Battery inspection method

Abstract

A battery inspection method including: a step for applying pressure to both surfaces of a plurality of laminates 1 in a direction along the lamination direction of the plurality of laminates 1 by means of an exterior body 70; a step for holding the plurality of laminates 1 in an environment of higher humidity than before applying pressure to the plurality of laminates 1 in a state in which the plurality of laminates 1 have pressure applied thereto, and measuring the amount of hydrogen sulfide generated by the plurality of laminates 1; and a step for determining occurrence of lamination deviation in the plurality of laminates 1 on the basis of the amount of hydrogen sulfide generated.

Description

Battery inspection method

[0001] The present invention relates to a battery inspection method.

[0002] Inspection methods for inspecting the stacking misalignment of a positive electrode, a negative electrode, and a separator have been known. For example, in the inspection method described in Patent Document 1, the negative electrode and the separator each have at least two holes at positions where they overlap when stacked, and when at least one of the negative electrode and the separator is stacked, the holes are in a through state, which is a requirement for determining that no stacking misalignment has occurred, and the inspection for stacking misalignment is performed.

[0003] JP 2014-49193 A

[0004] The above-described inspection method requires a step of forming at least two holes in the negative electrode and the separator, which increases the number of steps required for inspection.

[0005] The problem to be solved by the present invention is to provide a battery inspection method that reduces the number of steps for inspecting for stacking misalignment.

[0006] The present invention solves the above problem by including a step of applying pressure to both sides of the multi-layer structure via an outer casing in a direction along the stacking direction of the multi-layer structure, a step of holding the multi-layer structure in a pressurized state in an environment with higher humidity than before the multi-layer structure was pressed, and measuring the amount of hydrogen sulfide generated from the multi-layer structure, and a step of determining whether stacking misalignment has occurred in the multi-layer structure based on the amount of hydrogen sulfide generated.

[0007] According to the present invention, the number of steps required to inspect for stack misalignment can be reduced.

[0008] FIG. 1 is a cross-sectional view showing an all-solid-state battery and a pressure mechanism according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an all-solid-state battery and a pressure mechanism according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of an all-solid-state battery in a state where stacking misalignment has occurred in a multi-layer stack. FIG. 4 is a cross-sectional view of an all-solid-state battery in a state where stacking misalignment has occurred in a multi-layer stack. FIG. 5 is a flowchart showing steps of a battery inspection method according to an embodiment of the present invention. FIG. 6 is a graph showing the characteristics of the amount of hydrogen sulfide generated when stacking misalignment has occurred and a preset generation amount threshold. FIG. 7 is a block diagram of an all-solid-state battery held in a sealed container, a sealed container, and a hydrogen sulfide concentration measurement device. FIG. 8 is a graph showing the characteristics of the hydrogen sulfide concentration. FIG. 9 is a block diagram of an all-solid-state battery, a humidifier, a measurement device, and an agitator. FIG. 10A is a graph showing the characteristics of the amount of hydrogen sulfide generated measured by the measurement device and the generation amount threshold. FIG. 10B is a graph showing the characteristics of the amount of hydrogen sulfide generated measured by the measurement device and the generation amount threshold. FIG. 11 is a flowchart showing steps of a battery inspection method according to a second embodiment of the present invention.

[0009] First Embodiment A battery manufacturing method according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an all-solid-state battery 1A and a pressure mechanism 80. The all-solid-state battery 1A is a lithium secondary battery and includes a plurality of battery cells 1B and an exterior body 70. The battery cell 1B includes a positive electrode current collector 10, a negative electrode current collector 20, and a stack 30 interposed therebetween. By stacking a plurality of battery cells 1B along the stacking direction (z direction in FIG. 1 ), the multiple stack 1 is an assembly of a plurality of stacks 30 stacked along the stacking direction (z direction in FIG. 1 ) with the positive electrode current collector 10 and the negative electrode current collector 20 interposed therebetween. In the following description, the lithium secondary battery manufactured by the battery manufacturing method of this embodiment will be described as an all-solid-state battery 1A.

[0010] The positive electrode current collector 10 is a conductive plate-like (or foil-like) member and is made of, for example, a metal or a conductive resin, although it is not particularly limited thereto. Examples of metals that can be used include aluminum, nickel, iron, stainless steel, titanium, and copper. Alternatively, a clad material of nickel and aluminum, or a clad material of copper and aluminum may also be used. Examples of conductive resins include resins in which a conductive filler is added to a non-conductive polymer material.

