Composite flame retardant for all-solid-state battery, method for manufacturing same, and all-solid-state battery

Abstract

The present invention relates to: a composite flame retardant for an all-solid-state battery, the composite flame retardant comprising a core particle including a phosphorus-based flame retardant, and a coating layer on the surface of the core particle, wherein the coating layer includes boron nitride; and a method for manufacturing same. In particular, the composite flame retardant is obtained by mixing the phosphorus-based flame retardant and boron nitride by a mechano fusion method.

Description

Composite flame retardant for all-solid-state batteries, method of manufacturing the same, and all-solid-state batteries

[0001] The present invention relates to a composite flame retardant for all-solid-state batteries, a method for manufacturing the same, and an all-solid-state battery.

[0002]

[0003] Recently, driven by industrial demands, the development of batteries with high energy density and safety is actively underway. For example, lithium-ion batteries are being commercialized not only in the fields of information and communication devices but also in the automotive sector. In the automotive sector, safety is considered particularly important because it is directly related to human life.

[0004] Recently, all-solid-state batteries in which liquid electrolytes are replaced with solid electrolytes have been proposed. By not using flammable organic dispersion media, all-solid-state batteries can significantly reduce the likelihood of fire or explosion in the event of a short circuit. Therefore, these all-solid-state batteries can offer significantly higher safety compared to lithium-ion batteries that use liquid electrolytes.

[0005]

[0006] The problem that the present invention aims to solve is to provide a composite flame retardant for all-solid-state batteries having excellent thermal conductivity and flame retardancy, and a method for manufacturing the same.

[0007] Another problem that the present invention aims to solve is to provide an all-solid-state battery in which the composite flame retardant is applied to an elastic sheet.

[0008]

[0009] A composite flame retardant for an all-solid-state battery according to the concept of the present invention comprises a core particle comprising a phosphorus-based flame retardant; and a coating layer on the surface of the core particle, wherein the coating layer may comprise boron nitride.

[0010] A method for manufacturing a composite flame retardant for an all-solid-state battery according to another concept of the present invention may include mixing a phosphorus-based flame retardant and boron nitride in a mechano-fusion manner to obtain a composite flame retardant. The composite flame retardant comprises a core particle containing a phosphorus-based flame retardant; and a coating layer on the surface of the core particle, wherein the coating layer may contain boron nitride.

[0011] A solid-state battery according to another concept of the present invention may comprise a plurality of unit cells sequentially stacked; and an elastic sheet interposed between adjacent units among the plurality of unit cells. The elastic sheet may comprise a polymer resin and the composite flame retardant described above.

[0012]

[0013] A composite flame retardant for an all-solid-state battery according to one embodiment of the present invention can simultaneously possess excellent thermal conductivity and enhanced flame retardancy.

[0014] According to one embodiment of the present invention, an elastic sheet for an all-solid-state battery having the above-described effect can be manufactured.

[0015]

[0016] FIG. 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0017] FIG. 2 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention.

[0018] FIG. 3 is a plan view of an all-solid-state battery according to another embodiment of the present invention.

[0019] FIGS. 4 to 8 are cross-sectional views of an all-solid-state battery according to another embodiment of the present invention.

[0020] FIGS. 9 and FIGS. 10 are each schematic cross-sectional views of an all-solid-state battery including an elastic sheet according to one embodiment of the present invention.

[0021] FIG. 11 is a schematic diagram illustrating the structure of a composite flame retardant according to one embodiment of the present invention.

[0022] FIG. 12 is a schematic diagram illustrating the process of compounding a phosphorus-based flame retardant and boron nitride by mechano fusion treatment according to one embodiment.

[0023] FIG. 13 is a scanning electron microscope (SEM) image of a composite flame retardant according to Examples 1 to 4.

[0024] FIG. 14 is a TGA analysis graph for composite flame retardants and phosphorus-based flame retardants according to Examples 1 and 5.

[0025] FIG. 15 is an FT-IR analysis graph for composite flame retardants according to Examples 1 and 5.

[0026]

[0027] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0028] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0029] The embodiments described herein will be described with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0030] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components to the mentioned components.

[0031] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0032] Unless otherwise defined in this specification, particle size may be the average particle size. Additionally, particle size refers to the average particle size (D) which means the diameter of the particle whose cumulative volume in the particle size distribution is 50 volume%. 50 It means ). Average particle size (D 50The measurement can be performed using methods widely known to those skilled in the art, for example, by using a particle size analyzer, or by using transmission electron microscope (TEM) or scanning electron microscope (SEM) images. Alternatively, the measurement may be performed using a measuring device utilizing dynamic light scattering, and after analyzing the data to count the number of particles for each particle size range, the average particle size (D) is calculated from this. 50 ) values ​​can be obtained. Alternatively, it can be measured using the laser diffraction method. When measuring by the laser diffraction method, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and ultrasound at approximately 28 kHz is irradiated at an output of 60 W. Then, the average particle size (D) at the 50% reference of the particle size distribution in the measuring device 50 ) can be produced.

[0033]

[0034] FIG. 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0035] Referring to FIG. 1, an all-solid-state battery (10) according to one embodiment may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, not limited thereto, the unit cell (CEL) may further include an additional functional layer, such as an adhesion enhancing layer, disposed between the positive electrode layer (100) and the solid electrolyte layer (300) or between the negative electrode layer (200) and the solid electrolyte layer (300).

[0036] In one embodiment, the anode layer (100) may include an anode current collector (110) and an anode active material layer (120) disposed on the anode current collector (110). Although not illustrated, the anode active material layer (120) may include an anode active material, a solid electrolyte, a conductive material, and a binder.

[0037] The positive current collector (110) can provide a reference surface on which the positive active material layer (120) is placed. The positive current collector (110) may include, for example, a plate or foil comprising indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0038] Meanwhile, unlike as illustrated in FIG. 1, the positive current collector (110) may be omitted in one embodiment of the present invention. Although not illustrated, a carbon layer with a thickness of 0.1 μm to 4 μm may be further disposed between the positive current collector (110) and the positive active material layer (120) to increase the bonding strength between the positive current collector (110) and the positive active material layer (120).

[0039] The cathode active material may include a material capable of reversibly absorbing and desorbing lithium ions. The cathode active material may include, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not necessarily limited to these. The cathode active material may be a single material or a mixture of two or more materials.

[0040] Lithium transition metal oxides are, for example, Li a A 1-b B b D2(0.90≤a≤1, 0≤b≤0.5), Li a E 1-b B b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05), LiE 2-b B b O 4-c D c (0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Co b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Mn b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Ni 1-b-c Mn b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni b E c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Ni b Co c Mn d GeO2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1), Li a NiG bO2(0.9≤a≤1, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a MnG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-f It may be a compound represented by any one of Fe2(PO4)3 (0≤f≤2) or LiFePO4. In such a compound, the uppercase “A” is Ni, Co, Mn, or a combination thereof; the uppercase “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; the uppercase “D” is O, F, S, P, or a combination thereof; the uppercase “E” is Co, Mn, or a combination thereof; the uppercase “F” is F, S, P, or a combination thereof; the uppercase “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; the uppercase “Q” is Ti, Mo, Mn, or a combination thereof; the uppercase “I” is Cr, V, Fe, Sc, Y, or a combination thereof; and the uppercase “J” may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0041] The cathode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen and metal atomic layers are alternately and regularly arranged in a specific direction, thereby forming a two-dimensional plane for each atomic layer. The "cubic rock salt type structure" represents a sodium chloride (NaCl type) structure, which is a type of crystal structure; specifically, it exhibits a structure in which face-centered cubic lattices (fcc) formed by cations and anions, respectively, are offset from each other by half the ridge of the unit lattice. Lithium transition metal oxides having such a layered rock salt type structure, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn z O2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0042] The aforementioned compound contained in the cathode active material may be covered by a coating layer (not shown). The cathode active material may also be a mixture of the aforementioned compound and the compound to which the coating layer is added. Meanwhile, the coating layer added to the surface of the cathode active material may include, for example, oxides, hydroxides, oxyhydroxides, oxycarbonates, or hydroxycarbonates of the following coating elements. The compounds forming this coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the cathode active material. The method for forming the coating layer may be, for example, spray coating or immersion.

