Electrode Assembly and Secondary Battery Comprising the Same

Abstract

The present invention relates to an electrode assembly comprising an anode including an anode active material layer, a cathode including a cathode coating layer, and a solid electrolyte layer formed between the cathode and the anode, wherein the ratio of the area of ​​the cathode coating layer to the area of ​​the anode active material layer is 1.25 or more.

Description

Technology Field

[0001] The present invention relates to an electrode assembly comprising a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode coating layer, and a solid electrolyte layer formed between the negative electrode and the positive electrode, wherein the ratio of the area of ​​the negative electrode coating layer to the area of ​​the positive electrode active material layer is controlled to a specific range, and a secondary battery including the same. Background Technology

[0002] With the increasing technological development and demand for electronic devices, society's overall dependence on electrical energy is growing, leading to a rapid increase in the demand for secondary batteries capable of efficiently storing and utilizing electrical energy. Accordingly, there is a need for the technological development of secondary batteries with improved safety and lifespan characteristics.

[0003] Conventional secondary batteries generally use liquid electrolytes, as described in Korean Registered Patent No. 10-2176091; however, as safety issues such as short circuits arise due to repeated charging and discharging, secondary battery technologies utilizing solid electrolytes, such as all-solid-state batteries, are currently being developed.

[0004] However, for the commercialization of secondary batteries using solid electrolytes, it is necessary to secure lifespan performance comparable to that of conventional secondary batteries. To this end, efforts are being made to develop material technologies and improve moisture management within production lines, but there are limitations to the improvement in lifespan performance achieved through these measures.

[0005] Accordingly, there is a need to develop technologies to improve the lifespan characteristics of all-solid-state batteries using methods other than those mentioned above. Prior art literature

[0006] Korean Registered Patent No. 10-2176091 The problem to be solved

[0007] In order to solve the above-mentioned problem, the present invention aims to improve the lifespan characteristics of a secondary battery by adjusting the area ratio of the positive active material layer and the negative coating layer of the secondary battery to which a solid electrolyte is applied. means of solving the problem

[0008] The present invention may relate to an electrode assembly comprising an anode including an anode active material layer, a cathode including a cathode coating layer, and a solid electrolyte layer formed between the cathode and the anode, wherein the ratio of the area of ​​the cathode coating layer to the area of ​​the anode active material layer is 1.25 or more.

[0009] In one embodiment, the anode may comprise an anode current collector; and an anode active material layer formed on the anode current collector and facing the solid electrolyte layer.

[0010] In one embodiment, the cathode may comprise a cathode current collector; and a cathode coating layer formed between the cathode current collector and the solid electrolyte layer.

[0011] In one embodiment, the cathode coating layer may include one or more selected from a cathode active material layer and a non-cathode coating layer.

[0012] In one embodiment, the non-cathode coating layer may include one or more selected from silver (Ag), gold (Au), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), carbon (C), cobalt (Co), indium (In), manganese (Mn), titanium (Ti), aluminum (Al), copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), manganese monoxide (MnO), silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (Al2O3), zinc peroxide (ZnO2), indium oxide (In2O3), titanium sulfide (TiS2), iron sulfide (FeS), and lithium fluoride (LiF).

[0013] As one embodiment, the non-cathode coating layer may include a carbon material.

[0014] In one embodiment, the cathode may include a lithium affinity layer between the cathode current collector and the cathode coating layer.

[0015] In one embodiment, the lithium affinity layer may include one or more selected from silver (Ag), gold (Au), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), carbon (C), cobalt (Co), indium (In), manganese (Mn), titanium (Ti), aluminum (Al), copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), manganese monoxide (MnO), silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (Al2O3), zinc peroxide (ZnO2), indium oxide (In2O3), titanium sulfide (TiS2), iron sulfide (FeS), and lithium fluoride (LiF).

[0016] In one embodiment, the thickness of the lithium affinity layer may be characterized as being 10 nm to 500 nm based on the thickness of the negative electrode current collector of 1 μm to 30 μm.

[0017] In one embodiment, the thickness of the positive active material layer may be 30 μm to 400 μm, and the thickness of the negative coating layer may be 1 μm to 100 μm.

[0018] In one embodiment, the area of ​​the solid electrolyte layer may be equal to or larger than the area of ​​the cathode coating layer.

[0019] In one embodiment, the solid electrolyte layer may comprise a sulfide-based solid electrolyte.

[0020] The present invention may relate to a secondary battery comprising the electrode assembly.

[0021] The present invention may relate to an electronic device including the secondary battery. Effects of the invention

[0022] The electrode assembly to which the solid electrolyte of the present invention is applied and the secondary battery including the same achieve a significantly improved capacity retention rate in charge-discharge cycles by adjusting the area ratio of the negative electrode coating layer to the positive electrode active material layer, thereby enabling the improvement of the lifespan characteristics of the secondary battery. Brief explanation of the drawing

[0023] Figure 1 shows the results of measuring the capacity retention rate according to charge-discharge cycles for each all-solid-state battery prepared in the example and comparative example according to Experimental Example 1. Specific details for implementing the invention

[0024] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0025] Therefore, the configurations of the embodiments described in this specification are merely one of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; thus, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application. In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0026] In this specification, when a part is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Thus, for example, a composition comprising compound A may include compounds other than A. However, the term “comprising” also encompasses, in a more restrictive sense as a specific embodiment thereof, “essentially / essentially composed of” and “composed of,” so, for example, a “composition comprising compound A” may also be (essentially / essentially) composed of compound A.

[0027] In connection with this, terms such as “comprising” or “having,” as described in this specification, are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0028] In this specification, when any layer is described as being located “on” or “between” another arbitrary layer, this includes not only cases where any layer is in contact with another arbitrary layer, but also cases where another layer or material, etc., exists between the two layers.

[0029] Where in this specification a quantity, concentration, or other value or parameter is given as an enumeration of a range, a preferred range, a preferred upper limit, and a preferred lower limit, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the range is disclosed separately, specifically discloses all ranges that may be formed. Where a range of numerical values ​​is mentioned in this specification, unless otherwise stated, for example, without limiting terms such as greater than or less than, the range is intended to include its endpoint value and all integers and fractions within that range. The scope of the invention is not intended to be limited to the specific value mentioned when defining the range.