[0011] The negative electrode current collector 20, like the positive electrode current collector 10, is a conductive plate-like (or foil-like) member and is made of, for example, but not limited to, a metal or a conductive resin. The metal and the conductive resin may be the same materials as those used to make the positive electrode current collector 10. The material used to make the positive electrode current collector 10 and the material used to make the negative electrode current collector 20 may be the same or different.

[0012] A laminate 30 is interposed between the positive and negative electrode current collectors 10, 20. The laminate 30 is a power generating element having a positive electrode layer 40, a negative electrode layer 50, and a solid electrolyte layer 60. In the laminate 30, the positive electrode layer 40, the solid electrolyte layer 60, and the negative electrode layer 50 are stacked in this order along the z direction. The +Z direction in this embodiment corresponds to an example of the "stacking direction" in the present invention, and corresponds to the stacking direction of the positive electrode layer 40, the solid electrolyte layer 60, and the negative electrode layer 50.

[0013] The positive electrode layer 40 is formed on both main surfaces of the positive electrode current collector 10. The positive electrode layer 40 is not particularly limited, but can be formed by applying a paste containing a positive electrode active material and a binder to the main surface of the positive electrode current collector 10 and drying the paste. When the positive electrode current collector 10 is in contact with the exterior body 70, the positive electrode layer 40 is formed on one of the main surfaces of the positive electrode current collector 10.

[0014] The anode layer 50 is formed on both main surfaces of the anode current collector 20. The anode layer 50 contains lithium metal deposited on the main surface of the anode current collector 20. The volume of the anode layer 50 increases as lithium metal is deposited during charging of the all-solid-state battery 1A, and decreases as the lithium metal disappears (moves toward the positive electrode layer) during discharging. The anode layer 50 may have an intermediate layer to assist the deposition of lithium metal. The intermediate layer contains a material capable of absorbing and releasing lithium ions. Unlike the example of FIG. 1 , when the anode current collector 20 is in contact with an exterior body 70, the anode layer 50 is formed on one main surface of the anode current collector 20.

[0015] The type of anode active material contained in the anode layer 50 is not particularly limited, and examples thereof include carbon materials, metal oxides, and metal active materials. The anode active material may be a silicon-based anode active material or a tin-based anode active material, or may be metallic lithium or a lithium-containing alloy. Examples of lithium-containing alloys include alloys of Li with at least one of In, Al, Si, and Sn. Two or more anode active materials may be used in combination in the anode layer 50. When the anode active material is metallic lithium or a lithium-containing alloy, the all-solid-state battery 1A may be a so-called lithium deposition type in which lithium metal is deposited as the anode active material on the anode current collector 20 during charging. The anode layer 50 may also include a solid electrolyte and a binder.

[0016] The solid electrolyte layer 60 is interposed between the positive electrode layer 40 and the negative electrode layer 50. A sulfide-based solid electrolyte made of a material with low electronic conductivity can be used as this solid electrolyte. The solid electrolyte layer 60 corresponds to the "electrolyte layer" of the present invention.

[0017] In this embodiment, the positive electrode layer 40, the negative electrode layer 50, and the solid electrolyte layer 60 have rectangular cross sections, but are not limited to this and may have trapezoidal cross sections. In the example of FIG. 1 , the positive electrode current collector 10 and the negative electrode current collector 20 are separate members from the positive electrode layer 40 and the negative electrode layer 50, but they may be included in the positive electrode layer 40 and the negative electrode layer 50. In other words, the "positive electrode layer" of the present invention may be a member including the positive electrode current collector 10 and the positive electrode layer 40, and the "negative electrode layer" of the present invention may be a member including the negative electrode current collector 20 and the negative electrode layer 50. The battery cell 1B is composed of the positive electrode current collector 10, the negative electrode current collector 20, and the laminate 30.

[0018] The exterior body 70 is a member that sandwiches the multiple stack 1. The exterior body 70 has an upper exterior member and a lower exterior member, the upper exterior member covering the top surface of the upper negative electrode current collector 20, and the lower exterior member covering the bottom surface of the lower negative electrode current collector 20. The exterior body 70 seals the battery cells 1B in a state where a portion of the tabs (not shown) connected to the positive electrode current collector 10 and the negative electrode current collector 20 respectively protrudes outside the battery. Note that the cross section in FIG. 1 shows a state in which the exterior body 70 does not seal the multiple battery cells 1B.

