Method for manufacturing all-solid-state battery

Abstract

Provided is a method for manufacturing an all-solid-state battery with which it is possible, for an all-solid-state battery that comprises a Li metal or a Li alloy in a negative electrode at the time of manufacturing, to easily detect the presence or absence of a short-circuit cell before connecting a plurality of battery cells in parallel. The method for manufacturing an all-solid-state battery comprises: a press step for pressing a stack, in which a negative electrode that contains a lithium metal or a lithium alloy, a solid electrolyte layer, and a positive electrode are repeatedly disposed, so as to form an all-solid-state battery stack in which a plurality of battery cells are stacked; a temperature measurement step for measuring or estimating the temperature of at least a part of the all-solid-state battery stack during or after the press step; and a detection step for detecting the presence or absence of a short circuit in a battery cell on the basis of the temperature measured or estimated in the temperature measurement step. During the period from the start of the press step to the end of the detection step, a state in which the current collectors of electrodes having the same polarity are not electrically connected to each other is maintained for at least one of the negative electrode and the positive electrode.

Description

Manufacturing method for all-solid-state batteries

[0001] The present invention relates to a method for manufacturing an all-solid-state battery.

[0002] Patent Document 1 discloses an "anomaly detection system including a heat flow sensor that acquires the heat flux of a secondary battery, a charge / discharge device that charges or discharges the secondary battery at a constant current, and an inspection device that detects abnormalities in the secondary battery, wherein the inspection device acquires the heat flux of the secondary battery from the heat flow sensor multiple times over a predetermined period while the secondary battery is being charged or discharged at a constant current, and determines an abnormality if, during the predetermined period, the heat flux increases by more than a first predetermined amount from an initial heat flux acquired at a start time of the predetermined period and the magnitude of the difference between the initial heat flux and the heat flux acquired at an end time of the predetermined period is less than or equal to a second predetermined amount that is smaller than the first predetermined amount." This abnormality detection system is used to determine abnormalities in secondary batteries during an inspection process after the secondary batteries are manufactured.

[0003] Japanese Patent Application Laid-Open No. 2019-212484

[0004] In all-solid-state batteries containing lithium (Li) metal or a Li alloy in the negative electrode during manufacturing, battery cells are formed in a charged state. Because the battery cells are in a charged state from the beginning of manufacturing, for example, when connecting current collectors of the same polarity together to connect multiple battery cells in parallel after the battery cells are formed, if any of the battery cells contains an internally shorted battery cell (hereinafter also referred to as a shorted cell), current will flow from the other battery cells connected in parallel to the shorted cell, which is undesirable. There is a need for a technology that can easily detect the presence or absence of a shorted cell before connecting multiple battery cells formed in a charged state in parallel.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing an all-solid-state battery that can easily detect the presence or absence of a short-circuited cell before connecting multiple battery cells in parallel, for an all-solid-state battery that contains Li metal or a Li alloy in the negative electrode during manufacturing.

[0006] A method for manufacturing an all-solid-state battery according to one aspect of the present invention includes: a pressing step of pressing a laminate in which a negative electrode containing lithium metal or a lithium alloy, a solid electrolyte layer, and a positive electrode are repeatedly arranged to form an all-solid-state battery laminate in which a plurality of battery cells are stacked; a temperature measurement step of measuring or estimating the temperature of at least a part of the all-solid-state battery laminate during or after the pressing step; and a detection step of detecting the presence or absence of a short circuit in the battery cells based on the temperature measured or estimated in the temperature measurement step. From the start of the pressing step to the end of the detection step, a state in which the current collectors of at least one of the negative electrode and the positive electrode are electrically disconnected from each other is maintained.

[0007] According to one aspect of the present invention, in an all-solid-state battery that contains Li metal or a Li alloy in the negative electrode during manufacturing, it is possible to simply detect the presence or absence of a short-circuited cell before connecting multiple battery cells in parallel.

[0008] FIG. 1 is a cross-sectional view showing an example of the configuration of an all-solid-state battery manufactured by the manufacturing method according to the first embodiment. FIG. 2A is a plan view showing an example of the configuration of an anode used in the manufacturing method according to the first embodiment. FIG. 2B is a cross-sectional view showing an example of the configuration of an anode used in the manufacturing method according to the first embodiment. FIG. 3A is a plan view showing an example of the configuration of a cathode used in the manufacturing method according to the first embodiment. FIG. 3B is a cross-sectional view showing an example of the configuration of a cathode used in the manufacturing method according to the first embodiment. FIG. 4 is a cross-sectional view showing an example of the configuration of an all-solid-state battery laminate. FIG. 5 is a flowchart showing a method for manufacturing an all-solid-state battery according to the first embodiment. FIG. 6 is a schematic diagram for explaining step ST1 of the flowchart shown in FIG. 5. FIG. 7 is a diagram schematically showing the internal resistance and short-circuit resistance of a short-circuited cell. FIG. 8 is a graph schematically showing the relationship between the short-circuit resistance and heat generation in a short-circuited cell. FIG. 9 is a diagram schematically showing a comparative example of the present invention. FIG. 10 is a flowchart showing a method for manufacturing an all-solid-state battery according to the third embodiment.

