Manufacturing method for bipolar batteries

Abstract

This invention provides a method for manufacturing bipolar batteries that allows for the filling of gaps between battery modules with a foaming agent using a simple method. [Solution] The method for manufacturing a bipolar battery comprises a stacking step S11 in which battery modules and coolers are stacked alternately to create a laminate; an attachment step S12 in which a polyol-containing sheet is attached to at least one of the surfaces of adjacent battery modules in the stacking direction that are located higher than the liquid level of the foaming agent before foaming, and that are exposed from the cooler and facing each other; an insertion step S13 in which the laminate is inserted into the inside of a battery case; and a foaming step S14 in which the foaming agent is filled into the battery case until it reaches the liquid level and foams. The foaming agent is a two-component curing type foamed urethane containing a polyol and an isocyanate, with an isocyanate content higher than the polyol content.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bipolar battery.

Background Art

[0002] Conventionally, in such a technical field, for example, there is one described in Patent Document 1. In the method for manufacturing a bipolar battery described in Patent Document 1, a plurality of battery modules in which a positive electrode is formed on one surface of a current collector and a negative electrode is formed on the other surface are stacked via an electrolyte layer, and a filling material is filled into the space between adjacent current collectors in the stacking direction to surround the periphery of the positive electrode and the negative electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a bipolar battery in which a plurality of battery modules are stacked, in order to realize cooling of the battery modules, a cooler is disposed between adjacent battery modules, that is, a structure in which the battery modules and the cooler are alternately stacked and the cooler absorbs heat from the battery modules is often adopted. And, in order to restrain the stacked battery modules and the cooler in a battery case, after inserting the stacked battery modules and the cooler into the battery case, a measure is taken to fill the gap between the battery modules and the cooler and the battery case with a foaming agent.

[0005] However, because the battery modules and coolers are of different sizes, stacking them alternately creates gaps between adjacent battery modules in the stacking direction. Furthermore, since these gaps extend in a direction perpendicular to the stacking direction, natural foaming of the foaming agent alone is insufficient to penetrate these gaps. To solve this problem, a method of filling the battery case with foaming agent and then performing vacuuming (i.e., filling by reduced pressure) has been considered, but this introduces new problems such as the need to introduce large-scale equipment including a vacuum device.

[0006] The present invention was made to solve these technical problems, and aims to provide a method for manufacturing a bipolar battery that allows for the filling of gaps between battery modules with a foaming agent using a simple method. [Means for solving the problem]

[0007] The method for manufacturing a bipolar battery according to the present invention comprises: a lamination step of alternately stacking a plurality of battery modules and a plurality of coolers to produce a laminate; an attachment step of attaching a polyol-containing sheet to at least one of the surfaces of adjacent battery modules in the lamination direction that are located at a position higher than the liquid level of the foaming agent to be filled later, and that are exposed from the cooler and facing each other; an insertion step of inserting the laminate with the polyol-containing sheet attached into a pre-made battery case; and a foaming step of filling the battery case with the foaming agent until it reaches the liquid level and foaming, wherein the foaming agent is a two-component curable foamed urethane containing a polyol and an isocyanate, characterized in that the content of the isocyanate is higher than the content of the polyol.

[0008] The method for manufacturing a bipolar battery according to the present invention includes an attachment step of attaching a polyol-containing sheet to at least one of the surfaces of adjacent battery modules in the stacking direction that are located at a position higher than the liquid level of the foaming agent before foaming; an insertion step of inserting the stacked body with the polyol-containing sheet attached into a pre-fabricated battery case; and a foaming step of filling the battery case with foaming agent until it reaches the liquid level and then foaming. The foaming agent is a two-component curable foamed urethane containing polyol and isocyanate, with a higher isocyanate content than polyol content. That is, by using a foaming agent with a mixing ratio that results in an excess of isocyanate, the unreacted isocyanate in the foaming agent reacts with the polyol in the polyol-containing sheet, promoting foaming in the gaps between adjacent battery modules in the stacking direction. Therefore, the foaming agent can easily penetrate into the gaps between the battery modules. Moreover, since it does not require the introduction of large-scale equipment such as a vacuum device compared to the case where filling is done by vacuum, the manufacturing method is simplified. As a result, a simple method can be used to fill the gaps between battery modules with foaming agent. [Effects of the Invention]

