Thermoplastic resin sheet, method for producing thermoplastic resin sheet, and method for producing battery having thermoplastic resin sheet

Abstract

The invention relates to a thermoplastic resin sheet, a method for manufacturing the thermoplastic resin sheet, and a method for manufacturing a battery. This thermoplastic resin sheet is a sheet of a thermoplastic resin, and the thermoplastic resin sheet has a sheet-like core material having a lower coefficient of thermal expansion than the thermoplastic resin. According to the present invention, deformation of the thermoplastic resin sheet can be suppressed.

Description

Technical Field

[0001] This invention relates to thermoplastic resin sheets, methods for manufacturing thermoplastic resin sheets, and methods for manufacturing batteries having thermoplastic resin sheets. Background Technology

[0002] A thermoplastic resin sheet is known to function as an adhesive sheet, which holds two components at a certain distance and joins them together. For example, Patent Document 1 discloses a thermoplastic resin sheet having functional groups introduced on its surface through surface treatment, and exhibiting excellent initial adhesion and electrolyte resistance. Furthermore, a thermoplastic resin sheet is also known to function as a sealing sheet, which seals between two components.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: International Publication No. 2015 / 198737.

[0006] The problem the invention aims to solve

[0007] When a thermoplastic resin sheet is installed between two components, the thermoplastic resin sheet is heated to melt the thermoplastic resin inside. However, if the linear thermal expansion coefficients of the two components are low, the thermoplastic resin sheet may sometimes deform due to the difference in linear thermal expansion coefficients between the thermoplastic resin and the two components.

[0008] The present invention was made in response to the above-mentioned problems, and one of the exemplary objectives of one aspect of the present invention is to provide a technique for suppressing the deformation of thermoplastic resin sheets. Summary of the Invention

[0009] Solution for solving the problem

[0010] To address the aforementioned problems, one embodiment of the present invention provides a thermoplastic resin sheet having a sheet-like core material with a coefficient of thermal expansion lower than that of thermoplastic resin.

[0011] Another aspect of the present invention is a method for manufacturing a thermoplastic resin sheet. This method is a method for manufacturing a thermoplastic resin sheet as described in any of the above-described aspects, the method comprising clamping a core material with a sheet of thermoplastic resin.

[0012] Another aspect of the present invention is a method for manufacturing a thermoplastic resin sheet. This method is a method for manufacturing a thermoplastic resin sheet as described in any of the above-described aspects, wherein the manufacturing method includes impregnating a core material in the thermoplastic resin.

[0013] Another aspect of the present invention is a method for manufacturing a battery. This method includes the steps of: preparing a constituent element comprising a current collector and a thermoplastic resin sheet as described in any of the above embodiments; and assembling the prepared constituent element. Assembly includes heating the thermoplastic resin sheet while it is held in place by the current collector.

[0014] Invention Effects

[0015] According to one aspect of the present invention, deformation of thermoplastic resin sheets can be suppressed. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of the thermoplastic resin sheet used in the embodiment.

[0017] Figure 2 It is shown Figure 1 A process diagram illustrating the manufacturing process of thermoplastic resin sheets.

[0018] Figure 3 It shows having Figure 1 A diagram of a thermoplastic resin sheet battery.

[0019] Figure 4 (a) and (b) are diagrams showing batteries with thermoplastic resin sheets of comparative examples.

[0020] Figure 5 It is shown Figure 3 A process diagram illustrating the manufacturing process of a battery.

[0021] Figure 6 This is a cross-sectional view of a modified thermoplastic resin sheet.

[0022] Figure 7 This is a cross-sectional view of one of the multiple fibers in the case where the core material of the thermoplastic resin sheet in the modified example is a fiber structure. Detailed Implementation

[0023] Before detailing the embodiments, an overview of the embodiments will be provided. This embodiment relates to a thermoplastic resin sheet. The thermoplastic resin sheet functions as an adhesive sheet that holds two components at a certain distance and joins them together. In this case, the thermoplastic resin sheet penetrates into the fine irregularities on the surfaces of the two components by melting the thermoplastic resin, and the thermoplastic resin is cured in this state, thereby joining the two components to the thermoplastic resin sheet, that is, joining the two components to each other via the thermoplastic resin. Furthermore, the thermoplastic resin sheet also functions as a sealing sheet that seals between the two components. In this case, the thermoplastic resin sheet penetrates into the fine irregularities on the surfaces of the two components by melting the thermoplastic resin, thereby achieving sufficient sealing performance.

