All-solid-state battery and method for manufacturing same

Abstract

The present invention relates to an all-solid-state battery and a method for manufacturing same. More specifically, the all-solid-state battery of the present invention comprises: a positive electrode layer including a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector; a negative electrode layer; and a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer. The content of the residual solvent in the positive electrode active material layer or the solid electrolyte layer is 1,000 ppm or less.

Description

All-solid-state battery and method for manufacturing the same

[0001] The present invention relates to an all-solid-state battery and a method for manufacturing the same, and more specifically, to an all-solid-state battery containing a minute amount of residual solvent.

[0002]

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

[0004] Recently, all-solid-state batteries have been proposed in which the electrolyte of lithium-ion batteries is replaced with a solid electrolyte. By not using flammable electrolytes, all-solid-state batteries can significantly reduce the likelihood of fire or explosion in the event of a short circuit. Therefore, such all-solid-state batteries can possess excellent safety.

[0005]

[0006] The problem that the present invention aims to solve is to provide an all-solid-state battery with excellent lifespan characteristics by including a minute amount of residual solvent.

[0007] Another problem that the present invention aims to solve is to provide an all-solid-state battery having excellent flexibility of the anode layer and solid electrolyte layer while containing a very small amount of residual solvent.

[0008] Another problem that the present invention aims to solve is to provide a method for manufacturing an all-solid-state battery that contains a minute amount of residual solvent, has excellent flexibility of the anode layer and solid electrolyte layer, and excellent lifespan characteristics.

[0009]

[0010] A solid-state battery according to the concept of the present invention may comprise: a positive electrode layer comprising a positive current collector and a positive active material layer on the positive current collector; a negative electrode layer; and a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer. The positive active material layer comprises positive active material particles and solid electrolyte particles, and at least one of the positive active material layer and the solid electrolyte layer further comprises a residual solvent, wherein the content of the residual solvent in the positive active material layer or the solid electrolyte layer is 1,000 ppm or less, and the residual solvent may comprise a compound represented by the following chemical formula 1.

[0011] [Chemical Formula 1]

[0012] R-COO-R'

[0013] In the above chemical formula 1, R and R' are each independently alkyl groups having 4 to 6 carbon atoms.

[0014] An all-solid-state battery according to another concept of the present invention may include a positive electrode layer comprising a positive current collector and a positive active material layer on the positive current collector; a negative electrode layer; and a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer. The positive active material layer may include hexyl butyrate as a residual solvent, and the content of the hexyl butyrate in the positive active material layer may be 1,000 ppm or less.

[0015] A method for manufacturing an all-solid-state battery according to another concept of the present invention may comprise: preparing a positive electrode layer in which the content of a first residual solvent in the positive electrode active material layer is 1,000 ppm or less; preparing a solid electrolyte layer in which the content of a second residual solvent is 1,000 ppm or less; preparing a negative electrode layer; and interposing the solid electrolyte layer between the negative electrode layer and the positive electrode layer. Each of the first and second residual solvents may comprise a compound represented by the following chemical formula 1:

[0016] [Chemical Formula 1]

[0017] R-COO-R'

[0018] In the above chemical formula 1, R and R' are each independently alkyl groups having 4 to 6 carbon atoms.

[0019]

[0020] An all-solid-state battery according to one embodiment of the present invention contains a very small amount of low-polarity residual solvent with low reactivity, resulting in excellent lifespan characteristics.

[0021] An all-solid-state battery according to one embodiment of the present invention utilizes a solvent with low vapor pressure and high steric hindrance to maximize the dispersibility and uniformity of the binder, thereby ensuring excellent flexibility of the anode layer and solid electrolyte layer so that no cracks occur.

[0022]

[0023] FIG. 1 is a conceptual diagram briefly illustrating an all-solid-state battery according to embodiments of the present invention.

[0024] FIG. 2 is a cross-sectional view illustrating an anode layer according to one embodiment of the present invention.

[0025] Figure 3 is an enlarged view of the M region of Figure 2.

[0026] FIG. 4 is a cross-sectional view illustrating a solid electrolyte layer according to one embodiment of the present invention.

[0027] Figure 5 is an enlarged view of the M' region of Figure 4.

[0028] FIGS. 6a to 6c are cross-sectional views illustrating a method for manufacturing an all-solid-state battery according to an embodiment of the present invention.

[0029]

[0030] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0031] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0032] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0033] The embodiments described herein will be described with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0034] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components to the mentioned components.

[0035] In this specification, each of the phrases such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0036]

[0037] FIG. 1 is a cross-sectional view of an all-solid-state battery (10) according to one embodiment of the present invention.

[0038] Referring to FIG. 1, an all-solid-state battery (10) according to one embodiment includes a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, the all-solid-state battery (10) may further include an additional functional layer, such as an adhesion-enhancing layer, disposed between the positive electrode layer (100) and the solid electrolyte layer (300) or between the negative electrode layer (200) and the solid electrolyte layer (300).

[0039] An anode layer (100) of one embodiment includes an anode current collector (110) and an anode active material layer (120) disposed on the anode current collector (110). The anode active material layer (120) may include an anode active material, a solid electrolyte, a conductive material, and a binder.

[0040] The positive current collector (110) can provide a reference surface on which the positive active material layer (120) is placed. The positive current collector (110) may have a plate or foil form. For example, the positive current collector (110) may include 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.

[0041] Meanwhile, unlike as illustrated in FIG. 1, the positive current collector (110) may be omitted in one embodiment of the present invention. Although not illustrated, a carbon layer with a thickness of 0.1 μm to 4 μm may be further disposed between the positive current collector (110) and the positive active material layer (120) to increase the bonding strength between the positive current collector (110) and the positive active material layer (120).

[0042] The cathode active material is a material capable of reversibly absorbing and desorbing lithium ions. The cathode active material may include, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, as well as nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not necessarily limited to these. Each cathode active material may be a single material or a mixture of two or more materials.

[0043] Lithium transition metal oxides are, for example, Li a A 1-b B b D2(0.90≤a≤1, 0≤b≤0.5), Li a E 1-b B b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05), LiE 2-b B b O 4-c D c (0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Co b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Mn b B c D α(0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Nor 1-b-c Mn b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Nor b E c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Nor b Co c Mn d GeO2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1), Li a NiG b O2(0.9≤a≤1, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a MnG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-fIt is a compound represented by any one of Fe2(PO4)3 (0≤f≤2) or LiFePO4. In such compounds, the uppercase “A” is Ni, Co, Mn, or a combination thereof; the uppercase “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; the uppercase “D” is O, F, S, P, or a combination thereof; the uppercase “E” is Co, Mn, or a combination thereof; the uppercase “F” is F, S, P, or a combination thereof; the uppercase “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; the uppercase “Q” is Ti, Mo, Mn, or a combination thereof; the uppercase “I” is Cr, V, Fe, Sc, Y, or a combination thereof; and the uppercase “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0044] The cathode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen and metal atomic layers are alternately and regularly arranged in a specific direction, thereby forming a two-dimensional plane for each atomic layer. The "cubic rock salt type structure" represents a sodium chloride (NaCl) type structure, which is a type of crystal structure; specifically, it exhibits a structure in which face-centered cubic lattices (fcc) formed by cations and anions, respectively, are offset from each other by half the ridge of the unit lattice. Lithium transition metal oxides having such a layered rock salt type structure are, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0045] The aforementioned compound contained in the cathode active material may be covered by a coating layer (not shown). The cathode active material may also be a mixture of the aforementioned compound and the compound to which the coating layer is added. Meanwhile, the coating layer added to the surface of the cathode active material may include, for example, oxides, hydroxides, oxyhydroxides, oxycarbonates, or hydroxycarbonates of the following coating elements. The compounds forming this coating layer are amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the cathode active material. The method for forming the coating layer is, for example, spray coating or immersion.

[0046] When the positive electrode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), the capacity density of the all-solid-state battery (10) is increased, and the metal leaching of the positive electrode active material in the charged state can be reduced. As a result, the cycle characteristics of the all-solid-state battery (10) in the charged state are improved. Meanwhile, “cycle characteristics” is a characteristic that indicates the degree of deterioration of the all-solid-state battery (10) due to charging and discharging of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics has a small degree of deterioration due to charging and discharging, while an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration due to charging and discharging.

