Secondary battery inspection method and inspection device

Abstract

This secondary battery inspection method comprises: a step for positioning, in a chamber, a secondary battery cell that includes a sulfide solid electrolyte; a step for pressurizing the space in the chamber; a step for depressurizing the space in the chamber after the pressurization step; and a step for measuring the hydrogen sulfide concentration in the chamber after the depressurization step.

Description

Secondary battery inspection method and inspection device

[0001] The present invention relates to a method and apparatus for inspecting a secondary battery.

[0002] Secondary batteries such as lithium-ion secondary batteries are known. Among such secondary batteries, laminated secondary battery cells are known. In laminated secondary battery cells, a laminate film (exterior material) is used as a container. An electrode stack is housed inside the container. If a defect exists in the container of such a secondary battery cell, the contents may leak. Therefore, the container is inspected for defects as needed. It is preferable that the inspection be performed with high accuracy.

[0003] An example of a technique for inspecting secondary battery cells is disclosed in Patent Document 1 (Japanese Patent No. 5942065). Patent Document 1 discloses that an inspection device performs an airtightness inspection on a lithium-ion battery as an object to be inspected, that an electrolyte is sealed in a container in a lithium-ion battery, and that if the container is not completely sealed, the electrolyte will leak from the incompletely sealed area, and that during the inspection, it is determined whether airtightness is maintained based on the presence or absence of solvent gas that has evaporated from the electrolyte leaking from the incompletely sealed area.

[0004] The present inventors have been studying secondary battery cells that include a solid electrolyte (so-called solid-state battery). Specifically, they have been studying secondary battery cells that use a sulfide solid electrolyte as the solid electrolyte. They have also been studying how to inspect the containers of such secondary battery cells for defects.

[0005] In secondary battery cells using a solid electrolyte, there is no electrolyte solution. Even if there is a defect in the container, gas derived from the electrolyte solution is not generated. Therefore, the method described in Patent Document 1 cannot be used.

[0006] On the other hand, when a sulfide solid electrolyte reacts with moisture, hydrogen sulfide gas is generated. Therefore, if a defect exists in the container, the sulfide solid electrolyte reacts with moisture in the atmosphere and hydrogen sulfide gas is generated. Therefore, the present inventors thought that the presence or absence of a defect could be detected by measuring the hydrogen sulfide gas concentration.

[0007] However, if there is a minute defect in the container, the amount of air that enters the container per unit time is small, and therefore the amount of hydrogen sulfide gas generated when the sulfide solid electrolyte contained in the container reacts with moisture in the entering air is so small that it is difficult to detect.

[0008] It is conceivable to wait a long time to increase the concentration of hydrogen sulfide gas to a level that can be detected by a hydrogen sulfide gas concentration detector. That is, a secondary battery cell is placed in the chamber and left for a long time. This may increase the hydrogen sulfide gas concentration in the chamber to a level that can be detected. However, in this case, the test takes a long time.

[0009] Therefore, an object of the present invention is to provide a technique that can quickly inspect the container for defects in a secondary battery cell that uses a sulfide solid electrolyte.

[0010] In one aspect, a method for inspecting a secondary battery according to the present invention includes the steps of: placing a secondary battery cell including a sulfide solid electrolyte in a chamber; pressurizing a space in the chamber after the placing step; depressurizing the space in the chamber after the pressurizing step; and measuring a hydrogen sulfide concentration in the chamber after the depressurizing step.

[0011] In one aspect, an inspection device for a secondary battery according to the present invention includes a chamber that houses a secondary battery cell that includes a sulfide solid electrolyte, a pressurizing / depressurizing mechanism configured to pressurize and then depressurize a space within the chamber, and a concentration measurement mechanism configured to measure the hydrogen sulfide concentration within the chamber after the space within the chamber has been depressurized.