[0009] According to the present invention, a foaming agent can be filled into the gaps between battery modules using a simple method. [Brief explanation of the drawing]

[0010] [Figure 1] This is a flowchart showing a method for manufacturing a bipolar battery according to an embodiment. [Figure 2] This is a schematic cross-sectional view illustrating the foaming step (the state before foaming). [Figure 3] This is a schematic cross-sectional view illustrating the foaming step (the state during foaming). [Figure 4] This is a schematic cross-sectional view illustrating the foaming step (the state after foaming). [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the method for manufacturing a bipolar battery according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Also, in Figures 2 to 4, only a part of the cross-section of the bipolar battery (for example, the right half) is depicted. Furthermore, the following will describe an example in which the battery module and the cooler are stacked along the vertical direction, that is, an example in which the stacking direction is vertical.

[0012] Figure 1 is a flowchart showing a method for manufacturing a bipolar battery according to this embodiment. As shown in Figure 1, the method for manufacturing a bipolar battery according to this embodiment comprises a stacking step S11, a bonding step S12, an insertion step S13, and a foaming step S14.

[0013] In the lamination step S11, a laminate 10 is fabricated by alternately stacking multiple battery modules 11 and multiple coolers 12. A battery module 11 is, for example, a flat plate with multiple battery cells stacked on top of each other. Although not shown, each battery cell has bipolar electrodes, and current collectors and separators, each coated with positive and negative electrode active materials on both sides, are alternately stacked. Furthermore, each battery cell is formed in a structure that allows current to flow directly in the stacking direction of the bipolar electrodes. In the battery module 11, the stacking direction of the battery cells and the direction in which the current flows are the same. Also, in this embodiment, the stacking direction of the battery cells and the stacking direction of the battery module 11 and the cooler 12 are the same.

[0014] The cooler 12 has a flattened box shape with a space for circulating a coolant inside, and the coolant flowing inside absorbs heat from the battery module 11, thereby cooling the battery module 11. As shown in Figure 2, the cooler 12 is positioned between a pair of upper and lower battery modules 11 that are adjacent in the stacking direction, and is positioned to absorb heat from the pair of upper and lower battery modules 11. That is, the cooler 12 is sandwiched between the bottom surface 11b of the upper battery module 11 and the top surface 11a of the lower battery module 11 of the pair of upper and lower battery modules 11.

[0015] Although not shown in the figures, the cooler 12 includes, for example, a first metal plate bonded to the bottom surface 11b of the upper battery module 11, a second metal plate bonded to the top surface 11a of the lower battery module 11, and a metal corrugated plate positioned between the first and second metal plates to form a coolant flow path.

[0016] Therefore, in the lamination step S11, a laminate 10 is created by alternately stacking a plurality of pre-fabricated battery modules 11 and a plurality of coolers 12 along the vertical direction. At this time, a conductive adhesive is applied between the battery modules 11 and the coolers 12 to fix the battery modules 11 and the coolers 12 via the conductive adhesive.

[0017] As shown in Figure 2, for example, if the stacked structure 10 consists of four battery modules 11 and three coolers 12 stacked alternately, three gaps S are created between adjacent battery modules 11 and between the coolers 12 placed therein. More specifically, the gaps S are formed by the bottom surface 11b between the upper battery modules 11 of a pair of upper and lower battery modules 11, the top surface 11a of the lower battery module 11, and the side surface 12a of the cooler 12 placed between the upper and lower battery modules 11. These gaps S extend in a direction perpendicular to the vertical direction (stacking direction) (for example, the horizontal direction).

[0018] When the laminated body 10 is inserted into the battery case 20, the three gaps S described above will each be in communication with the inside of the battery case 20.

[0019] In the pasting step S12 following the lamination step S11, for battery modules 11 adjacent to each other in the vertical direction and located at positions higher than the liquid surface 14a before foaming of the foaming agent 14 to be filled later, a polyol-containing sheet 13 is pasted onto at least one of the opposing surfaces exposed from the cooler 12 between the battery modules 11.

