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

Abstract

The present invention relates to a solid electrolyte sheet comprising a solid electrolyte and a binder, wherein the binder comprises hydrogenated nitrile butadiene rubber (HNBR), the hydrogenated nitrile butadiene rubber has a content of a nitrile group repeating unit of 19-31 wt % and a residual double bond amount of 4% or less, and an average particle diameter (D50) of the solid electrolyte of 1-5 μm.

Description

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

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

[0002]

[0003] Research on the safety and energy density of high-capacity batteries is gaining attention, and all-solid-state batteries are gaining attention as next-generation batteries. These all-solid-state batteries replace liquid electrolytes, which can be prone to explosion, with solid electrolytes. This eliminates the use of flammable solvents within the battery, eliminating the risk of ignition or explosion caused by reactions like the decomposition of conventional electrolytes. This ensures battery safety.

[0004] In addition, since lithium metal or a lithium alloy can be used as the negative electrode material, the energy density in relation to the mass and volume of the battery can be improved. The solid electrolyte used in the above-mentioned all-solid-state battery is generally an inorganic solid electrolyte, and various studies are being conducted on a sulfide-based solid electrolyte having a composition such as Li6PS5Cl, which has an argyrodite structure among the above-mentioned all-solid-state batteries.

[0005] The practical application of all-solid-state batteries requires the production of large-area batteries. This necessitates the sheet-forming of the cathode, separator, and anode, as in conventional lithium-ion batteries. In particular, the separator in all-solid-state batteries consists of a solid electrolyte and a binder, and its properties (ionic conductivity, electrochemical stability, and chemical stability) vary depending on the manufacturing method and the selected solid electrolyte material.

[0006] In particular, the solid electrolyte layer used as a separator in an all-solid-state battery must prevent contact between the positive and negative electrodes during charge and discharge, suppress lithium dendrites, and facilitate the movement of lithium ions at a thin thickness to maximize battery energy density.

[0007] However, there is a problem that a large number of pores that generally exist between a plurality of solid electrolyte particles in a solid electrolyte layer may reduce the ionic conductivity of the solid electrolyte layer or cause lithium dendrite growth in the battery, resulting in a short circuit or deterioration of the rate characteristics of the battery.

[0008]

[0009] Accordingly, one object of the present invention is to provide a solid electrolyte sheet that has improved ionic conductivity by reducing internal voids, can suppress internal short circuits when applied to an all-solid-state battery, and can improve rate characteristics.

[0010] Another object of the present invention is to provide an all-solid-state battery comprising the solid electrolyte sheet.

[0011]

[0012] This application claims priority to Republic of Korea Patent Application No. 10-2024-0045343, filed April 4, 2024, the entire contents of which are incorporated herein by reference.

[0013] One embodiment of the present invention provides a solid electrolyte sheet comprising a solid electrolyte and a binder, wherein the binder comprises hydrogenated nitrile butadiene rubber (HNBR), wherein the hydrogenated nitrile butadiene rubber has a content of nitrile group repeating units of 19 to 31 wt% and a residual double bond amount of 4% or less, and wherein the average particle diameter (D50) of the solid electrolyte is 1 to 5 μm.

[0014] The above hydrogenated nitrile butadiene rubber may have a residual double bond content of 1.5% or less.

[0015] The above hydrogenated nitrile butadiene rubber has a Mooney viscosity (ML 1+4 , 100℃) can be 50 to 95 MU.

[0016] The content of the above binder may be 0.5 to 5 wt% based on the total weight of the solid electrolyte and binder.

[0017] The above solid electrolyte may be a sulfide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

[0018] The above sulfide-based solid electrolyte may have an argyrodite-based crystal structure.

[0019] The above sulfide-based solid electrolyte can be represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Li x1 P y1 S z1 D w1 M1 a1 M2 a2

[0022] In the above chemical formula 1, D is a halogen element such as F, Cl, Br, I or a combination thereof, M1 is B, Al, Si, Ge, In, Sn or a combination thereof, M2 is O, N, As, Se, Sb, Te or a combination thereof, and 4≤x1≤8, 0.5≤y1≤1.5, 3≤z1≤7, 0≤a1≤2, 0≤a2≤2.

[0023] The above halide-based solid electrolyte can be represented by the following chemical formula 2.

[0024] [Chemical Formula 2]

[0025] Li x2 M3 y2 A z2

[0026] In the above chemical formula 2, M3 is Sc, In, Zr, Lu, Er, Y, Ho or a combination thereof, A is a halogen element such as F, Cl, Br, I or a combination thereof, and 1.5≤x2≤3.5, 0.5≤y2≤1.5, 5≤z2≤7.