[0012] FIG. 1 is a schematic diagram showing an inspection apparatus according to an embodiment. FIG. 2 is a diagram schematically showing a cross section of a secondary battery cell. FIG. 3 is a schematic diagram showing an example of a volume change suppression mechanism. FIG. 4 is a flowchart showing an inspection method according to the present embodiment. FIG. 5 is a graph showing the relationship between chamber pressure and time during inspection. FIG. 6A is a diagram schematically showing the configuration inside the chamber before pressurization. FIG. 6B is a diagram schematically showing the configuration inside the chamber after pressurization. FIG. 6C is a diagram schematically showing the configuration inside the chamber in step S3. FIG. 7A is a schematic diagram showing a modified pressurization / depressurization mechanism. FIG. 7B is a schematic diagram showing another modified pressurization / depressurization mechanism. FIG. 8A is a schematic diagram showing a modified volume change suppression mechanism. FIG. 8B is a schematic diagram showing a modified volume change suppression mechanism. FIG. 8C is a schematic diagram showing a modified volume change suppression mechanism. FIG. 9 is a schematic diagram showing a modified inspection method. FIG. 10 is a schematic diagram showing an inspection apparatus according to a modified embodiment.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] 1 is a schematic diagram showing an inspection device 1 according to this embodiment. This inspection device 1 is used to inspect the container 11 of a secondary battery cell 6 for defects.

[0015] (1) Secondary Battery Cell First, a description will be given of the secondary battery cell 6 to be inspected. The secondary battery cell 6 is a so-called all-solid-state battery cell, and includes a sulfide solid electrolyte.

[0016] The secondary battery cell 6 is a so-called laminate type cell. The secondary battery cell 6 is plate-shaped. As shown in FIG. 1 , the secondary battery cell 6 has a case 11 and an electrode stack 10 housed in the case 11. A laminate film is used as the case 11. FIG. 2 is a diagram schematically showing a cross section of the secondary battery cell 6. As shown in FIG. 2 , the case 11 is formed by a pair of laminate films. The pair of laminate films are arranged to sandwich the electrode stack 10. The pair of laminate films are joined at their outer edges. The outer peripheries of the pair of laminate films are joined by, for example, thermal welding.

[0017] The electrode stack 10 is sealed in a container 11. The electrode stack 10 has a configuration in which a positive electrode layer, a negative electrode layer, a solid electrolyte layer, and the like are stacked. The sulfide solid electrolyte is contained in the solid electrolyte layer. Furthermore, the sulfide solid electrolyte may be contained in both the solid electrolyte layer and the positive electrode layer. A tab is connected to the electrode stack for extracting power. The tab extends to the outside so as to penetrate the joint portion of the laminate film.

[0018] (2) Inspection Apparatus Next, a description will be given of the inspection apparatus 1. As shown in Fig. 1, the inspection apparatus 1 has a chamber 2, a pressure increasing / depressurizing mechanism 3, a concentration measuring mechanism 4, and a volume change suppressing mechanism 5.

[0019] The chamber 2 is configured to house the secondary battery cell 6. The interior of the chamber 2 is an enclosed space. In the example shown in Fig. 1, the chamber 2 has a cylindrical shape that extends vertically.

[0020] The pressurizing / depressurizing mechanism 3 is configured to pressurize and depressurize the space within the chamber 2. In this specification, pressurizing means making the pressure within the chamber 2 higher than atmospheric pressure. Depressurizing means making the pressure within the chamber 2 lower than atmospheric pressure. Preferably, the pressurizing / depressurizing mechanism 3 is configured to change the volume of the space within the chamber while maintaining the chamber in a sealed state.

[0021] In the example shown in FIG. 1 , the pressurization / depressurization mechanism 3 includes a cylindrical portion 7 (cylinder), a closing member 8, and a drive mechanism 9. The cylindrical portion 7 is connected to a portion of the upper surface of the chamber 2. The closing member 8 is disposed inside the cylindrical portion 7. The closing member 8 closes the cylindrical portion 7 so that the internal space of the chamber 2 becomes a sealed space. The drive mechanism 9 is configured to move the closing member 8 in the direction in which the cylindrical portion extends. By moving the closing member 8 via the drive mechanism 9, the volume of the internal space of the chamber 2 changes while remaining sealed. This allows the pressure inside the chamber 2 to be changed while maintaining the sealed state.

[0022] The concentration measuring mechanism 4 is configured to detect hydrogen sulfide in the chamber 2. As the concentration measuring mechanism 4, for example, a gas chromatograph or the like can be used.

[0023] The volume change suppression mechanism 5 is disposed in the chamber 2 and is configured to suppress volume changes of the secondary battery cells 6. Specifically, the volume change suppression mechanism 5 is configured to sandwich the secondary battery cells 6 in the thickness direction.

