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

Abstract

A method for manufacturing an all-solid-state battery comprising a battery cell in which a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector, each having a rectangular flat-plate shape, are laminated in this order, a part of the positive electrode current collector and a part of the negative electrode current collector extending in a planar direction as current collector tabs, the method comprising: preparing a battery laminate in which a plurality of battery cells are laminated with the extension directions of at least the current collector tabs of the same polarity being aligned, and in which a second resin material is disposed in a position spaced apart by a first distance from an end face of the battery cell in a space formed by a pair of current collector tabs facing each other in a lamination direction, the second resin material extending from one current collector tab to the other current collector tab; installing the battery laminate inside a mold having a surface facing at least a surface of the battery laminate from which no current collector tabs extend when viewed from the lamination direction; applying a load in the lamination direction to the battery laminate; and filling the interior of the mold with a first resin material.

Description

Method for manufacturing all-solid-state battery and 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] In order to prevent deformation of the end portion of the battery laminate and the like, and short circuits caused by these, an all-solid-state battery in which the battery laminate is coated with a thermoplastic resin, a thermosetting resin, or the like is known. As a method for manufacturing such an all-solid-state battery, JP2018-133175A discloses a method in which an all-solid-state battery laminate in which a plurality of all-solid-state battery elements are laminated is housed in an outer package, and a filler is injected into the outer package in a state where the all-solid-state battery laminate is pressurized in the lamination direction.

[0003] However, in the method of the above document, since the current collecting tab protruding from the side surface of the all-solid-state battery laminate is not supported when the filler is injected, the current collecting tab may be deformed by the flow of the injected filler. The current collecting tabs are joined to each other of the tabs of the same polarity and connected to an external electrode, and are bent and deformed according to the expansion and contraction of the battery laminate. Therefore, when the filler hardens in a state where the current collecting tab is deformed, particularly when the number of laminations is increased, a large stress may be generated in the current collecting tab during bending deformation, leading to breakage.

[0004] Therefore, an object of the present invention is to provide a method for filling a filler without deforming the current collecting tab.

[0005] According to one aspect of the present invention, a method for manufacturing an all-solid-state battery is provided, comprising a battery cell in which a rectangular plate-shaped positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector are stacked in this order, and a portion of the positive electrode current collector and a portion of the negative electrode current collector extend in the planar direction as current collecting tabs. This method includes creating a battery stack in which a plurality of battery cells are stacked with the extension directions of at least the same electrode current collecting tabs aligned, and a second resin material extending from one current collecting tab to the other is placed at a position a first interval from the end face of the battery cell in the space formed by a pair of current collecting tabs facing each other in the stacking direction; placing the battery stack inside a mold having a surface that faces at least the surface of the battery stack from which the current collecting tabs do not extend when viewed from the stacking direction; applying a load in the stacking direction to the battery stack; and filling the mold with the first resin material.

[0006] Figure 1 is a cross-sectional view showing an example of an all-solid-state battery according to the first embodiment. Figure 2 is a cross-sectional view of the end of a modified battery stack. Figure 3 is a cross-sectional view of the end of a battery stack according to another modified embodiment. Figure 4 is a cross-sectional view of a foamed resin material. Figure 5 is a diagram showing the state before filling with the first resin material. Figure 6 is a diagram showing the state after filling with the first resin material. Figure 7 is a cross-sectional view showing an example of an all-solid-state battery in which the second resin material has an adhesive layer. Figure 8 is a view of the battery cells according to the second embodiment from the stacking direction. Figure 9 is a side view of the battery stack formed by stacking the battery cells of Figure 8, viewed from the direction of the arrow in Figure 8. Figure 10 is a side view of a comparative example.

[0007] Embodiments of the present invention will be described below with reference to the drawings.

[0008] [First Embodiment] Figure 1 is a cross-sectional view showing an example of an all-solid-state battery 1 manufactured by the method according to this embodiment.

[0009] The all-solid-state battery 1 comprises a battery stack 15 formed by stacking multiple battery cells 10, each cell in which a rectangular plate-shaped positive electrode current collector 2, a positive electrode layer 3, a solid electrolyte layer 4, a negative electrode layer 5, and a negative electrode current collector 6 are stacked in that order. The stacking dimension (also called thickness) of the positive electrode current collector 2 is about 5 to 50 μm, preferably about 8 to 20 μm. The thickness of the negative electrode current collector 6 is also about 5 to 50 μm, preferably about 8 to 20 μm. The negative electrode current collector 6 may include an intermediate layer. The thickness of the solid electrolyte layer 4 is about 5 to 100 μm. The thicknesses of both the positive electrode layer 3 and the negative electrode layer 5 are 10 to 500 μm.