[0047] The shape of the cathode active material may include particle shapes such as spheres or ellipsoids. The particle size and content of the cathode active material are not particularly limited.

[0048] The solid electrolyte may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. Sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (m, n are positive numbers, uppercase “Z” is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, uppercase “M” is one of P, Si, Ge, B, Al, Ga, In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include at least one selected from (0≤x≤2).

[0049] Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I xIt may be an argyrodite-type compound comprising one or more selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0050] Alternatively, sulfide-based solid electrolytes are Li 7-a-c M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)). Here, X may be F, Br, Cl, or a combination thereof. M may be candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof.

[0051] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. By having a density of 1.5 g / cc or higher for the azyrodite-type solid electrolyte, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0052] The solid electrolyte included in the positive electrode active material layer (120) may have a smaller average particle size (D50) compared to the solid electrolyte included in the solid electrolyte layer (300). For example, the average particle size (D50) of the solid electrolyte included in the positive electrode active material layer (120) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average particle size (D50) of the solid electrolyte included in the solid electrolyte layer (300). Meanwhile, the average particle size (D50) may be a median diameter measured using a laser particle size distribution meter.

[0053] The positive electrode active material layer (120) may include a conductive material. The conductive material may have conductivity without causing chemical changes in the all-solid-state battery (10), thereby increasing the conductivity of the positive electrode active material and the solid electrolyte. The conductive material may include a carbon-based material. The conductive material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0054] The positive active material layer (120) may further include a binder. The binder may include a material for bonding the positive active material, solid electrolyte, and conductive material included in the positive active material layer (120), and for improving the bonding strength with the positive current collector (110). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0055] Based on 100 parts by weight of the total positive active material, solid electrolyte, conductive material, and binder, the positive active material layer (120) may contain 70 parts by weight or more and 92 parts by weight or less of the positive active material. For example, the positive active material layer (120) may contain 85 parts by weight or more and 92 parts by weight of the positive active material. Based on 100 parts by weight of the total positive active material, solid electrolyte, conductive material, and binder, the positive active material layer (120) may contain 0.5 parts by weight or more and 1.5 parts by weight or less of the binder.

[0056] Based on 100 parts by weight of solid electrolyte, the positive active material layer (120) may contain 1 part by weight or more and 50 parts by weight or less of a conductive material. If the conductive material is included in the positive active material layer (120) in an amount less than 1 part by weight based on 100 parts by weight of solid electrolyte, the proportion of the conductive material decreases, and the electrical conductivity of the positive active material layer (120) may decrease. If the conductive material is included in the positive active material layer (120) in an amount exceeding 50 parts by weight based on 100 parts by weight of solid electrolyte, the proportion of the conductive material is excessively high, and a coating layer covering the surface of the solid electrolyte may not be properly formed.

[0057] The positive active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductivity aids in addition to the positive active material, solid electrolyte, conductive material, and binder described above.

[0058] The solid electrolyte layer (300) is disposed between the anode layer (100) and the cathode layer (200) and includes a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. The solid electrolyte included in the solid electrolyte layer (300) may be the same as or different from any one of the materials that can be included in the solid electrolyte included in the aforementioned anode active material layer (120).

[0059] The solid electrolyte layer (300) of one embodiment may include a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be manufactured by processing starting materials, such as Li2S or P2S5, by a melt quenching method or a mechanical milling method. Additionally, heat treatment may be performed after such processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. Furthermore, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above, for example. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form the solid electrolyte, the molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 50 : 50 to 90 : 10.

[0060] Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may be an argyrodite-type compound comprising one or more selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0061] Alternatively, sulfide-based solid electrolytes are Li 7-a-c M a PS 6-c X cIt may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)). Here, X may be F, Br, Cl, or I. M may be candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof.

[0062] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the azyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the solid electrolyte is, for example, 15 GPa to 35 GPa.

[0063] The solid electrolyte layer (300) may further include a binder. The binder included in the solid electrolyte layer (300) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these. The binder of the solid electrolyte layer (300) may be the same as or different from the binder included in the positive electrode active material layer (120) or the binder included in the coating layer (220).

[0064] The negative electrode layer (200) may include a negative electrode current collector (210) and a coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the coating layer (220) is placed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, that is, does not form any alloys or compounds with lithium. For example, the negative electrode current collector (210) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (210) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0065] The negative current collector (210) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (210) may, for example, have a plate-like or foil-like shape. Meanwhile, in one embodiment, the negative current collector (210) may be omitted.

[0066] The coating layer (220) can allow lithium metal to grow between the all-solid-state battery (10) and the negative current collector (210) during charging. The coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0067] The coating layer (220) may include metal and carbon. For example, the coating layer (220) may include at least one metal selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The coating layer (220) may include at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene. In one embodiment, the coating layer (220) may include a mixture of carbon black and silver (Ag).

[0068] The coating layer (220) may further include other additives in addition to metal and carbon. The coating layer (220) may further include at least one additive selected from the group consisting of, for example, binders, fillers, coating agents, dispersants, and ion-conducting aids.

[0069] The coating layer (220) may have a smaller thickness compared to the positive active material layer (120). The thickness of the coating layer (220) may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive active material layer (120). The thickness of the coating layer (220) may be, for example, 1 µm to 20 µm, 2 µm to 10 µm, or 3 µm to 7 µm. If the thickness of the coating layer (220) is excessively thin, lithium dendrites formed between the coating layer (220) and the negative current collector (210) may cause the coating layer (220) to collapse, thereby degrading the cycle characteristics of the all-solid-state battery (10). If the thickness of the coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) decreases and the internal resistance of the all-solid-state battery (10) due to the coating layer (220) increases, which may degrade the cycle characteristics of the all-solid-state battery (10).

[0070] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the coating layer (220) and the solid electrolyte layer (300).

[0071] The binder included in the coating layer (220) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these. The binder may include one or a plurality of different binders.

[0072] By including a binder in the coating layer (220), the coating layer (220) can be stably formed on the negative current collector (210). That is, the bonding strength between the coating layer (220) and the negative current collector (210) can be increased. In addition, cracking of the coating layer (220) is suppressed despite volume changes and / or relative position changes of the coating layer (220) during the charging and discharging process. If the coating layer (220) does not include a binder, the coating layer (220) can be easily separated from the negative current collector (210). As the coating layer (220) detaches from the negative current collector (210), the negative current collector (210) may come into contact with the solid electrolyte layer in the exposed portion of the negative current collector (210), thereby increasing the possibility of a short circuit.

[0073] The coating layer (220) is produced, for example, by providing a mixture in which the material constituting the coating layer (220) is dispersed onto a negative current collector (210). Since the material constituting the coating layer (220) includes a binder, stable dispersion of the material constituting the coating layer (220) is possible within the mixture. For example, when the mixture is applied onto the negative current collector (210) by a screen printing method, it is possible to suppress screen clogging (e.g., clogging by aggregates of metal and carbon) by the binder.

[0074] The coating layer (220) may have a smaller thickness compared to the positive active material layer (120). The thickness of the coating layer (220) may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive active material layer (120). The thickness of the coating layer (220) may be, for example, 1 µm to 20 µm, 2 µm to 10 µm, or 3 µm to 7 µm. If the thickness of the coating layer (220) is excessively thin, lithium dendrites formed between the coating layer (220) and the negative current collector (210) may cause the coating layer (220) to collapse, thereby degrading the cycle characteristics of the all-solid-state battery (10). If the thickness of the coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) decreases and the internal resistance of the all-solid-state battery (10) due to the coating layer (220) increases, which may degrade the cycle characteristics of the all-solid-state battery (10).

