Negative electrode for all-solid-state battery, all-solid-state battery comprising same, and method for manufacturing negative electrode for all-solid-state battery

Abstract

The present invention relates to a negative electrode for an all-solid-state battery, an all-solid-state battery comprising same, and a method for manufacturing a negative electrode for an all-solid-state battery. More specifically, the all-solid-state battery comprises: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The negative electrode layer comprises a negative electrode current collector, a first coating layer on the negative electrode current collector, and a second coating layer on the first coating layer, and the second coating layer includes a composite of lithium sulfide and a lithium salt.

Description

Anode for an all-solid-state battery, an all-solid-state battery including the same, and a method for manufacturing the anode for an all-solid-state battery

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

[0002] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries are being used not only in information and communication devices, but also in the automotive sector. Safety is particularly important in the automotive sector, as it is directly related to life.

[0003] Recently, all-solid-state batteries, which replace the electrolyte with a solid electrolyte, have been proposed. By eliminating the use of flammable organic dispersion media, all-solid-state batteries significantly reduce the risk of fire or explosion in the event of a short circuit. Therefore, these all-solid-state batteries can significantly improve safety compared to lithium-ion batteries that use electrolytes.

[0004] The problem to be solved by the present invention is to provide a cathode that suppresses side reactions at the interface between a solid electrolyte layer and a cathode, has high ionic conductivity, and is structurally stable.

[0005] Another problem to be solved by the present invention is to provide a method for manufacturing a cathode that suppresses side reactions at the interface between a solid electrolyte layer and a cathode, has high ionic conductivity, and is structurally stable.

[0006] According to the concept of the present invention, an all-solid-state battery comprises: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the negative electrode layer comprises a negative electrode current collector, a first coating layer on the negative electrode current collector, and a second coating layer on the first coating layer, and the second coating layer may comprise a complex of lithium sulfur (Li2S) and a lithium salt.

[0007] According to another concept of the present invention, an all-solid-state battery comprises: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the negative electrode layer comprises a lithium metal layer, a first coating layer on the lithium metal layer, and a second coating layer on the first coating layer, and the second coating layer may comprise a complex of lithium sulfur (Li2S) and a lithium salt, and a binder. The binder content in the second coating layer may be 5 wt% to 50 wt%.

[0008] According to another concept of the present invention, a method for manufacturing an anode for an all-solid-state battery may include providing an anode current collector; forming a first coating layer on the anode current collector; and forming a second coating layer on the first coating layer. Forming the second coating layer may include forming a complex by ball milling lithium sulfur and a lithium salt; mixing the complex and a binder to form a slurry; and applying the slurry on the first coating layer.

[0009] The anode for an all-solid-state battery according to the present invention may include a coating layer comprising a complex of lithium sulfur and a lithium salt. The coating layer suppresses side reactions at the interface between the solid electrolyte layer and the anode, thereby improving the life characteristics of the all-solid-state battery.

[0010] By using the method for manufacturing an anode for an all-solid-state battery according to the present invention, it is possible to manufacture an anode in which side reactions are suppressed and ionic conductivity and structural stability are improved.

[0011] Figure 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0012] Figure 2 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0013] FIG. 3 and FIG. 4 are a plan view and a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention, respectively.

[0014] Figure 5 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0015] FIG. 6 is a cross-sectional view of an all-solid-state battery including a gasket structure according to one embodiment of the present invention.

[0016] Figure 7 is an enlarged view of area M of Figure 1.

[0017] Figure 8 is a flowchart illustrating a method for manufacturing a negative electrode for an all-solid-state battery according to embodiments of the present invention.

[0018] Figure 9 is a FE-SEM measurement result of a cathode coating layer according to one embodiment of the present invention.

[0019] Figure 10 is a SEM-EDAX analysis result of a cathode coating layer according to one embodiment of the present invention.

[0020] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications. However, the description of these embodiments is provided solely to ensure a complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention.

[0021] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. Furthermore, in the drawings, the thicknesses of the components are exaggerated for the sake of clarity. Parts designated by the same reference numerals throughout the specification represent the same components.

[0022] Embodiments described herein will be described with reference to cross-sectional and / or plan views, which are ideal illustrations of the present invention. In the drawings, the thicknesses of films and regions are exaggerated for the purpose of effectively explaining the technical contents. Accordingly, the regions illustrated in the drawings have a schematic nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific shapes of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, and third are used to describe various components in various embodiments of the present specification, these components should not be limited by such terms. These terms are used only to distinguish one component from another. The embodiments described and illustrated herein also include complementary embodiments thereof.

[0023] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the words "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0024] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0025] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0026] Figure 1 is a cross-sectional view of an all-solid-state battery (10) according to one embodiment of the present invention.

[0027] 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 present invention is not limited thereto, and 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).

[0028] The positive electrode layer (100) of one embodiment includes a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on the positive electrode current collector (110). The positive electrode active material layer (120) may include a positive electrode active material, a solid electrolyte, a conductive material, and a binder.

[0029] The cathode current collector (110) can provide a reference surface on which the cathode active material layer (120) is arranged. The cathode current collector (110) can include a plate or foil including, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0030] Meanwhile, unlike that illustrated in FIG. 1, in one embodiment of the present invention, the positive electrode current collector (110) may be omitted. Although not illustrated, a carbon layer having a thickness of 0.1 μm to 4 μm may be additionally disposed between the positive electrode current collector (110) and the positive electrode active material layer (120) to increase the bonding strength between the positive electrode current collector (110) and the positive electrode active material layer (120).