[0009] An embodiment of the present invention (the present embodiment) will be described below. In the following drawings, identical or similar parts are designated by identical or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratios of each device and each component, and the like may differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. It goes without saying that the dimensional relationships and ratios of parts included in the drawings may differ from one another. The definitions of directions such as up and down in the following description are merely for the convenience of explanation and do not limit the technical concept of the present invention. For example, if an object is rotated 90 degrees and observed, up and down are read as being converted to left and right, and if it is rotated 180 degrees and observed, up and down are read as being reversed.

[0010] <Embodiment 1> (Configuration Example) FIG. 1 is a cross-sectional view showing a configuration example of an all-solid-state battery 1 manufactured by a manufacturing method according to the present embodiment 1. FIGS. 2A and 2B are a plan view and a cross-sectional view showing a configuration example of an anode 4 used in the manufacturing method according to the present embodiment 1. FIG. 2B shows a cross-section taken along line X1-X1′ of the plan view shown in FIG. 2A. FIGS. 3A and 3B are a plan view and a cross-sectional view showing a configuration example of a cathode 7 used in the manufacturing method according to the present embodiment 1. FIG. 3B shows a cross-section taken along line X2-X2′ of the plan view shown in FIG. 3A. As shown in FIG. 1, the all-solid-state battery 1 manufactured by the manufacturing method according to the present embodiment 1 includes an anode 4 having an anode layer 2 and an anode current collector 3, a cathode 7 having a cathode layer 5 and a cathode current collector 6, a solid electrolyte layer 8 disposed between the anode 4 and the cathode 7, an anode tab lead 11 joined to the anode current collector 3, a cathode tab lead 12 joined to the cathode current collector 6, and an exterior body (not shown).

[0011] As shown in FIGS. 2A and 2B , the negative electrode layer 2 is provided on both surfaces in the thickness direction of the negative electrode current collector 3 (top and bottom surfaces in FIG. 2B ). For example, the negative electrode 4 can be obtained by pressure-bonding lithium (Li) metal or a Li alloy to both surfaces of the negative electrode current collector 3 as the negative electrode layer 2. For the negative electrode current collector 3 and the negative electrode tab lead 11, for example, a metal foil such as copper (Cu), a Cu alloy, nickel, or a nickel alloy can be used, but is not limited to these. The negative electrode layer 2 is made of Li metal or a Li alloy. More specifically, examples of Li alloys include, but are not limited to, a Li-Mg alloy, a Li-Si alloy, a Li-Al alloy, a Li-Zn alloy, a Li-Sn alloy, and a Li-Bi alloy.

[0012] 3A and 3B , the positive electrode layer 5 is provided on both surfaces in the thickness direction of the positive electrode current collector 6 (top and bottom surfaces in FIG. 3B ). For example, a positive electrode 7 can be obtained by preparing a slurry by weighing and mixing predetermined amounts of a positive electrode active material, a sulfide solid electrolyte, a conductive additive, a binder, and an organic solvent, applying the slurry to both surfaces of the positive electrode current collector 6, and then drying the slurry. The positive electrode current collector 6 and the positive electrode tab lead 12 can be made of, for example, aluminum (Al) foil, but are not limited to these. The positive electrode layer 5 can be made of, for example, manganese dioxide, sulfide, or fluoride, but are not limited to these.

[0013] The solid electrolyte layer 8 shown in FIG. 1 may be made of any material as long as it functions as an electrolyte layer in a secondary battery. For example, the solid electrolyte layer 8 may include a sulfide solid electrolyte. Examples of sulfide solid electrolytes include materials containing Li, phosphorus (P), sulfur (S), and a halide. For example, the solid electrolyte layer 8 can be obtained by weighing and mixing predetermined amounts of the sulfide solid electrolyte, a binder, and an organic solvent to prepare a slurry, which is then applied to a substrate and dried. The anodes 4 and cathodes 7 are alternately stacked with the solid electrolyte layer 8 interposed therebetween to form an all-solid-state battery stack 10. A single battery cell 9 is formed by interposing the solid electrolyte layer 8 between the anode 4 and the cathode 7. The all-solid-state battery stack 10 includes multiple battery cells 9. Each battery cell 9 is charged and discharged by the exchange of alkali metal ions (e.g., Li ions) between the anode 4 and the cathode 7 via the solid electrolyte layer 8.

[0014] The all-solid-state battery stack 10, the welded portion 14 between the negative electrode tab lead 11 and the negative electrode current collector 3, and the welded portion 15 between the positive electrode tab lead 12 and the positive electrode current collector 6 are covered and sealed by an exterior body (not shown). The negative electrode tab lead 11 and the positive electrode tab lead 12 extend from the inside to the outside of the exterior body. FIG. 4 is a cross-sectional view showing an example of the configuration of the all-solid-state battery stack 10. FIG. 1 shows an embodiment in which the negative electrodes 4 and the positive electrodes 7 are alternately stacked in pairs with the solid electrolyte layer 8 interposed therebetween, but this is merely an example. In this embodiment, the number of stacked layers of the negative electrodes 4 and the positive electrodes 7 is not limited to two. As shown in FIG. 4, the number of stacked layers of the negative electrodes 4 and the positive electrodes 7 may each be three or more. Furthermore, the number of stacked layers of the negative electrodes 4 and the positive electrodes 7 may be the same or different. 4 shows an embodiment in which one more layer of the positive electrode 7 is provided than the negative electrode 4, and the positive electrode 7 is located in each of the uppermost and lowermost layers of the all-solid-state battery laminate 10, but this is merely one example. In the present embodiment, one more layer of the negative electrode 4 is provided than the positive electrode 7, and the negative electrode 4 may be located in each of the uppermost and lowermost layers of the all-solid-state battery laminate 10. Of course, the positive electrode 7 may be located in one of the uppermost and lowermost layers of the all-solid-state battery laminate 10, and the negative electrode 4 may be located in the other.

