All-solid-state battery

Abstract

The present invention relates to an all-solid-state battery comprising an electrolyte double layer and, more specifically, to an all-solid-state battery comprising: a positive electrode layer including a positive electrode current collector and a positive electrode active material layer; a negative electrode layer including a negative electrode current collector and a negative electrode coating layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The solid electrolyte layer includes a first solid electrolyte layer disposed adjacent to the positive electrode active material layer, and a second solid electrolyte layer disposed adjacent to the negative electrode coating layer. The negative electrode coating layer contains carbon and silver (Ag), the first solid electrolyte layer contains a first solid electrolyte, the second solid electrolyte layer contains a second solid electrolyte, and the positive electrode active material layer contains active material particles and a third solid electrolyte dispersed therebetween. The first solid electrolyte and the third solid electrolyte are each independently a halide-based solid electrolyte or a P-free, sulfide-based solid electrolyte, and the second solid electrolyte is a solid electrolyte having an argyrodite crystal structure.

Description

All-solid-state batteries

[0001] The present invention relates to an all-solid-state secondary 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 have been proposed, replacing the electrolyte in lithium-ion batteries with a solid electrolyte. 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 offer superior safety.

[0004]

[0005] The problem to be solved by the present invention is to provide an all-solid-state battery with improved redox stability and cell characteristics.

[0006] According to the concept of the present invention, an all-solid-state battery may include a positive electrode layer including a positive electrode current collector and a positive electrode active material layer; a negative electrode layer including a negative electrode current collector and a negative electrode coating layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer.

[0007] The solid electrolyte layer may include a first solid electrolyte layer disposed adjacent to the positive electrode active material layer; and a second solid electrolyte layer disposed adjacent to the negative electrode coating layer.

[0008] The cathode coating layer may include carbon and silver (Ag), the first solid electrolyte layer may include a first solid electrolyte, the second solid electrolyte layer may include a second solid electrolyte, and the positive active material layer may include active material particles and a third solid electrolyte dispersed therebetween.

[0009] The first solid electrolyte and the third solid electrolyte may each independently be a halide-based solid electrolyte or a sulfide-based solid electrolyte in which P is omitted, and the second solid electrolyte may be a solid electrolyte having an argyrodite crystal structure.

[0010] According to embodiments of the present invention, an all-solid-state battery may include a first solid electrolyte layer including a halide-based solid electrolyte or a sulfide-based solid electrolyte in which P is omitted, and a second solid electrolyte layer including a solid electrolyte having an argyrodite crystal structure. Accordingly, the first solid electrolyte layer in contact with the positive electrode may have high oxidation and thermal stability. The second solid electrolyte layer in contact with the negative electrode may have high reduction stability. As a result, the all-solid-state battery of the present invention may have improved cell characteristics.

[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 an enlarged cross-sectional view of area M of Figure 1.

[0013] Figure 3 is a plan view of an all-solid-state battery according to another embodiment of the present invention.

[0014] Figure 4 is a cross-sectional view taken along line A-A' of Figure 3.

[0015] 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.

[0016] Figure 6 is a graph showing the high-rate capacity retention rate of an all-solid-state battery according to an embodiment and a comparative example of the present invention.

[0017] Figure 7 is a graph showing the charge / discharge efficiency of an all-solid-state battery according to an embodiment and a comparative example of the present invention.

[0018] Figure 8 is a graph showing the change in discharge capacity according to the number of cycles of an all-solid-state battery according to an embodiment and a comparative example of the present invention.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023]

[0024] Fig. 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view of area M of Fig. 1.

[0025] Referring to FIG. 1, an all-solid-state battery (10) according to one embodiment may include 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).

[0026] The positive electrode layer (100) of one embodiment may include a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on the positive electrode current collector (110). Referring to FIG. 2, the positive electrode active material layer (120) may include a positive electrode active material (PAM), a third solid electrolyte (SE3), a conductive material, and a binder.