[0024] Fig. 3 is a schematic diagram showing an example of the volume change suppression mechanism 5. In the example shown in Fig. 3, the volume change suppression mechanism 5 has a plurality of rod-shaped members 14. Specifically, the volume change suppression mechanism 5 has two sets of rod-shaped member groups. Each set of rod-shaped member groups has four rod-shaped members 14 extending in parallel. The two sets of rod-shaped member groups are arranged with a gap between them so that the secondary battery cell 6 is sandwiched between them. By being sandwiched between the volume change suppression mechanism 5, volume change (specifically, expansion) of the container of the secondary battery cell 6 is prevented.

[0025] (3) Inspection Method Next, the inspection method according to this embodiment will be described. FIG. 4 is a flowchart showing the inspection method according to this embodiment. FIG. 5 is a graph showing the relationship between the pressure in the chamber and time during the inspection. As shown in FIG. 4, the inspection method according to this embodiment includes a step of placing a secondary battery cell (S1), a step of pressurizing (S2), a step of depressurizing (S3), and a step of measuring the hydrogen sulfide concentration (S4). Each step will be described in detail below.

[0026] (Step S1) Arranging the secondary battery cell First, the secondary battery cell 6 is arranged in the chamber 2. Then, the chamber 2 is sealed. The secondary battery cell is arranged so that it is sandwiched between the volume change suppression mechanisms 5.

[0027] (Step S2) Pressurization Next, the pressurization / depressurization mechanism 3 is operated to pressurize the inside of the chamber. Specifically, as shown in Fig. 5, the pressure inside the chamber 2 is increased until it reaches a predetermined pressure that exceeds atmospheric pressure. Then, that pressure is maintained for a predetermined time.

[0028] If a defect exists in the container 11, hydrogen sulfide is generated inside the secondary battery cell 6 in this step. This point will be described with reference to FIGS. 6A and 6B . FIGS. 6A and 6B are diagrams schematically illustrating the configuration inside the chamber 2 before and after pressurization. FIG. 6A illustrates the configuration before pressurization, and FIG. 6B illustrates the configuration after pressurization. As shown in FIG. 6A , air is present inside the chamber 2. The air contains moisture 12. When the chamber 2 is pressurized, a pressure difference occurs between the inside and outside of the container 11. Specifically, the pressure outside the container 11 becomes greater than the pressure inside the container. If a defect exists in the container 11, the pressure difference causes moisture 12 to enter the container 11 from the outside through the defect, as shown in FIG. 6B . The moisture that has entered the container 11 reaches the exposed portion of the solid electrolyte layer (typically the end surface of the electrode stack). As a result, the sulfide solid electrolyte reacts with the moisture, generating hydrogen sulfide 13.

[0029] (Step S3) Depressurization Next, the pressurization / depressurization mechanism 3 is operated to depressurize the inside of the chamber 2. Specifically, as shown in Fig. 5, the internal pressure of the chamber 2 is reduced to a predetermined pressure below atmospheric pressure. Then, this pressure is maintained for a predetermined time.

[0030] 6C is a diagram schematically illustrating the configuration inside the chamber in this step. By reducing the pressure inside the chamber 2, the pressure outside the container 11 becomes lower than the pressure inside the container 11. As a result, hydrogen sulfide 13 generated inside the container 11 moves to the outside of the container 11 through the defects.

[0031] (Step S4) Measurement of Hydrogen Sulfide Concentration Next, the hydrogen sulfide concentration in the chamber 2 is measured. Specifically, the gas in the chamber is supplied to the concentration measurement mechanism 4. The concentration measurement mechanism 4 then detects the hydrogen sulfide concentration. If a defect exists in the container 11, a certain concentration of hydrogen sulfide will be detected. Therefore, the presence or absence of a defect in the container 11 can be inspected based on the measurement results.

[0032] Note that, if the gas in chamber 2 can be sent to concentration measurement mechanism 4, this step may be performed while maintaining the reduced pressure state in step S3. However, it is generally difficult to send the gas in chamber 2 to concentration measurement mechanism 4 when the pressure in chamber 2 is reduced. Therefore, preferably, after step S3, the pressure in the chamber is returned to atmospheric pressure by pressure increase / decrease mechanism 3. Alternatively, the pressure in the chamber is increased to a pressure exceeding atmospheric pressure. Then, the gas in the chamber is sent to concentration measurement mechanism 4, and the hydrogen sulfide concentration is measured.

