Thermoplastic resin sheet, method for manufacturing a thermoplastic resin sheet, and method for manufacturing a battery equipped with a thermoplastic resin sheet

Abstract

This can suppress distortion in thermoplastic resin sheets. [Solution] The thermoplastic resin sheet is a sheet of thermoplastic resin and has a sheet-like core material whose coefficient of thermal expansion is lower than that of the thermoplastic resin.

Description

Technical Field

[0001] The present disclosure relates to a thermoplastic resin sheet, a method for manufacturing the thermoplastic resin sheet, and a method for manufacturing a battery including the thermoplastic resin sheet.

Background Art

[0002] A thermoplastic resin sheet that functions as an adhesive sheet for joining two members while maintaining a constant distance therebetween is known. For example, Patent Document 1 proposes a thermoplastic resin sheet having functional groups introduced by surface treatment on the surface and excellent in initial adhesiveness and adhesiveness to an electrolytic solution. In addition, a thermoplastic resin sheet that functions as a sealing sheet for sealing between two members is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a thermoplastic resin sheet is mounted between two members, the thermoplastic resin sheet is heated to melt the thermoplastic resin. However, when the linear thermal expansion coefficients of the two members are low, the thermoplastic resin sheet may be distorted due to the difference in the linear thermal expansion coefficients between the thermoplastic resin and the two members.

[0005] The present disclosure has been made in view of such problems, and an exemplary object of one aspect thereof is to provide a technique capable of suppressing distortion of a thermoplastic resin sheet.

Means for Solving the Problems

[0006] To solve the above problems, a thermoplastic resin sheet according to one embodiment of the present disclosure is a thermoplastic resin sheet having a sheet-like core material whose coefficient of thermal expansion is lower than that of the thermoplastic resin.

[0007] Another aspect of the present disclosure is a method for manufacturing a thermoplastic resin sheet. This method is a method for manufacturing a thermoplastic resin sheet as described above, and includes sandwiching a core material between sheets of thermoplastic resin.

[0008] Yet another aspect of this disclosure is also a method for manufacturing a thermoplastic resin sheet. This method is a method for manufacturing a thermoplastic resin sheet as described above, comprising immersing a core material in the thermoplastic resin.

[0009] Another aspect of the present disclosure is a method for manufacturing a battery. This method comprises preparing components including a current collector and a thermoplastic resin sheet as described above, and assembling the prepared components, the assembly of which includes heating the thermoplastic resin sheet with the thermoplastic resin sheet sandwiched between the current collectors. [Effects of the Invention]

[0010] According to certain aspects of this disclosure, distortion of the thermoplastic resin sheet can be suppressed. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view of a thermoplastic resin sheet according to an embodiment. [Figure 2] Figure 1 is a process diagram showing the manufacturing process of thermoplastic resin sheets. [Figure 3] This figure shows a battery equipped with a thermoplastic resin sheet. [Figure 4] Figures 4(a) and 4(b) show a battery equipped with a thermoplastic resin sheet according to a comparative example. [Figure 5] Figure 3 is a process diagram showing the manufacturing process of the battery. [Figure 6] This is a cross-sectional view of a modified thermoplastic resin sheet. [Figure 7] This is a cross-sectional view showing one of many fibers in a thermoplastic resin sheet where the core material is a fibrous structure, according to a modified example. [Modes for carrying out the invention]

[0012] Before describing the embodiments in detail, an overview of the embodiments will be given. This embodiment relates to a thermoplastic resin sheet. The thermoplastic resin sheet functions as an adhesive sheet that joins two members while maintaining a certain distance between them. In this case, the thermoplastic resin melts and penetrates into the fine irregularities on the surfaces of the two members, and as the thermoplastic resin hardens in that state, the two members and the thermoplastic resin sheet, that is, the two members are joined together via the thermoplastic resin. The thermoplastic resin sheet also functions as a sealing sheet that seals the space between the two members. In this case, the thermoplastic resin sheet exhibits sufficient sealing performance because the thermoplastic resin melts and penetrates into the fine irregularities on the surfaces of the two members.