[0019] The pressure mechanism 80 applies pressure to both surfaces of the multi-layer structure 1 via the exterior body 70 in the direction along the stacking direction (z direction in FIG. 1 ). The pressure mechanism 80 sandwiches the multi-layer structure 1 between a pair of pressure plates and applies a load to the stacking surfaces of the multi-layer structure 1 by moving the pressure plates so that the distance between the pair of pressure plates becomes shorter. An elastic body such as a spring or a motor may be used to move the pressure plates. Note that the specific mechanism of the pressure mechanism 80 is not particularly limited, and the pressure mechanism 80 may have, in addition to the pressure plates, end plates that hold the position of the multi-layer structure 30 and elastic bodies such as rubber.

[0020] In the example of FIG. 1, six laminates 30 are stacked, but the number of laminates 30 is not limited to six, and may be two to five, or seven or more.

[0021] In an all-solid-state battery 1A as shown in FIG. 1 , an oxide layer is formed on the side surface of the multi-layer stack 1. The oxide layer is formed to prevent deterioration of the solid electrolyte layer 60. In this embodiment, to form the oxide layer, the multi-layer stack 1 sandwiched between exterior bodies 70 is held in a high-humidity environment while being pressurized by a pressure mechanism 80. When the stack 30, which is an electrolyte-containing layer, is exposed to an environment containing high-humidity gas, an oxide layer is formed on the side surface of the stack 30, which is a contact portion between the stack 30 and the outside air containing high-humidity gas.

[0022] 1 , the multiple stacks 1 form an assembly aligned along the z direction without any misalignment in the x direction. The stacking surfaces (surfaces along the xy plane) of the multiple solid electrolyte layers 60 included in the multiple stacks 1 are pressurized by a pressure mechanism 80, and the multiple stacks 30 become dense. Therefore, high-humidity gas is less likely to penetrate into the solid electrolyte layers 60, and moisture and sulfide react on the side surfaces of each stack 30, generating hydrogen sulfide.

[0023] 2 is a cross-sectional view of the all-solid-state battery 1A shown in FIG. 1 , with a portion where water reacts with sulfide (hereinafter also referred to as a "reaction portion 90") added. As shown in FIG. 2 , the side surface of each laminate 30 serves as the reaction portion 90. An oxide film is formed in each reaction portion 90.

[0024] Next, the amount of hydrogen sulfide generated in an all-solid-state battery 1 in which stacking misalignment has occurred will be described. Fig. 3 shows a cross-sectional view of an all-solid-state battery 1A in a state in which stacking misalignment has occurred in the multiple laminated body 1. Stacking misalignment is a state in which at least one laminated body 30 is misaligned in a direction along the stacking surface relative to the other laminated bodies 30. In the example of Fig. 3, the position of the central battery cell 1B is misaligned in the x direction relative to the positions of the upper and lower battery cells 1B. Therefore, the multiple laminated body 1 does not form an assembly aligned along the z direction.

[0025] As shown in FIG. 3 , the multi-layer stack 1 sandwiched between the exterior body 70 is held in a high-humidity environment while being pressurized by the pressurizing mechanism 80. Each stacking surface (surface along the xy plane) of the multiple solid electrolyte layers 60 included in the multi-layer stack 1 receives pressure from the pressurizing mechanism 80. The stacking surfaces of each stack 30 are misaligned in the x direction due to stacking misalignment. As a result, pressure is not applied uniformly to the stacking surfaces, and areas of the main surface of the solid electrolyte layer 60 receive less pressure, resulting in a rough portion of the solid electrolyte layer 60. Portions of the main surface of the solid electrolyte layer 60 that are not stacked with other stacks 30 in the z direction become rough. High-humidity gas can easily penetrate these portions of the solid electrolyte layer 60, causing the moisture and sulfide contained in the high-humidity gas to react. When stacking misalignment occurs, the reaction area 90 where moisture and sulfide react spreads not only to the side surfaces of each stack 30 but also to the interior of the solid electrolyte layer 60.

[0026] FIG. 4 is a cross-sectional view of the all-solid-state battery 1A shown in FIG. 3 with a reaction section 90 added. As shown in FIG. 4 , the reaction section 90 is the side surface of each laminate 30 and the corresponding portion inside the solid electrolyte layer 60. That is, when stacking misalignment occurs, the reaction section 90 is larger than the reaction section 90 when no stacking misalignment occurs. The expansion of the reaction section 90 also increases the amount of hydrogen sulfide generated. That is, when stacking misalignment occurs, the reaction section 90 expands and the amount of hydrogen sulfide generated increases. In the inspection method of this embodiment, hydrogen sulfide is measured in the step of holding the multiple laminate 1 at high humidity to determine the presence or absence of stacking misalignment based on the correlation between stacking misalignment and the amount of hydrogen sulfide generated. Then, based on the measured amount of hydrogen sulfide generated, it is determined that stacking misalignment has occurred in the multiple laminate 1.