[0027] The above solid electrolyte sheet has an average number of pinholes of 10 / 25cm2 It could be as follows:

[0028] The above solid electrolyte sheet may have an ionic conductivity of 0.85 mS / cm or more at 30°C.

[0029] The above solid electrolyte sheet may further include a porous support.

[0030] The porous support may include a polymer resin made of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinylidene fluoride (PVDF), Teflon (PTFE), or a combination thereof.

[0031]

[0032] Another embodiment of the present invention provides an all-solid-state battery comprising: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, the solid electrolyte layer including the aforementioned solid electrolyte sheet.

[0033]

[0034] In one embodiment of the present invention, the solid electrolyte sheet includes a hydrogenated nitrile butadiene rubber (HNBR) binder having a controlled structure, so that internal voids within the solid electrolyte sheet can be efficiently reduced.

[0035] Accordingly, the ionic conductivity of the solid electrolyte sheet can be improved, and when applied to an all-solid-state battery, internal short circuits caused by lithium dendrites can be suppressed and rate characteristics can be improved.

[0036]

[0037] Figure 1 is a pinhole analysis image of a solid electrolyte sheet manufactured according to Example 1.

[0038] Figure 2 is a pinhole analysis image of a solid electrolyte sheet manufactured according to Example 4.

[0039] Figure 3 is a pinhole analysis image of a solid electrolyte sheet manufactured according to Comparative Example 2.

[0040] Figure 4 is a pinhole analysis image of a solid electrolyte sheet manufactured according to Comparative Example 9.

[0041]

[0042] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0043] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0044] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0045] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0046] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0047] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0048] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0049]

[0050] 1. Solid electrolyte sheet

[0051] A solid electrolyte sheet according to one embodiment of the present invention can be applied to a solid electrolyte layer in an all-solid-state battery.

[0052] More specifically, a solid electrolyte sheet according to one embodiment of the present invention includes a solid electrolyte and a binder.

[0053] At this time, the binder includes hydrogenated nitrile butadiene rubber (HNBR).

[0054] Nitrile butadiene rubber (NBR), a commonly used binder, contains double bonds in its carbon chain. These double bonds are highly reactive with sulfide-based solid electrolytes, which are commonly used in solid electrolytes. During the reaction, they harden, which can increase the interfacial resistance between the solid electrolyte particles. Furthermore, the volume of the sulfide-based solid electrolyte can expand, potentially causing cracks in the solid electrolyte layer.

[0055] In contrast, the binder according to the present invention substantially removes double bonds within the carbon chain as nitrile butadiene rubber (NBR) is hydrogenated. Accordingly, the above problems can be prevented.

[0056] In addition, the present inventors confirmed that the internal voids in the solid electrolyte sheet can be efficiently reduced by additionally controlling the degree of hydrogenation of hydrogenated nitrile butadiene rubber (HNBR) (which can be represented by the residual amount of double bonds), the content of nitrile group repeating units, Mooney viscosity, etc. In addition, by reducing the internal voids in the solid electrolyte sheet, the electrical connectivity between the solid electrolyte particle interfaces is improved, thereby improving the ionic conductivity of the solid electrolyte sheet, and when applied to an all-solid-state battery, short circuits are suppressed and high-rate discharge capacity (i.e., rate characteristics) can be improved, thereby completing the present invention.

[0057] Until now, research has been conducted only on the relationship between controlling the physical properties of hydrogenated nitrile butadiene rubber, such as the content of nitrile repeating units, and suppressing reactions with solid electrolytes. In contrast, the present invention focuses on reducing internal voids within a solid electrolyte sheet (solid electrolyte layer) by controlling the physical properties of hydrogenated nitrile butadiene rubber, which will be described in detail below.

[0058]

[0059] The binder according to the present invention comprises hydrogenated nitrile butadiene rubber (HNBR), wherein the content of nitrile group repeating units, the amount of residual double bonds, and Mooney viscosity can be additionally controlled.

[0060] First, the hydrogenated nitrile butadiene rubber (HNBR) has a nitrile repeating unit content of 19 to 31 wt%, more specifically, 19 to 26 wt%. When the nitrile repeating unit content satisfies the above range, the relative density increases, the curing speed increases, and the tensile strength improves due to the appropriate presence of acrylonitrile in the polymer structure, so that the internal voids in the solid electrolyte sheet (solid electrolyte layer when applied to an all-solid-state battery) can be efficiently reduced. Accordingly, the ionic conductivity of the solid electrolyte sheet is improved, and when applied to an all-solid-state battery, battery short circuit can be suppressed and high-rate discharge capacity (i.e., rate characteristics) can be improved.

[0061] The content of nitrile repeat units is expressed as "weight percent" based on the total weight of the hydrogenated nitrile-butadiene rubber polymer. Additionally, the content of nitrile repeat units can be determined by Fourier transform infrared spectroscopy and the Dumas combustion method, specifically according to ISO 24698-1.