[0030] Among the physical properties mentioned in this specification, if the measured temperature affects the property, the property is measured at room temperature unless specifically otherwise specified. The term "room temperature" refers to a natural temperature that has not been heated or cooled, and may mean, for example, any temperature within the range of about 10°C to 30°C, about 23°C, or about 25°C. Furthermore, unless specifically otherwise specified, the unit of temperature in this specification is °C.

[0031] In addition, among the physical properties mentioned in this specification, if the measured pressure affects the physical property, unless otherwise specifically defined, the physical property is measured at atmospheric pressure, that is, at about 1 atmosphere.

[0032] One aspect of the present invention provides an electrode assembly comprising a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode coating layer, and a solid electrolyte layer formed between the negative electrode and the positive electrode, wherein the ratio of the area of ​​the negative electrode coating layer to the area of ​​the positive electrode active material layer is 1.25 or more.

[0033] The above anode may comprise an anode current collector; and an anode active material layer formed on the anode current collector and facing the solid electrolyte layer.

[0034] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and may be made of, for example, copper (Cu), nickel (Ni), aluminum (Al), vanadium (V), gold (Au), platinum (Pt), chromium (Cr), iron (Fe), zinc (Zn), indium (In), germanium (Ge), lithium (Li), magnesium (Mg), stainless steel (e.g., SUS), titanium (Ti), cobalt (Co), or an alloy thereof.

[0035] The anode current collector may have a thickness of 5 μm to 300 μm, and fine irregularities may be formed on the surface of the anode current collector to increase the adhesion of the anode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc. The anode current collector may be omitted depending on the case.

[0036] The above-mentioned positive active material layer may include a positive active material. The above-mentioned positive active material may be a positive active material commonly used in lithium secondary batteries. Specifically, the above-mentioned positive active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound with the chemical formula Li (1-b) (Ni x M 1 (1-x) )M 2 y O2(here M 1 is at least one selected from Co and Mn, and M 2is at least one selected from Al, Zr, B, W, Mo, Cr, Ta, Nb, Mg, Ce, Hf, La, Ti, Sr, Ba, F, P, S, Na, Si, and Y, and 0 <b<0.1, 0.3≤x≤1, 0≤y≤0.1)의 층상구조 화합물; LiFe3O4등의 리튬 철 산화물; 화학식 Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 A lithium manganese complex oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4 in which part of the Li of the chemical formula is substituted with an alkaline earth metal ion; an exemplarily lithium iron phosphate compound (LFP) having the chemical formula LiFePO4; LiFe x M1 (1-x) P y M2 (1-y)O4(where, M1 = 1 or more of Mn, Co, Ni, Al, V, B, Cd, Cu, Mg, Zn, Ti, Nb, Zr and Cr, and 0 <x≤1, M2 = Si, N, S, Cl, Br, 및 F 중 1 이상이며, 0<y≤1)의 화학식을 갖는 리튬 철 금속 인산화물(LMFP); 등을 들 수 있지만, 이들만으로 한정되는 것은 아니다. 상기 양극은 Li-metal일 수도 있다.

[0037] Average particle size (D) of the above positive active material 50 ) may be 1 μm to 30 μm, specifically 2 μm to 20 μm, or 3 μm to 15 μm, but is not limited thereto. The above "average particle size (D 50 "" refers to the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size, and the said particle size may be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a solvent or the powder in a dry state is introduced into the measurement section under vacuum, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500). The particle size distribution is calculated by measuring the difference in diffraction patterns according to particle size as the particles pass through the laser beam. By calculating the particle diameter at the point where the cumulative distribution of particle numbers according to particle size is 50% in the measuring device, D 50 Particle size can be measured.

[0038] The content of the above positive active material may be included in an amount of 50% to 90% by weight, preferably 70% to 90% by weight, and more preferably 80% to 90% by weight, based on the total weight of the above positive active material layer, but is not limited thereto.

[0039] The above positive active material layer may additionally include one or more of a solid electrolyte, a conductive material, and a binder.

[0040] The solid electrolyte included in the above-mentioned positive electrode active material layer may include, but is not limited to, sulfide-based solid electrolytes, oxide-based solid electrolytes, polymer-based solid electrolytes, and / or halide-based solid electrolytes.

[0041] The above sulfide-based solid electrolyte contains sulfur atoms (S), has ionic conductivity of metals belonging to Group 1 or Group 2 of the periodic table, and may have electronic insulation properties. The above sulfide-based solid electrolyte preferably contains at least Li, S, and P as elements and has lithium ion conductivity, but may include other elements other than Li, S, and P depending on the purpose or case. As the above-mentioned sulfide-based solid electrolyte, for example, Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, Li2S-Ga2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-Al2S3, Li2S-SiS2, Li2S-Al2S3, Li2S-SiS2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, or Li 10 GeP2S 12The following may be included. For example, the sulfide-based solid electrolyte may be an argyrodite-based solid electrolyte. Preferably, the argyrodite-based solid electrolyte may be an argyrodite-based solid electrolyte comprising one or more selected from Li6PS5F, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0042] The above oxide-based solid electrolyte is, for example, LiPON, Li 3x La (2 / 3-x)(1 / 3-2x) TiO3(0.04 <x<0.16), Li 1+x Al x Ti 2-x (PO4)3(0 <x<2), Li 1+x Al x Ge 2-x (PO4)3(0 <x<2), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), LiSiO2TiO2(PO4)3), BaTiO3, Pb(Zr, Ti)O3, Pb 1-x La x Zr 1-y Ti y O3(0≤x<1, 0≤y<1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3, HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<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), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M is Te, Nb, or Zr, 1≤x≤10), Li7La3Zr2O 12 , Li 3+x La3Zr 2-a M a O 12 (M is Ga, W, Nb, Ta, or Al, 0 <a<2, 1≤x≤10) 또는 이들의 조합을 포함할 수 있다. 또한 산화물계 고체 전해질은 Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M-doped LLZO, M=Ga, W, Nb, Ta, or Al, 0 <a<2, 1≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체 전해질을 포함할 수 있다. 산화물계 고체 전해질은 결정질, 비정질, 유리질 또는 유리-세라믹일 수 있으며, 제조 방법 및 조성에 따라 다양한 결정 상태를 가질 수 있다.

