KR102224752B1 - Method for testing all solid state battery, method for producing all solid state battery, and method for producing battery pack - Google Patents

Abstract

[Problem] The present disclosure provides a method for inspecting an all-solid-state battery capable of accurately inspecting the presence or absence of a short circuit or a defect that causes a short circuit in a relatively simple method of measuring a current value by applying a voltage. The main purpose is to do it.
[Solution means] In the present disclosure, a resistance increasing step of increasing the resistance of an all-solid-state battery to 3.2×10 ⁵ Ω·cm ² or more, a voltage applying step of applying a voltage to the all-solid-state battery having increased resistance, and The problem is solved by providing an all-solid-state battery inspection method having a determination step of determining whether or not the all-solid-state battery is passed based on the current value measured in the voltage application step.

Description

All-solid-state battery inspection method, all-solid-state battery manufacturing method, and assembly battery manufacturing method {METHOD FOR TESTING ALL SOLID STATE BATTERY, METHOD FOR PRODUCING ALL SOLID STATE BATTERY, AND METHOD FOR PRODUCING BATTERY PACK}

The present disclosure relates to a method for inspecting an all-solid-state battery.

The all-solid-state battery is a battery having a solid electrolyte layer between the positive electrode active material layer and the negative electrode active material layer, and it is said that the simplification of the safety device is easier to achieve as compared to a liquid battery having an electrolyte solution containing a flammable organic solvent. Has the advantage of doing it.

On the other hand, although it is not a technology related to an all-solid-state battery, in Patent Document 1, the voltage is applied to a non-injected liquid battery (a battery before injecting an electrolyte) having a cell composed of a positive electrode plate, a negative electrode plate, and a separator. A battery short-circuit inspection method is disclosed in which a short-circuit inspection is performed by applying.

Japanese Unexamined Patent Application Publication No. 2001-110458

When manufacturing an all-solid-state battery, it is preferable to inspect the presence or absence of a short circuit (including a short circuit) or the presence or absence of a defect (for example, a foreign object) causing the short circuit. For example, in Patent Document 1, a short circuit test is performed by applying a voltage to a battery having a positive electrode plate, a negative electrode plate, and a separator and not having an electrolyte solution and measuring a current value. However, due to the characteristics of the solid electrolyte, it is difficult to simply apply such a test method to an all-solid battery.

The present disclosure has been made in view of the above circumstances, and is a relatively simple method of measuring a current value by applying a voltage, and of an all-solid-state battery capable of accurately inspecting the presence or absence of a short circuit or the presence or absence of a defect that causes a short circuit. Its main purpose is to provide an inspection method.

In order to solve the above problem, in the present disclosure, ^{a resistance increasing step of increasing the resistance of the all-solid battery to 3.2×10 5} Ω·cm ² or more, and applying a voltage to apply a voltage to the all-solid battery with increased resistance A method for inspecting an all-solid-state battery having a step and a determination step of determining whether or not the all-solid-state battery is passed based on a current value measured in the voltage application step is provided.

According to the present disclosure, it is a relatively simple method of measuring a current value by applying a voltage by subjecting an all-solid-state battery with increased resistance to a predetermined value as an inspection object. Can be inspected with good precision.

In the above disclosure, in the resistance increasing step, the resistance of the all-solid-state battery may be increased by freezing treatment.

In the above disclosure, the freezing treatment may be a treatment in which the temperature of the all-solid-state battery is -90°C or less.

In the above disclosure, the freezing treatment may be a treatment in which the temperature of the all-solid-state battery is -140°C or less.

In addition, in the present disclosure, a resistance increasing step of increasing the resistance of the all-solid-state battery by freezing treatment, a voltage application step of applying a voltage to the all-solid-state battery with increased resistance, and measurement in the voltage application step A method for inspecting an all-solid-state battery is provided having a determination step of determining whether the all-solid-state battery is passed or not based on the current value.

According to the present disclosure, it is a relatively simple method of measuring a current value by applying a voltage by subjecting an all-solid-state battery to which resistance has been increased by freezing treatment as an inspection object, and whether there is a short circuit or a defect that causes a short circuit. Can be inspected with good precision.

In the above disclosure, in the resistance increasing step, the resistance of the all-solid-state battery may be increased by reducing the restraining pressure of the all-solid-state battery.

In the above disclosure, the all-solid-state battery is a battery containing a sulfide solid electrolyte, and in the resistance increasing step, the voltage is applied by increasing the resistance of the all-solid-state battery whose voltage is adjusted to 1.5 V or more and 3.5 V or less. In the process, the voltage may be applied two or more times.

In addition, in the present disclosure, there is provided a method for manufacturing an all-solid-state battery having a preparation step of preparing an all-solid-state battery, and an inspection step of inspecting the all-solid-state battery using the above-described all-solid-state battery inspection method. .

According to the present disclosure, an all-solid-state battery with higher stability can be obtained by inspecting an all-solid-state battery using the above-described inspection method.

In addition, in the present disclosure, a preparation step of preparing an all-solid-state battery, an inspection step of inspecting the all-solid-state battery using the above-described inspection method for an all-solid-state battery, and the test determined as pass in the inspection step. A method for manufacturing an assembled battery having an assembly step of assembling the assembled battery by using a plurality of all-solid-state batteries is provided.