[0033] The above is an outline of the inspection method of this embodiment. As described above, according to the method of this embodiment, the chamber 2 is pressurized in step S2, so that if a defect is present, hydrogen sulfide can be generated in a short time. If pressurization is not performed, moisture transport from the outside to the inside of the container 11 occurs only by diffusion. Therefore, it takes time for the moisture to reach the solid electrolyte, and it takes time to generate hydrogen sulfide. In contrast, according to this embodiment, pressurization (step S2) is performed, so that moisture can reach the sulfide solid electrolyte in a short time due to a flow caused by a pressure gradient between the outside and inside of the container 11. Furthermore, a pressurized state promotes the reaction between moisture and the sulfide solid electrolyte. Therefore, hydrogen sulfide can be generated in a short time, and inspection can be performed in a short time.

[0034] In addition, according to this embodiment, the pressure inside the chamber 2 is reduced in step S3, so that hydrogen sulfide can be quickly transferred from the inside to the outside of the container 11. Furthermore, since the volume change suppression mechanism 5 is provided at this time, hydrogen sulfide can be moved to the outside of the container more quickly. If the volume change suppression mechanism 5 were not provided, the container 11 would expand when the pressure was reduced. As a result of the expansion of the container 11, hydrogen sulfide would be more likely to remain inside the container 11. In contrast, according to this embodiment, the volume change suppression mechanism 5 suppresses the expansion of the container. Therefore, in step S3 (reducing pressure), hydrogen sulfide 13 present inside the container 11 can be quickly moved to the outside of the container 11. From this perspective as well, the inspection can be performed in a short time.

[0035] Next, modifications of this embodiment will be described.

[0036] (Modification of the pressurizing / depressurizing mechanism) Fig. 7A is a schematic diagram showing a modification of the pressurizing / depressurizing mechanism 3. In this modification, the pressurizing / depressurizing mechanism 3 has a cylindrical portion 7, a closing member 8, and a drive mechanism 9, similar to the example shown in Fig. 1. The cylindrical portion 7 is connected to the upper surface of the chamber 2. However, the cylindrical portion 7 has a cross section with the same shape as the upper surface of the chamber 2. The cylindrical portion 7 is connected to the entire upper surface of the chamber 2. Even with this configuration, the pressure inside the chamber 2 can be changed by moving the closing member 8.

[0037] 7B is a schematic diagram showing another modified example of the pressurizing / depressurizing mechanism 3. In this modified example, the chamber 2 is rectangular parallelepiped-shaped. The pressurizing / depressurizing mechanism 3 includes a cylindrical portion 7, a closing member 8, and a drive mechanism 9, similar to the example shown in FIG. 1 . However, the cylindrical portion 7 is connected to one side of the chamber 2. Specifically, the cylindrical portion 7 has a cross section with the same shape as one side of the chamber 2, and is connected to the entire surface of one side of the chamber 2. Even with this configuration, the pressure inside the chamber 2 can be changed by reciprocating the closing member 8.

[0038] (Variations of the Volume Change Suppression Mechanism) The volume change suppression mechanism 5 may be configured to suppress expansion of the container 11. FIGS. 8A to 8C are schematic diagrams illustrating variations of the volume change suppression mechanism 5. In the example shown in FIG. 8A, a mesh-like member is used as the volume change suppression mechanism 5. In the example shown in FIG. 8B, a punched plate-like member is used as the volume change suppression mechanism 5. In the example shown in FIG. 8C, a porous member is used as the volume change suppression mechanism 5. Each of these members is used in pairs. That is, the secondary battery cell is sandwiched between the pair of members in the thickness direction. As a result, expansion of the container 11 in the thickness direction is suppressed. This suppresses volumetric change of the container 11, allowing hydrogen sulfide to be quickly removed from the container 11. Note that all of the members shown in FIGS. 8A to 8C are configured to allow gas to pass through. Therefore, the movement of moisture and hydrogen sulfide during pressurization and depressurization is not hindered by the volume change suppression mechanism 5.

