Solid electrolyte sheet and all-solid-state battery comprising same

Abstract

Provided are a solid electrolyte sheet having excellent sheet strength and ion conductivity, and an all-solid-state battery comprising same. The solid electrolyte sheet comprises: a porous support including glass fibers; and a sulfide-based solid electrolyte, wherein the ratio of the diameter of the glass fibers to the diameter of the solid electrolyte is 0.8 to 3.7.

Description

Solid electrolyte sheet and all-solid-state battery including the same

[0001] The present invention relates to a solid electrolyte sheet and an all-solid-state battery comprising the same.

[0002] The present invention claims priority based on Korean Patent Application No. 10-2024-0191004 filed on December 19, 2024, the entire contents of said application incorporated herein by reference.

[0003] As research on safety issues and energy density of high-capacity batteries gains attention, all-solid-state batteries are emerging as next-generation batteries. The aforementioned all-solid-state battery significantly improves battery safety by replacing flammable liquid electrolytes, which cause explosions, with solid electrolytes. Solid electrolytes used in all-solid-state batteries include oxide-based, sulfide-based, and polymer-based types; among these, active research is being conducted on sulfide-based solid electrolytes (such as argyrodite, Li6PS5Cl), which exhibit the highest ionic conductivity. For the commercialization of sulfide-based all-solid-state batteries, ease of fabricating large-area cells must be ensured. To achieve this, sheeting technology, which forms the solid electrolyte into a separator like in conventional lithium-ion batteries, is essential. To manufacture large-area solid electrolyte membranes, a method involving casting a solid electrolyte solution slurry onto a substrate is currently used; however, due to weak mechanical strength, this method is not only difficult to apply to roll-to-roll processes for mass production but is also not easy to handle during all-solid-state battery cell assembly.

[0004] Therefore, attempts have been made to provide solid electrolytes in sheet form (JP2024-022911), but they still fail to provide satisfactory physical properties in terms of the tensile strength of the sheets.

[0005] One embodiment aims to provide a solid electrolyte sheet having excellent sheet strength and excellent ion conductivity.

[0006] According to one embodiment, a solid electrolyte sheet is provided comprising a porous support including glass fibers and a sulfide-based solid electrolyte, wherein the ratio of the diameter of the glass fibers to the diameter of the solid electrolyte is 0.8 to 3.7.

[0007] A solid electrolyte sheet according to one embodiment enables the achievement of desired strength even in a thin film state by controlling the ratio of the diameter of the glass fibers of the porous support to the diameter of the solid electrolyte.

[0008] Since solid electrolyte sheets can achieve the desired strength even in a thin film state, large-area mass production becomes possible. Consequently, not only is cell assembly of all-solid-state batteries facilitated, but the energy density of all-solid-state batteries can also be increased.

[0009] Figure 1 is a graph showing the results of measuring the ionic conductivity of a sheet containing a solid electrolyte on a conventional nonwoven fabric support and a sheet containing a solid electrolyte on a glass fiber porous support.

[0010] Figure 2 is a graph showing the results of measuring the tensile strength of a sheet containing a solid electrolyte on a conventional nonwoven fabric support and a sheet containing a solid electrolyte on a glass fiber porous support.

[0011] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0012] A solid electrolyte sheet according to one embodiment is described below.

[0013] The solid electrolyte sheet comprises a porous support made of glass fiber and a solid electrolyte.

[0014] The glass fibers constituting the porous support can make the sheet self-supporting while suppressing a decrease in conductivity.

[0015] It is preferable that the porous support made of glass fibers has a thickness of 30 μm or less. Since a smaller film thickness of the porous support leads to a smaller film thickness of the solid electrolyte sheet and makes it easier for the energy density to increase when used in an all-solid-state battery, a thickness of 30 μm or less is preferred. In addition, the film thickness of the glass fiber fabric is preferably 5 μm or more from the perspective of the strength of the solid electrolyte sheet.

[0016] It is preferable that the porous support made of glass fibers has a mechanical strength of 3400 MPa.

[0017] It is preferable that the opening ratio of the porous support made of glass fiber be 40 to 60%. If the opening ratio is less than 40%, the amount of solid electrolyte included in the solid electrolyte sheet decreases, and the ionic conductivity decreases. If the opening ratio exceeds 60%, the proportion of the support (glass fiber fabric) included in the solid electrolyte sheet decreases, and the strength of the solid electrolyte sheet weakens, making it difficult to handle during manufacturing.