[0013] In any case, when a thermoplastic resin sheet is installed between two components, the thermoplastic resin sheet is heated to melt the thermoplastic resin. However, if the two components are made of materials with low linear thermal expansion coefficients, such as metal, the thermoplastic resin sheet may become distorted due to the difference in linear thermal expansion coefficients between the thermoplastic resin and the two components. In contrast, in this embodiment, the thermoplastic resin sheet has a core material with a lower linear thermal expansion coefficient than the thermoplastic resin. As a result, the overall linear thermal expansion coefficient of the thermoplastic resin sheet is reduced, and therefore the difference in linear thermal expansion coefficients between the thermoplastic resin sheet and the two components is reduced, suppressing distortion of the thermoplastic resin sheet.

[0014] Hereinafter, preferred embodiments will be described with reference to the drawings. The embodiments are illustrative rather than restrictive, and not all features and combinations thereof described in the embodiments are necessarily essential to the disclosure. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and repeated explanations are omitted as appropriate.

[0015] FIG. 1 is a cross-sectional view of a thermoplastic resin sheet 100 according to an embodiment. In FIG. 1, the thermoplastic resin sheet 100 is mounted between a first member 10 and a second member. The thermoplastic resin sheet 100 functions as an adhesive sheet for joining the first member 10 and the second member 12 at a certain interval and / or a sealing sheet for sealing between the first member 10 and the second member 12.

[0016] The thermoplastic resin sheet 100 includes a sheet-like core material 110 and two thermoplastic resin layers 120 that are layers of thermoplastic resin. The core material 110 is sandwiched between the two thermoplastic resin layers 120. That is, the thermoplastic resin sheet 100 is a sheet of thermoplastic resin having a sheet-like core material 110.

[0017] The magnitude relationship between the thicknesses of the core material 110 and the two thermoplastic resin layers 120 is not particularly limited. That is, the core material 110 may be thicker than the thermoplastic resin layer 120, or the thermoplastic resin sheet 100 may be thinner than the thermoplastic resin layer 120. The thicknesses of the two thermoplastic resin layers 120 are typically the same as each other, but may be different from each other.

[0018] The thermoplastic resin layer 120 may have a low linear thermal expansion rate, specifically, the following linear thermal expansion rate. In this case, even if the members 10 and 12 are made of metal (for example, aluminum, stainless steel, copper, nickel, etc.), that is, even if the members 10 and 12 have a low linear thermal expansion rate, the difference in the linear thermal expansion rate between the thermoplastic resin layer 120 and the members 10 and 12 is small, so that the distortion of the thermoplastic resin layer 120 and thus the thermoplastic resin sheet 100 is suppressed. -4 Hereinafter, it may have the following linear thermal expansion rate.

[0019] The thermoplastic resin layer 120 preferably has electrolyte resistance. Here, "electrolyte resistance" refers to the resistance to an electrolyte, which means a property that does not cause a chemical reaction even when in contact with the electrolyte, and thus does not deteriorate even when in contact with the electrolyte. When the thermoplastic resin layer 120 has electrolyte resistance, the thermoplastic resin sheet 100 can be used in an environment where it comes into contact with the electrolyte.

[0020] The thermoplastic resin layer 120 preferably has excellent electrolyte adhesion. Here, "electrolyte adhesion" refers to a property in which the adhesive force is maintained even when in contact with the electrolyte. When the thermoplastic resin layer 120 has excellent electrolyte adhesion, the thermoplastic resin sheet 100 can be used as an adhesive sheet in an environment where it comes into contact with the electrolyte.

[0021] The thermoplastic resin layer 120 may be a polyolefin-based resin to which functional groups are imparted by surface treatment. Examples of the polyolefin-based resin include polyethylene, polypropylene, and ethylene-propylene copolymers. In this case, the thermoplastic resin layer 120 has excellent electrolyte adhesion and excellent initial adhesion. Here, "initial adhesion" refers to the adhesion immediately after adhesion, and in comparison with "electrolyte adhesion", it can also be said to be the adhesion before contact with the electrolyte.

