Elastic sheet for all-solid-state secondary battery, and all-solid-state secondary battery

Abstract

Provided are an elastic sheet for an all-solid-state secondary battery, and an all-solid-state secondary battery, the elastic sheet comprising a polymer resin, a phosphorus-based flame retardant and a melamine-based flame retardant, wherein the weight ratio of the phosphorus-based flame retardant to the melamine-based flame retardant is 95:5 to 65:35.

Description

Elastic sheets for all-solid-state secondary batteries and all-solid-state secondary batteries

[0001] It relates to an elastic sheet for an all-solid-state secondary battery and an all-solid-state secondary battery.

[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, penetrations, 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] Provided are halogen-antimony-free elastic sheets and all-solid-state secondary batteries that are environmentally friendly and exhibit excellent flame retardancy even in the form of thin sheets with a thickness of 5 mm or less, and exhibit balanced physical properties without excessive cost increase or reduction in processability.

[0005] In one embodiment, an elastic sheet for an all-solid-state secondary battery is provided, which comprises a polymer resin, a phosphorus-based flame retardant, and a melamine-based flame retardant, wherein the weight ratio of the phosphorus-based flame retardant and the melamine-based flame retardant is 95:5 to 65:35.

[0006] In one embodiment, a method for producing a composite flame retardant for an all-solid-state secondary battery is provided, which comprises mixing a phosphorus-based flame retardant and a melamine-based flame retardant by mechanofusion.

[0007] In one embodiment, an all-solid-state secondary battery is provided, which comprises 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 at the outermost portion of the cell structures, wherein at least one of the elastic sheets comprises a polymer resin, a phosphorus-based flame retardant, and a melamine-based flame retardant, and a weight ratio of the phosphorus-based flame retardant and the melamine-based flame retardant is 95:5 to 65:35.

[0008] In one embodiment, an all-solid-state secondary battery is provided, comprising 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, a phosphorus-based flame retardant, and a melamine-based flame retardant, and a weight ratio of the phosphorus-based flame retardant and the melamine-based flame retardant is 95:5 to 65:35.

[0009] An elastic sheet for an all-solid-state secondary battery according to an embodiment is environmentally friendly, exhibits excellent flame retardancy even in a thin sheet form, and can exhibit balanced physical properties without excessive cost increase or reduction in processability.

[0010] Figures 1 to 3 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0011] Figure 4 is an optical microscope photograph of the elastic sheet surface of Example 1 and Comparative Example 3.

[0012] 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.

[0013] 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.

[0014] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0015] 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.

[0016] 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.

[0017] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0018] 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.

[0019] “Or” is not interpreted as exclusive, for example, “A or B” is interpreted as including A, B, A+B, etc.

[0020] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0021] elastic sheet

[0022] In one embodiment, an elastic sheet for an all-solid-state secondary battery is provided, which comprises a polymer resin, a phosphorus-based flame retardant, and a melamine-based flame retardant, wherein the weight ratio of the phosphorus-based flame retardant and the melamine-based flame retardant is 95:5 to 65:35.

[0023] In general, all-solid-state secondary batteries that use precipitated negative electrodes experience volume changes due to expansion and contraction of the negative electrode during the charge and discharge process. At this time, it is necessary to introduce a thin elastic sheet within the battery to cushion the volume change. The elastic sheet ensures that pressure is evenly transmitted to the cell structure (or electrode assembly), thereby improving contact between solid components. It also plays a role in relieving stress transmitted to the solid electrolyte, etc., and can cushion the volume change of the battery by suppressing the occurrence of cracks in the solid electrolyte due to the accumulation of stress according to the change in thickness of the electrode during charge and discharge. 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.

[0024] However, elastic sheets in foam form can be vulnerable to heat. In the event of a fire, the polymer or inorganic chains can decompose, generating flammable gases. These decomposition products can then react with oxygen and combust, triggering a chain reaction that further degrades the polymer resin. In particular, fire can release large amounts of toxic gases, making flame retardancy essential for elastic sheets.

