All-solid-state rechargeable battery

Abstract

The present invention relates to an all-solid-state rechargeable battery comprising a negative electrode, a positive electrode, and a solid electrolyte layer positioned between the negative electrode and the positive electrode, wherein the solid electrolyte layer includes, on the side that is in contact with the negative electrode, a region that comprises solid electrolyte particles and an electron conductive material.

Description

All-solid-state secondary battery

[0001] It is about all-solid-state secondary batteries.

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

[0003] Commercially available lithium secondary batteries use electrolytes containing flammable organic solvents, posing safety concerns that can lead to explosion or fire in the event of collisions, penetration, or other problems. Therefore, all-solid-state secondary batteries, which utilize solid electrolytes instead of the electrolyte, have been proposed. All-solid-state secondary batteries are safe because they are composed entirely of solid materials, eliminating the risk of electrolyte leakage and explosion. Furthermore, they facilitate the production of thin batteries, allowing for a reduction in the thickness of the anode, improving high-speed charge / discharge performance and enabling high-voltage operation and high-energy density.

[0004] Maximizing the contact area between the negative electrode and the solid electrolyte layer maximizes the movement path of lithium ions, improving contact uniformity to improve the movement uniformity of lithium ions, reducing the interfacial resistance, and maintaining contact between the negative electrode and the solid electrolyte layer even when the volume of the electrode changes during charge and discharge, thereby improving the performance of the all-solid-state secondary battery.

[0005] In one embodiment, an all-solid-state secondary battery is provided, comprising a cathode, an anode, and a solid electrolyte layer positioned between the cathode and the anode, wherein the solid electrolyte layer includes a region including solid electrolyte particles and an electron conductive material on a side in contact with the cathode.

[0006] In an all-solid-state secondary battery according to one embodiment, the contact area between the negative electrode and the solid electrolyte layer is maximized and the contact uniformity is high, so that the interfacial resistance is reduced, and the contact between the negative electrode and the solid electrolyte layer is maintained even when the electrode volume changes during charge and discharge, and the formation of lithium dendrites is suppressed, so that electrochemical characteristics such as the initial charge and discharge efficiency are improved.

[0007] Figures 1 and 2 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0008] Below, specific implementation examples are described in detail so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various different forms and is not limited to the implementation examples described herein.

[0009] 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.

[0010] Here, “combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0011] It should be understood that the terms "include," "comprising," or "having" herein 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.

[0012] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there are other elements in between. Conversely, when an element is said to be "directly over" another element, it means that there are no other elements in between.

[0013] Also, here, “layer” includes not only the shape formed on the entire surface when observed in a plan view, but also the shape formed on a portion of the surface.

[0014] The average particle size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope image or a scanning electron microscope image. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size can mean the diameter (D50) of particles in a particle size distribution that have a cumulative volume of 50% by volume. In addition, unless otherwise defined, the average particle size can be obtained by randomly measuring the sizes (diameters or major axis lengths) of about 20 particles in a scanning electron microscope image to obtain a particle size distribution, and taking the diameter (D50) of particles in the particle size distribution that have a cumulative volume of 50% by volume as the average particle size.

[0015] Here, “or” is not interpreted in an exclusive sense, for example, “A or B” is interpreted to include A, B, A+B, etc.

[0016] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0017] All-solid-state secondary battery

[0018] In one embodiment, an all-solid-state secondary battery is provided, comprising a cathode, an anode, and a solid electrolyte layer positioned between the cathode and the anode, wherein the solid electrolyte layer is characterized by including a region comprising solid electrolyte particles and an electron conductive material on a side in contact with the cathode.

[0019] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Referring to FIG. 1, the all-solid-state secondary 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 active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode collector (201) are laminated is housed in a battery case. The all-solid-state secondary battery (100') may further include an elastic layer (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). Although FIG. 1 illustrates one electrode assembly including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200), an all-solid-state secondary battery may be manufactured by laminating two or more electrode assemblies.

[0020] solid electrolyte layer

[0021] The above solid electrolyte layer comprises solid electrolyte particles. According to one embodiment, the solid electrolyte layer comprises a region comprising solid electrolyte particles and an electron-conductive material on the side in contact with the cathode. This region may be referred to as a portion of the solid electrolyte layer that contacts the cathode. Due to this region, the bonding area between the cathode and the solid electrolyte layer can be maximized, and voids at the interface can be minimized.

