Negative electrode for all-solid-state battery and all-solid-state battery including same

Abstract

The present invention relates to a negative electrode for an all-solid-state battery and an all-solid-state battery including same, the negative electrode including a negative electrode coating layer including flat Si nanoparticles, a sulfide-based solid electrolyte, a conductive material, and a binder.

Description

Anode for an all-solid-state battery and an all-solid-state battery comprising the same

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

[0002] Recently, rapid developments have been made in electronic devices that use batteries, such as cell phones, laptop computers, and electric vehicles.

[0003] Development of all-solid-state batteries using lithium metal as the cathode is underway. All-solid-state batteries are composed entirely of solid materials, specifically those using solid electrolytes. Because the electrolyte is solid, all-solid-state batteries are structurally robust, reducing the risk of fire or explosion due to leakage from external impacts. Furthermore, they can be shaped into a variety of battery shapes.

[0004] One embodiment provides an anode for an all-solid-state battery that exhibits reduced volume expansion during charge and discharge and excellent electrochemical properties.

[0005] Another embodiment provides an all-solid-state battery comprising the above negative electrode.

[0006] One embodiment provides an anode for an all-solid-state battery including a cathode coating layer including plate-shaped Si nanoparticles; a sulfide-based solid electrolyte; a conductive material; and a binder.

[0007] Another embodiment provides an all-solid-state battery comprising the cathode, the anode, and a solid electrolyte positioned between the cathode and the anode.

[0008] An all-solid-state battery cathode according to one embodiment can exhibit low volume expansion and excellent electrochemical properties.

[0009] Figure 1 is a drawing for explaining a plate-shaped particle shape according to one embodiment.

[0010] Figure 2 is a cross-sectional view schematically showing an all-solid-state battery according to one embodiment.

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0012] 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.

[0013] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0014] It should be understood that terms such as "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.

[0015] Throughout this specification, when it is said that a part "includes" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0016] In addition, the terms "about", "substantially", etc. used throughout this specification are used in the sense of numerical values ​​or near numerical values ​​when manufacturing and material tolerances inherent to the meanings stated are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that mention exact or absolute values ​​to aid understanding of this specification.

[0017] Throughout this specification, the description of “A and / or B” means “A or B or both.”

[0018] Unless otherwise specified herein, when a part such as a layer, film, region, or plate is said to be “on top of” another part, this includes not only cases where it is “directly on top of” the other part, but also cases where there are other parts in between.

[0019] In the present invention, "particle size" or "particle diameter" may be an average particle diameter. In addition, the average particle diameter may be defined as the average particle diameter (D50) based on 50% of the cumulative volume in a particle diameter distribution curve. The particle diameter may be measured by a method widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope, a scanning electron microscope, or a field emission scanning electron microscope (FE-SEM). Alternatively, the average particle diameter (D50) may be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from this. Alternatively, the average particle diameter (D50) may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle diameter (D50) based on 50% of the particle diameter distribution in the measuring device can be calculated.

[0020] "Thickness" may be measured, for example, from photographs taken with an optical microscope such as a scanning electron microscope.

[0021] An all-solid-state battery according to one embodiment comprises a plate-shaped Si nanoparticle; a sulfide-based solid electrolyte; a conductive material; and a cathode coating layer including a binder.

[0022] In one embodiment, the plate-shaped Si nanoparticles are included as a negative electrode active material.

[0023] Plate-shaped Si nanoparticle negative electrode active materials exhibit reduced volume expansion during charge and discharge compared to spherical Si nanoparticles. In one embodiment, the term "plate-shaped" refers to thin particles among particles having length, width, and thickness. Since the plate-shaped Si nanoparticles are thinner in the thickness direction than spherical Si nanoparticles having the same particle size, the volume expansion in the thickness direction can be greatly reduced. Therefore, the problem of volume expansion during charge and discharge does not occur, and the high capacity of Si can be utilized, thereby providing an all-solid-state battery having a high energy density.

