery, silicon-based active materials such as Si, Si alloys and silicon oxides as negative electrode active materials; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate. Substance: metal lithium, lithium alloy, or the like can be used. The solid electrolyte that can be contained in the negative electrode layer is preferably a sulfide solid electrolyte. The sulfide solid electrolyte is not particularly limited, and known sulfide solid electrolytes can be used. For example, the above-mentioned sulfide solid electrolyte can be exemplified. Examples of binders that can be contained in the negative electrode layer include the binders described above. Examples of the conductive agent that can be contained in the negative electrode layer include the conductive agents described above. The content of each component in the negative electrode layer may be the same as in the conventional case. The shape of the negative electrode layer may also be the same as the conventional one. In particular, a sheet-shaped negative electrode layer is preferable from the viewpoint of facilitating the formation of a sulfide all-solid-state battery. In this case, the thickness of the negative electrode layer is, for example, preferably 0.1 μm or more and 1 mm or less, more preferably 1 μm or more and 150 μm or less. However, it is preferable to determine the size (area and thickness) of the negative electrode layer such that the capacity of the negative electrode is larger than the capacity of the positive electrode.

The sulfide solid electrolyte layer contains at least a sulfide solid electrolyte. In addition to the sulfide solid electrolyte, the sulfide solid electrolyte layer can optionally contain a binder, a conductive agent, and the like. The sulfide solid electrolyte is not particularly limited, and known sulfide solid electrolytes can be used. For example, the above-mentioned sulfide solid electrolyte can be exemplified. Examples of binders that can be contained in the sulfide solid electrolyte layer include the binders described above. Examples of conductive agents that can be contained in the sulfide solid electrolyte layer include the conductive agents described above. The content of each component in the sulfide solid electrolyte layer may be the same as in the conventional case. The shape of the sulfide solid electrolyte layer may be the same as the conventional one. In particular, a sheet-shaped sulfide solid electrolyte layer is preferable from the viewpoint of easily constructing a sulfide all-solid-state battery. In this case, the thickness of the sulfide solid electrolyte layer is, for example, preferably 0.1 μm or more and 1 mm or less, more preferably 1 μm or more and 100 μm or less.

The positive electrode current collector and the negative electrode current collector may be made of metal foil, metal mesh, or the like. Metal foil is particularly preferred. Examples of metals forming the positive electrode current collector and the negative electrode current collector include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. Cu and Al are particularly preferred. The positive electrode current collector and the negative electrode current collector may have some kind of coating layer on their surfaces for adjusting resistance. The thickness of each of the positive electrode current collector and the negative electrode current collector is not particularly limited. For example, it is preferably 0.1 μm or more and 1 mm or less, more preferably 1 μm or more and 100 μm or less.

Such a sulfide all-solid-state battery can be produced by a known method. For example, it can be produced by stacking separately produced positive electrode layer, solid electrolyte layer, and negative electrode layer and pressing them. The positive electrode layer can be produced by applying a slurry containing components constituting the positive electrode layer to a substrate or a positive electrode current collector and drying the slurry. The negative electrode layer can be produced by applying a slurry containing components constituting the negative electrode layer to a substrate or a negative electrode current collector and drying the slurry. The solid electrolyte layer can be produced by coating a substrate with a slurry containing components constituting the solid electrolyte layer and drying the slurry.

Further, the all-solid-state sulfide battery produced as described above may be sealed with a metal laminate film or the like.

(Aging step S2)
The aging step S2 is a step of aging the sulfide all-solid-state battery produced as described above. As a result, it is possible to sulfurize the metallic foreign matter mixed in the positive electrode or negative electrode of the sulfide all-solid-state battery. Then, according to this, the sulfide all-solid-state battery in which metallic foreign matter is mixed can be short-circuited before shipment, and it is possible to prevent the outflow of defective products.

Preferably, the aging step S2 is set to conditions that satisfy the following formula (1). This is a formula calculated on the assumption that metallic foreign matter is mixed in the negative electrode current collector farthest from the positive electrode. This is because the positive electrode always has a higher potential than the negative electrode, so if the sulfuration is completed on the side of the negative electrode current collector farthest from the positive electrode, it can be considered that the sulfuration is completed on the positive electrode side as well. Here, in formula (1), the thickness of the negative electrode layer is x (μm), the thickness of the sulfide solid electrolyte layer is y (μm), the aging voltage is V (V), the aging temperature is T (° C.), and the number of aging days is D (day).
x+y≦[0.1905/{V·exp(0.03888·T)}]·D (1)

By setting the configuration of the sulfide all-solid-state battery and the conditions of the aging step S2 so as to satisfy the formula (1), it is possible to more reliably prevent outflow of defective products.