According to the present disclosure, a more stable assembled battery can be obtained by using the all-solid-state battery judged to pass in the inspection step.

The inspection method for an all-solid-state battery of the present disclosure is a relatively simple method of measuring a current value by applying a voltage, and has the effect of being able to accurately inspect the presence or absence of a short circuit or the presence or absence of a defect that causes a short circuit. Show.

1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present disclosure.
2 is a flow chart illustrating an example of a method for inspecting an all-solid-state battery according to the present disclosure.
3 is a schematic cross-sectional view showing an example of a preparation step in the present disclosure.
4 is a schematic perspective view illustrating a foreign material in the present disclosure.
5 is a graph showing the relationship between the battery voltage and the current ratio I ₂ /I _1.

Hereinafter, a method for inspecting an all-solid-state battery, a method for manufacturing an all-solid-state battery, and a method for manufacturing an assembled battery according to the present disclosure will be described in detail.

A. Test method for all-solid-state batteries

1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present disclosure. The all-solid-state battery 10 shown in FIG. 1 includes a positive electrode active material layer 1, a negative electrode active material layer 2, and a solid electrolyte layer 3 formed between the positive electrode active material layer 1 and the negative electrode active material layer 2 ). In addition, the all-solid-state battery 10 has a positive electrode current collector 4 that collects the positive electrode active material layer 1 and a negative electrode current collector 5 that collects the negative electrode active material layer 2.

2 is a flowchart illustrating an example of a method for inspecting an all-solid-state battery according to the present disclosure. When the method of inspecting an all-solid-state battery of the present disclosure is started, first, the resistance of the all-solid-state battery is increased (resistance increasing step, S1). For example, by freezing treatment, the resistance of the all-solid-state battery is increased. Next, a voltage is applied to the all-solid-state battery whose resistance has increased (voltage application step, S2). When the resistance of the all-solid-state battery is sufficiently high, a high voltage of about 1000 V can be applied, for example. Subsequently, the current generated when a voltage is applied is measured, and based on the measured current value, it is determined whether the all-solid-state battery is passed or not (judgment step, S3). For example, in a ratio determined to be (I _A / I _B) is, if the reference value is less than the acceptance of I _A to I _B used as a reference of the measured current value I _A and the acceptance determination current value I _B And, if it is more than the reference value, it is judged as disqualified. Accordingly, the inspection is ended.

According to the present disclosure, it is a relatively simple method of measuring a current value by applying a voltage by using an all-solid-state battery with increased resistance as an inspection object. Can be inspected. In particular, in the present disclosure, the presence or absence of a short circuit (internal short circuit) in the solid electrolyte layer can be inspected with good precision. In addition, a short paragraph is also included in a paragraph in this disclosure. The short-circuit refers to a short-circuit with a hardness that can be charged or discharged, although short-circuit itself has occurred. For example, if the insulating property of the solid electrolyte layer is low, a short short is likely to occur. On the other hand, as a defect causing a short circuit, for example, a foreign matter can be mentioned. For example, if a foreign material is present in or near the solid electrolyte layer, cracks are likely to occur in the solid electrolyte layer, and as a result, a short circuit is likely to occur.

As described above, in Patent Document 1, a short-circuit test is performed by applying a voltage to a battery having a positive electrode plate, a negative electrode plate, and a separator and not having an electrolytic solution to measure a current value. However, due to the characteristics of the solid electrolyte, it is difficult to simply apply such a test method to an all-solid battery. The reason is as follows. In a battery that has a positive electrode, a negative electrode, and a separator, and does not have an electrolytic solution, ion conduction is not performed between the positive and negative electrodes. In other words, since the battery does not function as a battery, the presence or absence of a short circuit can be easily inspected by applying a voltage between the positive and negative electrodes and measuring the current value. On the other hand, in the all-solid electrolyte layer, the solid electrolyte layer has insulating properties and ion conductivity. In other words, since a battery with a solid electrolyte layer functions as a battery, when a voltage is applied between the positive and negative electrodes, the all-solid battery is charged. Even if the current value is measured, the presence or absence of a short circuit is non-destructively inspected. It is difficult to do. In this way, it is difficult to simply apply the inspection method for a liquid-based battery to an all-solid-state battery.

In contrast, in the present disclosure, the resistance of the all-solid-state battery is increased by, for example, freezing treatment. Accordingly, it is possible to suppress a reaction occurring in the battery. By applying a voltage between the positive and negative electrodes of the battery in such a high resistance state and measuring a current value, the presence or absence of a short circuit or a defect that causes the short circuit can be inspected with good precision.

1. Resistance increase process

The resistance increasing step in the present disclosure is a step of increasing the resistance of the all-solid-state battery. In this step, the resistance of the all-solid-state battery ^{may be increased to, for example, 1×10 5} Ω·cm ² or more, or may be increased to 3.2×10 ⁵ Ω·cm ² or more, or 1×10 ⁶ Ω·cm ² It may be increased above, 1×10 ⁷ Ω·cm ² or more, 1×10 ⁸ Ω·cm ² or more, or 3.2×10 ⁸ Ω·cm ² or more. In addition, since the resistance of the all-solid-state battery is inversely proportional to the area, in the present disclosure, it is defined as ^{the resistance per unit area (Ω·cm 2 ).} In addition, the resistance of the all-solid-state battery can be obtained by the method described in Examples to be described later.