[0027] Next, a battery inspection method according to this embodiment will be described. Fig. 5 is a flowchart showing the steps of the battery inspection method. The battery to be inspected by the battery inspection method shown in Fig. 5 is a multi-layered body 1 formed by stacking a plurality of stacked bodies 30 in the stacking direction, each stacked body 30 including a positive electrode layer 40, a solid electrolyte layer 60, and a negative electrode layer 50, with a positive electrode current collector 10 and a negative electrode current collector 20 interposed therebetween.

[0028] In step S1, the multi-layer structure 1 is prepared. For example, if the pressure mechanism 80 is a mechanism that sandwiches the multi-layer structure 1 between a pair of pressure plates as shown in Fig. 1, the multi-layer structure 1 is placed between the pair of pressure plates via the outer casing 70, thereby preparing the multi-layer structure 1.

[0029] In step S2, the multi-layer stack 1 is sandwiched between the exterior body 70. In step S3, the pressure mechanism 80 presses both surfaces of the multi-layer stack 1 via the exterior body 70 in the direction along the stacking direction of the stack 30.

[0030] In step S4, with the stack 30 pressurized, the multiple stack 1 is held in an environment with higher humidity than before pressurizing the stack 30, and the amount of hydrogen sulfide generated from the multiple stack 1 (hereinafter also referred to as the "amount of hydrogen sulfide generated") is measured (hereinafter also referred to as the "measurement step"). In the measurement step of step S4, a humidifier and a device for measuring the amount of hydrogen sulfide generated are provided around the all-solid-state battery 1A. To achieve a high-humidity environment, the humidifier injects, for example, a high-humidity gas containing moisture toward the stack 30. The multiple battery cells 1B are exposed to the high-humidity environment in a pressurized state. Furthermore, when performing the measurement step of step S4, the humidity of the environment in which the stack 30 is held is higher than the humidity of the environment in the steps prior to the pressurization step of step S3. For example, the humidity of the environment when performing the measurement step of step S4 is higher than the humidity of the environment when performing the steps S1 and / or S2. Note that instead of injecting high-humidity gas using a humidifier, for example, the gas surrounding the battery cells 1B may be replaced with a high-humidity gas.

[0031] In step S5, it is determined whether the measured amount of hydrogen sulfide generated is equal to or greater than a predetermined generation amount threshold. The generation amount threshold is a preset threshold value determined experimentally. FIG. 6 is a graph showing the characteristics of the amount of hydrogen sulfide generated when stacking misalignment occurs and the preset generation amount threshold. The time on the horizontal axis corresponds to the elapsed time of the measurement process. As shown in the graph of "Generation Range Threshold," the amount of hydrogen sulfide generated gradually increases as time passes in the measurement process, and the generation amount threshold is set so that the amount of hydrogen sulfide generated remains constant from a predetermined time. The generation amount threshold may be set to be greater than the time characteristic of the amount of hydrogen sulfide generated in a multiple laminate 1 without stacking misalignment. When stacking misalignment occurs, the amount of hydrogen sulfide generated becomes greater than the generation amount threshold, as shown in the graph of "Stacking Misalignment" in FIG. 6.

[0032] The measured amount of hydrogen sulfide generated may be the amount generated per unit time or the integrated value of the amount generated. When comparing the amount generated per unit time with the generation amount threshold, the elapsed time from the start of injection of high-humidity gas to the time of the "generation region threshold" in Figure 6 can be matched. When comparing the integrated value of generation with the generation amount threshold, the integrated value of generation from the start of injection of high-humidity gas can be calculated, and the calculated integrated value of generation can be compared with the integrated value of the "generation region threshold" in Figure 6.

[0033] The generation amount threshold may be a value defined by the exposed surface area of ​​the solid electrolyte layer 60 and the amount of hydrogen sulfide generated per unit area from the sulfide-based solid electrolyte. The exposed surface area of ​​the solid electrolyte layer 60 corresponds to the side area of ​​the solid electrolyte layer 60 among the side surfaces of the laminate 30. The amount of hydrogen sulfide generated per unit area from the sulfide-based solid electrolyte is a value indicating the amount of hydrogen sulfide generated from the sulfide-based solid electrolyte per unit area, and is determined by the electrolyte material (SE material) contained in the solid electrolyte layer 60, the structure of the solid electrolyte layer 60, and the like. The generation amount threshold may be defined by the value obtained by multiplying the exposed surface area of ​​the solid electrolyte layer 60 by the amount of hydrogen sulfide generated per unit area from the sulfide-based solid electrolyte.