[0020] Specifically, for example, as shown in FIG. 2, when the foaming agent 14 is filled into the battery case 20 with the laminate 10 inserted into the battery case 20 later, among the three gaps S, the lowermost gap S is lower than the liquid surface 14a before foaming of the filled foaming agent 14, and the remaining two gaps S are higher than the liquid surface 14a. That is, the foaming agent 14 is filled inside the lowermost gap S, and the foaming agent 14 is not filled inside the remaining two gaps S respectively.

[0021] In such a situation, for the two gaps S located at positions higher than the liquid surface 14a, at least one of the opposing surfaces exposed from the cooler 12 between each adjacent pair of battery modules 11, that is, at least one of the bottom surface 11b of the upper battery module 11 and the top surface 11a of the lower battery module 11 exposed from the cooler 12 and facing each other, a polyol-containing sheet 13 is pasted.

[0022] In the present embodiment, the polyol-containing sheet 13 is pasted only on the top surface 11a of the lower battery module 11 that forms the gap S (see FIG. 2), but it may also be pasted only on the bottom surface 11b of the upper battery module 11 that forms the gap S, or on both the bottom surface 11b of the upper battery module 11 and the top surface 11a of the lower battery module 11. Note that the liquid surface 14a of the foaming agent 14 is determined by the filling amount of the foaming agent 14, the volume of the battery case 20, etc.

[0023] Furthermore, the area to which the polyol-containing sheet 13 is attached may be, for example, the entire area of ​​the bottom surface 11b of the upper battery module 11 and / or the top surface 11a of the lower battery module 11 that forms the gap S, or it may be only a part thereof.

[0024] The polyol-containing sheet 13 is, for example, a sheet impregnated with polyol. Examples of polyols contained in the polyol-containing sheet 13 include acrylic polyols, polyester polyols, epoxy polyols, alkyd polyols, and the like.

[0025] In the insertion step S13 following the attachment step S12, the laminate 10 to which the polyol-containing sheet 13 has been attached is inserted into the pre-fabricated battery case 20. As shown in Figure 2, the battery case 20 has, for example, a box-shaped case body 21 that opens upward and a lid portion 22 for closing the opening of the case body 21. The lid portion 22 and the case body 21 are fastened together with bolts, with flange portions 221 and 211 attached to them overlapping.

[0026] Therefore, in insertion step S13, the laminate 10 to which the polyol-containing sheet 13 is attached is placed inside the case body 21, and then the lid 22 is fastened to the case body 21.

[0027] In the foaming step S14 following the insertion step S13, the foaming agent 14 is filled into the battery case 20 and foamed. Specifically, as shown in Figure 2, for example, the foaming agent 14 is filled into the inside of the battery case 20 through a filling port formed in the battery case 20 until it reaches the liquid level 14a. The foaming agent 14 is a two-component curing type foamed urethane containing a polyol (main component) and an isocyanate (curing agent). In the foaming agent 14, the isocyanate content is higher than the polyol content.

[0028] Examples of polyols include acrylic polyols, polyester polyols, epoxy polyols, and alkyd polyols. As for isocyanates, bifunctional or more aliphatic or aromatic isocyanates can be used, such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylene diisocyanate, 4,4-diphenylmethane diisocyanate, and lysine diisocyanate.

[0029] At this time, the two liquids, polyol and isocyanate, are mixed in a ratio that results in an excess of isocyanate, and then filled into the battery case 20. The amount of foaming agent 14 to be filled is determined based on the filling volume and foaming ratio, etc. For example, if the foaming ratio is 2, half the amount of the filling volume is filled.

[0030] When the two liquids, polyol and isocyanate, are mixed, a foaming reaction occurs, and the foaming agent 14 expands and becomes larger. Therefore, as shown by the arrow in Figure 3, the foaming agent 14 expands vertically and also reaches the entrance of the gap S between adjacent battery modules 11 (i.e., the point where the gap S communicates with the inside of the battery case 20). As described above, in natural foaming, even if the foaming agent 14 reaches the entrance of the gap S between adjacent battery modules 11 and tries to enter the inside of the gap S, the foaming force of the foaming agent 14 is mainly concentrated in the vertical direction, so the force in the direction perpendicular to the vertical direction (for example, the horizontal direction) is weak, and the foaming agent 14 has difficulty entering the inside of the gap S.