[0024] In all cases, when a thermoplastic resin sheet is installed between two components, the sheet is heated to melt the resin. However, if the two components are metals or have low coefficients of linear thermal expansion, the sheet may deform due to the difference in their coefficients of linear thermal expansion. In this embodiment, the thermoplastic resin sheet has a core material with a coefficient of linear thermal expansion lower than that of the thermoplastic resin. This reduces the overall coefficient of linear thermal expansion of the thermoplastic resin sheet, thereby minimizing the difference in coefficients of linear thermal expansion between the sheet and the two components, and suppressing deformation of the sheet.

[0025] Preferred embodiments will now be described with reference to the accompanying drawings. These embodiments are illustrative and do not limit the invention; not all features or combinations thereof described in the embodiments are essential parts of the invention. Identical or equivalent constituent elements, components, and processes shown in the drawings are labeled with the same reference numerals, and repeated descriptions are omitted as appropriate.

[0026] Figure 1 This is a cross-sectional view of the thermoplastic resin sheet 100 of the embodiment. Figure 1 In this assembly, a thermoplastic resin sheet 100 is installed between the first component 10 and the second component 12. The thermoplastic resin sheet 100 functions as an adhesive sheet that maintains a certain distance between and joins the first component 10 and the second component 12, and / or as a sealing sheet that seals the space between the first component 10 and the second component 12.

[0027] The thermoplastic resin sheet 100 includes a sheet-like core material 110 and two thermoplastic resin layers 120 as 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.

[0028] There is no particular limitation on the relationship between the thickness of the core material 110 and the two thermoplastic resin layers 120. That is, the core material 110 can be thicker than the thermoplastic resin layer 120, or the core material 110 can be thinner than the thermoplastic resin layer 120. The thicknesses of the two thermoplastic resin layers 120 are typically the same, but they can also be different.

[0029] The thermoplastic resin layer 120 can have a low coefficient of linear thermal expansion, specifically 5.0 × 10⁻⁶. -4 In this case, even if components 10 and 12 are metals (e.g., aluminum, stainless steel, copper, nickel, etc.), that is, even if components 10 and 12 have low coefficients of linear thermal expansion, the deformation of the thermoplastic resin layer 120 and even the thermoplastic resin sheet 100 can be suppressed because the difference in the coefficients of linear thermal expansion between the thermoplastic resin layer 120 and components 10 and 12 is small.

[0030] The thermoplastic resin layer 120 preferably has electrolyte resistance. Here, "electrolyte resistance" refers to its resistance to electrolytes, meaning it does not undergo a chemical reaction even when in contact with an electrolyte, and therefore does not deteriorate even when in contact with an electrolyte. When the thermoplastic resin layer 120 has electrolyte resistance, the thermoplastic resin sheet 100 can be used in environments where it comes into contact with electrolytes.

[0031] The thermoplastic resin layer 120 preferably exhibits excellent electrolyte adhesion. Here, "electrolyte adhesion" refers to the property of maintaining adhesive strength even when in contact with an electrolyte. When the thermoplastic resin layer 120 exhibits excellent electrolyte adhesion, the thermoplastic resin sheet 100 can be used as an adhesive sheet in environments where it comes into contact with an electrolyte.

[0032] The thermoplastic resin layer 120 can be a polyolefin resin that has been given functional groups through surface treatment. Examples of polyolefin resins include polyethylene, polypropylene, and ethylene-propylene copolymers. In this case, the thermoplastic resin layer 120 exhibits excellent electrolyte adhesion and excellent initial adhesion. Here, "initial adhesion" refers to the immediate adhesion after bonding, and can also be described as adhesion before contact with the electrolyte, as opposed to "electrolyte resistance adhesion."

[0033] The thermoplastic resin layer 120 preferably has a low Young's modulus, specifically below 100 MPa. In this case, the thermoplastic resin layer 120 is less likely to peel off from the components 10 and 12.

[0034] The thermoplastic resin layer 120 preferably has low hygroscopicity. There is a concern that during bonding, the thermoplastic resin sheet 100 will be heated, and water absorbed by the thermoplastic resin layer 120 will vaporize and escape from the thermoplastic resin layer 120. Sometimes, pores may remain in the thermoplastic resin layer 120, potentially causing damage to the layer. Therefore, lower hygroscopicity of the thermoplastic resin layer 120 is preferred.