[0034] If the amount of hydrogen sulfide generated is equal to or greater than the predetermined generation amount threshold, it is determined in step S6 that a lamination misalignment has occurred in the multi-layer stack 1. If it is determined that a lamination misalignment has occurred, the control flow ends.

[0035] If the amount of hydrogen sulfide generated is less than a predetermined generation amount threshold, it is determined that no lamination misalignment has occurred, and then it is determined whether the elapsed time in the measurement process is less than a predetermined retention time. The elapsed time is the time from the time when the measurement process of step S4 was first performed. If the elapsed time is less than the predetermined retention time, the process returns to step S4, and the control flow from step S4 onwards is executed again. If the elapsed time reaches the predetermined retention time, a timeout occurs, and the control flow is terminated. In this way, by the control flow loop from step S4 to step S7, the multiple laminate 1 is pressurized, the multiple laminate 1 and the outer casing 70 are held in a high-humidity environment, and the amount of hydrogen sulfide generated is measured. Then, based on the measured amount of hydrogen sulfide generated, it is determined that lamination misalignment has occurred in the multiple laminate 1. The control flow from step S5 to step S7 corresponds to the determination process. Note that the timing of ending the measurement process and the determination process is not limited to the time when the retention time has elapsed (timeout), but may be the time when a predetermined amount of high-humidity gas is injected.

[0036] The above control flow may be performed within the manufacturing process of the all-solid-state battery 1A. In the manufacturing process, a step of manufacturing a multiple laminate 1 is performed before the control flow of step S1. The high humidity maintaining step of step S4 corresponds to a step of forming an oxide layer on the side surface of the laminate 30. Then, a step of sealing the exterior body 70 may be added to the all-solid-state battery 1A determined to have no stacking misalignment (a battery determined as "Yes" in the determination flow of step S7). Then, the all-solid-state battery 1A manufactured through the inspection process of the present embodiment can reduce the thickness of the battery cell 1B and form a thin oxide layer 90 on the side surface of the laminate 30. That is, the formation of an excessive oxide layer 90 is suppressed, deterioration of the solid electrolyte layer 60 is suppressed, and conductivity can be obtained.

[0037] As described above, the battery inspection method according to this embodiment includes the steps of sandwiching the multilayer stack 1 between the exterior body 70, applying pressure to both sides of the multilayer stack 1 via the exterior body 70 in the stacking direction, holding the multilayer stack 1 in a pressurized state in an environment with a higher humidity than before pressurizing the multilayer stack 1, and measuring the amount of hydrogen sulfide generated from the multilayer stack 1, and determining whether stacking misalignment has occurred in the multilayer stack based on the measured amount of hydrogen sulfide generated. This allows the amount of hydrogen sulfide generated to be measured in the measurement step and the presence or absence of stacking misalignment to be determined from the measurement results, thereby reducing the number of steps in the inspection process. Furthermore, stacking misalignment can be inspected during the manufacturing process of the all-solid-state battery 1A, thereby reducing the number of steps in the inspection process. Furthermore, stacks 1 determined to have stacking misalignment can be removed during the manufacturing process, thereby reducing the risk of internal short circuits. Furthermore, the formation of an excess oxide layer is suppressed, which suppresses deterioration of the solid electrolyte layer 60 and improves conductivity. As a result, deterioration of battery performance can be suppressed.

[0038] In this embodiment, if the measured amount of hydrogen sulfide generated is equal to or greater than the generation amount threshold in the determination step, it is determined that lamination misalignment has occurred in the multiple laminated body 1. This makes it possible to determine lamination misalignment from the amount of hydrogen sulfide generated.

[0039] In this embodiment, the generation amount threshold is a value determined by the exposed surface area of ​​the solid electrolyte layer 60 and the amount of hydrogen sulfide generated per unit area from the sulfide-based solid electrolyte. This allows the generation amount threshold to be set in accordance with changes in the exposed surface area of ​​the solid electrolyte layer 60 and / or the amount of hydrogen sulfide generated from the solid electrolyte layer 60, thereby improving the accuracy of determining whether stacking is misaligned. As a result, it is possible to prevent normal battery cells 1 that are not misaligned from being excluded from the manufacturing process.

[0040] In a first modification of this embodiment, the hydrogen sulfide concentration in the high-humidity gas in the sealed container may be measured with the multiple laminate 1 held in the sealed container. Fig. 7 is a block diagram of an all-solid-state battery 1A held in the sealed container, a sealed container 100, and a hydrogen sulfide concentration measuring device 200. The sealed container 100 has a high-humidity gas supply port 101 and an exhaust port 102. In the control flow of step S4 above, the high-humidity gas is supplied from the supply port 101, and hydrogen sulfide generated in the multiple laminate 1 is exhausted from the exhaust port 102. The hydrogen sulfide concentration measuring device 200 measures the hydrogen sulfide concentration at the exhaust port 102.