[0062]

[0063] Additionally, the hydrogenated nitrile butadiene rubber (HNBR) may have a residual double bond content of 4% or less, and more specifically, 1.5% or less or 1.0% or less.

[0064] “Residual double bond amount” refers to the amount of double bonds remaining within the carbon chain of hydrogenated nitrile butadiene rubber. The amount of residual double bonds is expressed as a percentage, and it refers to the percentage of repeating units in HNBR from which double bonds have not been removed divided by the sum of the CC and C=C repeating units in HNBR. In other words, the amount of residual double bonds can be expressed by the following equation 1.

[0065] [Relationship 1]

[0066] Amount of Residual Double Bonding (%) = [C=C] / ([C=C] + [CC]) * 100

[0067] The “residual double bond amount” can be measured using infrared spectroscopy.

[0068] Specifically, as the degree of hydrogenation of nitrile butadiene rubber increases, the amount of double bonds remaining in the carbon chain can decrease. At this time, when the amount of such residual double bonds satisfies the above range, the amount of unsaturated double bonds in the NBR polymer bond structure can be reduced, thereby increasing the bond strength between polymers. That is, as the bond strength between polymers binding the solid electrolyte particles increases, the internal voids within the solid electrolyte sheet (solid electrolyte layer when applied to an all-solid-state battery) can be efficiently reduced. Accordingly, the ionic conductivity of the solid electrolyte sheet is improved, and when this is applied to an all-solid-state battery, battery short circuit can be suppressed and high-rate discharge capacity (i.e., rate characteristics) can be improved.

[0069]

[0070] In addition, the hydrogenated nitrile butadiene rubber (HNBR) has a Mooney viscosity (ML 1+4 , 100℃) may be 50 to 95 MU, more specifically 60 to 90 MU.

[0071] “Mooney viscosity (ML) 1+4, 100℃)” can be obtained by measuring the hydrogenated nitrile butadiene rubber polymer at a temperature of 100℃ in accordance with ISO 289 / ASTM D 1646.

[0072] The Mooney viscosity of hydrogenated nitrile butadiene rubber is correlated with the molecular weight of the polymer, and as the molecular weight of the polymer increases, the Mooney viscosity may also increase. At this time, if the Mooney viscosity of the hydrogenated nitrile butadiene rubber is too low, the bonding strength between the polymers may be weakened, which may reduce the internal voids within the solid electrolyte sheet. If the Mooney viscosity of the hydrogenated nitrile butadiene rubber is too high, the bonding strength between the polymers may be too strong, which may cause aggregation between the solid electrolyte particles, which may instead reduce the internal voids within the solid electrolyte sheet. Therefore, when the Mooney viscosity of the hydrogenated nitrile butadiene rubber satisfies the above range, the internal voids within the solid electrolyte sheet (solid electrolyte layer when applied to an all-solid-state battery) can be efficiently reduced. Accordingly, the ionic conductivity of the solid electrolyte sheet is improved, and when applied to an all-solid-state battery, battery short circuits can be suppressed and high-rate discharge capacity (i.e., rate characteristics) can be improved.

[0073]

[0074] Hereinafter, the composition of hydrogenated nitrile butadiene rubber (HNBR) according to the present invention will be described in more detail.

[0075] The hydrogenated nitrile butadiene rubber (HNBR) according to the present invention may include a nitrile group-containing monomer repeating unit, an aliphatic conjugated diene monomer repeating unit, and other repeating units.

[0076] [Nitrile-containing monomer repeating unit]

[0077] Examples of the nitrile-containing monomer capable of forming a nitrile-containing monomer repeating unit include α,β-ethylenically unsaturated nitrile monomers. Specifically, the α,β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α,β-ethylenically unsaturated compound having a nitrile group, and examples thereof include acrylonitrile; α-halogenoacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile; and the like. Among these, from the viewpoint of further improving the output characteristics and high-temperature cycle characteristics of an all-solid-state secondary battery, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more preferable. Meanwhile, the nitrile group-containing monomer may be used alone, or two or more types may be combined in any ratio.

[0078] [Aliphatic conjugated diene monomer repeating unit]

[0079] Aliphatic conjugated diene monomers capable of forming aliphatic conjugated diene monomer repeating units are not particularly limited, and examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), and 2,3-dimethyl-1,3-butadiene. Among these, 1,3-butadiene is preferred from the viewpoint of further improving the output characteristics and high-temperature cycle characteristics of the all-solid-state secondary battery while sufficiently securing the flexibility of the solid electrolyte-containing layer. Meanwhile, the aliphatic conjugated diene monomer may be used singly, or two or more types may be combined in any ratio.

