Elastic sheet for all-solid rechargeable batteries, preparation method thereof, and all-solid rechargeable batteries comprising same

Abstract

The present invention relates to an elastic sheet for all-solid rechargeable batteries, which comprises a composite flame retardant and a polymer resin, the composite flame retardant comprising: a core particle containing a phosphorus-based flame retardant; and a coating layer enclosing the surface of the core particle and containing silica, wherein the phosphorus-based flame retardant of the core particle and the silica of the coating layer are chemically bonded through a mechano-fusion method, and the chemical bonding includes hydrogen bonding, amine bonding, amide bonding, ethylene bonding, or a combination thereof.

Description

Elastic sheet for all-solid-state secondary battery, method for manufacturing same, and all-solid-state secondary battery comprising same

[0001] The present invention relates to an elastic sheet for an all-solid-state secondary battery, a method for manufacturing the same, and an all-solid-state secondary battery including the same.

[0002] Lithium secondary batteries, which boast high energy density and portability, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, active research is underway to utilize high-energy-density lithium secondary batteries as power sources for hybrid and electric vehicles, or as power storage devices.

[0003] Commercially available lithium secondary batteries use electrolytes containing flammable organic solvents, posing safety concerns that can lead to explosions or fires in the event of collisions, penetration, or other problems. Therefore, semi-solid or all-solid-state batteries, which avoid the use of electrolytes, are being proposed. All-solid-state batteries are comprised entirely of solid materials, specifically those that utilize solid electrolytes. These all-solid-state batteries are safe, eliminating the risk of electrolyte leakage and explosion, and offer the advantage of being easy to manufacture in thin forms.

[0004] These all-solid-state batteries may experience volume changes during the charging and discharging process, and a technology has been proposed to introduce elastic sheets in the form of polymer foams or membranes such as urethane, acrylic, and silicone to cushion the volume changes. However, these elastic sheets are vulnerable to heat, and if a fire occurs, the polymer and inorganic chains decompose, generating flammable gases. As the decomposition products burn again, a chain reaction that decomposes the polymer resin may occur, causing continuous combustion. In particular, there is a problem of releasing a large amount of toxic gases in the event of a fire, so flame retardancy of elastic sheets is continuously receiving attention.

[0005] However, the use of organic and inorganic flame retardants, either singly or in combination, in elastic sheets reduces their dispersibility within the elastic sheet, necessitating the use of large quantities of flame retardants. Furthermore, this approach limits the flame retardancy that can be achieved. Furthermore, research is underway to improve this by coating the surface of phosphorus-based flame retardants with various substances to secure flame retardancy. However, the complex processing process and compatibility issues between phosphorus-based flame retardants and coating materials hinder mass production, hindering commercial success.

[0006] We provide an elastic sheet for all-solid-state secondary batteries that can further enhance the fire safety of these batteries. The elastic sheet is environmentally friendly, effectively reduces volatilization, enhances room-temperature and high-temperature flame retardancy, and exhibits excellent compatibility with resins.

[0007] In one embodiment, an elastic sheet for an all-solid-state secondary battery is provided, comprising a core particle containing a phosphorus flame retardant, a composite flame retardant including a coating layer covering the surface of the core particle and containing silica, and a polymer resin.

[0008] In one embodiment, a method for producing an elastic sheet for an all-solid-state secondary battery is provided, which comprises preparing a composite flame retardant by mixing a phosphorus flame retardant and silica by a mechano-fusion method, mixing the composite flame retardant and a polymer resin to prepare a composition, and forming a film.

[0009] In one embodiment, an all-solid-state secondary battery is provided, comprising two or more cell structures including a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, and elastic sheets positioned between and / or at the outermost surface of the cell structures.

[0010] An elastic sheet for an all-solid-state secondary battery according to an embodiment has high compatibility with a resin, excellent interfacial properties, and excellent resin dispersibility, making it suitable for application to an all-solid-state secondary battery and capable of implementing excellent flame retardancy.

[0011] The above-described elastic sheet for all-solid-state secondary batteries can suppress the volatility of phosphorus-based flame retardants, thereby imparting excellent flame retardancy at high temperatures. Furthermore, it is environmentally friendly because it does not contain compounds that cause environmental problems, such as wastewater problems caused by conventional processes, halogen-based flame retardants, or antimony-based flame retardant auxiliaries. In particular, it can be applied to highly flame-retardant elastic sheets that improve the dispersibility of flame retardants within the elastic sheet, thereby reducing the amount of flame retardants, and prevent the volatilization of phosphorus-based flame retardants at high temperatures, thereby maintaining high flame retardancy not only at room temperature but also at high temperatures.

[0012] Figure 1 is a schematic diagram illustrating a process for complexing a phosphorus flame retardant and silica by mechano-fusion treatment according to one embodiment.

[0013] Figures 2 to 4 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0014] Figure 5 is a scanning electron microscope (SEM) image of the composite flame retardant of Example 1.

[0015] Figure 6 is an SEM image of the composite flame retardant of Example 2.

[0016] Figure 7 is an SEM image of the composite flame retardant of Example 3.

[0017] Figure 8 is an SEM image of the fracture surface of the elastic sheet manufactured in Example 1.

[0018] Figure 9 is an SEM image of the fracture surface of the elastic sheet manufactured in Example 3.

[0019] Figure 10 is an SEM image of the fracture surface of the elastic sheet manufactured in Example 6.

[0020] Figure 11 is an SEM image of the fracture surface of the elastic sheet manufactured in Comparative Example 1.

[0021] Figure 12 is an SEM image of the fracture surface of the elastic sheet manufactured in Comparative Example 3.

[0022] Figure 13 is an SEM image of the fracture surface of the elastic sheet manufactured in Comparative Example 6.

[0023] Figure 14 is an FT-IR analysis graph for the composite flame retardant of Example 3 and the composite flame retardant of Comparative Example 3.

[0024] Below, specific implementation examples are described in detail to facilitate their implementation by those skilled in the art. However, the present invention may be implemented in various different forms and is not limited to the implementation examples described herein.

[0025] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0026] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0027] It should be understood that the terms "include," "comprise," or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0028] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there are other elements in between. Conversely, when an element is said to be "directly over" another element, it means that there are no other elements in between.

[0029] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0030] The average particle size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with transmission electron microscope images or scanning electron microscope images. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size is the diameter (D) of the particles in the particle size distribution that have a cumulative volume of 50% by volume. 50 ) can mean. In addition, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of major axis) of about 20 particles randomly in a scanning electron microscope image to obtain a particle size distribution, and the diameter (D) of the particle having a cumulative volume of 50% by volume in the particle size distribution 50 ) may be taken as the average particle diameter.

[0031] “Or” is not interpreted as exclusive, for example, “A or B” is interpreted as including A, B, A+B, etc.

[0032] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0033] An elastic sheet for an all-solid-state secondary battery according to one embodiment comprises a composite flame retardant including core particles containing a phosphorus flame retardant, and a coating layer covering the surface of the core particles and containing silica; and a polymer resin.

[0034] composite flame retardants

[0035] A composite flame retardant according to one embodiment comprises a core particle containing a phosphorus flame retardant, and a coating layer covering the surface of the core particle and containing silica.

[0036] Halogen-based flame retardants have been widely used in existing industrial applications. However, due to the risk of generating toxic chemicals such as halogenated hydrogen gas, they are subject to environmental regulations and their use is currently restricted. Phosphorus-based flame retardants are environmentally friendly flame retardants that are known to impart excellent flame retardant properties when added to resins, and are therefore being used as an alternative to halogen-based flame retardants. However, phosphorus-based flame retardants have limitations, such as poor interfacial properties and the potential for volatilization when incorporated into materials such as urethane, acrylic, and silicone resins.

[0037] According to one embodiment, a composite flame retardant is a composite flame retardant in which silica is coated on the surface of phosphorus-based flame retardant particles through a dry mixing method using the mechano-fusion method. This composite flame retardant has, first, excellent compatibility with polar resins such as urethane, acrylic resin, and silicone due to the silica located on the particle surface, excellent interfacial properties with the resin, and excellent processability and improved flame retardant performance due to the non-aggregation and good dispersion within the resin. Second, the composite flame retardant can reduce the volatilization problem of the phosphorus-based flame retardant by coating it with silica.

[0038] In particular, according to one embodiment, a composite flame retardant manufactured by the mechano-fusion method may have a phosphorus-based flame retardant in the core and silica in the coating layer formed by chemical bonding, and thus the bonding strength and contact surface area between the core and the coating layer are increased, so that the problem of volatilization of the phosphorus-based flame retardant can be effectively suppressed.

[0039] Such composite flame retardants can be applied to various components of all-solid-state secondary batteries, thereby further improving the fire safety of the all-solid-state secondary batteries. For example, the composite flame retardants can be applied to various locations of all-solid-state secondary batteries, such as elastic sheets, resin layers, flame-retardant sheets, insulation, adhesive sheets, positive electrodes, negative electrodes, and solid electrolyte layers. For example, the composite flame retardants can be applied to components whose basic materials are resin compositions such as urethane, acrylic resin, and silicone.

[0040] core particle

[0041] The core particles of the composite flame retardant have an average particle diameter (D 50 ) may be 0.5 ㎛ to 50 ㎛, for example, 0.6 ㎛ to 49 ㎛, or 0.8 ㎛ to 48 ㎛. Here, the average particle diameter is obtained by selecting 20 or so random particles from a scanning electron microscope image for particles, measuring their particle diameters (diameter, or major axis, or major axis length), and then obtaining a particle size distribution, and in the particle size distribution, the diameter (D) of the particles having a cumulative volume of 50% by volume 50 ) may be taken as the average particle diameter.