[0027] The positive electrode current collector (110) can provide a reference surface on which the positive electrode active material layer (120) is arranged. The positive electrode 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.

[0028] 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).

[0029] Referring to FIG. 2, the positive electrode active material (PAM) may include a material that can reversibly absorb and desorb lithium ions. The positive electrode active material (PAM) may include a plurality of particles. The positive electrode active material (PAM) 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, lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. The positive electrode active material (PAM) may be a single material or a mixture of two or more materials.

[0030] Lithium transition metal oxides include, for example, Li a A 1-b B bD2(0.90≤a≤1, 0≤b≤0.5), Li a HAVE BEEN 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 Mr 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 Mr 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 b HAVE BEEN c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Ni b Co c Mr 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 bO2(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-f A 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.

[0031] The cathode active material (PAM) 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 the sodium chloride type (NaCl type) structure, which is a type of crystal structure, and specifically refers to a structure in which the face-centered cubic lattice (fcc) formed by each cation and anion is 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 z O2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0032] The above-described compound included in the positive electrode active material (PAM) may be covered by a coating layer (not shown). The positive electrode active material (PAM) 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 (PAM) 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 for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material (PAM). The method for forming the coating layer may include, for example, spray coating, dipping, etc.

[0033] When the positive electrode active material (PAM) 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 positive electrode active material (PAM) 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 by 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.

[0034] The positive electrode active material (PAM) may have a particle shape such as a sphere or an ellipsoid, for example. The particle size and content of the positive electrode active material (PAM) are not particularly limited.

[0035] Referring to FIG. 2, the third solid electrolyte (SE3) may have a particle shape. The third solid electrolyte (SE3) may be dispersed between the positive electrode active materials (PAM). The third solid electrolyte (SE3) may include a halide-based solid electrolyte with excellent oxidation stability or a sulfide-based solid electrolyte with P omitted.

[0036] A halide-based solid electrolyte contains a halogen element as a main component of anions. Including a halogen element as a main component of anions means that the proportion (molar ratio) of the halogen element is the largest among all the anions constituting the halide-based solid electrolyte. The proportion of the halogen element to all the anions constituting the halide-based solid electrolyte may be, for example, 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. The halogen element may be one type or two or more types. In the latter case, the sum of the anion elements is taken as the proportion of the halogen element. In addition, the halide-based solid electrolyte may be a solid electrolyte that does not contain sulfur (S).

[0037] For example, a halide-based solid electrolyte can be represented by the following chemical formula 1.

[0038] [Chemical Formula 1]

[0039] Li a M b X6

[0040] In the above chemical formula 1, a may be 2.5 to 3, and b may be 1 to 1.1. M may be a metal or metalloid element other than Li, and may be at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Mg, Ca, Sr, Ba, Al, Ga, Bi, Zr, Hf, Sn, Ta, Pb, Sc, Y, and In. Preferably, M may include at least one of Y and In. X may be at least one selected from the group consisting of F, Cl, Br, and I, and preferably may include Cl. Specifically, the halide-based solid electrolyte may be Li3InCl6, Li3YCl6, or Li3YBr2Cl4.

[0041] A sulfide-based solid electrolyte with P omitted refers to a solid electrolyte represented by a composition formula that includes the element sulfur (S) and does not include the element P. Therefore, a solid electrolyte with an extremely small amount of P component, for example, P of 0.1 wt% or less, is included in a solid electrolyte with P omitted.

[0042] For example, a sulfide-based solid electrolyte with P omitted can be represented by the following chemical formula 2.

[0043] [Chemical Formula 2]

[0044] Li a M b S c X d

[0045] In the above chemical formula 2, 0 <a≤6, 0<b≤6, 0<c≤6, 0≤d≤6 일 수 있다. M은 Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, 및 La로 이루어진 군에서 선택된 적어도 하나를 포함할 수 있고, X는 F, Cl, Br, I, Se, Te, 및 O로 이루어진 군에서 선택된 적어도 하나를 포함할 수 있다.

