Positive electrode for all-solid state battery, method for manufacturing same, and all-solid state secondary battery comprising same

Abstract

The present invention relates to a positive electrode for an all-solid-state battery, a method for manufacturing same, and an all-solid-state battery comprising same. The positive electrode for an all-solid-state battery comprises: a positive electrode active material including a lithium transition metal composite oxide and a coating layer positioned on the surface of the oxide and containing a carbon-based material and polyethylene oxide; a positive electrode active material layer including polyethylene oxide, an inorganic solid electrolyte, and a lithium salt; and a current collector supporting the positive electrode active material layer.

Description

Anode for an all-solid-state battery, a method for manufacturing the same, and an all-solid-state secondary battery comprising the same

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

[0002] Recently, with reports of explosion risks in batteries using liquid electrolytes, development of all-solid-state secondary batteries is actively underway.

[0003] The cathode for an all-solid-state secondary battery consists of inorganic materials such as a cathode active material, a solid electrolyte, and a conductive agent. Here, the movement of lithium ions at the contact point between the solid particles of the cathode active material and the solid electrolyte has a major impact on battery performance. However, the volume change of the cathode active material during charge / discharge limits the physical bonding between the material and the solid electrolyte. To overcome this limitation, ongoing research is being conducted to improve the contact between the particles.

[0004] One embodiment provides a cathode for an all-solid-state battery having excellent safety and life characteristics.

[0005] Another embodiment provides a method for manufacturing a positive electrode for the above all-solid-state battery.

[0006] Another embodiment provides an all-solid-state battery comprising the above positive electrode.

[0007] One embodiment provides a positive electrode for an all-solid-state battery, comprising: a lithium transition metal composite oxide; a positive electrode active material positioned on the surface of the oxide and including a coating layer comprising a carbon-based material and polyethylene oxide; a positive electrode active material layer comprising polyethylene oxide; an inorganic solid electrolyte; and a lithium salt; and a current collector supporting the positive electrode active material layer.

[0008] Another embodiment provides a method for manufacturing a positive electrode for an all-solid-state battery, comprising the steps of: dry mixing a lithium transition metal composite oxide coated with a carbon-based material, a polyethylene oxide, an inorganic solid electrolyte, and a lithium salt to prepare a dry mixture; thermocompressing the dry mixture to prepare a positive electrode active material layer; and positioning the positive electrode active material layer on a current collector.

[0009] Another embodiment provides an all-solid-state battery comprising the positive electrode; the negative electrode; and a solid electrolyte layer positioned between the positive electrode and the negative electrode.

[0010] An all-solid-state battery cathode according to one embodiment has excellent structural safety, and thus can provide an all-solid-state battery with excellent safety and lifespan characteristics.

[0011] Figure 1 is a drawing showing the form in which a carbon-based material exists in a positive electrode active material according to one embodiment.

[0012] Figure 2 is a cross-sectional view schematically showing an all-solid-state battery according to one embodiment.

[0013] Figure 3 is a schematic perspective view of a cathode according to an embodiment.

[0014] Fig. 4 is a cross-sectional view taken along line II-II of Fig. 3.

[0015] Figures 5 and 6 are schematic plan views of holes included in a cathode according to one embodiment.

[0016] 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.

[0017] 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.

[0018] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Here, “or” is not interpreted in an exclusive sense, for example, “A or B” is interpreted to include A, B, A+B, etc.

[0023] 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 is another element in between. Conversely, when an element is said to be "directly over" another element, it means that there is no other element in between.

[0024] 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.

[0025] Unless otherwise defined herein, the particle size may be the average particle size. This average particle size refers to the average particle size (D50), which means the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. If the particle size is spherical, the diameter represents the particle diameter or the average particle size, and if the particle size is not spherical, the diameter may be the major axis length or the average major axis length. The average particle size (D50) can be measured by a method 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, a scanning electron microscope, or a field emission scanning electron microscope (FE-SEM). Alternatively, the average particle diameter (D50) can be obtained by measuring using 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, or by measuring using a laser diffraction method. When measuring using a laser diffraction method, more specifically, the particles to be measured are dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle diameter measuring device (e.g., Microtrac MT 3000), and ultrasonic waves of approximately 28 kHz are irradiated 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.

[0026] According to one embodiment, a positive electrode for an all-solid-state battery includes a positive electrode active material layer and a current collector supporting the positive electrode active material layer, wherein the positive electrode active material layer includes a positive electrode active material, polyethylene oxide, an inorganic solid electrolyte, and a lithium salt.

[0027] In addition, the positive electrode active material comprises a lithium transition metal composite oxide; a coating layer located on the surface of the oxide and containing a carbon-based material and polyethylene oxide. In this way, when the positive electrode active material layer contains both polyethylene oxide and an inorganic solid electrolyte, and the positive electrode active material further includes a coating layer containing a carbon-based material and polyethylene oxide on the surface, the interface of the positive electrode can be stabilized during charge and discharge, thereby effectively preventing a reduction in the lithium ion movement path and blockage of the current path.

[0028] In particular, since the positive electrode active material according to one embodiment includes a coating layer including a carbon-based material, it can effectively protect the lithium-transition metal composite oxide and realize a stable electrical conductivity path in the positive electrode manufacturing process, particularly in a solvent-free manufacturing process that does not use a solvent. In the manufacturing process that uses a solvent, the resistance may increase or the lifespan may be deteriorated due to problems such as blockage during lithium inlet / outlet due to damage and denaturation of the surface of the active material. These problems can be minimized by applying a solvent-free process that does not use a solvent. In the solvent-free manufacturing process that does not use a solvent, the conductive material may be unevenly distributed, which may cause a deterioration of the battery performance and damage the lithium-transition metal composite oxide. However, in the positive electrode active material according to one embodiment, the surface of the lithium-transition metal composite oxide is protected by a coating layer including a carbon-based material, so that these problems do not occur.