[0043] When the positive electrode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), the capacity density of the all-solid-state battery (10) is increased, and the metal leaching of the positive electrode active material in the charged state can be reduced. As a result, the cycle characteristics of the all-solid-state battery (10) in the charged state can be improved. Meanwhile, “cycle characteristics” is a characteristic that indicates the degree of deterioration of the all-solid-state battery (10) due to charging and discharging of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics has a small degree of deterioration due to charging and discharging, while an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration due to charging and discharging.

[0044] The shape of the cathode active material may include particle shapes such as spheres or ellipsoids. The particle size and content of the cathode active material are not particularly limited.

[0045] The solid electrolyte may have a particulate shape. The solid electrolyte may be dispersed among the cathode active materials. The solid electrolyte may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. Sulfide-based solid electrolytes are, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (m, n are positive numbers, uppercase “Z” is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, uppercase “M” is one of P, Si, Ge, B, Al, Ga, In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include at least one selected from (0≤x≤2).

[0046] Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I xIt may be an argyrodite-type compound comprising one or more selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0047] Alternatively, sulfide-based solid electrolytes are Li 7-a M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)). Here, X may be F, Br, Cl, or a combination thereof. M may be candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof.

[0048] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. By having a density of 1.5 g / cc or higher for the azyrodite-type solid electrolyte, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0049] The solid electrolyte included in the positive electrode active material layer (120) has an intermediate particle size average particle size (D) compared to the solid electrolyte included in the solid electrolyte layer (300). 50 ) may be small. For example, the average particle size (D) of the intermediate particle size of the solid electrolyte included in the positive electrode active material layer (120) 50 ) is the average particle size (D) of the intermediate particle size of the solid electrolyte included in the solid electrolyte layer (300). 50 It may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less. Meanwhile, the average particle size of the intermediate particle size (D 50 ) may be the median diameter measured using a laser particle size distribution meter.

[0050] The positive electrode active material layer (120) may include a conductive material. The conductive material may have conductivity without causing chemical changes in the all-solid-state battery (10), thereby increasing the conductivity of the positive electrode active material and the solid electrolyte. The conductive material may include a carbon-based material. The conductive material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0051] The positive active material layer (120) may further include a binder. The binder may include a material for bonding the positive active material, solid electrolyte, and conductive material included in the positive active material layer (120), and for improving the bonding strength with the positive current collector (110). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0052] Based on 100 parts by weight of the total positive active material, solid electrolyte, conductive material, and binder, the positive active material layer (120) may contain 85 parts by weight or more and 92 parts by weight or less of the positive active material. Based on 100 parts by weight of the total positive active material, solid electrolyte, conductive material, and binder, the positive active material layer (120) may contain 0.5 parts by weight or more and 1.5 parts by weight or less of the binder.

[0053] Based on 100 parts by weight of solid electrolyte, the positive active material layer (120) may contain 1 part by weight or more and 50 parts by weight or less of a conductive material. If the conductive material is included in the positive active material layer (120) in an amount less than 1 part by weight based on 100 parts by weight of solid electrolyte, the proportion of the conductive material decreases, and the electrical conductivity of the positive active material layer (120) may decrease. If the conductive material is included in the positive active material layer (120) in an amount exceeding 50 parts by weight based on 100 parts by weight of solid electrolyte, the proportion of the conductive material is excessively high, and a coating layer covering the surface of the solid electrolyte may not be properly formed.

[0054] The positive active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductivity aids in addition to the positive active material, solid electrolyte, conductive material, and binder described above.

[0055] Referring to FIG. 1, the solid electrolyte layer (300) may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics, disposed between the positive electrode layer (100) and the negative electrode layer (200). The solid electrolyte included in the solid electrolyte layer (300) may be the same as or different from any one of the materials that may be included in the solid electrolyte included in the aforementioned positive electrode active material layer (120).

[0056] The solid electrolyte layer (300) of one embodiment may include a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be manufactured by processing starting materials, such as Li2S or P2S5, by a melt quenching method or a mechanical milling method. Additionally, heat treatment may be performed after such processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. Furthermore, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above, for example. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form the solid electrolyte, the molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 50 : 50 to 90 : 10.

[0057] Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-It may be an argyrodite-type compound comprising one or more selected from xIx (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0058] The solid electrolyte layer (300) may further include a binder. The binder included in the solid electrolyte layer (300) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these. The binder of the solid electrolyte layer (300) may be the same as or different from the binder included in the positive electrode active material layer (120) or the binder included in the negative electrode active material layer (220).

[0059] Referring to FIG. 1, the cathode layer (200) may include a cathode current collector (210) and a cathode active material layer (220) disposed on the cathode current collector (210). The cathode active material layer (220) may include a cathode active material and a binder.

[0060] The negative electrode current collector (210) can provide a reference surface on which the negative electrode active material layer (220) is disposed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, that is, does not form any alloys or compounds with lithium. The material constituting the negative electrode current collector (210) may be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited to these, and any material used as an electrode current collector is possible. The thickness of the negative electrode current collector may be 1 μm to 20 μm, for example, 5 μm to 15 μm, for example, 7 μm to 10 μm.

[0061] The negative current collector (210) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (210) is, for example, in the form of a plate or foil. Meanwhile, in one embodiment, the negative current collector (210) may be omitted.

[0062] The negative electrode active material included in the negative electrode active material layer (220) may have a particle shape. The intermediate particle size average particle diameter (D) of the negative electrode active material having a particle shape. 50 ) may be, for example, 4㎛ or less, 2㎛ or less, 1㎛ or less, or 900nm or less. The intermediate particle size average diameter (D) of the negative electrode active material 50 ) can be, for example, 10 nm to 4 µm, 10 nm to 2 µm, or 10 nm to 900 nm. The average particle size (D) of the intermediate particle size within this range of the negative electrode active material 50 As it possesses ), the reversible absorption and / or desorption of lithium during charging and discharging may be more facilitated. Meanwhile, the intermediate particle size average (D 50 ) may be the median diameter measured using a laser particle size distribution meter.

[0063] The cathode active material may include, for example, one or more selected from carbon-based cathode active materials and metal or metalloid cathode active materials.

[0064] Carbon-based cathode active materials may be amorphous carbon. Amorphous carbon includes, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Kettjen black (KB), graphene, etc., but is not necessarily limited to these. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0065] The metal or metalloid cathode active material comprises one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited to these, and may be a metal cathode active material or a metalloid cathode active material that forms an alloy or compound with lithium. Meanwhile, nickel (Ni) does not form an alloy with lithium, so it does not qualify as a metal cathode active material.

[0066] The negative electrode active material layer (220) may include one type of negative electrode active material among these negative electrode active materials, or may include a mixture of multiple different negative electrode active materials. For example, the negative electrode active material layer (220) may include only amorphous carbon, or may include one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn).

[0067] In one embodiment, the negative electrode active material layer (220) may comprise a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture of amorphous carbon and gold (Au), etc., may be, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight, but is not necessarily limited to these ranges and may be selected according to the required characteristics of the all-solid-state battery (10). By having the negative electrode active material have such a composition, the cycle characteristics of the all-solid-state battery (10) may be further improved.

[0068] The binder included in the negative electrode active material layer (220) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these. The binder may include a single binder or a plurality of different binders.

[0069] By including a binder in the negative active material layer (220), the negative active material layer (220) can be stably formed on the negative current collector (210). That is, the bonding strength between the negative active material layer (220) and the negative current collector (210) can be increased. In addition, cracking of the negative active material layer (220) is suppressed despite volume changes and / or relative position changes of the negative active material layer (220) during the charging and discharging process. If the negative active material layer (220) does not include a binder, the negative active material layer (220) can be easily separated from the negative current collector (210). As the negative active material layer (220) detaches from the negative current collector (210), the negative current collector (210) may come into contact with the solid electrolyte layer in the exposed portion of the negative current collector (210), and accordingly, the possibility of a short circuit occurring increases.