[0024] The average aspect ratio of these plate-shaped Si nanoparticles may be 10 or less, or may be 10 to 1, or 5 to 2. When the aspect ratio of the plate-shaped Si nanoparticles is within the above range, the volume expansion reduction effect obtained due to the plate-shaped Si nanoparticles can be further enhanced.

[0025] In one embodiment, the aspect ratio refers to the ratio of the width / length, and may refer to the length ratio of the x-axis and the y-axis, which are substantially orthogonal to each other in one plane. In one embodiment, the width may refer to the length, and the length may refer to the width. In addition, if there is a major axis and a minor axis in one plane, the width may be the major axis, and the length may be the minor axis. For example, the aspect ratio may be the ratio of the major axis / the minor axis.

[0026] In one embodiment, the aspect ratio can be obtained from an SEM image. The average aspect ratio may be the average value of the aspect ratio measured by randomly selecting 20 particles from the SEM image.

[0027] In one embodiment, the plate-like Si nanoparticles may have substantially the same thickness at the center and at the edges when viewed from the side, or may be thicker at the center and thinner at the edges. The center thickness of the plate-like Si nanoparticles may be 20 nm to 80 nm, or may be 30 nm to 60 nm, or 40 nm to 60 nm. The edge thickness of the plate-like Si nanoparticles may be 3 nm to 80 nm, or may be 5 nm to 60 nm. In one embodiment, the center and edge thicknesses can be measured by SEM images.

[0028] When the thickness of the plate-shaped Si nanoparticles satisfies the above range, the volume expansion during charge and discharge can be further reduced.

[0029] Referring to Figure 1, the shape of this plate can be described as having a horizontal (x-axis, long axis), vertical (y-axis, short axis) and thickness (z-axis).

[0030] In one embodiment, the particle size of the plate-shaped Si nanoparticles may be 100 nm to 200 nm, 100 nm to 150 nm, or 100 nm to 130 nm. The particle size may be the length of the horizontal x-axis, for example, the long axis, in FIG. 1.

[0031] According to one embodiment, the plate-shaped Si nanoparticles have a small size of 100 nm to 200 nm and exhibit low crystallinity, which can improve lithium diffusivity and thus exhibit improved electrochemical properties.

[0032] According to one embodiment, the negative electrode includes a solid electrolyte, and since it includes a solid electrolyte rather than a liquid electrolyte within the battery, side reactions of the plate-shaped Si nanoparticles do not occur. Therefore, only the plate-shaped Si nanoparticles can be used as the active material in the negative electrode. When a liquid electrolyte is used as the electrolyte, if only the plate-shaped Si nanoparticles are used as the active material, excessive volume expansion due to side reactions with the electrolyte may occur.

[0033] In one embodiment, since the plate-shaped Si nanoparticles are included in the cathode coating layer, the content of the sulfide-based solid electrolyte can be optimized, for example, used in a small amount, thereby further increasing the capacity. For example, the mixing ratio of the sulfide-based solid electrolyte can be a weight ratio of 90:10 to 80:20, a weight ratio of 90:10 to 89:11, or a weight ratio of 89.5:10.5 to 89.4:10.6.

[0034] The content of the plate-shaped Si nanoparticles may be 86 wt% to 76 wt%, 85.5 wt% to 84 wt%, or 85 wt% to 84.5 wt%, based on 100 wt% of the total weight of the cathode coating layer. When the content of the plate-shaped Si nanoparticles is within the above range, a higher capacity all-solid-state battery can be obtained.

[0035] The content of the sulfide-based solid electrolyte may be 9 wt% to 20 wt%, 9.5 wt% to 12 wt%, or 10 wt% to 10.5 wt%, based on 100 wt% of the total weight of the negative electrode coating layer. When the content of the sulfide-based solid electrolyte is within the above range, lithium ion conduction can be facilitated.