[0025] Conventional flame retardant products include antimony-based flame retardants, halogen-based flame retardants, and brominated flame retardants. However, some European countries are attempting to strictly restrict their use due to concerns about the generation of dioxins during incineration. Therefore, there is a growing need to develop technologies for non-halogenated and non-brominated flame retardants that can ensure the flame retardancy of elastic sheets used in all-solid-state secondary batteries. In particular, most existing technologies have been aimed at ensuring flame retardancy in thick products, but in the future, thinner materials will be used in batteries and electronic products, so technologies that ensure flame retardancy in thin materials are required. Furthermore, there is a need to address the issue of deterioration in mechanical properties caused by the addition of large amounts of flame retardants to elastic sheets.

[0026] An elastic sheet according to an embodiment is an environmentally friendly flame-retardant elastic sheet that does not use an antimony-based flame retardant or a halogen-based flame retardant. By mixing a phosphorus-based flame retardant and a melamine-based flame retardant in a specific ratio, not only is the flame retardancy further improved through a synergistic effect, but the content of the phosphorus-based flame retardant is lowered to increase economic efficiency and improve mechanical properties, and excellent flame retardancy can be realized even at a thin thickness of 5 mm or less or 1 mm or less.

[0027] The weight ratio of the phosphorus flame retardant and the melamine flame retardant in the elastic sheet is characterized by being 95:5 to 65:35, and the weight ratio may be, for example, 95:5 to 70:30, or 90:10 to 70:30. By satisfying the above mixing ratio, a high flame retardancy of VTM-0 grade or higher can be realized, and since there is no agglomeration of flame retardant particles and the dispersibility is good, the processability, appearance quality, and flame retardancy can be improved, and the mechanical properties of the elastic sheet can also be maintained at a high level.

[0028] The total content of the phosphorus flame retardant and the melamine flame retardant can be changed depending on the polymer resin to be applied or as needed, but for example, it can be 10.5 wt% to 67.5 wt% with respect to 100 wt% of the elastic sheet, for example, it can be 15 wt% to 65 wt%, 20 wt% to 60 wt%, or 25 wt% to 50 wt%. If the content of the flame retardant is excessive, the processability may be reduced, and if the content of the flame retardant is too low, the flame retardant effect may be reduced.

[0029] The above-mentioned phosphorus-based flame retardant may be included in an amount of 10 wt% to 50 wt% based on 100 wt% of the elastic sheet, for example, 15 wt% to 50 wt%, or 20 wt% to 45 wt%. The above-mentioned melamine-based flame retardant may be included in an amount of 0.5 wt% to 17.5 wt% based on 100 wt% of the elastic sheet, for example, 1 wt% to 17 wt%, 2 wt% to 16 wt%, or 3 wt% to 15 wt%. When the content of each flame retardant satisfies the above range, excellent flame retardancy can be implemented while improving the mechanical properties of the elastic resin.

[0030] Inherent flame retardant

[0031] The flame retardant may be in particle form, and its average particle diameter (D 50 ) may be 5 ㎛ to 30 ㎛, for example, 6 ㎛ to 29 ㎛, or 8 ㎛ to 28 ㎛. 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.

[0032] The shape of the phosphorus flame retardant particles is not particularly limited and may be, for example, spherical, ellipsoidal, polyhedral, shapeless, etc.

[0033] The components of the above-mentioned phosphorus flame retardant are not particularly limited as long as they are generally of a type 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.

[0034] 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, cresyl diphenyl phosphate, triphenyl phosphate, tricresyl phosphate, tert-butylphenyl diphenyl phosphate, tris(2,4-dibromophenyl) phosphate, N,N'-bis(2-hydroxyethyl)aminomethyl phosphate, resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), tetraphenyl mp-phenylene diphosphate, tetrakis(2-chloroethyl)dichloroisopentyl diphosphate, dimethyl propane phosphonate, dimethyl methane phosphonate, diethyl ethane phosphonate, diethyl hydroxymethane phosphonate, aluminum diethyl phosphinate, zinc diethyl phosphinate, aluminum dipropyl It may include phosphinate, aluminum 2-carboxyethyl phenyl phosphinate, aluminum hypophosphite, or a combination thereof.

[0035] For example, the above flame retardant can be represented by chemical formula 1.