[0031] The cathode active material layer (120) may include a cathode active material, a solid electrolyte, a conductive material, and a binder.

[0032] A cathode active material is a material that can reversibly absorb and desorb lithium ions. The cathode active material may include, but is not necessarily limited to, 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, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. The cathode active materials may be used alone or as a mixture of two or more.

[0033] Lithium transition metal oxides include, 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-fA compound represented by any one of Fe2(PO4)3(0≤f≤2), LiFePO4. In these compounds, the capital letter “A” is Ni, Co, Mn, or a combination thereof, the capital letter “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, the capital letter “D” is O, F, S, P, or a combination thereof, the capital letter “E” is Co, Mn, or a combination thereof, the capital letter “F” is F, S, P, or a combination thereof, the capital letter “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, the capital letter “Q” is Ti, Mo, Mn, or a combination thereof, the capital letter “I” is Cr, V, Fe, Sc, Y, or a combination thereof, and the capital letter “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0034] 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 atomic layers and metal atomic layers are alternately and regularly arranged in a direction, and thereby each atomic layer forms a two-dimensional plane. The "cubic rock salt structure" refers to a sodium chloride type (NaCl type) structure, which is a type of crystal structure, and specifically refers to a structure in which face-centered cubic lattices (fcc) formed by cations and anions respectively are arranged with a displacement of half of the ridge of the unit lattice. Lithium transition metal oxides having this layered rock salt structure include, 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.

[0035] The above-described compound included in the positive electrode active material may be covered by a coating layer (not shown). The positive electrode active material may also be a mixture of the above-described compound and a compound to which a coating layer is added. Meanwhile, the coating layer added to the surface of the positive electrode active material may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of the coating elements below. The compound forming the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method of forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The method of forming the coating layer includes, for example, spray coating, dipping, etc.

[0036] When the cathode active material contains nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, for example, the capacity density of the all-solid-state battery (10) can be increased, thereby reducing metal dissolution of the cathode active material in a charged state. As a result, the cycle characteristics of the all-solid-state battery (10) in a charged state are improved. Meanwhile, the “cycle characteristics” are characteristics indicating the degree to which the all-solid-state battery (10) is deteriorated due to charge / discharge of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics may have a small degree of deterioration of the all-solid-state battery (10) due to charge / discharge, and an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration of the all-solid-state battery (10) due to charge / discharge.

[0037] The shape of the cathode active material may include particle shapes such as a sphere or an ellipsoid, for example. The particle size and content of the cathode active material are not particularly limited.

[0038] The solid electrolyte may have a particle shape. The solid electrolyte may be dispersed between the positive electrode active materials. The solid electrolyte may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics. Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiX (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, Li2S-P2S5-Z m S n (m, n are positive numbers, capital letter “Z” represents Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, capital letter “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).

[0039] Sulfide-based solid electrolytes include, 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-xI x It may be an argyrodite-type compound including at least one selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0040] Alternatively, the sulfide-based solid electrolyte is Li 7-a M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)), where X may be F, Br, Cl, or a combination thereof. 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 a combination thereof. Can be.

[0041] Alternatively, the sulfide-based solid electrolyte may be the same as the solid electrolyte included in the solid electrolyte layer (300) described later.

[0042] The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state battery can be reduced, and the defect of the solid electrolyte membrane being penetrated and short-circuited due to the formation of lithium dendrites can be prevented. The elastic modulus of the solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0043] The solid electrolyte included in the positive electrode active material layer (120) may have a smaller median particle size (D50) than the solid electrolyte included in the solid electrolyte layer (300). For example, the median 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 median particle size (D50) of the solid electrolyte included in the solid electrolyte layer (300). Meanwhile, the median particle size (D50) may be a median diameter measured using a laser particle size distribution meter.

[0044] The cathode 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 cathode active material and the solid electrolyte.

[0045] The conductive material may include a carbon-based material. For example, the conductive material may include one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0046] The positive electrode active material layer (120) may further include a binder. The binder may include a material for binding the positive electrode active material, solid electrolyte, and conductive material included in the positive electrode active material layer (120) and improving bonding strength with the positive electrode current collector (110). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0047] Based on 100 parts by weight of the total of the positive electrode active material, the solid electrolyte, the conductive material, and the binder, the positive electrode active material layer (120) may include 85 parts by weight or more and 92 parts by weight or less of the positive electrode active material. Based on 100 parts by weight of the total of the positive electrode active material, the solid electrolyte, the conductive material, and the binder, the positive electrode active material layer (120) may include 0.5 parts by weight or more and 1.5 parts by weight or less of the binder.

[0048] Based on 100 parts by weight of the solid electrolyte, the positive electrode active material layer (120) may include 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 electrode active material layer (120) in an amount of less than 1 part by weight based on 100 parts by weight of the solid electrolyte, the proportion of the conductive material may decrease, thereby lowering the electrical conductivity of the positive electrode active material layer (120). If the conductive material is included in the positive electrode active material layer (120) in an amount of more than 50 parts by weight based on 100 parts by weight of the solid electrolyte, the proportion of the conductive material may be excessively high, so that a covering layer covering the surface of the solid electrolyte may not be properly formed.

[0049] The cathode active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the cathode active material, solid electrolyte, conductive agent, and binder described above.