[0036] The content of the conductive material may be 6 wt% to 3 wt%, 5.5 wt% to 4.5 wt%, or 5 wt% to 4.8 wt%, based on 100 wt% of the total weight of the cathode coating layer. When the content of the conductive material is within the above range, it can play a more smooth electronic conduction role.

[0037] The content of the above binder may be 0.2 wt% to 0.1 wt% based on 100 wt% of the total weight of the cathode coating layer. When the content of the binder is within the above range, more appropriate adhesive strength may be achieved.

[0038] In one embodiment, the solid electrolyte may be a sulfide-based solid electrolyte, and the sulfide-based solid electrolyte has better ductility than when an oxide-based solid electrolyte, a halide-based solid electrolyte, or a solid polymer electrolyte is used, and thus can better enclose Si, thereby enabling better contact between the active material and the electrolyte. Accordingly, it can be used together with plate-shaped Si nanoparticles.

[0039] In one embodiment, the sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element, for example, I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS 27 -LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m and n are integers greater than or equal to 0 and less than or equal to 12, respectively, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are integers greater than or equal to 0 and less than or equal to 12, respectively; M is one of P, Si, Ge, B, Al, Ga In), Li aM b P c S d A e (a, b, c, d and e are each integers greater than or equal to 0 and less than or equal to 12, M is Ge, Sn, Si or a combination thereof, and A is one of F, Cl, Br, or I). The sulfide-based solid electrolyte may be, for example, Li 7-x PS 6-x F x (0≤x≤2), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) or Li 7-x PS 6-x I x (0≤x≤2) can be. Also, specifically, Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 It could be the back.

[0040] In one embodiment, the sulfide-based solid electrolyte may be an argyrodite-type sulfide-based solid electrolyte. The argyrodite-type sulfide-based solid electrolyte may be, for example, Li a M b P c S d A e (a, b, c, d, and e are all 0 or more and 12 or less, M is Ge, Sn, Si, or a combination thereof, and A is one of F, Cl, Br, or I). The argyrodite-type sulfide-based solid electrolyte particles have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It can have high ionic conductivity close to the S / cm range.

[0041] As specific examples, Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li6PS5I, 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 Cu 0.06 )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.

[0042] The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof. For example, the sulfide-based solid electrolyte may be obtained by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or in a molar ratio of 50:50 to 80:20. 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.

[0043] Methods for mixing sulfur-containing raw materials for manufacturing sulfide-based solid electrolytes include mechanical milling and solution methods. Mechanical milling involves placing the starting raw materials in a reactor and vigorously stirring them with a ball mill, thereby finely agitating the starting raw materials and mixing them. Using the solution method, the starting 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 manufactured by mixing sulfur-containing raw materials and heat-treating them twice or more, in which case a sulfide-based solid electrolyte with high ionic conductivity and robustness can be manufactured.

[0044] Of course, a commercially available solid electrolyte can be used as the sulfide-based solid electrolyte.

[0045] The above binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0046] Non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0047] The 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.

[0048] When using an aqueous binder as the cathode 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.

[0049] The dry binder is a polymeric material capable of being fiberized, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0050] 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.

[0051] According to one embodiment, a cathode includes a cathode current collector supporting the cathode coating layer. The cathode current collector may be selected from a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0052] The above-described cathode coating layer may further include additives such as fillers, dispersants, and ionic conductive agents. In addition, known materials generally used in all-solid-state batteries may be used as fillers, dispersants, and ionic conductive agents that can be included in the cathode coating layer.

[0053] The thickness of the cathode coating layer may be, for example, 1 µm to 500 µm, 1 µm to 200 µm, 1 µm to 100 µm, or 1 µm to 50 µm, but is not limited thereto.

[0054] According to one embodiment, the cathode may further include a current collector supporting the cathode coating layer.

