Method for manufacturing all-solid battery, and all-solid battery

Abstract

Provided is a method for manufacturing an all-solid battery with which, during manufacturing, even when a short circuit has occurred in a battery cell including a Li metal or a Li alloy in a negative electrode, it is possible to prevent a large current from flowing to a short-circuited cell. Also provided is an all-solid battery. The present invention comprises: a step for pressing a layered body, in which a negative electrode containing a lithium metal or a lithium alloy, a solid electrolyte layer, and a positive electrode are repetitively arranged in one direction, to form an all-solid battery layered body in which a plurality of battery cells are layered; and a step for welding a tab lead to a protruding portion, which is a part of a current collector of at least one of the negative electrode and the positive electrode and which protrudes from the all-solid battery layered body. The protruding portion is provided with an insulating material before pressing. The insulating material is an insulating film or an insulating sheet composed of a low-melting-point insulating material. A welded portion where the protruding portion and the tab lead are welded forms a non-insulating portion.

Description

All-solid-state battery manufacturing method, all-solid-state battery

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

[0002] Patent Document 1 discloses an all-solid-state battery including a positive electrode formed by laminating a first current collector layer and a first active material layer, a negative electrode formed by laminating a second current collector layer containing at least copper and a second active material layer, and a solid electrolyte layer disposed between the first active material layer and the second active material layer. In this all-solid-state battery, a second tab lead is joined to an end of the second current collector layer after lamination by a fastening means, and a removable insulating cover is provided on the second tab lead joined by the fastening means.

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

[0004] In an all-solid-state battery that contains lithium (Li) metal or a Li alloy in the negative electrode during manufacturing, there is a need for a technology that prevents a large current from flowing through a short-circuited battery cell (hereinafter also referred to as a short-circuited cell) even if a short circuit occurs in the battery cell during manufacturing.

[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 prevent a large current from flowing through a short-circuited cell even if a short circuit occurs in a battery cell containing Li metal or a Li alloy in the negative electrode during manufacturing, and an all-solid-state battery.

[0006] A method for manufacturing an all-solid-state battery according to one aspect of the present invention includes the steps 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 in one direction to form an all-solid-state battery laminate in which a plurality of battery cells are stacked; and welding a tab lead to a protruding portion that is a part of a current collector of at least one of the negative electrode and the positive electrode and protrudes from the all-solid-state battery laminate. An insulating material is provided on the protruding portion before pressing. The insulating material is an insulating film or insulating sheet made of a low-melting-point insulating material. The welded portion where the protruding portion and the tab lead are welded becomes a non-insulated portion.

[0007] According to one aspect of the present invention, even if a short circuit occurs in a battery cell containing Li metal or a Li alloy in the negative electrode during manufacturing, it is possible to prevent a large current from flowing through the short-circuited cell.

[0008] FIG. 1 is a cross-sectional view showing a configuration example of the first embodiment. FIG. 2 is a flowchart showing a manufacturing method of the first embodiment. FIG. 3A is a view showing a configuration example of a negative electrode in a lamination and pressure bonding process. FIG. 3B is a view showing a configuration example of a negative electrode in a lamination and pressure bonding process. FIG. 4A is a view showing a configuration example of a positive electrode in a lamination and pressure bonding process. FIG. 4B is a view showing a configuration example of a positive electrode in a lamination and pressure bonding process. FIG. 5 is a view explaining steps ST1 to ST4 of FIG. 2. FIG. 6 is a view explaining the welding process of FIG. 2. FIG. 7 is a graph illustrating changes in clamp temperature. FIG. 8 is a view showing a comparative example of the present invention. FIG. 9 is a view showing a configuration example of an insulating material according to the second embodiment. FIG. 10 is a cross-sectional view showing an insulating material according to the third embodiment. FIG. 11A is a view explaining the fourth embodiment. FIG. 11B is a view explaining the fourth embodiment. FIG. 12 is a schematic view illustrating the welding process of the fourth embodiment. FIG. 13 is a schematic view showing a modified example of the fourth embodiment. FIG. 14 is a view explaining the fifth embodiment. FIG. 15 is a view explaining the sixth embodiment. FIG. 16 is a view explaining the seventh embodiment. Fig. 17 is a diagram for explaining the seventh embodiment. Fig. 18 is a diagram for explaining the eighth 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. 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 13.

[0011] 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. 1 ). 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] 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. 1 ). 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 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.

[0014] The negative electrodes 4 and positive electrodes 7 are alternately stacked with solid electrolyte layers 8 interposed therebetween to form an all-solid-state battery stack 10. The solid electrolyte layer 8 is interposed between the negative electrode 4 and the positive electrode 7 to form one battery cell 9. The all-solid-state battery stack 10 includes a plurality of battery cells 9. In each battery cell 9, charging and discharging are performed by exchange of alkali metal ions (e.g., Li ions) between the negative electrode 4 and the positive electrode 7 via the solid electrolyte layer 8.

[0015] The all-solid-state battery laminate 10, a welded portion 14 between the negative electrode tab lead 11 and the negative electrode current collector 3, and a 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 13. The negative electrode tab lead 11 and the positive electrode tab lead 12 extend from the inside to the outside of the exterior body 13.

[0016] The negative electrode current collector 3 has a protruding portion 32 protruding from the all-solid-state battery laminate 10. The protruding direction of the protruding portion 32 is a direction intersecting the stacking direction of the all-solid-state battery laminate 10 (the up-down direction in FIG. 1 ; an example of "one direction" in the present invention), and is the left-right direction in FIG. 1 . The protruding portion 32 is at least a part of an uncoated portion of the negative electrode current collector 3 that is not coated with the negative electrode layer 2. An insulating material 36 is provided on at least one surface (e.g., upper surface 32 a) of the protruding portion 32 in the thickness direction. The insulating material 36 will be described later with reference to FIGS. 3A and 3B .