[0046] Other examples of sulfide-based solid electrolytes in which P is omitted include Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-B2S3, Li2S-GeS2, and Li2S-SiS2-Li. p MO q (p, q are positive numbers, M is one of Si, Ge, B, Al, Ga In) may include at least one selected from among.

[0047] The third solid electrolyte (SE3) in the positive electrode active material layer (120) may have a smaller median particle size (D50) than the first and second solid electrolytes (SE1, SE2) in the solid electrolyte layer (300) to be described later. 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.

[0048] The positive electrode active material layer (120) may include a conductive material. The conductive material may have conductivity without causing a chemical change in the all-solid-state battery (10), thereby increasing the conductivity of the positive electrode active material (PAM) and the third solid electrolyte (SE3). 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.

[0049] The positive electrode active material layer (120) may further include a binder. The binder may bind the positive electrode active material (PAM), the third solid electrolyte (SE3), and the conductive material within the positive electrode active material layer (120) to each other. The binder may include a material for improving the bonding strength between the positive electrode active material layer (120) and 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, polyacrylonitrile, and polymethyl methacrylate.

[0050] Based on 100 parts by weight of the total of the positive electrode active material (PAM), the third solid electrolyte (SE3), the conductive agent, 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 (PAM). Based on 100 parts by weight of the total of the positive electrode active material (PAM), the third solid electrolyte (SE3), the conductive agent, 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.

[0051] Based on 100 parts by weight of the third solid electrolyte (SE3), 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. When 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 third solid electrolyte (SE3), the proportion of the conductive material may decrease, thereby lowering the electrical conductivity of the positive electrode active material layer (120). When 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 third solid electrolyte (SE3), the proportion of the conductive material may be excessively high, so that a covering layer covering the surface of the third solid electrolyte (SE3) may not be properly formed.

[0052] The positive electrode active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the above-described positive electrode active material (PAM), third solid electrolyte (SE3), conductive agent, and binder.

[0053] The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the negative electrode coating layer (220) is disposed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound 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.

[0054] 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) may have, for example, a plate shape or a foil shape. Meanwhile, in one embodiment, the negative electrode current collector (210) may be omitted.

[0055] The negative electrode coating layer (220) can allow lithium metal to grow between it and the negative electrode current collector (210) when the all-solid-state battery (10) is charged. The negative electrode coating layer (220) can act as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0056] The cathode coating layer (220) may include a metal and carbon. For example, the cathode 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 cathode 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 cathode coating layer (220) may include a mixture of carbon black and silver (Ag).

[0057] The cathode coating layer (220) may further include additives other than metal and carbon. The cathode coating layer (220) may further include, for example, at least one additive selected from the group consisting of a binder, a filler, a coating agent, a dispersant, and an ion conductive additive.

[0058] The negative electrode coating layer (220) may have a smaller thickness than the positive electrode active material layer (120). The thickness of the negative electrode 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 negative electrode coating layer (220) may be, for example, 1 um to 20 um, 2 um to 10 um, or 3 um to 7 um. If the thickness of the negative electrode coating layer (220) is too thin, lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210) may cause the negative electrode coating layer (220) to collapse, thereby deteriorating the cycle characteristics of the all-solid-state battery (10). If the thickness of the cathode 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 cathode coating layer (220) may increase, resulting in a deterioration in cycle characteristics.

[0059] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte layer (300).

[0060] 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 any one of the materials included in the third solid electrolyte (SE3) in the positive electrode active material layer (120) described above.

[0061] 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).

[0062] Referring to FIG. 2, the first solid electrolyte layer (310) may include a first solid electrolyte (SE1). The first solid electrolyte (SE1) may have a particle shape such as a sphere or an ellipsoid. The first solid electrolyte (SE1) may be amorphous, crystalline, or a mixture thereof.

