Solid electrolyte carrier sheet

Abstract

To provide an extremely lightweight and thin unwoven fabric and a solid electrolyte carrier sheet.SOLUTION: There is provided a solid electrolyte carrier sheet which is a wet type unwoven fabric consisting of binder fibers (A) and non-binder fibers (B). In the solid electrolyte carrier sheet, the basis weight of the wet type unwoven fabric is 1 to 9 g / m2, the thickness is 2 to 9 μm and Gurley gas permeability is 0.5 sec / 100 cc or less. The average fiber diameter of the binder fibers (A) is 1 to 9 μm, and the non-binder fibers (B) consist of only non-binder fibers (B1) or consist of the non-binder fibers (B1) and non-binder fibers (B2). The average fiber diameter of the non-binder fibers (B1) is 0.1 to 0.9 μm, and the average fiber diameter of the non-binder fibers (B2) is 1 to 9 μm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sheet for supporting a solid electrolyte.

Background Art

[0002] In recent years, all-solid-state batteries have attracted attention as a next-generation technology for lithium-ion batteries. Conventional lithium-ion batteries use an organic solvent-based electrolyte, while all-solid-state batteries use a solid electrolyte. Since the conventional organic solvent-based electrolyte has a high flammability, there is a risk of ignition, and there is also a problem that the charge and discharge performance of the lithium-ion battery varies greatly depending on the temperature.

[0003] On the other hand, since all-solid-state batteries use a non-flammable solid electrolyte, the risk of ignition is small, the electrochemical stability is high, and it can be expected to exhibit stable performance in a wide temperature range. As the solid electrolyte, a sulfide-based electrolyte, an oxide-based electrolyte, etc. are used. Generally, this solid electrolyte is dispersed in a solvent together with a binder to prepare a slurry liquid, and this is applied to form a solid electrolyte layer.

[0004] However, in this preparation method, since the strength of the solid electrolyte layer is low, the handleability is poor. The handleability can be improved by increasing the film thickness, but since the lithium ion conductivity in the electrolyte depends on the thickness of the electrolyte layer, thinning of the solid electrolyte layer is required. Therefore, in order to achieve both handleability and lithium ion conductivity, it has been proposed to use a nonwoven fabric combining polypropylene fibers, polyethylene fibers, and fibrillated heat-resistant fibers as a supporting sheet for the solid electrolyte layer (Patent Document 1).

[0005] However, polypropylene and polyethylene, which are materials constituting the nonwoven fabric, have a melting point of 120 to 160°C and low heat resistance, so there is a risk that the shape of the solid electrolyte layer may change when exposed to high temperatures. The sheet for supporting a solid electrolyte requires thermal stability in order to exhibit stable battery performance in a wide temperature range.

[0006] Among these, fibrillated heat-resistant fibers are usually obtained by subjecting heat-resistant fibers with a relatively large fiber diameter to a fibrillation pretreatment such as beating with a refiner or beater. In this fibrillation pretreatment step, there is a risk of metal foreign matter being mixed in, and it is difficult to make the fiber diameter and cut length uniform. A nonwoven fabric obtained using non-uniform fibers causes non-uniformity in the thickness, voids, and pore diameter of the solid electrolyte layer.

[0007] Also, in order to make the solid electrolyte layer thinner, a solid electrolyte sheet with a nonwoven fabric thickness of 10 to 25 μm has been proposed (Patent Document 2). However, it has been difficult with conventional techniques to make the nonwoven fabric thinner than this.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above background. An object of the present invention is to provide a lightweight, thin-film, and uniform solid electrolyte-supporting sheet.

Means for Solving the Problems

[0010] That is, the present invention is a solid electrolyte-supporting sheet which is a wet nonwoven fabric composed of binder fibers (A) and non-binder fibers (B), and the wet nonwoven fabric has a basis weight of 1 to 9 g / m 2It has a thickness of 2 to 9 μm, a Gurley air permeability of 0.5 seconds / 100 cc or less, and the binder fiber (A) has an average fiber diameter of 1 to 9 μm. The non-binder fiber (B) consists of only the non-binder fiber (B1) or consists of the non-binder fiber (B1) and the non-binder fiber (B2). The non-binder fiber (B1) has an average fiber diameter of 0.1 to 0.9 μm, and the non-binder fiber (B2) has an average fiber diameter of 1 to 9 μm. It is a sheet for supporting a solid electrolyte, characterized by the above.