[0075] If the thickness of the coating layer (220) decreases, for example, the charging capacity of the coating layer (220) may also decrease. The charging capacity of the coating layer (220) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less compared to the charging capacity of the positive active material layer (120). The charging capacity of the coating layer (220) is, for example, 0.1% to 50%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% to 10%, 0.1% to 5%, or 0.1% to 2% compared to the charging capacity of the positive active material layer (120). If the charging capacity of the coating layer (220) is excessively small, the thickness of the coating layer (220) becomes very thin, and the same defect as the aforementioned defect that occurs when the thickness of the coating layer (220) becomes excessively thin may occur. If the charging capacity of the coating layer (220) increases excessively, the same defect as the aforementioned defect that occurs when the thickness of the coating layer (220) increases excessively may occur.

[0076] The charge capacity of the positive active material layer (120) can be obtained by multiplying the charge capacity density (mAh / g) of the positive active material by the mass of the positive active material in the positive active material layer (120). If the positive active material layer (120) contains various types of positive active materials, the [charge capacity density × mass] value is calculated for each positive active material, and the sum of these values ​​of the positive active materials is the charge capacity of the positive active material layer (120). The charge capacity of the coating layer (220) can also be calculated in the same way. That is, the charge capacity of the coating layer (220) is obtained by multiplying the charge capacity density (mAh / g) of the negative active material by the mass of the negative active material in the coating layer (220). If the coating layer (220) contains various types of negative active materials, the [charge capacity density × mass] value is calculated for each negative active material, and the sum of these values ​​of the negative active materials is the capacity of the coating layer (220). Here, the charge capacity density of the positive active material and the negative active material may be the capacity estimated using an all-solid-state half-cell using lithium metal as the counter electrode. The charge capacity of the positive active material layer (120) and the coating layer (220) can be directly measured by measuring the charge capacity using an all-solid-state half-cell. By dividing the measured charge capacity by the mass of each active material, the charge capacity density can be obtained. Meanwhile, in this specification, the “charge capacity” of the positive active material layer (120) and the coating layer (220) refers to the initial charge capacity measured during the first cycle of charging.

[0077]

[0078] When the anode layer of an all-solid-state battery is manufactured using a wet method, some solvent may not completely evaporate and may remain on the electrode; this residual solvent can cause continuous degradation of the sulfide-based solid electrolyte. Additionally, the residual solvent can reduce the ionic conductivity of the electrode by acting as a resistor. Similarly, when the solid electrolyte layer of an all-solid-state battery is manufactured using a wet method, the residual solvent can cause continuous degradation of the sulfide-based solid electrolyte and reduce the ionic conductivity of the solid electrolyte layer. In other words, if the content of residual solvent is excessively high, it can worsen the lifespan characteristics of the all-solid-state battery.

[0079] However, since residual solvent also plays a role in improving the flexibility of the anode layer and solid electrolyte layer, a drying process is typically performed so that a certain amount (e.g., 2,000 ppm) or more of solvent remains in order to prevent cracking of the anode layer and solid electrolyte layer and to improve durability.

[0080] The all-solid-state battery according to the embodiments of the present invention is manufactured using a predetermined low-reactivity, low-polarity solvent described below, thereby ensuring flexibility and excellent lifespan characteristics even while containing a very small amount of residual solvent.

[0081] Hereinafter, an anode layer according to embodiments of the present invention will be described in detail with reference to FIGS. 2 and FIGS. 3. FIGS. 2 is a cross-sectional view of an anode according to embodiments of the present invention. FIGS. 3 is an enlarged view of region M of FIGS. 2.

[0082] Referring to FIG. 2, the positive layer (100) may include a positive current collector (110) and a positive active material layer (120) on the positive current collector (110).

[0083] The positive current collector (110) may be the same as described above with reference to FIG. 1.

[0084] Referring to FIGS. 2 and 3, the positive active material layer (120) may include positive active material particles (PAM), first solid electrolyte particles (SOE1), and first residual solvent (RSL1).

[0085] The first residual solvent (RSL1) may be a liquid material that remains in the all-solid-state battery without being completely removed during the slurry drying process. In particular, it may be a liquid material that remains in the electrode. The first residual solvent (RSL1) may cause degradation of the solid electrolyte, thereby worsening lifespan characteristics, and may act as a resistor, thereby reducing ion conductivity.

[0086] The anode layer (100) according to the embodiments of the present invention can prevent deterioration of the sulfide-based solid electrolyte and improve the ionic conductivity of the anode layer (100) by including a very small amount of a low-polarity first residual solvent (RSL1).

[0087] The first residual solvent (RSL1) may be a low-polarity solvent with low reactivity with the sulfide-based solid electrolyte. In one embodiment, the first residual solvent (RSL1) has a δP value of 3.5 MPa, which is the polarity parameter of the Hansen solubility parameter (HSP). 0.5 It may be a low-polarity solvent with a value of 3.2 MPa or less. For example, the δP of the first residual solvent (RSL1) is 3.2 MPa. 0.5 Below, 2.5 MPa 0.5 2.0 MPa or less 0.5 It may be less than.

[0088] The Hansen solubility parameter is a solubility parameter introduced by Hildebrand that is divided into three components—δD, δP, and δH—and represented in three-dimensional space. δD represents the effect of nonpolar interactions, δP represents the effect of inter-dipole forces, and δH represents the effect of hydrogen bonding forces. Hansen solubility parameter values ​​for various monomers are listed, for example, in "Hansen Solubility Parameters: A Users Handbook" by Charles M. Hansen, and Hansen solubility parameter values ​​for monomers not listed can be estimated using computer software (Hansen Solubility Parameters in Practice (HSPiP)).

[0089] For example, the polarity parameter δP of the solvent being evaluated may be a value calculated by modeling the solubility characteristics of a reference solvent group using HSP. The reference solvent group may consist of solvents for which the solubility parameter (HSP) value is already known, for example, the reference solvent group may include hexane, toluene, chloroform, acetone, ethanol, dimethylformamide, water, etc.

[0090] First, the solvent to be evaluated can be mixed with a reference solvent and the absorbance can be measured to determine whether the solvent to be evaluated is soluble in the reference solvent. For example, if the absorbance is 0.2 or higher, the solvent to be evaluated can be considered to be soluble in the reference solvent.

[0091] Then, the solubility parameter values ​​(δD, δP, and δH) of the reference solvent group are plotted in a three-dimensional space using a Hansen sphere model. Through this, the interaction distance between the solvent to be evaluated and the reference solvent group can be calculated, and the polarity parameter value of the solvent to be evaluated can be estimated.

[0092] The first residual solvent (RSL1) has a small polarity within the above range, which can suppress the reaction with the sulfide-based solid electrolyte, thereby preventing the deterioration of the first solid electrolyte particle (SOE1). On the other hand, NMP (N-Methyl-2-pyrrolidone, δP = approximately 12.3 MPa) 0.5 Even if a very small amount of polar solvent such as ) remains, it can cause deterioration of the first solid electrolyte particle (SOE1) due to reaction with the sulfide-based solid electrolyte.

[0093] In one embodiment, the vapor pressure of the first residual solvent (RSL1) at 20°C may be 50 Pa or less. Specifically, it may be 20 Pa to 50 Pa, or 20 Pa to 35 Pa. Additionally, a solvent containing a long alkyl chain that causes large steric hindrance may contribute to suppressing vapor pressure (evaporation). If the vapor pressure exceeds the above range, cracks may occur due to the rapid evaporation of the solvent during the drying process. For example, if decalin with a vapor pressure of about 106 Pa at 20°C is used as a single solvent, cracks may occur in the anode layer due to the rapid evaporation of decalin during the drying process.

[0094] For example, the vapor pressure of the solvent can be measured using Techno Export’s Micro-Vapor Pressure Tester (VP TE-1000AE). Specifically, after the cathode active material layer is sliced ​​into a predetermined size, the vapor pressure can be measured using the above instrument under conditions of 20°C.

[0095] For example, the δP of the first residual solvent (RSL1) is 3.5 MPa 0.5 It is less than or equal to, and the vapor pressure at 20°C can be 50 Pa or less.