[0015] (Manufacturing Method) Next, a manufacturing method of the all-solid-state battery 1 according to the first embodiment will be described. FIG. 5 is a flowchart showing a manufacturing method of the all-solid-state battery 1 according to the first embodiment. Note that other steps may be included between the steps in the flowchart of FIG. 5. FIG. 6 is a schematic diagram for explaining step ST1 of the flowchart shown in FIG. 5. Note that the all-solid-state battery 1 is manufactured using various devices, such as a device for stacking the negative electrode 4, the positive electrode 7, and the solid electrolyte layer 8, a press device for pressing the all-solid-state battery stack 10, a device for measuring the temperature of the all-solid-state battery stack 10, and a welding device for welding the current collector and the tab lead. Hereinafter, these devices will be collectively referred to as manufacturing devices.

[0016] In step ST1 of FIG. 5 , the manufacturing equipment performs a pressing process to form an all-solid-state battery laminate 10. For example, as shown in step ST11 of FIG. 6 , a laminate 10′ is prepared in which an anode 4, a solid electrolyte layer 8, and a cathode 7 are repeatedly arranged. For example, a cathode 7 with a solid electrolyte layer 8 is arranged, in which the solid electrolyte layer 8 is pre-laminated on the cathode layer 5. This manufacturing method involves arranging the solid electrolyte layers 8 so as to sandwich the cathode 7, stacking them and applying pressure, and then removing the base material of the solid electrolyte layer 8 after pressing, thereby transferring the solid electrolyte layer 8 to the cathode 7. This manufacturing method allows the cathode 7 with the solid electrolyte layer 8 to be obtained. Next, the manufacturing equipment positions the anode 4 in a position facing the cathode 7 with the solid electrolyte layer 8 interposed therebetween. The steps of positioning the cathode 7 with the solid electrolyte layer 8 and positioning the anode 4 are then repeated a predetermined number of times (i.e., a predetermined number of times). This makes it possible to prepare an unpressurized laminate 10′ in which the negative electrode 4 containing Li metal or Li alloy as the negative electrode layer 2, the solid electrolyte layer 8, and the positive electrode 7 are repeatedly arranged in one direction (stacking direction; for example, the Z-axis direction).

[0017] In the manufacturing method according to the first embodiment, the solid electrolyte layer 8 may be provided on the negative electrode 4, not on the positive electrode 7. In this case, in step ST11, the process of disposing the positive electrode 7 and the process of disposing the negative electrode 4 with the solid electrolyte layer 8 are repeated a predetermined number of times. Alternatively, the solid electrolyte layer 8 may be prepared separately from the positive electrode 7 and the negative electrode 4. In this case, a process of disposing the solid electrolyte layer 8 may be performed between the process of disposing the positive electrode 7 and the process of disposing the negative electrode 4. Next, in step ST12 of FIG. 6 , the manufacturing apparatus applies a pressure P to the unbonded laminate 10′ at least in the stacking direction (e.g., the Z-axis direction). The pressure P is equal to or greater than the yield stress of Li metal, e.g., 5 MPa or greater. The yield stress of Li metal refers to the stress at which plasticity of Li metal begins. This pressing process causes the negative electrode layer 2 and the solid electrolyte layer 8, and the solid electrolyte layer 8 and the positive electrode layer 5, to be bonded together at high pressure, thereby forming the all-solid-state battery laminate 10.

[0018] By this molding, the anode layer 2 made of Li metal or Li alloy is pressure-bonded to the solid electrolyte layer 8. Therefore, each battery cell 9 included in the all-solid-state battery stack 10 is formed in a charged state. For example, each battery cell 9 included in the all-solid-state battery stack 10 is formed in a state of SOC (State Of Charge) of 100% or a high SOC (for example, 95%, 90%, or 85%).

[0019] In this manufacturing method, from the start of the pressing process in step ST1 to the end of the detection process in step ST3 (described later), the current collectors of at least one of the negative electrode 4 and the positive electrode 7 are maintained in a state where they are not electrically connected to each other. For example, at least one of the negative electrode current collectors 3 and the positive electrode current collectors 6 is covered with an insulating material to prevent contact between the negative electrode current collectors 3 and the positive electrode current collectors 6. This prevents contact between adjacent current collectors in the stacking direction on the side where the insulating material is present, even if a short-circuited cell occurs during the pressing process, thereby preventing the formation of an external parallel circuit. Even if a short-circuited cell occurs, a large current from flowing into the short-circuited cell can be prevented.