[0017] The positive electrode current collector 6 has a protruding portion 62 that protrudes from the all-solid-state battery stack 10. The protruding direction of the protruding portion 62 is a direction that intersects with the stacking direction of the all-solid-state battery stack 10, which is the left-right direction in FIG. 1 . The protruding portion 62 is at least a part of an uncoated portion of the positive electrode current collector 6 that is not coated with the positive electrode layer 5. An insulating material 37 is provided on an upper surface 62a of the protruding portion 62. The insulating material 37 will be described later with reference to FIGS. 4A and 4B .

[0018] (Manufacturing Method) Next, a manufacturing method of the all-solid-state battery 1 according to the first embodiment will be described. FIG. 2 is a flowchart showing a manufacturing method of the all-solid-state battery 1 according to the first embodiment. Note that other processes may be included between the flowchart of FIG. 2. FIGS. 3A and 3B are a plan view and a cross-sectional view showing an example of the configuration of the negative electrode 4 used in the lamination and pressure bonding process. The cross-section of the plan view shown in FIG. 3A taken along line X1-X1′ corresponds to the cross-section of FIG. 3B. FIGS. 4A and 4B are a plan view and a cross-sectional view showing an example of the configuration of the positive electrode 7 used in the lamination and pressure bonding process. The cross-section of the plan view shown in FIG. 4A taken along line X2-X2′ corresponds to the cross-sectional view of FIG. 4B. FIG. 5 is a schematic diagram for explaining steps ST1 to ST4 of the flowchart shown in FIG. 2. FIG. 6 is a schematic diagram for explaining steps ST5 to ST7 (welding process) of the flowchart shown in FIG. 2. The all-solid-state battery 1 is manufactured using various types of equipment, such as an equipment for stacking the negative electrode 4, the positive electrode 7, and the solid electrolyte layer 8, a press equipment for pressing the all-solid-state battery stack 10, an equipment for performing a discharge process on the all-solid-state battery stack 10, and a welding equipment for welding the current collector and the tab lead, etc. Hereinafter, these equipment will be collectively referred to as manufacturing equipment.

[0019] In step ST1 of FIG. 2 , the manufacturing apparatus places a cathode 7 with a solid electrolyte layer 8. For example, the cathode 7 with a solid electrolyte layer 8 is placed, in which the solid electrolyte layer 8 is pre-laminated on the cathode layer 5. This manufacturing method involves stacking the cathode 7 and the solid electrolyte layer 8 so that the cathode layer 5 and the solid electrolyte layer 8 are in contact with each other and applying pressure. After pressing, the substrate of the solid electrolyte layer 8 is removed, thereby transferring the solid electrolyte layer 8 to the cathode 7. This manufacturing method can obtain a cathode 7 with a solid electrolyte layer 8. Note that the manufacturing method according to the first embodiment is not limited to this. For example, the solid electrolyte layer 8 may be provided on the anode 4 instead of the cathode 7. In this case, step ST1 simply becomes a step of placing the cathode 7, and step ST2, described later, becomes a step of placing the anode 4 with the solid electrolyte layer 8. Alternatively, the solid electrolyte layer 8 may be prepared separately from the cathode 7 and the anode 4. In this case, for example, a step of disposing the solid electrolyte layer 8 may be provided between the step of disposing the positive electrode 7 (step ST1) and the step of disposing the negative electrode 4 (step ST2).

[0020] Next, in step ST2 of FIG. 2, the manufacturing equipment places the negative electrode 4 at a position facing the positive electrode 7 in the stacking direction with the solid electrolyte layer 8 interposed therebetween.

[0021] Steps ST1 and ST2 in Fig. 2 are the process of stacking one battery cell. Steps ST1 and ST2 are repeated a preset number of times (i.e., a predetermined number of times). The predetermined number of times is the number of stacked battery cells 9 (see Fig. 1). As a result, as shown in Fig. 5, an unpressed laminate 10' is formed in which an anode 4 containing Li metal or Li alloy as the anode layer 2, a solid electrolyte layer 8, and a cathode 7 are repeatedly arranged in the stacking direction.

[0022] 3A and 3B , the negative electrode current collector 3 has a coated portion 31 coated with the negative electrode layer 2 and an uncoated portion not coated with the negative electrode layer 2. At least a part of this uncoated portion protruding from the laminate 10′ (or the all-solid-state battery laminate 10 formed in the lamination and pressure bonding process) in a direction intersecting the lamination direction is the protruding portion 32. An insulating material 36 is provided on an upper surface 32a of the protruding portion 32. The thickness of the insulating material 36 is uniform until immediately before the welding process is performed. In this example, a lower surface 32b of the protruding portion 32, an end face 32c located at the tip in the protruding direction from the laminate 10′, and a side surface 32d are exposed from the insulating material 36.

[0023] The insulating material 36 is an insulating film or insulating sheet made of a low-melting-point insulating material whose melting temperature is lower than the welding temperature Temp-n at which the protrusion 32 and the negative electrode tab lead 11 (see FIG. 1) are welded in the welding process described below (for example, steps ST7 to ST9 in FIG. 2). When the insulating material 36 is an insulating film, it may be formed by applying a liquid insulating material to the surface of the protrusion 32 and drying it. When the insulating material 36 is an insulating sheet, an adhesive layer may be provided on one surface of the insulating sheet. Like the insulating sheet, the adhesive layer is also made of a low-melting-point insulating material whose melting temperature is lower than the welding temperature Temp-n. The insulating sheet may be attached to the surface of the protrusion 32 via this adhesive layer.