[0080] [Other repeating units]

[0081] Other repeating units are not particularly limited as long as they are repeating units derived from monomers copolymerizable with the above-described nitrile group-containing monomers and aliphatic conjugated diene monomers, but examples thereof include ethylenically unsaturated carboxylic acid ester monomer units.

[0082] As an ethylenically unsaturated carboxylic acid ester monomer capable of forming an ethylenically unsaturated carboxylic acid ester monomer unit, for example, a monomer composed of an ester of an ethylenically unsaturated monocarboxylic acid or a monomer composed of a diester of an ethylenically unsaturated dicarboxylic acid can be used.

[0083] Here, examples of monomers composed of esters of ethylenically unsaturated monocarboxylic acids include (meth)acrylic acid ester monomers. Meanwhile, in the present invention, “(meth)acrylic” means acrylic and / or methacrylic.

[0084] And, as (meth)acrylic acid ester monomers, acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butylacrylate, t-butylacrylate, isobutylacrylate, n-pentylacrylate, isopentyl acrylate, hexylacrylate, heptylacrylate, octylacrylate, 2-ethylhexylacrylate, nonylacrylate, decylacrylate, lauryl acrylate, n-tetradecylacrylate, and stearyl acrylate; Examples thereof include methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, and glycidyl methacrylate.

[0085] In addition, examples of monomers composed of diesters of ethylenically unsaturated dicarboxylic acids include maleic acid dialkyl esters such as diethyl maleate and dibutyl maleate; fumaric acid dialkyl esters such as diethyl fumarate and dibutyl fumarate; itaconic acid dialkyl esters such as diethyl itaconate and dibutyl itaconate; etc.

[0086] Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, n-butylacrylate, and dibutyl itaconate are preferable from the viewpoint of further improving the output characteristics and high-temperature cycle characteristics of all-solid-state secondary batteries. Meanwhile, the ethylenically unsaturated carboxylic acid ester monomers may be used singly, or two or more types may be combined in any ratio.

[0087] [Method for producing hydrogenated nitrile butadiene rubber]

[0088] The method for producing hydrogenated nitrile butadiene rubber is not particularly limited. Hydrogenated nitrile butadiene rubber can be produced, for example, by polymerizing a monomer composition containing the above-described monomers in an aqueous solvent. Meanwhile, the content ratio of each monomer in the monomer composition can be determined based on the content ratio of the desired monomer unit (repeating unit) in the polymer.

[0089] Meanwhile, the polymerization method can be any method, including solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization, without particular limitations. Furthermore, any polymerization reaction can be employed, including ionic polymerization, radical polymerization, living radical polymerization, various condensation polymerizations, and addition polymerization. Furthermore, during polymerization, a known emulsifier or polymerization initiator can be used, as needed.

[0090]

[0091] In addition, the average particle diameter (D50) of the solid electrolyte according to the present invention may be 1 to 5 μm, and more specifically, 1.5 to 4.5 μm or 2 to 4 μm. If the average particle diameter (D50) of the solid electrolyte is too small, there may be problems of deterioration in ionic conductivity and high-rate discharge capacity. If the average particle diameter (D50) of the solid electrolyte is too large, the surface quality of the solid electrolyte sheet may not be uniform, and voids may be generated between the solid electrolyte particles, which may cause a problem of battery short-circuit. In addition, when the average particle diameter (D50) of the solid electrolyte satisfies the above range, compatibility with the HNBR binder according to the present invention is improved, and internal voids in the solid electrolyte sheet (solid electrolyte layer when applied to an all-solid-state battery) can be efficiently reduced.

[0092] In this specification, the average particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) can be measured using, for example, the laser diffraction method.

[0093]

[0094] Meanwhile, the content of the binder according to the present invention may be 0.5 to 5 wt%, and more specifically, 0.5 to 3 wt%, based on the total weight of the solid electrolyte and binder. If the content of the binder is too low, the solid electrolyte particles may not bond well together, thereby reducing the effect of reducing internal voids within the solid electrolyte sheet. If the content of the binder is too high, the solid electrolyte particles may coagulate too strongly, thereby increasing the internal voids within the solid electrolyte sheet.

[0095]

[0096] The above solid electrolyte may be a sulfide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

[0097] The above sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (wherein m, n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (where p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga In), Li3PS4, Li7P3S 11 , Li 7-x PS 6-x Cl x (However, 0≤x≤2), Li 7-x PS 6-x Br x (where 0≤x≤2), and Li 7-x PS 6-x I x (However, there can be one or more selected from 0≤x≤2).

[0098] The above sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, a heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one of the above-described sulfide-based solid electrolyte materials that contains at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the solid electrolyte may be a material containing Li2S-P2S5.

[0099] From the perspective of more desirable implementation of ionic conductivity, the sulfide-based solid electrolyte may have an argyrodite-based crystal structure.