[0042] The shape of the core particle is not particularly limited as long as it is in particle form, and may be, for example, spherical, ellipsoidal, polyhedral, or shapeless.

[0043] The above-mentioned phosphorus flame retardant is not particularly limited as long as it is a type generally used in industry, and may include, for example, phosphate, phosphite, phosphonate, phosphinate, phosphine oxide, or a combination thereof. The phosphate, phosphite, phosphonate, phosphinate, and phosphine oxide have an organic functional group such as an alkyl group, an aryl group, or an alkenyl group, and the organic functional group may be substituted with a halogen group, an amine group, a hydroxyl group, or a thiol group. Here, the alkyl group may be an alkyl group having 1 to 20 carbon atoms, the aryl group may be an aryl group having 6 to 20 carbon atoms, and the alkenyl group may be an alkenyl group having 2 to 20 carbon atoms. The phosphate may be, for example, a trialkyl phosphate, an alkyldiaryl phosphate, a triaryl phosphate, an ammonium polyphosphate, etc., and the phosphinate may be a metal dialkyl phosphinate.

[0044] As a specific example, the phosphorus flame retardant is ammonium phosphate, ammonium polyphosphate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tripentyl phosphate, tris(2-ethylhexyl) phosphate, trioctyl phosphate, tris(2-butoxyethyl) phosphate, tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(2-chloropropyl) phosphate, tris(3-chloropropyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, tris(2,3-dibromopropyl) phosphate, tris(tribromoneopentyl) phosphate, trimethylpropane methylphosphonic oligomer, pentaerythritol phosphate, cyclic neopentyl thiophosphoric acid Anhydride, 2-ethylhexyl diphenyl phosphate, isodecyl diphenyl phosphate, dodecyl diphenyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, tricylenyl phosphate, xylenyl diphenyl phosphate, tert-butylphenyl diphenyl phosphate, phenyl di(isopropylphenyl)phosphate, tris(2,4-dibromophenyl) phosphate, N,N'-bis(2-hydroxyethyl)aminomethyl phosphate, resorcinol bis(diphenyl phosphate), phenyl diresorcinyl phosphate, bisphenol A bis(diphenyl phosphate), tetraphenyl mp-phenylene diphosphate, tetrakis(2-chloroethyl)dichloroisopentyl diphosphate, dimethyl propane phosphonate, dimethyl methane phosphonate, It may include diethyl ethane phosphonate, diethyl hydroxymethyl phosphonate, aluminum diethyl phosphinate, zinc diethyl phosphinate, aluminum dipropyl phosphinate, aluminum 2-carboxyethyl phenyl phosphinate, aluminum hypophosphite, or a combination thereof.

[0045] coating layer

[0046] According to one embodiment, the coating layer of the composite flame retardant is formed by mechanofusion, which will be described later, and may have a thickness of 0.1 μm to 6 μm, for example, 0.5 μm to 5 μm, 1 μm to 4 μm, or 2 μm to 3 μm. Here, the thickness of the coating layer can be measured, for example, through FIB, SEM, TEM, TOF-SIMS, XPS, or EDS analysis. For example, after milling and breaking one particle of the composite flame retardant through FIB, an SEM image is taken of the cross-section, and the thickness of the coating layer can be measured from the SEM image.

[0047] The coating layer may be in the form of a continuous film or in the form of an island. Considering that it is formed by the mechano-fusion method, the coating layer may exist in the form of a continuous film. For example, the silica in the coating layer may exist in the form of particles, and the particles may be connected to each other to form a coating layer. In this case, the average particle diameter (D) of the silica particles in the coating layer 50 ) may be, for example, 1 nm to 2000 nm, 2 nm to 1900 nm, or 3 nm to 1800 nm.

[0048] The silica in the coating layer may include crystalline silica, amorphous silica, or a combination thereof.

[0049] composite flame retardants

[0050] Unlike the conventional dry coating or wet coating method for complexing phosphorus-based flame retardants with silica, a composite flame retardant using the mechano-fusion method according to one embodiment may have a core phosphorus-based flame retardant and a coating layer silica chemically bonded together. The chemical bond may be, for example, a hydrogen bond, an amine bond, an amide bond, an ethylene bond, or a combination thereof. Such a composite flame retardant can effectively suppress the volatilization problem of the phosphorus-based flame retardant by increasing the bonding strength and contact surface area between the core and the coating layer.

[0051] The chemical bonding between the phosphorus-based flame retardant and silica can be confirmed, for example, through thermogravimetric analysis (TGA) or Fourier Transform Infrared Spectroscopy (FT-IR). For example, in TGA analysis, the composite flame retardant may exhibit a single temperature decrease as if it were a single compound, rather than each of the phosphorus-based flame retardant and silica exhibiting a temperature decrease individually. Accordingly, it can be interpreted that the phosphorus-based flame retardant and silica are chemically bonded within the composite flame retardant. In addition, in FT-IR analysis, the composite flame retardant may exhibit a peak corresponding to a specific bond, such as a hydrogen bond, through which the chemical bonding between the phosphorus-based flame retardant and silica can be confirmed.

[0052] Average particle size (D) of composite flame retardant 50 ) may be, for example, 0.6 μm to 56 μm, 0.8 μm to 50 μm, 1 μm to 45 μm, or 5 μm to 30 μm.

[0053] The ratio of the coating layer thickness to the core particle diameter may be 0.05 to 0.6, for example, 0.1 to 0.5 or 0.15 to 0.4. When this ratio is satisfied, the composite flame retardant can exhibit excellent flame retardant performance while effectively suppressing the volatilization problem of the phosphorus flame retardant and improving compatibility with the resin.

[0054] The weight ratio of the phosphorus-based flame retardant of the core particle and the silica of the coating layer can be from 50:50 to 99.9:0.1, for example, from 60:40 to 99.9:0.1, from 70:30 to 99.9:0.1, from 80:20 to 99.9:0.1, or from 90:10 to 99.9:0.1. When this weight ratio is satisfied, the composite flame retardant can effectively suppress the volatilization problem of the phosphorus-based flame retardant and improve compatibility with the resin while implementing excellent flame retardant performance.

[0055] elastic sheet

[0056] In one embodiment, an elastic sheet for an all-solid-state secondary battery is provided, which includes a polymer resin and the composite flame retardant.

[0057] The elastic sheet ensures that pressure is evenly transmitted to the cell structure (or electrode assembly) to ensure good contact between solid components, and also plays a role in alleviating stress transmitted to the solid electrolyte, etc., and can buffer changes in the volume of the battery by suppressing cracks from occurring in the solid electrolyte due to stress accumulation according to changes in the thickness of the electrode during charging and discharging. The elastic sheet can be positioned between the cell structures, or can be positioned on the outermost surface of the cell structures, or on the inner surface of the case.

[0058] The main materials used in elastic sheets are polymer resins such as urethane, acrylic, and silicone. These materials can act as combustibles and potentially contribute to fire if the battery temperature rises or sparks due to penetration or impact. Therefore, it is necessary to improve the flame retardancy of elastic sheets, and it is crucial to apply a flame retardant with excellent compatibility with the elastic sheet material. According to one embodiment, a composite flame retardant exhibits excellent flame retardancy for a long time due to minimal volatilization at high temperatures. In addition, it has excellent compatibility with the polymer resin, resulting in good interfacial properties with the resin and excellent dispersibility, making it suitable for use in elastic sheets. All-solid-state secondary batteries using such elastic sheets can further enhance fire safety without degrading electrochemical properties.

[0059] In the elastic sheet, the composite flame retardant may be included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the polymer resin, for example, 10 to 50 parts by weight, 20 to 50 parts by weight, 30 to 50 parts by weight, or 40 to 50 parts by weight. When the content of the composite flame retardant in the elastic sheet satisfies the above range, the elastic sheet can sufficiently perform the role of buffering the volume change of the all-solid-state battery, while improving flame retardancy and fire safety.

[0060] The main material of the elastic sheet is a polymer resin, the type of which is not particularly limited, but may include, for example, urethane resin, acrylic resin, silicone resin, fluorine-based resin, copolymers thereof, or mixtures thereof.

[0061] The above urethane resin may be referred to as polyurethane and refers to a homopolymer or copolymer having a urethane group. The acrylic resin may be, for example, polyacrylate and refers to a homopolymer or copolymer having an acrylic group. The silicone resin refers to a homopolymer or copolymer containing silicon, and the fluorine-based resin refers to a homopolymer or copolymer containing fluorine. These polymers can exhibit appropriate elasticity, modulus, and compressive strain, making them suitable for use as elastic sheets.

[0062] The urethane resin may be derived from a polyether polyol. The polyether polyol may have a functional group number of 2 to 4 and a number average molecular weight of 2000 to 4000. In addition to polyether polyol, a polyester polyol may also be used for the urethane resin. Examples of the polyester polyol include those obtained by condensation of low molecular weight polyols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, hexanediol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, diglycerin, sorbitol, and sucrose with succinic acid, adipic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, succinic anhydride, maleic anhydride, and phthalic anhydride. In addition, as polyester polyols, polyols that are ring-opening condensates of caprolactone and methylvalerolactone, which are classified as lactone esters, can be mentioned. As polycarbonate polyols, those obtained by dealcoholization reaction of polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol with dialkyl carbonate, dialkylene carbonate, diphenyl carbonate, and the like can be mentioned. The polycarbonate polyol may have 2 to 3 functional groups and a number average molecular weight of 500 or more and 1000 or less (or a hydroxyl value of 112 mgKOH / g or more and 224 mgKOH / g or less).

