Method for manufacturing all-solid-state battery

Abstract

Provided is a method for manufacturing an all-solid-state battery, namely an all-solid-state battery containing Li metal or an Li alloy in a negative electrode, said method making it possible at the time of manufacture to easily detect the presence or absence of a short-circuit cell before a plurality of battery cells are connected in parallel. This method for manufacturing an all-solid-state battery comprises: a pressing step for pressing a laminate consisting of a repeating arrangement of a negative electrode containing lithium metal or a lithium alloy, a solid electrolyte layer and a positive electrode, thereby forming an all-solid-state battery laminate in which a plurality of battery cells are laminated; a leaving step for leaving the all-solid-state battery laminate; a measurement step for measuring data resulting from the thickness of the battery cells after the leaving step; and a detection step for detecting the presence or absence of a short circuit in the battery cells on the basis of the data obtained in the measurement step. From the start of the pressing step to the end of the detection step, a state in which current collectors of the same electrode are not electrically connected to one another is maintained.

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 a method for inspecting a secondary battery, including the steps of charging the secondary battery, measuring a first voltage, which is the potential difference between the negative electrode and the battery case, while the secondary battery is compressed from the outside of the battery case, continuing to maintain the compressed state of the secondary battery for a predetermined maintenance time, measuring a second voltage, which is the potential difference between the negative electrode and the battery case, for a secondary battery whose compression time has reached or exceeded the maintenance time, and determining that the secondary battery is defective when at least one of the first voltage and the second voltage is smaller than a predetermined threshold voltage.

[0003] Japanese Patent Application Laid-Open No. 2023-149424

[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. For example, when current collectors of the same electrode are connected together to connect multiple battery cells formed in a charged state in parallel, if any of these battery cells contains an internally shorted battery cell (hereinafter also referred to as a shorted cell), current flows from the other battery cells connected in parallel to the shorted cell, which is undesirable. A technology is desired 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 leaving step of leaving the all-solid-state battery laminate, a measurement step of measuring data attributable to the thickness of the battery cells after the leaving step, and a detection step of detecting whether or not a short circuit has occurred in the battery cells based on the data obtained in the measurement step. From the start of the pressing step to the end of the detection step, a state in which current collectors of the same electrode are not electrically connected to 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. 2 is a cross-sectional view showing an example of the configuration of an all-solid-state battery laminate. FIG. 3 is a flowchart showing a manufacturing method of an all-solid-state battery according to the first embodiment. FIG. 4 is a schematic diagram for explaining step ST1 of the flowchart shown in FIG. 3. FIG. 5 is a schematic diagram for explaining steps ST2 to ST4 of the flowchart shown in FIG. 3. FIG. 6 is a schematic diagram showing the mechanism by which the thickness of a battery cell decreases when a short circuit occurs between the negative electrode and the positive electrode. FIG. 7 is a schematic diagram for explaining steps ST2 to ST4 according to the second embodiment of the present invention. FIG. 8 is a graph showing the difference in change in distance (thickness) depending on whether or not a short circuit occurs in the manufacturing method according to the second embodiment of the present invention. FIG. 9 is a schematic diagram for explaining steps ST2 to ST4 according to a modified example of the second embodiment of the present invention.

[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. 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 positive electrode 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] The negative electrode layer 2 is provided on both sides of the negative electrode current collector 3 in the thickness direction. For example, the negative electrode 4 can be obtained by pressure-bonding lithium (Li) metal or a Li alloy to both sides 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] The positive electrode layer 5 is provided on both sides in the thickness direction of the positive electrode current collector 6. 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 sides 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. 2 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 two layers with the solid electrolyte layer 8 interposed therebetween, but this is merely an example. In this embodiment, the number of stacked negative electrodes 4 and positive electrodes 7 is not limited to two. As shown in FIG. 2, the number of stacked negative electrodes 4 and positive electrodes 7 may be three or more. Furthermore, the number of stacked negative electrodes 4 and positive electrodes 7 may be the same or different. 2 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. 3 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. 3. FIG. 4 is a schematic diagram for explaining step ST1 of the flowchart shown in FIG. 3. FIG. 5 is a schematic diagram for explaining steps ST2 to ST4 of the flowchart shown in FIG. 3. 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 pressing force (pressure) applied by the press device, a device for measuring the thickness of the all-solid-state battery stack 10, a device for measuring the distance between current collectors, and a welding device for welding the current collectors and the tab leads. Hereinafter, these devices will be collectively referred to as manufacturing devices.