[0100] A sulfide-based solid electrolyte having an argyrodite crystal structure may contain, for example, Li, P, S, and halogen elements, and may further contain other doping elements as needed. By further including other doping elements in the argyrodite crystal structure, the moisture stability of the solid electrolyte may be improved, or the electrochemical properties, such as the capacity of the battery, may be more preferably realized.

[0101] For example, the sulfide-based solid electrolyte can be represented by the following chemical formula 1.

[0102] [Chemical Formula 1]

[0103] Li x1 P y1 S z1 D w1 M1 a1 M2 a2

[0104] In the above chemical formula 1, D is a halogen element such as F, Cl, Br, I or a combination thereof, M1 is B, Al, Si, Ga, Ge, In, Sn or a combination thereof, M2 is O, N, As, Se, Sb, Te or a combination thereof, and 4≤x1≤8, 0.5≤y1≤1.5, 3≤z1≤7, 0≤a1≤2, 0≤a2≤2.

[0105] In addition, the halide-based solid electrolyte can be represented by the following chemical formula 2.

[0106] [Chemical Formula 2]

[0107] Li x2 M3 y2 A z2

[0108] In the above chemical formula 2, M3 is Sc, In, Zr, Lu, Er, Y, Ho or a combination thereof, A is a halogen element such as F, Cl, Br, I or a combination thereof, and 1.5≤x2≤3.5, 0.5≤y2≤1.5, 5≤z2≤7.

[0109]

[0110] Meanwhile, the solid electrolyte sheet according to the present invention has an internal void effectively reduced according to the above-described configuration, so that the average number of pinholes in the solid electrolyte sheet is 10 / 25 cm. 2 It can be less than or equal to 5 / 25cm, more specifically 2 or 2.5 / 25cm 2 It may be as follows. In this specification, the average number of pinholes in a solid electrolyte sheet is the number of lights emitted through pinholes existing in a solid electrolyte sheet when a light emitting diode (LED) is placed on the back of the solid electrolyte sheet and the number of lights emitted through pinholes existing in the solid electrolyte sheet is 5x5 cm. 2 By counting per unit area, any 5x5 cm within the solid electrolyte sheet 2 It can be measured by calculating the average number of pinholes per 10 unit areas.

[0111] In addition, the solid electrolyte sheet according to the present invention has improved ionic conductivity as the internal void is reduced, and the ionic conductivity can be 0.85 mS / cm or more at 30°C, and more specifically, 1.05 mS / cm or more.

[0112] The above solid electrolyte sheet may further include a porous support. By further including a porous support, the solid electrolyte sheet can sufficiently improve mechanical rigidity and function as a self-supporting membrane.

[0113] The porous support may include, but is not necessarily limited to, a polymer resin made of, for example, polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinylidene fluoride (PVDF), Teflon (PTFE), or a combination thereof.

[0114]

[0115] 2. Method for manufacturing solid electrolyte sheets

[0116] The solid electrolyte sheet according to the present invention can be manufactured according to the following manufacturing method, which will be described below.

[0117]

[0118] First, a solid electrolyte composition is formed.

[0119] The above solid electrolyte composition may include a solvent along with the solid electrolyte and binder according to the present invention described above. Since the solid electrolyte and binder have been described in detail above, a detailed description thereof will be omitted.

[0120] The solvent may be, for example, xylene, toluene, isobutyl isobutyrate, or a combination thereof, but is not necessarily limited thereto, and any solvent used in the art may be used.

[0121] The above solid electrolyte composition may further include a dispersant that can improve the dispersibility of the solid content in the solid electrolyte composition, and may further include other additives as needed.

[0122]

[0123] Next, the solid electrolyte composition is applied onto a substrate or porous support.

[0124] The above substrate is not particularly limited as long as it is chemically stable with respect to the solid electrolyte composition. For example, the substrate may be, but is not necessarily limited to, PET (polyethylene terephthalate), PEN (polyethylenenaphthalate), PES (polyethersulfone), PC (polycarbonate), PP (polypropylene), or a combination thereof.

[0125] The porous support may include, but is not necessarily limited to, a polymer resin made of, for example, polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinylidene fluoride (PVDF), Teflon (PTFE), or a combination thereof.

[0126] The above application is not particularly limited as long as it is commonly used in the relevant technical field, but may be performed by, for example, a slurry casting method.

[0127]

[0128] Next, the solid electrolyte composition applied on the substrate or porous support is dried to remove the solvent in the solid electrolyte composition, thereby forming a solid electrolyte sheet.

[0129] The drying can be performed, for example, at a temperature of about 20 to 60°C.