[0011] In addition, when the non-binder fiber (B) consists of only the non-binder fiber (B1), the present invention is a sheet for supporting a solid electrolyte, which is a wet non-woven fabric composed of the binder fiber (A) and the non-binder fiber (B). The basis weight of the wet non-woven fabric is 1 to 9 g / m 2 It has a thickness of 2 to 9 μm, a Gurley air permeability of 0.5 seconds / 100 cc or less, and the binder fiber (A) has an average fiber diameter of 1 to 9 μm. The non-binder fiber (B) consists of only the non-binder fiber (B1), and the non-binder fiber (B1) has an average fiber diameter of 0.1 to 0.9 μm. It is a sheet for supporting a solid electrolyte, characterized by the above.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a lightweight and thin film sheet for supporting a solid electrolyte, which is uniform.

Embodiments for Carrying out the Invention

[0013] Hereinafter, the present invention will be described in detail. 〔Sheet for Supporting Solid Electrolyte〕 The wet non-woven fabric of the sheet for supporting a solid electrolyte of the present invention is composed of a binder fiber (A) and a non-binder fiber (B).

[0014] 〔Binder Fiber (A)〕 The binder fiber (A) is a heat-fusible fiber. For example, core-sheath type composite fibers or undrawn fibers can be used, and undrawn fibers are preferably used. When undrawn fibers are used, since the fibers are adhered to each other due to the softening of the fiber surface, film formation at the adhesion points is less likely to occur, and the uniformity is excellent.

[0015] The average fiber diameter of the binder fiber (A) is 1 to 9 μm, preferably 3 to 9 μm. If the average fiber diameter of the binder fiber is less than 1 μm, the rigidity and strength of the nonwoven fabric may be insufficient. If it exceeds 9 μm, it may be difficult to form a thin film, and thickness unevenness of the nonwoven fabric may easily occur.

[0016] 〔Core-sheath type composite fiber〕 As the core-sheath type composite fiber, a polymer of a binder component (for example, amorphous copolyester) that fuses at a temperature of 80 to 170 °C to exhibit an adhesion effect is arranged in the sheath portion, and another polymer having a melting point 20 °C or higher than these polymers (for example, polyesters such as polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate) is arranged in the core portion. The core-sheath type composite fiber is preferred.

[0017] As the core-sheath type composite fiber, those in which the binder component forms all or part of the surface of the single fiber can be used, and eccentric core-sheath type composite fibers or side-by-side type composite fibers may also be used.

[0018] The core-sheath type composite fiber is preferably a polyester fiber. Since polyester fibers have excellent dispersibility in water, fiber aggregation can be suppressed, and a nonwoven fabric with few unevenness and hole defects and excellent uniformity can be produced even with a low basis weight nonwoven fabric.

[0019] 〔Undrawn fiber〕 As the undrawn fiber, undrawn fibers of organic polymers are used, and preferably, undrawn fibers of polyester fibers and / or undrawn fibers of polyphenylene sulfide are used.

[0020] The undrawn fiber preferably has a birefringence Δn of 0.05 or less. These undrawn fibers are undrawn fibers spun at a spinning speed of, for example, 800 to 1200 m / min, preferably 900 to 1150 m / min.

[0021] The undrawn fibers are preferably undrawn polyester fibers. Since undrawn polyester fibers have excellent dispersibility in water, aggregation of the fibers can be suppressed, and a nonwoven fabric with few unevenness and hole defects and excellent uniformity can be produced even with a low basis weight nonwoven fabric.

[0022] Examples of the polyester of the undrawn polyester fibers include polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate. From the viewpoints of productivity and dispersibility in water, polyethylene terephthalate and polytrimethylene terephthalate are preferably used.

[0023] As the polyphenylene sulfide of the undrawn polyphenylene sulfide fibers, a polymer having phenylene sulfide as a repeating unit is used. Examples of this phenylene sulfide include p-phenylene sulfide, m-phenylene sulfide, o-phenylene sulfide, phenylene sulfide sulfone, phenylene sulfide ketone, phenylene sulfide ether, diphenylene sulfide, substituent-containing phenylene sulfide, and branched structure-containing phenylene sulfide, and p-phenylene sulfide is preferably used.