[0035] The core material 110 has a lower coefficient of linear thermal expansion than that of thermoplastic resin. Therefore, compared to the case where the thermoplastic resin sheet 100 does not have a core material 110, i.e., the thermoplastic resin sheet 100 consists only of a thermoplastic resin layer 120, the overall coefficient of linear thermal expansion of the thermoplastic resin sheet 100 is lower. Thus, even when components 10 and 12 are metals and have low coefficients of linear thermal expansion, the difference in coefficients of linear thermal expansion between the thermoplastic resin sheet 100 and components 10 and 12 is small, which can suppress deformation of the thermoplastic resin sheet 100. The core material 110 can also be formed from a polyester resin having a low coefficient of linear thermal expansion similar to that of metal, specifically PET (polyethylene terephthalate).

[0036] When the core material 110 is formed from a raw material with a melting point (such as resin, metal, etc.), the melting point of the core material 110 is preferably higher than that of the thermoplastic resin. Therefore, when mounting the thermoplastic resin sheet 100, 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, thus maintaining its shape. Because the core material 110 maintains its shape, the expansion of the thermoplastic resin layer 120 in the surface direction when it melts is suppressed.

[0037] When the core material 110 is formed from a raw material that does not have a melting point (such as wood, paper, etc.), the heat resistance temperature of the core material 110 is preferably higher than that of the thermoplastic resin. The heat resistance temperature can be the temperature at which the core material 110 can maintain its shape. Therefore, when mounting the thermoplastic resin sheet 100, if 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, the shape of the core material 110 can be maintained. With the presence of a core material 110 whose shape is maintained, the expansion of the thermoplastic resin layer 120 in the surface direction when it melts is suppressed.

[0038] The core material 110 preferably has a structure that can be impregnated with thermoplastic resin, specifically having at least fine pores and minor irregularities on its surface. In this case, the contact area between the core material 110 and the thermoplastic resin layer 120 is increased, thus improving the bonding strength between the core material and the thermoplastic resin. As a structure that can be impregnated with thermoplastic resin, the core material 110 can be a fibrous structure made of fibers. For example, the core material 110 can be a non-woven, woven, or braided fibrous structure. In this case, the core material 110 can be made of resin or metal. Furthermore, the core material 110 can also be made of wood, specifically paper.

[0039] The core material 110 can also be a component without fine pores or minor irregularities on its surface. In this case, the core material 110 can be a sheet material made of resin, metal, or the like.

[0040] The core material 110 preferably has electrolyte resistance. In this case, the thermoplastic sheet 100 can be used in environments that come into contact with electrolytes, even when the core material 110 is exposed.

[0041] The core material 110 preferably has excellent adhesion to the thermoplastic resin layer 120. In this case, the thermoplastic resin layer 120 is not easily peeled off from the core material 110.

[0042] The core material 110 preferably has low hygroscopicity, for example, lower than that of the thermoplastic resin layer 120. The reasons for preferring low hygroscopicity are the same as those for the thermoplastic resin layer 120.

[0043] The above describes the structure of the thermoplastic resin sheet 100. The manufacturing method of the thermoplastic resin sheet 100 will be explained next.

[0044] Figure 2 This is a process diagram showing the manufacturing process S10 of the thermoplastic resin sheet 100. The manufacturing process S10 includes the following processes: 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 the thermoplastic resin.

[0045] For example, in the forming process S14, the core material 110 is sandwiched between two sheets of thermoplastic resin, and pressure is applied while heating, thereby impregnating the core material 110 with thermoplastic resin, and forming two thermoplastic resin layers 120 that sandwich the core material 110.

[0046] For example, in the forming process S14, the core material 110 is conveyed in a roll-to-roll manner. During the conveying process, the core material 110 is impregnated in molten thermoplastic resin, thereby impregnating the core material 110 with thermoplastic resin and forming two thermoplastic resin layers 120 that hold the core material 110 together.

[0047] The following describes an application example of thermoplastic resin sheet 100.

[0048] Figure 3 This diagram illustrates a battery 200 having thermoplastic resin sheets 100. The battery 200 is a bipolar battery. The battery 200 has the following structure: a positive electrode layer 204 and a negative electrode layer 206 are stacked on each surface of rectangular plate-shaped or sheet-shaped current collectors 202, and these layers are overlapped multiple times. A spacer 208 is provided between opposing positive electrode layers 204 and negative electrode layers 206. Adjacent current collectors 202 are held at a certain distance and joined by two thermoplastic resin sheets 100. The spacer 208 is held between adjacent current collectors 202 by being clamped by the two thermoplastic resin sheets 100 at its periphery. The battery 200 is filled with an electrolyte 210 and sealed by the thermoplastic resin sheets 100. That is, in this battery 200, the thermoplastic resin sheet 100 functions as both an adhesive sheet and a sealing sheet.