[0063] Acrylic resins may be, for example, derived from C1 to C20 alkyl acrylates, hydroxy C1 to C20 alkyl acrylates, or combinations thereof. Here, C1 to C20 refers to the number of carbon atoms in the alkyl group, and may be, for example, C1 to C18, C1 to C15, C1 to C12, C1 to C10, C1 to C8, C1 to C5. Here, acrylate is a concept that includes acrylate and methacrylate.

[0064] The C1 to C20 alkyl acrylate can be, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylpentyl (meth)acrylate, 2-ethylheptyl (meth)acrylate, 2-ethylnonyl (meth)acrylate, 2-propylhexyl (meth)acrylate, and 2-propyloctyl (meth)acrylate, or combinations thereof.

[0065] The hydroxy C1 to C20 alkyl acrylate can be, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or a combination thereof.

[0066] For example, the acrylic resin may be derived from C1 to C20 alkyl acrylate and hydroxy C1 to C20 alkyl acrylate, and at this time, the mixing ratio of the C1 to C20 alkyl acrylate and the hydroxy C1 to C20 alkyl acrylate may be a weight ratio of 20:80 to 90:10, for example, a weight ratio of 30:70 to 90:10, 40:60 to 90:10, 50:50 to 90:10, 60:40 to 80:20. In this case, the acrylic resin may exhibit appropriate adhesiveness and is advantageous in realizing excellent compressive strength, stress relaxation rate, and recovery rate.

[0067] Acrylic resins may further include other repeating units derived from acrylic acid, alkoxy-containing acrylates, etc. In addition, the weight average molecular weight of the acrylic resin may be, but is not limited to, 400,000 to 2,000,000.

[0068] In addition to the polymer resin and the composite flame retardant, the elastic sheet may further include elastic particles. The elastic particles may be particles composed of an elastic polymer such as rubber. The elastic particles can increase the restoring force while maintaining the stress relaxation capacity of the polymer resin.

[0069] The elastic particles may be included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the polymer resin, for example, 0.5 to 4 parts by weight, or 1 to 3 parts by weight. When the elastic particles are included in this content range, the compressive strength, stress relaxation strength, and resilience can be maximized without lowering the density and adhesiveness of the polymer resin.

[0070] The elastic particles may comprise, for example, a polymer derived from natural rubber, an alkyl acrylate, an olefin, a butadiene, an isoprene, a styrene, an acrylonitrile, a copolymer thereof, or a combination thereof. The elastic particles may have, for example, a glass transition temperature of -70°C to 0°C.

[0071] The alkyl acrylate can be a C1 to C20 alkyl acrylate, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylpentyl (meth)acrylate, 2-ethylheptyl (meth)acrylate, 2-ethylnonyl (meth)acrylate, 2-propylhexyl (meth)acrylate, and 2-propyloctyl (meth)acrylate, or combinations thereof.

[0072] The elastic particles may include, for example, polyalkyl acrylate, ethylene-propylene-diene rubber, butadiene rubber, isoprene rubber, styrene-butadiene rubber, styrene-isoprene rubber, acrylonitrile-butadiene rubber, or combinations thereof.

[0073] The elastic particles may, for example, have a core-shell structure, which is advantageous in exhibiting an appropriate size and elasticity. The core and shell may each comprise, for example, a polyalkyl acrylate. For example, the core may comprise polybutyl (meth)acrylate, and the shell may comprise polymethyl (meth)acrylate. In this case, the dispersibility is excellent, and the compressive strength, stress relaxation capacity, and resilience of the elastic sheet can be improved.

[0074] Elastic particles can be, for example, nano-sized. Specifically, the size of the elastic particles (D 50) may be 10 nm to 900 nm, for example, 10 nm to 700 nm, 50 nm to 500 nm, or 100 nm to 400 nm. Elastic particles satisfying these sizes have excellent dispersibility in the elastic sheet and can increase the restoring force while maintaining the stress relaxation ability of the elastic sheet. Here, the size of the elastic particles can be expressed as an average particle diameter or a median particle diameter, and is the diameter (D) of particles having a cumulative volume of 50 vol% in the particle size distribution as measured by a particle size analyzer. 50 ) can mean.

[0075] The elastic sheet may further contain inorganic particles, in which case the modulus and compressive strength of the elastic sheet can be improved while simultaneously improving the recovery rate.

[0076] Inorganic particles may include, for example, alumina, titania, boehmite, barium sulfate, calcium carbonate, calcium phosphate, amorphous silica, mesoporous silica, fumed silica, crystalline glass particles, kaolin, talc, silica-alumina composite oxide particles, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica, magnesium oxide, or combinations thereof.

[0077] The inorganic particles may be included, for example, in an amount of 0.001 to 50 parts by weight, for example, 0.01 to 45 parts by weight, or 0.1 to 40 parts by weight, based on 100 parts by weight of the polymer resin. In this case, the compressive strength, stress relaxation rate, and recovery rate of the elastic sheet can be improved without deteriorating the properties of the polymer resin.

[0078] The average particle size of the inorganic particles may be 0.1 ㎛ to 5 ㎛, for example, 0.1 ㎛ to 2.5 ㎛, or 0.2 ㎛ to 2 ㎛. The average particle size is measured using a laser scattering particle size distribution meter, and is the median particle size (D) when 50% of the small particles are accumulated in volume conversion.50 ) may mean.

[0079] The elastic sheet may further include hollow particles. Hollow particles are particles with an internal void, and may be expressed as hollow spheres or hollow beads, and may be hollow nanoparticles or hollow microparticles. When the elastic sheet includes hollow particles, the sheet can increase compressive strength while maintaining an appropriate density and can exhibit a foam shape.

[0080] The hollow particles may be included in an amount of 1 to 8 parts by weight based on 100 parts by weight of the polymer resin, for example, 1 to 7 parts by weight, or 2 to 6 parts by weight. When the hollow particles are included in this content range, it is advantageous for producing an elastic sheet in a foam form, and the compressive strength, stress relaxation ability, and resilience of the elastic sheet can be improved.

[0081] The hollow particles may be inorganic hollow particles, organic hollow particles, or a combination thereof. That is, the hollow particles may be composed of an inorganic material or an organic material such as a polymer.

[0082] The inorganic hollow particles may include, for example, glass, a metal oxide, a metal carbide, a metal fluoride, or a combination thereof. Specifically, the inorganic hollow particles may be formed of glass, silicon oxide, nickel oxide, barium oxide, platinum oxide, zinc oxide, aluminum oxide, zirconium oxide, iron oxide, titanium oxide, calcium carbonate, magnesium fluoride, or a combination thereof, and as an example, the inorganic hollow particles may be glass bubbles.

[0083] The organic hollow particles may include, for example, an acrylic resin, a vinyl chloride resin, a urea resin, a phenolic resin, a rubber, or a combination thereof. Furthermore, the organic hollow particles may be expandable or non-expandable, and the expandable organic hollow particles may be, for example, expandable at 120°C to 150°C.

[0084] Size of hollow particles (D 50 ) may be, for example, a micro size, and specifically, may be 1 ㎛ to 100 ㎛, 5 ㎛ to 80 ㎛, 10 ㎛ to 60 ㎛, or 20 ㎛ to 50 ㎛. Hollow particles having such a size are advantageous for making an elastic sheet in a foam form, and can lower the density and improve stress relaxation and resilience while improving the compressive strength of the elastic sheet. Here, the size of the hollow particles can be expressed as an average particle diameter or a median particle diameter, and is the diameter (D) of particles having a cumulative volume of 50% by volume in a particle size distribution, as measured by a particle size analyzer. 50 ) can mean.

[0085] In addition to the above-mentioned components, the elastic sheet may further contain suitable additives, for example, pigments, antioxidants, lubricants, antistatic agents, initiators, crosslinking agents, coupling agents, and stabilizers. Each additive may be included in an appropriate amount according to the purpose, for example, the pigment may be included in an amount of 0.1 to 100 parts by weight, for example, 1 to 10 parts by weight, based on 100 parts by weight of the polymer resin, the antioxidant may be included in an amount of 0.1 to 100 parts by weight, for example, 1 to 10 parts by weight, based on 100 parts by weight of the polymer resin, the lubricant may be included in an amount of 0.1 to 100 parts by weight, for example, 1 to 10 parts by weight, based on 100 parts by weight of the polymer resin, the antistatic agent may be included in an amount of 0.1 to 100 parts by weight, for example, 1 to 20 parts by weight, based on 100 parts by weight of the polymer resin.

[0086] The thickness of the elastic sheet may be from 100 ㎛ to 1000 ㎛, for example, from 100 ㎛ to 800 ㎛, from 100 ㎛ to 600 ㎛, or from 100 ㎛ to 500 ㎛. The elastic sheet according to one embodiment may be a thin elastic sheet, that is, a sheet with a minimized thickness, in order to implement a thin battery or to maximize the capacity of the battery, and may have a thickness of, for example, from 100 ㎛ to 500 ㎛. The composite flame retardant according to one embodiment can have high dispersibility and excellent flame retardancy even in a sheet having such a thin thickness. That is, the composite flame retardant can be advantageously applied to a thin elastic sheet having a thickness of from 100 ㎛ to 500 ㎛.

[0087] The elastic sheet may be in the form of a relatively soft, low-modulus pad, or in the form of a relatively hard foam, or in the form of various injection-molded products.

[0088] An elastic sheet according to an embodiment can have excellent flame retardancy by including the composite flame retardant described above, and can have a flame retardancy rating of VTM-0 or higher according to the UL-94 standard.