[0024] In this case, p-phenylene sulfide preferably occupies 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol% of the repeating unit. That is, poly(p-phenylene sulfide) is most preferred.

[0025] 〔Non-binder fiber (B)〕 The non-binder fiber (B) consists of only the non-binder fiber (B1) or consists of the non-binder fiber (B1) and the non-binder fiber (B2).

[0026] The non-binder fiber (B1) has an average fiber diameter of 0.1 to 0.9 μm. If the average fiber diameter of the non-binder fiber (B1) is less than 0.1 μm, it becomes difficult to disperse, and it may pass through the mesh of the paper-making process, making it difficult to form a non-woven fabric. On the other hand, if it exceeds 0.9 μm, the number of constituent fibers is small when making a lightweight non-woven fabric, so the fiber network may become weak and sheet formation may become difficult.

[0027] When the non-binder fiber (B) consists of the non-binder fiber (B1) and the non-binder fiber (B2), the non-binder fiber (B2) has an average fiber diameter of 1 to 9 μm. If the average fiber diameter of the non-binder fiber (B2) is less than 1 μm, fiber entanglement and aggregation are likely to occur, and non-uniformity of the non-woven fabric is likely to occur. On the other hand, if it exceeds 9 μm, non-uniformity of the non-woven fabric may occur, and the number of constituent fibers is small when making a lightweight non-woven fabric, so the fiber network may become weak and sheet formation may become difficult.

[0028] When the non-binder fiber (B) consists of the non-binder fibers (B1) and (B2), examples of the non-binder fibers (B1) and (B2) include polyester fibers, polyphenylene sulfide fibers, polyamide fibers, and polyolefin fibers. Among them, the melting point of the preferred polyester fiber is 260 to 270 °C, which is excellent in heat resistance, solvent resistance, and hydrolysis resistance, and is a highly reliable fiber as a separator or a sheet for supporting a solid electrolyte. All of these are preferably drawn fibers.

[0029] When the non-binder fiber (B) consists only of the non-binder fiber (B1), the non-binder fiber (B1) is preferably a polyester fiber, and more preferably a drawn polyester fiber. Since the polyester fiber has excellent dispersibility in water, it can suppress fiber aggregation, and a non-woven fabric with few unevennesses and hole defects and excellent uniformity can be produced even with a low basis weight non-woven fabric.

[0030] Examples of the polyester for forming the polyester fiber include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polyethylene naphthalate. The polyester may be a copolyester.

[0031] When the non-binder fiber (B) consists only of the non-binder fiber (B1), from the viewpoint of dispersibility in water, it is preferable that both the binder fiber (A) and the non-binder fiber (B1) are polyester fibers.

[0032] When the non-binder fiber (B) consists of the non-binder fiber (B1) and the non-binder fiber (B2), from the viewpoint of dispersibility in water, it is preferable that the binder fiber (A), the non-binder fiber (B1), and the non-binder fiber (B2) are all polyester fibers.

[0033] The non-binder fiber (B1) preferably occupies 5 to 60% by weight of the weight of the wet nonwoven fabric from the viewpoints of the papermaking property of the nonwoven fabric, strength, and dimensional stability.

[0034] 〔Wet nonwoven fabric〕 The sheet for supporting the solid electrolyte of the present invention is a wet nonwoven fabric. By using a wet nonwoven fabric having the following conditions, a lightweight, thin-film, and uniform sheet for supporting the solid electrolyte can be obtained.

[0035] 〔Basis weight〕 The basis weight of the wet nonwoven fabric is 1 to 9 g / m 2 , preferably 1 to 5 g / m 2 , more preferably 1 to 2.5 g / m 2 . If the basis weight is less than 1 g / m 2 , the fiber network may be weak and it may be difficult to form a sheet. On the other hand, if it exceeds 9 g / m 2 , the resistance may increase, and since the volume increases, it is disadvantageous for making the battery compact.