[0022] The thermoplastic resin layer 120 preferably has a low Young's modulus, specifically a Young's modulus of 100 MPa or less. In this case, the thermoplastic resin layer 120 is difficult to peel off from the members 10 and 12.

[0023] The thermoplastic resin layer 120 preferably has low hygroscopicity. Here, the thermoplastic resin sheet 100 is heated during adhesion or the like, and after the water absorbed by the thermoplastic resin layer 120 vaporizes and escapes from the thermoplastic resin layer 120 due to the heat being applied, holes may remain in the thermoplastic resin layer 120, and there is a risk that the thermoplastic resin layer 120 may be damaged starting from the holes. Therefore, the lower the hygroscopicity of the thermoplastic resin layer 120, the more preferable.

[0024] The core material 110 has a lower coefficient of linear thermal expansion than the thermoplastic resin. As a result, the overall coefficient of linear thermal expansion of the thermoplastic resin sheet 100 is lower than when the thermoplastic resin sheet 100 does not have a core material 110, i.e., when the thermoplastic resin sheet 100 is composed only of the thermoplastic resin layer 120. Therefore, even when the members 10 and 12 are metal, i.e., have a low coefficient of linear thermal expansion, the difference in the coefficient of linear thermal expansion between the thermoplastic resin sheet 100 and the members 10 and 12 is small, and the distortion of the thermoplastic resin sheet 100 is suppressed. The core material 110 may be formed from a polyester resin having a low coefficient of linear thermal expansion similar to that of metal, specifically PET (polyethylene terephthalate).

[0025] When the core material 110 is made of a material with a melting point (e.g., resin, metal), the melting point of the core material 110 is preferably higher than the melting point of the thermoplastic resin. As a result, when the thermoplastic resin sheet 100 is attached, if the thermoplastic resin sheet 100 is heated at a temperature higher than the melting point of the thermoplastic resin but lower than the melting point of the core material 110, the core material 110 will not melt, and thus its shape can be maintained. The thermoplastic resin layer 120's spread in the planar direction when it melts is suppressed by the presence of the core material 110, whose shape is maintained.

[0026] When the core material 110 is made of a material that does not have a melting point (for example, wood or paper), the heat resistance temperature of the core material 110 is preferably higher than the heat resistance temperature of the thermoplastic resin. The heat resistance temperature may also be the temperature at which the core material 110 can maintain its shape. This allows the shape of the core material 110 to be maintained when the thermoplastic resin sheet 100 is heated at a temperature higher than the melting point of the thermoplastic resin but lower than the heat resistance temperature of the core material 110 during installation. The thermoplastic resin layer 120's spread in the planar direction when it melts is suppressed by the presence of the core material 110, whose shape is maintained.

[0027] The core material 110 preferably has a structure that can be impregnated with a thermoplastic resin, and more specifically, has pores or minute irregularities on at least its surface. In this case, the contact area between the core material 110 and the thermoplastic resin layer 120 increases, thereby improving the bonding strength between the core material and the thermoplastic resin. The core material 110 may be a fibrous structure composed of fibers, as a structure that can be impregnated with a thermoplastic resin. For example, the core material 110 may be a nonwoven, woven, or knitted fibrous structure. In this case, the core material 110 may be made of resin or metal. Alternatively, the core material 110 may be made of wood, specifically paper.

[0028] The core material 110 may be a material that does not have pores or minute irregularities on its surface. In this case, the core material 110 may be a plate material made of resin, metal, or the like.

[0029] The core material 110 preferably has electrolyte resistance. In this case, even when the core material 110 is exposed, the thermoplastic resin sheet 100 can be used in an environment where it comes into contact with the electrolyte.

[0030] Preferably, the core material 110 has excellent adhesion to the thermoplastic resin layer 120. In this case, the thermoplastic resin layer 120 is less likely to peel off from the core material 110.