[0089] Method for manufacturing elastic sheets

[0090] In one embodiment, a method for producing an elastic sheet for an all-solid-state secondary battery is provided, which comprises preparing a composite flame retardant by mixing a phosphorus flame retardant and silica by a mechano-fusion method, mixing the composite flame retardant and a polymer resin to prepare a composition, and forming a film.

[0091] Mechanofusion is a dry mixing or dry coating method that applies mechanical energy inside a chamber to generate compressive, shear, and frictional forces. It can be described as a high-energy mixing method. Through this method, a composite flame retardant can be manufactured, comprising core particles containing a phosphorus-based flame retardant, and a coating layer containing silica that surrounds the surface of the core particles. Furthermore, silica particles can be bonded to the core particles containing the phosphorus-based flame retardant through a mechanochemical reaction to form a coating layer.

[0092] Specifically, the process for manufacturing the composite flame retardant may include injecting a phosphorus flame retardant powder and silica powder into an inner chamber of a mechano-fusion device and rotating the inner chamber. Rotating the inner chamber may be performed at a speed of, for example, 100 rpm to 3000 rpm, 500 rpm to 3000 rpm, 1000 rpm to 3000 rpm, or 2000 rpm to 3000 rpm, and may be performed for 5 minutes to 60 minutes. In addition, the temperature of the inner chamber may be set to, for example, 15°C to 30°C, or 20°C to 30°C, and may be maintained at, for example, 25°C.

[0093] The mixing ratio of the above-mentioned flame retardant and the above-mentioned silica may be 50:50 to 99.9:0.1 by weight, for example, 60:40 to 99.9:0.1, 70:30 to 99.9:0.1, 80:20 to 99.9:0.1, or 90:10 to 99.9:0.1.

[0094] As a raw material to be injected, the phosphorus flame retardant is in particle form and has an average particle diameter (D 50 ) may be 0.5 ㎛ to 50 ㎛, for example 0.6 ㎛ to 49 ㎛, or 0.8 ㎛ to 48 ㎛. The silica is in the form of particles and has an average particle diameter (D 50) can be 1 nm to 2000 nm, 2 nm to 1900 nm, or 3 nm to 1800 nm.

[0095] All-solid-state secondary battery

[0096] In one embodiment, an all-solid-state secondary battery is provided, which includes a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode. The all-solid-state secondary battery is characterized by including the aforementioned composite flame retardant, thereby further improving fire safety.

[0097] For example, an all-solid-state secondary battery includes two or more cell structures including a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, and includes elastic sheets positioned between and at the outermost portion of the cell structures, and at least one of the elastic sheets may include the composite flame retardant described above.

[0098] Fig. 2 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Referring to Fig. 2, the all-solid-state secondary battery (100) has a structure in which a cell structure in which a negative electrode (400) including a negative electrode current collector (401) and a negative electrode active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode current collector (201) are laminated is housed in a battery case. Although Fig. 2 illustrates an assembly in which two cell structures including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200) are laminated, three or more cell structures may be laminated, for example, 2 to 200, 3 to 100, 4 to 50, etc. may be laminated.

[0099] The all-solid-state secondary battery (100) may further include an elastic sheet (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). That is, the elastic sheet (500) may be positioned between the cell structures and / or at the outermost surface of the cell structures. According to one embodiment, at least one of the elastic sheets (500) in the battery may be an elastic sheet including the aforementioned composite flame retardant. In this case, the flame retardancy and fire safety of the lithium secondary battery may be further improved.

[0100] In another embodiment, an all-solid-state secondary battery is provided, which includes a cell structure including a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, and a resin layer positioned on a side of the cell structure, wherein the resin layer includes a resin and the composite flame retardant described above. Fig. 3 is a cross-section of an all-solid-state secondary battery illustrating a resin layer. Referring to Fig. 3, an all-solid-state secondary battery (100) has a structure in which a cell structure in which a negative electrode (400) including a negative electrode current collector (401) and a negative electrode active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode current collector (201) are laminated is housed in a battery case.

[0101] The all-solid-state secondary battery (100) may further include an elastic sheet (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). That is, the elastic sheet (500) may be positioned between the cell structures and / or at the outermost surface of the cell structures. According to one embodiment, at least one of the elastic sheets (500) in the battery may be an elastic sheet including the aforementioned composite flame retardant. In this case, the flame retardancy and fire safety of the lithium secondary battery may be further improved.

[0102] The all-solid-state secondary battery (100) may further include a resin layer (600) on the side of the cell structure. That is, the resin layer (600) may be positioned on the side of the cell structure to maintain the shape of the cell structures and improve insulation, adhesiveness, heat dissipation, etc.

[0103] The resin, which is the main material of the resin layer, may include, but is not limited to, polyvinylidene fluoride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, polyurethane, nylon, polyamideimide, polyimide, poly(meth)acrylate, polyacrylonitrile, polystyrene, acrylic resin, or a combination thereof.

[0104] In the resin layer, the composite flame retardant may be included in an amount of 1 to 60 parts by weight based on 100 parts by weight of the resin, for example, 10 to 60 parts by weight, 20 to 60 parts by weight, 30 to 60 parts by weight, or 40 to 50 parts by weight. When the content of the composite flame retardant in the resin layer satisfies the above range, the resin layer can have improved flame retardancy and fire safety without changing its physical properties.

[0105] anode

[0106] In one embodiment, the device comprises a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises a positive electrode active material and optionally may comprise a solid electrolyte, a binder, and / or a conductive material.

[0107] positive electrode active material

[0108] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0109] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, lithium-rich layered oxide, or a combination thereof.

[0110] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more based on 100 mol% of metals excluding lithium in a lithium transition metal composite oxide. The nickel content in the high-nickel cathode active material may be 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and 99 mol% or less based on 100 mol% of metals excluding lithium. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0111] As a more specific example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Mn 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b X c O 2-α D α(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤0.5, 0 < α < 2);Li a Nor 1-b-c Mn b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2);Li a Nor b Co c L 1 d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1);; The a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); The a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); The a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); The a Mn2G b O4(0.90 ≤ a ≤1.8, 0.001 ≤ b ≤ 0.1); The a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); The (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); The a FePO4(0.90 ≤ to ≤ 1.8)

[0112] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X 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; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; Z is Cr, V, Fe, Sc, Y, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0113] The cathode active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 11, a lithium cobalt-based oxide represented by the following chemical formula 12, a lithium iron phosphate-based compound represented by the following chemical formula 13, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 14, or a combination thereof.

[0114] [Chemical Formula 11]

[0115] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0116] In the above chemical formula 11, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0117] In the above chemical formula 1, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0118] [Chemical Formula 12]

[0119] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0120] In the above chemical formula 12, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0121] [Chemical Formula 13]

[0122] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0123] In the above chemical formula 13, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0124] [Chemical Formula 14]

[0125] Li a4 Ni x4 Mny4 M 5 z4 O 2-b4 X b4

[0126] In the above chemical formula 14, 0.9≤a2≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0127] The average particle diameter (D) of the above positive electrode active material 50 ) may be 1 μm to 25 μm, for example, 3 μm to 25 μm, 1 μm to 20 μm, 1 μm to 18 μm, 3 μm to 15 μm, or 5 μm to 15 μm. For example, the positive electrode active material may have an average particle diameter (D 50 ) with small particles of 1 ㎛ to 9 ㎛ and an average particle diameter (D 50 ) may include particles having a particle size range of 10 ㎛ to 25 ㎛. The positive electrode active material having such a particle size range can be harmoniously mixed with other components in the positive electrode active material layer and can realize high capacity and high energy density. Here, the average particle size is obtained by selecting 20 or so random particles from a scanning electron microscope image of the positive electrode active material, measuring their particle sizes (diameter, or major axis, or major axis length), and then obtaining a particle size distribution, and in the particle size distribution, the diameter (D) of the particles having a cumulative volume of 50% by volume 50 ) may be taken as the average particle diameter.

[0128] The above-mentioned positive electrode active material may be in the form of a secondary particle formed by agglomeration of a plurality of primary particles, or may be in the form of a single particle. In addition, the above-mentioned positive electrode active material may be spherical or nearly spherical in shape, or may be polyhedral or irregular in shape.

[0129] Meanwhile, the positive electrode active material may include a buffer layer on the particle surface. The buffer layer may be expressed as a coating layer, a protective layer, etc., and may play a role in lowering the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte particles. For example, the buffer layer may include a lithium-metal-oxide, wherein the metal may be one or more elements selected from the group consisting of Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. The lithium-metal-oxide is excellent in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte particles while improving the performance of the positive electrode active material by facilitating the movement of lithium ions and electron conduction.

[0130] The positive electrode active material may be included in an amount of 55 wt% to 99.5 wt% based on 100 wt% of the positive electrode active material layer, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0131] bookbinder

[0132] The binder helps the positive electrode active material particles adhere well to each other and also helps the positive electrode active material adhere well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0133] Challenge

[0134] Conductive materials are used to impart conductivity to electrodes, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0135] The content of the binder and the conductive agent may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0136] The cathode active material layer may optionally further include a solid electrolyte. The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof, and specific descriptions thereof will be provided later in the section on the solid electrolyte layer.

[0137] For 100 wt% of the positive electrode active material layer, the solid electrolyte may be included in an amount of 0.1 wt% to 35 wt%, for example, 1 wt% to 35 wt%, 5 wt% to 30 wt%, 8 wt% to 25 wt%, or 10 wt% to 20 wt%.