In addition, the degree to which the resistance of the all-solid-state battery is increased varies depending on the purpose of the inspection. It is desirable to increase the resistance of the all-solid-state battery, the higher the difficulty is. As the purpose of the inspection, for example, a short-circuit inspection, a short-circuit inspection, and a foreign matter inspection can be mentioned. In addition, foreign matter inspection includes, for example, inspection of foreign matters penetrating the solid electrolyte layer, inspection of foreign matters not penetrating the solid electrolyte layer, inspection of foreign matters contained in the solid electrolyte layer, solid electrolyte layer and electrode active material layer (positive electrode The inspection of foreign matter contained between the active material layer or the negative electrode active material layer) is mentioned.

In the present disclosure, the resistance of the all-solid-state battery is usually increased by resistance increasing treatment. The resistance increasing treatment is not particularly limited, but is preferably a treatment capable of increasing the resistance of the all-solid-state battery to the extent that it does not function as a battery. In addition, it is preferable that the resistance increase processing is a processing of temporarily increasing the resistance of the all-solid-state battery. That is, after the voltage application step described later, it is preferable that it is a treatment capable of reducing the increased resistance.

As an example of the resistance increasing treatment, a freezing treatment is mentioned. In the freezing treatment, by lowering the temperature of the all-solid-state battery, reactions occurring in the battery are entirely suppressed or stopped, thereby increasing the resistance of the all-solid-state battery. In addition, for example, when freezing treatment is performed on the electrolyte, the volume change during freezing is large, and damage is easily caused to the battery. In contrast, the all-solid-state battery has an advantage that it is difficult to damage the battery because the volume change during freezing is small.

In the present disclosure, by freezing treatment, the temperature of the all-solid-state battery may be, for example, -45°C or less, -90°C or less, -100°C or less, or -120°C or less. It may be -135°C or less, or -140°C or less. Although it does not specifically limit as a freezing method, A method of making an all-solid-state battery contact a refrigerant is mentioned. Examples of the refrigerant include liquid helium, liquid nitrogen, liquid oxygen, and dry ice. In addition, as a refrigerant, a general freezing mixture may be used.

Another example of the resistance increasing treatment is a treatment of reducing the restraining pressure of the all-solid-state battery. In an all-solid-state battery, a restraining pressure is usually applied to reduce battery resistance. By reducing the constraining pressure, it is possible to increase the resistance of the all-solid-state battery. In addition, in this process, the restraining pressure may be set to zero. In addition, it is preferable to use this treatment as an auxiliary treatment to the freezing treatment.

The voltage of the all-solid-state battery immediately before performing the resistance increasing treatment is not particularly limited. Before performing the resistance increasing treatment, the all-solid-state battery may be charged, or the charging process may not be performed.

2. Voltage application process

The voltage application step according to the present disclosure is a step of applying a voltage to the all-solid-state battery having the increased resistance. The method of applying a voltage to the all-solid-state battery is not particularly limited, and for example, a method of applying a voltage by connecting an insulation resistance meter to a positive and negative terminal is exemplified.

Although the value of the voltage to be applied is not particularly limited, for example, it may be 1 V or more, 2 V or more, 100 V or more, 500 V or more, or 1000 V or more. The larger the voltage value, the larger the measured current value. On the other hand, the upper limit of the voltage to be applied is not particularly limited, but if a very high voltage is applied, there is a possibility of damaging the all-solid-state battery. For example, when the resistance of the all-solid-state battery at the time of measurement is sufficiently high, even if the applied voltage is increased, the current value decreases, so it is difficult to cause damage to the all-solid-state battery. On the other hand, when the resistance of the all-solid-state battery at the time of measurement is low, the current value increases when the applied voltage is increased, so it is easy to damage the all-solid-state battery. The value of the applied voltage is a value at which the current value flowing through the all-solid battery (particularly, the all-solid-state battery judged to be passed) is, for example, 5 mA or less, and may be a value such as 3.2 mA or less. In addition, the time to apply the voltage is, for example, 0.1 second or longer, and may be 0.5 second or longer. On the other hand, the time to apply the voltage is, for example, 10 seconds or less, and may be 5 seconds or less.

The number of times the voltage is applied to the all-solid-state battery is not particularly limited. The number of times the voltage is applied may be one time, two or more times, or three or more times. As the number of times the voltage is applied increases, the number of data to be obtained increases, and thus the accuracy of determination of whether or not to pass is basically improved.

3. Judging process

The determination step in the present disclosure is a step of determining whether or not the all-solid-state battery is passed based on the current value measured in the voltage application step.

The criteria for determining whether to pass or not can be appropriately set according to the purpose of the inspection. For example, the measured current value by I _A, when the current value that is the basis for the success-or-not determination to I _B, the ratio (I _A / I _B) of I _A to I _B, if the reference value is less than pass If it is determined that it is equal to or higher than the reference value, it can be determined that it is rejected. The reference value of I _A /I _B is not particularly limited, but is, for example, 1.5 or more, and may be 2 or more.