[0050] Referring to FIG. 1, the negative electrode layer (200) may include a negative electrode current collector (210), a first coating layer (220) on the negative electrode current collector, and a second coating layer (230) on the first coating layer.

[0051] The negative electrode current collector (210) can provide a reference surface on which the first coating layer (220) is disposed. The negative electrode current collector (210) can include, for example, a material that does not react with lithium, i.e., does not form an alloy or compound with lithium. The material constituting the negative electrode current collector (210) is not necessarily limited to, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that can be used as an electrode current collector can be used. The thickness of the negative electrode current collector can be 1 to 20 μm, for example, 5 to 15 μm, for example, 7 to 10 μm.

[0052] The negative electrode current collector (210) may be composed of one of the above-described metals, or may include an alloy or coating material of two or more metals. The negative electrode current collector (210) is, for example, in the form of a plate or foil. Meanwhile, in one embodiment, the negative electrode current collector (210) may be omitted.

[0053] Fig. 7 is an enlarged view of a cross-section of a first coating layer (220) and a second coating layer (230) according to one embodiment of the present invention. Fig. 7 is an enlarged view of area M of Fig. 1.

[0054] Referring to FIG. 7, the first coating layer (220) may include composite particles (AM) and a binder (BND1). The median particle size average particle diameter (D50) of the composite particles (AM) having a particle shape may be, for example, 4 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less. The median particle size average particle diameter (D50) of the composite particles (AM) may be, for example, 10 nm to 4 μm, 10 nm to 2 μm, or 10 nm to 900 nm. Since the composite particles (AM) have a median particle size average particle diameter (D50) in this range, reversible absorption and / or desorption of lithium may be easier during charge and discharge. Meanwhile, the median particle size average particle diameter (D50) may be a median diameter measured using a laser particle size distribution meter.

[0055] The composite particle (AM) may comprise one selected from among metals and metalloids and carbon. For example, the composite particle (AM) may be a composite particle of carbon and a metal.

[0056] Carbon may be amorphous carbon, in particular. Examples of amorphous carbon include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon.

[0057] The metal or metalloid includes, but is not limited to, one or more 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), and may be a metal or metalloid that forms an alloy or compound with lithium. On the other hand, nickel (Ni) does not form an alloy with lithium and therefore is not a metal included in the composite particle (AM).

[0058] The composite particle (AM) may contain one or more of these carbon and metals or metalloids, or may contain multiple different materials. For example, the composite particle (AM) may contain only amorphous carbon, or may contain one or more 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).

[0059] In one embodiment, the composite particle (AM) may include a mixture of amorphous carbon and one or more 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 mixing ratio of the mixture of amorphous carbon and gold (Au), etc., may be, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight, but is not necessarily limited to this range and may be selected depending on the characteristics of the required all-solid-state battery (10). When the composite particle (AM) has this composition, the cycle characteristics of the all-solid-state battery (10) may be further improved.

[0060] The composite particles (AM) according to embodiments of the present invention can evenly introduce metal particles onto the surface of the current collector. Accordingly, lithium can be evenly deposited between the first coating layer (220) including the composite particles (AM) and the conductive metal, thereby forming a uniform lithium metal layer on the surface of the negative electrode current collector.

[0061] In addition, the method for manufacturing the above composite particle (AM) can composite fine-sized metal particles and carbon materials, and when the resulting composite particle (AM) is introduced into an all-solid-state battery, lithium can be evenly deposited on the surface of the current collector as described above.

[0062] The binder (BND1) included in the first coating layer (220) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto. The binder (BND1) may include a single binder or a plurality of different binders.

[0063] Since the first coating layer (220) includes a binder (BND1), the first coating layer (220) can be stably formed on the negative electrode current collector (210). That is, the bonding strength between the first coating layer (220) and the negative electrode current collector (210) can be increased. In addition, cracking of the first coating layer (220) is suppressed despite changes in the volume and / or relative positions of the first coating layer (220) during the charge and discharge process. If the first coating layer (220) does not include a binder (BND1), the first coating layer (220) can be easily separated from the negative electrode current collector (210). As the first coating layer (220) is detached from the negative electrode current collector (210), the negative electrode current collector (210) can come into contact with the solid electrolyte layer (300) at the exposed portion, thereby increasing the possibility of a short circuit occurring.

[0064] The first coating layer (220) is manufactured, for example, by providing a mixture in which the materials constituting the first coating layer (220) are dispersed onto the negative electrode current collector (210). Since the binder (BND1) is included in the materials constituting the first coating layer (220), stable dispersion of the composite particles (AM) in the mixture is possible. For example, when the mixture is applied onto the negative electrode current collector (210) by screen printing, it is possible to suppress clogging of the screen (e.g., clogging by aggregates of the composite particles (AM)) by the binder (BND1).

[0065] The first coating layer (220) may further include other additives in addition to the composite particles (AM) and the binder (BND1). The first coating layer (220) may further include, for example, fillers, coating agents, dispersants, ion-conducting aids, etc.

[0066] The first coating layer (220) may have a smaller thickness than the positive electrode active material layer (120). The thickness of the first 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 electrode active material layer (120). The thickness of the first coating layer (220) may be, for example, 1 um to 20 um, 2 um to 15 um, 3 um to 15 um, or 3 um to 7 um. If the thickness of the first coating layer (220) is too thin, lithium dendrites formed between the first coating layer (220) and the negative electrode current collector (210) may cause the first coating layer (220) to collapse, thereby deteriorating the cycle characteristics of the all-solid-state battery (10). If the thickness of the first coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) may decrease and the internal resistance of the all-solid-state battery (10) due to the first coating layer (220) may increase, thereby deteriorating the cycle characteristics of the all-solid-state battery (10).