[0043] The above-mentioned polymer-based solid electrolyte is not particularly limited to any polymer material that is an ion-conducting material and is commonly used as a solid electrolyte material for all-solid-state batteries. The above-mentioned solid polymer electrolyte may include, for example, polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene oxide (PEO), polyethylene derivatives, alkylene oxide derivatives, phosphate ester polymers, polyaisation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, or polymers containing ionic dissociation groups. Alternatively, the above-mentioned polymer-based solid electrolyte may include, as a polymer resin, a branched copolymer, comb-like polymer, and cross-linked polymer resin, etc., in which an amorphous polymer such as polymethyl methacrylate (PMMA), polycarbonate, polysiloxane, and / or phosphazene is copolymerized as a comonomer to a polyethylene oxide (PEO) main chain.

[0044] The above-mentioned halide-based solid electrolyte may, for example, contain a halogen element as the main component of anion. Containing a halogen element as the main component of anion may mean that the proportion (molar ratio) of the halogen element is the highest among all anions constituting the halide-based solid electrolyte. The ratio of the halogen (X) element to all anions constituting the above-mentioned halide-based solid electrolyte may, for example, be 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. The halogen element may be one or more types. The above-mentioned halide-based solid electrolyte may, for example, not contain a sulfur element (S element). The above-mentioned halide-based solid electrolyte may, for example, contain a Li element, an M element (M is a metal other than Li), and an X element. X may, for example, be F, Cl, Br, I, or a combination thereof. The above halide-based solid electrolyte may include, for example, Br or Cl as X. The above halide-based solid electrolyte may include, for example, a metal element such as Sc, Y, B, Al, Ga, In, etc. as M. The composition of the above halide-based solid electrolyte is, for example, Li 6-3a M a Br b Cl c (M is a metal other than Li, and 0 <a<2, 0≤b≤6, 0≤c≤6, b+c=6)일 수 있다. 상기 할라이드계 고체 전해질은 예를 들어 Li3YBr6, Li3YCl6, Li3YBr2Cl4등일 수 있다.

[0045] The above positive active material layer may contain the solid electrolyte in an amount of 5% to 30% by weight, preferably 7% to 28% by weight, more preferably 10% to 25% by weight, based on the total weight of the positive active material layer, but is not limited thereto.

[0046] The conductive material in the positive electrode active material layer is used to impart conductivity to the electrode, and can be used without special restrictions as long as it has electronic conductivity without causing chemical changes. Examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and may include one of these alone or a mixture of two or more.

[0047] The above positive active material layer may contain the conductive material in an amount of 1% to 20% by weight, preferably 2% to 18% by weight, and more preferably 3% to 15% by weight, based on the total weight of the positive active material layer, but is not limited thereto.

[0048] The binder in the above-mentioned positive active material layer can serve to improve adhesion between positive active materials and / or adhesion between the positive active material and the positive current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol (PVA), polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. For example, polytetrafluoroethylene (PTFE) can be used as a binder in the above-mentioned positive active material layer.

[0049] The above positive active material layer may contain the binder in an amount of 1% to 20% by weight, preferably 2% to 18% by weight, and more preferably 3% to 15% by weight, based on the total weight of the positive active material layer.

[0050] The above-mentioned positive active material layer may further include additives. The additives may further include, for example, fillers, coating agents, dispersants, thickeners, or ion conductivity aids, and any known material generally used in electrodes may be used without limitation.

[0051] In addition to the aforementioned configuration, the anode may further include known configurations that can be included in the anode of a secondary battery.

[0052] The thickness of the positive electrode active material layer is 30 μm to 400 μm, preferably 35 μm to 380 μm, and more preferably 40 μm to 350 μm, but is not limited thereto. When the thickness of the positive electrode active material layer is controlled within the above range, the lithium ion migration path can be optimized and volume expansion and contraction during the charge-discharge process can be effectively controlled to improve the charge-discharge performance of the secondary battery.

[0053] The loading amount of the above positive active material layer is 5 mg / cm² 2 to 25 mg / cm² 2 It may be, preferably 6 mg / cm² 2 to 23 mg / cm² 2 It may be, and more preferably 8 mg / cm² 2 to 22 mg / cm² 2 It may be, but is not limited thereto. When the loading amount of the positive electrode active material layer is adjusted within the above range, the energy capacity of the secondary battery per unit area can be maximized and the uniform movement of lithium ions can be enabled, thereby improving charge / discharge efficiency.

[0054] The density of the above positive active material layer is 2.8 g / cm³ 3 Up to 3.5 g / cm² 3 It may be possible. The weight of the positive active material layer is the value obtained by subtracting the weight of the current collector from the total weight of the positive electrode, and the density of the positive active material layer can be calculated by dividing this by the volume value obtained by multiplying the area of ​​the positive active material layer by the thickness of the positive active material layer, but is not limited thereto. When the density of the positive active material layer is controlled within the above range, it is possible to improve the energy density of the secondary battery, optimize the lithium ion migration path, and ensure structural stability.

[0055] The positive active material layer may be formed on 80% to 95% of the surface of the positive current collector, preferably 82% to 95%, and more preferably 85% to 95%. If the positive active material layer is formed on an excessively small surface area of ​​less than 80% of the surface of the positive current collector, there may be problems with overload and reduced energy density in the coated current collector, and conversely, if it is coated on an excessively wide area of ​​more than 95%, there may be problems with reduced structural stability of the battery during the charging and discharging process.

[0056] The above cathode may comprise a cathode current collector; and a cathode coating layer formed between the cathode current collector and the solid electrolyte layer.

[0057] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the secondary battery, and for example, copper, stainless steel (e.g., SUS), aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated or coated with carbon, nickel, titanium, or silver, or aluminum-cadmium alloy may be used.