[0016] In step ST1 of FIG. 3 , 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. 4 , 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 a 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 anode 4 containing Li metal or Li alloy as the anode layer 2, the solid electrolyte layer 8, and the cathode 7 are repeatedly arranged in one direction (stacking 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. 4 , the manufacturing apparatus applies a pressure P to the unbonded laminate 10′ at least in the stacking 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 applies high pressure between the negative electrode layer 2 and the solid electrolyte layer 8, and between the solid electrolyte layer 8 and the positive electrode layer 5, to form 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 ST5 (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. 3 , the manufacturing apparatus performs a first measurement step of measuring first data attributable to the thickness of the battery cells 9. For example, as shown in FIG. 5 , the manufacturing apparatus applies a pressure PBef in the stacking direction of an all-solid-state battery stack 10 including a plurality of battery cells 9 to compress the thickness of each battery cell 9 to a preset (i.e., predetermined) thickness (t-Δt), and measures the applied pressure PBef as first data attributable to the thickness of the battery cell 9. Here, t is the designed thickness of each battery cell 9 before the pressure PBef is applied. Δt is the thickness compressed by the application of the pressure PBef to each battery cell 9 (i.e., the change in thickness due to elastic compression). tLi is the thickness of the Li metal or Li alloy contained as the anode layer 2 in each battery cell 9. The pressure PBef is a pressure lower than the yield stress of the Li metal or Li alloy constituting the anode layer 2. By setting the pressure PBef to a pressure lower than the yield stress, the battery cell 9 can be elastically deformed while suppressing plastic deformation of the negative electrode layer 2 .

[0021] Next, in step ST3 of FIG. 3 , the manufacturing apparatus performs a leaving step in which the all-solid-state battery stack 10 is left for a preset time (i.e., a predetermined time). In the leaving step, pressure is applied to the all-solid-state battery stack 10 including, for example, a plurality of battery cells 9 in the stacking direction to maintain the thickness of the all-solid-state battery stack 10 (i.e., the thickness of each battery cell 9) at the same thickness (t-Δt) as compressed in the first measurement step. Next, in step ST4 of FIG. 3 , the manufacturing apparatus performs a second measurement step in which second data attributable to the thickness of the battery cells 9 is measured. For example, as shown in FIG. 5 , the manufacturing apparatus measures, as second data, the pressure PAft required to maintain the thickness of the all-solid-state battery stack 10 (i.e., the thickness of each battery cell 9) at the same thickness (t-Δt) as compressed in the first measurement step. That is, the pressure PAft required to maintain the constant dimension system from the first measurement step is measured as second data. Note that the pressure PAft is also set to a pressure lower than the yield stress. The pressures applied in the first measurement step, the leaving step, and the second measurement step are each lower than the yield stress of the Li metal or Li alloy, thereby suppressing plastic deformation of the Li metal or Li alloy and suppressing changes in thickness due to plastic deformation.

[0022] From the start of the first measurement step to the end of the second measurement step, the all-solid-state battery stack 10 is preferably placed in an environment at room temperature (e.g., 25°C) or below. This reduces creep deformation and hardens the all-solid-state battery stack 10. A harder battery stack 10 increases the pressure change relative to the amount of displacement, improving the sensitivity of detecting pressure changes. Next, in step ST5 of FIG. 3 , the manufacturing apparatus performs a detection step of detecting the presence or absence of a short circuit in the battery cell 9 based on the first data and the second data. For example, the manufacturing apparatus detects the presence or absence of a short circuit in the battery cell 9 based on the change in pressure calculated from the first data and the second data. If this change exceeds a predetermined threshold, the manufacturing apparatus determines that a short circuit exists (i.e., NG), and if the change is equal to or less than the threshold, the manufacturing apparatus determines that a short circuit does not exist (i.e., OK). 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 stack 10, and the product is treated as a defective product, and the manufacturing process is terminated.