[0096] In one embodiment, the density of the first residual solvent (RSL1) may be 1 g / ml or less. Specifically, the density of the first residual solvent (RSL1) measured at 25°C may be 0.6 g / ml to 1.0 g / ml, or 0.8 g / ml to 1.0 g / ml. By having the above density range, appropriate viscosity can be secured. In addition, when using a low-polarity solvent with high steric hindrance, cracks can be prevented without adversely affecting cell performance even if the content of the first residual solvent (RSL1) in the positive active material layer (120) becomes 1,000 ppm or less.

[0097] In one embodiment, the first residual solvent (RSL1) may include a compound represented by the following chemical formula 1.

[0098] [Chemical Formula 1]

[0099] R-COO-R'

[0100] In the above chemical formula 1, R and R' can each independently be alkyls having 4 to 6 carbon atoms.

[0101] The above alkyl group having 4 to 6 carbon atoms may be an unsubstituted alkyl.

[0102] Specifically, the compound represented by the above chemical formula 1 may be butyl butyrate, butyl pentylate, butyl hexylate, pentyl pentylate, hexyl butyrate, butyl heptylate, hexyl pentylate, butyl octylate, pentyl heptylate, or hexyl hexylate.

[0103] In one embodiment, the first residual solvent (RSL1) may include hexyl butyrate. The content of hexyl butyrate in the first residual solvent (RSL1) may be 90 weight% or more or 99 weight% or more. As an example, the first residual solvent (RSL1) may be a hexyl butyrate single solvent.

[0104] In one embodiment, the content of the first residual solvent (RSL1) in the positive active material layer (120) may be 1,000 ppm or less. The content of the first residual solvent (RSL1) in the positive active material layer (120) may be greater than 0 ppm. Specifically, it may be 1 ppm to 1,000 ppm, 100 ppm to 1,000 ppm, 400 ppm to 1,000 ppm, 500 ppm to 1,000 ppm, 600 ppm to 800 ppm, or 600 ppm to 800 ppm. As an example, the content of hexyl butyrate in the positive active material layer (120) may be 1,000 ppm or less. Specifically, it may be 1 ppm to 1,000 ppm, 100 ppm to 1,000 ppm, 400 ppm to 1,000 ppm, 500 ppm to 1,000 ppm, 600 ppm to 800 ppm, or 600 ppm to 800 ppm. If the content of the first residual solvent (RSL1) exceeds the above range, the lifespan characteristics may be degraded due to the deterioration of the solid electrolyte, and the charge / discharge characteristics may be degraded due to the decrease in ion conductivity.

[0105] In one embodiment, the content of the first residual solvent (RSL1) in the positive electrode active material layer (120) can be measured through gas chromatography-mass spectrometry (GC-MS), thermogravimetric analysis (TGA), etc. For example, the content of the first residual solvent (RSL1) in the positive electrode active material layer (120) may be a value measured by gas chromatography-mass spectrometry (GC-MS).

[0106] For example, GC-MS can be performed using an Agilent GC system (8890 GC) and an MS system (5977B single quadrupole GC / MS). Specifically, the GC system conditions can be set as follows: i) the column is an Agilent J&W DB-5MS UI, ii) the flow rate of the carrier gas (helium, He) is 1.0 mL / min, iii) the oven temperature is maintained at 60°C for 2 minutes, then increased at a rate of 10°C / min and maintained at 280°C for 10 minutes, iv) the split ratio is 10:1. The MS system conditions can be set as follows: i) ionization energy: 70 eV, scan range: m / z 50-500. The content of the first residual solvent (RSL1) in the anode active material layer (120) may be measured under the above conditions.

[0107] The positive active material particle (PAM) may include at least one of the positive active materials described above with reference to FIG. 1. The first solid electrolyte particle (SOE1) may include at least one of the sulfide-based solid electrolytes described above with reference to FIG. 1.

[0108] In one embodiment, the positive active material particle (PAM) may include a nickel-based oxide having a layered rock salt structure. As an example, the positive active material particle (PAM) may include at least one of nickel cobalt manganese oxide (NCM) and nickel cobalt aluminum oxide (NCA).

[0109] In one embodiment, the average particle size (D50) of the positive active material particles (PAM) may be 5 μm to 25 μm. For example, the average particle size (D50) of the positive active material particles (PAM) may be 3 μm to 25 μm, 5 μm to 25 μm, 5 μm to 20 μm, or 8 μm to 18 μm. A positive active material having such a particle size range can be harmoniously mixed with other components within the positive active material layer and can achieve high capacity and high energy density. The average particle size of the positive active material particles (PAM) may be measured using a microscope image, for example, by measuring the size of about 20 particles in a scanning electron microscope image to obtain a particle size distribution and calculating D50 from there.

[0110] In one embodiment, the first solid electrolyte particle (SOE1) may include a sulfide-based solid electrolyte. As an example, the first solid electrolyte particle (SOE1) may include Li2S-P2S5, Li2S-P2S5-LiX (where X is F, Cl, Br, or I), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (m, n are positive numbers, uppercase “Z” is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, uppercase “M” is one of P, Si, Ge, B, Al, Ga, In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I xIt may include at least one selected from (0≤x≤2).

[0111] In one embodiment, the first solid electrolyte particle (SOE1) may include an azirodite-type sulfide-based solid electrolyte represented by the following chemical formula 2.

[0112] [Chemical Formula 2]

[0113] Li 7-a1-c1 M a1 PS 6-c1 X c1

[0114] In Chemical Formula 2, X can be Cl, Br, or I.

[0115] In Chemical Formula 2, M is candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or their It can be a combination.

[0116] In Chemical Formula 2, 0≤a1≤2 and 0≤c1≤2 may be possible.

[0117] In one embodiment, the average particle size (D50) of the first solid electrolyte particle (SOE1) may be 10.0 μm or less. For example, the average particle size (D50) of the first solid electrolyte particle (SOE1) may be 0.1 μm to 10.0 μm, 0.5 μm to 10.0 μm, 0.5 μm to 5.0 μm, 0.5 μm to 4.0 μm, 0.1 μm to 3.0 μm, 0.5 μm to 2.0 μm, or 0.5 μm to 1.5 μm. The first solid electrolyte particle (SOE1) may be a small particle having an average particle size (D50) of 0.5 μm to 1.0 μm. The first solid electrolyte particles (SOE1) with this particle size range can effectively penetrate between solid particles within the battery, and have excellent contact with the electrode active material and connectivity between solid electrolyte particles. The average particle size of the first solid electrolyte particles (SOE1) may be measured by microscopic images, for example, by measuring the size of about 20 particles in a scanning electron microscope image to obtain a particle size distribution and calculating D50 from it.

[0118] In one embodiment, the content of the positive active material particles (PAM) in the positive active material layer (120) may be 80% to 92% by weight. For example, it may be 80% to 92% by weight, 80% to 90% by weight, or 80% to 85% by weight.

[0119] Referring again to FIG. 3, in one embodiment, the positive active material layer (120) may further include a first binder (BND1). The first binder (BND1) may include at least one of the positive layer binders described above with reference to FIG. 1.

[0120] In one embodiment, based on 100% by weight of the total weight of the positive active material layer (120), the content of the first binder (BND1) may be 0.2% by weight to 2.0% by weight.

[0121] In one embodiment, the first binder (BND1) may include at least one of a rubber-based binder and a fluorovinylidene fluoride-based binder.

[0122] In one embodiment, the first binder (BND1) may include a rubber-based binder. As an example, the rubber-based binder may include at least one of SBR (styrene butadiene rubber), SBS (styrene butadiene block copolymer), SEBS (styrene ethylene butadiene styrene block copolymer), SIBS (styrene isobutylene styrene block copolymer) and EPDM (ethylene propylene diene monomer).

[0123] In one embodiment, based on 100% by weight of the total weight of the positive electrode active material layer (120), the content of the rubber-based binder may be 0.2% by weight to 2.0% by weight. The first binder (BND1) may further include a polyethyleneimine-based dispersant. The polyethyleneimine-based dispersant is a polymer comprising repeating units derived from ethyleneimine monomers. Based on 100% by weight of the total weight of the positive electrode active material layer (120), the content of the polyethyleneimine-based dispersant may be 0.2% by weight to 1.0% by weight.