[0029] In addition, compared to the case where the lithium transition metal composite oxide and the carbon material are simply physically mixed, the lithium transition metal composite oxide can be effectively activated and protected, thereby implementing capacity and reducing resistance to minimize side reactions, thereby ensuring sufficient stability.

[0030] In one embodiment, the coating layer may include a first layer located on the oxide surface and including a carbon-based material and polyethylene oxide, and a second layer including polyethylene oxide located on the first layer. The first layer may have a carbon-based material located in an island shape, and the polyethylene oxide may be located in a space between the carbon-based material. When the coating layer has the above structure, the conductivity of the positive electrode active material can be well maintained, while protecting the lithium transition metal composite oxide more effectively.

[0031] Therefore, the positive electrode active material according to one embodiment can exhibit improved life characteristics.

[0032] In one embodiment, the carbonaceous material may be a linear carbonaceous material, a point-like carbonaceous material, or a combination thereof. The linear carbonaceous material may be a carbon nanotube, a carbon nanofiber, a carbon nanowire, or a combination thereof, and the point-like carbonaceous material may be carbon black. The carbon black may be acetylene black, lamp black, thermal black, channel black, furnace black, or a combination thereof. The point-like carbonaceous material may be in a particle form, and such particle-like carbonaceous material, i.e., carbonaceous material particles, may be connected and positioned on the surface of the lithium transition metal composite oxide.

[0033] The form in which the carbonaceous material is positioned on the surface of the lithium transition metal composite oxide can be a linear carbonaceous material (a), a point-like carbonaceous material (b), or a mixture of a linear carbonaceous material and a point-like carbonaceous material (c), as shown in Fig. 1.

[0034] In one embodiment, the content of the carbon-based material may be 0.05 wt% to 3 wt%, 0.1 wt% to 1.5 wt%, or 0.1 wt% to 0.5 wt%, based on 100 wt% of the total positive electrode active material. When the content of the carbon-based material is within the above range, the carbon-based material can more effectively protect the lithium transition metal composite oxide.

[0035] According to one embodiment, the coating layer of the positive electrode active material includes polyethylene oxide, thereby improving chemical stability. The polyethylene oxide may have a weight average molecular weight (Mw) of 20,000 g / mol to 8,000,000 g / mol, and may have a weight average molecular weight (Mw) of 200,000 g / mol to 500,000 g / mol or 300,000 g / mol to 500,000 g / mol. When the weight average molecular weight (Mw) of the polyethylene oxide is within the above range, it may have the advantages of facilitating a battery manufacturing process and improving battery characteristics.

[0036] The content of polyethylene oxide is important as the total content included in the positive electrode active material layer, and there is no need to separately limit the content of polyethylene oxide included in the coating layer.

[0037] The above coating layer may exist in the form of islands discontinuously positioned on the surface of the lithium transition metal composite oxide, or may exist in the form of a continuous layer.

[0038] The thickness of the coating layer may be 1 nm to 200 nm, for example, 1 nm to 100 nm, 1 nm to 40 nm, 1 nm to 30 nm, 1 nm to 20 nm, 1 nm to 10 nm, or 2 nm to 10 nm. When the thickness of the coating layer is within the above range, the protective effect of the lithium transition metal composite oxide can be further improved while maintaining the lithium movement path and current path well.

[0039] In one embodiment, the lithium transition metal composite oxide may be represented by the following chemical formula 1.

[0040] [Chemical Formula 1]

[0041] Li a1 Ni x1 Co y1 M 1 y2 M 2 z1 O 2-b1 X b1

[0042] In the above chemical formula 1, 0.9≤a1≤1.8, 0.3≤x1<1, 0 <y1<0.7, 0<y2<0.7, 0≤z1≤0.1, x1+y1+y2+z1=1, 및 0≤b1≤0.1이고,

[0043] M 1 is Mn or Al,

[0044] M 2 is at least one element 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, Zn, and Zr, and X is at least one element selected from the group consisting of F, P, and S.

[0045] In another embodiment of the chemical formula 1, 0.8≤x1<1, 0 <y1<0.2, 및 0≤y2<0.2일 수 있고, 또는 0.9≤x1<1, 0<y1<0.1, 및 0<y2<0.1일 수도 있다. 상기 리튬 전이 금속 산화물이 니켈계 화합물, 특히 니켈 함량이 높은 니켈계 화합물(이하 “고니켈계 화합물”이라 칭함)은 고용량을 나타낼 수 있다.

[0046] When a coating layer according to an embodiment is applied to a high-nickel compound that exhibits a relatively large volume change during charging and discharging, it may be more effective.

[0047] In one embodiment, the content of the lithium transition metal composite oxide may be 80 wt% to 95 wt%, or 85 wt% to 95 wt%, based on 100 wt% of the total positive electrode active material. When the content of the lithium transition metal composite oxide is within the above range, a higher capacity may be obtained, and there may be advantages of improved electrochemical characteristics and lifespan.

[0048] The cathode active material according to one embodiment may have a particle shape such as, for example, a spherical, ellipsoidal, near-spherical, polyhedral, or irregular shape.