Although the upper limit of the aging temperature is not particularly limited, it is preferably 230°C or lower, more preferably 100°C or lower, and particularly preferably 80°C or lower. This is determined from the following viewpoints. That is, considering the essential battery materials, the upper temperature limit is considered to be about 230°C. When a binder is included, the upper temperature limit is considered to be about 100° C., which is the heat resistance temperature of the binder. Furthermore, when the entire battery is covered with a metal laminate film, the upper temperature limit is considered to be about 80° C., which is the heat resistance temperature of the metal laminate film. Although the lower limit of the aging temperature is not particularly limited, it is preferably 40°C or higher. The aging voltage and the number of aging days are appropriately set based on the configuration of the sulfide all-solid-state battery and other conditions.

(Initial charging step S3)
Initial charging step charging is a step of initially charging the sulfide all-solid-state battery that has been aged in the aging step S2. "Initial charge" means that the sulfide all-solid-state battery is charged for the first time. The conditions for initial charging are not particularly limited, and may be appropriately set according to the purpose.

(Discharging step S4)
The steps after the initial charging step S3 are not particularly limited, but a discharging step S4 may be provided. The discharging step S4 is a step of discharging the sulfide all-solid-state battery charged in the initial charging step S3. The discharge method of the sulfide all-solid-state battery is not particularly limited, and may be self-discharge, discharge using a discharge device, or a combination thereof. The discharge conditions are also not particularly limited, and may be appropriately set according to the purpose.

As described above, the manufacturing method of the sulfide all-solid-state battery of the present disclosure has been described using the manufacturing method 100 of the sulfide all-solid-state battery. As described above, the method for manufacturing a sulfide all-solid-state battery of the present disclosure is characterized by aging the sulfide all-solid-state battery before initial charging. As a result, batteries containing foreign matter can be detected by short-circuiting in advance before shipment. In addition, the method for manufacturing a sulfide all-solid-state battery of the present disclosure is applicable to any method for manufacturing a sulfide all-solid-state battery, but is suitable for manufacturing a lithium-ion sulfide all-solid-state battery.

Hereinafter, the method for manufacturing the sulfide all-solid-state battery of the present disclosure will be described using examples.

[Fabrication of sulfide all-solid-state battery]
(Preparation of negative electrode)
Negative electrode active material (lithium titanate (LTO): Li ₄ Ti ₅ O ₁₂ ), sulfide solid electrolyte (Li ₃ PS ₄ ), binder (PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer)), conductivity The agent (VGCF) was dissolved in butyl butyrate and dispersed with an ultrasonic homogenizer to prepare a negative electrode slurry.
Then, the prepared negative electrode slurry was applied onto a negative electrode current collector (Ni foil) and dried to obtain a negative electrode.

(Preparation of positive electrode)
Positive electrode active material (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ coated with LiNbO ₃ ), sulfide solid electrolyte (Li ₃ PS ₄ ), binder (PVDF-HFP), conductive agent (VGCF), butyric acid It was dissolved in butyl and dispersed with an ultrasonic homogenizer to prepare a positive electrode slurry.
Then, the prepared positive electrode slurry was applied onto a negative electrode current collector (Al foil) and dried to obtain a positive electrode.

(Sulfide solid electrolyte layer)
A sulfide solid electrolyte (Li ₃ PS ₄ ), a binder (PVDF-HFP), and a conductive agent (VGCF) were dissolved in butyl butyrate and dispersed with an ultrasonic homogenizer to prepare a solid electrolyte slurry.
Then, the produced solid electrolyte slurry was applied on an Al foil and dried to obtain a solid electrolyte layer.

(Fabrication of sulfide all-solid-state battery)
The negative electrode and the solid electrolyte layer were stacked so that the negative electrode layer side surface of the negative electrode and the solid electrolyte layer were in contact with each other, and after pressing at 1 ton/cm, the Al foil of the solid electrolyte layer was removed. Next, the surface of the positive electrode on the positive electrode layer side was placed on the solid electrolyte layer and pressed at 3 ton/cm. At this time, it was confirmed that the positive electrode layer, the solid electrolyte layer, and the negative electrode layer had a thickness of 50 μm for the positive electrode layer, 30 μm for the solid electrolyte layer, and 70 μm for the negative electrode layer. Then, the current collectors of the positive and negative electrodes and the tab with the welding tape were ultrasonically bonded, and then the whole was sealed with an aluminum laminate film to obtain an all-solid-state sulfide battery.