[0022] solid electrolyte particles

[0023] The above solid electrolyte particles may be, for example, sulfide-based solid electrolyte particles having excellent ion conductivity. The above sulfide-based solid electrolyte particles may be, for example, 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-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are integers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0024] Such sulfide-based solid electrolytes can be obtained, for example, by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or 50:50 to 80:20, and optionally heat-treating them. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be produced. Here, the ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0025] Methods for mixing sulfur-containing raw materials for producing sulfide-based solid electrolytes include mechanical milling or the solution method. Mechanical milling involves placing raw materials in a ball mill reactor and vigorously stirring them to finely atomize and mix them. Using the solution method, the raw materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, heat treatment after mixing can solidify the crystals of the solid electrolyte and improve ionic conductivity. For example, a sulfide-based solid electrolyte can be produced by mixing sulfur-containing raw materials and heat-treating them twice or more, resulting in a sulfide-based solid electrolyte with high ionic conductivity and robustness.

[0026] According to one embodiment, a sulfide-based solid electrolyte can be manufactured through, for example, a first heat treatment in which sulfur-containing raw materials are mixed and calcined at 120°C to 350°C, and a second heat treatment in which the first heat treatment result is mixed and calcined at 350°C to 800°C. The first heat treatment and the second heat treatment can each be performed in an inert gas or nitrogen atmosphere. The first heat treatment can be performed for 1 to 10 hours, and the second heat treatment can be performed for 5 to 20 hours. The first heat treatment can have the effect of milling small raw materials, and the second heat treatment can synthesize the final solid electrolyte. Through two or more such heat treatments, a high-performance sulfide-based solid electrolyte with high ionic conductivity and robustness can be obtained, and such a solid electrolyte can be said to be suitable for mass production. The temperature of the first heat treatment may be, for example, 150°C to 330°C, or 200°C to 300°C, and the temperature of the second heat treatment may be, for example, 380°C to 700°C, or 400°C to 600°C.

[0027] For example, the sulfide-based solid electrolyte may include an argyrodite-type sulfide. The argyrodite-type sulfide may be, for example, Li aM b P c S d A e (wherein 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 F, Cl, Br, or I) and can be expressed by the chemical formula, and a specific example is Li 7-x PS 6-x A x (x is 0.2 or more and 1.8 or less, and A is F, Cl, Br, or I) can be expressed by the chemical formula. The above argyrodite-type sulfide is specifically Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 It could be the back.

[0028] Sulfide-based solid electrolytes containing these argyrodite-type sulfides have an ionic conductivity of 10 that of typical liquid electrolytes at room temperature. -4 10 inland -2 It has a high ionic conductivity approaching the S / cm range, can form a close bond between a positive electrode active material and a solid electrolyte without causing a decrease in ionic conductivity, and further can form a close interface between an electrode layer and a solid electrolyte layer. An all-solid-state secondary battery including this can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0029] An argyrodite-type sulfide-based solid electrolyte can be manufactured, for example, by mixing lithium sulfide and phosphorus sulfide, and optionally, lithium halide. After mixing these, a heat treatment may be performed. The heat treatment may include, for example, two or more heat treatment steps. Here, manufacturing an argyrodite-type sulfide-based solid electrolyte may include, for example, a first heat treatment of mixing raw materials and calcining at 120°C to 350°C, and a second heat treatment of mixing the resultant of the first heat treatment again and calcining at 350°C to 800°C.

[0030] The average particle diameter (D50) of the solid electrolyte particles 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 ㎛. The solid electrolyte particles may be small particles having a size of 0.1 ㎛ to 1.5 ㎛, large particles having a size of 2.0 ㎛ to 5.0 ㎛, or a mixture thereof. The average particle diameter of the solid electrolyte particles may be measured by an electron microscope image, and for example, a particle size distribution may be obtained by measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image, and D50 may be calculated from this.

[0031] electronically conductive materials

[0032] The above electronically conductive material may be applied without limitation to any type as long as it has electronic conductivity and does not adversely affect the battery, and may include, for example, a carbon-based material, a metal-based material, a conductive polymer, or a combination thereof.

[0033] The carbon-based material may include, for example, natural graphite, artificial graphite, carbon black, acetylene black, Denka black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, or a combination thereof. The metal-based material may include Al, Ag, Au, Bi, Cu, Ni, Pd, Pt, Si, Sn, Zn, Zr, or a combination thereof. The conductive polymer may be, for example, a polyphenylene derivative.