[0023] In step ST5 of FIG. 3 , if the result is NG, the thickness of tLi decreases beyond a predetermined range. This point will be explained with reference to FIG. 6 . FIG. 6 is a schematic diagram showing the mechanism by which the thickness of the battery cell 9 decreases when the anode 4 and cathode 7 are short-circuited. As shown in FIG. 6 , when a short circuit occurs, Li ions are ionized to Li+, and electrons e− are generated. These e− electrons flow from the anode layer 2 to the cathode layer 5 along the short-circuit path. Li ions also move from the anode layer 2 to the cathode layer 5 along the short-circuit path. This causes the anode layer 2 to shrink and its thickness to decrease. The cathode layer 5 increases in thickness by absorbing Li ions, but because the decrease in the anode layer 2 is greater than the increase in the cathode layer 5, the overall thickness of the battery cell 9 decreases. This is the mechanism by which the thickness of the battery cell 9 decreases when a short circuit occurs. By using this mechanism, the presence or absence of a short circuit can be detected simply by the results of the storage step and the data measurements related to the thickness before and after the storage step, without performing any electrochemical operations.

[0024] The threshold value for determining whether or not a short circuit exists can be, for example, the following formula (1): When formula (1) is satisfied, it is determined that a short circuit exists. Ecell in formula (1) and in FIG. 5 indicates the Young's modulus of the battery cell 9. Furthermore, formula (1) is calculated from the following formulas (2) to (4). When the left term PAft of equation (5) (that is, the pressure PAft shown in FIG. 5) is smaller than the right term of equation (5), it is determined that a short circuit exists.

[0025] Through the above steps, the all-solid-state battery 1 shown in FIG. 1 is completed. In the manufacturing method according to the first embodiment, a tab joining step, a sealing step, a discharging step, and a charging step may be performed following step ST5 of the flowchart shown in FIG. 5 . In the tab joining step, 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 or laser welding that utilizes heat generated by friction between metals. In the sealing step, 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.

[0026] Effect 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 Li metal or a Li 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 first measurement step of measuring first data attributable to the thickness of the battery cells 9 after the pressing step; a leaving step of leaving the all-solid-state battery laminate 10 for a predetermined period of time after the first measurement step; a second measurement step of measuring second data attributable to the thickness of the battery cells 9 after the leaving step; and a detection step of detecting the presence or absence of a short circuit in the battery cells 9 based on the first data and the second data. From the start of the pressing step to the end of the detection step, the current collectors of the same electrode are maintained not to be electrically connected to each other for at least one of the negative electrode 4 and the positive electrode 7. This allows the presence or absence of a short circuit to be detected without performing an electrochemical operation. In an all-solid-state battery 1 that contains Li metal or a Li alloy in the negative electrode 4 during manufacture, it is possible to easily detect the presence or absence of a short-circuited cell before connecting a plurality of battery cells 9 in parallel (for example, before tab bonding). Note that this detection of the presence or absence of a short circuit can only be performed 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 at the time of a short circuit, and therefore the above method cannot be used to detect the presence or absence of a short circuit.

[0027] (Variation of First Embodiment) When the first data (e.g., pressure PBef) measured in the first measurement step is a design value or is a known value without variation between lots, the first data may be set as a constant, and the first data measurement step may be omitted. In the detection step, the presence or absence of a short circuit in the battery cell 9 may be detected based on the first data, which is a constant, and second data (an example of "data" in the present invention) measured in the second measurement step, or the presence or absence of a short circuit in the battery cell 9 may be detected based only on the second data.

[0028] <Embodiment 2> In the above-described embodiment 1, the pressures PBef and PAft due to the thickness of the battery cell 9 are measured as the first data and the second data, respectively. However, the measurements of the first data and the second data may be measurements of the thickness itself, rather than the pressure due to the thickness. FIG. 7 is a schematic diagram illustrating steps ST2 to ST4 according to embodiment 2 of the present invention. In this manufacturing method example 1, the pressing process of step ST1 shown in FIG. 3 is the same as in embodiment 1. As shown in FIG. 7, in step ST2, the manufacturing apparatus applies a pressure PBef to the all-solid-state battery stack 10 in the stacking direction and measures the distances d1Bef and d2Bef between adjacent negative electrode current collectors 3 in the stacking direction as the first data. Next, in step ST3, the manufacturing apparatus leaves the all-solid-state battery stack 10 for a predetermined time. This leaving process is the same as in embodiment 1. Next, in step ST4, the manufacturing equipment applies a pressure PAft to the all-solid-state battery stack 10 in the stacking direction, and measures the distances d1Aft and d2Aft between adjacent negative electrode current collectors 3 in the stacking direction as second data.