[0049] In addition, the average particle diameter of the positive electrode active material is not particularly limited and may be within a range applicable to positive electrode active materials of existing all-solid-state secondary batteries. For example, the average particle diameter of the positive electrode active material may be 1 μm to 25 μm, for example, 4 μm to 25 μm, 5 μm to 20 μm, 8 μm to 20 μm, or 10 μm to 18 μm. A positive electrode active material having such a particle diameter range can be harmoniously mixed with other components within the positive electrode active material layer and can realize high capacity and high energy density.

[0050] The above positive electrode active material may be in the form of secondary particles formed by agglomeration of a plurality of primary particles, or may be in the form of a single crystal.

[0051] [anode]

[0052] According to one embodiment, a positive electrode includes a positive electrode active material layer including the positive electrode active material, an inorganic solid electrolyte, and a lithium salt, and includes a current collector supporting the positive electrode active material layer.

[0053] In one embodiment, the positive electrode active material, the inorganic solid electrolyte, and the lithium salt may be physically mixed and present within the positive electrode active material layer, and the polyethylene oxide matrix and the positive electrode active material, the inorganic solid electrolyte, and the lithium salt may be dispersed within the matrix. When the positive electrode active material layer is in a form in which the positive electrode active material, the inorganic solid electrolyte, and the lithium salt are dispersed within the polyethylene oxide matrix, there may be an advantage of improving the electrochemical characteristics and lifespan in a safe all-solid-state battery.

[0054] <Cathode active material>

[0055] In one embodiment, the content of the positive electrode active material may be 80 wt% to 95 wt%, 80 wt% to 85 wt%, or 85 wt% to 90 wt%, based on 100 wt% of the total positive electrode active material layer. When included within the above range, the capacity of the all-solid-state battery can be maximized while further improving the lifespan characteristics.

[0056] Polyethylene oxide

[0057] The polyethylene oxide included in the positive electrode active material layer according to one embodiment may be the same as the polyethylene oxide included in the coating layer of the positive electrode active material. Accordingly, the weight average molecular weight of the polyethylene oxide is as described above.

[0058] The total content of polyethylene oxide included in the positive electrode active material layer may be 1 wt% to 20 wt%, 5 wt% to 15 wt%, or 5 wt% to 10 wt%, based on 100 wt% of the total positive electrode active material layer. When the content of polyethylene oxide is within the above range, the surface of the positive electrode active material can be better protected while ensuring ionic conductivity, thereby improving the long-term lifespan.

[0059] Inorganic solid electrolyte

[0060] The inorganic solid electrolyte included in the positive electrode active material layer according to one embodiment may be a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. When the positive electrode active material layer includes a sulfide-based solid electrolyte or an oxide-based solid electrolyte, a positive electrode active material layer with excellent ionic conductivity and stability can be formed.

[0061] The above sulfide-based solid electrolyte is, 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.

[0062] The above sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0063] 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.

[0064] 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.

[0065] Of course, a commercially available solid electrolyte can be used as the sulfide-based solid electrolyte.

[0066] For example, the sulfide-based solid electrolyte may include an argyrodite-type sulfide. The argyrodite-type sulfide may be, for example, Li a M 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. As a specific example, 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 Cl1.25 , (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.

[0067] 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 the positive electrode active material layer and the solid electrolyte layer. An all-solid-state secondary battery including the same can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0068] The above oxide-based solid electrolyte is, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li1+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= Ta, Te, Nb, Zr, or a combination thereof; x is an integer from 1 to 10), or a mixture thereof. In one embodiment, the oxide-based solid electrolyte may be a garnet-based ceramic, which is a garnet-based oxide-based solid electrolyte.

[0069] The average particle diameter (D50) of the above-mentioned inorganic solid electrolyte particles may be, for example, 0.1 ㎛ to 5.0 ㎛, and may be small particles of 0.1 ㎛ to 1.9 ㎛, or large particles of 2.0 ㎛ to 5.0 ㎛. For example, the average particle diameter (D50) of the inorganic solid electrolyte included in the positive electrode may be about 0.1 ㎛ to 1.9 ㎛, which may be smaller than the average particle diameter of the solid electrolyte included in the solid electrolyte layer. A solid electrolyte satisfying the above-mentioned average particle diameter range can effectively penetrate between positive electrode active materials, and has excellent contact with the positive electrode active material and excellent connectivity between solid electrolyte particles. Here, the average particle diameter may be measured by an electron microscope image, and for example, the 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 the D50 may be calculated from this.

[0070] With respect to the total weight of the positive electrode active material layer, the inorganic solid electrolyte may be included in an amount of 3 wt% to 15 wt%, for example, 5 wt% to 10 wt%, 7 wt% to 9 wt%, or 10 wt% to 12 wt%. When the content of the inorganic solid electrolyte is within the above range, a more stable positive electrode active material layer can be realized while further improving ionic conductivity.

[0071] Lithium salt

[0072] In the positive electrode active material layer, lithium salt plays a role in providing ionic conductivity.

[0073] The lithium salt may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0074] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0075] The content of the lithium salt may be 0.1 wt% to 7 wt%, 0.3 wt% to 1 wt%, or 0.5 wt% to 2 wt%, based on 100 wt% of the total weight of the positive electrode active material layer. When the content of the lithium salt is within the above range, ionic conductivity can be more sufficiently provided.

[0076] Challenge

[0077] The positive electrode active material layer according to one embodiment may further include a conductive material.

[0078] 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 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, carbon nanotube, etc.; metal-based materials containing copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0079] The content of the conductive material in the positive electrode active material layer may be 0.1 wt% to 5 wt% based on the total weight of the positive electrode active material layer.