[0031] The core material 110 preferably has low hygroscopicity, for example, lower hygroscopicity than the thermoplastic resin layer 120. The reason why low hygroscopicity is preferable is the same as for the thermoplastic resin layer 120.

[0032] The above describes the structure of the thermoplastic resin sheet 100. Next, the manufacturing method of the thermoplastic resin sheet 100 will be explained.

[0033] Figure 2 is a process diagram showing the manufacturing process S10 of the thermoplastic resin sheet 100. The manufacturing process S10 includes a preparation process S12 for preparing the core material 110 and the thermoplastic resin, and a forming process S14 for forming the thermoplastic resin sheet 100 using the prepared core material 110 and thermoplastic resin.

[0034] For example, in forming step S14, the core material 110 is sandwiched between two sheets of thermoplastic resin, and then heated and pressurized to impregnate the core material 110 with thermoplastic resin and form two thermoplastic resin layers 120 that sandwich the core material 110.

[0035] For example, in the forming process S14, the core material 110 is transported roll-to-roll, and during transport, the core material 110 is immersed in molten thermoplastic resin, thereby impregnating the core material 110 with thermoplastic resin and forming two thermoplastic resin layers 120 that sandwich the core material 110.

[0036] Next, we will explain some examples of applications for the thermoplastic resin sheet 100.

[0037] Figure 3 shows a battery 200 equipped with a thermoplastic resin sheet 100. The battery 200 is a bipolar battery. The battery 200 has a structure in which a positive electrode layer 204 and a negative electrode layer 206 are laminated on each surface of a rectangular plate-shaped or sheet-shaped current collector 202, and multiple such collectors are stacked. A separator 208 is provided between opposing positive electrode layers 204 and negative electrode layers 206. Adjacent current collectors 202 are joined together by two thermoplastic resin sheets 100, maintaining a constant distance between them. The separator 208 is held between adjacent current collectors 202 by having its periphery sandwiched between the two thermoplastic resin sheets 100. The inside of the battery 200 is filled with an electrolyte 210 and sealed by the thermoplastic resin sheet 100. In other words, in this battery 200, the thermoplastic resin sheet 100 functions as both an adhesive sheet and a sealing sheet.

[0038] The current collector 202 is made of a metal such as aluminum, stainless steel, copper, or nickel, and has a low coefficient of linear thermal expansion, specifically 1.0 × 10⁻⁶. -4It has the following very low coefficient of linear thermal expansion. In contrast, the thermoplastic resin sheet 100 has a core material 110, and the core material 110 has a lower coefficient of linear thermal expansion than the thermoplastic resin layer 120. Therefore, the overall coefficient of linear thermal expansion of the thermoplastic resin sheet 100 is lower than when the thermoplastic resin sheet 100 does not have a core material 110, that is, it is close to the coefficient of linear thermal expansion of the current collector 202. Consequently, when the thermoplastic resin sheet 100 is heated to assemble the battery 200 as described later, the distortion of the thermoplastic resin layer 120 and, by extension, the thermoplastic resin sheet 100 is suppressed, and higher adhesion or higher sealing performance can be achieved.

[0039] Figure 4 shows a battery 200X equipped with a thermoplastic resin sheet 100X according to a comparative example. Battery 200X is the same as battery 200, except that the thermoplastic resin sheet 100X does not have a core material. Figure 4(a) shows the state before the thermoplastic resin sheet 100X is installed, and Figure 4(b) shows the state after the thermoplastic resin sheet 100X is installed, that is, after heating to a temperature above the melting point of the thermoplastic resin and applying pressure. Because the thermoplastic resin sheet 100X according to the comparative example does not have a core material, when heated and pressurized it tends to spread in the planar direction, and as shown in Figure 4(b), it can spread both inward and outward. This results in battery 200X being formed with a thickness and external dimensions different from the design. In addition, there is a risk that the thermoplastic resin sheet 100X may come into contact with the positive electrode layer 204 or the negative electrode layer 206.