[0024] 4A and 4B , the positive electrode current collector 6 has a coated portion 61 coated with the positive electrode layer 5 and an uncoated portion not coated with the positive electrode layer 5. At least a portion of this uncoated portion protrudes from the laminate 10′ (or the all-solid-state battery laminate 10 formed in the lamination and pressure bonding process) in a direction intersecting the lamination direction to form a protruding portion 62. An insulating material 37 is provided on an upper surface 62a of the protruding portion 62. The thickness of the insulating material 37 is uniform until immediately before the welding process. In this example, a lower surface 62b of the protruding portion 62, an end face 62c located at the tip in the protruding direction from the laminate 10′, and a side surface 62d are exposed from the insulating material 37.

[0025] The insulating material 37 is an insulating film or insulating sheet made of a low-melting-point insulating material whose melting temperature is lower than the welding temperature Temp-p at which the protrusion 62 and the positive electrode tab lead 12 are welded in the welding process described below. When the insulating material 37 is an insulating film, it may be formed by applying a liquid insulating material to the surface of the protrusion 62 and drying it. When the insulating material 37 is an insulating sheet, an adhesive layer may be provided on one surface of the insulating sheet. Like the insulating sheet, the adhesive layer is also made of a low-melting-point insulating material whose melting temperature is lower than the welding temperature Temp-p. The insulating sheet may be attached to the surface of the protrusion 62 via this adhesive layer.

[0026] The insulating materials 36, 37 are preferably made of thermoplastic insulating materials such as polyethylene (melting temperature: 110°C to 130°C), polypropylene (melting temperature: 130°C to 170°C), polyvinyl chloride (melting temperature: 75°C to 85°C), polystyrene (melting temperature: 90°C to 105°C), and polycarbonate (melting temperature: 150°C to 155°C). The materials making up the insulating materials 36, 37 may be the same or different. For example, if the welding temperature Temp-n on the negative electrode side and the welding temperature Temp-p on the positive electrode side are different from each other, the materials for the insulating materials 36, 37 may be selected taking into account the respective welding temperatures.

[0027] Next, in step ST3 of Fig. 2, the manufacturing equipment performs a pressurizing process on the unbonded laminate 10'. For example, as shown in Fig. 5, the manufacturing equipment presses the laminate 10' at least in the stacking direction with a press pressure (i.e., a first surface pressure) P1. The press pressure P1 shown in Fig. 5 is equal to or greater than the yield stress of Li metal, for example, 5 MPa or greater. The yield stress of Li metal is the stress at which Li metal begins to become plastic. This pressing causes the anode layer 2 and the solid electrolyte layer 8, and the solid electrolyte layer 8 and the cathode layer 5, to be bonded together with high pressure, thereby forming the all-solid-state battery laminate 10.

[0028] By this molding, the anode layer 2 composed 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 100% SOC (State of Charge) or a high SOC (e.g., 95%, 90%, or 85%). Next, in step ST4 of FIG. 2 , the manufacturing apparatus performs an internal short-circuit test on the all-solid-state battery stack 10. For example, as shown in FIG. 5 , the manufacturing apparatus tests each of the multiple battery cells 9 included in the all-solid-state battery stack 10 to determine whether or not a short circuit has occurred between the anode 4 and the cathode 7. For example, as shown in FIG. 5 , a resistance measuring device 23 is connected to the anode current collector 3 and the cathode current collector 6 of the battery cell 9 to be tested. Terminals of the resistance measuring device 23 are connected to the protruding portion 32 of the negative electrode current collector 3 that is exposed from the insulating material 36 and to the protruding portion 62 of the positive electrode current collector 6 that is exposed from the insulating material 37. A DC voltage is then applied between the negative electrode current collector 3 and the positive electrode current collector 6 to measure the value of the current flowing through the battery cell 9. The internal resistance of the battery cell 9 is detected from this measurement value.

[0029] For example, if the detected internal resistance is equal to or greater than a preset value, the negative electrode current collector 3 and the positive electrode current collector 6 are insulated from each other, and the manufacturing device (inspection device) determines that there is no abnormality (i.e., OK). On the other hand, if the detected internal resistance is lower than a preset value (i.e., NG), there is a possibility that a short circuit has occurred between the negative electrode current collector 3 and the positive electrode current collector 6, and the manufacturing device determines that there is an abnormality (i.e., NG). An all-solid-state battery stack 10 including a battery cell 9 determined to have an abnormality is treated as a defective product, and the manufacturing process is terminated.

[0030] Next, in step ST5 of FIG. 2 , the manufacturing equipment clamps the protruding portion 32 of the negative electrode current collector 3 together with the negative electrode tab lead 11. The manufacturing equipment also clamps the protruding portion 62 of the positive electrode current collector 6 together with the positive electrode tab lead 12. For example, as shown in FIG. 6 , the protruding portion 32 of the negative electrode current collector 3 and the negative electrode tab lead 11 are arranged to overlap, and clamps 38 of a welding machine are placed above and below them. The welding machine is, for example, an ultrasonic welding machine that performs welding by utilizing heat generated by friction between metals. Then, the clamps 38 clamp the area that will become the weld 14 between the protruding portion 32 and the negative electrode tab lead 11 from above and below, bringing them into contact and applying stress. The magnitude of this stress (load) applied to the negative electrode side is kept below the yield stress of the negative electrode current collector 3. Although not shown, the positive electrode side is also similarly configured, with the clamps 38 clamping the area that will become the weld 15 between the protruding portion 62 and the positive electrode tab lead 12 from above and below, bringing them into contact and applying stress. The magnitude of the stress (load) applied to the positive electrode side is set to be equal to or less than the yield stress of the positive electrode current collector 6 .