[0138] In the positive electrode active material layer, the positive electrode active material may be comprised in an amount of 65 to 99 wt% and the solid electrolyte in an amount of 1 to 35 wt%, based on 100 wt% of the total of the positive electrode active material and the solid electrolyte, for example, the positive electrode active material may be comprised in an amount of 80 to 90 wt% and the solid electrolyte in an amount of 10 to 20 wt%. When the solid electrolyte is comprised in the positive electrode in such an amount, the efficiency and life characteristics of the all-solid-state secondary battery can be improved without reducing the capacity.

[0139] Al may be used as the above current collector, but is not limited thereto.

[0140] cathode

[0141] An anode for an all-solid-state secondary battery may include a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0142] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0143] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0144] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0145] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material is silicon, a silicon-carbon composite, SiOx(0 <x<2), Si-Q 합금(상기 Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소(Si를 제외함), 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합에서 선택됨), 또는 이들의 조합일 수 있다. 상기 Sn계 음극 활물질로는 Sn, SnO2, Sn계 합금 또는 이들의 조합일 수 있다.

[0146] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the composite may include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating layer (shell) positioned on the surface of the secondary particles. The amorphous carbon may also be positioned between the silicon primary particles, such that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0147] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0148] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in a mixture with a carbon-based negative electrode active material.

[0149] The content of the negative active material in the above negative active material layer may be 95 wt% to 99 wt% based on the total weight of the negative active material layer. For example, the negative active material layer may include 90 wt% to 99 wt% of the negative active material, 0.5 wt% to 5 wt% of the binder, and 0 wt% to 5 wt% of the conductive material.

[0150] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0151] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0152] The above-mentioned aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0153] When using an aqueous binder as the above-mentioned negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li.

[0154] The above dry binder is a polymeric material capable of being fiberized, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0155] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0156] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0157] As another example, the negative electrode for an all-solid-state secondary battery may be a precipitation-type negative electrode. The precipitation-type negative electrode may refer to a negative electrode that does not include a negative electrode active material when the battery is assembled, but in which lithium metal or the like is precipitated or deposited on the negative electrode when the battery is charged, and this acts as a negative electrode active material.

[0158] Fig. 4 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitated negative electrode. Referring to Fig. 4, the all-solid-state secondary battery (100) is a structure in which a cell structure in which a precipitated negative electrode (400) including a negative electrode current collector (401) and a negative electrode coating layer (405) positioned on the negative electrode current collector, a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode current collector (201) are laminated is housed in a battery case.

[0159] The all-solid-state secondary battery (100) may further include an elastic sheet (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). That is, the elastic sheet (500) may be positioned between the cell structures and / or at the outermost surface of the cell structures. According to one embodiment, at least one of the elastic sheets (500) in the battery may be an elastic sheet including the aforementioned composite flame retardant. In this case, the flame retardancy and fire safety of the lithium secondary battery may be further improved.

[0160] An all-solid-state secondary battery having such a precipitated negative electrode (400) starts initial charging in a state in which no negative electrode active material is present, and during charging, high-density lithium metal is precipitated or deposited between the current collector (401) and the negative electrode coating layer (405), or on the negative electrode coating layer (405), to form a lithium metal layer (404), which can function as a negative electrode active material. Accordingly, in an all-solid-state secondary battery that has been charged at least once, the precipitated negative electrode (400) may include, for example, a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The lithium metal layer (404) refers to a layer in which lithium metal or the like is precipitated during the charging process of the battery, and may be referred to as a metal layer, a lithium layer, a lithium deposition layer, or a negative electrode active material layer.

[0161] The above cathode coating layer (405) may be referred to as a lithium electrodeposition induction layer or a cathode catalyst layer, and may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0162] The metal may be a lithium-philic metal, and may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one of these or may be composed of several types of alloys. When the metal is present in the form of particles, the average particle diameter (D 50) may be less than about 4 μm, for example, 10 nm to 4 μm.

[0163] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microbeads, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof.

[0164] When the above-described negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state secondary battery can be improved. The above-described negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0165] The above-described cathode coating layer (405) may include, for example, the above-described lithium-philic metal and amorphous carbon, in which case the precipitation of the lithium metal may be effectively promoted. As a specific example, the cathode coating layer (405) may include a composite in which a lithium-philic metal is supported on amorphous carbon.

[0166] The above cathode coating layer (405) may further include a binder, and the binder may be, for example, a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0167] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 ㎛, or 500 nm to 10 ㎛, or 1 ㎛ to 5 ㎛.

[0168] The above-described precipitated negative electrode (400) may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type thereof or may be composed of multiple types of alloys. The thin film may further flatten the precipitated form of the lithium metal layer (404) and further improve the characteristics of the all-solid-state secondary battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0169] The lithium metal layer (404) may include lithium metal or a lithium alloy. The lithium alloy may be, for example, 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, or a Li-Si alloy.

[0170] The thickness of the lithium metal layer (404) may be 1 µm to 500 µm, 1 µm to 200 µm, 1 µm to 100 µm, or 1 µm to 50 µm. If the thickness of the lithium metal layer (404) is too thin, it may be difficult to perform the role of a lithium storage, and if it is too thick, the battery volume may increase and the performance may deteriorate.

[0171] When such a precipitation-type cathode is applied, the cathode coating layer (405) can play a role in protecting the lithium metal layer (404) and suppressing the precipitation growth of lithium deadlight. Accordingly, short-circuiting and capacity reduction of the all-solid-state battery can be suppressed, and the life characteristics can be improved.

[0172] solid electrolyte layer

[0173] The solid electrolyte layer includes a solid electrolyte. The solid electrolyte may be a type of inorganic solid electrolyte, and may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof. The solid electrolyte layer according to one embodiment may include a sulfide-based solid electrolyte.

[0174] Sulfide-based solid electrolyte

[0175] Sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5--LiX (where X is a halogen element, for example, I or Cl), 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 (m, n are integers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0176] A sulfide-based solid electrolyte can be obtained, for example, by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or 50:50 to 80:20, and optionally heat-treating them. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be produced. The ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0177] Methods for mixing sulfur-containing raw materials for producing sulfide-based solid electrolytes include mechanical milling or the solution method. Mechanical milling involves placing raw materials in a ball mill reactor and vigorously stirring them to finely atomize and mix them. Using the solution method, the raw materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, heat treatment after mixing can solidify the crystals of the solid electrolyte and improve ionic conductivity. For example, a sulfide-based solid electrolyte can be produced by mixing sulfur-containing raw materials and heat-treating them twice or more, resulting in a sulfide-based solid electrolyte with high ionic conductivity and robustness.

[0178] According to one embodiment, sulfide-based solid electrolyte particles can be manufactured through, for example, a first heat treatment in which sulfur-containing raw materials are mixed and calcined at 120°C to 350°C, and a second heat treatment in which the first heat treatment result is mixed and calcined at 350°C to 800°C. The first heat treatment and the second heat treatment can each be performed in an inert gas or nitrogen atmosphere. The first heat treatment can be performed for 1 to 10 hours, and the second heat treatment can be performed for 5 to 20 hours. The first heat treatment can have the effect of milling small raw materials, and the second heat treatment can synthesize the final solid electrolyte. Through two or more such heat treatments, a high-performance sulfide-based solid electrolyte with high ionic conductivity and robustness can be obtained, and such a solid electrolyte can be said to be suitable for mass production. The temperature of the first heat treatment may be, for example, 150°C to 330°C, or 200°C to 300°C, and the temperature of the second heat treatment may be, for example, 380°C to 700°C, or 400°C to 600°C.

[0179] For example, the sulfide-based solid electrolyte particles may include argyrodite-type sulfides. The argyrodite-type sulfide-based solid electrolyte particles may have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It has a high ionic conductivity approaching the S / cm range, can form a close bond between a positive electrode active material and a solid electrolyte without causing a decrease in ionic conductivity, and can further form a close interface between an electrode layer and a solid electrolyte layer. An all-solid-state secondary battery including the same can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0180] The argyrodite-type sulfide-based solid electrolyte particles may include, for example, a compound represented by the chemical formula 21 below.

[0181] [Chemical Formula 21]

[0182] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0183] In the above chemical formula 21, 4≤a≤8, and M 1 is Mg, Cu, Ag, or a combination thereof, and 0≤b<0.5, and M 2 is Na, K, or a combination thereof, 0≤c<0.5, and M 3 is Sn, Zn, Si, Sb, Ge, or a combination thereof, and 0 <d<4, 0≤e<1 이고, M 4 is O, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤12, 0≤g<2, and X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

[0184] For example, in chemical formula 21, a halide element (X) may be included as an essential element, in which case 0 <h≤2로 표시될 수 있다. 일 예로 화학식 21에 M 1 Elements may be required, in which case 0 <b<0.5로 표시될 수 있다. 화학식 21에서 M 3 can be understood as an element substituted in place of P and 0 <e<1일 수 있다. 화학식 21에서 M 4 is substituted in the S position, for example, 0 <g<2일 수 있으며 S의 비율인 f는 예를 들어 3≤f≤7일 수 있다. M 4 Go SO n If SO n It can be, for example, S4O6, S3O6, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, SO4, or SO5, and can be, for example, SO4.

[0185] For example, in chemical formula 21, a+b+c+h=7, d+e=1, and f+g+h=6.

[0186] As a specific example, argyrodite-type sulfide-based solid electrolyte particles include Li3PS4 and Li7P3S. 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS 4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO4) 0.05 )Cl 1.25 , (Li 5.69 Cu0.06 )P(S 4.60 (SO4) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO4) 0.025 )Cl 1.25 , or combinations thereof, but are not limited thereto.