[0130]

[0131] 3. All-solid-state battery

[0132] Another embodiment of the present invention provides an all-solid-state battery comprising: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, the solid electrolyte layer including the aforementioned solid electrolyte sheet.

[0133] More specifically, the above positive electrode layer may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

[0134] The above-described positive electrode active material layer may include, for example, a positive electrode active material and a solid electrolyte. The solid electrolyte included in the positive electrode active material layer may be the same as or different from the solid electrolyte included in the solid electrolyte sheet.

[0135] A cathode active material is a material that can reversibly absorb and desorb lithium ions. Examples of cathode active materials include, but are not limited to, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate; nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide; and the like. Any material used as a cathode active material in the relevant technical field may be used. The cathode active materials may be singly or in a mixture of two or more.

[0136] The above lithium transition metal oxide is, for example, Li a A 1-b B b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α(In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn dGeO2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); A compound represented by any one of the chemical formulas of LiFePO4. In this compound, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of this compound, and it is also possible to use a mixture of the above-mentioned compound and the compound having a coating layer added. The coating layer added to the surface of these compounds includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0137] The positive electrode active material layer may include, for example, a solid electrolyte. The solid electrolyte included in the positive electrode layer may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0138] The positive electrode active material layer may include, for example, a binder. The binder may include, but is not limited to, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and the like, and any binder used in the art may be used.

[0139] The positive electrode active material layer may include, for example, a conductive material. The conductive material may include, but is not limited to, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc., and any conductive material used in the relevant technical field may be used.

[0140] The positive electrode active material layer may further include, for example, additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the above-described positive electrode active material, solid electrolyte, binder, and conductive agent.

[0141] As fillers, coating agents, dispersants, ion conductive aids, etc. that the positive electrode active material layer may include, known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[0142] The positive electrode collector may be, for example, a plate or foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The thickness of the positive electrode collector may be, for example, 1 um to 100 um, 1 um to 50 um, 5 um to 25 um, or 10 um to 20 um.

[0143]

[0144] The above negative electrode layer may more specifically include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0145] The above negative electrode active material layer may include, for example, a negative electrode active material and a binder.

[0146] The above negative electrode active material may include, for example, a carbon-based negative electrode active material, a metal / metalloid negative electrode active material, or a combination thereof.

[0147] The above carbon-based negative electrode active material may be amorphous carbon. The amorphous carbon may include, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0148] The metal / metalloid negative electrode active material includes at least one selected from the group consisting of lithium (Li), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited thereto, and any metal negative electrode active material or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used.

[0149] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0150] By including a binder in the negative electrode active material layer, the negative electrode active material layer is stabilized on the negative electrode current collector. Furthermore, cracking of the negative electrode active material layer is suppressed despite changes in volume and / or relative position of the negative electrode active material layer during the charge / discharge process.

[0151] The negative active material layer may further include additives used in conventional all-solid-state batteries, such as fillers, coating agents, dispersants, and ion conductive aids.

[0152] The all-solid-state battery may further include a second negative electrode active material layer disposed between the negative electrode current collector and the negative electrode active material layer during charging. The second negative electrode active material layer may be deposited between the negative electrode current collector and the negative electrode current collector during the charging process, or may be further disposed on the negative electrode active material layer during electrode assembly. The second negative electrode active material layer may be a metal layer containing lithium or a lithium alloy. The lithium alloy includes, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, and the like, and any lithium alloy used in the art may be used. The second negative electrode active material layer may be made of one of these alloys and / or lithium, or may be made of multiple types of alloys and / or lithium.

[0153] The negative electrode current collector may be composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or compound. The negative electrode current collector may include, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that is used as an electrode current collector in the art may be used. The negative electrode current collector may be composed of one of the above-described metals, or may be composed of an alloy or a coating material of two or more metals. The negative electrode current collector may be, for example, in the form of a plate or foil.

[0154]

[0155] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0156]

[0157] Example 1

[0158] (1) Preparation of 3μm Li6PS5Cl argyrodite solid electrolyte

[0159] Li6PS5Cl was synthesized via a dry method. Specifically, Li2S, P2S5, and LiCl were weighed according to their compositions, mixed in a high-viscosity mill (Planetary Mill) at 300 rpm for 8 hours, and pellets were manufactured at 300 MPa. These pellets were heat-treated at 550°C in an argon (Ar) atmosphere to synthesize a Li6PS5Cl argyrodite-based solid electrolyte. The synthesized solid electrolyte was then ball milled to achieve an average particle size (D50) of 3 μm.

[0160] (2) Manufacturing of solid electrolyte sheets

[0161] The solid electrolyte prepared above was mixed with a xylene solvent containing 2 wt% of HNBR binder dissolved therein to form a solid electrolyte composition (slurry). At this time, the content of the HNBR binder was set to 2 wt% based on the total weight of the solid electrolyte and the HNBR binder. In addition, the content of the nitrile group repeating unit of the HNBR binder was 17 wt%, the amount of residual double bonds was 0.9%, and the Mooney viscosity (ML) was 1.5 g / cm. 1+4 , 100℃) was 39 MU.

