JP2020191183A - Method of manufacturing sulfide all-solid-state battery - Google Patents

Abstract

To provide a method of manufacturing sulfide all-solid-state batteries, capable of preventing the outflow of defective products.SOLUTION: In a method of manufacturing sulfide all-solid-state batteries, a sulfide all-solid-state battery including a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer arranged between the positive electrode layer, and the negative electrode layer is subjected to aging before initial charge.SELECTED DRAWING: Figure 1

Description

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

Conventionally, an aging step may be provided in a method for manufacturing a liquid battery. For example, Patent Document 1 discloses that the irreversible capacity can be reduced by performing an aging step before the initial charging of an alkaline secondary battery. This is because the material is deteriorated and an overvoltage is generated.

On the other hand, the method for manufacturing an all-solid-state battery may also include an aging step. For example, Patent Document 2 discloses that the assembled battery after the initial charge is aged in order to make the electrical characteristics of all the assembled batteries substantially the same. Patent Document 3 discloses that a monomer having a vinyl group or a derivative thereof is polymerized to form a polymer, and an aging step is performed in order to obtain a gel-like electrolyte or a solid electrolyte obtained by solidifying the monomer solution. .. Further, Patent Document 3 discloses that when manufacturing a lithium ion battery, an aging step is performed after the initial charging. Further, Patent Document 3 discloses that the initial charging state is maintained for 48 hours or more.

Japanese Unexamined Patent Publication No. 09-274932 JP 2015-118867 JP-A-2002-280074

Generally, when manufacturing a liquid battery, an aging process is performed before the initial charging. There are two reasons for this. The first is to form a film on the surface of the negative electrode. As a result, the resistance is reduced and the decomposition of the electrolyte is suppressed. The second is that by performing aging before the initial charging, the metallic foreign matter mixed in the positive electrode side is dissolved and deposited on the negative electrode side to promote a short circuit. As a result, it is possible to prevent the outflow of defective products by short-circuiting them in advance before shipping.

The second reason above is also an important idea for all-solid-state batteries. Generally, metals dissolve at high potentials and precipitate at low potentials. Therefore, in a liquid battery, by performing an aging step before the initial charging, metal foreign substances in the positive electrode can be dissolved, and the dissolved metal ions can be transported in the electrolyte by liquid diffusion and deposited on the negative electrode side. it can. As a result, the battery can be short-circuited. On the other hand, in the all-solid-state battery, even if the metal foreign matter is dissolved on the positive electrode side, the metal ion cannot be diffused in the electrolyte and cannot reach the negative electrode. That is, under normal conditions, the battery does not short-circuit.
Therefore, it has been difficult to prevent the outflow of defective products by short-circuiting the all-solid-state battery in advance before shipping.

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

As a result of diligent studies, the present inventors have found that by using a sulfide solid electrolyte as the solid electrolyte used for the all-solid electrolyte, it is possible to short-circuit in advance before shipping. Specifically, by using a sulfide solid electrolyte, the metal foreign matter mixed on both sides of the positive and negative electrodes and the sulfide solid electrolyte are chemically reacted (sulfurized), and when the sulfided metal foreign matter has conductivity, the battery It was found that a short circuit can occur.

Here, it is known that the above-mentioned sulfurization reaction is basically promoted when the potential is high. Therefore, the sulfurization of the metallic foreign matter mixed in the high potential positive electrode side is relatively easy, but the sulfurization of the metallic foreign matter mixed in the low potential negative electrode side is difficult. Therefore, since the progress of sulfurization of the metallic foreign matter mixed in the negative electrode side is slow, it is considered that a short circuit may not be detected during the durability test. Therefore, the present inventors have found that the detection rate of short-circuit occurrence is increased by performing an aging step before the initial charging in order to promote the progress of sulfurization of the metallic foreign matter mixed in the negative electrode side.

As described in Patent Documents 2 and 3, if the aging step is performed after the initial charging, the potential of the negative electrode is lowered, so that the sulfurization rate of the metal foreign matter is slow, and there is a possibility that a short circuit cannot be detected.

Based on the above findings, the present application provides sulfide having a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer arranged 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 battery is aged before the first charge.

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

It is a flowchart of the manufacturing method 100 of a sulfide all-solid-state battery. It is a figure which shows the relationship between the short circuit days and temperature in a sulfidation rate study experiment. It is a figure which shows the relationship between the sulfurization rate and temperature in a sulfurization rate examination experiment.