[0031] Next, in step ST6 of FIG. 2 , the manufacturing equipment applies stress to the portion of the negative electrode side that will become the weld 14 via the clamp 38, and heats this portion to a preset (i.e., predetermined) temperature via the clamp 38 and holds it at the predetermined temperature for a certain period of time. The positive electrode side is similarly heated to a predetermined temperature and held at that temperature for a certain period of time. FIG. 7 is a graph illustrating the temperature change of the clamp 38 in steps ST6 and ST7 of FIG. 2 . The horizontal axis of FIG. 7 represents time, and the vertical axis represents the temperature of the clamp 38. Because the clamp 38 is the heat source, the portion of the negative electrode side that will become the weld 14 and the portion of the positive electrode side that will become the weld 15 are heated to the same or nearly the same temperature as the clamp 38 shown in FIG. 7 while under load. As a result, the insulating materials 36 and 37 in the portions that will become the welds 14 and 15 melt and are pushed outward from the portions that will become the welds 14 and 15.

[0032] The temperature of the clamp 38 may be measured by contact or non-contact means. An example of a contact temperature measuring means is a thermocouple built into the clamp 38. An example of a non-contact temperature measuring means is an infrared temperature sensor. Furthermore, when a non-contact temperature measuring means is used, the temperature measurement location is not limited to the clamp 38, and may be the welds 14, 15 or each portion that will become the welds 14, 15.

[0033] Next, in step ST7 of FIG. 2 , the manufacturing equipment performs tab joining. Specifically, the manufacturing equipment welds the protruding portions 32 of the negative electrode current collectors 3 adjacent to each other in the stacking direction and welds them to the negative electrode tab lead 11 to form welds 14. Similarly, the manufacturing equipment welds the protruding portions 62 of the positive electrode current collectors 6 adjacent to each other in the stacking direction and welds them to the positive electrode tab lead 12 to form welds 15. As shown in FIGS. 6 and 7 , in step ST7, the portions that will become the welds 14 and 15 are pressed by the clamps 38, respectively, and are further heated by the clamps 38 to welding temperatures Temp-n and Temp-p for welding. The welding temperatures Temp-n and Temp-p are set according to the melting temperature of the metal material that constitutes the current collectors. For example, if the negative electrode current collector 3 and the positive electrode current collector 6 are made of the same type of metal, the welding temperatures Temp-n and Temp-p are set to the same temperature. When the negative electrode current collector 3 and the positive electrode current collector 6 are made of different metals, the welding temperatures Temp-n and Temp-p may be set to the same temperature or different temperatures, for example, 300°C or higher and 500°C or lower.

[0034] After welding, as shown in FIG. 7 , the welded portions 14 and 15 are cooled to a temperature lower than the melting temperatures of the insulating materials 36 and 37. Even during this cooling, the clamps 38 are in direct or indirect contact with the welded portions 14 and 15. The welding machine continues to apply pressure from the clamps 38 to the welded portions 14 and 15 until cooling is complete. Through the above processes, the all-solid-state battery 1 shown in FIG. 1 is completed. Note that in the manufacturing method according to the first embodiment, a sealing process, a discharging process, and a charging process may be performed following step ST7 of the flowchart shown in FIG. 2 . In the sealing process, the manufacturing equipment seals the all-solid-state battery stack 10 with the exterior body 13, excluding the negative electrode tab lead 11 and the positive electrode tab lead 12. In the discharging process, the manufacturing equipment performs a discharging operation on the all-solid-state battery stack 10 formed in a charged state. For example, a 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 the positive electrode tab lead 12 shown in FIG. 1 . During this discharging operation, in each battery cell 9, Li ions move from the anode 4 through the solid electrolyte layer 8 to the cathode 7 and are absorbed in the positive electrode layer 5. When the discharging operation is performed, the Li metal or Li alloy in the anode layer 2 decreases as the discharge progresses. When the discharge progresses to an SOC of 0%, the Li metal or Li alloy in the anode layer 2 is almost gone. In the charging step, the manufacturing apparatus performs a charging operation on the discharged all-solid-state battery stack 10. This charging operation is performed via the anode tab lead 11 and the positive electrode tab lead 12. During this charging operation, in each battery cell 9, the Li ions absorbed in the positive electrode layer 5 move to the anode current collector 3 through the solid electrolyte layer 8, and Li metal or Li alloy is precipitated as the anode layer 2.

[0035] Effect of First Embodiment As described above, the manufacturing method of the all-solid-state battery 1 according to the first embodiment includes a lamination and pressure bonding 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 in one direction (stacking direction) at least in the stacking direction to form an all-solid-state battery laminate 10 in which a plurality of battery cells 9 are stacked in the stacking direction, and a welding step of welding tab leads (e.g., negative electrode tab lead 11, positive electrode tab lead 12) to protruding portions (e.g., protruding portions 32, 62) that are part of current collectors (e.g., negative electrode current collector 3, positive electrode current collector 6) of at least one of the negative electrode 4 and the positive electrode 7 and protrude in a direction intersecting the stacking direction from the all-solid-state battery laminate 10. Before pressing in the lamination and pressure bonding step, insulating materials (e.g., insulating materials 36, 37) are provided on the protruding portions. The insulating material is an insulating film or insulating sheet made of a low-melting-point insulating material having a melting temperature lower than the welding temperature at which the protrusion and the tab lead are welded in the welding process. In the welding process, the protrusion and the tab lead are welded such that the welded parts (e.g., welded parts 14, 15) at which the protrusion and the tab lead are welded become non-insulated parts.