[0058] The above-mentioned negative current collector can typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities can be formed on the surface of the negative current collector to strengthen the bonding force of the negative active material. For example, it can be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

[0059] The above cathode coating layer may be a cathode active material layer or a non-cathode coating layer.

[0060] When the above-mentioned negative electrode coating layer is the above-mentioned negative electrode active material layer, the negative electrode may include the negative electrode active material layer immediately after battery manufacturing. The negative electrode active material included in the above-mentioned negative electrode active material layer may be a negative electrode active material commonly used in secondary batteries. Examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, or amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Ag, Au, Si alloy, Sn alloy, or Al alloy; SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, or lithium vanadium oxide (0<β≤2); or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film or lithium foil may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, or high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0061] The content of the above-mentioned negative electrode active material may be included in an amount of 60% to 90% by weight, preferably 65% ​​to 90% by weight, and more preferably 70% to 90% by weight, based on the total weight of the above-mentioned negative electrode active material layer, but is not limited thereto.

[0062] The above-mentioned negative electrode active material layer may additionally include a binder, and for example, the binder in the above-mentioned negative electrode active material layer may be polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol (PVA), polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), butadiene rubber (BR), nitrile butadiene rubber (NBR), styrene butadiene styrene block polymer (SBS), styrene ethylene butadiene block polymer (SEB), It may include, but is not limited to, styrene-(styrene butadiene)-styrene block polymers, natural rubber (NR), isoprene rubber (IR), fluororubber, polyethylene, or various copolymers thereof.

[0063] In the case of the binder in the above-mentioned cathode active material layer, it may be included in an amount of 1% to 30% by weight, preferably 15% to 25% by weight, based on the total weight of the above-mentioned cathode active material layer, but is not limited thereto.

[0064] The above-mentioned cathode active material layer may additionally include a solid electrolyte and / or a conductive material.

[0065] The solid electrolyte included in the above-mentioned cathode active material layer may include, but is not limited to, sulfide-based solid electrolytes, oxide-based solid electrolytes, polymer-based solid electrolytes, and / or halide-based solid electrolytes. The above description may apply equally to solid electrolytes.

[0066] The solid electrolyte in the above-mentioned negative electrode active material layer may be included in an amount of 5% to 30% by weight, preferably 10% to 25% by weight, based on the total weight of the above-mentioned negative electrode active material layer, but is not limited thereto.

[0067] The conductive material included in the above-mentioned cathode active material layer is used to impart conductivity to the electrode, and can be used without special restrictions as long as it has electronic conductivity without causing chemical changes. Examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be included.

[0068] The above-described negative electrode active material layer may contain the conductive material in an amount of 1% to 30% by weight, preferably 2% to 20% by weight, and more preferably 3% to 15% by weight, based on the total weight of the negative electrode active material layer, but is not limited thereto.

[0069] In addition, the above-mentioned cathode active material layer may further include additives. The additives may further include, for example, fillers, coating agents, dispersants, thickeners, or ion conductivity aids, and any known material generally used in electrodes may be used without limitation.

[0070] The thickness of the above-mentioned negative electrode active material layer may be 1 μm to 100 μm, preferably 20 μm to 90 μm, more preferably 30 μm to 80 μm, but is not limited thereto.

[0071] In the case where the above-mentioned negative electrode coating layer is a non-negative electrode coating layer, the above-mentioned non-negative electrode coating layer refers to a coating layer formed between a negative electrode current collector and a solid electrolyte layer in a secondary battery in which lithium is ionized and moves toward the positive electrode during discharge, and lithium is absorbed in the non-negative electrode coating layer during charging and lithium is precipitated between the negative electrode current collector and the non-negative electrode coating layer to form a metal layer after the charging capacity of the non-negative electrode coating layer is exceeded. The above-mentioned non-negative electrode coating layer may differ in composition and operating mechanism from a conventional negative electrode active material layer. The above-mentioned non-negative electrode coating layer can cover the lithium metal layer formed on the negative electrode current collector during the charging process to serve as a protective layer for the lithium metal layer and can suppress the precipitation growth of lithium dendrites, thereby suppressing short circuits and capacity degradation of the all-solid-state battery and improving performance.

[0072] When the above-mentioned cathode coating layer is a non-cathode coating layer, the cathode may use lithium or a lithium alloy as a cathode active material, and the non-cathode coating layer may include one or more types of lithium-affinity materials capable of forming an alloy or compound with lithium ions. The above lithium-affinity material may include one or more of silver (Ag), gold (Au), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), carbon (C), cobalt (Co), indium (In), manganese (Mn), titanium (Ti), aluminum (Al), copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), manganese monoxide (MnO), silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (Al2O3), zinc peroxide (ZnO2), indium oxide (In2O3), titanium sulfide (TiS2), iron sulfide (FeS), and lithium fluoride (LiF). It may be preferable to include silver (Ag) as the lithium-affinity material, but it is not limited thereto, and any material having similar physical properties or characteristics to the above material may be applied without special limitations.

[0073] The lithium-affinity material may be in an amount of 5% to 40% by weight based on the total weight of the non-cathode coating layer, preferably 10% to 40% by weight, more preferably 20% to 40% by weight, but is not limited thereto. If the content of the lithium-affinity material is excessively low, the lithium-affinity material remaining during discharge is reduced, making it difficult to suppress the occurrence of voids; conversely, if the content of the lithium-affinity material is excessively high, the average discharge potential is lowered, which may reduce the energy density of the battery.

[0074] Average particle size (D) of the above lithium-affinity material 50The average particle size may be 5 nm to 300 nm, 7 nm to 250 nm, or 10 nm to 200 nm, but is not limited thereto. The measurement method for the average particle size may be the same as the measurement method for the average particle size of the positive electrode active material.

[0075] The above-mentioned non-cathode coating layer may include a carbon material. Alternatively, the above-mentioned cathode coating layer may include the above-mentioned lithium-affinity material and the above-mentioned carbon material. Amorphous carbon black may be used as the carbon material. The above-mentioned amorphous carbon black may include one or more of amorphous carbon blacks selected from amorphous acetylene black, amorphous furnace black, and amorphous Ketjen black, amorphous activated carbon, amorphous graphene, and combinations thereof.