[0020] Next, in step ST2 of FIG. 5 , the manufacturing apparatus performs a temperature measurement process to measure or estimate the temperature of at least a portion of the all-solid-state battery stack 10. For example, in the temperature measurement process, the in-plane temperature is measured or estimated for at least one of the upper surface 10 a and the lower surface 10 b in the stacking direction (e.g., the Z-axis direction) of the all-solid-state battery stack 10. The method for measuring or estimating the temperature of the all-solid-state battery stack 10 may be contact or non-contact, and is not particularly limited. An example of a contact temperature measurement method is a method using a thermocouple. An example of a non-contact temperature measurement method is a method of measuring the temperature using an infrared radiation thermometer. The infrared radiation thermometer may be, for example, a spot radiation thermometer that measures the temperature at a spot (point), a scanning radiation thermometer that measures the temperature in a line (one-dimensional), or a thermal imaging camera (thermography) that measures the temperature using a planar image (two-dimensional). However, from the viewpoint of precisely measuring the in-plane temperature, a scanning radiation thermometer or a thermal imaging camera is preferable. The measured temperature is recorded, for example, in a recording medium such as a flash memory provided in the manufacturing device.

[0021] Next, in step ST3 of Fig. 5 , the manufacturing apparatus performs a detection step of detecting the presence or absence of a short circuit in the battery cells 9 included in the all-solid-state battery laminate 10 based on the temperatures measured or estimated in the temperature measurement step. For example, the manufacturing apparatus reads the in-plane temperatures recorded on the recording medium in step ST2 of Fig. 5 and compares the read temperatures with a preset threshold. The manufacturing apparatus determines that a short circuit exists (i.e., NG) if at least some of the read temperatures exceed the threshold, and determines that a short circuit does not exist (i.e., OK) if the read temperatures are equal to or lower than the threshold. If the determination is NG, there is a possibility that a short circuit exists between the negative electrode current collector 3 and the positive electrode current collector 6 in at least some of the multiple battery cells 9 included in the all-solid-state battery laminate 10, and therefore the product is treated as defective, and the manufacturing process is terminated.

[0022] As described above, if the temperature is higher than the threshold value in step ST3 of FIG. 5, the result is NG. This point will be explained with reference to FIGS. 7 and 8. FIG. 7 is a diagram schematically showing the internal resistance Ri and short-circuit resistance Rs of a short-circuited cell. As shown in FIG. 7, a short-circuited cell has the battery's internal resistance Ri and short-circuit resistance Rs as resistance components. The internal resistance Ri is a resistance component that the battery cell has regardless of whether or not there is a short circuit. On the other hand, the short-circuit resistance is a resistance component that only the short-circuited cell has, and is the resistance component of the short-circuit path between the negative electrode current collector and the positive electrode current collector. When a current I flows through a short-circuited cell due to electromotive force E, heat Wi is generated by the internal resistance Ri, and heat Ws is generated by the short-circuit resistance Rs. The heat Wi and Ws can be expressed, for example, by the following equations (1) and (2), respectively: Wi=E ２ Rs / (Ri+Rs) ２ ... (1) Ws = E ２ Ri / (Ri+Rs) ２ …(2)

[0023] FIG. 8 is a graph schematically illustrating the relationship between the short-circuit resistance Rs and the heat generation Wi and Ws in a short-circuited cell. The horizontal axis of FIG. 8 represents the short-circuit resistance Rs, and the vertical axis represents the heat generation (amount of heat). As shown in FIG. 8 , when the short-circuit resistance Rs is low (i.e., short-circuited), the heat generation Wi tends to be high. This is thought to be because when the short-circuit resistance Rs is low, a large amount of current I flows through the battery cell via the short-circuit path, causing the entire short-circuited cell to generate heat. On the other hand, when the short-circuit resistance Rs is high (i.e., not short-circuited), the heat generation Wi tends to be low. This is thought to be because when the short-circuit resistance Rs is high, almost no current I flows through the battery cell, causing almost no heat generation in the entire battery cell. Thus, there is a correlation between the heat generation Wi due to internal resistance and the short-circuit resistance Rs. When the short-circuit resistance Rs is low, the heat generation Wi is high, and when the short-circuit resistance Rs is high, the heat generation Wi is low. By setting a threshold value for the heat generation Wi and comparing this threshold value with the temperature of the entire battery cell, it is possible to detect whether or not a battery cell is short-circuited.

[0024] 8, the heat generation due to the short-circuit resistance has a peak. For example, when the short-circuit resistance Rs and the internal resistance Ri have the same value (Rs = Ri), the heat generation Ws due to the short-circuit resistance Rs and the heat generation Wi due to the internal resistance have the same value (Ws = Wi), and the heat generation Ws due to the short-circuit resistance Rs reaches a peak value. Therefore, by measuring or estimating the in-plane temperature of at least one of the upper surface 10a and the lower surface 10b of the all-solid-state battery laminate 10 and detecting the peak value of the heat generation Ws, it is possible to identify the location of this peak value as the short-circuit location.