[0036] 〔Thickness〕 The thickness of the wet nonwoven fabric is 2 to 9 μm. If the thickness is less than 2 μm, the strength of the nonwoven fabric may be insufficient, making it difficult to form the sheet for supporting the solid electrolyte. If it exceeds 9 μm, the resistance may increase.

[0037] 〔 Gurley air permeability 〕 The Gurley air permeability of the wet nonwoven fabric is 0.5 seconds / 100 cc or less, preferably 0.1 seconds / 100 cc or less. If the Gurley air permeability exceeds 0.5 seconds / 100 cc, the tightness of the sheet for supporting the solid electrolyte may be too high, and the resistance may increase.

[0038] 〔 Tensile strength 〕 The tensile strength of the wet nonwoven fabric in the MD direction is preferably 0.3 N / 15 mm or more. If the tensile strength is less than 0.3 N / 15 mm, the wet nonwoven fabric is likely to tear. This tensile strength is a value indicating the toughness of the sheet for supporting the solid electrolyte. In order not to cause tearing or splitting of the sheet for supporting the solid electrolyte during the manufacturing process of the sheet for supporting the solid electrolyte or the composite process of the sheet for supporting the solid electrolyte and the solid electrolyte, a certain toughness is required for the wet nonwoven fabric, and the greater the toughness, the better.

[0039] 〔 Thermal shrinkage rate 〕 The thermal shrinkage rate of the wet nonwoven fabric after standing at 180 °C for 1 hour is preferably 10% or less in both the MD direction and the CD direction. If the thermal shrinkage rate exceeds 10%, it is likely to cause shape changes at high temperatures, which is not preferable. This thermal shrinkage rate is preferably low in order to prevent shape changes such as tearing in the solid electrolyte layer due to shrinkage or melting of the sheet for supporting the solid electrolyte when the battery becomes hot.

[0040] 〔 Average pore diameter, maximum pore diameter 〕 The average pore diameter of the wet nonwoven fabric is preferably 20 μm or less. If the average pore diameter exceeds 20 μm, the solid electrolyte is likely to leak through, making it difficult to hold inside the nonwoven fabric, which is not preferable.

[0041] The maximum pore size / average pore size of the nonwoven fabric is preferably 20 or less. If the maximum pore size / average pore size exceeds 20, the nonwoven fabric has uneven pore sizes, which may cause non-uniformity of the solid electrolyte, resulting in reduced lifespan and increased resistance, which is not preferable.

[0042] 〔Porosity〕 The porosity of the wet nonwoven fabric is preferably 60% or more. If the porosity is less than 60%, the wet nonwoven fabric has few voids, making it difficult for the solid electrolyte to enter internally, which may cause non-uniformity of the solid electrolyte, resulting in reduced lifespan and increased resistance, which is not preferable.

[0043] 〔Solid electrolyte sheet〕 The present invention also provides a solid electrolyte sheet according to any one of claims 1 to 6, including a sheet for supporting a solid electrolyte and the solid electrolyte supported on its surface and inside.

[0044] Examples of the solid electrolyte include sulfide-based or oxide-based inorganic solid electrolytes and polymer electrolytes. As methods for compounding these solid electrolytes onto the sheet for supporting the solid electrolyte of the present invention, coating, dipping, and compression molding can be applied.

[0045] 〔Manufacturing method〕 The wet nonwoven fabric of the sheet for supporting the solid electrolyte of the present invention can be manufactured by subjecting it to heat treatment after papermaking using a normal fourdrinier paper machine, cylinder paper machine, vat paper machine, or by combining multiple of these to make multi-layer paper.

[0046] The raw material fibers of the nonwoven fabric are stirred with a pulper for 5 minutes or more to create a fiber slurry. Examples of the device used for fiber stirring include a pulper, refiner, beater, and mill, and preferably a pulper is used.

[0047] A non-woven fabric is made by the wet papermaking method using the prepared fiber slurry. By heat-treating this non-woven fabric, the binder fibers contained in the raw material fibers adhere between the fibers. This heat treatment can be performed using, for example, a Yankee dryer or an air-through dryer.