[0070] The negative electrode active material layer (220) is manufactured, for example, by providing a mixture in which the material constituting the negative electrode active material layer (220) is dispersed onto a negative electrode current collector (210). Since a binder is included in the material constituting the negative electrode active material layer (220), stable dispersion of the negative electrode active material is possible in the mixture. For example, when the mixture is applied onto the negative electrode current collector (210) by a screen printing method, it is possible to suppress clogging of the screen (for example, clogging caused by aggregates of the negative electrode active material) by the binder.

[0071] The negative electrode active material layer (220) may further include other additives in addition to the negative electrode active material and binder. The negative electrode active material layer (220) may further include, for example, fillers, coating agents, dispersants, ion conductivity aids, etc.

[0072] The negative electrode active material layer (220) may have a smaller thickness than the positive electrode active material layer (120). The thickness of the negative electrode active material layer (220) may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer (120). The thickness of the negative electrode active material layer (220) may be, for example, 1 μm to 20 μm, 2 μm to 10 μm, or 3 μm to 7 μm. If the thickness of the negative electrode active material layer (220) is excessively thin, lithium dendrites formed between the negative electrode active material layer (220) and the negative electrode current collector (210) may cause the negative electrode active material layer (220) to collapse, thereby degrading the cycle characteristics of the all-solid-state battery (10). If the thickness of the negative electrode active material layer (220) increases excessively, the energy density of the all-solid-state battery (10) decreases, and the internal resistance of the all-solid-state battery (10) due to the negative electrode active material layer (220) increases, which may degrade the cycle characteristics of the all-solid-state battery (10).

[0073] If the thickness of the negative electrode active material layer (220) decreases, for example, the charging capacity of the negative electrode active material layer (220) may also decrease. The charging capacity of the negative electrode active material layer (220) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less compared to the charging capacity of the positive electrode active material layer (120). The charging capacity of the negative electrode active material layer (220) is, for example, 0.1% to 50%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% to 10%, 0.1% to 5%, or 0.1% to 2% compared to the charging capacity of the positive electrode active material layer (120). If the charging capacity of the negative electrode active material layer (220) is excessively small, the thickness of the negative electrode active material layer (220) becomes very thin, and the same defect as the above-described defect that occurs when the thickness of the negative electrode active material layer (220) becomes excessively thin may occur. If the charging capacity of the negative electrode active material layer (220) increases excessively, the same defect as the above-described defect that occurs when the thickness of the negative electrode active material layer (220) increases excessively may occur.

[0074] The charge capacity of the positive active material layer (120) can be obtained by multiplying the charge capacity density (mAh / g) of the positive active material by the mass of the positive active material in the positive active material layer (120). If the positive active material layer (120) contains various types of positive active materials, the value [charge capacity density × mass] is calculated for each positive active material, and the sum of these values ​​of the positive active materials is the charge capacity of the positive active material layer (120). The charge capacity of the negative active material layer (220) can also be calculated in the same way. That is, the charge capacity of the negative active material layer (220) is obtained by multiplying the charge capacity density (mAh / g) of the negative active material by the mass of the negative active material in the negative active material layer (220). When the negative electrode active material layer (220) contains various types of negative electrode active materials, a value [charge capacity density × mass] is calculated for each negative electrode active material, and the sum of these values ​​of the negative electrode active materials is the capacity of the negative electrode active material layer (220). Here, the charge capacity density of the positive electrode active material and the negative electrode active material may be a capacity estimated using an all-solid-state half-cell using lithium metal as the counter electrode. The charge capacity of the positive electrode active material layer (120) and the negative electrode active material layer (220) can be directly measured by measuring the charge capacity using an all-solid-state half-cell. By dividing the measured charge capacity by the mass of each active material, the charge capacity density can be obtained. Meanwhile, in this specification, the “charge capacity” of the positive electrode active material layer (120) and the negative electrode active material layer (220) refers to the initial charge capacity measured during the first cycle of charging.

[0075] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the cathode active material layer (220) and the solid electrolyte layer (300).

[0076]

[0077] FIG. 2 is a cross-sectional view of an all-solid-state battery (10) according to another embodiment of the present invention.

[0078] Referring to FIG. 2, the solid electrolyte layer (300) may include a first solid electrolyte layer (310) and a second solid electrolyte layer (320). The first solid electrolyte layer (310) may be adjacent to the anode layer (100), and the second solid electrolyte layer (320) may be adjacent to the cathode layer (200).

[0079] The first solid electrolyte layer (310) and the second solid electrolyte layer (320) may have different thicknesses. The first solid electrolyte layer (310) may have a first thickness (TK1), and the second solid electrolyte layer (320) may have a second thickness (TK2). The first thickness (TK1) may be greater than the second thickness (TK2). For example, the first thickness (TK1) may be 2 to 100 times the second thickness (TK2).

[0080]

[0081] In other embodiments of the present invention to be described below, detailed descriptions of technical features that overlap with those previously described with reference to FIGS. 1 and FIG. 2 are omitted, and differences are described in detail.

[0082] FIG. 3 is a plan view of an all-solid-state battery (10) according to another embodiment of the present invention. FIG. 4 is a cross-sectional view along line A-A' of FIG. 3.

[0083] Referring to FIGS. 3 and 4, the area of ​​the anode layer (100) and the area of ​​the cathode layer (200) may differ from each other. Specifically, the area of ​​the cathode layer (200) may be larger than the area of ​​the anode layer (100). The anode layer (100) may be completely superimposed within the cathode layer (200).

[0084] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the anode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the cathode layer (200).

[0085] Specifically, the first solid electrolyte layer (310) may have a first width (WI1) in the first direction (D1). The second solid electrolyte layer (320) may have a second width (WI2) in the first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The first solid electrolyte layer (310) may have a third width (WI3) in the second direction (D2). The second solid electrolyte layer (320) may have a fourth width (WI4) in the second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0086] The all-solid-state battery (10) according to the present embodiment can be manufactured by forming a first laminate of a positive electrode layer (100) and a first solid electrolyte layer (310), forming a second laminate of a negative electrode layer (200) and a second solid electrolyte layer (320), and then laminating the first laminate and the second laminate.

[0087]

[0088] FIG. 5 is a cross-sectional view illustrating an all-solid-state battery (10) according to another embodiment of the present invention.

[0089] Referring to FIG. 5, the negative electrode layer (200) of the all-solid-state battery (10) may further include a lithium metal layer (400) between the negative electrode current collector (210) and the negative electrode active material layer (220). The thickness of the lithium metal layer (400) may increase further during charging of the all-solid-state battery (10). The negative electrode active material layer (220) acts as a protective layer for the lithium metal layer (400) and, at the same time, can suppress the growth of lithium dendrites from the lithium metal layer (400).

[0090] The lithium metal layer (400) may be a thin metal film containing lithium or a lithium alloy. The lithium alloy is not limited to, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., and any alloy used as a lithium alloy is possible. The lithium metal layer (400) may contain one of these alloys or lithium. Alternatively, the lithium metal layer (400) may contain various types of alloys.

[0091] The lithium metal layer (400) may have a fifth width (WI5) in the first direction (D1). The fifth width (WI5) may be equal to or greater than the first width (WI1). The fifth width (WI5) may be equal to or smaller than the second width (WI2). For example, the fifth width (WI5) may be greater than the first width (WI1) and smaller than the second width (WI2).

[0092]

[0093] FIG. 6 is a cross-sectional view illustrating an all-solid-state battery (10) according to another embodiment of the present invention.

[0094] Referring to FIG. 6, the all-solid-state battery (10) may further include a gasket structure (500). The gasket structure (500) can fill the step on the side of the all-solid-state battery (10) caused by the difference in area between the first laminate and the second laminate.

[0095] Referring again to FIG. 3, the gasket structure (500) can surround the sides of the first laminated body of the all-solid-state battery (10) according to the first and second directions (D1, D2). For example, the thickness of the gasket structure (500) may be substantially the same as the thickness of the first laminated body. This prevents damage to the step height of the side of the all-solid-state battery even when the first laminated body and the second laminated body, which have different areas, are laminated and pressed. 'Substantially the same thickness' may be defined as a thickness sufficient to prevent damage to the step height of the side of the all-solid-state battery (10) even when the first laminated body and the second laminated body, which have different areas, are laminated and pressed.

[0096] The gasket structure (500) may include resin and a composite flame retardant (CFR) to be described later.