[0036] This makes it possible to prevent the current collector of one battery cell 9 adjacent to the other battery cell 9 in the stacking direction from coming into contact with the current collector of the other battery cell 9 and becoming electrically conductive when forming the all-solid-state battery stack 10 (for example, in the stacking and pressing process) that includes Li metal or Li alloy in the negative electrode 4. This makes it possible to prevent the formation of an external parallel circuit due to contact between the current collectors. Even if a short circuit occurs in the battery cells 9 during the stacking and pressing process, it is possible to prevent a large current from flowing through the short-circuited battery cell (i.e., the short-circuited cell). This effect will be described in more detail using a comparative example.

[0037] FIG. 8 is a comparative example of the present invention, and is a diagram schematically illustrating the flow of current I when current collectors come into contact with each other when an internal short circuit occurs in a battery cell 109. During the lamination and compression process in which a negative electrode containing Li metal or a Li alloy, a solid electrolyte layer, and a positive electrode are stacked and pressed, an internal short circuit may occur in the battery cell 109. FIG. 8 illustrates a case in which a short circuit occurs 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.

[0038] In contrast, in the manufacturing method according to the first embodiment, insulating materials 36 and 37 are provided on the uncoated portions of the current collectors (for example, the protruding portion 32 of the negative electrode current collector 3 and the protruding portion 62 of the positive electrode current collector 6), respectively, and the protruding portions 32 and 62 are insulated. This makes it possible to prevent the formation of an external parallel circuit due to contact between adjacent current collectors in the stacking direction in the stacking compression process. Even if a short-circuited cell is included in the all-solid-state battery stack 10, the short-circuited cell is insulated from the other battery cells 9 by the insulating materials 36 and 37, so that no current flows into the short-circuited cell from the other battery cells 9. Since no large current flows in the short-circuited cell and only a current equivalent to the charge capacity of the short-circuited cell flows, heat generation in the short-circuited cell can be suppressed.

[0039] Furthermore, in the manufacturing method according to the first embodiment, the insulating material 36 on the negative electrode side is melted by the heat of welding between the protrusion 32 and the negative electrode tab lead 11, and is removed from the portion that will become the welded portion 14. Similarly, the insulating material 37 on the positive electrode side is melted by the heat of welding between the protrusion 62 and the positive electrode tab lead 12, and is removed from the portion that will become the welded portion 15. Since a dedicated process for removing the insulating materials 36 and 37 is not required, this contributes to shortening the manufacturing process and reducing manufacturing costs.

[0040] Furthermore, the manufacturing method according to the first embodiment may further include an inspection step between the lamination and pressure bonding step and the joining step, in which an internal short circuit of the battery cells 9 is inspected. In this way, the inspection step can inspect whether or not a short-circuited cell is included in the all-solid-state battery stack 10, while preventing the formation of an external parallel circuit due to contact between the current collectors.

[0041] The all-solid-state battery 1 according to the first embodiment includes an all-solid-state battery stack 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 in one direction (stacking direction) and a plurality of battery cells 9 are stacked in the stacking direction; tab leads (e.g., a negative electrode tab lead 11, a positive electrode tab lead 12) welded to protrusions (e.g., protrusions 32, 62) that are part of current collectors (e.g., a negative electrode current collector 3, a positive electrode current collector 6) of at least one of the negative electrode 4 and the positive electrode 7 and protrude from the all-solid-state battery stack 10 in a direction intersecting the stacking direction; and insulating materials (e.g., insulating materials 36, 37) provided on the protrusions. The insulating materials are insulating films or insulating sheets made of low-melting-point insulating materials having a melting temperature lower than the welding temperature at which the protrusions and the tab leads are welded. The welded portions between the protrusions and the tab leads include non-insulating portions. According to this, even if a short-circuited cell occurs in the lamination and compression bonding step when manufacturing an all-solid-state battery, it is possible to prevent a large current from flowing through the short-circuited cell.

[0042] (Modification of Embodiment 1) In the above-described Embodiment 1, the negative electrode current collector 3 and the positive electrode current collector 6 are provided with insulating materials 36 and 37, respectively. However, this embodiment is not limited to this. In this embodiment, an insulating material may be provided on one of the negative electrode current collector 3 and the positive electrode current collector 6, and no insulating material may be provided on the other. Even in this embodiment, contact between adjacent current collectors in the stacking direction on the side where the insulating material is present can be prevented, thereby preventing the formation of an external parallel circuit. Even if a short-circuited cell occurs, a large current can be prevented from flowing into the short-circuited cell. Note that when this modification is applied, it is preferable that an insulating material be provided on the negative electrode current collector 3 or the positive electrode current collector 6, whichever has higher thermal conductivity. This facilitates heat transfer from the current collector to the insulating material during the welding process, facilitating melting and removal of the insulating material by the welding heat. This modification may be applied not only to Embodiment 1 but also to each of the embodiments described below.