[0063] The first solid electrolyte (SE1) may include a halide-based solid electrolyte having excellent oxidation stability or a sulfide-based solid electrolyte in which P is omitted, similar to the third solid electrolyte (SE3) included in the positive electrode layer. For the halide-based solid electrolyte or the sulfide-based solid electrolyte in which P is omitted, refer to the description above regarding the third solid electrolyte (SE3). The first solid electrolyte (SE1) may be the same as or different from the third solid electrolyte (SE3).

[0064] The first solid electrolyte layer (310) 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, etc., but is not limited thereto. The binder of the first solid electrolyte layer (310) 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 negative electrode coating layer (220).

[0065] Referring to FIG. 2, the second solid electrolyte layer (320) may include a second solid electrolyte (SE2). The second solid electrolyte (SE2) may have a particle shape such as a sphere or an ellipsoid. The second solid electrolyte (SE2) may be amorphous, crystalline, or a mixture thereof.

[0066] The second solid electrolyte (SE2) may include an argyrodite-type solid electrolyte having high ionic conductivity and reduction stability. In one embodiment, the argyrodite-type solid electrolyte may be represented by the following chemical formula 3.

[0067] [Chemical Formula 3]

[0068] Li a M b PS 6-c X c

[0069] In the above chemical formula 3, 5≤a≤7, 0≤b≤0.1, 0≤c≤2, 5≤a+b≤7, M is at least one selected from the group consisting of Na, K, Fe, Mg, Ca, Ag, Cu, Zr, and Zn, and X is at least one selected from the group consisting of F, Cl, Br, and I. In particular, the argyrodite-type solid electrolyte may include at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0070] 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 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 second solid electrolyte (SE2) is, for example, 15 GPa to 35 GPa.

[0071]

[0072] The all-solid-state battery (10) according to embodiments of the present invention may have improved oxidation stability and thermal stability because the positive electrode active material layer (120) and the first solid electrolyte layer (310) include a halide-based solid electrolyte or a sulfide-based solid electrolyte in which P is omitted. In addition, the second solid electrolyte layer (320) adjacent to the negative electrode layer (200) may have improved reduction stability and ion conductivity because it includes an argyrodite-type solid electrolyte. As a result, the cell performance of the all-solid-state battery (10) according to the present invention may be improved.

[0073] Referring back to FIG. 1, the first solid electrolyte layer (310) and the second solid electrolyte layer (320) may have the same thickness or 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 1 to 5 times, 1 to 3 times, or 1 to 2 times the second thickness (TK2).

[0074] Fig. 3 is a plan view of an all-solid-state battery 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 that overlap with those previously described with reference to Figs. 1 and 2 will be omitted, and differences will be described in detail.

[0075] 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).

[0076] 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).

[0077] 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).

[0078] 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.

[0079] 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. 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 negative electrode coating layer (220). The thickness of the lithium metal layer (400) may further increase when the all-solid-state battery (10) is charged. The negative electrode 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).

[0080] 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.

[0081] 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).

[0082]

[0083] Example: Fabrication of an all-solid-state battery

[0084] (bipolar layer)

[0085] LiNi0.8Co0 as the cathode active material. 15 Mn0. 05 O2 (NCM) powder was prepared as a solid electrolyte, and Li3InCl6, a halide-based solid electrolyte, was prepared. 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.

[0086] (cathode layer)

[0087] 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 negative electrode active materials.

[0088] 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 slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet 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 laminate. The prepared laminate was cold roll pressed to flatten the surface, thereby preparing a negative electrode having a first negative electrode active material layer / negative electrode current collector structure.

[0089] (First solid electrolyte layer)

[0090] A halide-based solid electrolyte, Li3InCl6, was prepared as a solid electrolyte. A mixture was prepared by adding 1 part by weight of a styrene-butadiene rubber (SBR) binder to 100 parts by weight of the Li3InCl6 solid electrolyte. Xylene and diethylbenzene were added to the mixture and stirred to prepare a slurry. The prepared slurry was applied onto a nonwoven fabric using a blade coater and dried in air at 40°C to obtain a laminate. The obtained laminate was vacuum-dried at 40°C for 12 hours. A first solid electrolyte layer was prepared through the above process.