[0041] FIG. 8 is a graph showing the characteristics of hydrogen sulfide concentration. The horizontal axis corresponds to the elapsed time of the measurement process. The "Concentration Threshold (Sealed)" graph shows the concentration threshold set when the multilayer stack 1 is held in a sealed container 100 (hereinafter also referred to as a "sealed system"). The "Concentration Threshold (Open)" graph shows the concentration threshold set when the multilayer stack 1 is held in an open space rather than in a sealed container 100 (hereinafter also referred to as an "open system"). In the "sealed system," the concentration threshold is set to increase with the elapsed time of the measurement process. In the control flow of step S5 described above, the hydrogen sulfide concentration measured by the hydrogen sulfide concentration measuring device 200 is compared with the concentration threshold of the "Concentration Threshold (Sealed)." If the measured hydrogen sulfide concentration is equal to or greater than the concentration threshold, it is determined that stack misalignment has occurred, as in the control flow of step S6. If the measured hydrogen sulfide concentration is less than the concentration threshold, it is determined that stack misalignment has not occurred.

[0042] In the first modification, in the measurement step, the hydrogen sulfide concentration in the high-humidity gas inside the sealed container 100 is measured. Then, based on the measured concentration, it is determined that a stacking misalignment has occurred in the multi-layer stack 1. This makes it possible to determine the stacking misalignment from the hydrogen sulfide concentration. Furthermore, since a multi-layer stack 1 determined to have a stacking misalignment can be removed during the manufacturing stage, the risk of an internal short circuit can be reduced.

[0043] In addition, in the first modification, in the measurement step, high-humidity gas is supplied from the supply port 101, and the concentration of hydrogen sulfide is measured at the discharge port 102. This makes it possible to suppress a decrease in the supply rate of the high-humidity gas supplied to the multiple laminated body 1. It also makes it possible to prevent a decrease in the rate at which hydrogen sulfide is generated. As a result, the time required for the step of determining stack misalignment can be shortened.

[0044] Unlike the first modification, when measuring the hydrogen sulfide concentration in an open system, the measured hydrogen sulfide concentration can be compared with the concentration threshold value of "Concentration threshold value (open)."

[0045] In Modification 2 of this embodiment, the gas in the environment may be stirred in the measurement step. FIG. 9 is a block diagram of the all-solid-state battery 1A, the humidifying device 300, the measuring device 400, and the stirring device 500. The humidifying device 300 supplies high-humidity gas to the multiple laminate 1 in the measurement step. The measuring device 400 measures the amount of hydrogen sulfide generated in the high-humidity environment. The stirring device 500 stirs the gas in the high-humidity environment. The humidifying device 300, the measuring device 400, and the stirring device 500 may be provided in the sealed container 100, as in Modification 1. The stirring device 500 may stir the gas in the sealed container.

[0046] 10A and 10B are graphs showing the characteristics of the amount of hydrogen sulfide generated measured by the measuring device 400 and the generation amount threshold. The "measured value at point A" and "measured value at point B" in FIGS. 10A and 10B show the characteristics when the measurement points are points A and B in the high-humidity environment shown in FIG. 9 . Also, FIG. 10A shows the characteristics when the agitator 500 is not installed, and FIG. 10B shows the characteristics when the agitator 500 is installed. Comparing the measured values ​​at points A and B, the measured value of the amount of hydrogen sulfide generated at point B, which is close to the side of the multi-layer laminate 1, is greater than the measured value at point A. Comparing the measured values ​​with and without the agitator 500, the difference between the measured value at point B and the measured value at point A is large when the agitator 500 is not installed. Therefore, in the example of FIG. 10A , when the amount of hydrogen sulfide generated is measured at the measurement point A, the measured value is less than the generation amount threshold, and it is determined that no lamination misalignment has occurred. When the amount of hydrogen sulfide generated is measured at the measurement point B, the measured value is greater than the generation amount threshold, and it is determined that lamination misalignment has occurred. In other words, the results of determining the degree of stack misalignment may differ depending on the measurement point of hydrogen sulfide.