[0043] <Embodiment 2> In the above-described embodiment 1, the thicknesses of the insulating materials 36 and 37 are uniform until immediately before the welding process. However, this embodiment is not limited to this. FIG. 9 is a cross-sectional view showing an example of the configuration of the insulating material 36 according to embodiment 2. As shown in FIG. 9, the thickness of the insulating material 36 may be non-uniform from the beginning of film formation. For example, the insulating material 36 includes a first insulating material 361 covering a portion of the protruding portion 32 that will become the welded portion 14 and a second insulating material 362 covering a portion of the protruding portion 32 that will not become the welded portion 14 (non-welded portion). The first insulating material 361 and the second insulating material 362 are made of the same material and are continuously formed on the surface of the protruding portion 32. The thickness of the first insulating material 361 is thinner than the thickness of the second insulating material 362. This prevents contact between adjacent negative electrode current collectors 3 in the stacking direction, and facilitates the extrusion of the insulating material 36 from the portion that will become the welded portion 14 during the welding process.

[0044] Although the negative electrode side has been described in Fig. 9 , the same configuration as the negative electrode side shown in Fig. 9 may also be applied to the positive electrode side. That is, on the positive electrode side, the thickness of the insulating material 37 covering the portion that will become the welded portion 15 may be thinner than the thickness of the insulating material 37 covering other portions. This makes it easier to push the insulating material 37 outward from the portion that will become the welded portion 15 during the welding process.

[0045] Third Embodiment FIG. 10 is a cross-sectional view showing an example of the configuration of the insulating material 36 according to the third embodiment. In the third embodiment, a first insulating material 361 covering the portion of the protruding portion 32 that will become the welded portion 14 and a second insulating material 362 covering the non-welded portion of the protruding portion 32 are made of different materials. The melting temperature of the first insulating material 361 is lower than the melting temperature of the second insulating material 362. Because the first insulating material 361 melts more easily than the second insulating material 362, the welding process facilitates the extrusion of the insulating material 36 outward from the portion that will become the welded portion 15. Also, in the third embodiment, as in the second embodiment, the thickness of the first insulating material 361 may be thinner than the thickness of the second insulating material 362. This further facilitates the extrusion of the insulating material 36 outward from the portion that will become the welded portion 15. Note that while the negative electrode side is described in FIG. 10 , a configuration similar to that of the negative electrode side shown in FIG. 10 may also be applied to the positive electrode side.

[0046] 11A and 11B are diagrams illustrating the fourth embodiment, showing a plan view and a cross-sectional view illustrating an example of the configuration of a negative electrode 4 used in the stacking and pressure-bonding step. The cross-section of the plan view shown in FIG. 11A taken along line X3-X3′ corresponds to the cross-sectional view of FIG. 11B. FIG. 12 is a schematic diagram illustrating a welding step of the fourth embodiment. As shown in FIGS. 11A and 11B, in the fourth embodiment, before the welding step, an opening 36H is provided in the insulating material 36, opening above the portion that will become the weld 14. As shown in FIG. 12, in the welding step, the clamp 38 of a welding machine is brought into direct or indirect contact with the portion of the protrusion 32 exposed from the opening 36H of the insulating material 36, and the negative electrode tab lead 11 is welded to the protrusion 32. Even with this method, the negative electrode tab lead 11 can be joined to the protrusion 32 while preventing the formation of an external parallel circuit due to contact between negative electrode current collectors 3 adjacent to each other in the stacking direction. Furthermore, in the welding step, the clamp 38 can be placed in the opening 36H and pressurized and heated. This can prevent the insulating material 36 from adhering to the clamp 38. Furthermore, it is preferable that the diameter 36HR of the opening 36H of the insulating material 36 is larger than the diameter 38R of the contact surface (the lower surface in FIG. 13 ) of the clamp 38 that directly or indirectly contacts the protrusion 32. This can further prevent the insulating material 36 from adhering to the clamp 38.

[0047] FIG. 13 is a schematic diagram illustrating a modification of the fourth embodiment. As shown in FIG. 13 , the side surface 36Hc of the opening 36H of the insulating material 36 may be inclined relative to the bottom surface so that the diameter gradually increases from the bottom surface of the opening 36H (the upper surface of the protrusion 32 in FIG. 13 ) toward the opening end. During the welding process, a load is applied to the stacked protrusions 32. However, the inclination of the portion of the insulating material 36 facing the opening 36H facilitates the adhesion of the protrusions 32 to each other. This contributes to improving the adhesion between the protrusions 32 during the welding process. While the negative electrode side is described in FIGS. 12A , 12B , and 13 , a configuration similar to the negative electrode side shown in FIGS. 12A , 12B , and 13 may also be applied to the positive electrode side.

[0048] Fifth Embodiment In this fifth embodiment, a preferred thickness range of the insulating material 36 will be described. FIG. 14 is a diagram illustrating this fifth embodiment and is a schematic diagram showing the relationship between the distance T1 between current collectors of the same polarity and the thickness T2 of the insulating material 36. As shown in FIG. 14 , the distance T1 between current collectors is the distance between a first negative electrode current collector 3 (an example of the "first electrode" of the present invention) and a second negative electrode current collector 3 (an example of the "second electrode" of the present invention) adjacent to each other in the stacking direction in the all-solid-state battery stack 10 after the stacking and compression bonding process shown in FIG. 2 has been performed. This distance T1 between current collectors is also the total thickness of each layer (negative electrode layer 2, solid electrolyte layer 8, positive electrode 7, solid electrolyte layer 8, and negative electrode layer 2) located between the first negative electrode current collector 3 and the second negative electrode current collector 3. The distance T1 between current collectors and the thickness T2 of the insulating material 36 preferably satisfy the relationship T1≧T2. This prevents the insulating material 36 from interfering with the crimping of the stack 10' in the stacking and compression bonding process shown in Fig. 2. If T1 < T2, the insulating material 36 may push up or down the negative electrode current collector 3 of another battery cell adjacent in the stacking direction, which may increase the difficulty of crimping the stack 10'. Note that while Fig. 14 illustrates the relationship between the negative electrode current collector 3 and the insulating material 36, this relationship may also be applied to the positive electrode current collector 6 and the insulating material 37.