(Production of sulfide all-solid-state battery containing foreign matter)
In the above-described method for producing a sulfide all-solid-state battery, when the negative electrode layer and the sulfide solid electrolyte are superimposed, a Cu foil having a diameter of φ300 μm and a thickness of 10 μm is placed on the negative electrode layer and superimposed. A foreign matter-containing sulfide all-solid-state battery was produced in the same manner as in the production method of the sulfide all-solid-state battery.

[Cell activation step]
Five of each of the sulfide all-solid-state batteries and the sulfide all-solid-state batteries containing foreign matter prepared above were combined, and activation was performed under the following conditions using one set (10 in total). Charging was performed at 1/3 CC CV and 0.1 CCut Out, and discharging was performed at 1 CC CV and 0.1 CCut Out. Table 1 shows the conditions of the aging process.

(Comparative example 1)
Cell activation was performed in the following order of steps.
・Initial charging process: 2.95V charging, 25°C
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

(Comparative example 2)
Cell activation was performed in the following order of steps.
・Initial charging process: 2.95V charging, 25°C
・Aging process: 60°C, 7 days Storage/discharge step 1: 25°C, 3 days Self-discharge/discharge step 2: 1.5V discharge, 25°C

(Comparative Example 3)
Cell activation was performed in the following order of steps.
・Initial charging process: 2.95V charging, 25°C
・Aging process: 80°C, 7 days Storage/discharge step 1: 25°C, 3 days Self-discharge/discharge step 2: 1.5V discharge, 25°C

(Comparative Example 4)
Cell activation was performed in the following order of steps.
・Initial charging process: 1.5V charging, 25°C
・Aging process: 60°C, 7 days Storage/charging process: 2.95V charging, 25°C
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

(Comparative Example 5)
Cell activation was performed in the following order of steps.
・Aging process: 40℃, 7days storage ・Initial charging process: 2.95V charging, 25℃
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

(Comparative Example 6)
Cell activation was performed in the following order of steps.
・Aging process: 60℃, 3 days storage ・Initial charging process: 2.95V charging, 25℃
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

(Example 1)
Cell activation was performed in the following order of steps.
・Aging process: 60℃, 7days storage ・Initial charging process: 2.95V charging, 25℃
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

(Example 2)
Cell activation was performed in the following order of steps.
・Aging process: 80℃, 7days storage ・Initial charging process: 2.95V charging, 25℃
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

(Example 3)
Cell activation was performed in the following order of steps.
・Aging process: 80℃, 3 days storage ・Initial charging process: 2.95V charging, 25℃
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

(Example 4)
Cell activation was performed in the following order of steps.
・Aging process: 40℃, 10days Storage ・Initial charging process: 2.95V charging, 25℃
・Discharge step 1: 25°C, 3 days self-discharge ・Discharge step 2: 1.5V discharge, 25°C

[evaluation]
(Shipping inspection)
Each battery that has passed through the above steps is charged and discharged at 1C CV, 0.3C Cut out, and 1.5-2.95V, and the sulfide all-solid-state battery with an initial charge-discharge efficiency of 98% or more is regarded as a good product. evaluated.
Table 1 shows the results.

(An endurance test)
A durability test was performed on each of the batteries that had passed through the above steps under the conditions of SOC 80%, temperature 60° C., and storage period 90 days. In the endurance test, the voltage was measured and monitored every three days. A sulfide all-solid-state battery that did not drop by 50 mV/3 days or more at the time of voltage monitoring throughout the storage period was evaluated as a non-defective product.
Table 1 shows the results.

Here, the failure outflow rate in Table 1 is the percentage of the number of sulfide all-solid-state batteries containing foreign matter evaluated as non-defective at the time of shipment to the number of sulfide all-solid-state batteries containing foreign matter (five). The amount of sulfide is the amount of sulfide of the sulfide all-solid-state battery at the time of shipment, and is calculated based on the below-described formula (2). In Comparative Examples 1 to 4, the aging process was performed after the initial charging. The amount of sulfidation is a reference value.

From Table 1, in Comparative Examples 1 to 6, the number of non-defective products was 10 at the time of shipment, but the number was 5 after the endurance test. This is probably because the sulfide all-solid-state battery containing foreign matter caused a chemical short circuit during the endurance test.
On the other hand, in Examples 1 to 4, the number of non-defective products at the time of shipment was 5, and all the sulfide all-solid-state batteries containing foreign matter could be removed. This is probably because the sulfide all-solid-state battery containing foreign matter caused a chemical short circuit during the aging process.