[0018] It is preferable that the width of the porous support made of glass fiber be 120 mm or more. A width of 120 mm or more is advantageous in terms of productivity as it allows for processing into a roll type.

[0019] Using glass fibers containing SiO2, Al2O3, CaO, and B2O3 is advantageous for achieving the desired strength. MgO and NaO may be used as needed. 2, It may further include one or more selected from K2O, TiO2, and Fe2O3.

[0020] The glass fiber may contain 53–56 wt% SiO2, 13–16 wt% Al2O3, 22–23 wt% CaO, and 6–7 wt% B2O3. MgO and NaO may additionally be included. 2, One or more selected from K2O, TiO2, and Fe2O3 may be included in an amount of 0 to 1 wt%.

[0021] The solid electrolyte can be a sulfide-based solid electrolyte. Sulfide-based solid electrolytes are M a PN b S c X d It can be represented as follows. Here, M is Li, Na, or a combination thereof, N is B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, X: F, Cl, Br, I, or a combination thereof, X is O, Se, Te, or a combination thereof, and 0≤a≤6, 0≤b≤6, 0≤c≤6, 0≤d≤6. Specifically, the sulfide-based solid electrolyte is Li2S-P2S5-MY f It can be represented as. Here, Y is O, S, Se, Te, or a combination thereof, and 0.50 ≤ f ≤ 4. Or the sulfide-based solid electrolyte is M a PS c X d It can be represented as follows. Here, M is Li, Na, or a combination thereof, N is B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or a combination thereof, X is F, Cl, Br, or I, and 0≤a≤6, 0≤b≤6, 0≤c≤6, 0≤d≤6. Specifically, the above sulfide-based solid electrolyte is Li6PS5X (wherein X=Cl, Br, I), called the argyrodite type, Li 7-x PS 6-x X x (in the formula, X=Cl, Br, I, 0≤x≤1.8), etc., or Li called LGPS type 3.4 P 0.6 Si 0.4 S4, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl0.3 , Li 4-x　 Ge 1-x P x S4(in the equation, 0≤x≤1), Li 10 GeP2S 11.7 O 0.3 Examples include the above. The above sulfide-based solid electrolyte may be amorphous or crystalline, and the average particle size may be 50 nm to 50 µm or 100 nm to 10 µm, but is not limited thereto.

[0022] The sulfide-based solid electrolyte may be included in an amount of 30% or more, 40 to 80%, 50% or more, 50 to 80%, 55% or more, or 55 to 80% by weight based on the total weight of the organic-inorganic composite electrolyte.

[0023] The solid electrolyte sheet may further include a binder. As a binder, fluoropolymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and fluororubber, heat-resistant resins such as polyimide (PI) and polyamideimide (PAI), thermoplastic resins such as polypropylene and polyethylene, ethylenepropylene dimethyl ethylene (EPDM), sulfonated EPDM, natural butyl rubber (NBR), and hydrogenated nitrile butadiene rubber (HNBR) may be used alone or as a mixture of two or more types. In addition, water-based binders such as water dispersions of cellulose-based or styrene-butadiene rubber (SBR) may be used.

[0024] In the case where the solid electrolyte sheet includes a binder, the mixing ratio (weight%) of the solid electrolyte and the binder in the solid electrolyte sheet is preferably solid electrolyte:binder = 90.0:10.0 to 99.9:0.1, and more preferably solid electrolyte:binder = 99.0:1.0 to 99.9:0.1. In terms of the effect of imparting flexibility to the sheet, the amount of binder is preferably 0.1 weight% or more.

[0025] To achieve the desired tensile strength in a solid electrolyte sheet, the ratio of the diameter of the glass fiber to the diameter of the solid electrolyte must be between 0.8 and 3.7. If the ratio is 0.8 or less, the solid electrolyte particle size becomes too large, which reduces the contact interface and may lower the tensile strength. Furthermore, if the solid electrolyte particle size becomes too large, it cannot penetrate into the pores of the porous support made of glass fibers, making it impossible to obtain a sheet shape; consequently, the density of the sheet itself decreases, which may also lower the ionic conductivity. If the ratio is 3.7 or more, the solid electrolyte diameter becomes too small, which may lower the ionic conductivity due to low crystallinity. Therefore, to maintain tensile strength and ionic conductivity within the desired range, it is desirable to maintain a diameter ratio in the range of 0.8 to 3.7. More preferably, the ratio should be between 1.5 and 1.8 to optimize both tensile strength and ionic conductivity.