[0040] In contrast, in a battery 200 equipped with a thermoplastic resin sheet 100, since the thermoplastic resin sheet 100 has a core material 110, the spreading of the thermoplastic resin layer 120 in the planar direction is suppressed, thus avoiding the problems of the comparative example described above.

[0041] Next, we will explain the manufacturing method of battery 200.

[0042] Figure 5 is a process diagram showing the manufacturing process S20 of the battery 200. The manufacturing process S20 includes a preparation process S22 in which a thermoplastic resin sheet 100, a current collector 202, a positive electrode layer 204, a negative electrode layer 206, a separator 208, and an electrolyte 210 are prepared, and an assembly process S24 in which the prepared components are assembled.

[0043] In assembly step S24, two thermoplastic resin sheets 100 are sandwiched together using a predetermined jig and pressed, and the thermoplastic resin sheets 100 are heated through the current collectors 202 using a predetermined heating device to moderately melt the thermoplastic resin layer 120, and then the thermoplastic resin layer 120 is cooled and solidified. The temperature at which the thermoplastic resin sheets 100 are heated is higher than the melting point of the thermoplastic resin layer 120 and lower than the melting point of the core material 110. In this case, the core material 110 does not melt, and therefore its shape can be maintained.

[0044] The present disclosure has been described above based on embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure. Such modifications will be described below.

[0045] (modified version) Figure 6 is a cross-sectional view of a modified thermoplastic resin sheet 100. Figure 6 corresponds to Figure 1. In this example, the core material 110 has a double-layer structure. Specifically, the core material 110 includes an inner portion 110a and an outer portion 110b that sandwiches the inner portion 110a.

[0046] Figure 7 is a cross-sectional view showing a single fiber among many fibers in a thermoplastic resin sheet 100 where the core material 110 is a fibrous structure, according to another modified example. In this example, each fiber has a double structure. Specifically, the fibers of the core material 110 include an inner, string-like portion 110a located on the inside, and a hollow, string-like outer portion 110b that surrounds the inner portion 110a.

[0047] These core materials 110 have a lower coefficient of linear thermal expansion than the thermoplastic resin layer 120, at least in their inner portion 110a.

[0048] The inner portion 110a preferably has a higher melting point than the thermoplastic resin layer 120. The outer portion 110b has a lower melting point than the inner portion 110a. The outer portion 110b may have the same melting point as or lower than the thermoplastic resin layer 120. In this case, the outer portion 110b may be thinner than the inner portion 110a. When the thermoplastic resin sheet 100 is installed between the first member 10 and the second member 12, the thermoplastic resin sheet 100 is heated to a temperature higher than the melting point of the thermoplastic resin layer 120 and the outer portion 110b, and lower than the melting point of the inner portion 110a. As a result, the inner portion 110a does not melt, and the shape of the core material 110 can be maintained. The outer portion 110b melts together with the thermoplastic resin layer 120, and is therefore firmly bonded to the thermoplastic resin layer 120. In other words, the shape of the core material 110 can be maintained and it can be firmly bonded to the thermoplastic resin layer 120.

[0049] The inner portion 110a may be formed of a polyester resin, such as PET. The outer portion 110b may be formed of polyethylene, which has a lower melting point than polyester resins. Since polyethylene is compatible with thermoplastic resins, good heat welding (impregnation) between the outer portion 110b and the thermoplastic resin layer 120 is possible.

[0050] The above embodiments and variations can be generalized to obtain the following embodiments.

[0051] [Aspect 1] A sheet of thermoplastic resin, A thermoplastic resin sheet having a sheet-like core material with a coefficient of thermal expansion lower than that of the thermoplastic resin.

[0052] [Aspect 2] The melting point of the core material is higher than the melting point of the thermoplastic resin. A thermoplastic resin sheet as described in Embodiment 1.

[0053] [Aspect 3] The heat resistance temperature of the core material is higher than the melting point of the thermoplastic resin. A thermoplastic resin sheet as described in Embodiment 1.