[0029] FIG. 8 is a graph schematically illustrating the difference in distance (thickness) change depending on whether or not a short circuit occurs in the manufacturing method according to the second embodiment of the present invention. As shown in FIG. 8 , when there is no short circuit, the thickness of the Li metal or Li alloy constituting the negative electrode layer 2 does not decrease significantly over time, resulting in a small change in the distance between the current collectors. In contrast, when there is a short circuit, the thickness of the Li metal or Li alloy constituting the negative electrode layer 2 decreases over time, resulting in a large change in the distance between the current collectors. In the manufacturing method according to the second embodiment, it is preferable to obtain data regarding the change in distance (thickness) as shown in FIG. 8 in advance and set a threshold value based on this data. Note that when the negative electrode 4 includes an intermediate layer that absorbs Li, the rate of decrease of the Li metal or Li alloy tends to be high even when there is no short circuit. For this reason, it is preferable that the negative electrode 4 does not include an intermediate layer that absorbs Li.

[0030] In the detection process of step ST5 shown in FIG. 3 , the manufacturing apparatus detects whether or not a short circuit has occurred in the battery cell 9 based on a change in distance calculated from the first data and the second data. For example, with respect to the distance between adjacent first negative electrode current collectors 3 in the stacking direction, if the change in distance d1Bef-d1Aft before and after the leaving process is equal to or greater than a predetermined value (threshold), it is determined that a short circuit has occurred in the battery cell 9 located between the first negative electrode current collectors 3. If the change in distance d1Bef-d1Aft is less than the threshold, it is determined that a short circuit has occurred in the battery cell 9 located between the first negative electrode current collectors 3. Similarly, with respect to the distance between adjacent second negative electrode current collectors 3 in the stacking direction, if the change in distance d2Bef-d2Aft is equal to or greater than a threshold, it is determined that a short circuit has occurred in the battery cell 9 located between the second negative electrode current collectors 3. If the change in distance d2Bef-d2Aft is less than the threshold, it is determined that a short circuit has not occurred in the battery cell 9 located between the second negative electrode current collectors 3. Note that FIG. 7 illustrates a case where a short circuit occurs between the first negative electrode current collectors 3 and the change in distance d1Bef-d1Aft is equal to or greater than the threshold value.

[0031] Effect of Embodiment 2 According to the manufacturing method of Embodiment 2, it is possible to easily detect the presence or absence of a short circuit in the battery cell 9 without performing an electrochemical operation, similar to the manufacturing method of Embodiment 1. In an all-solid-state battery 1 that contains Li metal or Li alloy in the negative electrode 4 during manufacturing, it is possible to easily detect the presence or absence of a short-circuited cell before connecting multiple battery cells 9 in parallel (for example, before tab joining).

[0032] (Modifications of Embodiment 2) (1) Modification 1 In the above-described Embodiment 2, it has been described that the presence or absence of a short circuit is detected based on a change in the distance between adjacent negative electrode current collectors 3 in the stacking direction of the all-solid-state battery stack 10. However, in Embodiment 2, the presence or absence of a short circuit may be detected based on a change in the distance between adjacent positive electrode current collectors 6 in the stacking direction of the all-solid-state battery stack 10, rather than between the negative electrode current collectors 3, or the presence or absence of a short circuit may be detected based on a change in the distance between the negative electrode current collector 3 and the positive electrode current collector 6 adjacent in the stacking direction.

[0033] (2) Modification 2 The threshold value of the detection step may be defined in relation to the capacity of the positive electrode and the negative electrode. For example, for a layer located between the current collectors of at least one of the negative electrode 4 and the positive electrode 7 (for example, a layer located between the distances d1Bef and d1Aft in FIG. 7 or a layer located between the distances d2Bef and d2Aft in FIG. 7 ), the capacity per unit area and unit thickness of the negative electrode 4 may be defined as qck [mAh / (cm ２ ·μm)], and the capacity per unit area of ​​the positive electrode 7 is Qca [mAh / cm ２ ]. The change in thickness calculated from the first data and the second data is defined as Δt. Alternatively, in the second measurement process of step ST4 in FIG. 7, the difference in distance between the current collectors (for example, between distances d1Aft and d2Aft) is defined as Δt. In the detection process, it may be determined that a short circuit has occurred in the battery cell 9 when formula (6) is satisfied. This allows the determination criterion (threshold value) for determining whether or not a short circuit has occurred to be set based on the specifications of the battery cell 9, which can contribute to improving the determination accuracy.