[0034] The above-mentioned electronically conductive material may include, for example, a carbon-metal composite containing a carbon-based material and a metal-based material. In the carbon-metal composite, the carbon-based material may be an amorphous carbon material, and the metal-based material may be a lithium-philic metal including Al, Ag, Au, Bi, Pd, Pt, Si, Sn, Zn, or a combination thereof.

[0035] The above-mentioned electron conductive material may be, for example, in the form of particles. In this case, the average particle diameter (D50) of the electron conductive material may be, for example, 10 nm to 200 nm, or 50 nm to 150 nm, or 60 nm to 100 nm. In addition, the average particle diameter (D50) of the electron conductive material may be smaller than the average particle diameter (D50) of the solid electrolyte particles present in the region. Specifically, the ratio of the average particle diameter (D50) of the electron conductive material to the average particle diameter (D50) of the solid electrolyte particles may be 0.1 or less, and may be 0.01 to 0.1 or 0.2 to 0.09. When the particle diameter of the electron conductive material satisfies such a size or size ratio, the bonding area between the negative electrode and the solid electrolyte layer may be further increased, and thus the interfacial resistance may be lowered.

[0036] The average particle diameter of the above electronic conductive material may be obtained by measuring the size (diameter or length of the major axis) of about 20 particles in a scanning electron microscope image to obtain a particle size distribution and calculating D50 from this.

[0037] The electron conductive material may be included in the region at 5 wt% to 10 wt% based on 100 wt% of the total of the solid electrolyte particles and the electron conductive material. In addition, the electron conductive material may be included in the region at 3 wt% to 20 wt% based on 100 volume% of the region, for example, at 4 wt% to 15 wt%, or at 5 wt% to 10 wt%. Here, the region refers to a portion of the solid electrolyte layer that contacts the negative electrode, and includes the solid electrolyte particles and the electron conductive material. When the content of the electron conductive material satisfies the above range, the interfacial resistance between the negative electrode and the solid electrolyte layer can be effectively reduced without adversely affecting the battery.

[0038] The thickness of the above region may be 10% to 60% of the total thickness of the solid electrolyte layer, for example, 15% to 50%, or 20% to 40%. In this case, the interfacial resistance between the negative electrode and the solid electrolyte layer can be effectively controlled without deteriorating the performance of the all-solid-state secondary battery.

[0039] The above solid electrolyte layer may further include a binder in addition to the solid electrolyte. The above region may also further include a binder in addition to the solid electrolyte particles and the electronically conductive material.

[0040] The binder may include, for example, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, 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, or a combination thereof.

[0041] According to one embodiment, the solid electrolyte layer may be expressed as a multilayer structure of two or more layers, for example. The multilayer structure may include two layers, three or more layers, or two or more layers and five or fewer layers. For example, the solid electrolyte layer may include a first solid electrolyte layer in contact with the negative electrode and a second solid electrolyte layer in contact with the positive electrode. Here, the first solid electrolyte layer includes first solid electrolyte particles and an electron conductive material, which corresponds to the aforementioned “region.” The second solid electrolyte layer may include second solid electrolyte particles and not include an electron conductive material.

[0042] The first solid electrolyte and the second solid electrolyte may be identical or different. For example, the first solid electrolyte and the second solid electrolyte may have substantially the same composition and average particle size. In another example, the first solid electrolyte and the second solid electrolyte may have substantially the same composition but different average particle sizes.

[0043] The first solid electrolyte and the second solid electrolyte may be, for example, a sulfide-based solid electrolyte, and among them, may be an argyrodite-type sulfide-based solid electrolyte.

[0044] For example, the average particle diameter (D50) of the first solid electrolyte particles may be larger than the average particle diameter (D50) of the second solid electrolyte particles. In this case, the average particle diameter (D50) of the first solid electrolyte particles may be 2.0 μm to 5.0 μm, or 3.0 μm to 4.0 μm, and the average particle diameter (D50) of the second solid electrolyte particles may be 0.1 μm to 1.5 μm, or 0.1 μm to 1.0 μm, or 0.2 μm to 0.9 μm, or less than 1 μm.

[0045] As another example, the average particle diameter (D50) of the second solid electrolyte particles may be larger than the average particle diameter (D50) of the first solid electrolyte particles. In this case, the average particle diameter (D50) of the first solid electrolyte particles may be 0.1 μm to 1.5 μm, or 0.1 μm to 1.0 μm, or 0.2 μm to 0.9 μm, or less than 1 μm, and the average particle diameter (D50) of the second solid electrolyte particles may be 2.0 μm to 5.0 μm, or 3.0 μm to 4.0 μm.