[0124] In another embodiment, the first binder (BND1) may include a polyvinylidene fluoride-based binder. The polyvinylidene fluoride-based binder is a polymer comprising repeating units derived from vinylidene fluoride monomers, and specifically, the polyvinylidene fluoride-based binder may include at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE). As an example, the first binder (BND1) may include polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). In particular, using PVDF-HFP can further improve the flexibility of the anode layer (100).

[0125] In one embodiment, based on 100% by weight of the total weight of the positive active material layer (120), the content of the polyvinylidene fluoride-based binder may be 0.2% to 1.5% by weight. Specifically, the content of the polyvinylidene fluoride-based binder may be 0.5% to 1.2% by weight, or 0.5% to 1.0% by weight. By including the polyvinylidene fluoride-based binder within the above range, the ionic conductivity and electronic conductivity of the positive layer (100) can be maintained, while the binding force between the positive active material layer (120) and the positive current collector (110), and the binding force between the particles of the positive active material layer can be improved. Furthermore, the flexibility of the positive layer (100) can be improved.

[0126] In one embodiment, the positive active material layer (120) may further include a conductive material. The conductive material may include at least one of those described above with reference to FIG. 1.

[0127]

[0128] Hereinafter, a solid electrolyte layer according to embodiments of the present invention will be described in detail with reference to FIGS. 4 and FIGS. 5. FIGS. 4 is a cross-sectional view of an anode according to embodiments of the present invention. FIGS. 5 is an enlarged view of the M' region of FIGS. 4.

[0129] Referring to FIGS. 4 and 5, the solid electrolyte layer (300) may include a second solid electrolyte particle (SOE2) and a second residual solvent (RSL2).

[0130] In one embodiment, the second residual solvent (RSL2) may be a liquid material that remains in the all-solid-state battery without being completely removed during the slurry drying process, similar to the first residual solvent (RSL1) described above. In particular, the second residual solvent (RSL2) may be a liquid material that remains in the solid electrolyte layer. The second residual solvent (RSL2) may cause degradation of the solid electrolyte, thereby worsening lifespan characteristics, and may act as a resistor to reduce ion conductivity. However, the second residual solvent (RSL2) may exist in a very small amount to improve the flexibility of the electrode.

[0131] The solid electrolyte layer (300) according to the embodiments of the present invention can prevent deterioration of the sulfide-based solid electrolyte and improve the ion conductivity of the solid electrolyte layer (100) by including a very small amount of a low-polarity second residual solvent (RSL2).

[0132] The second residual solvent (RSL2) may be a low-polarity solvent. In one embodiment, the second residual solvent (RSL2) has a polarity parameter δP of the Hansen solubility parameter (HSP) of 3.5 MPa. 0.5 It may be a low-polarity solvent with a value of 3.5 MPa or less. For example, the δP of the second residual solvent (RSL2) is 3.5 MPa. 0.5 Below, 3.2 MPa 0.5 Below, 2.5 MPa 0.5 2.0 MPa or less 0.5 It may be less than.

[0133] The second residual solvent (RSL2) has a small polarity such as the above range, which can suppress the reaction with the sulfide-based solid electrolyte, thereby preventing the deterioration of the second solid electrolyte particles (SOE2).

[0134] In one embodiment, the vapor pressure of the second residual solvent (RSL2) at 20°C may be 50 Pa or less. Specifically, it may be 20 Pa to 50 Pa, or 20 Pa to 35 Pa. If the vapor pressure exceeds the above range, cracks may occur due to rapid evaporation of the solvent during the drying process. For example, if decalin with a vapor pressure of about 106 Pa at 20°C is used as a single solvent, cracks may occur in the solid electrolyte layer (300) due to rapid evaporation of the decalin during the drying process.

[0135] For example, the vapor pressure of a solvent can be measured using the Micro-Vapor Pressure Tester (VP TE-1000AE) of Techno Export. Specifically, after dividing the solid electrolyte layer into sections of a predetermined size, the vapor pressure can be measured using the above instrument under conditions of 20°C.

[0136] For example, the δP of the second residual solvent (RSL2) is 3.5 MPa 0.5 It is less than or equal to, and the vapor pressure at 20°C can be 50 Pa or less.

[0137] In one embodiment, the density of the second residual solvent (RSL2) may be 1 g / ml or less. Specifically, the density of the second residual solvent (RSL2) measured at 25°C may be 0.6 g / ml to 1.0 g / ml, or 0.8 g / ml to 1.0 g / ml. By having the above density range, appropriate viscosity can be secured. In addition, cracking can be prevented even if the content of the second residual solvent (RSL2) in the solid electrolyte layer (300) is 1,000 ppm or less.

[0138] In one embodiment, the second residual solvent (RSL2) may include a compound represented by the following chemical formula 1.

[0139] [Chemical Formula 1]

[0140] R-COO-R'

[0141] In the above chemical formula 1, R and R' can each independently be alkyls having 4 to 6 carbon atoms.

[0142] The above alkyl group having 4 to 6 carbon atoms may be an unsubstituted alkyl.

[0143] Specifically, the compound represented by the above chemical formula 1 may be butyl butyrate, butyl pentylate, butyl hexylate, pentyl pentylate, hexyl butyrate, butyl heptylate, hexyl pentylate, butyl octylate, pentyl heptylate, or hexyl hexylate.

[0144] In one embodiment, the second residual solvent (RSL2) may include hexyl butyrate. The content of hexyl butyrate in the second residual solvent (RSL2) may be 90 weight% or more or 99 weight% or more. As an example, the second residual solvent (RSL2) may be a hexyl butyrate single solvent.

[0145] In one embodiment, the content of the second residual solvent (RSL2) in the solid electrolyte layer (300) may be 1,000 ppm or less. The content of the second residual solvent (RSL2) in the solid electrolyte layer (300) may be greater than 0 ppm. Specifically, it may be 1 ppm to 1,000 ppm, 100 ppm to 1,000 ppm, 400 ppm to 1,000 ppm, 500 ppm to 1,000 ppm, 600 ppm to 800 ppm, or 600 ppm to 800 ppm. As an example, the content of hexyl butyrate in the positive electrode active material layer (120) may be 1,000 ppm or less. Specifically, it may be 1 ppm to 1,000 ppm, 100 ppm to 1,000 ppm, 400 ppm to 1,000 ppm, 500 ppm to 1,000 ppm, 600 ppm to 800 ppm, or 600 ppm to 800 ppm. If the content of the second residual solvent (RSL2) exceeds the above range, the lifespan characteristics may be degraded due to the deterioration of the solid electrolyte, and the charge / discharge characteristics may be degraded due to the decrease in ionic conductivity.

[0146] In one embodiment, the content of the second residual solvent (RSL2) in the solid electrolyte layer (300) can be measured through gas chromatography-mass spectrometry (GC-MS), thermogravimetric analysis (TGA), etc. For example, the content of the second residual solvent (RSL2) in the solid electrolyte layer (300) may be a value measured by gas chromatography-mass spectrometry (GC-MS).

[0147] The content of the second residual solvent (RSL2) in the solid electrolyte layer (300) can be measured in the same way as the measurement method of the first residual solvent (RSL1) in the anode active material layer (120) described above.

[0148] In one embodiment, the second solid electrolyte particle (SOE2) may include a sulfide-based solid electrolyte. As an example, the second solid electrolyte particle (SOE2) may include Li2S-P2S5, Li2S-P2S5-LiX (where X is F, Cl, Br, or I), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (m, n are positive numbers, uppercase “Z” is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, uppercase “M” is one of P, Si, Ge, B, Al, Ga, In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include at least one selected from (0≤x≤2).

[0149] In one embodiment, the second solid electrolyte particle (SOE2) may include an azirodite-type sulfide-based solid electrolyte represented by the following chemical formula 3.

[0150] [Chemical Formula 3]

[0151] Li 7-a2-c2 M a2 PS 6-c2 X c2

[0152] In Chemical Formula 3, X can be Cl, Br, or I.

[0153] In Chemical Formula 3, M is candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or their It can be a combination.

[0154] In Chemical Formula 3, 0≤a2≤2 and 0≤c2≤2 may be possible.