[0048] The temperature of the heat treatment is, for example, 80 to 200 °C, and the time is, for example, 10 to 600 seconds. After the heat treatment, calendering may be further performed using a metal / metal roller, a metal / paper roller, or a metal / elastic roller. When the wet non-woven fabric has a multi-layer structure, after obtaining the wet non-woven fabric, a plurality of wet non-woven fabrics can be adhered using a calendar machine or the like.

[0049] The solid electrolyte sheet can be manufactured by supporting the solid electrolyte on the surface and inside of the solid electrolyte supporting sheet of the present invention by a conventional method. For example, the solid electrolyte supporting sheet is fixed on a glass plate, the solid electrolyte slurry is coated on one side with a bar coater, dried at 80 to 90 °C for 3 to 10 minutes, and then calendered at room temperature at 20 to 40 kg / cm to obtain a solid electrolyte sheet.

Examples

[0050] Hereinafter, the present invention will be described with reference to examples. 1. Non-woven fabric material In the examples and comparative examples, the following fibers were used. · Binder fiber: Polyester-based undrawn binder fiber (average fiber diameter 4.3 μm, average fiber length 3.0 mm), "Teppirus TK08PN SD 0.2 dtex 3 mm" manufactured by Teijin Frontier Co., Ltd. · Non-binder fiber: Polyester fiber (average fiber diameter 0.7 μm, average fiber length 0.5 mm), "Nanofront" manufactured by Teijin Frontier Co., Ltd. · Non-binder fiber: Polyester fiber (average fiber diameter 3.1 μm, average fiber length 3.0 mm), "Teppirus TA04PN SD 0.1 dtex 3 mm" manufactured by Teijin Frontier Co., Ltd.

[0051] 2. Preparation of solid electrolyte 175 g of "PW-01" manufactured by Ohara Co., Ltd. as an oxide-based solid electrolyte and 30 g of "TRD2001" manufactured by JSR Co., Ltd. as a binder were added to 295 g of distilled water and stirred with a household mixer for 60 seconds. Then, 25 g of "RHEOBYK-425" manufactured by BYK Co., Ltd. was added as a rheology agent and stirred at 300 rpm for 1 hour using a homodisper to obtain a solid electrolyte slurry.

[0052] 3. Measurement and Evaluation The physical properties in the examples were measured and evaluated by the following methods. (1) Fiber diameter and average fiber diameter Using a transmission electron microscope TEM (with a length measurement function), fiber cross-section photos were taken and measured at magnifications of 1000 to 30000 times. For the fiber diameter, the diameter of the circumscribed circle of the single fiber cross-section was used. The average value of n = 5 was taken as the average fiber diameter.

[0053] (2) Fiber length and average fiber length Using a scanning electron microscope (SEM), the fibers were placed lying on a substrate, and the fiber length was measured at magnifications of 10 to 500 times. At that time, the fiber length was measured using the length measurement function of the SEM. The average value of n = 5 was taken as the average fiber length.

[0054] (3) Basis weight It was measured based on JIS P8124 (Method for Measuring the Grammage of Paper).

[0055] (4) Thickness The thickness was measured based on JIS P8118 (Method for Measuring the Thickness and Density of Paper and Paperboard). The measurement load was 75 g / cm 2 Samples were measured 5 times and the average value was taken as the thickness.

[0056] (5) Density It was calculated from the basis weight and thickness by the following formula. Here, W is the basis weight (g / m 2 ), and L is the thickness (mm). Density (g / cm 3 ) = (W / 10000) / (L / 10)

[0057] (6) Porosity It was calculated from the density of the nonwoven fabric and the resin density of the constituent fibers by the following formula. D is the density (g / cm 3 ), and R is the resin density (g / cm 3 ). Here, R is the density of the polyester resin, and the calculation was performed with R = 1.36. Porosity (%) = 100 - {(D / R) × 100}

[0058] (7) Gurley air permeability It was measured based on JIS P8117 (Test method for air permeability of paper and paperboard). At this time, 16 nonwoven fabric samples were laminated and the air permeability was measured, and the Gurley air permeability per sheet was calculated by multiplying by 1 / 16.

[0059] (8) Tensile strength It was measured based on JIS P8113 (Tensile strength and test method of paper and paperboard). The MD tensile strength is the tensile strength in the MD direction.