[0047] On the other hand, when the agitator 500 is installed, the difference between the measurement value at point B and the measurement value at point A is small. Therefore, in the example of FIG. 10B , when the amount of hydrogen sulfide generated is measured at measurement point A and when the amount of hydrogen sulfide generated is measured at measurement point B, the measured value is less than the generation amount threshold, and it is determined that no stacking misalignment has occurred. Even if the hydrogen sulfide measurement point is different, the result of the stacking misalignment determination is the same. This improves the accuracy of stacking misalignment determination. As a result, it is possible to prevent normal battery cells 1 without stacking misalignment from being excluded from the manufacturing process.

[0048] In the third modification of this embodiment, the measurement step may include a step of measuring the change over time in the amount of hydrogen sulfide generated, and the step of determining whether or not there is lamination misalignment may determine whether or not there is lamination misalignment based on the slope of the characteristic curve of the amount of hydrogen sulfide generated over time. As shown in FIG. 6 , when lamination misalignment occurs, the slope of the characteristic curve of the amount of hydrogen sulfide generated is greater than the slope of the generation rate threshold during the period when the amount of hydrogen sulfide generated increases. Therefore, the presence or absence of lamination misalignment can be determined from the slope of the generation rate threshold. Specifically, in the measurement step of step S4, the change over time in the amount of hydrogen sulfide generated is measured, and the time characteristic of the amount of hydrogen sulfide generated is calculated from the measurement results, thereby calculating the slope of the amount of hydrogen sulfide generated. In the determination step of step S5, it is determined whether or not the slope of the characteristic curve of the amount of hydrogen sulfide generated is equal to or greater than a predetermined slope threshold. If the slope of the characteristic curve of the amount of hydrogen sulfide generated is equal to or greater than the slope threshold, it is determined that there is lamination misalignment. This allows for the determination of whether or not there is lamination misalignment before hydrogen sulfide generation is complete. As a result, the time required for the step of determining whether or not there is lamination misalignment can be shortened.

[0049] In addition, in Modification 3, the slope threshold may be corrected according to the temperature or dew point of the environment in which the multiple stacked body 1 is held. The amount of hydrogen sulfide generated varies depending on the environmental temperature and dew point around the multiple stacked body 1. For example, the higher the dew point, the greater the amount of hydrogen sulfide generated and the greater the slope. Therefore, the slope threshold may be corrected so that the higher the dew point, the greater the slope threshold. This improves the accuracy of determining stack misalignment.

[0050] Second Embodiment FIG. 11 is a flowchart showing a battery inspection method according to a second embodiment.

[0051] The battery inspection method of this embodiment differs from the first embodiment in that a new process is added. In the battery manufacturing method, the structure of the all-solid-state battery inspected in this embodiment is the same as that in the first embodiment. Only the differences between the battery manufacturing method of the second embodiment and the first embodiment will be described below, and the same components as those in the first embodiment will be denoted by the same reference numerals and will not be described again.

[0052] In the second embodiment, the high humidity maintaining step is carried out in the following control flow: The control flow from step S11 to step S13 is the same as step S1 to step S3 in the first embodiment, and therefore a description thereof will be omitted.

[0053] In step S14, while the laminate 30 is being pressed, the multi-layer structure 1 is held in an environment with higher humidity than before the laminate 30 was pressed. In step S15, the weight and / or thickness of the multi-layer structure 1 is measured. The thickness of the multi-layer structure 1 corresponds to the distance between the pair of exterior bodies 70 that sandwich the multi-layer structure 1. The basis weight of the multi-layer structure 1 is calculated from the weight and thickness of the multi-layer structure 1.

[0054] The amount of hydrogen sulfide generated varies depending on variations in the basis weight and thickness of the multi-layer laminate 1. When lamination misalignment occurs, the exposed surface area of ​​the solid electrolyte layer 60 increases, resulting in a large change in the amount of hydrogen sulfide generated. In other words, the amount of hydrogen sulfide generated varies significantly when lamination misalignment occurs, but also varies depending on variations in the basis weight and thickness of the multi-layer laminate 1. Therefore, in this embodiment, a specified range of basis weight is set in advance, and when the calculated basis weight is outside the specified range of basis weight, the generation amount threshold is changed.

[0055] In step S16, it is determined whether the calculated basis weight is within a specified basis weight range. If the calculated basis weight is within the specified basis weight range, the generation amount threshold is not changed from the preset threshold. If the calculated basis weight is outside the specified basis weight range, in step S17, the generation amount threshold is changed according to the basis weight. Specifically, if the calculated basis weight is smaller than the lower limit of the specified basis weight range, the generation amount threshold is decreased so that it is smaller than the preset generation amount threshold. If the calculated basis weight is larger than the upper limit of the specified basis weight range, the generation amount threshold is increased so that it is larger than the preset generation amount threshold. In other words, the generation amount threshold is set according to the weight and thickness of the multiple laminate 1.