[0031] In this embodiment, since the polyol-containing sheet 13 is pre-attached to the top surface 11a of the lower battery module 11 that forms the gap S, the unreacted isocyanate in the foaming agent 14 reacts with the polyol in the polyol-containing sheet 13, promoting foaming in the gap S (see enlarged view of Figure 3). In other words, the polyol-containing sheet 13 plays a role in attracting the foaming agent 14 into the gap S. This makes it easier for the foaming agent 14 to enter the gap S between the battery modules.

[0032] As a result, as shown in Figure 4, the foaming agent 14 fills not only the gaps in the vertical direction (the gap between the battery case 20 and the laminate 10), but also the gaps S between adjacent battery modules 11 in the vertical direction.

[0033] The foaming agent 14 is in a liquid state before foaming, but changes from a liquid state to a cream state due to the foaming reaction, then becomes a gel state, and finally becomes a solid (hardened).

[0034] In the manufacturing method of a bipolar battery according to this embodiment, the method includes an attachment step S12 in which a polyol-containing sheet 13 is attached to at least one of the surfaces of adjacent battery modules 11 that are located higher than the liquid level 14a of the foaming agent 14 before foaming, which are exposed from the cooler 12 and face each other (i.e., the bottom surface 11b of the upper battery module 11 or the top surface 11a of the lower battery module 11 that form a gap S); an insertion step S13 in which the laminate 10 with the polyol-containing sheet 13 attached is inserted into the battery case 20; and a foaming step S14 in which the foaming agent 14 is filled into the battery case 20 until it reaches the liquid level 14a and foamed. The foaming agent 14 is a two-component curable foamed urethane containing a polyol and an isocyanate, with an isocyanate content higher than the polyol content.

[0035] In other words, in the manufacturing method of this embodiment, by using a foaming agent 14 having a mixing ratio that results in an excess of isocyanate, the unreacted isocyanate in the foaming agent 14 reacts with the polyol in the polyol-containing sheet 13, thereby promoting foaming in the gap S between adjacent battery modules 11 in the vertical direction. Consequently, the foaming agent can easily penetrate into the gap S. Moreover, since it does not require the introduction of large-scale equipment such as a vacuum device compared to the case where filling is done by vacuum, the manufacturing method is simplified. As a result, the foaming agent 14 can be filled into the gap S between the battery modules 11 using a simple method.

[0036] In this embodiment, the foaming agent 14 was described as being foamed urethane, but foamed epoxy resin or foamed silicone resin may be used instead. In that case, a sheet that promotes foaming of the foamed epoxy resin or foamed silicone resin is used instead of the polyol-containing sheet 13.

[0037] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design modifications can be made without departing from the spirit of the invention as described in the claims. [Explanation of Symbols]

[0038] 10: Laminate, 11: Battery module, 11a: Top surface, 11b: Bottom surface, 12: Cooler, 12a: Side surface, 13: Polyol-containing sheet, 14: Foaming agent, 14a: Liquid level, 20: Battery case, 21: Case body, 22: Lid, 211, 221: Flange, S: Gap

Claims

[Claim 1] A lamination step in which multiple battery modules and multiple coolers are alternately stacked to create a laminate, A bonding step of attaching a polyol-containing sheet to at least one of the surfaces of adjacent battery modules in the stacking direction that are located at a position higher than the liquid level of the foaming agent before foaming, and that are exposed to the cooler and facing each other. Insertion step of inserting the laminate to which the polyol-containing sheet is attached into the inside of a pre-fabricated battery case, A foaming step in which the foaming agent is filled into the battery case until it reaches the liquid level and foamed, Equipped with, The method for manufacturing a bipolar battery is characterized in that the foaming agent is a two-component curable foamed urethane containing a polyol and an isocyanate, and the content of the isocyanate is higher than the content of the polyol.

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