[0155] In one embodiment, the average particle size (D50) of the second solid electrolyte particle (SOE2) may be 10.0 μm or less. For example, the average particle size (D50) of the second solid electrolyte particle (SOE2) may be 0.1 μm to 10.0 μm, 0.5 μm to 10.0 μm, 0.5 μm to 5.0 μm, 0.5 μm to 4.0 μm, 0.1 μm to 3.0 μm, 0.5 μm to 2.0 μm, or 0.5 μm to 1.5 μm. The second solid electrolyte particle (SOE2) may be a small particle having an average particle size (D50) of 0.1 μm to 1.0 μm. Alternatively, the second solid electrolyte particle (SOE2) may be a large particle having an average particle size (D50) of 1.5 μm to 10.0 μm. The average particle size of the second solid electrolyte particle (SOE2) may be measured by a microscope image, for example, by measuring the size of about 20 particles in a scanning electron microscope image to obtain a particle size distribution and calculating D50 from it.

[0156] In one embodiment, the average particle size (D50) of the second solid electrolyte particle (SOE2) may be larger than the average particle size (D50) of the first solid electrolyte particle (SOE1) described above with reference to FIG. 3. Specifically, the first solid electrolyte particle (SOE1) may be a small particle with an average particle size (D50) of 0.1 μm to 1.0 μm, and the second solid electrolyte particle (SOE2) may be a large particle with an average particle size (D50) of 1.5 μm to 10.0 μm.

[0157] Referring again to FIG. 5, in one embodiment, the solid electrolyte layer (300) may further include a second binder (BND2). The second binder (BND2) may include at least one of the solid electrolyte layer binders described above with reference to FIG. 1.

[0158] In one embodiment, the second binder (BND2) may be the same as the first binder (BND1) described above with reference to FIG. 3.

[0159] In one embodiment, the second binder (BND2) may include a polyvinylidene fluoride-based binder. The polyvinylidene fluoride-based binder is a polymer comprising repeating units derived from vinylidene fluoride monomers, and specifically, the polyvinylidene fluoride-based binder may include at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE). As an example, the second binder (BND2) may include polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). In particular, using PVDF-HFP can further improve the flexibility of the solid electrolyte layer (300).

[0160] In one embodiment, based on 100% by weight of the total weight of the solid electrolyte layer (300), the content of the second binder (BND2) may be 0.2% by weight to 7% by weight. Specifically, based on 100% by weight of the total weight of the solid electrolyte layer (300), the content of the polyvinylidene fluoride-based binder may be 0.2% by weight to 5% by weight, 0.5% by weight to 3% by weight, or 0.5% by weight to 2.0% by weight. By including the polyvinylidene fluoride-based binder within the above range, the ionic conductivity and electronic conductivity of the solid electrolyte layer (100) can be maintained while improving the binding strength between particles within the solid electrolyte layer (300). Furthermore, the flexibility of the solid electrolyte layer (300) can be improved.

[0161]

[0162] Hereinafter, a method for manufacturing an all-solid-state battery including an anode layer and a solid electrolyte layer according to embodiments of the present invention will be described.

[0163] A method for manufacturing an all-solid-state battery according to one embodiment may include: preparing a positive electrode layer having a residual solvent content of 1,000 ppm or less; preparing a solid electrolyte layer having a residual solvent content of 1,000 ppm or less; preparing a negative electrode layer; and manufacturing an all-solid-state battery by placing the solid electrolyte layer between the positive electrode layer and the negative electrode layer.

[0164]

[0165] FIGS. 6a to 6c are cross-sectional views for explaining a method for manufacturing an all-solid-state battery according to one embodiment. Referring to FIGS. 6a and 6b, a method for manufacturing an all-solid-state battery according to one embodiment includes preparing a positive active material layer (110) having a residual solvent content of 1,000 ppm or less.

[0166] The positive active material slurry (PAS) may include positive active material particles (PAM), first solid electrolyte particles (SOE1), and a first binder (BND1) as solids. The positive active material particles (PAM), first solid electrolyte particles (SOE1), and first binder (BND1) may be the same as those described above with reference to FIG. 2 and FIG. 3. The positive active material slurry (PAS) may further include the conductive material described above with reference to FIG. 1 as solids.

[0167] In one embodiment, the content of the positive active material particles (PAM) in the solids within the positive active material slurry (PAS) may be 80% to 92% by weight. For example, it may be 80% to 92% by weight, 80% to 90% by weight, or 80% to 85% by weight.

[0168] The positive active material slurry (PAS) may contain a solvent. The solvent may be a low-polarity solvent with low reactivity with the solid electrolyte.

[0169] In one embodiment, the solvent in the cathode active material slurry (PAS) has a polarity parameter δP of the Hansen solubility parameter (HSP) of 3.5 MPa 0.5 It may be a low-polarity solvent with a value of 3.2 MPa or less. For example, the δP of the first residual solvent (RSL1) is 3.2 MPa. 0.5 Below, 2.5 MPa 0.5 2.0 MPa or less 0.5 It may be less than or equal to the following. The solvent may include hexyl butyrate.

[0170] For example, the solvent in the positive active material slurry (PAS) may be a single solvent of hexyl butyrate.

[0171] The solvent in the positive electrode active material slurry (PAS) evaporates through the drying process, and depending on the drying conditions, a very small amount may remain in the positive electrode layer.

[0172] Referring to FIG. 6a, in one embodiment, a positive active material slurry (PAS) can be applied and dried on a positive current collector (110) to form a positive active material layer (120). Through this, a positive layer (100) comprising a positive current collector (110) and a positive active material layer (120) on the positive current collector (110) can be prepared.

[0173] In another embodiment, although not illustrated, an anode active material slurry (PAS) can be applied and dried on a release film to form an anode active material layer (120). The formed anode active material layer (120) can be laminated and laminated onto an anode current collector (110) to prepare an anode layer (100).

[0174] Drying of the positive active material slurry (PAS) can be performed so that the residual solvent content in the positive layer (100) is 1,000 ppm or less. Specifically, drying of the positive active material slurry (PAS) can be performed so that the residual solvent content in the positive layer (100) is 1 ppm to 1,000 ppm, 100 ppm to 1,000 ppm, 400 ppm to 1,000 ppm, 500 ppm to 1,000 ppm, 600 ppm to 800 ppm, or 600 ppm to 800 ppm.

[0175] In one embodiment, drying can be performed in a vacuum environment.

[0176] In one embodiment, the drying temperature of the positive active material slurry (PAS) may be 60°C to 150°C. As an example, the drying temperature may be 60°C to 120°C, 60°C to 100°C, or 70°C to 90°C.

[0177] In one embodiment, the drying time of the positive active material slurry (PAS) can be appropriately selected according to the drying temperature. For example, the drying time may be 5 minutes to 120 minutes. For example, the drying time may be 10 minutes to 240 minutes, 15 minutes to 240 minutes, 10 minutes to 200 minutes, 15 minutes to 200 minutes, 15 minutes to 150 minutes, or 15 minutes to 80 minutes. For example, the positive active material slurry (PAS) may be dried at 70°C to 90°C for 15 minutes to 200 minutes after application to form a positive active material layer (120) with a residual solvent content of 1,000 ppm or less.

[0178] As a result, an anode layer (100) including an anode active material layer (120) having a residual solvent content of 1,000 ppm or less can be prepared.

[0179]

[0180] Referring again to FIG. 6a and FIG. 6b, a method for manufacturing an all-solid-state battery according to one embodiment includes preparing a solid electrolyte layer (300) having a residual solvent content of 1,000 ppm or less.

[0181] In one embodiment, a solid electrolyte slurry (SES) can be applied and dried on a release film to form a film-shaped solid electrolyte layer (300).

[0182] Drying of the solid electrolyte slurry (SES) can be performed so that the residual solvent content in the solid electrolyte layer (300) is 1,000 ppm or less. Specifically, drying of the solid electrolyte slurry (SES) can be performed so that the residual solvent content in the solid electrolyte layer (300) is 500 ppm to 1,000 ppm, 500 ppm to 800 ppm, or 600 ppm to 800 ppm.