[0026] Once the average diameter of the sulfide-based solid electrolyte is selected, the diameter of the glass fiber can be selected within the range required to achieve tensile strength.

[0027] In this way, by controlling the ratio of the average diameter of the glass fiber to the solid electrolyte, it is possible to form a solid electrolyte sheet as a thin film while simultaneously achieving a desired tensile strength. For example, the tensile strength of the solid electrolyte sheet is 40 kgf / cm² 2 You can do more than that.

[0028] In addition, a porous support composed of a solid electrolyte and glass fibers is effectively integrated to provide flexibility while simultaneously possessing excellent ion conductivity.

[0029] The solid electrolyte sheet may have an ionic conductivity of 0.5 mS / cm or more, or 1.0 mS / cm or more.

[0030] As a result of a 180° bending test, the solid electrolyte sheet can maintain an ionic conductivity of 80% or more, 90% or more, preferably 95% or more, or 99% or more relative to the initially measured ionic conductivity when measured after 100 cycles.

[0031] A solid electrolyte sheet can be manufactured by applying and drying a slurry of a sulfide-based solid electrolyte onto a woven fabric made of glass fibers. If necessary, the sheet may be pressed after drying. The preparation, application, and drying of the slurry can be carried out using conventionally known methods.

[0032] Examples of methods for manufacturing the slurry include a self-rotating mixer, a planetary mixer, a bead mill, a thin film rotary mixer, etc. Examples of methods for applying the slurry include a die-coating, a comma coat, a gravure coat, a roll coat, etc. Examples of methods for drying the slurry include hot air, infrared rays, lamps, etc. Examples of methods for pressing the sheet after drying include a roll press, a flat plate press, a cold isostatic press, a hot isostatic press, etc.

[0033] Except for including a solid electrolyte sheet according to one sun, an all-solid-state battery can be manufactured with a structure known in the art using conventional manufacturing methods and materials in the art.

[0034] The all-solid-state battery includes a positive electrode layer and a negative electrode layer, and includes an organic or inorganic electrolyte sheet between the positive electrode layer and the negative electrode layer, and the electrolyte sheet may include a solid electrolyte sheet according to one embodiment.

[0035] The materials constituting the positive and negative electrode layers, the method for manufacturing an all-solid-state battery using the same, and the manufactured all-solid-state battery can be carried out by various technologies known in the art.

[0036] The embodiments of the present invention described above will be explained in more detail through the following examples. However, the following examples are for illustrative purposes only and do not limit the scope of the present invention.

[0037] [Preparation Example]

[0038] [Solid Electrolyte Slurry]

[0039] As a sulfide-based solid electrolyte, argyrodite-type sulfide solid electrolyte Li 7-x　 PS 6-x　 Cl x　 A powder of (where x ≈ 1) was mixed with a binder solution in which 5 mass% of a rubber resin was dissolved in a low-polarity organic solvent that does not react with a sulfide-based solid electrolyte, and the low-polarity organic solvent was further added to adjust the viscosity and mixed with a self-rotating mixer to obtain a solid electrolyte slurry. At this time, the diameter of the sulfide-based solid electrolyte was prepared to be 3 μm.

[0040] [Porous support made of glass fibers]

[0041] A porous support made of glass fibers with a fiber diameter of 4.6 to 5.5 μm was prepared. The glass fibers used contained 53–56 wt% SiO2, 13–16 wt% Al2O3, 22–23 wt% CaO, 6–7 wt% B2O3, 1 wt% MgO, 1 wt% NaO2+K2O, and 1 wt% TiO2+Fe2O3. The thickness of the porous support was set to 26 μm.

[0042] [Solid Electrolyte Sheet]

[0043] A solid electrolyte slurry was applied onto a porous support made of glass fibers using an applicator with a predetermined clearance, dried in a dryer at 70°C for 1 hour under atmospheric pressure, and then dried in a dryer at 70°C for 20 hours under reduced pressure to complete the solid electrolyte sheet.

[0044] [Comparative Example]

[0045] A solid electrolyte sheet was completed by applying a solid electrolyte slurry with a solid electrolyte diameter of 3 μm using a nonwoven fabric as a porous support instead of a porous support containing glass fibers.

[0046] [Measurement of Tensile Strength and Ionic Conductivity]

[0047] Tensile strength and ionic conductivity were measured for the manufactured solid electrolyte sheet.

[0048] Figure 1 shows the results of measuring ionic conductivity, Figure 2 shows the results of measuring tensile strength, and the results summarizing their physical properties are shown in Table 1 below.