[0162] Thereafter, the solid electrolyte composition (slurry) was applied onto a PET (polyethylene terephthalate) substrate using a blade coating method.

[0163] Thereafter, the applied solid electrolyte composition (slurry) was dried at 50°C and then detached from the PET substrate to produce a solid electrolyte sheet.

[0164] (3) All-solid-state battery manufacturing

[0165] The above-mentioned manufactured solid electrolyte sheet is 0.785 cm 2 After punching out the area and placing it in the pressure cell, the composite electrode was loaded on top. The composite electrode was made by mixing the cathode slurry, which was a cathode active material (NCM811): solid electrolyte (Li6PS5Cl): conductive material (denka black) in a weight ratio of 70:29:1, and loading it with a thickness of 0.785 cm. 2 It was manufactured by loading 20.0 mg on the area and densifying to 300 MPa. Afterwards, the In-Li counter electrode was bonded at 50 MPa as the cathode, and the cell was fastened at the same pressure.

[0166]

[0167] Other Examples and Comparative Examples

[0168] A solid electrolyte sheet and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the content of the nitrile group repeating unit of the HNBR binder, the amount of residual double bonds, and the Mooney viscosity were prepared differently as shown in Table 1 below.

[0169]

[0170] Table 1 below summarizes the properties of the HNBR binder applied to the examples and comparative examples, the evaluation of the properties of the solid electrolyte sheet according to Experimental Example 1 described below, and the evaluation of the all-solid-state battery rate characteristics according to Experimental Example 2.

[0171] HNBR Binder PropertiesBinder Content (Based on the Total Weight of Solid Electrolyte and Binder) (Wt%)Solid Electrolyte Average Particle Diameter (D50) (μm)Solid Electrolyte Density (g / cm) 3 )Solid electrolyte sheetAll-solid batteryNitrile group repeating unit content (wt%)Residual double bond amount (%)Mooney viscosity (ML) 1+4 , 100℃)(MU)Ionic conductivity (mS / cm)Average number of pinholes (number / 25cm) 2 ) High-rate discharge capacity (mAh / g) @ 1.5C Comparative example 1170.939230.960.915 Short circuit comparison example 2170.974230.960.920 Short circuit comparison example 3173.574230.960.815 Short circuit comparison example 417570230.960.720 Short circuit example 1210.939230.9612140 Example 2210.967230.961.10168 Example 3210.974230.961.20176 Example 4210.980230.961.10182 Example 5213.574230.960.92153 Comparative example Paragraph 521574230.960.83 Comparison example 6330.939230.960.730 Paragraph comparison example 7330.974230.960.825 Paragraph comparison example 833539230.960.520 Paragraph comparison example 933574230.960.625 Paragraph

[0172] Experimental Example 1: Evaluation of Solid Electrolyte Sheet Properties

[0173] (1) Ionic conductivity

[0174] The solid electrolyte sheet manufactured according to the examples and comparative examples was used as a working electrode and the cell was fastened at a pressure of 70 MPa using SUS, and then the impedance was measured by applying a voltage of 10 mV at 30°C.

[0175] (2) Average number of pinholes and pinhole image analysis

[0176] A light emitting diode (LED) is placed on the back of the solid electrolyte sheet and the number of lights coming out through the pinholes present in the solid electrolyte sheet is 5x5 cm. 2 By counting per unit area, any 5x5 cm within the solid electrolyte sheet 2 The average number of pinholes for 10 unit areas was calculated to measure the average number of pinholes in the solid electrolyte sheets manufactured according to the examples and comparative examples.

[0177]

[0178] In addition, the internal pinholes of the solid electrolyte sheets manufactured according to Examples 1 and 4 and Comparative Examples 2 and 9 were observed using an LED back light, and the images are shown in FIGS. 1 to 4 in that order, respectively.

[0179]

[0180] Experimental Example 2: Evaluation of All-Solid-State Battery Rate Characteristics

[0181] After manufacturing the all-solid-state battery, it was aged at room temperature for 2 hours and then subjected to initial cycling. Capacity evaluation was performed with 180 mAh / g as the reference capacity, and the charge / discharge conditions were CC / CV 2.5~4.20 V, 1 / 20 C cut-off. One cycle was performed under 0.1 C charge / 0.1 C discharge conditions. At this time, the rate characteristic was evaluated by calculating the discharge capacity at 1.5 C current in the second cycle as a percentage of the discharge capacity in the first cycle.