[0010] A portion of the positive electrode current collector 2 and a portion of the negative electrode current collector 6 extend in the planar direction from the side surface of the battery cell 10 as the positive electrode current collector tab 11P and the negative electrode current collector tab 11N, respectively. In this embodiment, the positive electrode current collector tab 11P and the negative electrode current collector tab 11N extend in opposite directions, but they may extend in the same direction. Also, when there is no need to distinguish between the positive electrode current collector tab 11P and the negative electrode current collector tab 11N, they are simply referred to as current collector tab 11.

[0011] When stacking the battery cells 10, the extension directions of at least the current-collecting tabs of the same pole are aligned, that is, at least the positive electrode current-collecting tabs 11P extend in the same direction, and the negative electrode current-collecting tabs 11N extend in the same direction.

[0012] The outer circumference of the battery stack 15, when viewed from the stacking direction, is covered with a first resin material 7. The first resin material 7 is a thermoplastic resin having electronic insulating properties (e.g., PP, SBS, etc.).

[0013] The second resin material 8 is positioned on the outer periphery of the surface of the first resin material 7 in the direction from which the current-collecting tab 11 extends.

[0014] The second resin material 8 is a resin having electronic insulating properties, such as rubber, polyurethane, polyethylene, epoxy resin, or silicone resin. Regarding electronic insulating properties, the electronic resistance is 10. ５ It is sufficient if it is Ωcm or more, preferably 10 ６The density is Ωcm or greater. Furthermore, it is more preferable that the second resin material 8 is a foamed resin material having internal voids, such as polyurethane, polyethylene, or epoxy resin. Figure 4 is a cross-sectional view of the foamed resin material. In the case of a foamed resin material with internal voids, the amount of deformation due to pressure from the thickness direction becomes larger, so it becomes easier to follow the deformation caused by the application of load during the filling of the first resin material 7, which will be described later. It also becomes easier to follow the expansion and contraction associated with the charging and discharging of the all-solid-state battery 1.

[0015] Furthermore, it is preferable that the Young's modulus of the second resin material 8 is equal to or lower than that of the first resin material 7.

[0016] Furthermore, it is more preferable that the Young's modulus of the second resin material 8 is deformable by the filling pressure when filling the first resin material 7. The deformation referred to here is not a large deformation that would cause the current collector tab 11 to bend, but rather a small deformation that would release the pressure of the first resin material 7 that has been pumped in, so as not to cause the current collector tab 11 to bend at all.

[0017] In Figure 1, the planar end of the positive electrode current collector 2 on the side without the current collecting tab 11 is aligned with the planar ends of the positive electrode layer 3, the solid electrolyte layer 4, and the negative electrode layer 5, as well as the planar end of the negative electrode current collector 6 on the side without the current collecting tab 11. However, these may be misaligned. For example, as shown in Figure 2, the position of the planar end of the positive electrode layer 3 may be misaligned with the position of the planar ends of the negative electrode layer 5, etc. Also, in Figures 1 and 2, the space between the planar end of each layer and the second resin material 8 is filled with the first resin material 7. However, as long as the outer circumference of the battery stack 15 is covered, there may be a gap between the first resin material 7 and the planar end of each phase, as shown in Figure 3.

[0018] Next, the manufacturing process of the all-solid-state battery 1 will be explained with reference to Figures 5 and 6.

[0019] Figure 5 shows the state before filling with the first resin material 7. Figure 6 shows the state after filling with the first resin material 7.

[0020] When stacking the battery cells 10, the second resin material 8 is placed at a position a first interval from the end face of the battery cell 10 in the space formed by a pair of current-collecting tabs 11 facing each other in the stacking direction. The first interval is left to secure space for filling with the first resin material 7. The purpose of the first resin material 7 is to ensure the insulation of the battery stack 15 and to prevent deformation. For this reason, the first interval is set appropriately considering the characteristics of the first resin material 7 used and the dimensions required for the above purposes. After the all-solid-state battery 1 is completed, tab leads (not shown) are connected to the current-collecting tabs 11, so it is necessary to secure space for connecting to the tab leads. For this reason, when the second resin material 8 is installed, the current-collecting tabs 11 protrude outward in the planar direction from the second resin material 8.