[0055] The current collector may be, for example, 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, and may be in the form of a foil or sheet. The thickness of the negative electrode current collector may be 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0056] The current collector may be formed of the metal as a substrate and may further include a thin film formed on the substrate. The thin film includes an element capable of forming an alloy with lithium, and may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, or a combination thereof, but is not limited thereto, and any element capable of forming an alloy with lithium in the art may be used.

[0057] The thickness of the above thin film may be 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. When the thin film thickness is within the above range, the cycle life characteristics can be further improved.

[0058] All-solid-state battery

[0059] An all-solid-state battery according to one embodiment includes the cathode, the anode, and a solid electrolyte layer positioned between the cathode and the anode.

[0060] Solid electrolyte layer

[0061] In one embodiment, the solid electrolyte layer may include a solid electrolyte. It may be an inorganic solid electrolyte such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a solid polymer electrolyte.

[0062] The above sulfide-based solid electrolyte, oxide-based solid electrolyte, halide-based solid electrolyte, and solid polymer electrolyte are as described above. In addition, the sulfide-based solid electrolyte included in the solid electrolyte layer may be the same as or different from the sulfide-based solid electrolyte included in the cathode coating layer.

[0063] The above oxide-based solid electrolyte is, 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 a mixture thereof.

[0064] The above 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.

[0065] 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 for example, may be Cl, Br, or a combination thereof. In particular, in the halide-based solid electrolyte, at least one of Br and Cl is suitable as X.

[0066] The composition of the above halide-based solid electrolyte is not particularly limited, but for example, Li a M1X6 (M is Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof, X is F, Cl, Br, I, or a combination thereof, and 2≤a≤3) can be represented. The halide-based solid electrolyte may be, for example, Li2ZrCl6, Li 2.7 Y 0.7 Zr 0.3 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 In 0.5 Zr 0.5 Cl6, Li2In 0.5 Zr 0.5 Cl6, Li3YBr6, Li3YCl6, Li3YBr2Cl4, Li3YbCl6, Li 2.6 Hf 0.4 Yb 0.6 Cl6, or combinations thereof, but is not limited thereto.

[0067] The above solid electrolyte may be in the form of particles. At this time, the average particle diameter (D50) of the solid electrolyte may be 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.5 ㎛ to 5.0 ㎛, 0.5 ㎛ to 4.0 ㎛, 0.5 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.5 ㎛ to 1.0 ㎛.

[0068] The above solid polymer electrolytes include, for example, polyethylene oxide, poly(diallyldimethylammonium)trifluoromethanesulfonyl imide (poly(diallyldimethylammonium)TFSI), Cu3N, Li3N, LiPON, Li3PO4·Li2S·SiS2, Li2S·GeS2·Ga2S3, Li2O·11Al2O3, Na2O.11Al2O3, (Na,Li) 1+x Ti 2-x Al x (PO4)3(0.1≤x≤0.9), Li 1+x Hf 2-x Al x (PO4)3(0.1≤x≤0.9), Na3Zr2Si2PO 12 , Li3Zr2Si2PO 12 , Na5ZrP3O 12 , Na5TiP3O 12 , Na3Fe2P3O 12 , Na4NbP3O 12 , Na-Silicates, Li 0.3 La 0.5 TiO3, Na5MSi4O 12 (M is a rare earth element such as Nd, Gd, Dy), Li5ZrP3O 12 , Li5TiP3O 12 , Li3Fe2P3O 12 , Li4NbP3O 12 , Li 1+x (M,Al,Ga) x (Ge 1-y Ti y ) 2-x(PO4)3(0≤x≤0.8, 0≤y≤1.0, M is Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), Li 1+x+y Q x Ti 2-x Si y P 3-y O 12 (0 <x≤0.4, 0<y≤0.6, Q 는 Al 또는 Ga), Li6BaLa2Ta2O 12 , Li7La3Zr2O 12 , Li5La3Nb2O 12 , Li5La3M2O 12 (M is Nb, Ta) and Li 7+x A x La 3-x Zr2O 12 (0 <x<3, A는 Zn) 중에서 선택된 하나 이상을 포함할 수 있다.