[0097] The resin may include, for example, 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, but is not limited thereto.

[0098] In the gasket structure (500), the composite flame retardant (CFR) may be included in an amount of 1% to 60% by weight relative to the total weight of the gasket structure (500). If the content of the composite flame retardant (CFR) in the gasket structure (500) satisfies the above range, flame retardancy may be improved without a change in physical properties.

[0099]

[0100] FIGS. 7 and 8 are cross-sectional views illustrating an all-solid-state battery according to another embodiment of the present invention. In this embodiment, detailed descriptions of technical features that overlap with those previously described with reference to FIGS. 1 to 6 are omitted, and differences are described in detail.

[0101] Referring to FIG. 7, an all-solid-state battery (20) according to another embodiment may include a bi-cell structure. For example, the all-solid-state battery (20) may include a first unit cell (510) and a second unit cell (520). The all-solid-state battery (20) may be in the form of stacked all-solid-state batteries (10) described above with reference to FIG. 1 to 6.

[0102] For example, each of the first and second unit cells (510, 520) may include an anode layer (100), a cathode layer (200), and a solid electrolyte layer (300) disposed between the anode layer (100) and the cathode layer (200). The solid electrolyte layer (300) of each of the first and second unit cells (510, 520) may include an anode solid electrolyte layer (310) adjacent to the anode layer (100) and a cathode solid electrolyte layer (320) adjacent to the cathode layer (200). The second unit cell (520) may be arranged vertically symmetrically with respect to the first unit cell (510). The anode layer (100) of the first unit cell (510) and the anode layer (100) of the second unit cell (520) may face each other.

[0103] Referring to FIG. 8, an all-solid-state battery (20) according to another embodiment may further include a gasket structure (500). Since the gasket structure (500) is the same as previously described, a detailed description of it in this embodiment will be omitted.

[0104]

[0105] FIGS. 9 and FIGS. 10 are schematic cross-sectional views illustrating an all-solid-state battery to which an elastic sheet (ELS) according to an embodiment of the present invention is applied. In this embodiment, detailed descriptions of technical features that overlap with those previously described with reference to FIGS. 1 to 8 are omitted, and the differences are described in detail.

[0106] Referring to FIGS. 9 and 10, an all-solid-state battery (30) according to one embodiment of the present invention may include a plurality of unit cells (510, 520) sequentially stacked and an elastic sheet (ELS) interposed between adjacent units among the plurality of unit cells (510, 520).

[0107] For example, the all-solid-state battery (30) may additionally have an elastic sheet (ELS) positioned on the outermost edge of the first and second unit cells (510, 520).

[0108] Each of the plurality of unit cells (510, 520) may include at least one of a mono-cell and a bi-cell. The mono-cell may include the all-solid-state battery (10) of FIGS. 1 to 6. The bi-cell may include the all-solid-state battery (20) of FIGS. 7 to 8.

[0109] For example, referring to FIG. 9, each of the plurality of unit cells (510, 520) may be the all-solid-state battery (10) of FIG. 1. For example, referring to FIG. 10, each of the plurality of unit cells (510, 520) may be the all-solid-state battery (20) of FIG. 7.

[0110]

[0111] Elastic Sheet (ELS)

[0112] According to one embodiment, the elastic sheet (ELS) may include a polymer resin and a composite flame retardant (CFR) to be described later.

[0113] The elastic sheet (ELS) can serve to ensure that pressure is uniformly transmitted to the first and second unit cells (510, 520), thereby improving contact between solid components and relieving stress transmitted to the solid electrolyte, etc.

[0114] Additionally, the elastic sheet (ELS) can serve to buffer changes in the volume of the battery by suppressing cracks in the solid electrolyte caused by stress accumulation due to changes in the thickness of the electrode during charging and discharging. The elastic sheet (ELS) can be located between the first and second unit cells (510, 520), or on the outermost edge of the first and second unit cells (510, 520) or on the inner surface of the case.

[0115] The primary materials used in elastic sheets (ELS) may be polymer resins such as urethane, acrylic, and silicone. If the temperature of the battery rises or sparks are generated due to penetration or impact, these materials can act as combustible substances, potentially exacerbating a fire. Therefore, it is necessary to improve the flame retardancy of the elastic sheet (ELS), and it is important to apply a flame retardant that has excellent compatibility with the material of the elastic sheet (ELS).

[0116] The main material of the elastic sheet (ELS) is a polymer resin, and while the type is not particularly limited, it may include, for example, urethane resin, acrylic resin, silicone resin, fluoropolymer resin, copolymers thereof, or mixtures thereof.

[0117] Urethane resin can be referred to as polyurethane and means a homopolymer or copolymer having urethane groups. Acrylic resin can be, for example, polyacrylate and can mean a homopolymer or copolymer having acrylic groups. The silicone resin can mean a homopolymer or copolymer containing silicon, and the fluorine-based resin can mean a homopolymer or copolymer containing fluorine. These polymers can exhibit appropriate elasticity, modulus, and compressive strain, so they can be appropriately used as elastic sheets.

[0118] Urethane resin may be derived from polyether polyols. Polyether-based polyols may have 2 to 4 functional groups and a number average molecular weight of 2000 or more and 4000 or less. In addition to polyether polyols, polyester polyols may be used in urethane resins. Examples of polyester polyols include those obtained by the 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, polyester polyols may include polyols that are ring-opening condensates of caprolactone and methyl valerolactone, which are classified as lactone esters. Polycarbonate-based polyols may include those obtained by a dealolysis reaction between polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol and dialkyl carbonates, dialkylene carbonates, and diphenyl carbonates. Polycarbonate-based polyols may have a number of functional groups of 2 to 3 and a number average molecular weight of 500 or more and 1000 or less (or hydroxyl groups of 112 mgKOH / g or more and 224 mgKOH / g or less).

[0119] The acrylic resin may be derived from, as a specific example, C1 to C20 alkyl acrylates, hydroxy C1 to C20 alkyl acrylates, or a combination 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, or C1 to C5. The acrylates may include acrylates and methacrylates. The above C1 to C20 alkyl acrylates may 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 a combination thereof. The above hydroxy C1 to C20 alkyl acrylate may 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.

[0120] For example, the acrylic resin may be derived from C1 to C20 alkyl acrylates and hydroxy C1 to C20 alkyl acrylates, wherein the mixing ratio of C1 to C20 alkyl acrylates and hydroxy C1 to C20 alkyl acrylates may be a weight ratio of 20:80 to 90:10. For example, the mixing ratio may be a weight ratio of 30:70 to 90:10, 40:60 to 90:10, 50:50 to 90:10, or 60:40 to 80:20. In this case, the acrylic resin may exhibit appropriate tackiness and can achieve excellent compressive strength, stress relaxation rate, and recovery rate.

[0121] The acrylic resin may further include other repeating units derived from acrylic acid, alkoxy group-containing acrylates, etc. In addition, the weight average molecular weight of the acrylic resin may be 400,000 to 2,000,000, but is not limited thereto.

[0122] The composite flame retardant (CFR) according to the present invention, to be described below, can achieve excellent flame retardancy and thermal conductivity at high temperatures, making it suitable for application to elastic sheets (ELS). As a result, the safety of an all-solid-state battery incorporating an elastic sheet (ELS) containing the composite flame retardant (CFR) according to one embodiment can be further enhanced.

[0123] In the elastic sheet (ELS), the composite flame retardant (CFR) may be included in an amount of 1 to 60 parts by weight per 100 parts by weight of polymer resin. For example, the composite flame retardant (CFR) may be included in an amount of 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 per 100 parts by weight of polymer resin. When the content of the composite flame retardant (CFR) in the elastic sheet (ELS) satisfies the above range, the elastic sheet (ELS) can sufficiently perform the role of buffering volume changes of the all-solid-state battery (20), thereby improving flame retardancy and fire safety.

[0124] The elastic sheet (ELS) may further include elastic particles in addition to the polymer resin and composite flame retardant (CFR). The elastic particles may be particles made of an elastic polymer, such as rubber. The elastic particles can increase the resilience while maintaining the stress-relieving capacity of the polymer resin. The elastic particles may be included in an amount of 0.1 to 5 parts by weight, 0.5 to 4 parts by weight, or 1 to 3 parts by weight per 100 parts by weight of the polymer resin. When the elastic particles are included within this content range, the compressive strength, stress-relieving capacity, and resilience can be maximized without reducing the density and adhesiveness of the polymer resin.