[0046] In the first solid electrolyte layer, the average particle diameter (D50) of the electron conductive material may be smaller than the average particle diameter (D50) of the first solid electrolyte particles, and for example, the ratio of the average particle diameter (D50) of the electron conductive material to the average particle diameter (D50) of the first solid electrolyte particles may be 0.1 or less, and may be 0.01 to 0.1 or 0.2 to 0.09. In this case, the bonding area between the negative electrode and the solid electrolyte layer may be further increased, and thus the interfacial resistance may be lowered.

[0047] The electron conductive material may be included in the first solid electrolyte layer in an amount of 5 to 10 wt% based on 100 wt% of the total of the solid electrolyte particles and the electron conductive material. In addition, the electron conductive material may be included in an amount of 3 to 20 wt% based on 100 volume% of the first solid electrolyte layer, for example, 4 to 15 volume%, or 5 to 10 volume%. When the content of the electron conductive material satisfies the above range, the interfacial resistance between the negative electrode and the solid electrolyte layer can be effectively reduced without adversely affecting the battery.

[0048] The thickness of the first solid electrolyte layer and the thickness of the second solid electrolyte layer may be the same or different. For example, the thickness of the first solid electrolyte layer and the thickness of the second solid electrolyte layer may be substantially the same. The thickness of the first solid electrolyte layer may be from 10 μm to 200 μm, for example, from 10 μm to 150 μm, from 10 μm to 100 μm, or from 20 μm to 80 μm. The thickness of the second solid electrolyte layer may be from 10 μm to 200 μm, for example, from 10 μm to 150 μm, from 10 μm to 100 μm, or from 20 μm to 80 μm.

[0049] Meanwhile, the solid electrolyte layer may further include an oxide-based inorganic solid electrolyte in addition to a sulfide-based solid electrolyte. The oxide-based inorganic solid electrolyte may be, 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 yO3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr; x is an integer from 1 to 10), or mixtures thereof.

[0050] Meanwhile, the solid electrolyte layer, or the region, or the first solid electrolyte layer and the second solid electrolyte layer may each independently further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] cathode

[0059] An anode for an all-solid-state secondary battery comprises a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer comprises a negative electrode active material and may further comprise a binder and / or a conductive material. In this case, the aforementioned region or first solid electrolyte layer may be referred to as a surface in contact with the negative electrode active material layer.

[0060] The above negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0061] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0062] As the above lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0063] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and the Si-based negative electrode active material may be silicon, a silicon-carbon composite, or SiO. x (0 < x < 2), Si-Q alloy (wherein Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn-based negative electrode active materials include Sn, SnO2, Sn-R alloy (wherein R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and at least one of these may be mixed with SiO2 for use. The above elements Q and R may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0064] For example, the negative active material may include silicon-carbon composite particles. The average particle diameter (D50) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. The average particle diameter (D50) is measured by a particle size analyzer and refers to the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. With respect to 100 wt% of the silicon-carbon composite particles, silicon may be included in an amount of 10 wt% to 60 wt% and carbon may be included in an amount of 40 wt% to 90 wt%. The silicon-carbon composite particles may include, for example, a core including silicon particles and a carbon coating layer positioned on a surface of the core. The average particle diameter (D50) of the silicon particles in the core may be, for example, 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist as silicon alone, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is SiO x (0 <x<2)로 표시될 수 있다. 또한, 상기 탄소 코팅층의 두께는 약 5 nm 내지 100 nm일 수 있다.

[0065] For example, the silicon-carbon composite particle may include a core including silicon particles and crystalline carbon, and a carbon coating layer located on the surface of the core and including amorphous carbon. For example, in the silicon-carbon composite particle, the amorphous carbon may not be present in the core but may be present only in the carbon coating layer. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon may be formed from coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin (phenol resin, furan resin, polyimide resin, etc.). At this time, the content of the crystalline carbon may be 10 wt% to 70 wt%, and the content of the amorphous carbon may be 20 wt% to 40 wt% with respect to 100 wt% of the silicon-carbon composite particle.

[0066] In the above silicon-carbon composite particle, the core may include a void in the central portion. The radius of the void may be 30% to 50% of the radius of the silicon-carbon composite particle.

[0067] The silicon-carbon composite particles described above can effectively suppress problems such as volume expansion, structural collapse, or particle crushing due to charge and discharge, thereby preventing the phenomenon of conductive path disconnection, realizing high capacity and high efficiency, and are advantageous for use under high voltage or fast charging conditions.

[0068] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material. When the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight.