[0069] The above solid electrolyte is in the form of particles, and the average particle diameter (D50) may be 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.5 ㎛ to 5.0 ㎛, 0.5 ㎛ to 4.0 ㎛, 0.5 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.5 ㎛ to 1.0 ㎛.

[0070] The above solid electrolyte layer may further include a binder. This binder is, 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 these. copolymers, or combinations thereof.

[0071] The binder may be included in an amount of 0.1 wt% to 3 wt% based on 100 wt% of the solid electrolyte membrane, 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 membrane can be well combined without lowering the ionic conductivity of the solid electrolyte, thereby improving the durability and reliability of the battery.

[0072] The above solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the same on a base film, and drying the same. The solvent of the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. Since the solid electrolyte layer formation process is widely known in the art, a detailed description thereof will be omitted herein.

[0073] The thickness of the solid electrolyte layer may be, for example, 10 μm to 150 μm.

[0074] The solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0075] 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.

[0076] The above lithium salts include, for example, LiSCN, LiN(CN)2, Li(CF3SO2)3C, LiC4F9SO3, LiN(SO2CF2CF3)2, LiCl, LiF, LiBr, LiI, LiB(C2O4)2, LiBF4, LiBF3(C2F5), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, It may include LiN(SO2F)2), LiCF3SO3, LiAsF6, LiSbF6, LiClO4 or mixtures thereof.

[0077] In addition, the lithium salt may be an imide-based one, and for example, the imide-based lithium salt may include lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2). The lithium salt may maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with an ionic liquid.

[0078] The above ionic liquid has a melting point below room temperature and is a salt or room-temperature molten salt that is liquid at room temperature and consists only of ions.

[0079] The above ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, 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.

[0080] 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.

[0081] In the above solid electrolyte layer, the weight ratio of the solid electrolyte and 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.

[0082] Bipolar

[0083] According to one embodiment, a positive electrode of an all-solid-state battery includes a positive electrode current collector and a positive electrode active material layer positioned on one surface of the positive electrode current collector.

[0084] The above-mentioned positive electrode active material layer may include a positive electrode active material. The positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound). Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0085] 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, or a combination thereof.

[0086] As an example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 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 Ni 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); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Lia FePO4(0.90≤a≤1.8)

[0087] 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; L 1 is Mn, Al or a combination thereof.

[0088] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 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 in the lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0089] According to one implementation example, LiNi is used as the positive electrode active material. x Co y Al z O2(NCA), LiNi x Co y Mn z O2(NCM)(but, 0 <x<1, 0<y<1, 0<z<1, x+y+z=1) 등의 삼성분계 리튬 전이 금속 산화물을 들 수 있다.

[0090] Of course, it is also possible to use a compound having a coating layer on the surface of the compound, or it is also possible to use a mixture of the compound and a compound having a coating layer. The coating layer may include at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compounds forming these coating layers 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 forming process may use any coating method as long as it can coat the compound with these elements in a method that does not adversely affect the properties of the positive electrode active material (for example, spray coating, dipping, etc.), and since this is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0091] In addition, as the above coating layer, any known coating layer for the positive electrode active material of an all-solid-state battery can be applied. For example, it can be a buffer layer that plays a role in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte. For example, the buffer layer can include a lithium-metal-oxide, wherein the metal can 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. Specific examples of the buffer layer include Li2O-ZrO2 (LZO), LiNbO2, etc.

[0092] Furthermore, when the cathode active material is a ternary compound containing nickel, cobalt, and manganese, or nickel, cobalt, and aluminum, the capacity density of the all-solid-state battery can be further improved and metal dissolution from the cathode active material can be further reduced in a charged state. Consequently, the all-solid-state battery can exhibit improved long-term reliability and cycle performance in a charged state.