[0049] Sixth Embodiment In this sixth embodiment, a preferred relationship between the inter-collector distance T1 and the distance L between the solid electrolyte layer 8 and the insulating material 36 will be described. FIG. 15 is a cross-sectional view illustrating this sixth embodiment, showing the relationship between the inter-collector distance T1 and the distance L between the solid electrolyte layer 8 and the insulating material 36. As shown in FIG. 15, the inter-collector distance (e.g., the distance between the first negative electrode current collector 3 and the second negative electrode current collector 3) is designated as T1. Also, as shown in FIG. 15, the distance between the solid electrolyte layer 8 and the insulating material 36 is designated as L. The distance L is preferably equal to or less than half the inter-collector distance T1. In other words, it is preferable to satisfy the relationship L≦T×½. This makes it possible to more reliably prevent the negative electrode current collectors 3 from contacting each other and becoming electrically conductive, even when adjacent negative electrode current collectors 3 are closest to each other in the stacking direction. Although FIG. 15 illustrates the relationship between the negative electrode current collector 3 and the insulating material 36, this relationship may also be applied to the positive electrode current collector 6 and the insulating material 37.

[0050] 16 and 17 are diagrams for explaining the seventh embodiment, and are cross-sectional views showing configuration examples 1 and 2 of the all-solid-state battery stack 10 before a welding process. As shown in FIG. 16 , the insulating material 36 may be provided on the lower surface 32 b of the protruding portion 32 of the negative electrode current collector 3. The insulating material 37 may be provided on the lower surface 62 b of the protruding portion 62 of the positive electrode current collector 6. Alternatively, as shown in FIG. 17 , the insulating material 36 may be provided on the upper surface 32 a and the lower surface 32 b of the protruding portion 32 of the negative electrode current collector 3. The insulating material 37 may be provided on the upper surface 62 a and the lower surface 62 b of the protruding portion 62 of the positive electrode current collector 6. Although not shown, the insulating material 36 may be provided on the end surface 32 c or the side surface 32 d of the protruding portion 32 of the negative electrode current collector 3 (see FIGS. 3A and 3B ). An insulating material 37 may be provided on the end face 62 c or the side face 62 d (see FIGS. 4A and 4B ) of the protruding portion 62 of the positive electrode current collector 6. Even in this embodiment, it is possible to prevent the formation of an external parallel circuit due to contact between the current collectors, as in the first embodiment. Even if a short circuit occurs during the stacking and compression bonding process, it is possible to prevent a large current from flowing through the short-circuited cell.

[0051] Eighth Embodiment In the above-described first to seventh embodiments, a metal foil may be interposed between the insulating material 36 and the negative electrode tab lead 11 or between the insulating material 36 and the clamp 38. In the eighth embodiment, a case where a metal foil is interposed will be described. FIG. 18 is a schematic diagram illustrating steps ST5 to ST7 (welding process) according to the eighth embodiment. As shown in FIG. 18 , in the welding process according to the eighth embodiment, the clamp 38 of the welding machine is brought into contact with the portion that will become the weld 14 via the metal foil 39. For example, on the upper surface side of the portion that will become the weld 14, the clamp 38 is brought into contact with the insulating material 36 via the metal foil 39 and the negative electrode tab lead 11. On the lower surface side of the portion that will become the weld 14, the clamp 38 is brought into contact with the insulating material 36 via the metal foil 39. The welding process is then performed in this state. This prevents the insulating material 36 from adhering to the clamp 38. Since it is not necessary to remove the insulating material 36 from the clamp 38, the work required for welding machine maintenance can be reduced. This improves the continuity of workpiece processing and increases the efficiency of the manufacturing process.

[0052] The material of the metal foil 39 may be the same as or different from the current collector. However, using the same material as the current collector can be expected to improve the bonding strength between the current collector and the metal foil 39. While FIG. 18 illustrates the metal foil 39 being disposed on both the upper and lower surfaces of the portion that will become the weld 14, the metal foil 39 may be disposed on only one of these surfaces. When the insulating material 36 is provided on both sides of the protruding portion 32, it is preferable to dispose the metal foil 39 at least on the side where the negative electrode tab lead 11 is not disposed between the clamp 38 and the insulating material 36 (the lower surface side in FIG. 18). This reduces the amount of metal foil 39 used and prevents the insulating material 36 from adhering to the clamp 38. While FIG. 18 illustrates the negative electrode side, a configuration similar to the negative electrode side shown in FIG. 18 may also be applied to the positive electrode side.

[0053] Other Embodiments As described above, the present invention has been described with reference to exemplary 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 the present embodiment, the insulating material 36 may be provided on some, but not all, of the negative electrode current collectors 3 constituting the laminate 10′. For example, the insulating material 36 may be provided on every other negative electrode current collector 3 in the stacking direction. The same applies to the positive electrode current collector 6. Furthermore, welding between the current collector and the tab lead may be performed by laser welding. As such, it goes without saying that the present technology includes various embodiments not described herein. Various omissions, substitutions, and modifications of components may be made without departing from the spirit and scope of the above-described exemplary embodiments. Furthermore, the effects described herein are merely exemplary and are not limiting, and other effects may also be achieved.