[0091] (Second solid electrolyte layer)

[0092] Li, a solid electrolyte with an argyrodite crystal structure as a solid electrolyte 5.75 PS 4.75 Cl 1.25 was prepared. The above Li 5.75 PS 4.75 Cl 1.25A mixture was prepared by adding 1 part by weight of styrene-butadiene rubber (SBR) binder to 100 parts by weight of the solid electrolyte. Xylene and diethylbenzene were added to the mixture and stirred to prepare a slurry. The prepared slurry was applied onto a nonwoven fabric using a blade coater and dried in air at 40°C to obtain a laminate. The obtained laminate was vacuum-dried at 40°C for 12 hours. A second solid electrolyte layer was prepared through the above process.

[0093] (Manufacturing of all-solid-state batteries)

[0094] A first solid electrolyte layer was placed on the positive electrode layer. A second solid electrolyte layer was placed on the negative electrode layer. These layers were laminated to prepare a laminate. The prepared laminate was plate pressed at 25°C and a pressure of 100 MPa for 10 minutes to produce an all-solid-state battery.

[0095]

[0096] Comparative example

[0097] Li as the solid electrolyte of the first solid electrolyte layer 5.75 PS 4.75 Cl 1.25 An all-solid-state battery was manufactured in the same manner as in Example 1, except that .

[0098]

[0099] Evaluation Example 1: High-Rate Stability Evaluation

[0100] The charge-discharge characteristics of the all-solid-state battery were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state battery manufactured according to the examples and comparative examples in a constant temperature chamber at 45°C.

[0101] The battery was charged at a constant current of 0.1 C for approximately 10 hours until the battery voltage reached 4.25 V, and then charged at a constant voltage of 4.25 V until the current reached 0.05 C, followed by a 10-minute rest period, and then discharged at a constant current of 0.1 C for approximately 10 hours until the battery voltage reached 2.5 V, followed by a 10-minute rest period. (1st cycle).

[0102] Then, the battery was charged for about 3 hours at a constant current of 0.33 C until the battery voltage reached 4.25 V, left at 45°C for 40 hours, and rested for 10 minutes. After that, the battery was discharged for about 10 hours at a constant current of 0.1 C until the battery voltage reached 2.5 V, and rested for 10 minutes. (2nd cycle).

[0103] After that, the battery was charged at a constant current of 1.0C for about 1 hour until the battery voltage became 4.25V, and then charged at a constant voltage of 4.25V until the current became 0.05C, followed by a 10-minute rest time, and then discharged at a constant current of 0.1C for about 10 hours until the battery voltage became 2.5V, followed by a 10-minute rest time (3rd cycle).

[0104] The high-capacity maintenance rate was calculated according to Equation 1 below and is shown in Table 1 and Figure 6.

[0105] <Formula 1>

[0106] High-rate capacity retention rate (%) = (discharge capacity of the 3rd cycle / discharge capacity of the 1st cycle) X 100

[0107] High capacity retention rate (%) Example 83.4 Comparative example 64.1

[0108] Referring to Table 1 and FIG. 6, it can be confirmed that the all-solid-state battery according to the example exhibits a higher high-rate capacity retention rate compared to the all-solid-state battery according to the comparative example. This may indicate that the solid electrolyte layer according to the present invention has excellent oxidation stability.

[0109] Evaluation Example 2: Cycle Characteristics Evaluation and High Voltage Stability Evaluation

[0110] The charge-discharge characteristics of the all-solid-state battery were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state secondary batteries manufactured according to the examples and comparative examples in a constant temperature chamber at 45°C.