[0076] The carbon material may include one or more of amorphous carbon black, amorphous activated carbon, and amorphous graphene, and preferably may include amorphous carbon black, but is not limited thereto. The amorphous carbon black may include one or more of amorphous acetylene black, amorphous furnace black, and amorphous Ketjen black, but is not limited thereto.

[0077] The carbon material included in the above-mentioned non-cathode coating layer may contain oxygen. More specifically, the carbon material particles constituting the carbon material may contain an oxygen element content (atomic %, hereinafter at%) of 2 at% to 10 at% based on the total elements of the carbon material particles. When the oxygen is included in a content within the range of 2 at% to 10 at%, the surface roughness of the non-cathode coating layer and the operating characteristics of the battery may be further improved. In one embodiment of the present invention, the oxygen may exist in a form included in a functional group bonded to the carbon material particles. In addition, the functional group may include one or more selected from the group consisting of a carboxyl group, a hydroxyl group, an ether group, an ester group, an aldehyde group, a carbonyl group, and an amide group.

[0078] The carbon material particles containing an elemental oxygen content of 2 at% to 10 at% can be manufactured, for example, by oxidizing the carbon material. For example, oxygen functional groups can be introduced onto the surface of the carbon material by treating the carbon material with an acid and stirring and reacting it at a temperature of 25°C to 60°C. The type of acid is not particularly limited, and any acid capable of introducing oxygen functional groups onto the surface of the carbon material is possible. Examples of the acid include sulfuric acid, nitric acid, or mixtures thereof, and an oxidizing agent such as potassium permanganate may also be used.

[0079] The oxygen content contained in the carbon material particles can be measured using a photoelectron spectrometer (XPS or ESCA). For example, it can be measured using a K-Alpha (Thermo Fisher Scientific) device. In one embodiment of the present invention, the oxygen may be present on the surface of the carbon material particles. The surface does not refer only to the outer surface of the carbon material particles, but includes, for example, the inner surface of the pores if pores are present.

[0080] The above atomic composition ratios can be measured using a photoelectron spectrometer (XPS or ESCA). For example, the above composition ratios can be measured using a Nexsa4 (ThermoFisher Scientific) device.

[0081] The carbon material may be in an amount of 50% to 90% by weight based on the total weight of the non-cathode coating layer, preferably 60% to 90% by weight, more preferably 70% to 90% by weight, but is not limited thereto. By controlling the content of the carbon material in the non-cathode coating layer as described above, the charge and discharge efficiency of the battery can be improved.

[0082] Average particle size (D of the above carbon material particles)50 The average particle size may be 30 nm to 250 nm, specifically 40 nm to 240 nm, but is not limited thereto. The measurement method for the average particle size may be the same as the measurement method for the average particle size of the positive active material.

[0083] The thickness of the above-mentioned non-cathode coating layer may be 1 μm to 100 μm, preferably 20 μm to 90 μm, more preferably 30 μm to 80 μm, but is not limited thereto.

[0084] The above-mentioned cathode coating layer may additionally include a binder, and for example, the binder in the above-mentioned cathode coating layer may be polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol (PVA), polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), butadiene rubber (BR), nitrile butadiene rubber (NBR), styrene butadiene styrene block polymer (SBS), styrene ethylene butadiene block polymer (SEB), It may include, but is not limited to, styrene-(styrene butadiene)-styrene block polymers, natural rubber (NR), isoprene rubber (IR), fluororubber, polyethylene, or various copolymers thereof.

[0085] In the case of the binder in the above-mentioned non-cathode coating layer, it may be included in an amount of 1% to 30% by weight, preferably 5% to 25% by weight, based on the total weight of the above-mentioned non-cathode coating layer, but is not limited thereto.

[0086] The above-mentioned non-cathode coating layer may additionally include a solid electrolyte and / or a conductive material, and the above description may apply equally to this.

[0087] In addition, the above-mentioned non-cathode coating layer may further include additives. The additives may further include, for example, fillers, coating agents, dispersants, thickeners, or ion conductivity aids, and any known material generally used in electrodes may be used without limitation.

[0088] The above cathode coating layer may be formed on 80% to 95%, preferably 82% to 95%, and more preferably 85% to 95% of the total surface of the cathode current collector based on area. If the area on which the cathode coating layer is formed is excessively small, below the lower limit, there may be problems with overload and reduced energy density on the coated current collector, and conversely, if it is excessively large, exceeding the upper limit, there may be problems with reduced structural stability of the battery during the charging and discharging process.

[0089] The above cathode may include a lithium affinity layer between the cathode current collector and the cathode coating layer.

[0090] The lithium affinity layer may be formed by surface treating a lithium affinity material on a negative electrode current collector. The lithium affinity material in the lithium affinity layer may be the same as or different from the lithium affinity material in the non-negative electrode coating layer. Specifically, the lithium-affinity material in the lithium-affinity layer may be one or more selected from silver (Ag), gold (Au), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), carbon (C), cobalt (Co), indium (In), manganese (Mn), titanium (Ti), aluminum (Al), copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), manganese monoxide (MnO), silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (Al2O3), zinc peroxide (ZnO2), indium oxide (In2O3), titanium sulfide (TiS2), iron sulfide (FeS), and lithium fluoride (LiF), and any material capable of producing a similar or identical effect to these may be used as a lithium-affinity material. The lithium-affinity layer may also include materials capable of reacting with lithium ions to form compounds, such as carbon, titanium sulfide, iron sulfide, and combinations thereof. The above lithium affinity layer can be formed by one or more deposition methods selected from chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), sputtering, and plasma treatment.