[0125] The elastic particles may comprise, for example, natural rubber, alkyl acrylates, olefins, butadiene, isoprene, styrene, acrylonitrile, copolymers thereof, or combinations thereof. The elastic particles may have a glass transition temperature of, for example, -70°C to 0°C. The alkyl acrylate may be a C1 to C20 alkyl acrylate. For example, the alkyl acrylate may be 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 a combination thereof. 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 a combination thereof. The elastic particles may have a core-shell structure, for example, and in this case, may exhibit appropriate size and elasticity. Each of the above-mentioned core and shell may comprise polyalkyl acrylate. For example, the core may comprise polybutyl (meth)acrylate, and the shell may comprise polymethyl (meth)acrylate. The elastic particles may be nano-sized, for example. Specifically, the size of the elastic particles (D 50 ) can be 10 nm to 900 nm, 10 nm to 700 nm, 50 nm to 500 nm, or 100 nm to 400 nm. Here, the size of the elastic particle can be expressed as the average particle diameter or the median particle diameter, and is measured by a particle size analyzer, and is the diameter (D) of the particle at which the cumulative volume in the particle size distribution is 50 volume%. 50 It can mean ).

[0126] The elastic sheet (ELS) may further include inorganic particles. The inorganic particles can improve the modulus and compressive strength of the elastic sheet (ELS) while simultaneously improving the recovery rate. The 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 a combination thereof. The inorganic particles may be included, for example, in an amount of 0.001 to 50 parts by weight, 0.01 to 45 parts by weight, or 0.1 to 40 parts by weight per 100 parts by weight of the polymer resin. When the inorganic particles satisfy the above content in the elastic sheet (ELS), the compressive strength, stress relaxation rate, and recovery rate of the elastic sheet can be improved without degrading the properties of the polymer resin. The average particle size (D) of the inorganic particles 50 ) may be 0.1 μm to 5 μm, 0.1 μm to 2.5 μm, or 0.2 μm to 2 μm.

[0127] The elastic sheet (ELS) may further include hollow particles. Hollow particles are particles with a hollow interior and may be hollow spheres or hollow beads. Hollow particles may be hollow nanoparticles or hollow microparticles. When the elastic sheet (ELS) includes hollow particles, it can increase compressive strength while maintaining an appropriate density and may exhibit a foam form. Hollow particles may be included in an amount of 1 to 8 parts by weight, 1 to 7 parts by weight, or 2 to 6 parts by weight per 100 parts by weight of the polymer resin. When hollow particles are included in the elastic sheet (ELS) within the above content ranges, it is advantageous for making a foam-shaped elastic sheet (ELS) and can improve the compressive strength, stress relief, and resilience of the elastic sheet (ELS). The hollow particles may be inorganic hollow particles, organic hollow particles, or a combination thereof. That is, the hollow particles may be composed of inorganic materials or organic materials such as polymers. Inorganic hollow particles may comprise, for example, glass, metal oxides, metal carbides, metal fluorides, or combinations thereof. Specifically, inorganic hollow particles may be composed 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. As an example, inorganic hollow particles may be glass bubbles. Organic hollow particles may comprise, for example, acrylic resin, vinyl chloride resin, urea resin, phenolic resin, rubber, or combinations thereof. Additionally, organic hollow particles may be expandable or non-expandable. Expandable organic hollow particles may expand at a temperature of, for example, 120 °C to 150 °C. Size of hollow particles (D 50) may be a micro-size, specifically 1 μm to 100 μm, 5 μm to 80 μm, 10 μm to 60 μm, or 20 μm to 50 μm. Hollow particles having the above-described particle sizes are advantageous for making foam-type elastic sheets, and can improve the compressive strength of the elastic sheet while lowering density and improving stress relaxation and resilience. Here, the size of the hollow particles (D 50 ) can be expressed as the average particle size or median particle size, and is measured by a particle size analyzer, and is the diameter (D) of the particle at which the cumulative volume in the particle size distribution is 50 volume%. 50 It can mean ).

[0128] The elastic sheet (ELS) may further include suitable additives in addition to the aforementioned components. For example, it may further include initiators, crosslinking agents, coupling agents, foam stabilizers, etc. Each additive may be included in an appropriate amount to suit the purpose, for example, in an amount of 0.001 to 1 part by weight or 0.01 to 0.8 parts by weight per 100 parts by weight of the polymer resin.

[0129] The elastic sheet (ELS) may further comprise 0.1 to 10 parts by weight of pigment, 0.1 to 10 parts by weight of antioxidant, 0.1 to 10 parts by weight of lubricant, 0.1 to 10 parts by weight of antistatic agent, or a combination thereof, based on 100 parts by weight of polymer resin.

[0130] The thickness of the elastic sheet (ELS) may be 50 μm to 1000 μm, or 100 μm to 800 μm. The elastic sheet (ELS) according to one embodiment may be thinned, that is, its thickness may be minimized, to realize a thin battery or to maximize the capacity of the battery. For example, the thickness of the elastic sheet (ELS) may be 100 μm to 300 μm. The elastic sheet (ELS) may be in the form of a pad or foam, and may be in the form of various injection-molded products.

[0131] An elastic sheet (ELS) according to one embodiment can achieve excellent flame retardancy by including the aforementioned composite flame retardant, and may have a flame retardant rating of VTM-0 or higher according to UL-94 standards. The flame retardant rating is described in detail in Evaluation Example 4 below.

[0132] An elastic sheet (ELS) according to one embodiment may have a thermal conductivity of 1 W / mK to 2 W / mK at room temperature (25 ℃) and 2 W / mK to 3.5 W / mK at 45 ℃.

[0133]

[0134] Composite flame retardant (CFR)

[0135] Hereinafter, a composite flame retardant (CFR) according to one embodiment of the present invention will be examined in more detail.

[0136] FIG. 11 is a schematic diagram illustrating the structure of a composite flame retardant according to one embodiment of the present invention. Specifically, FIG. 11 is an enlarged view of the M region in the elastic sheet (ELS) of FIG. 9. FIG. 12 is a schematic diagram illustrating the process of compounding a phosphorus-based flame retardant and boron nitride by mechano fusion treatment according to one embodiment.

[0137] Referring to FIGS. 11 and 12, an elastic sheet (ELS) according to one embodiment of the present invention may include a composite flame retardant (CFR).

[0138] A composite flame retardant (CFR) according to one embodiment may include a core particle (COR) containing a phosphorus-based flame retardant (PHP) and a coating layer (CTL) located on the surface of the core particle (COR). The coating layer (CTL) may include boron nitride (BN).

[0139] Composite flame retardants (CFR) can coat boron nitride (BN) onto the particle surface of phosphorus-based flame retardants (PHP) through a dry mixing method using meccanofusion.

[0140] Average particle size (D of composite flame retardant (CFR)) 50 ) can be, for example, 1 μm to 70 μm, 2 μm to 50 μm, 8 μm to 30 μm, or 10 μm to 25 μm.

[0141] A composite flame retardant (CFR) may contain a phosphorus-based flame retardant (PHP) and boron nitride (BN) in a weight ratio of 60:40 to 90:10, 55:45 to 85:15, or 50:50 to 80:20. When the above weight ratios are satisfied, the composite flame retardant (CFR) can achieve excellent flame retardant performance and thermal conductivity.

[0142] According to one embodiment, a composite flame retardant (CFR) manufactured by a meccanofusion method may have a phosphorus-based flame retardant (PHP) of the core (COR) and a boron nitride (BN) of the coating layer (CTL) chemically bonded to each other.

[0143] The above chemical bonds may be, for example, hydrogen bonds, amine bonds, amide bonds, ethylene bonds, or combinations thereof. Such composite flame retardants (CFR) can increase the bonding strength and contact surface area between the core (COR) and the coating layer (CTL).

[0144] The chemical bonding between phosphorus-based flame retardants (PHP) and boron nitride (BN) can be confirmed, for example, through thermogravimetric analysis (TGA) or Fourier Transform Infrared Spectroscopy (FT-IR).