[0036] [Chemical Formula 1]

[0037]

[0038] In the above chemical formula 1, R1 and R2 are the same or different and each independently a C1 to C20 alkyl group or a C6 to C20 aryl group, M is at least one selected from Al, Bi, Ca, Ce, Fe, Ge, K, Li, Mg, Mn, Na, Sb, Sr, Ti, Zr, and a protonated nitrogen base, and n is an integer from 1 to 4. Here, C1 to C20 means that the number of carbon atoms is 1 to 20.

[0039] In the above chemical formula 1, for example, M may be Al or Zr, and R1 and R2 may each be a C1 to C6 alkyl group.

[0040] Melamine-based flame retardants

[0041] Melamine flame retardants may likewise be in particle form, the average particle diameter (D 50 ) may be, for example, 0.5 μm to 6 μm, 1 μm to 5 μm, or 2 μm to 4 μm.

[0042] The melamine-based flame retardant may include melamine, a melamine derivative, or a combination thereof, such as melamine, melamine cyanurate, melamine phosphate, melamine pyrophosphate, melamine polyphosphate, triphenyl isocyanurate, piperazine polyphosphate, or a combination thereof.

[0043] polymer resin

[0044] The polymer resin, which is the main material of the elastic sheet, is not particularly limited in type, but may include, for example, urethane resin, acrylic resin, silicone resin, fluorine resin, polyolefin resin, styrene resin, vinyl acetate resin, rubber resin, copolymers thereof, or mixtures thereof.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] elastic particles

[0053] In addition to the polymer resin and 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] inorganic particles

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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% is accumulated from the small particle side in volume conversion. 50 ) may mean.

[0065] hollow particles

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The inorganic hollow particles may include, for example, glass, metal oxides, metal carbides, metal fluorides, or combinations 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 combinations thereof, and as an example, the inorganic hollow particles may be glass bubbles.

[0070] 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.

[0071] 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.

[0072] Other additives

[0073] In addition to the components described above, the elastic sheet may further include appropriate additives, such as an initiator, a crosslinking agent, a coupling agent, a stabilizer, etc. Each additive may be included in an appropriate amount according to the purpose, for example, it may be included in an amount of 0.001 to 1 part by weight, for example, 0.01 to 0.8 parts by weight, based on 100 parts by weight of the polymer resin.

[0074] Additionally, the elastic sheet may further comprise 0.1 to 10 parts by weight of a pigment, 0.1 to 10 parts by weight of an antioxidant, 0.1 to 10 parts by weight of a lubricant, 0.1 to 10 parts by weight of an antistatic agent, or a combination thereof, per 100 parts by weight of the polymer resin.

[0075] Elastic sheet properties

[0076] The thickness of the elastic sheet may be approximately 100 μm to 5 mm, for example, 100 μm to 4000 μm, 100 μm to 3000 μm, 100 μm to 2000 μm, 100 μm to 1500 μm, 100 μm to 1000 μm, or 100 μm to 800 μm. In one embodiment, the elastic sheet may be an elastic sheet that has a thin thickness but can implement sufficient resilience to implement a thin battery or to maximize the capacity of the battery, for example, may have a thickness of 100 μm to 800 μm, 200 μm to 800 μm, 300 μm to 800 μm, or 400 μm to 800 μm.

[0077] 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.

[0078] An elastic sheet according to one embodiment can achieve excellent flame retardancy by including the aforementioned composite flame retardant, and can have a flame retardancy rating of VTM-0 or higher according to the UL-94 standard. The flame retardancy rating is specifically described in Evaluation Example 1 below.

[0079] In addition, the content of char remaining after burning the elastic sheet may be 30 wt% to 95 wt% based on 100 wt% of the elastic sheet before burning, and thus, it can be said to be a highly flame retardant elastic sheet that implements high flame retardancy.

[0080] All-solid-state secondary battery

[0081] 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.

[0082] For example, an all-solid-state secondary battery may include 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 may include elastic sheets positioned between and at the outermost layer of the cell structures. At least one of the elastic sheets may include a polymer resin, a phosphorus-based flame retardant, and a melamine-based flame retardant, and the weight ratio of the phosphorus-based flame retardant to the melamine-based flame retardant is 95:5 to 65:35.