[0091] As explained above, lithium-affinity materials may also be included in the non-cathode coating layer. However, as a result of repeated research by the applicant, it was confirmed that when the negative electrode current collector itself is surface-treated with a lithium-affinity material, lithium plating on the current collector is uniformly achieved even during rapid charging compared to when the negative electrode coating layer is directly laminated without such surface treatment, thereby significantly improving the rapid charging cycle capacity retention rate of the battery (especially, sulfide-based all-solid-state battery). That is, the lithium-affinity layer can be utilized as a layer that causes lithium metal to precipitate flatly on the surface side of the negative electrode current collector, for example, as a wetting layer.

[0092] Average particle size (D) of lithium-affinity material particles included in the above lithium-affinity layer 50 ) may be 10 nm to 50 µm, or 10 nm to 20 µm, and preferably may be 5 nm to 300 nm, 7 nm to 250 nm, or 10 nm to 200 nm, but is not limited thereto. If, the average particle size (D) of the lithium-affinity material particles 50 If ) is less than 10 nm, the particle size is excessively small, which may lead to problems with particle aggregation. In addition, the average particle size (D) of lithium-affinity material particles 50 If ) exceeds 50 μm, the surface area of ​​the particles decreases, and the alloy reaction with lithium may not proceed smoothly.

[0093] The thickness of the lithium affinity layer may be 10 nm to 500 nm, preferably 10 nm to 400 nm, and more preferably 10 nm to 300 nm, based on a thickness of 1 μm to 30 μm of the negative electrode current collector. If the thickness of the lithium affinity layer is less than 10 nm based on a thickness of 1 μm to 30 μm of the negative electrode current collector, it may be difficult to suppress the occurrence of voids because the lithium affinity material remaining during discharge is also reduced. In addition, if the thickness of the lithium affinity layer exceeds 500 nm based on a thickness of 1 μm to 30 μm of the negative electrode current collector, the cell efficiency may decrease, and the energy density may decrease. Furthermore, it may be preferable for the lithium affinity layer to be formed flatly on the negative electrode current collector to prevent the battery from cracking during the charging cycle.

[0094] The thickness ratio of the lithium affinity layer and the cathode coating layer may also affect the lithium plating reaction on the current collector. The thickness ratio of the lithium affinity layer and the cathode coating layer may be 1:20 to 1:500, preferably 1:30 to 1:200. In particular, if the thickness of the lithium affinity layer deviates from the above range and is excessively thin, a problem may arise where it fails to function as a lithium affinity layer.

[0095] The above lithium affinity layer may also be composed of two or more layers. In this case, each layer contains the aforementioned lithium affinity material, and each layer may contain a different type of lithium affinity material or a homogeneous type of lithium affinity material. In this case, there is no particular limitation on the thickness ratio between layers.

[0096] The area of ​​the lithium affinity layer may be formed to be 80% or more to 95% or less of the total surface of the negative electrode current collector, specifically 82% or more to 95% or 85% or more to 95% or less, but is not limited thereto. The area of ​​the lithium affinity layer may be larger than or equal to the area of ​​the negative electrode coating layer, but is not limited thereto.

[0097] The ratio of the area of ​​the negative coating layer to the area of ​​the positive active material layer is 1.25 or higher. When the above area ratio is less than 1.25, the capacity retention rate relative to the initial capacity is low, but when the above area ratio is adjusted to 1.25 or higher, a significant improvement in the capacity retention rate relative to the initial capacity is possible, and through this, the lifespan characteristics of the secondary battery can be improved.

[0098] The upper limit of the ratio of the area of ​​the cathode coating layer to the area of ​​the positive active material layer may be selected from 1.65, 1.7, 1.8, 1.9, or 2.0, but is not limited thereto. If the above area ratio becomes excessively large, the energy density of the secondary battery to which the above area ratio is applied may decrease, leading to problems such as reduced energy efficiency and deterioration of economic feasibility of the secondary battery; therefore, the above upper limit value may be appropriately adjusted considering the energy density of the secondary battery.

[0099] The above area ratio may be 1.25 or more to 2.0 or less, 1.25 or more to 1.9 or less, 1.25 or more to 1.8 or less, 1.25 or more to 1.7 or less, or 1.25 or more to 1.65 or less, but is not limited thereto. When the area ratio of the negative electrode coating layer to the area of ​​the positive electrode active material layer is less than 1.25, as confirmed in the following examples, the improvement in capacity retention rate relative to initial capacity is significantly small, and it can be confirmed that the improvement in lifespan characteristics is negligible. When the above area ratio exceeds 2.0, the energy density of the secondary battery to which the positive electrode and negative electrode are applied becomes excessively low, which may lead to problems such as reduced energy efficiency and deterioration of economic feasibility of the secondary battery.

[0100] In the case of secondary batteries, attempts are being made to improve lifespan performance through material development and improvements in moisture management within production lines; however, while there are limitations to the improvement achieved through these methods, the present invention confirms that the lifespan performance of secondary batteries can be significantly enhanced by controlling the area of ​​the positive active material layer and the area of ​​the negative coating layer as described above. Specifically, it was confirmed through cycle characteristic evaluation that when the ratio of the area of ​​the negative coating layer to the area of ​​the positive active material layer falls within the aforementioned range, the capacity retention rate relative to the initial capacity is significantly improved. Accordingly, the present invention identifies the range of area ratios between the positive active material layer and the negative coating layer that can significantly improve the capacity retention rate relative to the initial capacity and stably secure the long-term lifespan characteristics of the secondary battery.

[0101] In addition, when the thickness, loading amount, and / or density range of the anode active material layer presented above are simultaneously satisfied along with the area ratio range of the anode active material layer and the cathode coating layer of the present invention, significantly improved charge / discharge efficiency and lifespan characteristics can be achieved.

[0102] The above solid electrolyte layer may include an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a halide-based solid electrolyte. The above description may apply equally to the oxide-based solid electrolyte, the sulfide-based solid electrolyte, or the halide-based solid electrolyte. The above solid electrolyte may be in an amorphous state, a crystalline state, or a state in which amorphous and crystalline phases are mixed.

[0103] For example, the solid electrolyte layer may include a sulfide-based solid electrolyte, specifically Li2S-P2S5, Li2S-P2S5-LiX (X = halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m and n are positive, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2SSiS2-Li p MO q (p and q are positive, M is one of P, Si, Ge, B, Al, Ga or In), or may include a combination of these.