In addition, as described above, as the number of times the voltage is applied increases, the number of data obtained increases, and thus the accuracy of the pass determination is basically improved. On the other hand, when a voltage is applied multiple times to an all-solid-state battery containing a sulfide solid electrolyte, on the contrary, the accuracy of the pass or not determination sometimes decreases. Specifically, when a voltage is applied multiple times to an all-solid-state battery containing a sulfide solid electrolyte, the measured current value I _A may increase even if the product does not have a short circuit or defect. When the current value I _A increases, _{the value of I A} /I _B also increases, making it difficult to judge whether or not to pass. _{The reason why the current value I A} increases by applying the voltage multiple times is not completely clear, but the possibility that the sulfide solid electrolyte is deteriorated or deformed by the first voltage application, and conductive sulfide (e.g., CuS) is generated. There is a possibility.

On the other hand, by setting the voltage of the battery to 1.5 V or more and 3.5 V or less, it is possible to suppress an _{increase in the current value I A} (an increase in the _{value of I A} /I _{B) even when the voltage is applied multiple times.} In addition, since the number of data to be obtained increases, the accuracy of the pass determination is further improved. As described above, when the all-solid-state battery is a battery containing a sulfide solid electrolyte, in the resistance increasing step, the resistance of the all-solid-state battery whose voltage is adjusted to 1.5 V or more and 3.5 V or less is increased, and in the voltage application step, the voltage It is preferable to apply at least two times.

The voltage of the battery may be 1.7 V or higher, or 1.9 V or higher. On the other hand, the voltage of the battery may be 3.3 V or less, or 3.1 V or less. The voltage of the battery can be adjusted by, for example, charging processing.

4. All solid battery

The all-solid-state battery in the present disclosure is not particularly limited as long as it is a battery having a solid electrolyte layer, but it is preferably a battery in which metal ions are used as charge carriers. In particular, it is preferable that the all-solid-state battery according to the present disclosure is an all-solid-state lithium ion battery. Further, the all-solid-state battery may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged, and is useful, for example, as a vehicle-mounted battery. Further, the all-solid-state battery may be a battery having a power generation element having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, or may be a battery having a plurality of power generation elements. In the latter case, the all-solid-state battery may be a battery in which a plurality of power generation elements are connected in parallel, or a battery in which a plurality of power generation elements are connected in series. In addition, neighboring power generation elements may share the current collector.

(1) solid electrolyte layer

The solid electrolyte layer is a layer containing a solid electrolyte, and may further contain a binder. As a solid electrolyte, an inorganic solid electrolyte is mentioned, for example. Examples of the inorganic solid electrolyte include a sulfide solid electrolyte, an oxide solid electrolyte, a nitride solid electrolyte, and a halide solid electrolyte. In addition, it is preferable that the inorganic solid electrolyte has, for example, Li ion conductivity.

Examples of the sulfide solid electrolyte include a Li element, an X element (X is at least one of P, Si, Ge, Sn, B, Al, Ga, and In), and a solid electrolyte containing an S element. I can. In addition, the sulfide solid electrolyte may further contain a halogen element. In addition, as the oxide solid electrolyte, for example, Li element, Y element (Y is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, S), and O element. The solid electrolyte to be contained is mentioned. Further, examples of the nitride solid electrolyte include Li ₃ N, and examples of the halide solid electrolyte include LiCl, LiI, and LiBr.

Examples of the binder used in the solid electrolyte layer include rubber-based binders such as butylene rubber (BR) and styrene butadiene rubber (SBR), and fluoride-based binders such as polyvinylidene fluoride (PVdF).

The thickness of the solid electrolyte layer may be, for example, 0.1 µm or more, 1 µm or more, or 10 µm or more. On the other hand, the thickness of the solid electrolyte layer is, for example, 300 µm or less, and may be 100 µm or less.

(2) positive electrode active material layer

The positive electrode active material layer is a layer containing a positive electrode active material, and may further contain at least one of a solid electrolyte, a conductive material, and a binder.

As a positive electrode active material, an oxide active material and a sulfur active material are mentioned, for example. In addition, it is preferable that the positive electrode active material is capable of reacting with, for example, Li ions. As an oxide active material, for example, a rock salt layered _{active material such as LiCoO 2} , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O _{2 , LiMn 2} O ₄ , Spinel-type active materials, such as Li ₄ Ti ₅ O ₁₂ and Li(Ni _0.5 Mn _1.5 ) O _4, and olivine- _{type active materials such as LiFePO 4} , LiMnPO ₄ , LiNiPO ₄ , and LiCoPO _4. Further, a coating layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material. This is because the reaction between the positive electrode active material and the solid electrolyte can be suppressed.

Examples of the conductive fire material used for the positive electrode active material include carbon materials such as acetylene black (AB) and Ketjen black (KB). In addition, since the solid electrolyte and the binder used for the positive electrode active material are the same as those described in the column of the solid electrolyte described above, the description here is omitted.

The thickness of the positive electrode active material layer may be, for example, 0.1 µm or more, 1 µm or more, or 10 µm or more. On the other hand, the thickness of the positive electrode active material layer is, for example, 300 µm or less, and may be 100 µm or less. In addition, examples of the positive electrode current collector for performing current collection of the positive electrode active material layer include SUS foil and Al foil.

(3) negative electrode active material layer

The negative electrode active material layer is a layer containing a negative electrode active material, and may further contain at least one of a solid electrolyte, a conductive material, and a binder.