[0039] (Modification of the pressurization / depressurization cycle) In the inspection method shown in FIG. 5, pressurization (step S2) and depressurization (step S3) are each performed once. However, each of these may be performed multiple times. FIG. 9 is a schematic diagram showing a modification of the inspection method according to this embodiment. FIG. 9(a) schematically shows the relationship between time and the pressure in the chamber. FIG. 9(b) schematically shows the relationship between time and the hydrogen sulfide gas concentration in the chamber.

[0040] In this modified example, multiple cycles of pressurization and depressurization are performed, with one pressurization (step S2) and one depressurization (step S3) being one cycle. The pressurization and depressurization are repeated in a sealed state. By repeating pressurization and depressurization in a sealed state, the concentration of hydrogen sulfide gas in the chamber 2 increases, as shown in FIG. 9(b). This allows the inspection to be completed in a shorter time.

[0041] (Pressure in the chamber during pressurization) The pressure in the chamber 2 during pressurization (step S2) is preferably 100 kPa or less in gauge pressure. If the pressure exceeds 100 kPa, moisture present as water vapor in the chamber 2 may condense. The condensed water absorbs hydrogen sulfide gas. This may result in a decrease in the accuracy of measuring the hydrogen sulfide concentration. In contrast, if the pressure in the chamber 2 during pressurization is 100 kPa or less, condensation is less likely to occur and the measurement accuracy is less likely to decrease.

[0042] Furthermore, the pressure inside the chamber 2 during pressurization (step S2) is preferably 10 kPa or more in gauge pressure. Pressurization at such a pressure allows moisture outside the container 11 to move into the container 11 in a short period of time. Furthermore, the rate of reaction between moisture and the sulfide solid electrolyte can be sufficiently increased. As a result, hydrogen sulfide can be generated in a short period of time.

[0043] (Pressure in the chamber during decompression) The pressure in the chamber 2 during decompression (step S3) is preferably -100 kPa or higher in gauge pressure. If the pressure in the chamber 2 drops too much, the container 11 of the secondary battery cell 6 may expand excessively even if no defects are present. As a result, the container 11 may deform and wrinkles may form when the pressure is returned to atmospheric pressure. In contrast, if the pressure in the chamber 2 during decompression is -100 kPa or higher, the container 11 is less likely to expand, and the occurrence of wrinkles is suppressed.

[0044] On the other hand, the pressure inside the chamber 2 during depressurization (step S2) is preferably −10 kPa or less in gauge pressure. If the pressure is reduced to such a level, the hydrogen sulfide inside the container 11 can be moved to the outside of the container in a short period of time.

[0045] (Humidity) In this embodiment, hydrogen sulfide is generated by moisture in the chamber 2. Therefore, it is preferable that a certain amount of water vapor is present in the chamber. From this perspective, the relative humidity in the chamber 2 is, for example, 20 to 70%, and preferably 30 to 60%, under atmospheric pressure. The temperature in the chamber 2 is, for example, 15 to 25°C.

[0046] (Modification of Sample Gas Inlet) Next, a modification of the sample gas inlet will be described. Fig. 10 is a schematic diagram showing an inspection device according to this modification.

[0047] 8, in this modification, a plurality of sample gas inlets 15 (15-1 to 15-4) are provided in the chamber 2. Each sample gas inlet 15 is provided to send gas within the chamber 2 to the concentration measurement mechanism 4. In other words, the chamber 2 is connected to the concentration measurement mechanism 4 via each sample gas inlet 15.

[0048] Here, each sample gas inlet 15 is located near a specific portion of the secondary battery cell 6 .

[0049] Specifically, the electrode stack 10 of the secondary battery cell 6 has a shape with corners 16 when viewed along the stacking direction. As described above, the container 11 of the secondary battery cell 6 is formed of a pair of laminate films. The pair of laminate films are joined at an outer edge 17.

[0050] Each sample gas inlet 15 is located near a corner 16 of the electrode stack and / or near an outer edge 17 of the laminate film.