[0021] The second resin material 8 has both sides in the lamination direction in contact with opposing current collector tabs 11. Preferably, the thickness of the second resin material 8 is equal to the sum of the thicknesses of the positive electrode layer 3, the solid electrolyte layer 4, and the negative electrode layer 5 sandwiched between a pair of opposing current collector tabs 11 in the lamination direction.

[0022] Once the battery stack 15 comprising the second resin material 8 is created, the battery stack 15 is placed inside a mold 20 (see Figure 9) that has a surface facing at least the surface from which the current-collecting tabs 11 of the battery stack 15 do not extend when viewed from the stacking direction. In the case of the battery stack 15 in Figure 1, the mold 20 has a surface facing the side of the battery stack 15 that extends in a direction perpendicular to the direction in which the current-collecting tabs 11 extend (i.e., the surface on the near side of the paper and the surface on the far side of the paper).

[0023] Once the battery stack 15 is placed inside the formwork 20, a load in the stacking direction is applied to the battery stack 15.

[0024] Then, while maintaining the applied load, the first resin, which has been melted to a state where it can be pumped under pressure, is filled into the mold 20.

[0025] Once filling is complete, the first resin is cured while maintaining the applied load. The curing method is appropriately selected depending on the first resin used, such as UV curing or heat curing.

[0026] If the first resin material 7 is filled without the second resin material 8, the current collector tab 11 is not supported, and therefore the current collector tab 11 may deform due to the pressure of the flowing first resin material 7 and bend in a direction deviating from the planar direction. If the first resin material 7 is hardened in this state, the bending stress generated at the boundary between the current collector tab 11 and the first resin material 7 when the current collector tab 11 bends in response to the movement of the tab lead due to the expansion and contraction of the battery stack 15 will be greater than when the first resin material 7 is hardened without the current collector tab 11 being bent. In particular, when there are many stacks of battery cells 10, the above bending stress increases as you get closer to both ends in the stacking direction. And the greater the bending stress, the more likely the current collector tab 11 is to break due to repeated expansion and contraction of the battery stack 15.

[0027] In contrast, when the second resin material 8 is arranged as in this embodiment, the current collector tab 11 is supported by the battery cell 10 and the second resin material 8, and the first resin material 7 is filled into the space defined by the side surface of the battery cell 10 and the second resin material 8, thereby suppressing bending of the current collector tab 11. Therefore, damage to the current collector tab 11 due to repeated expansion and contraction of the battery stack 15 can be suppressed.

[0028] Furthermore, by setting the Young's modulus of the second resin material 8 to a degree that allows it to deform under pressure from the first resin material 7 being pumped in, it is possible to suppress the first resin material 7 from entering the gaps between the electrodes and current collectors or between the electrodes and solid electrolytes of the battery cell 10. In other words, if the second resin material 8 cannot be deformed, the first resin material 7, under increased pressure due to the filling pressure, may enter the gaps between the electrodes and current collectors, etc. However, if the second resin material 8 is deformable, the pressure of the first resin material 7 can be released by the deformation of the second resin material 8, thereby suppressing the entry of the first resin material 7 as described above.

[0029] Depending on the material used, the volume of the first resin material 7 may change upon hardening. However, if a gap forms between the first resin material 7 and the second resin material 8 after hardening, the first resin material 7 may deform or break when a constraining pressure is applied in the stacking direction when using the all-solid-state battery 1. This problem can be solved by making the Young's modulus of the second resin material 8 equal to or smaller than that of the first resin material 7. In other words, if the second resin material 8 is deformed by the first resin material 7 that has been pumped in, then when the volume of the first resin material 7 decreases due to hardening, the second resin material 8 will follow the volume change of the first resin material 7 and return to its pre-deformation state, thus suppressing the formation of a gap between the first resin material 7 and the second resin material 8 after hardening.

[0030] Furthermore, the battery stack 15 repeatedly expands and contracts during the use of the all-solid-state battery 1. If the second resin material 8 cannot follow the expansion and contraction of the battery stack 15 (mainly the increase and decrease in dimensions in the stacking direction), a gap may form between the second resin material 8 and the current collector tab 11 during expansion, potentially leading to damage to the current collector tab 11. On the other hand, if the second resin material 8 cannot follow the expansion and the second resin material 8 and the current collector tab 11 remain in close contact, the spacing between the current collector tabs 11 will differ between the area where the second resin material 8 is located and the area where the first resin material 7 is located. This can cause shear stress on the current collector tab 11, potentially leading to damage to the current collector tab 11. This problem can also be solved by making the Young's modulus of the second resin material 8 equal to or smaller than that of the Young's modulus of the first resin material 7. In other words, if the Young's modulus of the second resin material 8 is equal to or smaller than that of the first resin material 7, the second resin material 8 can follow the movement of the first resin material 7, so the distance between the current collection tabs 11 in the area where the second resin material 8 is placed and the area where the first resin material 7 is placed will be the same, and the above-mentioned shear stress will not occur.