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

In the method 100 for manufacturing a sulfide all-solid-state battery, a sulfide all-solid-state battery having a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer is aged before initial charging. It is characterized by that. Specifically, the method 100 for manufacturing a sulfide all-solid-state battery includes a step S1 for obtaining a sulfide all-solid-state battery (hereinafter, may be referred to as “sulfide all-solid-state battery manufacturing step S1”) and a sulfide all-solid-state battery. A step S2 for 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 for first charging the sulfide all-solid-state battery after the aging step S2 (hereinafter referred to as "aging step S2"). In the above, it is sometimes referred to as "initial charging step S3"). Further, after the initial charging step S3, a step S4 (hereinafter, may be referred to as “discharging step S4”) for discharging the sulfide all-solid-state battery may be provided.
FIG. 1 shows a flowchart of the manufacturing method 100.

(Sulfide all-solid-state battery manufacturing step S1)
The sulfide all-solid-state battery manufacturing step S1 is a step of manufacturing a sulfide all-solid-state battery having a sulfide all-solid electrolyte. The sulfide all-solid-state battery includes a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer. Further, a positive electrode current collector is arranged on the surface on the positive electrode side of at least the end surface of the sulfide all-solid-state battery in the stacking direction. Further, the negative electrode current collector is arranged on the surface on the negative electrode side of at least the end surface 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 the positive electrode active material. In addition to the positive electrode active material, the positive electrode layer may optionally contain a solid electrolyte, a binder, a conductive agent, and the like. As the positive electrode active material, a known positive electrode active material may be used. For example, when constructing a lithium ion battery, various types of positive electrode active materials such as lithium cobalt oxide, lithium nickel oxide, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , lithium manganate, and spinel-based lithium compounds are used. Lithium-containing composite oxides 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 a known sulfide solid electrolyte 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 S-P ₂ S ₅ , Li ₂ SP ₂ S. ₅ -LiI-LiBr, 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 , Li ₂ S-P ₂ S _5- GeS _Second grade can be mentioned. Examples of the binder that can be contained in the positive electrode layer include butadiene rubber (BR), butylene rubber (IIR), acrylate butadiene rubber (ABR), polyvinylidene fluoride (PVDF), and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-). HFP) and the like. Examples of the conductive agent that can be contained in the negative electrode layer include carbon materials such as acetylene black, Ketjen black, and vapor phase 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 before. The shape of the positive electrode layer may be the same as the conventional one. In particular, a sheet-shaped positive electrode layer is preferable from the viewpoint that a sulfide all-solid-state battery can be easily constructed. In this case, the thickness of the positive electrode layer is, for example, preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 150 μm or less.

The negative electrode layer contains at least the negative electrode active material. In addition to the negative electrode active material, the negative electrode layer may optionally contain a solid electrolyte, a binder, a conductive agent, and the like. As the negative electrode active material, a known negative electrode active material may be used. For example, in the case of forming a lithium ion battery, as a negative electrode active material, a silicon-based active material such as Si, Si alloy or silicon oxide; a carbon-based active material such as graphite or hard carbon; various oxide-based active materials such as lithium titanate. Material: Metallic lithium, lithium alloy, etc. 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. As the binder that can be contained in the negative electrode layer, for example, the above-mentioned binder can be exemplified. As the conductive agent that can be contained in the negative electrode layer, for example, the above-mentioned conductive agent can be exemplified. The content of each component in the negative electrode layer may be the same as before. The shape of the negative electrode layer may be the same as the conventional one. In particular, a sheet-shaped negative electrode layer is preferable from the viewpoint that a sulfide all-solid-state battery can be easily constructed. In this case, the thickness of the negative electrode layer is, for example, preferably 0.1 μm or more and 1 mm or less, and 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 so 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. The sulfide solid electrolyte layer may optionally contain a binder, a conductive agent, or the like in addition to the 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. As the binder that can be contained in the sulfide solid electrolyte layer, for example, the above-mentioned binder can be exemplified. As the conductive agent that can be contained in the sulfide solid electrolyte layer, for example, the above-mentioned conductive agent can be exemplified. The content of each component in the sulfide solid electrolyte layer may be the same as before. The shape of the sulfide solid electrolyte layer may be the same as before. In particular, a sheet-shaped sulfide solid electrolyte layer is preferable from the viewpoint that a sulfide all-solid-state battery can be easily constructed. In this case, the thickness of the sulfide solid electrolyte layer is preferably, for example, 0.1 μm or more and 1 mm or less, and 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 a metal foil, a metal mesh, or the like. Metal foil is particularly preferable. Examples of the metal constituting 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. Especially Cu and Al are preferable. The positive electrode current collector and the negative electrode current collector may have some coating layer for adjusting the resistance on the surface thereof. 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, and 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 laminating and pressing a positive electrode layer, a solid electrolyte layer, and a negative electrode layer prepared separately. The positive electrode layer can be produced by applying a slurry containing a component constituting the positive electrode layer to a base material or a positive electrode current collector and drying the slurry. The negative electrode layer can be produced by applying a slurry containing a component constituting the negative electrode layer to a base material or a negative electrode current collector and drying the slurry. The solid electrolyte layer can be produced by applying a slurry containing a component constituting the solid electrolyte layer to a base material and drying it.