[0069] The content of the negative active material in the above negative active material layer may be 95 wt% to 99 wt% with respect to the total weight of the negative active material layer.

[0070] In one embodiment, the negative electrode active material layer further includes a binder and may optionally further include a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer. In addition, when the negative electrode active material layer further includes a conductive material, the negative electrode active material layer may include 90 wt% to 98 wt% of the negative electrode active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material.

[0071] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. The binder may be an insoluble binder, a water-soluble binder, or a combination thereof.

[0072] The above-mentioned non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0073] The water-soluble binder may be a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0074] When a water-soluble binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity as a type of thickener 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. The amount of the thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0075] The above conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and is electronically conductive can be used. Examples of conductive materials that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0076] The negative electrode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0077] precipitation cathode

[0078] As another example, the negative electrode for an all-solid-state secondary battery may be a precipitation-type negative electrode. The precipitation-type negative electrode may refer to a negative electrode that does not include a negative electrode active material when the battery is assembled, but in which lithium metal or the like is precipitated or deposited on the negative electrode when the battery is charged, and this acts as a negative electrode active material.

[0079] Fig. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode. Referring to Fig. 2, the precipitation-type negative electrode (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state secondary battery including such a precipitation-type negative electrode (400') starts initial charging in a state in which no negative electrode active material is present, and during charging, high-density lithium metal is precipitated or deposited between the current collector (401) and the negative electrode coating layer (405) or on the negative electrode coating layer (405) to form a lithium metal layer (404), which may function as a negative electrode active material. Accordingly, in an all-solid-state secondary battery that has been charged more than once, the precipitation-type negative electrode (400') may include, for example, a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The lithium metal layer (404) refers to a layer in which lithium metal or the like is precipitated during the charging process of the battery, and may be referred to as a metal layer, a lithium layer, a lithium deposition layer, or a negative electrode active material layer.

[0080] In this case, the aforementioned area or first solid electrolyte layer can be said to be a surface in contact with the cathode coating layer (405).

[0081] The above cathode coating layer (405) may be referred to as a lithium electrodeposition induction layer or a cathode catalyst layer, and may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0082] The metal may be a lithium-philic metal, and may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one type of these or may be composed of several types of alloys. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, and may be, for example, 10 nm to 4 μm.

[0083] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microbeads, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof.

[0084] When the above-described negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state secondary battery can be improved. The above-described negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0085] The above-described cathode coating layer (405) may include, for example, the above-described lithium-philic metal and amorphous carbon, in which case the precipitation of the lithium metal may be effectively promoted. As a specific example, the cathode coating layer (405) may include a composite in which a lithium-philic metal is supported on amorphous carbon.

[0086] The above cathode coating layer (405) may further include a binder, and the binder may be, for example, a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0087] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 ㎛, or 500 nm to 10 ㎛, or 1 ㎛ to 5 ㎛.

[0088] The above-described precipitated negative electrode (400') may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type thereof or may be composed of multiple types of alloys. The thin film may further planarize the precipitated form of the lithium metal layer (404) and further improve the characteristics of the all-solid-state secondary battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0089] The lithium metal layer (404) may include lithium metal or a lithium alloy. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, or a Li-Si alloy.

[0090] The thickness of the lithium metal layer (404) may be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the lithium metal layer (404) is too thin, it may be difficult to perform the role of a lithium storage, and if it is too thick, the battery volume may increase and performance may deteriorate.

[0091] When such a precipitation-type cathode is applied, the cathode coating layer (405) can play a role in protecting the lithium metal layer (404) and suppressing the precipitation growth of lithium deadlight. Accordingly, short-circuiting and capacity reduction of the all-solid-state battery can be suppressed, and the life characteristics can be improved.

[0092] anode

[0093] In one embodiment, the battery comprises a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises a positive electrode active material and a solid electrolyte, and may optionally comprise a binder and / or a conductive material.

[0094] positive electrode active material

[0095] The above-mentioned positive electrode active material can be applied without limitation as long as it is generally used in all-solid-state secondary batteries. For example, the above-mentioned positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, and may include a compound represented by any one of the following chemical formulas.