[0145] Generally, halogen-based flame retardants have been widely used for conventional industrial purposes; however, due to the risk of generating toxic chemicals such as hydrogen halides, they are subject to environmental regulations and their use is currently restricted.

[0146] Phosphorus-based flame retardants (PHPs) are known to be environmentally friendly flame retardants that can impart excellent flame-retardant effects when added to resins, and are therefore used as a substitute for halogen-based flame retardants. However, phosphorus-based flame retardants (PHPs) have a problem in that their interfacial properties are not excellent when introduced into materials such as urethane, acrylic resins, and silicone resins.

[0147] According to one embodiment, the composite flame retardant (CFR) has excellent compatibility with polar resins such as urethane, acrylic resin, and silicone, in which boron nitride (BN) located on the particle surface of the phosphorus-based flame retardant (PHP). In addition, the composite flame retardant (CFR) has excellent interfacial characteristics with the resin, is well dispersed without aggregating within the resin, has excellent processability, and can even improve flame retardant performance. Furthermore, the composite flame retardant (CFR) can further improve flame retardant performance by exhibiting a synergistic effect through the composite formation of the phosphorus-based flame retardant (PHP) and the boron nitride (BN).

[0148] These composite flame retardants (CFRs) can be applied to various components of all-solid-state batteries, thereby further enhancing the fire safety of the all-solid-state batteries. For example, composite flame retardants (CFRs) can be applied within components based on resin compositions such as urethane, acrylic resin, and silicone.

[0149] The core particles (COR) may contain phosphorus-based flame retardants (PHP). The phosphorus-based flame retardants (PHP) are not specifically limited as long as they are of the types generally used in industry.

[0150] For example, a phosphorus-based flame retardant (PHP) may include phosphate, phosphite, phosphonate, phosphinate, phosphine oxide, or a combination thereof. The phosphate, phosphite, phosphonate, phosphine oxide, and phosphine oxide may have organic functional groups such as alkyl groups, aryl groups, and alkenyl groups, and the organic functional groups may be substituted with halogen groups, amine groups, hydroxyl groups, thiol groups, etc. 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. For example, phosphorus-based flame retardants (PHP) may include aluminum diethyl phosphinate (ADP), aluminum hypophosphite (AHP), triphenyl phosphate (TPP), resorcinol bis-(diphenyl phosphate) (RDP), tricresyl phosphate (TCP), ammonium polyphosphate (APP), lauryldiphenylphosphate (LDP), or a combination thereof.

[0151] The core particle (COR) has an average particle size (D 50 The ) may be 0.5 μm to 50 μm, 1 μm to 30 μm, or 2 μm to 20 μm. As long as the core particle (COR) is in the form of a particle, its shape is not particularly limited, and for example, the core particle (COR) may be spherical, elliptical, polyhedral, shapeless, etc.

[0152] The coating layer (CTL) may include boron nitride (BN). For example, the boron nitride (BN) may include hexagonal boron nitride, wurtzite boron nitride, cubic boron nitride, boron nitride nanosheets, boron nitride nanotubes, or a combination thereof.

[0153] The coating layer (CTL) is formed by mechano fusion, which will be described later, and may have a thickness of 0.1 μm to 100 μm, 1.0 μm to 50 μm, 1.5 μm to 10 μm, or 2 μm to 4 μm. Here, the thickness of the coating layer (CTL) can be measured, for example, through FIB, SEM, TEM, TOF-SIMS, XPS, or EDS analysis. For example, one particle of the composite flame retardant (CFR) can be milled and broken using FIB, and then photographed with SEM to measure the thickness of the coating layer (CTL) from the SEM image.

[0154] The coating layer (CTL) may be in the form of a continuous film formed by a mechano fusion process or in the form of an island. The coating layer (CTL) may exist in the form of a continuous film, and as an example, boron nitride (BN) in the coating layer (CTL) may exist in the form of multiple particles. In this specification, "island form" may refer to a form of coating that surrounds the surface of the core (COR) in the form of discontinuous dots.

[0155] The plurality of boron nitride (BN) particles mentioned above can be connected to each other to form a coating layer (CTL). The average particle size (D) of the boron nitride (BN) particles 50 ) may be 0.5 μm to 20 μm, 1.5 μm to 5 μm, or 2 μm to 4 μm.

[0156] The coating layer (CTL) may have a thickness ratio to the diameter of the core particle (COR) of 0.05 to 0.6, 0.1 to 0.5, or 0.15 to 0.4. When the coating layer (CTL) satisfies the above thickness ratio, the composite flame retardant (CFR) may have excellent flame retardant performance and thermal conductivity.

[0157]

[0158] Method for manufacturing a composite flame retardant

[0159] A method for manufacturing a composite flame retardant according to one embodiment may include mixing a phosphorus-based flame retardant (PHP) and a boron nitride (BN) in a mechano-fusion manner to obtain a composite flame retardant (CFR).

[0160] In the method for manufacturing a composite flame retardant according to the present invention, a detailed description of the overlapping technical features of the composite flame retardant (CFR) described above with reference to FIGS. 11 and 12 is omitted.

[0161] Referring to FIG. 12, meccanofusion can be described as a dry mixing or dry coating method that generates compressive force, shear force, and frictional force while applying mechanical energy inside a chamber, and can be described as a high-energy mixing method. Through the above method, a composite flame retardant (CFR) can be manufactured comprising a core particle (COR) containing a phosphorus-based flame retardant (PHP) and a coating layer (CTL) located on the surface of the core particle (COR) and containing boron nitride (BN).

[0162] For example, the method for manufacturing the composite flame retardant (CFR) may include administering phosphorus-based flame retardant (PHP) powder and boron nitride (BN) powder into the inner chamber of a meccanofusion device and rotating the inner chamber.

[0163] Rotating the inner chamber may be carried out 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. Rotating the inner chamber may be carried out for, for example, 5 minutes to 60 minutes.

[0164] The temperature of the inner chamber can be set to, for example, 15°C to 30°C or 20°C to 30°C, and can be maintained at, for example, 25°C.

[0165] The mixture may be prepared by adding phosphorus-based flame retardant (PHP) and boron nitride (BN) in a weight ratio of 60:40 to 90:10, 55:45 to 85:15, or 50:50 to 80:20.

[0166] The phosphorus-based flame retardant (PHP) introduced is in the form of particles, and its average particle size (D 50 ) may be 0.5 μm to 50 μm, 1 μm to 30 μm, or 2 μm to 20 μm. The boron nitride (BN) introduced is in the form of particles, and its average particle size (D 50 ) may be 0.5 μm to 20 μm, 1.5 μm to 5 μm, or 2 μm to 4 μm.

[0167] A composite flame retardant (CFR) obtained by mixing through a mechano-fusion method may have a phosphorus-based flame retardant (PHP) and a boron nitride (BN) chemically bonded to each other. According to one embodiment, the composite flame retardant (CFR) may form a coating layer (CTL) in which boron nitride (BN) particles are bonded to the surface of a core particle (COR) containing a phosphorus-based flame retardant (PHP) through a mechano-chemical reaction.

[0168]

[0169] The present invention will be explained in more detail below through examples. However, these examples are intended to illustrate the invention and the scope of the invention is not limited to these examples.

[0170]

[0171] Example 1

[0172] (Manufacture of composite flame retardants)

[0173] 60g of aluminum diethylphosphinate and 40g of hexagonal boron nitride were introduced into the chamber of a dry energy mixer, a mechanofusion. A composite flame retardant was prepared by applying mechanical energy by setting the rotation speed of the chamber to 2500 rpm.

[0174]

[0175] (Manufacturing of acrylic-based elastic sheets)

[0176] An acrylic resin was prepared in a ratio of 25 parts by weight of 2-ethylhexyl acrylate, 25 parts by weight of isobornyl acrylate, and 50 parts by weight of 4-hydrobutyl acrylate. Based on 100 parts by weight of the acrylic resin, 0.05 parts by weight of 1,6-hexanediol diacrylate (crosslinking agent), 0.25 parts by weight of Igacure 651 (initiator), 1 part by weight of polymer microspheres (820DET40), and 3.5 parts by weight of glass bubbles (K-1) were added and mixed for 2 hours. Finally, based on 100 parts by weight of the acrylic resin, 40 parts by weight of the composite flame retardant prepared in Example 1 were added to a planetary mixer and mixed for 20 minutes to prepare a composition for an elastic sheet. The above composition for the elastic sheet was applied onto a PET film and cured using UV coating equipment to produce an elastic sheet with a thickness of about 200 μm.