[0182]

[0183] Referring to FIGS. 1 to 4, it can be confirmed that the internal voids of the solid electrolyte sheet of the example are significantly reduced compared to the solid electrolyte sheet of the comparative example, even when viewed with the naked eye.

[0184] More specifically, referring to Table 1, in the cases of Examples 1 to 5 in which the content of the nitrile group repeating unit of the HNBR binder, the amount of residual double bonds, the average particle diameter (D50) of the solid electrolyte, and other various physical properties were appropriately controlled, it was confirmed that the average number of pinholes in the solid electrolyte sheet was significantly smaller than in the comparative example. Accordingly, it was confirmed that the solid electrolyte sheet had excellent ionic conductivity and excellent rate characteristics.

[0185] On the other hand, in Comparative Examples 1 to 9, where the content of the nitrile group repeating unit or the amount of residual double bonds in the HNBR binder was outside the range according to the present invention, it was confirmed that the average number of pinholes in the solid electrolyte sheet was greater than in the Examples. Accordingly, it was confirmed that the ionic conductivity of the solid electrolyte sheet was generally deteriorated compared to the Examples, and that a battery short circuit occurred during high-rate discharge.

[0186] Meanwhile, comparing Examples 1 and 5 and Examples 2 to 4, it was confirmed that in Examples 2 to 4, in which the Mooney viscosity and the amount of residual double bonds of the HNBR binder were additionally controlled more appropriately within the range according to the present invention, the average number of pinholes in the solid electrolyte sheet was implemented smaller than in Examples 1 and 5. Accordingly, it was confirmed that the ionic conductivity of the solid electrolyte sheet and the high-rate discharge capacity characteristics of the all-solid-state battery were implemented more preferably.

[0187]

[0188] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0189] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Contains a solid electrolyte and a binder, The above binder comprises hydrogenated nitrile butadiene rubber (HNBR), The above hydrogenated nitrile butadiene rubber has a content of nitrile group repeating units of 19 to 31 wt% and a residual double bond amount of 4% or less, The average particle diameter (D50) of the above solid electrolyte is 1 to 5 μm. Solid electrolyte sheet.

2. In paragraph 1, The above hydrogenated nitrile butadiene rubber is a solid electrolyte sheet having a residual double bond content of 1.5% or less.

3. In paragraph 1, The above hydrogenated nitrile butadiene rubber has a Mooney viscosity (ML 1+4 , 100℃) of 50 to 95 MU of solid electrolyte sheet.

4. In paragraph 1, A solid electrolyte sheet in which the content of the binder is 0.5 to 5 wt% based on the total weight of the solid electrolyte and binder.

5. In paragraph 1, The above solid electrolyte is a solid electrolyte sheet that is a sulfide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

6. In paragraph 5, The above sulfide-based solid electrolyte is a solid electrolyte sheet having an argyrodite-based crystal structure.

7. In paragraph 5, The above sulfide-based solid electrolyte is a solid electrolyte sheet represented by the following chemical formula 1: [Chemical Formula 1] The x1 P y1 S z1 D w1 M1 a1 M2 a2 In the above chemical formula 1, D is a halogen element such as F, Cl, Br, I or a combination thereof, M1 is B, Al, Si, Ga, Ge, In, Sn or a combination thereof, M2 is O, N, As, Se, Sb, Te or a combination thereof, and 4≤x1≤8, 0.5≤y1≤1.5, 3≤z1≤7, 0≤a1≤2, 0≤a2≤2.

8. In paragraph 5, The above halide-based solid electrolyte is a solid electrolyte sheet represented by the following chemical formula 2: [Chemical Formula 2] Li x2 M3 y2 A z2 In the above chemical formula 2, M3 is Sc, In, Zr, Lu, Er, Y, Ho or a combination thereof, A is a halogen element such as F, Cl, Br, I or a combination thereof, and 1.5≤x2≤3.5, 0.5≤y2≤1.5, 5≤z2≤7.

9. In paragraph 1, The above solid electrolyte sheet has an average number of pinholes of 10 / 25cm 2 Solid electrolyte sheet below.

10. In paragraph 1, The above solid electrolyte sheet is a solid electrolyte sheet having an ionic conductivity of 0.85 mS / cm or more at 30°C.

11. In paragraph 1, The above solid electrolyte sheet further comprises a porous support.

12. In paragraph 11, The above porous support is a solid electrolyte sheet comprising a polymer resin made of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinylidene fluoride (PVDF), Teflon (PTFE) or a combination thereof.

13. In paragraph 1, The above solid electrolyte sheet is a solid electrolyte sheet used as a solid electrolyte layer when applied to an all-solid-state battery.

14. An all-solid-state battery comprising a positive electrode layer; a negative electrode layer; and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, the solid electrolyte layer including the solid electrolyte sheet of claim 1.

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