[0034] (3) Modification 3 In the second embodiment, the presence or absence of a short circuit may be detected based on the difference in the distance between the current collectors 3 after the leaving step, rather than the change in the distance between the current collectors 3 before and after the leaving step. For example, with respect to d1Aft and d2Aft, which are the second data, if the absolute value of the difference between them (d1Aft - d2Aft) is equal to or greater than a predetermined value (threshold value), it may be determined that a short circuit has occurred in the battery cell 9, and if the absolute value is less than the threshold value, it may be determined that a short circuit has not occurred in the battery cell 9.

[0035] (4) Modification 4 The presence or absence of a short circuit may be detected based on the change in thickness (DBef-DAft) of the all-solid-state battery stack 10, instead of the distance between the current collectors, as shown in Fig. 7. Even with this method, the same effects as those of the second embodiment can be achieved.

[0036] (5) Modification 5 FIG. 9 is a schematic diagram illustrating steps ST2 to ST4 according to a modification of Embodiment 2 of the present invention. As shown in FIG. 9 , a pair of pressure-applying plates 20 may be disposed on both sides (top and bottom sides in FIG. 9 ) of the all-solid-state battery stack 10 in the stacking direction. For example, in the first measurement step of step ST2, the all-solid-state battery stack 10 including the battery cell 9 is sandwiched between the pair of stress-applying plates 20, a predetermined stress is applied between the pair of stress-applying plates 20 to compress the thickness of the all-solid-state battery stack 10, and the distance DBef between the pair of stress-applying plates 20 is measured as first data. In the leaving step of step ST3, the same magnitude of pressure as in the first measurement step is continuously applied between the pair of stress-applying plates 20. In the second measurement step of step ST4, the distance between the pair of stress-applying plates 20 is measured as second data DAft while the same magnitude of pressure is applied between the pair of stress-applying plates 20. In the detection step, the presence or absence of a short circuit in the battery cell 20 is detected based on a change in the distance calculated from the first data and the second data. From the start of step ST2 to the end of step ST4, the pressure P applied to the all-solid-state battery stack 10 may be constant (P const). Even with this method, the same effects as those of the second embodiment can be achieved.

[0037] (6) Modification 6 In the detection step, the change in distance (thickness) in a normal cell without a short circuit may be used as reference data, and the presence or absence of a short circuit may be detected based on a change in the data relative to the reference data. For example, for a change in distance (thickness) calculated from the first data measured in the first measurement step and the second data measured in the second measurement step, the change in distance (thickness) in a normal battery cell without a short circuit or a normal all-solid-state battery laminate without a short circuit may be used as the reference data. As an example, the "no short circuit" data in FIG. 8 may be used as the reference data. In the detection step, the change in distance (thickness) calculated from the first data and the second data is compared with the reference data to detect the presence or absence of a short circuit in the battery cell 9. This method also achieves the same effects as those in the second embodiment. This modification can also be applied to the first embodiment. For example, the change in distance (thickness) in the second embodiment may be a change in pressure in the first embodiment.

[0038] (7) Modification 7 The above-described modification of Embodiment 1 may also be applied to Embodiment 2. In Embodiment 2 as well, when the first data (for example, the distances dbef1 and dbef2 between the current collectors, and the thickness DBef of the all-solid-state battery laminate 10) are design values ​​or when there is no variation between lots, the first data may be set as a constant and measurement thereof may be omitted. In the detection step, the presence or absence of a short circuit in the battery cell 9 may be detected based on at least the second data.

[0039] <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 an embodiment of the present invention, from the start of the pressing process in step ST1 to the end of the detection process in step ST5, some, but not all, of the negative electrode current collectors 3 constituting the 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. 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. Various omissions, substitutions, and / or 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.

[0040] DESCRIPTION OF SYMBOLS 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, 11... negative electrode tab lead, 12... positive electrode tab lead, 14, 15... welded portion, 20... stress-applying plate

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 leaving step of leaving the all-solid-state battery laminate for a predetermined time after the pressing step; a measuring step of measuring data attributable to the thickness of the battery cells after the leaving step; and a detection step of detecting whether or not the battery cells are short-circuited based on the data, wherein a state in which current collectors of the same electrode are not electrically connected to each other for at least one of the negative electrode and the positive electrode 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 claim 1, further comprising a first measurement step between the pressing step and the leaving step, of measuring first data resulting from the thickness of the battery cell, where the measurement step is a second measurement step and the data measured in the second measurement step is second data, and in the detection step, detecting whether or not the battery cell is short-circuited based on the first data and the second data.