[0083] Fig. 1 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment. Referring to Fig. 1, an all-solid-state secondary battery (100) is 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. 1 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.

[0084] 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.

[0085] In another embodiment, an all-solid-state secondary battery is provided, comprising 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, a phosphorus-based flame retardant, and a melamine-based flame retardant, and a weight ratio of the phosphorus-based flame retardant and the melamine-based flame retardant is 95:5 to 65:35.

[0086] Figure 2 is a cross-section of an all-solid-state secondary battery illustrating a resin layer. The resin layer is positioned on the side of the cell structure, and can play a role in maintaining the shape of the cell structure and improving insulation, adhesiveness, heat dissipation, etc.

[0087] 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.

[0088] 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.

[0089] anode

[0090] 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.

[0091] positive electrode active material

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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 bO 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); The a Nor 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)

[0096] 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.

[0097] 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.

[0098] [Chemical Formula 11]

[0099] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0100] 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.

[0101] 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.

[0102] [Chemical Formula 12]

[0103] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0104] 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.

[0105] [Chemical Formula 13]

[0106] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0107] 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.

[0108] [Chemical Formula 14]

[0109] Li a4 Ni x4 Mny4 M 5 z4 O 2-b4 X b4

[0110] 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.

[0111] The average particle diameter (D) of the above positive electrode active material 50 ) may be 1 ㎛ to 25 ㎛, for example, 3 ㎛ to 25 ㎛, 1 ㎛ to 20 ㎛, 1 ㎛ to 18 ㎛, 3 ㎛ to 15 ㎛, or 5 ㎛ to 15 ㎛. 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 random particles from a scanning electron microscope image of the positive electrode active material, measuring the particle size (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.

[0112] 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.

[0113] 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.

[0114] 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%.

[0115] bookbinder

[0116] 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.

[0117] Challenge

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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%.

[0122] 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.

[0123] Al may be used as the above current collector, but is not limited thereto.

[0124] cathode

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] Fig. 3 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode. Referring to Fig. 3, the precipitation-type negative electrode (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state secondary battery including such a precipitation-type 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 may function as a negative electrode active material. Accordingly, in an all-solid-state secondary battery that has been charged more than once, the precipitation-type 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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 ㎛.

[0150] 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.

[0151] 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.

[0152] 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 performance may deteriorate.

[0153] 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.

[0154] solid electrolyte layer

[0155] 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.

[0156] Sulfide-based solid electrolyte

[0157] 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.

[0158] 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. Here, the ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] The argyrodite-type sulfide-based solid electrolyte particles may include, for example, a compound represented by the chemical formula 21 below.

[0163] [Chemical Formula 21]

[0164] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0165] 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.

[0166] 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.

[0167] For example, in chemical formula 21, a+b+c+h=7, d+e=1, and f+g+h=6.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] Oxide-based solid electrolyte

[0172] 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.

[0173] Halide-based solid electrolyte

[0174] 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.

[0175] 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 is, 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.

[0176] bookbinder

[0177] 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.

[0178] 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.

[0179] Other ingredients

[0180] The solid electrolyte layer may optionally further comprise an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] Example 1

[0192] 1. Manufacturing of elastic sheets

[0193] 10.425 parts by weight of 2-ethylhexyl acrylate, 10.425 parts by weight of isobornyl acrylate, and 25 parts by weight of 4-hydrobutyl acrylate were mixed, 0.025 parts by weight of 1,6-hexanediol diacrylate (crosslinker), 0.125 parts by weight of Igacure 651 (initiator), 0.5 parts by weight of polymer microspheres (820DET40), and 3.5 parts by weight of glass bubbles (K-1), 45 parts by weight of aluminum diethyl phosphinate (ADP) as a phosphorus-based flame retardant, and 5 parts by weight of melamine cyanurate (MC) as a melamine-based flame retardant were placed in a planetary mixer and mixed for two hours 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 400 μm.

[0194] 2. Manufacturing of all-solid-state secondary batteries

[0195] LiNi coated with Li2O-ZrO2 0.8 Co 0.15 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] Examples 2 to 3 and Comparative Examples 1 to 4

[0200] An elastic sheet and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1, except that the contents of the phosphorus-based flame retardant and the melamine-based flame retardant were changed as shown in Table 1 below.