[0187] An argyrodite-type sulfide-based solid electrolyte can be manufactured by mixing raw materials such as lithium sulfide, phosphorus sulfide, and optionally lithium halide. After mixing these, a heat treatment may be performed. The heat treatment may be performed at a temperature in the range of 400°C to 600°C, for example, 450°C to 500°C, or 460°C to 490°C, and for 5 to 30 hours, 10 to 24 hours, or 15 to 20 hours. When heat treating under the above conditions, ionic conductivity can be maximized. The heat treatment may include, for example, two or more heat treatment steps. Here, manufacturing an argyrodite-type sulfide-based solid electrolyte may include, for example, a first heat treatment of mixing raw materials and calcining at 120°C to 350°C, and a second heat treatment of mixing the first heat treatment resultant again and calcining at 350°C to 800°C.

[0188] Average particle diameter (D) of sulfide-based solid electrolyte particles 50) may be, for example, 0.1 ㎛ to 5.0 ㎛ or 0.1 ㎛ to 3.0 ㎛, may be small particles of 0.1 ㎛ to 1.9 ㎛, or may be large particles of 2.0 ㎛ to 5.0 ㎛. The sulfide-based solid electrolyte particles may be a mixture of small particles having an average particle diameter of 0.1 ㎛ to 1.9 ㎛ and large particles having an average particle diameter of 2.0 ㎛ to 5.0 ㎛. The average particle diameter of the sulfide-based solid electrolyte particles may be measured by an electron microscope image, and for example, a particle size distribution is obtained by measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image, where D 50 It may have been calculated.

[0189] Oxide-based solid electrolyte

[0190] Oxide-based solid electrolytes include, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12(0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr; x is an integer from 1 to 10), or mixtures thereof.

[0191] Halide-based solid electrolyte

[0192] The solid electrolyte layer may further include, for example, a halide-based solid electrolyte. The halide-based solid electrolyte contains a halogen element as a main component, and may mean that the ratio of the halide element to all elements constituting the solid electrolyte is 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. For example, the halide-based solid electrolyte may not contain a sulfur element.

[0193] The halide-based solid electrolyte may contain lithium element, a metal element other than lithium, and a halogen element. The metal element other than lithium may be Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof. The halogen element may be F, Cl, Br, I, or a combination thereof, and may be Cl, Br, or a combination thereof. The halide-based solid electrolyte may contain, for example, Li aM1X6 (M is Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof, X is F, Cl, Br, I, or a combination thereof, and 2≤a≤3) can be represented. The halide-based solid electrolyte may be, for example, Li2ZrCl6, Li 2.7 Y 0.7 Zr 0.3 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 In 0.5 Zr 0.5 Cl6, Li2In 0.5 Zr 0.5 Cl6, Li3YBr6, Li3YCl6, Li3YBr2Cl4, Li3YbCl6, Li 2.6 Hf 0.4 Yb 0.6 Cl6, or combinations thereof, but is not limited thereto.

[0194] bookbinder

[0195] The solid electrolyte layer may further include a binder. Binders include, for example, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, natural rubber, polydimethylsiloxane, polyethylene oxide, polyvinylpyrrolidone, polyvinylpyridine, chlorosulfonated polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polyamideimide, polyimide, poly(meth)acrylate, polyacrylonitrile, polystyrene, polyurethane, and the like. copolymers, or combinations thereof.

[0196] The binder may be included in an amount of 0.1 wt% to 3 wt% based on 100 wt% of the solid electrolyte layer, for example, 0.5 wt% to 2 wt%, or 0.5 wt% to 1.5 wt%. When the binder is included in the above range, the components within the solid electrolyte layer can be well combined without lowering the ionic conductivity of the solid electrolyte, thereby improving the durability and reliability of the battery.

[0197] Other ingredients

[0198] The solid electrolyte layer may optionally further comprise an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0199] The above alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte layer may be 1 M or more, for example, 1 M to 4 M. In this case, the lithium salt may improve ion conductivity by enhancing the lithium ion mobility of the solid electrolyte layer.

[0200] The lithium salt may be applied without limitation on type, and may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0201] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0202] Ionic liquids are salts or molten salts that are composed only of ions and are liquid at room temperature, with a melting point below room temperature.

[0203] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, trizolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may be a compound containing one or more anions selected from among.

[0204] The ionic liquid may be at least one selected from the group consisting of, for example, N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide.

[0205] In the solid electrolyte layer, the weight ratio of the solid electrolyte to the ionic liquid may be 0.1:99.9 to 90:10, for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte layer satisfying the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state secondary battery can be improved.

[0206] The above-mentioned all-solid-state secondary battery may be a unit cell having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative electrode, or a laminated battery in which the structure of the unit cell is repeated.

[0207] The shape of the above-mentioned all-solid-state secondary battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, etc. In addition, the above-mentioned all-solid-state secondary battery can be applied to large-sized batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state secondary battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring a large amount of power storage, and for example, it can be used in electric bicycles or power tools, etc. In addition, the above-mentioned all-solid-state secondary battery can be used in various fields such as portable electronic devices.

[0208] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0209] Example 1

[0210] 1. Manufacturing of composite flame retardants

[0211] 99.9 g of aluminum diethyl phosphinate (ADP) and 0.1 g of silica were placed in the chamber of a Mechano Fusion, a dry energy mixer. The chamber rotation speed was set to 2,500 rpm to provide mechanical energy, thereby producing a composite flame retardant.

[0212] Figure 5 is a SEM image of the composite flame retardant manufactured in Example 1. Referring to Figure 5, it can be seen that small particles of silica are strongly bonded to the surface of the large particle phosphorus flame retardant.

[0213] 2. Manufacturing of elastic sheets

[0214] 10.425 parts by weight of 2-ethylhexyl acrylate, 10.425 parts by weight of isobornyl acrylate, 25 parts by weight of 4-hydrobutyl acrylate, 0.025 parts by weight of 1,6-hexanediol diacrylate (crosslinker), and 0.125 parts by weight of Irgacure 651 (initiator) were added and mixed, and 0.5 parts by weight of polymer microspheres (820DET40) and 3.5 parts by weight of glass bubbles (K-1) were added as additives and mixed for 2 hours to prepare an acrylic resin. Next, 50 parts by weight of the composite flame retardant prepared above was added based on 100 parts by weight of the acrylic resin, and mixed for 20 minutes to prepare a composition for an elastic sheet. The composition was applied on a PET film and cured using UV coating equipment to prepare an elastic sheet having a thickness of about 300 μm.

[0215] 3. Manufacturing of all-solid-state secondary batteries

[0216] LiNi coated with Li2O-ZrO2 0.8 Co0.15 Mn 0.05 A cathode composition was prepared by mixing 85 wt% of an O2 cathode active material, 13.5 wt% of a lithium argyrodite-type solid electrolyte Li6PS5Cl, 1.0 wt% of a polyvinylidene fluoride binder, and 0.5 wt% of a carbon nanotube conductive material. The prepared cathode composition was coated on an aluminum cathode current collector, dried, and rolled to prepare a cathode.

[0217] Primary entry (D 50 ) carbon black with an average particle diameter (D) of about 30 nm 50 ) was prepared by mixing silver (Ag) having a diameter of approximately 60 nm in a weight ratio of 3:1, and 0.25 g of the above complex was added to 2 g of an NMP solution containing 7 wt% of polyvinylidene fluoride binder and mixed to prepare a negative electrode coating layer composition. This was applied to a nickel foil current collector using a bar coater and vacuum-dried to prepare a deposition-type negative electrode in which a negative electrode coating layer was formed on the current collector.

[0218] An argyrodite-type solid electrolyte Li6PS5Cl(D) was added to a binder solution in which an acrylic binder (SX-A334, Zeon) was dissolved in an isobutyryl isobutyrate (IBIB) solvent. 50= 3㎛) was added and stirred to prepare a slurry. The slurry contains 98.5 wt% of solid electrolyte and 1.5 wt% of binder. The slurry was applied onto a release PET film using a bar coater and dried at room temperature to prepare a solid electrolyte layer.

[0219] Bi-cell type cell structures were manufactured by stacking cathode / solid electrolyte / anode / solid electrolyte / cathode in that order. An elastic sheet manufactured between two cell structures and on the outermost surface of the cell structures was interposed. The laminated structure was placed in an aluminum pouch laminate film and subjected to warm isostatic pressing (WIP) at 80°C and 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery.

[0220] Example 2

[0221] In the manufacture of a composite flame retardant, a composite flame retardant was manufactured in substantially the same manner as in Example 1, except that 99.5 g of ADP and 0.5 g of silica were mixed, and an elastic sheet and an all-solid-state secondary battery were manufactured.

[0222] Figure 6 is a SEM image of the composite flame retardant manufactured in Example 2. It can be seen from Figure 6 that silica particles are strongly bonded to the surface of the phosphorus flame retardant particles.

[0223] Example 3

[0224] In the manufacture of a composite flame retardant, a composite flame retardant was manufactured in substantially the same manner as in Example 1, except that 99 g of ADP and 1 g of MC were mixed, and an elastic sheet and an all-solid-state secondary battery were manufactured.

[0225] Figure 7 is a SEM image of the composite flame retardant manufactured in Example 3. It can be seen from Figure 7 that silica particles are strongly bonded to the surface of the phosphorus flame retardant particles.

[0226] Comparative Example 1

[0227] A composite flame retardant was manufactured in substantially the same manner as in Example 1, except that a 3-roll machine was used instead of a mechanofusion dry mixer for mixing for 48 hours, and an elastic sheet and an all-solid-state secondary battery were manufactured.