[0080] Binder

[0081] The positive electrode active material layer according to one embodiment may further include a binder. The binder may be, for example, a polymer including polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, ethylene oxide, polyvinyl pyrrolidone, polyurethane, polyethylene, polypropylene, polyalkyl (meth)acrylate, styrene-butadiene rubber, acrylated styrene-butadiene rubber, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, acrylic rubber, natural rubber, epoxy resin, nylon, etc.

[0082] The content of the binder in the positive electrode active material layer may be approximately 0.1 wt% to 5 wt% based on the total weight of the positive electrode active material layer.

[0083] Current collector

[0084] The current collector may include, 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.

[0085] [Method of manufacturing anode]

[0086] According to one embodiment, a cathode can be manufactured by a process of dry mixing a lithium transition metal composite oxide coated with a carbon-based material, a polyethylene oxide, an inorganic solid electrolyte, and a lithium salt to produce a dry mixture; and thermally pressing the dry mixture onto a current collector. Each process is described in detail below.

[0087] First, a dry mixture is prepared by dry mixing a lithium transition metal composite oxide coated with a carbon-based material, polyethylene oxide, an inorganic solid electrolyte, and a lithium salt. This solvent-free dry mixing process allows for the uniform formation of a positive electrode active material layer, improving cycle life and safety. Furthermore, the absence of a solvent makes the process economical.

[0088] In particular, when a high-nickel compound with an uneven surface and thus somewhat low safety is used as a lithium transition metal composite oxide, a dry mixing process is performed, so that the effect of uniformly forming a positive electrode active material layer can be further increased.

[0089] The above polyethylene oxide can improve the ionic conductivity of the anode and is a polymer with a relatively low melting point of 50 to 70°C, so it can be usefully used in a dry mixing process.

[0090] The above dry mixing process can be carried out at a temperature of 50°C to 210°C, 70°C to 150°C, or 90°C to 150°C. When the dry mixing process is carried out in the above temperature range, mixing can be carried out more uniformly.

[0091] In the above mixing process, the mixing ratio of the lithium transition metal composite oxide coated with a carbon-based material, polyethylene oxide, inorganic solid electrolyte, and lithium salt can be appropriately adjusted so that the content in the final positive electrode is obtained as described above.

[0092] The lithium transition metal composite oxide coated with the carbonaceous material can be prepared by a dry or wet method. The dry method can be performed by chemical vapor deposition (CVD), plasma enhanced vapor deposition (PVD), or a dry mixing method in which the lithium transition metal composite oxide and the carbonaceous material are mixed without a solvent. The dry mixing can also be performed by high shear mixing. The wet method can be performed by mixing the lithium transition metal composite oxide and the carbonaceous material in a solvent, or by spraying a carbonaceous material liquid onto the lithium transition metal composite oxide. The solvent in the solvent or the carbonaceous material liquid can be ultrapure water, N-methylpyrrolidone, ethanol, methyl ethyl ketone, toluene, or a combination thereof.

[0093] The above carbon-based material may be positioned in an island shape on the surface of the lithium transition metal composite oxide. Since the carbon-based material is positioned in an island shape, a space may be formed between the carbon-based materials.

[0094] The carbon-based material, the lithium transition metal composite oxide, the polyethylene oxide, the inorganic solid electrolyte, and the lithium salt are as described above.

[0095] Next, the dry mixture is thermo-compressed to form a positive electrode active material layer.

[0096] By performing the above-described thermocompression process, a portion of the polyethylene oxide may melt and be positioned on the surface of the lithium transition metal composite oxide, thereby forming a coating layer together with the carbon-based material. For example, a portion of the polyethylene oxide may melt and be positioned within the spaces between the carbon-based materials. Additionally, the remaining polyethylene oxide that is not positioned within the spaces may be positioned over the entire surface. Accordingly, a first coating layer including the carbon-based material and the polyethylene oxide, and a second coating layer including the polyethylene oxide positioned on the first layer may be formed.

[0097] The above thermocompression process can be performed at 80°C to 210°C, or at 80°C to 150°C or 90°C to 150°C. When the above thermocompression process is performed in the above temperature range, a coating layer of a carbon-based material and polyethylene oxide can be well formed on the surface of the lithium transition metal composite oxide, and a more uniform positive electrode active material layer can be formed.

[0098] [All-solid-state secondary battery]

[0099] In one embodiment, an all-solid-state secondary battery is provided, which includes the aforementioned positive and negative electrodes and a solid electrolyte layer positioned between the positive and negative electrodes. The all-solid-state secondary battery may be expressed as an all-solid-state battery, an all-solid-state lithium secondary battery, or the like.

[0100] Fig. 2 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Referring to Fig. 2, the all-solid-state secondary battery (1) may have a structure in which an electrode assembly including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode current collector (201) is laminated and stored in a case such as a pouch. The all-solid-state secondary battery (1) 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. 2 illustrates one electrode assembly including the negative electrode (400), the solid electrolyte layer (300), and the positive electrode (200), an all-solid-state secondary battery may be manufactured by laminating two or more electrode assemblies.

[0101] <Cathode>

[0102] According to one embodiment, a cathode may include a current collector and a cathode layer positioned on one surface of the current collector.

[0103] The above negative electrode layer may be a negative electrode active material layer or a negative electrode coating layer. Alternatively, the above negative electrode layer may be a lithium metal layer.

[0104] The above negative electrode active material layer includes a negative electrode active material and may further include a binder, a conductive material, and / or a solid electrolyte.

[0105] The above negative active material may include 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.

[0106] 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.