[0025] In the detection process of step ST3 in Fig. 5 , it may be determined that a short circuit has occurred when the temperature measured or estimated in the temperature measurement process is higher than the environmental temperature (e.g., 25°C) in which the all-solid-state battery stack 10 is placed in the temperature measurement process of step ST2. That is, the threshold for detecting the presence or absence of a short circuit may be the environmental temperature in the temperature measurement process. This makes it possible to detect the presence or absence of a short circuit with higher accuracy. Furthermore, the temperature measurement process of step ST2 may be performed in a state in which the all-solid-state battery stack 10 is placed in an adiabatic environment. This makes it possible to suppress changes in the environmental temperature due to external factors, and therefore makes it possible to detect the presence or absence of a short circuit with higher accuracy.

[0026] The all-solid-state battery 1 shown in FIG. 1 is completed through steps ST1 to ST3 shown in FIG. 5 . In the manufacturing method according to the first embodiment, a tab joining process, a sealing process, a discharging process, and a charging process may be performed following step ST3 in the flowchart shown in FIG. 5 . In the tab joining process, the manufacturing equipment joins the negative electrode current collector 3 and the negative electrode tab lead 11, and also joins the positive electrode current collector 6 and the positive electrode tab lead 12, for an all-solid-state battery laminate 10 determined to be free of short circuits (i.e., OK). The joining method is not particularly limited, and examples include ultrasonic welding and laser welding that utilize heat generated by friction between metals. In the sealing process, the manufacturing equipment seals the all-solid-state battery laminate 10 with an exterior body, excluding the negative electrode tab lead 11 and the positive electrode tab lead 12. The weld 14 (see FIG. 1) between the negative electrode current collector 3 and the negative electrode tab lead 11 and the weld 15 (see FIG. 1) between the positive electrode current collector 6 and the positive electrode tab lead 12 are also sealed with an exterior body. In the discharging step, the manufacturing equipment performs a discharging operation on the all-solid-state battery stack 10 formed in a charged state. For example, the discharging operation is performed on all battery cells 9 included in the all-solid-state battery stack 10 via the negative electrode tab lead 11 and positive electrode tab lead 12 shown in FIG. 1 . During this discharging operation, in each battery cell 9, Li ions move from the negative electrode 4 to the positive electrode 7 via the solid electrolyte layer 8 and are occluded in the positive electrode layer 5. When the discharging operation is performed, Li metal or Li alloy as the negative electrode layer 2 decreases as the discharge progresses. When the discharge progresses to an SOC of 0%, the Li metal or Li alloy as the negative electrode layer 2 is almost gone. In the charging step, the manufacturing equipment performs an initial charging operation on the discharged all-solid-state battery stack 10. This charging operation is performed via the negative electrode tab lead 11 and positive electrode tab lead 12. During this charging operation, in each battery cell 9, Li ions absorbed in the positive electrode layer 5 move to the negative electrode current collector 3 through the solid electrolyte layer 8, and Li metal or Li alloy is deposited as the negative electrode layer 2.

[0027] (Effects of First Embodiment) As described above, the manufacturing method of the all-solid-state battery 1 according to the first embodiment of the present invention includes a pressing step of pressing a laminate 10′ in which a negative electrode 4 containing lithium metal or a lithium alloy, a solid electrolyte layer 8, and a positive electrode 7 are repeatedly arranged to form an all-solid-state battery laminate 10 in which a plurality of battery cells 9 are stacked, a temperature measurement step of measuring or estimating the temperature of at least a part of the all-solid-state battery laminate 10 after the pressing step, and a detection step of detecting the presence or absence of a short circuit in the battery cell 9 based on the temperature measured or estimated in the temperature measurement step. From the start of the pressing step to the end of the detection step, a state in which the current collectors of the same electrode (e.g., the negative electrode current collectors 3 and the positive electrode current collectors 6) are electrically disconnected from each other for at least one of the negative electrode 4 and the positive electrode 7.

[0028] This makes it possible to detect the presence or absence of a short circuit in the battery cell 9 without performing an electrochemical operation. In an all-solid-state battery 1 that contains Li metal or Li alloy in the negative electrode 4 during manufacture, it is possible to simply detect the presence or absence of a short-circuited cell before connecting multiple battery cells 9 in parallel (for example, before tab joining).

[0029] In the temperature measurement step, the temperature within at least one of the upper surface 10a and the lower surface 10b in the stacking direction (e.g., the Z-axis direction) of the all-solid-state battery stack 10 may be measured or estimated as first temperature data. In the detection step, the presence or absence of a short circuit may be detected based on the first temperature data. For example, if the temperature within at least one of the upper surface 10a and the lower surface 10b exceeds the ambient temperature, it may be determined that a short circuit has occurred. In addition, if the temperature within at least one of the upper surface 10a and the lower surface 10b has a temperature distribution similar to the heat generation Wi shown in FIG. 8 or a temperature distribution similar to the heat generation Ws, it may also be determined that a short circuit has occurred.

[0030] Furthermore, if a short circuit is detected in the detection step, the location of the short circuit within the plane (for example, the XY plane perpendicular to the Z-axis direction) may be identified based on the first temperature data. The location where the heat generation peaks in plan view (i.e., the location where the temperature is highest) is the location where the short circuit occurred within the plane. Identifying the location where the short circuit occurred within the plane makes it possible to analyze the cause of the short circuit and provide feedback to the manufacturing process, thereby enabling continuous improvement of the manufacturing process.