[0201] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 42-EHA10.42510.42510.42510.42510.42510.42510.42510.425iBoA10.42510.42510.42510.42510.42510.42510.4254-HBA2525252525252525 Crosslinker0.0250.0250.0250.0250.0250.0250.0250.025 Initiator0.1250.1250.1250.1250.1250.1250.1250.1250.125 Polymer Microsphere0.50.50.50.50.50.50.50.5 Glass Bubble3.53.53.53.53.53.5 Incorporation Flame retardant 454035302550-Melamine-based flame retardant 510152025-50 series:Melamine-based 90:1080:2070:3060:4050:50100:00:100

[0202] Evaluation Example 1: Flame Retardancy Evaluation

[0203] Each elastic sheet manufactured in Examples 1 to 3 and Comparative Examples 1 to 4 was evaluated for flame retardancy according to UL-94 VTM, and the results are shown in Table 2 below. Here, the UL 94 standard may 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 around a 13 mm diameter 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, the second combustion time, and the light emission time were recorded to evaluate the flame retardancy. For example, if the first combustion time and the 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.

[0204] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Flame retardant VTM-0 VTM-0 VTM-0 VTM-1 VTM-2 VTM-0 grades and above

[0205] Referring to Table 2, it can be seen that the elastic sheets of Examples 1 to 3 can implement excellent flame retardancy of VTM-0. Comparative Example 3 is a case where a phosphorus-based flame retardant was used alone, and the flame retardancy was shown to be high at VTM-0, but there were problems such as dispersion and volatilization as described below. Comparative Example 4 is a case where a melamine-based flame retardant was used alone, and the flame retardancy was shown to be very low, at an out-of-grade level. This shows that the phosphorus-based flame retardant contributes more to the flame retardant performance than the melamine-based flame retardant, and that the phosphorus-based flame retardant is the main flame retardant and the melamine-based flame retardant acts as an auxiliary flame retardant. Ultimately, when a melamine-based flame retardant, which can play a flame retardant auxiliary role according to one embodiment, is included at a certain ratio, not only does it implement high flame retardancy similar to when a phosphorus-based flame retardant is used alone, but it also reduces the amount of phosphorus-based flame retardant used, which can be advantageous in terms of economics.

[0206] Evaluation Example 2: Dispersibility Evaluation

[0207] The elastic sheets manufactured in Examples 1 to 3 and Comparative Examples 1 to 4 were visually observed to compare the dispersibility of the flame retardant. Fig. 4 shows optical microscope photographs of the surfaces of the elastic sheets of Example 1 and Comparative Example 3. Referring to Fig. 4, in the case of Example 1, no particular agglomeration phenomenon was observed, but in the case of Comparative Example 3, where only a phosphorus-based flame retardant was applied, agglomerated portions were observed due to poor dispersibility of the flame retardant. According to one embodiment, it can be seen that when a phosphorus-based flame retardant and a melamine-based flame retardant are mixed and used at a specific ratio, the dispersibility of the flame retardant is improved, thereby improving the processability, manufacturing high-quality molded products, and further enhancing the flame retardant performance.

[0208] Evaluation Example 3: Flame retardant volatility evaluation

[0209] In order to evaluate the volatility of the flame retardant, the elastic sheets manufactured in Examples 1 to 3 and Comparative Examples 1 to 4 were manufactured into specimens measuring 200 x 50 mm, the weight of each specimen was measured, and the specimens were left in an oven at 70°C for one week. The weight of the specimens was then measured, and the volatility was evaluated through the change in weight, and the results are shown in Table 3 below.

[0210] Sample weight (g) Heat treatment at 70℃ for 1 week Sample weight (g) Flame retardant volatility (%) Example 11.99231.92113.57% Example 21.94711.87873.51% Example 31.97391.90593.44% Comparative example 11.97151.90573.34% Comparative example 21.98471.92832.84% Comparative example 31.96811.89163.89% Comparative example 41.95741.95610.07%

[0211] Referring to Table 3 above, in Comparative Example 3, where only the phosphorus flame retardant was applied, the volatility was the highest at 3.89%. On the other hand, it can be seen that in Examples 1 to 3, the volatility of the flame retardant decreased compared to Comparative Example 3.