[0031] As shown in Figure 7, an adhesive layer 21 may be provided on at least one of the surfaces of the second resin material 8 that come into contact with the current collector tab 11. By bonding the second resin material 8 to the current collector tab via the adhesive layer 21, the adhesion force between the second resin material 8 and the current collector tab 11 is strengthened, which can suppress misalignment of the second resin material 8 when filling the first resin material 7. In addition, if the second resin material 8 is bonded during the assembly of the battery cell 10, it becomes easier to position the second resin material 8 during the subsequent assembly of the battery stack 15.

[0032] As described above, this embodiment provides a method for manufacturing an all-solid-state battery 1 comprising a battery cell 10 in which a rectangular flat plate-shaped positive electrode current collector 2, a positive electrode layer 3, a solid electrolyte layer 4, a negative electrode layer 5, and a negative electrode current collector 6 are stacked in this order, and a part of the positive electrode current collector 2 and a part of the negative electrode current collector 6 extend in the planar direction as current collector tabs 11. This method includes creating a battery stack 15 in which a plurality of battery cells 10 are stacked with the extension directions of at least the same electrode current collector tabs 11 aligned, and a second resin material 8 extending from one current collector tab 11 to the other current collector tab 11 is arranged at a position a first interval from the end face of the battery cell 10 in the space formed by a pair of current collector tabs 11 facing each other in the stacking direction; installing the battery stack 15 inside a mold 20 having a surface that faces at least the surface of the battery stack 15 from which the current collector tabs 11 do not extend when viewed from the stacking direction; applying a load in the stacking direction to the battery stack 15; and filling the mold 20 with the first resin material 7. As a result, the current collector tab 11 can be supported by the second resin material 8 while the first resin material 7 is filled, thus preventing bending and damage to the current collector tab 11 during filling.

[0033] In this embodiment, the above method is further modified to include curing the first resin material 7 while applying a load after filling it with the first resin material 7. This results in a battery stack 15 with high dimensional accuracy.

[0034] In this embodiment, the second resin material 8 is fixed to the current collector tab 11 via an adhesive layer 21 provided on at least one surface of the second resin material 8. This increases the adhesion between the current collector tab 11 and the second resin material 8, thereby suppressing displacement of the second resin material 8 when a load is applied to the battery stack 15. Furthermore, it facilitates the positioning of the second resin material 8 during the assembly process.

[0035] In this embodiment, the Young's modulus of the second resin material 8 is equal to or smaller than that of the first resin material 7 after curing. This makes the second resin material 8 more easily deformable in accordance with the expansion and contraction of the battery stack 15, thereby suppressing bending and damage of the current collector tab 11. Furthermore, because it is more easily able to follow the deformation of the first resin material 7 during curing, gaps are less likely to form between the first resin material 7 and the second resin material 8 after the first resin material 7 has cured.

[0036] In this embodiment, the second resin material 8 is deformable by the filling pressure when filling with the first resin material 7. This prevents the first resin material 7 from entering the space between the electrode and the current collector during filling.

[0037] In this embodiment, the second resin material 8 has electronic insulating properties. This prevents short circuits between the current collector tabs 11.

[0038] In this embodiment, the second resin material 8 is a foamed resin material having internal voids. This makes it easier for the thickness of the second resin material 8 to fluctuate in accordance with the thickness fluctuations of the battery cell 10, so that when the battery stack 15 is compressed to fill with the first resin material 7, it is easier to maintain the current collector tab 11 on the same plane as the positive and negative current collectors 2 and 6. As a result, it is easier to ensure airtightness when filling with the first resin material 7.

[0039] [Second Embodiment] Next, a second embodiment of the present invention will be described.

[0040] Figure 8 is a view of the battery cell 10 from the stacking direction. Figure 9 is a side view of the battery stack 15, which is formed by stacking the battery cells 10 shown in Figure 8, viewed from the direction of the arrow in Figure 8. Figure 10 is a side view of a comparative example.

[0041] The difference between this embodiment and the first embodiment lies in the form of the second resin material 8. In the view in the lamination direction, in the first embodiment, one second resin material 8 is arranged over the entire surface on which the current collecting tab 11 of the battery cell 10 extends, whereas in this embodiment, multiple second resin materials 8 are arranged at equal intervals in a direction perpendicular to the lamination direction.