[0107] As the above lithium metal alloy, an alloy of lithium and one or more metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0108] 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 합금(상기 Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소, 또는 이들의 조합에서 선택되는 원소이며, Si은 아님), 상기 Sn계 음극 활물질로는 Sn, SnO2, Sn-R 합금(상기 R은 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소, 또는 이들의 조합에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Q 및 R로는Mg, 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, 또는 이들의 조합에서 선택되는 것을 사용할 수 있다.

[0109] The above silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle diameter (D) of the silicon-carbon composite particles 50 ) may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon may also be located between the silicon primary particles, so that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0110] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles, and an amorphous carbon coating layer positioned on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon may include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0111] When the above silicon-carbon composite includes silicon and amorphous carbon, the content of silicon may be 10 wt% to 50 wt%, and the content of amorphous carbon may be 50 wt% to 90 wt%, based on 100 wt% of the silicon-carbon composite. In addition, when the composite includes silicon, amorphous carbon, and crystalline carbon, the content of silicon may be 10 wt% to 50 wt%, the content of crystalline carbon may be 10 wt% to 70 wt%, and the content of amorphous carbon may be 20 wt% to 40 wt%, based on 100 wt% of the silicon-carbon composite.

[0112] In addition, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle diameter (D) of the silicon particles (primary particles) 50 ) may be 10 nm to 1 ㎛, 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. 이때, 산화 정도를 나타내는 Si:O의 원자 함량 비율은 99:1 내지 33:67일 수 있다. 본 명세서에서, 별도의 정의가 없는 한, 평균 입경(D 50 ) means the diameter of the particle whose cumulative volume is 50% by volume in the particle size distribution.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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 include a non-aqueous binder, an aqueous binder, or a combination thereof.

[0117] The non-aqueous binder may include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene oxide, ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0118] The above-mentioned aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0119] A cellulose-based compound may be used as the negative electrode binder, or a cellulose-based compound may be used together with the aqueous binder. The cellulose-based compound may include carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, an alkali metal salt thereof, or a combination thereof. The alkali metal may be Na, K, or Li. The cellulose-based compound may function as a thickener capable of imparting viscosity, or may function as a binder. Accordingly, the content of the cellulose-based compound may be appropriately adjusted within the binder content, but may be, for example, 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0120] The conductive material is used to provide conductivity to the electrode, and may include, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, 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.

[0121] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0122] When the above-mentioned negative electrode layer is a negative electrode coating layer, it means that the negative electrode is a precipitation-type negative electrode. The precipitation-type negative electrode means a negative electrode that does not contain a negative electrode active material when the battery is assembled, but in which lithium metal or the like is precipitated when the battery is charged, and this acts as a negative electrode active material. In more detail, when the all-solid-state battery is charged, lithium ions are released from the positive electrode active material, pass through the solid electrolyte, and move toward the negative electrode, and are deposited on the negative electrode current collector, and as a result, a lithium-containing layer, for example, a lithium precipitation layer, can be formed on the current collector. A negative electrode having such a lithium-containing layer is called a precipitation-type negative electrode.

[0123] That is, a lithium-containing layer can be formed between the negative electrode current collector and the negative electrode layer.

[0124] The above charging process may be a chemical reaction process performed once to three times at 0.05C to 1C at about 25°C to 50°C.

[0125] The thickness of the lithium-containing layer may be 10 μm to 50 μm. For example, the thickness of the lithium-containing layer may be 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more, or 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. When the thickness of the lithium-containing layer is within the above range, there may be an advantage in that lithium may be reversibly precipitated during charge / discharge, thereby further improving the lifespan.

[0126] The cathode coating layer may include a metal, a carbon-based material, or a combination thereof that acts as a catalyst. For example, the cathode coating layer may include a metal supported on a carbon-based material, or a mixture of a metal and a carbon-based material. In one embodiment, the cathode coating layer may include a metal and a carbon-based material.

[0127] The carbonaceous material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof, or may be amorphous carbon. 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, acetylene black, Denka black, Ketjen black, furnace black, activated carbon, graphene, or a combination thereof. An example of the carbon black is Super P (Timcal). The amorphous carbon is not limited thereto, and any material classified as amorphous carbon in the relevant field may be used.

[0128] The above amorphous carbon may be a single particle, may have the form of a secondary particle formed by agglomeration of multiple primary particles, or may be a combination thereof.

[0129] The particle size of the above single particle may be 10 nm to 60 mm. In addition, the particle size of the above primary particle may be 20 nm to 100 nm, and the particle size of the above secondary particle may be 1 μm to 20 μm.

[0130] In one embodiment, the particle size of the primary particles may be 20 nm to 100 nm, 20 nm to 90 nm, 20 nm to 80 nm, or 30 nm to 70 nm.

[0131] In one embodiment, the particle size of the secondary particles may be 1 μm to 20 μm, 2 μm to 15 μm, or 3 μm to 10 μm.

[0132] The shape of the primary particles may be spherical, elliptical, plate-shaped, or a combination thereof, and in one embodiment, the shape of the primary particles may be spherical, elliptical, or a combination thereof.

[0133] The metal may be any one selected from Ag, Zn, Al, Sn, Mg, Ge, Cu, In, Ni, Bi, Au, Si, Pt, Pd or a combination thereof, and in one embodiment may be Ag. When the cathode coating layer includes the metal, the electrical conductivity of the cathode may be improved.

[0134] The metal may be a metal particle, and the metal particle may have a size of 5 nm to 800 nm. The size of the metal nanoparticles may be, for example, an average size of 5 nm to 800 nm, 5 nm to 700 nm, 5 nm to 500 nm, or 5 nm to 300 nm, but is not limited thereto, and any particle having a nanometer size may be appropriately used. When the size of the metal particle is within the above range, the battery characteristics (e.g., life characteristics) of the all-solid-state battery can be improved.