[0051] Providing the sample gas inlet 15 at the above-described position allows for efficient detection of defects in the container 11. The corners 16 of the electrode stack and the outer edge 17 of the laminate film are areas of the container 11 where defects are likely to occur. When manufacturing a secondary battery cell 6, the electrode stack 10 is typically housed within a pair of laminate films by cup molding. During this process, the laminate film is significantly stretched at the corners 16 of the electrode stack 10. Therefore, defects are likely to occur in the laminate film, which is the container 11, at the corners 16 of the electrode stack 10. Furthermore, the laminate film is sealed at the outer edge 17 by thermocompression or the like. During this process, poor sealing may occur due to the inclusion of foreign matter or insufficient heat. Therefore, the outer edge 17 of the laminate film is also likely to cause defects. Providing the sample gas inlet 15 near these defect-prone areas facilitates detection of hydrogen sulfide. This allows for more efficient inspection of the container 11 for defects.

[0052] Specifically, each sample gas inlet 15 is preferably located within 10 cm from a corner 16 of the electrode stack or an outer edge 17 of the laminate film.

[0053] In a preferred embodiment, the volume inside the chamber 2 under normal conditions (at atmospheric pressure) is 50 times or less the volume of the secondary battery cell 6 to be measured. Under such conditions, it is preferable that each sample gas inlet 15 is located within 10 cm of a corner 16 of the electrode stack or an outer edge 17 of the laminate film.

[0054] Although a plurality of sample gas intake ports 15 may be provided, the present invention is not limited to this and a single port may also be provided.

[0055] [Additional Notes] The main configuration and effects of this embodiment will be summarized below as additional notes.

[0056] (Supplementary Note 1) A method for inspecting a secondary battery, comprising: a step (S1) of placing a secondary battery cell 6 including a sulfide solid electrolyte in a chamber 2; a step (S2) of pressurizing the space in the chamber 2 after the placing step; a step (S3) of depressurizing the space in the chamber 2 after the pressurizing step; and a step (S4) of measuring a hydrogen sulfide concentration in the chamber 2 after the depressurizing step.

[0057] According to this method, since the pressurizing step is performed, if a defect exists in the secondary battery cell, hydrogen sulfide can be generated in a short time, and as a result, inspection can be performed in a short time.

[0058] (Supplementary Note 2) The inspection method according to Supplementary Note 1, wherein the step (S2) of reducing the pressure includes reducing the pressure of the space within the chamber while suppressing a change in volume of the secondary battery cell.

[0059] This method suppresses volumetric changes in the secondary battery cell, allowing hydrogen sulfide inside the secondary battery cell to be moved to the outside of the secondary battery cell in a short time, thereby enabling inspection to be completed in a shorter time.

[0060] (Supplementary Note 3) The inspection method according to Supplementary Note 1 or 2, wherein the pressurizing step and the depressurizing step are each performed multiple times.

[0061] According to this method, the hydrogen sulfide in the chamber can be increased by repeating the steps of pressurizing and depressurizing, thereby enabling the test to be completed in a shorter time.

[0062] (Supplementary Note 4) The inspection method according to any one of Supplementary Notes 1 to 3, wherein the step of reducing the pressure includes a step of reducing the pressure of the space in the chamber to a pressure lower than atmospheric pressure.

[0063] This method allows hydrogen sulfide generated inside the container to be quickly removed from the container, thereby enabling the test to be completed in a shorter time.

[0064] (Supplementary Note 5) The inspection method according to any one of Supplementary Notes 1 to 4, wherein the pressure in the chamber in the pressurizing step is 100 kPa or less in gauge pressure.

[0065] This method can prevent condensation during pressurization and prevent hydrogen sulfide from dissolving in the condensed water, resulting in more accurate measurement of the hydrogen sulfide concentration and more accurate testing.

[0066] (Supplementary Note 6) The inspection method according to any one of Supplementary Notes 1 to 5, wherein the pressure in the chamber in the depressurizing step is −100 kPa or more in gauge pressure.

[0067] This method can prevent the secondary battery cells from expanding excessively during the depressurizing step, thereby preventing wrinkles from occurring in the secondary battery cells after the pressure is returned to atmospheric pressure.

[0068] (Supplementary Note 7) The inspection method according to any one of claims 1 to 6, wherein the relative humidity in the chamber is 20 to 70% under atmospheric pressure.

[0069] According to this method, hydrogen sulfide can be generated quickly in the pressurizing step, and condensation can be prevented.

[0070] (Appendix 8) A secondary battery inspection device comprising: a chamber 2 that houses a secondary battery cell 6 including a sulfide solid electrolyte; a pressurizing / depressurizing mechanism 3 that is configured to pressurize the space in the chamber 2 and then depressurize it; and a concentration measurement mechanism 4 that is configured to measure the hydrogen sulfide concentration in the chamber 2 after the space in the chamber 2 has been depressurized.