[0060] (9) Heat shrinkage rate A nonwoven fabric sample of MD 100 mm × CD 100 mm was left in a dryer at 180 °C for 1 hour. Then, the heat shrinkage rate was calculated from the lengths of the nonwoven fabric sample in the MD direction and the CD direction.

[0061] (10) Average pore diameter, maximum pore diameter Using a palm porometer (model: CFP-1200A) manufactured by PMI, based on ASTM-F-316, the average pore diameter and the maximum pore diameter were measured by a pore size distribution measurement test (WET UP / DRY UP method). For the test liquid, GALPORE manufactured by Porometer was used.

[0062] (11) Sheet forming property The sheet forming property was evaluated when sheet forming was performed with aiming marks. Those in which a sheet could be formed were marked as "〇", and those in which a sheet could not be formed were marked as "×".

[0063] [Example 1] Using 50% by weight of the above-mentioned polyester undrawn binder fiber (average fiber diameter 4.3 μm, average fiber length 3.0 mm) "Teppirus TK08PN SD 0.2 dtex 3 mm" manufactured by Teijin Frontier Co., Ltd. as the binder fiber and 50% by weight of the above-mentioned polyester fiber (average fiber diameter 0.7 μm, average fiber length 0.5 mm) "Nanofront" manufactured by Teijin Frontier Co., Ltd. as the non-binder fiber, a fiber slurry was prepared by stirring in a pulper for 5 minutes.

[0064] Using this fiber slurry, a non-woven fabric was produced by the wet papermaking method, then transferred to a Yankee dryer at a line pressure of 0.3 kg / cm, and dried at 120°C for 30 seconds to adjust to a predetermined basis weight and thickness, obtaining a wet non-woven fabric sheet for supporting a solid electrolyte. Furthermore, the sheet for supporting a solid electrolyte was fixed on a glass plate, and the solid electrolyte slurry was coated on one side with a bar coater and dried at 80°C for 5 minutes. Then, a solid electrolyte sheet was produced by calendering at room temperature at 30 kg / cm. The evaluation results are shown in Table 1 and Table 2.

[0065] The obtained sheet for supporting a solid electrolyte had a basis weight of 2.1 g / m 2 and a thickness of 5.0 μm. While being lightweight and thin-film, it had a high porosity of 68.8%, a small Gurley air permeability of 0.026 seconds / 100 cc, and low resistance. Also, since it was composed only of polyester fibers, the heat shrinkage rate at 180°C was small, and it had excellent heat resistance. And because of its low basis weight and high porosity, the solid electrolyte could penetrate inside, and the solid electrolyte sheet after coating was thin-film and had a high density.

[0066] 〔Example 2〕 A wet non-woven fabric with different basis weight and thickness was produced in the same composition and method as in Example 1 to obtain a sheet for supporting a solid electrolyte which was a wet non-woven fabric. At this time, the basis weight was adjusted by adjusting the liquid feeding amount of the fiber slurry. Other conditions were carried out in the same manner as in Example 1. Furthermore, a solid electrolyte sheet was prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2. Similar to Example 1, the non-woven fabric was a thin film, had low resistance, and was excellent in heat resistance. Also, similar to Example 1, the solid electrolyte sheet was a thin film and had a high density.

[0067] 〔Comparative Example 1〕 A wet non-woven fabric with different basis weights and thicknesses was produced in the same composition and method as in Example 1, and then a sheet for supporting a solid electrolyte, which was a wet non-woven fabric, was obtained by calendering at 180 °C under 50 kg / cm². Furthermore, a solid electrolyte sheet was prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0068] Due to the high basis weight of the non-woven fabric, the thickness remained as thick as 10 μm or more even after calendering. Also, since the porosity was low, it became a dense non-woven fabric and the Gurley air permeability increased. For this reason, the resistance was high as a sheet for supporting a solid electrolyte. Also, since the porosity was low and it was a dense non-woven fabric, it was difficult for the solid electrolyte to penetrate inside, and it was a thick-film and low-density solid electrolyte sheet.