[0049] The current collector 202 is made of metals such as aluminum, stainless steel, copper, and nickel, and has a low coefficient of linear thermal expansion, specifically 1.0 × 10⁻⁶. -4The following is an extremely low coefficient of linear thermal expansion. In contrast, the thermoplastic resin sheet 100 has a core material 110, which 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 that of the thermoplastic resin sheet 100 without the core material 110, i.e., closer to the coefficient of linear thermal expansion of the current collector 202. Therefore, the deformation of the thermoplastic resin layer 120 and even the thermoplastic resin sheet 100 when heated for assembling the battery 200, as described later, is suppressed, enabling higher adhesion or higher sealing performance.

[0050] Figure 4 This is a diagram showing a battery 200X with a comparative example of a thermoplastic resin sheet 100X. Battery 200X is identical to battery 200 except that the thermoplastic resin sheet 100X does not have a core material. Figure 4 (a) shows the condition before the thermoplastic resin sheet 100X is installed. Figure 4 (b) Shows the situation after the thermoplastic resin sheet 100X is installed, that is, after being heated to a temperature above the melting point of the thermoplastic resin while being pressurized. The comparative example thermoplastic resin sheet 100X does not have a core material; therefore, if pressure is applied while heating, it is prone to expand along the surface direction, such as... Figure 4 As shown in (b), it extends both inward and outward. This results in the battery 200X being formed with a thickness and external dimensions different from the design. In addition, the thermoplastic sheet 100X may come into contact with the positive electrode layer 204 or the negative electrode layer 206.

[0051] In contrast, in the battery 200 having a thermoplastic resin sheet 100, the thermoplastic resin sheet 100 has a core material 110, so the expansion of the thermoplastic resin layer 120 along the surface direction is suppressed, avoiding the problem of the comparative example mentioned above.

[0052] The manufacturing method of battery 200 will be explained next.

[0053] Figure 5 This is a process diagram showing the manufacturing process S20 of battery 200. Manufacturing process S20 includes the following processes: preparation process S22, which prepares thermoplastic resin sheet 100, current collector 202, positive electrode layer 204, negative electrode layer 206, spacer 208 and electrolyte 210; and assembly process S24, which assembles the prepared constituent elements.

[0054] In assembly step S24, adjacent current collectors 202 along with two thermoplastic resin sheets 100 are clamped and pressurized using a specified clamp. A specified heating device is used to heat the thermoplastic resin sheets 100 through the current collectors 202, causing the thermoplastic resin layer 120 to partially melt. The thermoplastic resin layer 120 is then cooled and solidified. The heating temperature of the thermoplastic resin sheets 100 is higher than the melting point of the thermoplastic resin layer 120 but lower than the melting point of the core material 110. In this case, the core material 110 does not melt, thus maintaining its shape.

[0055] The present invention has been described above based on embodiments. Those skilled in the art should understand that these embodiments are merely examples, and various modifications exist in the combination of their constituent elements and processing techniques; such modifications also fall within the scope of the present invention. Such modifications are described below.

[0056] (Modified example)

[0057] Figure 6 This is a cross-sectional view of the thermoplastic resin sheet 100 of the modified example. Figure 6 Corresponding to Figure 1 In this example, the core material 110 has a dual structure. Specifically, the core material 110 includes an inner portion 110a and an outer portion 110b that holds the inner portion 110a.

[0058] Figure 7 This is a cross-sectional view of one of the multiple fibers in a case where the core material 110 of the thermoplastic resin sheet 100 is a fibrous structure, illustrating another variation. In this example, each fiber has a dual structure. Specifically, the fiber of the core material 110 includes an inner fibrous portion 110a located on the inside and a hollow fibrous outer portion 110b covering the periphery of the inner fibrous portion 110a.

[0059] Of these core materials 110, at least the inner portion 110a has a lower coefficient of linear thermal expansion than the thermoplastic resin layer 120.

[0060] The inner portion 110a preferably has a melting point higher than that of the thermoplastic resin layer 120. The outer portion 110b has a melting point lower than that of the inner portion 110a. The outer portion 110b may also have a melting point equal to or lower than that of 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 mounted between the first member 10 and the second member 12, the thermoplastic resin sheet 100 is heated to a temperature higher than that of the thermoplastic resin layer 120 and the outer portion 110b but lower than that of the inner portion 110a. As a result, the inner portion 110a does not melt, thus maintaining the shape of the core material 110. The outer portion 110b melts together with the thermoplastic resin layer 120, thus bonding firmly with the thermoplastic resin layer 120. That is, the shape of the core material 110 can be maintained, and it can be firmly bonded to the thermoplastic resin layer 120.