As a negative electrode active material, a metal active material and a carbon active material are mentioned, for example. In addition, it is preferable that the negative electrode active material is capable of reacting with, for example, Li ions. As a metal active material, a metal simple substance, a metal alloy, and a metal oxide are mentioned, for example. Examples of the metal elements contained in the metal active material include Li, Si, Sn, In, and Al. It is preferable that a metal alloy is an alloy containing the said metal element as a main component. Examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon.

Since the solid electrolyte, the conductive material, and the binder used for the negative electrode active material are the same as those described in the columns of the solid electrolyte and the positive electrode active material layer described above, the description here is omitted.

The thickness of the negative electrode active material layer may be, for example, 0.1 µm or more, 1 µm or more, or 10 µm or more. On the other hand, the thickness of the negative electrode active material layer is, for example, 300 µm or less, and may be 100 µm or less. Further, examples of the negative electrode current collector for performing current collection of the negative electrode active material layer include SUS foil and Cu foil.

(4) All solid battery

The all-solid-state battery according to the present disclosure is a battery containing the above-described inorganic solid electrolyte. Among them, it is preferable that the inorganic solid electrolyte is a sulfide solid electrolyte. It is preferable that the sulfide solid electrolyte is contained in at least one of a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer. Among them, it is preferable that the sulfide solid electrolyte is contained in at least the solid electrolyte layer.

B. Manufacturing method of all-solid-state battery

The manufacturing method of an all-solid-state battery of the present disclosure includes a preparation step of preparing an all-solid-state battery, and an inspection step of inspecting the all-solid-state battery using the above-described inspection method.

According to the present disclosure, an all-solid-state battery with higher stability can be obtained by inspecting an all-solid-state battery using the above-described inspection method.

1. Preparation process

The preparation process is a process of preparing an all-solid-state battery (all-solid-state battery before the inspection process). The method for preparing the all-solid-state battery is not particularly limited, and may be produced by itself or purchased from another person. In the former case, a general method of manufacturing an all-solid-state battery can be employed.

3 is a schematic cross-sectional view showing an example of a preparation step in the present disclosure. First, the positive electrode current collector 4 is prepared (Fig. 3(a)). Subsequently, a slurry containing at least a positive electrode active material is applied onto the positive electrode current collector 4 and dried to obtain a positive electrode having the positive electrode current collector 4 and the positive electrode active material layer 1 (Fig. 3(b)). ). Next, the negative electrode current collector 5 is prepared (Fig. 3(c)). Subsequently, on the negative electrode current collector 5, a slurry containing at least a negative electrode active material is applied and dried to obtain a negative electrode having the negative electrode current collector 5 and the negative electrode active material layer 2 (Fig. 3(d)). ). Subsequently, a slurry containing at least a solid electrolyte is applied, dried, and pressed to form the solid electrolyte layer 3 (Fig. 3(e)). Then, both are disposed so that one surface of the solid electrolyte layer 3 and the positive electrode active material layer 1 of the positive electrode face each other. Then, both are arranged so that the other surface of the solid electrolyte layer 3 and the negative electrode active material layer 2 of the negative electrode face each other. Thereafter, by pressing, the all-solid-state battery 10 is obtained (Fig. 3(f)).

2. Inspection process

In the inspection process, the all-solid-state battery (the all-solid-state battery prepared in the preparation process) is described in "A. This is a step of inspecting using the method described in "Inspection Method for All-solid-state Batteries". About the inspection method, since it is the same as the above-mentioned content, description here is abbreviate|omitted. In addition, normally, an all-solid-state battery judged to pass in the inspection process is selected.

C. Manufacturing method of battery pack

The manufacturing method of the assembled battery of the present disclosure includes a preparation step for preparing an all-solid-state battery, an inspection step for inspecting the all-solid-state battery by using the above-described inspection method, and the previous determined as pass in the inspection step. It has an assembly process of assembling an assembled battery by using a plurality of solid batteries.

According to the present disclosure, a more stable assembled battery can be obtained by using the all-solid-state battery judged to pass in the inspection step. About the preparation process and the inspection process, said "B. It is the same as the content described in "Method of manufacturing an all-solid-state battery", so the description here is omitted. In addition, the assembly process is also the same as the assembly process of a general battery pack. The assembled battery of the present disclosure may be a battery in which a plurality of all-solid batteries are connected in parallel, or may be a battery in which a plurality of all-solid batteries are connected in series. Further, neighboring all-solid-state batteries may share a current collector.

In addition, this disclosure is not limited to the said embodiment. The above-described embodiment is an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present disclosure and has the same operation and effect is included in the technical scope of the present disclosure.

[Example]

[Production Example 1]

(Production of positive drama)

A positive electrode mixture slurry containing lithium cobalt oxide as a positive electrode active material, 70Li ₂ S-30P ₂ S ₅ glass ceramic as a solid active material, and polyvinylidene fluoride (PVDF) as a binder was prepared. The positive electrode mixture slurry was applied to one side of the SUS foil as a positive electrode current collector and dried to obtain a positive electrode having a positive electrode active material layer on the positive electrode current collector (Fig. 3(a), (b)).