[0096] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0097] 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);

[0098] Li a E 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0099] Li a E 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0100] Li a Ni 1-b-c Co b X c D α (0.90 ≤ a ≤1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 <α ≤ 2);

[0101] Li a Ni 1-b-c Co b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0102] Li a Ni 1-b-c Co b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0103] Li a Ni 1-b-c Mr b X c D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2);

[0104] Li a Ni 1-b-c Mr b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0105] Li a Ni 1-b-c Mr b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0106] Li a Ni b HAVE BEEN c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0107] Li a Ni b Co c Mrd G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1);

[0108] Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0109] Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0110] Li a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0111] Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0112] Li a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0113] QO2; QS2; LiQS2;

[0114] V2O5; LiV2O5;

[0115] LiZO2;

[0116] LiNiVO4;

[0117] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0118] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0119] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0120] In the above chemical formulas, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

[0121] The above-mentioned positive electrode active material may be, for example, lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt oxide (NC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium nickel manganese oxide (NM), lithium manganese oxide (LMO), or lithium iron phosphate (LFP).

[0122] The positive electrode active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 11, a lithium cobalt-based oxide represented by the following chemical formula 12, a lithium iron phosphate-based compound represented by the following chemical formula 13, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 14, or a combination thereof.

[0123] [Chemical Formula 11]

[0124] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0125] In the above chemical formula 11, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0126] In the above chemical formula 1, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0127] [Chemical Formula 12]

[0128] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0129] In the above chemical formula 12, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0130] [Chemical Formula 13]

[0131] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0132] In the above chemical formula 13, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0133] [Chemical Formula 14]

[0134] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0135] In the above chemical formula 14, 0.9≤a2≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0136] The average particle diameter (D50) 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 diameter (D50) of 1 μm to 9 μm and large particles having an average particle diameter (D50) of 10 μm to 25 μm. A positive electrode active material having such a particle diameter range can be harmoniously mixed with other components within a positive electrode active material layer and can realize high capacity and high energy density. Here, the average particle diameter may be obtained by selecting 20 or so random particles from a scanning electron microscope image of the positive electrode active material, measuring their particle diameters (diameter, major axis, or major axis length), obtaining a particle size distribution, and then taking the diameter (D50) of particles having a cumulative volume of 50% by volume from the particle size distribution as the average particle diameter.

[0137] The above-mentioned positive electrode active material may be in the form of a secondary particle formed by agglomeration of a plurality of primary particles, or may be in the form of a single particle. In addition, the above-mentioned positive electrode active material may be spherical or nearly spherical in shape, or may be polyhedral or irregular in shape.

[0138] Meanwhile, the positive electrode active material may include a buffer layer on the particle surface. The buffer layer may be expressed as a coating layer, a protective layer, etc., and may play a role in lowering the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte particles. For example, the buffer layer may include a lithium-metal-oxide, wherein the metal may be one or more elements selected from the group consisting of Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. The lithium-metal-oxide is excellent in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte particles while improving the performance of the positive electrode active material by facilitating the movement of lithium ions and electron conduction.

[0139] The positive electrode active material may be included in an amount of 55 wt% to 99 wt% based on 100 wt% of the positive electrode active material layer, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0140] solid electrolyte

[0141] The solid electrolyte included in the positive electrode active material layer may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof, and may be, for example, an argyrodite-type sulfide-based solid electrolyte. Since the solid electrolyte has been described above, a detailed description thereof will be omitted.

[0142] With respect to 100 wt% of the above 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%.

[0143] In addition, 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 based on the total weight of the positive electrode active material and the solid electrolyte, 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.

[0144] bookbinder

[0145] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector, and representative examples thereof include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0146] The content of the binder in the positive electrode active material layer may be approximately 0.1 wt% to 5 wt% with respect to 100 wt% of the positive electrode active material layer.

[0147] Challenge

[0148] The above-described positive electrode active material layer may further include a conductive material. The conductive material is used to provide conductivity to the electrode, and any material that does not cause a chemical change and is electronically conductive in the battery to be constructed may be used. Examples of conductive materials that may be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; 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.

[0149] The content of the conductive material in the positive electrode active material layer may be 0 wt% to 3 wt%, 0.01 wt% to 2 wt%, or 0.1 wt% to 1 wt% with respect to 100 wt% of the positive electrode active material layer.

[0150] Aluminum foil may be used as the positive electrode current collector, but is not limited thereto.

[0151] The above-mentioned all-solid-state secondary battery may be a unit cell having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative electrode, or a laminated battery in which the structure of the unit cell is repeated.

[0152] 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.

[0153] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0154] Example 1

[0155] 1. Manufacturing of the cathode

[0156] An Ag / C composite was prepared by mixing carbon black having a primary particle size (D50) of approximately 30 nm and silver (Ag) having an average particle size (D50) of approximately 60 nm in a weight ratio of 3:1, and 0.25 g of the composite was added to 2 g of an NMP solution containing 7 wt% polyvinylidene fluoride binder and mixed to prepare a negative electrode coating layer composition. This was applied to a nickel foil current collector using a bar coater, vacuum-dried, and then rolled to prepare a deposition-type negative electrode in which a negative electrode coating layer was formed on the current collector.