[0061] 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. Polyethylene is compatible with thermoplastic resins, so the outer portion 110b and the thermoplastic resin layer 120 can be well thermally bonded (impregnated).

[0062] When summarizing the above implementation methods and variations, the following approach can be obtained.

[0063] [Method 1]

[0064] A thermoplastic resin sheet, which is a sheet of thermoplastic resin.

[0065] The aforementioned thermoplastic resin sheet has a sheet-like core material with a coefficient of thermal expansion lower than that of the aforementioned thermoplastic resin.

[0066] [Method 2]

[0067] According to the thermoplastic resin sheet of method 1, wherein,

[0068] The melting point of the core material is higher than that of the thermoplastic resin.

[0069] [Method 3]

[0070] According to the thermoplastic resin sheet of method 1, wherein,

[0071] The heat resistance temperature of the core material is higher than the melting point of the thermoplastic resin.

[0072] [Method 4]

[0073] The thermoplastic resin sheet according to any one of methods 1 to 3, wherein,

[0074] The core material mentioned above is resin.

[0075] [Method 5]

[0076] The thermoplastic resin sheet according to any one of methods 1 to 4, wherein,

[0077] The core material described above is a fiber structure.

[0078] [Method 6]

[0079] The thermoplastic resin sheet according to any one of methods 1 to 5, wherein,

[0080] The core material described above is impregnated with thermoplastic resin.

[0081] [Method 7]

[0082] The thermoplastic resin sheet according to any one of methods 1 to 6, wherein,

[0083] The core material described above is a fibrous structure, and each fiber of the fibrous structure has a dual structure, comprising an inner portion with a melting point higher than that of the thermoplastic resin and an outer portion with a melting point lower than that of the inner portion.

[0084] The melting point of the outer portion is equal to or lower than the melting point of the thermoplastic resin.

[0085] [Method 8]

[0086] A method for manufacturing a thermoplastic resin sheet, which is the method for manufacturing a thermoplastic resin sheet according to any one of methods 1 to 7.

[0087] The manufacturing method described above includes clamping the core material with a sheet of the aforementioned thermoplastic resin.

[0088] [Method 9]

[0089] A method for manufacturing a thermoplastic resin sheet, which is the method for manufacturing a thermoplastic resin sheet according to any one of methods 1 to 7.

[0090] The manufacturing method described above includes impregnating the core material in the aforementioned thermoplastic resin.

[0091] [Method 10]

[0092] A method for manufacturing a battery includes the following steps:

[0093] Prepare constituent elements including a current collector and a thermoplastic resin sheet according to any one of methods 1 to 7; and

[0094] Components for assembly preparation

[0095] The above assembly includes heating the thermoplastic resin sheet while it is held in place by a current collector.

[0096] [Method 11]

[0097] According to the battery manufacturing method of method 10, wherein,

[0098] The heating described above includes heating to a temperature higher than the melting point of the thermoplastic resin and lower than the melting point of the core material.

[0099] Explanation of reference numerals in the attached figures

[0100] 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 thermoplastic resin sheet, which is a sheet of thermoplastic resin. The thermoplastic resin sheet has a sheet-like core material with a coefficient of thermal expansion lower than that of the thermoplastic resin.

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

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

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

5. The thermoplastic resin sheet according to claim 1, wherein, The core material is a fiber structure.

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

7. The thermoplastic resin sheet according to claim 1, wherein, The core material is a fibrous structure, and each fiber of the fibrous structure has a dual structure, comprising an inner portion with a melting point higher than that of the thermoplastic resin and an outer portion with a melting point lower than that of the inner portion. The melting point of the outer portion is equal to or lower than the melting point of the thermoplastic resin.

8. A method for manufacturing a thermoplastic resin sheet, which is the method for manufacturing a thermoplastic resin sheet according to any one of claims 1 to 7. The manufacturing method includes clamping the core material with a sheet of the thermoplastic resin.

9. A method for manufacturing a thermoplastic resin sheet, which is the method for manufacturing a thermoplastic resin sheet according to any one of claims 1 to 7. The manufacturing method includes impregnating the core material in the thermoplastic resin.

10. A method for manufacturing a battery, comprising the following steps: Prepare a constituent element comprising a current collector and a thermoplastic resin sheet according to any one of claims 1 to 7; and Components for assembly preparation The assembly includes heating the thermoplastic sheet while it is held in place by a current collector.

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

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