Each test example is examined in detail below.
First, Comparative Examples 2 and 4 and Example 1 are compared. In Comparative Examples 2 and 4, the initial charging process is performed before the aging process. On the other hand, in Example 1, the aging process is performed before the initial charging process. As mentioned above, metal sulfidation is accelerated on the high voltage side. Therefore, it becomes difficult to sulfurize by charging. Therefore, in Comparative Examples 2 and 4 in which the aging process was performed after the initial charging process, the sulfurization did not progress sufficiently, so it is considered that defective products could not be detected at the time of shipment. On the other hand, in Example 1, in which the aging process was performed before the initial charging process, the sulfurization progressed sufficiently, so it is considered that the short circuit of the battery could be detected at the time of shipment.

For a detailed explanation of the reaction between the sulfide solid electrolyte (Li ₂ S) and Cu, which is a metal foreign matter, see A.K. Hayashi et al. , Electrochem. Comm. , 2003. Further, CuS generated by the reaction between the sulfide solid electrolyte and Cu has electronic conductivity. This is for example L. Liu et al. , Solid State Ionics, 2013. It is described in.

In Comparative Examples 2 to 4, a voltage drop occurred in about 50 days in the endurance test. From this, it can be expected that about 60 days are probably required to sulfurize the metal foreign matter in the charged state and short-circuit the battery.

From the results of Comparative Example 5 and Examples 1 and 2, it can be seen that the short-circuit detectability differs depending on the temperature in the aging process. During the storage period of 7 days, if the temperature was 60° C. or higher, the sulfide all-solid-state battery containing foreign matter could be detected at the time of shipment. This is probably because the sulfide all-solid-state battery containing foreign matter caused a chemical short circuit during the aging process.

From Comparative Example 6 and Examples 3 and 4, it can be seen that the higher the temperature of the aging process, the shorter the number of days of the aging process. This is because when the temperature of the aging process is 60° C., defective products cannot be detected at the time of shipment after 3 days, but when the temperature is 80° C., defective products can be detected at the time of shipment after 3 days.

(Sulfidation rate study)
Furthermore, the sulfidation rate in the aging process was investigated.
A sulfide all-solid-state battery shown in Table 2 was produced using the positive electrode, negative electrode, and sulfide solid electrolyte layer produced as described above. Then, an aging test was performed under the conditions shown in Table 2. Here, the number of days of voltage drop (number of days of short circuit) is the number of days until the voltage drops by 50 mV or more. The sulfidation rate is the quotient of the sum of the thickness of the negative electrode and the thickness of the sulfide solid electrolyte layer and the voltage drop days.
FIG. 2 shows the relationship between voltage drop days (short-circuit days) and temperature, and FIG. 3 shows the relationship between sulfurization rate and temperature.

From FIG. 2, it was found that the higher the temperature, the shorter the voltage drop days (short circuit days). Therefore, it is considered that temperature accelerates the sulfurization of foreign metals. It was also found that the specific sulfurization rate was 0.1905/{V·exp(0.03888·T) (μm·day ⁻¹ ). This is obtained by approximating the results of FIG. Therefore, the amount of sulfidation can be calculated by multiplying this by the number of days of voltage drop. The formula for calculating the amount of sulfurization is shown in the following formula (2). Here, the aging voltage is V (V), the aging temperature is T (°C), and the number of aging days is D (day).
[0.1905/{V·exp(0.03888·T)}]·D (2)

The battery has a negative electrode current collector made of Cu. Therefore, it is considered that sulfuration occurs from the side of the negative electrode current collector. Therefore, assuming that the metal foreign matter is on the negative electrode current collector farthest from the positive electrode, the aging process is set so as to satisfy the following formula (3), so that defective products can be detected before shipment. It is considered to be. Here, x (μm) is the thickness of the negative electrode layer, and y (μm) is the thickness of the sulfide solid electrolyte layer.
x+y≦[0.1905/{V·exp(0.03888·T)}]·D (3)

Claims (1)

A method for producing a sulfide all-solid-state battery, comprising aging a sulfide all-solid-state battery having a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer before initial charging. and
The production method, wherein the sulfide amount of the sulfide all-solid-state battery at the time of shipment calculated based on the following formula (2) is 31 or more.
[0.1905/{V·exp(0.03888·T)}]·D (2)
In the formula (2), V is the aging voltage (V), T is the aging temperature (° C.), and D is the number of aging days (day).

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