[0093] The average particle size of the positive electrode active material may be 1 μm to 25 μm, for example, 3 μm to 25 μm, 1 μm to 20 μm, 1 μm to 18 μm, 3 μm to 15 μm, or 5 μm to 15 μm. For example, the positive electrode active material may include small particles having an average particle size (D50) of 1 μm to 9 μm and large particles having an average particle size (D50) of 10 μm to 25 μm. A positive electrode active material having such a particle size range can be harmoniously mixed with other components within a positive electrode active material layer and can realize high capacity and high energy density.

[0094] 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 crystal. In addition, the above-mentioned positive electrode active material may be in the form of a spherical or nearly spherical shape, or may be polyhedral or irregular.

[0095] In addition, the content of the positive electrode active material in the positive electrode active material layer is not particularly limited, and may be within a range applicable to the positive electrode layer of a conventional all-solid-state secondary battery. For example, with respect to the total 100 wt% of the positive electrode active material layer, the positive electrode active material may be included in an amount of 55 wt% to 99.5 wt%, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0096] The above positive electrode active material layer may further include a binder and / or a conductive material.

[0097] The above binder may include, but is not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0098] The above binder may be included in an amount of 0.1 wt% to 5 wt%, or 0.1 wt% to 3 wt%, based on 100 wt% of the total positive electrode active material layer. Within the above content range, the binder can sufficiently exhibit adhesive ability without deteriorating battery performance.

[0099] 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. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotubes; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0100] The conductive material may be included in an amount of 0.1 wt% to 5 wt%, or 0.1 wt% to 3 wt%, based on 100 wt% of the total weight of the positive electrode active material layer. Within the above content range, the conductive material can improve electrical conductivity without degrading battery performance.

[0101] The above-described positive electrode active material layer may additionally include a solid electrolyte. The solid electrolyte included in the positive electrode active material layer may be an inorganic solid electrolyte such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a solid polymer electrolyte. The solid electrolyte is as described in the above-described solid electrolyte, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0102] With respect to the total weight 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%. In addition, with respect to the total weight of the positive electrode active material and the solid electrolyte in the positive electrode active material layer, 65 wt% to 99 wt% of the positive electrode active material and 1 wt% to 35 wt% of the solid electrolyte may be included, for example, 80 wt% to 90 wt% of the positive electrode active material and 10 wt% to 20 wt% of the solid electrolyte may be included. When the solid electrolyte is included in the positive electrode in such an amount, the efficiency and life characteristics of the all-solid-state battery can be improved without reducing the capacity. The above solid electrolyte may be included in an amount of 0.1 to 10 wt% to 30 wt% based on 100 wt% of the total positive electrode active material layer.

[0103] Elastic layer

[0104] An all-solid-state battery according to one embodiment may further include an elastic layer for buffering thickness changes that occur during charging and discharging. The elastic layer may be positioned between the negative electrode and the case.

[0105] The above elastic layer may be a material having an elastic recovery rate of 50% or more and an insulating function, and specifically may be silicone rubber, acrylic rubber, fluorine rubber, nylon, synthetic rubber, or a combination thereof. The above cushioning material may be in the form of a polymer sheet.

[0106] <Method for manufacturing an all-solid-state battery>

[0107] An all-solid-state battery according to one embodiment can be manufactured by a step of preparing a laminate by positioning a cathode, an anode, and a solid electrolyte layer between the cathode and the anode, and pressing the laminate.

[0108] The pressurizing process can be performed at a temperature ranging from 25°C to 90°C. In addition, the pressurizing process can be performed by pressurizing at a pressure of 550 MPa or less, for example, 500 MPa or less, for example, 1 MPa to 500 MPa. The pressurizing time can vary depending on the temperature and pressure, and can be, for example, less than 30 minutes. The pressurizing process can be, for example, isostatic pressing, roll pressing, plate pressing, or warm isostatic pressing.