[0067] When the thickness of the first coating layer (220) decreases, the charging capacity of the first coating layer (220) may also decrease, for example. The charging capacity of the first 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 than the charging capacity of the positive electrode active material layer (120). The charging capacity of the first 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% than the charging capacity of the positive electrode active material layer (120). If the charging capacity of the first coating layer (220) is excessively small, the thickness of the first coating layer (220) becomes very thin, and the same defects as those described above that occur when the thickness of the first coating layer (220) becomes excessively thin may occur. If the charging capacity of the first coating layer (220) increases excessively, the same defects as those described above that occur when the thickness of the first coating layer (220) increases excessively may occur.

[0068] Referring again to FIG. 7, a second coating layer (230) including a complex of lithium sulfur and lithium salt (CPX) may be disposed on the first coating layer (220).

[0069] The second coating layer (230) is disposed between the first coating layer (220) and the solid electrolyte layer (300), thereby stabilizing the interface between the negative electrode (200) and the solid electrolyte layer (300) and suppressing the occurrence of side reactions at the interface.

[0070] In one embodiment, the second coating layer (230) can prevent Li2S from being generated by suppressing a side reaction at the interface between the negative electrode (200) and the solid electrolyte layer (300). Li2S generated by the side reaction exists alone, unlike Li2S included in the complex (CPX), and thus has low ionic conductivity. Therefore, when Li2S is generated by the side reaction, the lithium ion transfer capability of the negative electrode (200) may be significantly reduced, which may accelerate the deterioration of the cell lifespan. Furthermore, Li2S generated by the side reaction may act as an ionic resistor, which may cause a problem in which a large overvoltage is applied to the battery.

[0071] The anode (200) for an all-solid-state battery according to the present invention can suppress the generation of Li2S at the interface between the anode (200) and the solid electrolyte layer (300) by including a second coating layer (230). As a result, it is possible to prevent a large overvoltage from being applied to the battery and improve its lifespan characteristics.

[0072] The second coating layer (230) may include a complex (CPX) of lithium sulfur and a lithium salt. The complex (CPX) may have superior ionic conductivity, unlike lithium sulfur existing alone. Therefore, even if the second coating layer (230) is included in the negative electrode (200), ionic conductivity may not be reduced.

[0073] The lithium salt compound included in the complex (CPX) may be, for example, a binary compound composed of lithium and one element selected from Groups 13 to 17 of the Periodic Table of Elements. The binary compound may include, for example, one or more selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3. The lithium salt compound may be, for example, a ternary compound composed of lithium and two elements selected from Groups 13 to 17 of the Periodic Table of Elements. The ternary compound may include, for example, one or more selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. For example, the lithium salt compound may be one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI.

[0074] The content of lithium sulfur included in the complex (CPX) may be 20 mol% or more. For example, the content of lithium sulfur in the complex may be 20 mol% to 99 mol%, 30 mol% to 90 mol%, 30 mol% to 90 mol%, or 40 mol% to 80 mol%. When the lithium sulfur content satisfies the above-described range, the complex (CPX) may have excellent ionic conductivity and excellent structural stability.

[0075] The content of the complex (CPX) in the second coating layer (230) may be 20 wt% or more. For example, the content of the complex (CPX) may be 20 wt% to 99 wt%, 40 wt% to 95 wt%, or 50 wt% to 95 wt%. When the content of the complex (CPX) satisfies the above-described range, side reactions at the interface between the solid electrolyte layer (300) and the negative electrode (200) can be effectively suppressed.

[0076] The second coating layer (230) may further include a binder (BND2). The binder (BND2) included in the second coating layer (230) may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto. For example, the binder (BND2) may include at least one selected from the group consisting of styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. In one embodiment, the binder (BND2) included in the second coating layer (230) may include only one type of binder, or may include two or more different types of binders.

[0077] The binder (BND2) of the second coating layer (230) may be the same as or different from the binder included in the positive electrode active material layer (120) or the binder (BND1) included in the first coating layer (220). Since the second coating layer (230) includes the binder (BND2), the second coating layer (230) can be stably formed on the first coating layer (220). That is, the bonding strength between the second coating layer (230) and the first coating layer (220) can be increased.

[0078] The content of the binder (BND2) in the second coating layer (230) may be 1 wt% to 80 wt%, 3 wt% to 60 wt%, or 5 wt% to 50 wt%. If the content of the binder (BND2) is too small, the second coating layer may not be formed stably. On the other hand, if the content of the binder (BND2) is too large, the ionic conductivity of the all-solid-state battery may deteriorate, and the capacity of the battery may decrease. If the content of the binder (BND2) in the second coating layer (230) satisfies the above range, side reactions can be effectively suppressed, while the structural stability of the negative electrode (200) can be improved without deteriorating the ionic conductivity.

[0079] The second coating layer (230) may have a smaller thickness than the first coating layer (220). The thickness of the second coating layer (230) may be, for example, 0.5 um to 10 um, 0.5 um to 10 um, or 1 um to 5 um. If the thickness of the second coating layer (230) is too thin, side reactions at the interface between the negative electrode (200) and the solid electrolyte layer (300) may not be sufficiently prevented. If the thickness of the second coating layer (230) is too thick, the energy density of the all-solid-state battery may decrease and the internal resistance may increase.