[0183] In one embodiment, drying can be performed in a vacuum environment.

[0184] In one embodiment, the drying temperature of the solid electrolyte slurry (SES) may be 60°C to 150°C. As an example, the drying temperature may be 60°C to 120°C, 60°C to 100°C, or 70°C to 90°C.

[0185] In one embodiment, the drying time of the solid electrolyte slurry (SES) can be appropriately selected according to the drying temperature. For example, the drying time may be 5 minutes to 240 minutes. For example, the drying time may be 10 minutes to 240 minutes, 15 minutes to 240 minutes, 10 minutes to 200 minutes, 15 minutes to 200 minutes, 15 minutes to 150 minutes, or 15 minutes to 80 minutes.

[0186] For example, a solid electrolyte slurry (SES) can be applied and then dried at 70°C to 90°C for 15 to 200 minutes to form a solid electrolyte layer (120) with a residual solvent content of 1,000 ppm or less.

[0187] As a result, a solid electrolyte layer (300) with a residual solvent content of 1,000 ppm or less can be prepared.

[0188]

[0189] A method for manufacturing an all-solid-state battery according to one embodiment may include preparing a negative electrode layer. Specifically, a negative electrode layer (200) may be prepared by forming a coating layer (220) on a negative electrode current collector (210). The negative electrode current collector (210) and the coating layer (220) may be the same as those described above with reference to FIG. 1.

[0190] In one embodiment, referring to FIG. 6c, a solid electrolyte layer (300) can be interposed between the anode layer (100) and the cathode layer (200) described above to manufacture an all-solid-state battery.

[0191]

[0192] Hereinafter, embodiments and comparative examples of the present invention are described. However, the following embodiments are merely examples of the present invention, and the present invention is not limited to the following embodiments.

[0193]

[0194] Example 1

[0195] (Cathode layer manufacturing)

[0196] A Ni foil with a thickness of 10 μm was prepared as a cathode current collector. Additionally, carbon black (CB) with a primary particle size of approximately 30 nm and silver (Ag) particles with an average particle size (D50) of approximately 60 nm were prepared as cathode coating layer materials. 4 g of a mixed powder, prepared by mixing carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1, was placed in a container, and 4 g of an NMP solution containing 7 wt% of PVDF binder (Kureha # 9300) was added to prepare a mixed solution. Subsequently, a slurry was prepared by stirring the mixed solution while gradually adding NMP to it. The prepared slurry was applied to a Ni sheet using a bar coater and dried in air at 80°C for 10 minutes. The resulting laminate was vacuum dried at 40°C for 10 hours. The dried laminate was cold-roll-pressed at a pressure of 1.5 ton / cm to flatten the surface of the cathode coating layer of the laminate. The cathode layer was fabricated through the above process.

[0197] (Anode layer manufacturing)

[0198] LiNi with an average particle size (D50) of 8 µm as a positive electrode active material 0.8 Co 0.1 Al 0.1O2(NCA) was prepared. Li6PS5Cl, an argyrodite-type crystal (D50 = 0.5 μm, crystalline), was prepared as the solid electrolyte. PVDF-HFP was prepared as the binder. Carbon nanofibers (CNF) were prepared as the conductive material. These materials were added to a hexyl butyrate solvent and mixed in a weight ratio of positive active material : solid electrolyte : conductive material : binder = 84 : 11.5 : 3 : 1.5 to prepare a positive active material slurry. The positive active material slurry was applied onto carbon-coated aluminum foil and dried at 80°C for 15 minutes to prepare a positive layer.

[0199] (Manufacturing of solid electrolyte membranes)

[0200] A Li6PS5Cl sulfide-based solid electrolyte (D50 = 3 μm, crystalline), which is an argyrodite-type crystal, was prepared. PVDF-HFP was prepared as a binder. A solid electrolyte slurry was prepared by adding the solid electrolyte and the binder to a hexyl butyrate solvent and mixing them so that the weight ratio of solid electrolyte to binder was 98.5 to 1.5. After molding the solid electrolyte slurry into a sheet shape, a solid electrolyte membrane (which subsequently forms the solid electrolyte layer of the all-solid-state battery) was prepared by drying at 80°C for 15 minutes.

[0201] (Solid-state battery)

[0202] An all-solid-state battery was manufactured by sequentially stacking the cathode layer, solid electrolyte layer, and anode layer prepared in the manner described above, and then performing lamination.

[0203]

[0204] Example 2

[0205] An all-solid-state battery was prepared in the same manner as in Example 1, except that the positive active material slurry and the solid electrolyte slurry were each coated, dried at 80°C for 15 minutes, and then vacuum dried at 80°C for 1 hour.

[0206]

[0207] Example 3

[0208] An all-solid-state battery was prepared in the same manner as in Example 1, except that the positive active material slurry and the solid electrolyte slurry were each coated, dried at 80°C for 15 minutes, and then vacuum dried at 80°C for 2 hours.

[0209]

[0210] Example 4

[0211] An all-solid-state battery was prepared in the same manner as in Example 1, except that the positive active material slurry and the solid electrolyte slurry were each coated, dried at 80°C for 15 minutes, and then vacuum dried at 80°C for 3 hours.

[0212]

[0213] Comparative Example 1

[0214] An all-solid-state battery was prepared in the same manner as in Example 1, except that the positive active material slurry and the solid electrolyte slurry were each dried at 80°C for 12 minutes after application.

[0215]

[0216] Comparative Example 2

[0217] An all-solid-state battery was prepared in the same manner as in Example 1, except that the positive active material slurry and the solid electrolyte slurry were each dried at 80°C for 10 minutes after application.

[0218]

[0219] Comparative Example 3

[0220] An all-solid-state battery was prepared in the same manner as in Example 1, except that the positive active material slurry and the solid electrolyte slurry were each dried at 80°C for 8 minutes after application.

[0221]

[0222] Comparative Example 4

[0223] The anode layer and solid electrolyte layer were prepared in the same manner as in Example 1, except for the following i) and ii):

[0224] i) Decalin was used instead of hexyl butyrate as a solvent when preparing the cathode active material slurry, and the coated cathode active material slurry was dried at 80°C for 15 minutes.

[0225] ii) When preparing the solid electrolyte slurry, decalin was used instead of hexyl butyrate as a solvent, and the coated solid electrolyte slurry was dried at 80°C for 15 minutes.

[0226] As shown in the results of Table 1 below, multiple cracks occurred in the manufactured anode layer and solid electrolyte layer, making it impossible to manufacture an all-solid-state battery.

[0227] The anode layer and solid electrolyte layer prepared according to the above-described examples and comparative examples were each stirred in methanol. After separating the solid components using a centrifuge, gas chromatography-mass spectrometry (GC-MS) was performed on the remaining solution to measure the amount of residual solvent.

[0228] Residual Solvent Residual solvent content in anode layer (ppm) Residual solvent content in solid electrolyte layer (ppm) Example 1: Hexyl Butylate 920914 Example 2: Hexyl Butylate 773752 Example 3: Hexyl Butylate 618602 Example 4: Hexyl Butylate 532515 Comparative Example 1: Hexyl Butylate 12311221 Comparative Example 2: Hexyl Butylate 15101564 Comparative Example 3: Hexyl Butylate 20101994 Comparative Example 4: Decalin 845820

[0229] Evaluation Example 1: Whether cracks occurred. For each example and comparative example, after manufacturing three anode layers and solid electrolyte layers, whether surface cracks occurred was checked and is shown in Table 2.

[0230] Number of cracked anode layers Number of cracked solid electrolyte layers Example 100 Example 200 Example 300 Example 410 Comparative Example 100 Comparative Example 200 Comparative Example 300 Comparative Example 432

[0231] Referring to Table 2, it can be seen that when decalin is used instead of hexyl butyrate as the solvent, cracks occur in the anode layer and solid electrolyte layer when dried to a residual solvent content of 1,000 ppm or less (see Comparative Example 4). On the other hand, when hexyl butyrate is used as the solvent, it can be seen that cracks do not occur in the anode layer and solid electrolyte layer even when dried to a solvent content of 1,000 ppm or less (see Examples 1 to 4).