[0157] 2. Formation of the first solid electrolyte layer

[0158] A first composition was prepared by adding 95 wt% of an argyrodite-type solid electrolyte Li6PS5Cl (D50=0.7 ㎛) and 5 wt% of an amorphous carbon material having an average particle size of about 100 nm as an electron conductive material to a binder solution prepared by dissolving an acrylic binder (SX-A334, Zeon) in an isobutyryl isobutyrate (IBIB) solvent, and stirring the solution. The first composition was applied onto the cathode coating layer of the prepared cathode using a blade coater, thereby forming a first solid electrolyte layer.

[0159] 3. Formation of the second solid electrolyte layer

[0160] A second composition is prepared by adding an argyrodite-type solid electrolyte Li6PS5Cl (D50=3.5㎛) to a binder solution in which an acrylic binder (SX-A334, Zeon) is dissolved in an IBIB solvent and stirring. The second composition is applied onto the first solid electrolyte layer using a blade coater to form a second solid electrolyte layer, and drying is performed at 80°C for 10 minutes.

[0161] 4. Manufacturing of the anode

[0162] LiNi coated with Li2O-ZrO2 0.9 Co 0.05 Mn 0.05 A positive electrode composition is prepared by mixing 85 wt% of an O2 positive electrode active material, 13.5 wt% of an argyrodite-type solid electrolyte (Li6PS5Cl), 1.0 wt% of a PVdF binder, and 0.5 wt% of a carbon nanotube conductive material in an IBIB solvent. The prepared positive electrode composition is coated on a positive electrode current collector using a bar coater, and dried in a convection oven at 80°C for 10 minutes, thereby preparing a positive electrode having a positive electrode active material layer formed on the current collector.

[0163] 5. Manufacturing of all-solid-state secondary batteries

[0164] In the manufactured positive electrode, the positive electrode is laminated on the second solid electrolyte layer such that the positive electrode active material layer touches the second solid electrolyte layer. The assembly, in which the negative electrode, the first solid electrolyte layer, the second solid electrolyte layer, and the positive electrode are laminated in that order, is inserted into a pouch, sealed, and subjected to warm isostatic pressing (WIP) at a high temperature of 85°C and 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery.

[0165] In the manufactured all-solid-state secondary battery, the thickness of each of the first solid electrolyte layer and the second solid electrolyte layer was approximately 50 μm.

[0166] Example 2

[0167] An all-solid-state secondary battery was manufactured in substantially the same manner as in Example 1, except that the electronic conductive material introduced into the first solid electrolyte layer in Example 1 was changed to 5 wt% of nano silver particles having an average particle diameter of about 150 nm.

[0168] Comparative Example 1

[0169] An all-solid-state secondary battery was manufactured in substantially the same manner as in Example 1, except that the first solid electrolyte layer was not formed and only the second solid electrolyte layer was formed with twice the thickness.

[0170] Comparative Example 2

[0171] An all-solid-state secondary battery was manufactured in substantially the same manner as in Example 1, except that the second solid electrolyte layer was not formed and only the first solid electrolyte layer was formed with twice the thickness.

[0172] Evaluation Example 1: Battery Performance Evaluation

[0173] For the all-solid-state secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 2, initial charging and discharging was performed by charging at a constant current of 0.1 C at 45°C to an upper limit voltage of 4.25 V and then discharging at 0.1 C to an end voltage of 2.5 V. Table 1 below shows the initial charge amount, initial discharge amount, and the ratio of discharge amount to charge amount as efficiency.

[0174] Charge capacity (mAh / g)Discharge capacity (mAh / g)Efficiency (%)Example 1242.1209.586.5Example 2250.8216.686.4Comparative example 1242.0207.785.8Comparative example 2244.2190.878.1

[0175] Referring to Table 1 and Figure 3, it can be confirmed that Examples 1 and 2 have higher initial discharge amount and initial charge / discharge efficiency than Comparative Examples 1 and 2.

[0176] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention.