(Production of negative play)

A negative electrode mixture slurry containing graphite as a negative electrode active material, 70Li ₂ S-30P ₂ S ₅ glass ceramic as a solid active material, and PVDF as a binder was prepared. The negative electrode slurry was applied to both surfaces of the SUS foil as a negative electrode current collector and dried to obtain negative electrodes each having a negative electrode active material layer on both surfaces of the negative electrode current collector (Figs. 3(c) and (d)).

(Preparation of solid electrolyte layer)

A solid electrolyte _{mixture slurry containing 70Li 2} S-30P ₂ S ₅ glass ceramic as a solid electrolyte and butadiene rubber (BR) as a binder was prepared. The solid electrolyte mixture slurry was applied, dried, and pressure was applied to obtain a solid electrolyte layer (Fig. 3(e)).

(Production of evaluation cell)

A positive electrode was disposed on one side of the solid electrolyte layer, a negative electrode was disposed on the other side of the solid electrolyte layer, and pressure was applied to obtain a cell for evaluation (no foreign matter) (Fig. 3(f)). In addition, the thickness of the solid electrolyte layer was 30 µm. In addition, the voltage of the obtained evaluation cell was about 0V to 0.2V.

[Production Example 2]

As shown in Fig. 4, a foreign material (conductive foreign material) 11 made of SUS304 having an L-shape was prepared. Except having used this foreign material, it carried out similarly to manufacture example 1, and obtained the cell for evaluation (with a foreign material). Specifically, between the solid electrolyte layer and the positive electrode active material layer at a timing after the preparation of the solid electrolyte layer shown in Fig. 3(e) and before the production of the evaluation cell shown in Fig. 3(f), Except having arranged the foreign material, it carried out similarly to manufacture example 1, and obtained the cell for evaluation (with a foreign material). In addition, foreign matter contained in the evaluation cell is present in a state that does not penetrate the solid electrolyte layer.

[Example 1]

To the evaluation cell (without foreign matter) obtained in Production Example 1, a restraining pressure of 10 MPa was applied in the thickness direction. Subsequently, the constrained evaluation cell was left still in a box made of foamed styrol. Subsequently, liquid nitrogen was injected into the box so that the cell for evaluation was completely immersed. In addition, when liquid nitrogen was reduced, additional injection was appropriately performed. Accordingly, the temperature of the evaluation cell was lowered to -190°C and frozen. In addition, the temperature of the evaluation cell was measured by attaching a T-type thermocouple to the cell surface.

(resistance measurement)

The resistance between the positive and negative terminals of the frozen evaluation cell (no foreign matter) was measured using a digital multimeter (manufactured by Agilent, 34410A). To the resulting resistance, by multiplying the facing area (1000cm ²⁾ of the positive electrode active material layer and the negative electrode active material layer was obtained from the resistance (Ω · cm ^2). As a result, the resistance of the evaluation cell exceeded the ^{measurement limit (1.2×10 17} Ω·cm ^{2 ).}

(Current measurement)

An insulation resistance meter (made by ADCMT, 8340A, ULTRA HIGH RESISTANCE METER) was connected to the positive and negative terminal of the frozen evaluation cell (no foreign matter), and 1000 V was applied to measure the _{current value I 1.} As a result, the current value I ₁ was 9.8 × 10 ^-9 mA. On the other hand, the temperature of the evaluation cell (with foreign matter) obtained in Production Example 2 was lowered to -190°C in the same manner as above, and then frozen. With respect to the frozen evaluation cell (with foreign _{matter), the current value I 2} was similarly measured. As a result, the current value I ₂ was 6.3 mA. Here, when the judgment criterion capable of detecting a foreign material was set as whether or not I ₂ /I ₁ ≥ 1.5 was satisfied, in Example 1, detection of the foreign material was possible.

In addition, I ₁ and I ₂ and I _A and I _B mentioned above have the following relationship. I _B is a current value that serves as a criterion for determining whether to pass or not, and is an absolute standard set according to the purpose. In contrast, I _A is a current value actually measured in the cell to be inspected. On the other hand, I ₁ is a current value that is actually measured in an evaluation cell (without foreign matter) imitating a good product, and in that it is approximately the same as the standard, _{it can be interpreted in the same meaning as I B,} and it is said that it is actually measured. In may also be interpreted as the same meaning as _{I A.} On the other hand, I ₂ is a current value actually measured in an evaluation cell (with foreign matter) imitating a defective product, and can be basically interpreted as the same meaning as _{I A.} In addition, as shown in Example 10 described later, for example, if the number of voltage application is increased, I ₁ may increase. Depending on the amount of I _{1 increase, I 1} may not be interpreted in the same meaning as _{I B} , which is an absolute criterion for determining whether or not to pass. In such a case, I ₂ /I ₁ means a relative criterion for determining whether or not a foreign object can be detected. In other words, I _A / I _B is a criterion for determining whether to pass or not as a product, whereas I ₂ /I ₁ may refer to a criterion for determining whether or not a product passes, but it is determined whether or not a foreign object can be detected. In some cases, it means a relative criterion. In addition, the preferable range of _{I 2} /I ₁ is the same as the preferable range of _{I A} /I _{B described above.}

(Damage evaluation)

For the evaluation cell (no foreign matter) obtained in Production Example 1, resistance measurement by charging was performed before freezing. Specifically, it was charged under the condition of 1A at 25°C for 10 seconds, and the increased voltage (ΔV) was measured, and the resistance R ₁ was obtained from the relationship of R=ΔV/I. Subsequently, the cell for evaluation (no foreign matter) after the current measurement was charged in the same manner as above to obtain a _{resistance R 2.} Here, when R ₂ /R ₁ ≥1.1, it was evaluated as being damaged by voltage application, and when R ₂ /R ₁ <1.1, it was evaluated as having no damage by voltage application. In Example 1, there was no damage to the cell.