[0071] With this configuration, the chamber is pressurized, so that hydrogen sulfide can be generated in a short time if a defect exists in the secondary battery cell 6. Then, by measuring the concentration of the generated hydrogen sulfide, the secondary battery cell 6 can be inspected for defects in a short time.

[0072] (Supplementary Note 9) The inspection device according to Supplementary Note 8, further comprising a volume change suppression mechanism 5 configured to suppress a change in volume of the secondary battery cell when the pressure is reduced by the pressurizing / depressurizing mechanism 3.

[0073] According to this configuration, the volume change of the secondary battery cell is suppressed, and the hydrogen sulfide inside the secondary battery cell can be moved to the outside of the secondary battery cell in a short time, which makes it possible to perform the inspection in a shorter time.

[0074] (Supplementary Note 10) The inspection device according to Supplementary Note 8 or 9, wherein the pressurizing / depressurizing mechanism 3 is configured to change the volume of the space within the chamber 2 while maintaining the sealed state.

[0075] With this configuration, the pressure inside the chamber 2 can be changed without the hydrogen sulfide gas concentration inside the chamber 2 decreasing due to leakage of the generated hydrogen sulfide gas to the outside or the inflow of air from the outside.

[0076] (Appendix 11) An inspection device as described in any of Appendices 8 to 10, wherein the secondary battery cell 6 has an electrode stack 10 having a corner 16 when viewed along the stacking direction, and a pair of laminate films covering the electrode stack 10, the pair of laminate films being joined at an outer edge 17, and the chamber is provided with a sample gas inlet 15 connected to a concentration measurement mechanism, and the sample gas inlet 15 is located near the corner 16 of the electrode stack 10 and / or near the outer edge 17 of the laminate film.

[0077] With this configuration, the sample gas inlet is located near the area where defects are likely to occur, making it easier to detect hydrogen sulfide when a defect is present, thereby enabling more accurate defect inspection.

Claims

1. A method for inspecting a secondary battery, comprising: placing a secondary battery cell including a sulfide solid electrolyte in a chamber; pressurizing the space in the chamber after the placing step; depressurizing the space in the chamber after the pressurizing step; and measuring a hydrogen sulfide concentration in the chamber after the depressurizing step.

2. An inspection method according to claim 1, wherein the step of reducing the pressure includes a step of reducing the pressure in the space within the chamber while suppressing volumetric changes in the secondary battery cells.

3. An inspection method according to claim 1, wherein the pressurizing step and the depressurizing step are each performed multiple times.

4. An inspection method according to claim 1, wherein said step of reducing the pressure includes a step of reducing the pressure in the space within said chamber to a pressure lower than atmospheric pressure.

5. An inspection method according to claim 1, wherein the pressure inside the chamber in the pressurizing step is 100 kPa or less in gauge pressure.

6. An inspection method according to claim 1, wherein the pressure inside the chamber in the depressurizing step is -100 kPa or higher in gauge pressure.

7. An inspection method according to claim 1, wherein the relative humidity in the chamber is 20 to 70% under atmospheric pressure.

8. A secondary battery inspection device comprising: a chamber that houses a secondary battery cell containing a sulfide solid electrolyte; a pressurizing / depressurizing mechanism configured to pressurize and then depressurize a space within the chamber; and a concentration measurement mechanism configured to measure the hydrogen sulfide concentration within the chamber after the space within the chamber has been depressurized.

9. An inspection device according to claim 8, further comprising a volume change suppression mechanism configured to suppress volume change of the secondary battery cell when pressure is reduced by the pressurization / depressurization mechanism.

10. An inspection device according to claim 8, wherein the pressurizing / depressurizing mechanism is configured to change the volume of the space within the chamber while maintaining the chamber in a sealed state.

11. An inspection device as described in claim 8, wherein the secondary battery cell has an electrode laminate having corners when viewed along the stacking direction, and a pair of laminate films covering the electrode laminate, the pair of laminate films being joined at their outer edges, and the chamber is provided with a sample gas inlet connected to the concentration measurement mechanism, and the sample gas inlet is located near the corners of the electrode laminate and / or near the outer edges of the laminate films.

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