[0177]

[0178] Example 2

[0179] In the manufacture of the composite flame retardant, 70g of aluminum diethylphosphinate and 30g of hexagonal boron nitride were mixed, except that the composite flame retardant was manufactured in the same manner as in Example 1 and an elastic sheet was manufactured.

[0180]

[0181] Example 3

[0182] In the manufacture of the composite flame retardant, 80g of aluminum diethylphosphinate and 20g of hexagonal boron nitride were mixed, except that the composite flame retardant was manufactured in the same manner as in Example 1 and an elastic sheet was manufactured.

[0183]

[0184] Example 4

[0185] In the manufacture of the composite flame retardant, 90 g of aluminum diethylphosphinate and 10 g of hexagonal boron nitride were mixed, except that the composite flame retardant was manufactured in the same manner as in Example 1 and an elastic sheet was manufactured.

[0186]

[0187] Example 5

[0188] (Manufacture of composite flame retardants)

[0189] 60g of aluminum diethylphosphinate and 40g of hexagonal boron nitride were introduced into the chamber of a dry energy mixer, a mechanofusion. A composite flame retardant was prepared by applying mechanical energy by setting the rotation speed of the chamber to 2500 rpm.

[0190]

[0191] (Manufacture of urethane-based elastic sheets)

[0192] A composition for an elastic sheet was prepared by adding 35 parts by weight of the composite flame retardant prepared in Example 5 above, 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), 0.125 parts by weight of dibutyltin dilaure (metal catalyst), 3.5 parts by weight of glass bubbles (S60), and 0.35 parts by weight of polymer microspheres (FN-100MD) into a planetary mixer and mixing for 2 hours. The composition for an elastic sheet was applied onto a substrate and heat-treated in an oven at a temperature of 150°C to produce an elastic sheet with a thickness of approximately 200 μm.

[0193]

[0194] Example 6

[0195] In the preparation of the composite flame retardant, 70g of aluminum diethylphosphinate and 30g of hexagonal boron nitride were mixed, except that the composite flame retardant was prepared in the same manner as in Example 5 and an elastic sheet was prepared.

[0196]

[0197] Example 7

[0198] In the preparation of the composite flame retardant, 80 g of aluminum diethylphosphinate and 20 g of hexagonal boron nitride were mixed, except that the composite flame retardant was prepared in the same manner as in Example 5 and an elastic sheet was prepared.

[0199]

[0200] Example 8

[0201] In the preparation of the composite flame retardant, 90 g of aluminum diethylphosphinate and 10 g of hexagonal boron nitride were mixed, except that the composite flame retardant was prepared in the same manner as in Example 5 and an elastic sheet was prepared.

[0202]

[0203] Comparative Example 1

[0204] A composite flame retardant was prepared in the same manner as in Example 1, except that a 3-roll machine was used as a dry mixer instead of a meccanofusion and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0205]

[0206] Comparative Example 2

[0207] A composite flame retardant was prepared in the same manner as in Example 2, except that a 3-roll machine was used as a dry mixer instead of a mechano fusion machine and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0208]

[0209] Comparative Example 3

[0210] A composite flame retardant was prepared in the same manner as in Example 3, except that a 3-roll machine was used as a dry mixer instead of a mechano fusion machine and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0211]

[0212] Comparative Example 4

[0213] A composite flame retardant was prepared in the same manner as in Example 4, except that a 3-roll machine was used as a dry mixer instead of a mechano fusion machine and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0214]

[0215] Comparative Example 5

[0216] A composite flame retardant was prepared in the same manner as in Example 5, except that a 3-roll machine was used as a dry mixer instead of a mechano fusion machine and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0217]

[0218] Comparative Example 6

[0219] A composite flame retardant was prepared in the same manner as in Example 6, except that a 3-roll machine was used as a dry mixer instead of a mechano fusion machine and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0220]

[0221] Comparative Example 7

[0222] A composite flame retardant was prepared in the same manner as in Example 7, except that a 3-roll machine was used as a dry mixer instead of a meccanofusion and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0223]

[0224] Comparative Example 8

[0225] A composite flame retardant was prepared in the same manner as in Example 8, except that a 3-roll machine was used as a dry mixer instead of a mechano fusion machine and mixed for 48 hours when preparing the composite flame retardant, and an elastic sheet was prepared.

[0226]

[0227] Specifically, the compositions for elastic sheets according to the examples and comparative examples were prepared according to the compositions of Table 1 and Table 2 below.

[0228] Classification (parts by weight) Examples 1 to 4 Comparative Examples 1 to 4 2-Ethylhexyl acrylate 25 2 5 Isobonyl acrylate 25 2 5 4-hydroxybutyl acrylate 50 5 0 1,6-Hexanediol diacrylate (crosslinking agent) 0.05 0.05 Igacure 651 (initiator) 0.25 0.25 8 2 0 DET40 (polymer microsphere) 11 K-1 (glass bubble) 3.5 3.5 Composite flame retardant 40 40

[0229] Classification (parts by weight) Examples 5 to 8 Comparative Examples 5 to 8 CP6001 (Polyol) 5 6.12 5 6.12 Luprante M11s (Isocyanate) 4.8 8 4.8 8 1,4-butandiol (Crosslinking agent) 0.02 5 0.025 Dibutyltin dilaurae (Metal catalyst) 0.12 5 0.125 S60 (Glass bubble) 3.5 3.5 FN-100MD (Polymer microsphere) 0.35 0.35 Composite flame retardant 35 35

[0230]

[0231] Evaluation Example 1: Composite flame retardant structure

[0232] The composite flame retardants prepared in Examples 1 to 4 were photographed using a Scanning Electron Microscope (SEM).

[0233] Figure 13 is an SEM image of the composite flame retardants prepared in Examples 1 to 4.

[0234] Referring to Fig. 13, it can be seen that the composite flame retardant prepared in the example has a core-shell structure formed by coating small particles of boron nitride on the surface of large particles of phosphorus-based flame retardant.

[0235]

[0236] Evaluation Example 2: Thermogravimetric Analysis

[0237] Thermogravimetric analysis (TGA) was performed on each of the composite flame retardants and phosphorus-based flame retardants prepared in Examples 1 and 5 to determine the char content and decomposition temperature trends, and Figure 14 shows the weight change according to temperature.

[0238] Referring to Fig. 14, it can be seen that the phosphorus-based flame retardant decomposes more rapidly than in Examples 1 and 5, forming carbonized material from a low temperature.

[0239] In addition, it can be seen that Example 1 has a higher thermal decomposition temperature than Example 5 and has a larger amount of remaining carbon.

[0240] This is because the rigid interface between the chemically bonded phosphorus-based flame retardant and boron nitride requires high temperatures to decompose due to contact, and since complete decomposition does not occur even at high temperatures, the amount of carbides increases.

[0241] Accordingly, it can be interpreted that the phosphorus-based flame retardant and boron nitride form a chemical bond within the composite flame retardant through mechano fusion.

[0242]

[0243] Evaluation Example 3: FT-IR

[0244] To determine whether the mechano-chemical reaction of the composite flame retardant according to the example is formed by mechano-fusion, Fourier transform infrared spectral analysis (FT-IR) was performed on each of the composite flame retardants prepared in Examples 1 and 5, and the results are shown in FIG. 15.

[0245] Referring to FIG. 15, in Example 1, hydrogen bonds, which are chemical bonds between the phosphorus-based flame retardant and boron nitride, are formed by mechanofusion, and the BN bond peak is at 1348 cm⁻¹. -1 From 1371 cm -1 It can be confirmed that it has moved to. In other words, it is confirmed that hydrogen bonds are formed at the interface between the phosphorus-based flame retardant and the boron nitride by mechano fusion treatment.