[0069] 〔Comparative Example 2〕 As the binder fiber, 50% by weight of the above-mentioned polyester-based undrawn binder fiber (average fiber diameter 4.3 μm, average fiber length 3.0 mm, "Terials TK08PN SD 0.2 dtex 3 mm" manufactured by Teijin Frontier Co., Ltd.) and, as the non-binder fiber, 50% by weight of the above-mentioned polyester fiber (average fiber diameter 3.1 μm, average fiber length 3.0 mm, "Terials TA04PN SD 0.1 dtex 3 mm" manufactured by Teijin Frontier Co., Ltd.) were used, and a non-woven fabric with a target basis weight of 2 g / m² was prepared in the same manner as in Example 1. 2 of non-woven fabric was attempted to be made. In this example, since the fiber network was weak, a wet non-woven fabric could not be formed.

[0070] 〔Comparative Example 3〕 With the same composition as in Comparative Example 2 and in the same method as in Example 1, a target basis weight of 3 g / m² 2A nonwoven fabric was prepared to obtain a solid electrolyte-supporting sheet that is a wet nonwoven fabric. Further, a solid electrolyte sheet was prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0071] Compared with Example 1, since the fiber diameter of the fibers constituting the nonwoven fabric was thick, the thickness was as thick as 10 μm or more. Also, since the fiber network was small, the average pore diameter was as large as 34.6 μm. Therefore, there was a lot of bleeding of the solid electrolyte during coating, and it was difficult to hold the solid electrolyte inside, so the density was low.

[0072] [Comparative Example 4] With the same composition as in Comparative Example 2 and in the same manner as in Example 1, a nonwoven fabric with a target basis weight of 10 g / m 2 was prepared, and by calendering in the same manner as in Comparative Example 1, a solid electrolyte-supporting sheet that is a wet nonwoven fabric was obtained.

[0073] Since the basis weight of the nonwoven fabric was high, even after calendering, the thickness was as thick as 10 μm or more. Also, since the nonwoven fabric had a low porosity, it was difficult for the solid electrolyte to penetrate inside, and it was a thick-film and low-density solid electrolyte sheet.

[0074] [Table 1]

[0075] [Table 2]

Industrial Applicability

[0076] The solid electrolyte-supporting sheet of the present invention can be used as a member of a battery. According to the present invention, by using a lightweight and thin-film wet nonwoven fabric, when the solid electrolyte is supported, the entire solid electrolyte layer can be made thinner. Thereby, the resistance of the electrolyte layer of the battery can be reduced, the battery output can be improved, and the battery can be miniaturized.

Claims

1. A sheet for supporting a solid electrolyte, which is a wet nonwoven fabric composed of binder fibers (A) and non-binder fibers (B), and the wet nonwoven fabric has a basis weight of 1 to 9 g / m ２ and a thickness of 2 to 9 μm, a Gurley air permeability of 0.5 seconds / 100 cc or less, and the binder fibers (A) have an average fiber diameter of 1 to 9 μm. The non-binder fibers (B) consist of only non-binder fibers (B1) or consist of non-binder fibers (B1) and non-binder fibers (B2). The non-binder fibers (B1) have an average fiber diameter of 0.1 to 0.9 μm, and the non-binder fibers (B2) have an average fiber diameter of 1 to 9 μm. A sheet for supporting a solid electrolyte, characterized in that.

2. The sheet for supporting a solid electrolyte according to claim 1, wherein the non-binder fibers (B1) account for 5 to 60% by weight of the weight of the wet nonwoven fabric.

3. The sheet for supporting a solid electrolyte according to claim 1, wherein both the binder fibers (A) and the non-binder fibers (B1) are polyester fibers.

4. The sheet for supporting a solid electrolyte according to claim 1, wherein the tensile strength in the MD direction is 0.3 N / 15 mm or more.

5. The sheet for supporting a solid electrolyte according to claim 1, wherein the heat shrinkage rate after standing at 180°C for 1 hour is 10% or less in both the MD direction and the CD direction.

6. The sheet for supporting a solid electrolyte according to claim 1, wherein the average pore diameter is 20 μm or less, and the maximum pore diameter / average pore diameter is 20 or less.

7. A solid electrolyte sheet according to any one of claims 1 to 6, comprising the sheet for supporting a solid electrolyte according to claim 1 and a solid electrolyte supported on its surface and inside.

Images