[0212] Below, examples and comparative examples of urethane-based elastic sheets and the evaluation results thereof are described.

[0213] Example 4

[0214] A composition for an elastic sheet was prepared by putting 56.12 parts by weight of CP6001 as a polyol component, 4.88 parts by weight of Luprante M11s as an isocyanate component, 0.025 parts by weight of 1,4-butanediol as a crosslinking agent, 0.125 parts by weight of dibutyltin dilaurate as a metal catalyst, 3.5 parts by weight of Glassbubble S60, 0.35 parts by weight of thermally expandable microspheres FN-100MD, 31.5 parts by weight of aluminum diethyl phosphinate (ADP) as a phosphorus-based flame retardant, and 4.5 parts by weight of melamine cyanurate (MC) as a melamine-based flame retardant into a planetary mixer and mixing for two hours. The composition was applied onto a PET film and heated to 100°C to 150°C to prepare an elastic sheet having a thickness of about 400 μm.

[0215] Other than that, an all-solid-state secondary battery was manufactured in substantially the same manner as Example 1.

[0216] Examples 5 to 8 and Comparative Examples 5 to 10

[0217] Elastic sheets and all-solid-state secondary batteries were manufactured in substantially the same manner as in Example 1, except that the contents of the phosphorus-based flame retardant and the melamine-based flame retardant, or other components, were changed as shown in Tables 4 and 5 below. Example 8 and Comparative Example 10 are cases where elastic sheets were manufactured by omitting glass bubbles and thermally expandable microspheres and injecting nitrogen gas at a rate of 200 cc / min and stirring for 5 minutes.

[0218] Example 4 Example 5 Example 6 Example 7 Example 8 Polyol 56.1256.1256.1259.6659.66 Isocyanate 4.884.884.885.195.19 Crosslinker 0.0250.0250.0250.0250.025 Metal catalyst 0.1250.1250.1250.1250.125 Glass bubble 3.53.53.5--Thermal expansion microsphere 0.350.350.35--Nitrogen (200 cc / min)----O Phosphorus flame retardant 30.52824.524.524.5 Melamine Flame retardant 4.5710.510.510.5 series:melamine series 87:1380:2070:3070:3070:30

[0219] Comparative Example 5Comparative Example 6Comparative Example 7Comparative Example 8Comparative Example 9Comparative Example 10Polyol56.1256.1256.1256.1259.6659.66Isocyanate4.884.884.884.885.195.19Crosslinker0.0250.0250.0250.0250.0250.0250.025Metal Catalyst0.1250.1250.1250.1250.1250.125Glass Bubble3.53.53.5--Thermal Expansion Microsphere0.350.350.350.35--Nitrogen (200cc / min)-----OPhosphorus Flame Retardant352117.5-2121Melamine Flame retardant-1417.5351414: Melamine series 100:060:4050:500:10060:4060:40

[0220] Evaluation Example 3: Flame Retardancy Evaluation

[0221] The elastic sheets of Examples 4 to 8 and Comparative Examples 5 to 10 were evaluated for flame retardancy using the same method as in Evaluation Example 1, and the results are shown in Tables 6 and 7 below.

[0222] Example 4 Example 5 Example 6 Example 7 Example 8 Flame retardant VTM-0 VTM-0 VTM-0 VTM-0 VTM-0

[0223] Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Flame retardancy VTM-0 VTM-1 VTM-2 Grade Other VTM-1 VTM-1

[0224] Referring to Tables 6 and 7 above, it can be confirmed that the elastic sheets according to Examples 4 to 8 can implement high flame retardancy of VTM-0.

[0225] Comparing Comparative Examples 5 and 8, Comparative Example 5, which used only a phosphorus-based flame retardant, achieved VTM-0, but Comparative Example 8, which used only a melamine-based flame retardant, showed out-of-grade performance. This means that, as in the case of acrylic elastic sheets, in the case of urethane elastic sheets, the phosphorus-based flame retardant is the main flame retardant and the melamine-based flame retardant acts as an auxiliary flame retardant.