3. The method for manufacturing an all-solid-state battery according to claim 2, wherein in the first measuring step, pressure is applied to the battery cell to compress the thickness of the battery cell and the applied pressure is measured as the first data; in the leaving step, pressure is applied to the battery cell to maintain the thickness of the battery cell at the same thickness as the thickness compressed in the first measuring step; in the second measuring step, a pressure required to maintain the same thickness is measured as the second data; and in the detecting step, presence or absence of a short circuit in the battery cell is detected based on a change in pressure calculated from the first data and the second data.

4. The method for manufacturing an all-solid-state battery according to claim 3, wherein in the first measurement step, pressure is applied to the battery cell to compress the thickness of the battery cell to a preset thickness, and in the detection step, if a change in the pressure applied to the battery cell exceeds a preset threshold, it is determined that a short circuit has occurred, and if the change in the pressure is equal to or less than the threshold, it is determined that no short circuit has occurred.

5. The method for manufacturing an all-solid-state battery according to claim 3, wherein a designed thickness of the battery cell before pressure is applied is t, the pressure measured as the first data is PBef, the thickness of the lithium metal or the lithium alloy included in the battery cell is tLi, the Young's modulus of the battery cell is Ecell, and the pressure measured as the second data is PAft, and in the detection step, it is determined that a short circuit has occurred in the battery cell when the following formula (1) is satisfied:

6. The method for manufacturing an all-solid-state battery according to claim 2 or 3, wherein in the first measurement step, a thickness of the all-solid-state battery laminate including the battery cell is measured as the first data; in the second measurement step, a thickness of the all-solid-state battery laminate including the battery cell is measured as the second data; and in the detection step, presence or absence of a short circuit in the battery cell is detected based on a change in thickness calculated from the first data and the second data.

7. The method for manufacturing an all-solid-state battery according to claim 2 or 3, wherein at least in the second measuring step, the distance between at least one current collector of the negative electrode and the positive electrode is measured as the second data, and in the detecting step, the presence or absence of a short circuit in the battery cell is detected based on the difference in the distance between the current collectors after the leaving step.

8. The method for manufacturing an all-solid-state battery according to claim 2 or 3, wherein in the first measurement step, the distance between at least one current collector of the negative electrode and the positive electrode is measured as the first data, and in the detection step, the presence or absence of a short circuit in the battery cell is detected based on a change in the distance between the current collectors calculated from the first data and the second data.

9. The method for producing an all-solid-state battery according to claim 8, wherein, for a layer located between at least one current collector of the negative electrode and the positive electrode, the capacity per unit area / unit thickness of the negative electrode is qck, the capacity per unit area of ​​the positive electrode is Qca, and the change in distance calculated from the first data and the second data or the difference in distance between current collectors in the second measurement step is Δt, in the detection step, it is determined that a short circuit has occurred in the battery cell when the following formula (2) is established:

10. The method for manufacturing an all-solid-state battery according to claim 2, wherein in the first measuring step, the all-solid-state battery laminate including the battery cell is sandwiched between a pair of stress-applying plates, a preset stress is applied between the pair of stress-applying plates to compress the thickness of the all-solid-state battery laminate, and the distance between the pair of stress-applying plates is measured as the first data; in the leaving step, a pressure of the same magnitude as in the first measuring step is continuously applied between the pair of stress-applying plates; in the second measuring step, the distance between the pair of stress-applying plates is measured as the second data while the same magnitude of pressure is being applied between the pair of stress-applying plates; and in the detecting step, the presence or absence of a short circuit in the battery cell is detected based on a change in distance calculated from the first data and the second data.

11. The method for manufacturing an all-solid-state battery according to claim 2 or 3, wherein, for the change calculated from the first data and the second data, the change in a normal battery cell without a short circuit or a normal all-solid-state battery laminate without a short circuit is used as reference data, and in the detection step, the presence or absence of a short circuit in the battery cell is detected based on the change and the reference data.

12. The method for manufacturing an all-solid-state battery according to claim 2 or 3, wherein the pressures applied in the first measurement step, the leaving step, and the second measurement step are lower than the yield stress of the lithium metal or the lithium alloy contained in the negative electrode.

13. The method for manufacturing an all-solid-state battery according to claim 2 or 3, wherein the all-solid-state battery stack is placed in an environment of 25°C or less from the start of the first measurement step to the end of the second measurement step.

14. The method for producing an all-solid-state battery according to claim 1 or 2, wherein the negative electrode does not include an intermediate layer that absorbs lithium.

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