[0246] Therefore, in FT-IR analysis, the composite flame retardant may exhibit peaks corresponding to specific bonds, such as hydrogen bonds, and through this, the chemical bonding between the phosphorus-based flame retardant and boron nitride can be confirmed.

[0247]

[0248] Evaluation Example 4: Evaluation of Flame Retardancy and Thermal Conductivity

[0249] Each elastic sheet prepared in Examples 1 to 8 and Comparative Examples 1 to 8 was evaluated for flame retardancy according to UL-94 VTM, and the results are shown in Tables 3 and 4 below.

[0250] Here, the UL 94 standard may be followed as the UL 94 standard for flame retardancy testing of plastic materials published by Underwriters Laboratories. Specifically, a film-type specimen measuring 200 x 50 mm was rolled onto a 13 mm diameter mandrel, the top part was taped, and it was secured using a clamp. After applying flame contact to the specimen twice for 3 seconds, the flame retardancy was evaluated by recording the first combustion time, the second combustion time, and the luminescence time. 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.

[0251] Thermal conductivity was measured by preparing each elastic sheet prepared in Examples 1 to 8 and Comparative Examples 1 to 8 as a 30 x 30 mm specimen, and then measuring the thermal conductivity of each sample using a C-Therm TCi Thermal Conductivity Analyzer. The results are shown in Tables 3 and 4 below.

[0252]

[0253] Classification Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Flame Retardancy VTM-0 VTM-0 VTM-0 VTM-0 VTM-2 VTM-2 VTM-2 VTM-1 Thermal Conductivity (W / mK, 25℃) 1.74 1.45 1.28 1.06 0.8 1.073 0.65 0.58 Thermal Conductivity (W / mK, 45℃) 3.13 2.89 2.46 2.08 1.14 1.01 0.94 0.86

[0254] Classification Example 5 Example 6 Example 7 Example 8 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Flame Retardancy VTM-0 VTM-0 VTM-0 VTM-0 VTM-2 VTM-1 VTM-1 VTM-1 Thermal Conductivity (W / mK, 25℃) 1.83 1.5 1.47 1.18 0.90 0.8 10.68 0.53 Thermal Conductivity (W / mK, 45℃) 3.27 3.02 2.56 2.12 1.19 1.08 0.99 0.64

[0255]

[0256] Referring to Tables 3 and 4, it can be confirmed that the elastic sheets containing the composite flame retardants according to Examples 1 to 8 can achieve excellent flame retardancy of the VTM-0 grade, unlike Comparative Examples 1 to 8. Through this, it can be confirmed that the flame-retardant elastic sheets containing the composite flame retardants produced by meccanofusion possess excellent flame retardancy. In addition, it can be confirmed that the composite flame retardant according to the examples secures excellent flame retardancy by chemically bonding boron nitride with the phosphorus-based flame retardant.

[0257] The elastic sheets according to Examples 1 to 8 showed a more pronounced improvement in thermal conductivity as the surface of the phosphorus-based flame retardant was coated more densely as the boron nitride content ratio increased.

[0258] In addition, it can be confirmed that the thermal conductivity of the elastic sheets according to Examples 1 to 8 is significantly higher at a high temperature (45°C) than at room temperature (25°C). This is because at temperatures higher than room temperature, phonons can move rapidly due to thermal energy.

[0259] In addition, it can be confirmed that urethane-based elastic sheets containing a small amount of composite flame retardant (Examples 1 to 4) have superior thermal conductivity compared to acrylic-based elastic sheets (Examples 5 to 8). This is because the NH bonds or C=O bonds of the urethane groups formed hydrogen bonds with the nitrogen (N) atoms of the boron nitride.

[0260]

[0261] Although embodiments of the present invention have been described above with reference to the attached drawings, the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Core particles containing a phosphorus-based flame retardant; and The above-mentioned core particle includes a coating layer on its surface, The above coating layer comprises boron nitride (BN), Composite flame retardant for all-solid-state batteries.

2. In Paragraph 1, Average particle size (D of the above core particles) 50 ) is 0.5 μm to 50 μm, Composite flame retardant for all-solid-state batteries.

3. In Paragraph 1, The above-mentioned phosphorus-based flame retardant comprises phosphate, phosphite, phosphonate, phosphinate, phosphine oxide, or a combination thereof. Composite flame retardant for all-solid-state batteries.

4. In Paragraph 1, The above-mentioned phosphorus-based flame retardant is a composite flame retardant for all-solid-state batteries comprising aluminum diethyl phosphinate (ADP), aluminum hypophosphite (AHP), triphenyl phosphate (TPP), resorcinol bis-(diphenyl phosphate) (RDP), tricresyl phosphate (TCP), ammonium polyphosphate (APP), lauryldiphenylphosphate (LDP), or a combination thereof.

5. In Paragraph 1, The thickness of the coating layer is 0.1 μm to 100 μm, Composite flame retardant for all-solid-state batteries.

6. In Paragraph 1, The above coating layer comprises a plurality of boron nitride particles, and The above plurality of boron nitride particles are connected to each other to form the coating layer, Composite flame retardant for all-solid-state batteries.

7. In Paragraph 6, The average particle size (D) of the plurality of boron nitride particles mentioned above 50 ) is 0.5 μm to 20 μm, Composite flame retardant for all-solid-state batteries.

8. In Paragraph 1, The above boron nitride comprises hexagonal boron nitride, wurtzite boron nitride, cubic boron nitride, boron nitride nanosheets, boron nitride nanotubes, or a combination thereof. Composite flame retardant for all-solid-state batteries.

9. In Paragraph 1, The above-mentioned phosphorus-based flame retardant and the above-mentioned boron nitride are chemically bonded to each other. Composite flame retardant for all-solid-state batteries.

10. In Paragraph 1, The above phosphorus-based flame retardant and the above boron nitride are bonded by hydrogen bonds, amine bonds, amide bonds, ethylene bonds, or a combination thereof. Composite flame retardant for all-solid-state batteries.

11. In Paragraph 1, Average particle size (D) of the above composite flame retardant 50 ) is 1 μm to 70 μm, Composite flame retardant for all-solid-state batteries.

12. In Paragraph 1, The weight ratio of the above phosphorus-based flame retardant and the above boron nitride is 60:40 to 90:10, Composite flame retardant for all-solid-state batteries.

13. A composite flame retardant obtained by mixing a phosphorus-based flame retardant and boron nitride (BN) by a meccanofusion method, wherein The above composite flame retardant is: Core particles containing a phosphorus-based flame retardant; and The above-mentioned core particle includes a coating layer on its surface, The above coating layer comprises boron nitride, Method for manufacturing a composite flame retardant for all-solid-state batteries.

14. In Paragraph 13, The above meccanofusion comprises rotating an inner chamber at a speed of 100 rpm to 3000 rpm for 5 to 60 minutes, Method for manufacturing a composite flame retardant for all-solid-state batteries.

15. In Paragraph 13, The above meccanofusion includes maintaining the temperature of the inner chamber at 15 °C to 30 °C, Method for manufacturing a composite flame retardant for all-solid-state batteries.

16. In Paragraph 13, The above meccano fusion is a mixture of the above phosphorus-based flame retardant and the above boron nitride in a weight ratio of 60:40 to 90:

10. Method for manufacturing a composite flame retardant for all-solid-state batteries.

17. In Paragraph 13, The above composite flame retardant is one in which the above phosphorus-based flame retardant and the above boron nitride are chemically bonded to each other. Method for manufacturing a composite flame retardant for all-solid-state batteries.

18. In Paragraph 13, Average particle size (D) of the above phosphorus-based flame retardant 50 ) is 0.5 μm to 50 μm, and Average particle size (D) of the above boron nitride 50 ) is 0.5 μm to 20 μm, Method for manufacturing a composite flame retardant for all-solid-state batteries.

19. Multiple unit cells stacked sequentially; and It includes an elastic sheet interposed between adjacent units among the plurality of unit cells mentioned above, The above elastic sheet comprises a polymer resin and a composite flame retardant according to any one of claims 1 to 12, All-solid-state battery.

20. In Paragraph 19, The above polymer resin is an all-solid-state battery comprising urethane resin, acrylic resin, silicone resin, fluoropolymer, copolymers thereof, or mixtures thereof.

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