[0054] [Aspect 4] The aforementioned core material is resin. A thermoplastic resin sheet according to any one of embodiments 1 to 3.

[0055] [Aspect 5] The aforementioned core material is a fibrous structure. A thermoplastic resin sheet according to any one of embodiments 1 to 4.

[0056] [Aspect 6] The core material is impregnated with a thermoplastic resin. A thermoplastic resin sheet according to any one of embodiments 1 to 5.

[0057] [Aspect 7] The core material is a fibrous structure, and each fiber has a double structure including an inner portion with a higher melting point than the thermoplastic resin and an outer portion with a lower melting point than the inner portion. The melting point of the outer portion is the same as or lower than the melting point of the thermoplastic resin. A thermoplastic resin sheet according to any one of embodiments 1 to 6.

[0058] [Aspect 8] A method for manufacturing a thermoplastic resin sheet according to any one of embodiments 1 to 7, This includes sandwiching the core material between sheets of thermoplastic resin. A method for manufacturing thermoplastic resin sheets.

[0059] [Aspect 9] A method for manufacturing a thermoplastic resin sheet according to any one of embodiments 1 to 7, This includes immersing the core material in the thermoplastic resin. A method for manufacturing thermoplastic resin sheets.

[0060] [Aspect 10] A method for manufacturing a battery, The preparation of a current collector and a component including a thermoplastic resin sheet as described in any of embodiments 1 to 7, It involves assembling the prepared components, The assembly described above includes heating the thermoplastic resin sheet while the thermoplastic resin sheet is sandwiched between the current collectors. Battery manufacturing method.

[0061] [Aspect 11] The aforementioned heating includes heating to a temperature higher than the melting point of the thermoplastic resin and lower than the melting point of the core material. A method for manufacturing a battery as described in aspect 10. [Explanation of Symbols]

[0062] 100 thermoplastic resin sheet, 110 core material, 110a inner part, 110b outer part, 120 thermoplastic resin layer, 200 battery, 202 current collector.

Claims

1. A sheet of thermoplastic resin, A thermoplastic resin sheet having a sheet-like core material with a coefficient of thermal expansion lower than that of the thermoplastic resin.

2. The melting point of the core material is higher than the melting point of the thermoplastic resin. The thermoplastic resin sheet according to claim 1.

3. The heat resistance temperature of the core material is higher than the melting point of the thermoplastic resin. The thermoplastic resin sheet according to claim 1.

4. The aforementioned core material is resin. The thermoplastic resin sheet according to claim 1.

5. The aforementioned core material is a fibrous structure. The thermoplastic resin sheet according to claim 1.

6. The core material is impregnated with a thermoplastic resin. The thermoplastic resin sheet according to claim 1.

7. The core material is a fibrous structure, and each fiber has a double structure including an inner portion with a higher melting point than the thermoplastic resin and an outer portion with a lower melting point than the inner portion. The melting point of the outer portion is the same as or lower than the melting point of the thermoplastic resin. The thermoplastic resin sheet according to claim 1.

8. A method for manufacturing a thermoplastic resin sheet according to any one of claims 1 to 7, This includes sandwiching the core material between sheets of thermoplastic resin. A method for manufacturing thermoplastic resin sheets.

9. A method for manufacturing a thermoplastic resin sheet according to any one of claims 1 to 7, This includes immersing the core material in the thermoplastic resin. A method for manufacturing thermoplastic resin sheets.

10. A method for manufacturing a battery, The preparation of a component comprising a current collector and a thermoplastic resin sheet according to any one of claims 1 to 7, It involves assembling the prepared components, The assembly described above includes heating the thermoplastic resin sheet while the thermoplastic resin sheet is sandwiched between the current collectors. Battery manufacturing method.

11. The aforementioned heating includes heating to a temperature higher than the melting point of the thermoplastic resin and lower than the melting point of the core material. A method for manufacturing a battery according to claim 10.

Images