[0049] (Conventional) Nonwoven fabric support Glass fiber support Ionic conductivity (mS / cm) 30 Film thickness (um) *After WIP 5560 Electrochemical stability Stable (0~4.3V) Stable (0~4.3V) Density (Poinhole test) Good Good Tensile strength (kgf / cm2) 4.7977.8

[0050] From the results in Figures 1 and 2 and Table 1, it can be seen that the tensile strength increased by approximately 16 times while having a similar ionic conductivity (1.0 mS / cm) compared to conventionally widely applied nonwoven fabrics. To investigate the effect of the ratio of the diameter of the glass fibers of the porous support to the diameter of the solid electrolyte on ionic conductivity and tensile strength, solid electrolyte sheets were prepared using the same method described above, but with the diameter of the solid electrolyte varying from 1 μm to 7.5 μm, and then the tensile strength and ionic conductivity were measured.

[0051] The results are listed in Table 2 below.

[0052] Classification Porous Support Glass Fiber Diameter (um) Solid Electrolyte Diameter (um) Glass Fiber Diameter / Solid Electrolyte Diameter Specific Tensile Strength (kgf / cm) 2) Ion Conductivity (mS / cm) Comparative Examples Non-woven fabric 3 - 4.79 1.3 Experimental Example 1 Glass fiber 14.6~5.58 0.10.3 Experimental Example 2 Same 1.53.1~3.779.8 0.5 Experimental Example 3 Same 22.3~2.878.7 0.6 Experimental Example 4 Same 2.51.8~2.278.10.7 Experimental Example 5 Same 31.5~1.877.8 1.0 Experimental Example 6 Same 3.51.3~1.667.2 1.0 Experimental Example 7 Same 41.2~1.455.3 1.0 Experimental Example 8 Same 4.51.0~1.250 1.0 Experimental Example 9 Same 50.8~1.142.7 1.1 Experimental Example 10 Same as above 7.50.6~0.7380.2

[0053] It can be seen that the overall tensile strength is improved when glass fibers are used compared to when nonwoven fabric is used, which is the comparative example in Table 2. Meanwhile, looking at the results of Experimental Examples 1 to 10, it can be seen that in order to maintain tensile strength of 40 or higher while maintaining ionic conductivity of at least 0.5, the ratio of the diameter of the glass fiber to the diameter of the solid electrolyte must be 0.8 to 3.7. Among these, the case where the ratio of the diameter of the glass fiber to the diameter of the solid electrolyte is 0.8 to 1.8 is considered a desirable range, as it allows tensile strength to be maintained at 40 or higher while ionic conductivity to be 1.0 or higher. Furthermore, it can be seen that when the ratio of the diameter of the glass fiber to the diameter of the solid electrolyte is 1.5 to 1.8, both tensile strength and ionic conductivity can be controlled to optimal values.

[0054] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention.

Claims

1. A porous support comprising glass fibers; and It includes a sulfide-based solid electrolyte, A solid electrolyte sheet in which the ratio of the diameter of the glass fiber to the diameter of the solid electrolyte is 0.8 to 3.

7.

2. In Paragraph 1, A solid electrolyte sheet in which the ratio of the diameter of the glass fiber to the diameter of the solid electrolyte is 0.8 to 1.

8.

3. In Paragraph 1, A solid electrolyte sheet in which the ratio of the diameter of the glass fiber to the diameter of the solid electrolyte is 1.5 to 1.

8.

4. In Paragraph 1, The above solid electrolyte sheet has an ionic conductivity of 0.5 mS / cm or higher and a tensile strength of 40 kgf / cm 2 A solid electrolyte sheet with an ideal shape.

5. In Paragraph 1, A solid electrolyte sheet having a thickness of 5 to 30 μm of the porous support.

6. In Paragraph 1, The above glass fiber is a solid electrolyte sheet comprising SiO2, Al2O3, CaO, and B2O3.

7. In Paragraph 6, The above glass fiber is SiO2 53~56 wt%, Al2O3 13~16 wt%, CaO 22~23 wt%, and A solid electrolyte sheet containing 6~7 wt% B2O3.

8. In Paragraph 6, The above glass fibers are MgO, NaO 2, A solid electrolyte sheet further comprising one or more selected from K2O, TiO2, and Fe2O3.

9. An all-solid-state battery comprising a solid electrolyte sheet according to any one of claims 1 to 8.

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