[0104] In addition, the above sulfide-based solid electrolyte may include a solid electrolyte represented by the following chemical formula 1.

[0105] [Chemical Formula 1]

[0106] Li x M' y PS z A w

[0107] In the above chemical formula 1, x, y, z, and w are independently 0 or more and 6 or less, M' is one or more selected from As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, and Ta, and A is one or more selected from F, Cl, Br, and I.

[0108] In addition, the above sulfide-based solid electrolyte may be used that includes sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, it may be used that includes Li2S-P2S5. When using a sulfide-based solid electrolyte material that includes Li2S-P2S5, the mixed molar ratio of Li2S and P2S5 may be selected in the range of, for example, Li2S : P2S5 = 50 : 50 to 90 : 10. The above sulfide-based solid electrolyte may include Li2S-P2S5-based sulfide glass or Li2S-P2S5-based glass ceramic, but is not limited thereto.

[0109] The solid electrolyte layer may additionally include a binder. The binder in the solid electrolyte layer may be subject to the foregoing description of the binder in the cathode and anode, but is not limited thereto. For example, the binder may be a resin such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or polyacrylic acid, but is not limited thereto.

[0110] The solid electrolyte layer may have an area equal to or larger than the area of ​​the cathode coating layer, and, for example, the area ratio of the solid electrolyte layer to the cathode coating layer may be 1 or more to 2 or less, 1 or more to 1.9 or less, 1 or more to 1.8 or less, 1 or more to 1.7 or less, 1 or more to 1.6 or less, or greater than 1 to 1.5 or less, but is not limited thereto. When the area ratio of the solid electrolyte layer to the cathode coating layer satisfies the above range, the area of ​​the solid electrolyte layer is sufficiently secured to prevent external contact between electrodes, thereby preventing short circuits, while simultaneously enabling optimization of the energy density of the battery.

[0111] The thickness of the solid electrolyte layer may be 5 μm to 500 μm, preferably 10 μm to 400 μm, more preferably 50 μm to 300 μm, but is not limited thereto.

[0112] The electrode assembly may include a separator. The separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions; generally, any separator used in an electrode assembly may be used without special limitations. Specifically, as the separator, a porous polymer film made of a polyolefin-based polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. To ensure heat resistance or mechanical strength, a coated separator containing ceramic components or polymer materials may be used, and optionally, it may be used in a single-layer or multi-layer structure.

[0113] In the case of the electrode assembly of the present invention, a solid electrolyte layer is included. In such a case, the separator may include a solid electrolyte, and the solid electrolyte layer may perform the role of a separator. For example, in the case of a secondary battery including a solid electrolyte layer as in the present invention, an additional separator structure may be omitted.

[0114] One aspect of the present invention provides a secondary battery comprising the electrode assembly. The secondary battery may include an additional electrolyte in addition to the solid electrolyte in the electrode assembly. The electrolyte may be any type of electrolyte that is typically available for use in the manufacture of the secondary battery without limitation.

[0115] For example, the electrolyte may include a liquid electrolyte, and may include, for example, an organic solvent and a lithium salt.

[0116] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0117] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, as the anion of the above lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2.

[0118] The above secondary battery may be a solid-state battery. The above secondary battery may be pouch-type, prismatic, or cylindrical, and its shape and size may be applied without restriction as long as it is a commonly used secondary battery.

[0119] One aspect of the present invention may provide an electronic device including the secondary battery. Specifically, the electronic device may include, without limitation, a battery module or battery pack including the secondary battery as a unit cell, a battery pack including the battery module, and an electronic device including the secondary battery, battery module, or battery pack as a power source. As an example, specific examples of the electronic device include, but are not limited to, a power tool that moves by receiving power from an electric motor; electric vehicles including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; electric two-wheeled vehicles including an electric bicycle (E-bike) or an electric scooter (E-scooter); an electric golf cart; and a power storage system (e.g., a capacitor, an ESS, etc.).

[0120] In the following, the present invention is described in detail with reference to examples to specifically explain the disclosure of the present invention as described above and the intended functions and effects of the present invention. However, the examples may be modified in various different forms, and the scope of this specification is not to be interpreted as being limited only to these examples. It is emphasized that the examples are provided to represent the present invention and to explain it more specifically to those skilled in the art.

[0122] Examples and Comparative Examples

[0123] Example 1.

[0124] To manufacture the cathode, a composition for manufacturing a cathode coating layer was prepared by mixing amorphous carbon black, Ag, and a PVdF binder (based on solid content) in an NMP solution at a weight ratio of 30:10:2.8. A SUS foil with a thickness of 10 μm was used as the cathode current collector. The composition for manufacturing the cathode coating layer was applied to the surface of the cathode current collector and dried to obtain a laminate, which was then pressed to obtain a cathode coating layer with an area of ​​5.96 cm². 2 A cathode with a thickness of 10 μm was manufactured.

[0125] To manufacture the cathode, NCM811 as the cathode active material, Li2S-P2S5 as the solid electrolyte, carbon black as the conductive material, and SBR as the binder were prepared and mixed in a weight ratio of 85:13:1:1 to prepare a composition for forming the cathode active material layer. An aluminum current collector with a thickness of 14 μm was used as the cathode current collector. The composition for forming the cathode active material layer was applied to the surface of the cathode current collector and dried to obtain a laminate. The laminate was then pressed to obtain a cathode active material layer with an area of ​​4 cm². 2 A phosphorus anode was manufactured.

[0126] An all-solid-state battery was fabricated by sequentially stacking a solid electrolyte layer fabricated using a sulfide-based solid electrolyte Li2S-P2S5 and a fabricated anode on the above-mentioned cathode, thereby including an electrode assembly having an area ratio of the cathode coating layer to the area of ​​the anode active material layer of 1.49.

[0127] Example 2.

[0128] In Example 1, the area of ​​the cathode coating layer is 6.52 cm² 2 It is fabricated, and the area of ​​the positive active material layer is 4 cm² 2 An all-solid-state battery was fabricated in the same manner as in Example 1, except that the ratio of the area of ​​the negative electrode coating layer to the area of ​​the positive electrode active material layer was 1.63.