[0031] The detection of the presence or absence of a short circuit in this embodiment can be performed only in an all-solid-state battery (or an all-solid-state battery stack) that contains Li metal or a Li alloy in the negative electrode during manufacture. In an all-solid-state battery that does not contain Li metal or a Li alloy in the negative electrode during manufacture, Li is not present in the negative electrode during a short circuit, and therefore the above-described method cannot be used to detect the presence or absence of a short circuit.

[0032] FIG. 9 is a comparative example of the present invention, and is a schematic diagram illustrating a case where current collectors are brought into contact with each other when an internal short circuit has occurred in a battery cell 109. During the process of stacking and pressing a negative electrode containing Li metal or a Li alloy, a solid electrolyte layer, and a positive electrode, an internal short circuit may occur in the battery cell 109. FIG. 9 illustrates a case where a short circuit has occurred between the negative electrode 4 and the positive electrode 7 in one battery cell (short-circuited cell) 109S among the multiple battery cells 109 included in the all-solid-state battery stack 110. In this state, when the negative electrode current collectors 3 come into contact with each other and the positive electrode current collectors 6 come into contact with each other, an external parallel circuit is formed. In this external parallel circuit, current I flows from all of the non-shorted battery cells 109 to the short-circuited cell 109S, resulting in a large current. A large current flowing through the short-circuited cell 109S may cause the short-circuited cell 109S to generate a large amount of heat, which is undesirable.

[0033] In contrast, in the manufacturing method according to the first embodiment, the temperature of the all-solid-state battery 1 is measured or estimated before current collectors of the same electrode (e.g., negative electrode current collectors 3, positive electrode current collectors 6) are brought into contact with each other, and the presence or absence of a short circuit in the battery cell 9 is detected based on the measurement or estimation result. This makes it possible to sort out and remove an all-solid-state battery stack including a short-circuited cell as a defective product before current collectors of the same electrode come into contact with each other. In the process of bringing current collectors of the same electrode into contact with each other (e.g., the tab joining process), only non-defective all-solid-state battery stacks 10 that do not include short-circuited cells can be handled, and therefore, no significant heat generation due to short-circuited cells can be prevented. This further improves the safety of the manufacturing process.

[0034] (Modification) In the above-described first embodiment, as shown in FIG. 5 , the temperature measurement step is performed after the pressing step. However, the present invention is not limited to this. In the present embodiment, the temperature measurement step may be performed during the pressing step, or may be performed both during and after the pressing step. In the manufacturing process of an all-solid-state battery, short circuits in battery cells are likely to occur during the pressing step. Therefore, by measuring or estimating the temperature of the laminate 10′ or the all-solid-state battery laminate 10 during the pressing step, it may be possible to further improve the detection sensitivity for the presence or absence of a short circuit.

[0035] Furthermore, the pressing process may be stopped when the maximum temperature measured or estimated during the pressing process reaches the melting point of the Li metal or Li alloy constituting the negative electrode layer 2. This can prevent the Li metal or Li alloy from melting and flowing out to the positive electrode 7, thereby further improving the safety of the manufacturing process. These modifications may be applied not only to the first embodiment but also to the second and third embodiments described below.

[0036] Second Embodiment In the above embodiment, the in-plane temperature of at least one of the upper surface 10a and the lower surface 10b of the all-solid-state battery stack 10 is measured or estimated. However, in the embodiment of the present invention, the locations where the temperature is measured are not limited to the upper surface 10a and the lower surface 10b of the all-solid-state battery stack 10. In the temperature measurement process of step ST2 in FIG. 5 , the temperature in the stacking direction (e.g., the Z-axis direction) of the all-solid-state battery stack 10 may be measured or estimated as the second temperature data. For example, the temperature of a side surface 10c (see FIG. 4 ) along the stacking direction of the all-solid-state battery stack 10 may be measured or estimated as the second temperature data. The side surface 10c includes the side surfaces of the anode current collector 3, the anode layer 2, the solid electrolyte layer 8, the cathode layer 5, and the cathode current collector 6.

[0037] In the temperature measurement step, the temperature of the side surface 10c may be measured or estimated using a scanning radiation thermometer or a thermal imaging camera. Alternatively, a thermocouple may be attached to a protruding portion of the negative electrode current collector 3 and the positive electrode current collector 6 that protrudes from the side surface 10c of the all-solid-state battery stack 10, and the temperature of the side surface 10c of the all-solid-state battery stack 10 may be measured at regular intervals along the stacking direction. In the inspection step of step ST3 in FIG. 5 , the presence or absence of a short circuit may be detected based on the temperature in the stacking direction (second temperature data). For example, if the temperature in the stacking direction exceeds the ambient temperature, it may be determined that a short circuit has occurred. Furthermore, if the temperature in the stacking direction has a temperature distribution similar to the heat generation Wi or the heat generation Ws shown in FIG. 8 , it may also be determined that a short circuit has occurred.

[0038] According to the manufacturing method of the second embodiment of the present invention, it is possible to detect the presence or absence of a short circuit without performing an electrochemical operation, as in the manufacturing method of the first embodiment. In an all-solid-state battery 1 containing Li metal or a Li alloy in the negative electrode 4 during manufacturing, it is possible to simply detect the presence or absence of a short-circuited cell before connecting a plurality of battery cells 9 in parallel (for example, before tab joining).