[0080]

[0081] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the first coating layer (220) and the solid electrolyte layer (300).

[0082] A solid electrolyte layer (300) may be provided between the positive electrode layer (100) and the negative electrode layer (200). The solid electrolyte layer (300) may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics. The solid electrolyte in the solid electrolyte layer (300) may be the same as or different from the solid electrolyte included in the positive electrode active material layer (120) described above.

[0083] In one embodiment, the solid electrolyte included in the solid electrolyte layer (300) may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, a sulfide-based solid electrolyte material that includes at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the solid electrolyte may be a material including Li2S-P2S5. When using a sulfide-based solid electrolyte material that includes Li2S-P2S5 to form the solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0084] Sulfide-based solid electrolytes include, 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 including at least one selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0085] Alternatively, the sulfide-based solid electrolyte is Li 7-a M a PS 6-c X cIt may be an argyrodite-type compound containing (0≤a≤2, 0≤c≤2), where X may be F, Br, Cl, or a combination thereof. 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 a combination thereof. Can be.

[0086] The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. When the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state battery is reduced, and the defect of the solid electrolyte membrane being penetrated and short-circuited due to the formation of lithium dendrites can be prevented. The elastic modulus of the solid electrolyte is, for example, 15 GPa to 35 GPa.

[0087] The solid electrolyte layer (300) may further include a binder. The binder included in the solid electrolyte layer (300) may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and the like, but is not limited thereto. For example, the binder may include at least one selected from the group consisting of styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. 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 first coating layer (220).

[0088]

[0089] Figure 2 is a cross-sectional view of an all-solid-state battery (10) according to another embodiment of the present invention.

[0090] Referring to FIG. 2, the solid electrolyte layer (300) may include a first solid electrolyte layer (310) and a second solid electrolyte layer (320). The first solid electrolyte layer (310) may be adjacent to the positive electrode layer (100), and the second solid electrolyte layer (320) may be adjacent to the negative electrode layer (200).

[0091] The first solid electrolyte layer (310) and the second solid electrolyte layer (320) may have different thicknesses. The first solid electrolyte layer (310) may have a first thickness (TK1), and the second solid electrolyte layer (320) may have a second thickness (TK2). The first thickness (TK1) may be greater than the second thickness (TK2). For example, the first thickness (TK1) may be 2 to 100 times greater than the second thickness (TK2).

[0092]

[0093] Fig. 3 is a plan view of an all-solid-state battery (10) according to another embodiment of the present invention. Fig. 4 is a cross-sectional view taken along line A-A' of Fig. 3. In this embodiment, detailed descriptions of technical features overlapping with those previously described with reference to Figs. 1 and 2 will be omitted, and differences will be described in detail.

[0094] Referring to FIGS. 3 and 4, the area of ​​the anode layer (100) and the area of ​​the cathode layer (200) may be different from each other. Specifically, the area of ​​the cathode layer (200) may be larger than the area of ​​the anode layer (100). The anode layer (100) may be completely overlapped within the cathode layer (200).

[0095] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the positive electrode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the negative electrode layer (200).

[0096] Specifically, the first solid electrolyte layer (310) may have a first width (WI1) in a first direction (D1). The second solid electrolyte layer (320) may have a second width (WI2) in the first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The first solid electrolyte layer (310) may have a third width (WI3) in the second direction (D2). The second solid electrolyte layer (320) may have a fourth width (WI4) in the second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0097] The all-solid-state battery (10) according to the present embodiment can be manufactured by forming a first laminate of a positive electrode layer (100) and a first solid electrolyte layer (310), forming a second laminate of a negative electrode layer (200) and a second solid electrolyte layer (320), and then laminating the first laminate and the second laminate.

[0098]

[0099] FIG. 5 is a cross-sectional view taken along line A-A' of FIG. 3 to explain an all-solid-state battery according to another embodiment of the present invention.

[0100] Referring to FIG. 5, the negative electrode layer (200) of the all-solid-state battery (10) may further include a lithium metal layer (400) between the negative electrode current collector (210) and the first coating layer (220). The thickness of the lithium metal layer (400) may further increase when the all-solid-state battery (10) is charged. The first coating layer (220) serves as a protective layer for the lithium metal layer (400), and at the same time, may suppress the growth of lithium dendrites from the lithium metal layer (400).

[0101] The lithium metal layer (400) may be a metal thin film containing lithium or a lithium alloy. The lithium alloy may include, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., and any lithium alloy may be used. The lithium metal layer (400) may contain one of these alloys or lithium. Alternatively, the lithium metal layer (400) may contain various types of alloys.

[0102] The lithium metal layer (400) may have a fifth width (WI5) in the first direction (D1). The fifth width (WI5) may be equal to or greater than the first width (WI1). The fifth width (WI5) may be equal to or less than the second width (WI2). For example, the fifth width (WI5) may be greater than the first width (WI1) and less than the second width (WI2).

[0103]

[0104] FIG. 6 is a cross-sectional view illustrating an all-solid-state battery according to another embodiment of the present invention.