[0232] Evaluation Example 2: Measurement of ionic conductivity of the anode layer and solid electrolyte layer

[0233] The ionic conductivity of the anode layer and the solid electrolyte layer according to the examples and comparative examples was evaluated.

[0234] The positive active material layer (coating) prepared in each example and comparative example was die-cut into a circular shape with a diameter of 10 mm, and a sample was prepared with substrates attached to both sides, placed in a measuring jig, and pressed with a pressure of 10 Nm. The impedance of the prepared sample was measured at an amplitude of 10 mV, a frequency of 0.01 Hz to 1 MHz, and 45°C. The resistance value was determined from the arc of the Nyquist plot of the impedance measurement results, and the ionic conductivity was calculated by considering the area and thickness of the specimen. The measurement results are shown in Table 3 below.

[0235] A sample for measuring ionic conductivity was prepared by punching a solid electrolyte layer prepared in each example and comparative example into a circular shape with a diameter of 10 mm, placing it in a mold, applying pressure of 350 mPa, and then coating both sides of the pellet with an indium (In) thin film. The impedance of the prepared sample was measured at an amplitude of 10 mV, a frequency of 0.01 Hz to 1 MHz, and 45°C. The resistance value was determined from the arc of the Nyquist plot of the impedance measurement results, and the ionic conductivity was calculated by considering the area and thickness of the specimen. The measurement results are shown in Table 3 below.

[0236] Anode active material layer ionic conductivity (mS / cm) Solid electrolyte layer ionic conductivity (mS / cm) Example 10.76 4.14 Example 20.76 4.16 Example 30.78 4.17 Example 40.79 4.17 Comparative Example 10.20 2.05 Comparative Example 20.16 1.48 Comparative Example 30.09 1.02

[0237] Referring to Table 3, it can be seen that the ionic conductivity decreases significantly when the residual solvent in the anode layer and solid electrolyte layer exceeds 1,000 ppm (see Comparative Examples 1 to 3).

[0238]

[0239] Evaluation Example 3: Life Characteristics

[0240] The lifespan characteristics of the all-solid-state batteries manufactured according to the examples and comparative examples were evaluated through charge-discharge tests. The all-solid-state batteries were placed in a chamber at 45°C to perform charge-discharge. A constant current of 0.33C was charged until the battery voltage reached 4.25V, and then charged at a constant voltage of 4.25V until the current value reached 0.1C. Subsequently, discharge was performed at a constant current of 0.33C until the battery voltage reached 2.5V. This charge-discharge cycle was performed 50 times. A 10-minute rest period was observed after each charge and discharge step in each cycle. The discharge capacity of the 1st and 50th charge-discharge cycles was measured, and the capacity retention rate (%) was calculated using Equation 1 below. The discharge capacity and the capacity retention rate of the all-solid-state batteries according to the 50-cycle examples and comparative examples were measured and are shown in Table 4.

[0241] [Equation 1]

[0242] Capacity Retention Rate (%) = [Discharge Capacity of 50 Cycles / Discharge Capacity of 1 Cycle] × 100

[0243] Volume Retention Rate (%) Example 198.1 Example 298.5 Example 398.2 Example 498.6 Comparative Example 195.1 Comparative Example 293.8 Comparative Example 391.2

[0244] Referring to Table 4, it can be seen that the capacity retention rate decreases significantly when the residual solvent in the anode layer and solid electrolyte layer exceeds 1,000 ppm (see Comparative Examples 1 to 3).

Claims

1. A positive electrode layer including a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector; A negative electrode layer; and Including a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer, The positive electrode active material layer includes positive electrode active material particles and solid electrolyte particles, At least one of the positive electrode active material layer and the solid electrolyte layer further includes a residual solvent, The content of the residual solvent in the positive electrode active material layer or the solid electrolyte layer is 1,000 ppm or less, The residual solvent includes a compound represented by the following Chemical Formula 1, all-solid-state battery: [Chemical Formula 1] R-COO-R' In Chemical Formula 1, each of R and R' is independently an alkyl having 4 to 6 carbon atoms.

2. The all-solid-state battery according to claim 1, The compound represented by Chemical Formula 1 is hexyl butyrate.

3. The all-solid-state battery according to claim 1, Each of the positive electrode active material layer and the solid electrolyte layer includes the residual solvent, The content of the residual solvent in each of the positive electrode active material layer and the solid electrolyte layer is 1,000 ppm or less.

4. The all-solid-state battery according to claim 1, The positive electrode active material particles include a lithium transition metal oxide, The lithium transition metal oxide has a layered rock salt-type crystal structure and includes nickel.

5. The all-solid-state battery according to claim 1, The average particle diameter of the positive electrode active material particles is 5 μm to 25 μm.

6. The all-solid-state battery according to claim 1, The solid electrolyte particles include an argyrodite-type sulfide-based solid electrolyte represented by the following Chemical Formula 2: [Chemical Formula 2] Li 7-a1-c1 M a1 PS 6-c1 X c1 In Chemical Formula 2, X is Cl, Br, or I; M is scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi) or a combination thereof; and, 0 ≤ a1 ≤ 2 and 0 ≤ c1 ≤ 2.

7. According to claim 1, The all-solid-state battery, wherein an average particle diameter of the solid electrolyte particles is from 0.1 µm to 10.0 µm.

8. According to claim 1, The positive electrode active material layer further includes a binder, The all-solid-state battery, wherein based on 100% by weight of the total weight of the positive electrode active material layer, a content of the binder is from 0.2% by weight to 2% by weight.

9. According to claim 8, The all-solid-state battery, wherein the binder includes at least one of a rubber-based binder and a polyvinylidene fluoride-based binder.

10. According to claim 1, The all-solid-state battery, wherein a content of a residual solvent in the positive electrode active material layer or the solid electrolyte layer is measured through gas chromatography mass spectrometry.

11. A positive electrode layer including a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector; A negative electrode layer; and An all-solid-state battery including a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer, wherein the positive electrode active material layer includes hexyl butyrate as a residual solvent, The all-solid-state battery, wherein a content of the hexyl butyrate in the positive electrode active material layer is 1,000 ppm or less. 1 ​ ​ ​ All-solid-state battery in which the average particle diameter of the second solid electrolyte particles is larger than the average particle diameter of the first solid electrolyte particles.

14. The method according to claim 12, wherein the average particle diameter of the first solid electrolyte particles is 0.1 µm to 1.0 µm, and the average particle diameter of the second solid electrolyte particles is 1.5 µm to 10.0 µm, all-solid-state battery.

15. The method according to claim 12, wherein the solid electrolyte layer further contains hexyl butyrate, and the content of hexyl butyrate in the solid electrolyte layer is 1,000 ppm or less, all-solid-state battery.

16. The method according to claim 11, wherein the content of the residual solvent in the positive electrode active material layer is measured by gas chromatography-mass spectrometry, all-solid-state battery.

17. Preparing a positive electrode layer in which the content of the first residual solvent in the positive electrode active material layer is 1,000 ppm or less; preparing a solid electrolyte layer in which the content of the second residual solvent is 1,000 ppm or less; preparing a negative electrode layer; and including interposing the solid electrolyte layer between the negative electrode layer and the positive electrode layer, where each of the first and second residual solvents contains a compound represented by the following Chemical Formula 1: Manufacturing method of all-solid-state battery: [Chemical Formula 1] R-COO-R' In Chemical Formula 1, each of R and R' is independently an alkyl having 4 to 6 carbon atoms.

18. The method according to claim 17, where the compound represented by Chemical Formula 1 is hexyl butyrate, manufacturing method of all-solid-state battery.

19. The method according to claim 17, where preparing the positive electrode layer is: coating a positive electrode active material slurry on a positive electrode current collector or a separator film; and drying the positive electrode active material slurry, where the drying temperature is 60°C to 150°C, manufacturing method of all-solid-state battery.

20. The method according to claim 17, where preparing the solid electrolyte layer is: coating a solid electrolyte slurry on a separator film; and drying the solid electrolyte slurry, where the drying temperature is 60°C to 150°C, manufacturing method of all-solid-state battery.

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