[0039] Furthermore, if a short circuit is detected in the detection step, the location of the short circuit in the stacking direction (e.g., the Z-axis direction) may be identified based on the second temperature data. The location where the heat generation in the stacking direction peaks (i.e., the location where the temperature is highest) is the location where the short circuit occurred in the stacking direction. Identifying the location where the short circuit occurred in the stacking direction makes it possible to analyze the cause of the short circuit and provide feedback to the manufacturing process, thereby enabling continuous improvement of the manufacturing process.

[0040] <Embodiment 3> In embodiment 3 of the present invention, the presence or absence of a short circuit may be detected by combining embodiments 1 and 2. Fig. 10 is a flowchart showing a method for manufacturing the all-solid-state battery 1 according to embodiment 3. Note that other processes may be included between the flowchart in Fig. 10. In Fig. 10, the pressing process in step ST1 is the pressing process described in embodiment 1. In Fig. 10, the first temperature measurement process in step ST21 is the temperature measurement process described in embodiment 1, and the temperature measurement process in step ST22 is the temperature measurement process described in embodiment 2.

[0041] In step ST21, the in-plane temperature of at least one of the upper surface 10a and the lower surface 10b in the stacking direction of the all-solid-state battery stack 10 is measured or estimated as first temperature data. In step ST22, the temperature in the stacking direction of the all-solid-state battery stack is measured or estimated as second temperature data. The first temperature data and the second temperature data are recorded, for example, in a recording medium such as a flash memory provided in the manufacturing apparatus.

[0042] In step ST3 of FIG. 10 , the manufacturing apparatus detects the presence or absence of a short circuit in the battery cells included in the all-solid-state battery laminate based on the first temperature data and the second temperature data. For example, the manufacturing apparatus reads the first temperature data and the second temperature data recorded on the recording medium in steps ST21 and ST22 of FIG. 10 and compares the read temperatures with a preset threshold. A threshold is set in advance for each of the first temperature data and the second temperature data. The manufacturing apparatus determines that a short circuit exists (i.e., NG) if at least one of the first temperature data and the second temperature data exceeds the threshold, and determines that a short circuit does not exist (i.e., OK) if the first temperature data and the second temperature data are equal to or less than the threshold. If the determination is NG, there is a possibility that a short circuit exists between the negative electrode current collector 3 and the positive electrode current collector 6 in at least some of the multiple battery cells 9 included in the all-solid-state battery laminate 10, and the product is treated as defective, and the manufacturing process is terminated.

[0043] According to the manufacturing method of the third embodiment, even when it is difficult to detect a short circuit using the first temperature data (for example, when a short circuit occurs at an intermediate position in the stacking direction, away from each of the upper surface 10a and the lower surface 10b of the all-solid-state battery stack 10), it is possible to detect a short circuit based on the second temperature data. Furthermore, even when it is difficult to detect a short circuit using the second temperature data (for example, when a short circuit occurs at a central position in the X-Y plane, away from the side surface 10c of the all-solid-state battery stack 10), it is possible to detect a short circuit based on the first temperature data. Therefore, it is possible to further improve the detection sensitivity for the presence or absence of a short circuit.

[0044] Furthermore, if a short circuit is detected in the detection process of step ST3, the location of the short circuit in the all-solid-state battery stack may be identified based on the first temperature data and the second temperature data. For example, the manufacturing device identifies the location of the short circuit in the plane based on the first temperature data. Furthermore, the manufacturing device identifies the location of the short circuit in the stacking direction based on the second temperature data. By combining the location of the short circuit in the plane (e.g., the X-Y plane) and the location of the short circuit in the stacking direction (e.g., the Z-axis direction), it is possible to identify the location of the short circuit in three dimensions. This enables more detailed analysis of the cause of the short circuit and feedback to the manufacturing process. This enables continuous and more effective improvement of the manufacturing process.

[0045] <Other Embodiments> As described above, the present invention has been described with reference to embodiments and modifications. However, the descriptions and drawings that form part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments and modifications will be apparent to those skilled in the art from this disclosure. For example, in embodiments of the present invention, from the start of the pressing process in step ST1 to the end of the detection process in step ST5, not all of the negative electrode current collectors 3 constituting the laminate 10′ or the all-solid-state battery laminate 10 may be covered with an insulating material. For example, every other negative electrode current collector 3 in the stacking direction may be covered with an insulating material. At least some of the negative electrode current collectors 3 may be maintained in a state where they are not electrically connected to each other. The same applies to the positive electrode current collector 6. As such, it goes without saying that the present technology includes various embodiments not described herein. At least one of various omissions, substitutions, and modifications of components may be made without departing from the spirit of the above-described embodiments. Furthermore, the effects described herein are merely exemplary and are not limiting, and other effects may also be achieved.