[0228] Comparative Example 2

[0229] A composite flame retardant was prepared in substantially the same manner as in Example 2, except that a 3-roll machine was used instead of a mechanofusion as a dry mixer during the preparation of the composite flame retardant, and mixing was performed for 48 hours, and an elastic sheet and an all-solid-state secondary battery were prepared.

[0230] Comparative Example 3

[0231] A composite flame retardant was prepared in substantially the same manner as in Example 3, except that a 3-roll machine was used instead of a mechanofusion as a dry mixer during the preparation of the composite flame retardant, and mixing was performed for 48 hours, and an elastic sheet and an all-solid-state secondary battery were prepared.

[0232] Example 4

[0233] 1. Manufacturing of composite flame retardants

[0234] A composite flame retardant was prepared in substantially the same manner as in Example 1.

[0235] 2. Manufacturing of elastic sheets

[0236] 56.12 parts by weight of polyol (CP6001), 4.88 parts by weight of isocyanate (Luprante M11s), 0.025 parts by weight of 1,4-butanediol (crosslinking agent), and 0.125 parts by weight of dibutyltin dilaurate (metal catalyst) were added and mixed, and 0.35 parts by weight of heat-expandable microspheres (FN-100MD) and 3.5 parts by weight of glass bubbles (S60) were added as additives and mixed for 2 hours to prepare an acrylic resin. Next, 35 parts by weight of the composite flame retardant prepared above was added based on 100 parts by weight of the acrylic resin, and mixed for 20 minutes to prepare a composition for an elastic sheet. The composition was applied on a PET film and heated to 100 to 150°C to prepare an elastic sheet having a thickness of about 300 μm.

[0237] 3. Manufacturing of all-solid-state secondary batteries

[0238] A composite flame retardant was prepared in substantially the same manner as in Example 1.

[0239] Example 5

[0240] In the manufacture of a composite flame retardant, a composite flame retardant was manufactured in substantially the same manner as in Example 4, except that 99.5 g of ADP and 0.5 g of MC were mixed, and an elastic sheet and an all-solid-state secondary battery were manufactured.

[0241] Example 6

[0242] In the manufacture of a composite flame retardant, a composite flame retardant was manufactured in substantially the same manner as in Example 4, except that 99 g of ADP and 1 g of MC were mixed, and an elastic sheet and an all-solid-state secondary battery were manufactured.

[0243] Example 7

[0244] 1. Manufacturing of composite flame retardants

[0245] A composite flame retardant was prepared in substantially the same manner as in Example 1.

[0246] 2. Manufacturing of elastic sheets

[0247] 59.66 parts by weight of polyol (CP6001), 5.19 parts by weight of isocyanate (Luprante M11s), 0.025 parts by weight of 1,4-butanediol (crosslinking agent), and 0.125 parts by weight of dibutyltin dilaurate (metal catalyst) were added and mixed, and nitrogen gas was introduced at a rate of 200 cc / min and stirred for 5 minutes to prepare an acrylic resin. Next, 35 parts by weight of the composite flame retardant prepared above was added based on 100 parts by weight of the acrylic resin, and mixed for 20 minutes to prepare a composition for an elastic sheet. The composition was applied on a PET film and heated to 100 to 150°C to prepare an elastic sheet having a thickness of about 300 μm.

[0248] Comparative Example 4

[0249] A composite flame retardant was prepared in substantially the same manner as in Example 4, except that a 3-roll machine was used instead of a mechanofusion as a dry mixer during the preparation of the composite flame retardant, and mixing was performed for 48 hours, and an elastic sheet and an all-solid-state secondary battery were prepared.

[0250] Comparative Example 5

[0251] A composite flame retardant was prepared in substantially the same manner as in Example 5, except that a 3-roll machine was used instead of a mechanofusion as a dry mixer during the preparation of the composite flame retardant, and mixing was performed for 48 hours, and an elastic sheet and an all-solid-state secondary battery were prepared.

[0252] Comparative Example 6

[0253] A composite flame retardant was prepared in substantially the same manner as in Example 6, except that a 3-roll machine was used instead of a mechanofusion as a dry mixer during the preparation of the composite flame retardant, and mixing was performed for 48 hours, and an elastic sheet and an all-solid-state secondary battery were prepared.

[0254] Comparative Example 7

[0255] A composite flame retardant was prepared in substantially the same manner as in Example 7, except that a 3-roll machine was used instead of a mechanofusion as a dry mixer during the preparation of the composite flame retardant, and mixing was performed for 48 hours, and an elastic sheet and an all-solid-state secondary battery were prepared.

[0256]

[0257] Evaluation Example 1: Observation of elastic sheet fracture surface

[0258] The elastic sheets manufactured in Examples 1, 3, and 6 and the elastic sheets manufactured in Comparative Examples 1, 3, and 6 were cooled in liquid nitrogen, fractured, and the cross-sections were photographed using SEM. The SEM image of the fracture surface of the elastic sheet of Example 1 is shown in FIG. 8, the SEM image of the fracture surface of the elastic sheet of Example 3 is shown in FIG. 9, the SEM image of the fracture surface of the elastic sheet of Example 6 is shown in FIG. 10, the SEM image of the fracture surface of the elastic sheet of Comparative Example 1 is shown in FIG. 11, the SEM image of the fracture surface of the elastic sheet of Comparative Example 2 is shown in FIG. 12, and the SEM image of the fracture surface of the elastic sheet of Comparative Example 6 is shown in FIG. 13. Referring to FIGS. 8 to 13, it can be confirmed that in the elastic sheets of Examples 1, 3, and 6, unlike Comparative Examples 1, 3, and 6, there are no pores at the interface between the composite flame retardant and the polymer resin. It can be seen that the interfacial affinity between the composite flame retardant and the polymer resin is improved, so that no voids exist and the compatibility between the two materials is improved.

[0259]

[0260] Evaluation Example 2: FT-IR

[0261] In order to confirm whether the mechano-chemical reaction of the composite flame retardant according to the example is formed by mechanofusion, Fourier transform infrared spectroscopy (FT-IR) was performed on the composite flame retardant of example 3 and the composite flame retardant of comparative example 3, and the results are shown in Fig. 14. Referring to Fig. 14, in Example 3, a hydrogen bond, which is a chemical bond between the phosphorus-based flame retardant and silica, was formed by mechanofusion, and the wavelength of 1063 to 1059 cm -1 and 1046 to 1038 cm -1 We can see that the peak has shifted, i.e., from 1063 to 1059 cm -1 and 1046 to 1038 cm -1If a peak appears, it can be seen that a hydrogen bond was formed between the phosphorus-based flame retardant and silica by the mechanofusion treatment. On the other hand, in the case of Comparative Example 3, it was confirmed that no hydrogen bond was formed between the phosphorus-based flame retardant and silica.

[0262]

[0263] Evaluation Example 3: Volatility Evaluation of Flame Retardant in Elastic Sheet

[0264] In order to evaluate the volatility of the flame retardant in the elastic sheet to which the composite flame retardants of ADP, Examples 1 to 7 and Comparative Examples 1 to 7 were applied, each elastic sheet was manufactured into a sample sized 200 x 50 mm, the weight of each sample was measured, and after leaving it in an oven at 70°C for 7 days, the weight of the sample was measured, and the volatility was evaluated through the change in weight, and the results for the elastic sheet to which the acrylic composite flame retardant was applied are shown in Table 1, and the results for the elastic sheet to which the urethane composite flame retardant was applied are shown in Table 2.

[0265]

[0266] Initial sample weight Sample weight after one week at 70℃ Flame retardant volatility (%) ADP 2.75 16 2.57 14 6.55% Example 12.78 74 2.76 77 0.71% Example 22.95 28 2.93 56 0.58% Example 32.90 68 2.89 0 3 0.57% Comparative example 12.88 6 12.73 9 5.07% Comparative example 22.87 0 4 2.72 6 7 5.01% Comparative example 32.93 18 2.78 4 5.03%

[0267] Referring to Table 1, it can be confirmed that the degree of volatilization of the flame retardant in Examples 1 to 3 is significantly lower than that in Comparative Examples 1 to 3. Comparative Examples 1 to 3 showed a tendency to volatilize similarly to the phosphorus-based flame retardant, whereas in the case of Examples 1 to 3, the degree of volatilization of the flame retardant was significantly lower than that of the phosphorus-based flame retardant and Comparative Examples 1 to 3.

[0268]

[0269] Initial sample weight Sample weight after one week at 70℃ Flame retardant volatility (%) Example 42.56 6 12.55 32 0.50% Example 52.43 25 2.42 39 0.35% Example 62.59 7 22.59 0 5 0.26% Example 72.56 0 42.55 32 0.28% Comparative example 42.45 44 2.31 7 6 5.57% Comparative example 52.67 0 42.52 1 5 5.58% Comparative example 62.57 47 2.43 48 5.43% Comparative example 72.52 57 2.38 9 8 5.38%

[0270] Referring to Table 2, it can be confirmed that the degree of volatilization of the flame retardant in Examples 4 to 7 is significantly lower than that in Comparative Examples 4 to 7. Comparative Examples 4 to 7 showed a tendency to volatilize similarly to the phosphorus-based flame retardant, whereas in the case of Examples 4 to 7, the degree of volatilization of the flame retardant was significantly lower than that of the phosphorus-based flame retardant and Comparative Examples 4 to 7. These results show that when silica is coated on the surface of a phosphorus-based flame retardant and chemically complexed, volatilization of the phosphorus-based flame retardant can be effectively prevented, and the flame retardancy of an elastic sheet can be secured for a long time in a high-temperature environment.