[0109] 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 positive electrode / solid electrolyte layer / negative electrode / solid electrolyte layer / positive electrode, or a laminated battery in which the structure of the unit cell is repeated.

[0110] 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-scale 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.

[0111] Fig. 2 is a cross-sectional view of an all-solid-state battery according to an embodiment. Referring to Fig. 2, the all-solid-state battery (100) may have a structure in which an electrode assembly in which a negative electrode (400) including a negative electrode collector (401) and a negative electrode coating layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode collector (201) are laminated is housed in a case (500) such as a pouch. The all-solid-state battery (100) may further include an elastic layer on the outer side of at least one of the positive electrode (200) and the negative electrode (400).

[0112] Although one electrode assembly including a cathode (400), a solid electrolyte layer (300), and a cathode (200) is illustrated in FIG. 1, an all-solid-state battery may be manufactured by stacking two or more electrode assemblies. For example, 2 to 100, 3 to 50, 4 to 20, etc. may be stacked.

[0113] Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0114] (Example 1)

[0115] 1) Cathode manufacturing

[0116] A cathode coating layer composition was prepared by adding 85 wt% of plate-shaped Si nanoparticles (average aspect ratio (major axis / minor axis): 10, particle size: 100 nm, center thickness: 60 nm, edge thickness: 20 nm), 10 wt% of argyrodite-type solid electrolyte Li6PS5Cl, 4.9 wt% of styrene-butadiene rubber, and 0.1 wt% of carbon black to a water solvent.

[0117] The above negative electrode coating layer composition was applied to a nickel foil current collector and vacuum dried to manufacture a negative electrode.

[0118] 2) Anode manufacturing

[0119] LiNi 0.8 Co 0.15 Mn 0.05 A cathode composition was prepared by mixing 85 wt% of O2 cathode active material, 13.5 wt% of lithium argyrodite-type solid electrolyte Li6PS5Cl, 1.0 wt% of polyvinylidene fluoride binder, and 0.5 wt% of carbon nanotube conductive material in an N-methyl pyrrolidone solvent.

[0120] The manufactured positive electrode composition was coated on an aluminum positive electrode current collector, dried, and rolled to manufacture a positive electrode.

[0121] 3) Manufacturing of solid electrolyte layer

[0122] An isobutyl isobutylate binder solution (solid content: 50 wt%) containing butyl acrylate, an acrylate polymer, was added to an argyrodite-type solid electrolyte Li6PS5Cl and mixed. At this time, the mixing ratio of the solid electrolyte and the binder was set to a weight ratio of 98.7:1.3.

[0123] The above mixing process was performed using a sinky mixer. 2 mm zirconia balls were added to the resulting mixture and stirred again using the sinky mixer to produce a slurry. The slurry was cast onto a polytetrafluoroethylene film and dried at room temperature to produce a solid electrolyte layer with a thickness of 100 μm.

[0124] 4) All-solid-state battery manufacturing

[0125] After sequentially stacking the above-mentioned negative electrode, the above-mentioned solid electrolyte layer, and the above-mentioned positive electrode, an all-solid-state battery was manufactured by applying hydrostatic pressure of 380 MPa.

[0126] (Comparative Example 1)

[0127] A cathode coating layer composition was prepared by adding 85 wt% of spherical Si nanoparticles with an average particle diameter of 100 nm, 10 wt% of argyrodite-type solid electrolyte Li6PS5Cl, 4.9 wt% of styrene-butadiene rubber, and 0.1 wt% of carbon black to a water solvent.

[0128] The above negative electrode coating layer composition was applied to a nickel foil current collector and vacuum dried to manufacture a negative electrode.

[0129] An all-solid-state battery was manufactured using the above negative electrode in the same manner as in Example 1.