[Example 2]

Except having changed the applied voltage to 2V, it carried out similarly to Example 1, and performed the current measurement and damage evaluation.

[Example 3]

Resistance measurement, current measurement, and damage evaluation were performed in the same manner as in Example 1, except that the temperature of the evaluation cell at the time of freezing was changed to -140°C.

[Examples 4 to 6]

Except having changed the applied voltage to 200V, 2V, and 500V, respectively, it carried out similarly to Example 3, and performed current measurement and damage evaluation.

[Example 7]

Resistance measurement, current measurement, and damage evaluation were performed in the same manner as in Example 1, except that the evaluation cell was not restrained and the temperature of the evaluation cell during freezing was changed to -135°C.

[Example 8]

Except having changed the applied voltage to 2V, it carried out similarly to Example 7, and performed the current measurement and damage evaluation.

[Reference Example 1]

Resistance measurement, current measurement, and damage evaluation were performed in the same manner as in Example 1, except that the temperature of the evaluation cell at the time of freezing was changed to -135°C.

[Reference Example 2]

Except having changed the applied voltage to 2V, it carried out similarly to Reference Example 1, and performed the current measurement and damage evaluation.

[Reference Example 3]

Resistance measurement, current measurement, and damage evaluation were performed in the same manner as in Example 1, except that the temperature of the evaluation cell during freezing was changed to -120°C.

[Reference Example 4]

Except having changed the applied voltage to 2V, it carried out similarly to Reference Example 3, and performed the current measurement and damage evaluation.

[Reference Example 5]

Resistance measurement, current measurement, and damage evaluation were performed in the same manner as in Reference Example 3, except that the evaluation cell was not restrained.

As shown in Table 1, in Examples 1 to 8, by increasing the resistance of the all-solid-state battery to 3.2×10 ⁸ Ω·cm ² or more, the presence or absence of a defect causing a short circuit could be inspected with good precision. On the other hand, as shown in Table 2, in Reference Examples 1 to 5, since the increase in resistance of the all-solid-state battery was small, the presence or absence of a defect causing a short circuit could not be inspected with good precision. However, as described above, in the evaluation cell used in Reference Examples 1 to 5 (the evaluation cell produced in Production Example 2), the foreign matter is present in a state that does not penetrate the solid electrolyte layer. The difficulty is high. For this reason, even under the inspection conditions in Reference Examples 1 to 5, for example, in the case of inspection for the presence or absence of an unshorted, the unshorted can be detected.

In addition, when comparing Examples 1 and 2 with Examples 3 to 6, it was confirmed that the lower the freezing temperature, the higher the resistance of the all-solid-state battery. On the other hand, Example 7 has a higher freezing temperature than Example 6, but since Example 7 did not restrain the all-solid-state battery, the resistance (Ω·cm ² ) was higher than that of Example 6. In this way, the resistance of the all-solid-state battery could be adjusted not only by the temperature at the time of freezing but also by the restraining pressure.

In addition, when the damage to the evaluation cell is considered, the current value is 3.2 mA (Example 3) or less when measuring the current for the evaluation cell (evaluation cell produced in Preparation Example 1) that does not have foreign substances. , It has been suggested that it is desirable to adjust the resistance (Ω·cm ^{2) and the applied voltage.} That is, when the resistance (Ω·cm ² ) is sufficiently high, it is possible to increase the applied voltage, but when the resistance (Ω·cm ² ) is relatively low, it has been suggested that it is preferable to adjust the applied voltage to be low.

[Production Example 3]

A cell for evaluation (with a foreign material) was obtained in the same manner as in Production Example 2 except that the foreign material was made to pass through the solid electrolyte layer. In addition, a part of the foreign material is in point contact with the positive electrode active material layer, and a short short has occurred.

[Example 9]

Using the evaluation cell (with foreign matter) obtained in Preparation Example 3 instead of the evaluation cell (with foreign matter) obtained in Preparation Example 2, the temperature of the evaluation cell at the time of freezing was changed to -90°C, and the applied voltage was 2V. Except having changed to, it carried out similarly to Example 1, and performed the resistance measurement and the current measurement.

As shown in Table 3, in Example 9, by increasing the resistance of the all-solid-state battery, the presence or absence of a short circuit could be inspected with good precision.

[Example 10]

An evaluation cell (without foreign matter) and an evaluation cell (with foreign matter) were obtained in the same manner as in Production Examples 1 and 2, except that Al foil was used as the positive electrode current collector and Cu foil was used as the negative electrode current collector. A plurality of the obtained evaluation cells (without foreign matter) and evaluation cells (with foreign matter) were prepared, and a restraining pressure of 10 MPa was applied in the thickness direction, respectively. After that, each of them was charged so that the battery voltage was in the range of 0V to 4.0V. Subsequently, the filled evaluation cell was left still in a box made of foamed styrol. Subsequently, liquid nitrogen was injected into the box so that the cell for evaluation was completely immersed. In addition, when liquid nitrogen was reduced, additional injection was appropriately performed. Accordingly, the temperature of the evaluation cell was lowered to -150°C and frozen. In addition, the temperature of the evaluation cell was measured by attaching a T-type thermocouple to the cell surface.