Further, the sulfide all-solid-state 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, the metal foreign matter mixed in the positive electrode or the negative electrode of the sulfide all-solid-state battery can be sulfided. According to this, the sulfide all-solid-state battery mixed with the metal foreign matter can be short-circuited before shipping, and the outflow of defective products can be prevented.

Preferably, the aging step S2 is set under the condition satisfying the following formula (1). This formula is calculated on the assumption that a metal foreign substance is mixed in the negative electrode current collector side farthest from the positive electrode. This is because the positive electrode always has a higher potential than the negative electrode, and if sulfurization is completed on the negative electrode current collector side farthest from the positive electrode, it can be considered that sulfurization is completed on the positive electrode side as well. Here, in the 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 set. It was designated as 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), the outflow of defective products can be prevented more reliably.

The upper limit of the aging temperature is not particularly limited, but is preferably 230 ° C. or lower, more preferably 100 ° C. or lower, and particularly preferably 80 ° C. or lower. This was determined from the following viewpoints. That is, considering the essential battery materials, it is considered that the temperature upper limit is about 230 ° C. When a binder is included, it is considered that the temperature upper limit is about 100 ° C., which is the heat resistant temperature of the binder. Further, when the entire battery is covered with the metal laminate film, it is considered that the temperature upper limit is about 80 ° C., which is the heat resistant temperature of the metal laminate film. The lower limit of the aging temperature is not particularly limited, but 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 process S3)
The initial charging step charging is a step of first charging the sulfide all-solid-state battery aged in the aging step S2. "First 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.

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

From the 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 producing a sulfide all-solid-state battery of the present disclosure is characterized in that the sulfide all-solid-state battery is aged before the first charge. As a result, the battery containing foreign matter can be short-circuited and detected in advance before shipment. Further, the method for producing a sulfide all-solid-state battery of the present disclosure is applicable to any method for producing a sulfide all-solid-state battery, but is suitable for a method for producing a lithium-ion sulfide all-solid-state battery.

Hereinafter, a method for producing the sulfide all-solid-state battery of the present disclosure will be described with reference to Examples.

[Manufacturing 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) butyrate 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 onto the Al foil and dried to obtain a solid electrolyte layer.

(Making a sulfide all-solid-state battery)
The negative electrode and the solid electrolyte layer were stacked so that the surface of the negative electrode on the negative electrode layer side and the solid electrolyte layer were in contact with each other, and the solid electrolyte layer was pressed at 1 ton / cm, and then the Al foil of the solid electrolyte layer was removed. Next, the surface of the positive electrode on the positive electrode layer side was superposed on the solid electrolyte layer and pressed at 3 ton / cm. At this time, it was confirmed that the thicknesses of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer were the positive electrode layer: 50 μm, the solid electrolyte layer: 30 μm, and the negative electrode layer: 70 μm. Then, the current collector 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 a sulfide all-solid-state battery.

(Making a sulfide all-solid-state battery containing foreign matter)
In the above method for producing a sulfide all-solid-state battery, except that when the negative electrode layer and the sulfide solid electrolyte are superposed, Cu foils having a diameter of 300 μm and a thickness of 10 μm are placed on the negative electrode layer and superposed. A sulfide all-solid-state battery containing a foreign substance was produced in the same manner as in the method for producing a sulfide all-solid-state battery.

[Cell activation process]
Five sulfide all-solid-state batteries and five foreign-containing sulfide all-solid-state batteries produced above were combined and activated using one set (10 in total) under the following conditions. Charging was performed at 1/3 CC CV and 0.1 CCu Out, and discharging was performed at 1 CC CV and 0.1 CCu Out. The conditions of the aging process are shown in Table 1.