[0054] 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, 13... outer casing, 23... resistance measuring device, 31, 61... coated portion, 32, 62... protruding portion (at least a part of uncoated portion), 32a, 62a... upper surface, 32b, 62b... lower surface, 32c, 62c... end surface, 32d, 62d... side surface, 36, 37... insulating material, 36H... opening, 36Hc... side surface, 38... clamp, 109S... short-circuited cell, 361... first insulating material, 362... second insulating material

Claims

1. A method for manufacturing an all-solid-state battery, comprising: a lamination and compression step of pressing a laminate in at least one direction, in which a negative electrode containing lithium metal or a lithium alloy, a solid electrolyte layer, and a positive electrode are repeatedly arranged in the same direction, to form an all-solid-state battery laminate in which a plurality of battery cells are stacked in the same direction; and a welding step of welding a tab lead to a protruding portion that is a part of a current collector of at least one of the negative electrode and the positive electrode and protrudes from the all-solid-state battery laminate in a direction intersecting the one direction, wherein an insulating material is provided on the protruding portion before the pressing in the lamination and compression step, and the insulating material is an insulating film or insulating sheet made of a low-melting point insulating material whose melting temperature is lower than the welding temperature at which the protruding portion and the tab lead are welded in the welding step, and wherein the protruding portion and the tab lead are welded in the welding step so that the welded portion is a non-insulated portion.

2. The method for manufacturing an all-solid-state battery according to claim 1, wherein at least a portion of the protruding portion that will become the welded portion is covered with the insulating material, and in the welding step, the insulating material is melted by welding heat between the protruding portion and the tab lead, and the insulating material is removed from the welded portion.

3. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein in the welding step, the temperature of the portion to be welded is maintained at a temperature lower than the welding temperature and higher than the melting temperature of the insulating material for a predetermined time, and after the predetermined time has elapsed, the temperature of the portion to be welded is raised to the welding temperature.

4. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein in the welding step, a welding machine is brought into direct or indirect contact with the portion to be welded, and a load from the welding machine to the welded portion is maintained until the temperature of the welded portion becomes lower than the melting temperature of the insulating material.

5. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein in the welding step, a welder is brought into contact with the portion to be welded via a metal foil.

6. The method for producing an all-solid-state battery according to claim 5, wherein the metal foil is made of the same material as the current collector.

7. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein in the welding step, a welding machine is brought into direct or indirect contact with the portion to be welded, and the load applied from the welding machine to the welded portion is kept below the yield stress of the current collector.

8. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein the insulating material comprises a first insulating material covering a portion of the protruding portion that will become the welded portion, and a second insulating material covering a portion of the protruding portion that will not become the welded portion, and the first insulating material has a melting temperature lower than that of the second insulating material.

9. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein the insulating material comprises a first insulating material covering a portion of the protruding portion that will become the welded portion, and a second insulating material covering a portion of the protruding portion that will not become the welded portion, and the first insulating material is thinner than the second insulating material.

10. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein, before the welding step, an opening is provided in the insulating material that opens above the portion that will become the weld, and in the welding step, a welding machine is brought into direct or indirect contact with the portion of the protruding portion that is exposed from the opening, and the tab lead is welded to the protruding portion.

11. The method for manufacturing an all-solid-state battery according to claim 10, wherein the diameter of the opening is larger than the diameter of a contact surface that comes into direct or indirect contact with the protrusion in the welding machine.

12. The method for manufacturing an all-solid-state battery according to claim 10, wherein the side surface of the opening is inclined relative to the bottom surface so that the diameter gradually increases from the bottom surface of the opening toward the opening end.

13. The method for manufacturing an all-solid-state battery according to claim 1 or 2, further comprising an inspection step between the lamination and pressure bonding step and the welding step, for inspecting the battery cells for internal short circuits.

14. The method for manufacturing an all-solid-state battery according to claim 1 or 2, wherein the electrodes include a first electrode and a second electrode having the same polarity as the first electrode and adjacent to the first electrode in the one direction, and in the all-solid-state battery laminate after the pressing, when the total thickness of each layer located between the current collector of the first electrode and the current collector of the second electrode is T1 and the thickness of the insulating material is T2, T1 is equal to or greater than T2.

15. An all-solid-state battery comprising: an all-solid-state battery laminate in which a negative electrode containing lithium metal or a lithium alloy, a solid electrolyte layer, and a positive electrode are repeatedly arranged in one direction, and a plurality of battery cells are stacked in said one direction; a tab lead welded to a protrusion that is part of a current collector of at least one of the negative electrode and the positive electrode and protrudes from said all-solid-state battery laminate in a direction intersecting said one direction; and an insulating material provided on said protrusion, wherein said insulating material is an insulating film or insulating sheet made of a low-melting point insulating material whose melting temperature is lower than the welding temperature at which said protrusion and said tab lead are welded, and wherein the welded portion between said protrusion and said tab lead has a non-insulating portion.

16. The all-solid-state battery according to claim 15, wherein the insulating material is provided on at least one surface of the protrusion in the thickness direction.

17. The all-solid-state battery according to claim 15 or 16, wherein the electrodes include a first electrode and a second electrode having the same polarity as the first electrode and adjacent to the first electrode in the one direction, wherein L is a distance between an electrode layer of the electrode and the insulating material, and T1 is a total thickness of each layer in the all-solid-state battery stack located between the current collector of the first electrode and the current collector of the second electrode, and L is not more than 1 / 2 of T1.

18. The all-solid-state battery according to claim 15 or 16, wherein the negative electrode has a negative electrode current collector, the positive electrode has a positive electrode current collector, and the insulating material is provided on the protruding portion of one of the negative electrode current collector and the positive electrode current collector, while the insulating material is not provided on the protruding portion of the other current collector.

19. The all-solid-state battery according to claim 18, wherein the one current collector has a higher thermal conductivity than the other current collector.

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