[0046] The present invention can also adopt the following configurations: (1) A method for manufacturing an all-solid-state battery, comprising: a pressing step of pressing a laminate including an anode containing lithium metal or a lithium alloy, a solid electrolyte layer, and a cathode arranged in an alternating manner to form an all-solid-state battery laminate including a plurality of stacked battery cells; a temperature measurement step of measuring or estimating the temperature of at least a part of the all-solid-state battery laminate during or after the pressing step; and a detection step of detecting the presence or absence of a short circuit in the battery cells based on the temperature measured or estimated in the temperature measurement step, wherein, for at least one of the anode and the cathode, a state in which current collectors of the same electrode are not electrically connected to each other is maintained from the start of the pressing step to the end of the detection step. (2) The method for manufacturing an all-solid-state battery according to (1), wherein, in the temperature measurement step, the temperature within at least one of the upper surface and the lower surface in the stacking direction of the all-solid-state battery laminate is measured or estimated as first temperature data, and, in the detection step, the presence or absence of the short circuit is detected based on the first temperature data. (3) The method for manufacturing an all-solid-state battery according to (2), wherein, if the short circuit is detected in the detecting step, a location of the short circuit in the plane is identified based on the first temperature data. (4) The method for manufacturing an all-solid-state battery according to any one of (1) to (3), wherein, in the temperature measuring step, a temperature in a stacking direction of the all-solid-state battery laminate is measured or estimated as second temperature data, and, in the detecting step, the presence or absence of the short circuit is detected based on the second temperature data. (5) The method for manufacturing an all-solid-state battery according to (4), wherein, if the short circuit is detected in the detecting step, a location of the short circuit in the stacking direction is identified based on the second temperature data. (6) The method for manufacturing an all-solid-state battery according to any one of (1) to (5), wherein, in the detecting step, it is determined that the short circuit has occurred if the temperature measured or estimated in the temperature measuring step is higher than an environmental temperature in which the all-solid-state battery laminate is placed in the temperature measuring step.(7) The method for manufacturing an all-solid-state battery according to any one of (1) to (6), wherein the temperature measurement step is performed during the pressing step, and when the maximum temperature measured or estimated in the temperature measurement step reaches the melting point of the lithium metal or the lithium alloy contained in the negative electrode, the pressing step is stopped. (8) The method for manufacturing an all-solid-state battery according to any one of (1) to (7), wherein the temperature measurement step is performed in a state where the all-solid-state battery laminate is placed in an adiabatic environment.

[0047] 1... all-solid-state battery, 2... negative electrode layer, 3... negative electrode current collector, 4... negative electrode, 5... positive electrode layer, 6... positive electrode current collector, 7... positive electrode, 8... solid electrolyte layer, 9, 109... battery cell, 10'... laminate, 10, 110... all-solid-state battery laminate, 10a... upper surface, 10b... lower surface, 10c... side surface, 11... negative electrode tab lead, 12... positive electrode tab lead, 14, 15... welded portion, 109S... short-circuited cell, Ri... internal resistance, Rs... short-circuit resistance

Claims

1. A method for manufacturing an all-solid-state battery, comprising: a pressing step of pressing a laminate in which a negative electrode containing lithium metal or a lithium alloy, a solid electrolyte layer, and a positive electrode are repeatedly arranged, to form an all-solid-state battery laminate in which a plurality of battery cells are stacked; a temperature measurement step of measuring or estimating the temperature of at least a part of the all-solid-state battery laminate during or after the pressing step; and a detection step of detecting whether or not the battery cells are short-circuited based on the temperature measured or estimated in the temperature measurement step, wherein a state in which current collectors of the same electrode are not electrically connected to each other is maintained for at least one of the negative electrode and the positive electrode from the start of the pressing step to the end of the detection step.

2. The method for manufacturing an all-solid-state battery according to claim 1, wherein in the temperature measurement step, a temperature within at least one of an upper surface and a lower surface in a stacking direction of the all-solid-state battery laminate is measured or estimated as first temperature data, and in the detection step, the presence or absence of the short circuit is detected based on the first temperature data.

3. The method for manufacturing an all-solid-state battery according to claim 2, wherein, if the short circuit is detected in the detection step, the location of the short circuit within the surface is identified based on the first temperature data.

4. The method for manufacturing an all-solid-state battery according to any one of claims 1 to 3, wherein in the temperature measurement step, a temperature in a stacking direction of the all-solid-state battery stack is measured or estimated as second temperature data, and in the detection step, the presence or absence of the short circuit is detected based on the second temperature data.

5. The method for manufacturing an all-solid-state battery according to claim 4, wherein, if the short circuit is detected in the detection step, the location of the short circuit in the stacking direction is identified based on the second temperature data.

6. The method for manufacturing an all-solid-state battery according to any one of claims 1 to 3, wherein in the detection step, it is determined that the short circuit has occurred if the temperature measured or estimated in the temperature measurement step is higher than the environmental temperature in which the all-solid-state battery stack is placed in the temperature measurement step.

7. The method for manufacturing an all-solid-state battery according to any one of claims 1 to 3, wherein the temperature measurement step is performed during the pressing step, and when the highest temperature measured or estimated in the temperature measurement step reaches the melting point of the lithium metal or the lithium alloy contained in the negative electrode, the pressing step is stopped.

8. The method for manufacturing an all-solid-state battery according to any one of claims 1 to 3, wherein the temperature measurement step is performed with the all-solid-state battery stack placed in an adiabatic environment.

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