[0056] In step S18, the amount of hydrogen sulfide generated from the multiple laminated body 1 is measured. The control flow from step S19 to step S21 is the same as step S5 to step S7 in the first embodiment, and therefore a description thereof will be omitted. Note that if the generation amount threshold is changed, the measured amount of hydrogen sulfide generated is compared with the changed generation amount threshold in the control flow of step S19.

[0057] As described above, in this embodiment, the generation amount threshold is set according to the weight and thickness of the multiple stack 1. This allows the generation amount threshold to be set in accordance with changes in the amount of hydrogen sulfide generated due to variations in unit weight. As a result, the accuracy of determining stack misalignment can be improved. Furthermore, it is possible to prevent normal battery cells 1 that are not experiencing stack misalignment from being excluded from the manufacturing process.

[0058] In this embodiment, the generation amount threshold may be set according to either the weight or the thickness of the multi-layered body 1. For example, when calculating the basis weight, the thickness of the multi-layered body 1 may be set as a fixed value, the weight of the multi-layered body 1 may be measured, and the basis weight may be calculated from the weight.

[0059] In addition, as a fourth modification of this embodiment, the generation amount threshold may be set according to the temperature of the multi-layer stack 1. In the fourth modification, a specified temperature range is set in advance. When the temperature of the multi-layer stack 1 is outside the specified temperature range, the generation amount threshold is changed. When the temperature of the multi-layer stack 1 is lower than the lower limit of the specified temperature range, the generation amount threshold is decreased so that it is smaller than the preset generation amount threshold. When the temperature of the multi-layer stack 1 is higher than the lower limit of the specified temperature range, the generation amount threshold is increased so that it is larger than the preset generation amount threshold. In this way, the generation amount threshold may be set according to at least one element of the weight, thickness, and temperature of the multi-layer stack 1.

[0060] 1A All-solid-state battery 1B Battery cell 1 Multiple laminated body 10 Positive electrode current collector 20 Negative electrode current collector 30 Laminated body 40 Positive electrode layer 50 Negative electrode layer 60 Solid electrolyte layer 70 Exterior body 80 Pressurizing mechanism 90 Reaction section

Claims

1. A battery inspection method for a lithium secondary battery, comprising the steps of: sandwiching a plurality of stacked laminates, each stacked along a stacking direction, in an exterior body; applying pressure to both sides of the stacked laminate via the exterior body in a direction along the stacking direction; holding the stacked laminate in a pressurized state in an environment with a higher humidity than before the pressurization of the stacked laminate, and measuring the amount of hydrogen sulfide generated from the stacked laminate; and determining whether a stacking misalignment has occurred in the stacked laminate based on the measured amount of hydrogen sulfide generated.

2. A battery inspection method according to claim 1, wherein in the determination step, it is determined that lamination misalignment has occurred in the multiple laminates if the measured amount of hydrogen sulfide generated is equal to or greater than a predetermined generation amount threshold.

3. A battery inspection method according to claim 2, wherein the generation amount threshold is a value determined by the exposed surface area of ​​the electrolyte layer and the amount of hydrogen sulfide generated per unit area from the sulfide-based solid electrolyte.

4. A battery inspection method according to claim 2 or 3, wherein the generation amount threshold is set according to at least one of the weight, thickness, and temperature of the multiple laminated bodies.

5. A battery inspection method according to any one of claims 1 to 4, wherein in the measuring step, the multiple stacks are held in a sealed container, and the hydrogen sulfide concentration in the high humidity gas inside the sealed container is measured.

6. A battery inspection method according to claim 5, wherein the sealed container has a supply port for the high-humidity gas and an exhaust port for the high-humidity gas, and in the measuring step, the high-humidity gas is supplied from the supply port and the concentration of the hydrogen sulfide is measured at the exhaust port.

7. A battery inspection method according to any one of claims 1 to 5, wherein the measuring step includes a step of agitating the gas in the environment.

8. A battery inspection method according to any one of claims 1 to 4, wherein the measuring step includes a step of measuring the change over time in the amount of hydrogen sulfide generated, and the determining step determines the stack misalignment based on the slope of the characteristic of the amount of hydrogen sulfide generated versus time.

9. A battery inspection method according to claim 8, wherein in the determining step, if the slope of the characteristic of the amount of hydrogen sulfide generated versus time is equal to or greater than a predetermined slope threshold, it is determined that stack misalignment has occurred in the multiple laminates, and the slope threshold is corrected according to the temperature or dew point of the environment.

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