[0226] In addition, it was confirmed that not only Examples 4 to 6, but also Example 7 excluding glass bubbles and thermally expandable microspheres, and Example 8 in which nitrogen gas was injected to form a foam all exhibited the characteristics of VTM-0. The above results show that acrylic elastic sheets and urethane elastic sheets can achieve VTM-0 when the ratio of phosphorus flame retardant and melamine flame retardant satisfies 95:5 to 65:35.

[0227] 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.

[0228] [Explanation of symbols]

[0229] 100: All-solid-state battery 200: Cathode

[0230] 201: Cathode current collector 203: Cathode active material layer

[0231] 300: Solid electrolyte layer 400: Cathode

[0232] 401: Negative current collector 403: Negative active material layer

[0233] 404: Lithium metal layer 405: Cathode coating layer

[0234] 500: Elastic layer 600: Resin layer

Claims

1. Contains polymer resin, phosphorus flame retardant, and melamine flame retardant, An elastic sheet for an all-solid-state secondary battery, wherein the weight ratio of the above-mentioned phosphorus-based flame retardant and the above-mentioned melamine-based flame retardant is 95:5 to 65:

35.

2. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the weight ratio of the above-mentioned phosphorus-based flame retardant and the above-mentioned melamine-based flame retardant is 90:10 to 70:

30.

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, The above-mentioned flame retardant is an elastic sheet for an all-solid-state secondary battery represented by the chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, R1 and R2 are the same or different and are each independently a C1 to C20 alkyl group or a C6 to C20 aryl group, M is at least one selected from Al, Bi, Ca, Ce, Fe, Ge, K, Li, Mg, Mn, Na, Sb, Sr, Ti, Zr, and a protonated nitrogen base, and n is an integer of 1 to 4.

6. In paragraph 1, The above flame retardant is in particle form and has an average particle diameter (D 50 ) is an elastic sheet for an all-solid-state secondary battery having a thickness of 5 ㎛ to 30 ㎛.

7. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the above-mentioned flame retardant is contained in an amount of 10 to 50 wt% based on 100 wt% of the elastic sheet.

8. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the melamine-based flame retardant comprises melamine, melamine cyanurate, melamine phosphate, melamine pyrophosphate, melamine polyphosphate, triphenyl isocyanurate, piperazine polyphosphate, or a combination thereof.

9. In paragraph 1, The above melamine-based flame retardant is in particle form and has an average particle diameter (D 50 ) is an elastic sheet for an all-solid-state secondary battery having a thickness of 0.5 ㎛ to 6 ㎛.

10. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the above-mentioned mela-based flame retardant is contained in an amount of 0.5 wt% to 17.5 wt% based on 100 wt% of the elastic sheet.

11. 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 polyolefin resin, a styrene-based resin, a vinyl acetate-based resin, a rubber resin, a copolymer thereof, or a mixture thereof.

12. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the thickness of the elastic sheet is 100 ㎛ to 5 mm.

13. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the thickness of the elastic sheet is 300 ㎛ to 800 ㎛.

14. In paragraph 1, The above elastic sheet is an elastic sheet for an all-solid-state secondary battery in the form of foam rubber, sheet, or injection molded product.

15. 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.

16. In paragraph 1, An elastic sheet for an all-solid-state secondary battery, wherein the content of char remaining after burning the elastic sheet is 30 to 95 wt% based on 100 wt% of the elastic sheet before burning.

17. 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, Including elastic sheets positioned between and at the outermost portion of the above cell structures, An all-solid-state secondary battery wherein at least one of the elastic sheets comprises a polymer resin, a phosphorus-based flame retardant, and a melamine-based flame retardant, and a weight ratio of the phosphorus-based flame retardant and the melamine-based flame retardant is 95:5 to 65:

35.

18. A cell structure comprising a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, and Including a resin layer located on the side of the above cell structure, An all-solid-state secondary battery wherein the resin layer comprises resin, a phosphorus-based flame retardant, and a melamine-based flame retardant, and the weight ratio of the phosphorus-based flame retardant and the melamine-based flame retardant is 95:5 to 65:35.

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