[0105] Referring to FIG. 6, the all-solid-state battery (10) may include a gasket structure (400). The gasket structure (400) may fill in the step difference in the side surface of the all-solid-state battery (10) caused by the difference in the area of ​​the first laminate and the second laminate. The gasket structure (400) may surround the side surfaces of the first laminate of the all-solid-state battery (10) along the first and second directions (D1, D2). For example, the thickness of the gasket structure (400) may be substantially the same as the thickness of the first laminate. Accordingly, even when the first and second laminates having different areas are laminated and pressed, damage to the step difference in the side surface of the all-solid-state battery can be prevented. The term “substantially the same thickness” may be defined as a thickness that can prevent damage to the step difference in the side surface of the all-solid-state battery even when the first and second laminates having different areas are laminated and pressed.

[0106]

[0107] Hereinafter, a method for manufacturing an anode for an all-solid-state battery according to embodiments of the present invention will be described in more detail. FIG. 8 is a flowchart illustrating a method for manufacturing an anode for an all-solid-state battery according to embodiments of the present invention.

[0108] Referring to FIG. 8, a method for manufacturing a negative electrode for an all-solid-state battery may include providing a negative electrode current collector (S100), forming a first coating layer on the negative electrode current collector (S200), and forming a second coating layer on the first coating layer (S300). Forming the second coating layer (S300) may include forming a complex by ball milling lithium sulfur and a lithium salt (S310), mixing the complex and a binder to form a slurry (S320), and applying the slurry on the first coating layer (S330).

[0109] For the manufacture of an anode for an all-solid-state battery, an anode current collector may be provided (S100). The anode current collector may be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, and any material that can be used as an electrode current collector may be used. The anode current collector may be composed of one of the above-described metals, or may include an alloy or a coating material of two or more metals. The anode current collector may be provided in the form of a plate or foil, for example.

[0110] A first coating layer can be formed on the negative electrode current collector (S200). Composite particles, binders, etc. included in the first coating layer can be added to a polar solvent or a non-polar solvent to form a slurry. The prepared slurry can be applied to the negative electrode current collector and dried to form the first coating layer.

[0111] Application can be performed in a conventional manner. For example, application can be performed using a bar coater, blade coater, etc. Any method capable of applying slurry can be used and is not limited to the examples described. After drying, a pressurization process can be additionally performed. Pressurization is not necessarily limited to these methods, but any pressurization method used in the art can be used.

[0112] To form a second coating layer on the first coating layer (S300), lithium sulfur and a lithium salt may be milled to form a composite (S310). Lithium sulfur and a lithium salt may be introduced in a molar ratio of 6:4 to 9:1, 7:3 to 9:1, or 7:3 to 8:2.

[0113] The milling conditions for lithium sulfur and lithium salts are not particularly limited; any conditions that allow the formation of a complex of Li2S and lithium salts are acceptable. Milling can be performed, for example, dry or wet in a solvent.

[0114] In one embodiment, Li2S particles and a lithium salt may be placed in a ball mill and stirred at a speed of 100 to 1000 rpm for 1 to 20 hours to prepare a complex of Li2S and a lithium salt. The stirring may be performed more than once.

[0115] As lithium salts, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or combinations thereof can be used.

[0116] The prepared lithium sulfur and lithium salt complex can be mixed with a binder to form a second coating layer slurry (S320). The slurry can be added so that the content of the complex relative to the content of the binder is 1 to 9. In one embodiment, the content of the complex relative to the content of the binder can be 1 to 5, 1.5 to 3, or 1.5 to 2.5.

[0117] The binder may include, for example, at least one selected from the group consisting of styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. However, the binder is not limited to the examples described.

[0118] For example, the binder may be provided as a binder solution. The binder solution may include a binder and a solvent. For example, the binder content may be 2% to 10% by weight relative to the total weight of the binder solution.

[0119] A second coating layer slurry may be applied onto the first coating layer and dried to form a second coating layer (S330). Application may be performed using a conventional method. For example, application may be performed using a bar coater, blade coater, or the like. Application may be performed using any method capable of applying slurry, and is not limited to the examples described.

[0120] Drying can be performed in a conventional manner. For example, drying can be performed under vacuum conditions. Drying can be performed once or twice or more times. After drying, a pressurization process can be performed. Pressurization can be performed using, for example, a roll press or a flat press, but is not limited to these methods. Any pressurization method used in the art can be used.

[0121]

[0122] Hereinafter, the present invention will be described in more detail through examples. However, these examples are intended to exemplify the present invention and the scope of the present invention is not limited to these examples.

[0123]

[0124] Example 1: Preparation of cathode

[0125] (Manufacture of Li2S-lithium salt complex)

[0126] Li2S and LiI were mixed at a molar ratio of 5:5. The mixture was mechanically milled using a ball mill to prepare a Li2-LiI complex. The milling conditions were 25°C, 600 rpm, and 10 h.

[0127] (Cathode manufacturing)

[0128] A 10 ㎛ thick SUS foil was prepared as a negative electrode collector. Carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as composite particle raw materials. The Li2S-LiI composite and a binder were prepared as materials for the second coating layer.

[0129] A mixed powder of 4 g of 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 thereto to prepare a mixed solution. A first coating layer slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared first coating layer slurry was applied to a SUS sheet using a bar coater and dried in the air at 80°C for 10 minutes to prepare a negative electrode current collector-first coating layer laminate.

[0130] An NMP solution containing 7 wt% of PVDF-HFP binder was prepared. The Li2S-LiI complex was added to the solution so that the weight ratio of the Li2S-LiI complex to the PVDF-HFP binder was 95:5, and mixed with a thinky mixer to prepare a second coating layer slurry. The prepared second coating layer slurry was applied onto the first coating layer using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum-dried at 40°C for 10 hours to prepare a negative electrode laminate.