[0042] Since the first resin material 7 serves to protect the ends of the battery laminate 15, it is necessary to cover all of the outer periphery of the battery laminate 15 when viewed in the stacking direction. In contrast, since the purpose of the second resin material 8 is to support the current collector tab 11 when filling the first resin material 7, it may be arranged at intervals as described above.

[0043] Also, when the second resin material 8 is arranged at intervals, if the first resin material 7 is supplied excessively due to variations in the filling pressure, the space between adjacent second resin materials 8 serves as a relief space for the first resin material 7. Thereby, it is possible to suppress the entry of the first resin material 7 between the electrode and the current collector or the damage of the battery laminate 15 due to the excessive supply of the first resin material 7.

[0044] From the viewpoint of supporting the current collector tab 11, as shown in FIG. 9, it is desirable that the installation positions of the second resin materials 8 coincide between the battery cells 10. When the installation positions of the second resin materials 8 do not coincide between the battery cells 10 as shown in FIG. 10, when a load in the stacking direction is applied during the manufacture of the battery laminate 15 or during battery use, the current collector tab 11 may be deformed at a portion where the arrangement positions of the upper and lower second resin materials 8 are displaced (for example, portion A in FIG. 10). In contrast, if the arrangement positions of the second resin materials 8 coincide as shown in FIG. 9, in other words, if a plurality of second resin materials 8 in the stacking direction are arranged in a straight line along the direction of the load, the above deformation can be suppressed.

[0045] As described above, in the present embodiment, the second resin materials 8 are arranged at equal intervals in a direction perpendicular to the stacking direction when viewed from the stacking direction. Thereby, even if the first resin material 7 is supplied excessively due to variations in the filling pressure during the filling of the first resin material 7, the first resin material 7 can be released into the gaps between adjacent second resin materials 8, so that damage to the battery laminate 15 can be suppressed.

[0046] As described above, the embodiments of the present invention have been described. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Claims

1. A method for manufacturing an all-solid-state battery comprising a battery cell in which a rectangular flat plate-shaped positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector are stacked in this order, and a part of the positive electrode current collector and a part of the negative electrode current collector extend in the planar direction as current collecting tabs, comprising: creating a battery stack in which a plurality of the battery cells are stacked with the extension directions of at least the same electrode current collecting tabs aligned, and a second resin material extending from one current collecting tab to the other is disposed at a position a first interval from the end face of the battery cell in the space formed by a pair of current collecting tabs facing each other in the stacking direction; installing the battery stack inside a mold having a surface that, when viewed from the stacking direction, faces at least the surface of the battery stack from which the current collecting tabs do not extend; applying a load in the stacking direction to the battery stack; and filling the mold with the first resin material.

2. A method for manufacturing an all-solid-state battery according to claim 1, further comprising curing the first resin material while applying the load after filling the first resin material.

3. A method for manufacturing an all-solid-state battery according to claim 1, wherein the second resin material is arranged at equal intervals in a direction perpendicular to the stacking direction when viewed from the stacking direction.

4. A method for manufacturing an all-solid-state battery according to claim 1, wherein the second resin material is fixed to the current collector tab via an adhesive layer provided on at least one surface of the second resin material.

5. A method for manufacturing an all-solid-state battery according to claim 1, wherein the Young's modulus of the second resin material is equal to or less than the Young's modulus of the first resin material after curing.

6. A method for manufacturing an all-solid-state battery according to claim 1, wherein the second resin material is deformable by the filling pressure when filling the first resin material.

7. A method for manufacturing an all-solid-state battery according to claim 1, wherein the second resin material has electronic insulating properties.

8. A method for manufacturing an all-solid-state battery according to claim 1, wherein the second resin material is a foamed resin material having voids inside.

9. An all-solid-state battery comprising a battery cell in which a rectangular flat positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector are stacked in this order, and a part of the positive electrode current collector and a part of the negative electrode current collector extend as current collecting tabs in a direction perpendicular to the stacking direction, wherein the all-solid-state battery comprises: a battery stack in which a plurality of the battery cells are stacked such that the extension directions of the current collecting tabs of at least the same electrode are aligned; a first resin material covering the outer circumference of the battery stack when viewed from the stacking direction; and a second resin material provided on the outer circumference side of at least the surface of the first resin material in the direction in which the current collecting tabs extend.

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