[0177] [Explanation of symbols]

[0178] 100: All-solid-state battery 200: Cathode

[0179] 201: Cathode current collector 203: Cathode active material layer

[0180] 300: Solid electrolyte layer 400: Cathode

[0181] 401: Negative current collector 403: Negative active material layer

[0182] 400': Precipitation type cathode 404: Lithium metal layer

[0183] 405: Cathode coating layer 500: Elastic layer

Claims

1. An all-solid-state secondary battery comprising a cathode, an anode, and a solid electrolyte layer positioned between the cathode and the anode, An all-solid-state secondary battery, wherein the solid electrolyte layer includes a region including solid electrolyte particles and an electron conductive material on the side in contact with the negative electrode.

2. In paragraph 1, An all-solid-state secondary battery in which the above solid electrolyte particles are sulfide-based solid electrolyte particles.

3. In paragraph 2, The above sulfide-based solid electrolyte particles are an all-solid-state secondary battery containing argyrodite-based sulfide.

4. In paragraph 1, An all-solid-state secondary battery wherein the average particle diameter (D50) of the above sulfide-based solid electrolyte particles is 0.1 ㎛ to 5.0 ㎛.

5. In paragraph 1, The above electronically conductive material is an all-solid-state secondary battery including a carbon-based material, a metal-based material, a conductive polymer, or a combination thereof.

6. In paragraph 5, The above carbon-based material includes natural graphite, artificial graphite, carbon black, acetylene black, Denka black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, or a combination thereof. The above metal material is an all-solid-state secondary battery including Al, Ag, Au, Bi, Cu, Ni, Pd, Pt, Si, Sn, Zn, Zr, or a combination thereof.

7. In paragraph 1, The above electronic conductive material is an all-solid-state secondary battery including a carbon-metal composite containing a carbon-based material and a metal-based material.

8. In paragraph 7, An all-solid-state secondary battery in which the carbon-metal composite in which the carbon-based material is an amorphous carbon material and the metal-based material is a lithium-philic metal including Al, Ag, Au, Bi, Pd, Pt, Si, Sn, Zn or a combination thereof.

9. In paragraph 1, An all-solid-state secondary battery wherein the above-mentioned electronic conductive material is in the form of particles, and the average particle diameter (D50) of the particles is 10 nm to 200 nm.

10. In paragraph 1, An all-solid-state secondary battery wherein the electronic conductive material is in the form of particles and the average particle diameter (D50) of the particles is smaller than the average particle diameter (D50) of the solid electrolyte particles.

11. In paragraph 10, An all-solid-state secondary battery in which the ratio of the average particle diameter (D50) of the electron conductive material to the average particle diameter (D50) of the solid electrolyte particles is 0.1 or less.

12. In paragraph 1, An all-solid-state secondary battery comprising 5 to 10 wt% of an electron conductive material relative to 100 wt% of the total of solid electrolyte particles and electron conductive materials in the above region.

13. In paragraph 1, An all-solid-state secondary battery comprising 3 to 20 volume% of an electronically conductive material relative to 100 volume% of the above region.

14. In paragraph 1, An all-solid-state secondary battery wherein the thickness of the above region is 10% to 60% of the total thickness of the solid electrolyte layer.

15. In paragraph 1, The solid electrolyte layer includes a first solid electrolyte layer in contact with the cathode and a second solid electrolyte layer in contact with the anode, The first solid electrolyte layer comprises first solid electrolyte particles and an electronically conductive material, An all-solid-state secondary battery, wherein the second solid electrolyte layer comprises second solid electrolyte particles.

16. In paragraph 15, An all-solid-state secondary battery wherein the average particle diameter (D50) of the first solid electrolyte particles is larger than the average particle diameter (D50) of the second solid electrolyte particles.

17. In paragraph 15, An all-solid-state secondary battery wherein the average particle diameter (D50) of the second solid electrolyte particles is larger than the average particle diameter (D50) of the first solid electrolyte particles.

18. In paragraph 15, The thickness of the first solid electrolyte layer is 10 ㎛ to 200 ㎛, An all-solid-state secondary battery wherein the thickness of the second solid electrolyte layer is 10 ㎛ to 200 ㎛.

19. In paragraph 1, The negative electrode comprises a current collector and a negative electrode coating layer positioned on the current collector and containing a lithium-philic metal, a carbon material, or a combination thereof, An all-solid-state secondary battery comprising a lithium metal layer formed by charging between the above-described current collector and the negative electrode coating layer.

20. In paragraph 1, The above positive electrode includes a current collector and a positive electrode active material layer positioned on the current collector and containing a positive electrode active material, The above-mentioned positive electrode active material is an all-solid-state secondary battery including lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium iron phosphate oxide, or a combination thereof.

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