[0135] When the cathode coating layer includes a carbon-based material and metal particles, the mixing ratio of the carbon-based material and the metal particles may be a weight ratio of 1:1 to 99:1. For example, the weight ratio of the carbon-based material and the metal particles may be 1:1 to 5:1, 1:1 to 10:1, 1:1 to 20:1, 1:1 to 30:1, 1:1 to 40:1, 1:1 to 50:1, 1:1 to 60:1, 1:1 to 70:1, 1:1 to 80:1, or 1:1 to 90:1. When the carbon-based material and the metal particles are included in the weight ratio, the electrical conductivity of the cathode may be further improved.

[0136] Additionally, the cathode coating layer may further include a binder, a conductive material, and / or a solid electrolyte.

[0137] The above binder and the above conductive material are the same as those described in the negative electrode active material layer.

[0138] The above solid electrolyte may be a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte and the oxide-based solid electrolyte are as described above for the positive electrode. The solid electrolyte included in the negative electrode may be the same as or different from the solid electrolyte included in the positive electrode.

[0139] The above-described cathode 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 layer.

[0140] The thickness of the above cathode coating layer may be 1 µm to 15 µm, or may be 5 µm to 10 µm.

[0141] 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 current collector may be 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0142] In one embodiment, the negative electrode may be a non-cathode composed only of a current collector, for example, without including a negative electrode coating layer or a negative electrode active material layer. 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.

[0143] According to another embodiment, the cathode may be a patterned cathode including a metal substrate having a plurality of holes; a protective layer formed on the metal substrate and having through holes exposing the holes; and an electrolyte membrane including a liquid electrolyte layer positioned within the holes and a solid electrolyte layer covering the protective layer and the through holes.

[0144] Fig. 3 is a perspective view of a patterned cathode according to another embodiment and a cross-sectional view taken along line II-II of Fig. 4. It includes a metal substrate (10), a protective layer (12) formed on the metal substrate (10), a plurality of holes (14) formed in the protective layer (12) and the metal substrate (10), and an electrolyte layer (100) covering the plurality of holes (14).

[0145] The above metal substrate (10) may be a current collector of the negative electrode.

[0146] The above hole (14) is formed in the protective layer (12) and the metal substrate (10), and the plane shape may be circular, but is not limited thereto, and may be formed in a polygonal shape, as in FIG. 5. In addition, the hole (14) may be formed as one in a required size, but may be divided into multiple parts, as in FIG. 6, to include multiple small holes (15).

[0147] The size of the hole (14) can be determined according to the volume of the reaction product formed by the reaction of lithium in the metal substrate and the electrolyte layer.

[0148] The width (or diameter) (D) of the hole (14) may be 0.5 μm to 2000 μm, and may be formed with an area of ​​10% to 90% of the area of ​​the metal substrate (10). When the area occupied by the hole (14) is within the above range, an excellent capacity can be obtained, volume expansion can be suppressed more effectively, and a negative electrode with excellent structural safety can be obtained.

[0149] The depth of the hole (14) can be formed to be more than half the thickness of the metal substrate (14), and is not formed by penetrating the metal substrate (10).

[0150] The protective layer may include a chemically stable material that is difficult for lithium to penetrate. The protective layer may be, for example, polyimide, polypropylene, polyethylene, polyethylene terephthalate, polyvinylidene fluoride, polyphenylpropanolamine, or a combination thereof. The thickness of the protective layer may be 0.2 μm to 100 μm, 1 μm to 80 μm, or 2 μm to 50 μm.

[0151] The above protective layer (12) may be formed with a through hole (16) that is connected to the hole (14), and after forming the protective layer (12), a hole (14) is formed in the protective layer (12) and the metal substrate (10), so that the planar shapes of the through hole (16) and the hole (14) may have the same shape.

[0152] The above electrolyte membrane (100) may include a liquid electrolyte layer (103) filling the hole (14) and a solid electrolyte layer (101) formed on the entire surface of the protective layer (12) covering the hole (14).

[0153] The above liquid electrolyte layer may include a liquid electrolyte containing a non-aqueous organic solvent and a lithium salt. Since the pores are filled with this liquid electrolyte layer, the reaction product between the lithium contained in the electrolyte and the metal substrate generated during charge and discharge is located within the pores, thereby preventing cracks from occurring due to volume expansion of the reaction product and enabling charge and discharge to occur uniformly.

[0154] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0155] The above non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0156] Examples of the carbonate solvent that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of the ester solvent that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. In addition, examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol, and examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0157] The above non-aqueous organic solvents can be used alone or in combination of two or more, and when two or more are used in combination, the mixing ratio can be appropriately adjusted depending on the desired battery performance, which can be widely understood by those working in the relevant field.

[0158] In addition, when using a carbonate solvent, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0159] The above non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent. For example, a carbonate-based solvent and an aromatic hydrocarbon-based organic solvent may be mixed and used in a volume ratio of 1:1 to 30:1.

[0160] The above electrolyte may further include a vinylethyl carbonate, vinylene carbonate or ethylene carbonate compound to improve battery life.

[0161] Representative examples of the above ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0162] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), lithium bis(oxalato)borate (LiBOB).

[0163] It is recommended that the concentration of lithium salt be within the range of 0.1 M to 2.0 M. When the concentration of lithium salt is within the above range, the electrolyte can exhibit excellent performance due to its appropriate ionic conductivity and viscosity, and lithium ions can move effectively.