[0131] The above laminate was pressed to manufacture a cathode. In the manufactured cathode, the thickness of the first coating layer was 10 μm, and the thickness of the second coating layer was 2 μm.

[0132]

[0133] Example 2

[0134] A negative electrode was manufactured in the same manner as in Example 1, except that the mixing ratio was adjusted so that the weight ratio of the Li2S-LiI complex and the binder was 80:20 when manufacturing the second coating layer slurry.

[0135]

[0136] Example 3

[0137] A negative electrode was manufactured in the same manner as in Example 1, except that the mixing ratio was adjusted so that the weight ratio of the Li2S-LiI complex and the binder was 70:30 when manufacturing the second coating layer slurry.

[0138]

[0139] Example 4

[0140] A negative electrode was manufactured in the same manner as in Example 1, except that the mixing ratio of the Li2S-LiI complex and the binder was adjusted to a weight ratio of 60:40 when manufacturing the second coating layer slurry.

[0141]

[0142] Example 5

[0143] A negative electrode was manufactured in the same manner as in Example 1, except that the mixing ratio was adjusted so that the weight ratio of the Li2S-LiI complex and the binder was 50:50 when manufacturing the second coating layer slurry.

[0144]

[0145] Example 6

[0146] A negative electrode was manufactured in the same manner as in Example 1, except that the second coating layer slurry was applied so that the thickness of the second coating layer was 1 μm.

[0147]

[0148] Example 7

[0149] A negative electrode was manufactured in the same manner as in Example 1, except that the second coating layer slurry was applied so that the thickness of the second coating layer was 9 μm.

[0150]

[0151] Comparative Example 1

[0152] A negative electrode was manufactured in the same manner as in Example 1, except that the negative electrode was manufactured by pressing the first coating layer laminate of the negative electrode current collector without the second coating layer.

[0153]

[0154] Manufacturing example: Manufacturing of all-solid-state batteries

[0155] (positive electrode active material)

[0156] Cathode active material LiNi0.8Co0. 15 Mn0. 05 O2 (NCM) powder was prepared.

[0157] (bipolar layer)

[0158] LiNi0.8Co0 as the positive electrode active material described above. 15 Mn0. 05 O2 (NCM) powder was prepared. A crystalline argyrodite-based solid electrolyte (Li6PS5Cl) was prepared as a solid electrolyte. A polytetrafluoroethylene (PTFE) binder (Teflon binder from DuPont) was prepared as a binder. Carbon nanofibers (CNF) were prepared as a conductive material. These materials were mixed in a weight ratio of positive electrode active material: solid electrolyte: conductive material: binder = 84.2:11.5:2.9:1.4, and the mixture was formed into a large sheet shape to manufacture a positive electrode sheet. The manufactured positive electrode sheet was pressed onto a positive electrode current collector made of 18 μm thick carbon-coated aluminum foil to manufacture a positive electrode layer. The thickness of the positive electrode active material layer included in the positive electrode layer was approximately 100 μm.

[0159] (cathode layer)

[0160] The cathodes manufactured according to Examples 1 to 7 and Comparative Examples were used as the cathode layer.

[0161] (solid electrolyte layer)

[0162] A solid electrolyte solution was prepared by adding argyrodite-type solid electrolyte Li6PS5Cl to an isobutylyl isobutylate binder solution containing an acrylate polymer (solid content: 50 wt%, mixing ratio of the solid electrolyte and binder: 98.7:1.3 wt ratio).

[0163] The above solid electrolyte solution was applied to a heterogeneous polytetrafluoroethylene film and dried at 60°C for 2 hours to produce a solid electrolyte layer having a thickness of 100 μm.

[0164] (Manufacturing of all-solid-state batteries)

[0165] (1) Full cell manufacturing

[0166] The cathode layer, solid electrolyte layer, and anode layer manufactured as described above were sequentially laminated. The laminate was sealed in a pouch shape and subjected to warm isostatic pressing (WIP) at a high temperature of 80°C and 500 MPa for 30 minutes to manufacture an all-solid-state battery.

[0167] (2) Half cell manufacturing

[0168] A coin half cell was manufactured using the cathode layer, solid electrolyte layer, and counter electrode (lithium metal) manufactured as described above.

[0169]

[0170] Evaluation Example 1: Overvoltage Evaluation

[0171] Overvoltage evaluation was performed on the half cell manufactured according to the manufacturing example as follows.

[0172] The half-cell was charged at 0.05C, and the voltage began to drop at OCV (Open Circuit Voltage, approximately 2.5V). The voltage was then measured until an inflection point occurred around 0mV. This result, the initial overvoltage, is shown in Table 1.

[0173] Second coating layer inner composite content (wt%)Second coating layer thickness (um)Initial overvoltage (mV)Example 195215Example 280216Example 370218Example 460219Example 550219Example 695115Example 795918Comparative Example 1-020

[0174] Referring to Table 1, it can be confirmed that the all-solid-state batteries according to Examples 1 to 7, which include a coating layer comprising a complex of Li2S and a lithium salt, have a lower overvoltage compared to the all-solid-state batteries according to the comparative examples.