(Comparative Example 1)
Cell activation was carried out in the following step order.
・ Initial charging process: 2.95V charging, 25 ℃
・ Discharge process 1: 25 ℃, 3days self-discharge ・ Discharge process 2: 1.5V discharge, 25 ℃

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

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

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

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

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

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

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

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

(Example 4)
Cell activation was carried out in the following step order.
・ Aging process: 40 ℃, 10 days storage ・ Initial charging process: 2.95V charging, 25 ℃
・ Discharge process 1: 25 ℃, 3days self-discharge ・ Discharge process 2: 1.5V discharge, 25 ℃

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

(An endurance test)
Each of the batteries that passed the above steps was subjected to a durability test under the conditions of SOC 80%, temperature 60 ° C., and storage period 90 days. In the durability test, the voltage was measured and monitored every 3 days. Throughout the storage period, sulfide all-solid-state batteries that did not drop by 50 mV / 3 days or more at the time of voltage monitoring were evaluated as non-defective products.
The results are shown in Table 1.

Here, the defective outflow rate in Table 1 is a percentage of the number of foreign-containing sulfide all-solid-state batteries evaluated as good products at the time of shipment with respect to the number of foreign-containing sulfide all-solid-state batteries (5). The amount of sulfurization is the amount of sulfurization of the sulfide all-solid-state battery at the time of shipment, and is calculated based on the formula (2) described later. In Comparative Examples 1 to 4, the aging process is performed after the initial charging. The amount of sulfide is a reference value.

From Table 1, in Comparative Examples 1 to 6, the number of non-defective products at the time of shipment was 10, but after the durability test, it was 5. It is considered that this is because the sulfide all-solid-state battery containing foreign matter was chemically short-circuited during the durability 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 substances could be removed. It is considered that this is because the sulfide all-solid-state battery containing foreign matter was chemically short-circuited in the aging process.

Each test example will be examined in detail below.
First, Comparative Examples 2 and 4 and Example 1 are compared. In Comparative Examples 2 and 4, the initial charging step is performed before the aging step. On the other hand, in the first embodiment, the aging step is performed before the initial charging step. As mentioned above, sulfurization of metals is promoted on the high voltage side. Therefore, it becomes difficult to sulfurize by charging. Therefore, it is probable that in Comparative Examples 2 and 4 in which the aging step was carried out after the initial charging step, the sulfurization did not proceed sufficiently, so that the defective product could not be detected at the time of shipment. On the other hand, in Example 1 in which the aging step was carried out before the initial charging step, sulfurization proceeded sufficiently, and it is considered that a short circuit of the battery could be detected at the time of shipment.

Incidentally, the detailed description of the reaction between Cu is a metal foreign object as the sulfide solid electrolyte (Li 2 _S), A. Hayashi et al. , Electrochem. Comm. , 2003 can be referred to. Further, CuS produced by the reaction between the sulfide solid electrolyte and Cu has electron conductivity. This is, for example, L. Liu et al. , Solid State Inics, 2013. It is described in.

In Comparative Examples 2 to 4, a voltage drop occurred in about 50 days in the durability test. From this, it can be expected that it will take about 60 days to sulphurize 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 detectability of the short circuit differs depending on the temperature in the aging step. During the storage period of 7 days, a sulfide all-solid-state battery containing a foreign substance could be detected at the time of shipment at 60 ° C. or higher. It is considered that this is because the sulfide all-solid-state battery containing foreign matter was chemically short-circuited during the aging process.

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

(Sulfurization rate examination)
Furthermore, the sulfurization rate in the aging process was examined.
The sulfide all-solid-state battery shown in Table 2 was prepared using the positive electrode, the negative electrode, and the sulfide solid electrolyte layer prepared as described above. Then, the aging test was carried out under the conditions shown in Table 2. Here, the number of days of voltage drop (number of short-circuit days) is the number of days until the voltage drops by 50 mV or more. The sulfurization rate is a quotient of the sum of the thickness of the negative electrode and the thickness of the sulfide solid electrolyte layer and the number of days of voltage drop.
Further, FIG. 2 shows the relationship between the voltage drop days (short-circuit days) and the temperature, and FIG. 3 shows the relationship between the sulfurization rate and the temperature.

From FIG. 2, it was found that the number of voltage drop days (short-circuit days) decreases as the temperature rises. Therefore, it is considered that the sulfurization of the foreign metal is promoted by the temperature. 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 sulfide can be calculated by multiplying this by the number of days of voltage drop. The formula for calculating the amount of sulfide is shown in the following formula (2). Here, the aging voltage was V (V), the aging temperature was T (° C.), and the number of aging days was D (day).
[0.1905 / {V ・ exp (0.03888 ・ T)}] ・ D ・ ・ ・ (2)

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

Claims (1)

A sulfide all-solid-state battery having a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer is aged before initial charging.
A method for manufacturing a sulfide all-solid-state battery.

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