[0271]

[0272] Evaluation Example 4: Flame Retardancy Evaluation

[0273] The elastic sheets manufactured in Examples 1 to 7 and Comparative Examples 1 to 7 were evaluated for flame retardancy according to UL-94 VTM, and the results for the elastic sheets to which the acrylic composite flame retardant was applied are shown in Table 3, and the results for the elastic sheets to which the urethane composite flame retardant was applied are shown in Table 4. In addition, each specimen was left in an oven at 70°C for a week and then the flame retardancy was evaluated using the same method.

[0274] Here, the UL 94 standard can follow the UL 94 flame retardancy test standard for plastic materials published by Underwriters Laboratories. Specifically, a film-shaped specimen measuring 200 x 50 mm was rolled onto a 13 mm diameter rod (mandrel), taped at the top, fixed using a clamp, and flame was applied to the specimen twice for 3 seconds each. Then, the first combustion time, second combustion time, and light emission time were recorded to evaluate the flame retardancy. For example, if the first combustion time and second combustion time are each within 10 seconds, the sum of the combustion times of all five specimens is within 50 seconds, and there is no ignition of the lower cotton pad, it is evaluated as VTM-0.

[0275]

[0276] Flame retardant grade (thickness 300㎛) after one week at 70℃ Example 1 VTM-0 Example 2 VTM-0 Example 3 VTM-0 Comparative Example 1 VTM-2 Comparative Example 2 VTM-2 Comparative Example 3 VTM-2

[0277] Referring to Table 3, the results of evaluating flame retardancy after leaving it at 70°C for one week show that the elastic sheets containing the composite flame retardants according to Examples 1 to 3 can achieve excellent flame retardancy of the VTM-0 grade, unlike Comparative Examples 1 to 3.

[0278]

[0279] Flame retardant grade (thickness 300㎛) after one week at 70℃ Example 4 VTM-0 Example 5 VTM-0 Example 6 VTM-0 Example 7 VTM-0 Comparative Example 4 VTM-2 Comparative Example 5 VTM-2 Comparative Example 6 VTM-2 Comparative Example 7 VTM-2

[0280] Referring to Table 4, the results of evaluating the flame retardancy after leaving it at 70℃ for one week show that the elastic sheets containing the composite flame retardants according to Examples 4 to 7 can achieve excellent flame retardancy of the VTM-0 grade, unlike Comparative Examples 4 to 7. Through this, it can be confirmed that the flame retardant elastic sheet containing the composite flame retardant produced through mechanofusion can significantly reduce the volatility of the phosphorus flame retardant due to the improved interfacial affinity between materials, thereby producing an elastic sheet with excellent flame retardancy continuously even in a high-temperature environment.

[0281] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention.

[0282] [Explanation of symbols]

[0283] 100: All-solid-state battery 200: Cathode

[0284] 201: Cathode current collector 203: Cathode active material layer

[0285] 300: Solid electrolyte layer 400: Cathode

[0286] 401: Negative current collector 403: Negative active material layer

[0287] 404: Lithium metal layer 405: Cathode coating layer

[0288] 500: Elastic layer 600: Resin layer

Claims

1. A composite flame retardant comprising a core particle containing a phosphorus flame retardant, and a coating layer covering the surface of the core particle and containing silica; and An elastic sheet for an all-solid-state secondary battery comprising a polymer resin.

2. In paragraph 1, The average particle diameter (D) of the above core particles 50 ) is an elastic sheet for an all-solid-state secondary battery having a thickness of 0.5 ㎛ to 50 ㎛.

3. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the above-mentioned flame retardant comprises phosphate, phosphite, phosphonate, phosphinate, phosphine oxide, or a combination thereof.

4. In paragraph 1, The above-mentioned phosphorus flame retardants are ammonium phosphate, ammonium polyphosphate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tripentyl phosphate, tris(2-ethylhexyl) phosphate, trioctyl phosphate, tris(2-butoxyethyl) phosphate, tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(2-chloropropyl) phosphate, tris(3-chloropropyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, tris(2,3-dibromopropyl) phosphate, tris(tribromoneopentyl) phosphate, trimethylpropane methylphosphonic oligomer, pentaerythritol phosphate, cyclic neopentyl thiophosphoric anhydride, 2-Ethylhexyl diphenyl phosphate, isodecyl diphenyl phosphate, dodecyl diphenyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, tricylenyl phosphate, xylenyl diphenyl phosphate, tert-butylphenyl diphenyl phosphate, phenyl di(isopropylphenyl)phosphate, tris(2,4-dibromophenyl) phosphate, N,N'-bis(2-hydroxyethyl)aminomethyl phosphate, resorcinol bis(diphenyl phosphate), phenyl diresorcinyl phosphate, bisphenol A bis(diphenyl phosphate), tetraphenyl mp-phenylene diphosphate, tetrakis(2-chloroethyl)dichloroisopentyl diphosphate, dimethyl propane phosphonate, dimethyl methane phosphonate, diethyl An elastic sheet for an all-solid-state secondary battery comprising ethane phosphonate, diethyl hydroxymethyl phosphonate, aluminum diethyl phosphinate, zinc diethyl phosphinate, aluminum dipropyl phosphinate, aluminum 2-carboxyethyl phenyl phosphinate, aluminum hypophosphite, or a combination thereof.

5. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the thickness of the coating layer is 0.1 ㎛ to 6 ㎛.

6. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the coating layer is in the form of a continuous film or an island.

7. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the silica exists in the form of particles in the coating layer, and the particles are connected to each other to form a coating layer.

8. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the average particle diameter of the silica particles in the coating layer is 1 nm to 2000 nm.

9. In paragraph 1, The above silica is an elastic sheet for an all-solid-state secondary battery comprising crystalline silica, amorphous silica, or a combination thereof.

10. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the phosphorus flame retardant of the core particle and the silica of the coating layer are chemically bonded.

11. In paragraph 10, An elastic sheet for an all-solid-state secondary battery, wherein the phosphorus flame retardant of the core particles and the silica of the coating layer are bonded by a hydrogen bond, an amine bond, an amide bond, an ethylene bond, or a combination thereof.

12. In paragraph 1, Average particle size (D) of composite flame retardant 50 ) is an elastic sheet for an all-solid-state secondary battery having a thickness of 0.6 ㎛ to 56 ㎛.

13. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the ratio of the thickness of the coating layer to the diameter of the core particle is 0.05 to 0.

6.

14. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the weight ratio of the phosphorus flame retardant of the core particle and the silica of the coating layer is 90:10 to 99.9:0.

1.

15. In paragraph 1, The above polymer resin is an elastic sheet for an all-solid-state secondary battery comprising a urethane resin, an acrylic resin, a silicone resin, a fluorine-based resin, a copolymer thereof, or a mixture thereof.

16. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the composite flame retardant is contained in an amount of 1 to 50 parts by weight relative to 100 parts by weight of the polymer resin.

17. In paragraph 1, An elastic sheet for an all-solid-state secondary battery further comprising 1 to 10 parts by weight of a pigment, 1 to 10 parts by weight of an antioxidant, 1 to 10 parts by weight of a lubricant, and 1 to 20 parts by weight of an antistatic agent, relative to 100 parts by weight of the polymer resin.

18. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the thickness of the elastic sheet is 100 ㎛ to 1000 ㎛.

19. In paragraph 1, Elastic sheet for all-solid-state secondary batteries with a flame retardancy rating of VTM-0 or higher according to UL-94 standards.

20. A composite flame retardant is manufactured by mixing a phosphorus flame retardant and silica using the mechano-fusion method. A method for producing an elastic sheet for an all-solid-state secondary battery, comprising preparing a composition by mixing the above-mentioned composite flame retardant and polymer resin and forming a film.

21. In paragraph 20, The above mechano-fusion method comprises rotating the inner chamber at a speed of 100 rpm to 3000 rpm for 5 to 60 minutes.

22. In paragraph 20, The above mechano-fusion is a method for manufacturing an elastic sheet for an all-solid-state secondary battery, which includes maintaining the temperature of the internal chamber at 15°C to 30°C.

23. In paragraph 20, A method for producing an elastic sheet for an all-solid-state secondary battery, wherein the mixing ratio of the above-mentioned flame retardant and the above-mentioned silica is 90:10 to 99.9:0.1 by weight.

24. In paragraph 20, The above flame retardant is in particle form and has an average particle diameter (D 50 ) is 0.5 ㎛ to 50 ㎛, The above silica is in particle form and its average particle diameter (D 50 ) is a method for manufacturing an elastic sheet for an all-solid-state secondary battery having a thickness of 1 nm to 2000 nm.

25. In paragraph 20, By mixing the above-mentioned phosphorus flame retardant and silica by a mechano-fusion method, a composite flame retardant is obtained, which includes core particles containing the phosphorus flame retardant and a coating layer located on the surface of the core particles and containing silica. A method for manufacturing an elastic sheet for an all-solid-state secondary battery, wherein the phosphorus flame retardant and silica in the above composite flame retardant are chemically bonded.

26. In paragraph 20, A method for producing an elastic sheet for an all-solid-state secondary battery, wherein the above-mentioned composite flame retardant is mixed in an amount of 1 to 50 parts by weight per 100 parts by weight of the above-mentioned polymer resin.

27. In paragraph 20, A method for manufacturing an elastic sheet for an all-solid-state secondary battery, wherein the polymer resin comprises a urethane resin, an acrylic resin, a silicone resin, a fluorine-based resin, a copolymer thereof, or a mixture thereof.

28. Comprising two or more cell structures including a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, comprising elastic sheets positioned between and / or at the outermost surface of the cell structures; An all-solid-state secondary battery wherein at least one of the elastic sheets is an elastic sheet according to any one of claims 1 to 19.

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