[0130] Experimental Example 1) Measurement of initial Coulomb efficiency

[0131] The all-solid-state batteries manufactured in Example 1 and Comparative Example 1 were charged and discharged once at 0.1 C at 25°C. The discharge capacity / charge capacity ratio was obtained, and the results are shown in Table 1 below as the initial coulombic efficiency.

[0132] Experimental Example 2) Battery Thickness Evaluation

[0133] The all-solid-state batteries manufactured in Example 1 and Comparative Example 1 were subjected to 50 charge-discharge cycles at 0.1 C at 25°C. The rate of increase in battery thickness after the cycle was calculated using Equation 1 below. The results are shown in Table 1 below.

[0134] [Formula 1]

[0135] Thickness increase rate (%) = [(Battery thickness after charging and discharging - Battery thickness before charging and discharging) / Battery thickness before charging and discharging] * 100

[0136] Experimental Example 3) Measurement of capacity retention rate

[0137] The all-solid-state batteries manufactured in Example 1 and Comparative Examples 1 to 4 were subjected to 200 charge-discharge cycles at 0.1 C within a voltage range of 2.5 V to 4.25 V at 25°C. The ratio of the discharge capacity at each cycle to the single discharge capacity was calculated. The results are presented in Table 1 below as capacity retention rates.

[0138] Thickness increase rate (%) Initial coulombic efficiency (%) Capacity retention rate (%) Example 140% 84% 83% Comparative example 143% 82% 75%

[0139]

[0140] As shown in Table 1 above, it can be seen that the all-solid-state battery of Example 1 has a lower thickness increase rate and exhibits superior initial coulombic efficiency and capacity retention rate compared to Comparative Example 1.

[0141] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. A cathode coating layer comprising plate-shaped Si nanoparticles; a sulfide-based solid electrolyte; a conductive material; and a binder. A cathode for an all-solid-state battery comprising:

2. In paragraph 1, The above plate-shaped Si nanoparticles are a negative electrode for an all-solid-state battery having an average aspect ratio of 10 or less.

3. In paragraph 2, The above plate-shaped Si nanoparticles are an all-solid-state battery negative electrode having an average aspect ratio of 10 to 1.

4. In paragraph 1, An all-solid-state battery negative electrode, wherein the central thickness of the above plate-shaped Si nanoparticles is 20 nm to 80 nm.

5. In paragraph 1, An all-solid-state battery negative electrode having an edge thickness of 3 nm to 80 nm of the above plate-shaped Si nanoparticles.

6. In paragraph 1, An all-solid-state battery negative electrode having a particle size of the above plate-shaped Si nanoparticles of 100 nm to 200 nm.

7. In paragraph 1, An all-solid-state battery negative electrode having a mixing ratio of the above plate-shaped Si nanoparticles and the above sulfide-based solid electrolyte of 90:10 to 80:20 by weight.

8. In paragraph 1, An all-solid-state battery negative electrode having a content of the above plate-shaped Si nanoparticles of 86 to 76 wt% based on 100 wt% of the total negative electrode coating layer.

9. In paragraph 1, An all-solid-state battery negative electrode having a content of the above sulfide-based solid electrolyte of 9 to 20 wt% based on 100 wt% of the total negative electrode coating layer.

10. In paragraph 1, An all-solid-state battery negative electrode in which the content of the above-mentioned conductive material is 6% to 3% by weight based on 100% by weight of the entire negative electrode coating layer.

11. In paragraph 1, An all-solid-state battery negative electrode having a binder content of 0.2% to 0.1% by weight relative to 100% by weight of the entire negative electrode coating layer.

12. In paragraph 1, The above sulfide-based solid electrolyte is an all-solid-state battery negative electrode that is an argyrodite-type solid electrolyte.

13. The cathode of any one of paragraphs 1 to 12; Bipolar; and A solid electrolyte layer positioned between the cathode and the anode An all-solid-state battery comprising:

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