[0111] The cycle characteristic evaluation was performed in the same manner as the high-voltage stability evaluation up to the third cycle, and then the battery voltage was charged at a constant current of 0.33C for approximately 3 hours until it reached 4.25 V, and then the current was charged at a constant voltage of 0.1 C from 4.25 V, followed by a 10-minute rest period, and then discharged 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. (4th cycle)

[0112] Afterwards, charge and discharge were performed in the same manner as the fourth cycle, and the cycle characteristics were evaluated. The charge and discharge efficiency of the all-solid-state battery is shown in Fig. 7. Referring to Fig. 7, it can be confirmed that the all-solid-state battery according to the embodiment has improved charge and discharge efficiency and cycle characteristics compared to the all-solid-state battery according to the comparative example, thereby enhancing high-voltage stability.

[0113] The change in discharge capacity according to the number of cycles of an all-solid-state battery is shown in Fig. 8. Referring to Fig. 8, it can be confirmed that the all-solid-state battery according to the present invention has improved cycle characteristics.

[0114]

[0115] While embodiments of the present invention have been described with reference to the attached drawings, the present invention may be implemented in other specific forms without altering the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are exemplary in all respects and are not limiting.

Claims

1. A cathode layer including a cathode current collector and a cathode active material layer; A cathode layer including a cathode current collector and a cathode coating layer; and Including a solid electrolyte layer between the positive electrode layer and the negative electrode layer, The above solid electrolyte layer: A first solid electrolyte layer disposed adjacent to the positive electrode active material layer; and A second solid electrolyte layer is disposed adjacent to the cathode coating layer, The above cathode coating layer includes carbon and silver (Ag), The first solid electrolyte layer includes a first solid electrolyte, The second solid electrolyte layer includes a second solid electrolyte, The above positive electrode active material layer includes active material particles and a third solid electrolyte dispersed between them, The first solid electrolyte and the third solid electrolyte are each independently a halide-based solid electrolyte or a sulfide-based solid electrolyte in which P is omitted, An all-solid-state battery wherein the second solid electrolyte is a solid electrolyte having an argyrodite crystal structure.

2. In paragraph 1, The first solid electrolyte and the third solid electrolyte are the same or different from each other. All-solid-state battery.

3. In paragraph 1, An all-solid-state battery in which the thickness ratio of the first solid electrolyte layer and the second solid electrolyte layer is 1:1 to 2:

1.

4. In paragraph 1, The above halide-based solid electrolyte is an all-solid-state battery including a compound represented by the following chemical formula 1: [Chemical Formula 1] Li a M b X6 In the above chemical formula 1, 2.5≤a≤3, 1≤b≤1.1, M is at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Mg, Ca, Sr, Ba, Al, Ga, Bi, Zr, Hf, Sn, Ta, Pb, Sc, Y and In, and X is at least one selected from the group consisting of F, Cl, Br and I.

5. In paragraph 4, wherein M comprises at least one of Y and In, All-solid-state battery.

6. In paragraph 4, The above X is an all-solid-state battery in which Cl.

7. In paragraph 1, The above sulfide-based solid electrolyte in which P is omitted is an all-solid-state battery including a compound represented by the following chemical formula 2: [Chemical Formula 2] Li a M b S c X d In the above chemical formula 2, 0 <a≤6, 0<b≤6, 0<c≤6, 0≤d≤6 이고, M is at least one selected from the group consisting of Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, and La.

8. In paragraph 1, The above sulfide-based solid electrolytes in which P is omitted are Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-B2S3, Li2S-GeS2, Li2S-SiS2-Li p MO q An all-solid-state battery comprising at least one selected from the group consisting of (p, q are positive numbers, M is one of Si, Ge, B, Al, Ga In).

9. In paragraph 1, The solid electrolyte having the above argyrodite crystal structure is an all-solid-state battery including a compound represented by the following chemical formula 3: [Chemical Formula 3] Li a M b PS 6-c X c In the above chemical formula 3, 5≤a≤7, 0≤b≤0.1, 0≤c≤2, 5≤a+b≤7, M is at least one selected from the group consisting of Na, K, Fe, Mg, Ca, Ag, Cu, Zr, and Zn, and X is at least one selected from the group consisting of F, Cl, Br, and I.

10. In paragraph 1, An all-solid-state battery, wherein the cathode coating layer comprises at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene.

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

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