[0164] The solid electrolyte layer (103) may be positioned to cover the protective layer (12) and the through hole (14). The thickness of the solid electrolyte layer may be 1 µm to 200 µm, and may also be 2 µm to 100 µm or 5 µm to 50 µm.

[0165] <Solid electrolyte layer>

[0166] The above solid electrolyte layer may include a solid electrolyte. The solid electrolyte 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. In one embodiment, the solid electrolyte may be a sulfide-based solid electrolyte.

[0167] The above sulfide-based solid electrolyte and the above oxide-based solid electrolyte are as described above, and may be the same as or different from the solid electrolyte included in the positive electrode.

[0168] The above halide-based solid electrolyte may include a Li element, an M element (M is a metal other than Li), and an X element (X is a halogen). As X, for example, F, Cl, Br, and I may be mentioned. In particular, in the halide-based solid electrolyte, at least one of Br and Cl is suitable as X. In addition, as the M, for example, a metal element such as Sc, Y, B, Al, Ga, or In may be mentioned.

[0169] The composition of the above halide-based solid electrolyte is not particularly limited, but Li 6-3a M a Br b Cl c (In the formula, M is a metal other than Li, and 0 <a<2, 0≤b≤6, 0≤c≤6, b+c=6)로 표현될 수 있다. 이때, 상기 a는 0.75 이상일 수 있고, 1 이상일 수 있고, a는, 1.5 이하일 수 있다. 상기 b는 1 이상일 수 있고, 2 이상일 수 있다. 또한, 상기 c는, 3 이상일 수 있고, 4 이상일 수도 있다. 상기 할라이드계 고체 전해질의 구체적인 예로는 Li3YBr6, Li3YCl6또는 Li3YBr2Cl4를 들 수 있다.

[0170] 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(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.

[0171] Meanwhile, the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer may be larger than the average particle diameter (D50) of the solid electrolyte included in the positive electrode. In this case, the energy density of the all-solid-state secondary battery can be maximized while increasing the mobility of lithium ions, thereby improving the overall performance. For example, the average particle diameter (D50) of the solid electrolyte included in the positive electrode can be 0.1 ㎛ to 1.9 ㎛, or 0.1 ㎛ to 1.0 ㎛, and the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300) can be 2.0 ㎛ to 5.0 ㎛, or 2.0 ㎛ to 4.0 ㎛, or 2.5 ㎛ to 3.5 ㎛. When these particle diameter ranges are satisfied, the energy density of the all-solid-state secondary battery can be maximized while facilitating the transport of lithium ions, thereby suppressing resistance, and thus improving the overall performance of the all-solid-state secondary battery. Here, the average particle diameter (D50) of the solid electrolyte may be measured using a particle size analyzer using laser diffraction.

[0172] The above solid electrolyte layer may further include a binder. At this time, the binder may be, but is not limited to, styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, and any binder used in the relevant technical field may be used. The acrylate polymer may be butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0173] 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 for the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. The solid electrolyte layer formation process is widely known in the art, so a detailed description thereof will be omitted.

[0174] The thickness of the solid electrolyte layer may be, for example, 10 μm to 150 μm.

[0175] The solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0176] The 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 mobility of lithium ions in the solid electrolyte layer.

[0177] The lithium salt may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0178] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] (Example 1)

[0187] 1. Manufacturing of positive electrode active material

[0188] LiNi 0.944 Co0.04 Al 0.012 Mn 0.004 LiNi coated with carbon nanotubes was prepared by mixing O2 and carbon nanotubes at a weight ratio of 99.7:0.3 using a high shear mixing method. 0.944 Co 0.04 Al 0.012 Mn 0.004 O2 was manufactured.

[0189] The above product, polyethylene oxide (weight average molecular weight: 300,000 g / mol), sulfide-based solid electrolyte particles (Li6PS5Cl, D50=0.85㎛), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dry mixed at a weight ratio of 92:5:2.5:0.5. This dry mixing was performed at 100°C.

[0190] The obtained dry product was thermo-compressed at 140°C to form a positive electrode active material layer. LiNi, on which a coating layer including carbon nanotubes and polyethylene oxide was formed, was formed on the positive electrode active material layer. 0.944 Co 0.04 Al 0.012 Mn 0.004 An O2 cathode active material was manufactured. The thickness of the coating layer was 10 nm.

[0191] The above positive electrode active material layer was placed on a stainless steel current collector and rolled to manufacture a positive electrode.

[0192] 3. Manufacturing of the cathode

[0193] An aluminum foil current collector was used as the cathode.

[0194] 4. Preparation of solid electrolyte layer

[0195] An argyrodite-type sulfide-based solid electrolyte (Li6PS5Cl, D50=3㎛) was added to a binder solution prepared by dissolving an acrylic binder (SX-A334, Zeon) in an isobutyl isobutyrate (IBIB) solvent, stirring in a sinky mixer to adjust the viscosity to an appropriate level, adding 2 mm zirconia balls, and stirring again in the sinky mixer to prepare a slurry. In the prepared slurry, the content of the solid electrolyte was 98.5 wt%, and the content of the binder was 1.5 wt%.

[0196] The above slurry was applied onto a polyethylene film using a bar coater and dried at room temperature (25°C), and then the polyethylene film was removed to prepare a solid electrolyte layer.

[0197] 5. Manufacturing of all-solid-state secondary batteries

[0198] After stacking the positive electrode, solid electrolyte layer, and negative electrode in that order, they were sealed in a pouch shape and subjected to hydrostatic pressing at a high temperature of 80°C and 500 MPa for 30 minutes to manufacture an all-solid-state battery.