[0129] Example 3.

[0130] An all-solid-state battery with a lithium-affinity layer applied to the negative electrode was fabricated as follows. A SUS foil with a thickness of 10 μm was used as the negative electrode current collector, and the surface of the negative electrode current collector was coated with lithium fluoride (LiF), a lithium-affinity material, using atomic layer deposition and dried, so that an area of ​​5.96 cm² on the negative electrode current collector 2 A lithium affinity layer with a thickness of 50 nm was formed.

[0131] A composition for manufacturing a cathode coating layer was prepared as in Example 1, and the composition was applied to the surface of the lithium affinity layer and dried to obtain a laminate. Subsequently, the laminate was pressed so that the area of ​​the cathode coating layer was 5.96 cm² 2 A cathode with a thickness of 10 μm was manufactured.

[0132] On the above-fabricated cathode, the area of ​​the solid electrolyte layer and the anode active material layer prepared in the same manner as in Example 1 is 4 cm² 2 An all-solid-state battery was fabricated by sequentially stacking positive electrodes to include an electrode assembly having an area ratio of the negative electrode coating layer to the area of ​​the positive electrode active material layer of 1.49.

[0133] Example 4.

[0134] In Example 3, the area of ​​the cathode coating layer is 6.52 cm² 2 It is fabricated, and the area of ​​the positive active material layer is 4 cm² 2 An all-solid-state battery was fabricated in the same manner as in Example 3, except that the ratio of the area of ​​the negative electrode coating layer to the area of ​​the positive electrode active material layer was 1.63.

[0135] Comparative Example 1.

[0136] In Example 1, the area of ​​the cathode coating layer is 4.92 cm² 2 It is fabricated, and the area of ​​the positive active material layer is 4 cm² 2An all-solid-state battery was fabricated in the same manner as in Example 1, except that the ratio of the area of ​​the negative electrode coating layer to the area of ​​the positive electrode active material layer was 1.23.

[0137] Comparative Example 2.

[0138] In Example 3, the area of ​​the cathode coating layer is 4.92 cm² 2 It is fabricated, and the area of ​​the positive active material layer is 4 cm² 2 An all-solid-state battery was fabricated in the same manner as in Example 3, except that the ratio of the area of ​​the negative electrode coating layer to the area of ​​the positive electrode active material layer was 1.23.

[0140] Experimental Example 1. Evaluation of Charge / Discharge Performance

[0141] The capacity retention rate according to charge-discharge cycles under rapid charging conditions was measured for each all-solid-state battery prepared in Examples 1 to 4 and Comparative Examples 1 to 2. Specifically, the capacity retention rate (%) after 150 cycles was measured with the following charge-discharge conditions defined as one cycle at an operating temperature of 60°C, and the results are shown in Table 1 and Figure 1.

[0142] (Charging / Discharging Conditions)

[0143] Charging: 1C, 4.25V CC / CV, 0.1C cut-off

[0144] Discharge: 0.33C, 3.0V, CC

[0145] division Cycle retention(%)@150 cycles Example 1 94.6 Example 2 95.2 Example 3 95.1 Example 4 96.1 Comparative Example 1 92.2 Comparative Example 2 92.8

Claims

Claim 1 An electrode assembly comprising an anode including an anode active material layer, a cathode including a cathode coating layer, and a solid electrolyte layer formed between the cathode and the anode, wherein the ratio of the area of ​​the cathode coating layer to the area of ​​the anode active material layer is 1.25 or more. Claim 2 An electrode assembly according to claim 1, wherein the positive electrode comprises a positive current collector; and a positive active material layer formed on the positive current collector and facing the solid electrolyte layer. Claim 3 An electrode assembly according to claim 1, wherein the cathode comprises a cathode current collector; and a cathode coating layer formed between the cathode current collector and the solid electrolyte layer. Claim 4 An electrode assembly according to claim 1, wherein the cathode coating layer comprises one or more selected from a cathode active material layer and a non-cathode coating layer. Claim 5 An electrode assembly according to claim 4, wherein the non-cathode coating layer comprises one or more selected from silver (Ag), gold (Au), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), carbon (C), cobalt (Co), indium (In), manganese (Mn), titanium (Ti), aluminum (Al), copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), manganese monoxide (MnO), silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (Al2O3), zinc peroxide (ZnO2), indium oxide (In2O3), titanium sulfide (TiS2), iron sulfide (FeS), and lithium fluoride (LiF). Claim 6 In paragraph 4, the electrode assembly comprises a non-cathode coating layer including a carbon material. Claim 7 An electrode assembly according to paragraph 3, comprising a lithium affinity layer between the negative electrode current collector and the negative electrode coating layer. Claim 8 An electrode assembly according to claim 7, wherein the lithium affinity layer comprises one or more selected from silver (Ag), gold (Au), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), carbon (C), cobalt (Co), indium (In), manganese (Mn), titanium (Ti), aluminum (Al), copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), manganese monoxide (MnO), silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (Al2O3), zinc peroxide (ZnO2), indium oxide (In2O3), titanium sulfide (TiS2), iron sulfide (FeS), and lithium fluoride (LiF). Claim 9 An electrode assembly according to claim 7, wherein the thickness of the lithium affinity layer is 10 nm to 500 nm based on the thickness of the negative current collector of 1 μm to 30 μm. Claim 10 An electrode assembly according to claim 1, wherein the thickness of the positive active material layer is 30 μm to 400 μm and the thickness of the negative coating layer is 1 μm to 100 μm. Claim 11 An electrode assembly according to claim 1, wherein the area of ​​the solid electrolyte layer is equal to or larger than the area of ​​the cathode coating layer. Claim 12 An electrode assembly according to claim 1, wherein the solid electrolyte layer comprises a sulfide-based solid electrolyte. Claim 13 A secondary battery comprising an electrode assembly according to any one of claims 1 to 12. Claim 14 An electronic device including a secondary battery of paragraph 13.

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