Connect an insulation resistance meter (ADCMT, 8340A, ULTRA HIGH RESISTANCE METER) to the positive and negative terminal of the frozen evaluation cell (no foreign matter), and apply 200V (for 2 seconds) three times, and the current value of the third time I ₁ Was measured. Also for the frozen evaluation cell (with foreign matter), 200 V (for 2 seconds) was similarly applied three times, and the current value I ₂ at the third time was measured.

The relationship between the battery voltage and the current ratio I ₂ /I ₁ is shown in FIG. 5. As shown in FIG. 5, when the battery voltage was 1.5V or more and 3.5V or less, I ₂ /I ₁ ≥1.5 was satisfied. In addition, _{1.5, which is the lower limit of I 2} /I ₁ , is an example of a reference, and the larger the lower limit value is, the easier it is to detect a foreign matter.

On the other hand, when the battery voltage was less than 1.5V, I ₂ /I ₁ ≥1.5 was not satisfied. I ₂ was about the same regardless of the battery voltage, but I _{1 in the case where the battery voltage was less than 1.5 V was greater than I 1 in the} case where the battery voltage was 1.5 V or more and 3.5 V or less. That is, as a result of increasing _{I 1} by applying the voltage a plurality of times, the value of _{I 2} /I _{1 decreased.} As the reason, when the battery voltage is less than 1.5 V, the possibility that the sulfide solid electrolyte is deteriorated or deformed by the first voltage application, and the possibility of generating conductive sulfides (for example, CuS) are mentioned. As a result, it is estimated that the resistance in the cell is lowered and I _{1 is increased.}

In addition, even when the battery voltage was greater than 3.5V, I ₂ /I ₁ ≥1.5 was not satisfied. I ₂ was about the same regardless of the battery voltage, but I _{1 in the case where the battery voltage was greater than 3.5 V was greater than I 1 in the} case where the battery voltage was 1.5 V or more and 3.5 V or less. That is, as a result of increasing _{I 1} by applying the voltage a plurality of times, the value of _{I 2} /I _{1 decreased.} The reason for this is that when the battery voltage is greater than 3.5V, there is a possibility that cracks may occur in the solid electrolyte layer due to expansion by charging, the possibility that foreign substances will be buried in the cracks, and deterioration (for example, dissolution) of foreign substances due to high voltage. The possibility of occurrence is mentioned. As a result, it is estimated that the resistance in the cell is lowered and I _{1 is increased.}

As described above, when the battery voltage is 1.5 V or more and 3.5 V or less, it has been confirmed that the increase in _{I 1 due to voltage application is suppressed.} In addition, since the number of data to be obtained increases, the accuracy of the pass or not determination has been further improved.

One… Positive electrode active material layer
2… Negative electrode active material layer
3… Solid electrolyte layer
4… Positive electrode current collector
5… Negative electrode current collector
10… All solid battery
11... bow

Claims (9)

A resistance increasing process that increases the resistance of the all-solid-state battery to 3.2×10 ⁵ Ω·cm ^{2 or more,}
A voltage application step of applying a voltage to the all-solid-state battery with increased resistance,
An all-solid-state battery inspection method having a determination step of determining whether or not the all-solid-state battery is passed based on a current value measured in the voltage application step. The method of claim 1,
In the resistance increasing step, the resistance of the all-solid battery is increased by freezing treatment. The method of claim 2,
The method for inspecting an all-solid-state battery, wherein the freezing treatment is a treatment in which the temperature of the all-solid-state battery is -90°C or less. The method of claim 2,
The method for inspecting an all-solid-state battery, wherein the freezing treatment is a treatment in which the temperature of the all-solid-state battery is -140°C or less. A resistance increasing step of increasing the resistance of the all-solid-state battery by freezing treatment, and
A voltage application step of applying a voltage to the all-solid-state battery with increased resistance,
An all-solid-state battery inspection method having a determination step of determining whether or not the all-solid-state battery is passed based on a current value measured in the voltage application step. The method according to any one of claims 1 to 5,
In the resistance increasing step, the resistance of the all-solid-state battery is increased by a treatment of reducing the restraining pressure of the all-solid-state battery. The method according to any one of claims 1 to 5,
The all-solid-state battery is a battery containing a sulfide solid electrolyte,
In the resistance increasing process, increasing the resistance of the all-solid-state battery whose voltage is adjusted to 1.5V or more and 3.5V or less,
In the voltage application step, a method for inspecting an all-solid-state battery in which a voltage is applied two or more times. The preparation process of preparing an all-solid battery,
A method for manufacturing an all-solid-state battery having an inspection step of inspecting the all-solid-state battery by using the method for testing the all-solid-state battery according to any one of claims 1 to 5. The preparation process of preparing an all-solid battery,
An inspection step of inspecting the all-solid-state battery using the inspection method for an all-solid-state battery according to any one of claims 1 to 5;
A method for manufacturing an assembled battery having an assembling step of assembling an assembled battery by using a plurality of the all-solid-state batteries determined to pass in the inspection step.

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