[0199] (Comparative Example 1)

[0200] LiNi 0.944 Co 0.04 Al 0.012 Mn 0.004 O 2, Polyethylene oxide (weight average molecular weight: 300,000 g / mol), sulfide-based solid electrolyte particles (Li6PS5Cl, D50=0.85㎛), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dry mixed at a weight ratio of 92:5:2.5:0.5. This dry mixing was performed at 100°C.

[0201] A positive electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the obtained dry product was used.

[0202] Evaluation Example: Life Characteristics Evaluation

[0203] For the batteries manufactured in Example 1 and Comparative Example 1, the batteries were charged at a constant current of 0.1 C at 45°C to an upper limit voltage of 4.25 V, charged at a constant voltage of 0.05 C, and then discharged at 0.1 C to an end-of-discharge voltage of 2.5 V to perform initial charge-discharge. Thereafter, cycles of charging at 0.33 C and discharging at 0.33 C in a voltage range of 2.5 V to 4.25 V at 45°C were repeated 100 times to evaluate the life characteristics.

[0204] As a result, the capacity retention rate of Example 1 was found to be superior to that of Comparative Example 1.

[0205] 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.

Claims

1. A lithium transition metal composite oxide; a cathode active material located on the surface of the oxide and including a coating layer including a carbon-based material and polyethylene oxide; a cathode active material layer including polyethylene oxide; an inorganic solid electrolyte; and a lithium salt; and A current collector supporting the above-mentioned positive electrode active material layer A cathode for an all-solid-state battery comprising:

2. In paragraph 1, The above carbon-based material is a positive electrode for an all-solid-state battery, which is a linear carbon-based material, a point-shaped carbon-based material, or a combination thereof.

3. In paragraph 2, The above linear carbon material is a positive electrode for an all-solid-state battery, which is a carbon nanotube, a carbon nanofiber, a carbon nanowire or a combination thereof.

4. In paragraph 2, The above dot-shaped carbon material is a positive electrode for an all-solid-state battery made of carbon black.

5. In paragraph 1, The above lithium transition metal composite oxide is a positive electrode for an all-solid-state battery represented by the following chemical formula 1. [Chemical Formula 1] Li a1 Ni x1 Co y1 M 1 y2 M 2 z1 O 2-b1 X b1 (In the above chemical formula 1, 0.9≤a1≤1.8, 0.3≤x1<1, 0 <y1<0.7, 0<y2<0.7, 0≤z1≤0.1, x1+y1+y2+z1=1, 및 0≤b1≤0.1이고, M 1 is Mn or Al, M 2 is 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, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

6. In paragraph 5, In the above chemical formula 1, 0.8≤x1<1, 0 <y1<0.2, 및 0≤y2<0.2인 전고체 전지용 양극.

7. In paragraph 5, In the above chemical formula 1, 0.9≤x1<1, 0 <y1<0.1, 및 0<y2<0.1인 전고체 전지용 양극.

8. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the weight average molecular weight (Mw) of the polyethylene oxide is 20,000 g / mol to 8,000,000 g / mol.

9. In paragraph 1, The above inorganic solid electrolyte is a positive electrode for an all-solid-state battery, which is a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

10. In paragraph 1, The above inorganic solid electrolyte is an all-solid-state battery positive electrode, which is an argyrodite-type sulfide-based solid electrolyte, a garnet-type oxide-based solid electrolyte, or a combination thereof.

11. In paragraph 1, An all-solid-state battery positive electrode having a content of the above-mentioned inorganic solid electrolyte of 3 wt% to 15 wt% based on 100 wt% of the total positive electrode active material layer.

12. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the content of the lithium salt is 0.1 wt% to 7 wt% based on 100 wt% of the total positive electrode active material layer.

13. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the content of the positive electrode active material is 80 to 95 wt% based on 100 wt% of the total positive electrode active material layer.

14. In paragraph 1, The positive electrode active material layer is an all-solid-state battery positive electrode in which the positive electrode active material, the inorganic solid electrolyte, and the lithium salt are dispersed in the polyethylene oxide matrix and the matrix.

15. A dry mixture is prepared by dry mixing a lithium transition metal composite oxide coated with a carbon-based material, polyethylene oxide, an inorganic solid electrolyte, and a lithium salt; The above dry mixture is thermo-compressed to produce a positive electrode active material layer, The above positive electrode active material layer is positioned on the current collector. A method for manufacturing a positive electrode for an all-solid-state battery including a process.

16. In paragraph 15, A method for manufacturing a positive electrode for an all-solid-state battery, wherein the above dry mixing process is performed at 50°C to 210°C.

17. In paragraph 15, A method for manufacturing a positive electrode for an all-solid-state battery, wherein the above-mentioned thermal compression process is performed at a temperature of 80°C to 210°C.

18. An anode according to any one of paragraphs 1 to 14; cathode; and A solid electrolyte layer positioned between the anode and cathode An all-solid-state battery comprising:

19. In paragraph 18, An all-solid-state battery wherein the solid electrolyte layer includes a sulfide-based solid electrolyte.

20. In paragraph 18, An all-solid-state battery wherein the above cathode is composed of a cathode current collector.

21. In paragraph 18, An all-solid-state battery comprising: a metal substrate having a plurality of holes; a protective layer formed on the metal substrate and having through holes exposing the holes; and an electrolyte membrane including a liquid electrolyte layer positioned within the holes and a solid electrolyte layer covering the protective layer and the through holes.

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