[0175]

[0176] Evaluation Example 2: Evaluation of All-Solid-State Battery Life Characteristics

[0177] The life characteristics of the complete cells manufactured according to the manufacturing example were evaluated. The life characteristics were evaluated by the following charge-discharge tests. The charge-discharge tests were performed by placing the all-solid-state battery in a 45°C constant-temperature chamber.

[0178] The first cycle was performed by charging the battery at a constant current of 0.33C for approximately 3 hours until the battery voltage reached 4.25 V, then charging at a constant voltage of 0.1 C at 4.25 V, followed by a 10-minute rest period, and then discharging at a constant current of 0.33 C for approximately 3 hours until the battery voltage reached 2.5 V, followed by a 10-minute rest period.

[0179] After the second cycle, charging and discharging were performed up to 100 cycles under the same conditions as the first cycle. The life characteristics are shown in Table 2 below. In Table 2, the capacity retention rate is expressed by the following mathematical equation 1.

[0180] <Mathematical Formula 1>

[0181] Capacity retention rate [%]=[100 th Discharge capacity in cycles / 1 st Discharge capacity in cycle] × 100

[0182]

[0183] Second coating layer inner composite content (wt%)Second coating layer thickness (um)Capacity retention rate (%)Example 195288Example 280288Example 370287Example 460285Example 550283Example 695187Example 795983Comparative example 1-070

[0184] Referring to Table 2, it can be seen that the all-solid-state batteries according to the examples have a better capacity retention rate than the all-solid-state batteries according to the comparative examples.

[0185]

[0186] Evaluation Example 3: FE-SEM and SEM-EDAX Analysis

[0187] The cross-sections of the negative electrodes manufactured according to the examples and comparative examples before charge / discharge were measured using a field emission scanning electron microscope (FE-SEM), and the results are shown in Fig. 9. Additionally, SEM-EDAX analysis was performed, and the results are shown in Fig. 10 and Table 3.

[0188] Elemental content (wt%)CAgSI1st coating layer area (point 1)9218002nd coating layer area (point 2)002377

[0189] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. Including an anode layer; a cathode layer; and a solid electrolyte layer between the anode layer and the cathode layer, The cathode layer includes a cathode current collector, a first coating layer on the cathode current collector, and a second coating layer on the first coating layer, An all-solid-state battery wherein the second coating layer comprises a complex of lithium sulfur (Li2S) and a lithium salt.

2. In paragraph 1, An all-solid-state battery wherein the content of lithium sulfur in the complex is 20 mol% to 90 mol%.

3. In paragraph 1, An all-solid-state battery, wherein the lithium salt comprises at least one selected from the group consisting of LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3.

4. In paragraph 1, An all-solid-state battery wherein the content of the complex in the second coating layer is 50 wt% to 95 wt%.

5. In paragraph 1, An all-solid-state battery wherein the second coating layer further comprises a binder.

6. In paragraph 5 An all-solid-state battery, wherein the binder comprises at least one selected from the group consisting of styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

7. In paragraph 1, An all-solid-state battery wherein the thickness of the second coating layer is 0.5 μm to 10 μm.

8. In paragraph 1, An all-solid-state battery wherein the first coating layer comprises a metal and a carbon-based material.

9. In paragraph 8, The metal comprises at least one selected from the group consisting of Ag, Zn, Al, Sn, Mg, Ge, Cu, In, Ni, Bi, Au, Si, Pt and Pd, The above carbon-based material is an all-solid-state battery comprising crystalline carbon, amorphous carbon or a combination thereof.

10. In paragraph 8, An all-solid-state battery, wherein the thickness of the first coating layer is 3 μm to 15 μm.

11. In paragraph 1, An all-solid-state battery, wherein the negative electrode layer further comprises a lithium metal layer between the negative electrode current collector and the first coating layer.

12. In paragraph 1, The above solid electrolyte layer is an all-solid-state battery including a sulfide-based solid electrolyte.

13. In paragraph 12, The above sulfide-based solid electrolyte is Li a M b P c S d A e An all-solid-state battery wherein (a, b, c, d, and e are all 0 or greater and 12 or less, M is Ge, Sn, Si, or a combination thereof, and A is one of F, Cl, Br, or I).

14. Including a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, The cathode layer includes a lithium metal layer, a first coating layer on the lithium metal layer, and a second coating layer on the first coating layer, The second coating layer comprises a complex of lithium sulfur (Li2S) and a lithium salt, and a binder. An all-solid-state battery wherein the content of the binder in the first coating layer is 5 wt% to 50 wt%.

15. Providing a negative electrode collector; Forming a first coating layer on the negative electrode current collector; and Including forming a second coating layer on the first coating layer, Forming the second coating layer: Forming a complex by ball milling lithium sulfur and lithium salt; Mixing the above complex and binder to form a slurry; and A method for manufacturing a negative electrode for an all-solid-state battery, comprising applying the slurry on the first coating layer.

16. In paragraph 15, A method for manufacturing an anode for an all-solid-state battery, wherein the content of lithium sulfur in the complex is 20 mol% to 90 mol%.

17. In paragraph 15, A method for manufacturing an anode for an all-solid-state battery, wherein the content of the complex in the second coating layer is 50 wt% to 95 wt%.

18. In paragraph 15, A method for manufacturing a negative electrode for an all-solid-state battery, wherein the content of the binder in the second coating layer is 5 wt% to 50 wt%.

19. In paragraph 15, A method for manufacturing an anode for an all-solid-state battery, wherein the first coating layer comprises a metal and a carbon-based material.

Images